diff --git a/src/ai/ai_config.cpp b/src/ai/ai_config.cpp
--- a/src/ai/ai_config.cpp
+++ b/src/ai/ai_config.cpp
@@ -31,7 +31,7 @@ ScriptConfigItem _start_date_config = {
 	AI::START_NEXT_DEVIATION,
 	30,
 	SCRIPTCONFIG_NONE,
-	NULL,
+	nullptr,
 	false
 };
 
@@ -52,7 +52,7 @@ AIConfig::AIConfig(const AIConfig *confi
 	} else {
 		config = &_settings_game.ai_config[company];
 	}
-	if (*config == NULL) *config = new AIConfig();
+	if (*config == nullptr) *config = new AIConfig();
 	return *config;
 }
 
@@ -69,7 +69,7 @@ ScriptInfo *AIConfig::FindInfo(const cha
 bool AIConfig::ResetInfo(bool force_exact_match)
 {
 	this->info = (ScriptInfo *)AI::FindInfo(this->name, force_exact_match ? this->version : -1, force_exact_match);
-	return this->info != NULL;
+	return this->info != nullptr;
 }
 
 void AIConfig::PushExtraConfigList()
@@ -90,7 +90,7 @@ void AIConfig::ClearConfigList()
 
 int AIConfig::GetSetting(const char *name) const
 {
-	if (this->info == NULL) {
+	if (this->info == nullptr) {
 		SettingValueList::const_iterator it = this->settings.find(name);
 		if (it == this->settings.end()) {
 			assert(strcmp("start_date", name) == 0);
@@ -111,7 +111,7 @@ int AIConfig::GetSetting(const char *nam
 
 void AIConfig::SetSetting(const char *name, int value)
 {
-	if (this->info == NULL) {
+	if (this->info == nullptr) {
 		if (strcmp("start_date", name) != 0) return;
 		value = Clamp(value, AI::START_NEXT_MIN, AI::START_NEXT_MAX);
 
diff --git a/src/ai/ai_core.cpp b/src/ai/ai_core.cpp
--- a/src/ai/ai_core.cpp
+++ b/src/ai/ai_core.cpp
@@ -26,8 +26,8 @@
 #include "../safeguards.h"
 
 /* static */ uint AI::frame_counter = 0;
-/* static */ AIScannerInfo *AI::scanner_info = NULL;
-/* static */ AIScannerLibrary *AI::scanner_library = NULL;
+/* static */ AIScannerInfo *AI::scanner_info = nullptr;
+/* static */ AIScannerLibrary *AI::scanner_library = nullptr;
 
 /* static */ bool AI::CanStartNew()
 {
@@ -44,9 +44,9 @@
 
 	AIConfig *config = AIConfig::GetConfig(company, AIConfig::SSS_FORCE_GAME);
 	AIInfo *info = config->GetInfo();
-	if (info == NULL || (rerandomise_ai && config->IsRandom())) {
+	if (info == nullptr || (rerandomise_ai && config->IsRandom())) {
 		info = AI::scanner_info->SelectRandomAI();
-		assert(info != NULL);
+		assert(info != nullptr);
 		/* Load default data and store the name in the settings */
 		config->Change(info->GetName(), -1, false, true);
 	}
@@ -56,7 +56,7 @@
 	Company *c = Company::Get(company);
 
 	c->ai_info = info;
-	assert(c->ai_instance == NULL);
+	assert(c->ai_instance == nullptr);
 	c->ai_instance = new AIInstance();
 	c->ai_instance->Initialize(info);
 
@@ -111,8 +111,8 @@
 	Company *c = Company::Get(company);
 
 	delete c->ai_instance;
-	c->ai_instance = NULL;
-	c->ai_info = NULL;
+	c->ai_instance = nullptr;
+	c->ai_info = nullptr;
 
 	cur_company.Restore();
 
@@ -164,10 +164,10 @@
 
 /* static */ void AI::Initialize()
 {
-	if (AI::scanner_info != NULL) AI::Uninitialize(true);
+	if (AI::scanner_info != nullptr) AI::Uninitialize(true);
 
 	AI::frame_counter = 0;
-	if (AI::scanner_info == NULL) {
+	if (AI::scanner_info == nullptr) {
 		TarScanner::DoScan(TarScanner::AI);
 		AI::scanner_info = new AIScannerInfo();
 		AI::scanner_info->Initialize();
@@ -187,17 +187,17 @@
 	} else {
 		delete AI::scanner_info;
 		delete AI::scanner_library;
-		AI::scanner_info = NULL;
-		AI::scanner_library = NULL;
+		AI::scanner_info = nullptr;
+		AI::scanner_library = nullptr;
 
 		for (CompanyID c = COMPANY_FIRST; c < MAX_COMPANIES; c++) {
-			if (_settings_game.ai_config[c] != NULL) {
+			if (_settings_game.ai_config[c] != nullptr) {
 				delete _settings_game.ai_config[c];
-				_settings_game.ai_config[c] = NULL;
+				_settings_game.ai_config[c] = nullptr;
 			}
-			if (_settings_newgame.ai_config[c] != NULL) {
+			if (_settings_newgame.ai_config[c] != nullptr) {
 				delete _settings_newgame.ai_config[c];
-				_settings_newgame.ai_config[c] = NULL;
+				_settings_newgame.ai_config[c] = nullptr;
 			}
 		}
 	}
@@ -209,10 +209,10 @@
 	 *  the AIConfig. If not, remove the AI from the list (which will assign
 	 *  a random new AI on reload). */
 	for (CompanyID c = COMPANY_FIRST; c < MAX_COMPANIES; c++) {
-		if (_settings_game.ai_config[c] != NULL && _settings_game.ai_config[c]->HasScript()) {
+		if (_settings_game.ai_config[c] != nullptr && _settings_game.ai_config[c]->HasScript()) {
 			if (!_settings_game.ai_config[c]->ResetInfo(true)) {
 				DEBUG(script, 0, "After a reload, the AI by the name '%s' was no longer found, and removed from the list.", _settings_game.ai_config[c]->GetName());
-				_settings_game.ai_config[c]->Change(NULL);
+				_settings_game.ai_config[c]->Change(nullptr);
 				if (Company::IsValidAiID(c)) {
 					/* The code belonging to an already running AI was deleted. We can only do
 					 * one thing here to keep everything sane and that is kill the AI. After
@@ -226,10 +226,10 @@
 				Company::Get(c)->ai_info = _settings_game.ai_config[c]->GetInfo();
 			}
 		}
-		if (_settings_newgame.ai_config[c] != NULL && _settings_newgame.ai_config[c]->HasScript()) {
+		if (_settings_newgame.ai_config[c] != nullptr && _settings_newgame.ai_config[c]->HasScript()) {
 			if (!_settings_newgame.ai_config[c]->ResetInfo(false)) {
 				DEBUG(script, 0, "After a reload, the AI by the name '%s' was no longer found, and removed from the list.", _settings_newgame.ai_config[c]->GetName());
-				_settings_newgame.ai_config[c]->Change(NULL);
+				_settings_newgame.ai_config[c]->Change(nullptr);
 			}
 		}
 	}
@@ -283,7 +283,7 @@
 {
 	if (!_networking || _network_server) {
 		Company *c = Company::GetIfValid(company);
-		assert(c != NULL && c->ai_instance != NULL);
+		assert(c != nullptr && c->ai_instance != nullptr);
 
 		Backup<CompanyByte> cur_company(_current_company, company, FILE_LINE);
 		c->ai_instance->Save();
@@ -297,7 +297,7 @@
 {
 	if (!_networking || _network_server) {
 		Company *c = Company::GetIfValid(company);
-		assert(c != NULL && c->ai_instance != NULL);
+		assert(c != nullptr && c->ai_instance != nullptr);
 
 		Backup<CompanyByte> cur_company(_current_company, company, FILE_LINE);
 		c->ai_instance->Load(version);
diff --git a/src/ai/ai_gui.cpp b/src/ai/ai_gui.cpp
--- a/src/ai/ai_gui.cpp
+++ b/src/ai/ai_gui.cpp
@@ -139,13 +139,13 @@ struct AIListWindow : public Window {
 				break;
 			}
 			case WID_AIL_INFO_BG: {
-				AIInfo *selected_info = NULL;
+				AIInfo *selected_info = nullptr;
 				ScriptInfoList::const_iterator it = this->info_list->begin();
-				for (int i = 1; selected_info == NULL && it != this->info_list->end(); i++, it++) {
+				for (int i = 1; selected_info == nullptr && it != this->info_list->end(); i++, it++) {
 					if (this->selected == i - 1) selected_info = static_cast<AIInfo *>((*it).second);
 				}
 				/* Some info about the currently selected AI. */
-				if (selected_info != NULL) {
+				if (selected_info != nullptr) {
 					int y = r.top + WD_FRAMERECT_TOP;
 					SetDParamStr(0, selected_info->GetAuthor());
 					DrawString(r.left + WD_FRAMETEXT_LEFT, r.right - WD_FRAMETEXT_RIGHT, y, STR_AI_LIST_AUTHOR);
@@ -153,7 +153,7 @@ struct AIListWindow : public Window {
 					SetDParam(0, selected_info->GetVersion());
 					DrawString(r.left + WD_FRAMETEXT_LEFT, r.right - WD_FRAMETEXT_RIGHT, y, STR_AI_LIST_VERSION);
 					y += FONT_HEIGHT_NORMAL + WD_PAR_VSEP_NORMAL;
-					if (selected_info->GetURL() != NULL) {
+					if (selected_info->GetURL() != nullptr) {
 						SetDParamStr(0, selected_info->GetURL());
 						DrawString(r.left + WD_FRAMETEXT_LEFT, r.right - WD_FRAMETEXT_RIGHT, y, STR_AI_LIST_URL);
 						y += FONT_HEIGHT_NORMAL + WD_PAR_VSEP_NORMAL;
@@ -172,7 +172,7 @@ struct AIListWindow : public Window {
 	void ChangeAI()
 	{
 		if (this->selected == -1) {
-			GetConfig(slot)->Change(NULL);
+			GetConfig(slot)->Change(nullptr);
 		} else {
 			ScriptInfoList::const_iterator it = this->info_list->begin();
 			for (int i = 0; i < this->selected; i++) it++;
@@ -407,7 +407,7 @@ struct AISettingsWindow : public Window 
 				} else {
 					DrawArrowButtons(buttons_left, y + button_y_offset, COLOUR_YELLOW, (this->clicked_button == i) ? 1 + (this->clicked_increase != rtl) : 0, editable && current_value > config_item.min_value, editable && current_value < config_item.max_value);
 				}
-				if (config_item.labels != NULL && config_item.labels->Contains(current_value)) {
+				if (config_item.labels != nullptr && config_item.labels->Contains(current_value)) {
 					SetDParam(idx++, STR_JUST_RAW_STRING);
 					SetDParamStr(idx++, config_item.labels->Find(current_value)->second);
 				} else {
@@ -805,7 +805,7 @@ struct AIConfigWindow : public Window {
 	 */
 	static bool IsEditable(CompanyID slot)
 	{
-		if (slot == OWNER_DEITY) return _game_mode != GM_NORMAL || Game::GetInstance() != NULL;
+		if (slot == OWNER_DEITY) return _game_mode != GM_NORMAL || Game::GetInstance() != nullptr;
 
 		if (_game_mode != GM_NORMAL) {
 			return slot > 0 && slot <= GetGameSettings().difficulty.max_no_competitors;
@@ -825,7 +825,7 @@ struct AIConfigWindow : public Window {
 			case WID_AIC_GAMELIST: {
 				StringID text = STR_AI_CONFIG_NONE;
 
-				if (GameConfig::GetConfig()->GetInfo() != NULL) {
+				if (GameConfig::GetConfig()->GetInfo() != nullptr) {
 					SetDParamStr(0, GameConfig::GetConfig()->GetInfo()->GetName());
 					text = STR_JUST_RAW_STRING;
 				}
@@ -843,7 +843,7 @@ struct AIConfigWindow : public Window {
 
 					if ((_game_mode != GM_NORMAL && i == 0) || (_game_mode == GM_NORMAL && Company::IsValidHumanID(i))) {
 						text = STR_AI_CONFIG_HUMAN_PLAYER;
-					} else if (AIConfig::GetConfig((CompanyID)i)->GetInfo() != NULL) {
+					} else if (AIConfig::GetConfig((CompanyID)i)->GetInfo() != nullptr) {
 						SetDParamStr(0, AIConfig::GetConfig((CompanyID)i)->GetInfo()->GetName());
 						text = STR_JUST_RAW_STRING;
 					} else {
@@ -861,7 +861,7 @@ struct AIConfigWindow : public Window {
 	void OnClick(Point pt, int widget, int click_count) override
 	{
 		if (widget >= WID_AIC_TEXTFILE && widget < WID_AIC_TEXTFILE + TFT_END) {
-			if (this->selected_slot == INVALID_COMPANY || GetConfig(this->selected_slot) == NULL) return;
+			if (this->selected_slot == INVALID_COMPANY || GetConfig(this->selected_slot) == nullptr) return;
 
 			ShowScriptTextfileWindow((TextfileType)(widget - WID_AIC_TEXTFILE), this->selected_slot);
 			return;
@@ -928,7 +928,7 @@ struct AIConfigWindow : public Window {
 				if (!_network_available) {
 					ShowErrorMessage(STR_NETWORK_ERROR_NOTAVAILABLE, INVALID_STRING_ID, WL_ERROR);
 				} else {
-					ShowNetworkContentListWindow(NULL, CONTENT_TYPE_AI, CONTENT_TYPE_GAME);
+					ShowNetworkContentListWindow(nullptr, CONTENT_TYPE_AI, CONTENT_TYPE_GAME);
 				}
 				break;
 		}
@@ -955,7 +955,7 @@ struct AIConfigWindow : public Window {
 		this->SetWidgetDisabledState(WID_AIC_MOVE_DOWN, this->selected_slot == OWNER_DEITY || this->selected_slot == INVALID_COMPANY || !IsEditable((CompanyID)(this->selected_slot + 1)));
 
 		for (TextfileType tft = TFT_BEGIN; tft < TFT_END; tft++) {
-			this->SetWidgetDisabledState(WID_AIC_TEXTFILE + tft, this->selected_slot == INVALID_COMPANY || (GetConfig(this->selected_slot)->GetTextfile(tft, this->selected_slot) == NULL));
+			this->SetWidgetDisabledState(WID_AIC_TEXTFILE + tft, this->selected_slot == INVALID_COMPANY || (GetConfig(this->selected_slot)->GetTextfile(tft, this->selected_slot) == nullptr));
 		}
 	}
 };
@@ -1024,7 +1024,7 @@ struct AIDebugWindow : public Window {
 	{
 		if (ai_debug_company == OWNER_DEITY) {
 			GameInstance *game = Game::GetInstance();
-			return game == NULL || game->IsDead();
+			return game == nullptr || game->IsDead();
 		}
 		return !Company::IsValidAiID(ai_debug_company) || Company::Get(ai_debug_company)->ai_instance->IsDead();
 	}
@@ -1038,7 +1038,7 @@ struct AIDebugWindow : public Window {
 	{
 		switch (company) {
 			case INVALID_COMPANY: return false;
-			case OWNER_DEITY:     return Game::GetInstance() != NULL;
+			case OWNER_DEITY:     return Game::GetInstance() != nullptr;
 			default:              return Company::IsValidAiID(company);
 		}
 	}
@@ -1063,7 +1063,7 @@ struct AIDebugWindow : public Window {
 		}
 
 		/* If no AI is available, see if there is a game script. */
-		if (Game::GetInstance() != NULL) ChangeToAI(OWNER_DEITY);
+		if (Game::GetInstance() != nullptr) ChangeToAI(OWNER_DEITY);
 	}
 
 	/**
@@ -1140,7 +1140,7 @@ struct AIDebugWindow : public Window {
 
 		/* Set button colour for Game Script. */
 		GameInstance *game = Game::GetInstance();
-		bool valid = game != NULL;
+		bool valid = game != nullptr;
 		bool dead = valid && game->IsDead();
 		bool paused = valid && game->IsPaused();
 
@@ -1154,7 +1154,7 @@ struct AIDebugWindow : public Window {
 
 		ScriptLog::LogData *log = this->GetLogPointer();
 
-		int scroll_count = (log == NULL) ? 0 : log->used;
+		int scroll_count = (log == nullptr) ? 0 : log->used;
 		if (this->vscroll->GetCount() != scroll_count) {
 			this->vscroll->SetCount(scroll_count);
 
@@ -1162,7 +1162,7 @@ struct AIDebugWindow : public Window {
 			this->SetWidgetDirty(WID_AID_SCROLLBAR);
 		}
 
-		if (log == NULL) return;
+		if (log == nullptr) return;
 
 		/* Detect when the user scrolls the window. Enable autoscroll when the
 		 * bottom-most line becomes visible. */
@@ -1188,7 +1188,7 @@ struct AIDebugWindow : public Window {
 			case WID_AID_NAME_TEXT:
 				if (ai_debug_company == OWNER_DEITY) {
 					const GameInfo *info = Game::GetInfo();
-					assert(info != NULL);
+					assert(info != nullptr);
 					SetDParam(0, STR_AI_DEBUG_NAME_AND_VERSION);
 					SetDParamStr(1, info->GetName());
 					SetDParam(2, info->GetVersion());
@@ -1196,7 +1196,7 @@ struct AIDebugWindow : public Window {
 					SetDParam(0, STR_EMPTY);
 				} else {
 					const AIInfo *info = Company::Get(ai_debug_company)->ai_info;
-					assert(info != NULL);
+					assert(info != nullptr);
 					SetDParam(0, STR_AI_DEBUG_NAME_AND_VERSION);
 					SetDParamStr(1, info->GetName());
 					SetDParam(2, info->GetVersion());
@@ -1212,12 +1212,12 @@ struct AIDebugWindow : public Window {
 		switch (widget) {
 			case WID_AID_LOG_PANEL: {
 				ScriptLog::LogData *log = this->GetLogPointer();
-				if (log == NULL) return;
+				if (log == nullptr) return;
 
 				int y = this->top_offset;
 				for (int i = this->vscroll->GetPosition(); this->vscroll->IsVisible(i) && i < log->used; i++) {
 					int pos = (i + log->pos + 1 - log->used + log->count) % log->count;
-					if (log->lines[pos] == NULL) break;
+					if (log->lines[pos] == nullptr) break;
 
 					TextColour colour;
 					switch (log->type[pos]) {
@@ -1357,7 +1357,7 @@ struct AIDebugWindow : public Window {
 			/* Get the log instance of the active company */
 			ScriptLog::LogData *log = this->GetLogPointer();
 
-			if (log != NULL) {
+			if (log != nullptr) {
 				this->break_string_filter.ResetState();
 				this->break_string_filter.AddLine(log->lines[log->pos]);
 				if (this->break_string_filter.GetState()) {
@@ -1385,8 +1385,8 @@ struct AIDebugWindow : public Window {
 
 		this->SelectValidDebugCompany();
 
-		ScriptLog::LogData *log = ai_debug_company != INVALID_COMPANY ? this->GetLogPointer() : NULL;
-		this->vscroll->SetCount((log == NULL) ? 0 : log->used);
+		ScriptLog::LogData *log = ai_debug_company != INVALID_COMPANY ? this->GetLogPointer() : nullptr;
+		this->vscroll->SetCount((log == nullptr) ? 0 : log->used);
 
 		/* Update company buttons */
 		for (CompanyID i = COMPANY_FIRST; i < MAX_COMPANIES; i++) {
@@ -1394,7 +1394,7 @@ struct AIDebugWindow : public Window {
 			this->SetWidgetLoweredState(i + WID_AID_COMPANY_BUTTON_START, ai_debug_company == i);
 		}
 
-		this->SetWidgetDisabledState(WID_AID_SCRIPT_GAME, Game::GetGameInstance() == NULL);
+		this->SetWidgetDisabledState(WID_AID_SCRIPT_GAME, Game::GetGameInstance() == nullptr);
 		this->SetWidgetLoweredState(WID_AID_SCRIPT_GAME, ai_debug_company == OWNER_DEITY);
 
 		this->SetWidgetLoweredState(WID_AID_BREAK_STR_ON_OFF_BTN, this->break_check_enabled);
@@ -1437,7 +1437,7 @@ static EventState AIDebugGlobalHotkeys(i
 {
 	if (_game_mode != GM_NORMAL) return ES_NOT_HANDLED;
 	Window *w = ShowAIDebugWindow(INVALID_COMPANY);
-	if (w == NULL) return ES_NOT_HANDLED;
+	if (w == nullptr) return ES_NOT_HANDLED;
 	return w->OnHotkey(hotkey);
 }
 
@@ -1530,14 +1530,14 @@ Window *ShowAIDebugWindow(CompanyID show
 {
 	if (!_networking || _network_server) {
 		AIDebugWindow *w = (AIDebugWindow *)BringWindowToFrontById(WC_AI_DEBUG, 0);
-		if (w == NULL) w = new AIDebugWindow(&_ai_debug_desc, 0);
+		if (w == nullptr) w = new AIDebugWindow(&_ai_debug_desc, 0);
 		if (show_company != INVALID_COMPANY) w->ChangeToAI(show_company);
 		return w;
 	} else {
 		ShowErrorMessage(STR_ERROR_AI_DEBUG_SERVER_ONLY, INVALID_STRING_ID, WL_INFO);
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -1563,7 +1563,7 @@ void ShowAIDebugWindowIfAIError()
 	}
 
 	GameInstance *g = Game::GetGameInstance();
-	if (g != NULL && g->IsDead()) {
+	if (g != nullptr && g->IsDead()) {
 		ShowAIDebugWindow(OWNER_DEITY);
 	}
 }
diff --git a/src/ai/ai_info.cpp b/src/ai/ai_info.cpp
--- a/src/ai/ai_info.cpp
+++ b/src/ai/ai_info.cpp
@@ -65,8 +65,8 @@ template <> const char *GetClassName<AII
 /* static */ SQInteger AIInfo::Constructor(HSQUIRRELVM vm)
 {
 	/* Get the AIInfo */
-	SQUserPointer instance = NULL;
-	if (SQ_FAILED(sq_getinstanceup(vm, 2, &instance, 0)) || instance == NULL) return sq_throwerror(vm, "Pass an instance of a child class of AIInfo to RegisterAI");
+	SQUserPointer instance = nullptr;
+	if (SQ_FAILED(sq_getinstanceup(vm, 2, &instance, 0)) || instance == nullptr) return sq_throwerror(vm, "Pass an instance of a child class of AIInfo to RegisterAI");
 	AIInfo *info = (AIInfo *)instance;
 
 	SQInteger res = ScriptInfo::Constructor(vm, info);
@@ -100,7 +100,7 @@ template <> const char *GetClassName<AII
 	}
 
 	/* Remove the link to the real instance, else it might get deleted by RegisterAI() */
-	sq_setinstanceup(vm, 2, NULL);
+	sq_setinstanceup(vm, 2, nullptr);
 	/* Register the AI to the base system */
 	info->GetScanner()->RegisterScript(info);
 	return 0;
@@ -112,7 +112,7 @@ template <> const char *GetClassName<AII
 	SQUserPointer instance;
 	sq_getinstanceup(vm, 2, &instance, 0);
 	AIInfo *info = (AIInfo *)instance;
-	info->api_version = NULL;
+	info->api_version = nullptr;
 
 	SQInteger res = ScriptInfo::Constructor(vm, info);
 	if (res != 0) return res;
@@ -122,7 +122,7 @@ template <> const char *GetClassName<AII
 	info->api_version = stredup(buf);
 
 	/* Remove the link to the real instance, else it might get deleted by RegisterAI() */
-	sq_setinstanceup(vm, 2, NULL);
+	sq_setinstanceup(vm, 2, nullptr);
 	/* Register the AI to the base system */
 	static_cast<AIScannerInfo *>(info->GetScanner())->SetDummyAI(info);
 	return 0;
@@ -131,7 +131,7 @@ template <> const char *GetClassName<AII
 AIInfo::AIInfo() :
 	min_loadable_version(0),
 	use_as_random(false),
-	api_version(NULL)
+	api_version(nullptr)
 {
 }
 
diff --git a/src/ai/ai_info.hpp b/src/ai/ai_info.hpp
--- a/src/ai/ai_info.hpp
+++ b/src/ai/ai_info.hpp
@@ -59,7 +59,7 @@ private:
 /** All static information from an AI library like name, version, etc. */
 class AILibrary : public ScriptInfo {
 public:
-	AILibrary() : ScriptInfo(), category(NULL) {};
+	AILibrary() : ScriptInfo(), category(nullptr) {};
 	~AILibrary();
 
 	/**
diff --git a/src/ai/ai_instance.cpp b/src/ai/ai_instance.cpp
--- a/src/ai/ai_instance.cpp
+++ b/src/ai/ai_instance.cpp
@@ -216,10 +216,10 @@ void AIInstance::Died()
 	ShowAIDebugWindow(_current_company);
 
 	const AIInfo *info = AIConfig::GetConfig(_current_company, AIConfig::SSS_FORCE_GAME)->GetInfo();
-	if (info != NULL) {
+	if (info != nullptr) {
 		ShowErrorMessage(STR_ERROR_AI_PLEASE_REPORT_CRASH, INVALID_STRING_ID, WL_WARNING);
 
-		if (info->GetURL() != NULL) {
+		if (info->GetURL() != nullptr) {
 			ScriptLog::Info("Please report the error to the following URL:");
 			ScriptLog::Info(info->GetURL());
 		}
@@ -258,7 +258,7 @@ void CcAI(const CommandCost &result, Til
 	 * when the company does not exist anymore.
 	 */
 	const Company *c = Company::GetIfValid(_current_company);
-	if (c == NULL || c->ai_instance == NULL) return;
+	if (c == nullptr || c->ai_instance == nullptr) return;
 
 	c->ai_instance->DoCommandCallback(result, tile, p1, p2);
 	c->ai_instance->Continue();
diff --git a/src/ai/ai_scanner.cpp b/src/ai/ai_scanner.cpp
--- a/src/ai/ai_scanner.cpp
+++ b/src/ai/ai_scanner.cpp
@@ -23,7 +23,7 @@
 
 AIScannerInfo::AIScannerInfo() :
 	ScriptScanner(),
-	info_dummy(NULL)
+	info_dummy(nullptr)
 {
 }
 
@@ -94,14 +94,14 @@ AIInfo *AIScannerInfo::SelectRandomAI() 
 
 AIInfo *AIScannerInfo::FindInfo(const char *nameParam, int versionParam, bool force_exact_match)
 {
-	if (this->info_list.size() == 0) return NULL;
-	if (nameParam == NULL) return NULL;
+	if (this->info_list.size() == 0) return nullptr;
+	if (nameParam == nullptr) return nullptr;
 
 	char ai_name[1024];
 	strecpy(ai_name, nameParam, lastof(ai_name));
 	strtolower(ai_name);
 
-	AIInfo *info = NULL;
+	AIInfo *info = nullptr;
 	int version = -1;
 
 	if (versionParam == -1) {
@@ -110,7 +110,7 @@ AIInfo *AIScannerInfo::FindInfo(const ch
 
 		/* If we didn't find a match AI, maybe the user included a version */
 		char *e = strrchr(ai_name, '.');
-		if (e == NULL) return NULL;
+		if (e == nullptr) return nullptr;
 		*e = '\0';
 		e++;
 		versionParam = atoi(e);
@@ -165,7 +165,7 @@ AILibrary *AIScannerLibrary::FindLibrary
 
 	/* Check if the library + version exists */
 	ScriptInfoList::iterator iter = this->info_list.find(library_name);
-	if (iter == this->info_list.end()) return NULL;
+	if (iter == this->info_list.end()) return nullptr;
 
 	return static_cast<AILibrary *>((*iter).second);
 }
diff --git a/src/ai/ai_scanner.hpp b/src/ai/ai_scanner.hpp
--- a/src/ai/ai_scanner.hpp
+++ b/src/ai/ai_scanner.hpp
@@ -32,7 +32,7 @@ public:
 	 * @param nameParam The name of the AI.
 	 * @param versionParam The version of the AI, or -1 if you want the latest.
 	 * @param force_exact_match Only match name+version, never latest.
-	 * @return NULL if no match found, otherwise the AI that matched.
+	 * @return nullptr if no match found, otherwise the AI that matched.
 	 */
 	class AIInfo *FindInfo(const char *nameParam, int versionParam, bool force_exact_match);
 
@@ -60,7 +60,7 @@ public:
 	 * Find a library in the pool.
 	 * @param library The library name to find.
 	 * @param version The version the library should have.
-	 * @return The library if found, NULL otherwise.
+	 * @return The library if found, nullptr otherwise.
 	 */
 	class AILibrary *FindLibrary(const char *library, int version);
 
diff --git a/src/aircraft_cmd.cpp b/src/aircraft_cmd.cpp
--- a/src/aircraft_cmd.cpp
+++ b/src/aircraft_cmd.cpp
@@ -143,7 +143,7 @@ static StationID FindNearestHangar(const
 		if (v->acache.cached_max_range_sqr != 0) {
 			/* Check if our current destination can be reached from the depot airport. */
 			const Station *cur_dest = GetTargetAirportIfValid(v);
-			if (cur_dest != NULL && DistanceSquare(st->airport.tile, cur_dest->airport.tile) > v->acache.cached_max_range_sqr) continue;
+			if (cur_dest != nullptr && DistanceSquare(st->airport.tile, cur_dest->airport.tile) > v->acache.cached_max_range_sqr) continue;
 		}
 		if (distance < best || index == INVALID_STATION) {
 			best = distance;
@@ -295,7 +295,7 @@ CommandCost CmdBuildAircraft(TileIndex t
 		v->cargo_type = e->GetDefaultCargoType();
 		u->cargo_type = CT_MAIL;
 
-		v->name = NULL;
+		v->name = nullptr;
 		v->last_station_visited = INVALID_STATION;
 		v->last_loading_station = INVALID_STATION;
 
@@ -379,7 +379,7 @@ bool Aircraft::FindClosestDepot(TileInde
 {
 	const Station *st = GetTargetAirportIfValid(this);
 	/* If the station is not a valid airport or if it has no hangars */
-	if (st == NULL || !CanVehicleUseStation(this, st) || !st->airport.HasHangar()) {
+	if (st == nullptr || !CanVehicleUseStation(this, st) || !st->airport.HasHangar()) {
 		/* the aircraft has to search for a hangar on its own */
 		StationID station = FindNearestHangar(this);
 
@@ -388,8 +388,8 @@ bool Aircraft::FindClosestDepot(TileInde
 		st = Station::Get(station);
 	}
 
-	if (location    != NULL) *location    = st->xy;
-	if (destination != NULL) *destination = st->index;
+	if (location    != nullptr) *location    = st->xy;
+	if (destination != nullptr) *destination = st->index;
 
 	return true;
 }
@@ -408,7 +408,7 @@ static void CheckIfAircraftNeedsService(
 
 	const Station *st = Station::Get(v->current_order.GetDestination());
 
-	assert(st != NULL);
+	assert(st != nullptr);
 
 	/* only goto depot if the target airport has a depot */
 	if (st->airport.HasHangar() && CanVehicleUseStation(v, st)) {
@@ -531,7 +531,7 @@ void SetAircraftPosition(Aircraft *v, in
 	u->UpdatePositionAndViewport();
 
 	u = u->Next();
-	if (u != NULL) {
+	if (u != nullptr) {
 		u->x_pos = x;
 		u->y_pos = y;
 		u->z_pos = z + ROTOR_Z_OFFSET;
@@ -552,7 +552,7 @@ void HandleAircraftEnterHangar(Aircraft 
 	Aircraft *u = v->Next();
 	u->vehstatus |= VS_HIDDEN;
 	u = u->Next();
-	if (u != NULL) {
+	if (u != nullptr) {
 		u->vehstatus |= VS_HIDDEN;
 		u->cur_speed = 0;
 	}
@@ -725,8 +725,8 @@ void GetAircraftFlightLevelBounds(const 
 	/* Make faster planes fly higher so that they can overtake slower ones */
 	base_altitude += min(20 * (v->vcache.cached_max_speed / 200) - 90, 0);
 
-	if (min_level != NULL) *min_level = base_altitude + AIRCRAFT_MIN_FLYING_ALTITUDE;
-	if (max_level != NULL) *max_level = base_altitude + AIRCRAFT_MAX_FLYING_ALTITUDE;
+	if (min_level != nullptr) *min_level = base_altitude + AIRCRAFT_MIN_FLYING_ALTITUDE;
+	if (max_level != nullptr) *max_level = base_altitude + AIRCRAFT_MAX_FLYING_ALTITUDE;
 }
 
 /**
@@ -801,8 +801,8 @@ template int GetAircraftFlightLevel(Airc
  */
 static byte AircraftGetEntryPoint(const Aircraft *v, const AirportFTAClass *apc, Direction rotation)
 {
-	assert(v != NULL);
-	assert(apc != NULL);
+	assert(v != nullptr);
+	assert(apc != nullptr);
 
 	/* In the case the station doesn't exit anymore, set target tile 0.
 	 * It doesn't hurt much, aircraft will go to next order, nearest hangar
@@ -810,7 +810,7 @@ static byte AircraftGetEntryPoint(const 
 	TileIndex tile = 0;
 
 	const Station *st = Station::GetIfValid(v->targetairport);
-	if (st != NULL) {
+	if (st != nullptr) {
 		/* Make sure we don't go to INVALID_TILE if the airport has been removed. */
 		tile = (st->airport.tile != INVALID_TILE) ? st->airport.tile : st->xy;
 	}
@@ -844,13 +844,13 @@ static bool AircraftController(Aircraft 
 {
 	int count;
 
-	/* NULL if station is invalid */
+	/* nullptr if station is invalid */
 	const Station *st = Station::GetIfValid(v->targetairport);
 	/* INVALID_TILE if there is no station */
 	TileIndex tile = INVALID_TILE;
 	Direction rotation = DIR_N;
 	uint size_x = 1, size_y = 1;
-	if (st != NULL) {
+	if (st != nullptr) {
 		if (st->airport.tile != INVALID_TILE) {
 			tile = st->airport.tile;
 			rotation = st->airport.rotation;
@@ -864,7 +864,7 @@ static bool AircraftController(Aircraft 
 	const AirportFTAClass *afc = tile == INVALID_TILE ? GetAirport(AT_DUMMY) : st->airport.GetFTA();
 
 	/* prevent going to INVALID_TILE if airport is deleted. */
-	if (st == NULL || st->airport.tile == INVALID_TILE) {
+	if (st == nullptr || st->airport.tile == INVALID_TILE) {
 		/* Jump into our "holding pattern" state machine if possible */
 		if (v->pos >= afc->nofelements) {
 			v->pos = v->previous_pos = AircraftGetEntryPoint(v, afc, DIR_N);
@@ -904,7 +904,7 @@ static bool AircraftController(Aircraft 
 				v->tile = 0;
 
 				int z_dest;
-				GetAircraftFlightLevelBounds(v, &z_dest, NULL);
+				GetAircraftFlightLevelBounds(v, &z_dest, nullptr);
 
 				/* Reached altitude? */
 				if (v->z_pos >= z_dest) {
@@ -921,7 +921,7 @@ static bool AircraftController(Aircraft 
 	if (amd.flag & AMED_HELI_LOWER) {
 		SetBit(v->flags, VAF_HELI_DIRECT_DESCENT);
 
-		if (st == NULL) {
+		if (st == nullptr) {
 			/* FIXME - AircraftController -> if station no longer exists, do not land
 			 * helicopter will circle until sign disappears, then go to next order
 			 * what to do when it is the only order left, right now it just stays in 1 place */
@@ -1127,7 +1127,7 @@ static bool HandleCrashedAircraft(Aircra
 	Station *st = GetTargetAirportIfValid(v);
 
 	/* make aircraft crash down to the ground */
-	if (v->crashed_counter < 500 && st == NULL && ((v->crashed_counter % 3) == 0) ) {
+	if (v->crashed_counter < 500 && st == nullptr && ((v->crashed_counter % 3) == 0) ) {
 		int z = GetSlopePixelZ(Clamp(v->x_pos, 0, MapMaxX() * TILE_SIZE), Clamp(v->y_pos, 0, MapMaxY() * TILE_SIZE));
 		v->z_pos -= 1;
 		if (v->z_pos == z) {
@@ -1158,7 +1158,7 @@ static bool HandleCrashedAircraft(Aircra
 		/* clear runway-in on all airports, set by crashing plane
 		 * small airports use AIRPORT_BUSY, city airports use RUNWAY_IN_OUT_block, etc.
 		 * but they all share the same number */
-		if (st != NULL) {
+		if (st != nullptr) {
 			CLRBITS(st->airport.flags, RUNWAY_IN_block);
 			CLRBITS(st->airport.flags, RUNWAY_IN_OUT_block); // commuter airport
 			CLRBITS(st->airport.flags, RUNWAY_IN2_block);    // intercontinental
@@ -1232,7 +1232,7 @@ void HandleMissingAircraftOrders(Aircraf
 	 *    actually stops.
 	 */
 	const Station *st = GetTargetAirportIfValid(v);
-	if (st == NULL) {
+	if (st == nullptr) {
 		Backup<CompanyByte> cur_company(_current_company, v->owner, FILE_LINE);
 		CommandCost ret = DoCommand(v->tile, v->index, 0, DC_EXEC, CMD_SEND_VEHICLE_TO_DEPOT);
 		cur_company.Restore();
@@ -1288,17 +1288,17 @@ static void CrashAirplane(Aircraft *v)
 	v->Next()->cargo.Truncate();
 	const Station *st = GetTargetAirportIfValid(v);
 	StringID newsitem;
-	if (st == NULL) {
+	if (st == nullptr) {
 		newsitem = STR_NEWS_PLANE_CRASH_OUT_OF_FUEL;
 	} else {
 		SetDParam(1, st->index);
 		newsitem = STR_NEWS_AIRCRAFT_CRASH;
 	}
 
-	AI::NewEvent(v->owner, new ScriptEventVehicleCrashed(v->index, v->tile, st == NULL ? ScriptEventVehicleCrashed::CRASH_AIRCRAFT_NO_AIRPORT : ScriptEventVehicleCrashed::CRASH_PLANE_LANDING));
-	Game::NewEvent(new ScriptEventVehicleCrashed(v->index, v->tile, st == NULL ? ScriptEventVehicleCrashed::CRASH_AIRCRAFT_NO_AIRPORT : ScriptEventVehicleCrashed::CRASH_PLANE_LANDING));
+	AI::NewEvent(v->owner, new ScriptEventVehicleCrashed(v->index, v->tile, st == nullptr ? ScriptEventVehicleCrashed::CRASH_AIRCRAFT_NO_AIRPORT : ScriptEventVehicleCrashed::CRASH_PLANE_LANDING));
+	Game::NewEvent(new ScriptEventVehicleCrashed(v->index, v->tile, st == nullptr ? ScriptEventVehicleCrashed::CRASH_AIRCRAFT_NO_AIRPORT : ScriptEventVehicleCrashed::CRASH_PLANE_LANDING));
 
-	AddVehicleNewsItem(newsitem, NT_ACCIDENT, v->index, st != NULL ? st->index : INVALID_STATION);
+	AddVehicleNewsItem(newsitem, NT_ACCIDENT, v->index, st != nullptr ? st->index : INVALID_STATION);
 
 	ModifyStationRatingAround(v->tile, v->owner, -160, 30);
 	if (_settings_client.sound.disaster) SndPlayVehicleFx(SND_12_EXPLOSION, v);
@@ -1392,8 +1392,8 @@ void AircraftNextAirportPos_and_Order(Ai
 	}
 
 	const Station *st = GetTargetAirportIfValid(v);
-	const AirportFTAClass *apc = st == NULL ? GetAirport(AT_DUMMY) : st->airport.GetFTA();
-	Direction rotation = st == NULL ? DIR_N : st->airport.rotation;
+	const AirportFTAClass *apc = st == nullptr ? GetAirport(AT_DUMMY) : st->airport.GetFTA();
+	Direction rotation = st == nullptr ? DIR_N : st->airport.rotation;
 	v->pos = v->previous_pos = AircraftGetEntryPoint(v, apc, rotation);
 }
 
@@ -1418,7 +1418,7 @@ void AircraftLeaveHangar(Aircraft *v, Di
 
 		/* Rotor blades */
 		u = u->Next();
-		if (u != NULL) {
+		if (u != nullptr) {
 			u->vehstatus &= ~VS_HIDDEN;
 			u->cur_speed = 80;
 		}
@@ -1605,7 +1605,7 @@ static void AircraftEventHandler_Flying(
 		 * it is possible to choose from multiple landing runways, so loop until a free one is found */
 		byte landingtype = (v->subtype == AIR_HELICOPTER) ? HELILANDING : LANDING;
 		const AirportFTA *current = apc->layout[v->pos].next;
-		while (current != NULL) {
+		while (current != nullptr) {
 			if (current->heading == landingtype) {
 				/* save speed before, since if AirportHasBlock is false, it resets them to 0
 				 * we don't want that for plane in air
@@ -1761,7 +1761,7 @@ static bool AirportMove(Aircraft *v, con
 	v->previous_pos = v->pos; // save previous location
 
 	/* there is only one choice to move to */
-	if (current->next == NULL) {
+	if (current->next == nullptr) {
 		if (AirportSetBlocks(v, current, apc)) {
 			v->pos = current->next_position;
 			UpdateAircraftCache(v);
@@ -1780,7 +1780,7 @@ static bool AirportMove(Aircraft *v, con
 			return false;
 		}
 		current = current->next;
-	} while (current != NULL);
+	} while (current != nullptr);
 
 	DEBUG(misc, 0, "[Ap] cannot move further on Airport! (pos %d state %d) for vehicle %d", v->pos, v->state, v->index);
 	NOT_REACHED();
@@ -1830,7 +1830,7 @@ static bool AirportSetBlocks(Aircraft *v
 		 * this means more blocks should be checked/set */
 		const AirportFTA *current = current_pos;
 		if (current == reference) current = current->next;
-		while (current != NULL) {
+		while (current != nullptr) {
 			if (current->heading == current_pos->heading && current->block != 0) {
 				airport_flags |= current->block;
 				break;
@@ -1938,7 +1938,7 @@ static bool AirportFindFreeTerminal(Airc
 		const Station *st = Station::Get(v->targetairport);
 		const AirportFTA *temp = apc->layout[v->pos].next;
 
-		while (temp != NULL) {
+		while (temp != nullptr) {
 			if (temp->heading == 255) {
 				if (!(st->airport.flags & temp->block)) {
 					/* read which group do we want to go to?
@@ -2037,9 +2037,9 @@ static bool AircraftEventHandler(Aircraf
 		/* Check the distance to the next destination. This code works because the target
 		 * airport is only updated after take off and not on the ground. */
 		Station *cur_st = Station::GetIfValid(v->targetairport);
-		Station *next_st = v->current_order.IsType(OT_GOTO_STATION) || v->current_order.IsType(OT_GOTO_DEPOT) ? Station::GetIfValid(v->current_order.GetDestination()) : NULL;
+		Station *next_st = v->current_order.IsType(OT_GOTO_STATION) || v->current_order.IsType(OT_GOTO_DEPOT) ? Station::GetIfValid(v->current_order.GetDestination()) : nullptr;
 
-		if (cur_st != NULL && cur_st->airport.tile != INVALID_TILE && next_st != NULL && next_st->airport.tile != INVALID_TILE) {
+		if (cur_st != nullptr && cur_st->airport.tile != INVALID_TILE && next_st != nullptr && next_st->airport.tile != INVALID_TILE) {
 			uint dist = DistanceSquare(cur_st->airport.tile, next_st->airport.tile);
 			AircraftHandleDestTooFar(v, dist > v->acache.cached_max_range_sqr);
 		}
@@ -2077,16 +2077,16 @@ bool Aircraft::Tick()
  * Returns aircraft's target station if v->target_airport
  * is a valid station with airport.
  * @param v vehicle to get target airport for
- * @return pointer to target station, NULL if invalid
+ * @return pointer to target station, nullptr if invalid
  */
 Station *GetTargetAirportIfValid(const Aircraft *v)
 {
 	assert(v->type == VEH_AIRCRAFT);
 
 	Station *st = Station::GetIfValid(v->targetairport);
-	if (st == NULL) return NULL;
+	if (st == nullptr) return nullptr;
 
-	return st->airport.tile == INVALID_TILE ? NULL : st;
+	return st->airport.tile == INVALID_TILE ? nullptr : st;
 }
 
 /**
diff --git a/src/aircraft_gui.cpp b/src/aircraft_gui.cpp
--- a/src/aircraft_gui.cpp
+++ b/src/aircraft_gui.cpp
@@ -36,7 +36,7 @@ void DrawAircraftDetails(const Aircraft 
 	int y_offset = (v->Next()->cargo_cap != 0) ? -(FONT_HEIGHT_NORMAL + 1): 0;
 	Money feeder_share = 0;
 
-	for (const Aircraft *u = v; u != NULL; u = u->Next()) {
+	for (const Aircraft *u = v; u != nullptr; u = u->Next()) {
 		if (u->IsNormalAircraft()) {
 			SetDParam(0, u->engine_type);
 			SetDParam(1, u->build_year);
diff --git a/src/airport.cpp b/src/airport.cpp
--- a/src/airport.cpp
+++ b/src/airport.cpp
@@ -46,7 +46,7 @@
  * @param delta_z Height of the airport above the land.
  */
 #define HELIPORT(name, num_helipads, delta_z) \
-	AIRPORT_GENERIC(name, NULL, num_helipads, AirportFTAClass::HELICOPTERS, delta_z)
+	AIRPORT_GENERIC(name, nullptr, num_helipads, AirportFTAClass::HELICOPTERS, delta_z)
 
 AIRPORT(country, 0, true)
 AIRPORT(city, 0, false)
@@ -58,7 +58,7 @@ HELIPORT(helidepot, 1, 0)
 AIRPORT(intercontinental, 2, false)
 HELIPORT(helistation, 3, 0)
 HELIPORT(oilrig, 1, 54)
-AIRPORT_GENERIC(dummy, NULL, 0, AirportFTAClass::ALL, 0)
+AIRPORT_GENERIC(dummy, nullptr, 0, AirportFTAClass::ALL, 0)
 
 #undef HELIPORT
 #undef AIRPORT
@@ -135,7 +135,7 @@ AirportFTAClass::~AirportFTAClass()
 {
 	for (uint i = 0; i < nofelements; i++) {
 		AirportFTA *current = layout[i].next;
-		while (current != NULL) {
+		while (current != nullptr) {
 			AirportFTA *next = current->next;
 			free(current);
 			current = next;
@@ -195,7 +195,7 @@ static AirportFTA *AirportBuildAutomata(
 			current = current->next;
 			internalcounter++;
 		}
-		current->next = NULL;
+		current->next = nullptr;
 		internalcounter++;
 	}
 	return FAutomata;
diff --git a/src/airport_gui.cpp b/src/airport_gui.cpp
--- a/src/airport_gui.cpp
+++ b/src/airport_gui.cpp
@@ -161,7 +161,7 @@ static EventState AirportToolbarGlobalHo
 {
 	if (_game_mode != GM_NORMAL || !CanBuildVehicleInfrastructure(VEH_AIRCRAFT)) return ES_NOT_HANDLED;
 	Window *w = ShowBuildAirToolbar();
-	if (w == NULL) return ES_NOT_HANDLED;
+	if (w == nullptr) return ES_NOT_HANDLED;
 	return w->OnHotkey(hotkey);
 }
 
@@ -198,11 +198,11 @@ static WindowDesc _air_toolbar_desc(
  *
  * If the terraform toolbar is linked to the toolbar, that window is also opened.
  *
- * @return newly opened airport toolbar, or NULL if the toolbar could not be opened.
+ * @return newly opened airport toolbar, or nullptr if the toolbar could not be opened.
  */
 Window *ShowBuildAirToolbar()
 {
-	if (!Company::IsValidID(_local_company)) return NULL;
+	if (!Company::IsValidID(_local_company)) return nullptr;
 
 	DeleteWindowByClass(WC_BUILD_TOOLBAR);
 	return AllocateWindowDescFront<BuildAirToolbarWindow>(&_air_toolbar_desc, TRANSPORT_AIR);
diff --git a/src/articulated_vehicles.cpp b/src/articulated_vehicles.cpp
--- a/src/articulated_vehicles.cpp
+++ b/src/articulated_vehicles.cpp
@@ -31,9 +31,9 @@ static const uint MAX_ARTICULATED_PARTS 
  * @param mirrored Returns whether the part shall be flipped.
  * @return engine to add or INVALID_ENGINE
  */
-static EngineID GetNextArticulatedPart(uint index, EngineID front_type, Vehicle *front = NULL, bool *mirrored = NULL)
+static EngineID GetNextArticulatedPart(uint index, EngineID front_type, Vehicle *front = nullptr, bool *mirrored = nullptr)
 {
-	assert(front == NULL || front->engine_type == front_type);
+	assert(front == nullptr || front->engine_type == front_type);
 
 	const Engine *front_engine = Engine::Get(front_type);
 
@@ -44,12 +44,12 @@ static EngineID GetNextArticulatedPart(u
 		/* 8 bits, bit 7 for mirroring */
 		callback = GB(callback, 0, 8);
 		if (callback == 0xFF) return INVALID_ENGINE;
-		if (mirrored != NULL) *mirrored = HasBit(callback, 7);
+		if (mirrored != nullptr) *mirrored = HasBit(callback, 7);
 		callback = GB(callback, 0, 7);
 	} else {
 		/* 15 bits, bit 14 for mirroring */
 		if (callback == 0x7FFF) return INVALID_ENGINE;
-		if (mirrored != NULL) *mirrored = HasBit(callback, 14);
+		if (mirrored != nullptr) *mirrored = HasBit(callback, 14);
 		callback = GB(callback, 0, 14);
 	}
 
@@ -80,7 +80,7 @@ uint CountArticulatedParts(EngineID engi
 	 * either, so it doesn't matter how many articulated parts there are. */
 	if (!Vehicle::CanAllocateItem()) return 0;
 
-	Vehicle *v = NULL;
+	Vehicle *v = nullptr;
 	if (!purchase_window) {
 		v = new Vehicle();
 		v->engine_type = engine_type;
@@ -108,7 +108,7 @@ static inline uint16 GetVehicleDefaultCa
 {
 	const Engine *e = Engine::Get(engine);
 	CargoID cargo = (e->CanCarryCargo() ? e->GetDefaultCargoType() : (CargoID)CT_INVALID);
-	if (cargo_type != NULL) *cargo_type = cargo;
+	if (cargo_type != nullptr) *cargo_type = cargo;
 	if (cargo == CT_INVALID) return 0;
 	return e->GetDisplayDefaultCapacity();
 }
@@ -290,15 +290,15 @@ bool IsArticulatedVehicleCarryingDiffere
 		if (v->cargo_type != CT_INVALID && v->GetEngine()->CanCarryCargo()) {
 			if (first_cargo == CT_INVALID) first_cargo = v->cargo_type;
 			if (first_cargo != v->cargo_type) {
-				if (cargo_type != NULL) *cargo_type = CT_INVALID;
+				if (cargo_type != nullptr) *cargo_type = CT_INVALID;
 				return true;
 			}
 		}
 
-		v = v->HasArticulatedPart() ? v->GetNextArticulatedPart() : NULL;
-	} while (v != NULL);
+		v = v->HasArticulatedPart() ? v->GetNextArticulatedPart() : nullptr;
+	} while (v != nullptr);
 
-	if (cargo_type != NULL) *cargo_type = first_cargo;
+	if (cargo_type != nullptr) *cargo_type = first_cargo;
 	return false;
 }
 
@@ -330,8 +330,8 @@ void CheckConsistencyOfArticulatedVehicl
 		assert(v->cargo_type < NUM_CARGO);
 		real_default_capacity[v->cargo_type] += v->cargo_cap;
 
-		v = v->HasArticulatedPart() ? v->GetNextArticulatedPart() : NULL;
-	} while (v != NULL);
+		v = v->HasArticulatedPart() ? v->GetNextArticulatedPart() : nullptr;
+	} while (v != nullptr);
 
 	/* Check whether the vehicle carries more cargoes than expected */
 	bool carries_more = false;
diff --git a/src/autoreplace.cpp b/src/autoreplace.cpp
--- a/src/autoreplace.cpp
+++ b/src/autoreplace.cpp
@@ -29,11 +29,11 @@ static EngineRenew *GetEngineReplacement
 {
 	EngineRenew *er = (EngineRenew *)erl;
 
-	while (er != NULL) {
+	while (er != nullptr) {
 		if (er->from == engine && GroupIsInGroup(group, er->group_id)) return er;
 		er = er->next;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -46,12 +46,12 @@ void RemoveAllEngineReplacement(EngineRe
 	EngineRenew *er = (EngineRenew *)(*erl);
 	EngineRenew *next;
 
-	while (er != NULL) {
+	while (er != nullptr) {
 		next = er->next;
 		delete er;
 		er = next;
 	}
-	*erl = NULL; // Empty list
+	*erl = nullptr; // Empty list
 }
 
 /**
@@ -66,12 +66,12 @@ void RemoveAllEngineReplacement(EngineRe
 EngineID EngineReplacement(EngineRenewList erl, EngineID engine, GroupID group, bool *replace_when_old)
 {
 	const EngineRenew *er = GetEngineReplacement(erl, engine, group);
-	if (er == NULL && (group == DEFAULT_GROUP || (Group::IsValidID(group) && !Group::Get(group)->replace_protection))) {
+	if (er == nullptr && (group == DEFAULT_GROUP || (Group::IsValidID(group) && !Group::Get(group)->replace_protection))) {
 		/* We didn't find anything useful in the vehicle's own group so we will try ALL_GROUP */
 		er = GetEngineReplacement(erl, engine, ALL_GROUP);
 	}
-	if (replace_when_old != NULL) *replace_when_old = er == NULL ? false : er->replace_when_old;
-	return er == NULL ? INVALID_ENGINE : er->to;
+	if (replace_when_old != nullptr) *replace_when_old = er == nullptr ? false : er->replace_when_old;
+	return er == nullptr ? INVALID_ENGINE : er->to;
 }
 
 /**
@@ -88,7 +88,7 @@ CommandCost AddEngineReplacement(EngineR
 {
 	/* Check if the old vehicle is already in the list */
 	EngineRenew *er = GetEngineReplacement(*erl, old_engine, group);
-	if (er != NULL) {
+	if (er != nullptr) {
 		if (flags & DC_EXEC) {
 			er->to = new_engine;
 			er->replace_when_old = replace_when_old;
@@ -122,12 +122,12 @@ CommandCost AddEngineReplacement(EngineR
 CommandCost RemoveEngineReplacement(EngineRenewList *erl, EngineID engine, GroupID group, DoCommandFlag flags)
 {
 	EngineRenew *er = (EngineRenew *)(*erl);
-	EngineRenew *prev = NULL;
+	EngineRenew *prev = nullptr;
 
-	while (er != NULL) {
+	while (er != nullptr) {
 		if (er->from == engine && er->group_id == group) {
 			if (flags & DC_EXEC) {
-				if (prev == NULL) { // First element
+				if (prev == nullptr) { // First element
 					/* The second becomes the new first element */
 					*erl = (EngineRenewList)er->next;
 				} else {
diff --git a/src/autoreplace_cmd.cpp b/src/autoreplace_cmd.cpp
--- a/src/autoreplace_cmd.cpp
+++ b/src/autoreplace_cmd.cpp
@@ -98,9 +98,9 @@ bool CheckAutoreplaceValidity(EngineID f
  */
 void CheckCargoCapacity(Vehicle *v)
 {
-	assert(v == NULL || v->First() == v);
+	assert(v == nullptr || v->First() == v);
 
-	for (Vehicle *src = v; src != NULL; src = src->Next()) {
+	for (Vehicle *src = v; src != nullptr; src = src->Next()) {
 		assert(src->cargo.TotalCount() == src->cargo.ActionCount(VehicleCargoList::MTA_KEEP));
 
 		/* Do we need to more cargo away? */
@@ -108,7 +108,7 @@ void CheckCargoCapacity(Vehicle *v)
 
 		/* We need to move a particular amount. Try that on the other vehicles. */
 		uint to_spread = src->cargo.TotalCount() - src->cargo_cap;
-		for (Vehicle *dest = v; dest != NULL && to_spread != 0; dest = dest->Next()) {
+		for (Vehicle *dest = v; dest != nullptr && to_spread != 0; dest = dest->Next()) {
 			assert(dest->cargo.TotalCount() == dest->cargo.ActionCount(VehicleCargoList::MTA_KEEP));
 			if (dest->cargo.TotalCount() >= dest->cargo_cap || dest->cargo_type != src->cargo_type) continue;
 
@@ -135,7 +135,7 @@ static void TransferCargo(Vehicle *old_v
 {
 	assert(!part_of_chain || new_head->IsPrimaryVehicle());
 	/* Loop through source parts */
-	for (Vehicle *src = old_veh; src != NULL; src = src->Next()) {
+	for (Vehicle *src = old_veh; src != nullptr; src = src->Next()) {
 		assert(src->cargo.TotalCount() == src->cargo.ActionCount(VehicleCargoList::MTA_KEEP));
 		if (!part_of_chain && src->type == VEH_TRAIN && src != old_veh && src != Train::From(old_veh)->other_multiheaded_part && !src->IsArticulatedPart()) {
 			/* Skip vehicles, which do not belong to old_veh */
@@ -145,7 +145,7 @@ static void TransferCargo(Vehicle *old_v
 		if (src->cargo_type >= NUM_CARGO || src->cargo.TotalCount() == 0) continue;
 
 		/* Find free space in the new chain */
-		for (Vehicle *dest = new_head; dest != NULL && src->cargo.TotalCount() > 0; dest = dest->Next()) {
+		for (Vehicle *dest = new_head; dest != nullptr && src->cargo.TotalCount() > 0; dest = dest->Next()) {
 			assert(dest->cargo.TotalCount() == dest->cargo.ActionCount(VehicleCargoList::MTA_KEEP));
 			if (!part_of_chain && dest->type == VEH_TRAIN && dest != new_head && dest != Train::From(new_head)->other_multiheaded_part && !dest->IsArticulatedPart()) {
 				/* Skip vehicles, which do not belong to new_head */
@@ -216,7 +216,7 @@ static CargoID GetNewCargoTypeForReplace
 		/* the old engine didn't have cargo capacity, but the new one does
 		 * now we will figure out what cargo the train is carrying and refit to fit this */
 
-		for (v = v->First(); v != NULL; v = v->Next()) {
+		for (v = v->First(); v != nullptr; v = v->Next()) {
 			if (!v->GetEngine()->CanCarryCargo()) continue;
 			/* Now we found a cargo type being carried on the train and we will see if it is possible to carry to this one */
 			if (HasBit(available_cargo_types, v->cargo_type)) return v->cargo_type;
@@ -280,7 +280,7 @@ static CommandCost GetNewEngineType(cons
  */
 static CommandCost BuildReplacementVehicle(Vehicle *old_veh, Vehicle **new_vehicle, bool part_of_chain)
 {
-	*new_vehicle = NULL;
+	*new_vehicle = nullptr;
 
 	/* Shall the vehicle be replaced? */
 	const Company *c = Company::Get(_current_company);
@@ -330,14 +330,14 @@ static inline CommandCost CmdStartStopVe
 /**
  * Issue a train vehicle move command
  * @param v The vehicle to move
- * @param after The vehicle to insert 'v' after, or NULL to start new chain
+ * @param after The vehicle to insert 'v' after, or nullptr to start new chain
  * @param flags the command flags to use
  * @param whole_chain move all vehicles following 'v' (true), or only 'v' (false)
  * @return success or error
  */
 static inline CommandCost CmdMoveVehicle(const Vehicle *v, const Vehicle *after, DoCommandFlag flags, bool whole_chain)
 {
-	return DoCommand(0, v->index | (whole_chain ? 1 : 0) << 20, after != NULL ? after->index : INVALID_VEHICLE, flags | DC_NO_CARGO_CAP_CHECK, CMD_MOVE_RAIL_VEHICLE);
+	return DoCommand(0, v->index | (whole_chain ? 1 : 0) << 20, after != nullptr ? after->index : INVALID_VEHICLE, flags | DC_NO_CARGO_CAP_CHECK, CMD_MOVE_RAIL_VEHICLE);
 }
 
 /**
@@ -395,11 +395,11 @@ static CommandCost ReplaceFreeUnit(Vehic
 	CommandCost cost = CommandCost(EXPENSES_NEW_VEHICLES, 0);
 
 	/* Build and refit replacement vehicle */
-	Vehicle *new_v = NULL;
+	Vehicle *new_v = nullptr;
 	cost.AddCost(BuildReplacementVehicle(old_v, &new_v, false));
 
 	/* Was a new vehicle constructed? */
-	if (cost.Succeeded() && new_v != NULL) {
+	if (cost.Succeeded() && new_v != nullptr) {
 		*nothing_to_do = false;
 
 		if ((flags & DC_EXEC) != 0) {
@@ -449,17 +449,17 @@ static CommandCost ReplaceChain(Vehicle 
 		uint16 old_total_length = CeilDiv(Train::From(old_head)->gcache.cached_total_length, TILE_SIZE) * TILE_SIZE;
 
 		int num_units = 0; ///< Number of units in the chain
-		for (Train *w = Train::From(old_head); w != NULL; w = w->GetNextUnit()) num_units++;
+		for (Train *w = Train::From(old_head); w != nullptr; w = w->GetNextUnit()) num_units++;
 
 		Train **old_vehs = CallocT<Train *>(num_units); ///< Will store vehicles of the old chain in their order
-		Train **new_vehs = CallocT<Train *>(num_units); ///< New vehicles corresponding to old_vehs or NULL if no replacement
+		Train **new_vehs = CallocT<Train *>(num_units); ///< New vehicles corresponding to old_vehs or nullptr if no replacement
 		Money *new_costs = MallocT<Money>(num_units);   ///< Costs for buying and refitting the new vehicles
 
 		/* Collect vehicles and build replacements
 		 * Note: The replacement vehicles can only successfully build as long as the old vehicles are still in their chain */
 		int i;
 		Train *w;
-		for (w = Train::From(old_head), i = 0; w != NULL; w = w->GetNextUnit(), i++) {
+		for (w = Train::From(old_head), i = 0; w != nullptr; w = w->GetNextUnit(), i++) {
 			assert(i < num_units);
 			old_vehs[i] = w;
 
@@ -468,41 +468,41 @@ static CommandCost ReplaceChain(Vehicle 
 			if (cost.Failed()) break;
 
 			new_costs[i] = ret.GetCost();
-			if (new_vehs[i] != NULL) *nothing_to_do = false;
+			if (new_vehs[i] != nullptr) *nothing_to_do = false;
 		}
-		Train *new_head = (new_vehs[0] != NULL ? new_vehs[0] : old_vehs[0]);
+		Train *new_head = (new_vehs[0] != nullptr ? new_vehs[0] : old_vehs[0]);
 
 		/* Note: When autoreplace has already failed here, old_vehs[] is not completely initialized. But it is also not needed. */
 		if (cost.Succeeded()) {
 			/* Separate the head, so we can start constructing the new chain */
 			Train *second = Train::From(old_head)->GetNextUnit();
-			if (second != NULL) cost.AddCost(CmdMoveVehicle(second, NULL, DC_EXEC | DC_AUTOREPLACE, true));
+			if (second != nullptr) cost.AddCost(CmdMoveVehicle(second, nullptr, DC_EXEC | DC_AUTOREPLACE, true));
 
-			assert(Train::From(new_head)->GetNextUnit() == NULL);
+			assert(Train::From(new_head)->GetNextUnit() == nullptr);
 
 			/* Append engines to the new chain
 			 * We do this from back to front, so that the head of the temporary vehicle chain does not change all the time.
 			 * That way we also have less trouble when exceeding the unitnumber limit.
 			 * OTOH the vehicle attach callback is more expensive this way :s */
-			Train *last_engine = NULL; ///< Shall store the last engine unit after this step
+			Train *last_engine = nullptr; ///< Shall store the last engine unit after this step
 			if (cost.Succeeded()) {
 				for (int i = num_units - 1; i > 0; i--) {
-					Train *append = (new_vehs[i] != NULL ? new_vehs[i] : old_vehs[i]);
+					Train *append = (new_vehs[i] != nullptr ? new_vehs[i] : old_vehs[i]);
 
 					if (RailVehInfo(append->engine_type)->railveh_type == RAILVEH_WAGON) continue;
 
-					if (new_vehs[i] != NULL) {
+					if (new_vehs[i] != nullptr) {
 						/* Move the old engine to a separate row with DC_AUTOREPLACE. Else
 						 * moving the wagon in front may fail later due to unitnumber limit.
 						 * (We have to attach wagons without DC_AUTOREPLACE.) */
-						CmdMoveVehicle(old_vehs[i], NULL, DC_EXEC | DC_AUTOREPLACE, false);
+						CmdMoveVehicle(old_vehs[i], nullptr, DC_EXEC | DC_AUTOREPLACE, false);
 					}
 
-					if (last_engine == NULL) last_engine = append;
+					if (last_engine == nullptr) last_engine = append;
 					cost.AddCost(CmdMoveVehicle(append, new_head, DC_EXEC, false));
 					if (cost.Failed()) break;
 				}
-				if (last_engine == NULL) last_engine = new_head;
+				if (last_engine == nullptr) last_engine = new_head;
 			}
 
 			/* When wagon removal is enabled and the new engines without any wagons are already longer than the old, we have to fail */
@@ -513,8 +513,8 @@ static CommandCost ReplaceChain(Vehicle 
 			 */
 			if (cost.Succeeded()) {
 				for (int i = num_units - 1; i > 0; i--) {
-					assert(last_engine != NULL);
-					Vehicle *append = (new_vehs[i] != NULL ? new_vehs[i] : old_vehs[i]);
+					assert(last_engine != nullptr);
+					Vehicle *append = (new_vehs[i] != nullptr ? new_vehs[i] : old_vehs[i]);
 
 					if (RailVehInfo(append->engine_type)->railveh_type == RAILVEH_WAGON) {
 						/* Insert wagon after 'last_engine' */
@@ -524,7 +524,7 @@ static CommandCost ReplaceChain(Vehicle 
 						 * to the train becoming too long, or the train becoming longer
 						 * would move the vehicle to the empty vehicle chain. */
 						if (wagon_removal && (res.Failed() ? res.GetErrorMessage() == STR_ERROR_TRAIN_TOO_LONG : new_head->gcache.cached_total_length > old_total_length)) {
-							CmdMoveVehicle(append, NULL, DC_EXEC | DC_AUTOREPLACE, false);
+							CmdMoveVehicle(append, nullptr, DC_EXEC | DC_AUTOREPLACE, false);
 							break;
 						}
 
@@ -543,7 +543,7 @@ static CommandCost ReplaceChain(Vehicle 
 				assert(new_head->gcache.cached_total_length <= _settings_game.vehicle.max_train_length * TILE_SIZE);
 				for (int i = 1; i < num_units; i++) {
 					Vehicle *wagon = new_vehs[i];
-					if (wagon == NULL) continue;
+					if (wagon == nullptr) continue;
 					if (wagon->First() == new_head) break;
 
 					assert(RailVehInfo(wagon->engine_type)->railveh_type == RAILVEH_WAGON);
@@ -551,7 +551,7 @@ static CommandCost ReplaceChain(Vehicle 
 					/* Sell wagon */
 					CommandCost ret = DoCommand(0, wagon->index, 0, DC_EXEC, GetCmdSellVeh(wagon));
 					assert(ret.Succeeded());
-					new_vehs[i] = NULL;
+					new_vehs[i] = nullptr;
 
 					/* Revert the money subtraction when the vehicle was built.
 					 * This value is different from the sell value, esp. because of refitting */
@@ -572,7 +572,7 @@ static CommandCost ReplaceChain(Vehicle 
 				for (int i = 0; i < num_units; i++) {
 					Vehicle *w = old_vehs[i];
 					/* Is the vehicle again part of the new chain?
-					 * Note: We cannot test 'new_vehs[i] != NULL' as wagon removal might cause to remove both */
+					 * Note: We cannot test 'new_vehs[i] != nullptr' as wagon removal might cause to remove both */
 					if (w->First() == new_head) continue;
 
 					if ((flags & DC_EXEC) != 0) TransferCargo(w, new_head, true);
@@ -582,8 +582,8 @@ static CommandCost ReplaceChain(Vehicle 
 					 *       it from failing due to engine limits. */
 					cost.AddCost(DoCommand(0, w->index, 0, flags | DC_AUTOREPLACE, GetCmdSellVeh(w)));
 					if ((flags & DC_EXEC) != 0) {
-						old_vehs[i] = NULL;
-						if (i == 0) old_head = NULL;
+						old_vehs[i] = nullptr;
+						if (i == 0) old_head = nullptr;
 					}
 				}
 
@@ -596,9 +596,9 @@ static CommandCost ReplaceChain(Vehicle 
 			if ((flags & DC_EXEC) == 0) {
 				/* Separate the head, so we can reattach the old vehicles */
 				Train *second = Train::From(old_head)->GetNextUnit();
-				if (second != NULL) CmdMoveVehicle(second, NULL, DC_EXEC | DC_AUTOREPLACE, true);
+				if (second != nullptr) CmdMoveVehicle(second, nullptr, DC_EXEC | DC_AUTOREPLACE, true);
 
-				assert(Train::From(old_head)->GetNextUnit() == NULL);
+				assert(Train::From(old_head)->GetNextUnit() == nullptr);
 
 				for (int i = num_units - 1; i > 0; i--) {
 					CommandCost ret = CmdMoveVehicle(old_vehs[i], old_head, DC_EXEC | DC_AUTOREPLACE, false);
@@ -610,9 +610,9 @@ static CommandCost ReplaceChain(Vehicle 
 		/* Finally undo buying of new vehicles */
 		if ((flags & DC_EXEC) == 0) {
 			for (int i = num_units - 1; i >= 0; i--) {
-				if (new_vehs[i] != NULL) {
+				if (new_vehs[i] != nullptr) {
 					DoCommand(0, new_vehs[i]->index, 0, DC_EXEC, GetCmdSellVeh(new_vehs[i]));
-					new_vehs[i] = NULL;
+					new_vehs[i] = nullptr;
 				}
 			}
 		}
@@ -622,11 +622,11 @@ static CommandCost ReplaceChain(Vehicle 
 		free(new_costs);
 	} else {
 		/* Build and refit replacement vehicle */
-		Vehicle *new_head = NULL;
+		Vehicle *new_head = nullptr;
 		cost.AddCost(BuildReplacementVehicle(old_head, &new_head, true));
 
 		/* Was a new vehicle constructed? */
-		if (cost.Succeeded() && new_head != NULL) {
+		if (cost.Succeeded() && new_head != nullptr) {
 			*nothing_to_do = false;
 
 			/* The new vehicle is constructed, now take over orders and everything... */
@@ -666,7 +666,7 @@ static CommandCost ReplaceChain(Vehicle 
 CommandCost CmdAutoreplaceVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Vehicle *v = Vehicle::GetIfValid(p1);
-	if (v == NULL) return CMD_ERROR;
+	if (v == nullptr) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -690,12 +690,12 @@ CommandCost CmdAutoreplaceVehicle(TileIn
 	/* Test whether any replacement is set, before issuing a whole lot of commands that would end in nothing changed */
 	Vehicle *w = v;
 	bool any_replacements = false;
-	while (w != NULL) {
+	while (w != nullptr) {
 		EngineID e;
 		CommandCost cost = GetNewEngineType(w, c, false, e);
 		if (cost.Failed()) return cost;
 		any_replacements |= (e != INVALID_ENGINE);
-		w = (!free_wagon && w->type == VEH_TRAIN ? Train::From(w)->GetNextUnit() : NULL);
+		w = (!free_wagon && w->type == VEH_TRAIN ? Train::From(w)->GetNextUnit() : nullptr);
 	}
 
 	CommandCost cost = CommandCost(EXPENSES_NEW_VEHICLES, 0);
@@ -756,7 +756,7 @@ CommandCost CmdAutoreplaceVehicle(TileIn
 CommandCost CmdSetAutoReplace(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Company *c = Company::GetIfValid(_current_company);
-	if (c == NULL) return CMD_ERROR;
+	if (c == nullptr) return CMD_ERROR;
 
 	EngineID old_engine_type = GB(p2, 0, 16);
 	EngineID new_engine_type = GB(p2, 16, 16);
diff --git a/src/autoreplace_func.h b/src/autoreplace_func.h
--- a/src/autoreplace_func.h
+++ b/src/autoreplace_func.h
@@ -16,7 +16,7 @@
 #include "company_base.h"
 
 void RemoveAllEngineReplacement(EngineRenewList *erl);
-EngineID EngineReplacement(EngineRenewList erl, EngineID engine, GroupID group, bool *replace_when_old = NULL);
+EngineID EngineReplacement(EngineRenewList erl, EngineID engine, GroupID group, bool *replace_when_old = nullptr);
 CommandCost AddEngineReplacement(EngineRenewList *erl, EngineID old_engine, EngineID new_engine, GroupID group, bool replace_when_old, DoCommandFlag flags);
 CommandCost RemoveEngineReplacement(EngineRenewList *erl, EngineID engine, GroupID group, DoCommandFlag flags);
 
@@ -38,7 +38,7 @@ static inline void RemoveAllEngineReplac
  * @return The engine type to replace with, or INVALID_ENGINE if no
  * replacement is in the list.
  */
-static inline EngineID EngineReplacementForCompany(const Company *c, EngineID engine, GroupID group, bool *replace_when_old = NULL)
+static inline EngineID EngineReplacementForCompany(const Company *c, EngineID engine, GroupID group, bool *replace_when_old = nullptr)
 {
 	return EngineReplacement(c->engine_renew_list, engine, group, replace_when_old);
 }
diff --git a/src/base_consist.cpp b/src/base_consist.cpp
--- a/src/base_consist.cpp
+++ b/src/base_consist.cpp
@@ -30,7 +30,7 @@ void BaseConsist::CopyConsistPropertiesF
 	if (this == src) return;
 
 	free(this->name);
-	this->name = src->name != NULL ? stredup(src->name) : NULL;
+	this->name = src->name != nullptr ? stredup(src->name) : nullptr;
 
 	this->current_order_time = src->current_order_time;
 	this->lateness_counter = src->lateness_counter;
diff --git a/src/base_consist.h b/src/base_consist.h
--- a/src/base_consist.h
+++ b/src/base_consist.h
@@ -31,7 +31,7 @@ struct BaseConsist {
 
 	uint16 vehicle_flags;               ///< Used for gradual loading and other miscellaneous things (@see VehicleFlags enum)
 
-	BaseConsist() : name(NULL) {}
+	BaseConsist() : name(nullptr) {}
 	virtual ~BaseConsist();
 
 	void CopyConsistPropertiesFrom(const BaseConsist *src);
diff --git a/src/base_media_base.h b/src/base_media_base.h
--- a/src/base_media_base.h
+++ b/src/base_media_base.h
@@ -118,9 +118,9 @@ struct BaseSet {
 	 * @param isocode the isocode to search for
 	 * @return the description
 	 */
-	const char *GetDescription(const char *isocode = NULL) const
+	const char *GetDescription(const char *isocode = nullptr) const
 	{
-		if (isocode != NULL) {
+		if (isocode != nullptr) {
 			/* First the full ISO code */
 			for (const auto &pair : this->description) {
 				if (strcmp(pair.first, isocode) == 0) return pair.second;
@@ -151,17 +151,17 @@ struct BaseSet {
 	/**
 	 * Search a textfile file next to this base media.
 	 * @param type The type of the textfile to search for.
-	 * @return The filename for the textfile, \c NULL otherwise.
+	 * @return The filename for the textfile, \c nullptr otherwise.
 	 */
 	const char *GetTextfile(TextfileType type) const
 	{
 		for (uint i = 0; i < NUM_FILES; i++) {
 			const char *textfile = ::GetTextfile(type, BASESET_DIR, this->files[i].filename);
-			if (textfile != NULL) {
+			if (textfile != nullptr) {
 				return textfile;
 			}
 		}
-		return NULL;
+		return nullptr;
 	}
 };
 
@@ -231,7 +231,7 @@ template <class Tbase_set> /* static */ 
  * @param ci The content info to compare it to.
  * @param md5sum Should the MD5 checksum be tested as well?
  * @param s The list with sets.
- * @return The filename of the first file of the base set, or \c NULL if there is no match.
+ * @return The filename of the first file of the base set, or \c nullptr if there is no match.
  */
 template <class Tbase_set>
 const char *TryGetBaseSetFile(const ContentInfo *ci, bool md5sum, const Tbase_set *s);
diff --git a/src/base_media_func.h b/src/base_media_func.h
--- a/src/base_media_func.h
+++ b/src/base_media_func.h
@@ -23,7 +23,7 @@
  */
 #define fetch_metadata(name) \
 	item = metadata->GetItem(name, false); \
-	if (item == NULL || StrEmpty(item->value)) { \
+	if (item == nullptr || StrEmpty(item->value)) { \
 		DEBUG(grf, 0, "Base " SET_TYPE "set detail loading: %s field missing.", name); \
 		DEBUG(grf, 0, "  Is %s readable for the user running OpenTTD?", full_filename); \
 		return false; \
@@ -50,7 +50,7 @@ bool BaseSet<T, Tnum_files, Tsearch_in_t
 	this->description[stredup("")] = stredup(item->value);
 
 	/* Add the translations of the descriptions too. */
-	for (const IniItem *item = metadata->item; item != NULL; item = item->next) {
+	for (const IniItem *item = metadata->item; item != nullptr; item = item->next) {
 		if (strncmp("description.", item->name, 12) != 0) continue;
 
 		this->description[stredup(item->name + 12)] = stredup(item->value);
@@ -65,7 +65,7 @@ bool BaseSet<T, Tnum_files, Tsearch_in_t
 	this->version = atoi(item->value);
 
 	item = metadata->GetItem("fallback", false);
-	this->fallback = (item != NULL && strcmp(item->value, "0") != 0 && strcmp(item->value, "false") != 0);
+	this->fallback = (item != nullptr && strcmp(item->value, "0") != 0 && strcmp(item->value, "false") != 0);
 
 	/* For each of the file types we want to find the file, MD5 checksums and warning messages. */
 	IniGroup *files  = ini->GetGroup("files");
@@ -75,14 +75,14 @@ bool BaseSet<T, Tnum_files, Tsearch_in_t
 		MD5File *file = &this->files[i];
 		/* Find the filename first. */
 		item = files->GetItem(BaseSet<T, Tnum_files, Tsearch_in_tars>::file_names[i], false);
-		if (item == NULL || (item->value == NULL && !allow_empty_filename)) {
+		if (item == nullptr || (item->value == nullptr && !allow_empty_filename)) {
 			DEBUG(grf, 0, "No " SET_TYPE " file for: %s (in %s)", BaseSet<T, Tnum_files, Tsearch_in_tars>::file_names[i], full_filename);
 			return false;
 		}
 
 		const char *filename = item->value;
-		if (filename == NULL) {
-			file->filename = NULL;
+		if (filename == nullptr) {
+			file->filename = nullptr;
 			/* If we list no file, that file must be valid */
 			this->valid_files++;
 			this->found_files++;
@@ -93,7 +93,7 @@ bool BaseSet<T, Tnum_files, Tsearch_in_t
 
 		/* Then find the MD5 checksum */
 		item = md5s->GetItem(filename, false);
-		if (item == NULL || item->value == NULL) {
+		if (item == nullptr || item->value == nullptr) {
 			DEBUG(grf, 0, "No MD5 checksum specified for: %s (in %s)", filename, full_filename);
 			return false;
 		}
@@ -119,8 +119,8 @@ bool BaseSet<T, Tnum_files, Tsearch_in_t
 
 		/* Then find the warning message when the file's missing */
 		item = origin->GetItem(filename, false);
-		if (item == NULL) item = origin->GetItem("default", false);
-		if (item == NULL) {
+		if (item == nullptr) item = origin->GetItem("default", false);
+		if (item == nullptr) {
 			DEBUG(grf, 1, "No origin warning message specified for: %s", filename);
 			file->missing_warning = stredup("");
 		} else {
@@ -163,21 +163,21 @@ bool BaseMedia<Tbase_set>::AddFile(const
 
 	char *path = stredup(filename + basepath_length);
 	char *psep = strrchr(path, PATHSEPCHAR);
-	if (psep != NULL) {
+	if (psep != nullptr) {
 		psep[1] = '\0';
 	} else {
 		*path = '\0';
 	}
 
 	if (set->FillSetDetails(ini, path, filename)) {
-		Tbase_set *duplicate = NULL;
-		for (Tbase_set *c = BaseMedia<Tbase_set>::available_sets; c != NULL; c = c->next) {
+		Tbase_set *duplicate = nullptr;
+		for (Tbase_set *c = BaseMedia<Tbase_set>::available_sets; c != nullptr; c = c->next) {
 			if (strcmp(c->name, set->name) == 0 || c->shortname == set->shortname) {
 				duplicate = c;
 				break;
 			}
 		}
-		if (duplicate != NULL) {
+		if (duplicate != nullptr) {
 			/* The more complete set takes precedence over the version number. */
 			if ((duplicate->valid_files == set->valid_files && duplicate->version >= set->version) ||
 					duplicate->valid_files > set->valid_files) {
@@ -205,7 +205,7 @@ bool BaseMedia<Tbase_set>::AddFile(const
 			}
 		} else {
 			Tbase_set **last = &BaseMedia<Tbase_set>::available_sets;
-			while (*last != NULL) last = &(*last)->next;
+			while (*last != nullptr) last = &(*last)->next;
 
 			*last = set;
 			ret = true;
@@ -238,7 +238,7 @@ template <class Tbase_set>
 		return true;
 	}
 
-	for (const Tbase_set *s = BaseMedia<Tbase_set>::available_sets; s != NULL; s = s->next) {
+	for (const Tbase_set *s = BaseMedia<Tbase_set>::available_sets; s != nullptr; s = s->next) {
 		if (strcmp(name, s->name) == 0) {
 			BaseMedia<Tbase_set>::used_set = s;
 			CheckExternalFiles();
@@ -258,7 +258,7 @@ template <class Tbase_set>
 /* static */ char *BaseMedia<Tbase_set>::GetSetsList(char *p, const char *last)
 {
 	p += seprintf(p, last, "List of " SET_TYPE " sets:\n");
-	for (const Tbase_set *s = BaseMedia<Tbase_set>::available_sets; s != NULL; s = s->next) {
+	for (const Tbase_set *s = BaseMedia<Tbase_set>::available_sets; s != nullptr; s = s->next) {
 		p += seprintf(p, last, "%18s: %s", s->name, s->GetDescription());
 		int invalid = s->GetNumInvalid();
 		if (invalid != 0) {
@@ -281,7 +281,7 @@ template <class Tbase_set>
 
 template <class Tbase_set> const char *TryGetBaseSetFile(const ContentInfo *ci, bool md5sum, const Tbase_set *s)
 {
-	for (; s != NULL; s = s->next) {
+	for (; s != nullptr; s = s->next) {
 		if (s->GetNumMissing() != 0) continue;
 
 		if (s->shortname != ci->unique_id) continue;
@@ -296,14 +296,14 @@ template <class Tbase_set> const char *T
 		}
 		if (memcmp(md5, ci->md5sum, sizeof(md5)) == 0) return s->files[0].filename;
 	}
-	return NULL;
+	return nullptr;
 }
 
 template <class Tbase_set>
 /* static */ bool BaseMedia<Tbase_set>::HasSet(const ContentInfo *ci, bool md5sum)
 {
-	return (TryGetBaseSetFile(ci, md5sum, BaseMedia<Tbase_set>::available_sets) != NULL) ||
-			(TryGetBaseSetFile(ci, md5sum, BaseMedia<Tbase_set>::duplicate_sets) != NULL);
+	return (TryGetBaseSetFile(ci, md5sum, BaseMedia<Tbase_set>::available_sets) != nullptr) ||
+			(TryGetBaseSetFile(ci, md5sum, BaseMedia<Tbase_set>::duplicate_sets) != nullptr);
 }
 
 /**
@@ -314,7 +314,7 @@ template <class Tbase_set>
 /* static */ int BaseMedia<Tbase_set>::GetNumSets()
 {
 	int n = 0;
-	for (const Tbase_set *s = BaseMedia<Tbase_set>::available_sets; s != NULL; s = s->next) {
+	for (const Tbase_set *s = BaseMedia<Tbase_set>::available_sets; s != nullptr; s = s->next) {
 		if (s != BaseMedia<Tbase_set>::used_set && s->GetNumMissing() != 0) continue;
 		n++;
 	}
@@ -329,7 +329,7 @@ template <class Tbase_set>
 /* static */ int BaseMedia<Tbase_set>::GetIndexOfUsedSet()
 {
 	int n = 0;
-	for (const Tbase_set *s = BaseMedia<Tbase_set>::available_sets; s != NULL; s = s->next) {
+	for (const Tbase_set *s = BaseMedia<Tbase_set>::available_sets; s != nullptr; s = s->next) {
 		if (s == BaseMedia<Tbase_set>::used_set) return n;
 		if (s->GetNumMissing() != 0) continue;
 		n++;
@@ -344,7 +344,7 @@ template <class Tbase_set>
 template <class Tbase_set>
 /* static */ const Tbase_set *BaseMedia<Tbase_set>::GetSet(int index)
 {
-	for (const Tbase_set *s = BaseMedia<Tbase_set>::available_sets; s != NULL; s = s->next) {
+	for (const Tbase_set *s = BaseMedia<Tbase_set>::available_sets; s != nullptr; s = s->next) {
 		if (s != BaseMedia<Tbase_set>::used_set && s->GetNumMissing() != 0) continue;
 		if (index == 0) return s;
 		index--;
diff --git a/src/base_station_base.h b/src/base_station_base.h
--- a/src/base_station_base.h
+++ b/src/base_station_base.h
@@ -220,7 +220,7 @@ struct SpecializedStation : public BaseS
 	 */
 	static inline T *GetIfValid(size_t index)
 	{
-		return IsValidID(index) ? Get(index) : NULL;
+		return IsValidID(index) ? Get(index) : nullptr;
 	}
 
 	/**
diff --git a/src/blitter/32bpp_anim.cpp b/src/blitter/32bpp_anim.cpp
--- a/src/blitter/32bpp_anim.cpp
+++ b/src/blitter/32bpp_anim.cpp
@@ -414,7 +414,7 @@ void Blitter_32bppAnim::CopyToBuffer(con
 	uint32 *udst = (uint32 *)dst;
 	const uint32 *src = (const uint32 *)video;
 
-	if (this->anim_buf == NULL) return;
+	if (this->anim_buf == nullptr) return;
 
 	const uint16 *anim_line = this->ScreenToAnimOffset((const uint32 *)video) + this->anim_buf;
 
diff --git a/src/blitter/32bpp_anim.hpp b/src/blitter/32bpp_anim.hpp
--- a/src/blitter/32bpp_anim.hpp
+++ b/src/blitter/32bpp_anim.hpp
@@ -26,8 +26,8 @@ protected:
 
 public:
 	Blitter_32bppAnim() :
-		anim_buf(NULL),
-		anim_alloc(NULL),
+		anim_buf(nullptr),
+		anim_alloc(nullptr),
 		anim_buf_width(0),
 		anim_buf_height(0),
 		anim_buf_pitch(0)
diff --git a/src/blitter/8bpp_optimized.cpp b/src/blitter/8bpp_optimized.cpp
--- a/src/blitter/8bpp_optimized.cpp
+++ b/src/blitter/8bpp_optimized.cpp
@@ -167,7 +167,7 @@ Sprite *Blitter_8bppOptimized::Encode(co
 			uint trans = 0;
 			uint pixels = 0;
 			uint last_colour = 0;
-			byte *count_dst = NULL;
+			byte *count_dst = nullptr;
 
 			/* Store the scaled image */
 			const SpriteLoader::CommonPixel *src = &sprite[i].data[y * sprite[i].width];
@@ -176,11 +176,11 @@ Sprite *Blitter_8bppOptimized::Encode(co
 				uint colour = src++->m;
 
 				if (last_colour == 0 || colour == 0 || pixels == 255) {
-					if (count_dst != NULL) {
+					if (count_dst != nullptr) {
 						/* Write how many non-transparent bytes we get */
 						*count_dst = pixels;
 						pixels = 0;
-						count_dst = NULL;
+						count_dst = nullptr;
 					}
 					/* As long as we find transparency bytes, keep counting */
 					if (colour == 0 && trans != 255) {
@@ -206,7 +206,7 @@ Sprite *Blitter_8bppOptimized::Encode(co
 				}
 			}
 
-			if (count_dst != NULL) *count_dst = pixels;
+			if (count_dst != nullptr) *count_dst = pixels;
 
 			/* Write line-ending */
 			*dst = 0; dst++;
diff --git a/src/blitter/factory.hpp b/src/blitter/factory.hpp
--- a/src/blitter/factory.hpp
+++ b/src/blitter/factory.hpp
@@ -48,7 +48,7 @@ private:
 	 */
 	static Blitter **GetActiveBlitter()
 	{
-		static Blitter *s_blitter = NULL;
+		static Blitter *s_blitter = nullptr;
 		return &s_blitter;
 	}
 
@@ -58,8 +58,8 @@ protected:
 	 * @param name        The name of the blitter.
 	 * @param description A longer description for the blitter.
 	 * @param usable      Whether the blitter is usable (on the current computer). For example for disabling SSE blitters when the CPU can't handle them.
-	 * @pre name != NULL.
-	 * @pre description != NULL.
+	 * @pre name != nullptr.
+	 * @pre description != nullptr.
 	 * @pre There is no blitter registered with this name.
 	 */
 	BlitterFactory(const char *name, const char *description, bool usable = true) :
@@ -96,7 +96,7 @@ public:
 	static Blitter *SelectBlitter(const char *name)
 	{
 		BlitterFactory *b = GetBlitterFactory(name);
-		if (b == NULL) return NULL;
+		if (b == nullptr) return nullptr;
 
 		Blitter *newb = b->CreateInstance();
 		delete *GetActiveBlitter();
@@ -109,7 +109,7 @@ public:
 	/**
 	 * Get the blitter factory with the given name.
 	 * @param name the blitter factory to select.
-	 * @return The blitter factory, or NULL when there isn't one with the wanted name.
+	 * @return The blitter factory, or nullptr when there isn't one with the wanted name.
 	 */
 	static BlitterFactory *GetBlitterFactory(const char *name)
 	{
@@ -128,7 +128,7 @@ public:
 		}
 #endif /* defined(WITH_COCOA) */
 #endif /* defined(DEDICATED) */
-		if (GetBlitters().size() == 0) return NULL;
+		if (GetBlitters().size() == 0) return nullptr;
 		const char *bname = (StrEmpty(name)) ? default_blitter : name;
 
 		Blitters::iterator it = GetBlitters().begin();
@@ -138,7 +138,7 @@ public:
 				return b;
 			}
 		}
-		return NULL;
+		return nullptr;
 	}
 
 	/**
diff --git a/src/blitter/null.hpp b/src/blitter/null.hpp
--- a/src/blitter/null.hpp
+++ b/src/blitter/null.hpp
@@ -21,7 +21,7 @@ public:
 	void Draw(Blitter::BlitterParams *bp, BlitterMode mode, ZoomLevel zoom) override {};
 	void DrawColourMappingRect(void *dst, int width, int height, PaletteID pal) override {};
 	Sprite *Encode(const SpriteLoader::Sprite *sprite, AllocatorProc *allocator) override;
-	void *MoveTo(void *video, int x, int y) override { return NULL; };
+	void *MoveTo(void *video, int x, int y) override { return nullptr; };
 	void SetPixel(void *video, int x, int y, uint8 colour) override {};
 	void DrawRect(void *video, int width, int height, uint8 colour) override {};
 	void DrawLine(void *video, int x, int y, int x2, int y2, int screen_width, int screen_height, uint8 colour, int width, int dash) override {};
diff --git a/src/bmp.cpp b/src/bmp.cpp
--- a/src/bmp.cpp
+++ b/src/bmp.cpp
@@ -319,7 +319,7 @@ static inline bool BmpRead24(BmpBuffer *
 bool BmpReadHeader(BmpBuffer *buffer, BmpInfo *info, BmpData *data)
 {
 	uint32 header_size;
-	assert(info != NULL);
+	assert(info != nullptr);
 	MemSetT(info, 0);
 
 	/* Reading BMP header */
@@ -390,7 +390,7 @@ bool BmpReadHeader(BmpBuffer *buffer, Bm
  */
 bool BmpReadBitmap(BmpBuffer *buffer, BmpInfo *info, BmpData *data)
 {
-	assert(info != NULL && data != NULL);
+	assert(info != nullptr && data != nullptr);
 
 	data->bitmap = CallocT<byte>(info->width * info->height * ((info->bpp == 24) ? 3 : 1));
 
@@ -413,7 +413,7 @@ bool BmpReadBitmap(BmpBuffer *buffer, Bm
 
 void BmpDestroyData(BmpData *data)
 {
-	assert(data != NULL);
+	assert(data != nullptr);
 	free(data->palette);
 	free(data->bitmap);
 }
diff --git a/src/bootstrap_gui.cpp b/src/bootstrap_gui.cpp
--- a/src/bootstrap_gui.cpp
+++ b/src/bootstrap_gui.cpp
@@ -40,7 +40,7 @@ static const struct NWidgetPart _backgro
  * Window description for the background window to prevent smearing.
  */
 static WindowDesc _background_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_BOOTSTRAP, WC_NONE,
 	0,
 	_background_widgets, lengthof(_background_widgets)
@@ -73,7 +73,7 @@ static const NWidgetPart _nested_boostra
 
 /** Window description for the download window */
 static WindowDesc _bootstrap_download_status_window_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_NETWORK_STATUS_WINDOW, WC_NONE,
 	WDF_MODAL,
 	_nested_boostrap_download_status_window_widgets, lengthof(_nested_boostrap_download_status_window_widgets)
@@ -118,7 +118,7 @@ static const NWidgetPart _bootstrap_quer
 
 /** The window description for the query. */
 static WindowDesc _bootstrap_query_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_CONFIRM_POPUP_QUERY, WC_NONE,
 	0,
 	_bootstrap_query_widgets, lengthof(_bootstrap_query_widgets)
@@ -214,7 +214,7 @@ public:
  */
 bool HandleBootstrap()
 {
-	if (BaseGraphics::GetUsedSet() != NULL) return true;
+	if (BaseGraphics::GetUsedSet() != nullptr) return true;
 
 	/* No user interface, bail out with an error. */
 	if (BlitterFactory::GetCurrentBlitter()->GetScreenDepth() == 0) goto failure;
@@ -255,7 +255,7 @@ bool HandleBootstrap()
 	if (_exit_game) return false;
 
 	/* Try to probe the graphics. Should work this time. */
-	if (!BaseGraphics::SetSet(NULL)) goto failure;
+	if (!BaseGraphics::SetSet(nullptr)) goto failure;
 
 	/* Finally we can continue heading for the menu. */
 	_game_mode = GM_MENU;
diff --git a/src/bridge_gui.cpp b/src/bridge_gui.cpp
--- a/src/bridge_gui.cpp
+++ b/src/bridge_gui.cpp
@@ -392,7 +392,7 @@ void ShowBuildBridgeWindow(TileIndex sta
 	StringID errmsg = INVALID_STRING_ID;
 	CommandCost ret = DoCommand(end, start, type, CommandFlagsToDCFlags(GetCommandFlags(CMD_BUILD_BRIDGE)) | DC_QUERY_COST, CMD_BUILD_BRIDGE);
 
-	GUIBridgeList *bl = NULL;
+	GUIBridgeList *bl = nullptr;
 	if (ret.Failed()) {
 		errmsg = ret.GetErrorMessage();
 	} else {
@@ -427,7 +427,7 @@ void ShowBuildBridgeWindow(TileIndex sta
 		}
 	}
 
-	if (bl != NULL && bl->size() != 0) {
+	if (bl != nullptr && bl->size() != 0) {
 		new BuildBridgeWindow(&_build_bridge_desc, start, end, type, bl);
 	} else {
 		delete bl;
diff --git a/src/build_vehicle_gui.cpp b/src/build_vehicle_gui.cpp
--- a/src/build_vehicle_gui.cpp
+++ b/src/build_vehicle_gui.cpp
@@ -833,7 +833,7 @@ static int DrawAircraftPurchaseInfo(int 
  */
 static uint ShowAdditionalText(int left, int right, int y, EngineID engine)
 {
-	uint16 callback = GetVehicleCallback(CBID_VEHICLE_ADDITIONAL_TEXT, 0, 0, engine, NULL);
+	uint16 callback = GetVehicleCallback(CBID_VEHICLE_ADDITIONAL_TEXT, 0, 0, engine, nullptr);
 	if (callback == CALLBACK_FAILED || callback == 0x400) return y;
 	const GRFFile *grffile = Engine::Get(engine)->GetGRF();
 	if (callback > 0x400) {
@@ -1180,7 +1180,7 @@ struct BuildVehicleWindow : Window {
 
 		if (!this->listview_mode) {
 			/* Query for cost and refitted capacity */
-			CommandCost ret = DoCommand(this->window_number, this->sel_engine | (cargo << 24), 0, DC_QUERY_COST, GetCmdBuildVeh(this->vehicle_type), NULL);
+			CommandCost ret = DoCommand(this->window_number, this->sel_engine | (cargo << 24), 0, DC_QUERY_COST, GetCmdBuildVeh(this->vehicle_type), nullptr);
 			if (ret.Succeeded()) {
 				this->te.cost          = ret.GetCost() - e->GetCost();
 				this->te.capacity      = _returned_refit_capacity;
@@ -1316,7 +1316,7 @@ struct BuildVehicleWindow : Window {
 
 		this->eng_list.clear();
 
-		const Station *st = this->listview_mode ? NULL : Station::GetByTile(this->window_number);
+		const Station *st = this->listview_mode ? nullptr : Station::GetByTile(this->window_number);
 
 		/* Make list of all available planes.
 		 * Also check to see if the previously selected plane is still available,
@@ -1408,8 +1408,8 @@ struct BuildVehicleWindow : Window {
 				break;
 
 			case WID_BV_SHOW_HIDE: {
-				const Engine *e = (this->sel_engine == INVALID_ENGINE) ? NULL : Engine::Get(this->sel_engine);
-				if (e != NULL) {
+				const Engine *e = (this->sel_engine == INVALID_ENGINE) ? nullptr : Engine::Get(this->sel_engine);
+				if (e != nullptr) {
 					DoCommandP(0, 0, this->sel_engine | (e->IsHidden(_current_company) ? 0 : (1u << 31)), CMD_SET_VEHICLE_VISIBILITY);
 				}
 				break;
@@ -1477,8 +1477,8 @@ struct BuildVehicleWindow : Window {
 				break;
 
 			case WID_BV_SHOW_HIDE: {
-				const Engine *e = (this->sel_engine == INVALID_ENGINE) ? NULL : Engine::Get(this->sel_engine);
-				if (e != NULL && e->IsHidden(_local_company)) {
+				const Engine *e = (this->sel_engine == INVALID_ENGINE) ? nullptr : Engine::Get(this->sel_engine);
+				if (e != nullptr && e->IsHidden(_local_company)) {
 					SetDParam(0, STR_BUY_VEHICLE_TRAIN_SHOW_TOGGLE_BUTTON + this->vehicle_type);
 				} else {
 					SetDParam(0, STR_BUY_VEHICLE_TRAIN_HIDE_TOGGLE_BUTTON + this->vehicle_type);
@@ -1567,9 +1567,9 @@ struct BuildVehicleWindow : Window {
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
-		DoCommandP(0, this->rename_engine, 0, CMD_RENAME_ENGINE | CMD_MSG(STR_ERROR_CAN_T_RENAME_TRAIN_TYPE + this->vehicle_type), NULL, str);
+		DoCommandP(0, this->rename_engine, 0, CMD_RENAME_ENGINE | CMD_MSG(STR_ERROR_CAN_T_RENAME_TRAIN_TYPE + this->vehicle_type), nullptr, str);
 	}
 
 	void OnDropdownSelect(int widget, int index) override
diff --git a/src/cargoaction.cpp b/src/cargoaction.cpp
--- a/src/cargoaction.cpp
+++ b/src/cargoaction.cpp
@@ -121,7 +121,7 @@ bool CargoDelivery::operator()(CargoPack
 bool CargoLoad::operator()(CargoPacket *cp)
 {
 	CargoPacket *cp_new = this->Preprocess(cp);
-	if (cp_new == NULL) return false;
+	if (cp_new == nullptr) return false;
 	cp_new->SetLoadPlace(this->load_place);
 	this->source->RemoveFromCache(cp_new, cp_new->Count());
 	this->destination->Append(cp_new, VehicleCargoList::MTA_KEEP);
@@ -136,7 +136,7 @@ bool CargoLoad::operator()(CargoPacket *
 bool CargoReservation::operator()(CargoPacket *cp)
 {
 	CargoPacket *cp_new = this->Preprocess(cp);
-	if (cp_new == NULL) return false;
+	if (cp_new == nullptr) return false;
 	cp_new->SetLoadPlace(this->load_place);
 	this->source->reserved_count += cp_new->Count();
 	this->source->RemoveFromCache(cp_new, cp_new->Count());
@@ -152,7 +152,7 @@ bool CargoReservation::operator()(CargoP
 bool CargoReturn::operator()(CargoPacket *cp)
 {
 	CargoPacket *cp_new = this->Preprocess(cp);
-	if (cp_new == NULL) cp_new = cp;
+	if (cp_new == nullptr) cp_new = cp;
 	assert(cp_new->Count() <= this->destination->reserved_count);
 	this->source->RemoveFromMeta(cp_new, VehicleCargoList::MTA_LOAD, cp_new->Count());
 	this->destination->reserved_count -= cp_new->Count();
@@ -168,7 +168,7 @@ bool CargoReturn::operator()(CargoPacket
 bool CargoTransfer::operator()(CargoPacket *cp)
 {
 	CargoPacket *cp_new = this->Preprocess(cp);
-	if (cp_new == NULL) return false;
+	if (cp_new == nullptr) return false;
 	this->source->RemoveFromMeta(cp_new, VehicleCargoList::MTA_TRANSFER, cp_new->Count());
 	/* No transfer credits here as they were already granted during Stage(). */
 	this->destination->Append(cp_new, cp_new->NextStation());
@@ -183,7 +183,7 @@ bool CargoTransfer::operator()(CargoPack
 bool CargoShift::operator()(CargoPacket *cp)
 {
 	CargoPacket *cp_new = this->Preprocess(cp);
-	if (cp_new == NULL) cp_new = cp;
+	if (cp_new == nullptr) cp_new = cp;
 	this->source->RemoveFromMeta(cp_new, VehicleCargoList::MTA_KEEP, cp_new->Count());
 	this->destination->Append(cp_new, VehicleCargoList::MTA_KEEP);
 	return cp_new == cp;
@@ -197,7 +197,7 @@ bool CargoShift::operator()(CargoPacket 
 bool StationCargoReroute::operator()(CargoPacket *cp)
 {
 	CargoPacket *cp_new = this->Preprocess(cp);
-	if (cp_new == NULL) cp_new = cp;
+	if (cp_new == nullptr) cp_new = cp;
 	StationID next = this->ge->GetVia(cp_new->SourceStation(), this->avoid, this->avoid2);
 	assert(next != this->avoid && next != this->avoid2);
 	if (this->source != this->destination) {
@@ -220,7 +220,7 @@ bool StationCargoReroute::operator()(Car
 bool VehicleCargoReroute::operator()(CargoPacket *cp)
 {
 	CargoPacket *cp_new = this->Preprocess(cp);
-	if (cp_new == NULL) cp_new = cp;
+	if (cp_new == nullptr) cp_new = cp;
 	if (cp_new->NextStation() == this->avoid || cp_new->NextStation() == this->avoid2) {
 		cp->SetNextStation(this->ge->GetVia(cp_new->SourceStation(), this->avoid, this->avoid2));
 	}
diff --git a/src/cargopacket.cpp b/src/cargopacket.cpp
--- a/src/cargopacket.cpp
+++ b/src/cargopacket.cpp
@@ -86,11 +86,11 @@ CargoPacket::CargoPacket(uint16 count, b
 /**
  * Split this packet in two and return the split off part.
  * @param new_size Size of the split part.
- * @return Split off part, or NULL if no packet could be allocated!
+ * @return Split off part, or nullptr if no packet could be allocated!
  */
 CargoPacket *CargoPacket::Split(uint new_size)
 {
-	if (!CargoPacket::CanAllocateItem()) return NULL;
+	if (!CargoPacket::CanAllocateItem()) return nullptr;
 
 	Money fs = this->FeederShare(new_size);
 	CargoPacket *cp_new = new CargoPacket(new_size, this->days_in_transit, this->source, this->source_xy, this->loaded_at_xy, fs, this->source_type, this->source_id);
@@ -248,12 +248,12 @@ template <class Tinst, class Tcont>
  * @param cp Cargo packet to add.
  * @param action Either MTA_KEEP if you want to add the packet directly or MTA_LOAD
  * if you want to reserve it first.
- * @pre cp != NULL
+ * @pre cp != nullptr
  * @pre action == MTA_LOAD || (action == MTA_KEEP && this->designation_counts[MTA_LOAD] == 0)
  */
 void VehicleCargoList::Append(CargoPacket *cp, MoveToAction action)
 {
-	assert(cp != NULL);
+	assert(cp != nullptr);
 	assert(action == MTA_LOAD ||
 			(action == MTA_KEEP && this->action_counts[MTA_LOAD] == 0));
 	this->AddToMeta(cp, action);
@@ -689,11 +689,11 @@ uint VehicleCargoList::Reroute(uint max_
  * @note Do not use the cargo packet anymore after it has been appended to this CargoList!
  * @param next the next hop
  * @param cp the cargo packet to add
- * @pre cp != NULL
+ * @pre cp != nullptr
  */
 void StationCargoList::Append(CargoPacket *cp, StationID next)
 {
-	assert(cp != NULL);
+	assert(cp != nullptr);
 	this->AddToCache(cp);
 
 	StationCargoPacketMap::List &list = this->packets[next];
@@ -776,7 +776,7 @@ uint StationCargoList::Truncate(uint max
 	uint prev_count = this->count;
 	uint moved = 0;
 	uint loop = 0;
-	bool do_count = cargo_per_source != NULL;
+	bool do_count = cargo_per_source != nullptr;
 	while (max_move > moved) {
 		for (Iterator it(this->packets.begin()); it != this->packets.end();) {
 			CargoPacket *cp = *it;
diff --git a/src/cargopacket.h b/src/cargopacket.h
--- a/src/cargopacket.h
+++ b/src/cargopacket.h
@@ -549,7 +549,7 @@ public:
 
 	uint Reserve(uint max_move, VehicleCargoList *dest, TileIndex load_place, StationIDStack next);
 	uint Load(uint max_move, VehicleCargoList *dest, TileIndex load_place, StationIDStack next);
-	uint Truncate(uint max_move = UINT_MAX, StationCargoAmountMap *cargo_per_source = NULL);
+	uint Truncate(uint max_move = UINT_MAX, StationCargoAmountMap *cargo_per_source = nullptr);
 	uint Reroute(uint max_move, StationCargoList *dest, StationID avoid, StationID avoid2, const GoodsEntry *ge);
 
 	/**
diff --git a/src/cargotype.h b/src/cargotype.h
--- a/src/cargotype.h
+++ b/src/cargotype.h
@@ -152,7 +152,7 @@ static inline bool IsCargoInClass(CargoI
 	return (CargoSpec::Get(c)->classes & cc) != 0;
 }
 
-#define FOR_ALL_CARGOSPECS_FROM(var, start) for (size_t cargospec_index = start; var = NULL, cargospec_index < CargoSpec::GetArraySize(); cargospec_index++) \
+#define FOR_ALL_CARGOSPECS_FROM(var, start) for (size_t cargospec_index = start; var = nullptr, cargospec_index < CargoSpec::GetArraySize(); cargospec_index++) \
 		if ((var = CargoSpec::Get(cargospec_index))->IsValid())
 #define FOR_ALL_CARGOSPECS(var) FOR_ALL_CARGOSPECS_FROM(var, 0)
 
diff --git a/src/cheat_gui.cpp b/src/cheat_gui.cpp
--- a/src/cheat_gui.cpp
+++ b/src/cheat_gui.cpp
@@ -186,9 +186,9 @@ struct CheatEntry {
 static const CheatEntry _cheats_ui[] = {
 	{SLE_INT32, STR_CHEAT_MONEY,           &_money_cheat_amount,                    &_cheats.money.been_used,            &ClickMoneyCheat         },
 	{SLE_UINT8, STR_CHEAT_CHANGE_COMPANY,  &_local_company,                         &_cheats.switch_company.been_used,   &ClickChangeCompanyCheat },
-	{SLE_BOOL,  STR_CHEAT_EXTRA_DYNAMITE,  &_cheats.magic_bulldozer.value,          &_cheats.magic_bulldozer.been_used,  NULL                     },
-	{SLE_BOOL,  STR_CHEAT_CROSSINGTUNNELS, &_cheats.crossing_tunnels.value,         &_cheats.crossing_tunnels.been_used, NULL                     },
-	{SLE_BOOL,  STR_CHEAT_NO_JETCRASH,     &_cheats.no_jetcrash.value,              &_cheats.no_jetcrash.been_used,      NULL                     },
+	{SLE_BOOL,  STR_CHEAT_EXTRA_DYNAMITE,  &_cheats.magic_bulldozer.value,          &_cheats.magic_bulldozer.been_used,  nullptr                     },
+	{SLE_BOOL,  STR_CHEAT_CROSSINGTUNNELS, &_cheats.crossing_tunnels.value,         &_cheats.crossing_tunnels.been_used, nullptr                     },
+	{SLE_BOOL,  STR_CHEAT_NO_JETCRASH,     &_cheats.no_jetcrash.value,              &_cheats.no_jetcrash.been_used,      nullptr                     },
 	{SLE_BOOL,  STR_CHEAT_SETUP_PROD,      &_cheats.setup_prod.value,               &_cheats.setup_prod.been_used,       &ClickSetProdCheat       },
 	{SLE_UINT8, STR_CHEAT_EDIT_MAX_HL,     &_settings_game.construction.max_heightlevel, &_cheats.edit_max_hl.been_used, &ClickChangeMaxHlCheat   },
 	{SLE_INT32, STR_CHEAT_CHANGE_DATE,     &_cur_year,                              &_cheats.change_date.been_used,      &ClickChangeDateCheat    },
@@ -365,7 +365,7 @@ struct CheatWindow : Window {
 		switch (ce->type) {
 			case SLE_BOOL:
 				value ^= 1;
-				if (ce->proc != NULL) ce->proc(value, 0);
+				if (ce->proc != nullptr) ce->proc(value, 0);
 				break;
 
 			default:
@@ -393,7 +393,7 @@ struct CheatWindow : Window {
 	void OnQueryTextFinished(char *str) override
 	{
 		/* Was 'cancel' pressed or nothing entered? */
-		if (str == NULL || StrEmpty(str)) return;
+		if (str == nullptr || StrEmpty(str)) return;
 
 		const CheatEntry *ce = &_cheats_ui[clicked_widget];
 		int oldvalue = (int32)ReadValue(ce->variable, ce->type);
diff --git a/src/clear_cmd.cpp b/src/clear_cmd.cpp
--- a/src/clear_cmd.cpp
+++ b/src/clear_cmd.cpp
@@ -389,15 +389,15 @@ extern const TileTypeProcs _tile_type_cl
 	DrawTile_Clear,           ///< draw_tile_proc
 	GetSlopePixelZ_Clear,     ///< get_slope_z_proc
 	ClearTile_Clear,          ///< clear_tile_proc
-	NULL,                     ///< add_accepted_cargo_proc
+	nullptr,                     ///< add_accepted_cargo_proc
 	GetTileDesc_Clear,        ///< get_tile_desc_proc
 	GetTileTrackStatus_Clear, ///< get_tile_track_status_proc
-	NULL,                     ///< click_tile_proc
-	NULL,                     ///< animate_tile_proc
+	nullptr,                     ///< click_tile_proc
+	nullptr,                     ///< animate_tile_proc
 	TileLoop_Clear,           ///< tile_loop_proc
 	ChangeTileOwner_Clear,    ///< change_tile_owner_proc
-	NULL,                     ///< add_produced_cargo_proc
-	NULL,                     ///< vehicle_enter_tile_proc
+	nullptr,                     ///< add_produced_cargo_proc
+	nullptr,                     ///< vehicle_enter_tile_proc
 	GetFoundation_Clear,      ///< get_foundation_proc
 	TerraformTile_Clear,      ///< terraform_tile_proc
 };
diff --git a/src/command.cpp b/src/command.cpp
--- a/src/command.cpp
+++ b/src/command.cpp
@@ -361,7 +361,7 @@ static const Command _command_proc_table
 };
 
 /*!
- * This function range-checks a cmd, and checks if the cmd is not NULL
+ * This function range-checks a cmd, and checks if the cmd is not nullptr
  *
  * @param cmd The integer value of a command
  * @return true if the command is valid (and got a CommandProc function)
@@ -370,7 +370,7 @@ bool IsValidCommand(uint32 cmd)
 {
 	cmd &= CMD_ID_MASK;
 
-	return cmd < lengthof(_command_proc_table) && _command_proc_table[cmd].proc != NULL;
+	return cmd < lengthof(_command_proc_table) && _command_proc_table[cmd].proc != nullptr;
 }
 
 /*!
@@ -594,7 +594,7 @@ bool DoCommandP(TileIndex tile, uint32 p
 		ShowCostOrIncomeAnimation(x, y, GetSlopePixelZ(x, y), res.GetCost());
 	}
 
-	if (!estimate_only && !only_sending && callback != NULL) {
+	if (!estimate_only && !only_sending && callback != nullptr) {
 		callback(res, tile, p1, p2);
 	}
 
@@ -637,7 +637,7 @@ CommandCost DoCommandPInternal(TileIndex
 	CommandProc *proc = _command_proc_table[cmd_id].proc;
 	/* Shouldn't happen, but you never know when someone adds
 	 * NULLs to the _command_proc_table. */
-	assert(proc != NULL);
+	assert(proc != nullptr);
 
 	/* Command flags are used internally */
 	CommandFlags cmd_flags = GetCommandFlags(cmd);
@@ -750,7 +750,7 @@ CommandCost DoCommandPInternal(TileIndex
 	/* update last build coordinate of company. */
 	if (tile != 0) {
 		Company *c = Company::GetIfValid(_current_company);
-		if (c != NULL) c->last_build_coordinate = tile;
+		if (c != nullptr) c->last_build_coordinate = tile;
 	}
 
 	SubtractMoneyFromCompany(res2);
diff --git a/src/command_func.h b/src/command_func.h
--- a/src/command_func.h
+++ b/src/command_func.h
@@ -34,10 +34,10 @@ static const CommandCost CMD_ERROR = Com
  */
 #define return_cmd_error(errcode) return CommandCost(errcode);
 
-CommandCost DoCommand(TileIndex tile, uint32 p1, uint32 p2, DoCommandFlag flags, uint32 cmd, const char *text = NULL);
+CommandCost DoCommand(TileIndex tile, uint32 p1, uint32 p2, DoCommandFlag flags, uint32 cmd, const char *text = nullptr);
 CommandCost DoCommand(const CommandContainer *container, DoCommandFlag flags);
 
-bool DoCommandP(TileIndex tile, uint32 p1, uint32 p2, uint32 cmd, CommandCallback *callback = NULL, const char *text = NULL, bool my_cmd = true);
+bool DoCommandP(TileIndex tile, uint32 p1, uint32 p2, uint32 cmd, CommandCallback *callback = nullptr, const char *text = nullptr, bool my_cmd = true);
 bool DoCommandP(const CommandContainer *container, bool my_cmd = true);
 
 CommandCost DoCommandPInternal(TileIndex tile, uint32 p1, uint32 p2, uint32 cmd, CommandCallback *callback, const char *text, bool my_cmd, bool estimate_only);
diff --git a/src/command_type.h b/src/command_type.h
--- a/src/command_type.h
+++ b/src/command_type.h
@@ -36,25 +36,25 @@ public:
 	/**
 	 * Creates a command cost return with no cost and no error
 	 */
-	CommandCost() : expense_type(INVALID_EXPENSES), cost(0), message(INVALID_STRING_ID), success(true), textref_stack_grffile(NULL), textref_stack_size(0) {}
+	CommandCost() : expense_type(INVALID_EXPENSES), cost(0), message(INVALID_STRING_ID), success(true), textref_stack_grffile(nullptr), textref_stack_size(0) {}
 
 	/**
 	 * Creates a command return value the is failed with the given message
 	 */
-	explicit CommandCost(StringID msg) : expense_type(INVALID_EXPENSES), cost(0), message(msg), success(false), textref_stack_grffile(NULL), textref_stack_size(0) {}
+	explicit CommandCost(StringID msg) : expense_type(INVALID_EXPENSES), cost(0), message(msg), success(false), textref_stack_grffile(nullptr), textref_stack_size(0) {}
 
 	/**
 	 * Creates a command cost with given expense type and start cost of 0
 	 * @param ex_t the expense type
 	 */
-	explicit CommandCost(ExpensesType ex_t) : expense_type(ex_t), cost(0), message(INVALID_STRING_ID), success(true), textref_stack_grffile(NULL), textref_stack_size(0) {}
+	explicit CommandCost(ExpensesType ex_t) : expense_type(ex_t), cost(0), message(INVALID_STRING_ID), success(true), textref_stack_grffile(nullptr), textref_stack_size(0) {}
 
 	/**
 	 * Creates a command return value with the given start cost and expense type
 	 * @param ex_t the expense type
 	 * @param cst the initial cost of this command
 	 */
-	CommandCost(ExpensesType ex_t, const Money &cst) : expense_type(ex_t), cost(cst), message(INVALID_STRING_ID), success(true), textref_stack_grffile(NULL), textref_stack_size(0) {}
+	CommandCost(ExpensesType ex_t, const Money &cst) : expense_type(ex_t), cost(cst), message(INVALID_STRING_ID), success(true), textref_stack_grffile(nullptr), textref_stack_size(0) {}
 
 
 	/**
diff --git a/src/company_base.h b/src/company_base.h
--- a/src/company_base.h
+++ b/src/company_base.h
@@ -98,7 +98,7 @@ struct CompanyProperties {
 
 	// TODO: Change some of these member variables to use relevant INVALID_xxx constants
 	CompanyProperties()
-		: name_2(0), name_1(0), name(NULL), president_name_1(0), president_name_2(0), president_name(NULL),
+		: name_2(0), name_1(0), name(nullptr), president_name_1(0), president_name_2(0), president_name(nullptr),
 		  face(0), money(0), money_fraction(0), current_loan(0), colour(0), block_preview(0),
 		  location_of_HQ(0), last_build_coordinate(0), share_owners(), inaugurated_year(0),
 		  months_of_bankruptcy(0), bankrupt_asked(0), bankrupt_timeout(0), bankrupt_value(0),
@@ -137,7 +137,7 @@ struct Company : CompanyPool::PoolItem<&
 	static inline bool IsValidAiID(size_t index)
 	{
 		const Company *c = Company::GetIfValid(index);
-		return c != NULL && c->is_ai;
+		return c != nullptr && c->is_ai;
 	}
 
 	/**
@@ -149,7 +149,7 @@ struct Company : CompanyPool::PoolItem<&
 	static inline bool IsValidHumanID(size_t index)
 	{
 		const Company *c = Company::GetIfValid(index);
-		return c != NULL && !c->is_ai;
+		return c != nullptr && !c->is_ai;
 	}
 
 	/**
diff --git a/src/company_cmd.cpp b/src/company_cmd.cpp
--- a/src/company_cmd.cpp
+++ b/src/company_cmd.cpp
@@ -193,7 +193,7 @@ bool CheckCompanyHasMoney(CommandCost &c
 {
 	if (cost.GetCost() > 0) {
 		const Company *c = Company::GetIfValid(_current_company);
-		if (c != NULL && cost.GetCost() > c->money) {
+		if (c != nullptr && cost.GetCost() > c->money) {
 			SetDParam(0, cost.GetCost());
 			cost.MakeError(STR_ERROR_NOT_ENOUGH_CASH_REQUIRES_CURRENCY);
 			return false;
@@ -239,7 +239,7 @@ static void SubtractMoneyFromAnyCompany(
 void SubtractMoneyFromCompany(CommandCost cost)
 {
 	Company *c = Company::GetIfValid(_current_company);
-	if (c != NULL) SubtractMoneyFromAnyCompany(c, cost);
+	if (c != nullptr) SubtractMoneyFromAnyCompany(c, cost);
 }
 
 /**
@@ -353,7 +353,7 @@ static void GenerateCompanyName(Company 
 
 	StringID str;
 	uint32 strp;
-	if (t->name == NULL && IsInsideMM(t->townnametype, SPECSTR_TOWNNAME_START, SPECSTR_TOWNNAME_LAST + 1)) {
+	if (t->name == nullptr && IsInsideMM(t->townnametype, SPECSTR_TOWNNAME_START, SPECSTR_TOWNNAME_LAST + 1)) {
 		str = t->townnametype - SPECSTR_TOWNNAME_START + SPECSTR_COMPANY_NAME_START;
 		strp = t->townnameparts;
 
@@ -539,7 +539,7 @@ void ResetCompanyLivery(Company *c)
  */
 Company *DoStartupNewCompany(bool is_ai, CompanyID company = INVALID_COMPANY)
 {
-	if (!Company::CanAllocateItem()) return NULL;
+	if (!Company::CanAllocateItem()) return nullptr;
 
 	/* we have to generate colour before this company is valid */
 	Colours colour = GenerateCompanyColour();
@@ -548,7 +548,7 @@ Company *DoStartupNewCompany(bool is_ai,
 	if (company == INVALID_COMPANY) {
 		c = new Company(STR_SV_UNNAMED, is_ai);
 	} else {
-		if (Company::IsValidID(company)) return NULL;
+		if (Company::IsValidID(company)) return nullptr;
 		c = new (company) Company(STR_SV_UNNAMED, is_ai);
 	}
 
@@ -670,7 +670,7 @@ static void HandleBankruptcyTakeover(Com
 	/* Did we ask everyone for bankruptcy? If so, bail out. */
 	if (c->bankrupt_asked == MAX_UVALUE(CompanyMask)) return;
 
-	Company *c2, *best = NULL;
+	Company *c2, *best = nullptr;
 	int32 best_performance = -1;
 
 	/* Ask the company with the highest performance history first */
@@ -706,7 +706,7 @@ void OnTick_Companies()
 	if (_game_mode == GM_EDITOR) return;
 
 	Company *c = Company::GetIfValid(_cur_company_tick_index);
-	if (c != NULL) {
+	if (c != nullptr) {
 		if (c->name_1 != 0) GenerateCompanyName(c);
 		if (c->bankrupt_asked != 0) HandleBankruptcyTakeover(c);
 	}
@@ -759,14 +759,14 @@ void CompaniesYearlyLoop()
 /**
  * Fill the CompanyNewsInformation struct with the required data.
  * @param c the current company.
- * @param other the other company (use \c NULL if not relevant).
+ * @param other the other company (use \c nullptr if not relevant).
  */
 void CompanyNewsInformation::FillData(const Company *c, const Company *other)
 {
 	SetDParam(0, c->index);
 	GetString(this->company_name, STR_COMPANY_NAME, lastof(this->company_name));
 
-	if (other == NULL) {
+	if (other == nullptr) {
 		*this->other_company_name = '\0';
 	} else {
 		SetDParam(0, other->index);
@@ -832,8 +832,8 @@ CommandCost CmdCompanyCtrl(TileIndex til
 			/* When replaying the client ID is not a valid client; there
 			 * are actually no clients at all. However, the company has to
 			 * be created, otherwise we cannot rerun the game properly.
-			 * So only allow a NULL client info in that case. */
-			if (ci == NULL) return CommandCost();
+			 * So only allow a nullptr client info in that case. */
+			if (ci == nullptr) return CommandCost();
 #endif /* NOT DEBUG_DUMP_COMMANDS */
 
 			/* Delete multiplayer progress bar */
@@ -842,7 +842,7 @@ CommandCost CmdCompanyCtrl(TileIndex til
 			Company *c = DoStartupNewCompany(false);
 
 			/* A new company could not be created, revert to being a spectator */
-			if (c == NULL) {
+			if (c == nullptr) {
 				if (_network_server) {
 					ci->client_playas = COMPANY_SPECTATOR;
 					NetworkUpdateClientInfo(ci->client_id);
@@ -874,7 +874,7 @@ CommandCost CmdCompanyCtrl(TileIndex til
 
 			if (company_id != INVALID_COMPANY && (company_id >= MAX_COMPANIES || Company::IsValidID(company_id))) return CMD_ERROR;
 			Company *c = DoStartupNewCompany(true, company_id);
-			if (c != NULL) NetworkServerNewCompany(c, NULL);
+			if (c != nullptr) NetworkServerNewCompany(c, nullptr);
 			break;
 		}
 
@@ -883,7 +883,7 @@ CommandCost CmdCompanyCtrl(TileIndex til
 			if (reason >= CRR_END) return CMD_ERROR;
 
 			Company *c = Company::GetIfValid(company_id);
-			if (c == NULL) return CMD_ERROR;
+			if (c == nullptr) return CMD_ERROR;
 
 			if (!(flags & DC_EXEC)) return CommandCost();
 
@@ -1055,7 +1055,7 @@ static bool IsUniqueCompanyName(const ch
 	const Company *c;
 
 	FOR_ALL_COMPANIES(c) {
-		if (c->name != NULL && strcmp(c->name, name) == 0) return false;
+		if (c->name != nullptr && strcmp(c->name, name) == 0) return false;
 	}
 
 	return true;
@@ -1082,7 +1082,7 @@ CommandCost CmdRenameCompany(TileIndex t
 	if (flags & DC_EXEC) {
 		Company *c = Company::Get(_current_company);
 		free(c->name);
-		c->name = reset ? NULL : stredup(text);
+		c->name = reset ? nullptr : stredup(text);
 		MarkWholeScreenDirty();
 		CompanyAdminUpdate(c);
 	}
@@ -1100,7 +1100,7 @@ static bool IsUniquePresidentName(const 
 	const Company *c;
 
 	FOR_ALL_COMPANIES(c) {
-		if (c->president_name != NULL && strcmp(c->president_name, name) == 0) return false;
+		if (c->president_name != nullptr && strcmp(c->president_name, name) == 0) return false;
 	}
 
 	return true;
@@ -1129,11 +1129,11 @@ CommandCost CmdRenamePresident(TileIndex
 		free(c->president_name);
 
 		if (reset) {
-			c->president_name = NULL;
+			c->president_name = nullptr;
 		} else {
 			c->president_name = stredup(text);
 
-			if (c->name_1 == STR_SV_UNNAMED && c->name == NULL) {
+			if (c->name_1 == STR_SV_UNNAMED && c->name == nullptr) {
 				char buf[80];
 
 				seprintf(buf, lastof(buf), "%s Transport", text);
@@ -1150,13 +1150,13 @@ CommandCost CmdRenamePresident(TileIndex
 
 /**
  * Get the service interval for the given company and vehicle type.
- * @param c The company, or NULL for client-default settings.
+ * @param c The company, or nullptr for client-default settings.
  * @param type The vehicle type to get the interval for.
  * @return The service interval.
  */
 int CompanyServiceInterval(const Company *c, VehicleType type)
 {
-	const VehicleDefaultSettings *vds = (c == NULL) ? &_settings_client.company.vehicle : &c->settings.vehicle;
+	const VehicleDefaultSettings *vds = (c == nullptr) ? &_settings_client.company.vehicle : &c->settings.vehicle;
 	switch (type) {
 		default: NOT_REACHED();
 		case VEH_TRAIN:    return vds->servint_trains;
diff --git a/src/company_gui.cpp b/src/company_gui.cpp
--- a/src/company_gui.cpp
+++ b/src/company_gui.cpp
@@ -569,7 +569,7 @@ private:
 	{
 		uint32 used_colours = 0;
 		const Company *c;
-		const Livery *livery, *default_livery = NULL;
+		const Livery *livery, *default_livery = nullptr;
 		bool primary = widget == WID_SCL_PRI_COL_DROPDOWN;
 		byte default_col;
 
@@ -603,7 +603,7 @@ private:
 		}
 
 		DropDownList list;
-		if (default_livery != NULL) {
+		if (default_livery != nullptr) {
 			/* Add COLOUR_END to put the colour out of range, but also allow us to show what the default is */
 			default_col = (primary ? default_livery->colour1 : default_livery->colour2) + COLOUR_END;
 			list.emplace_back(new DropDownListColourItem(default_col, false));
@@ -612,13 +612,13 @@ private:
 			list.emplace_back(new DropDownListColourItem(i, HasBit(used_colours, i)));
 		}
 
-		byte sel = (default_livery == NULL || HasBit(livery->in_use, primary ? 0 : 1)) ? (primary ? livery->colour1 : livery->colour2) : default_col;
+		byte sel = (default_livery == nullptr || HasBit(livery->in_use, primary ? 0 : 1)) ? (primary ? livery->colour1 : livery->colour2) : default_col;
 		ShowDropDownList(this, std::move(list), sel, widget);
 	}
 
 	static int CDECL GroupNameSorter(const Group * const *a, const Group * const *b)
 	{
-		static const Group *last_group[2] = { NULL, NULL };
+		static const Group *last_group[2] = { nullptr, nullptr };
 		static char         last_name[2][64] = { "", "" };
 
 		if (*a != last_group[0]) {
@@ -1100,7 +1100,7 @@ static WindowDesc _select_company_livery
 void ShowCompanyLiveryWindow(CompanyID company, GroupID group)
 {
 	SelectCompanyLiveryWindow *w = (SelectCompanyLiveryWindow *)BringWindowToFrontById(WC_COMPANY_COLOUR, company);
-	if (w == NULL) {
+	if (w == nullptr) {
 		new SelectCompanyLiveryWindow(&_select_company_livery_desc, company, group);
 	} else if (group != INVALID_GROUP) {
 		w->SetSelectedGroup(company, group);
@@ -1711,10 +1711,10 @@ public:
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 		/* Set a new company manager face number */
 		if (!StrEmpty(str)) {
-			this->face = strtoul(str, NULL, 10);
+			this->face = strtoul(str, nullptr, 10);
 			ScaleAllCompanyManagerFaceBits(this->face);
 			ShowErrorMessage(STR_FACE_FACECODE_SET, INVALID_STRING_ID, WL_INFO);
 			this->UpdateData();
@@ -2633,17 +2633,17 @@ struct CompanyWindow : Window
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
 		switch (this->query_widget) {
 			default: NOT_REACHED();
 
 			case WID_C_PRESIDENT_NAME:
-				DoCommandP(0, 0, 0, CMD_RENAME_PRESIDENT | CMD_MSG(STR_ERROR_CAN_T_CHANGE_PRESIDENT), NULL, str);
+				DoCommandP(0, 0, 0, CMD_RENAME_PRESIDENT | CMD_MSG(STR_ERROR_CAN_T_CHANGE_PRESIDENT), nullptr, str);
 				break;
 
 			case WID_C_COMPANY_NAME:
-				DoCommandP(0, 0, 0, CMD_RENAME_COMPANY | CMD_MSG(STR_ERROR_CAN_T_CHANGE_COMPANY_NAME), NULL, str);
+				DoCommandP(0, 0, 0, CMD_RENAME_COMPANY | CMD_MSG(STR_ERROR_CAN_T_CHANGE_COMPANY_NAME), nullptr, str);
 				break;
 
 			case WID_C_COMPANY_JOIN:
@@ -2796,7 +2796,7 @@ static const NWidgetPart _nested_buy_com
 };
 
 static WindowDesc _buy_company_desc(
-	WDP_AUTO, NULL, 0, 0,
+	WDP_AUTO, nullptr, 0, 0,
 	WC_BUY_COMPANY, WC_NONE,
 	WDF_CONSTRUCTION,
 	_nested_buy_company_widgets, lengthof(_nested_buy_company_widgets)
diff --git a/src/console.cpp b/src/console.cpp
--- a/src/console.cpp
+++ b/src/console.cpp
@@ -32,7 +32,7 @@ FILE *_iconsole_output_file;
 
 void IConsoleInit()
 {
-	_iconsole_output_file = NULL;
+	_iconsole_output_file = nullptr;
 	_redirect_console_to_client = INVALID_CLIENT_ID;
 	_redirect_console_to_admin  = INVALID_ADMIN_ID;
 
@@ -43,14 +43,14 @@ void IConsoleInit()
 
 static void IConsoleWriteToLogFile(const char *string)
 {
-	if (_iconsole_output_file != NULL) {
+	if (_iconsole_output_file != nullptr) {
 		/* if there is an console output file ... also print it there */
 		const char *header = GetLogPrefix();
 		if ((strlen(header) != 0 && fwrite(header, strlen(header), 1, _iconsole_output_file) != 1) ||
 				fwrite(string, strlen(string), 1, _iconsole_output_file) != 1 ||
 				fwrite("\n", 1, 1, _iconsole_output_file) != 1) {
 			fclose(_iconsole_output_file);
-			_iconsole_output_file = NULL;
+			_iconsole_output_file = nullptr;
 			IConsolePrintF(CC_DEFAULT, "cannot write to log file");
 		}
 	}
@@ -58,10 +58,10 @@ static void IConsoleWriteToLogFile(const
 
 bool CloseConsoleLogIfActive()
 {
-	if (_iconsole_output_file != NULL) {
+	if (_iconsole_output_file != nullptr) {
 		IConsolePrintF(CC_DEFAULT, "file output complete");
 		fclose(_iconsole_output_file);
-		_iconsole_output_file = NULL;
+		_iconsole_output_file = nullptr;
 		return true;
 	}
 
@@ -203,22 +203,22 @@ bool GetArgumentInteger(uint32 *value, c
 template<class T>
 void IConsoleAddSorted(T **base, T *item_new)
 {
-	if (*base == NULL) {
+	if (*base == nullptr) {
 		*base = item_new;
 		return;
 	}
 
-	T *item_before = NULL;
+	T *item_before = nullptr;
 	T *item = *base;
 	/* The list is alphabetically sorted, insert the new item at the correct location */
-	while (item != NULL) {
+	while (item != nullptr) {
 		if (strcmp(item->name, item_new->name) > 0) break; // insert here
 
 		item_before = item;
 		item = item->next;
 	}
 
-	if (item_before == NULL) {
+	if (item_before == nullptr) {
 		*base = item_new;
 	} else {
 		item_before->next = item_new;
@@ -251,7 +251,7 @@ void IConsoleCmdRegister(const char *nam
 {
 	IConsoleCmd *item_new = MallocT<IConsoleCmd>(1);
 	item_new->name = RemoveUnderscores(stredup(name));
-	item_new->next = NULL;
+	item_new->next = nullptr;
 	item_new->proc = proc;
 	item_new->hook = hook;
 
@@ -261,16 +261,16 @@ void IConsoleCmdRegister(const char *nam
 /**
  * Find the command pointed to by its string
  * @param name command to be found
- * @return return Cmdstruct of the found command, or NULL on failure
+ * @return return Cmdstruct of the found command, or nullptr on failure
  */
 IConsoleCmd *IConsoleCmdGet(const char *name)
 {
 	IConsoleCmd *item;
 
-	for (item = _iconsole_cmds; item != NULL; item = item->next) {
+	for (item = _iconsole_cmds; item != nullptr; item = item->next) {
 		if (strcmp(item->name, name) == 0) return item;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -280,7 +280,7 @@ IConsoleCmd *IConsoleCmdGet(const char *
  */
 void IConsoleAliasRegister(const char *name, const char *cmd)
 {
-	if (IConsoleAliasGet(name) != NULL) {
+	if (IConsoleAliasGet(name) != nullptr) {
 		IConsoleError("an alias with this name already exists; insertion aborted");
 		return;
 	}
@@ -289,7 +289,7 @@ void IConsoleAliasRegister(const char *n
 	char *cmd_aliased = stredup(cmd);
 	IConsoleAlias *item_new = MallocT<IConsoleAlias>(1);
 
-	item_new->next = NULL;
+	item_new->next = nullptr;
 	item_new->cmdline = cmd_aliased;
 	item_new->name = new_alias;
 
@@ -299,17 +299,17 @@ void IConsoleAliasRegister(const char *n
 /**
  * Find the alias pointed to by its string
  * @param name alias to be found
- * @return return Aliasstruct of the found alias, or NULL on failure
+ * @return return Aliasstruct of the found alias, or nullptr on failure
  */
 IConsoleAlias *IConsoleAliasGet(const char *name)
 {
 	IConsoleAlias *item;
 
-	for (item = _iconsole_aliases; item != NULL; item = item->next) {
+	for (item = _iconsole_aliases; item != nullptr; item = item->next) {
 		if (strcmp(item->name, name) == 0) return item;
 	}
 
-	return NULL;
+	return nullptr;
 }
 /**
  * An alias is just another name for a command, or for more commands
@@ -478,7 +478,7 @@ void IConsoleCmdExec(const char *cmdstr)
 		}
 	}
 
-	for (uint i = 0; i < lengthof(tokens) && tokens[i] != NULL; i++) {
+	for (uint i = 0; i < lengthof(tokens) && tokens[i] != nullptr; i++) {
 		DEBUG(console, 8, "Token %d is: '%s'", i, tokens[i]);
 	}
 
@@ -489,12 +489,12 @@ void IConsoleCmdExec(const char *cmdstr)
 	 */
 	RemoveUnderscores(tokens[0]);
 	IConsoleCmd *cmd = IConsoleCmdGet(tokens[0]);
-	if (cmd != NULL) {
-		ConsoleHookResult chr = (cmd->hook == NULL ? CHR_ALLOW : cmd->hook(true));
+	if (cmd != nullptr) {
+		ConsoleHookResult chr = (cmd->hook == nullptr ? CHR_ALLOW : cmd->hook(true));
 		switch (chr) {
 			case CHR_ALLOW:
 				if (!cmd->proc(t_index, tokens)) { // index started with 0
-					cmd->proc(0, NULL); // if command failed, give help
+					cmd->proc(0, nullptr); // if command failed, give help
 				}
 				return;
 
@@ -505,7 +505,7 @@ void IConsoleCmdExec(const char *cmdstr)
 
 	t_index--;
 	IConsoleAlias *alias = IConsoleAliasGet(tokens[0]);
-	if (alias != NULL) {
+	if (alias != nullptr) {
 		IConsoleAliasExec(alias, t_index, &tokens[1]);
 		return;
 	}
diff --git a/src/console_cmds.cpp b/src/console_cmds.cpp
--- a/src/console_cmds.cpp
+++ b/src/console_cmds.cpp
@@ -349,7 +349,7 @@ DEF_CONSOLE_CMD(ConLoad)
 	const char *file = argv[1];
 	_console_file_list.ValidateFileList();
 	const FiosItem *item = _console_file_list.FindItem(file);
-	if (item != NULL) {
+	if (item != nullptr) {
 		if (GetAbstractFileType(item->type) == FT_SAVEGAME) {
 			_switch_mode = SM_LOAD_GAME;
 			_file_to_saveload.SetMode(item->type);
@@ -378,7 +378,7 @@ DEF_CONSOLE_CMD(ConRemove)
 	const char *file = argv[1];
 	_console_file_list.ValidateFileList();
 	const FiosItem *item = _console_file_list.FindItem(file);
-	if (item != NULL) {
+	if (item != nullptr) {
 		if (!FiosDelete(item->name)) {
 			IConsolePrintF(CC_ERROR, "%s: Failed to delete file", file);
 		}
@@ -420,7 +420,7 @@ DEF_CONSOLE_CMD(ConChangeDirectory)
 	const char *file = argv[1];
 	_console_file_list.ValidateFileList(true);
 	const FiosItem *item = _console_file_list.FindItem(file);
-	if (item != NULL) {
+	if (item != nullptr) {
 		switch (item->type) {
 			case FIOS_TYPE_DIR: case FIOS_TYPE_DRIVE: case FIOS_TYPE_PARENT:
 				FiosBrowseTo(item);
@@ -448,7 +448,7 @@ DEF_CONSOLE_CMD(ConPrintWorkingDirectory
 	_console_file_list.ValidateFileList(true);
 	_console_file_list.InvalidateFileList();
 
-	FiosGetDescText(&path, NULL);
+	FiosGetDescText(&path, nullptr);
 	IConsolePrint(CC_DEFAULT, path);
 	return true;
 }
@@ -474,7 +474,7 @@ static bool ConKickOrBan(const char *arg
 {
 	uint n;
 
-	if (strchr(argv, '.') == NULL && strchr(argv, ':') == NULL) { // banning with ID
+	if (strchr(argv, '.') == nullptr && strchr(argv, ':') == nullptr) { // banning with ID
 		ClientID client_id = (ClientID)atoi(argv);
 
 		/* Don't kill the server, or the client doing the rcon. The latter can't be kicked because
@@ -487,7 +487,7 @@ static bool ConKickOrBan(const char *arg
 		}
 
 		NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(client_id);
-		if (ci == NULL) {
+		if (ci == nullptr) {
 			IConsoleError("Invalid client");
 			return true;
 		}
@@ -688,7 +688,7 @@ DEF_CONSOLE_CMD(ConClientNickChange)
 		return true;
 	}
 
-	if (NetworkClientInfo::GetByClientID(client_id) == NULL) {
+	if (NetworkClientInfo::GetByClientID(client_id) == nullptr) {
 		IConsoleError("Invalid client");
 		return true;
 	}
@@ -759,7 +759,7 @@ DEF_CONSOLE_CMD(ConMoveClient)
 	CompanyID company_id = (CompanyID)(atoi(argv[2]) <= MAX_COMPANIES ? atoi(argv[2]) - 1 : atoi(argv[2]));
 
 	/* check the client exists */
-	if (ci == NULL) {
+	if (ci == nullptr) {
 		IConsoleError("Invalid client-id, check the command 'clients' for valid client-id's.");
 		return true;
 	}
@@ -887,8 +887,8 @@ DEF_CONSOLE_CMD(ConNetworkConnect)
 	if (argc < 2) return false;
 	if (_networking) NetworkDisconnect(); // we are in network-mode, first close it!
 
-	const char *port = NULL;
-	const char *company = NULL;
+	const char *port = nullptr;
+	const char *company = nullptr;
 	char *ip = argv[1];
 	/* Default settings: default port and new company */
 	uint16 rport = NETWORK_DEFAULT_PORT;
@@ -897,7 +897,7 @@ DEF_CONSOLE_CMD(ConNetworkConnect)
 	ParseConnectionString(&company, &port, ip);
 
 	IConsolePrintF(CC_DEFAULT, "Connecting to %s...", ip);
-	if (company != NULL) {
+	if (company != nullptr) {
 		join_as = (CompanyID)atoi(company);
 		IConsolePrintF(CC_DEFAULT, "    company-no: %d", join_as);
 
@@ -908,7 +908,7 @@ DEF_CONSOLE_CMD(ConNetworkConnect)
 			join_as--;
 		}
 	}
-	if (port != NULL) {
+	if (port != nullptr) {
 		rport = atoi(port);
 		IConsolePrintF(CC_DEFAULT, "    port: %s", port);
 	}
@@ -933,7 +933,7 @@ DEF_CONSOLE_CMD(ConExec)
 
 	FILE *script_file = FioFOpenFile(argv[1], "r", BASE_DIR);
 
-	if (script_file == NULL) {
+	if (script_file == nullptr) {
 		if (argc == 2 || atoi(argv[2]) != 0) IConsoleError("script file not found");
 		return true;
 	}
@@ -941,7 +941,7 @@ DEF_CONSOLE_CMD(ConExec)
 	_script_running = true;
 
 	char cmdline[ICON_CMDLN_SIZE];
-	while (_script_running && fgets(cmdline, sizeof(cmdline), script_file) != NULL) {
+	while (_script_running && fgets(cmdline, sizeof(cmdline), script_file) != nullptr) {
 		/* Remove newline characters from the executing script */
 		for (char *cmdptr = cmdline; *cmdptr != '\0'; cmdptr++) {
 			if (*cmdptr == '\n' || *cmdptr == '\r') {
@@ -992,7 +992,7 @@ DEF_CONSOLE_CMD(ConScript)
 
 		IConsolePrintF(CC_DEFAULT, "file output started to: %s", argv[1]);
 		_iconsole_output_file = fopen(argv[1], "ab");
-		if (_iconsole_output_file == NULL) IConsoleError("could not open file");
+		if (_iconsole_output_file == nullptr) IConsoleError("could not open file");
 	}
 
 	return true;
@@ -1031,7 +1031,7 @@ DEF_CONSOLE_CMD(ConNewGame)
 		return true;
 	}
 
-	StartNewGameWithoutGUI((argc == 2) ? strtoul(argv[1], NULL, 10) : GENERATE_NEW_SEED);
+	StartNewGameWithoutGUI((argc == 2) ? strtoul(argv[1], nullptr, 10) : GENERATE_NEW_SEED);
 	return true;
 }
 
@@ -1283,7 +1283,7 @@ DEF_CONSOLE_CMD(ConRescanNewGRF)
 		return true;
 	}
 
-	ScanNewGRFFiles(NULL);
+	ScanNewGRFFiles(nullptr);
 
 	return true;
 }
@@ -1326,7 +1326,7 @@ DEF_CONSOLE_CMD(ConAlias)
 	if (argc < 3) return false;
 
 	alias = IConsoleAliasGet(argv[1]);
-	if (alias == NULL) {
+	if (alias == nullptr) {
 		IConsoleAliasRegister(argv[1], argv[2]);
 	} else {
 		free(alias->cmdline);
@@ -1348,7 +1348,7 @@ DEF_CONSOLE_CMD(ConScreenShot)
 	if (argc > 3) return false;
 
 	ScreenshotType type = SC_VIEWPORT;
-	const char *name = NULL;
+	const char *name = nullptr;
 
 	if (argc > 1) {
 		if (strcmp(argv[1], "big") == 0) {
@@ -1386,7 +1386,7 @@ DEF_CONSOLE_CMD(ConInfoCmd)
 	if (argc < 2) return false;
 
 	const IConsoleCmd *cmd = IConsoleCmdGet(argv[1]);
-	if (cmd == NULL) {
+	if (cmd == nullptr) {
 		IConsoleError("the given command was not found");
 		return true;
 	}
@@ -1394,7 +1394,7 @@ DEF_CONSOLE_CMD(ConInfoCmd)
 	IConsolePrintF(CC_DEFAULT, "command name: %s", cmd->name);
 	IConsolePrintF(CC_DEFAULT, "command proc: %p", cmd->proc);
 
-	if (cmd->hook != NULL) IConsoleWarning("command is hooked");
+	if (cmd->hook != nullptr) IConsoleWarning("command is hooked");
 
 	return true;
 }
@@ -1452,16 +1452,16 @@ DEF_CONSOLE_CMD(ConHelp)
 
 		RemoveUnderscores(argv[1]);
 		cmd = IConsoleCmdGet(argv[1]);
-		if (cmd != NULL) {
-			cmd->proc(0, NULL);
+		if (cmd != nullptr) {
+			cmd->proc(0, nullptr);
 			return true;
 		}
 
 		alias = IConsoleAliasGet(argv[1]);
-		if (alias != NULL) {
+		if (alias != nullptr) {
 			cmd = IConsoleCmdGet(alias->cmdline);
-			if (cmd != NULL) {
-				cmd->proc(0, NULL);
+			if (cmd != nullptr) {
+				cmd->proc(0, nullptr);
 				return true;
 			}
 			IConsolePrintF(CC_ERROR, "ERROR: alias is of special type, please see its execution-line: '%s'", alias->cmdline);
@@ -1491,9 +1491,9 @@ DEF_CONSOLE_CMD(ConListCommands)
 		return true;
 	}
 
-	for (const IConsoleCmd *cmd = _iconsole_cmds; cmd != NULL; cmd = cmd->next) {
-		if (argv[1] == NULL || strstr(cmd->name, argv[1]) != NULL) {
-			if (cmd->hook == NULL || cmd->hook(false) != CHR_HIDE) IConsolePrintF(CC_DEFAULT, "%s", cmd->name);
+	for (const IConsoleCmd *cmd = _iconsole_cmds; cmd != nullptr; cmd = cmd->next) {
+		if (argv[1] == nullptr || strstr(cmd->name, argv[1]) != nullptr) {
+			if (cmd->hook == nullptr || cmd->hook(false) != CHR_HIDE) IConsolePrintF(CC_DEFAULT, "%s", cmd->name);
 		}
 	}
 
@@ -1507,8 +1507,8 @@ DEF_CONSOLE_CMD(ConListAliases)
 		return true;
 	}
 
-	for (const IConsoleAlias *alias = _iconsole_aliases; alias != NULL; alias = alias->next) {
-		if (argv[1] == NULL || strstr(alias->name, argv[1]) != NULL) {
+	for (const IConsoleAlias *alias = _iconsole_aliases; alias != nullptr; alias = alias->next) {
+		if (argv[1] == nullptr || strstr(alias->name, argv[1]) != nullptr) {
 			IConsolePrintF(CC_DEFAULT, "%s => %s", alias->name, alias->cmdline);
 		}
 	}
@@ -1717,8 +1717,8 @@ static void OutputContentState(const Con
 
 DEF_CONSOLE_CMD(ConContent)
 {
-	static ContentCallback *cb = NULL;
-	if (cb == NULL) {
+	static ContentCallback *cb = nullptr;
+	if (cb == nullptr) {
 		cb = new ConsoleContentCallback();
 		_network_content_client.AddCallback(cb);
 	}
@@ -1776,7 +1776,7 @@ DEF_CONSOLE_CMD(ConContent)
 	if (strcasecmp(argv[1], "state") == 0) {
 		IConsolePrintF(CC_WHITE, "id, type, state, name");
 		for (ConstContentIterator iter = _network_content_client.Begin(); iter != _network_content_client.End(); iter++) {
-			if (argc > 2 && strcasestr((*iter)->name, argv[2]) == NULL) continue;
+			if (argc > 2 && strcasestr((*iter)->name, argv[2]) == nullptr) continue;
 			OutputContentState(*iter);
 		}
 		return true;
@@ -1841,7 +1841,7 @@ DEF_CONSOLE_CMD(ConListSettings)
 
 	if (argc > 2) return false;
 
-	IConsoleListSettings((argc == 2) ? argv[1] : NULL);
+	IConsoleListSettings((argc == 2) ? argv[1] : nullptr);
 	return true;
 }
 
diff --git a/src/console_gui.cpp b/src/console_gui.cpp
--- a/src/console_gui.cpp
+++ b/src/console_gui.cpp
@@ -78,7 +78,7 @@ struct IConsoleLine {
 	static const IConsoleLine *Get(uint index)
 	{
 		const IConsoleLine *item = IConsoleLine::front;
-		while (index != 0 && item != NULL) {
+		while (index != 0 && item != nullptr) {
 			index--;
 			item = item->previous;
 		}
@@ -96,14 +96,14 @@ struct IConsoleLine {
 	static bool Truncate()
 	{
 		IConsoleLine *cur = IConsoleLine::front;
-		if (cur == NULL) return false;
+		if (cur == nullptr) return false;
 
 		int count = 1;
-		for (IConsoleLine *item = cur->previous; item != NULL; count++, cur = item, item = item->previous) {
+		for (IConsoleLine *item = cur->previous; item != nullptr; count++, cur = item, item = item->previous) {
 			if (item->time > _settings_client.gui.console_backlog_timeout &&
 					count > _settings_client.gui.console_backlog_length) {
 				delete item;
-				cur->previous = NULL;
+				cur->previous = nullptr;
 				return true;
 			}
 
@@ -119,12 +119,12 @@ struct IConsoleLine {
 	static void Reset()
 	{
 		delete IConsoleLine::front;
-		IConsoleLine::front = NULL;
+		IConsoleLine::front = nullptr;
 		IConsoleLine::size = 0;
 	}
 };
 
-/* static */ IConsoleLine *IConsoleLine::front = NULL;
+/* static */ IConsoleLine *IConsoleLine::front = nullptr;
 /* static */ int IConsoleLine::size  = 0;
 
 
@@ -162,7 +162,7 @@ static const struct NWidgetPart _nested_
 };
 
 static WindowDesc _console_window_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_CONSOLE, WC_NONE,
 	0,
 	_nested_console_window_widgets, lengthof(_nested_console_window_widgets)
@@ -207,7 +207,7 @@ struct IConsoleWindow : Window
 
 		GfxFillRect(0, 0, this->width - 1, this->height - 1, PC_BLACK);
 		int ypos = this->height - this->line_height;
-		for (const IConsoleLine *print = IConsoleLine::Get(IConsoleWindow::scroll); print != NULL; print = print->previous) {
+		for (const IConsoleLine *print = IConsoleLine::Get(IConsoleWindow::scroll); print != nullptr; print = print->previous) {
 			SetDParamStr(0, print->buffer);
 			ypos = DrawStringMultiLine(5, right, -this->line_height, ypos, STR_JUST_RAW_STRING, print->colour, SA_LEFT | SA_BOTTOM | SA_FORCE) - ICON_LINE_SPACING;
 			if (ypos < 0) break;
@@ -287,7 +287,7 @@ struct IConsoleWindow : Window
 				const char *cmd = IConsoleHistoryAdd(_iconsole_cmdline.buf);
 				IConsoleClearCommand();
 
-				if (cmd != NULL) IConsoleCmdExec(cmd);
+				if (cmd != nullptr) IConsoleCmdExec(cmd);
 				break;
 			}
 
@@ -335,7 +335,7 @@ struct IConsoleWindow : Window
 
 	const char *GetMarkedText(size_t *length) const override
 	{
-		if (_iconsole_cmdline.markend == 0) return NULL;
+		if (_iconsole_cmdline.markend == 0) return nullptr;
 
 		*length = _iconsole_cmdline.markend - _iconsole_cmdline.markpos;
 		return _iconsole_cmdline.buf + _iconsole_cmdline.markpos;
@@ -364,7 +364,7 @@ struct IConsoleWindow : Window
 	{
 		int delta = min(this->width - this->line_offset - _iconsole_cmdline.pixels - ICON_RIGHT_BORDERWIDTH, 0);
 
-		if (!IsInsideMM(pt.y, this->height - this->line_height, this->height)) return NULL;
+		if (!IsInsideMM(pt.y, this->height - this->line_height, this->height)) return nullptr;
 
 		return GetCharAtPosition(_iconsole_cmdline.buf, pt.x - delta);
 	}
@@ -459,10 +459,10 @@ static const char *IConsoleHistoryAdd(co
 	while (IsWhitespace(*cmd)) cmd++;
 
 	/* Do not put empty command in history */
-	if (StrEmpty(cmd)) return NULL;
+	if (StrEmpty(cmd)) return nullptr;
 
 	/* Do not put in history if command is same as previous */
-	if (_iconsole_history[0] == NULL || strcmp(_iconsole_history[0], cmd) != 0) {
+	if (_iconsole_history[0] == nullptr || strcmp(_iconsole_history[0], cmd) != 0) {
 		free(_iconsole_history[ICON_HISTORY_SIZE - 1]);
 		memmove(&_iconsole_history[1], &_iconsole_history[0], sizeof(_iconsole_history[0]) * (ICON_HISTORY_SIZE - 1));
 		_iconsole_history[0] = stredup(cmd);
@@ -479,10 +479,10 @@ static const char *IConsoleHistoryAdd(co
  */
 static void IConsoleHistoryNavigate(int direction)
 {
-	if (_iconsole_history[0] == NULL) return; // Empty history
+	if (_iconsole_history[0] == nullptr) return; // Empty history
 	_iconsole_historypos = Clamp(_iconsole_historypos + direction, -1, ICON_HISTORY_SIZE - 1);
 
-	if (direction > 0 && _iconsole_history[_iconsole_historypos] == NULL) _iconsole_historypos--;
+	if (direction > 0 && _iconsole_history[_iconsole_historypos] == nullptr) _iconsole_historypos--;
 
 	if (_iconsole_historypos == -1) {
 		_iconsole_cmdline.DeleteAll();
diff --git a/src/console_internal.h b/src/console_internal.h
--- a/src/console_internal.h
+++ b/src/console_internal.h
@@ -69,7 +69,7 @@ extern IConsoleAlias *_iconsole_aliases;
 void IConsoleClearBuffer();
 
 /* Commands */
-void IConsoleCmdRegister(const char *name, IConsoleCmdProc *proc, IConsoleHook *hook = NULL);
+void IConsoleCmdRegister(const char *name, IConsoleCmdProc *proc, IConsoleHook *hook = nullptr);
 void IConsoleAliasRegister(const char *name, const char *cmd);
 IConsoleCmd *IConsoleCmdGet(const char *name);
 IConsoleAlias *IConsoleAliasGet(const char *name);
diff --git a/src/core/alloc_func.hpp b/src/core/alloc_func.hpp
--- a/src/core/alloc_func.hpp
+++ b/src/core/alloc_func.hpp
@@ -53,23 +53,23 @@ static inline void CheckAllocationConstr
  * @note the memory contains garbage data (i.e. possibly non-zero values).
  * @tparam T the type of the variable(s) to allocation.
  * @param num_elements the number of elements to allocate of the given type.
- * @return NULL when num_elements == 0, non-NULL otherwise.
+ * @return nullptr when num_elements == 0, non-nullptr otherwise.
  */
 template <typename T>
 static inline T *MallocT(size_t num_elements)
 {
 	/*
 	 * MorphOS cannot handle 0 elements allocations, or rather that always
-	 * returns NULL. So we do that for *all* allocations, thus causing it
+	 * returns nullptr. So we do that for *all* allocations, thus causing it
 	 * to behave the same on all OSes.
 	 */
-	if (num_elements == 0) return NULL;
+	if (num_elements == 0) return nullptr;
 
 	/* Ensure the size does not overflow. */
 	CheckAllocationConstraints<T>(num_elements);
 
 	T *t_ptr = (T*)malloc(num_elements * sizeof(T));
-	if (t_ptr == NULL) MallocError(num_elements * sizeof(T));
+	if (t_ptr == nullptr) MallocError(num_elements * sizeof(T));
 	return t_ptr;
 }
 
@@ -81,20 +81,20 @@ static inline T *MallocT(size_t num_elem
  * @note the memory contains all zero values.
  * @tparam T the type of the variable(s) to allocation.
  * @param num_elements the number of elements to allocate of the given type.
- * @return NULL when num_elements == 0, non-NULL otherwise.
+ * @return nullptr when num_elements == 0, non-nullptr otherwise.
  */
 template <typename T>
 static inline T *CallocT(size_t num_elements)
 {
 	/*
 	 * MorphOS cannot handle 0 elements allocations, or rather that always
-	 * returns NULL. So we do that for *all* allocations, thus causing it
+	 * returns nullptr. So we do that for *all* allocations, thus causing it
 	 * to behave the same on all OSes.
 	 */
-	if (num_elements == 0) return NULL;
+	if (num_elements == 0) return nullptr;
 
 	T *t_ptr = (T*)calloc(num_elements, sizeof(T));
-	if (t_ptr == NULL) MallocError(num_elements * sizeof(T));
+	if (t_ptr == nullptr) MallocError(num_elements * sizeof(T));
 	return t_ptr;
 }
 
@@ -107,26 +107,26 @@ static inline T *CallocT(size_t num_elem
  * @tparam T the type of the variable(s) to allocation.
  * @param t_ptr the previous allocation to extend/shrink.
  * @param num_elements the number of elements to allocate of the given type.
- * @return NULL when num_elements == 0, non-NULL otherwise.
+ * @return nullptr when num_elements == 0, non-nullptr otherwise.
  */
 template <typename T>
 static inline T *ReallocT(T *t_ptr, size_t num_elements)
 {
 	/*
 	 * MorphOS cannot handle 0 elements allocations, or rather that always
-	 * returns NULL. So we do that for *all* allocations, thus causing it
+	 * returns nullptr. So we do that for *all* allocations, thus causing it
 	 * to behave the same on all OSes.
 	 */
 	if (num_elements == 0) {
 		free(t_ptr);
-		return NULL;
+		return nullptr;
 	}
 
 	/* Ensure the size does not overflow. */
 	CheckAllocationConstraints<T>(num_elements);
 
 	t_ptr = (T*)realloc(static_cast<void *>(t_ptr), num_elements * sizeof(T));
-	if (t_ptr == NULL) ReallocError(num_elements * sizeof(T));
+	if (t_ptr == nullptr) ReallocError(num_elements * sizeof(T));
 	return t_ptr;
 }
 
diff --git a/src/core/alloc_type.hpp b/src/core/alloc_type.hpp
--- a/src/core/alloc_type.hpp
+++ b/src/core/alloc_type.hpp
@@ -73,7 +73,7 @@ private:
 
 public:
 	/** Create a new buffer */
-	ReusableBuffer() : buffer(NULL), count(0) {}
+	ReusableBuffer() : buffer(nullptr), count(0) {}
 	/** Clear the buffer */
 	~ReusableBuffer() { free(this->buffer); }
 
diff --git a/src/core/kdtree.hpp b/src/core/kdtree.hpp
--- a/src/core/kdtree.hpp
+++ b/src/core/kdtree.hpp
@@ -108,11 +108,11 @@ class Kdtree {
 		std::vector<T> elements = this->FreeSubtree(this->root);
 		elements.push_back(root_element);
 
-		if (include_element != NULL) {
+		if (include_element != nullptr) {
 			elements.push_back(*include_element);
 			initial_count++;
 		}
-		if (exclude_element != NULL) {
+		if (exclude_element != nullptr) {
 			typename std::vector<T>::iterator removed = std::remove(elements.begin(), elements.end(), *exclude_element);
 			elements.erase(removed, elements.end());
 			initial_count--;
@@ -377,7 +377,7 @@ public:
 	 */
 	void Rebuild()
 	{
-		this->Rebuild(NULL, NULL);
+		this->Rebuild(nullptr, nullptr);
 	}
 
 	/**
@@ -390,7 +390,7 @@ public:
 		if (this->Count() == 0) {
 			this->root = this->AddNode(element);
 		} else {
-			if (!this->IsUnbalanced() || !this->Rebuild(&element, NULL)) {
+			if (!this->IsUnbalanced() || !this->Rebuild(&element, nullptr)) {
 				this->InsertRecursive(element, this->root, 0);
 				this->IncrementUnbalanced();
 			}
@@ -408,7 +408,7 @@ public:
 	{
 		size_t count = this->Count();
 		if (count == 0) return;
-		if (!this->IsUnbalanced() || !this->Rebuild(NULL, &element)) {
+		if (!this->IsUnbalanced() || !this->Rebuild(nullptr, &element)) {
 			/* If the removed element is the root node, this modifies this->root */
 			this->root = this->RemoveRecursive(element, this->root, 0);
 			this->IncrementUnbalanced();
diff --git a/src/core/mem_func.hpp b/src/core/mem_func.hpp
--- a/src/core/mem_func.hpp
+++ b/src/core/mem_func.hpp
@@ -78,7 +78,7 @@ static inline int MemCmpT(const T *ptr1,
 template <typename T>
 static inline void MemReverseT(T *ptr1, T *ptr2)
 {
-	assert(ptr1 != NULL && ptr2 != NULL);
+	assert(ptr1 != nullptr && ptr2 != nullptr);
 	assert(ptr1 < ptr2);
 
 	do {
@@ -95,7 +95,7 @@ static inline void MemReverseT(T *ptr1, 
 template <typename T>
 static inline void MemReverseT(T *ptr, size_t num)
 {
-	assert(ptr != NULL);
+	assert(ptr != nullptr);
 
 	MemReverseT(ptr, ptr + (num - 1));
 }
diff --git a/src/core/pool_func.hpp b/src/core/pool_func.hpp
--- a/src/core/pool_func.hpp
+++ b/src/core/pool_func.hpp
@@ -39,8 +39,8 @@ DEFINE_POOL_METHOD(inline)::Pool(const c
 		checked(0),
 #endif /* OTTD_ASSERT */
 		cleaning(false),
-		data(NULL),
-		alloc_cache(NULL)
+		data(nullptr),
+		alloc_cache(nullptr)
 { }
 
 /**
@@ -71,7 +71,7 @@ DEFINE_POOL_METHOD(inline size_t)::FindF
 	size_t index = this->first_free;
 
 	for (; index < this->first_unused; index++) {
-		if (this->data[index] == NULL) return index;
+		if (this->data[index] == nullptr) return index;
 	}
 
 	if (index < this->size) {
@@ -96,17 +96,17 @@ DEFINE_POOL_METHOD(inline size_t)::FindF
  * @param size size of item
  * @param index index of item
  * @pre index < this->size
- * @pre this->Get(index) == NULL
+ * @pre this->Get(index) == nullptr
  */
 DEFINE_POOL_METHOD(inline void *)::AllocateItem(size_t size, size_t index)
 {
-	assert(this->data[index] == NULL);
+	assert(this->data[index] == nullptr);
 
 	this->first_unused = max(this->first_unused, index + 1);
 	this->items++;
 
 	Titem *item;
-	if (Tcache && this->alloc_cache != NULL) {
+	if (Tcache && this->alloc_cache != nullptr) {
 		assert(sizeof(Titem) == size);
 		item = (Titem *)this->alloc_cache;
 		this->alloc_cache = this->alloc_cache->next;
@@ -164,7 +164,7 @@ DEFINE_POOL_METHOD(void *)::GetNew(size_
 
 	if (index >= this->size) this->ResizeFor(index);
 
-	if (this->data[index] != NULL) {
+	if (this->data[index] != nullptr) {
 		SlErrorCorruptFmt("%s index " PRINTF_SIZE " already in use", this->name, index);
 	}
 
@@ -174,13 +174,13 @@ DEFINE_POOL_METHOD(void *)::GetNew(size_
 /**
  * Deallocates memory used by this index and marks item as free
  * @param index item to deallocate
- * @pre unit is allocated (non-NULL)
- * @note 'delete NULL' doesn't cause call of this function, so it is safe
+ * @pre unit is allocated (non-nullptr)
+ * @note 'delete nullptr' doesn't cause call of this function, so it is safe
  */
 DEFINE_POOL_METHOD(void)::FreeItem(size_t index)
 {
 	assert(index < this->size);
-	assert(this->data[index] != NULL);
+	assert(this->data[index] != nullptr);
 	if (Tcache) {
 		AllocCache *ac = (AllocCache *)this->data[index];
 		ac->next = this->alloc_cache;
@@ -188,7 +188,7 @@ DEFINE_POOL_METHOD(void)::FreeItem(size_
 	} else {
 		free(this->data[index]);
 	}
-	this->data[index] = NULL;
+	this->data[index] = nullptr;
 	this->first_free = min(this->first_free, index);
 	this->items--;
 	if (!this->cleaning) Titem::PostDestructor(index);
@@ -199,16 +199,16 @@ DEFINE_POOL_METHOD(void)::CleanPool()
 {
 	this->cleaning = true;
 	for (size_t i = 0; i < this->first_unused; i++) {
-		delete this->Get(i); // 'delete NULL;' is very valid
+		delete this->Get(i); // 'delete nullptr;' is very valid
 	}
 	assert(this->items == 0);
 	free(this->data);
 	this->first_unused = this->first_free = this->size = 0;
-	this->data = NULL;
+	this->data = nullptr;
 	this->cleaning = false;
 
 	if (Tcache) {
-		while (this->alloc_cache != NULL) {
+		while (this->alloc_cache != nullptr) {
 			AllocCache *ac = this->alloc_cache;
 			this->alloc_cache = ac->next;
 			free(ac);
diff --git a/src/core/pool_type.hpp b/src/core/pool_type.hpp
--- a/src/core/pool_type.hpp
+++ b/src/core/pool_type.hpp
@@ -91,7 +91,7 @@ struct Pool : PoolBase {
 	size_t size;         ///< Current allocated size
 	size_t first_free;   ///< No item with index lower than this is free (doesn't say anything about this one!)
 	size_t first_unused; ///< This and all higher indexes are free (doesn't say anything about first_unused-1 !)
-	size_t items;        ///< Number of used indexes (non-NULL)
+	size_t items;        ///< Number of used indexes (non-nullptr)
 #ifdef OTTD_ASSERT
 	size_t checked;      ///< Number of items we checked for
 #endif /* OTTD_ASSERT */
@@ -115,13 +115,13 @@ struct Pool : PoolBase {
 	}
 
 	/**
-	 * Tests whether given index can be used to get valid (non-NULL) Titem
+	 * Tests whether given index can be used to get valid (non-nullptr) Titem
 	 * @param index index to examine
-	 * @return true if PoolItem::Get(index) will return non-NULL pointer
+	 * @return true if PoolItem::Get(index) will return non-nullptr pointer
 	 */
 	inline bool IsValidID(size_t index)
 	{
-		return index < this->first_unused && this->Get(index) != NULL;
+		return index < this->first_unused && this->Get(index) != nullptr;
 	}
 
 	/**
@@ -150,7 +150,7 @@ struct Pool : PoolBase {
 		 * Allocates space for new Titem
 		 * @param size size of Titem
 		 * @return pointer to allocated memory
-		 * @note can never fail (return NULL), use CanAllocate() to check first!
+		 * @note can never fail (return nullptr), use CanAllocate() to check first!
 		 */
 		inline void *operator new(size_t size)
 		{
@@ -164,7 +164,7 @@ struct Pool : PoolBase {
 		 */
 		inline void operator delete(void *p)
 		{
-			if (p == NULL) return;
+			if (p == nullptr) return;
 			Titem *pn = (Titem *)p;
 			assert(pn == Tpool->Get(pn->index));
 			Tpool->FreeItem(pn->index);
@@ -175,7 +175,7 @@ struct Pool : PoolBase {
 		 * @param size size of Titem
 		 * @param index index of item
 		 * @return pointer to allocated memory
-		 * @note can never fail (return NULL), use CanAllocate() to check first!
+		 * @note can never fail (return nullptr), use CanAllocate() to check first!
 		 * @pre index has to be unused! Else it will crash
 		 */
 		inline void *operator new(size_t size, size_t index)
@@ -228,9 +228,9 @@ struct Pool : PoolBase {
 		}
 
 		/**
-		 * Tests whether given index can be used to get valid (non-NULL) Titem
+		 * Tests whether given index can be used to get valid (non-nullptr) Titem
 		 * @param index index to examine
-		 * @return true if PoolItem::Get(index) will return non-NULL pointer
+		 * @return true if PoolItem::Get(index) will return non-nullptr pointer
 		 */
 		static inline bool IsValidID(size_t index)
 		{
@@ -252,11 +252,11 @@ struct Pool : PoolBase {
 		 * Returns Titem with given index
 		 * @param index of item to get
 		 * @return pointer to Titem
-		 * @note returns NULL for invalid index
+		 * @note returns nullptr for invalid index
 		 */
 		static inline Titem *GetIfValid(size_t index)
 		{
-			return index < Tpool->first_unused ? Tpool->Get(index) : NULL;
+			return index < Tpool->first_unused ? Tpool->Get(index) : nullptr;
 		}
 
 		/**
@@ -282,7 +282,7 @@ struct Pool : PoolBase {
 		 * Dummy function called after destructor of each member.
 		 * If you want to use it, override it in PoolItem's subclass.
 		 * @param index index of deleted item
-		 * @note when this function is called, PoolItem::Get(index) == NULL.
+		 * @note when this function is called, PoolItem::Get(index) == nullptr.
 		 * @note it's called only when !CleaningPool()
 		 */
 		static inline void PostDestructor(size_t index) { }
@@ -314,8 +314,8 @@ private:
 };
 
 #define FOR_ALL_ITEMS_FROM(type, iter, var, start) \
-	for (size_t iter = start; var = NULL, iter < type::GetPoolSize(); iter++) \
-		if ((var = type::Get(iter)) != NULL)
+	for (size_t iter = start; var = nullptr, iter < type::GetPoolSize(); iter++) \
+		if ((var = type::Get(iter)) != nullptr)
 
 #define FOR_ALL_ITEMS(type, iter, var) FOR_ALL_ITEMS_FROM(type, iter, var, 0)
 
diff --git a/src/core/smallmatrix_type.hpp b/src/core/smallmatrix_type.hpp
--- a/src/core/smallmatrix_type.hpp
+++ b/src/core/smallmatrix_type.hpp
@@ -46,13 +46,13 @@ protected:
 
 public:
 
-	SmallMatrix() : data(NULL), width(0), height(0), capacity(0) {}
+	SmallMatrix() : data(nullptr), width(0), height(0), capacity(0) {}
 
 	/**
 	 * Copy constructor.
 	 * @param other The other matrix to copy.
 	 */
-	SmallMatrix(const SmallMatrix &other) : data(NULL), width(0), height(0), capacity(0)
+	SmallMatrix(const SmallMatrix &other) : data(nullptr), width(0), height(0), capacity(0)
 	{
 		this->Assign(other);
 	}
@@ -112,7 +112,7 @@ public:
 		this->width = 0;
 		this->capacity = 0;
 		free(this->data);
-		this->data = NULL;
+		this->data = nullptr;
 	}
 
 	/**
@@ -216,8 +216,8 @@ public:
 	inline void Resize(uint new_width, uint new_height)
 	{
 		uint new_capacity = new_width * new_height;
-		T *new_data = NULL;
-		void (*copy)(T *dest, const T *src, size_t count) = NULL;
+		T *new_data = nullptr;
+		void (*copy)(T *dest, const T *src, size_t count) = nullptr;
 		if (new_capacity > this->capacity) {
 			/* If the data doesn't fit into current capacity, resize and copy ... */
 			new_data = MallocT<T>(new_capacity);
diff --git a/src/core/sort_func.hpp b/src/core/sort_func.hpp
--- a/src/core/sort_func.hpp
+++ b/src/core/sort_func.hpp
@@ -53,8 +53,8 @@ static inline void GSortT(T *base, size_
 {
 	if (num < 2) return;
 
-	assert(base != NULL);
-	assert(comparator != NULL);
+	assert(base != nullptr);
+	assert(comparator != nullptr);
 
 	T *a = base;
 	T *b = base + 1;
diff --git a/src/crashlog.cpp b/src/crashlog.cpp
--- a/src/crashlog.cpp
+++ b/src/crashlog.cpp
@@ -70,9 +70,9 @@
 
 #include "safeguards.h"
 
-/* static */ const char *CrashLog::message = NULL;
-/* static */ char *CrashLog::gamelog_buffer = NULL;
-/* static */ const char *CrashLog::gamelog_last = NULL;
+/* static */ const char *CrashLog::message = nullptr;
+/* static */ char *CrashLog::gamelog_buffer = nullptr;
+/* static */ const char *CrashLog::gamelog_last = nullptr;
 
 char *CrashLog::LogCompiler(char *buffer, const char *last) const
 {
@@ -168,18 +168,18 @@ char *CrashLog::LogConfiguration(char *b
 			" Sound driver: %s\n"
 			" Sound set:    %s (%u)\n"
 			" Video driver: %s\n\n",
-			BlitterFactory::GetCurrentBlitter() == NULL ? "none" : BlitterFactory::GetCurrentBlitter()->GetName(),
-			BaseGraphics::GetUsedSet() == NULL ? "none" : BaseGraphics::GetUsedSet()->name,
-			BaseGraphics::GetUsedSet() == NULL ? UINT32_MAX : BaseGraphics::GetUsedSet()->version,
-			_current_language == NULL ? "none" : _current_language->file,
-			MusicDriver::GetInstance() == NULL ? "none" : MusicDriver::GetInstance()->GetName(),
-			BaseMusic::GetUsedSet() == NULL ? "none" : BaseMusic::GetUsedSet()->name,
-			BaseMusic::GetUsedSet() == NULL ? UINT32_MAX : BaseMusic::GetUsedSet()->version,
+			BlitterFactory::GetCurrentBlitter() == nullptr ? "none" : BlitterFactory::GetCurrentBlitter()->GetName(),
+			BaseGraphics::GetUsedSet() == nullptr ? "none" : BaseGraphics::GetUsedSet()->name,
+			BaseGraphics::GetUsedSet() == nullptr ? UINT32_MAX : BaseGraphics::GetUsedSet()->version,
+			_current_language == nullptr ? "none" : _current_language->file,
+			MusicDriver::GetInstance() == nullptr ? "none" : MusicDriver::GetInstance()->GetName(),
+			BaseMusic::GetUsedSet() == nullptr ? "none" : BaseMusic::GetUsedSet()->name,
+			BaseMusic::GetUsedSet() == nullptr ? UINT32_MAX : BaseMusic::GetUsedSet()->version,
 			_networking ? (_network_server ? "server" : "client") : "no",
-			SoundDriver::GetInstance() == NULL ? "none" : SoundDriver::GetInstance()->GetName(),
-			BaseSounds::GetUsedSet() == NULL ? "none" : BaseSounds::GetUsedSet()->name,
-			BaseSounds::GetUsedSet() == NULL ? UINT32_MAX : BaseSounds::GetUsedSet()->version,
-			VideoDriver::GetInstance() == NULL ? "none" : VideoDriver::GetInstance()->GetName()
+			SoundDriver::GetInstance() == nullptr ? "none" : SoundDriver::GetInstance()->GetName(),
+			BaseSounds::GetUsedSet() == nullptr ? "none" : BaseSounds::GetUsedSet()->name,
+			BaseSounds::GetUsedSet() == nullptr ? UINT32_MAX : BaseSounds::GetUsedSet()->version,
+			VideoDriver::GetInstance() == nullptr ? "none" : VideoDriver::GetInstance()->GetName()
 	);
 
 	buffer += seprintf(buffer, last,
@@ -197,14 +197,14 @@ char *CrashLog::LogConfiguration(char *b
 	buffer += seprintf(buffer, last, "AI Configuration (local: %i) (current: %i):\n", (int)_local_company, (int)_current_company);
 	const Company *c;
 	FOR_ALL_COMPANIES(c) {
-		if (c->ai_info == NULL) {
+		if (c->ai_info == nullptr) {
 			buffer += seprintf(buffer, last, " %2i: Human\n", (int)c->index);
 		} else {
 			buffer += seprintf(buffer, last, " %2i: %s (v%d)\n", (int)c->index, c->ai_info->GetName(), c->ai_info->GetVersion());
 		}
 	}
 
-	if (Game::GetInfo() != NULL) {
+	if (Game::GetInfo() != nullptr) {
 		buffer += seprintf(buffer, last, " GS: %s (v%d)\n", Game::GetInfo()->GetName(), Game::GetInfo()->GetVersion());
 	}
 	buffer += seprintf(buffer, last, "\n");
@@ -263,7 +263,7 @@ char *CrashLog::LogLibraries(char *buffe
 #endif
 
 #ifdef WITH_PNG
-	buffer += seprintf(buffer, last, " PNG:        %s\n", png_get_libpng_ver(NULL));
+	buffer += seprintf(buffer, last, " PNG:        %s\n", png_get_libpng_ver(nullptr));
 #endif /* WITH_PNG */
 
 #ifdef WITH_SDL
@@ -312,7 +312,7 @@ char *CrashLog::LogRecentNews(char *buff
 {
 	buffer += seprintf(buffer, last, "Recent news messages:\n");
 
-	for (NewsItem *news = _oldest_news; news != NULL; news = news->next) {
+	for (NewsItem *news = _oldest_news; news != nullptr; news = news->next) {
 		YearMonthDay ymd;
 		ConvertDateToYMD(news->date, &ymd);
 		buffer += seprintf(buffer, last, "(%i-%02i-%02i) StringID: %u, Type: %u, Ref1: %u, %u, Ref2: %u, %u\n",
@@ -331,7 +331,7 @@ char *CrashLog::LogRecentNews(char *buff
  */
 char *CrashLog::FillCrashLog(char *buffer, const char *last) const
 {
-	time_t cur_time = time(NULL);
+	time_t cur_time = time(nullptr);
 	buffer += seprintf(buffer, last, "*** OpenTTD Crash Report ***\n\n");
 	buffer += seprintf(buffer, last, "Crash at: %s", asctime(gmtime(&cur_time)));
 
@@ -369,7 +369,7 @@ bool CrashLog::WriteCrashLog(const char 
 	seprintf(filename, filename_last, "%scrash.log", _personal_dir);
 
 	FILE *file = FioFOpenFile(filename, "w", NO_DIRECTORY);
-	if (file == NULL) return false;
+	if (file == nullptr) return false;
 
 	size_t len = strlen(buffer);
 	size_t written = fwrite(buffer, 1, len, file);
@@ -396,7 +396,7 @@ bool CrashLog::WriteSavegame(char *filen
 {
 	/* If the map array doesn't exist, saving will fail too. If the map got
 	 * initialised, there is a big chance the rest is initialised too. */
-	if (_m == NULL) return false;
+	if (_m == nullptr) return false;
 
 	try {
 		GamelogEmergency();
@@ -421,7 +421,7 @@ bool CrashLog::WriteSavegame(char *filen
 bool CrashLog::WriteScreenshot(char *filename, const char *filename_last) const
 {
 	/* Don't draw when we have invalid screen size */
-	if (_screen.width < 1 || _screen.height < 1 || _screen.dst_ptr == NULL) return false;
+	if (_screen.width < 1 || _screen.height < 1 || _screen.dst_ptr == nullptr) return false;
 
 	bool res = MakeScreenshot(SC_CRASHLOG, "crash");
 	if (res) strecpy(filename, _full_screenshot_name, filename_last);
@@ -504,7 +504,7 @@ bool CrashLog::MakeCrashLog() const
  */
 /* static */ void CrashLog::AfterCrashLogCleanup()
 {
-	if (MusicDriver::GetInstance() != NULL) MusicDriver::GetInstance()->Stop();
-	if (SoundDriver::GetInstance() != NULL) SoundDriver::GetInstance()->Stop();
-	if (VideoDriver::GetInstance() != NULL) VideoDriver::GetInstance()->Stop();
+	if (MusicDriver::GetInstance() != nullptr) MusicDriver::GetInstance()->Stop();
+	if (SoundDriver::GetInstance() != nullptr) SoundDriver::GetInstance()->Stop();
+	if (VideoDriver::GetInstance() != nullptr) VideoDriver::GetInstance()->Stop();
 }
diff --git a/src/crashlog.h b/src/crashlog.h
--- a/src/crashlog.h
+++ b/src/crashlog.h
@@ -48,7 +48,7 @@ protected:
 	 * Writes actually encountered error to the buffer.
 	 * @param buffer  The begin where to write at.
 	 * @param last    The last position in the buffer to write to.
-	 * @param message Message passed to use for possible errors. Can be NULL.
+	 * @param message Message passed to use for possible errors. Can be nullptr.
 	 * @return the position of the \c '\0' character after the buffer.
 	 */
 	virtual char *LogError(char *buffer, const char *last, const char *message) const = 0;
diff --git a/src/date_gui.cpp b/src/date_gui.cpp
--- a/src/date_gui.cpp
+++ b/src/date_gui.cpp
@@ -148,7 +148,7 @@ struct SetDateWindow : Window {
 				break;
 
 			case WID_SD_SET_DATE:
-				if (this->callback != NULL) this->callback(this, ConvertYMDToDate(this->date.year, this->date.month, this->date.day));
+				if (this->callback != nullptr) this->callback(this, ConvertYMDToDate(this->date.year, this->date.month, this->date.day));
 				delete this;
 				break;
 		}
@@ -197,7 +197,7 @@ static const NWidgetPart _nested_set_dat
 
 /** Description of the date setting window. */
 static WindowDesc _set_date_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_SET_DATE, WC_NONE,
 	0,
 	_nested_set_date_widgets, lengthof(_nested_set_date_widgets)
diff --git a/src/debug.cpp b/src/debug.cpp
--- a/src/debug.cpp
+++ b/src/debug.cpp
@@ -120,14 +120,14 @@ static void debug_print(const char *dbg,
 	}
 	if (strcmp(dbg, "desync") == 0) {
 		static FILE *f = FioFOpenFile("commands-out.log", "wb", AUTOSAVE_DIR);
-		if (f == NULL) return;
+		if (f == nullptr) return;
 
 		fprintf(f, "%s%s\n", GetLogPrefix(), buf);
 		fflush(f);
 #ifdef RANDOM_DEBUG
 	} else if (strcmp(dbg, "random") == 0) {
 		static FILE *f = FioFOpenFile("random-out.log", "wb", AUTOSAVE_DIR);
-		if (f == NULL) return;
+		if (f == nullptr) return;
 
 		fprintf(f, "%s\n", buf);
 		fflush(f);
@@ -200,7 +200,7 @@ void SetDebugString(const char *s)
 		while (*s >= 'a' && *s <= 'z') s++;
 
 		/* check debugging levels */
-		p = NULL;
+		p = nullptr;
 		for (i = debug_level; i != endof(debug_level); ++i) {
 			if (s == t + strlen(i->name) && strncmp(t, i->name, s - t) == 0) {
 				p = i->level;
@@ -211,7 +211,7 @@ void SetDebugString(const char *s)
 		if (*s == '=') s++;
 		v = strtoul(s, &end, 0);
 		s = end;
-		if (p != NULL) {
+		if (p != nullptr) {
 			*p = v;
 		} else {
 			ShowInfoF("Unknown debug level '%.*s'", (int)(s - t), t);
@@ -246,13 +246,13 @@ const char *GetDebugString()
 /**
  * Get the prefix for logs; if show_date_in_logs is enabled it returns
  * the date, otherwise it returns nothing.
- * @return the prefix for logs (do not free), never NULL
+ * @return the prefix for logs (do not free), never nullptr
  */
 const char *GetLogPrefix()
 {
 	static char _log_prefix[24];
 	if (_settings_client.gui.show_date_in_logs) {
-		time_t cur_time = time(NULL);
+		time_t cur_time = time(nullptr);
 		strftime(_log_prefix, sizeof(_log_prefix), "[%Y-%m-%d %H:%M:%S] ", localtime(&cur_time));
 	} else {
 		*_log_prefix = '\0';
diff --git a/src/dedicated.cpp b/src/dedicated.cpp
--- a/src/dedicated.cpp
+++ b/src/dedicated.cpp
@@ -11,8 +11,8 @@
 
 #include "stdafx.h"
 
-char *_log_file = NULL; ///< File to reroute output of a forked OpenTTD to
-FILE *_log_fd   = NULL; ///< File to reroute output of a forked OpenTTD to
+char *_log_file = nullptr; ///< File to reroute output of a forked OpenTTD to
+FILE *_log_fd   = nullptr; ///< File to reroute output of a forked OpenTTD to
 
 #if defined(UNIX)
 
@@ -41,7 +41,7 @@ void DedicatedFork()
 		case 0: { // We're the child
 			/* Open the log-file to log all stuff too */
 			_log_fd = fopen(_log_file, "a");
-			if (_log_fd == NULL) {
+			if (_log_fd == nullptr) {
 				perror("Unable to open logfile");
 				exit(1);
 			}
diff --git a/src/depend/depend.cpp b/src/depend/depend.cpp
--- a/src/depend/depend.cpp
+++ b/src/depend/depend.cpp
@@ -54,7 +54,7 @@
  *
  * Copies the source string to the destination buffer with respect of the
  * terminating null-character and the last pointer to the last element in
- * the destination buffer. If the last pointer is set to NULL no boundary
+ * the destination buffer. If the last pointer is set to nullptr no boundary
  * check is performed.
  *
  * @note usage: strecpy(dst, src, lastof(dst));
@@ -85,7 +85,7 @@ char *strecpy(char *dst, const char *src
  *
  * Appends the source string to the destination string with respect of the
  * terminating null-character and and the last pointer to the last element
- * in the destination buffer. If the last pointer is set to NULL no
+ * in the destination buffer. If the last pointer is set to nullptr no
  * boundary check is performed.
  *
  * @note usage: strecat(dst, src, lastof(dst));
@@ -163,13 +163,13 @@ public:
 	File(const char *filename)
 	{
 		this->fp = fopen(filename, "r");
-		if (this->fp == NULL) {
+		if (this->fp == nullptr) {
 			fprintf(stdout, "Could not open %s for reading\n", filename);
 			exit(1);
 		}
 		this->dirname = strdup(filename);
 		char *last = strrchr(this->dirname, '/');
-		if (last != NULL) {
+		if (last != nullptr) {
 			*last = '\0';
 		} else {
 			*this->dirname = '\0';
@@ -247,7 +247,7 @@ public:
 	 * Create the lexer and fill the keywords table.
 	 * @param file the file to read from.
 	 */
-	Lexer(const File *file) : file(file), current_char('\0'), string(NULL), token(TOKEN_UNKNOWN)
+	Lexer(const File *file) : file(file), current_char('\0'), string(nullptr), token(TOKEN_UNKNOWN)
 	{
 		this->keywords["define"]  = TOKEN_DEFINE;
 		this->keywords["defined"] = TOKEN_DEFINED;
@@ -293,7 +293,7 @@ public:
 
 	/**
 	 * Read the currenty processed string.
-	 * @return the string, can be NULL.
+	 * @return the string, can be nullptr.
 	 */
 	const char *GetString() const
 	{
@@ -308,7 +308,7 @@ public:
 	{
 		for (;;) {
 			free(this->string);
-			this->string = NULL;
+			this->string = nullptr;
 			this->token  = TOKEN_UNKNOWN;
 
 			switch (this->current_char) {
@@ -503,7 +503,7 @@ private:
  * @param dirname the directory to look in.
  * @param filename the file to look for.
  * @param local whether to look locally (in dirname) for the file.
- * @return the absolute path, or NULL if the file doesn't exist.
+ * @return the absolute path, or nullptr if the file doesn't exist.
  */
 const char *GeneratePath(const char *dirname, const char *filename, bool local)
 {
@@ -517,7 +517,7 @@ const char *GeneratePath(const char *dir
 		while (*p == '.') {
 			if (*(++p) == '.') {
 				char *s = strrchr(path, '/');
-				if (s != NULL) *s = '\0';
+				if (s != nullptr) *s = '\0';
 				p += 2;
 			}
 		}
@@ -535,7 +535,7 @@ const char *GeneratePath(const char *dir
 		while (*p == '.') {
 			if (*(++p) == '.') {
 				char *s = strrchr(path, '/');
-				if (s != NULL) *s = '\0';
+				if (s != nullptr) *s = '\0';
 				p += 2;
 			}
 		}
@@ -545,7 +545,7 @@ const char *GeneratePath(const char *dir
 		if (access(path, R_OK) == 0) return strdup(path);
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -730,7 +730,7 @@ void ScanFile(const char *filename, cons
 									break;
 								}
 								const char *h = GeneratePath(file.GetDirname(), lexer.GetString(), lexer.GetToken() == TOKEN_LOCAL);
-								if (h != NULL) {
+								if (h != nullptr) {
 									StringMap::iterator it = _headers.find(h);
 									if (it == _headers.end()) {
 										it = (_headers.insert(StringMapItem(strdup(h), new StringSet()))).first;
@@ -745,7 +745,7 @@ void ScanFile(const char *filename, cons
 										char path[PATH_MAX];
 										strecpy(path, filename, lastof(path));
 										*(strrchr(path, '.')) = '\0';
-										strecat(path, ext != NULL ? ext : ".o", lastof(path));
+										strecat(path, ext != nullptr ? ext : ".o", lastof(path));
 										curfile = _files.find(path);
 										if (curfile == _files.end()) {
 											curfile = (_files.insert(StringMapItem(strdup(path), new StringSet()))).first;
@@ -909,9 +909,9 @@ void ScanFile(const char *filename, cons
 int main(int argc, char *argv[])
 {
 	bool ignorenext = true;
-	char *filename = NULL;
-	char *ext = NULL;
-	char *delimiter = NULL;
+	char *filename = nullptr;
+	char *ext = nullptr;
+	char *delimiter = nullptr;
 	bool append = false;
 	bool verbose = false;
 
@@ -936,25 +936,25 @@ int main(int argc, char *argv[])
 			/* Define */
 			if (strncmp(argv[i], "-D", 2) == 0) {
 				char *p = strchr(argv[i], '=');
-				if (p != NULL) *p = '\0';
+				if (p != nullptr) *p = '\0';
 				_defines.insert(strdup(&argv[i][2]));
 				continue;
 			}
 			/* Output file */
 			if (strncmp(argv[i], "-f", 2) == 0) {
-				if (filename != NULL) continue;
+				if (filename != nullptr) continue;
 				filename = strdup(&argv[i][2]);
 				continue;
 			}
 			/* Object file extension */
 			if (strncmp(argv[i], "-o", 2) == 0) {
-				if (ext != NULL) continue;
+				if (ext != nullptr) continue;
 				ext = strdup(&argv[i][2]);
 				continue;
 			}
 			/* Starting string delimiter */
 			if (strncmp(argv[i], "-s", 2) == 0) {
-				if (delimiter != NULL) continue;
+				if (delimiter != nullptr) continue;
 				delimiter = strdup(&argv[i][2]);
 				continue;
 			}
@@ -966,22 +966,22 @@ int main(int argc, char *argv[])
 	}
 
 	/* Default output file is Makefile */
-	if (filename == NULL) filename = strdup("Makefile");
+	if (filename == nullptr) filename = strdup("Makefile");
 
 	/* Default delimiter string */
-	if (delimiter == NULL) delimiter = strdup("# DO NOT DELETE");
+	if (delimiter == nullptr) delimiter = strdup("# DO NOT DELETE");
 
 	char backup[PATH_MAX];
 	strecpy(backup, filename, lastof(backup));
 	strecat(backup, ".bak", lastof(backup));
 
-	char *content = NULL;
+	char *content = nullptr;
 	long size = 0;
 
 	/* Read in the current file; so we can overwrite everything from the
 	 * end of non-depend data marker down till the end. */
 	FILE *src = fopen(filename, "rb");
-	if (src != NULL) {
+	if (src != nullptr) {
 		fseek(src, 0, SEEK_END);
 		if ((size = ftell(src)) < 0) {
 			fprintf(stderr, "Could not read %s\n", filename);
@@ -1009,7 +1009,7 @@ int main(int argc, char *argv[])
 
 		/* Then append it to the real file. */
 		src = fopen(backup, "r");
-		while (fgets(content, size, src) != NULL) {
+		while (fgets(content, size, src) != nullptr) {
 			fputs(content, dst);
 			if (!strncmp(content, delimiter, strlen(delimiter))) found_delimiter = true;
 			if (!append && found_delimiter) break;
diff --git a/src/depot_cmd.cpp b/src/depot_cmd.cpp
--- a/src/depot_cmd.cpp
+++ b/src/depot_cmd.cpp
@@ -33,7 +33,7 @@ static bool IsUniqueDepotName(const char
 	const Depot *d;
 
 	FOR_ALL_DEPOTS(d) {
-		if (d->name != NULL && strcmp(d->name, name) == 0) return false;
+		if (d->name != nullptr && strcmp(d->name, name) == 0) return false;
 	}
 
 	return true;
@@ -51,7 +51,7 @@ static bool IsUniqueDepotName(const char
 CommandCost CmdRenameDepot(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Depot *d = Depot::GetIfValid(p1);
-	if (d == NULL) return CMD_ERROR;
+	if (d == nullptr) return CMD_ERROR;
 
 	CommandCost ret = CheckTileOwnership(d->xy);
 	if (ret.Failed()) return ret;
@@ -67,7 +67,7 @@ CommandCost CmdRenameDepot(TileIndex til
 		free(d->name);
 
 		if (reset) {
-			d->name = NULL;
+			d->name = nullptr;
 			MakeDefaultName(d);
 		} else {
 			d->name = stredup(text);
diff --git a/src/depot_gui.cpp b/src/depot_gui.cpp
--- a/src/depot_gui.cpp
+++ b/src/depot_gui.cpp
@@ -133,16 +133,16 @@ static void TrainDepotMoveVehicle(const 
 
 	if (v == wagon) return;
 
-	if (wagon == NULL) {
-		if (head != NULL) wagon = head->Last();
+	if (wagon == nullptr) {
+		if (head != nullptr) wagon = head->Last();
 	} else {
 		wagon = wagon->Previous();
-		if (wagon == NULL) return;
+		if (wagon == nullptr) return;
 	}
 
 	if (wagon == v) return;
 
-	DoCommandP(v->tile, v->index | (_ctrl_pressed ? 1 : 0) << 20, wagon == NULL ? INVALID_VEHICLE : wagon->index, CMD_MOVE_RAIL_VEHICLE | CMD_MSG(STR_ERROR_CAN_T_MOVE_VEHICLE));
+	DoCommandP(v->tile, v->index | (_ctrl_pressed ? 1 : 0) << 20, wagon == nullptr ? INVALID_VEHICLE : wagon->index, CMD_MOVE_RAIL_VEHICLE | CMD_MSG(STR_ERROR_CAN_T_MOVE_VEHICLE));
 }
 
 static VehicleCellSize _base_block_sizes_depot[VEH_COMPANY_END];    ///< Cell size for vehicle images in the depot view.
@@ -228,7 +228,7 @@ void InitDepotWindowBlockSizes()
 		if (!e->IsEnabled()) continue;
 
 		uint w = TRAININFO_DEFAULT_VEHICLE_WIDTH;
-		if (e->GetGRF() != NULL && is_custom_sprite(e->u.rail.image_index)) {
+		if (e->GetGRF() != nullptr && is_custom_sprite(e->u.rail.image_index)) {
 			w = e->GetGRF()->traininfo_vehicle_width;
 			if (w != VEHICLEINFO_FULL_VEHICLE_WIDTH) {
 				/* Hopeless.
@@ -279,7 +279,7 @@ struct DepotWindow : Window {
 		this->unitnumber_digits = 2;
 
 		this->CreateNestedTree();
-		this->hscroll = (this->type == VEH_TRAIN ? this->GetScrollbar(WID_D_H_SCROLL) : NULL);
+		this->hscroll = (this->type == VEH_TRAIN ? this->GetScrollbar(WID_D_H_SCROLL) : nullptr);
 		this->vscroll = this->GetScrollbar(WID_D_V_SCROLL);
 		/* Don't show 'rename button' of aircraft hangar */
 		this->GetWidget<NWidgetStacked>(WID_D_SHOW_RENAME)->SetDisplayedPlane(type == VEH_AIRCRAFT ? SZSP_NONE : 0);
@@ -469,8 +469,8 @@ struct DepotWindow : Window {
 			/* Clicking on 'line' / 'block' without a vehicle */
 			if (this->type == VEH_TRAIN) {
 				/* End the dragging */
-				d->head  = NULL;
-				d->wagon = NULL;
+				d->head  = nullptr;
+				d->wagon = nullptr;
 				return MODE_DRAG_VEHICLE;
 			} else {
 				return MODE_ERROR; // empty block, so no vehicle is selected
@@ -490,7 +490,7 @@ struct DepotWindow : Window {
 			wagon = true;
 		}
 
-		const Train *v = NULL;
+		const Train *v = nullptr;
 		if (this->type == VEH_TRAIN) {
 			v = Train::From(*veh);
 			d->head = d->wagon = v;
@@ -525,12 +525,12 @@ struct DepotWindow : Window {
 		x -= this->header_width;
 
 		/* find the vehicle in this row that was clicked */
-		for (; v != NULL; v = v->Next()) {
+		for (; v != nullptr; v = v->Next()) {
 			x -= v->GetDisplayImageWidth();
 			if (x < 0) break;
 		}
 
-		d->wagon = (v != NULL ? v->GetFirstEnginePart() : NULL);
+		d->wagon = (v != nullptr ? v->GetFirstEnginePart() : nullptr);
 
 		return MODE_DRAG_VEHICLE;
 	}
@@ -542,8 +542,8 @@ struct DepotWindow : Window {
 	 */
 	void DepotClick(int x, int y)
 	{
-		GetDepotVehiclePtData gdvp = { NULL, NULL };
-		const Vehicle *v = NULL;
+		GetDepotVehiclePtData gdvp = { nullptr, nullptr };
+		const Vehicle *v = nullptr;
 		DepotGUIAction mode = this->GetVehicleFromDepotWndPt(x, y, &v, &gdvp);
 
 		if (this->type == VEH_TRAIN) v = gdvp.wagon;
@@ -553,14 +553,14 @@ struct DepotWindow : Window {
 				return;
 
 			case MODE_DRAG_VEHICLE: { // start dragging of vehicle
-				if (v != NULL && VehicleClicked(v)) return;
+				if (v != nullptr && VehicleClicked(v)) return;
 
 				VehicleID sel = this->sel;
 
 				if (this->type == VEH_TRAIN && sel != INVALID_VEHICLE) {
 					this->sel = INVALID_VEHICLE;
 					TrainDepotMoveVehicle(v, sel, gdvp.head);
-				} else if (v != NULL) {
+				} else if (v != nullptr) {
 					SetObjectToPlaceWnd(SPR_CURSOR_MOUSE, PAL_NONE, HT_DRAG, this);
 					SetMouseCursorVehicle(v, EIT_IN_DEPOT);
 					_cursor.vehchain = _ctrl_pressed;
@@ -728,7 +728,7 @@ struct DepotWindow : Window {
 			uint max_width = ScaleGUITrad(VEHICLEINFO_FULL_VEHICLE_WIDTH);
 			for (uint num = 0; num < this->vehicle_list.size(); num++) {
 				uint width = 0;
-				for (const Train *v = Train::From(this->vehicle_list[num]); v != NULL; v = v->Next()) {
+				for (const Train *v = Train::From(this->vehicle_list[num]); v != nullptr; v = v->Next()) {
 					width += v->GetDisplayImageWidth();
 				}
 				max_width = max(max_width, width);
@@ -839,24 +839,24 @@ struct DepotWindow : Window {
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
 		/* Do depot renaming */
-		DoCommandP(0, GetDepotIndex(this->window_number), 0, CMD_RENAME_DEPOT | CMD_MSG(STR_ERROR_CAN_T_RENAME_DEPOT), NULL, str);
+		DoCommandP(0, GetDepotIndex(this->window_number), 0, CMD_RENAME_DEPOT | CMD_MSG(STR_ERROR_CAN_T_RENAME_DEPOT), nullptr, str);
 	}
 
 	bool OnRightClick(Point pt, int widget) override
 	{
 		if (widget != WID_D_MATRIX) return false;
 
-		GetDepotVehiclePtData gdvp = { NULL, NULL };
-		const Vehicle *v = NULL;
+		GetDepotVehiclePtData gdvp = { nullptr, nullptr };
+		const Vehicle *v = nullptr;
 		NWidgetBase *nwi = this->GetWidget<NWidgetBase>(WID_D_MATRIX);
 		DepotGUIAction mode = this->GetVehicleFromDepotWndPt(pt.x - nwi->pos_x, pt.y - nwi->pos_y, &v, &gdvp);
 
 		if (this->type == VEH_TRAIN) v = gdvp.wagon;
 
-		if (v == NULL || mode != MODE_DRAG_VEHICLE) return false;
+		if (v == nullptr || mode != MODE_DRAG_VEHICLE) return false;
 
 		CargoArray capacity, loaded;
 
@@ -865,7 +865,7 @@ struct DepotWindow : Window {
 
 		/* loop through vehicle chain and collect cargoes */
 		uint num = 0;
-		for (const Vehicle *w = v; w != NULL; w = w->Next()) {
+		for (const Vehicle *w = v; w != nullptr; w = w->Next()) {
 			if (w->cargo_cap > 0 && w->cargo_type < NUM_CARGO) {
 				capacity[w->cargo_type] += w->cargo_cap;
 				loaded  [w->cargo_type] += w->cargo.StoredCount();
@@ -910,7 +910,7 @@ struct DepotWindow : Window {
 	{
 		if (_ctrl_pressed) {
 			/* Share-clone, do not open new viewport, and keep tool active */
-			DoCommandP(this->window_number, v->index, 1, CMD_CLONE_VEHICLE | CMD_MSG(STR_ERROR_CAN_T_BUY_TRAIN + v->type), NULL);
+			DoCommandP(this->window_number, v->index, 1, CMD_CLONE_VEHICLE | CMD_MSG(STR_ERROR_CAN_T_BUY_TRAIN + v->type), nullptr);
 		} else {
 			/* Copy-clone, open viewport for new vehicle, and deselect the tool (assume player wants to changs things on new vehicle) */
 			if (DoCommandP(this->window_number, v->index, 0, CMD_CLONE_VEHICLE | CMD_MSG(STR_ERROR_CAN_T_BUY_TRAIN + v->type), CcCloneVehicle)) {
@@ -965,20 +965,20 @@ struct DepotWindow : Window {
 		}
 
 		NWidgetBase *matrix = this->GetWidget<NWidgetBase>(widget);
-		const Vehicle *v = NULL;
-		GetDepotVehiclePtData gdvp = {NULL, NULL};
+		const Vehicle *v = nullptr;
+		GetDepotVehiclePtData gdvp = {nullptr, nullptr};
 
 		if (this->GetVehicleFromDepotWndPt(pt.x - matrix->pos_x, pt.y - matrix->pos_y, &v, &gdvp) != MODE_DRAG_VEHICLE) return;
 
 		VehicleID new_vehicle_over = INVALID_VEHICLE;
-		if (gdvp.head != NULL) {
-			if (gdvp.wagon == NULL && gdvp.head->Last()->index != this->sel) { // ..at the end of the train.
+		if (gdvp.head != nullptr) {
+			if (gdvp.wagon == nullptr && gdvp.head->Last()->index != this->sel) { // ..at the end of the train.
 				/* NOTE: As a wagon can't be moved at the begin of a train, head index isn't used to mark a drag-and-drop
 				 * destination inside a train. This head index is then used to indicate that a wagon is inserted at
 				 * the end of the train.
 				 */
 				new_vehicle_over = gdvp.head->index;
-			} else if (gdvp.wagon != NULL && gdvp.head != gdvp.wagon &&
+			} else if (gdvp.wagon != nullptr && gdvp.head != gdvp.wagon &&
 					gdvp.wagon->index != this->sel &&
 					gdvp.wagon->Previous()->index != this->sel) { // ..over an existing wagon.
 				new_vehicle_over = gdvp.wagon->index;
@@ -995,7 +995,7 @@ struct DepotWindow : Window {
 	{
 		switch (widget) {
 			case WID_D_MATRIX: {
-				const Vehicle *v = NULL;
+				const Vehicle *v = nullptr;
 				VehicleID sel = this->sel;
 
 				this->sel = INVALID_VEHICLE;
@@ -1003,20 +1003,20 @@ struct DepotWindow : Window {
 
 				NWidgetBase *nwi = this->GetWidget<NWidgetBase>(WID_D_MATRIX);
 				if (this->type == VEH_TRAIN) {
-					GetDepotVehiclePtData gdvp = { NULL, NULL };
+					GetDepotVehiclePtData gdvp = { nullptr, nullptr };
 
 					if (this->GetVehicleFromDepotWndPt(pt.x - nwi->pos_x, pt.y - nwi->pos_y, &v, &gdvp) == MODE_DRAG_VEHICLE && sel != INVALID_VEHICLE) {
-						if (gdvp.wagon != NULL && gdvp.wagon->index == sel && _ctrl_pressed) {
+						if (gdvp.wagon != nullptr && gdvp.wagon->index == sel && _ctrl_pressed) {
 							DoCommandP(Vehicle::Get(sel)->tile, Vehicle::Get(sel)->index, true,
 									CMD_REVERSE_TRAIN_DIRECTION | CMD_MSG(STR_ERROR_CAN_T_REVERSE_DIRECTION_RAIL_VEHICLE));
-						} else if (gdvp.wagon == NULL || gdvp.wagon->index != sel) {
+						} else if (gdvp.wagon == nullptr || gdvp.wagon->index != sel) {
 							this->vehicle_over = INVALID_VEHICLE;
 							TrainDepotMoveVehicle(gdvp.wagon, sel, gdvp.head);
-						} else if (gdvp.head != NULL && gdvp.head->IsFrontEngine()) {
+						} else if (gdvp.head != nullptr && gdvp.head->IsFrontEngine()) {
 							ShowVehicleViewWindow(gdvp.head);
 						}
 					}
-				} else if (this->GetVehicleFromDepotWndPt(pt.x - nwi->pos_x, pt.y - nwi->pos_y, &v, NULL) == MODE_DRAG_VEHICLE && v != NULL && sel == v->index) {
+				} else if (this->GetVehicleFromDepotWndPt(pt.x - nwi->pos_x, pt.y - nwi->pos_y, &v, nullptr) == MODE_DRAG_VEHICLE && v != nullptr && sel == v->index) {
 					ShowVehicleViewWindow(v);
 				}
 				break;
@@ -1052,7 +1052,7 @@ struct DepotWindow : Window {
 			this->RaiseWidget(WID_D_SELL);
 			this->SetWidgetDirty(WID_D_SELL);
 		}
-		if (this->nested_array[WID_D_SELL] != NULL && !this->IsWidgetDisabled(WID_D_SELL_CHAIN)) {
+		if (this->nested_array[WID_D_SELL] != nullptr && !this->IsWidgetDisabled(WID_D_SELL_CHAIN)) {
 			this->RaiseWidget(WID_D_SELL_CHAIN);
 			this->SetWidgetDirty(WID_D_SELL_CHAIN);
 		}
@@ -1098,7 +1098,7 @@ static void DepotSellAllConfirmationCall
  */
 void ShowDepotWindow(TileIndex tile, VehicleType type)
 {
-	if (BringWindowToFrontById(WC_VEHICLE_DEPOT, tile) != NULL) return;
+	if (BringWindowToFrontById(WC_VEHICLE_DEPOT, tile) != nullptr) return;
 
 	WindowDesc *desc;
 	switch (type) {
@@ -1126,7 +1126,7 @@ void DeleteDepotHighlightOfVehicle(const
 	if (_special_mouse_mode != WSM_DRAGDROP) return;
 
 	w = dynamic_cast<DepotWindow*>(FindWindowById(WC_VEHICLE_DEPOT, v->tile));
-	if (w != NULL) {
+	if (w != nullptr) {
 		if (w->sel == v->index) ResetObjectToPlace();
 	}
 }
diff --git a/src/disaster_vehicle.cpp b/src/disaster_vehicle.cpp
--- a/src/disaster_vehicle.cpp
+++ b/src/disaster_vehicle.cpp
@@ -137,11 +137,11 @@ DisasterVehicle::DisasterVehicle(int x, 
 		case ST_HELICOPTER:
 		case ST_BIG_UFO:
 		case ST_BIG_UFO_DESTROYER:
-			GetAircraftFlightLevelBounds(this, &this->z_pos, NULL);
+			GetAircraftFlightLevelBounds(this, &this->z_pos, nullptr);
 			break;
 
 		case ST_HELICOPTER_ROTORS:
-			GetAircraftFlightLevelBounds(this, &this->z_pos, NULL);
+			GetAircraftFlightLevelBounds(this, &this->z_pos, nullptr);
 			this->z_pos += ROTOR_Z_OFFSET;
 			break;
 
@@ -190,7 +190,7 @@ void DisasterVehicle::UpdatePosition(int
 	this->UpdatePositionAndViewport();
 
 	DisasterVehicle *u = this->Next();
-	if (u != NULL) {
+	if (u != nullptr) {
 		int safe_x = Clamp(x, 0, MapMaxX() * TILE_SIZE);
 		int safe_y = Clamp(y - 1, 0, MapMaxY() * TILE_SIZE);
 
@@ -203,7 +203,7 @@ void DisasterVehicle::UpdatePosition(int
 		u->UpdateImage();
 		u->UpdatePositionAndViewport();
 
-		if ((u = u->Next()) != NULL) {
+		if ((u = u->Next()) != nullptr) {
 			u->x_pos = x;
 			u->y_pos = y;
 			u->z_pos = z + ROTOR_Z_OFFSET;
@@ -357,7 +357,7 @@ static bool DisasterTick_Ufo(DisasterVeh
 	} else {
 		/* Target a vehicle */
 		RoadVehicle *u = RoadVehicle::Get(v->dest_tile);
-		assert(u != NULL && u->type == VEH_ROAD && u->IsFrontEngine());
+		assert(u != nullptr && u->type == VEH_ROAD && u->IsFrontEngine());
 
 		uint dist = Delta(v->x_pos, u->x_pos) + Delta(v->y_pos, u->y_pos);
 
@@ -748,16 +748,16 @@ static void Disaster_Airplane_Init()
 {
 	if (!Vehicle::CanAllocateItem(2)) return;
 
-	Industry *i, *found = NULL;
+	Industry *i, *found = nullptr;
 
 	FOR_ALL_INDUSTRIES(i) {
 		if ((GetIndustrySpec(i->type)->behaviour & INDUSTRYBEH_AIRPLANE_ATTACKS) &&
-				(found == NULL || Chance16(1, 2))) {
+				(found == nullptr || Chance16(1, 2))) {
 			found = i;
 		}
 	}
 
-	if (found == NULL) return;
+	if (found == nullptr) return;
 
 	/* Start from the bottom (south side) of the map */
 	int x = (MapSizeX() + 9) * TILE_SIZE - 1;
@@ -774,16 +774,16 @@ static void Disaster_Helicopter_Init()
 {
 	if (!Vehicle::CanAllocateItem(3)) return;
 
-	Industry *i, *found = NULL;
+	Industry *i, *found = nullptr;
 
 	FOR_ALL_INDUSTRIES(i) {
 		if ((GetIndustrySpec(i->type)->behaviour & INDUSTRYBEH_CHOPPER_ATTACKS) &&
-				(found == NULL || Chance16(1, 2))) {
+				(found == nullptr || Chance16(1, 2))) {
 			found = i;
 		}
 	}
 
-	if (found == NULL) return;
+	if (found == nullptr) return;
 
 	int x = -16 * (int)TILE_SIZE;
 	int y = TileY(found->location.tile) * TILE_SIZE + 37;
@@ -966,7 +966,7 @@ void ReleaseDisastersTargetingVehicle(Ve
 				/* Revert to target-searching */
 				v->current_order.SetDestination(0);
 				v->dest_tile = RandomTile();
-				GetAircraftFlightLevelBounds(v, &v->z_pos, NULL);
+				GetAircraftFlightLevelBounds(v, &v->z_pos, nullptr);
 				v->age = 0;
 			}
 		}
diff --git a/src/dock_gui.cpp b/src/dock_gui.cpp
--- a/src/dock_gui.cpp
+++ b/src/dock_gui.cpp
@@ -60,7 +60,7 @@ void CcPlaySound_SPLAT_WATER(const Comma
  * @param[out] tile_to   The tile till where to show a selection for the aqueduct.
  * @return The other end of the aqueduct, or otherwise a tile in line with the aqueduct to cause the right error message.
  */
-static TileIndex GetOtherAqueductEnd(TileIndex tile_from, TileIndex *tile_to = NULL)
+static TileIndex GetOtherAqueductEnd(TileIndex tile_from, TileIndex *tile_to = nullptr)
 {
 	int z;
 	DiagDirection dir = GetInclinedSlopeDirection(GetTileSlope(tile_from, &z));
@@ -83,7 +83,7 @@ static TileIndex GetOtherAqueductEnd(Til
 		if (length > max_length) break;
 
 		if (GetTileMaxZ(endtile) > z) {
-			if (tile_to != NULL) *tile_to = endtile;
+			if (tile_to != nullptr) *tile_to = endtile;
 			break;
 		}
 	}
@@ -287,7 +287,7 @@ static EventState DockToolbarGlobalHotke
 {
 	if (_game_mode != GM_NORMAL) return ES_NOT_HANDLED;
 	Window *w = ShowBuildDocksToolbar();
-	if (w == NULL) return ES_NOT_HANDLED;
+	if (w == nullptr) return ES_NOT_HANDLED;
 	return w->OnHotkey(hotkey);
 }
 
@@ -341,11 +341,11 @@ static WindowDesc _build_docks_toolbar_d
  *
  * If the terraform toolbar is linked to the toolbar, that window is also opened.
  *
- * @return newly opened water toolbar, or NULL if the toolbar could not be opened.
+ * @return newly opened water toolbar, or nullptr if the toolbar could not be opened.
  */
 Window *ShowBuildDocksToolbar()
 {
-	if (!Company::IsValidID(_local_company)) return NULL;
+	if (!Company::IsValidID(_local_company)) return nullptr;
 
 	DeleteWindowByClass(WC_BUILD_TOOLBAR);
 	return AllocateWindowDescFront<BuildDocksToolbarWindow>(&_build_docks_toolbar_desc, TRANSPORT_WATER);
@@ -382,7 +382,7 @@ static WindowDesc _build_docks_scen_tool
 /**
  * Open the build water toolbar window for the scenario editor.
  *
- * @return newly opened water toolbar, or NULL if the toolbar could not be opened.
+ * @return newly opened water toolbar, or nullptr if the toolbar could not be opened.
  */
 Window *ShowBuildDocksScenToolbar()
 {
@@ -475,7 +475,7 @@ static const NWidgetPart _nested_build_d
 };
 
 static WindowDesc _build_dock_station_desc(
-	WDP_AUTO, NULL, 0, 0,
+	WDP_AUTO, nullptr, 0, 0,
 	WC_BUILD_STATION, WC_BUILD_TOOLBAR,
 	WDF_CONSTRUCTION,
 	_nested_build_dock_station_widgets, lengthof(_nested_build_dock_station_widgets)
@@ -568,7 +568,7 @@ static const NWidgetPart _nested_build_d
 };
 
 static WindowDesc _build_docks_depot_desc(
-	WDP_AUTO, NULL, 0, 0,
+	WDP_AUTO, nullptr, 0, 0,
 	WC_BUILD_DEPOT, WC_BUILD_TOOLBAR,
 	WDF_CONSTRUCTION,
 	_nested_build_docks_depot_widgets, lengthof(_nested_build_docks_depot_widgets)
diff --git a/src/driver.cpp b/src/driver.cpp
--- a/src/driver.cpp
+++ b/src/driver.cpp
@@ -41,10 +41,10 @@ const char *GetDriverParam(const char * 
 {
 	size_t len;
 
-	if (parm == NULL) return NULL;
+	if (parm == nullptr) return nullptr;
 
 	len = strlen(name);
-	for (; *parm != NULL; parm++) {
+	for (; *parm != nullptr; parm++) {
 		const char *p = *parm;
 
 		if (strncmp(p, name, len) == 0) {
@@ -52,7 +52,7 @@ const char *GetDriverParam(const char * 
 			if (p[len] == '\0') return p + len;
 		}
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -63,7 +63,7 @@ const char *GetDriverParam(const char * 
  */
 bool GetDriverParamBool(const char * const *parm, const char *name)
 {
-	return GetDriverParam(parm, name) != NULL;
+	return GetDriverParam(parm, name) != nullptr;
 }
 
 /**
@@ -76,7 +76,7 @@ bool GetDriverParamBool(const char * con
 int GetDriverParamInt(const char * const *parm, const char *name, int def)
 {
 	const char *p = GetDriverParam(parm, name);
-	return p != NULL ? atoi(p) : def;
+	return p != nullptr ? atoi(p) : def;
 }
 
 /**
@@ -120,8 +120,8 @@ bool DriverFactoryBase::SelectDriverImpl
 				Driver *newd = d->CreateInstance();
 				*GetActiveDriver(type) = newd;
 
-				const char *err = newd->Start(NULL);
-				if (err == NULL) {
+				const char *err = newd->Start(nullptr);
+				if (err == nullptr) {
 					DEBUG(driver, 1, "Successfully probed %s driver '%s'", GetDriverTypeName(type), d->name);
 					delete oldd;
 					return true;
@@ -141,8 +141,8 @@ bool DriverFactoryBase::SelectDriverImpl
 		/* Extract the driver name and put parameter list in parm */
 		strecpy(buffer, name, lastof(buffer));
 		parm = strchr(buffer, ':');
-		parms[0] = NULL;
-		if (parm != NULL) {
+		parms[0] = nullptr;
+		if (parm != nullptr) {
 			uint np = 0;
 			/* Tokenize the parm. */
 			do {
@@ -150,7 +150,7 @@ bool DriverFactoryBase::SelectDriverImpl
 				if (np < lengthof(parms) - 1) parms[np++] = parm;
 				while (*parm != '\0' && *parm != ',') parm++;
 			} while (*parm == ',');
-			parms[np] = NULL;
+			parms[np] = nullptr;
 		}
 
 		/* Find this driver */
@@ -168,7 +168,7 @@ bool DriverFactoryBase::SelectDriverImpl
 			Driver *newd = d->CreateInstance();
 
 			const char *err = newd->Start(parms);
-			if (err != NULL) {
+			if (err != nullptr) {
 				delete newd;
 				usererror("Unable to load driver '%s'. The error was: %s", d->name, err);
 			}
diff --git a/src/driver.h b/src/driver.h
--- a/src/driver.h
+++ b/src/driver.h
@@ -26,7 +26,7 @@ public:
 	/**
 	 * Start this driver.
 	 * @param parm Parameters passed to the driver.
-	 * @return NULL if everything went okay, otherwise an error message.
+	 * @return nullptr if everything went okay, otherwise an error message.
 	 */
 	virtual const char *Start(const char * const *parm) = 0;
 
@@ -86,7 +86,7 @@ private:
 	 */
 	static Driver **GetActiveDriver(Driver::Type type)
 	{
-		static Driver *s_driver[3] = { NULL, NULL, NULL };
+		static Driver *s_driver[3] = { nullptr, nullptr, nullptr };
 		return &s_driver[type];
 	}
 
@@ -116,7 +116,7 @@ public:
 	{
 		for (Driver::Type dt = Driver::DT_BEGIN; dt < Driver::DT_END; dt++) {
 			Driver *driver = *GetActiveDriver(dt);
-			if (driver != NULL) driver->Stop();
+			if (driver != nullptr) driver->Stop();
 		}
 	}
 
diff --git a/src/economy.cpp b/src/economy.cpp
--- a/src/economy.cpp
+++ b/src/economy.cpp
@@ -401,7 +401,7 @@ void ChangeOwnershipOfCompanyItems(Owner
 		FOR_ALL_VEHICLES(v) {
 			if (v->owner == old_owner && IsCompanyBuildableVehicleType(v->type)) {
 				if (new_owner == INVALID_OWNER) {
-					if (v->Previous() == NULL) delete v;
+					if (v->Previous() == nullptr) delete v;
 				} else {
 					if (v->IsEngineCountable()) GroupStatistics::CountEngine(v, -1);
 					if (v->IsPrimaryVehicle()) GroupStatistics::CountVehicle(v, -1);
@@ -476,7 +476,7 @@ void ChangeOwnershipOfCompanyItems(Owner
 				}
 
 				/* Invalidate the vehicle's cargo payment "owner cache". */
-				if (v->cargo_payment != NULL) v->cargo_payment->owner = NULL;
+				if (v->cargo_payment != nullptr) v->cargo_payment->owner = nullptr;
 			}
 		}
 
@@ -959,7 +959,7 @@ Money GetPrice(Price index, uint cost_fa
 	if (index >= PR_END) return 0;
 
 	Money cost = _price[index] * cost_factor;
-	if (grf_file != NULL) shift += grf_file->price_base_multipliers[index];
+	if (grf_file != nullptr) shift += grf_file->price_base_multipliers[index];
 
 	if (shift >= 0) {
 		cost <<= shift;
@@ -1180,7 +1180,7 @@ CargoPayment::~CargoPayment()
 {
 	if (this->CleaningPool()) return;
 
-	this->front->cargo_payment = NULL;
+	this->front->cargo_payment = nullptr;
 
 	if (this->visual_profit == 0 && this->visual_transfer == 0) return;
 
@@ -1211,7 +1211,7 @@ CargoPayment::~CargoPayment()
  */
 void CargoPayment::PayFinalDelivery(const CargoPacket *cp, uint count)
 {
-	if (this->owner == NULL) {
+	if (this->owner == nullptr) {
 		this->owner = Company::Get(this->front->owner);
 	}
 
@@ -1259,7 +1259,7 @@ void PrepareUnload(Vehicle *front_v)
 	/* Start unloading at the first possible moment */
 	front_v->load_unload_ticks = 1;
 
-	assert(front_v->cargo_payment == NULL);
+	assert(front_v->cargo_payment == nullptr);
 	/* One CargoPayment per vehicle and the vehicle limit equals the
 	 * limit in number of CargoPayments. Can't go wrong. */
 	assert_compile(CargoPaymentPool::MAX_SIZE == VehiclePool::MAX_SIZE);
@@ -1267,9 +1267,9 @@ void PrepareUnload(Vehicle *front_v)
 	front_v->cargo_payment = new CargoPayment(front_v);
 
 	StationIDStack next_station = front_v->GetNextStoppingStation();
-	if (front_v->orders.list == NULL || (front_v->current_order.GetUnloadType() & OUFB_NO_UNLOAD) == 0) {
+	if (front_v->orders.list == nullptr || (front_v->current_order.GetUnloadType() & OUFB_NO_UNLOAD) == 0) {
 		Station *st = Station::Get(front_v->last_station_visited);
-		for (Vehicle *v = front_v; v != NULL; v = v->Next()) {
+		for (Vehicle *v = front_v; v != nullptr; v = v->Next()) {
 			const GoodsEntry *ge = &st->goods[v->cargo_type];
 			if (v->cargo_cap > 0 && v->cargo.TotalCount() > 0) {
 				v->cargo.Stage(
@@ -1300,7 +1300,7 @@ static uint GetLoadAmount(Vehicle *v)
 
 	if (_settings_game.order.gradual_loading) {
 		uint16 cb_load_amount = CALLBACK_FAILED;
-		if (e->GetGRF() != NULL && e->GetGRF()->grf_version >= 8) {
+		if (e->GetGRF() != nullptr && e->GetGRF()->grf_version >= 8) {
 			/* Use callback 36 */
 			cb_load_amount = GetVehicleProperty(v, PROP_VEHICLE_LOAD_AMOUNT, CALLBACK_FAILED);
 		} else if (HasBit(e->info.callback_mask, CBM_VEHICLE_LOAD_AMOUNT)) {
@@ -1336,8 +1336,8 @@ static uint GetLoadAmount(Vehicle *v)
 template<class Taction>
 bool IterateVehicleParts(Vehicle *v, Taction action)
 {
-	for (Vehicle *w = v; w != NULL;
-			w = w->HasArticulatedPart() ? w->GetNextArticulatedPart() : NULL) {
+	for (Vehicle *w = v; w != nullptr;
+			w = w->HasArticulatedPart() ? w->GetNextArticulatedPart() : nullptr) {
 		if (!action(w)) return false;
 		if (w->type == VEH_TRAIN) {
 			Train *train = Train::From(w);
@@ -1564,8 +1564,8 @@ static void ReserveConsist(Station *st, 
 	/* If there is a cargo payment not all vehicles of the consist have tried to do the refit.
 	 * In that case, only reserve if it's a fixed refit and the equivalent of "articulated chain"
 	 * a vehicle belongs to already has the right cargo. */
-	bool must_reserve = !u->current_order.IsRefit() || u->cargo_payment == NULL;
-	for (Vehicle *v = u; v != NULL; v = v->Next()) {
+	bool must_reserve = !u->current_order.IsRefit() || u->cargo_payment == nullptr;
+	for (Vehicle *v = u; v != nullptr; v = v->Next()) {
 		assert(v->cargo_cap >= v->cargo.RemainingCount());
 
 		/* Exclude various ways in which the vehicle might not be the head of an equivalent of
@@ -1577,7 +1577,7 @@ static void ReserveConsist(Station *st, 
 				(must_reserve || u->current_order.GetRefitCargo() == v->cargo_type)) {
 			IterateVehicleParts(v, ReserveCargoAction(st, next_station));
 		}
-		if (consist_capleft == NULL || v->cargo_cap == 0) continue;
+		if (consist_capleft == nullptr || v->cargo_cap == 0) continue;
 		(*consist_capleft)[v->cargo_type] += v->cargo_cap - v->cargo.RemainingCount();
 	}
 }
@@ -1618,9 +1618,9 @@ static void LoadUnloadVehicle(Vehicle *f
 	bool use_autorefit = front->current_order.IsRefit() && front->current_order.GetRefitCargo() == CT_AUTO_REFIT;
 	CargoArray consist_capleft;
 	if (_settings_game.order.improved_load && use_autorefit ?
-			front->cargo_payment == NULL : (front->current_order.GetLoadType() & OLFB_FULL_LOAD) != 0) {
+			front->cargo_payment == nullptr : (front->current_order.GetLoadType() & OLFB_FULL_LOAD) != 0) {
 		ReserveConsist(st, front,
-				(use_autorefit && front->load_unload_ticks != 0) ? &consist_capleft : NULL,
+				(use_autorefit && front->load_unload_ticks != 0) ? &consist_capleft : nullptr,
 				&next_station);
 	}
 
@@ -1652,7 +1652,7 @@ static void LoadUnloadVehicle(Vehicle *f
 	CargoPayment *payment = front->cargo_payment;
 
 	uint artic_part = 0; // Articulated part we are currently trying to load. (not counting parts without capacity)
-	for (Vehicle *v = front; v != NULL; v = v->Next()) {
+	for (Vehicle *v = front; v != nullptr; v = v->Next()) {
 		if (v == front || !v->Previous()->HasArticulatedPart()) artic_part = 0;
 		if (v->cargo_cap == 0) continue;
 		artic_part++;
@@ -1664,7 +1664,7 @@ static void LoadUnloadVehicle(Vehicle *f
 			uint amount_unloaded = _settings_game.order.gradual_loading ? min(cargo_count, GetLoadAmount(v)) : cargo_count;
 			bool remaining = false; // Are there cargo entities in this vehicle that can still be unloaded here?
 
-			assert(payment != NULL);
+			assert(payment != nullptr);
 			payment->SetCargo(v->cargo_type);
 
 			if (!HasBit(ge->status, GoodsEntry::GES_ACCEPTANCE) && v->cargo.ActionCount(VehicleCargoList::MTA_DELIVER) > 0) {
@@ -1916,7 +1916,7 @@ void LoadUnloadStation(Station *st)
 	/* No vehicle is here... */
 	if (st->loading_vehicles.empty()) return;
 
-	Vehicle *last_loading = NULL;
+	Vehicle *last_loading = nullptr;
 	std::list<Vehicle *>::iterator iter;
 
 	/* Check if anything will be loaded at all. Otherwise we don't need to reserve either. */
@@ -1936,7 +1936,7 @@ void LoadUnloadStation(Station *st)
 	 * consist in a station which is not allowed to load yet because its
 	 * load_unload_ticks is still not 0.
 	 */
-	if (last_loading == NULL) return;
+	if (last_loading == nullptr) return;
 
 	for (iter = st->loading_vehicles.begin(); iter != st->loading_vehicles.end(); ++iter) {
 		Vehicle *v = *iter;
@@ -2018,7 +2018,7 @@ CommandCost CmdBuyShareInCompany(TileInd
 
 	/* Check if buying shares is allowed (protection against modified clients)
 	 * Cannot buy own shares */
-	if (c == NULL || !_settings_game.economy.allow_shares || _current_company == target_company) return CMD_ERROR;
+	if (c == nullptr || !_settings_game.economy.allow_shares || _current_company == target_company) return CMD_ERROR;
 
 	/* Protect new companies from hostile takeovers */
 	if (_cur_year - c->inaugurated_year < 6) return_cmd_error(STR_ERROR_PROTECTED);
@@ -2068,7 +2068,7 @@ CommandCost CmdSellShareInCompany(TileIn
 	Company *c = Company::GetIfValid(target_company);
 
 	/* Cannot sell own shares */
-	if (c == NULL || _current_company == target_company) return CMD_ERROR;
+	if (c == nullptr || _current_company == target_company) return CMD_ERROR;
 
 	/* Check if selling shares is allowed (protection against modified clients).
 	 * However, we must sell shares of companies being closed down. */
@@ -2107,7 +2107,7 @@ CommandCost CmdBuyCompany(TileIndex tile
 {
 	CompanyID target_company = (CompanyID)p1;
 	Company *c = Company::GetIfValid(target_company);
-	if (c == NULL) return CMD_ERROR;
+	if (c == nullptr) return CMD_ERROR;
 
 	/* Disable takeovers when not asked */
 	if (!HasBit(c->bankrupt_asked, _current_company)) return CMD_ERROR;
diff --git a/src/effectvehicle.cpp b/src/effectvehicle.cpp
--- a/src/effectvehicle.cpp
+++ b/src/effectvehicle.cpp
@@ -595,7 +595,7 @@ assert_compile(lengthof(_effect_transpar
  */
 EffectVehicle *CreateEffectVehicle(int x, int y, int z, EffectVehicleType type)
 {
-	if (!Vehicle::CanAllocateItem()) return NULL;
+	if (!Vehicle::CanAllocateItem()) return nullptr;
 
 	EffectVehicle *v = new EffectVehicle();
 	v->subtype = type;
diff --git a/src/elrail.cpp b/src/elrail.cpp
--- a/src/elrail.cpp
+++ b/src/elrail.cpp
@@ -82,7 +82,7 @@ static inline TLG GetTLG(TileIndex t)
 /**
  * Finds which Electrified Rail Bits are present on a given tile.
  * @param t tile to check
- * @param override pointer to PCP override, can be NULL
+ * @param override pointer to PCP override, can be nullptr
  * @return trackbits of tile if it is electrified
  */
 static TrackBits GetRailTrackBitsUniversal(TileIndex t, byte *override)
@@ -101,7 +101,7 @@ static TrackBits GetRailTrackBitsUnivers
 		case MP_TUNNELBRIDGE:
 			if (GetTunnelBridgeTransportType(t) != TRANSPORT_RAIL) return TRACK_BIT_NONE;
 			if (!HasRailCatenary(GetRailType(t))) return TRACK_BIT_NONE;
-			if (override != NULL && (IsTunnel(t) || GetTunnelBridgeLength(t, GetOtherBridgeEnd(t)) > 0)) {
+			if (override != nullptr && (IsTunnel(t) || GetTunnelBridgeLength(t, GetOtherBridgeEnd(t)) > 0)) {
 				*override = 1 << GetTunnelBridgeDirection(t);
 			}
 			return DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t));
@@ -326,7 +326,7 @@ static void DrawRailCatenaryRailway(cons
 		/* Here's one of the main headaches. GetTileSlope does not correct for possibly
 		 * existing foundataions, so we do have to do that manually later on.*/
 		tileh[TS_NEIGHBOUR] = GetTileSlope(neighbour);
-		trackconfig[TS_NEIGHBOUR] = GetRailTrackBitsUniversal(neighbour, NULL);
+		trackconfig[TS_NEIGHBOUR] = GetRailTrackBitsUniversal(neighbour, nullptr);
 		wireconfig[TS_NEIGHBOUR] = MaskWireBits(neighbour, trackconfig[TS_NEIGHBOUR]);
 		if (IsTunnelTile(neighbour) && i != GetTunnelBridgeDirection(neighbour)) wireconfig[TS_NEIGHBOUR] = trackconfig[TS_NEIGHBOUR] = TRACK_BIT_NONE;
 
diff --git a/src/engine.cpp b/src/engine.cpp
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -69,9 +69,9 @@ assert_compile(lengthof(_orig_rail_vehic
 const uint EngineOverrideManager::NUM_DEFAULT_ENGINES = _engine_counts[VEH_TRAIN] + _engine_counts[VEH_ROAD] + _engine_counts[VEH_SHIP] + _engine_counts[VEH_AIRCRAFT];
 
 Engine::Engine() :
-	name(NULL),
+	name(nullptr),
 	overrides_count(0),
-	overrides(NULL)
+	overrides(nullptr)
 {
 }
 
@@ -162,7 +162,7 @@ bool Engine::IsEnabled() const
 uint32 Engine::GetGRFID() const
 {
 	const GRFFile *file = this->GetGRF();
-	return file == NULL ? 0 : file->grfid;
+	return file == nullptr ? 0 : file->grfid;
 }
 
 /**
@@ -199,28 +199,28 @@ bool Engine::CanCarryCargo() const
 /**
  * Determines capacity of a given vehicle from scratch.
  * For aircraft the main capacity is determined. Mail might be present as well.
- * @param v Vehicle of interest; NULL in purchase list
+ * @param v Vehicle of interest; nullptr in purchase list
  * @param mail_capacity returns secondary cargo (mail) capacity of aircraft
  * @return Capacity
  */
 uint Engine::DetermineCapacity(const Vehicle *v, uint16 *mail_capacity) const
 {
-	assert(v == NULL || this->index == v->engine_type);
-	if (mail_capacity != NULL) *mail_capacity = 0;
+	assert(v == nullptr || this->index == v->engine_type);
+	if (mail_capacity != nullptr) *mail_capacity = 0;
 
 	if (!this->CanCarryCargo()) return 0;
 
 	bool new_multipliers = HasBit(this->info.misc_flags, EF_NO_DEFAULT_CARGO_MULTIPLIER);
 	CargoID default_cargo = this->GetDefaultCargoType();
-	CargoID cargo_type = (v != NULL) ? v->cargo_type : default_cargo;
+	CargoID cargo_type = (v != nullptr) ? v->cargo_type : default_cargo;
 
-	if (mail_capacity != NULL && this->type == VEH_AIRCRAFT && IsCargoInClass(cargo_type, CC_PASSENGERS)) {
+	if (mail_capacity != nullptr && this->type == VEH_AIRCRAFT && IsCargoInClass(cargo_type, CC_PASSENGERS)) {
 		*mail_capacity = GetEngineProperty(this->index, PROP_AIRCRAFT_MAIL_CAPACITY, this->u.air.mail_capacity, v);
 	}
 
 	/* Check the refit capacity callback if we are not in the default configuration, or if we are using the new multiplier algorithm. */
 	if (HasBit(this->info.callback_mask, CBM_VEHICLE_REFIT_CAPACITY) &&
-			(new_multipliers || default_cargo != cargo_type || (v != NULL && v->cargo_subtype != 0))) {
+			(new_multipliers || default_cargo != cargo_type || (v != nullptr && v->cargo_subtype != 0))) {
 		uint16 callback = GetVehicleCallback(CBID_VEHICLE_REFIT_CAPACITY, 0, 0, this->index, v);
 		if (callback != CALLBACK_FAILED) return callback;
 	}
@@ -233,7 +233,7 @@ uint Engine::DetermineCapacity(const Veh
 			capacity = GetEngineProperty(this->index, PROP_TRAIN_CARGO_CAPACITY,        this->u.rail.capacity, v);
 
 			/* In purchase list add the capacity of the second head. Always use the plain property for this. */
-			if (v == NULL && this->u.rail.railveh_type == RAILVEH_MULTIHEAD) capacity += this->u.rail.capacity;
+			if (v == nullptr && this->u.rail.railveh_type == RAILVEH_MULTIHEAD) capacity += this->u.rail.capacity;
 			break;
 
 		case VEH_ROAD:
@@ -869,7 +869,7 @@ void ClearEnginesHiddenFlagOfCompany(Com
 CommandCost CmdSetVehicleVisibility(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Engine *e = Engine::GetIfValid(GB(p2, 0, 31));
-	if (e == NULL || _current_company >= MAX_COMPANIES) return CMD_ERROR;
+	if (e == nullptr || _current_company >= MAX_COMPANIES) return CMD_ERROR;
 	if (!IsEngineBuildable(e->index, e->type, _current_company)) return CMD_ERROR;
 
 	if ((flags & DC_EXEC) != 0) {
@@ -893,7 +893,7 @@ CommandCost CmdSetVehicleVisibility(Tile
 CommandCost CmdWantEnginePreview(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Engine *e = Engine::GetIfValid(p1);
-	if (e == NULL || !(e->flags & ENGINE_EXCLUSIVE_PREVIEW) || e->preview_company != _current_company) return CMD_ERROR;
+	if (e == nullptr || !(e->flags & ENGINE_EXCLUSIVE_PREVIEW) || e->preview_company != _current_company) return CMD_ERROR;
 
 	if (flags & DC_EXEC) AcceptEnginePreview(p1, _current_company);
 
@@ -1021,7 +1021,7 @@ static bool IsUniqueEngineName(const cha
 	const Engine *e;
 
 	FOR_ALL_ENGINES(e) {
-		if (e->name != NULL && strcmp(e->name, name) == 0) return false;
+		if (e->name != nullptr && strcmp(e->name, name) == 0) return false;
 	}
 
 	return true;
@@ -1039,7 +1039,7 @@ static bool IsUniqueEngineName(const cha
 CommandCost CmdRenameEngine(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Engine *e = Engine::GetIfValid(p1);
-	if (e == NULL) return CMD_ERROR;
+	if (e == nullptr) return CMD_ERROR;
 
 	bool reset = StrEmpty(text);
 
@@ -1052,7 +1052,7 @@ CommandCost CmdRenameEngine(TileIndex ti
 		free(e->name);
 
 		if (reset) {
-			e->name = NULL;
+			e->name = nullptr;
 		} else {
 			e->name = stredup(text);
 		}
@@ -1077,7 +1077,7 @@ bool IsEngineBuildable(EngineID engine, 
 	const Engine *e = Engine::GetIfValid(engine);
 
 	/* check if it's an engine that is in the engine array */
-	if (e == NULL) return false;
+	if (e == nullptr) return false;
 
 	/* check if it's an engine of specified type */
 	if (e->type != type) return false;
@@ -1113,7 +1113,7 @@ bool IsEngineRefittable(EngineID engine)
 	const Engine *e = Engine::GetIfValid(engine);
 
 	/* check if it's an engine that is in the engine array */
-	if (e == NULL) return false;
+	if (e == nullptr) return false;
 
 	if (!e->CanCarryCargo()) return false;
 
diff --git a/src/engine_base.h b/src/engine_base.h
--- a/src/engine_base.h
+++ b/src/engine_base.h
@@ -83,7 +83,7 @@ struct Engine : EnginePool::PoolItem<&_e
 		return this->info.cargo_type;
 	}
 
-	uint DetermineCapacity(const Vehicle *v, uint16 *mail_capacity = NULL) const;
+	uint DetermineCapacity(const Vehicle *v, uint16 *mail_capacity = nullptr) const;
 
 	bool CanCarryCargo() const;
 
@@ -98,9 +98,9 @@ struct Engine : EnginePool::PoolItem<&_e
 	 * @return The default capacity
 	 * @see GetDefaultCargoType
 	 */
-	uint GetDisplayDefaultCapacity(uint16 *mail_capacity = NULL) const
+	uint GetDisplayDefaultCapacity(uint16 *mail_capacity = nullptr) const
 	{
-		return this->DetermineCapacity(NULL, mail_capacity);
+		return this->DetermineCapacity(nullptr, mail_capacity);
 	}
 
 	Money GetRunningCost() const;
diff --git a/src/error.h b/src/error.h
--- a/src/error.h
+++ b/src/error.h
@@ -43,7 +43,7 @@ protected:
 public:
 	ErrorMessageData(const ErrorMessageData &data);
 	~ErrorMessageData();
-	ErrorMessageData(StringID summary_msg, StringID detailed_msg, uint duration = 0, int x = 0, int y = 0, const GRFFile *textref_stack_grffile = NULL, uint textref_stack_size = 0, const uint32 *textref_stack = NULL);
+	ErrorMessageData(StringID summary_msg, StringID detailed_msg, uint duration = 0, int x = 0, int y = 0, const GRFFile *textref_stack_grffile = nullptr, uint textref_stack_size = 0, const uint32 *textref_stack = nullptr);
 
 	/** Check whether error window shall display a company manager face */
 	bool HasFace() const { return face != INVALID_COMPANY; }
@@ -56,7 +56,7 @@ public:
 
 void ScheduleErrorMessage(const ErrorMessageData &data);
 
-void ShowErrorMessage(StringID summary_msg, StringID detailed_msg, WarningLevel wl, int x = 0, int y = 0, const GRFFile *textref_stack_grffile = NULL, uint textref_stack_size = 0, const uint32 *textref_stack = NULL);
+void ShowErrorMessage(StringID summary_msg, StringID detailed_msg, WarningLevel wl, int x = 0, int y = 0, const GRFFile *textref_stack_grffile = nullptr, uint textref_stack_size = 0, const uint32 *textref_stack = nullptr);
 void ClearErrorMessages();
 void ShowFirstError();
 void UnshowCriticalError();
diff --git a/src/error_gui.cpp b/src/error_gui.cpp
--- a/src/error_gui.cpp
+++ b/src/error_gui.cpp
@@ -76,7 +76,7 @@ ErrorMessageData::ErrorMessageData(const
 {
 	*this = data;
 	for (size_t i = 0; i < lengthof(this->strings); i++) {
-		if (this->strings[i] != NULL) {
+		if (this->strings[i] != nullptr) {
 			this->strings[i] = stredup(this->strings[i]);
 			this->decode_params[i] = (size_t)this->strings[i];
 		}
@@ -357,7 +357,7 @@ void ShowFirstError()
 void UnshowCriticalError()
 {
 	ErrmsgWindow *w = (ErrmsgWindow*)FindWindowById(WC_ERRMSG, 0);
-	if (_window_system_initialized && w != NULL) {
+	if (_window_system_initialized && w != nullptr) {
 		if (w->IsCritical()) _error_list.push_front(*w);
 		_window_system_initialized = false;
 		delete w;
@@ -377,7 +377,7 @@ void UnshowCriticalError()
  */
 void ShowErrorMessage(StringID summary_msg, StringID detailed_msg, WarningLevel wl, int x, int y, const GRFFile *textref_stack_grffile, uint textref_stack_size, const uint32 *textref_stack)
 {
-	assert(textref_stack_size == 0 || (textref_stack_grffile != NULL && textref_stack != NULL));
+	assert(textref_stack_size == 0 || (textref_stack_grffile != nullptr && textref_stack != nullptr));
 	if (summary_msg == STR_NULL) summary_msg = STR_EMPTY;
 
 	if (wl != WL_INFO) {
@@ -408,7 +408,7 @@ void ShowErrorMessage(StringID summary_m
 	data.CopyOutDParams();
 
 	ErrmsgWindow *w = (ErrmsgWindow*)FindWindowById(WC_ERRMSG, 0);
-	if (w != NULL && w->IsCritical()) {
+	if (w != nullptr && w->IsCritical()) {
 		/* A critical error is currently shown. */
 		if (wl == WL_CRITICAL) {
 			/* Push another critical error in the queue of errors,
diff --git a/src/fileio.cpp b/src/fileio.cpp
--- a/src/fileio.cpp
+++ b/src/fileio.cpp
@@ -99,7 +99,7 @@ void FioSeekTo(size_t pos, int mode)
 static void FioRestoreFile(int slot)
 {
 	/* Do we still have the file open, or should we reopen it? */
-	if (_fio.handles[slot] == NULL) {
+	if (_fio.handles[slot] == nullptr) {
 		DEBUG(misc, 6, "Restoring file '%s' in slot '%d' from disk", _fio.filenames[slot], slot);
 		FioOpenFile(slot, _fio.filenames[slot]);
 	}
@@ -120,7 +120,7 @@ void FioSeekToFile(uint8 slot, size_t po
 	FioRestoreFile(slot);
 #endif /* LIMITED_FDS */
 	f = _fio.handles[slot];
-	assert(f != NULL);
+	assert(f != nullptr);
 	_fio.cur_fh = f;
 	_fio.filename = _fio.filenames[slot];
 	FioSeekTo(pos, SEEK_SET);
@@ -196,13 +196,13 @@ void FioReadBlock(void *ptr, size_t size
  */
 static inline void FioCloseFile(int slot)
 {
-	if (_fio.handles[slot] != NULL) {
+	if (_fio.handles[slot] != nullptr) {
 		fclose(_fio.handles[slot]);
 
 		free(_fio.shortnames[slot]);
-		_fio.shortnames[slot] = NULL;
+		_fio.shortnames[slot] = nullptr;
 
-		_fio.handles[slot] = NULL;
+		_fio.handles[slot] = nullptr;
 #if defined(LIMITED_FDS)
 		_fio.open_handles--;
 #endif /* LIMITED_FDS */
@@ -229,7 +229,7 @@ static void FioFreeHandle()
 		slot = -1;
 		/* Find the file that is used the least */
 		for (i = 0; i < lengthof(_fio.handles); i++) {
-			if (_fio.handles[i] != NULL && _fio.usage_count[i] < count) {
+			if (_fio.handles[i] != nullptr && _fio.usage_count[i] < count) {
 				count = _fio.usage_count[i];
 				slot  = i;
 			}
@@ -255,7 +255,7 @@ void FioOpenFile(int slot, const char *f
 	FioFreeHandle();
 #endif /* LIMITED_FDS */
 	f = FioFOpenFile(filename, "rb", subdir);
-	if (f == NULL) usererror("Cannot open file '%s'", filename);
+	if (f == nullptr) usererror("Cannot open file '%s'", filename);
 	long pos = ftell(f);
 	if (pos < 0) usererror("Cannot read file '%s'", filename);
 
@@ -265,9 +265,9 @@ void FioOpenFile(int slot, const char *f
 
 	/* Store the filename without path and extension */
 	const char *t = strrchr(filename, PATHSEPCHAR);
-	_fio.shortnames[slot] = stredup(t == NULL ? filename : t);
+	_fio.shortnames[slot] = stredup(t == nullptr ? filename : t);
 	char *t2 = strrchr(_fio.shortnames[slot], '.');
-	if (t2 != NULL) *t2 = '\0';
+	if (t2 != nullptr) *t2 = '\0';
 	strtolower(_fio.shortnames[slot]);
 
 #if defined(LIMITED_FDS)
@@ -312,7 +312,7 @@ static TarLinkList _tar_linklist[NUM_SUB
 bool FioCheckFileExists(const char *filename, Subdirectory subdir)
 {
 	FILE *f = FioFOpenFile(filename, "rb", subdir);
-	if (f == NULL) return false;
+	if (f == nullptr) return false;
 
 	FioFCloseFile(f);
 	return true;
@@ -351,7 +351,7 @@ char *FioGetFullPath(char *buf, const ch
  * @param last End of the destination buffer.
  * @param subdir Subdirectory to try.
  * @param filename Filename to look for.
- * @return \a buf containing the path if the path was found, else \c NULL.
+ * @return \a buf containing the path if the path was found, else \c nullptr.
  */
 char *FioFindFullPath(char *buf, const char *last, Subdirectory subdir, const char *filename)
 {
@@ -369,7 +369,7 @@ char *FioFindFullPath(char *buf, const c
 #endif
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 char *FioAppendDirectory(char *buf, const char *last, Searchpath sp, Subdirectory subdir)
@@ -407,7 +407,7 @@ static FILE *FioFOpenFileSp(const char *
 	wchar_t Lmode[5];
 	MultiByteToWideChar(CP_ACP, 0, mode, -1, Lmode, lengthof(Lmode));
 #endif
-	FILE *f = NULL;
+	FILE *f = nullptr;
 	char buf[MAX_PATH];
 
 	if (subdir == NO_DIRECTORY) {
@@ -417,16 +417,16 @@ static FILE *FioFOpenFileSp(const char *
 	}
 
 #if defined(_WIN32)
-	if (mode[0] == 'r' && GetFileAttributes(OTTD2FS(buf)) == INVALID_FILE_ATTRIBUTES) return NULL;
+	if (mode[0] == 'r' && GetFileAttributes(OTTD2FS(buf)) == INVALID_FILE_ATTRIBUTES) return nullptr;
 #endif
 
 	f = fopen(buf, mode);
 #if !defined(_WIN32)
-	if (f == NULL && strtolower(buf + ((subdir == NO_DIRECTORY) ? 0 : strlen(_searchpaths[sp]) - 1))) {
+	if (f == nullptr && strtolower(buf + ((subdir == NO_DIRECTORY) ? 0 : strlen(_searchpaths[sp]) - 1))) {
 		f = fopen(buf, mode);
 	}
 #endif
-	if (f != NULL && filesize != NULL) {
+	if (f != nullptr && filesize != nullptr) {
 		/* Find the size of the file */
 		fseek(f, 0, SEEK_END);
 		*filesize = ftell(f);
@@ -438,21 +438,21 @@ static FILE *FioFOpenFileSp(const char *
 /**
  * Opens a file from inside a tar archive.
  * @param entry The entry to open.
- * @param[out] filesize If not \c NULL, size of the opened file.
- * @return File handle of the opened file, or \c NULL if the file is not available.
+ * @param[out] filesize If not \c nullptr, size of the opened file.
+ * @return File handle of the opened file, or \c nullptr if the file is not available.
  * @note The file is read from within the tar file, and may not return \c EOF after reading the whole file.
  */
 FILE *FioFOpenFileTar(TarFileListEntry *entry, size_t *filesize)
 {
 	FILE *f = fopen(entry->tar_filename, "rb");
-	if (f == NULL) return f;
+	if (f == nullptr) return f;
 
 	if (fseek(f, entry->position, SEEK_SET) < 0) {
 		fclose(f);
-		return NULL;
+		return nullptr;
 	}
 
-	if (filesize != NULL) *filesize = entry->size;
+	if (filesize != nullptr) *filesize = entry->size;
 	return f;
 }
 
@@ -460,22 +460,22 @@ FILE *FioFOpenFileTar(TarFileListEntry *
  * Opens a OpenTTD file somewhere in a personal or global directory.
  * @param filename Name of the file to open.
  * @param subdir Subdirectory to open.
- * @return File handle of the opened file, or \c NULL if the file is not available.
+ * @return File handle of the opened file, or \c nullptr if the file is not available.
  */
 FILE *FioFOpenFile(const char *filename, const char *mode, Subdirectory subdir, size_t *filesize)
 {
-	FILE *f = NULL;
+	FILE *f = nullptr;
 	Searchpath sp;
 
 	assert(subdir < NUM_SUBDIRS || subdir == NO_DIRECTORY);
 
 	FOR_ALL_SEARCHPATHS(sp) {
 		f = FioFOpenFileSp(filename, mode, sp, subdir, filesize);
-		if (f != NULL || subdir == NO_DIRECTORY) break;
+		if (f != nullptr || subdir == NO_DIRECTORY) break;
 	}
 
 	/* We can only use .tar in case of data-dir, and read-mode */
-	if (f == NULL && mode[0] == 'r' && subdir != NO_DIRECTORY) {
+	if (f == nullptr && mode[0] == 'r' && subdir != NO_DIRECTORY) {
 		static const uint MAX_RESOLVED_LENGTH = 2 * (100 + 100 + 155) + 1; // Enough space to hold two filenames plus link. See 'TarHeader'.
 		char resolved_name[MAX_RESOLVED_LENGTH];
 
@@ -508,11 +508,11 @@ FILE *FioFOpenFile(const char *filename,
 
 	/* Sometimes a full path is given. To support
 	 * the 'subdirectory' must be 'removed'. */
-	if (f == NULL && subdir != NO_DIRECTORY) {
+	if (f == nullptr && subdir != NO_DIRECTORY) {
 		switch (subdir) {
 			case BASESET_DIR:
 				f = FioFOpenFile(filename, mode, OLD_GM_DIR, filesize);
-				if (f != NULL) break;
+				if (f != nullptr) break;
 				FALLTHROUGH;
 			case NEWGRF_DIR:
 				f = FioFOpenFile(filename, mode, OLD_DATA_DIR, filesize);
@@ -536,7 +536,7 @@ void FioCreateDirectory(const char *name
 	/* Ignore directory creation errors; they'll surface later on, and most
 	 * of the time they are 'directory already exists' errors anyhow. */
 #if defined(_WIN32)
-	CreateDirectory(OTTD2FS(name), NULL);
+	CreateDirectory(OTTD2FS(name), nullptr);
 #elif defined(OS2) && !defined(__INNOTEK_LIBC__)
 	mkdir(OTTD2FS(name));
 #else
@@ -573,7 +573,7 @@ bool AppendPathSeparator(char *buf, cons
 const char *FioTarFirstDir(const char *tarname, Subdirectory subdir)
 {
 	TarList::iterator it = _tar_list[subdir].find(tarname);
-	if (it == _tar_list[subdir].end()) return NULL;
+	if (it == _tar_list[subdir].end()) return nullptr;
 	return (*it).second.dirname;
 }
 
@@ -675,7 +675,7 @@ bool TarScanner::AddFile(Subdirectory sd
 bool TarScanner::AddFile(const char *filename, size_t basepath_length, const char *tar_filename)
 {
 	/* No tar within tar. */
-	assert(tar_filename == NULL);
+	assert(tar_filename == nullptr);
 
 	/* The TAR-header, repeated for every file */
 	struct TarHeader {
@@ -708,11 +708,11 @@ bool TarScanner::AddFile(const char *fil
 	 * a number of reasons we cannot open the file.
 	 * Most common case is when we simply have not
 	 * been given read access. */
-	if (f == NULL) return false;
+	if (f == nullptr) return false;
 
 	const char *dupped_filename = stredup(filename);
 	_tar_list[this->subdir][filename].filename = dupped_filename;
-	_tar_list[this->subdir][filename].dirname = NULL;
+	_tar_list[this->subdir][filename].dirname = nullptr;
 
 	TarLinkList links; ///< Temporary list to collect links
 
@@ -801,13 +801,13 @@ bool TarScanner::AddFile(const char *fil
 				 * Note: The destination of links must not contain any directory-links. */
 				strecpy(dest, name, lastof(dest));
 				char *destpos = strrchr(dest, PATHSEPCHAR);
-				if (destpos == NULL) destpos = dest;
+				if (destpos == nullptr) destpos = dest;
 				*destpos = '\0';
 
 				char *pos = link;
 				while (*pos != '\0') {
 					char *next = strchr(pos, PATHSEPCHAR);
-					if (next == NULL) {
+					if (next == nullptr) {
 						next = pos + strlen(pos);
 					} else {
 						/* Terminate the substring up to the path separator character. */
@@ -826,7 +826,7 @@ bool TarScanner::AddFile(const char *fil
 						/* Truncate 'dest' after last PATHSEPCHAR.
 						 * This assumes that the truncated part is a real directory and not a link. */
 						destpos = strrchr(dest, PATHSEPCHAR);
-						if (destpos == NULL) destpos = dest;
+						if (destpos == nullptr) destpos = dest;
 						*destpos = '\0';
 					} else {
 						/* Append at end of 'dest' */
@@ -856,7 +856,7 @@ bool TarScanner::AddFile(const char *fil
 
 				/* Store the first directory name we detect */
 				DEBUG(misc, 6, "Found dir in tar: %s", name);
-				if (_tar_list[this->subdir][filename].dirname == NULL) _tar_list[this->subdir][filename].dirname = stredup(name);
+				if (_tar_list[this->subdir][filename].dirname == nullptr) _tar_list[this->subdir][filename].dirname = stredup(name);
 				break;
 
 			default:
@@ -911,13 +911,13 @@ bool ExtractTar(const char *tar_filename
 	const char *dirname = (*it).second.dirname;
 
 	/* The file doesn't have a sub directory! */
-	if (dirname == NULL) return false;
+	if (dirname == nullptr) return false;
 
 	char filename[MAX_PATH];
 	strecpy(filename, tar_filename, lastof(filename));
 	char *p = strrchr(filename, PATHSEPCHAR);
 	/* The file's path does not have a separator? */
-	if (p == NULL) return false;
+	if (p == nullptr) return false;
 
 	p++;
 	strecpy(p, dirname, lastof(filename));
@@ -934,14 +934,14 @@ bool ExtractTar(const char *tar_filename
 		/* First open the file in the .tar. */
 		size_t to_copy = 0;
 		FILE *in = FioFOpenFileTar(&(*it2).second, &to_copy);
-		if (in == NULL) {
+		if (in == nullptr) {
 			DEBUG(misc, 6, "Extracting %s failed; could not open %s", filename, tar_filename);
 			return false;
 		}
 
 		/* Now open the 'output' file. */
 		FILE *out = fopen(filename, "wb");
-		if (out == NULL) {
+		if (out == nullptr) {
 			DEBUG(misc, 6, "Extracting %s failed; could not open %s", filename, filename);
 			fclose(in);
 			return false;
@@ -993,12 +993,12 @@ static bool ChangeWorkingDirectoryToExec
 	bool success = false;
 #ifdef WITH_COCOA
 	char *app_bundle = strchr(tmp, '.');
-	while (app_bundle != NULL && strncasecmp(app_bundle, ".app", 4) != 0) app_bundle = strchr(&app_bundle[1], '.');
+	while (app_bundle != nullptr && strncasecmp(app_bundle, ".app", 4) != 0) app_bundle = strchr(&app_bundle[1], '.');
 
-	if (app_bundle != NULL) *app_bundle = '\0';
+	if (app_bundle != nullptr) *app_bundle = '\0';
 #endif /* WITH_COCOA */
 	char *s = strrchr(tmp, PATHSEPCHAR);
-	if (s != NULL) {
+	if (s != nullptr) {
 		*s = '\0';
 		if (chdir(tmp) != 0) {
 			DEBUG(misc, 0, "Directory with the binary does not exist?");
@@ -1022,13 +1022,13 @@ static bool ChangeWorkingDirectoryToExec
 bool DoScanWorkingDirectory()
 {
 	/* No working directory, so nothing to do. */
-	if (_searchpaths[SP_WORKING_DIR] == NULL) return false;
+	if (_searchpaths[SP_WORKING_DIR] == nullptr) return false;
 
 	/* Working directory is root, so do nothing. */
 	if (strcmp(_searchpaths[SP_WORKING_DIR], PATHSEP) == 0) return false;
 
 	/* No personal/home directory, so the working directory won't be that. */
-	if (_searchpaths[SP_PERSONAL_DIR] == NULL) return true;
+	if (_searchpaths[SP_PERSONAL_DIR] == nullptr) return true;
 
 	char tmp[MAX_PATH];
 	seprintf(tmp, lastof(tmp), "%s%s", _searchpaths[SP_WORKING_DIR], PERSONAL_DIR);
@@ -1044,7 +1044,7 @@ void DetermineBasePaths(const char *exe)
 {
 	char tmp[MAX_PATH];
 #if defined(WITH_XDG_BASEDIR) && defined(WITH_PERSONAL_DIR)
-	const char *xdg_data_home = xdgDataHome(NULL);
+	const char *xdg_data_home = xdgDataHome(nullptr);
 	seprintf(tmp, lastof(tmp), "%s" PATHSEP "%s", xdg_data_home,
 			PERSONAL_DIR[0] == '.' ? &PERSONAL_DIR[1] : PERSONAL_DIR);
 	free(xdg_data_home);
@@ -1053,7 +1053,7 @@ void DetermineBasePaths(const char *exe)
 	_searchpaths[SP_PERSONAL_DIR_XDG] = stredup(tmp);
 #endif
 #if defined(OS2) || !defined(WITH_PERSONAL_DIR)
-	_searchpaths[SP_PERSONAL_DIR] = NULL;
+	_searchpaths[SP_PERSONAL_DIR] = nullptr;
 #else
 #ifdef __HAIKU__
 	BPath path;
@@ -1065,17 +1065,17 @@ void DetermineBasePaths(const char *exe)
 	 * variables in any way. It can also contain all kinds of
 	 * unvalidated data we rather not want internally. */
 	const char *homedir = getenv("HOME");
-	if (homedir != NULL) {
+	if (homedir != nullptr) {
 		homedir = stredup(homedir);
 	}
 
-	if (homedir == NULL) {
+	if (homedir == nullptr) {
 		const struct passwd *pw = getpwuid(getuid());
-		homedir = (pw == NULL) ? NULL : stredup(pw->pw_dir);
+		homedir = (pw == nullptr) ? nullptr : stredup(pw->pw_dir);
 	}
 #endif
 
-	if (homedir != NULL) {
+	if (homedir != nullptr) {
 		ValidateString(homedir);
 		seprintf(tmp, lastof(tmp), "%s" PATHSEP "%s", homedir, PERSONAL_DIR);
 		AppendPathSeparator(tmp, lastof(tmp));
@@ -1083,7 +1083,7 @@ void DetermineBasePaths(const char *exe)
 		_searchpaths[SP_PERSONAL_DIR] = stredup(tmp);
 		free(homedir);
 	} else {
-		_searchpaths[SP_PERSONAL_DIR] = NULL;
+		_searchpaths[SP_PERSONAL_DIR] = nullptr;
 	}
 #endif
 
@@ -1092,10 +1092,10 @@ void DetermineBasePaths(const char *exe)
 	AppendPathSeparator(tmp, lastof(tmp));
 	_searchpaths[SP_SHARED_DIR] = stredup(tmp);
 #else
-	_searchpaths[SP_SHARED_DIR] = NULL;
+	_searchpaths[SP_SHARED_DIR] = nullptr;
 #endif
 
-	if (getcwd(tmp, MAX_PATH) == NULL) *tmp = '\0';
+	if (getcwd(tmp, MAX_PATH) == nullptr) *tmp = '\0';
 	AppendPathSeparator(tmp, lastof(tmp));
 	_searchpaths[SP_WORKING_DIR] = stredup(tmp);
 
@@ -1103,14 +1103,14 @@ void DetermineBasePaths(const char *exe)
 
 	/* Change the working directory to that one of the executable */
 	if (ChangeWorkingDirectoryToExecutable(exe)) {
-		if (getcwd(tmp, MAX_PATH) == NULL) *tmp = '\0';
+		if (getcwd(tmp, MAX_PATH) == nullptr) *tmp = '\0';
 		AppendPathSeparator(tmp, lastof(tmp));
 		_searchpaths[SP_BINARY_DIR] = stredup(tmp);
 	} else {
-		_searchpaths[SP_BINARY_DIR] = NULL;
+		_searchpaths[SP_BINARY_DIR] = nullptr;
 	}
 
-	if (_searchpaths[SP_WORKING_DIR] != NULL) {
+	if (_searchpaths[SP_WORKING_DIR] != nullptr) {
 		/* Go back to the current working directory. */
 		if (chdir(_searchpaths[SP_WORKING_DIR]) != 0) {
 			DEBUG(misc, 0, "Failed to return to working directory!");
@@ -1118,7 +1118,7 @@ void DetermineBasePaths(const char *exe)
 	}
 
 #if !defined(GLOBAL_DATA_DIR)
-	_searchpaths[SP_INSTALLATION_DIR] = NULL;
+	_searchpaths[SP_INSTALLATION_DIR] = nullptr;
 #else
 	seprintf(tmp, lastof(tmp), "%s", GLOBAL_DATA_DIR);
 	AppendPathSeparator(tmp, lastof(tmp));
@@ -1128,7 +1128,7 @@ void DetermineBasePaths(const char *exe)
 extern void cocoaSetApplicationBundleDir();
 	cocoaSetApplicationBundleDir();
 #else
-	_searchpaths[SP_APPLICATION_BUNDLE_DIR] = NULL;
+	_searchpaths[SP_APPLICATION_BUNDLE_DIR] = nullptr;
 #endif
 }
 #endif /* defined(_WIN32) */
@@ -1148,7 +1148,7 @@ void DeterminePaths(const char *exe)
 #if defined(WITH_XDG_BASEDIR) && defined(WITH_PERSONAL_DIR)
 	char config_home[MAX_PATH];
 
-	const char *xdg_config_home = xdgConfigHome(NULL);
+	const char *xdg_config_home = xdgConfigHome(nullptr);
 	seprintf(config_home, lastof(config_home), "%s" PATHSEP "%s", xdg_config_home,
 			PERSONAL_DIR[0] == '.' ? &PERSONAL_DIR[1] : PERSONAL_DIR);
 	free(xdg_config_home);
@@ -1163,19 +1163,19 @@ void DeterminePaths(const char *exe)
 	}
 
 	char *config_dir;
-	if (_config_file != NULL) {
+	if (_config_file != nullptr) {
 		config_dir = stredup(_config_file);
 		char *end = strrchr(config_dir, PATHSEPCHAR);
-		if (end == NULL) {
+		if (end == nullptr) {
 			config_dir[0] = '\0';
 		} else {
 			end[1] = '\0';
 		}
 	} else {
 		char personal_dir[MAX_PATH];
-		if (FioFindFullPath(personal_dir, lastof(personal_dir), BASE_DIR, "openttd.cfg") != NULL) {
+		if (FioFindFullPath(personal_dir, lastof(personal_dir), BASE_DIR, "openttd.cfg") != nullptr) {
 			char *end = strrchr(personal_dir, PATHSEPCHAR);
-			if (end != NULL) end[1] = '\0';
+			if (end != nullptr) end[1] = '\0';
 			config_dir = stredup(personal_dir);
 			_config_file = str_fmt("%sopenttd.cfg", config_dir);
 		} else {
@@ -1187,14 +1187,14 @@ void DeterminePaths(const char *exe)
 					SP_PERSONAL_DIR, SP_BINARY_DIR, SP_WORKING_DIR, SP_SHARED_DIR, SP_INSTALLATION_DIR
 				};
 
-			config_dir = NULL;
+			config_dir = nullptr;
 			for (uint i = 0; i < lengthof(new_openttd_cfg_order); i++) {
 				if (IsValidSearchPath(new_openttd_cfg_order[i])) {
 					config_dir = stredup(_searchpaths[new_openttd_cfg_order[i]]);
 					break;
 				}
 			}
-			assert(config_dir != NULL);
+			assert(config_dir != nullptr);
 #endif
 			_config_file = str_fmt("%sopenttd.cfg", config_dir);
 		}
@@ -1277,27 +1277,27 @@ void SanitizeFilename(char *filename)
  * @param filename Name of the file to load.
  * @param[out] lenp Length of loaded data.
  * @param maxsize Maximum size to load.
- * @return Pointer to new memory containing the loaded data, or \c NULL if loading failed.
+ * @return Pointer to new memory containing the loaded data, or \c nullptr if loading failed.
  * @note If \a maxsize less than the length of the file, loading fails.
  */
 void *ReadFileToMem(const char *filename, size_t *lenp, size_t maxsize)
 {
 	FILE *in = fopen(filename, "rb");
-	if (in == NULL) return NULL;
+	if (in == nullptr) return nullptr;
 
 	fseek(in, 0, SEEK_END);
 	size_t len = ftell(in);
 	fseek(in, 0, SEEK_SET);
 	if (len > maxsize) {
 		fclose(in);
-		return NULL;
+		return nullptr;
 	}
 	byte *mem = MallocT<byte>(len + 1);
 	mem[len] = 0;
 	if (fread(mem, len, 1, in) != 1) {
 		fclose(in);
 		free(mem);
-		return NULL;
+		return nullptr;
 	}
 	fclose(in);
 
@@ -1309,14 +1309,14 @@ void *ReadFileToMem(const char *filename
  * Helper to see whether a given filename matches the extension.
  * @param extension The extension to look for.
  * @param filename  The filename to look in for the extension.
- * @return True iff the extension is NULL, or the filename ends with it.
+ * @return True iff the extension is nullptr, or the filename ends with it.
  */
 static bool MatchesExtension(const char *extension, const char *filename)
 {
-	if (extension == NULL) return true;
+	if (extension == nullptr) return true;
 
 	const char *ext = strrchr(filename, extension[0]);
-	return ext != NULL && strcasecmp(ext, extension) == 0;
+	return ext != nullptr && strcasecmp(ext, extension) == 0;
 }
 
 /**
@@ -1337,9 +1337,9 @@ static uint ScanPath(FileScanner *fs, co
 	struct dirent *dirent;
 	DIR *dir;
 
-	if (path == NULL || (dir = ttd_opendir(path)) == NULL) return 0;
+	if (path == nullptr || (dir = ttd_opendir(path)) == nullptr) return 0;
 
-	while ((dirent = readdir(dir)) != NULL) {
+	while ((dirent = readdir(dir)) != nullptr) {
 		const char *d_name = FS2OTTD(dirent->d_name);
 		char filename[MAX_PATH];
 
@@ -1355,7 +1355,7 @@ static uint ScanPath(FileScanner *fs, co
 			num += ScanPath(fs, extension, filename, basepath_length, recursive);
 		} else if (S_ISREG(sb.st_mode)) {
 			/* File */
-			if (MatchesExtension(extension, filename) && fs->AddFile(filename, basepath_length, NULL)) num++;
+			if (MatchesExtension(extension, filename) && fs->AddFile(filename, basepath_length, nullptr)) num++;
 		}
 	}
 
diff --git a/src/fileio_func.h b/src/fileio_func.h
--- a/src/fileio_func.h
+++ b/src/fileio_func.h
@@ -30,7 +30,7 @@ void FioSkipBytes(int n);
 /**
  * The search paths OpenTTD could search through.
  * At least one of the slots has to be filled with a path.
- * NULL paths tell that there is no such path for the
+ * nullptr paths tell that there is no such path for the
  * current operating system.
  */
 extern const char *_searchpaths[NUM_SEARCHPATHS];
@@ -42,14 +42,14 @@ extern const char *_searchpaths[NUM_SEAR
  */
 static inline bool IsValidSearchPath(Searchpath sp)
 {
-	return sp < NUM_SEARCHPATHS && _searchpaths[sp] != NULL;
+	return sp < NUM_SEARCHPATHS && _searchpaths[sp] != nullptr;
 }
 
 /** Iterator for all the search paths */
 #define FOR_ALL_SEARCHPATHS(sp) for (sp = SP_FIRST_DIR; sp < NUM_SEARCHPATHS; sp++) if (IsValidSearchPath(sp))
 
 void FioFCloseFile(FILE *f);
-FILE *FioFOpenFile(const char *filename, const char *mode, Subdirectory subdir, size_t *filesize = NULL);
+FILE *FioFOpenFile(const char *filename, const char *mode, Subdirectory subdir, size_t *filesize = nullptr);
 bool FioCheckFileExists(const char *filename, Subdirectory subdir);
 char *FioGetFullPath(char *buf, const char *last, Searchpath sp, Subdirectory subdir, const char *filename);
 char *FioFindFullPath(char *buf, const char *last, Subdirectory subdir, const char *filename);
@@ -107,7 +107,7 @@ public:
 		ALL      = BASESET | NEWGRF | AI | SCENARIO | GAME, ///< Scan for everything.
 	};
 
-	bool AddFile(const char *filename, size_t basepath_length, const char *tar_filename = NULL) override;
+	bool AddFile(const char *filename, size_t basepath_length, const char *tar_filename = nullptr) override;
 
 	bool AddFile(Subdirectory sd, const char *filename);
 
diff --git a/src/fios.cpp b/src/fios.cpp
--- a/src/fios.cpp
+++ b/src/fios.cpp
@@ -105,7 +105,7 @@ void FileList::BuildFileList(AbstractFil
  * Find file information of a file by its name from the file list.
  * @param file The filename to return information about. Can be the actual name
  *             or a numbered entry into the filename list.
- * @return The information on the file, or \c NULL if the file is not available.
+ * @return The information on the file, or \c nullptr if the file is not available.
  */
 const FiosItem *FileList::FindItem(const char *file)
 {
@@ -130,14 +130,14 @@ const FiosItem *FileList::FindItem(const
 		if (strcmp(long_file, item->title) == 0) return item;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
  * Get descriptive texts. Returns the path and free space
  * left on the device
  * @param path string describing the path
- * @param total_free total free space in megabytes, optional (can be NULL)
+ * @param total_free total free space in megabytes, optional (can be nullptr)
  * @return StringID describing the path (free space or failure)
  */
 StringID FiosGetDescText(const char **path, uint64 *total_free)
@@ -149,7 +149,7 @@ StringID FiosGetDescText(const char **pa
 /**
  * Browse to a new path based on the passed \a item, starting at #_fios_path.
  * @param *item Item telling us what to do.
- * @return A filename w/path if we reached a file, otherwise \c NULL.
+ * @return A filename w/path if we reached a file, otherwise \c nullptr.
  */
 const char *FiosBrowseTo(const FiosItem *item)
 {
@@ -164,13 +164,13 @@ const char *FiosBrowseTo(const FiosItem 
 			break;
 
 		case FIOS_TYPE_PARENT: {
-			/* Check for possible NULL ptr */
+			/* Check for possible nullptr ptr */
 			char *s = strrchr(_fios_path, PATHSEPCHAR);
-			if (s != NULL && s != _fios_path) {
+			if (s != nullptr && s != _fios_path) {
 				s[0] = '\0'; // Remove last path separator character, so we can go up one level.
 			}
 			s = strrchr(_fios_path, PATHSEPCHAR);
-			if (s != NULL) {
+			if (s != nullptr) {
 				s[1] = '\0'; // go up a directory
 			}
 			break;
@@ -194,13 +194,13 @@ const char *FiosBrowseTo(const FiosItem 
 			return item->name;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
  * Construct a filename from its components in destination buffer \a buf.
  * @param buf Destination buffer.
- * @param path Directory path, may be \c NULL.
+ * @param path Directory path, may be \c nullptr.
  * @param name Filename.
  * @param ext Filename extension (use \c "" for no extension).
  * @param last Last element of buffer \a buf.
@@ -211,7 +211,7 @@ static void FiosMakeFilename(char *buf, 
 
 	/* Don't append the extension if it is already there */
 	period = strrchr(name, '.');
-	if (period != NULL && strcasecmp(period, ext) == 0) ext = "";
+	if (period != nullptr && strcasecmp(period, ext) == 0) ext = "";
 	seprintf(buf, last, "%s" PATHSEP "%s%s", path, name, ext);
 }
 
@@ -288,7 +288,7 @@ public:
 bool FiosFileScanner::AddFile(const char *filename, size_t basepath_length, const char *tar_filename)
 {
 	const char *ext = strrchr(filename, '.');
-	if (ext == NULL) return false;
+	if (ext == nullptr) return false;
 
 	char fios_title[64];
 	fios_title[0] = '\0'; // reset the title;
@@ -320,7 +320,7 @@ bool FiosFileScanner::AddFile(const char
 	const char *t = fios_title;
 	if (StrEmpty(fios_title)) {
 		t = strrchr(filename, PATHSEPCHAR);
-		t = (t == NULL) ? filename : (t + 1);
+		t = (t == nullptr) ? filename : (t + 1);
 	}
 	strecpy(fios->title, t, lastof(fios->title));
 	str_validate(fios->title, lastof(fios->title));
@@ -357,8 +357,8 @@ static void FiosGetFileList(SaveLoadOper
 	}
 
 	/* Show subdirectories */
-	if ((dir = ttd_opendir(_fios_path)) != NULL) {
-		while ((dirent = readdir(dir)) != NULL) {
+	if ((dir = ttd_opendir(_fios_path)) != nullptr) {
+		while ((dirent = readdir(dir)) != nullptr) {
 			strecpy(d_name, FS2OTTD(dirent->d_name), lastof(d_name));
 
 			/* found file must be directory, but not '.' or '..' */
@@ -390,9 +390,9 @@ static void FiosGetFileList(SaveLoadOper
 	/* Show files */
 	FiosFileScanner scanner(fop, callback_proc, file_list);
 	if (subdir == NO_DIRECTORY) {
-		scanner.Scan(NULL, _fios_path, false);
+		scanner.Scan(nullptr, _fios_path, false);
 	} else {
-		scanner.Scan(NULL, subdir, true, true);
+		scanner.Scan(nullptr, subdir, true, true);
 	}
 
 	QSortT(file_list.Get(sort_start), file_list.Length() - sort_start, CompareFiosItems);
@@ -418,7 +418,7 @@ static void GetFileTitle(const char *fil
 	strecat(buf, ".title", lastof(buf));
 
 	FILE *f = FioFOpenFile(buf, "r", subdir);
-	if (f == NULL) return;
+	if (f == nullptr) return;
 
 	size_t read = fread(title, 1, last - title, f);
 	assert(title + read <= last);
@@ -432,8 +432,8 @@ static void GetFileTitle(const char *fil
  * @param fop Purpose of collecting the list.
  * @param file Name of the file to check.
  * @param ext A pointer to the extension identifier inside file
- * @param title Buffer if a callback wants to lookup the title of the file; NULL to skip the lookup
- * @param last Last available byte in buffer (to prevent buffer overflows); not used when title == NULL
+ * @param title Buffer if a callback wants to lookup the title of the file; nullptr to skip the lookup
+ * @param last Last available byte in buffer (to prevent buffer overflows); not used when title == nullptr
  * @return a FIOS_TYPE_* type of the found file, FIOS_TYPE_INVALID if not a savegame
  * @see FiosGetFileList
  * @see FiosGetSavegameList
@@ -447,7 +447,7 @@ FiosType FiosGetSavegameListCallback(Sav
 	 * .SV2 Transport Tycoon Deluxe (Patch) saved 2-player game */
 
 	/* Don't crash if we supply no extension */
-	if (ext == NULL) return FIOS_TYPE_INVALID;
+	if (ext == nullptr) return FIOS_TYPE_INVALID;
 
 	if (strcasecmp(ext, ".sav") == 0) {
 		GetFileTitle(file, title, last, SAVE_DIR);
@@ -457,7 +457,7 @@ FiosType FiosGetSavegameListCallback(Sav
 	if (fop == SLO_LOAD) {
 		if (strcasecmp(ext, ".ss1") == 0 || strcasecmp(ext, ".sv1") == 0 ||
 				strcasecmp(ext, ".sv2") == 0) {
-			if (title != NULL) GetOldSaveGameName(file, title, last);
+			if (title != nullptr) GetOldSaveGameName(file, title, last);
 			return FIOS_TYPE_OLDFILE;
 		}
 	}
@@ -473,10 +473,10 @@ FiosType FiosGetSavegameListCallback(Sav
  */
 void FiosGetSavegameList(SaveLoadOperation fop, FileList &file_list)
 {
-	static char *fios_save_path = NULL;
-	static char *fios_save_path_last = NULL;
+	static char *fios_save_path = nullptr;
+	static char *fios_save_path_last = nullptr;
 
-	if (fios_save_path == NULL) {
+	if (fios_save_path == nullptr) {
 		fios_save_path = MallocT<char>(MAX_PATH);
 		fios_save_path_last = fios_save_path + MAX_PATH - 1;
 		FioGetDirectory(fios_save_path, fios_save_path_last, SAVE_DIR);
@@ -528,11 +528,11 @@ static FiosType FiosGetScenarioListCallb
  */
 void FiosGetScenarioList(SaveLoadOperation fop, FileList &file_list)
 {
-	static char *fios_scn_path = NULL;
-	static char *fios_scn_path_last = NULL;
+	static char *fios_scn_path = nullptr;
+	static char *fios_scn_path_last = nullptr;
 
 	/* Copy the default path on first run or on 'New Game' */
-	if (fios_scn_path == NULL) {
+	if (fios_scn_path == nullptr) {
 		fios_scn_path = MallocT<char>(MAX_PATH);
 		fios_scn_path_last = fios_scn_path + MAX_PATH - 1;
 		FioGetDirectory(fios_scn_path, fios_scn_path_last, SCENARIO_DIR);
@@ -599,10 +599,10 @@ static FiosType FiosGetHeightmapListCall
  */
 void FiosGetHeightmapList(SaveLoadOperation fop, FileList &file_list)
 {
-	static char *fios_hmap_path = NULL;
-	static char *fios_hmap_path_last = NULL;
+	static char *fios_hmap_path = nullptr;
+	static char *fios_hmap_path_last = nullptr;
 
-	if (fios_hmap_path == NULL) {
+	if (fios_hmap_path == nullptr) {
 		fios_hmap_path = MallocT<char>(MAX_PATH);
 		fios_hmap_path_last = fios_hmap_path + MAX_PATH - 1;
 		FioGetDirectory(fios_hmap_path, fios_hmap_path_last, HEIGHTMAP_DIR);
@@ -624,9 +624,9 @@ void FiosGetHeightmapList(SaveLoadOperat
  */
 const char *FiosGetScreenshotDir()
 {
-	static char *fios_screenshot_path = NULL;
+	static char *fios_screenshot_path = nullptr;
 
-	if (fios_screenshot_path == NULL) {
+	if (fios_screenshot_path == nullptr) {
 		fios_screenshot_path = MallocT<char>(MAX_PATH);
 		FioGetDirectory(fios_screenshot_path, fios_screenshot_path + MAX_PATH - 1, SCREENSHOT_DIR);
 	}
@@ -676,7 +676,7 @@ public:
 	bool AddFile(const char *filename, size_t basepath_length, const char *tar_filename) override
 	{
 		FILE *f = FioFOpenFile(filename, "r", SCENARIO_DIR);
-		if (f == NULL) return false;
+		if (f == nullptr) return false;
 
 		ScenarioIdentifier id;
 		int fret = fscanf(f, "%i", &id.scenid);
@@ -695,7 +695,7 @@ public:
 		strecpy(basename, filename, lastof(basename));
 		*strrchr(basename, '.') = '\0';
 		f = FioFOpenFile(basename, "rb", SCENARIO_DIR, &size);
-		if (f == NULL) return false;
+		if (f == nullptr) return false;
 
 		/* calculate md5sum */
 		while ((len = fread(buffer, 1, (size > sizeof(buffer)) ? sizeof(buffer) : size, f)) != 0 && size != 0) {
@@ -718,7 +718,7 @@ static ScenarioScanner _scanner;
  * Find a given scenario based on its unique ID.
  * @param ci The content info to compare it to.
  * @param md5sum Whether to look at the md5sum or the id.
- * @return The filename of the file, else \c NULL.
+ * @return The filename of the file, else \c nullptr.
  */
 const char *FindScenario(const ContentInfo *ci, bool md5sum)
 {
@@ -731,7 +731,7 @@ const char *FindScenario(const ContentIn
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -742,7 +742,7 @@ const char *FindScenario(const ContentIn
  */
 bool HasScenario(const ContentInfo *ci, bool md5sum)
 {
-	return (FindScenario(ci, md5sum) != NULL);
+	return (FindScenario(ci, md5sum) != nullptr);
 }
 
 /**
diff --git a/src/fios.h b/src/fios.h
--- a/src/fios.h
+++ b/src/fios.h
@@ -48,8 +48,8 @@ struct LoadCheckData {
 	struct LoggedAction *gamelog_action;          ///< Gamelog actions
 	uint gamelog_actions;                         ///< Number of gamelog actions
 
-	LoadCheckData() : error_data(NULL), grfconfig(NULL),
-			grf_compatibility(GLC_NOT_FOUND), gamelog_action(NULL), gamelog_actions(0)
+	LoadCheckData() : error_data(nullptr), grfconfig(nullptr),
+			grf_compatibility(GLC_NOT_FOUND), gamelog_action(nullptr), gamelog_actions(0)
 	{
 		this->Clear();
 	}
@@ -77,7 +77,7 @@ struct LoadCheckData {
 	 */
 	bool HasNewGrfs()
 	{
-		return this->checkable && this->error == INVALID_STRING_ID && this->grfconfig != NULL;
+		return this->checkable && this->error == INVALID_STRING_ID && this->grfconfig != nullptr;
 	}
 
 	void Clear();
diff --git a/src/fios_gui.cpp b/src/fios_gui.cpp
--- a/src/fios_gui.cpp
+++ b/src/fios_gui.cpp
@@ -51,7 +51,7 @@ void LoadCheckData::Clear()
 	this->checkable = false;
 	this->error = INVALID_STRING_ID;
 	free(this->error_data);
-	this->error_data = NULL;
+	this->error_data = nullptr;
 
 	this->map_size_x = this->map_size_y = 256; // Default for old savegames which do not store mapsize.
 	this->current_date = 0;
@@ -63,7 +63,7 @@ void LoadCheckData::Clear()
 	companies.clear();
 
 	GamelogFree(this->gamelog_action, this->gamelog_actions);
-	this->gamelog_action = NULL;
+	this->gamelog_action = nullptr;
 	this->gamelog_actions = 0;
 
 	ClearGRFConfigList(&this->grfconfig);
@@ -273,7 +273,7 @@ private:
 	SaveLoadOperation fop;        ///< File operation to perform.
 	FileList fios_items;          ///< Save game list.
 	FiosItem o_dir;
-	const FiosItem *selected;     ///< Selected game in #fios_items, or \c NULL.
+	const FiosItem *selected;     ///< Selected game in #fios_items, or \c nullptr.
 	Scrollbar *vscroll;
 
 	StringFilter string_filter; ///< Filter for available games.
@@ -417,7 +417,7 @@ public:
 				break;
 
 			case WID_SL_BACKGROUND: {
-				static const char *path = NULL;
+				static const char *path = nullptr;
 				static StringID str = STR_ERROR_UNABLE_TO_READ_DRIVE;
 				static uint64 tot = 0;
 
@@ -461,7 +461,7 @@ public:
 						r.right - WD_FRAMERECT_RIGHT, r.top + FONT_HEIGHT_NORMAL * 2 + WD_FRAMERECT_TOP + WD_FRAMERECT_BOTTOM, PC_GREY);
 				DrawString(r.left, r.right, r.top + FONT_HEIGHT_NORMAL / 2 + WD_FRAMERECT_TOP, STR_SAVELOAD_DETAIL_CAPTION, TC_FROMSTRING, SA_HOR_CENTER);
 
-				if (this->selected == NULL) break;
+				if (this->selected == nullptr) break;
 
 				uint y = r.top + FONT_HEIGHT_NORMAL * 2 + WD_PAR_VSEP_NORMAL + WD_FRAMERECT_TOP + WD_FRAMERECT_BOTTOM;
 				uint y_max = r.bottom - FONT_HEIGHT_NORMAL - WD_FRAMERECT_BOTTOM;
@@ -517,7 +517,7 @@ public:
 						if (y > y_max) break;
 
 						/* NewGrf compatibility */
-						SetDParam(0, _load_check_data.grfconfig == NULL ? STR_NEWGRF_LIST_NONE :
+						SetDParam(0, _load_check_data.grfconfig == nullptr ? STR_NEWGRF_LIST_NONE :
 								STR_NEWGRF_LIST_ALL_FOUND + _load_check_data.grf_compatibility);
 						DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, y, STR_SAVELOAD_DETAIL_GRFSTATUS);
 						y += FONT_HEIGHT_NORMAL;
@@ -533,7 +533,7 @@ public:
 						for (auto &pair : _load_check_data.companies) {
 							SetDParam(0, pair.first + 1);
 							const CompanyProperties &c = *pair.second;
-							if (c.name != NULL) {
+							if (c.name != nullptr) {
 								SetDParam(1, STR_JUST_RAW_STRING);
 								SetDParamStr(2, c.name);
 							} else {
@@ -607,7 +607,7 @@ public:
 				break;
 
 			case WID_SL_LOAD_BUTTON:
-				if (this->selected != NULL && !_load_check_data.HasErrors()) {
+				if (this->selected != nullptr && !_load_check_data.HasErrors()) {
 					const char *name = FiosBrowseTo(this->selected);
 					_file_to_saveload.SetMode(this->selected->type);
 					_file_to_saveload.SetName(name);
@@ -652,7 +652,7 @@ public:
 				const FiosItem *file = this->fios_items.Get(y);
 
 				const char *name = FiosBrowseTo(file);
-				if (name != NULL) {
+				if (name != nullptr) {
 					if (click_count == 1) {
 						if (this->selected != file) {
 							this->selected = file;
@@ -700,8 +700,8 @@ public:
 					assert(this->fop == SLO_LOAD);
 					switch (this->abstract_filetype) {
 						default: NOT_REACHED();
-						case FT_SCENARIO:  ShowNetworkContentListWindow(NULL, CONTENT_TYPE_SCENARIO);  break;
-						case FT_HEIGHTMAP: ShowNetworkContentListWindow(NULL, CONTENT_TYPE_HEIGHTMAP); break;
+						case FT_SCENARIO:  ShowNetworkContentListWindow(nullptr, CONTENT_TYPE_SCENARIO);  break;
+						case FT_HEIGHTMAP: ShowNetworkContentListWindow(nullptr, CONTENT_TYPE_HEIGHTMAP); break;
 					}
 				}
 				break;
@@ -776,14 +776,14 @@ public:
 		switch (data) {
 			case SLIWD_RESCAN_FILES:
 				/* Rescan files */
-				this->selected = NULL;
+				this->selected = nullptr;
 				_load_check_data.Clear();
 				if (!gui_scope) break;
 
 				_fios_path_changed = true;
 				this->fios_items.BuildFileList(this->abstract_filetype, this->fop);
 				this->vscroll->SetCount((uint)this->fios_items.Length());
-				this->selected = NULL;
+				this->selected = nullptr;
 				_load_check_data.Clear();
 
 				/* We reset the files filtered */
@@ -799,12 +799,12 @@ public:
 
 				switch (this->abstract_filetype) {
 					case FT_HEIGHTMAP:
-						this->SetWidgetDisabledState(WID_SL_LOAD_BUTTON, this->selected == NULL || _load_check_data.HasErrors());
+						this->SetWidgetDisabledState(WID_SL_LOAD_BUTTON, this->selected == nullptr || _load_check_data.HasErrors());
 						break;
 
 					case FT_SAVEGAME:
 					case FT_SCENARIO: {
-						bool disabled = this->selected == NULL || _load_check_data.HasErrors();
+						bool disabled = this->selected == nullptr || _load_check_data.HasErrors();
 						if (!_settings_client.gui.UserIsAllowedToChangeNewGRFs()) {
 							disabled |= _load_check_data.HasNewGrfs() && _load_check_data.grf_compatibility == GLC_NOT_FOUND;
 						}
@@ -839,7 +839,7 @@ public:
 
 						if (&(this->fios_items[i]) == this->selected && this->fios_items_shown[i] == false) {
 							/* The selected element has been filtered out */
-							this->selected = NULL;
+							this->selected = nullptr;
 							this->OnInvalidateData(SLIWD_SELECTION_CHANGES);
 						}
 					}
diff --git a/src/fontcache.cpp b/src/fontcache.cpp
--- a/src/fontcache.cpp
+++ b/src/fontcache.cpp
@@ -41,7 +41,7 @@ FontCache::FontCache(FontSize fs) : pare
 		ascender(_default_font_ascender[fs]), descender(_default_font_ascender[fs] - _default_font_height[fs]),
 		units_per_em(1)
 {
-	assert(this->parent == NULL || this->fs == this->parent->fs);
+	assert(this->parent == nullptr || this->fs == this->parent->fs);
 	FontCache::caches[this->fs] = this;
 	Layouter::ResetFontCache(this->fs);
 }
@@ -84,7 +84,7 @@ public:
 	virtual int GetHeight() const;
 	virtual bool GetDrawGlyphShadow();
 	virtual GlyphID MapCharToGlyph(WChar key) { assert(IsPrintable(key)); return SPRITE_GLYPH | key; }
-	virtual const void *GetFontTable(uint32 tag, size_t &length) { length = 0; return NULL; }
+	virtual const void *GetFontTable(uint32 tag, size_t &length) { length = 0; return nullptr; }
 	virtual const char *GetFontName() { return "sprite"; }
 	virtual bool IsBuiltInFont() { return true; }
 };
@@ -93,7 +93,7 @@ public:
  * Create a new sprite font cache.
  * @param fs The font size to create the cache for.
  */
-SpriteFontCache::SpriteFontCache(FontSize fs) : FontCache(fs), glyph_to_spriteid_map(NULL)
+SpriteFontCache::SpriteFontCache(FontSize fs) : FontCache(fs), glyph_to_spriteid_map(nullptr)
 {
 	this->InitializeUnicodeGlyphMap();
 }
@@ -108,14 +108,14 @@ SpriteFontCache::~SpriteFontCache()
 
 SpriteID SpriteFontCache::GetUnicodeGlyph(GlyphID key)
 {
-	if (this->glyph_to_spriteid_map[GB(key, 8, 8)] == NULL) return 0;
+	if (this->glyph_to_spriteid_map[GB(key, 8, 8)] == nullptr) return 0;
 	return this->glyph_to_spriteid_map[GB(key, 8, 8)][GB(key, 0, 8)];
 }
 
 void SpriteFontCache::SetUnicodeGlyph(GlyphID key, SpriteID sprite)
 {
-	if (this->glyph_to_spriteid_map == NULL) this->glyph_to_spriteid_map = CallocT<SpriteID*>(256);
-	if (this->glyph_to_spriteid_map[GB(key, 8, 8)] == NULL) this->glyph_to_spriteid_map[GB(key, 8, 8)] = CallocT<SpriteID>(256);
+	if (this->glyph_to_spriteid_map == nullptr) this->glyph_to_spriteid_map = CallocT<SpriteID*>(256);
+	if (this->glyph_to_spriteid_map[GB(key, 8, 8)] == nullptr) this->glyph_to_spriteid_map[GB(key, 8, 8)] = CallocT<SpriteID>(256);
 	this->glyph_to_spriteid_map[GB(key, 8, 8)][GB(key, 0, 8)] = sprite;
 }
 
@@ -159,13 +159,13 @@ void SpriteFontCache::InitializeUnicodeG
  */
 void SpriteFontCache::ClearGlyphToSpriteMap()
 {
-	if (this->glyph_to_spriteid_map == NULL) return;
+	if (this->glyph_to_spriteid_map == nullptr) return;
 
 	for (uint i = 0; i < 256; i++) {
 		free(this->glyph_to_spriteid_map[i]);
 	}
 	free(this->glyph_to_spriteid_map);
-	this->glyph_to_spriteid_map = NULL;
+	this->glyph_to_spriteid_map = nullptr;
 }
 
 void SpriteFontCache::ClearFontCache()
@@ -258,7 +258,7 @@ public:
 	virtual bool IsBuiltInFont() { return false; }
 };
 
-FT_Library _library = NULL;
+FT_Library _library = nullptr;
 
 FreeTypeSettings _freetype;
 
@@ -271,9 +271,9 @@ static const byte SHADOW_COLOUR = 2;
  * @param face   The font that has to be loaded.
  * @param pixels The number of pixels this font should be high.
  */
-FreeTypeFontCache::FreeTypeFontCache(FontSize fs, FT_Face face, int pixels) : FontCache(fs), face(face), req_size(pixels), glyph_to_sprite(NULL)
+FreeTypeFontCache::FreeTypeFontCache(FontSize fs, FT_Face face, int pixels) : FontCache(fs), face(face), req_size(pixels), glyph_to_sprite(nullptr)
 {
-	assert(face != NULL);
+	assert(face != nullptr);
 
 	this->SetFontSize(fs, face, pixels);
 }
@@ -286,7 +286,7 @@ void FreeTypeFontCache::SetFontSize(Font
 		pixels = scaled_height;
 
 		TT_Header *head = (TT_Header *)FT_Get_Sfnt_Table(this->face, ft_sfnt_head);
-		if (head != NULL) {
+		if (head != nullptr) {
 			/* Font height is minimum height plus the difference between the default
 			 * height for this font size and the small size. */
 			int diff = scaled_height - ScaleFontTrad(_default_font_height[FS_SMALL]);
@@ -338,7 +338,7 @@ void FreeTypeFontCache::SetFontSize(Font
  */
 static void LoadFreeTypeFont(FontSize fs)
 {
-	FreeTypeSubSetting *settings = NULL;
+	FreeTypeSubSetting *settings = nullptr;
 	switch (fs) {
 		default: NOT_REACHED();
 		case FS_SMALL:  settings = &_freetype.small;  break;
@@ -349,7 +349,7 @@ static void LoadFreeTypeFont(FontSize fs
 
 	if (StrEmpty(settings->font)) return;
 
-	if (_library == NULL) {
+	if (_library == nullptr) {
 		if (FT_Init_FreeType(&_library) != FT_Err_Ok) {
 			ShowInfoF("Unable to initialize FreeType, using sprite fonts instead");
 			return;
@@ -358,7 +358,7 @@ static void LoadFreeTypeFont(FontSize fs
 		DEBUG(freetype, 2, "Initialized");
 	}
 
-	FT_Face face = NULL;
+	FT_Face face = nullptr;
 	FT_Error error = FT_New_Face(_library, settings->font, 0, &face);
 
 	if (error != FT_Err_Ok) error = GetFontByFaceName(settings->font, &face);
@@ -384,7 +384,7 @@ static void LoadFreeTypeFont(FontSize fs
 				}
 			}
 
-			if (found != NULL) {
+			if (found != nullptr) {
 				error = FT_Set_Charmap(face, found);
 				if (error == FT_Err_Ok) goto found_face;
 			}
@@ -408,7 +408,7 @@ found_face:
 FreeTypeFontCache::~FreeTypeFontCache()
 {
 	FT_Done_Face(this->face);
-	this->face = NULL;
+	this->face = nullptr;
 	this->ClearFontCache();
 
 	for (auto &iter : this->font_tables) {
@@ -422,12 +422,12 @@ FreeTypeFontCache::~FreeTypeFontCache()
 void FreeTypeFontCache::ClearFontCache()
 {
 	/* Font scaling might have changed, determine font size anew if it was automatically selected. */
-	if (this->face != NULL) this->SetFontSize(this->fs, this->face, this->req_size);
+	if (this->face != nullptr) this->SetFontSize(this->fs, this->face, this->req_size);
 
-	if (this->glyph_to_sprite == NULL) return;
+	if (this->glyph_to_sprite == nullptr) return;
 
 	for (int i = 0; i < 256; i++) {
-		if (this->glyph_to_sprite[i] == NULL) continue;
+		if (this->glyph_to_sprite[i] == nullptr) continue;
 
 		for (int j = 0; j < 256; j++) {
 			if (this->glyph_to_sprite[i][j].duplicate) continue;
@@ -438,27 +438,27 @@ void FreeTypeFontCache::ClearFontCache()
 	}
 
 	free(this->glyph_to_sprite);
-	this->glyph_to_sprite = NULL;
+	this->glyph_to_sprite = nullptr;
 
 	Layouter::ResetFontCache(this->fs);
 }
 
 FreeTypeFontCache::GlyphEntry *FreeTypeFontCache::GetGlyphPtr(GlyphID key)
 {
-	if (this->glyph_to_sprite == NULL) return NULL;
-	if (this->glyph_to_sprite[GB(key, 8, 8)] == NULL) return NULL;
+	if (this->glyph_to_sprite == nullptr) return nullptr;
+	if (this->glyph_to_sprite[GB(key, 8, 8)] == nullptr) return nullptr;
 	return &this->glyph_to_sprite[GB(key, 8, 8)][GB(key, 0, 8)];
 }
 
 
 void FreeTypeFontCache::SetGlyphPtr(GlyphID key, const GlyphEntry *glyph, bool duplicate)
 {
-	if (this->glyph_to_sprite == NULL) {
+	if (this->glyph_to_sprite == nullptr) {
 		DEBUG(freetype, 3, "Allocating root glyph cache for size %u", this->fs);
 		this->glyph_to_sprite = CallocT<GlyphEntry*>(256);
 	}
 
-	if (this->glyph_to_sprite[GB(key, 8, 8)] == NULL) {
+	if (this->glyph_to_sprite[GB(key, 8, 8)] == nullptr) {
 		DEBUG(freetype, 3, "Allocating glyph cache for range 0x%02X00, size %u", GB(key, 8, 8), this->fs);
 		this->glyph_to_sprite[GB(key, 8, 8)] = CallocT<GlyphEntry>(256);
 	}
@@ -497,7 +497,7 @@ const Sprite *FreeTypeFontCache::GetGlyp
 
 	/* Check for the glyph in our cache */
 	GlyphEntry *glyph = this->GetGlyphPtr(key);
-	if (glyph != NULL && glyph->sprite != NULL) return glyph->sprite;
+	if (glyph != nullptr && glyph->sprite != nullptr) return glyph->sprite;
 
 	FT_GlyphSlot slot = this->face->glyph;
 
@@ -535,7 +535,7 @@ const Sprite *FreeTypeFontCache::GetGlyp
 			};
 
 			Sprite *spr = BlitterFactory::GetCurrentBlitter()->Encode(&builtin_questionmark, AllocateFont);
-			assert(spr != NULL);
+			assert(spr != nullptr);
 			new_glyph.sprite = spr;
 			new_glyph.width  = spr->width + (this->fs != FS_NORMAL);
 			this->SetGlyphPtr(key, &new_glyph, false);
@@ -611,7 +611,7 @@ uint FreeTypeFontCache::GetGlyphWidth(Gl
 	if ((key & SPRITE_GLYPH) != 0) return this->parent->GetGlyphWidth(key);
 
 	GlyphEntry *glyph = this->GetGlyphPtr(key);
-	if (glyph == NULL || glyph->sprite == NULL) {
+	if (glyph == nullptr || glyph->sprite == nullptr) {
 		this->GetGlyph(key);
 		glyph = this->GetGlyphPtr(key);
 	}
@@ -639,9 +639,9 @@ const void *FreeTypeFontCache::GetFontTa
 	}
 
 	FT_ULong len = 0;
-	FT_Byte *result = NULL;
+	FT_Byte *result = nullptr;
 
-	FT_Load_Sfnt_Table(this->face, tag, 0, NULL, &len);
+	FT_Load_Sfnt_Table(this->face, tag, 0, nullptr, &len);
 
 	if (len > 0) {
 		result = MallocT<FT_Byte>(len);
@@ -685,6 +685,6 @@ void UninitFreeType()
 
 #ifdef WITH_FREETYPE
 	FT_Done_FreeType(_library);
-	_library = NULL;
+	_library = nullptr;
 #endif /* WITH_FREETYPE */
 }
diff --git a/src/fontcache.h b/src/fontcache.h
--- a/src/fontcache.h
+++ b/src/fontcache.h
@@ -147,7 +147,7 @@ public:
 	 */
 	inline bool HasParent()
 	{
-		return this->parent != NULL;
+		return this->parent != nullptr;
 	}
 
 	/**
diff --git a/src/fontdetection.cpp b/src/fontdetection.cpp
--- a/src/fontdetection.cpp
+++ b/src/fontdetection.cpp
@@ -53,7 +53,7 @@ const char *GetShortPath(const TCHAR *lo
 #ifdef UNICODE
 	WCHAR short_path_w[MAX_PATH];
 	GetShortPathName(long_path, short_path_w, lengthof(short_path_w));
-	WideCharToMultiByte(CP_ACP, 0, short_path_w, -1, short_path, lengthof(short_path), NULL, NULL);
+	WideCharToMultiByte(CP_ACP, 0, short_path_w, -1, short_path, lengthof(short_path), nullptr, nullptr);
 #else
 	/* Technically not needed, but do it for consistency. */
 	GetShortPathName(long_path, short_path, lengthof(short_path));
@@ -101,7 +101,7 @@ FT_Error GetFontByFaceName(const char *f
 		DWORD vbuflen = lengthof(vbuffer);
 		DWORD dbuflen = lengthof(dbuffer);
 
-		ret = RegEnumValue(hKey, index, vbuffer, &vbuflen, NULL, NULL, (byte*)dbuffer, &dbuflen);
+		ret = RegEnumValue(hKey, index, vbuffer, &vbuflen, nullptr, nullptr, (byte*)dbuffer, &dbuflen);
 		if (ret != ERROR_SUCCESS) goto registry_no_font_found;
 
 		/* The font names in the registry are of the following 3 forms:
@@ -114,16 +114,16 @@ FT_Error GetFontByFaceName(const char *f
 		 * by '&'. Our best bet will be to do substr match for the fontname
 		 * and then let FreeType figure out which index to load */
 		s = _tcschr(vbuffer, _T('('));
-		if (s != NULL) s[-1] = '\0';
+		if (s != nullptr) s[-1] = '\0';
 
-		if (_tcschr(vbuffer, _T('&')) == NULL) {
+		if (_tcschr(vbuffer, _T('&')) == nullptr) {
 			if (_tcsicmp(vbuffer, font_namep) == 0) break;
 		} else {
-			if (_tcsstr(vbuffer, font_namep) != NULL) break;
+			if (_tcsstr(vbuffer, font_namep) != nullptr) break;
 		}
 	}
 
-	if (!SUCCEEDED(OTTDSHGetFolderPath(NULL, CSIDL_FONTS, NULL, SHGFP_TYPE_CURRENT, vbuffer))) {
+	if (!SUCCEEDED(OTTDSHGetFolderPath(nullptr, CSIDL_FONTS, nullptr, SHGFP_TYPE_CURRENT, vbuffer))) {
 		DEBUG(freetype, 0, "SHGetFolderPath cannot return fonts directory");
 		goto folder_error;
 	}
@@ -175,7 +175,7 @@ registry_no_font_found:
 static const char *GetEnglishFontName(const ENUMLOGFONTEX *logfont)
 {
 	static char font_name[MAX_PATH];
-	const char *ret_font_name = NULL;
+	const char *ret_font_name = nullptr;
 	uint pos = 0;
 	HDC dc;
 	HGDIOBJ oldfont;
@@ -184,11 +184,11 @@ static const char *GetEnglishFontName(co
 	uint16 format, count, stringOffset, platformId, encodingId, languageId, nameId, length, offset;
 
 	HFONT font = CreateFontIndirect(&logfont->elfLogFont);
-	if (font == NULL) goto err1;
+	if (font == nullptr) goto err1;
 
-	dc = GetDC(NULL);
+	dc = GetDC(nullptr);
 	oldfont = SelectObject(dc, font);
-	dw = GetFontData(dc, 'eman', 0, NULL, 0);
+	dw = GetFontData(dc, 'eman', 0, nullptr, 0);
 	if (dw == GDI_ERROR) goto err2;
 
 	buf = MallocT<byte>(dw);
@@ -236,10 +236,10 @@ err3:
 	free(buf);
 err2:
 	SelectObject(dc, oldfont);
-	ReleaseDC(NULL, dc);
+	ReleaseDC(nullptr, dc);
 	DeleteObject(font);
 err1:
-	return ret_font_name == NULL ? WIDE_TO_MB((const TCHAR*)logfont->elfFullName) : ret_font_name;
+	return ret_font_name == nullptr ? WIDE_TO_MB((const TCHAR*)logfont->elfFullName) : ret_font_name;
 }
 
 class FontList {
@@ -249,10 +249,10 @@ protected:
 	uint capacity;
 
 public:
-	FontList() : fonts(NULL), items(0), capacity(0) { };
+	FontList() : fonts(nullptr), items(0), capacity(0) { };
 
 	~FontList() {
-		if (this->fonts == NULL) return;
+		if (this->fonts == nullptr) return;
 
 		for (uint i = 0; i < this->items; i++) {
 			free(this->fonts[i]);
@@ -303,12 +303,12 @@ static int CALLBACK EnumFontCallback(con
 		FONTSIGNATURE fs;
 		memset(&fs, 0, sizeof(fs));
 		HFONT font = CreateFontIndirect(&logfont->elfLogFont);
-		if (font != NULL) {
-			HDC dc = GetDC(NULL);
+		if (font != nullptr) {
+			HDC dc = GetDC(nullptr);
 			HGDIOBJ oldfont = SelectObject(dc, font);
 			GetTextCharsetInfo(dc, &fs, 0);
 			SelectObject(dc, oldfont);
-			ReleaseDC(NULL, dc);
+			ReleaseDC(nullptr, dc);
 			DeleteObject(font);
 		}
 		if ((fs.fsCsb[0] & info->locale.lsCsbSupported[0]) == 0 && (fs.fsCsb[1] & info->locale.lsCsbSupported[1]) == 0) return 1;
@@ -322,7 +322,7 @@ static int CALLBACK EnumFontCallback(con
 	strecpy(font_name + strlen(font_name) + 1, english_name, lastof(font_name));
 
 	/* Check whether we can actually load the font. */
-	bool ft_init = _library != NULL;
+	bool ft_init = _library != nullptr;
 	bool found = false;
 	FT_Face face;
 	/* Init FreeType if needed. */
@@ -333,13 +333,13 @@ static int CALLBACK EnumFontCallback(con
 	if (!ft_init) {
 		/* Uninit FreeType if we did the init. */
 		FT_Done_FreeType(_library);
-		_library = NULL;
+		_library = nullptr;
 	}
 
 	if (!found) return 1;
 
 	info->callback->SetFontNames(info->settings, font_name);
-	if (info->callback->FindMissingGlyphs(NULL)) return 1;
+	if (info->callback->FindMissingGlyphs(nullptr)) return 1;
 	DEBUG(freetype, 1, "Fallback font: %s (%s)", font_name, english_name);
 	return 0; // stop enumerating
 }
@@ -362,9 +362,9 @@ bool SetFallbackFont(FreeTypeSettings *s
 	font.lfFaceName[0] = '\0';
 	font.lfPitchAndFamily = 0;
 
-	HDC dc = GetDC(NULL);
+	HDC dc = GetDC(nullptr);
 	int ret = EnumFontFamiliesEx(dc, &font, (FONTENUMPROC)&EnumFontCallback, (LPARAM)&langInfo, 0);
-	ReleaseDC(NULL, dc);
+	ReleaseDC(nullptr, dc);
 	return ret == 0;
 }
 
@@ -400,14 +400,14 @@ FT_Error GetFontByFaceName(const char *f
 		CFRelease(name);
 
 		/* Loop over all matches until we can get a path for one of them. */
-		for (CFIndex i = 0; descs != NULL && i < CFArrayGetCount(descs) && os_err != noErr; i++) {
-			CTFontRef font = CTFontCreateWithFontDescriptor((CTFontDescriptorRef)CFArrayGetValueAtIndex(descs, i), 0.0, NULL);
+		for (CFIndex i = 0; descs != nullptr && i < CFArrayGetCount(descs) && os_err != noErr; i++) {
+			CTFontRef font = CTFontCreateWithFontDescriptor((CTFontDescriptorRef)CFArrayGetValueAtIndex(descs, i), 0.0, nullptr);
 			CFURLRef fontURL = (CFURLRef)CTFontCopyAttribute(font, kCTFontURLAttribute);
 			if (CFURLGetFileSystemRepresentation(fontURL, true, file_path, lengthof(file_path))) os_err = noErr;
 			CFRelease(font);
 			CFRelease(fontURL);
 		}
-		if (descs != NULL) CFRelease(descs);
+		if (descs != nullptr) CFRelease(descs);
 	} else
 #endif
 	{
@@ -467,7 +467,7 @@ bool SetFallbackFont(FreeTypeSettings *s
 			/* Just copy the first part of the isocode. */
 			strecpy(lang, language_isocode, lastof(lang));
 			char *sep = strchr(lang, '_');
-			if (sep != NULL) *sep = '\0';
+			if (sep != nullptr) *sep = '\0';
 		}
 
 		/* Create a font descriptor matching the wanted language and latin (english) glyphs. */
@@ -487,7 +487,7 @@ bool SetFallbackFont(FreeTypeSettings *s
 		CFRelease(mandatory_attribs);
 		CFRelease(lang_desc);
 
-		for (CFIndex i = 0; descs != NULL && i < CFArrayGetCount(descs); i++) {
+		for (CFIndex i = 0; descs != nullptr && i < CFArrayGetCount(descs); i++) {
 			CTFontDescriptorRef font = (CTFontDescriptorRef)CFArrayGetValueAtIndex(descs, i);
 
 			/* Get font traits. */
@@ -515,13 +515,13 @@ bool SetFallbackFont(FreeTypeSettings *s
 
 			/* Save result. */
 			callback->SetFontNames(settings, name);
-			if (!callback->FindMissingGlyphs(NULL)) {
+			if (!callback->FindMissingGlyphs(nullptr)) {
 				DEBUG(freetype, 2, "CT-Font for %s: %s", language_isocode, name);
 				result = true;
 				break;
 			}
 		}
-		if (descs != NULL) CFRelease(descs);
+		if (descs != nullptr) CFRelease(descs);
 	} else
 #endif
 	{
@@ -530,7 +530,7 @@ bool SetFallbackFont(FreeTypeSettings *s
 		 * are available to the application. */
 		ATSFontIterator itr;
 		ATSFontRef font;
-		ATSFontIteratorCreate(kATSFontContextLocal, NULL, NULL, kATSOptionFlagsDefaultScope, &itr);
+		ATSFontIteratorCreate(kATSFontContextLocal, nullptr, nullptr, kATSOptionFlagsDefaultScope, &itr);
 		while (!result && ATSFontIteratorNext(itr, &font) == noErr) {
 			/* Get font name. */
 			char name[128];
@@ -545,14 +545,14 @@ bool SetFallbackFont(FreeTypeSettings *s
 			if (monospace != callback->Monospace()) continue;
 
 			/* We only want the base font and not bold or italic variants. */
-			if (strstr(name, "Italic") != NULL || strstr(name, "Bold")) continue;
+			if (strstr(name, "Italic") != nullptr || strstr(name, "Bold")) continue;
 
 			/* Skip some inappropriate or ugly looking fonts that have better alternatives. */
 			if (name[0] == '.' || strncmp(name, "Apple Symbols", 13) == 0 || strncmp(name, "LastResort", 10) == 0) continue;
 
 			/* Save result. */
 			callback->SetFontNames(settings, name);
-			if (!callback->FindMissingGlyphs(NULL)) {
+			if (!callback->FindMissingGlyphs(nullptr)) {
 				DEBUG(freetype, 2, "ATS-Font for %s: %s", language_isocode, name);
 				result = true;
 				break;
@@ -566,10 +566,10 @@ bool SetFallbackFont(FreeTypeSettings *s
 		/* For some OS versions, the font 'Arial Unicode MS' does not report all languages it
 		 * supports. If we didn't find any other font, just try it, maybe we get lucky. */
 		callback->SetFontNames(settings, "Arial Unicode MS");
-		result = !callback->FindMissingGlyphs(NULL);
+		result = !callback->FindMissingGlyphs(nullptr);
 	}
 
-	callback->FindMissingGlyphs(NULL);
+	callback->FindMissingGlyphs(nullptr);
 	return result;
 }
 
@@ -599,7 +599,7 @@ FT_Error GetFontByFaceName(const char *f
 		/* Split & strip the font's style */
 		font_family = stredup(font_name);
 		font_style = strchr(font_family, ',');
-		if (font_style != NULL) {
+		if (font_style != nullptr) {
 			font_style[0] = '\0';
 			font_style++;
 			while (*font_style == ' ' || *font_style == '\t') font_style++;
@@ -607,13 +607,13 @@ FT_Error GetFontByFaceName(const char *f
 
 		/* Resolve the name and populate the information structure */
 		pat = FcNameParse((FcChar8*)font_family);
-		if (font_style != NULL) FcPatternAddString(pat, FC_STYLE, (FcChar8*)font_style);
+		if (font_style != nullptr) FcPatternAddString(pat, FC_STYLE, (FcChar8*)font_style);
 		FcConfigSubstitute(0, pat, FcMatchPattern);
 		FcDefaultSubstitute(pat);
 		fs = FcFontSetCreate();
 		match = FcFontMatch(0, pat, &result);
 
-		if (fs != NULL && match != NULL) {
+		if (fs != nullptr && match != nullptr) {
 			int i;
 			FcChar8 *family;
 			FcChar8 *style;
@@ -627,7 +627,7 @@ FT_Error GetFontByFaceName(const char *f
 						FcPatternGetString(fs->fonts[i], FC_STYLE,  0, &style)  == FcResultMatch) {
 
 					/* The correct style? */
-					if (font_style != NULL && strcasecmp(font_style, (char*)style) != 0) continue;
+					if (font_style != nullptr && strcasecmp(font_style, (char*)style) != 0) continue;
 
 					/* Font config takes the best shot, which, if the family name is spelled
 					 * wrongly a 'random' font, so check whether the family name is the
@@ -660,29 +660,29 @@ bool SetFallbackFont(FreeTypeSettings *s
 	char lang[16];
 	seprintf(lang, lastof(lang), ":lang=%s", language_isocode);
 	char *split = strchr(lang, '_');
-	if (split != NULL) *split = '\0';
+	if (split != nullptr) *split = '\0';
 
 	/* First create a pattern to match the wanted language. */
 	FcPattern *pat = FcNameParse((FcChar8*)lang);
 	/* We only want to know the filename. */
-	FcObjectSet *os = FcObjectSetBuild(FC_FILE, FC_SPACING, FC_SLANT, FC_WEIGHT, NULL);
+	FcObjectSet *os = FcObjectSetBuild(FC_FILE, FC_SPACING, FC_SLANT, FC_WEIGHT, nullptr);
 	/* Get the list of filenames matching the wanted language. */
-	FcFontSet *fs = FcFontList(NULL, pat, os);
+	FcFontSet *fs = FcFontList(nullptr, pat, os);
 
 	/* We don't need these anymore. */
 	FcObjectSetDestroy(os);
 	FcPatternDestroy(pat);
 
-	if (fs != NULL) {
+	if (fs != nullptr) {
 		int best_weight = -1;
-		const char *best_font = NULL;
+		const char *best_font = nullptr;
 
 		for (int i = 0; i < fs->nfont; i++) {
 			FcPattern *font = fs->fonts[i];
 
-			FcChar8 *file = NULL;
+			FcChar8 *file = nullptr;
 			FcResult res = FcPatternGetString(font, FC_FILE, 0, &file);
-			if (res != FcResultMatch || file == NULL) {
+			if (res != FcResultMatch || file == nullptr) {
 				continue;
 			}
 
@@ -701,7 +701,7 @@ bool SetFallbackFont(FreeTypeSettings *s
 
 			callback->SetFontNames(settings, (const char*)file);
 
-			bool missing = callback->FindMissingGlyphs(NULL);
+			bool missing = callback->FindMissingGlyphs(nullptr);
 			DEBUG(freetype, 1, "Font \"%s\" misses%s glyphs", file, missing ? "" : " no");
 
 			if (!missing) {
@@ -710,7 +710,7 @@ bool SetFallbackFont(FreeTypeSettings *s
 			}
 		}
 
-		if (best_font != NULL) {
+		if (best_font != nullptr) {
 			ret = true;
 			callback->SetFontNames(settings, best_font);
 			InitFreeType(callback->Monospace());
diff --git a/src/game/game_config.cpp b/src/game/game_config.cpp
--- a/src/game/game_config.cpp
+++ b/src/game/game_config.cpp
@@ -25,7 +25,7 @@
 	} else {
 		config = &_settings_game.game_config;
 	}
-	if (*config == NULL) *config = new GameConfig();
+	if (*config == nullptr) *config = new GameConfig();
 	return *config;
 }
 
@@ -42,5 +42,5 @@ ScriptInfo *GameConfig::FindInfo(const c
 bool GameConfig::ResetInfo(bool force_exact_match)
 {
 	this->info = (ScriptInfo *)Game::FindInfo(this->name, force_exact_match ? this->version : -1, force_exact_match);
-	return this->info != NULL;
+	return this->info != nullptr;
 }
diff --git a/src/game/game_core.cpp b/src/game/game_core.cpp
--- a/src/game/game_core.cpp
+++ b/src/game/game_core.cpp
@@ -25,10 +25,10 @@
 #include "../safeguards.h"
 
 /* static */ uint Game::frame_counter = 0;
-/* static */ GameInfo *Game::info = NULL;
-/* static */ GameInstance *Game::instance = NULL;
-/* static */ GameScannerInfo *Game::scanner_info = NULL;
-/* static */ GameScannerLibrary *Game::scanner_library = NULL;
+/* static */ GameInfo *Game::info = nullptr;
+/* static */ GameInstance *Game::instance = nullptr;
+/* static */ GameScannerInfo *Game::scanner_info = nullptr;
+/* static */ GameScannerLibrary *Game::scanner_library = nullptr;
 
 /* static */ void Game::GameLoop()
 {
@@ -36,7 +36,7 @@
 		PerformanceMeasurer::SetInactive(PFE_GAMESCRIPT);
 		return;
 	}
-	if (Game::instance == NULL) {
+	if (Game::instance == nullptr) {
 		PerformanceMeasurer::SetInactive(PFE_GAMESCRIPT);
 		return;
 	}
@@ -58,11 +58,11 @@
 
 /* static */ void Game::Initialize()
 {
-	if (Game::instance != NULL) Game::Uninitialize(true);
+	if (Game::instance != nullptr) Game::Uninitialize(true);
 
 	Game::frame_counter = 0;
 
-	if (Game::scanner_info == NULL) {
+	if (Game::scanner_info == nullptr) {
 		TarScanner::DoScan(TarScanner::GAME);
 		Game::scanner_info = new GameScannerInfo();
 		Game::scanner_info->Initialize();
@@ -73,14 +73,14 @@
 
 /* static */ void Game::StartNew()
 {
-	if (Game::instance != NULL) return;
+	if (Game::instance != nullptr) return;
 
 	/* Clients shouldn't start GameScripts */
 	if (_networking && !_network_server) return;
 
 	GameConfig *config = GameConfig::GetConfig(GameConfig::SSS_FORCE_GAME);
 	GameInfo *info = config->GetInfo();
-	if (info == NULL) return;
+	if (info == nullptr) return;
 
 	config->AnchorUnchangeableSettings();
 
@@ -101,8 +101,8 @@
 	Backup<CompanyByte> cur_company(_current_company, FILE_LINE);
 
 	delete Game::instance;
-	Game::instance = NULL;
-	Game::info = NULL;
+	Game::instance = nullptr;
+	Game::info = nullptr;
 
 	cur_company.Restore();
 
@@ -111,33 +111,33 @@
 	} else {
 		delete Game::scanner_info;
 		delete Game::scanner_library;
-		Game::scanner_info = NULL;
-		Game::scanner_library = NULL;
+		Game::scanner_info = nullptr;
+		Game::scanner_library = nullptr;
 
-		if (_settings_game.game_config != NULL) {
+		if (_settings_game.game_config != nullptr) {
 			delete _settings_game.game_config;
-			_settings_game.game_config = NULL;
+			_settings_game.game_config = nullptr;
 		}
-		if (_settings_newgame.game_config != NULL) {
+		if (_settings_newgame.game_config != nullptr) {
 			delete _settings_newgame.game_config;
-			_settings_newgame.game_config = NULL;
+			_settings_newgame.game_config = nullptr;
 		}
 	}
 }
 
 /* static */ void Game::Pause()
 {
-	if (Game::instance != NULL) Game::instance->Pause();
+	if (Game::instance != nullptr) Game::instance->Pause();
 }
 
 /* static */ void Game::Unpause()
 {
-	if (Game::instance != NULL) Game::instance->Unpause();
+	if (Game::instance != nullptr) Game::instance->Unpause();
 }
 
 /* static */ bool Game::IsPaused()
 {
-	return Game::instance != NULL? Game::instance->IsPaused() : false;
+	return Game::instance != nullptr? Game::instance->IsPaused() : false;
 }
 
 /* static */ void Game::NewEvent(ScriptEvent *event)
@@ -152,7 +152,7 @@
 	}
 
 	/* Check if Game instance is alive */
-	if (Game::instance == NULL) {
+	if (Game::instance == nullptr) {
 		event->Release();
 		return;
 	}
@@ -169,23 +169,23 @@
 {
 	/* Check for both newgame as current game if we can reload the GameInfo inside
 	 *  the GameConfig. If not, remove the Game from the list. */
-	if (_settings_game.game_config != NULL && _settings_game.game_config->HasScript()) {
+	if (_settings_game.game_config != nullptr && _settings_game.game_config->HasScript()) {
 		if (!_settings_game.game_config->ResetInfo(true)) {
 			DEBUG(script, 0, "After a reload, the GameScript by the name '%s' was no longer found, and removed from the list.", _settings_game.game_config->GetName());
-			_settings_game.game_config->Change(NULL);
-			if (Game::instance != NULL) {
+			_settings_game.game_config->Change(nullptr);
+			if (Game::instance != nullptr) {
 				delete Game::instance;
-				Game::instance = NULL;
-				Game::info = NULL;
+				Game::instance = nullptr;
+				Game::info = nullptr;
 			}
-		} else if (Game::instance != NULL) {
+		} else if (Game::instance != nullptr) {
 			Game::info = _settings_game.game_config->GetInfo();
 		}
 	}
-	if (_settings_newgame.game_config != NULL && _settings_newgame.game_config->HasScript()) {
+	if (_settings_newgame.game_config != nullptr && _settings_newgame.game_config->HasScript()) {
 		if (!_settings_newgame.game_config->ResetInfo(false)) {
 			DEBUG(script, 0, "After a reload, the GameScript by the name '%s' was no longer found, and removed from the list.", _settings_newgame.game_config->GetName());
-			_settings_newgame.game_config->Change(NULL);
+			_settings_newgame.game_config->Change(nullptr);
 		}
 	}
 }
@@ -206,7 +206,7 @@
 
 /* static */ void Game::Save()
 {
-	if (Game::instance != NULL && (!_networking || _network_server)) {
+	if (Game::instance != nullptr && (!_networking || _network_server)) {
 		Backup<CompanyByte> cur_company(_current_company, OWNER_DEITY, FILE_LINE);
 		Game::instance->Save();
 		cur_company.Restore();
@@ -217,7 +217,7 @@
 
 /* static */ void Game::Load(int version)
 {
-	if (Game::instance != NULL && (!_networking || _network_server)) {
+	if (Game::instance != nullptr && (!_networking || _network_server)) {
 		Backup<CompanyByte> cur_company(_current_company, OWNER_DEITY, FILE_LINE);
 		Game::instance->Load(version);
 		cur_company.Restore();
diff --git a/src/game/game_info.cpp b/src/game/game_info.cpp
--- a/src/game/game_info.cpp
+++ b/src/game/game_info.cpp
@@ -55,8 +55,8 @@ template <> const char *GetClassName<Gam
 /* static */ SQInteger GameInfo::Constructor(HSQUIRRELVM vm)
 {
 	/* Get the GameInfo */
-	SQUserPointer instance = NULL;
-	if (SQ_FAILED(sq_getinstanceup(vm, 2, &instance, 0)) || instance == NULL) return sq_throwerror(vm, "Pass an instance of a child class of GameInfo to RegisterGame");
+	SQUserPointer instance = nullptr;
+	if (SQ_FAILED(sq_getinstanceup(vm, 2, &instance, 0)) || instance == nullptr) return sq_throwerror(vm, "Pass an instance of a child class of GameInfo to RegisterGame");
 	GameInfo *info = (GameInfo *)instance;
 
 	SQInteger res = ScriptInfo::Constructor(vm, info);
@@ -82,7 +82,7 @@ template <> const char *GetClassName<Gam
 	}
 
 	/* Remove the link to the real instance, else it might get deleted by RegisterGame() */
-	sq_setinstanceup(vm, 2, NULL);
+	sq_setinstanceup(vm, 2, nullptr);
 	/* Register the Game to the base system */
 	info->GetScanner()->RegisterScript(info);
 	return 0;
@@ -91,7 +91,7 @@ template <> const char *GetClassName<Gam
 GameInfo::GameInfo() :
 	min_loadable_version(0),
 	is_developer_only(false),
-	api_version(NULL)
+	api_version(nullptr)
 {
 }
 
diff --git a/src/game/game_info.hpp b/src/game/game_info.hpp
--- a/src/game/game_info.hpp
+++ b/src/game/game_info.hpp
@@ -51,7 +51,7 @@ private:
 /** All static information from an Game library like name, version, etc. */
 class GameLibrary : public ScriptInfo {
 public:
-	GameLibrary() : ScriptInfo(), category(NULL) {};
+	GameLibrary() : ScriptInfo(), category(nullptr) {};
 	~GameLibrary();
 
 	/**
diff --git a/src/game/game_instance.cpp b/src/game/game_instance.cpp
--- a/src/game/game_instance.cpp
+++ b/src/game/game_instance.cpp
@@ -239,10 +239,10 @@ void GameInstance::Died()
 	ShowAIDebugWindow(OWNER_DEITY);
 
 	const GameInfo *info = Game::GetInfo();
-	if (info != NULL) {
+	if (info != nullptr) {
 		ShowErrorMessage(STR_ERROR_AI_PLEASE_REPORT_CRASH, INVALID_STRING_ID, WL_WARNING);
 
-		if (info->GetURL() != NULL) {
+		if (info->GetURL() != nullptr) {
 			ScriptLog::Info("Please report the error to the following URL:");
 			ScriptLog::Info(info->GetURL());
 		}
diff --git a/src/game/game_scanner.cpp b/src/game/game_scanner.cpp
--- a/src/game/game_scanner.cpp
+++ b/src/game/game_scanner.cpp
@@ -35,14 +35,14 @@ void GameScannerInfo::RegisterAPI(class 
 
 GameInfo *GameScannerInfo::FindInfo(const char *nameParam, int versionParam, bool force_exact_match)
 {
-	if (this->info_list.size() == 0) return NULL;
-	if (nameParam == NULL) return NULL;
+	if (this->info_list.size() == 0) return nullptr;
+	if (nameParam == nullptr) return nullptr;
 
 	char game_name[1024];
 	strecpy(game_name, nameParam, lastof(game_name));
 	strtolower(game_name);
 
-	GameInfo *info = NULL;
+	GameInfo *info = nullptr;
 	int version = -1;
 
 	if (versionParam == -1) {
@@ -51,7 +51,7 @@ GameInfo *GameScannerInfo::FindInfo(cons
 
 		/* If we didn't find a match Game script, maybe the user included a version */
 		char *e = strrchr(game_name, '.');
-		if (e == NULL) return NULL;
+		if (e == nullptr) return nullptr;
 		*e = '\0';
 		e++;
 		versionParam = atoi(e);
@@ -106,7 +106,7 @@ GameLibrary *GameScannerLibrary::FindLib
 
 	/* Check if the library + version exists */
 	ScriptInfoList::iterator iter = this->info_list.find(library_name);
-	if (iter == this->info_list.end()) return NULL;
+	if (iter == this->info_list.end()) return nullptr;
 
 	return static_cast<GameLibrary *>((*iter).second);
 }
diff --git a/src/game/game_scanner.hpp b/src/game/game_scanner.hpp
--- a/src/game/game_scanner.hpp
+++ b/src/game/game_scanner.hpp
@@ -23,7 +23,7 @@ public:
 	 * @param nameParam The name of the game script.
 	 * @param versionParam The version of the game script, or -1 if you want the latest.
 	 * @param force_exact_match Only match name+version, never latest.
-	 * @return NULL if no match found, otherwise the game script that matched.
+	 * @return nullptr if no match found, otherwise the game script that matched.
 	 */
 	class GameInfo *FindInfo(const char *nameParam, int versionParam, bool force_exact_match);
 
@@ -44,7 +44,7 @@ public:
 	 * Find a library in the pool.
 	 * @param library The library name to find.
 	 * @param version The version the library should have.
-	 * @return The library if found, NULL otherwise.
+	 * @return The library if found, nullptr otherwise.
 	 */
 	class GameLibrary *FindLibrary(const char *library, int version);
 
diff --git a/src/game/game_text.cpp b/src/game/game_text.cpp
--- a/src/game/game_text.cpp
+++ b/src/game/game_text.cpp
@@ -63,11 +63,11 @@ void NORETURN CDECL strgen_fatal(const c
 /**
  * Create a new container for language strings.
  * @param language The language name.
- * @param end If not NULL, terminate \a language at this position.
+ * @param end If not nullptr, terminate \a language at this position.
  */
 LanguageStrings::LanguageStrings(const char *language, const char *end)
 {
-	this->language = stredup(language, end != NULL ? end - 1 : NULL);
+	this->language = stredup(language, end != nullptr ? end - 1 : nullptr);
 }
 
 /** Free everything. */
@@ -79,31 +79,31 @@ LanguageStrings::~LanguageStrings()
 /**
  * Read all the raw language strings from the given file.
  * @param file The file to read from.
- * @return The raw strings, or NULL upon error.
+ * @return The raw strings, or nullptr upon error.
  */
 std::unique_ptr<LanguageStrings> ReadRawLanguageStrings(const char *file)
 {
 	try {
 		size_t to_read;
 		FILE *fh = FioFOpenFile(file, "rb", GAME_DIR, &to_read);
-		if (fh == NULL) return NULL;
+		if (fh == nullptr) return nullptr;
 
 		FileCloser fhClose(fh);
 
 		const char *langname = strrchr(file, PATHSEPCHAR);
-		if (langname == NULL) {
+		if (langname == nullptr) {
 			langname = file;
 		} else {
 			langname++;
 		}
 
 		/* Check for invalid empty filename */
-		if (*langname == '.' || *langname == 0) return NULL;
+		if (*langname == '.' || *langname == 0) return nullptr;
 
 		std::unique_ptr<LanguageStrings> ret(new LanguageStrings(langname, strchr(langname, '.')));
 
 		char buffer[2048];
-		while (to_read != 0 && fgets(buffer, sizeof(buffer), fh) != NULL) {
+		while (to_read != 0 && fgets(buffer, sizeof(buffer), fh) != nullptr) {
 			size_t len = strlen(buffer);
 
 			/* Remove trailing spaces/newlines from the string. */
@@ -122,7 +122,7 @@ std::unique_ptr<LanguageStrings> ReadRaw
 
 		return ret;
 	} catch (...) {
-		return NULL;
+		return nullptr;
 	}
 }
 
@@ -146,7 +146,7 @@ struct StringListReader : StringReader {
 
 	char *ReadLine(char *buffer, const char *last) override
 	{
-		if (this->p == this->end) return NULL;
+		if (this->p == this->end) return nullptr;
 
 		strecpy(buffer, this->p->c_str(), last);
 		this->p++;
@@ -237,7 +237,7 @@ public:
 		if (strcmp(filename, exclude) == 0) return true;
 
 		auto ls = ReadRawLanguageStrings(filename);
-		if (ls == NULL) return false;
+		if (ls == nullptr) return false;
 
 		gs->raw_strings.push_back(std::move(ls));
 		return true;
@@ -254,14 +254,14 @@ GameStrings *LoadTranslations()
 	char filename[512];
 	strecpy(filename, info->GetMainScript(), lastof(filename));
 	char *e = strrchr(filename, PATHSEPCHAR);
-	if (e == NULL) return NULL;
+	if (e == nullptr) return nullptr;
 	e++; // Make 'e' point after the PATHSEPCHAR
 
 	strecpy(e, "lang" PATHSEP "english.txt", lastof(filename));
-	if (!FioCheckFileExists(filename, GAME_DIR)) return NULL;
+	if (!FioCheckFileExists(filename, GAME_DIR)) return nullptr;
 
 	auto ls = ReadRawLanguageStrings(filename);
-	if (ls == NULL) return NULL;
+	if (ls == nullptr) return nullptr;
 
 	GameStrings *gs = new GameStrings();
 	try {
@@ -274,7 +274,7 @@ GameStrings *LoadTranslations()
 
 		const char *tar_filename = info->GetTarFile();
 		TarList::iterator iter;
-		if (tar_filename != NULL && (iter = _tar_list[GAME_DIR].find(tar_filename)) != _tar_list[GAME_DIR].end()) {
+		if (tar_filename != nullptr && (iter = _tar_list[GAME_DIR].find(tar_filename)) != _tar_list[GAME_DIR].end()) {
 			/* The main script is in a tar file, so find all files that
 			 * are in the same tar and add them to the langfile scanner. */
 			TarFileList::iterator tar;
@@ -297,7 +297,7 @@ GameStrings *LoadTranslations()
 		return gs;
 	} catch (...) {
 		delete gs;
-		return NULL;
+		return nullptr;
 	}
 }
 
@@ -327,7 +327,7 @@ void GameStrings::Compile()
 }
 
 /** The currently loaded game strings. */
-GameStrings *_current_data = NULL;
+GameStrings *_current_data = nullptr;
 
 /**
  * Get the string pointer of a particular game string.
@@ -348,7 +348,7 @@ void RegisterGameTranslation(Squirrel *e
 {
 	delete _current_data;
 	_current_data = LoadTranslations();
-	if (_current_data == NULL) return;
+	if (_current_data == nullptr) return;
 
 	HSQUIRRELVM vm = engine->GetVM();
 	sq_pushroottable(vm);
@@ -373,19 +373,19 @@ void RegisterGameTranslation(Squirrel *e
  */
 void ReconsiderGameScriptLanguage()
 {
-	if (_current_data == NULL) return;
+	if (_current_data == nullptr) return;
 
 	char temp[MAX_PATH];
 	strecpy(temp, _current_language->file, lastof(temp));
 
 	/* Remove the extension */
 	char *l = strrchr(temp, '.');
-	assert(l != NULL);
+	assert(l != nullptr);
 	*l = '\0';
 
 	/* Skip the path */
 	char *language = strrchr(temp, PATHSEPCHAR);
-	assert(language != NULL);
+	assert(language != nullptr);
 	language++;
 
 	for (auto &p : _current_data->compiled_strings) {
diff --git a/src/game/game_text.hpp b/src/game/game_text.hpp
--- a/src/game/game_text.hpp
+++ b/src/game/game_text.hpp
@@ -23,7 +23,7 @@ struct LanguageStrings {
 	const char *language; ///< Name of the language (base filename).
 	StringList lines;     ///< The lines of the file to pass into the parser/encoder.
 
-	LanguageStrings(const char *language, const char *end = NULL);
+	LanguageStrings(const char *language, const char *end = nullptr);
 	~LanguageStrings();
 };
 
diff --git a/src/gamelog.cpp b/src/gamelog.cpp
--- a/src/gamelog.cpp
+++ b/src/gamelog.cpp
@@ -34,9 +34,9 @@ extern byte   _sl_minor_version;    ///<
 
 static GamelogActionType _gamelog_action_type = GLAT_NONE; ///< action to record if anything changes
 
-LoggedAction *_gamelog_action = NULL;        ///< first logged action
+LoggedAction *_gamelog_action = nullptr;        ///< first logged action
 uint _gamelog_actions         = 0;           ///< number of actions
-static LoggedAction *_current_action = NULL; ///< current action we are logging, NULL when there is no action active
+static LoggedAction *_current_action = nullptr; ///< current action we are logging, nullptr when there is no action active
 
 
 /**
@@ -81,9 +81,9 @@ void GamelogStopAction()
 {
 	assert(_gamelog_action_type != GLAT_NONE); // nobody should try to stop if there is no action in progress
 
-	bool print = _current_action != NULL;
+	bool print = _current_action != nullptr;
 
-	_current_action = NULL;
+	_current_action = nullptr;
 	_gamelog_action_type = GLAT_NONE;
 
 	if (print) GamelogPrintDebug(5);
@@ -114,9 +114,9 @@ void GamelogReset()
 	assert(_gamelog_action_type == GLAT_NONE);
 	GamelogFree(_gamelog_action, _gamelog_actions);
 
-	_gamelog_action  = NULL;
+	_gamelog_action  = nullptr;
 	_gamelog_actions = 0;
-	_current_action  = NULL;
+	_current_action  = nullptr;
 }
 
 /**
@@ -132,18 +132,18 @@ static char *PrintGrfInfo(char *buf, con
 {
 	char txt[40];
 
-	if (md5sum != NULL) {
+	if (md5sum != nullptr) {
 		md5sumToString(txt, lastof(txt), md5sum);
 		buf += seprintf(buf, last, "GRF ID %08X, checksum %s", BSWAP32(grfid), txt);
 	} else {
 		buf += seprintf(buf, last, "GRF ID %08X", BSWAP32(grfid));
 	}
 
-	if (gc != NULL) {
+	if (gc != nullptr) {
 		buf += seprintf(buf, last, ", filename: %s (md5sum matches)", gc->filename);
 	} else {
 		gc = FindGRFConfig(grfid, FGCM_ANY);
-		if (gc != NULL) {
+		if (gc != nullptr) {
 			buf += seprintf(buf, last, ", filename: %s (matches GRFID only)", gc->filename);
 		} else {
 			buf += seprintf(buf, last, ", unknown GRF");
@@ -273,7 +273,7 @@ void GamelogPrint(GamelogPrintProc *proc
 				case GLCT_GRFREM: {
 					GrfIDMapping::Pair *gm = grf_names.Find(lc->grfrem.grfid);
 					buf += seprintf(buf, lastof(buffer), la->at == GLAT_LOAD ? "Missing NewGRF: " : "Removed NewGRF: ");
-					buf = PrintGrfInfo(buf, lastof(buffer), lc->grfrem.grfid, NULL, gm != grf_names.End() ? gm->second.gc : NULL);
+					buf = PrintGrfInfo(buf, lastof(buffer), lc->grfrem.grfid, nullptr, gm != grf_names.End() ? gm->second.gc : nullptr);
 					if (gm == grf_names.End()) {
 						buf += seprintf(buf, lastof(buffer), ". Gamelog inconsistency: GrfID was never added!");
 					} else {
@@ -299,7 +299,7 @@ void GamelogPrint(GamelogPrintProc *proc
 				case GLCT_GRFPARAM: {
 					GrfIDMapping::Pair *gm = grf_names.Find(lc->grfrem.grfid);
 					buf += seprintf(buf, lastof(buffer), "GRF parameter changed: ");
-					buf = PrintGrfInfo(buf, lastof(buffer), lc->grfparam.grfid, NULL, gm != grf_names.End() ? gm->second.gc : NULL);
+					buf = PrintGrfInfo(buf, lastof(buffer), lc->grfparam.grfid, nullptr, gm != grf_names.End() ? gm->second.gc : nullptr);
 					if (gm == grf_names.End()) buf += seprintf(buf, lastof(buffer), ". Gamelog inconsistency: GrfID was never added!");
 					break;
 				}
@@ -308,7 +308,7 @@ void GamelogPrint(GamelogPrintProc *proc
 					GrfIDMapping::Pair *gm = grf_names.Find(lc->grfrem.grfid);
 					buf += seprintf(buf, lastof(buffer), "GRF order changed: %08X moved %d places %s",
 						BSWAP32(lc->grfmove.grfid), abs(lc->grfmove.offset), lc->grfmove.offset >= 0 ? "down" : "up" );
-					buf = PrintGrfInfo(buf, lastof(buffer), lc->grfmove.grfid, NULL, gm != grf_names.End() ? gm->second.gc : NULL);
+					buf = PrintGrfInfo(buf, lastof(buffer), lc->grfmove.grfid, nullptr, gm != grf_names.End() ? gm->second.gc : nullptr);
 					if (gm == grf_names.End()) buf += seprintf(buf, lastof(buffer), ". Gamelog inconsistency: GrfID was never added!");
 					break;
 				}
@@ -321,7 +321,7 @@ void GamelogPrint(GamelogPrintProc *proc
 							buf += seprintf(buf, lastof(buffer), "Rail vehicle changes length outside a depot: GRF ID %08X, internal ID 0x%X", BSWAP32(lc->grfbug.grfid), (uint)lc->grfbug.data);
 							break;
 					}
-					buf = PrintGrfInfo(buf, lastof(buffer), lc->grfbug.grfid, NULL, gm != grf_names.End() ? gm->second.gc : NULL);
+					buf = PrintGrfInfo(buf, lastof(buffer), lc->grfbug.grfid, nullptr, gm != grf_names.End() ? gm->second.gc : nullptr);
 					if (gm == grf_names.End()) buf += seprintf(buf, lastof(buffer), ". Gamelog inconsistency: GrfID was never added!");
 					break;
 				}
@@ -372,21 +372,21 @@ void GamelogPrintDebug(int level)
 
 /**
  * Allocates new LoggedChange and new LoggedAction if needed.
- * If there is no action active, NULL is returned.
+ * If there is no action active, nullptr is returned.
  * @param ct type of change
- * @return new LoggedChange, or NULL if there is no action active
+ * @return new LoggedChange, or nullptr if there is no action active
  */
 static LoggedChange *GamelogChange(GamelogChangeType ct)
 {
-	if (_current_action == NULL) {
-		if (_gamelog_action_type == GLAT_NONE) return NULL;
+	if (_current_action == nullptr) {
+		if (_gamelog_action_type == GLAT_NONE) return nullptr;
 
 		_gamelog_action  = ReallocT(_gamelog_action, _gamelog_actions + 1);
 		_current_action  = &_gamelog_action[_gamelog_actions++];
 
 		_current_action->at      = _gamelog_action_type;
 		_current_action->tick    = _tick_counter;
-		_current_action->change  = NULL;
+		_current_action->change  = nullptr;
 		_current_action->changes = 0;
 	}
 
@@ -416,7 +416,7 @@ void GamelogEmergency()
  */
 bool GamelogTestEmergency()
 {
-	const LoggedChange *emergency = NULL;
+	const LoggedChange *emergency = nullptr;
 
 	const LoggedAction *laend = &_gamelog_action[_gamelog_actions];
 	for (const LoggedAction *la = _gamelog_action; la != laend; la++) {
@@ -426,7 +426,7 @@ bool GamelogTestEmergency()
 		}
 	}
 
-	return (emergency != NULL);
+	return (emergency != nullptr);
 }
 
 /**
@@ -437,7 +437,7 @@ void GamelogRevision()
 	assert(_gamelog_action_type == GLAT_START || _gamelog_action_type == GLAT_LOAD);
 
 	LoggedChange *lc = GamelogChange(GLCT_REVISION);
-	if (lc == NULL) return;
+	if (lc == nullptr) return;
 
 	memset(lc->revision.text, 0, sizeof(lc->revision.text));
 	strecpy(lc->revision.text, GetGamelogRevisionString(), lastof(lc->revision.text));
@@ -454,7 +454,7 @@ void GamelogMode()
 	assert(_gamelog_action_type == GLAT_START || _gamelog_action_type == GLAT_LOAD || _gamelog_action_type == GLAT_CHEAT);
 
 	LoggedChange *lc = GamelogChange(GLCT_MODE);
-	if (lc == NULL) return;
+	if (lc == nullptr) return;
 
 	lc->mode.mode      = _game_mode;
 	lc->mode.landscape = _settings_game.game_creation.landscape;
@@ -468,7 +468,7 @@ void GamelogOldver()
 	assert(_gamelog_action_type == GLAT_LOAD);
 
 	LoggedChange *lc = GamelogChange(GLCT_OLDVER);
-	if (lc == NULL) return;
+	if (lc == nullptr) return;
 
 	lc->oldver.type = _savegame_type;
 	lc->oldver.version = (_savegame_type == SGT_OTTD ? ((uint32)_sl_version << 8 | _sl_minor_version) : _ttdp_version);
@@ -485,7 +485,7 @@ void GamelogSetting(const char *name, in
 	assert(_gamelog_action_type == GLAT_SETTING);
 
 	LoggedChange *lc = GamelogChange(GLCT_SETTING);
-	if (lc == NULL) return;
+	if (lc == nullptr) return;
 
 	lc->setting.name = stredup(name);
 	lc->setting.oldval = oldval;
@@ -499,7 +499,7 @@ void GamelogSetting(const char *name, in
  */
 void GamelogTestRevision()
 {
-	const LoggedChange *rev = NULL;
+	const LoggedChange *rev = nullptr;
 
 	const LoggedAction *laend = &_gamelog_action[_gamelog_actions];
 	for (const LoggedAction *la = _gamelog_action; la != laend; la++) {
@@ -509,7 +509,7 @@ void GamelogTestRevision()
 		}
 	}
 
-	if (rev == NULL || strcmp(rev->revision.text, GetGamelogRevisionString()) != 0 ||
+	if (rev == nullptr || strcmp(rev->revision.text, GetGamelogRevisionString()) != 0 ||
 			rev->revision.modified != _openttd_revision_modified ||
 			rev->revision.newgrf != _openttd_newgrf_version) {
 		GamelogRevision();
@@ -522,7 +522,7 @@ void GamelogTestRevision()
  */
 void GamelogTestMode()
 {
-	const LoggedChange *mode = NULL;
+	const LoggedChange *mode = nullptr;
 
 	const LoggedAction *laend = &_gamelog_action[_gamelog_actions];
 	for (const LoggedAction *la = _gamelog_action; la != laend; la++) {
@@ -532,7 +532,7 @@ void GamelogTestMode()
 		}
 	}
 
-	if (mode == NULL || mode->mode.mode != _game_mode || mode->mode.landscape != _settings_game.game_creation.landscape) GamelogMode();
+	if (mode == nullptr || mode->mode.mode != _game_mode || mode->mode.landscape != _settings_game.game_creation.landscape) GamelogMode();
 }
 
 
@@ -547,7 +547,7 @@ static void GamelogGRFBug(uint32 grfid, 
 	assert(_gamelog_action_type == GLAT_GRFBUG);
 
 	LoggedChange *lc = GamelogChange(GLCT_GRFBUG);
-	if (lc == NULL) return;
+	if (lc == nullptr) return;
 
 	lc->grfbug.data  = data;
 	lc->grfbug.grfid = grfid;
@@ -603,7 +603,7 @@ void GamelogGRFRemove(uint32 grfid)
 	assert(_gamelog_action_type == GLAT_LOAD || _gamelog_action_type == GLAT_GRF);
 
 	LoggedChange *lc = GamelogChange(GLCT_GRFREM);
-	if (lc == NULL) return;
+	if (lc == nullptr) return;
 
 	lc->grfrem.grfid = grfid;
 }
@@ -619,7 +619,7 @@ void GamelogGRFAdd(const GRFConfig *newg
 	if (!IsLoggableGrfConfig(newg)) return;
 
 	LoggedChange *lc = GamelogChange(GLCT_GRFADD);
-	if (lc == NULL) return;
+	if (lc == nullptr) return;
 
 	lc->grfadd = newg->ident;
 }
@@ -634,7 +634,7 @@ void GamelogGRFCompatible(const GRFIdent
 	assert(_gamelog_action_type == GLAT_LOAD || _gamelog_action_type == GLAT_GRF);
 
 	LoggedChange *lc = GamelogChange(GLCT_GRFCOMPAT);
-	if (lc == NULL) return;
+	if (lc == nullptr) return;
 
 	lc->grfcompat = *newg;
 }
@@ -649,7 +649,7 @@ static void GamelogGRFMove(uint32 grfid,
 	assert(_gamelog_action_type == GLAT_GRF);
 
 	LoggedChange *lc = GamelogChange(GLCT_GRFMOVE);
-	if (lc == NULL) return;
+	if (lc == nullptr) return;
 
 	lc->grfmove.grfid  = grfid;
 	lc->grfmove.offset = offset;
@@ -665,7 +665,7 @@ static void GamelogGRFParameters(uint32 
 	assert(_gamelog_action_type == GLAT_GRF);
 
 	LoggedChange *lc = GamelogChange(GLCT_GRFPARAM);
-	if (lc == NULL) return;
+	if (lc == nullptr) return;
 
 	lc->grfparam.grfid = grfid;
 }
@@ -679,7 +679,7 @@ void GamelogGRFAddList(const GRFConfig *
 {
 	assert(_gamelog_action_type == GLAT_START || _gamelog_action_type == GLAT_LOAD);
 
-	for (; newg != NULL; newg = newg->next) {
+	for (; newg != nullptr; newg = newg->next) {
 		GamelogGRFAdd(newg);
 	}
 }
@@ -697,14 +697,14 @@ struct GRFList {
 static GRFList *GenerateGRFList(const GRFConfig *grfc)
 {
 	uint n = 0;
-	for (const GRFConfig *g = grfc; g != NULL; g = g->next) {
+	for (const GRFConfig *g = grfc; g != nullptr; g = g->next) {
 		if (IsLoggableGrfConfig(g)) n++;
 	}
 
 	GRFList *list = (GRFList*)MallocT<byte>(sizeof(GRFList) + n * sizeof(GRFConfig*));
 
 	list->n = 0;
-	for (const GRFConfig *g = grfc; g != NULL; g = g->next) {
+	for (const GRFConfig *g = grfc; g != nullptr; g = g->next) {
 		if (IsLoggableGrfConfig(g)) list->grf[list->n++] = g;
 	}
 
diff --git a/src/genworld.cpp b/src/genworld.cpp
--- a/src/genworld.cpp
+++ b/src/genworld.cpp
@@ -82,8 +82,8 @@ static void CleanupGeneration()
 	/* Show all vital windows again, because we have hidden them */
 	if (_gw.threaded && _game_mode != GM_MENU) ShowVitalWindows();
 	SetModalProgress(false);
-	_gw.proc     = NULL;
-	_gw.abortp   = NULL;
+	_gw.proc     = nullptr;
+	_gw.abortp   = nullptr;
 	_gw.threaded = false;
 
 	DeleteWindowByClass(WC_MODAL_PROGRESS);
@@ -171,7 +171,7 @@ static void _GenerateWorld()
 			if (_game_mode != GM_EDITOR) {
 				Game::StartNew();
 
-				if (Game::GetInstance() != NULL) {
+				if (Game::GetInstance() != nullptr) {
 					SetGeneratingWorldProgress(GWP_RUNSCRIPT, 2500);
 					_generating_world = true;
 					for (i = 0; i < 2500; i++) {
@@ -192,7 +192,7 @@ static void _GenerateWorld()
 
 		SetGeneratingWorldProgress(GWP_GAME_START, 1);
 		/* Call any callback */
-		if (_gw.proc != NULL) _gw.proc();
+		if (_gw.proc != nullptr) _gw.proc();
 		IncreaseGeneratingWorldProgress(GWP_GAME_START);
 
 		CleanupGeneration();
@@ -278,7 +278,7 @@ void HandleGeneratingWorldAbortion()
 	/* Clean up - in SE create an empty map, otherwise, go to intro menu */
 	_switch_mode = (_game_mode == GM_EDITOR) ? SM_EDITOR : SM_MENU;
 
-	if (_gw.abortp != NULL) _gw.abortp();
+	if (_gw.abortp != nullptr) _gw.abortp();
 
 	CleanupGeneration();
 
@@ -302,7 +302,7 @@ void GenerateWorld(GenWorldMode mode, ui
 	_gw.size_y = size_y;
 	SetModalProgress(true);
 	_gw.abort  = false;
-	_gw.abortp = NULL;
+	_gw.abortp = nullptr;
 	_gw.lc     = _local_company;
 	_gw.quit_thread   = false;
 	_gw.threaded      = true;
@@ -345,7 +345,7 @@ void GenerateWorld(GenWorldMode mode, ui
 	ShowGenerateWorldProgress();
 
 	/* Centre the view on the map */
-	if (FindWindowById(WC_MAIN_WINDOW, 0) != NULL) {
+	if (FindWindowById(WC_MAIN_WINDOW, 0) != nullptr) {
 		ScrollMainWindowToTile(TileXY(MapSizeX() / 2, MapSizeY() / 2), true);
 	}
 }
diff --git a/src/genworld.h b/src/genworld.h
--- a/src/genworld.h
+++ b/src/genworld.h
@@ -60,8 +60,8 @@ struct GenWorldInfo {
 	CompanyID lc;          ///< The local_company before generating
 	uint size_x;           ///< X-size of the map
 	uint size_y;           ///< Y-size of the map
-	GWDoneProc *proc;      ///< Proc that is called when done (can be NULL)
-	GWAbortProc *abortp;   ///< Proc that is called when aborting (can be NULL)
+	GWDoneProc *proc;      ///< Proc that is called when done (can be nullptr)
+	GWAbortProc *abortp;   ///< Proc that is called when aborting (can be nullptr)
 	std::thread thread;    ///< The thread we are in (joinable if a thread was created)
 };
 
diff --git a/src/genworld_gui.cpp b/src/genworld_gui.cpp
--- a/src/genworld_gui.cpp
+++ b/src/genworld_gui.cpp
@@ -442,7 +442,7 @@ struct GenerateLandscapeWindow : public 
 
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
 	{
-		const StringID *strs = NULL;
+		const StringID *strs = nullptr;
 		switch (widget) {
 			case WID_GL_MAX_HEIGHTLEVEL_TEXT:
 				SetDParam(0, MAX_TILE_HEIGHT);
@@ -509,7 +509,7 @@ struct GenerateLandscapeWindow : public 
 			default:
 				return;
 		}
-		if (strs != NULL) {
+		if (strs != nullptr) {
 			while (*strs != INVALID_STRING_ID) {
 				*size = maxdim(*size, GetStringBoundingBox(*strs++));
 			}
@@ -761,7 +761,7 @@ struct GenerateLandscapeWindow : public 
 	void OnQueryTextFinished(char *str) override
 	{
 		/* Was 'cancel' pressed? */
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
 		int32 value;
 		if (!StrEmpty(str)) {
@@ -808,14 +808,14 @@ struct GenerateLandscapeWindow : public 
 };
 
 static WindowDesc _generate_landscape_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_GENERATE_LANDSCAPE, WC_NONE,
 	0,
 	_nested_generate_landscape_widgets, lengthof(_nested_generate_landscape_widgets)
 );
 
 static WindowDesc _heightmap_load_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_GENERATE_LANDSCAPE, WC_NONE,
 	0,
 	_nested_heightmap_load_widgets, lengthof(_nested_heightmap_load_widgets)
@@ -1110,7 +1110,7 @@ static const NWidgetPart _nested_create_
 };
 
 static WindowDesc _create_scenario_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_GENERATE_LANDSCAPE, WC_NONE,
 	0,
 	_nested_create_scenario_widgets, lengthof(_nested_create_scenario_widgets)
@@ -1138,7 +1138,7 @@ static const NWidgetPart _nested_generat
 
 
 static WindowDesc _generate_progress_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_MODAL_PROGRESS, WC_NONE,
 	0,
 	_nested_generate_progress_widgets, lengthof(_nested_generate_progress_widgets)
diff --git a/src/gfx.cpp b/src/gfx.cpp
--- a/src/gfx.cpp
+++ b/src/gfx.cpp
@@ -53,8 +53,8 @@ static byte _stringwidth_table[FS_END][2
 DrawPixelInfo *_cur_dpi;
 byte _colour_gradient[COLOUR_END][8];
 
-static void GfxMainBlitterViewport(const Sprite *sprite, int x, int y, BlitterMode mode, const SubSprite *sub = NULL, SpriteID sprite_id = SPR_CURSOR_MOUSE);
-static void GfxMainBlitter(const Sprite *sprite, int x, int y, BlitterMode mode, const SubSprite *sub = NULL, SpriteID sprite_id = SPR_CURSOR_MOUSE, ZoomLevel zoom = ZOOM_LVL_NORMAL);
+static void GfxMainBlitterViewport(const Sprite *sprite, int x, int y, BlitterMode mode, const SubSprite *sub = nullptr, SpriteID sprite_id = SPR_CURSOR_MOUSE);
+static void GfxMainBlitter(const Sprite *sprite, int x, int y, BlitterMode mode, const SubSprite *sub = nullptr, SpriteID sprite_id = SPR_CURSOR_MOUSE, ZoomLevel zoom = ZOOM_LVL_NORMAL);
 
 static ReusableBuffer<uint8> _cursor_backup;
 
@@ -76,7 +76,7 @@ static const uint DIRTY_BLOCK_HEIGHT   =
 static const uint DIRTY_BLOCK_WIDTH    = 64;
 
 static uint _dirty_bytes_per_line = 0;
-static byte *_dirty_blocks = NULL;
+static byte *_dirty_blocks = nullptr;
 extern uint _dirty_block_colour;
 
 void GfxScroll(int left, int top, int width, int height, int xo, int yo)
@@ -367,7 +367,7 @@ static int DrawLayoutLine(const Paragrap
 
 	truncation &= max_w < w;         // Whether we need to do truncation.
 	int dot_width = 0;               // Cache for the width of the dot.
-	const Sprite *dot_sprite = NULL; // Cache for the sprite of the dot.
+	const Sprite *dot_sprite = nullptr; // Cache for the sprite of the dot.
 
 	if (truncation) {
 		/*
@@ -734,11 +734,11 @@ Point GetCharPosInString(const char *str
  * @param str String to test.
  * @param x Position relative to the start of the string.
  * @param start_fontsize Font size to start the text with.
- * @return Pointer to the character at the position or NULL if there is no character at the position.
+ * @return Pointer to the character at the position or nullptr if there is no character at the position.
  */
 const char *GetCharAtPosition(const char *str, int x, FontSize start_fontsize)
 {
-	if (x < 0) return NULL;
+	if (x < 0) return nullptr;
 
 	Layouter layout(str, INT32_MAX, TC_FROMSTRING, start_fontsize);
 	return layout.GetCharAtPosition(x);
@@ -768,7 +768,7 @@ Dimension GetSpriteSize(SpriteID sprid, 
 {
 	const Sprite *sprite = GetSprite(sprid, ST_NORMAL);
 
-	if (offset != NULL) {
+	if (offset != nullptr) {
 		offset->x = UnScaleByZoom(sprite->x_offs, zoom);
 		offset->y = UnScaleByZoom(sprite->y_offs, zoom);
 	}
@@ -874,7 +874,7 @@ static void GfxBlitter(const Sprite * co
 	x += sprite->x_offs;
 	y += sprite->y_offs;
 
-	if (sub == NULL) {
+	if (sub == nullptr) {
 		/* No clipping. */
 		bp.skip_left = 0;
 		bp.skip_top = 0;
@@ -1011,7 +1011,7 @@ void DoPaletteAnimations()
 	uint i;
 	uint j;
 
-	if (blitter != NULL && blitter->UsePaletteAnimation() == Blitter::PALETTE_ANIMATION_NONE) {
+	if (blitter != nullptr && blitter->UsePaletteAnimation() == Blitter::PALETTE_ANIMATION_NONE) {
 		palette_animation_counter = 0;
 	}
 
@@ -1096,7 +1096,7 @@ void DoPaletteAnimations()
 		if (j >= EPV_CYCLES_GLITTER_WATER) j -= EPV_CYCLES_GLITTER_WATER;
 	}
 
-	if (blitter != NULL && blitter->UsePaletteAnimation() == Blitter::PALETTE_ANIMATION_NONE) {
+	if (blitter != nullptr && blitter->UsePaletteAnimation() == Blitter::PALETTE_ANIMATION_NONE) {
 		palette_animation_counter = old_tc;
 	} else {
 		if (memcmp(old_val, &_cur_palette.palette[PALETTE_ANIM_START], sizeof(old_val)) != 0 && _cur_palette.count_dirty == 0) {
@@ -1203,7 +1203,7 @@ void ScreenSizeChanged()
 void UndrawMouseCursor()
 {
 	/* Don't undraw the mouse cursor if the screen is not ready */
-	if (_screen.dst_ptr == NULL) return;
+	if (_screen.dst_ptr == nullptr) return;
 
 	if (_cursor.visible) {
 		Blitter *blitter = BlitterFactory::GetCurrentBlitter();
@@ -1216,7 +1216,7 @@ void UndrawMouseCursor()
 void DrawMouseCursor()
 {
 	/* Don't draw the mouse cursor if the screen is not ready */
-	if (_screen.dst_ptr == NULL) return;
+	if (_screen.dst_ptr == nullptr) return;
 
 	Blitter *blitter = BlitterFactory::GetCurrentBlitter();
 
@@ -1578,7 +1578,7 @@ static void SwitchAnimatedCursor()
 {
 	const AnimCursor *cur = _cursor.animate_cur;
 
-	if (cur == NULL || cur->sprite == AnimCursor::LAST) cur = _cursor.animate_list;
+	if (cur == nullptr || cur->sprite == AnimCursor::LAST) cur = _cursor.animate_list;
 
 	SetCursorSprite(cur->sprite, _cursor.sprite_seq[0].pal);
 
@@ -1628,7 +1628,7 @@ void SetMouseCursor(CursorID sprite, Pal
 void SetAnimatedMouseCursor(const AnimCursor *table)
 {
 	_cursor.animate_list = table;
-	_cursor.animate_cur = NULL;
+	_cursor.animate_cur = nullptr;
 	_cursor.sprite_seq[0].pal = PAL_NONE;
 	SwitchAnimatedCursor();
 }
diff --git a/src/gfx_func.h b/src/gfx_func.h
--- a/src/gfx_func.h
+++ b/src/gfx_func.h
@@ -72,7 +72,7 @@ extern Dimension _cur_resolution;
 extern Palette _cur_palette; ///< Current palette
 
 void HandleKeypress(uint keycode, WChar key);
-void HandleTextInput(const char *str, bool marked = false, const char *caret = NULL, const char *insert_location = NULL, const char *replacement_end = NULL);
+void HandleTextInput(const char *str, bool marked = false, const char *caret = nullptr, const char *insert_location = nullptr, const char *replacement_end = nullptr);
 void HandleCtrlChanged();
 void HandleMouseEvents();
 void UpdateWindows();
@@ -88,9 +88,9 @@ static const int DRAW_STRING_BUFFER = 20
 void RedrawScreenRect(int left, int top, int right, int bottom);
 void GfxScroll(int left, int top, int width, int height, int xo, int yo);
 
-Dimension GetSpriteSize(SpriteID sprid, Point *offset = NULL, ZoomLevel zoom = ZOOM_LVL_GUI);
-void DrawSpriteViewport(SpriteID img, PaletteID pal, int x, int y, const SubSprite *sub = NULL);
-void DrawSprite(SpriteID img, PaletteID pal, int x, int y, const SubSprite *sub = NULL, ZoomLevel zoom = ZOOM_LVL_GUI);
+Dimension GetSpriteSize(SpriteID sprid, Point *offset = nullptr, ZoomLevel zoom = ZOOM_LVL_GUI);
+void DrawSpriteViewport(SpriteID img, PaletteID pal, int x, int y, const SubSprite *sub = nullptr);
+void DrawSprite(SpriteID img, PaletteID pal, int x, int y, const SubSprite *sub = nullptr, ZoomLevel zoom = ZOOM_LVL_GUI);
 
 /** How to align the to-be drawn text. */
 enum StringAlignment {
diff --git a/src/gfx_layout.cpp b/src/gfx_layout.cpp
--- a/src/gfx_layout.cpp
+++ b/src/gfx_layout.cpp
@@ -174,7 +174,7 @@ public:
 	std::unique_ptr<const Line> NextLine(int max_width) override
 	{
 		icu::ParagraphLayout::Line *l = p->nextLine(max_width);
-		return std::unique_ptr<const Line>(l == NULL ? NULL : new ICULine(l));
+		return std::unique_ptr<const Line>(l == nullptr ? nullptr : new ICULine(l));
 	}
 };
 
@@ -208,10 +208,10 @@ public:
 		LEErrorCode status = LE_NO_ERROR;
 		/* ParagraphLayout does not copy "buff", so it must stay valid.
 		 * "runs" is copied according to the ICU source, but the documentation does not specify anything, so this might break somewhen. */
-		icu::ParagraphLayout *p = new icu::ParagraphLayout(buff, length, &runs, NULL, NULL, NULL, _current_text_dir == TD_RTL ? UBIDI_DEFAULT_RTL : UBIDI_DEFAULT_LTR, false, status);
+		icu::ParagraphLayout *p = new icu::ParagraphLayout(buff, length, &runs, nullptr, nullptr, nullptr, _current_text_dir == TD_RTL ? UBIDI_DEFAULT_RTL : UBIDI_DEFAULT_LTR, false, status);
 		if (status != LE_NO_ERROR) {
 			delete p;
-			return NULL;
+			return nullptr;
 		}
 
 		return new ICUParagraphLayout(p);
@@ -234,7 +234,7 @@ public:
  * visual runs.
  *
  * One constructs this class with the text that needs to be split into
- * lines. Then nextLine is called with the maximum width until NULL is
+ * lines. Then nextLine is called with the maximum width until nullptr is
  * returned. Each nextLine call creates VisualRuns which contain the
  * length of text that are to be drawn with the same font. In other
  * words, the result of this class is a list of sub strings with their
@@ -358,9 +358,9 @@ FallbackParagraphLayout::FallbackVisualR
 	this->glyph_to_char = other.glyph_to_char;
 	this->glyphs = other.glyphs;
 
-	other.positions = NULL;
-	other.glyph_to_char = NULL;
-	other.glyphs = NULL;
+	other.positions = nullptr;
+	other.glyph_to_char = nullptr;
+	other.glyphs = nullptr;
 }
 
 /** Free all data. */
@@ -496,7 +496,7 @@ void FallbackParagraphLayout::Reflow()
 /**
  * Construct a new line with a maximum width.
  * @param max_width The maximum width of the string.
- * @return A Line, or NULL when at the end of the paragraph.
+ * @return A Line, or nullptr when at the end of the paragraph.
  */
 std::unique_ptr<const ParagraphLayouter::Line> FallbackParagraphLayout::NextLine(int max_width)
 {
@@ -504,13 +504,13 @@ std::unique_ptr<const ParagraphLayouter:
 	 *  - split a line at a newline character, or at a space where we can break a line.
 	 *  - split for a visual run whenever a new line happens, or the font changes.
 	 */
-	if (this->buffer == NULL) return NULL;
+	if (this->buffer == nullptr) return nullptr;
 
 	std::unique_ptr<FallbackLine> l(new FallbackLine());
 
 	if (*this->buffer == '\0') {
 		/* Only a newline. */
-		this->buffer = NULL;
+		this->buffer = nullptr;
 		l->emplace_back(this->runs.front().second, this->buffer, 0, 0);
 		return std::move(l); // Not supposed to be needed, but clang-3.8 barfs otherwise.
 	}
@@ -526,7 +526,7 @@ std::unique_ptr<const ParagraphLayouter:
 	const WChar *next_run = this->buffer_begin + iter->first;
 
 	const WChar *begin = this->buffer;
-	const WChar *last_space = NULL;
+	const WChar *last_space = nullptr;
 	const WChar *last_char;
 	int width = 0;
 	for (;;) {
@@ -534,7 +534,7 @@ std::unique_ptr<const ParagraphLayouter:
 		last_char = this->buffer;
 
 		if (c == '\0') {
-			this->buffer = NULL;
+			this->buffer = nullptr;
 			break;
 		}
 
@@ -547,7 +547,7 @@ std::unique_ptr<const ParagraphLayouter:
 			next_run = this->buffer_begin + iter->first;
 			begin = this->buffer;
 
-			last_space = NULL;
+			last_space = nullptr;
 		}
 
 		if (IsWhitespace(c)) last_space = this->buffer;
@@ -561,11 +561,11 @@ std::unique_ptr<const ParagraphLayouter:
 				if (width == char_width) {
 					/* The character is wider than allowed width; don't know
 					 * what to do with this case... bail out! */
-					this->buffer = NULL;
+					this->buffer = nullptr;
 					return std::move(l); // Not supposed to be needed, but clang-3.8 barfs otherwise.
 				}
 
-				if (last_space == NULL) {
+				if (last_space == nullptr) {
 					/* No space has been found. Just terminate at our current
 					 * location. This usually happens for languages that do not
 					 * require spaces in strings, like Chinese, Japanese and
@@ -595,7 +595,7 @@ std::unique_ptr<const ParagraphLayouter:
 /**
  * Helper for getting a ParagraphLayouter of the given type.
  *
- * @note In case no ParagraphLayouter could be constructed, line.layout will be NULL.
+ * @note In case no ParagraphLayouter could be constructed, line.layout will be nullptr.
  * @param line The cache item to store our layouter in.
  * @param str The string to create a layouter for.
  * @param state The state of the font and color.
@@ -604,7 +604,7 @@ std::unique_ptr<const ParagraphLayouter:
 template <typename T>
 static inline void GetLayouter(Layouter::LineCacheItem &line, const char *&str, FontState &state)
 {
-	if (line.buffer != NULL) free(line.buffer);
+	if (line.buffer != nullptr) free(line.buffer);
 
 	typename T::CharType *buff_begin = MallocT<typename T::CharType>(DRAW_STRING_BUFFER);
 	const typename T::CharType *buffer_last = buff_begin + DRAW_STRING_BUFFER;
@@ -679,7 +679,7 @@ Layouter::Layouter(const char *str, int 
 		}
 
 		LineCacheItem& line = GetCachedParagraphLayout(str, lineend - str, state);
-		if (line.layout != NULL) {
+		if (line.layout != nullptr) {
 			/* Line is in cache */
 			str = lineend + 1;
 			state = line.state_after;
@@ -693,7 +693,7 @@ Layouter::Layouter(const char *str, int 
 
 #ifdef WITH_ICU_LX
 			GetLayouter<ICUParagraphLayoutFactory>(line, str, state);
-			if (line.layout == NULL) {
+			if (line.layout == nullptr) {
 				static bool warned = false;
 				if (!warned) {
 					DEBUG(misc, 0, "ICU layouter bailed on the font. Falling back to the fallback layouter");
@@ -706,9 +706,9 @@ Layouter::Layouter(const char *str, int 
 #endif
 
 #ifdef WITH_UNISCRIBE
-			if (line.layout == NULL) {
+			if (line.layout == nullptr) {
 				GetLayouter<UniscribeParagraphLayoutFactory>(line, str, state);
-				if (line.layout == NULL) {
+				if (line.layout == nullptr) {
 					state = old_state;
 					str = old_str;
 				}
@@ -716,16 +716,16 @@ Layouter::Layouter(const char *str, int 
 #endif
 
 #ifdef WITH_COCOA
-			if (line.layout == NULL) {
+			if (line.layout == nullptr) {
 				GetLayouter<CoreTextParagraphLayoutFactory>(line, str, state);
-				if (line.layout == NULL) {
+				if (line.layout == nullptr) {
 					state = old_state;
 					str = old_str;
 				}
 			}
 #endif
 
-			if (line.layout == NULL) {
+			if (line.layout == nullptr) {
 				GetLayouter<FallbackParagraphLayoutFactory>(line, str, state);
 			}
 		}
@@ -733,7 +733,7 @@ Layouter::Layouter(const char *str, int 
 		/* Move all lines into a local cache so we can reuse them later on more easily. */
 		for (;;) {
 			auto l = line.layout->NextLine(maxw);
-			if (l == NULL) break;
+			if (l == nullptr) break;
 			this->push_back(std::move(l));
 		}
 	} while (c != '\0');
@@ -804,7 +804,7 @@ Point Layouter::GetCharPosition(const ch
 /**
  * Get the character that is at a position.
  * @param x Position in the string.
- * @return Pointer to the character at the position or NULL if no character is at the position.
+ * @return Pointer to the character at the position or nullptr if no character is at the position.
  */
 const char *Layouter::GetCharAtPosition(int x) const
 {
@@ -835,7 +835,7 @@ const char *Layouter::GetCharAtPosition(
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -883,7 +883,7 @@ void Layouter::ResetFontCache(FontSize s
  */
 Layouter::LineCacheItem &Layouter::GetCachedParagraphLayout(const char *str, size_t len, const FontState &state)
 {
-	if (linecache == NULL) {
+	if (linecache == nullptr) {
 		/* Create linecache on first access to avoid trouble with initialisation order of static variables. */
 		linecache = new LineCache();
 	}
@@ -899,7 +899,7 @@ Layouter::LineCacheItem &Layouter::GetCa
  */
 void Layouter::ResetLineCache()
 {
-	if (linecache != NULL) linecache->clear();
+	if (linecache != nullptr) linecache->clear();
 }
 
 /**
@@ -907,7 +907,7 @@ void Layouter::ResetLineCache()
  */
 void Layouter::ReduceLineCache()
 {
-	if (linecache != NULL) {
+	if (linecache != nullptr) {
 		/* TODO LRU cache would be fancy, but not exactly necessary */
 		if (linecache->size() > 4096) ResetLineCache();
 	}
diff --git a/src/gfx_layout.h b/src/gfx_layout.h
--- a/src/gfx_layout.h
+++ b/src/gfx_layout.h
@@ -177,7 +177,7 @@ public:
 		FontState state_after;     ///< Font state after the line.
 		ParagraphLayouter *layout; ///< Layout of the line.
 
-		LineCacheItem() : buffer(NULL), layout(NULL) {}
+		LineCacheItem() : buffer(nullptr), layout(nullptr) {}
 		~LineCacheItem() { delete layout; free(buffer); }
 	};
 private:
diff --git a/src/gfxinit.cpp b/src/gfxinit.cpp
--- a/src/gfxinit.cpp
+++ b/src/gfxinit.cpp
@@ -120,7 +120,7 @@ static void LoadGrfFileIndexed(const cha
  */
 void CheckExternalFiles()
 {
-	if (BaseGraphics::GetUsedSet() == NULL || BaseSounds::GetUsedSet() == NULL) return;
+	if (BaseGraphics::GetUsedSet() == nullptr || BaseSounds::GetUsedSet() == nullptr) return;
 
 	const GraphicsSet *used_set = BaseGraphics::GetUsedSet();
 
@@ -265,7 +265,7 @@ static bool SwitchNewGRFBlitter()
 	 */
 	uint depth_wanted_by_base = BaseGraphics::GetUsedSet()->blitter == BLT_32BPP ? 32 : 8;
 	uint depth_wanted_by_grf = _support8bpp == S8BPP_NONE ? 32 : 8;
-	for (GRFConfig *c = _grfconfig; c != NULL; c = c->next) {
+	for (GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
 		if (c->status == GCS_DISABLED || c->status == GCS_NOT_FOUND || HasBit(c->flags, GCF_INIT_ONLY)) continue;
 		if (c->palette & GRFP_BLT_32BPP) depth_wanted_by_grf = 32;
 	}
@@ -307,18 +307,18 @@ static bool SwitchNewGRFBlitter()
 			VideoDriver::GetInstance()->ReleaseBlitterLock();
 			return false;
 		}
-		if (BlitterFactory::GetBlitterFactory(repl_blitter) == NULL) continue;
+		if (BlitterFactory::GetBlitterFactory(repl_blitter) == nullptr) continue;
 
 		DEBUG(misc, 1, "Switching blitter from '%s' to '%s'... ", cur_blitter, repl_blitter);
 		Blitter *new_blitter = BlitterFactory::SelectBlitter(repl_blitter);
-		if (new_blitter == NULL) NOT_REACHED();
+		if (new_blitter == nullptr) NOT_REACHED();
 		DEBUG(misc, 1, "Successfully switched to %s.", repl_blitter);
 		break;
 	}
 
 	if (!VideoDriver::GetInstance()->AfterBlitterChange()) {
 		/* Failed to switch blitter, let's hope we can return to the old one. */
-		if (BlitterFactory::SelectBlitter(cur_blitter) == NULL || !VideoDriver::GetInstance()->AfterBlitterChange()) usererror("Failed to reinitialize video driver. Specify a fixed blitter in the config");
+		if (BlitterFactory::SelectBlitter(cur_blitter) == nullptr || !VideoDriver::GetInstance()->AfterBlitterChange()) usererror("Failed to reinitialize video driver. Specify a fixed blitter in the config");
 	}
 
 	VideoDriver::GetInstance()->ReleaseBlitterLock();
@@ -362,7 +362,7 @@ bool GraphicsSet::FillSetDetails(IniFile
 
 		/* Get optional blitter information. */
 		item = metadata->GetItem("blitter", false);
-		this->blitter = (item != NULL && *item->value == '3') ? BLT_32BPP : BLT_8BPP;
+		this->blitter = (item != nullptr && *item->value == '3') ? BLT_32BPP : BLT_8BPP;
 	}
 	return ret;
 }
@@ -380,7 +380,7 @@ bool GraphicsSet::FillSetDetails(IniFile
 {
 	size_t size = 0;
 	FILE *f = FioFOpenFile(file->filename, "rb", subdir, &size);
-	if (f == NULL) return MD5File::CR_NO_FILE;
+	if (f == nullptr) return MD5File::CR_NO_FILE;
 
 	size_t max = GRFGetSizeOfDataSection(f);
 
@@ -404,7 +404,7 @@ MD5File::ChecksumResult MD5File::CheckMD
 	size_t size;
 	FILE *f = FioFOpenFile(this->filename, "rb", subdir, &size);
 
-	if (f == NULL) return CR_NO_FILE;
+	if (f == nullptr) return CR_NO_FILE;
 
 	size = min(size, max_size);
 
@@ -434,14 +434,14 @@ template <class T, size_t Tnum_files, bo
 template <class Tbase_set>
 /* static */ bool BaseMedia<Tbase_set>::DetermineBestSet()
 {
-	if (BaseMedia<Tbase_set>::used_set != NULL) return true;
+	if (BaseMedia<Tbase_set>::used_set != nullptr) return true;
 
-	const Tbase_set *best = NULL;
-	for (const Tbase_set *c = BaseMedia<Tbase_set>::available_sets; c != NULL; c = c->next) {
+	const Tbase_set *best = nullptr;
+	for (const Tbase_set *c = BaseMedia<Tbase_set>::available_sets; c != nullptr; c = c->next) {
 		/* Skip unusable sets */
 		if (c->GetNumMissing() != 0) continue;
 
-		if (best == NULL ||
+		if (best == nullptr ||
 				(best->fallback && !c->fallback) ||
 				best->valid_files < c->valid_files ||
 				(best->valid_files == c->valid_files && (
@@ -452,7 +452,7 @@ template <class Tbase_set>
 	}
 
 	BaseMedia<Tbase_set>::used_set = best;
-	return BaseMedia<Tbase_set>::used_set != NULL;
+	return BaseMedia<Tbase_set>::used_set != nullptr;
 }
 
 template <class Tbase_set>
diff --git a/src/goal.cpp b/src/goal.cpp
--- a/src/goal.cpp
+++ b/src/goal.cpp
@@ -93,7 +93,7 @@ CommandCost CmdCreateGoal(TileIndex tile
 		g->dst = p2;
 		g->company = company;
 		g->text = stredup(text);
-		g->progress = NULL;
+		g->progress = nullptr;
 		g->completed = false;
 
 		if (g->company == INVALID_COMPANY) {
@@ -187,7 +187,7 @@ CommandCost CmdSetGoalProgress(TileIndex
 		Goal *g = Goal::Get(p1);
 		free(g->progress);
 		if (StrEmpty(text)) {
-			g->progress = NULL;
+			g->progress = nullptr;
 		} else {
 			g->progress = stredup(text);
 		}
diff --git a/src/goal_base.h b/src/goal_base.h
--- a/src/goal_base.h
+++ b/src/goal_base.h
@@ -34,7 +34,7 @@ struct Goal : GoalPool::PoolItem<&_goal_
 	inline Goal() { }
 
 	/**
-	 * (Empty) destructor has to be defined else operator delete might be called with NULL parameter
+	 * (Empty) destructor has to be defined else operator delete might be called with nullptr parameter
 	 */
 	inline ~Goal() { free(this->text); free(this->progress); }
 };
diff --git a/src/goal_gui.cpp b/src/goal_gui.cpp
--- a/src/goal_gui.cpp
+++ b/src/goal_gui.cpp
@@ -223,7 +223,7 @@ struct GoalListWindow : public Window {
 						}
 
 						case GC_PROGRESS:
-							if (s->progress != NULL) {
+							if (s->progress != nullptr) {
 								SetDParamStr(0, s->progress);
 								StringID str = s->completed ? STR_GOALS_PROGRESS_COMPLETE : STR_GOALS_PROGRESS;
 								int progress_x = x;
@@ -282,7 +282,7 @@ struct GoalListWindow : public Window {
 		uint max_width = 0;
 		Goal *s;
 		FOR_ALL_GOALS(s) {
-			if (s->progress != NULL) {
+			if (s->progress != nullptr) {
 				SetDParamStr(0, s->progress);
 				StringID str = s->completed ? STR_GOALS_PROGRESS_COMPLETE : STR_GOALS_PROGRESS;
 				uint str_width = GetStringBoundingBox(str).width;
@@ -473,7 +473,7 @@ static const NWidgetPart _nested_goal_qu
 };
 
 static WindowDesc _goal_question_list_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_GOAL_QUESTION, WC_NONE,
 	WDF_CONSTRUCTION,
 	_nested_goal_question_widgets, lengthof(_nested_goal_question_widgets)
diff --git a/src/graph_gui.cpp b/src/graph_gui.cpp
--- a/src/graph_gui.cpp
+++ b/src/graph_gui.cpp
@@ -595,7 +595,7 @@ public:
 		int numd = 0;
 		for (CompanyID k = COMPANY_FIRST; k < MAX_COMPANIES; k++) {
 			c = Company::GetIfValid(k);
-			if (c != NULL) {
+			if (c != nullptr) {
 				this->colours[numd] = _colour_gradient[c->colour][6];
 				for (int j = this->num_on_x_axis, i = 0; --j >= 0;) {
 					this->cost[numd][i] = (j >= c->num_valid_stat_ent) ? INVALID_DATAPOINT : GetGraphData(c, j);
diff --git a/src/ground_vehicle.cpp b/src/ground_vehicle.cpp
--- a/src/ground_vehicle.cpp
+++ b/src/ground_vehicle.cpp
@@ -30,7 +30,7 @@ void GroundVehicle<T, Type>::PowerChange
 	uint32 number_of_parts = 0;
 	uint16 max_track_speed = v->GetDisplayMaxSpeed();
 
-	for (const T *u = v; u != NULL; u = u->Next()) {
+	for (const T *u = v; u != nullptr; u = u->Next()) {
 		uint32 current_power = u->GetPower() + u->GetPoweredPartPower(u);
 		total_power += current_power;
 
@@ -83,7 +83,7 @@ void GroundVehicle<T, Type>::CargoChange
 	assert(this->First() == this);
 	uint32 weight = 0;
 
-	for (T *u = T::From(this); u != NULL; u = u->Next()) {
+	for (T *u = T::From(this); u != nullptr; u = u->Next()) {
 		uint32 current_weight = u->GetWeight();
 		weight += current_weight;
 		/* Slope steepness is in percent, result in N. */
@@ -198,7 +198,7 @@ bool GroundVehicle<T, Type>::IsChainInDe
 	if (!IsDepotTypeTile(v->tile, (TransportType)Type) || v->cur_speed != 0) return false;
 
 	/* Check whether the rest is also already trying to enter the depot. */
-	for (; v != NULL; v = v->Next()) {
+	for (; v != nullptr; v = v->Next()) {
 		if (!v->T::IsInDepot() || v->tile != this->tile) return false;
 	}
 
diff --git a/src/ground_vehicle.hpp b/src/ground_vehicle.hpp
--- a/src/ground_vehicle.hpp
+++ b/src/ground_vehicle.hpp
@@ -102,7 +102,7 @@ struct GroundVehicle : public Specialize
 	uint Crash(bool flooded) override
 	{
 		/* Crashed vehicles aren't going up or down */
-		for (T *v = T::From(this); v != NULL; v = v->Next()) {
+		for (T *v = T::From(this); v != nullptr; v = v->Next()) {
 			ClrBit(v->gv_flags, GVF_GOINGUP_BIT);
 			ClrBit(v->gv_flags, GVF_GOINGDOWN_BIT);
 		}
@@ -117,7 +117,7 @@ struct GroundVehicle : public Specialize
 	{
 		int64 incl = 0;
 
-		for (const T *u = T::From(this); u != NULL; u = u->Next()) {
+		for (const T *u = T::From(this); u != nullptr; u = u->Next()) {
 			if (HasBit(u->gv_flags, GVF_GOINGUP_BIT)) {
 				incl += u->gcache.cached_slope_resistance;
 			} else if (HasBit(u->gv_flags, GVF_GOINGDOWN_BIT)) {
diff --git a/src/group_cmd.cpp b/src/group_cmd.cpp
--- a/src/group_cmd.cpp
+++ b/src/group_cmd.cpp
@@ -225,7 +225,7 @@ void GroupStatistics::Clear()
 		g->statistics.ClearAutoreplace();
 	}
 
-	for (EngineRenewList erl = c->engine_renew_list; erl != NULL; erl = erl->next) {
+	for (EngineRenewList erl = c->engine_renew_list; erl != nullptr; erl = erl->next) {
 		const Engine *e = Engine::Get(erl->from);
 		GroupStatistics &stats = GroupStatistics::Get(company, erl->group_id, e->type);
 		if (!stats.autoreplace_defined) {
@@ -277,7 +277,7 @@ void PropagateChildLivery(const Group *g
 	Vehicle *v;
 	FOR_ALL_VEHICLES(v) {
 		if (v->group_id == g->index && (!v->IsGroundVehicle() || v->IsFrontEngine())) {
-			for (Vehicle *u = v; u != NULL; u = u->Next()) {
+			for (Vehicle *u = v; u != nullptr; u = u->Next()) {
 				u->colourmap = PAL_NONE;
 				u->InvalidateNewGRFCache();
 			}
@@ -324,7 +324,7 @@ CommandCost CmdCreateGroup(TileIndex til
 	if (!Group::CanAllocateItem()) return CMD_ERROR;
 
 	const Group *pg = Group::GetIfValid(GB(p2, 0, 16));
-	if (pg != NULL) {
+	if (pg != nullptr) {
 		if (pg->owner != _current_company) return CMD_ERROR;
 		if (pg->vehicle_type != vt) return CMD_ERROR;
 	}
@@ -335,7 +335,7 @@ CommandCost CmdCreateGroup(TileIndex til
 		g->vehicle_type = vt;
 		g->parent = INVALID_GROUP;
 
-		if (pg == NULL) {
+		if (pg == nullptr) {
 			const Company *c = Company::Get(_current_company);
 			g->livery.colour1 = c->livery[LS_DEFAULT].colour1;
 			g->livery.colour2 = c->livery[LS_DEFAULT].colour2;
@@ -368,7 +368,7 @@ CommandCost CmdCreateGroup(TileIndex til
 CommandCost CmdDeleteGroup(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Group *g = Group::GetIfValid(p1);
-	if (g == NULL || g->owner != _current_company) return CMD_ERROR;
+	if (g == nullptr || g->owner != _current_company) return CMD_ERROR;
 
 	/* Remove all vehicles from the group */
 	DoCommand(0, p1, 0, flags, CMD_REMOVE_ALL_VEHICLES_GROUP);
@@ -424,7 +424,7 @@ CommandCost CmdDeleteGroup(TileIndex til
 CommandCost CmdAlterGroup(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Group *g = Group::GetIfValid(GB(p1, 0, 16));
-	if (g == NULL || g->owner != _current_company) return CMD_ERROR;
+	if (g == nullptr || g->owner != _current_company) return CMD_ERROR;
 
 	if (!HasBit(p1, 16)) {
 		/* Rename group */
@@ -438,13 +438,13 @@ CommandCost CmdAlterGroup(TileIndex tile
 			/* Delete the old name */
 			free(g->name);
 			/* Assign the new one */
-			g->name = reset ? NULL : stredup(text);
+			g->name = reset ? nullptr : stredup(text);
 		}
 	} else {
 		/* Set group parent */
 		const Group *pg = Group::GetIfValid(GB(p2, 0, 16));
 
-		if (pg != NULL) {
+		if (pg != nullptr) {
 			if (pg->owner != _current_company) return CMD_ERROR;
 			if (pg->vehicle_type != g->vehicle_type) return CMD_ERROR;
 
@@ -454,7 +454,7 @@ CommandCost CmdAlterGroup(TileIndex tile
 		}
 
 		if (flags & DC_EXEC) {
-			g->parent = (pg == NULL) ? INVALID_GROUP : pg->index;
+			g->parent = (pg == nullptr) ? INVALID_GROUP : pg->index;
 			GroupStatistics::UpdateAutoreplace(g->owner);
 
 			if (g->livery.in_use == 0) {
@@ -498,7 +498,7 @@ static void AddVehicleToGroup(Vehicle *v
 		case VEH_AIRCRAFT:
 			if (v->IsEngineCountable()) UpdateNumEngineGroup(v, v->group_id, new_g);
 			v->group_id = new_g;
-			for (Vehicle *u = v; u != NULL; u = u->Next()) {
+			for (Vehicle *u = v; u != nullptr; u = u->Next()) {
 				u->colourmap = PAL_NONE;
 				u->InvalidateNewGRFCache();
 				u->UpdateViewport(true);
@@ -526,7 +526,7 @@ CommandCost CmdAddVehicleGroup(TileIndex
 	Vehicle *v = Vehicle::GetIfValid(GB(p2, 0, 20));
 	GroupID new_g = p1;
 
-	if (v == NULL || (!Group::IsValidID(new_g) && !IsDefaultGroupID(new_g) && new_g != NEW_GROUP)) return CMD_ERROR;
+	if (v == nullptr || (!Group::IsValidID(new_g) && !IsDefaultGroupID(new_g) && new_g != NEW_GROUP)) return CMD_ERROR;
 
 	if (Group::IsValidID(new_g)) {
 		Group *g = Group::Get(new_g);
@@ -537,7 +537,7 @@ CommandCost CmdAddVehicleGroup(TileIndex
 
 	if (new_g == NEW_GROUP) {
 		/* Create new group. */
-		CommandCost ret = CmdCreateGroup(0, flags, v->type, 0, NULL);
+		CommandCost ret = CmdCreateGroup(0, flags, v->type, 0, nullptr);
 		if (ret.Failed()) return ret;
 
 		new_g = _new_group_id;
@@ -548,7 +548,7 @@ CommandCost CmdAddVehicleGroup(TileIndex
 
 		if (HasBit(p2, 31)) {
 			/* Add vehicles in the shared order list as well. */
-			for (Vehicle *v2 = v->FirstShared(); v2 != NULL; v2 = v2->NextShared()) {
+			for (Vehicle *v2 = v->FirstShared(); v2 != nullptr; v2 = v2->NextShared()) {
 				if (v2->group_id != new_g) AddVehicleToGroup(v2, new_g);
 			}
 		}
@@ -592,7 +592,7 @@ CommandCost CmdAddSharedVehicleGroup(Til
 				if (v->group_id != id_g) continue;
 
 				/* For each shared vehicles add it to the group */
-				for (Vehicle *v2 = v->FirstShared(); v2 != NULL; v2 = v2->NextShared()) {
+				for (Vehicle *v2 = v->FirstShared(); v2 != nullptr; v2 = v2->NextShared()) {
 					if (v2->group_id != id_g) DoCommand(tile, id_g, v2->index, flags, CMD_ADD_VEHICLE_GROUP, text);
 				}
 			}
@@ -620,7 +620,7 @@ CommandCost CmdRemoveAllVehiclesGroup(Ti
 	GroupID old_g = p1;
 	Group *g = Group::GetIfValid(old_g);
 
-	if (g == NULL || g->owner != _current_company) return CMD_ERROR;
+	if (g == nullptr || g->owner != _current_company) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
 		Vehicle *v;
@@ -657,7 +657,7 @@ CommandCost CmdSetGroupLivery(TileIndex 
 	bool primary = !HasBit(p2, 8);
 	Colours colour = Extract<Colours, 16, 8>(p2);
 
-	if (g == NULL || g->owner != _current_company) return CMD_ERROR;
+	if (g == nullptr || g->owner != _current_company) return CMD_ERROR;
 
 	if (colour >= COLOUR_END && colour != INVALID_COLOUR) return CMD_ERROR;
 
@@ -709,7 +709,7 @@ static void SetGroupReplaceProtection(Gr
 CommandCost CmdSetGroupReplaceProtection(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Group *g = Group::GetIfValid(p1);
-	if (g == NULL || g->owner != _current_company) return CMD_ERROR;
+	if (g == nullptr || g->owner != _current_company) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
 		if (HasBit(p2, 1)) {
@@ -750,7 +750,7 @@ void SetTrainGroupID(Train *v, GroupID n
 
 	assert(v->IsFrontEngine() || IsDefaultGroupID(new_g));
 
-	for (Vehicle *u = v; u != NULL; u = u->Next()) {
+	for (Vehicle *u = v; u != nullptr; u = u->Next()) {
 		if (u->IsEngineCountable()) UpdateNumEngineGroup(u, u->group_id, new_g);
 
 		u->group_id = new_g;
@@ -777,7 +777,7 @@ void UpdateTrainGroupID(Train *v)
 	assert(v->IsFrontEngine() || v->IsFreeWagon());
 
 	GroupID new_g = v->IsFrontEngine() ? v->group_id : (GroupID)DEFAULT_GROUP;
-	for (Vehicle *u = v; u != NULL; u = u->Next()) {
+	for (Vehicle *u = v; u != nullptr; u = u->Next()) {
 		if (u->IsEngineCountable()) UpdateNumEngineGroup(u, u->group_id, new_g);
 
 		u->group_id = new_g;
diff --git a/src/group_gui.cpp b/src/group_gui.cpp
--- a/src/group_gui.cpp
+++ b/src/group_gui.cpp
@@ -146,7 +146,7 @@ private:
 	/** Sort the groups by their name */
 	static int CDECL GroupNameSorter(const Group * const *a, const Group * const *b)
 	{
-		static const Group *last_group[2] = { NULL, NULL };
+		static const Group *last_group[2] = { nullptr, nullptr };
 		static char         last_name[2][64] = { "", "" };
 
 		if (*a != last_group[0]) {
@@ -780,7 +780,7 @@ public:
 
 			case WID_GL_REPLACE_PROTECTION: {
 				const Group *g = Group::GetIfValid(this->vli.index);
-				if (g != NULL) {
+				if (g != nullptr) {
 					DoCommandP(0, this->vli.index, (g->replace_protection ? 0 : 1) | (_ctrl_pressed << 1), CMD_SET_GROUP_REPLACE_PROTECTION);
 				}
 				break;
@@ -841,7 +841,7 @@ public:
 				uint id_g = this->group_sb->GetScrolledRowFromWidget(pt.y, this, WID_GL_LIST_GROUP, 0, this->tiny_step_height);
 				GroupID new_g = id_g >= this->groups.size() ? NEW_GROUP : this->groups[id_g]->index;
 
-				DoCommandP(0, new_g, vindex | (_ctrl_pressed ? 1 << 31 : 0), CMD_ADD_VEHICLE_GROUP | CMD_MSG(STR_ERROR_GROUP_CAN_T_ADD_VEHICLE), new_g == NEW_GROUP ? CcAddVehicleNewGroup : NULL);
+				DoCommandP(0, new_g, vindex | (_ctrl_pressed ? 1 << 31 : 0), CMD_ADD_VEHICLE_GROUP | CMD_MSG(STR_ERROR_GROUP_CAN_T_ADD_VEHICLE), new_g == NEW_GROUP ? CcAddVehicleNewGroup : nullptr);
 				break;
 			}
 
@@ -873,7 +873,7 @@ public:
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str != NULL) DoCommandP(0, this->group_rename, 0, CMD_ALTER_GROUP | CMD_MSG(STR_ERROR_GROUP_CAN_T_RENAME), NULL, str);
+		if (str != nullptr) DoCommandP(0, this->group_rename, 0, CMD_ALTER_GROUP | CMD_MSG(STR_ERROR_GROUP_CAN_T_RENAME), nullptr, str);
 		this->group_rename = INVALID_GROUP;
 	}
 
@@ -1033,7 +1033,7 @@ void ShowCompanyGroup(CompanyID company,
  * Finds a group list window determined by vehicle type and owner
  * @param vt vehicle type
  * @param owner owner of groups
- * @return pointer to VehicleGroupWindow, NULL if not found
+ * @return pointer to VehicleGroupWindow, nullptr if not found
  */
 static inline VehicleGroupWindow *FindVehicleGroupWindow(VehicleType vt, Owner owner)
 {
@@ -1054,7 +1054,7 @@ void CcCreateGroup(const CommandCost &re
 	assert(p1 <= VEH_AIRCRAFT);
 
 	VehicleGroupWindow *w = FindVehicleGroupWindow((VehicleType)p1, _current_company);
-	if (w != NULL) w->ShowRenameGroupWindow(_new_group_id, true);
+	if (w != nullptr) w->ShowRenameGroupWindow(_new_group_id, true);
 }
 
 /**
@@ -1084,5 +1084,5 @@ void DeleteGroupHighlightOfVehicle(const
 	if (_special_mouse_mode != WSM_DRAGDROP) return;
 
 	VehicleGroupWindow *w = FindVehicleGroupWindow(v->type, v->owner);
-	if (w != NULL) w->UnselectVehicle(v->index);
+	if (w != nullptr) w->UnselectVehicle(v->index);
 }
diff --git a/src/heightmap.cpp b/src/heightmap.cpp
--- a/src/heightmap.cpp
+++ b/src/heightmap.cpp
@@ -47,7 +47,7 @@ static void ReadHeightmapPNGImageData(by
 {
 	uint x, y;
 	byte gray_palette[256];
-	png_bytep *row_pointers = NULL;
+	png_bytep *row_pointers = nullptr;
 	bool has_palette = png_get_color_type(png_ptr, info_ptr) == PNG_COLOR_TYPE_PALETTE;
 	uint channels = png_get_channels(png_ptr, info_ptr);
 
@@ -99,33 +99,33 @@ static void ReadHeightmapPNGImageData(by
 
 /**
  * Reads the heightmap and/or size of the heightmap from a PNG file.
- * If map == NULL only the size of the PNG is read, otherwise a map
+ * If map == nullptr only the size of the PNG is read, otherwise a map
  * with grayscale pixels is allocated and assigned to *map.
  */
 static bool ReadHeightmapPNG(const char *filename, uint *x, uint *y, byte **map)
 {
 	FILE *fp;
-	png_structp png_ptr = NULL;
-	png_infop info_ptr  = NULL;
+	png_structp png_ptr = nullptr;
+	png_infop info_ptr  = nullptr;
 
 	fp = FioFOpenFile(filename, "rb", HEIGHTMAP_DIR);
-	if (fp == NULL) {
+	if (fp == nullptr) {
 		ShowErrorMessage(STR_ERROR_PNGMAP, STR_ERROR_PNGMAP_FILE_NOT_FOUND, WL_ERROR);
 		return false;
 	}
 
-	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
-	if (png_ptr == NULL) {
+	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
+	if (png_ptr == nullptr) {
 		ShowErrorMessage(STR_ERROR_PNGMAP, STR_ERROR_PNGMAP_MISC, WL_ERROR);
 		fclose(fp);
 		return false;
 	}
 
 	info_ptr = png_create_info_struct(png_ptr);
-	if (info_ptr == NULL || setjmp(png_jmpbuf(png_ptr))) {
+	if (info_ptr == nullptr || setjmp(png_jmpbuf(png_ptr))) {
 		ShowErrorMessage(STR_ERROR_PNGMAP, STR_ERROR_PNGMAP_MISC, WL_ERROR);
 		fclose(fp);
-		png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+		png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
 		return false;
 	}
 
@@ -134,14 +134,14 @@ static bool ReadHeightmapPNG(const char 
 	/* Allocate memory and read image, without alpha or 16-bit samples
 	 * (result is either 8-bit indexed/grayscale or 24-bit RGB) */
 	png_set_packing(png_ptr);
-	png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_PACKING | PNG_TRANSFORM_STRIP_ALPHA | PNG_TRANSFORM_STRIP_16, NULL);
+	png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_PACKING | PNG_TRANSFORM_STRIP_ALPHA | PNG_TRANSFORM_STRIP_16, nullptr);
 
 	/* Maps of wrong colour-depth are not used.
 	 * (this should have been taken care of by stripping alpha and 16-bit samples on load) */
 	if ((png_get_channels(png_ptr, info_ptr) != 1) && (png_get_channels(png_ptr, info_ptr) != 3) && (png_get_bit_depth(png_ptr, info_ptr) != 8)) {
 		ShowErrorMessage(STR_ERROR_PNGMAP, STR_ERROR_PNGMAP_IMAGE_TYPE, WL_ERROR);
 		fclose(fp);
-		png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+		png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
 		return false;
 	}
 
@@ -152,11 +152,11 @@ static bool ReadHeightmapPNG(const char 
 	if ((uint64)width * height >= (size_t)-1) {
 		ShowErrorMessage(STR_ERROR_PNGMAP, STR_ERROR_HEIGHTMAP_TOO_LARGE, WL_ERROR);
 		fclose(fp);
-		png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+		png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
 		return false;
 	}
 
-	if (map != NULL) {
+	if (map != nullptr) {
 		*map = MallocT<byte>(width * height);
 		ReadHeightmapPNGImageData(*map, png_ptr, info_ptr);
 	}
@@ -165,7 +165,7 @@ static bool ReadHeightmapPNG(const char 
 	*y = height;
 
 	fclose(fp);
-	png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+	png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
 	return true;
 }
 
@@ -180,7 +180,7 @@ static void ReadHeightmapBMPImageData(by
 	uint x, y;
 	byte gray_palette[256];
 
-	if (data->palette != NULL) {
+	if (data->palette != nullptr) {
 		uint i;
 		bool all_gray = true;
 
@@ -229,7 +229,7 @@ static void ReadHeightmapBMPImageData(by
 
 /**
  * Reads the heightmap and/or size of the heightmap from a BMP file.
- * If map == NULL only the size of the BMP is read, otherwise a map
+ * If map == nullptr only the size of the BMP is read, otherwise a map
  * with grayscale pixels is allocated and assigned to *map.
  */
 static bool ReadHeightmapBMP(const char *filename, uint *x, uint *y, byte **map)
@@ -243,7 +243,7 @@ static bool ReadHeightmapBMP(const char 
 	memset(&data, 0, sizeof(data));
 
 	f = FioFOpenFile(filename, "rb", HEIGHTMAP_DIR);
-	if (f == NULL) {
+	if (f == nullptr) {
 		ShowErrorMessage(STR_ERROR_BMPMAP, STR_ERROR_PNGMAP_FILE_NOT_FOUND, WL_ERROR);
 		return false;
 	}
@@ -265,7 +265,7 @@ static bool ReadHeightmapBMP(const char 
 		return false;
 	}
 
-	if (map != NULL) {
+	if (map != nullptr) {
 		if (!BmpReadBitmap(&buffer, &info, &data)) {
 			ShowErrorMessage(STR_ERROR_BMPMAP, STR_ERROR_BMPMAP_IMAGE_TYPE, WL_ERROR);
 			fclose(f);
@@ -449,7 +449,7 @@ void FixSlopes()
  * @param filename Name of the file to load.
  * @param[out] x Length of the image.
  * @param[out] y Height of the image.
- * @param[in,out] map If not \c NULL, destination to store the loaded block of image data.
+ * @param[in,out] map If not \c nullptr, destination to store the loaded block of image data.
  * @return Whether loading was successful.
  */
 static bool ReadHeightMap(DetailedFileType dft, const char *filename, uint *x, uint *y, byte **map)
@@ -478,7 +478,7 @@ static bool ReadHeightMap(DetailedFileTy
  */
 bool GetHeightmapDimensions(DetailedFileType dft, const char *filename, uint *x, uint *y)
 {
-	return ReadHeightMap(dft, filename, x, y, NULL);
+	return ReadHeightMap(dft, filename, x, y, nullptr);
 }
 
 /**
@@ -491,7 +491,7 @@ bool GetHeightmapDimensions(DetailedFile
 void LoadHeightmap(DetailedFileType dft, const char *filename)
 {
 	uint x, y;
-	byte *map = NULL;
+	byte *map = nullptr;
 
 	if (!ReadHeightMap(dft, filename, &x, &y, &map)) {
 		free(map);
diff --git a/src/highscore.cpp b/src/highscore.cpp
--- a/src/highscore.cpp
+++ b/src/highscore.cpp
@@ -129,7 +129,7 @@ void SaveToHighScore()
 {
 	FILE *fp = fopen(_highscore_file, "wb");
 
-	if (fp != NULL) {
+	if (fp != nullptr) {
 		uint i;
 		HighScore *hs;
 
@@ -159,7 +159,7 @@ void LoadFromHighScore()
 
 	memset(_highscore_table, 0, sizeof(_highscore_table));
 
-	if (fp != NULL) {
+	if (fp != nullptr) {
 		uint i;
 		HighScore *hs;
 
diff --git a/src/highscore_gui.cpp b/src/highscore_gui.cpp
--- a/src/highscore_gui.cpp
+++ b/src/highscore_gui.cpp
@@ -135,7 +135,7 @@ struct EndGameWindow : EndGameHighScoreB
 		Point pt = this->GetTopLeft(640, 480);
 
 		const Company *c = Company::GetIfValid(_local_company);
-		if (c == NULL) return;
+		if (c == nullptr) return;
 
 		/* We need to get performance from last year because the image is shown
 		 * at the start of the new year when these things have already been copied */
@@ -210,14 +210,14 @@ static const NWidgetPart _nested_highsco
 };
 
 static WindowDesc _highscore_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_HIGHSCORE, WC_NONE,
 	0,
 	_nested_highscore_widgets, lengthof(_nested_highscore_widgets)
 );
 
 static WindowDesc _endgame_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_ENDSCREEN, WC_NONE,
 	0,
 	_nested_highscore_widgets, lengthof(_nested_highscore_widgets)
diff --git a/src/hotkeys.cpp b/src/hotkeys.cpp
--- a/src/hotkeys.cpp
+++ b/src/hotkeys.cpp
@@ -24,7 +24,7 @@ char *_hotkeys_file;
  * List of all HotkeyLists.
  * This is a pointer to ensure initialisation order with the various static HotkeyList instances.
  */
-static std::vector<HotkeyList*> *_hotkey_lists = NULL;
+static std::vector<HotkeyList*> *_hotkey_lists = nullptr;
 
 /** String representation of a keycode */
 struct KeycodeNames {
@@ -254,7 +254,7 @@ void Hotkey::AddKeycode(uint16 keycode)
 HotkeyList::HotkeyList(const char *ini_group, Hotkey *items, GlobalHotkeyHandlerFunc global_hotkey_handler) :
 	global_hotkey_handler(global_hotkey_handler), ini_group(ini_group), items(items)
 {
-	if (_hotkey_lists == NULL) _hotkey_lists = new std::vector<HotkeyList*>();
+	if (_hotkey_lists == nullptr) _hotkey_lists = new std::vector<HotkeyList*>();
 	_hotkey_lists->push_back(this);
 }
 
@@ -270,11 +270,11 @@ HotkeyList::~HotkeyList()
 void HotkeyList::Load(IniFile *ini)
 {
 	IniGroup *group = ini->GetGroup(this->ini_group);
-	for (Hotkey *hotkey = this->items; hotkey->name != NULL; ++hotkey) {
+	for (Hotkey *hotkey = this->items; hotkey->name != nullptr; ++hotkey) {
 		IniItem *item = group->GetItem(hotkey->name, false);
-		if (item != NULL) {
+		if (item != nullptr) {
 			hotkey->keycodes.clear();
-			if (item->value != NULL) ParseHotkeys(hotkey, item->value);
+			if (item->value != nullptr) ParseHotkeys(hotkey, item->value);
 		}
 	}
 }
@@ -286,7 +286,7 @@ void HotkeyList::Load(IniFile *ini)
 void HotkeyList::Save(IniFile *ini) const
 {
 	IniGroup *group = ini->GetGroup(this->ini_group);
-	for (const Hotkey *hotkey = this->items; hotkey->name != NULL; ++hotkey) {
+	for (const Hotkey *hotkey = this->items; hotkey->name != nullptr; ++hotkey) {
 		IniItem *item = group->GetItem(hotkey->name, true);
 		item->SetValue(SaveKeycodes(hotkey));
 	}
@@ -300,7 +300,7 @@ void HotkeyList::Save(IniFile *ini) cons
  */
 int HotkeyList::CheckMatch(uint16 keycode, bool global_only) const
 {
-	for (const Hotkey *list = this->items; list->name != NULL; ++list) {
+	for (const Hotkey *list = this->items; list->name != nullptr; ++list) {
 		auto begin = list->keycodes.begin();
 		auto end = list->keycodes.end();
 		if (std::find(begin, end, keycode | WKC_GLOBAL_HOTKEY) != end || (!global_only && std::find(begin, end, keycode) != end)) {
@@ -344,7 +344,7 @@ void SaveHotkeysToConfig()
 void HandleGlobalHotkeys(WChar key, uint16 keycode)
 {
 	for (HotkeyList *list : *_hotkey_lists) {
-		if (list->global_hotkey_handler == NULL) continue;
+		if (list->global_hotkey_handler == nullptr) continue;
 
 		int hotkey = list->CheckMatch(keycode, true);
 		if (hotkey >= 0 && (list->global_hotkey_handler(hotkey) == ES_HANDLED)) return;
diff --git a/src/hotkeys.h b/src/hotkeys.h
--- a/src/hotkeys.h
+++ b/src/hotkeys.h
@@ -32,7 +32,7 @@ struct Hotkey {
 	std::vector<uint16> keycodes;
 };
 
-#define HOTKEY_LIST_END Hotkey((uint16)0, NULL, -1)
+#define HOTKEY_LIST_END Hotkey((uint16)0, nullptr, -1)
 
 struct IniFile;
 
@@ -42,7 +42,7 @@ struct IniFile;
 struct HotkeyList {
 	typedef EventState (*GlobalHotkeyHandlerFunc)(int hotkey);
 
-	HotkeyList(const char *ini_group, Hotkey *items, GlobalHotkeyHandlerFunc global_hotkey_handler = NULL);
+	HotkeyList(const char *ini_group, Hotkey *items, GlobalHotkeyHandlerFunc global_hotkey_handler = nullptr);
 	~HotkeyList();
 
 	void Load(IniFile *ini);
diff --git a/src/industry_cmd.cpp b/src/industry_cmd.cpp
--- a/src/industry_cmd.cpp
+++ b/src/industry_cmd.cpp
@@ -101,7 +101,7 @@ IndustryType GetIndustryType(TileIndex t
 	assert(IsTileType(tile, MP_INDUSTRY));
 
 	const Industry *ind = Industry::GetByTile(tile);
-	assert(ind != NULL);
+	assert(ind != nullptr);
 	return ind->type;
 }
 
@@ -200,11 +200,11 @@ void Industry::PostDestructor(size_t ind
 
 /**
  * Return a random valid industry.
- * @return random industry, NULL if there are no industries
+ * @return random industry, nullptr if there are no industries
  */
 /* static */ Industry *Industry::GetRandom()
 {
-	if (Industry::GetNumItems() == 0) return NULL;
+	if (Industry::GetNumItems() == 0) return nullptr;
 	int num = RandomRange((uint16)Industry::GetNumItems());
 	size_t index = MAX_UVALUE(size_t);
 
@@ -316,7 +316,7 @@ static void DrawTile_Industry(TileInfo *
 		 * DrawNewIndustry will return false if ever the resolver could not
 		 * find any sprite to display.  So in this case, we will jump on the
 		 * substitute gfx instead. */
-		if (indts->grf_prop.spritegroup[0] != NULL && DrawNewIndustryTile(ti, ind, gfx, indts)) {
+		if (indts->grf_prop.spritegroup[0] != nullptr && DrawNewIndustryTile(ti, ind, gfx, indts)) {
 			return;
 		} else {
 			/* No sprite group (or no valid one) found, meaning no graphics associated.
@@ -385,7 +385,7 @@ static Foundation GetFoundation_Industry
 	 */
 	if (gfx >= NEW_INDUSTRYTILEOFFSET) {
 		const IndustryTileSpec *indts = GetIndustryTileSpec(gfx);
-		if (indts->grf_prop.spritegroup[0] != NULL && HasBit(indts->callback_mask, CBM_INDT_DRAW_FOUNDATIONS)) {
+		if (indts->grf_prop.spritegroup[0] != nullptr && HasBit(indts->callback_mask, CBM_INDT_DRAW_FOUNDATIONS)) {
 			uint32 callback_res = GetIndustryTileCallback(CBID_INDTILE_DRAW_FOUNDATIONS, 0, 0, gfx, Industry::GetByTile(tile), tile);
 			if (callback_res != CALLBACK_FAILED && !ConvertBooleanCallback(indts->grf_prop.grffile, CBID_INDTILE_DRAW_FOUNDATIONS, callback_res)) return FOUNDATION_NONE;
 		}
@@ -475,7 +475,7 @@ static void GetTileDesc_Industry(TileInd
 		td->str = STR_LAI_TOWN_INDUSTRY_DESCRIPTION_UNDER_CONSTRUCTION;
 	}
 
-	if (is->grf_prop.grffile != NULL) {
+	if (is->grf_prop.grffile != nullptr) {
 		td->grf = GetGRFConfig(is->grf_prop.grffile->grfid)->GetName();
 	}
 }
@@ -799,7 +799,7 @@ static void TileLoopIndustry_BubbleGener
 		EV_BUBBLE
 	);
 
-	if (v != NULL) v->animation_substate = dir;
+	if (v != nullptr) v->animation_substate = dir;
 }
 
 static void TileLoop_Industry(TileIndex tile)
@@ -1106,7 +1106,7 @@ static void ChopLumberMillTrees(Industry
 	}
 
 	TileIndex tile = i->location.tile;
-	if (CircularTileSearch(&tile, 40, SearchLumberMillTrees, NULL)) { // 40x40 tiles  to search.
+	if (CircularTileSearch(&tile, 40, SearchLumberMillTrees, nullptr)) { // 40x40 tiles  to search.
 		i->produced_cargo_waiting[0] = min(0xffff, i->produced_cargo_waiting[0] + 45); // Found a tree, add according value to waiting cargo.
 	}
 }
@@ -1339,11 +1339,11 @@ static CheckNewIndustryProc * const _che
  * Find a town for the industry, while checking for multiple industries in the same town.
  * @param tile Position of the industry to build.
  * @param type Industry type.
- * @param[out] t Pointer to return town for the new industry, \c NULL is written if no good town can be found.
+ * @param[out] t Pointer to return town for the new industry, \c nullptr is written if no good town can be found.
  * @return Succeeded or failed command.
  *
- * @pre \c *t != NULL
- * @post \c *t points to a town on success, and \c NULL on failure.
+ * @pre \c *t != nullptr
+ * @post \c *t points to a town on success, and \c nullptr on failure.
  */
 static CommandCost FindTownForIndustry(TileIndex tile, int type, Town **t)
 {
@@ -1354,7 +1354,7 @@ static CommandCost FindTownForIndustry(T
 	const Industry *i;
 	FOR_ALL_INDUSTRIES(i) {
 		if (i->type == (byte)type && i->town == *t) {
-			*t = NULL;
+			*t = nullptr;
 			return_cmd_error(STR_ERROR_ONLY_ONE_ALLOWED_PER_TOWN);
 		}
 	}
@@ -1391,7 +1391,7 @@ bool IsSlopeRefused(Slope current, Slope
  * @param[out] custom_shape_check Perform custom check for the site.
  * @return Failed or succeeded command.
  */
-static CommandCost CheckIfIndustryTilesAreFree(TileIndex tile, const IndustryTileTable *it, uint itspec_index, int type, uint16 initial_random_bits, Owner founder, IndustryAvailabilityCallType creation_type, bool *custom_shape_check = NULL)
+static CommandCost CheckIfIndustryTilesAreFree(TileIndex tile, const IndustryTileTable *it, uint itspec_index, int type, uint16 initial_random_bits, Owner founder, IndustryAvailabilityCallType creation_type, bool *custom_shape_check = nullptr)
 {
 	bool refused_slope = false;
 	bool custom_shape = false;
@@ -1451,7 +1451,7 @@ static CommandCost CheckIfIndustryTilesA
 		}
 	} while ((++it)->ti.x != -0x80);
 
-	if (custom_shape_check != NULL) *custom_shape_check = custom_shape;
+	if (custom_shape_check != nullptr) *custom_shape_check = custom_shape;
 
 	/* It is almost impossible to have a fully flat land in TG, so what we
 	 *  do is that we check if we can make the land flat later on. See
@@ -1588,7 +1588,7 @@ static bool CheckIfCanLevelIndustryPlatf
 static CommandCost CheckIfFarEnoughFromConflictingIndustry(TileIndex tile, int type)
 {
 	const IndustrySpec *indspec = GetIndustrySpec(type);
-	const Industry *i = NULL;
+	const Industry *i = nullptr;
 
 	/* On a large map with many industries, it may be faster to check an area. */
 	static const int dmax = 14;
@@ -1652,7 +1652,7 @@ static void AdvertiseIndustryOpening(con
  */
 static void PopulateStationsNearby(Industry *ind)
 {
-	if (ind->neutral_station != NULL && !_settings_game.station.serve_neutral_industries) {
+	if (ind->neutral_station != nullptr && !_settings_game.station.serve_neutral_industries) {
 		/* Industry has a neutral station. Use it and ignore any other nearby stations. */
 		ind->stations_near.insert(ind->neutral_station);
 		ind->neutral_station->industries_near.clear();
@@ -1874,7 +1874,7 @@ static void DoCreateNewIndustry(Industry
  * @param[out] ip Pointer to store newly created industry.
  * @return Succeeded or failed command.
  *
- * @post \c *ip contains the newly created industry if all checks are successful and the \a flags request actual creation, else it contains \c NULL afterwards.
+ * @post \c *ip contains the newly created industry if all checks are successful and the \a flags request actual creation, else it contains \c nullptr afterwards.
  */
 static CommandCost CreateNewIndustryHelper(TileIndex tile, IndustryType type, DoCommandFlag flags, const IndustrySpec *indspec, uint itspec_index, uint32 random_var8f, uint16 random_initial_bits, Owner founder, IndustryAvailabilityCallType creation_type, Industry **ip)
 {
@@ -1882,7 +1882,7 @@ static CommandCost CreateNewIndustryHelp
 	const IndustryTileTable *it = indspec->table[itspec_index];
 	bool custom_shape_check = false;
 
-	*ip = NULL;
+	*ip = nullptr;
 
 	std::vector<ClearedObjectArea> object_areas(_cleared_object_areas);
 	CommandCost ret = CheckIfIndustryTilesAreFree(tile, it, itspec_index, type, random_initial_bits, founder, creation_type, &custom_shape_check);
@@ -1904,10 +1904,10 @@ static CommandCost CreateNewIndustryHelp
 	ret = CheckIfFarEnoughFromConflictingIndustry(tile, type);
 	if (ret.Failed()) return ret;
 
-	Town *t = NULL;
+	Town *t = nullptr;
 	ret = FindTownForIndustry(tile, type, &t);
 	if (ret.Failed()) return ret;
-	assert(t != NULL);
+	assert(t != nullptr);
 
 	ret = CheckIfIndustryIsAllowed(tile, type, t);
 	if (ret.Failed()) return ret;
@@ -1963,7 +1963,7 @@ CommandCost CmdBuildIndustry(TileIndex t
 	CommandCost ret = CommandCost(STR_ERROR_SITE_UNSUITABLE);
 	const bool deity_prospect = _current_company == OWNER_DEITY && !HasBit(p1, 16);
 
-	Industry *ind = NULL;
+	Industry *ind = nullptr;
 	if (deity_prospect || (_game_mode != GM_EDITOR && _current_company != OWNER_DEITY && _settings_game.construction.raw_industry_construction == 2 && indspec->IsRawIndustry())) {
 		if (flags & DC_EXEC) {
 			/* Prospected industries are build as OWNER_TOWN to not e.g. be build on owned land of the founder */
@@ -2005,7 +2005,7 @@ CommandCost CmdBuildIndustry(TileIndex t
 		if (ret.Failed()) return ret;
 	}
 
-	if ((flags & DC_EXEC) && ind != NULL && _game_mode != GM_EDITOR) {
+	if ((flags & DC_EXEC) && ind != nullptr && _game_mode != GM_EDITOR) {
 		AdvertiseIndustryOpening(ind);
 	}
 
@@ -2018,7 +2018,7 @@ CommandCost CmdBuildIndustry(TileIndex t
  * @param tile The location to build the industry.
  * @param type The industry type to build.
  * @param creation_type The circumstances the industry is created under.
- * @return the created industry or NULL if it failed.
+ * @return the created industry or nullptr if it failed.
  */
 static Industry *CreateNewIndustry(TileIndex tile, IndustryType type, IndustryAvailabilityCallType creation_type)
 {
@@ -2026,9 +2026,9 @@ static Industry *CreateNewIndustry(TileI
 
 	uint32 seed = Random();
 	uint32 seed2 = Random();
-	Industry *i = NULL;
+	Industry *i = nullptr;
 	CommandCost ret = CreateNewIndustryHelper(tile, type, DC_EXEC, indspec, RandomRange(indspec->num_table), seed, GB(seed2, 0, 16), OWNER_NONE, creation_type, &i);
-	assert(i != NULL || ret.Failed());
+	assert(i != nullptr || ret.Failed());
 	return i;
 }
 
@@ -2110,16 +2110,16 @@ static uint GetNumberOfIndustries()
  * than to try a few times before concluding it does not work.
  * @param type     Industry type of the desired industry.
  * @param try_hard Try very hard to find a place. (Used to place at least one industry per type.)
- * @return Pointer to created industry, or \c NULL if creation failed.
+ * @return Pointer to created industry, or \c nullptr if creation failed.
  */
 static Industry *PlaceIndustry(IndustryType type, IndustryAvailabilityCallType creation_type, bool try_hard)
 {
 	uint tries = try_hard ? 10000u : 2000u;
 	for (; tries > 0; tries--) {
 		Industry *ind = CreateNewIndustry(RandomTile(), type, creation_type);
-		if (ind != NULL) return ind;
+		if (ind != nullptr) return ind;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -2385,7 +2385,7 @@ void IndustryBuildData::TryBuildNewIndus
 
 		/* Try to create the industry. */
 		const Industry *ind = PlaceIndustry(it, IACT_RANDOMCREATION, false);
-		if (ind == NULL) {
+		if (ind == nullptr) {
 			this->builddata[it].wait_count = this->builddata[it].max_wait + 1; // Compensate for decrementing below.
 			this->builddata[it].max_wait = min(1000, this->builddata[it].max_wait + 2);
 		} else {
@@ -2474,7 +2474,7 @@ static int WhoCanServiceIndustry(Industr
 		bool c_accepts = false;
 		bool c_produces = false;
 		if (v->type == VEH_TRAIN && v->IsFrontEngine()) {
-			for (const Vehicle *u = v; u != NULL; u = u->Next()) {
+			for (const Vehicle *u = v; u != nullptr; u = u->Next()) {
 				CanCargoServiceIndustry(u->cargo_type, ind, &c_accepts, &c_produces);
 			}
 		} else if (v->type == VEH_ROAD || v->type == VEH_SHIP || v->type == VEH_AIRCRAFT) {
@@ -2493,7 +2493,7 @@ static int WhoCanServiceIndustry(Industr
 			if (o->IsType(OT_GOTO_STATION) && !(o->GetUnloadType() & OUFB_TRANSFER)) {
 				/* Vehicle visits a station to load or unload */
 				Station *st = Station::Get(o->GetDestination());
-				assert(st != NULL);
+				assert(st != nullptr);
 
 				/* Same cargo produced by industry is dropped here => not serviced by vehicle v */
 				if ((o->GetUnloadType() & OUFB_UNLOAD) && !c_accepts) break;
@@ -2774,7 +2774,7 @@ void IndustryDailyLoop()
 			_industry_builder.TryBuildNewIndustry();
 		} else {
 			Industry *i = Industry::GetRandom();
-			if (i != NULL) {
+			if (i != nullptr) {
 				ChangeIndustryProduction(i, false);
 				SetWindowDirty(WC_INDUSTRY_VIEW, i->index);
 			}
@@ -2932,8 +2932,8 @@ extern const TileTypeProcs _tile_type_in
 	AnimateTile_Industry,        // animate_tile_proc
 	TileLoop_Industry,           // tile_loop_proc
 	ChangeTileOwner_Industry,    // change_tile_owner_proc
-	NULL,                        // add_produced_cargo_proc
-	NULL,                        // vehicle_enter_tile_proc
+	nullptr,                        // add_produced_cargo_proc
+	nullptr,                        // vehicle_enter_tile_proc
 	GetFoundation_Industry,      // get_foundation_proc
 	TerraformTile_Industry,      // terraform_tile_proc
 };
diff --git a/src/industry_gui.cpp b/src/industry_gui.cpp
--- a/src/industry_gui.cpp
+++ b/src/industry_gui.cpp
@@ -76,7 +76,7 @@ static void ShowIndustryCargoesWindow(In
  * Gets the string to display after the cargo name (using callback 37)
  * @param cargo the cargo for which the suffix is requested, meaning depends on presence of flag 18 in prop 1A
  * @param cst the cargo suffix type (for which window is it requested). @see CargoSuffixType
- * @param ind the industry (NULL if in fund window)
+ * @param ind the industry (nullptr if in fund window)
  * @param ind_type the industry type
  * @param indspec the industry spec
  * @param suffix is filled with the string to display
@@ -138,7 +138,7 @@ enum CargoSuffixInOut {
  * Gets all strings to display after the cargoes of industries (using callback 37)
  * @param use_input get suffixes for output cargoes or input cargoes?
  * @param cst the cargo suffix type (for which window is it requested). @see CargoSuffixType
- * @param ind the industry (NULL if in fund window)
+ * @param ind the industry (nullptr if in fund window)
  * @param ind_type the industry type
  * @param indspec the industry spec
  * @param cargoes array with cargotypes. for CT_INVALID no suffix will be determined
@@ -438,7 +438,7 @@ public:
 					CargoSuffix cargo_suffix[lengthof(indsp->accepts_cargo)];
 
 					/* Measure the accepted cargoes, if any. */
-					GetAllCargoSuffixes(CARGOSUFFIX_IN, CST_FUND, NULL, this->index[i], indsp, indsp->accepts_cargo, cargo_suffix);
+					GetAllCargoSuffixes(CARGOSUFFIX_IN, CST_FUND, nullptr, this->index[i], indsp, indsp->accepts_cargo, cargo_suffix);
 					std::string cargostring = this->MakeCargoListString(indsp->accepts_cargo, cargo_suffix, lengthof(indsp->accepts_cargo), STR_INDUSTRY_VIEW_REQUIRES_N_CARGO);
 					Dimension strdim = GetStringBoundingBox(cargostring.c_str());
 					if (strdim.width > max_minwidth) {
@@ -448,7 +448,7 @@ public:
 					d = maxdim(d, strdim);
 
 					/* Measure the produced cargoes, if any. */
-					GetAllCargoSuffixes(CARGOSUFFIX_OUT, CST_FUND, NULL, this->index[i], indsp, indsp->produced_cargo, cargo_suffix);
+					GetAllCargoSuffixes(CARGOSUFFIX_OUT, CST_FUND, nullptr, this->index[i], indsp, indsp->produced_cargo, cargo_suffix);
 					cargostring = this->MakeCargoListString(indsp->produced_cargo, cargo_suffix, lengthof(indsp->produced_cargo), STR_INDUSTRY_VIEW_PRODUCES_N_CARGO);
 					strdim = GetStringBoundingBox(cargostring.c_str());
 					if (strdim.width > max_minwidth) {
@@ -551,18 +551,18 @@ public:
 				CargoSuffix cargo_suffix[lengthof(indsp->accepts_cargo)];
 
 				/* Draw the accepted cargoes, if any. Otherwise, will print "Nothing". */
-				GetAllCargoSuffixes(CARGOSUFFIX_IN, CST_FUND, NULL, this->selected_type, indsp, indsp->accepts_cargo, cargo_suffix);
+				GetAllCargoSuffixes(CARGOSUFFIX_IN, CST_FUND, nullptr, this->selected_type, indsp, indsp->accepts_cargo, cargo_suffix);
 				std::string cargostring = this->MakeCargoListString(indsp->accepts_cargo, cargo_suffix, lengthof(indsp->accepts_cargo), STR_INDUSTRY_VIEW_REQUIRES_N_CARGO);
 				y = DrawStringMultiLine(left, right, y, bottom, cargostring.c_str());
 
 				/* Draw the produced cargoes, if any. Otherwise, will print "Nothing". */
-				GetAllCargoSuffixes(CARGOSUFFIX_OUT, CST_FUND, NULL, this->selected_type, indsp, indsp->produced_cargo, cargo_suffix);
+				GetAllCargoSuffixes(CARGOSUFFIX_OUT, CST_FUND, nullptr, this->selected_type, indsp, indsp->produced_cargo, cargo_suffix);
 				cargostring = this->MakeCargoListString(indsp->produced_cargo, cargo_suffix, lengthof(indsp->produced_cargo), STR_INDUSTRY_VIEW_PRODUCES_N_CARGO);
 				y = DrawStringMultiLine(left, right, y, bottom, cargostring.c_str());
 
 				/* Get the additional purchase info text, if it has not already been queried. */
 				if (HasBit(indsp->callback_mask, CBM_IND_FUND_MORE_TEXT)) {
-					uint16 callback_res = GetIndustryCallback(CBID_INDUSTRY_FUND_MORE_TEXT, 0, 0, NULL, this->selected_type, INVALID_TILE);
+					uint16 callback_res = GetIndustryCallback(CBID_INDUSTRY_FUND_MORE_TEXT, 0, 0, nullptr, this->selected_type, INVALID_TILE);
 					if (callback_res != CALLBACK_FAILED && callback_res != 0x400) {
 						if (callback_res > 0x400) {
 							ErrorUnknownCallbackResult(indsp->grf_prop.grffile->grfid, CBID_INDUSTRY_FUND_MORE_TEXT, callback_res);
@@ -589,12 +589,12 @@ public:
 				if (y < this->count) { // Is it within the boundaries of available data?
 					this->selected_index = y;
 					this->selected_type = this->index[y];
-					const IndustrySpec *indsp = (this->selected_type == INVALID_INDUSTRYTYPE) ? NULL : GetIndustrySpec(this->selected_type);
+					const IndustrySpec *indsp = (this->selected_type == INVALID_INDUSTRYTYPE) ? nullptr : GetIndustrySpec(this->selected_type);
 
 					this->SetDirty();
 
 					if (_thd.GetCallbackWnd() == this &&
-							((_game_mode != GM_EDITOR && _settings_game.construction.raw_industry_construction == 2 && indsp != NULL && indsp->IsRawIndustry()) ||
+							((_game_mode != GM_EDITOR && _settings_game.construction.raw_industry_construction == 2 && indsp != nullptr && indsp->IsRawIndustry()) ||
 							this->selected_type == INVALID_INDUSTRYTYPE ||
 							!this->enabled[this->selected_index])) {
 						/* Reset the button state if going to prospecting or "build many industries" */
@@ -717,8 +717,8 @@ public:
 		if (!gui_scope) return;
 		this->SetupArrays();
 
-		const IndustrySpec *indsp = (this->selected_type == INVALID_INDUSTRYTYPE) ? NULL : GetIndustrySpec(this->selected_type);
-		if (indsp == NULL) this->enabled[this->selected_index] = _settings_game.difficulty.industry_density != ID_FUND_ONLY;
+		const IndustrySpec *indsp = (this->selected_type == INVALID_INDUSTRYTYPE) ? nullptr : GetIndustrySpec(this->selected_type);
+		if (indsp == nullptr) this->enabled[this->selected_index] = _settings_game.difficulty.industry_density != ID_FUND_ONLY;
 		this->SetButtons();
 	}
 };
@@ -1048,7 +1048,7 @@ public:
 
 	void OnResize() override
 	{
-		if (this->viewport != NULL) {
+		if (this->viewport != nullptr) {
 			NWidgetViewport *nvp = this->GetWidget<NWidgetViewport>(WID_IV_VIEWPORT);
 			nvp->UpdateViewportCoordinates(this);
 
@@ -1215,7 +1215,7 @@ protected:
 		}
 
 		if (!this->industries.Sort()) return;
-		IndustryDirectoryWindow::last_industry = NULL; // Reset name sorter sort cache
+		IndustryDirectoryWindow::last_industry = nullptr; // Reset name sorter sort cache
 		this->SetWidgetDirty(WID_ID_INDUSTRY_LIST); // Set the modified widget dirty
 	}
 
@@ -1493,7 +1493,7 @@ public:
 };
 
 Listing IndustryDirectoryWindow::last_sorting = {false, 0};
-const Industry *IndustryDirectoryWindow::last_industry = NULL;
+const Industry *IndustryDirectoryWindow::last_industry = nullptr;
 
 /* Available station sorting functions. */
 GUIIndustryList::SortFunction * const IndustryDirectoryWindow::sorter_funcs[] = {
@@ -1898,8 +1898,8 @@ struct CargoesField {
 
 	/**
 	 * Decide which cargo was clicked at in a #CFT_CARGO field.
-	 * @param left  Left industry neighbour if available (else \c NULL should be supplied).
-	 * @param right Right industry neighbour if available (else \c NULL should be supplied).
+	 * @param left  Left industry neighbour if available (else \c nullptr should be supplied).
+	 * @param right Right industry neighbour if available (else \c nullptr should be supplied).
 	 * @param pt    Click position in the cargo field.
 	 * @return Cargo clicked at, or #INVALID_CARGO if none.
 	 */
@@ -1929,7 +1929,7 @@ struct CargoesField {
 		/* row = 0 -> at first horizontal row, row = 1 -> second horizontal row, 2 = 3rd horizontal row. */
 		if (col == 0) {
 			if (this->u.cargo.supp_cargoes[row] != INVALID_CARGO) return this->u.cargo.vertical_cargoes[this->u.cargo.supp_cargoes[row]];
-			if (left != NULL) {
+			if (left != nullptr) {
 				if (left->type == CFT_INDUSTRY) return left->u.industry.other_produced[row];
 				if (left->type == CFT_CARGO_LABEL && !left->u.cargo_label.left_align) return left->u.cargo_label.cargoes[row];
 			}
@@ -1937,7 +1937,7 @@ struct CargoesField {
 		}
 		if (col == this->u.cargo.num_cargoes) {
 			if (this->u.cargo.cust_cargoes[row] != INVALID_CARGO) return this->u.cargo.vertical_cargoes[this->u.cargo.cust_cargoes[row]];
-			if (right != NULL) {
+			if (right != nullptr) {
 				if (right->type == CFT_INDUSTRY) return right->u.industry.other_accepted[row];
 				if (right->type == CFT_CARGO_LABEL && right->u.cargo_label.left_align) return right->u.cargo_label.cargoes[row];
 			}
@@ -2678,8 +2678,8 @@ struct IndustryCargoesWindow : public Wi
 						break;
 
 					case CFT_CARGO: {
-						CargoesField *lft = (fieldxy.x > 0) ? this->fields[fieldxy.y].columns + fieldxy.x - 1 : NULL;
-						CargoesField *rgt = (fieldxy.x < 4) ? this->fields[fieldxy.y].columns + fieldxy.x + 1 : NULL;
+						CargoesField *lft = (fieldxy.x > 0) ? this->fields[fieldxy.y].columns + fieldxy.x - 1 : nullptr;
+						CargoesField *rgt = (fieldxy.x < 4) ? this->fields[fieldxy.y].columns + fieldxy.x + 1 : nullptr;
 						CargoID cid = fld->CargoClickedAt(lft, rgt, xy);
 						if (cid != INVALID_CARGO) this->ComputeCargoDisplay(cid);
 						break;
@@ -2703,7 +2703,7 @@ struct IndustryCargoesWindow : public Wi
 				if (_settings_client.sound.click_beep) SndPlayFx(SND_15_BEEP);
 
 				if (this->IsWidgetLowered(WID_IC_NOTIFY)) {
-					if (FindWindowByClass(WC_SMALLMAP) == NULL) ShowSmallMap();
+					if (FindWindowByClass(WC_SMALLMAP) == nullptr) ShowSmallMap();
 					this->NotifySmallmap();
 				}
 				break;
@@ -2764,8 +2764,8 @@ struct IndustryCargoesWindow : public Wi
 		CargoID cid = INVALID_CARGO;
 		switch (fld->type) {
 			case CFT_CARGO: {
-				CargoesField *lft = (fieldxy.x > 0) ? this->fields[fieldxy.y].columns + fieldxy.x - 1 : NULL;
-				CargoesField *rgt = (fieldxy.x < 4) ? this->fields[fieldxy.y].columns + fieldxy.x + 1 : NULL;
+				CargoesField *lft = (fieldxy.x > 0) ? this->fields[fieldxy.y].columns + fieldxy.x - 1 : nullptr;
+				CargoesField *rgt = (fieldxy.x < 4) ? this->fields[fieldxy.y].columns + fieldxy.x + 1 : nullptr;
 				cid = fld->CargoClickedAt(lft, rgt, xy);
 				break;
 			}
@@ -2777,7 +2777,7 @@ struct IndustryCargoesWindow : public Wi
 
 			case CFT_INDUSTRY:
 				if (fld->u.industry.ind_type < NUM_INDUSTRYTYPES && (this->ind_cargo >= NUM_INDUSTRYTYPES || fieldxy.x != 2)) {
-					GuiShowTooltips(this, STR_INDUSTRY_CARGOES_INDUSTRY_TOOLTIP, 0, NULL, close_cond);
+					GuiShowTooltips(this, STR_INDUSTRY_CARGOES_INDUSTRY_TOOLTIP, 0, nullptr, close_cond);
 				}
 				return true;
 
@@ -2822,7 +2822,7 @@ static void ShowIndustryCargoesWindow(In
 	}
 
 	Window *w = BringWindowToFrontById(WC_INDUSTRY_CARGOES, 0);
-	if (w != NULL) {
+	if (w != nullptr) {
 		w->InvalidateData(id);
 		return;
 	}
diff --git a/src/ini.cpp b/src/ini.cpp
--- a/src/ini.cpp
+++ b/src/ini.cpp
@@ -29,7 +29,7 @@
 
 /**
  * Create a new ini file with given group names.
- * @param list_group_names A \c NULL terminated list with group names that should be loaded as lists instead of variables. @see IGT_LIST
+ * @param list_group_names A \c nullptr terminated list with group names that should be loaded as lists instead of variables. @see IGT_LIST
  */
 IniFile::IniFile(const char * const *list_group_names) : IniLoadFile(list_group_names)
 {
@@ -52,23 +52,23 @@ bool IniFile::SaveToDisk(const char *fil
 	strecpy(file_new, filename, lastof(file_new));
 	strecat(file_new, ".new", lastof(file_new));
 	FILE *f = fopen(file_new, "w");
-	if (f == NULL) return false;
+	if (f == nullptr) return false;
 
-	for (const IniGroup *group = this->group; group != NULL; group = group->next) {
+	for (const IniGroup *group = this->group; group != nullptr; group = group->next) {
 		if (group->comment) fputs(group->comment, f);
 		fprintf(f, "[%s]\n", group->name);
-		for (const IniItem *item = group->item; item != NULL; item = item->next) {
-			if (item->comment != NULL) fputs(item->comment, f);
+		for (const IniItem *item = group->item; item != nullptr; item = item->next) {
+			if (item->comment != nullptr) fputs(item->comment, f);
 
 			/* protect item->name with quotes if needed */
-			if (strchr(item->name, ' ') != NULL ||
+			if (strchr(item->name, ' ') != nullptr ||
 					item->name[0] == '[') {
 				fprintf(f, "\"%s\"", item->name);
 			} else {
 				fprintf(f, "%s", item->name);
 			}
 
-			fprintf(f, " = %s\n", item->value == NULL ? "" : item->value);
+			fprintf(f, " = %s\n", item->value == nullptr ? "" : item->value);
 		}
 	}
 	if (this->comment) fputs(this->comment, f);
diff --git a/src/ini_load.cpp b/src/ini_load.cpp
--- a/src/ini_load.cpp
+++ b/src/ini_load.cpp
@@ -23,7 +23,7 @@
  * @param name   the name of the item
  * @param last   the last element of the name of the item
  */
-IniItem::IniItem(IniGroup *parent, const char *name, const char *last) : next(NULL), value(NULL), comment(NULL)
+IniItem::IniItem(IniGroup *parent, const char *name, const char *last) : next(nullptr), value(nullptr), comment(nullptr)
 {
 	this->name = stredup(name, last);
 	str_validate(this->name, this->name + strlen(this->name));
@@ -58,7 +58,7 @@ void IniItem::SetValue(const char *value
  * @param name   the name of the group
  * @param last   the last element of the name of the group
  */
-IniGroup::IniGroup(IniLoadFile *parent, const char *name, const char *last) : next(NULL), type(IGT_VARIABLES), item(NULL), comment(NULL)
+IniGroup::IniGroup(IniLoadFile *parent, const char *name, const char *last) : next(nullptr), type(IGT_VARIABLES), item(nullptr), comment(nullptr)
 {
 	this->name = stredup(name, last);
 	str_validate(this->name, this->name + strlen(this->name));
@@ -67,16 +67,16 @@ IniGroup::IniGroup(IniLoadFile *parent, 
 	*parent->last_group = this;
 	parent->last_group = &this->next;
 
-	if (parent->list_group_names != NULL) {
-		for (uint i = 0; parent->list_group_names[i] != NULL; i++) {
+	if (parent->list_group_names != nullptr) {
+		for (uint i = 0; parent->list_group_names[i] != nullptr; i++) {
 			if (strcmp(this->name, parent->list_group_names[i]) == 0) {
 				this->type = IGT_LIST;
 				return;
 			}
 		}
 	}
-	if (parent->seq_group_names != NULL) {
-		for (uint i = 0; parent->seq_group_names[i] != NULL; i++) {
+	if (parent->seq_group_names != nullptr) {
+		for (uint i = 0; parent->seq_group_names[i] != nullptr; i++) {
 			if (strcmp(this->name, parent->seq_group_names[i]) == 0) {
 				this->type = IGT_SEQUENCE;
 				return;
@@ -100,18 +100,18 @@ IniGroup::~IniGroup()
  * and create is true it creates a new item.
  * @param name   name of the item to find.
  * @param create whether to create an item when not found or not.
- * @return the requested item or NULL if not found.
+ * @return the requested item or nullptr if not found.
  */
 IniItem *IniGroup::GetItem(const char *name, bool create)
 {
-	for (IniItem *item = this->item; item != NULL; item = item->next) {
+	for (IniItem *item = this->item; item != nullptr; item = item->next) {
 		if (strcmp(item->name, name) == 0) return item;
 	}
 
-	if (!create) return NULL;
+	if (!create) return nullptr;
 
 	/* otherwise make a new one */
-	return new IniItem(this, name, NULL);
+	return new IniItem(this, name, nullptr);
 }
 
 /**
@@ -120,18 +120,18 @@ IniItem *IniGroup::GetItem(const char *n
 void IniGroup::Clear()
 {
 	delete this->item;
-	this->item = NULL;
+	this->item = nullptr;
 	this->last_item = &this->item;
 }
 
 /**
  * Construct a new in-memory Ini file representation.
- * @param list_group_names A \c NULL terminated list with group names that should be loaded as lists instead of variables. @see IGT_LIST
- * @param seq_group_names  A \c NULL terminated list with group names that should be loaded as lists of names. @see IGT_SEQUENCE
+ * @param list_group_names A \c nullptr terminated list with group names that should be loaded as lists instead of variables. @see IGT_LIST
+ * @param seq_group_names  A \c nullptr terminated list with group names that should be loaded as lists of names. @see IGT_SEQUENCE
  */
 IniLoadFile::IniLoadFile(const char * const *list_group_names, const char * const *seq_group_names) :
-		group(NULL),
-		comment(NULL),
+		group(nullptr),
+		comment(nullptr),
 		list_group_names(list_group_names),
 		seq_group_names(seq_group_names)
 {
@@ -151,20 +151,20 @@ IniLoadFile::~IniLoadFile()
  * @param name name of the group to find.
  * @param len  the maximum length of said name (\c 0 means length of the string).
  * @param create_new Allow creation of group if it does not exist.
- * @return The requested group if it exists or was created, else \c NULL.
+ * @return The requested group if it exists or was created, else \c nullptr.
  */
 IniGroup *IniLoadFile::GetGroup(const char *name, size_t len, bool create_new)
 {
 	if (len == 0) len = strlen(name);
 
 	/* does it exist already? */
-	for (IniGroup *group = this->group; group != NULL; group = group->next) {
+	for (IniGroup *group = this->group; group != nullptr; group = group->next) {
 		if (!strncmp(group->name, name, len) && group->name[len] == 0) {
 			return group;
 		}
 	}
 
-	if (!create_new) return NULL;
+	if (!create_new) return nullptr;
 
 	/* otherwise make a new one */
 	IniGroup *group = new IniGroup(this, name, name + len - 1);
@@ -179,19 +179,19 @@ IniGroup *IniLoadFile::GetGroup(const ch
 void IniLoadFile::RemoveGroup(const char *name)
 {
 	size_t len = strlen(name);
-	IniGroup *prev = NULL;
+	IniGroup *prev = nullptr;
 	IniGroup *group;
 
 	/* does it exist already? */
-	for (group = this->group; group != NULL; prev = group, group = group->next) {
+	for (group = this->group; group != nullptr; prev = group, group = group->next) {
 		if (strncmp(group->name, name, len) == 0) {
 			break;
 		}
 	}
 
-	if (group == NULL) return;
+	if (group == nullptr) return;
 
-	if (prev != NULL) {
+	if (prev != nullptr) {
 		prev->next = prev->next->next;
 		if (this->last_group == &group->next) this->last_group = &prev->next;
 	} else {
@@ -199,7 +199,7 @@ void IniLoadFile::RemoveGroup(const char
 		if (this->last_group == &group->next) this->last_group = &this->group;
 	}
 
-	group->next = NULL;
+	group->next = nullptr;
 	delete group;
 }
 
@@ -214,15 +214,15 @@ void IniLoadFile::LoadFromDisk(const cha
 	assert(this->last_group == &this->group);
 
 	char buffer[1024];
-	IniGroup *group = NULL;
+	IniGroup *group = nullptr;
 
-	char *comment = NULL;
+	char *comment = nullptr;
 	uint comment_size = 0;
 	uint comment_alloc = 0;
 
 	size_t end;
 	FILE *in = this->OpenFile(filename, subdir, &end);
-	if (in == NULL) return;
+	if (in == nullptr) return;
 
 	end += ftell(in);
 
@@ -238,7 +238,7 @@ void IniLoadFile::LoadFromDisk(const cha
 		*e = '\0';
 
 		/* Skip comments and empty lines outside IGT_SEQUENCE groups. */
-		if ((group == NULL || group->type != IGT_SEQUENCE) && (*s == '#' || *s == ';' || *s == '\0')) {
+		if ((group == nullptr || group->type != IGT_SEQUENCE) && (*s == '#' || *s == ';' || *s == '\0')) {
 			uint ns = comment_size + (e - s + 1);
 			uint a = comment_alloc;
 			/* add to comment */
@@ -267,7 +267,7 @@ void IniLoadFile::LoadFromDisk(const cha
 				group->comment = stredup(comment, comment + comment_size - 1);
 				comment_size = 0;
 			}
-		} else if (group != NULL) {
+		} else if (group != nullptr) {
 			if (group->type == IGT_SEQUENCE) {
 				/* A sequence group, use the line as item name without further interpretation. */
 				IniItem *item = new IniItem(group, buffer, e - 1);
@@ -305,9 +305,9 @@ void IniLoadFile::LoadFromDisk(const cha
 			if (e > t && e[-1] == '\"') e--;
 			*e = '\0';
 
-			/* If the value was not quoted and empty, it must be NULL */
-			item->value = (!quoted && e == t) ? NULL : stredup(t);
-			if (item->value != NULL) str_validate(item->value, item->value + strlen(item->value));
+			/* If the value was not quoted and empty, it must be nullptr */
+			item->value = (!quoted && e == t) ? nullptr : stredup(t);
+			if (item->value != nullptr) str_validate(item->value, item->value + strlen(item->value));
 		} else {
 			/* it's an orphan item */
 			this->ReportFileError("ini: '", buffer, "' outside of group");
diff --git a/src/ini_type.h b/src/ini_type.h
--- a/src/ini_type.h
+++ b/src/ini_type.h
@@ -28,7 +28,7 @@ struct IniItem {
 	char *value;   ///< The value of this item
 	char *comment; ///< The comment associated with this item
 
-	IniItem(struct IniGroup *parent, const char *name, const char *last = NULL);
+	IniItem(struct IniGroup *parent, const char *name, const char *last = nullptr);
 	~IniItem();
 
 	void SetValue(const char *value);
@@ -43,7 +43,7 @@ struct IniGroup {
 	char *name;          ///< name of group
 	char *comment;       ///< comment for group
 
-	IniGroup(struct IniLoadFile *parent, const char *name, const char *last = NULL);
+	IniGroup(struct IniLoadFile *parent, const char *name, const char *last = nullptr);
 	~IniGroup();
 
 	IniItem *GetItem(const char *name, bool create);
@@ -55,10 +55,10 @@ struct IniLoadFile {
 	IniGroup *group;                      ///< the first group in the ini
 	IniGroup **last_group;                ///< the last group in the ini
 	char *comment;                        ///< last comment in file
-	const char * const *list_group_names; ///< NULL terminated list with group names that are lists
-	const char * const *seq_group_names;  ///< NULL terminated list with group names that are sequences.
+	const char * const *list_group_names; ///< nullptr terminated list with group names that are lists
+	const char * const *seq_group_names;  ///< nullptr terminated list with group names that are sequences.
 
-	IniLoadFile(const char * const *list_group_names = NULL, const char * const *seq_group_names = NULL);
+	IniLoadFile(const char * const *list_group_names = nullptr, const char * const *seq_group_names = nullptr);
 	virtual ~IniLoadFile();
 
 	IniGroup *GetGroup(const char *name, size_t len = 0, bool create_new = true);
@@ -71,7 +71,7 @@ struct IniLoadFile {
 	 * @param filename Name of the INI file.
 	 * @param subdir The subdir to load the file from.
 	 * @param[out] size Size of the opened file.
-	 * @return File handle of the opened file, or \c NULL.
+	 * @return File handle of the opened file, or \c nullptr.
 	 */
 	virtual FILE *OpenFile(const char *filename, Subdirectory subdir, size_t *size) = 0;
 
@@ -86,7 +86,7 @@ struct IniLoadFile {
 
 /** Ini file that supports both loading and saving. */
 struct IniFile : IniLoadFile {
-	IniFile(const char * const *list_group_names = NULL);
+	IniFile(const char * const *list_group_names = nullptr);
 
 	bool SaveToDisk(const char *filename);
 
diff --git a/src/intro_gui.cpp b/src/intro_gui.cpp
--- a/src/intro_gui.cpp
+++ b/src/intro_gui.cpp
@@ -269,7 +269,7 @@ static const NWidgetPart _nested_select_
 };
 
 static WindowDesc _select_game_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_SELECT_GAME, WC_NONE,
 	0,
 	_nested_select_game_widgets, lengthof(_nested_select_game_widgets)
@@ -303,7 +303,7 @@ void AskExitGame()
 	ShowQuery(
 		STR_QUIT_CAPTION,
 		STR_QUIT_ARE_YOU_SURE_YOU_WANT_TO_EXIT_OPENTTD,
-		NULL,
+		nullptr,
 		AskExitGameCallback
 	);
 }
@@ -322,7 +322,7 @@ void AskExitToGameMenu()
 	ShowQuery(
 		STR_ABANDON_GAME_CAPTION,
 		(_game_mode != GM_EDITOR) ? STR_ABANDON_GAME_QUERY : STR_ABANDON_SCENARIO_QUERY,
-		NULL,
+		nullptr,
 		AskExitToGameMenuCallback
 	);
 }
diff --git a/src/landscape.cpp b/src/landscape.cpp
--- a/src/landscape.cpp
+++ b/src/landscape.cpp
@@ -82,12 +82,12 @@ extern const byte _slope_to_sprite_offse
 /**
  * Description of the snow line throughout the year.
  *
- * If it is \c NULL, a static snowline height is used, as set by \c _settings_game.game_creation.snow_line_height.
+ * If it is \c nullptr, a static snowline height is used, as set by \c _settings_game.game_creation.snow_line_height.
  * Otherwise it points to a table loaded from a newGRF file that describes the variable snowline.
  * @ingroup SnowLineGroup
  * @see GetSnowLine() GameCreationSettings
  */
-static SnowLine *_snow_line = NULL;
+static SnowLine *_snow_line = nullptr;
 
 /**
  * Map 2D viewport or smallmap coordinate to 3D world or tile coordinate.
@@ -104,7 +104,7 @@ static SnowLine *_snow_line = NULL;
  */
 Point InverseRemapCoords2(int x, int y, bool clamp_to_map, bool *clamped)
 {
-	if (clamped != NULL) *clamped = false; // Not clamping yet.
+	if (clamped != nullptr) *clamped = false; // Not clamping yet.
 
 	/* Initial x/y world coordinate is like if the landscape
 	 * was completely flat on height 0. */
@@ -122,7 +122,7 @@ Point InverseRemapCoords2(int x, int y, 
 		Point old_pt = pt;
 		pt.x = Clamp(pt.x, -extra_tiles * TILE_SIZE, max_x);
 		pt.y = Clamp(pt.y, -extra_tiles * TILE_SIZE, max_y);
-		if (clamped != NULL) *clamped = (pt.x != old_pt.x) || (pt.y != old_pt.y);
+		if (clamped != nullptr) *clamped = (pt.x != old_pt.x) || (pt.y != old_pt.y);
 	}
 
 	/* Now find the Z-world coordinate by fix point iteration.
@@ -147,7 +147,7 @@ Point InverseRemapCoords2(int x, int y, 
 		Point old_pt = pt;
 		pt.x = Clamp(pt.x, min_coord, max_x);
 		pt.y = Clamp(pt.y, min_coord, max_y);
-		if (clamped != NULL) *clamped = *clamped || (pt.x != old_pt.x) || (pt.y != old_pt.y);
+		if (clamped != nullptr) *clamped = *clamped || (pt.x != old_pt.x) || (pt.y != old_pt.y);
 	}
 
 	return pt;
@@ -418,7 +418,7 @@ void GetSlopePixelZOnEdge(Slope tileh, D
  * If a tile does not have a foundation, the function returns the same as GetTileSlope.
  *
  * @param tile The tile of interest.
- * @param z returns the z of the foundation slope. (Can be NULL, if not needed)
+ * @param z returns the z of the foundation slope. (Can be nullptr, if not needed)
  * @return The slope on top of the foundation.
  */
 Slope GetFoundationSlope(TileIndex tile, int *z)
@@ -426,7 +426,7 @@ Slope GetFoundationSlope(TileIndex tile,
 	Slope tileh = GetTileSlope(tile, z);
 	Foundation f = _tile_type_procs[GetTileType(tile)]->get_foundation_proc(tile, tileh);
 	uint z_inc = ApplyFoundationToSlope(f, &tileh);
-	if (z != NULL) *z += z_inc;
+	if (z != nullptr) *z += z_inc;
 	return tileh;
 }
 
@@ -572,7 +572,7 @@ void DrawFoundation(TileInfo *ti, Founda
 void DoClearSquare(TileIndex tile)
 {
 	/* If the tile can have animation and we clear it, delete it from the animated tile list. */
-	if (_tile_type_procs[GetTileType(tile)]->animate_tile_proc != NULL) DeleteAnimatedTile(tile);
+	if (_tile_type_procs[GetTileType(tile)]->animate_tile_proc != nullptr) DeleteAnimatedTile(tile);
 
 	MakeClear(tile, CLEAR_GRASS, _generating_world ? 3 : 0);
 	MarkTileDirtyByTile(tile);
@@ -616,7 +616,7 @@ void GetTileDesc(TileIndex tile, TileDes
  */
 bool IsSnowLineSet()
 {
-	return _snow_line != NULL;
+	return _snow_line != nullptr;
 }
 
 /**
@@ -645,7 +645,7 @@ void SetSnowLine(byte table[SNOW_LINE_MO
  */
 byte GetSnowLine()
 {
-	if (_snow_line == NULL) return _settings_game.game_creation.snow_line_height;
+	if (_snow_line == nullptr) return _settings_game.game_creation.snow_line_height;
 
 	YearMonthDay ymd;
 	ConvertDateToYMD(_date, &ymd);
@@ -659,7 +659,7 @@ byte GetSnowLine()
  */
 byte HighestSnowLine()
 {
-	return _snow_line == NULL ? _settings_game.game_creation.snow_line_height : _snow_line->highest_value;
+	return _snow_line == nullptr ? _settings_game.game_creation.snow_line_height : _snow_line->highest_value;
 }
 
 /**
@@ -669,7 +669,7 @@ byte HighestSnowLine()
  */
 byte LowestSnowLine()
 {
-	return _snow_line == NULL ? _settings_game.game_creation.snow_line_height : _snow_line->lowest_value;
+	return _snow_line == nullptr ? _settings_game.game_creation.snow_line_height : _snow_line->lowest_value;
 }
 
 /**
@@ -679,7 +679,7 @@ byte LowestSnowLine()
 void ClearSnowLine()
 {
 	free(_snow_line);
-	_snow_line = NULL;
+	_snow_line = nullptr;
 }
 
 /**
@@ -702,8 +702,8 @@ CommandCost CmdLandscapeClear(TileIndex 
 		cost.AddCost(GetWaterClass(tile) == WATER_CLASS_CANAL ? _price[PR_CLEAR_CANAL] : _price[PR_CLEAR_WATER]);
 	}
 
-	Company *c = (flags & (DC_AUTO | DC_BANKRUPT)) ? NULL : Company::GetIfValid(_current_company);
-	if (c != NULL && (int)GB(c->clear_limit, 16, 16) < 1) {
+	Company *c = (flags & (DC_AUTO | DC_BANKRUPT)) ? nullptr : Company::GetIfValid(_current_company);
+	if (c != nullptr && (int)GB(c->clear_limit, 16, 16) < 1) {
 		return_cmd_error(STR_ERROR_CLEARING_LIMIT_REACHED);
 	}
 
@@ -711,7 +711,7 @@ CommandCost CmdLandscapeClear(TileIndex 
 
 	/* If this tile was the first tile which caused object destruction, always
 	 * pass it on to the tile_type_proc. That way multiple test runs and the exec run stay consistent. */
-	if (coa != NULL && coa->first_tile != tile) {
+	if (coa != nullptr && coa->first_tile != tile) {
 		/* If this tile belongs to an object which was already cleared via another tile, pretend it has been
 		 * already removed.
 		 * However, we need to check stuff, which is not the same for all object tiles. (e.g. being on water or not) */
@@ -725,7 +725,7 @@ CommandCost CmdLandscapeClear(TileIndex 
 	}
 
 	if (flags & DC_EXEC) {
-		if (c != NULL) c->clear_limit -= 1 << 16;
+		if (c != nullptr) c->clear_limit -= 1 << 16;
 		if (do_clear) DoClearSquare(tile);
 	}
 	return cost;
@@ -750,8 +750,8 @@ CommandCost CmdClearArea(TileIndex tile,
 	CommandCost last_error = CMD_ERROR;
 	bool had_success = false;
 
-	const Company *c = (flags & (DC_AUTO | DC_BANKRUPT)) ? NULL : Company::GetIfValid(_current_company);
-	int limit = (c == NULL ? INT32_MAX : GB(c->clear_limit, 16, 16));
+	const Company *c = (flags & (DC_AUTO | DC_BANKRUPT)) ? nullptr : Company::GetIfValid(_current_company);
+	int limit = (c == nullptr ? INT32_MAX : GB(c->clear_limit, 16, 16));
 
 	TileIterator *iter = HasBit(p2, 0) ? (TileIterator *)new DiagonalTileIterator(tile, p1) : new OrthogonalTileIterator(tile, p1);
 	for (; *iter != INVALID_TILE; ++(*iter)) {
@@ -761,7 +761,7 @@ CommandCost CmdClearArea(TileIndex tile,
 			last_error = ret;
 
 			/* We may not clear more tiles. */
-			if (c != NULL && GB(c->clear_limit, 16, 16) < 1) break;
+			if (c != nullptr && GB(c->clear_limit, 16, 16) < 1) break;
 			continue;
 		}
 
@@ -862,7 +862,7 @@ static void GenerateTerrain(int type, ui
 	uint32 r = Random();
 
 	const Sprite *templ = GetSprite((((r >> 24) * _genterrain_tbl_1[type]) >> 8) + _genterrain_tbl_2[type] + 4845, ST_MAPGEN);
-	if (templ == NULL) usererror("Map generator sprites could not be loaded");
+	if (templ == nullptr) usererror("Map generator sprites could not be loaded");
 
 	uint x = r & MapMaxX();
 	uint y = (r >> MapLogX()) & MapMaxY();
@@ -1065,7 +1065,7 @@ static bool MakeLake(TileIndex tile, voi
 			MakeRiver(tile, Random());
 			/* Remove desert directly around the river tile. */
 			TileIndex t = tile;
-			CircularTileSearch(&t, RIVER_OFFSET_DESERT_DISTANCE, RiverModifyDesertZone, NULL);
+			CircularTileSearch(&t, RIVER_OFFSET_DESERT_DISTANCE, RiverModifyDesertZone, nullptr);
 			return false;
 		}
 	}
@@ -1132,12 +1132,12 @@ static void River_GetNeighbours(AyStar *
 /* AyStar callback when an route has been found. */
 static void River_FoundEndNode(AyStar *aystar, OpenListNode *current)
 {
-	for (PathNode *path = &current->path; path != NULL; path = path->parent) {
+	for (PathNode *path = &current->path; path != nullptr; path = path->parent) {
 		TileIndex tile = path->node.tile;
 		if (!IsWaterTile(tile)) {
 			MakeRiver(tile, Random());
 			/* Remove desert directly around the river tile. */
-			CircularTileSearch(&tile, RIVER_OFFSET_DESERT_DISTANCE, RiverModifyDesertZone, NULL);
+			CircularTileSearch(&tile, RIVER_OFFSET_DESERT_DISTANCE, RiverModifyDesertZone, nullptr);
 		}
 	}
 }
@@ -1249,7 +1249,7 @@ static bool FlowRiver(TileIndex spring, 
 			end = lakeCenter;
 			MakeRiver(lakeCenter, Random());
 			/* Remove desert directly around the river tile. */
-			CircularTileSearch(&lakeCenter, RIVER_OFFSET_DESERT_DISTANCE, RiverModifyDesertZone, NULL);
+			CircularTileSearch(&lakeCenter, RIVER_OFFSET_DESERT_DISTANCE, RiverModifyDesertZone, nullptr);
 			lakeCenter = end;
 			uint range = RandomRange(8) + 3;
 			CircularTileSearch(&lakeCenter, range, MakeLake, &height);
@@ -1280,7 +1280,7 @@ static void CreateRivers()
 		IncreaseGeneratingWorldProgress(GWP_RIVER);
 		for (int tries = 0; tries < 128; tries++) {
 			TileIndex t = RandomTile();
-			if (!CircularTileSearch(&t, 8, FindSpring, NULL)) continue;
+			if (!CircularTileSearch(&t, 8, FindSpring, nullptr)) continue;
 			if (FlowRiver(t, t)) break;
 		}
 	}
diff --git a/src/landscape.h b/src/landscape.h
--- a/src/landscape.h
+++ b/src/landscape.h
@@ -36,7 +36,7 @@ byte LowestSnowLine();
 void ClearSnowLine();
 
 int GetSlopeZInCorner(Slope tileh, Corner corner);
-Slope GetFoundationSlope(TileIndex tile, int *z = NULL);
+Slope GetFoundationSlope(TileIndex tile, int *z = nullptr);
 
 uint GetPartialPixelZ(int x, int y, Slope corners);
 int GetSlopePixelZ(int x, int y);
@@ -62,12 +62,12 @@ static inline int GetSlopePixelZInCorner
  * If a tile does not have a foundation, the function returns the same as GetTilePixelSlope.
  *
  * @param tile The tile of interest.
- * @param z returns the z of the foundation slope. (Can be NULL, if not needed)
+ * @param z returns the z of the foundation slope. (Can be nullptr, if not needed)
  * @return The slope on top of the foundation.
  */
 static inline Slope GetFoundationPixelSlope(TileIndex tile, int *z)
 {
-	assert(z != NULL);
+	assert(z != nullptr);
 	Slope s = GetFoundationSlope(tile, z);
 	*z *= TILE_HEIGHT;
 	return s;
@@ -117,7 +117,7 @@ static inline Point InverseRemapCoords(i
 	return pt;
 }
 
-Point InverseRemapCoords2(int x, int y, bool clamp_to_map = false, bool *clamped = NULL);
+Point InverseRemapCoords2(int x, int y, bool clamp_to_map = false, bool *clamped = nullptr);
 
 uint ApplyFoundationToSlope(Foundation f, Slope *s);
 /**
diff --git a/src/linkgraph/linkgraph_gui.cpp b/src/linkgraph/linkgraph_gui.cpp
--- a/src/linkgraph/linkgraph_gui.cpp
+++ b/src/linkgraph/linkgraph_gui.cpp
@@ -301,7 +301,7 @@ void LinkGraphOverlay::DrawStationDots(c
 {
 	for (StationSupplyList::const_iterator i(this->cached_stations.begin()); i != this->cached_stations.end(); ++i) {
 		const Station *st = Station::GetIfValid(i->first);
-		if (st == NULL) continue;
+		if (st == nullptr) continue;
 		Point pt = this->GetStationMiddle(st);
 		if (!this->IsPointVisible(pt, dpi, 3 * this->scale)) continue;
 
@@ -345,7 +345,7 @@ void LinkGraphOverlay::DrawStationDots(c
  */
 Point LinkGraphOverlay::GetStationMiddle(const Station *st) const
 {
-	if (this->window->viewport != NULL) {
+	if (this->window->viewport != nullptr) {
 		return GetViewportStationMiddle(this->window->viewport, st);
 	} else {
 		/* assume this is a smallmap */
@@ -399,7 +399,7 @@ NWidgetBase *MakeCargoesLegendLinkGraphG
 {
 	static const uint ENTRIES_PER_ROW = CeilDiv(NUM_CARGO, 5);
 	NWidgetVertical *panel = new NWidgetVertical(NC_EQUALSIZE);
-	NWidgetHorizontal *row = NULL;
+	NWidgetHorizontal *row = nullptr;
 	for (uint i = 0; i < NUM_CARGO; ++i) {
 		if (i % ENTRIES_PER_ROW == 0) {
 			if (row) panel->Add(row);
@@ -563,7 +563,7 @@ bool LinkGraphLegendWindow::OnTooltip(Po
 {
 	if (IsInsideMM(widget, WID_LGL_COMPANY_FIRST, WID_LGL_COMPANY_LAST + 1)) {
 		if (this->IsWidgetDisabled(widget)) {
-			GuiShowTooltips(this, STR_LINKGRAPH_LEGEND_SELECT_COMPANIES, 0, NULL, close_cond);
+			GuiShowTooltips(this, STR_LINKGRAPH_LEGEND_SELECT_COMPANIES, 0, nullptr, close_cond);
 		} else {
 			uint64 params[2];
 			CompanyID cid = (CompanyID)(widget - WID_LGL_COMPANY_FIRST);
diff --git a/src/linkgraph/linkgraphjob.cpp b/src/linkgraph/linkgraphjob.cpp
--- a/src/linkgraph/linkgraphjob.cpp
+++ b/src/linkgraph/linkgraphjob.cpp
@@ -102,7 +102,7 @@ LinkGraphJob::~LinkGraphJob()
 
 		/* The station can have been deleted. Remove all flows originating from it then. */
 		Station *st = Station::GetIfValid(from.Station());
-		if (st == NULL) {
+		if (st == nullptr) {
 			this->EraseFlows(node_id);
 			continue;
 		}
@@ -122,7 +122,7 @@ LinkGraphJob::~LinkGraphJob()
 			if (from[it->first].Flow() == 0) continue;
 			StationID to = (*this)[it->first].Station();
 			Station *st2 = Station::GetIfValid(to);
-			if (st2 == NULL || st2->goods[this->Cargo()].link_graph != this->link_graph.index ||
+			if (st2 == nullptr || st2->goods[this->Cargo()].link_graph != this->link_graph.index ||
 					st2->goods[this->Cargo()].node != it->first ||
 					(*lg)[node_id][it->first].LastUpdate() == INVALID_DATE) {
 				/* Edge has been removed. Delete flows. */
@@ -240,7 +240,7 @@ void Path::Fork(Path *base, uint cap, in
  */
 uint Path::AddFlow(uint new_flow, LinkGraphJob &job, uint max_saturation)
 {
-	if (this->parent != NULL) {
+	if (this->parent != nullptr) {
 		LinkGraphJob::Edge edge = job[this->parent->node][this->node];
 		if (max_saturation != UINT_MAX) {
 			uint usable_cap = edge.Capacity() * max_saturation / 100;
@@ -270,6 +270,6 @@ Path::Path(NodeID n, bool source) :
 	capacity(source ? UINT_MAX : 0),
 	free_capacity(source ? INT_MAX : INT_MIN),
 	flow(0), node(n), origin(source ? n : INVALID_NODE),
-	num_children(0), parent(NULL)
+	num_children(0), parent(nullptr)
 {}
 
diff --git a/src/linkgraph/linkgraphjob.h b/src/linkgraph/linkgraphjob.h
--- a/src/linkgraph/linkgraphjob.h
+++ b/src/linkgraph/linkgraphjob.h
@@ -403,9 +403,9 @@ public:
 	 */
 	inline void Detach()
 	{
-		if (this->parent != NULL) {
+		if (this->parent != nullptr) {
 			this->parent->num_children--;
-			this->parent = NULL;
+			this->parent = nullptr;
 		}
 	}
 
diff --git a/src/linkgraph/mcf.cpp b/src/linkgraph/mcf.cpp
--- a/src/linkgraph/mcf.cpp
+++ b/src/linkgraph/mcf.cpp
@@ -104,7 +104,7 @@ public:
 	 * @param job Job to iterate on.
 	 */
 	GraphEdgeIterator(LinkGraphJob &job) : job(job),
-		i(NULL, NULL, INVALID_NODE), end(NULL, NULL, INVALID_NODE)
+		i(nullptr, nullptr, INVALID_NODE), end(nullptr, nullptr, INVALID_NODE)
 	{}
 
 	/**
@@ -262,7 +262,7 @@ void MultiCommodityFlow::Dijkstra(NodeID
 	Tedge_iterator iter(this->job);
 	uint size = this->job.Size();
 	AnnoSet annos;
-	paths.resize(size, NULL);
+	paths.resize(size, nullptr);
 	for (NodeID node = 0; node < size; ++node) {
 		Tannotation *anno = new Tannotation(node, node == source_node);
 		anno->UpdateAnnotation();
@@ -305,16 +305,16 @@ void MultiCommodityFlow::Dijkstra(NodeID
 void MultiCommodityFlow::CleanupPaths(NodeID source_id, PathVector &paths)
 {
 	Path *source = paths[source_id];
-	paths[source_id] = NULL;
+	paths[source_id] = nullptr;
 	for (PathVector::iterator i = paths.begin(); i != paths.end(); ++i) {
 		Path *path = *i;
-		if (path == NULL) continue;
+		if (path == nullptr) continue;
 		if (path->GetParent() == source) path->Detach();
-		while (path != source && path != NULL && path->GetFlow() == 0) {
+		while (path != source && path != nullptr && path->GetFlow() == 0) {
 			Path *parent = path->GetParent();
 			path->Detach();
 			if (path->GetNumChildren() == 0) {
-				paths[path->GetNode()] = NULL;
+				paths[path->GetNode()] = nullptr;
 				delete path;
 			}
 			path = parent;
@@ -404,7 +404,7 @@ bool MCF1stPass::EliminateCycles(PathVec
 	/* this node has already been searched */
 	if (at_next_pos == Path::invalid_path) return false;
 
-	if (at_next_pos == NULL) {
+	if (at_next_pos == nullptr) {
 		/* Summarize paths; add up the paths with the same source and next hop
 		 * in one path each. */
 		PathList &paths = this->job[next_id].Paths();
@@ -450,7 +450,7 @@ bool MCF1stPass::EliminateCycles(PathVec
 		 * could be found in this branch, thus it has to be searched again next
 		 * time we spot it.
 		 */
-		path[next_id] = found ? NULL : Path::invalid_path;
+		path[next_id] = found ? nullptr : Path::invalid_path;
 		return found;
 	}
 
@@ -474,11 +474,11 @@ bool MCF1stPass::EliminateCycles()
 {
 	bool cycles_found = false;
 	uint size = this->job.Size();
-	PathVector path(size, NULL);
+	PathVector path(size, nullptr);
 	for (NodeID node = 0; node < size; ++node) {
 		/* Starting at each node in the graph find all cycles involving this
 		 * node. */
-		std::fill(path.begin(), path.end(), (Path *)NULL);
+		std::fill(path.begin(), path.end(), (Path *)nullptr);
 		cycles_found |= this->EliminateCycles(path, node, node);
 	}
 	return cycles_found;
@@ -505,7 +505,7 @@ MCF1stPass::MCF1stPass(LinkGraphJob &job
 				Edge edge = job[source][dest];
 				if (edge.UnsatisfiedDemand() > 0) {
 					Path *path = paths[dest];
-					assert(path != NULL);
+					assert(path != nullptr);
 					/* Generally only allow paths that don't exceed the
 					 * available capacity. But if no demand has been assigned
 					 * yet, make an exception and allow any valid path *once*. */
diff --git a/src/linkgraph/refresh.cpp b/src/linkgraph/refresh.cpp
--- a/src/linkgraph/refresh.cpp
+++ b/src/linkgraph/refresh.cpp
@@ -28,11 +28,11 @@
 /* static */ void LinkRefresher::Run(Vehicle *v, bool allow_merge, bool is_full_loading)
 {
 	/* If there are no orders we can't predict anything.*/
-	if (v->orders.list == NULL) return;
+	if (v->orders.list == nullptr) return;
 
 	/* Make sure the first order is a useful order. */
 	const Order *first = v->orders.list->GetNextDecisionNode(v->GetOrder(v->cur_implicit_order_index), 0);
-	if (first == NULL) return;
+	if (first == nullptr) return;
 
 	HopSet seen_hops;
 	LinkRefresher refresher(v, &seen_hops, allow_merge, is_full_loading);
@@ -75,7 +75,7 @@ LinkRefresher::LinkRefresher(Vehicle *ve
 	memset(this->capacities, 0, sizeof(this->capacities));
 
 	/* Assemble list of capacities and set last loading stations to 0. */
-	for (Vehicle *v = this->vehicle; v != NULL; v = v->Next()) {
+	for (Vehicle *v = this->vehicle; v != nullptr; v = v->Next()) {
 		this->refit_capacities.push_back(RefitDesc(v->cargo_type, v->cargo_cap, v->refit_cap));
 		if (v->refit_cap > 0) {
 			assert(v->cargo_type < NUM_CARGO);
@@ -94,7 +94,7 @@ bool LinkRefresher::HandleRefit(CargoID 
 	this->cargo = refit_cargo;
 	RefitList::iterator refit_it = this->refit_capacities.begin();
 	bool any_refit = false;
-	for (Vehicle *v = this->vehicle; v != NULL; v = v->Next()) {
+	for (Vehicle *v = this->vehicle; v != nullptr; v = v->Next()) {
 		const Engine *e = Engine::Get(v->engine_type);
 		if (!HasBit(e->info.refit_mask, this->cargo)) {
 			++refit_it;
@@ -164,10 +164,10 @@ void LinkRefresher::ResetRefit()
  */
 const Order *LinkRefresher::PredictNextOrder(const Order *cur, const Order *next, uint8 flags, uint num_hops)
 {
-	/* next is good if it's either NULL (then the caller will stop the
+	/* next is good if it's either nullptr (then the caller will stop the
 	 * evaluation) or if it's not conditional and the caller allows it to be
 	 * chosen (by setting USE_NEXT). */
-	while (next != NULL && (!HasBit(flags, USE_NEXT) || next->IsType(OT_CONDITIONAL))) {
+	while (next != nullptr && (!HasBit(flags, USE_NEXT) || next->IsType(OT_CONDITIONAL))) {
 
 		/* After the first step any further non-conditional order is good,
 		 * regardless of previous USE_NEXT settings. The case of cur and next or
@@ -177,7 +177,7 @@ const Order *LinkRefresher::PredictNextO
 		if (next->IsType(OT_CONDITIONAL)) {
 			const Order *skip_to = this->vehicle->orders.list->GetNextDecisionNode(
 					this->vehicle->orders.list->GetOrderAt(next->GetConditionSkipToOrder()), num_hops);
-			if (skip_to != NULL && num_hops < this->vehicle->orders.list->GetNumOrders()) {
+			if (skip_to != nullptr && num_hops < this->vehicle->orders.list->GetNumOrders()) {
 				/* Make copies of capacity tracking lists. There is potential
 				 * for optimization here: If the vehicle never refits we don't
 				 * need to copy anything. Also, if we've seen the branched link
@@ -204,7 +204,7 @@ void LinkRefresher::RefreshStats(const O
 {
 	StationID next_station = next->GetDestination();
 	Station *st = Station::GetIfValid(cur->GetDestination());
-	if (st != NULL && next_station != INVALID_STATION && next_station != st->index) {
+	if (st != nullptr && next_station != INVALID_STATION && next_station != st->index) {
 		for (CargoID c = 0; c < NUM_CARGO; c++) {
 			/* Refresh the link and give it a minimum capacity. */
 
@@ -226,7 +226,7 @@ void LinkRefresher::RefreshStats(const O
 			 * loading. Don't do that if the vehicle has been waiting for longer than the entire
 			 * order list is supposed to take, though. If that is the case the total duration is
 			 * probably far off and we'd greatly overestimate the capacity by increasing.*/
-			if (this->is_full_loading && this->vehicle->orders.list != NULL &&
+			if (this->is_full_loading && this->vehicle->orders.list != nullptr &&
 					st->index == vehicle->last_station_visited &&
 					this->vehicle->orders.list->GetTotalDuration() >
 					(Ticks)this->vehicle->current_order_time) {
@@ -260,7 +260,7 @@ void LinkRefresher::RefreshStats(const O
  */
 void LinkRefresher::RefreshLinks(const Order *cur, const Order *next, uint8 flags, uint num_hops)
 {
-	while (next != NULL) {
+	while (next != nullptr) {
 
 		if ((next->IsType(OT_GOTO_DEPOT) || next->IsType(OT_GOTO_STATION)) && next->IsRefit()) {
 			SetBit(flags, WAS_REFIT);
@@ -288,7 +288,7 @@ void LinkRefresher::RefreshLinks(const O
 		}
 
 		next = this->PredictNextOrder(cur, next, flags, num_hops);
-		if (next == NULL) break;
+		if (next == nullptr) break;
 		Hop hop(cur->index, next->index, this->cargo);
 		if (this->seen_hops->find(hop) != this->seen_hops->end()) {
 			break;
diff --git a/src/main_gui.cpp b/src/main_gui.cpp
--- a/src/main_gui.cpp
+++ b/src/main_gui.cpp
@@ -72,7 +72,7 @@ void HandleOnEditText(const char *str)
 	switch (_rename_what) {
 		case 3: { // Give money, you can only give money in excess of loan
 			const Company *c = Company::GetIfValid(_local_company);
-			if (c == NULL) break;
+			if (c == nullptr) break;
 			Money money = min(c->money - c->current_loan, (Money)(atoi(str) / _currency->rate));
 
 			uint32 money_c = Clamp(ClampToI32(money), 0, 20000000); // Clamp between 20 million and 0
@@ -124,7 +124,7 @@ void ShowNetworkGiveMoneyWindow(CompanyI
 {
 	_rename_id = company;
 	_rename_what = 3;
-	ShowQueryString(STR_EMPTY, STR_NETWORK_GIVE_MONEY_CAPTION, 30, NULL, CS_NUMERAL, QSF_NONE);
+	ShowQueryString(STR_EMPTY, STR_NETWORK_GIVE_MONEY_CAPTION, 30, nullptr, CS_NUMERAL, QSF_NONE);
 }
 
 
@@ -139,7 +139,7 @@ bool DoZoomInOutWindow(ZoomStateChange h
 {
 	ViewPort *vp;
 
-	assert(w != NULL);
+	assert(w != nullptr);
 	vp = w->viewport;
 
 	switch (how) {
@@ -173,7 +173,7 @@ bool DoZoomInOutWindow(ZoomStateChange h
 			w->viewport->follow_vehicle = INVALID_VEHICLE;
 			break;
 	}
-	if (vp != NULL) { // the vp can be null when how == ZOOM_NONE
+	if (vp != nullptr) { // the vp can be null when how == ZOOM_NONE
 		vp->virtual_left = w->viewport->scrollpos_x;
 		vp->virtual_top = w->viewport->scrollpos_y;
 	}
@@ -184,7 +184,7 @@ bool DoZoomInOutWindow(ZoomStateChange h
 
 void ZoomInOrOutToCursorWindow(bool in, Window *w)
 {
-	assert(w != NULL);
+	assert(w != nullptr);
 
 	if (_game_mode != GM_MENU) {
 		ViewPort *vp = w->viewport;
@@ -394,7 +394,7 @@ struct MainWindow : Window
 			case GHK_CHAT: // smart chat; send to team if any, otherwise to all
 				if (_networking) {
 					const NetworkClientInfo *cio = NetworkClientInfo::GetByClientID(_network_own_client_id);
-					if (cio == NULL) break;
+					if (cio == nullptr) break;
 
 					ShowNetworkChatQueryWindow(NetworkClientPreferTeamChat(cio) ? DESTTYPE_TEAM : DESTTYPE_BROADCAST, cio->client_playas);
 				}
@@ -407,7 +407,7 @@ struct MainWindow : Window
 			case GHK_CHAT_COMPANY: // send text to all team mates
 				if (_networking) {
 					const NetworkClientInfo *cio = NetworkClientInfo::GetByClientID(_network_own_client_id);
-					if (cio == NULL) break;
+					if (cio == nullptr) break;
 
 					ShowNetworkChatQueryWindow(DESTTYPE_TEAM, cio->client_playas);
 				}
@@ -442,7 +442,7 @@ struct MainWindow : Window
 
 	void OnResize() override
 	{
-		if (this->viewport != NULL) {
+		if (this->viewport != nullptr) {
 			NWidgetViewport *nvp = this->GetWidget<NWidgetViewport>(WID_M_VIEWPORT);
 			nvp->UpdateViewportCoordinates(this);
 			this->refresh.SetInterval(LINKGRAPH_DELAY);
@@ -517,7 +517,7 @@ static Hotkey global_hotkeys[] = {
 HotkeyList MainWindow::hotkeys("global", global_hotkeys);
 
 static WindowDesc _main_window_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_MAIN_WINDOW, WC_NONE,
 	0,
 	_nested_main_window_widgets, lengthof(_nested_main_window_widgets),
diff --git a/src/map.cpp b/src/map.cpp
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -29,8 +29,8 @@ uint _map_size_y;    ///< Size of the ma
 uint _map_size;      ///< The number of tiles on the map
 uint _map_tile_mask; ///< _map_size - 1 (to mask the mapsize)
 
-Tile *_m = NULL;          ///< Tiles of the map
-TileExtended *_me = NULL; ///< Extended Tiles of the map
+Tile *_m = nullptr;          ///< Tiles of the map
+TileExtended *_me = nullptr; ///< Extended Tiles of the map
 
 
 /**
@@ -254,12 +254,12 @@ uint DistanceFromEdgeDir(TileIndex tile,
  * @param proc: callback testing function pointer.
  * @param user_data to be passed to the callback function. Depends on the implementation
  * @return result of the search
- * @pre proc != NULL
+ * @pre proc != nullptr
  * @pre size > 0
  */
 bool CircularTileSearch(TileIndex *tile, uint size, TestTileOnSearchProc proc, void *user_data)
 {
-	assert(proc != NULL);
+	assert(proc != nullptr);
 	assert(size > 0);
 
 	if (size % 2 == 1) {
@@ -292,12 +292,12 @@ bool CircularTileSearch(TileIndex *tile,
  * @param proc callback testing function pointer.
  * @param user_data to be passed to the callback function. Depends on the implementation
  * @return result of the search
- * @pre proc != NULL
+ * @pre proc != nullptr
  * @pre radius > 0
  */
 bool CircularTileSearch(TileIndex *tile, uint radius, uint w, uint h, TestTileOnSearchProc proc, void *user_data)
 {
-	assert(proc != NULL);
+	assert(proc != nullptr);
 	assert(radius > 0);
 
 	uint x = TileX(*tile) + w + 1;
diff --git a/src/misc/binaryheap.hpp b/src/misc/binaryheap.hpp
--- a/src/misc/binaryheap.hpp
+++ b/src/misc/binaryheap.hpp
@@ -72,7 +72,7 @@ public:
 	{
 		this->Clear();
 		free(this->data);
-		this->data = NULL;
+		this->data = nullptr;
 	}
 
 protected:
diff --git a/src/misc/blob.hpp b/src/misc/blob.hpp
--- a/src/misc/blob.hpp
+++ b/src/misc/blob.hpp
@@ -86,9 +86,9 @@ public:
 	/** move constructor - take ownership of blob data */
 	inline ByteBlob(BlobHeader * const & src)
 	{
-		assert(src != NULL);
+		assert(src != nullptr);
 		header = src;
-		*const_cast<BlobHeader**>(&src) = NULL;
+		*const_cast<BlobHeader**>(&src) = nullptr;
 	}
 
 	/** destructor */
@@ -221,7 +221,7 @@ public:
 	/** append new bytes at the end of existing data bytes - reallocates if necessary */
 	inline void AppendRaw(const void *p, size_t num_bytes)
 	{
-		assert(p != NULL);
+		assert(p != nullptr);
 		if (num_bytes > 0) {
 			memcpy(Append(num_bytes), p, num_bytes);
 		}
@@ -317,8 +317,8 @@ public:
 
 		OnTransfer(const OnTransfer& src) : header(src.header)
 		{
-			assert(src.header != NULL);
-			*const_cast<typename base::BlobHeader**>(&src.header) = NULL;
+			assert(src.header != nullptr);
+			*const_cast<typename base::BlobHeader**>(&src.header) = nullptr;
 		}
 
 		OnTransfer(CBlobT& src) : header(src.header)
@@ -328,7 +328,7 @@ public:
 
 		~OnTransfer()
 		{
-			assert(header == NULL);
+			assert(header == nullptr);
 		}
 	};
 
diff --git a/src/misc/countedptr.hpp b/src/misc/countedptr.hpp
--- a/src/misc/countedptr.hpp
+++ b/src/misc/countedptr.hpp
@@ -34,8 +34,8 @@ protected:
 	Tcls *m_pT;
 
 public:
-	/** default (NULL) construct or construct from a raw pointer */
-	inline CCountedPtr(Tcls *pObj = NULL) : m_pT(pObj)
+	/** default (nullptr) construct or construct from a raw pointer */
+	inline CCountedPtr(Tcls *pObj = nullptr) : m_pT(pObj)
 	{
 		AddRef();
 	}
@@ -56,16 +56,16 @@ protected:
 	/** add one ref to the underlaying object */
 	inline void AddRef()
 	{
-		if (m_pT != NULL) m_pT->AddRef();
+		if (m_pT != nullptr) m_pT->AddRef();
 	}
 
 public:
 	/** release smart pointer (and decrement ref count) if not null */
 	inline void Release()
 	{
-		if (m_pT != NULL) {
+		if (m_pT != nullptr) {
 			Tcls *pT = m_pT;
-			m_pT = NULL;
+			m_pT = nullptr;
 			pT->Release();
 		}
 	}
@@ -73,21 +73,21 @@ public:
 	/** dereference of smart pointer - const way */
 	inline const Tcls *operator->() const
 	{
-		assert(m_pT != NULL);
+		assert(m_pT != nullptr);
 		return m_pT;
 	}
 
 	/** dereference of smart pointer - non const way */
 	inline Tcls *operator->()
 	{
-		assert(m_pT != NULL);
+		assert(m_pT != nullptr);
 		return m_pT;
 	}
 
 	/** raw pointer casting operator - const way */
 	inline operator const Tcls*() const
 	{
-		assert(m_pT == NULL);
+		assert(m_pT == nullptr);
 		return m_pT;
 	}
 
@@ -100,7 +100,7 @@ public:
 	/** operator & to support output arguments */
 	inline Tcls** operator&()
 	{
-		assert(m_pT == NULL);
+		assert(m_pT == nullptr);
 		return &m_pT;
 	}
 
@@ -121,16 +121,16 @@ public:
 	/** assignment operator helper */
 	inline void Assign(Tcls *pT);
 
-	/** one way how to test for NULL value */
+	/** one way how to test for nullptr value */
 	inline bool IsNull() const
 	{
-		return m_pT == NULL;
+		return m_pT == nullptr;
 	}
 
-	/** another way how to test for NULL value */
+	/** another way how to test for nullptr value */
 	//inline bool operator == (const CCountedPtr &sp) const {return m_pT == sp.m_pT;}
 
-	/** yet another way how to test for NULL value */
+	/** yet another way how to test for nullptr value */
 	//inline bool operator != (const CCountedPtr &sp) const {return m_pT != sp.m_pT;}
 
 	/** assign pointer w/o incrementing ref count */
@@ -144,7 +144,7 @@ public:
 	inline Tcls *Detach()
 	{
 		Tcls *pT = m_pT;
-		m_pT = NULL;
+		m_pT = nullptr;
 		return pT;
 	}
 };
@@ -154,10 +154,10 @@ inline void CCountedPtr<Tcls_>::Assign(T
 {
 	/* if they are the same, we do nothing */
 	if (pT != m_pT) {
-		if (pT != NULL) pT->AddRef();        // AddRef new pointer if any
+		if (pT != nullptr) pT->AddRef();        // AddRef new pointer if any
 		Tcls *pTold = m_pT;                  // save original ptr
 		m_pT = pT;                           // update m_pT to new value
-		if (pTold != NULL) pTold->Release(); // release old ptr if any
+		if (pTold != nullptr) pTold->Release(); // release old ptr if any
 	}
 }
 
diff --git a/src/misc/dbg_helpers.h b/src/misc/dbg_helpers.h
--- a/src/misc/dbg_helpers.h
+++ b/src/misc/dbg_helpers.h
@@ -155,8 +155,8 @@ struct DumpTarget {
 	{
 		static size_t type_id = ++LastTypeId();
 
-		if (s == NULL) {
-			/* No need to dump NULL struct. */
+		if (s == nullptr) {
+			/* No need to dump nullptr struct. */
 			WriteLine("%s = <null>", name);
 			return;
 		}
diff --git a/src/misc/fixedsizearray.hpp b/src/misc/fixedsizearray.hpp
--- a/src/misc/fixedsizearray.hpp
+++ b/src/misc/fixedsizearray.hpp
@@ -94,7 +94,7 @@ public:
 		Clear();
 		/* free the memory block occupied by items */
 		free(((byte*)data) - HeaderSize);
-		data = NULL;
+		data = nullptr;
 	}
 
 	/** Clear (destroy) all items */
diff --git a/src/misc/getoptdata.cpp b/src/misc/getoptdata.cpp
--- a/src/misc/getoptdata.cpp
+++ b/src/misc/getoptdata.cpp
@@ -26,7 +26,7 @@ int GetOptData::GetOpt()
 	const OptionData *odata;
 
 	char *s = this->cont;
-	if (s == NULL) {
+	if (s == nullptr) {
 		if (this->numleft == 0) return -1; // No arguments left -> finished.
 
 		s = this->argv[0];
@@ -37,8 +37,8 @@ int GetOptData::GetOpt()
 
 		/* Is it a long option? */
 		for (odata = this->options; odata->flags != ODF_END; odata++) {
-			if (odata->longname != NULL && !strcmp(odata->longname, s)) { // Long options always use the entire argument.
-				this->cont = NULL;
+			if (odata->longname != nullptr && !strcmp(odata->longname, s)) { // Long options always use the entire argument.
+				this->cont = nullptr;
 				goto set_optval;
 			}
 		}
@@ -49,19 +49,19 @@ int GetOptData::GetOpt()
 	/* Is it a short option? */
 	for (odata = this->options; odata->flags != ODF_END; odata++) {
 		if (odata->shortname != '\0' && *s == odata->shortname) {
-			this->cont = (s[1] != '\0') ? s + 1 : NULL;
+			this->cont = (s[1] != '\0') ? s + 1 : nullptr;
 
 set_optval: // Handle option value of *odata .
-			this->opt = NULL;
+			this->opt = nullptr;
 			switch (odata->flags) {
 				case ODF_NO_VALUE:
 					return odata->id;
 
 				case ODF_HAS_VALUE:
 				case ODF_OPTIONAL_VALUE:
-					if (this->cont != NULL) { // Remainder of the argument is the option value.
+					if (this->cont != nullptr) { // Remainder of the argument is the option value.
 						this->opt = this->cont;
-						this->cont = NULL;
+						this->cont = nullptr;
 						return odata->id;
 					}
 					/* No more arguments, either return an error or a value-less option. */
diff --git a/src/misc/getoptdata.h b/src/misc/getoptdata.h
--- a/src/misc/getoptdata.h
+++ b/src/misc/getoptdata.h
@@ -25,12 +25,12 @@ struct OptionData {
 	byte id;              ///< Unique identification of this option data, often the same as #shortname.
 	char shortname;       ///< Short option letter if available, else use \c '\0'.
 	uint16 flags;         ///< Option data flags. @see OptionDataFlags
-	const char *longname; ///< Long option name including '-'/'--' prefix, use \c NULL if not available.
+	const char *longname; ///< Long option name including '-'/'--' prefix, use \c nullptr if not available.
 };
 
 /** Data storage for parsing command line options. */
 struct GetOptData {
-	char *opt;                 ///< Option value, if available (else \c NULL).
+	char *opt;                 ///< Option value, if available (else \c nullptr).
 	int numleft;               ///< Number of arguments left in #argv.
 	char **argv;               ///< Remaining command line arguments.
 	const OptionData *options; ///< Command line option descriptions.
@@ -43,11 +43,11 @@ struct GetOptData {
 	 * @param options Command line option descriptions.
 	 */
 	GetOptData(int argc, char **argv, const OptionData *options) :
-			opt(NULL),
+			opt(nullptr),
 			numleft(argc),
 			argv(argv),
 			options(options),
-			cont(NULL)
+			cont(nullptr)
 	{
 	}
 
@@ -58,7 +58,7 @@ struct GetOptData {
  * General macro for creating an option.
  * @param id        Identification of the option.
  * @param shortname Short option name. Use \c '\0' if not used.
- * @param longname  Long option name including leading '-' or '--'. Use \c NULL if not used.
+ * @param longname  Long option name including leading '-' or '--'. Use \c nullptr if not used.
  * @param flags     Flags of the option.
  */
 #define GETOPT_GENERAL(id, shortname, longname, flags) { id, shortname, flags, longname }
@@ -66,21 +66,21 @@ struct GetOptData {
 /**
  * Short option without value.
  * @param shortname Short option name. Use \c '\0' if not used.
- * @param longname  Long option name including leading '-' or '--'. Use \c NULL if not used.
+ * @param longname  Long option name including leading '-' or '--'. Use \c nullptr if not used.
  */
 #define GETOPT_NOVAL(shortname, longname) GETOPT_GENERAL(shortname, shortname, longname, ODF_NO_VALUE)
 
 /**
  * Short option with value.
  * @param shortname Short option name. Use \c '\0' if not used.
- * @param longname  Long option name including leading '-' or '--'. Use \c NULL if not used.
+ * @param longname  Long option name including leading '-' or '--'. Use \c nullptr if not used.
  */
 #define GETOPT_VALUE(shortname, longname) GETOPT_GENERAL(shortname, shortname, longname, ODF_HAS_VALUE)
 
 /**
  * Short option with optional value.
  * @param shortname Short option name. Use \c '\0' if not used.
- * @param longname  Long option name including leading '-' or '--'. Use \c NULL if not used.
+ * @param longname  Long option name including leading '-' or '--'. Use \c nullptr if not used.
  * @note Options with optional values are hopelessly ambiguous, eg "-opt -value", avoid them.
  */
 #define GETOPT_OPTVAL(shortname, longname) GETOPT_GENERAL(shortname, shortname, longname, ODF_OPTIONAL_VALUE)
@@ -90,23 +90,23 @@ struct GetOptData {
  * Short option without value.
  * @param shortname Short option name. Use \c '\0' if not used.
  */
-#define GETOPT_SHORT_NOVAL(shortname) GETOPT_NOVAL(shortname, NULL)
+#define GETOPT_SHORT_NOVAL(shortname) GETOPT_NOVAL(shortname, nullptr)
 
 /**
  * Short option with value.
  * @param shortname Short option name. Use \c '\0' if not used.
  */
-#define GETOPT_SHORT_VALUE(shortname) GETOPT_VALUE(shortname, NULL)
+#define GETOPT_SHORT_VALUE(shortname) GETOPT_VALUE(shortname, nullptr)
 
 /**
  * Short option with optional value.
  * @param shortname Short option name. Use \c '\0' if not used.
  * @note Options with optional values are hopelessly ambiguous, eg "-opt -value", avoid them.
  */
-#define GETOPT_SHORT_OPTVAL(shortname) GETOPT_OPTVAL(shortname, NULL)
+#define GETOPT_SHORT_OPTVAL(shortname) GETOPT_OPTVAL(shortname, nullptr)
 
 /** Option terminator. */
-#define GETOPT_END() { '\0', '\0', ODF_END, NULL}
+#define GETOPT_END() { '\0', '\0', ODF_END, nullptr}
 
 
 #endif /* GETOPTDATA_H */
diff --git a/src/misc/hashtable.hpp b/src/misc/hashtable.hpp
--- a/src/misc/hashtable.hpp
+++ b/src/misc/hashtable.hpp
@@ -21,42 +21,42 @@ struct CHashTableSlotT
 
 	Titem_ *m_pFirst;
 
-	inline CHashTableSlotT() : m_pFirst(NULL) {}
+	inline CHashTableSlotT() : m_pFirst(nullptr) {}
 
 	/** hash table slot helper - clears the slot by simple forgetting its items */
 	inline void Clear()
 	{
-		m_pFirst = NULL;
+		m_pFirst = nullptr;
 	}
 
 	/** hash table slot helper - linear search for item with given key through the given blob - const version */
 	inline const Titem_ *Find(const Key &key) const
 	{
-		for (const Titem_ *pItem = m_pFirst; pItem != NULL; pItem = pItem->GetHashNext()) {
+		for (const Titem_ *pItem = m_pFirst; pItem != nullptr; pItem = pItem->GetHashNext()) {
 			if (pItem->GetKey() == key) {
 				/* we have found the item, return it */
 				return pItem;
 			}
 		}
-		return NULL;
+		return nullptr;
 	}
 
 	/** hash table slot helper - linear search for item with given key through the given blob - non-const version */
 	inline Titem_ *Find(const Key &key)
 	{
-		for (Titem_ *pItem = m_pFirst; pItem != NULL; pItem = pItem->GetHashNext()) {
+		for (Titem_ *pItem = m_pFirst; pItem != nullptr; pItem = pItem->GetHashNext()) {
 			if (pItem->GetKey() == key) {
 				/* we have found the item, return it */
 				return pItem;
 			}
 		}
-		return NULL;
+		return nullptr;
 	}
 
 	/** hash table slot helper - add new item to the slot */
 	inline void Attach(Titem_ &new_item)
 	{
-		assert(new_item.GetHashNext() == NULL);
+		assert(new_item.GetHashNext() == nullptr);
 		new_item.SetHashNext(m_pFirst);
 		m_pFirst = &new_item;
 	}
@@ -66,12 +66,12 @@ struct CHashTableSlotT
 	{
 		if (m_pFirst == &item_to_remove) {
 			m_pFirst = item_to_remove.GetHashNext();
-			item_to_remove.SetHashNext(NULL);
+			item_to_remove.SetHashNext(nullptr);
 			return true;
 		}
 		Titem_ *pItem = m_pFirst;
 		for (;;) {
-			if (pItem == NULL) {
+			if (pItem == nullptr) {
 				return false;
 			}
 			Titem_ *pNextItem = pItem->GetHashNext();
@@ -79,7 +79,7 @@ struct CHashTableSlotT
 			pItem = pNextItem;
 		}
 		pItem->SetHashNext(item_to_remove.GetHashNext());
-		item_to_remove.SetHashNext(NULL);
+		item_to_remove.SetHashNext(nullptr);
 		return true;
 	}
 
@@ -87,27 +87,27 @@ struct CHashTableSlotT
 	inline Titem_ *Detach(const Key &key)
 	{
 		/* do we have any items? */
-		if (m_pFirst == NULL) {
-			return NULL;
+		if (m_pFirst == nullptr) {
+			return nullptr;
 		}
 		/* is it our first item? */
 		if (m_pFirst->GetKey() == key) {
 			Titem_ &ret_item = *m_pFirst;
 			m_pFirst = m_pFirst->GetHashNext();
-			ret_item.SetHashNext(NULL);
+			ret_item.SetHashNext(nullptr);
 			return &ret_item;
 		}
 		/* find it in the following items */
 		Titem_ *pPrev = m_pFirst;
-		for (Titem_ *pItem = m_pFirst->GetHashNext(); pItem != NULL; pPrev = pItem, pItem = pItem->GetHashNext()) {
+		for (Titem_ *pItem = m_pFirst->GetHashNext(); pItem != nullptr; pPrev = pItem, pItem = pItem->GetHashNext()) {
 			if (pItem->GetKey() == key) {
 				/* we have found the item, unlink and return it */
 				pPrev->SetHashNext(pItem->GetHashNext());
-				pItem->SetHashNext(NULL);
+				pItem->SetHashNext(nullptr);
 				return pItem;
 			}
 		}
-		return NULL;
+		return nullptr;
 	}
 };
 
@@ -211,7 +211,7 @@ public:
 		int hash = CalcHash(key);
 		Slot &slot = m_slots[hash];
 		Titem_ *item = slot.Detach(key);
-		if (item != NULL) {
+		if (item != nullptr) {
 			m_num_items--;
 		}
 		return item;
@@ -221,7 +221,7 @@ public:
 	Titem_& Pop(const Tkey &key)
 	{
 		Titem_ *item = TryPop(key);
-		assert(item != NULL);
+		assert(item != nullptr);
 		return *item;
 	}
 
@@ -250,7 +250,7 @@ public:
 	{
 		int hash = CalcHash(new_item);
 		Slot &slot = m_slots[hash];
-		assert(slot.Find(new_item.GetKey()) == NULL);
+		assert(slot.Find(new_item.GetKey()) == nullptr);
 		slot.Attach(new_item);
 		m_num_items++;
 	}
diff --git a/src/misc_cmd.cpp b/src/misc_cmd.cpp
--- a/src/misc_cmd.cpp
+++ b/src/misc_cmd.cpp
@@ -166,7 +166,7 @@ CommandCost CmdPause(TileIndex tile, DoC
 			ShowQuery(
 				STR_NEWGRF_UNPAUSE_WARNING_TITLE,
 				STR_NEWGRF_UNPAUSE_WARNING,
-				NULL,
+				nullptr,
 				AskUnsafeUnpauseCallback
 			);
 		} else {
diff --git a/src/misc_gui.cpp b/src/misc_gui.cpp
--- a/src/misc_gui.cpp
+++ b/src/misc_gui.cpp
@@ -168,10 +168,10 @@ public:
 		td.rail_speed = 0;
 		td.road_speed = 0;
 
-		td.grf = NULL;
+		td.grf = nullptr;
 
 		CargoArray acceptance;
-		AddAcceptedCargo(tile, acceptance, NULL);
+		AddAcceptedCargo(tile, acceptance, nullptr);
 		GetTileDesc(tile, &td);
 
 		uint line_nr = 0;
@@ -194,7 +194,7 @@ public:
 		/* Cost to clear/revenue when cleared */
 		StringID str = STR_LAND_AREA_INFORMATION_COST_TO_CLEAR_N_A;
 		Company *c = Company::GetIfValid(_local_company);
-		if (c != NULL) {
+		if (c != nullptr) {
 			assert(_current_company == _local_company);
 			CommandCost costclear = DoCommand(tile, 0, 0, DC_QUERY_COST, CMD_LANDSCAPE_CLEAR);
 			if (costclear.Succeeded()) {
@@ -223,7 +223,7 @@ public:
 
 		/* Local authority */
 		SetDParam(0, STR_LAND_AREA_INFORMATION_LOCAL_AUTHORITY_NONE);
-		if (t != NULL) {
+		if (t != nullptr) {
 			SetDParam(0, STR_TOWN_NAME);
 			SetDParam(1, t->index);
 		}
@@ -294,7 +294,7 @@ public:
 		}
 
 		/* NewGRF name */
-		if (td.grf != NULL) {
+		if (td.grf != nullptr) {
 			SetDParamStr(0, td.grf);
 			GetString(this->landinfo_data[line_nr], STR_LAND_AREA_INFORMATION_NEWGRF_NAME, lastof(this->landinfo_data[line_nr]));
 			line_nr++;
@@ -382,7 +382,7 @@ static const NWidgetPart _nested_about_w
 };
 
 static WindowDesc _about_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_GAME_OPTIONS, WC_NONE,
 	0,
 	_nested_about_widgets, lengthof(_nested_about_widgets)
@@ -638,7 +638,7 @@ static const NWidgetPart _nested_tooltip
 };
 
 static WindowDesc _tool_tips_desc(
-	WDP_MANUAL, NULL, 0, 0, // Coordinates and sizes are not used,
+	WDP_MANUAL, nullptr, 0, 0, // Coordinates and sizes are not used,
 	WC_TOOLTIPS, WC_NONE,
 	WDF_NO_FOCUS,
 	_nested_tooltips_widgets, lengthof(_nested_tooltips_widgets)
@@ -880,7 +880,7 @@ Rect QueryString::GetBoundingRect(const 
  * @param w Window the edit box is in.
  * @param wid Widget index.
  * @param pt Position to test.
- * @return Pointer to the character at the position or NULL if no character is at the position.
+ * @return Pointer to the character at the position or nullptr if no character is at the position.
  */
 const char *QueryString::GetCharAtPosition(const Window *w, int wid, const Point &pt) const
 {
@@ -898,7 +898,7 @@ const char *QueryString::GetCharAtPositi
 	int top    = wi->pos_y + WD_FRAMERECT_TOP;
 	int bottom = wi->pos_y + wi->current_y - 1 - WD_FRAMERECT_BOTTOM;
 
-	if (!IsInsideMM(pt.y, top, bottom)) return NULL;
+	if (!IsInsideMM(pt.y, top, bottom)) return nullptr;
 
 	/* Clamp caret position to be inside our current width. */
 	const Textbuf *tb = &this->text;
@@ -990,10 +990,10 @@ struct QueryStringWindow : public Window
 
 	void OnOk()
 	{
-		if (this->editbox.orig == NULL || strcmp(this->editbox.text.buf, this->editbox.orig) != 0) {
-			/* If the parent is NULL, the editbox is handled by general function
+		if (this->editbox.orig == nullptr || strcmp(this->editbox.text.buf, this->editbox.orig) != 0) {
+			/* If the parent is nullptr, the editbox is handled by general function
 			 * HandleOnEditText */
-			if (this->parent != NULL) {
+			if (this->parent != nullptr) {
 				this->parent->OnQueryTextFinished(this->editbox.text.buf);
 			} else {
 				HandleOnEditText(this->editbox.text.buf);
@@ -1021,10 +1021,10 @@ struct QueryStringWindow : public Window
 
 	~QueryStringWindow()
 	{
-		if (!this->editbox.handled && this->parent != NULL) {
+		if (!this->editbox.handled && this->parent != nullptr) {
 			Window *parent = this->parent;
-			this->parent = NULL; // so parent doesn't try to delete us again
-			parent->OnQueryTextFinished(NULL);
+			this->parent = nullptr; // so parent doesn't try to delete us again
+			parent->OnQueryTextFinished(nullptr);
 		}
 	}
 };
@@ -1057,7 +1057,7 @@ static WindowDesc _query_string_desc(
  * @param caption StringID of text shown in caption of querywindow
  * @param maxsize maximum size in bytes or characters (including terminating '\0') depending on flags
  * @param parent pointer to a Window that will handle the events (ok/cancel) of this
- *        window. If NULL, results are handled by global function HandleOnEditText
+ *        window. If nullptr, results are handled by global function HandleOnEditText
  * @param afilter filters out unwanted character input
  * @param flags various flags, @see QueryStringFlags
  */
@@ -1094,7 +1094,7 @@ struct QueryWindow : public Window {
 
 	~QueryWindow()
 	{
-		if (this->proc != NULL) this->proc(this->parent, false);
+		if (this->proc != nullptr) this->proc(this->parent, false);
 	}
 
 	void SetStringParameters(int widget) const override
@@ -1138,11 +1138,11 @@ struct QueryWindow : public Window {
 				QueryCallbackProc *proc = this->proc;
 				Window *parent = this->parent;
 				/* Prevent the destructor calling the callback function */
-				this->proc = NULL;
+				this->proc = nullptr;
 				delete this;
-				if (proc != NULL) {
+				if (proc != nullptr) {
 					proc(parent, true);
-					proc = NULL;
+					proc = nullptr;
 				}
 				break;
 			}
@@ -1158,9 +1158,9 @@ struct QueryWindow : public Window {
 		switch (keycode) {
 			case WKC_RETURN:
 			case WKC_NUM_ENTER:
-				if (this->proc != NULL) {
+				if (this->proc != nullptr) {
 					this->proc(this->parent, true);
-					this->proc = NULL;
+					this->proc = nullptr;
 				}
 				FALLTHROUGH;
 
@@ -1187,7 +1187,7 @@ static const NWidgetPart _nested_query_w
 };
 
 static WindowDesc _query_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_CONFIRM_POPUP_QUERY, WC_NONE,
 	WDF_MODAL,
 	_nested_query_widgets, lengthof(_nested_query_widgets)
@@ -1198,13 +1198,13 @@ static WindowDesc _query_desc(
  * The window is aligned to the centre of its parent.
  * @param caption string shown as window caption
  * @param message string that will be shown for the window
- * @param parent pointer to parent window, if this pointer is NULL the parent becomes
+ * @param parent pointer to parent window, if this pointer is nullptr the parent becomes
  * the main window WC_MAIN_WINDOW
  * @param callback callback function pointer to set in the window descriptor
  */
 void ShowQuery(StringID caption, StringID message, Window *parent, QueryCallbackProc *callback)
 {
-	if (parent == NULL) parent = FindWindowById(WC_MAIN_WINDOW, 0);
+	if (parent == nullptr) parent = FindWindowById(WC_MAIN_WINDOW, 0);
 
 	const Window *w;
 	FOR_ALL_WINDOWS_FROM_BACK(w) {
diff --git a/src/mixer.cpp b/src/mixer.cpp
--- a/src/mixer.cpp
+++ b/src/mixer.cpp
@@ -39,7 +39,7 @@ struct MixerChannel {
 static MixerChannel _channels[8];
 static uint32 _play_rate = 11025;
 static uint32 _max_size = UINT_MAX;
-static MxStreamCallback _music_stream = NULL;
+static MxStreamCallback _music_stream = nullptr;
 
 /**
  * The theoretical maximum volume for a single sound sample. Multiple sound
@@ -175,11 +175,11 @@ MixerChannel *MxAllocateChannel()
 	for (mc = _channels; mc != endof(_channels); mc++) {
 		if (!mc->active) {
 			free(mc->memory);
-			mc->memory = NULL;
+			mc->memory = nullptr;
 			return mc;
 		}
 	}
-	return NULL;
+	return nullptr;
 }
 
 void MxSetChannelRawSrc(MixerChannel *mc, int8 *mem, size_t size, uint rate, bool is16bit)
@@ -238,6 +238,6 @@ bool MxInitialize(uint rate)
 {
 	_play_rate = rate;
 	_max_size  = UINT_MAX / _play_rate;
-	_music_stream = NULL; /* rate may have changed, any music source is now invalid */
+	_music_stream = nullptr; /* rate may have changed, any music source is now invalid */
 	return true;
 }
diff --git a/src/music.cpp b/src/music.cpp
--- a/src/music.cpp
+++ b/src/music.cpp
@@ -25,11 +25,11 @@
  * @param filename Name of CAT file to read from
  * @param entrynum Index of entry whose name to read
  * @return Pointer to string, caller is responsible for freeing memory,
- *         NULL if entrynum does not exist.
+ *         nullptr if entrynum does not exist.
  */
 char *GetMusicCatEntryName(const char *filename, size_t entrynum)
 {
-	if (!FioCheckFileExists(filename, BASESET_DIR)) return NULL;
+	if (!FioCheckFileExists(filename, BASESET_DIR)) return nullptr;
 
 	FioOpenFile(CONFIG_SLOT, filename, BASESET_DIR);
 	uint32 ofs = FioReadDword();
@@ -43,7 +43,7 @@ char *GetMusicCatEntryName(const char *f
 		name[namelen] = '\0';
 		return name;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -52,12 +52,12 @@ char *GetMusicCatEntryName(const char *f
  * @param entrynum Index of entry to read
  * @param[out] entrylen Receives length of data read
  * @return Pointer to buffer with data read, caller is responsible for freeind memory,
- *         NULL if entrynum does not exist.
+ *         nullptr if entrynum does not exist.
  */
 byte *GetMusicCatEntryData(const char *filename, size_t entrynum, size_t &entrylen)
 {
 	entrylen = 0;
-	if (!FioCheckFileExists(filename, BASESET_DIR)) return NULL;
+	if (!FioCheckFileExists(filename, BASESET_DIR)) return nullptr;
 
 	FioOpenFile(CONFIG_SLOT, filename, BASESET_DIR);
 	uint32 ofs = FioReadDword();
@@ -72,7 +72,7 @@ byte *GetMusicCatEntryData(const char *f
 		FioReadBlock(data, entrylen);
 		return data;
 	}
-	return NULL;
+	return nullptr;
 }
 
 INSTANTIATE_BASE_MEDIA_METHODS(BaseMedia<MusicSet>, MusicSet)
@@ -99,13 +99,13 @@ template <class Tbase_set>
 template <class Tbase_set>
 /* static */ bool BaseMedia<Tbase_set>::DetermineBestSet()
 {
-	if (BaseMedia<Tbase_set>::used_set != NULL) return true;
+	if (BaseMedia<Tbase_set>::used_set != nullptr) return true;
 
-	const Tbase_set *best = NULL;
-	for (const Tbase_set *c = BaseMedia<Tbase_set>::available_sets; c != NULL; c = c->next) {
+	const Tbase_set *best = nullptr;
+	for (const Tbase_set *c = BaseMedia<Tbase_set>::available_sets; c != nullptr; c = c->next) {
 		if (c->GetNumMissing() != 0) continue;
 
-		if (best == NULL ||
+		if (best == nullptr ||
 				(best->fallback && !c->fallback) ||
 				best->valid_files < c->valid_files ||
 				(best->valid_files == c->valid_files &&
@@ -115,7 +115,7 @@ template <class Tbase_set>
 	}
 
 	BaseMedia<Tbase_set>::used_set = best;
-	return BaseMedia<Tbase_set>::used_set != NULL;
+	return BaseMedia<Tbase_set>::used_set != nullptr;
 }
 
 bool MusicSet::FillSetDetails(IniFile *ini, const char *path, const char *full_filename)
@@ -129,7 +129,7 @@ bool MusicSet::FillSetDetails(IniFile *i
 		uint tracknr = 1;
 		for (uint i = 0; i < lengthof(this->songinfo); i++) {
 			const char *filename = this->files[i].filename;
-			if (names == NULL || StrEmpty(filename) || this->files[i].check_result == MD5File::CR_NO_FILE) {
+			if (names == nullptr || StrEmpty(filename) || this->files[i].check_result == MD5File::CR_NO_FILE) {
 				this->songinfo[i].songname[0] = '\0';
 				continue;
 			}
@@ -137,12 +137,12 @@ bool MusicSet::FillSetDetails(IniFile *i
 			this->songinfo[i].filename = filename; // non-owned pointer
 
 			IniItem *item = catindex->GetItem(_music_file_names[i], false);
-			if (item != NULL && !StrEmpty(item->value)) {
+			if (item != nullptr && !StrEmpty(item->value)) {
 				/* Song has a CAT file index, assume it's MPS MIDI format */
 				this->songinfo[i].filetype = MTT_MPSMIDI;
 				this->songinfo[i].cat_index = atoi(item->value);
 				char *songname = GetMusicCatEntryName(filename, this->songinfo[i].cat_index);
-				if (songname == NULL) {
+				if (songname == nullptr) {
 					DEBUG(grf, 0, "Base music set song missing from CAT file: %s/%d", filename, this->songinfo[i].cat_index);
 					this->songinfo[i].songname[0] = '\0';
 					continue;
@@ -157,17 +157,17 @@ bool MusicSet::FillSetDetails(IniFile *i
 			/* As we possibly add a path to the filename and we compare
 			 * on the filename with the path as in the .obm, we need to
 			 * keep stripping path elements until we find a match. */
-			for (; trimmed_filename != NULL; trimmed_filename = strchr(trimmed_filename, PATHSEPCHAR)) {
+			for (; trimmed_filename != nullptr; trimmed_filename = strchr(trimmed_filename, PATHSEPCHAR)) {
 				/* Remove possible double path separator characters from
 				 * the beginning, so we don't start reading e.g. root. */
 				while (*trimmed_filename == PATHSEPCHAR) trimmed_filename++;
 
 				item = names->GetItem(trimmed_filename, false);
-				if (item != NULL && !StrEmpty(item->value)) break;
+				if (item != nullptr && !StrEmpty(item->value)) break;
 			}
 
 			if (this->songinfo[i].filetype == MTT_STANDARDMIDI) {
-				if (item != NULL && !StrEmpty(item->value)) {
+				if (item != nullptr && !StrEmpty(item->value)) {
 					strecpy(this->songinfo[i].songname, item->value, lastof(this->songinfo[i].songname));
 				} else {
 					DEBUG(grf, 0, "Base music set song name missing: %s", filename);
@@ -184,9 +184,9 @@ bool MusicSet::FillSetDetails(IniFile *i
 			}
 
 			item = timingtrim->GetItem(trimmed_filename, false);
-			if (item != NULL && !StrEmpty(item->value)) {
+			if (item != nullptr && !StrEmpty(item->value)) {
 				const char *endpos = strchr(item->value, ':');
-				if (endpos != NULL) {
+				if (endpos != nullptr) {
 					this->songinfo[i].override_start = atoi(item->value);
 					this->songinfo[i].override_end = atoi(endpos + 1);
 				}
diff --git a/src/music/allegro_m.cpp b/src/music/allegro_m.cpp
--- a/src/music/allegro_m.cpp
+++ b/src/music/allegro_m.cpp
@@ -20,7 +20,7 @@
 #include "../safeguards.h"
 
 static FMusicDriver_Allegro iFMusicDriver_Allegro;
-static MIDI *_midi = NULL;
+static MIDI *_midi = nullptr;
 
 /**
  * There are multiple modules that might be using Allegro and
@@ -30,14 +30,14 @@ extern int _allegro_instance_count;
 
 const char *MusicDriver_Allegro::Start(const char * const *param)
 {
-	if (_allegro_instance_count == 0 && install_allegro(SYSTEM_AUTODETECT, &errno, NULL)) {
+	if (_allegro_instance_count == 0 && install_allegro(SYSTEM_AUTODETECT, &errno, nullptr)) {
 		DEBUG(driver, 0, "allegro: install_allegro failed '%s'", allegro_error);
 		return "Failed to set up Allegro";
 	}
 	_allegro_instance_count++;
 
 	/* Initialise the sound */
-	if (install_sound(DIGI_AUTODETECT, MIDI_AUTODETECT, NULL) != 0) {
+	if (install_sound(DIGI_AUTODETECT, MIDI_AUTODETECT, nullptr) != 0) {
 		DEBUG(driver, 0, "allegro: install_sound failed '%s'", allegro_error);
 		return "Failed to set up Allegro sound";
 	}
@@ -48,13 +48,13 @@ const char *MusicDriver_Allegro::Start(c
 		return "No sound card found";
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 void MusicDriver_Allegro::Stop()
 {
-	if (_midi != NULL) destroy_midi(_midi);
-	_midi = NULL;
+	if (_midi != nullptr) destroy_midi(_midi);
+	_midi = nullptr;
 
 	if (--_allegro_instance_count == 0) allegro_exit();
 }
@@ -63,12 +63,12 @@ void MusicDriver_Allegro::PlaySong(const
 {
 	std::string filename = MidiFile::GetSMFFile(song);
 
-	if (_midi != NULL) destroy_midi(_midi);
+	if (_midi != nullptr) destroy_midi(_midi);
 	if (!filename.empty()) {
 		_midi = load_midi(filename.c_str());
 		play_midi(_midi, false);
 	} else {
-		_midi = NULL;
+		_midi = nullptr;
 	}
 }
 
diff --git a/src/music/bemidi.cpp b/src/music/bemidi.cpp
--- a/src/music/bemidi.cpp
+++ b/src/music/bemidi.cpp
@@ -28,7 +28,7 @@ static FMusicDriver_BeMidi iFMusicDriver
 
 const char *MusicDriver_BeMidi::Start(const char * const *parm)
 {
-	return NULL;
+	return nullptr;
 }
 
 void MusicDriver_BeMidi::Stop()
diff --git a/src/music/cocoa_m.cpp b/src/music/cocoa_m.cpp
--- a/src/music/cocoa_m.cpp
+++ b/src/music/cocoa_m.cpp
@@ -35,8 +35,8 @@
 static FMusicDriver_Cocoa iFMusicDriver_Cocoa;
 
 
-static MusicPlayer    _player = NULL;
-static MusicSequence  _sequence = NULL;
+static MusicPlayer    _player = nullptr;
+static MusicSequence  _sequence = nullptr;
 static MusicTimeStamp _seq_length = 0;
 static bool           _playing = false;
 static byte           _volume = 127;
@@ -45,12 +45,12 @@ static byte           _volume = 127;
 /** Set the volume of the current sequence. */
 static void DoSetVolume()
 {
-	if (_sequence == NULL) return;
+	if (_sequence == nullptr) return;
 
 	AUGraph graph;
 	MusicSequenceGetAUGraph(_sequence, &graph);
 
-	AudioUnit output_unit = NULL;
+	AudioUnit output_unit = nullptr;
 
 	/* Get output audio unit */
 	UInt32 node_count = 0;
@@ -82,7 +82,7 @@ static void DoSetVolume()
 		{
 #if (MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_5)
 			ComponentDescription desc;
-			AUGraphGetNodeInfo(graph, node, &desc, NULL, NULL, &unit);
+			AUGraphGetNodeInfo(graph, node, &desc, nullptr, nullptr, &unit);
 			comp_type = desc.componentType;
 #endif
 		}
@@ -92,7 +92,7 @@ static void DoSetVolume()
 			break;
 		}
 	}
-	if (output_unit == NULL) {
+	if (output_unit == nullptr) {
 		DEBUG(driver, 1, "cocoa_m: Failed to get output node to set volume");
 		return;
 	}
@@ -109,7 +109,7 @@ const char *MusicDriver_Cocoa::Start(con
 {
 	if (NewMusicPlayer(&_player) != noErr) return "failed to create music player";
 
-	return NULL;
+	return nullptr;
 }
 
 
@@ -131,8 +131,8 @@ bool MusicDriver_Cocoa::IsSongPlaying()
  */
 void MusicDriver_Cocoa::Stop()
 {
-	if (_player != NULL) DisposeMusicPlayer(_player);
-	if (_sequence != NULL) DisposeMusicSequence(_sequence);
+	if (_player != nullptr) DisposeMusicPlayer(_player);
+	if (_sequence != nullptr) DisposeMusicSequence(_sequence);
 }
 
 
@@ -148,9 +148,9 @@ void MusicDriver_Cocoa::PlaySong(const M
 	DEBUG(driver, 2, "cocoa_m: trying to play '%s'", filename.c_str());
 
 	this->StopSong();
-	if (_sequence != NULL) {
+	if (_sequence != nullptr) {
 		DisposeMusicSequence(_sequence);
-		_sequence = NULL;
+		_sequence = nullptr;
 	}
 
 	if (filename.empty()) return;
@@ -190,7 +190,7 @@ void MusicDriver_Cocoa::PlaySong(const M
 	CFRelease(url);
 
 	/* Construct audio graph */
-	AUGraph graph = NULL;
+	AUGraph graph = nullptr;
 
 	MusicSequenceGetAUGraph(_sequence, &graph);
 	AUGraphOpen(graph);
@@ -204,7 +204,7 @@ void MusicDriver_Cocoa::PlaySong(const M
 	MusicSequenceGetTrackCount(_sequence, &num_tracks);
 	_seq_length = 0;
 	for (UInt32 i = 0; i < num_tracks; i++) {
-		MusicTrack     track = NULL;
+		MusicTrack     track = nullptr;
 		MusicTimeStamp track_length = 0;
 		UInt32         prop_size = sizeof(MusicTimeStamp);
 		MusicSequenceGetIndTrack(_sequence, i, &track);
@@ -230,7 +230,7 @@ void MusicDriver_Cocoa::PlaySong(const M
 void MusicDriver_Cocoa::StopSong()
 {
 	MusicPlayerStop(_player);
-	MusicPlayerSetSequence(_player, NULL);
+	MusicPlayerSetSequence(_player, nullptr);
 	_playing = false;
 }
 
diff --git a/src/music/dmusic.cpp b/src/music/dmusic.cpp
--- a/src/music/dmusic.cpp
+++ b/src/music/dmusic.cpp
@@ -141,16 +141,16 @@ static struct {
 /** Handle to our worker thread. */
 static std::thread _dmusic_thread;
 /** Event to signal the thread that it should look at a state change. */
-static HANDLE _thread_event = NULL;
+static HANDLE _thread_event = nullptr;
 /** Lock access to playback data that is not thread-safe. */
 static std::mutex _thread_mutex;
 
 /** The direct music object manages buffers and ports. */
-static IDirectMusic *_music = NULL;
+static IDirectMusic *_music = nullptr;
 /** The port object lets us send MIDI data to the synthesizer. */
-static IDirectMusicPort *_port = NULL;
+static IDirectMusicPort *_port = nullptr;
 /** The buffer object collects the data to sent. */
-static IDirectMusicBuffer *_buffer = NULL;
+static IDirectMusicBuffer *_buffer = nullptr;
 /** List of downloaded DLS instruments. */
 static std::vector<IDirectMusicDownload *> _dls_downloads;
 
@@ -438,7 +438,7 @@ bool DLSFile::LoadFile(const TCHAR *file
 	DEBUG(driver, 2, "DMusic: Try to load DLS file %s", FS2OTTD(file));
 
 	FILE *f = _tfopen(file, _T("rb"));
-	if (f == NULL) return false;
+	if (f == nullptr) return false;
 
 	FileCloser f_scope(f);
 
@@ -879,13 +879,13 @@ static const char *LoadDefaultDLSFile(co
 	if ((caps.dwFlags & (DMUS_PC_DLS | DMUS_PC_DLS2)) != 0 && (caps.dwFlags & DMUS_PC_GMINHARDWARE) == 0) {
 		DLSFile dls_file;
 
-		if (user_dls == NULL) {
+		if (user_dls == nullptr) {
 			/* Try loading the default GM DLS file stored in the registry. */
 			HKEY hkDM;
 			if (SUCCEEDED(RegOpenKeyEx(HKEY_LOCAL_MACHINE, _T("Software\\Microsoft\\DirectMusic"), 0, KEY_READ, &hkDM))) {
 				TCHAR dls_path[MAX_PATH];
 				DWORD buf_size = sizeof(dls_path); // Buffer size as to be given in bytes!
-				if (SUCCEEDED(RegQueryValueEx(hkDM, _T("GMFilePath"), NULL, NULL, (LPBYTE)dls_path, &buf_size))) {
+				if (SUCCEEDED(RegQueryValueEx(hkDM, _T("GMFilePath"), nullptr, nullptr, (LPBYTE)dls_path, &buf_size))) {
 					TCHAR expand_path[MAX_PATH * 2];
 					ExpandEnvironmentStrings(dls_path, expand_path, lengthof(expand_path));
 					if (!dls_file.LoadFile(expand_path)) DEBUG(driver, 1, "Failed to load default GM DLS file from registry");
@@ -906,7 +906,7 @@ static const char *LoadDefaultDLSFile(co
 		}
 
 		/* Get download port and allocate download IDs. */
-		IDirectMusicPortDownload *download_port = NULL;
+		IDirectMusicPortDownload *download_port = nullptr;
 		if (FAILED(_port->QueryInterface(IID_IDirectMusicPortDownload, (LPVOID *)&download_port))) return "Can't get download port";
 
 		DWORD dlid_wave = 0, dlid_inst = 0;
@@ -920,7 +920,7 @@ static const char *LoadDefaultDLSFile(co
 
 		/* Download wave data. */
 		for (DWORD i = 0; i < dls_file.waves.size(); i++) {
-			IDirectMusicDownload *dl_wave = NULL;
+			IDirectMusicDownload *dl_wave = nullptr;
 			if (FAILED(download_port->AllocateBuffer((DWORD)(sizeof(WAVE_DOWNLOAD) + dwAppend * dls_file.waves[i].fmt.wf.nBlockAlign + dls_file.waves[i].data.size()), &dl_wave))) {
 				download_port->Release();
 				return "Can't allocate wave download buffer";
@@ -984,7 +984,7 @@ static const char *LoadDefaultDLSFile(co
 			i_size += offsets * sizeof(ULONG);
 
 			/* Allocate download buffer. */
-			IDirectMusicDownload *dl_inst = NULL;
+			IDirectMusicDownload *dl_inst = nullptr;
 			if (FAILED(download_port->AllocateBuffer((DWORD)i_size, &dl_inst))) {
 				download_port->Release();
 				return "Can't allocate instrument download buffer";
@@ -1085,19 +1085,19 @@ static const char *LoadDefaultDLSFile(co
 		download_port->Release();
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 
 const char *MusicDriver_DMusic::Start(const char * const *parm)
 {
 	/* Initialize COM */
-	if (FAILED(CoInitializeEx(NULL, COINITBASE_MULTITHREADED))) return "COM initialization failed";
+	if (FAILED(CoInitializeEx(nullptr, COINITBASE_MULTITHREADED))) return "COM initialization failed";
 
 	/* Create the DirectMusic object */
 	if (FAILED(CoCreateInstance(
 				CLSID_DirectMusic,
-				NULL,
+				nullptr,
 				CLSCTX_INPROC,
 				IID_IDirectMusic,
 				(LPVOID*)&_music
@@ -1106,7 +1106,7 @@ const char *MusicDriver_DMusic::Start(co
 	}
 
 	/* Assign sound output device. */
-	if (FAILED(_music->SetDirectSound(NULL, NULL))) return "Can't set DirectSound interface";
+	if (FAILED(_music->SetDirectSound(nullptr, nullptr))) return "Can't set DirectSound interface";
 
 	/* MIDI events need to be send to the synth in time before their playback time
 	 * has come. By default, we try send any events at least 50 ms before playback. */
@@ -1149,7 +1149,7 @@ const char *MusicDriver_DMusic::Start(co
 	params.dwSize = sizeof(DMUS_PORTPARAMS);
 	params.dwValidParams = DMUS_PORTPARAMS_CHANNELGROUPS;
 	params.dwChannelGroups = 1;
-	if (FAILED(_music->CreatePort(guidPort, &params, &_port, NULL))) return "Failed to create port";
+	if (FAILED(_music->CreatePort(guidPort, &params, &_port, nullptr))) return "Failed to create port";
 	/* Activate port. */
 	if (FAILED(_port->Activate(TRUE))) return "Failed to activate port";
 
@@ -1159,19 +1159,19 @@ const char *MusicDriver_DMusic::Start(co
 	desc.dwSize = sizeof(DMUS_BUFFERDESC);
 	desc.guidBufferFormat = KSDATAFORMAT_SUBTYPE_DIRECTMUSIC;
 	desc.cbBuffer = 1024;
-	if (FAILED(_music->CreateMusicBuffer(&desc, &_buffer, NULL))) return "Failed to create music buffer";
+	if (FAILED(_music->CreateMusicBuffer(&desc, &_buffer, nullptr))) return "Failed to create music buffer";
 
 	/* On soft-synths (e.g. the default DirectMusic one), we might need to load a wavetable set to get music. */
 	const char *dls = LoadDefaultDLSFile(GetDriverParam(parm, "dls"));
-	if (dls != NULL) return dls;
+	if (dls != nullptr) return dls;
 
 	/* Create playback thread and synchronization primitives. */
-	_thread_event = CreateEvent(NULL, FALSE, FALSE, NULL);
-	if (_thread_event == NULL) return "Can't create thread shutdown event";
+	_thread_event = CreateEvent(nullptr, FALSE, FALSE, nullptr);
+	if (_thread_event == nullptr) return "Can't create thread shutdown event";
 
 	if (!StartNewThread(&_dmusic_thread, "ottd:dmusic", &MidiThreadProc)) return "Can't create MIDI output thread";
 
-	return NULL;
+	return nullptr;
 }
 
 
@@ -1191,34 +1191,34 @@ void MusicDriver_DMusic::Stop()
 
 	/* Unloaded any instruments we loaded. */
 	if (_dls_downloads.size() > 0) {
-		IDirectMusicPortDownload *download_port = NULL;
+		IDirectMusicPortDownload *download_port = nullptr;
 		_port->QueryInterface(IID_IDirectMusicPortDownload, (LPVOID *)&download_port);
 
 		/* Instruments refer to waves. As the waves are at the beginning of the download list,
 		 * do the unload from the back so that references are cleared properly. */
-		for (std::vector<IDirectMusicDownload *>::reverse_iterator i = _dls_downloads.rbegin(); download_port != NULL && i != _dls_downloads.rend(); i++) {
+		for (std::vector<IDirectMusicDownload *>::reverse_iterator i = _dls_downloads.rbegin(); download_port != nullptr && i != _dls_downloads.rend(); i++) {
 			download_port->Unload(*i);
 			(*i)->Release();
 		}
 		_dls_downloads.clear();
 
-		if (download_port != NULL) download_port->Release();
+		if (download_port != nullptr) download_port->Release();
 	}
 
-	if (_buffer != NULL) {
+	if (_buffer != nullptr) {
 		_buffer->Release();
-		_buffer = NULL;
+		_buffer = nullptr;
 	}
 
-	if (_port != NULL) {
+	if (_port != nullptr) {
 		_port->Activate(FALSE);
 		_port->Release();
-		_port = NULL;
+		_port = nullptr;
 	}
 
-	if (_music != NULL) {
+	if (_music != nullptr) {
 		_music->Release();
-		_music = NULL;
+		_music = nullptr;
 	}
 
 	CloseHandle(_thread_event);
diff --git a/src/music/extmidi.cpp b/src/music/extmidi.cpp
--- a/src/music/extmidi.cpp
+++ b/src/music/extmidi.cpp
@@ -52,7 +52,7 @@ const char *MusicDriver_ExtMidi::Start(c
 	if (StrEmpty(command)) command = EXTERNAL_PLAYER " " MIDI_ARG;
 #endif
 
-	/* Count number of arguments, but include 3 extra slots: 1st for command, 2nd for song title, and 3rd for terminating NULL. */
+	/* Count number of arguments, but include 3 extra slots: 1st for command, 2nd for song title, and 3rd for terminating nullptr. */
 	uint num_args = 3;
 	for (const char *t = command; *t != '\0'; t++) if (*t == ' ') num_args++;
 
@@ -63,7 +63,7 @@ const char *MusicDriver_ExtMidi::Start(c
 	uint p = 1;
 	while (true) {
 		this->params[p] = strchr(this->params[p - 1], ' ');
-		if (this->params[p] == NULL) break;
+		if (this->params[p] == nullptr) break;
 
 		this->params[p][0] = '\0';
 		this->params[p]++;
@@ -75,7 +75,7 @@ const char *MusicDriver_ExtMidi::Start(c
 
 	this->song[0] = '\0';
 	this->pid = -1;
-	return NULL;
+	return nullptr;
 }
 
 void MusicDriver_ExtMidi::Stop()
@@ -103,7 +103,7 @@ void MusicDriver_ExtMidi::StopSong()
 
 bool MusicDriver_ExtMidi::IsSongPlaying()
 {
-	if (this->pid != -1 && waitpid(this->pid, NULL, WNOHANG) == this->pid) {
+	if (this->pid != -1 && waitpid(this->pid, nullptr, WNOHANG) == this->pid) {
 		this->pid = -1;
 	}
 	if (this->pid == -1 && this->song[0] != '\0') this->DoPlay();
@@ -146,7 +146,7 @@ void MusicDriver_ExtMidi::DoStop()
 	 * 5 seconds = 5000 milliseconds, 10 ms per cycle => 500 cycles. */
 	for (int i = 0; i < 500; i++) {
 		kill(this->pid, SIGTERM);
-		if (waitpid(this->pid, NULL, WNOHANG) == this->pid) {
+		if (waitpid(this->pid, nullptr, WNOHANG) == this->pid) {
 			/* It has shut down, so we are done */
 			this->pid = -1;
 			return;
@@ -159,6 +159,6 @@ void MusicDriver_ExtMidi::DoStop()
 	/* Gracefully stopping failed. Do it the hard way
 	 * and wait till the process finally died. */
 	kill(this->pid, SIGKILL);
-	waitpid(this->pid, NULL, 0);
+	waitpid(this->pid, nullptr, 0);
 	this->pid = -1;
 }
diff --git a/src/music/fluidsynth.cpp b/src/music/fluidsynth.cpp
--- a/src/music/fluidsynth.cpp
+++ b/src/music/fluidsynth.cpp
@@ -39,7 +39,7 @@ static const char *default_sf[] = {
 	"/usr/share/sounds/sf2/TimGM6mb.sf2",
 	"/usr/share/sounds/sf2/FluidR3_GS.sf2",
 
-	NULL
+	nullptr
 };
 
 static void RenderMusicStream(int16 *buffer, size_t samples)
@@ -81,18 +81,18 @@ const char *MusicDriver_FluidSynth::Star
 		if (sfont_id == FLUID_FAILED) return "Could not open sound font";
 	}
 
-	_midi.player = NULL;
+	_midi.player = nullptr;
 
 	uint32 samplerate = MxSetMusicSource(RenderMusicStream);
 	fluid_synth_set_sample_rate(_midi.synth, samplerate);
 	DEBUG(driver, 1, "Fluidsynth: samplerate %.0f", (float)samplerate);
 
-	return NULL;
+	return nullptr;
 }
 
 void MusicDriver_FluidSynth::Stop()
 {
-	MxSetMusicSource(NULL);
+	MxSetMusicSource(nullptr);
 	this->StopSong();
 	delete_fluid_synth(_midi.synth);
 	delete_fluid_settings(_midi.settings);
@@ -117,13 +117,13 @@ void MusicDriver_FluidSynth::PlaySong(co
 	if (fluid_player_add(_midi.player, filename.c_str()) != FLUID_OK) {
 		DEBUG(driver, 0, "Could not open music file");
 		delete_fluid_player(_midi.player);
-		_midi.player = NULL;
+		_midi.player = nullptr;
 		return;
 	}
 	if (fluid_player_play(_midi.player) != FLUID_OK) {
 		DEBUG(driver, 0, "Could not start midi player");
 		delete_fluid_player(_midi.player);
-		_midi.player = NULL;
+		_midi.player = nullptr;
 		return;
 	}
 }
@@ -138,7 +138,7 @@ void MusicDriver_FluidSynth::StopSong()
 	}
 	delete_fluid_player(_midi.player);
 	fluid_synth_system_reset(_midi.synth);
-	_midi.player = NULL;
+	_midi.player = nullptr;
 }
 
 bool MusicDriver_FluidSynth::IsSongPlaying()
diff --git a/src/music/midifile.cpp b/src/music/midifile.cpp
--- a/src/music/midifile.cpp
+++ b/src/music/midifile.cpp
@@ -24,7 +24,7 @@
 /* SMF reader based on description at: http://www.somascape.org/midi/tech/mfile.html */
 
 
-static MidiFile *_midifile_instance = NULL;
+static MidiFile *_midifile_instance = nullptr;
 
 /**
  * Owning byte buffer readable as a stream.
@@ -426,7 +426,7 @@ bool MidiFile::LoadFile(const char *file
 
 	bool success = false;
 	FILE *file = FioFOpenFile(filename, "rb", Subdirectory::BASESET_DIR);
-	if (file == NULL) return false;
+	if (file == nullptr) return false;
 
 	SMFHeader header;
 	if (!ReadSMFHeader(file, header)) goto cleanup;
@@ -815,7 +815,7 @@ bool MidiFile::LoadSong(const MusicSongI
 		{
 			size_t songdatalen = 0;
 			byte *songdata = GetMusicCatEntryData(song.filename, song.cat_index, songdatalen);
-			if (songdata != NULL) {
+			if (songdata != nullptr) {
 				bool result = this->LoadMpsData(songdata, songdatalen);
 				free(songdata);
 				return result;
@@ -1024,7 +1024,7 @@ std::string MidiFile::GetSMFFile(const M
 	char basename[MAX_PATH];
 	{
 		const char *fnstart = strrchr(song.filename, PATHSEPCHAR);
-		if (fnstart == NULL) {
+		if (fnstart == nullptr) {
 			fnstart = song.filename;
 		} else {
 			fnstart++;
@@ -1054,7 +1054,7 @@ std::string MidiFile::GetSMFFile(const M
 	byte *data;
 	size_t datalen;
 	data = GetMusicCatEntryData(song.filename, song.cat_index, datalen);
-	if (data == NULL) return std::string();
+	if (data == nullptr) return std::string();
 
 	MidiFile midifile;
 	if (!midifile.LoadMpsData(data, datalen)) {
@@ -1082,7 +1082,7 @@ static bool CmdDumpSMF(byte argc, char *
 		return false;
 	}
 
-	if (_midifile_instance == NULL) {
+	if (_midifile_instance == nullptr) {
 		IConsolePrint(CC_ERROR, "There is no MIDI file loaded currently, make sure music is playing, and you're using a driver that works with raw MIDI.");
 		return false;
 	}
@@ -1120,7 +1120,7 @@ MidiFile::MidiFile()
 MidiFile::~MidiFile()
 {
 	if (_midifile_instance == this) {
-		_midifile_instance = NULL;
+		_midifile_instance = nullptr;
 	}
 }
 
diff --git a/src/music/null_m.h b/src/music/null_m.h
--- a/src/music/null_m.h
+++ b/src/music/null_m.h
@@ -17,7 +17,7 @@
 /** The music player that does nothing. */
 class MusicDriver_Null : public MusicDriver {
 public:
-	const char *Start(const char * const *param) override { return NULL; }
+	const char *Start(const char * const *param) override { return nullptr; }
 
 	void Stop() override { }
 
diff --git a/src/music/os2_m.cpp b/src/music/os2_m.cpp
--- a/src/music/os2_m.cpp
+++ b/src/music/os2_m.cpp
@@ -45,7 +45,7 @@ static long CDECL MidiSendCommand(const 
 	va_start(va, cmd);
 	vseprintf(buf, lastof(buf), cmd, va);
 	va_end(va);
-	return mciSendString(buf, NULL, 0, NULL, 0);
+	return mciSendString(buf, nullptr, 0, nullptr, 0);
 }
 
 /** OS/2's music player's factory. */
@@ -78,7 +78,7 @@ void MusicDriver_OS2::SetVolume(byte vol
 bool MusicDriver_OS2::IsSongPlaying()
 {
 	char buf[16];
-	mciSendString("status song mode", buf, sizeof(buf), NULL, 0);
+	mciSendString("status song mode", buf, sizeof(buf), nullptr, 0);
 	return strcmp(buf, "playing") == 0 || strcmp(buf, "seeking") == 0;
 }
 
diff --git a/src/music/qtmidi.cpp b/src/music/qtmidi.cpp
--- a/src/music/qtmidi.cpp
+++ b/src/music/qtmidi.cpp
@@ -60,7 +60,7 @@ static void SetMIDITypeIfNeeded(const FS
 
 	assert(ref);
 
-	if (noErr != FSGetCatalogInfo(ref, kFSCatInfoNodeFlags | kFSCatInfoFinderInfo, &catalogInfo, NULL, NULL, NULL)) return;
+	if (noErr != FSGetCatalogInfo(ref, kFSCatInfoNodeFlags | kFSCatInfoFinderInfo, &catalogInfo, nullptr, nullptr, nullptr)) return;
 	if (!(catalogInfo.nodeFlags & kFSNodeIsDirectoryMask)) {
 		FileInfo * const info = (FileInfo *) catalogInfo.finderInfo;
 		if (info->fileType != MIDI_TYPE && !(info->finderFlags & kIsAlias)) {
@@ -94,8 +94,8 @@ static bool LoadMovieForMIDIFile(const c
 	short refnum = 0;
 	short resid  = 0;
 
-	assert(path != NULL);
-	assert(moov != NULL);
+	assert(path != nullptr);
+	assert(moov != nullptr);
 
 	DEBUG(driver, 2, "qtmidi: start loading '%s'...", path);
 
@@ -116,15 +116,15 @@ static bool LoadMovieForMIDIFile(const c
 		return false;
 	}
 
-	if (noErr != FSPathMakeRef((const UInt8 *) path, &fsref, NULL)) return false;
+	if (noErr != FSPathMakeRef((const UInt8 *) path, &fsref, nullptr)) return false;
 	SetMIDITypeIfNeeded(&fsref);
 
-	if (noErr != FSGetCatalogInfo(&fsref, kFSCatInfoNone, NULL, NULL, &fsspec, NULL)) return false;
+	if (noErr != FSGetCatalogInfo(&fsref, kFSCatInfoNone, nullptr, nullptr, &fsspec, nullptr)) return false;
 	if (OpenMovieFile(&fsspec, &refnum, fsRdPerm) != noErr) return false;
 	DEBUG(driver, 3, "qtmidi: '%s' successfully opened", path);
 
-	if (noErr != NewMovieFromFile(moov, refnum, &resid, NULL,
-				newMovieActive | newMovieDontAskUnresolvedDataRefs, NULL)) {
+	if (noErr != NewMovieFromFile(moov, refnum, &resid, nullptr,
+				newMovieActive | newMovieDontAskUnresolvedDataRefs, nullptr)) {
 		CloseMovieFile(refnum);
 		return false;
 	}
@@ -191,7 +191,7 @@ static int   _quicktime_state  = QT_STAT
 const char *MusicDriver_QtMidi::Start(const char * const *parm)
 {
 	InitQuickTimeIfNeeded();
-	return (_quicktime_started) ? NULL : "can't initialize QuickTime";
+	return (_quicktime_started) ? nullptr : "can't initialize QuickTime";
 }
 
 
@@ -215,7 +215,7 @@ bool MusicDriver_QtMidi::IsSongPlaying()
 			MoviesTask(_quicktime_movie, 0);
 			/* Check wether movie ended. */
 			if (IsMovieDone(_quicktime_movie) ||
-					(GetMovieTime(_quicktime_movie, NULL) >=
+					(GetMovieTime(_quicktime_movie, nullptr) >=
 					 GetMovieDuration(_quicktime_movie))) {
 				_quicktime_state = QT_STATE_STOP;
 			}
diff --git a/src/music/win32_m.cpp b/src/music/win32_m.cpp
--- a/src/music/win32_m.cpp
+++ b/src/music/win32_m.cpp
@@ -396,7 +396,7 @@ const char *MusicDriver_Win32::Start(con
 		if (timeBeginPeriod(_midi.time_period) == MMSYSERR_NOERROR) {
 			/* success */
 			DEBUG(driver, 2, "Win32-MIDI: Start: timer resolution is %d", (int)_midi.time_period);
-			return NULL;
+			return nullptr;
 		}
 	}
 	midiOutClose(_midi.midi_out);
diff --git a/src/network/core/address.cpp b/src/network/core/address.cpp
--- a/src/network/core/address.cpp
+++ b/src/network/core/address.cpp
@@ -25,7 +25,7 @@ const char *NetworkAddress::GetHostname(
 {
 	if (StrEmpty(this->hostname) && this->address.ss_family != AF_UNSPEC) {
 		assert(this->address_length != 0);
-		getnameinfo((struct sockaddr *)&this->address, this->address_length, this->hostname, sizeof(this->hostname), NULL, 0, NI_NUMERICHOST);
+		getnameinfo((struct sockaddr *)&this->address, this->address_length, this->hostname, sizeof(this->hostname), nullptr, 0, NI_NUMERICHOST);
 	}
 	return this->hostname;
 }
@@ -131,7 +131,7 @@ const sockaddr_storage *NetworkAddress::
 		 * bothered to implement the specifications and allow '0' as value
 		 * that means "don't care whether it is SOCK_STREAM or SOCK_DGRAM".
 		 */
-		this->Resolve(this->address.ss_family, SOCK_STREAM, AI_ADDRCONFIG, NULL, ResolveLoopProc);
+		this->Resolve(this->address.ss_family, SOCK_STREAM, AI_ADDRCONFIG, nullptr, ResolveLoopProc);
 		this->resolved = true;
 	}
 	return &this->address;
@@ -145,7 +145,7 @@ const sockaddr_storage *NetworkAddress::
 bool NetworkAddress::IsFamily(int family)
 {
 	if (!this->IsResolved()) {
-		this->Resolve(family, SOCK_STREAM, AI_ADDRCONFIG, NULL, ResolveLoopProc);
+		this->Resolve(family, SOCK_STREAM, AI_ADDRCONFIG, nullptr, ResolveLoopProc);
 	}
 	return this->address.ss_family == family;
 }
@@ -167,7 +167,7 @@ bool NetworkAddress::IsInNetmask(const c
 
 	/* Check for CIDR separator */
 	const char *chr_cidr = strchr(netmask, '/');
-	if (chr_cidr != NULL) {
+	if (chr_cidr != nullptr) {
 		int tmp_cidr = atoi(chr_cidr + 1);
 
 		/* Invalid CIDR, treat as single host */
@@ -232,7 +232,7 @@ SOCKET NetworkAddress::Resolve(int famil
 	seprintf(port_name, lastof(port_name), "%u", this->GetPort());
 
 	bool reset_hostname = false;
-	/* Setting both hostname to NULL and port to 0 is not allowed.
+	/* Setting both hostname to nullptr and port to 0 is not allowed.
 	 * As port 0 means bind to any port, the other must mean that
 	 * we want to bind to 'all' IPs. */
 	if (StrEmpty(this->hostname) && this->address_length == 0 && this->GetPort() == 0) {
@@ -242,7 +242,7 @@ SOCKET NetworkAddress::Resolve(int famil
 		strecpy(this->hostname, fam == AF_INET ? "0.0.0.0" : "::", lastof(this->hostname));
 	}
 
-	int e = getaddrinfo(StrEmpty(this->hostname) ? NULL : this->hostname, port_name, &hints, &ai);
+	int e = getaddrinfo(StrEmpty(this->hostname) ? nullptr : this->hostname, port_name, &hints, &ai);
 
 	if (reset_hostname) strecpy(this->hostname, "", lastof(this->hostname));
 
@@ -255,18 +255,18 @@ SOCKET NetworkAddress::Resolve(int famil
 	}
 
 	SOCKET sock = INVALID_SOCKET;
-	for (struct addrinfo *runp = ai; runp != NULL; runp = runp->ai_next) {
+	for (struct addrinfo *runp = ai; runp != nullptr; runp = runp->ai_next) {
 		/* When we are binding to multiple sockets, make sure we do not
 		 * connect to one with exactly the same address twice. That's
 		 * of course totally unneeded ;) */
-		if (sockets != NULL) {
+		if (sockets != nullptr) {
 			NetworkAddress address(runp->ai_addr, (int)runp->ai_addrlen);
 			if (sockets->Contains(address)) continue;
 		}
 		sock = func(runp);
 		if (sock == INVALID_SOCKET) continue;
 
-		if (sockets == NULL) {
+		if (sockets == nullptr) {
 			this->address_length = (int)runp->ai_addrlen;
 			assert(sizeof(this->address) >= runp->ai_addrlen);
 			memcpy(&this->address, runp->ai_addr, runp->ai_addrlen);
@@ -323,7 +323,7 @@ SOCKET NetworkAddress::Connect()
 {
 	DEBUG(net, 1, "Connecting to %s", this->GetAddressAsString());
 
-	return this->Resolve(AF_UNSPEC, SOCK_STREAM, AI_ADDRCONFIG, NULL, ConnectLoopProc);
+	return this->Resolve(AF_UNSPEC, SOCK_STREAM, AI_ADDRCONFIG, nullptr, ConnectLoopProc);
 }
 
 /**
@@ -386,9 +386,9 @@ static SOCKET ListenLoopProc(addrinfo *r
  */
 void NetworkAddress::Listen(int socktype, SocketList *sockets)
 {
-	assert(sockets != NULL);
+	assert(sockets != nullptr);
 
-	/* Setting both hostname to NULL and port to 0 is not allowed.
+	/* Setting both hostname to nullptr and port to 0 is not allowed.
 	 * As port 0 means bind to any port, the other must mean that
 	 * we want to bind to 'all' IPs. */
 	if (this->address_length == 0 && this->address.ss_family == AF_UNSPEC &&
diff --git a/src/network/core/address.h b/src/network/core/address.h
--- a/src/network/core/address.h
+++ b/src/network/core/address.h
@@ -84,7 +84,7 @@ public:
 		if (*hostname == '[') hostname++;
 		strecpy(this->hostname, StrEmpty(hostname) ? "" : hostname, lastof(this->hostname));
 		char *tmp = strrchr(this->hostname, ']');
-		if (tmp != NULL) *tmp = '\0';
+		if (tmp != nullptr) *tmp = '\0';
 
 		memset(&this->address, 0, sizeof(this->address));
 		this->address.ss_family = family;
diff --git a/src/network/core/host.cpp b/src/network/core/host.cpp
--- a/src/network/core/host.cpp
+++ b/src/network/core/host.cpp
@@ -45,7 +45,7 @@ static void NetworkFindBroadcastIPsInter
 		return;
 	}
 
-	char *output_pointer = NULL;
+	char *output_pointer = nullptr;
 	int output_length = _netstat(sock, &output_pointer, 1);
 	if (output_length < 0) {
 		DEBUG(net, 0, "[core] error running _netstat");
@@ -94,9 +94,9 @@ static void NetworkFindBroadcastIPsInter
 
 	if (getifaddrs(&ifap) != 0) return;
 
-	for (ifa = ifap; ifa != NULL; ifa = ifa->ifa_next) {
+	for (ifa = ifap; ifa != nullptr; ifa = ifa->ifa_next) {
 		if (!(ifa->ifa_flags & IFF_BROADCAST)) continue;
-		if (ifa->ifa_broadaddr == NULL) continue;
+		if (ifa->ifa_broadaddr == nullptr) continue;
 		if (ifa->ifa_broadaddr->sa_family != AF_INET) continue;
 
 		NetworkAddress addr(ifa->ifa_broadaddr, sizeof(sockaddr));
@@ -116,7 +116,7 @@ static void NetworkFindBroadcastIPsInter
 	INTERFACE_INFO *ifo = CallocT<INTERFACE_INFO>(num);
 
 	for (;;) {
-		if (WSAIoctl(sock, SIO_GET_INTERFACE_LIST, NULL, 0, ifo, num * sizeof(*ifo), &len, NULL, NULL) == 0) break;
+		if (WSAIoctl(sock, SIO_GET_INTERFACE_LIST, nullptr, 0, ifo, num * sizeof(*ifo), &len, nullptr, nullptr) == 0) break;
 		free(ifo);
 		if (WSAGetLastError() != WSAEFAULT) {
 			closesocket(sock);
diff --git a/src/network/core/packet.cpp b/src/network/core/packet.cpp
--- a/src/network/core/packet.cpp
+++ b/src/network/core/packet.cpp
@@ -24,10 +24,10 @@
  */
 Packet::Packet(NetworkSocketHandler *cs)
 {
-	assert(cs != NULL);
+	assert(cs != nullptr);
 
 	this->cs     = cs;
-	this->next   = NULL;
+	this->next   = nullptr;
 	this->pos    = 0; // We start reading from here
 	this->size   = 0;
 	this->buffer = MallocT<byte>(SEND_MTU);
@@ -39,8 +39,8 @@ Packet::Packet(NetworkSocketHandler *cs)
  */
 Packet::Packet(PacketType type)
 {
-	this->cs                   = NULL;
-	this->next                 = NULL;
+	this->cs                   = nullptr;
+	this->next                 = nullptr;
 
 	/* Skip the size so we can write that in before sending the packet */
 	this->pos                  = 0;
@@ -62,7 +62,7 @@ Packet::~Packet()
  */
 void Packet::PrepareToSend()
 {
-	assert(this->cs == NULL && this->next == NULL);
+	assert(this->cs == nullptr && this->next == nullptr);
 
 	this->buffer[0] = GB(this->size, 0, 8);
 	this->buffer[1] = GB(this->size, 8, 8);
@@ -149,7 +149,7 @@ void Packet::Send_uint64(uint64 data)
  */
 void Packet::Send_string(const char *data)
 {
-	assert(data != NULL);
+	assert(data != nullptr);
 	/* The <= *is* valid due to the fact that we are comparing sizes and not the index. */
 	assert(this->size + strlen(data) + 1 <= SEND_MTU);
 	while ((this->buffer[this->size++] = *data++) != '\0') {}
@@ -187,7 +187,7 @@ bool Packet::CanReadFromPacket(uint byte
  */
 void Packet::ReadRawPacketSize()
 {
-	assert(this->cs != NULL && this->next == NULL);
+	assert(this->cs != nullptr && this->next == nullptr);
 	this->size  = (PacketSize)this->buffer[0];
 	this->size += (PacketSize)this->buffer[1] << 8;
 }
diff --git a/src/network/core/tcp.cpp b/src/network/core/tcp.cpp
--- a/src/network/core/tcp.cpp
+++ b/src/network/core/tcp.cpp
@@ -24,7 +24,7 @@
  */
 NetworkTCPSocketHandler::NetworkTCPSocketHandler(SOCKET s) :
 		NetworkSocketHandler(),
-		packet_queue(NULL), packet_recv(NULL),
+		packet_queue(nullptr), packet_recv(nullptr),
 		sock(s), writable(false)
 {
 }
@@ -43,13 +43,13 @@ NetworkRecvStatus NetworkTCPSocketHandle
 	NetworkSocketHandler::CloseConnection(error);
 
 	/* Free all pending and partially received packets */
-	while (this->packet_queue != NULL) {
+	while (this->packet_queue != nullptr) {
 		Packet *p = this->packet_queue->next;
 		delete this->packet_queue;
 		this->packet_queue = p;
 	}
 	delete this->packet_recv;
-	this->packet_recv = NULL;
+	this->packet_recv = nullptr;
 
 	return NETWORK_RECV_STATUS_OKAY;
 }
@@ -63,7 +63,7 @@ NetworkRecvStatus NetworkTCPSocketHandle
 void NetworkTCPSocketHandler::SendPacket(Packet *packet)
 {
 	Packet *p;
-	assert(packet != NULL);
+	assert(packet != nullptr);
 
 	packet->PrepareToSend();
 
@@ -74,12 +74,12 @@ void NetworkTCPSocketHandler::SendPacket
 
 	/* Locate last packet buffered for the client */
 	p = this->packet_queue;
-	if (p == NULL) {
+	if (p == nullptr) {
 		/* No packets yet */
 		this->packet_queue = packet;
 	} else {
 		/* Skip to the last packet */
-		while (p->next != NULL) p = p->next;
+		while (p->next != nullptr) p = p->next;
 		p->next = packet;
 	}
 }
@@ -104,7 +104,7 @@ SendPacketsState NetworkTCPSocketHandler
 	if (!this->IsConnected()) return SPS_CLOSED;
 
 	p = this->packet_queue;
-	while (p != NULL) {
+	while (p != nullptr) {
 		res = send(this->sock, (const char*)p->buffer + p->pos, p->size - p->pos, 0);
 		if (res == -1) {
 			int err = GET_LAST_ERROR();
@@ -142,15 +142,15 @@ SendPacketsState NetworkTCPSocketHandler
 
 /**
  * Receives a packet for the given client
- * @return The received packet (or NULL when it didn't receive one)
+ * @return The received packet (or nullptr when it didn't receive one)
  */
 Packet *NetworkTCPSocketHandler::ReceivePacket()
 {
 	ssize_t res;
 
-	if (!this->IsConnected()) return NULL;
+	if (!this->IsConnected()) return nullptr;
 
-	if (this->packet_recv == NULL) {
+	if (this->packet_recv == nullptr) {
 		this->packet_recv = new Packet(this);
 	}
 
@@ -167,15 +167,15 @@ Packet *NetworkTCPSocketHandler::Receive
 					/* Something went wrong... (104 is connection reset by peer) */
 					if (err != 104) DEBUG(net, 0, "recv failed with error %d", err);
 					this->CloseConnection();
-					return NULL;
+					return nullptr;
 				}
 				/* Connection would block, so stop for now */
-				return NULL;
+				return nullptr;
 			}
 			if (res == 0) {
 				/* Client/server has left */
 				this->CloseConnection();
-				return NULL;
+				return nullptr;
 			}
 			p->pos += res;
 		}
@@ -185,7 +185,7 @@ Packet *NetworkTCPSocketHandler::Receive
 
 		if (p->size > SEND_MTU) {
 			this->CloseConnection();
-			return NULL;
+			return nullptr;
 		}
 	}
 
@@ -198,22 +198,22 @@ Packet *NetworkTCPSocketHandler::Receive
 				/* Something went wrong... (104 is connection reset by peer) */
 				if (err != 104) DEBUG(net, 0, "recv failed with error %d", err);
 				this->CloseConnection();
-				return NULL;
+				return nullptr;
 			}
 			/* Connection would block */
-			return NULL;
+			return nullptr;
 		}
 		if (res == 0) {
 			/* Client/server has left */
 			this->CloseConnection();
-			return NULL;
+			return nullptr;
 		}
 
 		p->pos += res;
 	}
 
 	/* Prepare for receiving a new packet */
-	this->packet_recv = NULL;
+	this->packet_recv = nullptr;
 
 	p->PrepareToRead();
 	return p;
@@ -236,7 +236,7 @@ bool NetworkTCPSocketHandler::CanSendRec
 	FD_SET(this->sock, &write_fd);
 
 	tv.tv_sec = tv.tv_usec = 0; // don't block at all.
-	if (select(FD_SETSIZE, &read_fd, &write_fd, NULL, &tv) < 0) return false;
+	if (select(FD_SETSIZE, &read_fd, &write_fd, nullptr, &tv) < 0) return false;
 
 	this->writable = !!FD_ISSET(this->sock, &write_fd);
 	return FD_ISSET(this->sock, &read_fd) != 0;
diff --git a/src/network/core/tcp.h b/src/network/core/tcp.h
--- a/src/network/core/tcp.h
+++ b/src/network/core/tcp.h
@@ -52,7 +52,7 @@ public:
 	 * Whether there is something pending in the send queue.
 	 * @return true when something is pending in the send queue.
 	 */
-	bool HasSendQueue() { return this->packet_queue != NULL; }
+	bool HasSendQueue() { return this->packet_queue != nullptr; }
 
 	NetworkTCPSocketHandler(SOCKET s = INVALID_SOCKET);
 	~NetworkTCPSocketHandler();
diff --git a/src/network/core/tcp_admin.cpp b/src/network/core/tcp_admin.cpp
--- a/src/network/core/tcp_admin.cpp
+++ b/src/network/core/tcp_admin.cpp
@@ -115,7 +115,7 @@ NetworkRecvStatus NetworkAdminSocketHand
 NetworkRecvStatus NetworkAdminSocketHandler::ReceivePackets()
 {
 	Packet *p;
-	while ((p = this->ReceivePacket()) != NULL) {
+	while ((p = this->ReceivePacket()) != nullptr) {
 		NetworkRecvStatus res = this->HandlePacket(p);
 		if (res != NETWORK_RECV_STATUS_OKAY) return res;
 	}
diff --git a/src/network/core/tcp_connect.cpp b/src/network/core/tcp_connect.cpp
--- a/src/network/core/tcp_connect.cpp
+++ b/src/network/core/tcp_connect.cpp
@@ -33,7 +33,7 @@ TCPConnecter::TCPConnecter(const Network
 	address(address)
 {
 	_tcp_connecters.push_back(this);
-	if (!StartNewThread(NULL, "ottd:tcp", &TCPConnecter::ThreadEntry, this)) {
+	if (!StartNewThread(nullptr, "ottd:tcp", &TCPConnecter::ThreadEntry, this)) {
 		this->Connect();
 	}
 }
diff --git a/src/network/core/tcp_content.cpp b/src/network/core/tcp_content.cpp
--- a/src/network/core/tcp_content.cpp
+++ b/src/network/core/tcp_content.cpp
@@ -47,8 +47,8 @@ void ContentInfo::TransferFrom(ContentIn
 		free(this->dependencies);
 		free(this->tags);
 		memcpy(this, other, sizeof(ContentInfo));
-		other->dependencies = NULL;
-		other->tags = NULL;
+		other->dependencies = nullptr;
+		other->tags = nullptr;
 	}
 }
 
@@ -98,11 +98,11 @@ bool ContentInfo::IsValid() const
 /**
  * Search a textfile file next to this file in the content list.
  * @param type The type of the textfile to search for.
- * @return The filename for the textfile, \c NULL otherwise.
+ * @return The filename for the textfile, \c nullptr otherwise.
  */
 const char *ContentInfo::GetTextfile(TextfileType type) const
 {
-	if (this->state == INVALID) return NULL;
+	if (this->state == INVALID) return nullptr;
 	const char *tmp;
 	switch (this->type) {
 		default: NOT_REACHED();
@@ -120,7 +120,7 @@ const char *ContentInfo::GetTextfile(Tex
 			break;
 		case CONTENT_TYPE_NEWGRF: {
 			const GRFConfig *gc = FindGRFConfig(BSWAP32(this->unique_id), FGCM_EXACT, this->md5sum);
-			tmp = gc != NULL ? gc->filename : NULL;
+			tmp = gc != nullptr ? gc->filename : nullptr;
 			break;
 		}
 		case CONTENT_TYPE_BASE_GRAPHICS:
@@ -138,7 +138,7 @@ const char *ContentInfo::GetTextfile(Tex
 			tmp = FindScenario(this, true);
 			break;
 	}
-	if (tmp == NULL) return NULL;
+	if (tmp == nullptr) return nullptr;
 	return ::GetTextfile(type, GetContentInfoSubDir(this->type), tmp);
 }
 #endif /* OPENTTD_MSU */
@@ -209,7 +209,7 @@ bool NetworkContentSocketHandler::Receiv
 	Packet *p;
 	static const int MAX_PACKETS_TO_RECEIVE = 42;
 	int i = MAX_PACKETS_TO_RECEIVE;
-	while (--i != 0 && (p = this->ReceivePacket()) != NULL) {
+	while (--i != 0 && (p = this->ReceivePacket()) != nullptr) {
 		bool cont = this->HandlePacket(p);
 		delete p;
 		if (!cont) return true;
diff --git a/src/network/core/tcp_game.cpp b/src/network/core/tcp_game.cpp
--- a/src/network/core/tcp_game.cpp
+++ b/src/network/core/tcp_game.cpp
@@ -26,7 +26,7 @@
  * Create a new socket for the game connection.
  * @param s The socket to connect with.
  */
-NetworkGameSocketHandler::NetworkGameSocketHandler(SOCKET s) : info(NULL), client_id(INVALID_CLIENT_ID),
+NetworkGameSocketHandler::NetworkGameSocketHandler(SOCKET s) : info(nullptr), client_id(INVALID_CLIENT_ID),
 		last_frame(_frame_counter), last_frame_server(_frame_counter), last_packet(_realtime_tick)
 {
 	this->sock = s;
@@ -134,7 +134,7 @@ NetworkRecvStatus NetworkGameSocketHandl
 NetworkRecvStatus NetworkGameSocketHandler::ReceivePackets()
 {
 	Packet *p;
-	while ((p = this->ReceivePacket()) != NULL) {
+	while ((p = this->ReceivePacket()) != nullptr) {
 		NetworkRecvStatus res = HandlePacket(p);
 		delete p;
 		if (res != NETWORK_RECV_STATUS_OKAY) return res;
diff --git a/src/network/core/tcp_game.h b/src/network/core/tcp_game.h
--- a/src/network/core/tcp_game.h
+++ b/src/network/core/tcp_game.h
@@ -130,12 +130,12 @@ struct CommandPacket;
 /** A queue of CommandPackets. */
 class CommandQueue {
 	CommandPacket *first; ///< The first packet in the queue.
-	CommandPacket *last;  ///< The last packet in the queue; only valid when first != NULL.
+	CommandPacket *last;  ///< The last packet in the queue; only valid when first != nullptr.
 	uint count;           ///< The number of items in the queue.
 
 public:
 	/** Initialise the command queue. */
-	CommandQueue() : first(NULL), last(NULL), count(0) {}
+	CommandQueue() : first(nullptr), last(nullptr), count(0) {}
 	/** Clear the command queue. */
 	~CommandQueue() { this->Free(); }
 	void Append(CommandPacket *p);
@@ -537,7 +537,7 @@ public:
 	 */
 	inline void SetInfo(NetworkClientInfo *info)
 	{
-		assert(info != NULL && this->info == NULL);
+		assert(info != nullptr && this->info == nullptr);
 		this->info = info;
 	}
 
diff --git a/src/network/core/tcp_http.cpp b/src/network/core/tcp_http.cpp
--- a/src/network/core/tcp_http.cpp
+++ b/src/network/core/tcp_http.cpp
@@ -43,11 +43,11 @@ NetworkHTTPSocketHandler::NetworkHTTPSoc
 	redirect_depth(depth),
 	sock(s)
 {
-	size_t bufferSize = strlen(url) + strlen(host) + strlen(GetNetworkRevisionString()) + (data == NULL ? 0 : strlen(data)) + 128;
+	size_t bufferSize = strlen(url) + strlen(host) + strlen(GetNetworkRevisionString()) + (data == nullptr ? 0 : strlen(data)) + 128;
 	char *buffer = AllocaM(char, bufferSize);
 
 	DEBUG(net, 7, "[tcp/http] requesting %s%s", host, url);
-	if (data != NULL) {
+	if (data != nullptr) {
 		seprintf(buffer, buffer + bufferSize - 1, "POST %s HTTP/1.0\r\nHost: %s\r\nUser-Agent: OpenTTD/%s\r\nContent-Type: text/plain\r\nContent-Length: %d\r\n\r\n%s\r\n", url, host, GetNetworkRevisionString(), (int)strlen(data), data);
 	} else {
 		seprintf(buffer, buffer + bufferSize - 1, "GET %s HTTP/1.0\r\nHost: %s\r\nUser-Agent: OpenTTD/%s\r\n\r\n", url, host, GetNetworkRevisionString());
@@ -108,7 +108,7 @@ static const char * const LOCATION      
 int NetworkHTTPSocketHandler::HandleHeader()
 {
 	assert(strlen(HTTP_1_0) == strlen(HTTP_1_1));
-	assert(strstr(this->recv_buffer, END_OF_HEADER) != NULL);
+	assert(strstr(this->recv_buffer, END_OF_HEADER) != nullptr);
 
 	/* We expect a HTTP/1.[01] reply */
 	if (strncmp(this->recv_buffer, HTTP_1_0, strlen(HTTP_1_0)) != 0 &&
@@ -122,7 +122,7 @@ int NetworkHTTPSocketHandler::HandleHead
 
 		/* Get the length of the document to receive */
 		char *length = strcasestr(this->recv_buffer, CONTENT_LENGTH);
-		if (length == NULL) return_error("[tcp/http] missing 'content-length' header");
+		if (length == nullptr) return_error("[tcp/http] missing 'content-length' header");
 
 		/* Skip the header */
 		length += strlen(CONTENT_LENGTH);
@@ -163,7 +163,7 @@ int NetworkHTTPSocketHandler::HandleHead
 
 	/* Redirect to other URL */
 	char *uri = strcasestr(this->recv_buffer, LOCATION);
-	if (uri == NULL) return_error("[tcp/http] missing 'location' header for redirect");
+	if (uri == nullptr) return_error("[tcp/http] missing 'location' header for redirect");
 
 	uri += strlen(LOCATION);
 
@@ -178,7 +178,7 @@ int NetworkHTTPSocketHandler::HandleHead
 	if (ret != 0) return ret;
 
 	/* We've relinquished control of data now. */
-	this->data = NULL;
+	this->data = nullptr;
 
 	/* Restore the header. */
 	*end_of_line = '\r';
@@ -195,22 +195,22 @@ int NetworkHTTPSocketHandler::HandleHead
 /* static */ int NetworkHTTPSocketHandler::Connect(char *uri, HTTPCallback *callback, const char *data, int depth)
 {
 	char *hname = strstr(uri, "://");
-	if (hname == NULL) return_error("[tcp/http] invalid location");
+	if (hname == nullptr) return_error("[tcp/http] invalid location");
 
 	hname += 3;
 
 	char *url = strchr(hname, '/');
-	if (url == NULL) return_error("[tcp/http] invalid location");
+	if (url == nullptr) return_error("[tcp/http] invalid location");
 
 	*url = '\0';
 
 	/* Fetch the hostname, and possible port number. */
-	const char *company = NULL;
-	const char *port = NULL;
+	const char *company = nullptr;
+	const char *port = nullptr;
 	ParseConnectionString(&company, &port, hname);
-	if (company != NULL) return_error("[tcp/http] invalid hostname");
+	if (company != nullptr) return_error("[tcp/http] invalid hostname");
 
-	NetworkAddress address(hname, port == NULL ? 80 : atoi(port));
+	NetworkAddress address(hname, port == nullptr ? 80 : atoi(port));
 
 	/* Restore the URL. */
 	*url = '/';
@@ -246,7 +246,7 @@ int NetworkHTTPSocketHandler::Receive()
 		if (res == 0) {
 			if (this->recv_length != 0) return -1;
 
-			this->callback->OnReceiveData(NULL, 0);
+			this->callback->OnReceiveData(nullptr, 0);
 			return 0;
 		}
 
@@ -261,7 +261,7 @@ int NetworkHTTPSocketHandler::Receive()
 			char *end_of_header = strstr(this->recv_buffer, END_OF_HEADER);
 			this->recv_buffer[end] = prev;
 
-			if (end_of_header == NULL) {
+			if (end_of_header == nullptr) {
 				if (read == lengthof(this->recv_buffer)) {
 					DEBUG(net, 0, "[tcp/http] header too big");
 					return -1;
@@ -308,7 +308,7 @@ int NetworkHTTPSocketHandler::Receive()
 	}
 
 	tv.tv_sec = tv.tv_usec = 0; // don't block at all.
-	int n = select(FD_SETSIZE, &read_fd, NULL, NULL, &tv);
+	int n = select(FD_SETSIZE, &read_fd, nullptr, nullptr, &tv);
 	if (n == -1) return;
 
 	for (auto iter = _http_connections.begin(); iter < _http_connections.end(); /* nothing */) {
diff --git a/src/network/core/tcp_http.h b/src/network/core/tcp_http.h
--- a/src/network/core/tcp_http.h
+++ b/src/network/core/tcp_http.h
@@ -26,9 +26,9 @@ struct HTTPCallback {
 
 	/**
 	 * We're receiving data.
-	 * @param data   the received data, NULL when all data has been received.
+	 * @param data   the received data, nullptr when all data has been received.
 	 * @param length the amount of received data, 0 when all data has been received.
-	 * @note When NULL is sent the HTTP socket handler is closed/freed.
+	 * @note When nullptr is sent the HTTP socket handler is closed/freed.
 	 */
 	virtual void OnReceiveData(const char *data, size_t length) = 0;
 
@@ -68,7 +68,7 @@ public:
 	~NetworkHTTPSocketHandler();
 
 	static int Connect(char *uri, HTTPCallback *callback,
-			const char *data = NULL, int depth = 0);
+			const char *data = nullptr, int depth = 0);
 
 	static void HTTPReceive();
 };
@@ -91,7 +91,7 @@ public:
 	 */
 	NetworkHTTPContentConnecter(const NetworkAddress &address,
 			HTTPCallback *callback, const char *url,
-			const char *data = NULL, int depth = 0) :
+			const char *data = nullptr, int depth = 0) :
 		TCPConnecter(address),
 		callback(callback),
 		url(stredup(url)),
@@ -116,7 +116,7 @@ public:
 	{
 		new NetworkHTTPSocketHandler(s, this->callback, this->address.GetHostname(), this->url, this->data, this->depth);
 		/* We've relinquished control of data now. */
-		this->data = NULL;
+		this->data = nullptr;
 	}
 };
 
diff --git a/src/network/core/tcp_listen.h b/src/network/core/tcp_listen.h
--- a/src/network/core/tcp_listen.h
+++ b/src/network/core/tcp_listen.h
@@ -116,7 +116,7 @@ public:
 		}
 
 		tv.tv_sec = tv.tv_usec = 0; // don't block at all.
-		if (select(FD_SETSIZE, &read_fd, &write_fd, NULL, &tv) < 0) return false;
+		if (select(FD_SETSIZE, &read_fd, &write_fd, nullptr, &tv) < 0) return false;
 
 		/* accept clients.. */
 		for (auto &s : sockets) {
diff --git a/src/network/core/udp.cpp b/src/network/core/udp.cpp
--- a/src/network/core/udp.cpp
+++ b/src/network/core/udp.cpp
@@ -24,12 +24,12 @@
  */
 NetworkUDPSocketHandler::NetworkUDPSocketHandler(NetworkAddressList *bind)
 {
-	if (bind != NULL) {
+	if (bind != nullptr) {
 		for (NetworkAddress &addr : *bind) {
 			this->bind.push_back(addr);
 		}
 	} else {
-		/* As hostname NULL and port 0/NULL don't go well when
+		/* As hostname nullptr and port 0/nullptr don't go well when
 		 * resolving it we need to add an address for each of
 		 * the address families we support. */
 		this->bind.emplace_back(nullptr, 0, AF_INET);
@@ -176,13 +176,13 @@ void NetworkUDPSocketHandler::SendNetwor
 		uint count = 0;
 
 		/* Count number of GRFs to send information about */
-		for (c = info->grfconfig; c != NULL; c = c->next) {
+		for (c = info->grfconfig; c != nullptr; c = c->next) {
 			if (!HasBit(c->flags, GCF_STATIC)) count++;
 		}
 		p->Send_uint8 (count); // Send number of GRFs
 
 		/* Send actual GRF Identifications */
-		for (c = info->grfconfig; c != NULL; c = c->next) {
+		for (c = info->grfconfig; c != nullptr; c = c->next) {
 			if (!HasBit(c->flags, GCF_STATIC)) this->SendGRFIdentifier(p, &c->ident);
 		}
 	}
diff --git a/src/network/core/udp.h b/src/network/core/udp.h
--- a/src/network/core/udp.h
+++ b/src/network/core/udp.h
@@ -229,7 +229,7 @@ protected:
 	 */
 	virtual void HandleIncomingNetworkGameInfoGRFConfig(GRFConfig *config) { NOT_REACHED(); }
 public:
-	NetworkUDPSocketHandler(NetworkAddressList *bind = NULL);
+	NetworkUDPSocketHandler(NetworkAddressList *bind = nullptr);
 
 	/** On destructing of this class, the socket needs to be closed */
 	virtual ~NetworkUDPSocketHandler() { this->Close(); }
diff --git a/src/network/network.cpp b/src/network/network.cpp
--- a/src/network/network.cpp
+++ b/src/network/network.cpp
@@ -57,7 +57,7 @@ bool _network_available;  ///< is networ
 bool _network_dedicated;  ///< are we a dedicated server?
 bool _is_network_server;  ///< Does this client wants to be a network-server?
 NetworkServerGameInfo _network_game_info; ///< Information about our game.
-NetworkCompanyState *_network_company_states = NULL; ///< Statistics about some companies.
+NetworkCompanyState *_network_company_states = nullptr; ///< Statistics about some companies.
 ClientID _network_own_client_id;      ///< Our client identifier.
 ClientID _redirect_console_to_client; ///< If not invalid, redirect the console output to a client.
 bool _network_need_advertise;         ///< Whether we need to advertise.
@@ -119,7 +119,7 @@ NetworkClientInfo::~NetworkClientInfo()
 /**
  * Return the CI given it's client-identifier
  * @param client_id the ClientID to search for
- * @return return a pointer to the corresponding NetworkClientInfo struct or NULL when not found
+ * @return return a pointer to the corresponding NetworkClientInfo struct or nullptr when not found
  */
 /* static */ NetworkClientInfo *NetworkClientInfo::GetByClientID(ClientID client_id)
 {
@@ -129,13 +129,13 @@ NetworkClientInfo::~NetworkClientInfo()
 		if (ci->client_id == client_id) return ci;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
  * Return the client state given it's client-identifier
  * @param client_id the ClientID to search for
- * @return return a pointer to the corresponding NetworkClientSocket struct or NULL when not found
+ * @return return a pointer to the corresponding NetworkClientSocket struct or nullptr when not found
  */
 /* static */ ServerNetworkGameSocketHandler *ServerNetworkGameSocketHandler::GetByClientID(ClientID client_id)
 {
@@ -145,7 +145,7 @@ NetworkClientInfo::~NetworkClientInfo()
 		if (cs->client_id == client_id) return cs;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 byte NetworkSpectatorCount()
@@ -378,7 +378,7 @@ void NetworkHandlePauseChange(PauseMode 
 
 			char buffer[DRAW_STRING_BUFFER];
 			GetString(buffer, str, lastof(buffer));
-			NetworkTextMessage(NETWORK_ACTION_SERVER_MESSAGE, CC_DEFAULT, false, NULL, buffer);
+			NetworkTextMessage(NETWORK_ACTION_SERVER_MESSAGE, CC_DEFAULT, false, nullptr, buffer);
 			break;
 		}
 
@@ -541,7 +541,7 @@ void NetworkClose(bool close_admins)
 		}
 		ServerNetworkGameSocketHandler::CloseListeners();
 		ServerNetworkAdminSocketHandler::CloseListeners();
-	} else if (MyClient::my_client != NULL) {
+	} else if (MyClient::my_client != nullptr) {
 		MyClient::SendQuit();
 		MyClient::my_client->CloseConnection(NETWORK_RECV_STATUS_CONN_LOST);
 	}
@@ -554,7 +554,7 @@ void NetworkClose(bool close_admins)
 	NetworkFreeLocalCommandQueue();
 
 	free(_network_company_states);
-	_network_company_states = NULL;
+	_network_company_states = nullptr;
 
 	InitializeNetworkPools(close_admins);
 }
@@ -608,8 +608,8 @@ void NetworkTCPQueryServer(NetworkAddres
 void NetworkAddServer(const char *b)
 {
 	if (*b != '\0') {
-		const char *port = NULL;
-		const char *company = NULL;
+		const char *port = nullptr;
+		const char *company = nullptr;
 		char host[NETWORK_HOSTNAME_LENGTH];
 		uint16 rport;
 
@@ -619,7 +619,7 @@ void NetworkAddServer(const char *b)
 		rport = NETWORK_DEFAULT_PORT;
 
 		ParseConnectionString(&company, &port, host);
-		if (port != NULL) rport = atoi(port);
+		if (port != nullptr) rport = atoi(port);
 
 		NetworkUDPQueryServer(NetworkAddress(host, rport), true);
 	}
@@ -649,7 +649,7 @@ void NetworkRebuildHostList()
 {
 	_network_host_list.clear();
 
-	for (NetworkGameList *item = _network_game_list; item != NULL; item = item->next) {
+	for (NetworkGameList *item = _network_game_list; item != nullptr; item = item->next) {
 		if (item->manually) _network_host_list.emplace_back(item->address.GetAddressAsString(false));
 	}
 }
@@ -884,21 +884,21 @@ void NetworkGameLoop()
 		static FILE *f = FioFOpenFile("commands.log", "rb", SAVE_DIR);
 		static Date next_date = 0;
 		static uint32 next_date_fract;
-		static CommandPacket *cp = NULL;
+		static CommandPacket *cp = nullptr;
 		static bool check_sync_state = false;
 		static uint32 sync_state[2];
-		if (f == NULL && next_date == 0) {
+		if (f == nullptr && next_date == 0) {
 			DEBUG(net, 0, "Cannot open commands.log");
 			next_date = 1;
 		}
 
-		while (f != NULL && !feof(f)) {
+		while (f != nullptr && !feof(f)) {
 			if (_date == next_date && _date_fract == next_date_fract) {
-				if (cp != NULL) {
-					NetworkSendCommand(cp->tile, cp->p1, cp->p2, cp->cmd & ~CMD_FLAGS_MASK, NULL, cp->text, cp->company);
+				if (cp != nullptr) {
+					NetworkSendCommand(cp->tile, cp->p1, cp->p2, cp->cmd & ~CMD_FLAGS_MASK, nullptr, cp->text, cp->company);
 					DEBUG(net, 0, "injecting: %08x; %02x; %02x; %06x; %08x; %08x; %08x; \"%s\" (%s)", _date, _date_fract, (int)_current_company, cp->tile, cp->p1, cp->p2, cp->cmd, cp->text, GetCommandName(cp->cmd));
 					free(cp);
-					cp = NULL;
+					cp = nullptr;
 				}
 				if (check_sync_state) {
 					if (sync_state[0] == _random.state[0] && sync_state[1] == _random.state[1]) {
@@ -912,16 +912,16 @@ void NetworkGameLoop()
 				}
 			}
 
-			if (cp != NULL || check_sync_state) break;
+			if (cp != nullptr || check_sync_state) break;
 
 			char buff[4096];
-			if (fgets(buff, lengthof(buff), f) == NULL) break;
+			if (fgets(buff, lengthof(buff), f) == nullptr) break;
 
 			char *p = buff;
 			/* Ignore the "[date time] " part of the message */
 			if (*p == '[') {
 				p = strchr(p, ']');
-				if (p == NULL) break;
+				if (p == nullptr) break;
 				p += 2;
 			}
 
@@ -968,10 +968,10 @@ void NetworkGameLoop()
 				NOT_REACHED();
 			}
 		}
-		if (f != NULL && feof(f)) {
+		if (f != nullptr && feof(f)) {
 			DEBUG(net, 0, "End of commands.log");
 			fclose(f);
-			f = NULL;
+			f = nullptr;
 		}
 #endif /* DEBUG_DUMP_COMMANDS */
 		if (_frame_counter >= _frame_counter_max) {
diff --git a/src/network/network_admin.cpp b/src/network/network_admin.cpp
--- a/src/network/network_admin.cpp
+++ b/src/network/network_admin.cpp
@@ -234,12 +234,12 @@ NetworkRecvStatus ServerNetworkAdminSock
 NetworkRecvStatus ServerNetworkAdminSocketHandler::SendClientInfo(const NetworkClientSocket *cs, const NetworkClientInfo *ci)
 {
 	/* Only send data when we're a proper client, not just someone trying to query the server. */
-	if (ci == NULL) return NETWORK_RECV_STATUS_OKAY;
+	if (ci == nullptr) return NETWORK_RECV_STATUS_OKAY;
 
 	Packet *p = new Packet(ADMIN_PACKET_SERVER_CLIENT_INFO);
 
 	p->Send_uint32(ci->client_id);
-	p->Send_string(cs == NULL ? "" : const_cast<NetworkAddress &>(cs->client_address).GetHostname());
+	p->Send_string(cs == nullptr ? "" : const_cast<NetworkAddress &>(cs->client_address).GetHostname());
 	p->Send_string(ci->client_name);
 	p->Send_uint8 (ci->client_lang);
 	p->Send_uint32(ci->join_date);
@@ -734,16 +734,16 @@ NetworkRecvStatus ServerNetworkAdminSock
 			/* The admin is requesting client info. */
 			const NetworkClientSocket *cs;
 			if (d1 == UINT32_MAX) {
-				this->SendClientInfo(NULL, NetworkClientInfo::GetByClientID(CLIENT_ID_SERVER));
+				this->SendClientInfo(nullptr, NetworkClientInfo::GetByClientID(CLIENT_ID_SERVER));
 				FOR_ALL_CLIENT_SOCKETS(cs) {
 					this->SendClientInfo(cs, cs->GetInfo());
 				}
 			} else {
 				if (d1 == CLIENT_ID_SERVER) {
-					this->SendClientInfo(NULL, NetworkClientInfo::GetByClientID(CLIENT_ID_SERVER));
+					this->SendClientInfo(nullptr, NetworkClientInfo::GetByClientID(CLIENT_ID_SERVER));
 				} else {
 					cs = NetworkClientSocket::GetByClientID((ClientID)d1);
-					if (cs != NULL) this->SendClientInfo(cs, cs->GetInfo());
+					if (cs != nullptr) this->SendClientInfo(cs, cs->GetInfo());
 				}
 			}
 			break;
@@ -757,7 +757,7 @@ NetworkRecvStatus ServerNetworkAdminSock
 				}
 			} else {
 				company = Company::GetIfValid(d1);
-				if (company != NULL) this->SendCompanyInfo(company);
+				if (company != nullptr) this->SendCompanyInfo(company);
 			}
 			break;
 
@@ -884,7 +884,7 @@ void NetworkAdminClientError(ClientID cl
  */
 void NetworkAdminCompanyInfo(const Company *company, bool new_company)
 {
-	if (company == NULL) {
+	if (company == nullptr) {
 		DEBUG(net, 1, "[admin] Empty company given for update");
 		return;
 	}
@@ -906,7 +906,7 @@ void NetworkAdminCompanyInfo(const Compa
  */
 void NetworkAdminCompanyUpdate(const Company *company)
 {
-	if (company == NULL) return;
+	if (company == nullptr) return;
 
 	ServerNetworkAdminSocketHandler *as;
 	FOR_ALL_ACTIVE_ADMIN_SOCKETS(as) {
@@ -992,7 +992,7 @@ void NetworkAdminGameScript(const char *
  */
 void NetworkAdminCmdLogging(const NetworkClientSocket *owner, const CommandPacket *cp)
 {
-	ClientID client_id = owner == NULL ? _network_own_client_id : owner->client_id;
+	ClientID client_id = owner == nullptr ? _network_own_client_id : owner->client_id;
 
 	ServerNetworkAdminSocketHandler *as;
 	FOR_ALL_ACTIVE_ADMIN_SOCKETS(as) {
diff --git a/src/network/network_chat_gui.cpp b/src/network/network_chat_gui.cpp
--- a/src/network/network_chat_gui.cpp
+++ b/src/network/network_chat_gui.cpp
@@ -46,7 +46,7 @@ struct ChatMessage {
 };
 
 /* used for chat window */
-static ChatMessage *_chatmsg_list = NULL; ///< The actual chat message list.
+static ChatMessage *_chatmsg_list = nullptr; ///< The actual chat message list.
 static bool _chatmessage_dirty = false;   ///< Does the chat message need repainting?
 static bool _chatmessage_visible = false; ///< Is a chat message visible.
 static bool _chat_tab_completion_active;  ///< Whether tab completion is active.
@@ -57,7 +57,7 @@ static uint MAX_CHAT_MESSAGES = 0;      
  * the left and pixels from the bottom. The height is the maximum height.
  */
 static PointDimension _chatmsg_box;
-static uint8 *_chatmessage_backup = NULL; ///< Backup in case text is moved.
+static uint8 *_chatmessage_backup = nullptr; ///< Backup in case text is moved.
 
 /**
  * Count the chat messages.
@@ -360,7 +360,7 @@ struct NetworkChatWindow : public Window
 			}
 		}
 
-		return NULL;
+		return nullptr;
 	}
 
 	/**
@@ -371,7 +371,7 @@ struct NetworkChatWindow : public Window
 	static char *ChatTabCompletionFindText(char *buf)
 	{
 		char *p = strrchr(buf, ' ');
-		if (p == NULL) return buf;
+		if (p == nullptr) return buf;
 
 		*p = '\0';
 		return p + 1;
@@ -400,7 +400,7 @@ struct NetworkChatWindow : public Window
 		tb_buf  = ChatTabCompletionFindText(pre_buf);
 		tb_len  = strlen(tb_buf);
 
-		while ((cur_name = ChatTabCompletionNextItem(&item)) != NULL) {
+		while ((cur_name = ChatTabCompletionNextItem(&item)) != nullptr) {
 			item++;
 
 			if (_chat_tab_completion_active) {
@@ -543,7 +543,7 @@ static const NWidgetPart _nested_chat_wi
 
 /** The description of the chat window. */
 static WindowDesc _chat_window_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_SEND_NETWORK_MSG, WC_NONE,
 	0,
 	_nested_chat_window_widgets, lengthof(_nested_chat_window_widgets)
diff --git a/src/network/network_client.cpp b/src/network/network_client.cpp
--- a/src/network/network_client.cpp
+++ b/src/network/network_client.cpp
@@ -50,7 +50,7 @@ struct PacketReader : LoadFilter {
 	size_t read_bytes;                      ///< The total number of read bytes.
 
 	/** Initialise everything. */
-	PacketReader() : LoadFilter(NULL), buf(NULL), bufe(NULL), block(NULL), written_bytes(0), read_bytes(0)
+	PacketReader() : LoadFilter(nullptr), buf(nullptr), bufe(nullptr), block(nullptr), written_bytes(0), read_bytes(0)
 	{
 	}
 
@@ -143,9 +143,9 @@ void ClientNetworkEmergencySave()
  * Create a new socket for the client side of the game connection.
  * @param s The socket to connect with.
  */
-ClientNetworkGameSocketHandler::ClientNetworkGameSocketHandler(SOCKET s) : NetworkGameSocketHandler(s), savegame(NULL), status(STATUS_INACTIVE)
+ClientNetworkGameSocketHandler::ClientNetworkGameSocketHandler(SOCKET s) : NetworkGameSocketHandler(s), savegame(nullptr), status(STATUS_INACTIVE)
 {
-	assert(ClientNetworkGameSocketHandler::my_client == NULL);
+	assert(ClientNetworkGameSocketHandler::my_client == nullptr);
 	ClientNetworkGameSocketHandler::my_client = this;
 }
 
@@ -153,7 +153,7 @@ ClientNetworkGameSocketHandler::ClientNe
 ClientNetworkGameSocketHandler::~ClientNetworkGameSocketHandler()
 {
 	assert(ClientNetworkGameSocketHandler::my_client == this);
-	ClientNetworkGameSocketHandler::my_client = NULL;
+	ClientNetworkGameSocketHandler::my_client = nullptr;
 
 	delete this->savegame;
 }
@@ -301,7 +301,7 @@ void ClientNetworkGameSocketHandler::Cli
 
 
 /** Our client's connection. */
-ClientNetworkGameSocketHandler * ClientNetworkGameSocketHandler::my_client = NULL;
+ClientNetworkGameSocketHandler * ClientNetworkGameSocketHandler::my_client = nullptr;
 
 /** Last frame we performed an ack. */
 static uint32 last_ack_frame;
@@ -320,9 +320,9 @@ static uint8 _network_server_max_spectat
 CompanyID _network_join_as;
 
 /** Login password from -p argument */
-const char *_network_join_server_password = NULL;
+const char *_network_join_server_password = nullptr;
 /** Company password from -P argument */
-const char *_network_join_company_password = NULL;
+const char *_network_join_company_password = nullptr;
 
 /** Make sure the server ID length is the same as a md5 hash. */
 assert_compile(NETWORK_SERVER_ID_LENGTH == 16 * 2 + 1);
@@ -533,7 +533,7 @@ NetworkRecvStatus ClientNetworkGameSocke
  */
 bool ClientNetworkGameSocketHandler::IsConnected()
 {
-	return my_client != NULL && my_client->status == STATUS_ACTIVE;
+	return my_client != nullptr && my_client->status == STATUS_ACTIVE;
 }
 
 
@@ -542,7 +542,7 @@ bool ClientNetworkGameSocketHandler::IsC
  *   DEF_CLIENT_RECEIVE_COMMAND has parameter: Packet *p
  ************/
 
-extern bool SafeLoad(const char *filename, SaveLoadOperation fop, DetailedFileType dft, GameMode newgm, Subdirectory subdir, struct LoadFilter *lf = NULL);
+extern bool SafeLoad(const char *filename, SaveLoadOperation fop, DetailedFileType dft, GameMode newgm, Subdirectory subdir, struct LoadFilter *lf = nullptr);
 
 NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_FULL(Packet *p)
 {
@@ -576,7 +576,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 		if (current >= MAX_COMPANIES) return NETWORK_RECV_STATUS_CLOSE_QUERY;
 
 		NetworkCompanyInfo *company_info = GetLobbyCompanyInfo(current);
-		if (company_info == NULL) return NETWORK_RECV_STATUS_CLOSE_QUERY;
+		if (company_info == nullptr) return NETWORK_RECV_STATUS_CLOSE_QUERY;
 
 		p->Recv_string(company_info->company_name, sizeof(company_info->company_name));
 		company_info->inaugurated_year = p->Recv_uint32();
@@ -619,7 +619,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 	if (this->HasClientQuit()) return NETWORK_RECV_STATUS_CONN_LOST;
 
 	ci = NetworkClientInfo::GetByClientID(client_id);
-	if (ci != NULL) {
+	if (ci != nullptr) {
 		if (playas == ci->client_playas && strcmp(name, ci->client_name) != 0) {
 			/* Client name changed, display the change */
 			NetworkTextMessage(NETWORK_ACTION_NAME_CHANGE, CC_DEFAULT, false, ci->client_name, name);
@@ -714,7 +714,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 
 		/* Check whether we know this GRF */
 		const GRFConfig *f = FindGRFConfig(c.grfid, FGCM_EXACT, c.md5sum);
-		if (f == NULL) {
+		if (f == nullptr) {
 			/* We do not know this GRF, bail out of initialization */
 			char buf[sizeof(c.md5sum) * 2 + 1];
 			md5sumToString(buf, lastof(buf), c.md5sum);
@@ -800,7 +800,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 	if (this->status < STATUS_AUTHORIZED || this->status >= STATUS_MAP) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
 	this->status = STATUS_MAP;
 
-	if (this->savegame != NULL) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
+	if (this->savegame != nullptr) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
 
 	this->savegame = new PacketReader();
 
@@ -818,7 +818,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_MAP_SIZE(Packet *p)
 {
 	if (this->status != STATUS_MAP) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
-	if (this->savegame == NULL) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
+	if (this->savegame == nullptr) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
 
 	_network_join_bytes_total = p->Recv_uint32();
 	SetWindowDirty(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_JOIN);
@@ -829,7 +829,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_MAP_DATA(Packet *p)
 {
 	if (this->status != STATUS_MAP) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
-	if (this->savegame == NULL) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
+	if (this->savegame == nullptr) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
 
 	/* We are still receiving data, put it to the file */
 	this->savegame->AddPacket(p);
@@ -843,7 +843,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_MAP_DONE(Packet *p)
 {
 	if (this->status != STATUS_MAP) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
-	if (this->savegame == NULL) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
+	if (this->savegame == nullptr) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
 
 	_network_join_status = NETWORK_JOIN_STATUS_PROCESSING;
 	SetWindowDirty(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_JOIN);
@@ -856,12 +856,12 @@ NetworkRecvStatus ClientNetworkGameSocke
 	 * game, which would cause us to free this->savegame twice.
 	 */
 	LoadFilter *lf = this->savegame;
-	this->savegame = NULL;
+	this->savegame = nullptr;
 	lf->Reset();
 
 	/* The map is done downloading, load it */
 	ClearErrorMessages();
-	bool load_success = SafeLoad(NULL, SLO_LOAD, DFT_GAME_FILE, GM_NORMAL, NO_DIRECTORY, lf);
+	bool load_success = SafeLoad(nullptr, SLO_LOAD, DFT_GAME_FILE, GM_NORMAL, NO_DIRECTORY, lf);
 
 	/* Long savegame loads shouldn't affect the lag calculation! */
 	this->last_packet = _realtime_tick;
@@ -887,7 +887,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 			 * the server will give us a client-id and let us in */
 			_network_join_status = NETWORK_JOIN_STATUS_REGISTERING;
 			ShowJoinStatusWindow();
-			NetworkSendCommand(0, CCA_NEW, 0, CMD_COMPANY_CTRL, NULL, NULL, _local_company);
+			NetworkSendCommand(0, CCA_NEW, 0, CMD_COMPANY_CTRL, nullptr, nullptr, _local_company);
 		}
 	} else {
 		/* take control over an existing company */
@@ -952,7 +952,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 	cp.frame    = p->Recv_uint32();
 	cp.my_cmd   = p->Recv_bool();
 
-	if (err != NULL) {
+	if (err != nullptr) {
 		IConsolePrintF(CC_ERROR, "WARNING: %s from server, dropping...", err);
 		return NETWORK_RECV_STATUS_MALFORMED_PACKET;
 	}
@@ -967,7 +967,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 	if (this->status != STATUS_ACTIVE) return NETWORK_RECV_STATUS_MALFORMED_PACKET;
 
 	char name[NETWORK_NAME_LENGTH], msg[NETWORK_CHAT_LENGTH];
-	const NetworkClientInfo *ci = NULL, *ci_to;
+	const NetworkClientInfo *ci = nullptr, *ci_to;
 
 	NetworkAction action = (NetworkAction)p->Recv_uint8();
 	ClientID client_id = (ClientID)p->Recv_uint32();
@@ -976,7 +976,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 	int64 data = p->Recv_uint64();
 
 	ci_to = NetworkClientInfo::GetByClientID(client_id);
-	if (ci_to == NULL) return NETWORK_RECV_STATUS_OKAY;
+	if (ci_to == nullptr) return NETWORK_RECV_STATUS_OKAY;
 
 	/* Did we initiate the action locally? */
 	if (self_send) {
@@ -1009,7 +1009,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 		ci = ci_to;
 	}
 
-	if (ci != NULL) {
+	if (ci != nullptr) {
 		NetworkTextMessage(action, GetDrawStringCompanyColour(ci->client_playas), self_send, name, msg, data);
 	}
 	return NETWORK_RECV_STATUS_OKAY;
@@ -1022,8 +1022,8 @@ NetworkRecvStatus ClientNetworkGameSocke
 	ClientID client_id = (ClientID)p->Recv_uint32();
 
 	NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(client_id);
-	if (ci != NULL) {
-		NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, ci->client_name, NULL, GetNetworkErrorMsg((NetworkErrorCode)p->Recv_uint8()));
+	if (ci != nullptr) {
+		NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, ci->client_name, nullptr, GetNetworkErrorMsg((NetworkErrorCode)p->Recv_uint8()));
 		delete ci;
 	}
 
@@ -1039,8 +1039,8 @@ NetworkRecvStatus ClientNetworkGameSocke
 	ClientID client_id = (ClientID)p->Recv_uint32();
 
 	NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(client_id);
-	if (ci != NULL) {
-		NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, ci->client_name, NULL, STR_NETWORK_MESSAGE_CLIENT_LEAVING);
+	if (ci != nullptr) {
+		NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, ci->client_name, nullptr, STR_NETWORK_MESSAGE_CLIENT_LEAVING);
 		delete ci;
 	} else {
 		DEBUG(net, 0, "Unknown client (%d) is leaving the game", client_id);
@@ -1059,7 +1059,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 	ClientID client_id = (ClientID)p->Recv_uint32();
 
 	NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(client_id);
-	if (ci != NULL) {
+	if (ci != nullptr) {
 		NetworkTextMessage(NETWORK_ACTION_JOIN, CC_DEFAULT, false, ci->client_name);
 	}
 
@@ -1129,7 +1129,7 @@ NetworkRecvStatus ClientNetworkGameSocke
 
 	const NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(client_id);
 	/* Just make sure we do not try to use a client_index that does not exist */
-	if (ci == NULL) return NETWORK_RECV_STATUS_OKAY;
+	if (ci == nullptr) return NETWORK_RECV_STATUS_OKAY;
 
 	/* if not valid player, force spectator, else check player exists */
 	if (!Company::IsValidID(company_id)) company_id = COMPANY_SPECTATOR;
@@ -1253,7 +1253,7 @@ void NetworkUpdateClientName()
 {
 	NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(_network_own_client_id);
 
-	if (ci == NULL) return;
+	if (ci == nullptr) return;
 
 	/* Don't change the name if it is the same as the old name */
 	if (strcmp(ci->client_name, _settings_client.network.client_name) != 0) {
diff --git a/src/network/network_command.cpp b/src/network/network_command.cpp
--- a/src/network/network_command.cpp
+++ b/src/network/network_command.cpp
@@ -21,7 +21,7 @@
 
 /** Table with all the callbacks we'll use for conversion*/
 static CommandCallback * const _callback_table[] = {
-	/* 0x00 */ NULL,
+	/* 0x00 */ nullptr,
 	/* 0x01 */ CcBuildPrimaryVehicle,
 	/* 0x02 */ CcBuildAirport,
 	/* 0x03 */ CcBuildBridge,
@@ -60,8 +60,8 @@ void CommandQueue::Append(CommandPacket 
 {
 	CommandPacket *add = MallocT<CommandPacket>(1);
 	*add = *p;
-	add->next = NULL;
-	if (this->first == NULL) {
+	add->next = nullptr;
+	if (this->first == nullptr) {
 		this->first = add;
 	} else {
 		this->last->next = add;
@@ -79,15 +79,15 @@ CommandPacket *CommandQueue::Pop(bool ig
 {
 	CommandPacket **prev = &this->first;
 	CommandPacket *ret = this->first;
-	CommandPacket *prev_item = NULL;
+	CommandPacket *prev_item = nullptr;
 	if (ignore_paused && _pause_mode != PM_UNPAUSED) {
-		while (ret != NULL && !IsCommandAllowedWhilePaused(ret->cmd)) {
+		while (ret != nullptr && !IsCommandAllowedWhilePaused(ret->cmd)) {
 			prev_item = ret;
 			prev = &ret->next;
 			ret = ret->next;
 		}
 	}
-	if (ret != NULL) {
+	if (ret != nullptr) {
 		if (ret == this->last) this->last = prev_item;
 		*prev = ret->next;
 		this->count--;
@@ -104,17 +104,17 @@ CommandPacket *CommandQueue::Peek(bool i
 {
 	if (!ignore_paused || _pause_mode == PM_UNPAUSED) return this->first;
 
-	for (CommandPacket *p = this->first; p != NULL; p = p->next) {
+	for (CommandPacket *p = this->first; p != nullptr; p = p->next) {
 		if (IsCommandAllowedWhilePaused(p->cmd)) return p;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /** Free everything that is in the queue. */
 void CommandQueue::Free()
 {
 	CommandPacket *cp;
-	while ((cp = this->Pop()) != NULL) {
+	while ((cp = this->Pop()) != nullptr) {
 		free(cp);
 	}
 	assert(this->count == 0);
@@ -147,7 +147,7 @@ void NetworkSendCommand(TileIndex tile, 
 	c.cmd      = cmd;
 	c.callback = callback;
 
-	strecpy(c.text, (text != NULL) ? text : "", lastof(c.text));
+	strecpy(c.text, (text != nullptr) ? text : "", lastof(c.text));
 
 	if (_network_server) {
 		/* If we are the server, we queue the command in our 'special' queue.
@@ -180,7 +180,7 @@ void NetworkSendCommand(TileIndex tile, 
  */
 void NetworkSyncCommandQueue(NetworkClientSocket *cs)
 {
-	for (CommandPacket *p = _local_execution_queue.Peek(); p != NULL; p = p->next) {
+	for (CommandPacket *p = _local_execution_queue.Peek(); p != nullptr; p = p->next) {
 		CommandPacket c = *p;
 		c.callback = 0;
 		cs->outgoing_queue.Append(&c);
@@ -197,7 +197,7 @@ void NetworkExecuteLocalCommandQueue()
 	CommandQueue &queue = (_network_server ? _local_execution_queue : ClientNetworkGameSocketHandler::my_client->incoming_queue);
 
 	CommandPacket *cp;
-	while ((cp = queue.Peek()) != NULL) {
+	while ((cp = queue.Peek()) != nullptr) {
 		/* The queue is always in order, which means
 		 * that the first element will be executed first. */
 		if (_frame_counter < cp->frame) break;
@@ -245,13 +245,13 @@ static void DistributeCommandPacket(Comm
 		if (cs->status >= NetworkClientSocket::STATUS_MAP) {
 			/* Callbacks are only send back to the client who sent them in the
 			 *  first place. This filters that out. */
-			cp.callback = (cs != owner) ? NULL : callback;
+			cp.callback = (cs != owner) ? nullptr : callback;
 			cp.my_cmd = (cs == owner);
 			cs->outgoing_queue.Append(&cp);
 		}
 	}
 
-	cp.callback = (cs != owner) ? NULL : callback;
+	cp.callback = (cs != owner) ? nullptr : callback;
 	cp.my_cmd = (cs == owner);
 	_local_execution_queue.Append(&cp);
 }
@@ -271,7 +271,7 @@ static void DistributeQueue(CommandQueue
 #endif
 
 	CommandPacket *cp;
-	while (--to_go >= 0 && (cp = queue->Pop(true)) != NULL) {
+	while (--to_go >= 0 && (cp = queue->Pop(true)) != nullptr) {
 		DistributeCommandPacket(*cp, owner);
 		NetworkAdminCmdLogging(owner, cp);
 		free(cp);
@@ -282,7 +282,7 @@ static void DistributeQueue(CommandQueue
 void NetworkDistributeCommands()
 {
 	/* First send the server's commands. */
-	DistributeQueue(&_local_wait_queue, NULL);
+	DistributeQueue(&_local_wait_queue, nullptr);
 
 	/* Then send the queues of the others. */
 	NetworkClientSocket *cs;
@@ -295,7 +295,7 @@ void NetworkDistributeCommands()
  * Receives a command from the network.
  * @param p the packet to read from.
  * @param cp the struct to write the data to.
- * @return an error message. When NULL there has been no error.
+ * @return an error message. When nullptr there has been no error.
  */
 const char *NetworkGameSocketHandler::ReceiveCommand(Packet *p, CommandPacket *cp)
 {
@@ -314,7 +314,7 @@ const char *NetworkGameSocketHandler::Re
 	if (callback >= lengthof(_callback_table))  return "invalid callback";
 
 	cp->callback = _callback_table[callback];
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -338,7 +338,7 @@ void NetworkGameSocketHandler::SendComma
 
 	if (callback == lengthof(_callback_table)) {
 		DEBUG(net, 0, "Unknown callback. (Pointer: %p) No callback sent", cp->callback);
-		callback = 0; // _callback_table[0] == NULL
+		callback = 0; // _callback_table[0] == nullptr
 	}
 	p->Send_uint8 (callback);
 }
diff --git a/src/network/network_content.cpp b/src/network/network_content.cpp
--- a/src/network/network_content.cpp
+++ b/src/network/network_content.cpp
@@ -35,7 +35,7 @@ ClientNetworkContentSocketHandler _netwo
 /** Wrapper function for the HasProc */
 static bool HasGRFConfig(const ContentInfo *ci, bool md5sum)
 {
-	return FindGRFConfig(BSWAP32(ci->unique_id), md5sum ? FGCM_EXACT : FGCM_ANY, md5sum ? ci->md5sum : NULL) != NULL;
+	return FindGRFConfig(BSWAP32(ci->unique_id), md5sum ? FGCM_EXACT : FGCM_ANY, md5sum ? ci->md5sum : nullptr) != nullptr;
 }
 
 /**
@@ -79,7 +79,7 @@ bool ClientNetworkContentSocketHandler::
 	}
 
 	/* Find the appropriate check function */
-	HasProc proc = NULL;
+	HasProc proc = nullptr;
 	switch (ci->type) {
 		case CONTENT_TYPE_NEWGRF:
 			proc = HasGRFConfig;
@@ -122,7 +122,7 @@ bool ClientNetworkContentSocketHandler::
 			break;
 	}
 
-	if (proc != NULL) {
+	if (proc != nullptr) {
 		if (proc(ci, true)) {
 			ci->state = ContentInfo::ALREADY_HERE;
 		} else {
@@ -241,7 +241,7 @@ void ClientNetworkContentSocketHandler::
  */
 void ClientNetworkContentSocketHandler::RequestContentList(ContentVector *cv, bool send_md5sum)
 {
-	if (cv == NULL) return;
+	if (cv == nullptr) return;
 
 	this->Connect();
 
@@ -374,12 +374,12 @@ void ClientNetworkContentSocketHandler::
  * @param ci         the information to get the filename from
  * @param compressed should the filename end with .gz?
  * @return a statically allocated buffer with the filename or
- *         NULL when no filename could be made.
+ *         nullptr when no filename could be made.
  */
 static char *GetFullFilename(const ContentInfo *ci, bool compressed)
 {
 	Subdirectory dir = GetContentInfoSubDir(ci->type);
-	if (dir == NO_DIRECTORY) return NULL;
+	if (dir == NO_DIRECTORY) return nullptr;
 
 	static char buf[MAX_PATH];
 	FioGetFullPath(buf, lastof(buf), SP_AUTODOWNLOAD_DIR, dir, ci->filename);
@@ -400,14 +400,14 @@ static bool GunzipFile(const ContentInfo
 
 	/* Need to open the file with fopen() to support non-ASCII on Windows. */
 	FILE *ftmp = fopen(GetFullFilename(ci, true), "rb");
-	if (ftmp == NULL) return false;
+	if (ftmp == nullptr) return false;
 	/* Duplicate the handle, and close the FILE*, to avoid double-closing the handle later. */
 	gzFile fin = gzdopen(dup(fileno(ftmp)), "rb");
 	fclose(ftmp);
 
 	FILE *fout = fopen(GetFullFilename(ci, false), "wb");
 
-	if (fin == NULL || fout == NULL) {
+	if (fin == nullptr || fout == nullptr) {
 		ret = false;
 	} else {
 		byte buff[8192];
@@ -441,8 +441,8 @@ static bool GunzipFile(const ContentInfo
 		}
 	}
 
-	if (fin != NULL) gzclose(fin);
-	if (fout != NULL) fclose(fout);
+	if (fin != nullptr) gzclose(fin);
+	if (fout != nullptr) fclose(fout);
 
 	return ret;
 #else
@@ -452,7 +452,7 @@ static bool GunzipFile(const ContentInfo
 
 bool ClientNetworkContentSocketHandler::Receive_SERVER_CONTENT(Packet *p)
 {
-	if (this->curFile == NULL) {
+	if (this->curFile == nullptr) {
 		delete this->curInfo;
 		/* When we haven't opened a file this must be our first packet with metadata. */
 		this->curInfo = new ContentInfo;
@@ -473,7 +473,7 @@ bool ClientNetworkContentSocketHandler::
 			ShowErrorMessage(STR_CONTENT_ERROR_COULD_NOT_DOWNLOAD, STR_CONTENT_ERROR_COULD_NOT_DOWNLOAD_FILE_NOT_WRITABLE, WL_ERROR);
 			this->Close();
 			fclose(this->curFile);
-			this->curFile = NULL;
+			this->curFile = nullptr;
 
 			return false;
 		}
@@ -494,14 +494,14 @@ bool ClientNetworkContentSocketHandler::
 {
 	if (!this->curInfo->IsValid()) {
 		delete this->curInfo;
-		this->curInfo = NULL;
+		this->curInfo = nullptr;
 		return false;
 	}
 
 	if (this->curInfo->filesize != 0) {
 		/* The filesize is > 0, so we are going to download it */
 		const char *filename = GetFullFilename(this->curInfo, true);
-		if (filename == NULL || (this->curFile = fopen(filename, "wb")) == NULL) {
+		if (filename == nullptr || (this->curFile = fopen(filename, "wb")) == nullptr) {
 			/* Unless that fails of course... */
 			DeleteWindowById(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_CONTENT_DOWNLOAD);
 			ShowErrorMessage(STR_CONTENT_ERROR_COULD_NOT_DOWNLOAD, STR_CONTENT_ERROR_COULD_NOT_DOWNLOAD_FILE_NOT_WRITABLE, WL_ERROR);
@@ -520,7 +520,7 @@ void ClientNetworkContentSocketHandler::
 	/* We read nothing; that's our marker for end-of-stream.
 	 * Now gunzip the tar and make it known. */
 	fclose(this->curFile);
-	this->curFile = NULL;
+	this->curFile = nullptr;
 
 	if (GunzipFile(this->curInfo)) {
 		unlink(GetFullFilename(this->curInfo, true));
@@ -554,25 +554,25 @@ void ClientNetworkContentSocketHandler::
 	this->http_response.shrink_to_fit();
 	this->http_response_index = -2;
 
-	if (this->curFile != NULL) {
+	if (this->curFile != nullptr) {
 		/* Revert the download progress when we are going for the old system. */
 		long size = ftell(this->curFile);
 		if (size > 0) this->OnDownloadProgress(this->curInfo, (int)-size);
 
 		fclose(this->curFile);
-		this->curFile = NULL;
+		this->curFile = nullptr;
 	}
 }
 
 void ClientNetworkContentSocketHandler::OnReceiveData(const char *data, size_t length)
 {
-	assert(data == NULL || length != 0);
+	assert(data == nullptr || length != 0);
 
 	/* Ignore any latent data coming from a connection we closed. */
 	if (this->http_response_index == -2) return;
 
 	if (this->http_response_index == -1) {
-		if (data != NULL) {
+		if (data != nullptr) {
 			/* Append the rest of the response. */
 			memcpy(grow(this->http_response, (uint)length), data, length);
 			return;
@@ -585,7 +585,7 @@ void ClientNetworkContentSocketHandler::
 		}
 	}
 
-	if (data != NULL) {
+	if (data != nullptr) {
 		/* We have data, so write it to the file. */
 		if (fwrite(data, 1, length, this->curFile) != length) {
 			/* Writing failed somehow, let try via the old method. */
@@ -598,7 +598,7 @@ void ClientNetworkContentSocketHandler::
 		return;
 	}
 
-	if (this->curFile != NULL) {
+	if (this->curFile != nullptr) {
 		/* We've finished downloading a file. */
 		this->AfterDownload();
 	}
@@ -616,7 +616,7 @@ void ClientNetworkContentSocketHandler::
 	this->curInfo = new ContentInfo;
 
 /** Check p for not being null and return calling OnFailure if that's not the case. */
-#define check_not_null(p) { if ((p) == NULL) { this->OnFailure(); return; } }
+#define check_not_null(p) { if ((p) == nullptr) { this->OnFailure(); return; } }
 /** Check p for not being null and then terminate, or return calling OnFailure. */
 #define check_and_terminate(p) { check_not_null(p); *(p) = '\0'; }
 
@@ -695,8 +695,8 @@ void ClientNetworkContentSocketHandler::
 ClientNetworkContentSocketHandler::ClientNetworkContentSocketHandler() :
 	NetworkContentSocketHandler(),
 	http_response_index(-2),
-	curFile(NULL),
-	curInfo(NULL),
+	curFile(nullptr),
+	curInfo(nullptr),
 	isConnecting(false),
 	lastActivity(_realtime_tick)
 {
@@ -706,7 +706,7 @@ ClientNetworkContentSocketHandler::Clien
 ClientNetworkContentSocketHandler::~ClientNetworkContentSocketHandler()
 {
 	delete this->curInfo;
-	if (this->curFile != NULL) fclose(this->curFile);
+	if (this->curFile != nullptr) fclose(this->curFile);
 
 	for (ContentInfo *ci : this->infos) delete ci;
 }
@@ -798,14 +798,14 @@ void ClientNetworkContentSocketHandler::
 /**
  * Get the content info based on a ContentID
  * @param cid the ContentID to search for
- * @return the ContentInfo or NULL if not found
+ * @return the ContentInfo or nullptr if not found
  */
 ContentInfo *ClientNetworkContentSocketHandler::GetContent(ContentID cid)
 {
 	for (ContentInfo *ci : this->infos) {
 		if (ci->id == cid) return ci;
 	}
-	return NULL;
+	return nullptr;
 }
 
 
@@ -816,7 +816,7 @@ ContentInfo *ClientNetworkContentSocketH
 void ClientNetworkContentSocketHandler::Select(ContentID cid)
 {
 	ContentInfo *ci = this->GetContent(cid);
-	if (ci == NULL || ci->state != ContentInfo::UNSELECTED) return;
+	if (ci == nullptr || ci->state != ContentInfo::UNSELECTED) return;
 
 	ci->state = ContentInfo::SELECTED;
 	this->CheckDependencyState(ci);
@@ -829,7 +829,7 @@ void ClientNetworkContentSocketHandler::
 void ClientNetworkContentSocketHandler::Unselect(ContentID cid)
 {
 	ContentInfo *ci = this->GetContent(cid);
-	if (ci == NULL || !ci->IsSelected()) return;
+	if (ci == nullptr || !ci->IsSelected()) return;
 
 	ci->state = ContentInfo::UNSELECTED;
 	this->CheckDependencyState(ci);
@@ -937,7 +937,7 @@ void ClientNetworkContentSocketHandler::
 		 * selected and thus can unselect when a dependency is removed. */
 		for (uint i = 0; i < ci->dependency_count; i++) {
 			ContentInfo *c = this->GetContent(ci->dependencies[i]);
-			if (c == NULL) {
+			if (c == nullptr) {
 				this->DownloadContentInfo(ci->dependencies[i]);
 			} else if (c->state == ContentInfo::UNSELECTED) {
 				c->state = ContentInfo::AUTOSELECTED;
@@ -963,7 +963,7 @@ void ClientNetworkContentSocketHandler::
 
 	for (uint i = 0; i < ci->dependency_count; i++) {
 		const ContentInfo *c = this->GetContent(ci->dependencies[i]);
-		if (c == NULL) {
+		if (c == nullptr) {
 			DownloadContentInfo(ci->dependencies[i]);
 			continue;
 		}
@@ -1068,7 +1068,7 @@ void ClientNetworkContentSocketHandler::
 void ClientNetworkContentSocketHandler::OnDownloadComplete(ContentID cid)
 {
 	ContentInfo *ci = this->GetContent(cid);
-	if (ci != NULL) {
+	if (ci != nullptr) {
 		ci->state = ContentInfo::ALREADY_HERE;
 	}
 
diff --git a/src/network/network_content.h b/src/network/network_content.h
--- a/src/network/network_content.h
+++ b/src/network/network_content.h
@@ -147,7 +147,7 @@ public:
 
 extern ClientNetworkContentSocketHandler _network_content_client;
 
-void ShowNetworkContentListWindow(ContentVector *cv = NULL, ContentType type1 = CONTENT_TYPE_END, ContentType type2 = CONTENT_TYPE_END);
+void ShowNetworkContentListWindow(ContentVector *cv = nullptr, ContentType type1 = CONTENT_TYPE_END, ContentType type2 = CONTENT_TYPE_END);
 
 void ShowMissingContentWindow(const struct GRFConfig *list);
 
diff --git a/src/network/network_content_gui.cpp b/src/network/network_content_gui.cpp
--- a/src/network/network_content_gui.cpp
+++ b/src/network/network_content_gui.cpp
@@ -95,7 +95,7 @@ static const NWidgetPart _nested_network
 
 /** Window description for the download window */
 static WindowDesc _network_content_download_status_window_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_NETWORK_STATUS_WINDOW, WC_NONE,
 	WDF_MODAL,
 	_nested_network_content_download_status_window_widgets, lengthof(_nested_network_content_download_status_window_widgets)
@@ -238,7 +238,7 @@ public:
 					break;
 
 				case CONTENT_TYPE_NEWGRF:
-					ScanNewGRFFiles(NULL);
+					ScanNewGRFFiles(nullptr);
 					break;
 
 				case CONTENT_TYPE_SCENARIO:
@@ -480,7 +480,7 @@ class NetworkContentListWindow : public 
 		}
 
 		/* previously selected item not in list anymore */
-		this->selected = NULL;
+		this->selected = nullptr;
 		this->list_pos = 0;
 	}
 
@@ -501,7 +501,7 @@ class NetworkContentListWindow : public 
 	/** Make sure that the currently selected content info is within the visible part of the matrix */
 	void ScrollToSelected()
 	{
-		if (this->selected == NULL) return;
+		if (this->selected == nullptr) return;
 
 		this->vscroll->ScrollTowards(this->list_pos);
 	}
@@ -521,7 +521,7 @@ public:
 			Window(desc),
 			auto_select(select_all),
 			filter_editbox(EDITBOX_MAX_SIZE),
-			selected(NULL),
+			selected(nullptr),
 			list_pos(0)
 	{
 		this->checkbox_size = maxdim(maxdim(GetSpriteSize(SPR_BOX_EMPTY), GetSpriteSize(SPR_BOX_CHECKED)), GetSpriteSize(SPR_BLOT));
@@ -685,7 +685,7 @@ public:
 		SetDParam(0, this->filesize_sum);
 		DrawString(r.left + DETAIL_LEFT, r.right - DETAIL_RIGHT, r.bottom - FONT_HEIGHT_NORMAL - WD_PAR_VSEP_NORMAL, STR_CONTENT_TOTAL_DOWNLOAD_SIZE);
 
-		if (this->selected == NULL) return;
+		if (this->selected == nullptr) return;
 
 		/* And fill the rest of the details when there's information to place there */
 		DrawStringMultiLine(r.left + WD_INSET_LEFT, r.right - WD_INSET_RIGHT, r.top + DETAIL_TITLE_HEIGHT / 2, r.top + DETAIL_TITLE_HEIGHT, STR_CONTENT_DETAIL_SUBTITLE_UNSELECTED + this->selected->state, TC_FROMSTRING, SA_CENTER);
@@ -779,7 +779,7 @@ public:
 	void OnClick(Point pt, int widget, int click_count) override
 	{
 		if (widget >= WID_NCL_TEXTFILE && widget < WID_NCL_TEXTFILE + TFT_END) {
-			if (this->selected == NULL || this->selected->state != ContentInfo::ALREADY_HERE) return;
+			if (this->selected == nullptr || this->selected->state != ContentInfo::ALREADY_HERE) return;
 
 			ShowContentTextfileWindow((TextfileType)(widget - WID_NCL_TEXTFILE), this->selected);
 			return;
@@ -842,14 +842,14 @@ public:
 				break;
 
 			case WID_NCL_OPEN_URL:
-				if (this->selected != NULL) {
+				if (this->selected != nullptr) {
 					extern void OpenBrowser(const char *url);
 					OpenBrowser(this->selected->url);
 				}
 				break;
 
 			case WID_NCL_DOWNLOAD:
-				if (BringWindowToFrontById(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_CONTENT_DOWNLOAD) == NULL) new NetworkContentDownloadStatusWindow();
+				if (BringWindowToFrontById(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_CONTENT_DOWNLOAD) == nullptr) new NetworkContentDownloadStatusWindow();
 				break;
 
 			case WID_NCL_SEARCH_EXTERNAL:
@@ -893,7 +893,7 @@ public:
 			case WKC_SPACE:
 			case WKC_RETURN:
 				if (keycode == WKC_RETURN || !IsWidgetFocused(WID_NCL_FILTER)) {
-					if (this->selected != NULL) {
+					if (this->selected != nullptr) {
 						_network_content_client.ToggleSelectedState(this->selected);
 						this->content.ForceResort();
 						this->InvalidateData();
@@ -1005,13 +1005,13 @@ public:
 		}
 
 		/* If data == 2 then the status window caused this OnInvalidate */
-		this->SetWidgetDisabledState(WID_NCL_DOWNLOAD, this->filesize_sum == 0 || (FindWindowById(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_CONTENT_DOWNLOAD) != NULL && data != 2));
+		this->SetWidgetDisabledState(WID_NCL_DOWNLOAD, this->filesize_sum == 0 || (FindWindowById(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_CONTENT_DOWNLOAD) != nullptr && data != 2));
 		this->SetWidgetDisabledState(WID_NCL_UNSELECT, this->filesize_sum == 0);
 		this->SetWidgetDisabledState(WID_NCL_SELECT_ALL, !show_select_all);
 		this->SetWidgetDisabledState(WID_NCL_SELECT_UPDATE, !show_select_upgrade);
-		this->SetWidgetDisabledState(WID_NCL_OPEN_URL, this->selected == NULL || StrEmpty(this->selected->url));
+		this->SetWidgetDisabledState(WID_NCL_OPEN_URL, this->selected == nullptr || StrEmpty(this->selected->url));
 		for (TextfileType tft = TFT_BEGIN; tft < TFT_END; tft++) {
-			this->SetWidgetDisabledState(WID_NCL_TEXTFILE + tft, this->selected == NULL || this->selected->state != ContentInfo::ALREADY_HERE || this->selected->GetTextfile(tft) == NULL);
+			this->SetWidgetDisabledState(WID_NCL_TEXTFILE + tft, this->selected == nullptr || this->selected->state != ContentInfo::ALREADY_HERE || this->selected->GetTextfile(tft) == nullptr);
 		}
 
 		this->GetWidget<NWidgetCore>(WID_NCL_CANCEL)->widget_data = this->filesize_sum == 0 ? STR_AI_SETTINGS_CLOSE : STR_AI_LIST_CANCEL;
@@ -1131,7 +1131,7 @@ static WindowDesc _network_content_list_
 
 /**
  * Show the content list window with a given set of content
- * @param cv the content to show, or NULL when it has to search for itself
+ * @param cv the content to show, or nullptr when it has to search for itself
  * @param type1 the first type to (only) show or #CONTENT_TYPE_END to show all.
  * @param type2 the second type to (only) show in addition to type1. If type2 is != #CONTENT_TYPE_END, then also type1 should be != #CONTENT_TYPE_END.
  *   If type2 != #CONTENT_TYPE_END, then type1 != type2 must be true.
@@ -1141,7 +1141,7 @@ void ShowNetworkContentListWindow(Conten
 #if defined(WITH_ZLIB)
 	std::bitset<CONTENT_TYPE_END> types;
 	_network_content_client.Clear();
-	if (cv == NULL) {
+	if (cv == nullptr) {
 		assert(type1 != CONTENT_TYPE_END || type2 == CONTENT_TYPE_END);
 		assert(type1 == CONTENT_TYPE_END || type1 != type2);
 		_network_content_client.RequestContentList(type1);
@@ -1154,11 +1154,11 @@ void ShowNetworkContentListWindow(Conten
 	}
 
 	DeleteWindowById(WC_NETWORK_WINDOW, WN_NETWORK_WINDOW_CONTENT_LIST);
-	new NetworkContentListWindow(&_network_content_list_desc, cv != NULL, types);
+	new NetworkContentListWindow(&_network_content_list_desc, cv != nullptr, types);
 #else
 	ShowErrorMessage(STR_CONTENT_NO_ZLIB, STR_CONTENT_NO_ZLIB_SUB, WL_ERROR);
 	/* Connection failed... clean up the mess */
-	if (cv != NULL) {
+	if (cv != nullptr) {
 		for (ContentInfo *ci : *cv) delete ci;
 	}
 #endif /* WITH_ZLIB */
diff --git a/src/network/network_func.h b/src/network/network_func.h
--- a/src/network/network_func.h
+++ b/src/network/network_func.h
@@ -51,7 +51,7 @@ void NetworkPopulateCompanyStats(Network
 
 void NetworkUpdateClientInfo(ClientID client_id);
 void NetworkClientsToSpectators(CompanyID cid);
-void NetworkClientConnectGame(NetworkAddress address, CompanyID join_as, const char *join_server_password = NULL, const char *join_company_password = NULL);
+void NetworkClientConnectGame(NetworkAddress address, CompanyID join_as, const char *join_server_password = nullptr, const char *join_company_password = nullptr);
 void NetworkClientRequestMove(CompanyID company, const char *pass = "");
 void NetworkClientSendRcon(const char *password, const char *command);
 void NetworkClientSendChat(NetworkAction action, DestType type, int dest, const char *msg, int64 data = 0);
diff --git a/src/network/network_gamelist.cpp b/src/network/network_gamelist.cpp
--- a/src/network/network_gamelist.cpp
+++ b/src/network/network_gamelist.cpp
@@ -22,10 +22,10 @@
 
 #include "../safeguards.h"
 
-NetworkGameList *_network_game_list = NULL;
+NetworkGameList *_network_game_list = nullptr;
 
 /** The games to insert when the GUI thread has time for us. */
-static std::atomic<NetworkGameList *> _network_game_delayed_insertion_list(NULL);
+static std::atomic<NetworkGameList *> _network_game_delayed_insertion_list(nullptr);
 
 /**
  * Add a new item to the linked gamelist, but do it delayed in the next tick
@@ -43,12 +43,12 @@ static void NetworkGameListHandleDelayed
 {
 	while (true) {
 		NetworkGameList *ins_item = _network_game_delayed_insertion_list.load(std::memory_order_relaxed);
-		while (ins_item != NULL && !_network_game_delayed_insertion_list.compare_exchange_weak(ins_item, ins_item->next, std::memory_order_acq_rel)) {}
-		if (ins_item == NULL) break; // No item left.
+		while (ins_item != nullptr && !_network_game_delayed_insertion_list.compare_exchange_weak(ins_item, ins_item->next, std::memory_order_acq_rel)) {}
+		if (ins_item == nullptr) break; // No item left.
 
 		NetworkGameList *item = NetworkGameListAddItem(ins_item->address);
 
-		if (item != NULL) {
+		if (item != nullptr) {
 			if (StrEmpty(item->info.server_name)) {
 				ClearGRFConfigList(&item->info.grfconfig);
 				memset(&item->info, 0, sizeof(item->info));
@@ -78,22 +78,22 @@ NetworkGameList *NetworkGameListAddItem(
 	if (StrEmpty(hostname) ||
 			strcmp(hostname, "0.0.0.0") == 0 ||
 			strcmp(hostname, "::") == 0) {
-		return NULL;
+		return nullptr;
 	}
 
 	NetworkGameList *item, *prev_item;
 
-	prev_item = NULL;
-	for (item = _network_game_list; item != NULL; item = item->next) {
+	prev_item = nullptr;
+	for (item = _network_game_list; item != nullptr; item = item->next) {
 		if (item->address == address) return item;
 		prev_item = item;
 	}
 
 	item = CallocT<NetworkGameList>(1);
-	item->next = NULL;
+	item->next = nullptr;
 	item->address = address;
 
-	if (prev_item == NULL) {
+	if (prev_item == nullptr) {
 		_network_game_list = item;
 	} else {
 		prev_item->next = item;
@@ -111,10 +111,10 @@ NetworkGameList *NetworkGameListAddItem(
  */
 void NetworkGameListRemoveItem(NetworkGameList *remove)
 {
-	NetworkGameList *prev_item = NULL;
-	for (NetworkGameList *item = _network_game_list; item != NULL; item = item->next) {
+	NetworkGameList *prev_item = nullptr;
+	for (NetworkGameList *item = _network_game_list; item != nullptr; item = item->next) {
 		if (remove == item) {
-			if (prev_item == NULL) {
+			if (prev_item == nullptr) {
 				_network_game_list = remove->next;
 			} else {
 				prev_item->next = remove->next;
@@ -123,7 +123,7 @@ void NetworkGameListRemoveItem(NetworkGa
 			/* Remove GRFConfig information */
 			ClearGRFConfigList(&remove->info.grfconfig);
 			free(remove);
-			remove = NULL;
+			remove = nullptr;
 
 			DEBUG(net, 4, "[gamelist] removed server from list");
 			NetworkRebuildHostList();
@@ -148,7 +148,7 @@ void NetworkGameListRequery()
 	if (++requery_cnt < REQUERY_EVERY_X_GAMELOOPS) return;
 	requery_cnt = 0;
 
-	for (NetworkGameList *item = _network_game_list; item != NULL; item = item->next) {
+	for (NetworkGameList *item = _network_game_list; item != nullptr; item = item->next) {
 		item->retries++;
 		if (item->retries < REFRESH_GAMEINFO_X_REQUERIES && (item->online || item->retries >= MAX_GAME_LIST_REQUERY_COUNT)) continue;
 
@@ -165,15 +165,15 @@ void NetworkGameListRequery()
  */
 void NetworkAfterNewGRFScan()
 {
-	for (NetworkGameList *item = _network_game_list; item != NULL; item = item->next) {
+	for (NetworkGameList *item = _network_game_list; item != nullptr; item = item->next) {
 		/* Reset compatibility state */
 		item->info.compatible = item->info.version_compatible;
 
-		for (GRFConfig *c = item->info.grfconfig; c != NULL; c = c->next) {
+		for (GRFConfig *c = item->info.grfconfig; c != nullptr; c = c->next) {
 			assert(HasBit(c->flags, GCF_COPY));
 
 			const GRFConfig *f = FindGRFConfig(c->ident.grfid, FGCM_EXACT, c->ident.md5sum);
-			if (f == NULL) {
+			if (f == nullptr) {
 				/* Don't know the GRF, so mark game incompatible and the (possibly)
 				 * already resolved name for this GRF (another server has sent the
 				 * name of the GRF already. */
diff --git a/src/network/network_gui.cpp b/src/network/network_gui.cpp
--- a/src/network/network_gui.cpp
+++ b/src/network/network_gui.cpp
@@ -129,13 +129,13 @@ public:
 		this->resize_y = 0; // We never resize in this direction
 
 		/* First initialise some variables... */
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			child_wid->SetupSmallestSize(w, init_array);
 			this->smallest_y = max(this->smallest_y, child_wid->smallest_y + child_wid->padding_top + child_wid->padding_bottom);
 		}
 
 		/* ... then in a second pass make sure the 'current' sizes are set. Won't change for most widgets. */
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			child_wid->current_x = child_wid->smallest_x;
 			child_wid->current_y = this->smallest_y;
 		}
@@ -172,7 +172,7 @@ public:
 		uint position = 0; // Place to put next child relative to origin of the container.
 		uint i = rtl ? lengthof(this->visible) - 1 : 0;
 		child_wid = rtl ? this->tail : this->head;
-		while (child_wid != NULL) {
+		while (child_wid != nullptr) {
 			if (this->visible[i]) {
 				child_wid->AssignSizePosition(sizing, x + position, y, child_wid->current_x, this->current_y, rtl);
 				position += child_wid->current_x;
@@ -186,7 +186,7 @@ public:
 	void Draw(const Window *w) override
 	{
 		int i = 0;
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			if (!this->visible[i++]) continue;
 
 			child_wid->Draw(w);
@@ -195,15 +195,15 @@ public:
 
 	NWidgetCore *GetWidgetFromPos(int x, int y) override
 	{
-		if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return NULL;
+		if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return nullptr;
 
 		int i = 0;
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			if (!this->visible[i++]) continue;
 			NWidgetCore *nwid = child_wid->GetWidgetFromPos(x, y);
-			if (nwid != NULL) return nwid;
+			if (nwid != nullptr) return nwid;
 		}
-		return NULL;
+		return nullptr;
 	}
 
 	/**
@@ -252,7 +252,7 @@ protected:
 		/* Create temporary array of games to use for listing */
 		this->servers.clear();
 
-		for (NetworkGameList *ngl = _network_game_list; ngl != NULL; ngl = ngl->next) {
+		for (NetworkGameList *ngl = _network_game_list; ngl != nullptr; ngl = ngl->next) {
 			this->servers.push_back(ngl);
 		}
 
@@ -364,8 +364,8 @@ protected:
 
 	static bool CDECL NGameSearchFilter(NetworkGameList * const *item, StringFilter &sf)
 	{
-		assert(item != NULL);
-		assert((*item) != NULL);
+		assert(item != nullptr);
+		assert((*item) != nullptr);
 
 		sf.ResetState();
 		sf.AddLine((*item)->info.server_name);
@@ -460,7 +460,7 @@ public:
 	NetworkGameWindow(WindowDesc *desc) : Window(desc), name_editbox(NETWORK_CLIENT_NAME_LENGTH), filter_editbox(120)
 	{
 		this->list_pos = SLP_INVALID;
-		this->server = NULL;
+		this->server = nullptr;
 
 		this->lock_offset = 5;
 		this->blot_offset = this->lock_offset + 3 + GetSpriteSize(SPR_LOCK).width;
@@ -479,7 +479,7 @@ public:
 
 		this->last_joined = NetworkGameListAddItem(NetworkAddress(_settings_client.network.last_host, _settings_client.network.last_port));
 		this->server = this->last_joined;
-		if (this->last_joined != NULL) NetworkUDPQueryServer(this->last_joined->address);
+		if (this->last_joined != nullptr) NetworkUDPQueryServer(this->last_joined->address);
 
 		this->requery_timer.SetInterval(MILLISECONDS_PER_TICK);
 
@@ -576,7 +576,7 @@ public:
 
 			case WID_NG_LASTJOINED:
 				/* Draw the last joined server, if any */
-				if (this->last_joined != NULL) this->DrawServerLine(this->last_joined, r.top, this->last_joined == this->server);
+				if (this->last_joined != nullptr) this->DrawServerLine(this->last_joined, r.top, this->last_joined == this->server);
 				break;
 
 			case WID_NG_DETAILS:
@@ -606,16 +606,16 @@ public:
 
 		NetworkGameList *sel = this->server;
 		/* 'Refresh' button invisible if no server selected */
-		this->SetWidgetDisabledState(WID_NG_REFRESH, sel == NULL);
+		this->SetWidgetDisabledState(WID_NG_REFRESH, sel == nullptr);
 		/* 'Join' button disabling conditions */
-		this->SetWidgetDisabledState(WID_NG_JOIN, sel == NULL || // no Selected Server
+		this->SetWidgetDisabledState(WID_NG_JOIN, sel == nullptr || // no Selected Server
 				!sel->online || // Server offline
 				sel->info.clients_on >= sel->info.clients_max || // Server full
 				!sel->info.compatible); // Revision mismatch
 
 		/* 'NewGRF Settings' button invisible if no NewGRF is used */
-		this->GetWidget<NWidgetStacked>(WID_NG_NEWGRF_SEL)->SetDisplayedPlane(sel == NULL || !sel->online || sel->info.grfconfig == NULL);
-		this->GetWidget<NWidgetStacked>(WID_NG_NEWGRF_MISSING_SEL)->SetDisplayedPlane(sel == NULL || !sel->online || sel->info.grfconfig == NULL || !sel->info.version_compatible || sel->info.compatible);
+		this->GetWidget<NWidgetStacked>(WID_NG_NEWGRF_SEL)->SetDisplayedPlane(sel == nullptr || !sel->online || sel->info.grfconfig == nullptr);
+		this->GetWidget<NWidgetStacked>(WID_NG_NEWGRF_MISSING_SEL)->SetDisplayedPlane(sel == nullptr || !sel->online || sel->info.grfconfig == nullptr || !sel->info.version_compatible || sel->info.compatible);
 
 		this->DrawWidgets();
 	}
@@ -628,7 +628,7 @@ public:
 
 		/* Draw the right menu */
 		GfxFillRect(r.left + 1, r.top + 1, r.right - 1, r.top + detail_height - 1, PC_DARK_BLUE);
-		if (sel == NULL) {
+		if (sel == nullptr) {
 			DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + 6 + 4 + FONT_HEIGHT_NORMAL, STR_NETWORK_SERVER_LIST_GAME_INFO, TC_FROMSTRING, SA_HOR_CENTER);
 		} else if (!sel->online) {
 			DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + 6 + 4 + FONT_HEIGHT_NORMAL, sel->info.server_name, TC_ORANGE, SA_HOR_CENTER); // game name
@@ -722,8 +722,8 @@ public:
 
 			case WID_NG_MATRIX: { // Show available network games
 				uint id_v = this->vscroll->GetScrolledRowFromWidget(pt.y, this, WID_NG_MATRIX);
-				this->server = (id_v < this->servers.size()) ? this->servers[id_v] : NULL;
-				this->list_pos = (server == NULL) ? SLP_INVALID : id_v;
+				this->server = (id_v < this->servers.size()) ? this->servers[id_v] : nullptr;
+				this->list_pos = (server == nullptr) ? SLP_INVALID : id_v;
 				this->SetDirty();
 
 				/* FIXME the disabling should go into some InvalidateData, which is called instead of the SetDirty */
@@ -732,7 +732,7 @@ public:
 			}
 
 			case WID_NG_LASTJOINED: {
-				if (this->last_joined != NULL) {
+				if (this->last_joined != nullptr) {
 					this->server = this->last_joined;
 
 					/* search the position of the newly selected server */
@@ -767,7 +767,7 @@ public:
 				break;
 
 			case WID_NG_JOIN: // Join Game
-				if (this->server != NULL) {
+				if (this->server != nullptr) {
 					seprintf(_settings_client.network.last_host, lastof(_settings_client.network.last_host), "%s", this->server->address.GetHostname());
 					_settings_client.network.last_port = this->server->address.GetPort();
 					ShowNetworkLobbyWindow(this->server);
@@ -775,15 +775,15 @@ public:
 				break;
 
 			case WID_NG_REFRESH: // Refresh
-				if (this->server != NULL) NetworkUDPQueryServer(this->server->address);
+				if (this->server != nullptr) NetworkUDPQueryServer(this->server->address);
 				break;
 
 			case WID_NG_NEWGRF: // NewGRF Settings
-				if (this->server != NULL) ShowNewGRFSettings(false, false, false, &this->server->info.grfconfig);
+				if (this->server != nullptr) ShowNewGRFSettings(false, false, false, &this->server->info.grfconfig);
 				break;
 
 			case WID_NG_NEWGRF_MISSING: // Find missing content online
-				if (this->server != NULL) ShowMissingContentWindow(this->server->info.grfconfig);
+				if (this->server != nullptr) ShowMissingContentWindow(this->server->info.grfconfig);
 				break;
 		}
 	}
@@ -862,11 +862,11 @@ public:
 			return ES_HANDLED;
 		}
 
-		if (this->server != NULL) {
+		if (this->server != nullptr) {
 			if (keycode == WKC_DELETE) { // Press 'delete' to remove servers
 				NetworkGameListRemoveItem(this->server);
-				if (this->server == this->last_joined) this->last_joined = NULL;
-				this->server = NULL;
+				if (this->server == this->last_joined) this->last_joined = nullptr;
+				this->server = nullptr;
 				this->list_pos = SLP_INVALID;
 			}
 		}
@@ -1244,7 +1244,7 @@ struct NetworkStartServerWindow : public
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
 		if (this->widget_id == WID_NSS_SETPWD) {
 			strecpy(_settings_client.network.server_password, str, lastof(_settings_client.network.server_password));
@@ -1344,7 +1344,7 @@ static const NWidgetPart _nested_network
 };
 
 static WindowDesc _network_start_server_window_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_NETWORK_WINDOW, WC_NONE,
 	0,
 	_nested_network_start_server_window_widgets, lengthof(_nested_network_start_server_window_widgets)
@@ -1631,7 +1631,7 @@ static const NWidgetPart _nested_network
 };
 
 static WindowDesc _network_lobby_window_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_NETWORK_WINDOW, WC_NONE,
 	0,
 	_nested_network_lobby_window_widgets, lengthof(_nested_network_lobby_window_widgets)
@@ -1660,7 +1660,7 @@ static void ShowNetworkLobbyWindow(Netwo
 NetworkCompanyInfo *GetLobbyCompanyInfo(CompanyID company)
 {
 	NetworkLobbyWindow *lobby = dynamic_cast<NetworkLobbyWindow*>(FindWindowById(WC_NETWORK_WINDOW, WN_NETWORK_WINDOW_LOBBY));
-	return (lobby != NULL && company < MAX_COMPANIES) ? &lobby->company_info[company] : NULL;
+	return (lobby != nullptr && company < MAX_COMPANIES) ? &lobby->company_info[company] : nullptr;
 }
 
 /* The window below gives information about the connected clients
@@ -1680,7 +1680,7 @@ static const NWidgetPart _nested_client_
 };
 
 static WindowDesc _client_list_popup_desc(
-	WDP_AUTO, NULL, 0, 0,
+	WDP_AUTO, nullptr, 0, 0,
 	WC_CLIENT_LIST_POPUP, WC_CLIENT_LIST,
 	0,
 	_nested_client_list_popup_widgets, lengthof(_nested_client_list_popup_widgets)
@@ -1825,7 +1825,7 @@ struct NetworkClientListPopupWindow : Wi
 		} else {
 			if (index < this->actions.size() && _cursor.pos.y >= this->top) {
 				const NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(this->client_id);
-				if (ci != NULL) this->actions[index].proc(ci);
+				if (ci != nullptr) this->actions[index].proc(ci);
 			}
 
 			DeleteWindowByClass(WC_CLIENT_LIST_POPUP);
@@ -1840,7 +1840,7 @@ static void PopupClientList(ClientID cli
 {
 	DeleteWindowByClass(WC_CLIENT_LIST_POPUP);
 
-	if (NetworkClientInfo::GetByClientID(client_id) == NULL) return;
+	if (NetworkClientInfo::GetByClientID(client_id) == nullptr) return;
 
 	new NetworkClientListPopupWindow(&_client_list_popup_desc, x, y, client_id);
 }
@@ -1986,7 +1986,7 @@ struct NetworkClientListWindow : Window 
 				client_no--;
 			}
 
-			if (ci != NULL) PopupClientList(ci->client_id, pt.x + this->left, pt.y + this->top);
+			if (ci != nullptr) PopupClientList(ci->client_id, pt.x + this->left, pt.y + this->top);
 		}
 	}
 
@@ -2133,7 +2133,7 @@ static const NWidgetPart _nested_network
 };
 
 static WindowDesc _network_join_status_window_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_NETWORK_STATUS_WINDOW, WC_NONE,
 	WDF_MODAL,
 	_nested_network_join_status_window_widgets, lengthof(_nested_network_join_status_window_widgets)
@@ -2148,7 +2148,7 @@ void ShowJoinStatusWindow()
 void ShowNetworkNeedPassword(NetworkPasswordType npt)
 {
 	NetworkJoinStatusWindow *w = (NetworkJoinStatusWindow *)FindWindowById(WC_NETWORK_STATUS_WINDOW, WN_NETWORK_STATUS_WINDOW_JOIN);
-	if (w == NULL) return;
+	if (w == nullptr) return;
 	w->password_type = npt;
 
 	StringID caption;
@@ -2227,7 +2227,7 @@ static const NWidgetPart _nested_network
 };
 
 static WindowDesc _network_company_password_window_desc(
-	WDP_AUTO, NULL, 0, 0,
+	WDP_AUTO, nullptr, 0, 0,
 	WC_COMPANY_PASSWORD_WINDOW, WC_NONE,
 	0,
 	_nested_network_company_password_window_widgets, lengthof(_nested_network_company_password_window_widgets)
diff --git a/src/network/network_internal.h b/src/network/network_internal.h
--- a/src/network/network_internal.h
+++ b/src/network/network_internal.h
@@ -149,8 +149,8 @@ bool IsNetworkCompatibleVersion(const ch
  * Everything we need to know about a command to be able to execute it.
  */
 struct CommandPacket : CommandContainer {
-	/** Make sure the pointer is NULL. */
-	CommandPacket() : next(NULL), company(INVALID_COMPANY), frame(0), my_cmd(false) {}
+	/** Make sure the pointer is nullptr. */
+	CommandPacket() : next(nullptr), company(INVALID_COMPANY), frame(0), my_cmd(false) {}
 	CommandPacket *next; ///< the next command packet (if in queue)
 	CompanyID company;   ///< company that is executing the command
 	uint32 frame;        ///< the frame in which this packet is executed
diff --git a/src/network/network_server.cpp b/src/network/network_server.cpp
--- a/src/network/network_server.cpp
+++ b/src/network/network_server.cpp
@@ -67,7 +67,7 @@ struct PacketWriter : SaveFilter {
 	 * Create the packet writer.
 	 * @param cs The socket handler we're making the packets for.
 	 */
-	PacketWriter(ServerNetworkGameSocketHandler *cs) : SaveFilter(NULL), cs(cs), current(NULL), total_size(0), packets(NULL)
+	PacketWriter(ServerNetworkGameSocketHandler *cs) : SaveFilter(nullptr), cs(cs), current(nullptr), total_size(0), packets(nullptr)
 	{
 	}
 
@@ -76,11 +76,11 @@ struct PacketWriter : SaveFilter {
 	{
 		std::unique_lock<std::mutex> lock(this->mutex);
 
-		if (this->cs != NULL) this->exit_sig.wait(lock);
+		if (this->cs != nullptr) this->exit_sig.wait(lock);
 
 		/* This must all wait until the Destroy function is called. */
 
-		while (this->packets != NULL) {
+		while (this->packets != nullptr) {
 			Packet *p = this->packets->next;
 			delete this->packets;
 			this->packets = p;
@@ -93,7 +93,7 @@ struct PacketWriter : SaveFilter {
 	 * Begin the destruction of this packet writer. It can happen in two ways:
 	 * in the first case the client disconnected while saving the map. In this
 	 * case the saving has not finished and killed this PacketWriter. In that
-	 * case we simply set cs to NULL, triggering the appending to fail due to
+	 * case we simply set cs to nullptr, triggering the appending to fail due to
 	 * the connection problem and eventually triggering the destructor. In the
 	 * second case the destructor is already called, and it is waiting for our
 	 * signal which we will send. Only then the packets will be removed by the
@@ -103,7 +103,7 @@ struct PacketWriter : SaveFilter {
 	{
 		std::unique_lock<std::mutex> lock(this->mutex);
 
-		this->cs = NULL;
+		this->cs = nullptr;
 
 		this->exit_sig.notify_all();
 		lock.unlock();
@@ -124,7 +124,7 @@ struct PacketWriter : SaveFilter {
 	 */
 	bool HasPackets()
 	{
-		return this->packets != NULL;
+		return this->packets != nullptr;
 	}
 
 	/**
@@ -136,7 +136,7 @@ struct PacketWriter : SaveFilter {
 
 		Packet *p = this->packets;
 		this->packets = p->next;
-		p->next = NULL;
+		p->next = nullptr;
 
 		return p;
 	}
@@ -144,23 +144,23 @@ struct PacketWriter : SaveFilter {
 	/** Append the current packet to the queue. */
 	void AppendQueue()
 	{
-		if (this->current == NULL) return;
+		if (this->current == nullptr) return;
 
 		Packet **p = &this->packets;
-		while (*p != NULL) {
+		while (*p != nullptr) {
 			p = &(*p)->next;
 		}
 		*p = this->current;
 
-		this->current = NULL;
+		this->current = nullptr;
 	}
 
 	void Write(byte *buf, size_t size) override
 	{
 		/* We want to abort the saving when the socket is closed. */
-		if (this->cs == NULL) SlError(STR_NETWORK_ERROR_LOSTCONNECTION);
+		if (this->cs == nullptr) SlError(STR_NETWORK_ERROR_LOSTCONNECTION);
 
-		if (this->current == NULL) this->current = new Packet(PACKET_SERVER_MAP_DATA);
+		if (this->current == nullptr) this->current = new Packet(PACKET_SERVER_MAP_DATA);
 
 		std::lock_guard<std::mutex> lock(this->mutex);
 
@@ -183,7 +183,7 @@ struct PacketWriter : SaveFilter {
 	void Finish() override
 	{
 		/* We want to abort the saving when the socket is closed. */
-		if (this->cs == NULL) SlError(STR_NETWORK_ERROR_LOSTCONNECTION);
+		if (this->cs == nullptr) SlError(STR_NETWORK_ERROR_LOSTCONNECTION);
 
 		std::lock_guard<std::mutex> lock(this->mutex);
 
@@ -226,9 +226,9 @@ ServerNetworkGameSocketHandler::~ServerN
 	if (_redirect_console_to_client == this->client_id) _redirect_console_to_client = INVALID_CLIENT_ID;
 	OrderBackup::ResetUser(this->client_id);
 
-	if (this->savegame != NULL) {
+	if (this->savegame != nullptr) {
 		this->savegame->Destroy();
-		this->savegame = NULL;
+		this->savegame = nullptr;
 	}
 }
 
@@ -236,12 +236,12 @@ Packet *ServerNetworkGameSocketHandler::
 {
 	/* Only allow receiving when we have some buffer free; this value
 	 * can go negative, but eventually it will become positive again. */
-	if (this->receive_limit <= 0) return NULL;
+	if (this->receive_limit <= 0) return nullptr;
 
 	/* We can receive a packet, so try that and if needed account for
 	 * the amount of received data. */
 	Packet *p = this->NetworkTCPSocketHandler::ReceivePacket();
-	if (p != NULL) this->receive_limit -= p->size;
+	if (p != nullptr) this->receive_limit -= p->size;
 	return p;
 }
 
@@ -264,7 +264,7 @@ NetworkRecvStatus ServerNetworkGameSocke
 
 		this->GetClientName(client_name, lastof(client_name));
 
-		NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, client_name, NULL, STR_NETWORK_ERROR_CLIENT_CONNECTION_LOST);
+		NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, client_name, nullptr, STR_NETWORK_ERROR_CLIENT_CONNECTION_LOST);
 
 		/* Inform other clients of this... strange leaving ;) */
 		FOR_ALL_CLIENT_SOCKETS(new_cs) {
@@ -361,7 +361,7 @@ NetworkRecvStatus ServerNetworkGameSocke
 
 	/* Add the local player (if not dedicated) */
 	const NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(CLIENT_ID_SERVER);
-	if (ci != NULL && Company::IsValidID(ci->client_playas)) {
+	if (ci != nullptr && Company::IsValidID(ci->client_playas)) {
 		strecpy(clients[ci->client_playas], ci->client_name, lastof(clients[ci->client_playas]));
 	}
 
@@ -371,7 +371,7 @@ NetworkRecvStatus ServerNetworkGameSocke
 		((ServerNetworkGameSocketHandler*)csi)->GetClientName(client_name, lastof(client_name));
 
 		ci = csi->GetInfo();
-		if (ci != NULL && Company::IsValidID(ci->client_playas)) {
+		if (ci != nullptr && Company::IsValidID(ci->client_playas)) {
 			if (!StrEmpty(clients[ci->client_playas])) {
 				strecat(clients[ci->client_playas], ", ", lastof(clients[ci->client_playas]));
 			}
@@ -434,7 +434,7 @@ NetworkRecvStatus ServerNetworkGameSocke
 
 		DEBUG(net, 1, "'%s' made an error and has been disconnected. Reason: '%s'", client_name, str);
 
-		NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, client_name, NULL, strid);
+		NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, client_name, nullptr, strid);
 
 		FOR_ALL_CLIENT_SOCKETS(new_cs) {
 			if (new_cs->status > STATUS_AUTHORIZED && new_cs != this) {
@@ -463,12 +463,12 @@ NetworkRecvStatus ServerNetworkGameSocke
 	const GRFConfig *c;
 	uint grf_count = 0;
 
-	for (c = _grfconfig; c != NULL; c = c->next) {
+	for (c = _grfconfig; c != nullptr; c = c->next) {
 		if (!HasBit(c->flags, GCF_STATIC)) grf_count++;
 	}
 
 	p->Send_uint8 (grf_count);
-	for (c = _grfconfig; c != NULL; c = c->next) {
+	for (c = _grfconfig; c != nullptr; c = c->next) {
 		if (!HasBit(c->flags, GCF_STATIC)) this->SendGRFIdentifier(p, &c->ident);
 	}
 
@@ -607,7 +607,7 @@ NetworkRecvStatus ServerNetworkGameSocke
 		if (last_packet) {
 			/* Done reading, make sure saving is done as well */
 			this->savegame->Destroy();
-			this->savegame = NULL;
+			this->savegame = nullptr;
 
 			/* Set the status to DONE_MAP, no we will wait for the client
 			 *  to send it is ready (maybe that happens like never ;)) */
@@ -615,17 +615,17 @@ NetworkRecvStatus ServerNetworkGameSocke
 
 			/* Find the best candidate for joining, i.e. the first joiner. */
 			NetworkClientSocket *new_cs;
-			NetworkClientSocket *best = NULL;
+			NetworkClientSocket *best = nullptr;
 			FOR_ALL_CLIENT_SOCKETS(new_cs) {
 				if (new_cs->status == STATUS_MAP_WAIT) {
-					if (best == NULL || best->GetInfo()->join_date > new_cs->GetInfo()->join_date || (best->GetInfo()->join_date == new_cs->GetInfo()->join_date && best->client_id > new_cs->client_id)) {
+					if (best == nullptr || best->GetInfo()->join_date > new_cs->GetInfo()->join_date || (best->GetInfo()->join_date == new_cs->GetInfo()->join_date && best->client_id > new_cs->client_id)) {
 						best = new_cs;
 					}
 				}
 			}
 
 			/* Is there someone else to join? */
-			if (best != NULL) {
+			if (best != nullptr) {
 				/* Let the first start joining. */
 				best->status = STATUS_AUTHORIZED;
 				best->SendMap();
@@ -946,9 +946,9 @@ NetworkRecvStatus ServerNetworkGameSocke
 
 	this->status = STATUS_NEWGRFS_CHECK;
 
-	if (_grfconfig == NULL) {
+	if (_grfconfig == nullptr) {
 		/* Behave as if we received PACKET_CLIENT_NEWGRFS_CHECKED */
-		return this->Receive_CLIENT_NEWGRFS_CHECKED(NULL);
+		return this->Receive_CLIENT_NEWGRFS_CHECKED(nullptr);
 	}
 
 	return this->SendNewGRFCheck();
@@ -1032,7 +1032,7 @@ NetworkRecvStatus ServerNetworkGameSocke
 
 		this->GetClientName(client_name, lastof(client_name));
 
-		NetworkTextMessage(NETWORK_ACTION_JOIN, CC_DEFAULT, false, client_name, NULL, this->client_id);
+		NetworkTextMessage(NETWORK_ACTION_JOIN, CC_DEFAULT, false, client_name, nullptr, this->client_id);
 
 		/* Mark the client as pre-active, and wait for an ACK
 		 *  so we know he is done loading and in sync with us */
@@ -1089,7 +1089,7 @@ NetworkRecvStatus ServerNetworkGameSocke
 
 	NetworkClientInfo *ci = this->GetInfo();
 
-	if (err != NULL) {
+	if (err != nullptr) {
 		IConsolePrintF(CC_ERROR, "WARNING: %s from client %d (IP: %s).", err, ci->client_id, this->GetClientIP());
 		return this->SendError(NETWORK_ERROR_NOT_EXPECTED);
 	}
@@ -1155,7 +1155,7 @@ NetworkRecvStatus ServerNetworkGameSocke
 
 	DEBUG(net, 2, "'%s' reported an error and is closing its connection (%s)", client_name, str);
 
-	NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, client_name, NULL, strid);
+	NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, client_name, nullptr, strid);
 
 	FOR_ALL_CLIENT_SOCKETS(new_cs) {
 		if (new_cs->status > STATUS_AUTHORIZED) {
@@ -1182,7 +1182,7 @@ NetworkRecvStatus ServerNetworkGameSocke
 
 	this->GetClientName(client_name, lastof(client_name));
 
-	NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, client_name, NULL, STR_NETWORK_MESSAGE_CLIENT_LEAVING);
+	NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, client_name, nullptr, STR_NETWORK_MESSAGE_CLIENT_LEAVING);
 
 	FOR_ALL_CLIENT_SOCKETS(new_cs) {
 		if (new_cs->status > STATUS_AUTHORIZED && new_cs != this) {
@@ -1262,7 +1262,7 @@ void NetworkServerSendChat(NetworkAction
 			if ((ClientID)dest == CLIENT_ID_SERVER) {
 				ci = NetworkClientInfo::GetByClientID(from_id);
 				/* Display the text locally, and that is it */
-				if (ci != NULL) {
+				if (ci != nullptr) {
 					NetworkTextMessage(action, GetDrawStringCompanyColour(ci->client_playas), false, ci->client_name, msg, data);
 
 					if (_settings_client.network.server_admin_chat) {
@@ -1284,7 +1284,7 @@ void NetworkServerSendChat(NetworkAction
 				if (from_id == CLIENT_ID_SERVER) {
 					ci = NetworkClientInfo::GetByClientID(from_id);
 					ci_to = NetworkClientInfo::GetByClientID((ClientID)dest);
-					if (ci != NULL && ci_to != NULL) {
+					if (ci != nullptr && ci_to != nullptr) {
 						NetworkTextMessage(action, GetDrawStringCompanyColour(ci->client_playas), true, ci_to->client_name, msg, data);
 					}
 				} else {
@@ -1301,10 +1301,10 @@ void NetworkServerSendChat(NetworkAction
 			/* If this is false, the message is already displayed on the client who sent it. */
 			bool show_local = true;
 			/* Find all clients that belong to this company */
-			ci_to = NULL;
+			ci_to = nullptr;
 			FOR_ALL_CLIENT_SOCKETS(cs) {
 				ci = cs->GetInfo();
-				if (ci != NULL && ci->client_playas == (CompanyID)dest) {
+				if (ci != nullptr && ci->client_playas == (CompanyID)dest) {
 					cs->SendChat(action, from_id, false, msg, data);
 					if (cs->client_id == from_id) show_local = false;
 					ci_to = ci; // Remember a client that is in the company for company-name
@@ -1318,17 +1318,17 @@ void NetworkServerSendChat(NetworkAction
 
 			ci = NetworkClientInfo::GetByClientID(from_id);
 			ci_own = NetworkClientInfo::GetByClientID(CLIENT_ID_SERVER);
-			if (ci != NULL && ci_own != NULL && ci_own->client_playas == dest) {
+			if (ci != nullptr && ci_own != nullptr && ci_own->client_playas == dest) {
 				NetworkTextMessage(action, GetDrawStringCompanyColour(ci->client_playas), false, ci->client_name, msg, data);
 				if (from_id == CLIENT_ID_SERVER) show_local = false;
 				ci_to = ci_own;
 			}
 
 			/* There is no such client */
-			if (ci_to == NULL) break;
+			if (ci_to == nullptr) break;
 
 			/* Display the message locally (so you know you have sent it) */
-			if (ci != NULL && show_local) {
+			if (ci != nullptr && show_local) {
 				if (from_id == CLIENT_ID_SERVER) {
 					char name[NETWORK_NAME_LENGTH];
 					StringID str = Company::IsValidID(ci_to->client_playas) ? STR_COMPANY_NAME : STR_NETWORK_SPECTATORS;
@@ -1357,7 +1357,7 @@ void NetworkServerSendChat(NetworkAction
 			NetworkAdminChat(action, desttype, from_id, msg, data, from_admin);
 
 			ci = NetworkClientInfo::GetByClientID(from_id);
-			if (ci != NULL) {
+			if (ci != nullptr) {
 				NetworkTextMessage(action, GetDrawStringCompanyColour(ci->client_playas), false, ci->client_name, msg, data);
 			}
 			break;
@@ -1428,7 +1428,7 @@ NetworkRecvStatus ServerNetworkGameSocke
 
 	if (this->HasClientQuit()) return NETWORK_RECV_STATUS_CONN_LOST;
 
-	if (ci != NULL) {
+	if (ci != nullptr) {
 		/* Display change */
 		if (NetworkFindName(client_name, lastof(client_name))) {
 			NetworkTextMessage(NETWORK_ACTION_NAME_CHANGE, CC_DEFAULT, false, ci->client_name, client_name);
@@ -1591,7 +1591,7 @@ void NetworkUpdateClientInfo(ClientID cl
 	NetworkClientSocket *cs;
 	NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(client_id);
 
-	if (ci == NULL) return;
+	if (ci == nullptr) return;
 
 	DEBUG(desync, 1, "client: %08x; %02x; %02x; %04x", _date, _date_fract, (int)ci->client_playas, client_id);
 
@@ -1712,7 +1712,7 @@ bool NetworkFindName(char *new_name, con
 		}
 		/* Check if it is the same as the server-name */
 		ci = NetworkClientInfo::GetByClientID(CLIENT_ID_SERVER);
-		if (ci != NULL) {
+		if (ci != nullptr) {
 			if (strcmp(ci->client_name, new_name) == 0) found_name = false; // name already in use
 		}
 
@@ -1743,7 +1743,7 @@ bool NetworkServerChangeClientName(Clien
 	}
 
 	ci = NetworkClientInfo::GetByClientID(client_id);
-	if (ci == NULL) return false;
+	if (ci == nullptr) return false;
 
 	NetworkTextMessage(NETWORK_ACTION_NAME_CHANGE, CC_DEFAULT, true, ci->client_name, new_name);
 
@@ -1778,7 +1778,7 @@ void NetworkServerSetCompanyPassword(Com
 static void NetworkHandleCommandQueue(NetworkClientSocket *cs)
 {
 	CommandPacket *cp;
-	while ((cp = cs->outgoing_queue.Pop()) != NULL) {
+	while ((cp = cs->outgoing_queue.Pop()) != nullptr) {
 		cs->SendCommand(cp);
 		free(cp);
 	}
@@ -1964,7 +1964,7 @@ void NetworkServerShowStatusToConsole()
 	NetworkClientSocket *cs;
 	FOR_ALL_CLIENT_SOCKETS(cs) {
 		NetworkClientInfo *ci = cs->GetInfo();
-		if (ci == NULL) continue;
+		if (ci == nullptr) continue;
 		uint lag = NetworkCalculateLag(cs);
 		const char *status;
 
@@ -2131,7 +2131,7 @@ void ServerNetworkGameSocketHandler::Get
 {
 	const NetworkClientInfo *ci = this->GetInfo();
 
-	if (ci == NULL || StrEmpty(ci->client_name)) {
+	if (ci == nullptr || StrEmpty(ci->client_name)) {
 		seprintf(client_name, last, "Client #%4d", this->client_id);
 	} else {
 		strecpy(client_name, ci->client_name, last);
@@ -2162,12 +2162,12 @@ void NetworkPrintClients()
 
 /**
  * Perform all the server specific administration of a new company.
- * @param c  The newly created company; can't be NULL.
- * @param ci The client information of the client that made the company; can be NULL.
+ * @param c  The newly created company; can't be nullptr.
+ * @param ci The client information of the client that made the company; can be nullptr.
  */
 void NetworkServerNewCompany(const Company *c, NetworkClientInfo *ci)
 {
-	assert(c != NULL);
+	assert(c != nullptr);
 
 	if (!_network_server) return;
 
@@ -2175,18 +2175,18 @@ void NetworkServerNewCompany(const Compa
 	_network_company_states[c->index].password[0] = '\0';
 	NetworkServerUpdateCompanyPassworded(c->index, false);
 
-	if (ci != NULL) {
-		/* ci is NULL when replaying, or for AIs. In neither case there is a client. */
+	if (ci != nullptr) {
+		/* ci is nullptr when replaying, or for AIs. In neither case there is a client. */
 		ci->client_playas = c->index;
 		NetworkUpdateClientInfo(ci->client_id);
-		NetworkSendCommand(0, 0, 0, CMD_RENAME_PRESIDENT, NULL, ci->client_name, c->index);
+		NetworkSendCommand(0, 0, 0, CMD_RENAME_PRESIDENT, nullptr, ci->client_name, c->index);
 	}
 
 	/* Announce new company on network. */
 	NetworkAdminCompanyInfo(c, true);
 
-	if (ci != NULL) {
-		/* ci is NULL when replaying, or for AIs. In neither case there is a client.
+	if (ci != nullptr) {
+		/* ci is nullptr when replaying, or for AIs. In neither case there is a client.
 		   We need to send Admin port update here so that they first know about the new company
 		   and then learn about a possibly joining client (see FS#6025) */
 		NetworkServerSendChat(NETWORK_ACTION_COMPANY_NEW, DESTTYPE_BROADCAST, 0, "", ci->client_id, c->index + 1);
diff --git a/src/network/network_udp.cpp b/src/network/network_udp.cpp
--- a/src/network/network_udp.cpp
+++ b/src/network/network_udp.cpp
@@ -45,9 +45,9 @@ static const uint32 ADVERTISE_NORMAL_INT
 static const uint32 ADVERTISE_RETRY_INTERVAL  =      10 * 1000; ///< re-advertise when no response after this many ms (10 seconds)
 static const uint32 ADVERTISE_RETRY_TIMES     =              3; ///< give up re-advertising after this much failed retries
 
-NetworkUDPSocketHandler *_udp_client_socket = NULL; ///< udp client socket
-NetworkUDPSocketHandler *_udp_server_socket = NULL; ///< udp server socket
-NetworkUDPSocketHandler *_udp_master_socket = NULL; ///< udp master socket
+NetworkUDPSocketHandler *_udp_client_socket = nullptr; ///< udp client socket
+NetworkUDPSocketHandler *_udp_server_socket = nullptr; ///< udp server socket
+NetworkUDPSocketHandler *_udp_master_socket = nullptr; ///< udp master socket
 
 /**
  * Helper function doing the actual work for querying the server.
@@ -69,7 +69,7 @@ static void DoNetworkUDPQueryServer(Netw
 	if (needs_mutex) lock.lock();
 	/* Init the packet */
 	Packet p(PACKET_UDP_CLIENT_FIND_SERVER);
-	if (_udp_client_socket != NULL) _udp_client_socket->SendPacket(&p, &address);
+	if (_udp_client_socket != nullptr) _udp_client_socket->SendPacket(&p, &address);
 }
 
 /**
@@ -79,7 +79,7 @@ static void DoNetworkUDPQueryServer(Netw
  */
 void NetworkUDPQueryServer(NetworkAddress address, bool manually)
 {
-	if (address.IsResolved() || !StartNewThread(NULL, "ottd:udp-query", &DoNetworkUDPQueryServer, std::move(address), true, std::move(manually))) {
+	if (address.IsResolved() || !StartNewThread(nullptr, "ottd:udp-query", &DoNetworkUDPQueryServer, std::move(address), true, std::move(manually))) {
 		DoNetworkUDPQueryServer(address, true, manually);
 	}
 }
@@ -261,7 +261,7 @@ void ServerNetworkUDPSocketHandler::Rece
 
 		/* Find the matching GRF file */
 		f = FindGRFConfig(c.grfid, FGCM_EXACT, c.md5sum);
-		if (f == NULL) continue; // The GRF is unknown to this server
+		if (f == nullptr) continue; // The GRF is unknown to this server
 
 		/* If the reply might exceed the size of the packet, only reply
 		 * the current list and do not send the other data.
@@ -332,7 +332,7 @@ void ClientNetworkUDPSocketHandler::Rece
 		const GRFConfig *c;
 		uint in_request_count = 0;
 
-		for (c = item->info.grfconfig; c != NULL; c = c->next) {
+		for (c = item->info.grfconfig; c != nullptr; c = c->next) {
 			if (c->status == GCS_NOT_FOUND) item->info.compatible = false;
 			if (c->status != GCS_NOT_FOUND || strcmp(c->GetName(), UNKNOWN_GRF_NAME_PLACEHOLDER) != 0) continue;
 			in_request[in_request_count] = c;
@@ -431,7 +431,7 @@ void ClientNetworkUDPSocketHandler::Rece
 		 * If it exists and not resolved yet, then name of the fake GRF is
 		 * overwritten with the name from the reply. */
 		GRFTextWrapper *unknown_name = FindUnknownGRFName(c.grfid, c.md5sum, false);
-		if (unknown_name != NULL && strcmp(GetGRFStringFromGRFText(unknown_name->text), UNKNOWN_GRF_NAME_PLACEHOLDER) == 0) {
+		if (unknown_name != nullptr && strcmp(GetGRFStringFromGRFText(unknown_name->text), UNKNOWN_GRF_NAME_PLACEHOLDER) == 0) {
 			AddGRFTextToList(&unknown_name->text, name);
 		}
 	}
@@ -441,7 +441,7 @@ void ClientNetworkUDPSocketHandler::Hand
 {
 	/* Find the matching GRF file */
 	const GRFConfig *f = FindGRFConfig(config->ident.grfid, FGCM_EXACT, config->ident.md5sum);
-	if (f == NULL) {
+	if (f == nullptr) {
 		/* Don't know the GRF, so mark game incompatible and the (possibly)
 		 * already resolved name for this GRF (another server has sent the
 		 * name of the GRF already */
@@ -521,7 +521,7 @@ static void NetworkUDPRemoveAdvertiseThr
 	p.Send_uint16(_settings_client.network.server_port);
 
 	std::lock_guard<std::mutex> lock(_network_udp_mutex);
-	if (_udp_master_socket != NULL) _udp_master_socket->SendPacket(&p, &out_addr, true);
+	if (_udp_master_socket != nullptr) _udp_master_socket->SendPacket(&p, &out_addr, true);
 }
 
 /**
@@ -533,7 +533,7 @@ void NetworkUDPRemoveAdvertise(bool bloc
 	/* Check if we are advertising */
 	if (!_networking || !_network_server || !_network_udp_server) return;
 
-	if (blocking || !StartNewThread(NULL, "ottd:udp-advert", &NetworkUDPRemoveAdvertiseThread)) {
+	if (blocking || !StartNewThread(nullptr, "ottd:udp-advert", &NetworkUDPRemoveAdvertiseThread)) {
 		NetworkUDPRemoveAdvertiseThread();
 	}
 }
@@ -573,7 +573,7 @@ static void NetworkUDPAdvertiseThread()
 	p.Send_uint64(_session_key);
 
 	std::lock_guard<std::mutex> lock(_network_udp_mutex);
-	if (_udp_master_socket != NULL) _udp_master_socket->SendPacket(&p, &out_addr, true);
+	if (_udp_master_socket != nullptr) _udp_master_socket->SendPacket(&p, &out_addr, true);
 }
 
 /**
@@ -614,7 +614,7 @@ void NetworkUDPAdvertise()
 	if (_next_advertisement < _last_advertisement) _next_advertisement = UINT32_MAX;
 	if (_next_retry         < _last_advertisement) _next_retry         = UINT32_MAX;
 
-	if (!StartNewThread(NULL, "ottd:udp-advert", &NetworkUDPAdvertiseThread)) {
+	if (!StartNewThread(nullptr, "ottd:udp-advert", &NetworkUDPAdvertiseThread)) {
 		NetworkUDPAdvertiseThread();
 	}
 }
@@ -623,10 +623,10 @@ void NetworkUDPAdvertise()
 void NetworkUDPInitialize()
 {
 	/* If not closed, then do it. */
-	if (_udp_server_socket != NULL) NetworkUDPClose();
+	if (_udp_server_socket != nullptr) NetworkUDPClose();
 
 	DEBUG(net, 1, "[udp] initializing listeners");
-	assert(_udp_client_socket == NULL && _udp_server_socket == NULL && _udp_master_socket == NULL);
+	assert(_udp_client_socket == nullptr && _udp_server_socket == nullptr && _udp_master_socket == nullptr);
 
 	std::lock_guard<std::mutex> lock(_network_udp_mutex);
 
@@ -654,9 +654,9 @@ void NetworkUDPClose()
 	delete _udp_client_socket;
 	delete _udp_server_socket;
 	delete _udp_master_socket;
-	_udp_client_socket = NULL;
-	_udp_server_socket = NULL;
-	_udp_master_socket = NULL;
+	_udp_client_socket = nullptr;
+	_udp_server_socket = nullptr;
+	_udp_master_socket = nullptr;
 
 	_network_udp_server = false;
 	_network_udp_broadcast = 0;
diff --git a/src/newgrf.cpp b/src/newgrf.cpp
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -394,7 +394,7 @@ static GRFFile *GetFileByGRFID(uint32 gr
 	for (GRFFile * const file : _grf_files) {
 		if (file->grfid == grfid) return file;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -407,31 +407,31 @@ static GRFFile *GetFileByFilename(const 
 	for (GRFFile * const file : _grf_files) {
 		if (strcmp(file->filename, filename) == 0) return file;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /** Reset all NewGRFData that was used only while processing data */
 static void ClearTemporaryNewGRFData(GRFFile *gf)
 {
 	/* Clear the GOTO labels used for GRF processing */
-	for (GRFLabel *l = gf->label; l != NULL;) {
+	for (GRFLabel *l = gf->label; l != nullptr;) {
 		GRFLabel *l2 = l->next;
 		free(l);
 		l = l2;
 	}
-	gf->label = NULL;
+	gf->label = nullptr;
 }
 
 /**
  * Disable a GRF
  * @param message Error message or STR_NULL.
- * @param config GRFConfig to disable, NULL for current.
+ * @param config GRFConfig to disable, nullptr for current.
  * @return Error message of the GRF for further customisation.
  */
-static GRFError *DisableGrf(StringID message = STR_NULL, GRFConfig *config = NULL)
+static GRFError *DisableGrf(StringID message = STR_NULL, GRFConfig *config = nullptr)
 {
 	GRFFile *file;
-	if (config != NULL) {
+	if (config != nullptr) {
 		file = GetFileByGRFID(config->ident.grfid);
 	} else {
 		config = _cur.grfconfig;
@@ -439,7 +439,7 @@ static GRFError *DisableGrf(StringID mes
 	}
 
 	config->status = GCS_DISABLED;
-	if (file != NULL) ClearTemporaryNewGRFData(file);
+	if (file != nullptr) ClearTemporaryNewGRFData(file);
 	if (config == _cur.grfconfig) _cur.skip_sprites = -1;
 
 	if (message != STR_NULL) {
@@ -589,7 +589,7 @@ static void SetNewGRFOverride(uint32 sou
  * @param file NewGRF that wants to change the engine.
  * @param type Vehicle type.
  * @param internal_id Engine ID inside the NewGRF.
- * @param static_access If the engine is not present, return NULL instead of allocating a new engine. (Used for static Action 0x04).
+ * @param static_access If the engine is not present, return nullptr instead of allocating a new engine. (Used for static Action 0x04).
  * @return The requested engine.
  */
 static Engine *GetNewEngine(const GRFFile *file, VehicleType type, uint16 internal_id, bool static_access = false)
@@ -604,7 +604,7 @@ static Engine *GetNewEngine(const GRFFil
 		if (override != 0) {
 			scope_grfid = override;
 			const GRFFile *grf_match = GetFileByGRFID(override);
-			if (grf_match == NULL) {
+			if (grf_match == nullptr) {
 				grfmsg(5, "Tried mapping from GRFID %x to %x but target is not loaded", BSWAP32(file->grfid), BSWAP32(override));
 			} else {
 				grfmsg(5, "Mapping from GRFID %x to %x", BSWAP32(file->grfid), BSWAP32(override));
@@ -615,7 +615,7 @@ static Engine *GetNewEngine(const GRFFil
 		EngineID engine = _engine_mngr.GetID(type, internal_id, scope_grfid);
 		if (engine != INVALID_ENGINE) {
 			Engine *e = Engine::Get(engine);
-			if (e->grf_prop.grffile == NULL) e->grf_prop.grffile = file;
+			if (e->grf_prop.grffile == nullptr) e->grf_prop.grffile = file;
 			return e;
 		}
 	}
@@ -625,7 +625,7 @@ static Engine *GetNewEngine(const GRFFil
 	if (engine != INVALID_ENGINE) {
 		Engine *e = Engine::Get(engine);
 
-		if (e->grf_prop.grffile == NULL) {
+		if (e->grf_prop.grffile == nullptr) {
 			e->grf_prop.grffile = file;
 			grfmsg(5, "Replaced engine at index %d for GRFID %x, type %d, index %d", e->index, BSWAP32(file->grfid), type, internal_id);
 		}
@@ -639,11 +639,11 @@ static Engine *GetNewEngine(const GRFFil
 		return e;
 	}
 
-	if (static_access) return NULL;
+	if (static_access) return nullptr;
 
 	if (!Engine::CanAllocateItem()) {
 		grfmsg(0, "Can't allocate any more engines");
-		return NULL;
+		return nullptr;
 	}
 
 	size_t engine_pool_size = Engine::GetPoolSize();
@@ -735,7 +735,7 @@ static void MapSpriteMappingRecolour(Pal
  * @param[out] max_palette_offset Optionally returns the number of sprites in the spriteset of the palette. (0 if no spritset)
  * @return Read TileLayoutFlags.
  */
-static TileLayoutFlags ReadSpriteLayoutSprite(ByteReader *buf, bool read_flags, bool invert_action1_flag, bool use_cur_spritesets, int feature, PalSpriteID *grf_sprite, uint16 *max_sprite_offset = NULL, uint16 *max_palette_offset = NULL)
+static TileLayoutFlags ReadSpriteLayoutSprite(ByteReader *buf, bool read_flags, bool invert_action1_flag, bool use_cur_spritesets, int feature, PalSpriteID *grf_sprite, uint16 *max_sprite_offset = nullptr, uint16 *max_palette_offset = nullptr)
 {
 	grf_sprite->sprite = buf->ReadWord();
 	grf_sprite->pal = buf->ReadWord();
@@ -754,7 +754,7 @@ static TileLayoutFlags ReadSpriteLayoutS
 			grf_sprite->pal = PAL_NONE;
 		} else {
 			SpriteID sprite = use_cur_spritesets ? _cur.GetSprite(feature, index) : index;
-			if (max_sprite_offset != NULL) *max_sprite_offset = use_cur_spritesets ? _cur.GetNumEnts(feature, index) : UINT16_MAX;
+			if (max_sprite_offset != nullptr) *max_sprite_offset = use_cur_spritesets ? _cur.GetNumEnts(feature, index) : UINT16_MAX;
 			SB(grf_sprite->sprite, 0, SPRITE_WIDTH, sprite);
 			SetBit(grf_sprite->sprite, SPRITE_MODIFIER_CUSTOM_SPRITE);
 		}
@@ -772,7 +772,7 @@ static TileLayoutFlags ReadSpriteLayoutS
 			grf_sprite->pal = PAL_NONE;
 		} else {
 			SpriteID sprite = use_cur_spritesets ? _cur.GetSprite(feature, index) : index;
-			if (max_palette_offset != NULL) *max_palette_offset = use_cur_spritesets ? _cur.GetNumEnts(feature, index) : UINT16_MAX;
+			if (max_palette_offset != nullptr) *max_palette_offset = use_cur_spritesets ? _cur.GetNumEnts(feature, index) : UINT16_MAX;
 			SB(grf_sprite->pal, 0, SPRITE_WIDTH, sprite);
 			SetBit(grf_sprite->pal, SPRITE_MODIFIER_CUSTOM_SPRITE);
 		}
@@ -797,7 +797,7 @@ static void ReadSpriteLayoutRegisters(By
 {
 	if (!(flags & TLF_DRAWING_FLAGS)) return;
 
-	if (dts->registers == NULL) dts->AllocateRegisters();
+	if (dts->registers == nullptr) dts->AllocateRegisters();
 	TileLayoutRegisters &regs = const_cast<TileLayoutRegisters&>(dts->registers[index]);
 	regs.flags = flags & TLF_DRAWING_FLAGS;
 
@@ -924,9 +924,9 @@ static bool ReadSpriteLayout(ByteReader 
 	/* When the Action1 sets are unknown, everything should be 0 (no spriteset usage) or UINT16_MAX (some spriteset usage) */
 	assert(use_cur_spritesets || (is_consistent && (dts->consistent_max_offset == 0 || dts->consistent_max_offset == UINT16_MAX)));
 
-	if (!is_consistent || dts->registers != NULL) {
+	if (!is_consistent || dts->registers != nullptr) {
 		dts->consistent_max_offset = 0;
-		if (dts->registers == NULL) dts->AllocateRegisters();
+		if (dts->registers == nullptr) dts->AllocateRegisters();
 
 		for (uint i = 0; i < num_building_sprites + 1; i++) {
 			TileLayoutRegisters &regs = const_cast<TileLayoutRegisters&>(dts->registers[i]);
@@ -1045,7 +1045,7 @@ static ChangeInfoResult RailVehicleChang
 
 	for (int i = 0; i < numinfo; i++) {
 		Engine *e = GetNewEngine(_cur.grffile, VEH_TRAIN, engine + i);
-		if (e == NULL) return CIR_INVALID_ID; // No engine could be allocated, so neither can any next vehicles
+		if (e == nullptr) return CIR_INVALID_ID; // No engine could be allocated, so neither can any next vehicles
 
 		EngineInfo *ei = &e->info;
 		RailVehicleInfo *rvi = &e->u.rail;
@@ -1339,7 +1339,7 @@ static ChangeInfoResult RoadVehicleChang
 
 	for (int i = 0; i < numinfo; i++) {
 		Engine *e = GetNewEngine(_cur.grffile, VEH_ROAD, engine + i);
-		if (e == NULL) return CIR_INVALID_ID; // No engine could be allocated, so neither can any next vehicles
+		if (e == nullptr) return CIR_INVALID_ID; // No engine could be allocated, so neither can any next vehicles
 
 		EngineInfo *ei = &e->info;
 		RoadVehicleInfo *rvi = &e->u.road;
@@ -1527,7 +1527,7 @@ static ChangeInfoResult ShipVehicleChang
 
 	for (int i = 0; i < numinfo; i++) {
 		Engine *e = GetNewEngine(_cur.grffile, VEH_SHIP, engine + i);
-		if (e == NULL) return CIR_INVALID_ID; // No engine could be allocated, so neither can any next vehicles
+		if (e == nullptr) return CIR_INVALID_ID; // No engine could be allocated, so neither can any next vehicles
 
 		EngineInfo *ei = &e->info;
 		ShipVehicleInfo *svi = &e->u.ship;
@@ -1699,7 +1699,7 @@ static ChangeInfoResult AircraftVehicleC
 
 	for (int i = 0; i < numinfo; i++) {
 		Engine *e = GetNewEngine(_cur.grffile, VEH_AIRCRAFT, engine + i);
-		if (e == NULL) return CIR_INVALID_ID; // No engine could be allocated, so neither can any next vehicles
+		if (e == nullptr) return CIR_INVALID_ID; // No engine could be allocated, so neither can any next vehicles
 
 		EngineInfo *ei = &e->info;
 		AircraftVehicleInfo *avi = &e->u.air;
@@ -1857,13 +1857,13 @@ static ChangeInfoResult StationChangeInf
 	}
 
 	/* Allocate station specs if necessary */
-	if (_cur.grffile->stations == NULL) _cur.grffile->stations = CallocT<StationSpec*>(NUM_STATIONS_PER_GRF);
+	if (_cur.grffile->stations == nullptr) _cur.grffile->stations = CallocT<StationSpec*>(NUM_STATIONS_PER_GRF);
 
 	for (int i = 0; i < numinfo; i++) {
 		StationSpec *statspec = _cur.grffile->stations[stid + i];
 
 		/* Check that the station we are modifying is defined. */
-		if (statspec == NULL && prop != 0x08) {
+		if (statspec == nullptr && prop != 0x08) {
 			grfmsg(2, "StationChangeInfo: Attempt to modify undefined station %u, ignoring", stid + i);
 			return CIR_INVALID_ID;
 		}
@@ -1873,7 +1873,7 @@ static ChangeInfoResult StationChangeInf
 				StationSpec **spec = &_cur.grffile->stations[stid + i];
 
 				/* Property 0x08 is special; it is where the station is allocated */
-				if (*spec == NULL) *spec = CallocT<StationSpec>(1);
+				if (*spec == nullptr) *spec = CallocT<StationSpec>(1);
 
 				/* Swap classid because we read it in BE meaning WAYP or DFLT */
 				uint32 classid = buf->ReadDWord();
@@ -1929,7 +1929,7 @@ static ChangeInfoResult StationChangeInf
 				byte srcid = buf->ReadByte();
 				const StationSpec *srcstatspec = _cur.grffile->stations[srcid];
 
-				if (srcstatspec == NULL) {
+				if (srcstatspec == nullptr) {
 					grfmsg(1, "StationChangeInfo: Station %u is not defined, cannot copy sprite layout to %u.", srcid, stid + i);
 					continue;
 				}
@@ -1981,7 +1981,7 @@ static ChangeInfoResult StationChangeInf
 
 					if (number > statspec->platforms[l]) {
 						statspec->layouts[l] = ReallocT(statspec->layouts[l], number);
-						/* We expect NULL being 0 here, but C99 guarantees that. */
+						/* We expect nullptr being 0 here, but C99 guarantees that. */
 						memset(statspec->layouts[l] + statspec->platforms[l], 0,
 						       (number - statspec->platforms[l]) * sizeof(**statspec->layouts));
 
@@ -2012,7 +2012,7 @@ static ChangeInfoResult StationChangeInf
 				byte srcid = buf->ReadByte();
 				const StationSpec *srcstatspec = _cur.grffile->stations[srcid];
 
-				if (srcstatspec == NULL) {
+				if (srcstatspec == nullptr) {
 					grfmsg(1, "StationChangeInfo: Station %u is not defined, cannot copy tile layout to %u.", srcid, stid + i);
 					continue;
 				}
@@ -2174,7 +2174,7 @@ static ChangeInfoResult BridgeChangeInfo
 				byte tableid = buf->ReadByte();
 				byte numtables = buf->ReadByte();
 
-				if (bridge->sprite_table == NULL) {
+				if (bridge->sprite_table == nullptr) {
 					/* Allocate memory for sprite table pointers and zero out */
 					bridge->sprite_table = CallocT<PalSpriteID*>(7);
 				}
@@ -2186,7 +2186,7 @@ static ChangeInfoResult BridgeChangeInfo
 						continue;
 					}
 
-					if (bridge->sprite_table[tableid] == NULL) {
+					if (bridge->sprite_table[tableid] == nullptr) {
 						bridge->sprite_table[tableid] = MallocT<PalSpriteID>(32);
 					}
 
@@ -2320,14 +2320,14 @@ static ChangeInfoResult TownHouseChangeI
 	}
 
 	/* Allocate house specs if they haven't been allocated already. */
-	if (_cur.grffile->housespec == NULL) {
+	if (_cur.grffile->housespec == nullptr) {
 		_cur.grffile->housespec = CallocT<HouseSpec*>(NUM_HOUSES_PER_GRF);
 	}
 
 	for (int i = 0; i < numinfo; i++) {
 		HouseSpec *housespec = _cur.grffile->housespec[hid + i];
 
-		if (prop != 0x08 && housespec == NULL) {
+		if (prop != 0x08 && housespec == nullptr) {
 			/* If the house property 08 is not yet set, ignore this property */
 			ChangeInfoResult cir = IgnoreTownHouseProperty(prop, buf);
 			if (cir > ret) ret = cir;
@@ -2351,7 +2351,7 @@ static ChangeInfoResult TownHouseChangeI
 				}
 
 				/* Allocate space for this house. */
-				if (*house == NULL) *house = CallocT<HouseSpec>(1);
+				if (*house == nullptr) *house = CallocT<HouseSpec>(1);
 
 				housespec = *house;
 
@@ -2562,13 +2562,13 @@ static ChangeInfoResult TownHouseChangeI
  * Get the language map associated with a given NewGRF and language.
  * @param grfid       The NewGRF to get the map for.
  * @param language_id The (NewGRF) language ID to get the map for.
- * @return The LanguageMap, or NULL if it couldn't be found.
+ * @return The LanguageMap, or nullptr if it couldn't be found.
  */
 /* static */ const LanguageMap *LanguageMap::GetLanguageMap(uint32 grfid, uint8 language_id)
 {
 	/* LanguageID "MAX_LANG", i.e. 7F is any. This language can't have a gender/case mapping, but has to be handled gracefully. */
 	const GRFFile *grffile = GetFileByGRFID(grfid);
-	return (grffile != NULL && grffile->language_map != NULL && language_id < MAX_LANG) ? &grffile->language_map[language_id] : NULL;
+	return (grffile != nullptr && grffile->language_map != nullptr && language_id < MAX_LANG) ? &grffile->language_map[language_id] : nullptr;
 }
 
 /**
@@ -2751,8 +2751,8 @@ static ChangeInfoResult GlobalVarChangeI
 			case 0x14:   // Case translation table
 			case 0x15: { // Plural form translation
 				uint curidx = gvid + i; // The current index, i.e. language.
-				const LanguageMetadata *lang = curidx < MAX_LANG ? GetLanguage(curidx) : NULL;
-				if (lang == NULL) {
+				const LanguageMetadata *lang = curidx < MAX_LANG ? GetLanguage(curidx) : nullptr;
+				if (lang == nullptr) {
 					grfmsg(1, "GlobalVarChangeInfo: Language %d is not known, ignoring", curidx);
 					/* Skip over the data. */
 					if (prop == 0x15) {
@@ -2765,7 +2765,7 @@ static ChangeInfoResult GlobalVarChangeI
 					break;
 				}
 
-				if (_cur.grffile->language_map == NULL) _cur.grffile->language_map = new LanguageMap[MAX_LANG];
+				if (_cur.grffile->language_map == nullptr) _cur.grffile->language_map = new LanguageMap[MAX_LANG];
 
 				if (prop == 0x15) {
 					uint plural_form = buf->ReadByte();
@@ -3135,14 +3135,14 @@ static ChangeInfoResult IndustrytilesCha
 	}
 
 	/* Allocate industry tile specs if they haven't been allocated already. */
-	if (_cur.grffile->indtspec == NULL) {
+	if (_cur.grffile->indtspec == nullptr) {
 		_cur.grffile->indtspec = CallocT<IndustryTileSpec*>(NUM_INDUSTRYTILES_PER_GRF);
 	}
 
 	for (int i = 0; i < numinfo; i++) {
 		IndustryTileSpec *tsp = _cur.grffile->indtspec[indtid + i];
 
-		if (prop != 0x08 && tsp == NULL) {
+		if (prop != 0x08 && tsp == nullptr) {
 			ChangeInfoResult cir = IgnoreIndustryTileProperty(prop, buf);
 			if (cir > ret) ret = cir;
 			continue;
@@ -3160,7 +3160,7 @@ static ChangeInfoResult IndustrytilesCha
 				}
 
 				/* Allocate space for this industry. */
-				if (*tilespec == NULL) {
+				if (*tilespec == nullptr) {
 					*tilespec = CallocT<IndustryTileSpec>(1);
 					tsp = *tilespec;
 
@@ -3370,14 +3370,14 @@ static bool ValidateIndustryLayout(const
 /** Clean the tile table of the IndustrySpec if it's needed. */
 static void CleanIndustryTileTable(IndustrySpec *ind)
 {
-	if (HasBit(ind->cleanup_flag, CLEAN_TILELAYOUT) && ind->table != NULL) {
+	if (HasBit(ind->cleanup_flag, CLEAN_TILELAYOUT) && ind->table != nullptr) {
 		for (int j = 0; j < ind->num_table; j++) {
 			/* remove the individual layouts */
 			free(ind->table[j]);
 		}
 		/* remove the layouts pointers */
 		free(ind->table);
-		ind->table = NULL;
+		ind->table = nullptr;
 	}
 }
 
@@ -3399,14 +3399,14 @@ static ChangeInfoResult IndustriesChange
 	}
 
 	/* Allocate industry specs if they haven't been allocated already. */
-	if (_cur.grffile->industryspec == NULL) {
+	if (_cur.grffile->industryspec == nullptr) {
 		_cur.grffile->industryspec = CallocT<IndustrySpec*>(NUM_INDUSTRYTYPES_PER_GRF);
 	}
 
 	for (int i = 0; i < numinfo; i++) {
 		IndustrySpec *indsp = _cur.grffile->industryspec[indid + i];
 
-		if (prop != 0x08 && indsp == NULL) {
+		if (prop != 0x08 && indsp == nullptr) {
 			ChangeInfoResult cir = IgnoreIndustryProperty(prop, buf);
 			if (cir > ret) ret = cir;
 			continue;
@@ -3431,7 +3431,7 @@ static ChangeInfoResult IndustriesChange
 				/* Allocate space for this industry.
 				 * Only need to do it once. If ever it is called again, it should not
 				 * do anything */
-				if (*indspec == NULL) {
+				if (*indspec == nullptr) {
 					*indspec = CallocT<IndustrySpec>(1);
 					indsp = *indspec;
 
@@ -3819,14 +3819,14 @@ static ChangeInfoResult AirportChangeInf
 	}
 
 	/* Allocate industry specs if they haven't been allocated already. */
-	if (_cur.grffile->airportspec == NULL) {
+	if (_cur.grffile->airportspec == nullptr) {
 		_cur.grffile->airportspec = CallocT<AirportSpec*>(NUM_AIRPORTS_PER_GRF);
 	}
 
 	for (int i = 0; i < numinfo; i++) {
 		AirportSpec *as = _cur.grffile->airportspec[airport + i];
 
-		if (as == NULL && prop != 0x08 && prop != 0x09) {
+		if (as == nullptr && prop != 0x08 && prop != 0x09) {
 			grfmsg(2, "AirportChangeInfo: Attempt to modify undefined airport %u, ignoring", airport + i);
 			return CIR_INVALID_ID;
 		}
@@ -3850,7 +3850,7 @@ static ChangeInfoResult AirportChangeInf
 				/* Allocate space for this airport.
 				 * Only need to do it once. If ever it is called again, it should not
 				 * do anything */
-				if (*spec == NULL) {
+				if (*spec == nullptr) {
 					*spec = MallocT<AirportSpec>(1);
 					as = *spec;
 
@@ -4037,14 +4037,14 @@ static ChangeInfoResult ObjectChangeInfo
 	}
 
 	/* Allocate object specs if they haven't been allocated already. */
-	if (_cur.grffile->objectspec == NULL) {
+	if (_cur.grffile->objectspec == nullptr) {
 		_cur.grffile->objectspec = CallocT<ObjectSpec*>(NUM_OBJECTS_PER_GRF);
 	}
 
 	for (int i = 0; i < numinfo; i++) {
 		ObjectSpec *spec = _cur.grffile->objectspec[id + i];
 
-		if (prop != 0x08 && spec == NULL) {
+		if (prop != 0x08 && spec == nullptr) {
 			/* If the object property 08 is not yet set, ignore this property */
 			ChangeInfoResult cir = IgnoreObjectProperty(prop, buf);
 			if (cir > ret) ret = cir;
@@ -4056,7 +4056,7 @@ static ChangeInfoResult ObjectChangeInfo
 				ObjectSpec **ospec = &_cur.grffile->objectspec[id + i];
 
 				/* Allocate space for this object. */
-				if (*ospec == NULL) {
+				if (*ospec == nullptr) {
 					*ospec = CallocT<ObjectSpec>(1);
 					(*ospec)->views = 1; // Default for NewGRFs that don't set it.
 				}
@@ -4378,14 +4378,14 @@ static ChangeInfoResult AirportTilesChan
 	}
 
 	/* Allocate airport tile specs if they haven't been allocated already. */
-	if (_cur.grffile->airtspec == NULL) {
+	if (_cur.grffile->airtspec == nullptr) {
 		_cur.grffile->airtspec = CallocT<AirportTileSpec*>(NUM_AIRPORTTILES_PER_GRF);
 	}
 
 	for (int i = 0; i < numinfo; i++) {
 		AirportTileSpec *tsp = _cur.grffile->airtspec[airtid + i];
 
-		if (prop != 0x08 && tsp == NULL) {
+		if (prop != 0x08 && tsp == nullptr) {
 			grfmsg(2, "AirportTileChangeInfo: Attempt to modify undefined airport tile %u. Ignoring.", airtid + i);
 			return CIR_INVALID_ID;
 		}
@@ -4402,7 +4402,7 @@ static ChangeInfoResult AirportTilesChan
 				}
 
 				/* Allocate space for this airport tile. */
-				if (*tilespec == NULL) {
+				if (*tilespec == nullptr) {
 					*tilespec = CallocT<AirportTileSpec>(1);
 					tsp = *tilespec;
 
@@ -4513,10 +4513,10 @@ static void FeatureChangeInfo(ByteReader
 		/* GSF_GLOBALVAR */     GlobalVarChangeInfo,
 		/* GSF_INDUSTRYTILES */ IndustrytilesChangeInfo,
 		/* GSF_INDUSTRIES */    IndustriesChangeInfo,
-		/* GSF_CARGOES */       NULL, // Cargo is handled during reservation
+		/* GSF_CARGOES */       nullptr, // Cargo is handled during reservation
 		/* GSF_SOUNDFX */       SoundEffectChangeInfo,
 		/* GSF_AIRPORTS */      AirportChangeInfo,
-		/* GSF_SIGNALS */       NULL,
+		/* GSF_SIGNALS */       nullptr,
 		/* GSF_OBJECTS */       ObjectChangeInfo,
 		/* GSF_RAILTYPES */     RailTypeChangeInfo,
 		/* GSF_AIRPORTTILES */  AirportTilesChangeInfo,
@@ -4535,7 +4535,7 @@ static void FeatureChangeInfo(ByteReader
 	grfmsg(6, "FeatureChangeInfo: Feature 0x%02X, %d properties, to apply to %d+%d",
 	               feature, numprops, engine, numinfo);
 
-	if (feature >= lengthof(handler) || handler[feature] == NULL) {
+	if (feature >= lengthof(handler) || handler[feature] == nullptr) {
 		if (feature != GSF_CARGOES) grfmsg(1, "FeatureChangeInfo: Unsupported feature 0x%02X, skipping", feature);
 		return;
 	}
@@ -4573,7 +4573,7 @@ static void SafeChangeInfo(ByteReader *b
 				uint32 s = buf->ReadDWord();
 				buf->ReadDWord(); // dest
 				const GRFConfig *grfconfig = GetGRFConfig(s);
-				if (grfconfig != NULL && !HasBit(grfconfig->flags, GCF_STATIC)) {
+				if (grfconfig != nullptr && !HasBit(grfconfig->flags, GCF_STATIC)) {
 					is_safe = false;
 					break;
 				}
@@ -4697,9 +4697,9 @@ static const SpriteGroup *GetGroupFromGr
 		return new CallbackResultSpriteGroup(groupid, _cur.grffile->grf_version >= 8);
 	}
 
-	if (groupid > MAX_SPRITEGROUP || _cur.spritegroups[groupid] == NULL) {
+	if (groupid > MAX_SPRITEGROUP || _cur.spritegroups[groupid] == nullptr) {
 		grfmsg(1, "GetGroupFromGroupID(0x%02X:0x%02X): Groupid 0x%04X does not exist, leaving empty", setid, type, groupid);
-		return NULL;
+		return nullptr;
 	}
 
 	return _cur.spritegroups[groupid];
@@ -4722,7 +4722,7 @@ static const SpriteGroup *CreateGroupFro
 
 	if (!_cur.IsValidSpriteSet(feature, spriteid)) {
 		grfmsg(1, "CreateGroupFromGroupID(0x%02X:0x%02X): Sprite set %u invalid", setid, type, spriteid);
-		return NULL;
+		return nullptr;
 	}
 
 	SpriteID spriteset_start = _cur.GetSprite(feature, spriteid);
@@ -4748,7 +4748,7 @@ static void NewSpriteGroup(ByteReader *b
 	 *                 otherwise it specifies a number of entries, the exact
 	 *                 meaning depends on the feature
 	 * V feature-specific-data (huge mess, don't even look it up --pasky) */
-	SpriteGroup *act_group = NULL;
+	SpriteGroup *act_group = nullptr;
 
 	uint8 feature = buf->ReadByte();
 	if (feature >= GSF_END) {
@@ -5128,7 +5128,7 @@ static CargoID TranslateCargo(uint8 feat
 
 static bool IsValidGroupID(uint16 groupid, const char *function)
 {
-	if (groupid > MAX_SPRITEGROUP || _cur.spritegroups[groupid] == NULL) {
+	if (groupid > MAX_SPRITEGROUP || _cur.spritegroups[groupid] == nullptr) {
 		grfmsg(1, "%s: Spritegroup 0x%04X out of range or empty, skipping.", function, groupid);
 		return false;
 	}
@@ -5165,7 +5165,7 @@ static void VehicleMapSpriteGroup(ByteRe
 	EngineID *engines = AllocaM(EngineID, idcount);
 	for (uint i = 0; i < idcount; i++) {
 		Engine *e = GetNewEngine(_cur.grffile, (VehicleType)feature, buf->ReadExtendedByte());
-		if (e == NULL) {
+		if (e == nullptr) {
 			/* No engine could be allocated?!? Deal with it. Okay,
 			 * this might look bad. Also make sure this NewGRF
 			 * gets disabled, as a half loaded one is bad. */
@@ -5263,9 +5263,9 @@ static void StationMapSpriteGroup(ByteRe
 		if (ctype == CT_INVALID) continue;
 
 		for (uint i = 0; i < idcount; i++) {
-			StationSpec *statspec = _cur.grffile->stations == NULL ? NULL : _cur.grffile->stations[stations[i]];
-
-			if (statspec == NULL) {
+			StationSpec *statspec = _cur.grffile->stations == nullptr ? nullptr : _cur.grffile->stations[stations[i]];
+
+			if (statspec == nullptr) {
 				grfmsg(1, "StationMapSpriteGroup: Station with ID 0x%02X does not exist, skipping", stations[i]);
 				continue;
 			}
@@ -5278,14 +5278,14 @@ static void StationMapSpriteGroup(ByteRe
 	if (!IsValidGroupID(groupid, "StationMapSpriteGroup")) return;
 
 	for (uint i = 0; i < idcount; i++) {
-		StationSpec *statspec = _cur.grffile->stations == NULL ? NULL : _cur.grffile->stations[stations[i]];
-
-		if (statspec == NULL) {
+		StationSpec *statspec = _cur.grffile->stations == nullptr ? nullptr : _cur.grffile->stations[stations[i]];
+
+		if (statspec == nullptr) {
 			grfmsg(1, "StationMapSpriteGroup: Station with ID 0x%02X does not exist, skipping", stations[i]);
 			continue;
 		}
 
-		if (statspec->grf_prop.grffile != NULL) {
+		if (statspec->grf_prop.grffile != nullptr) {
 			grfmsg(1, "StationMapSpriteGroup: Station with ID 0x%02X mapped multiple times, skipping", stations[i]);
 			continue;
 		}
@@ -5312,7 +5312,7 @@ static void TownHouseMapSpriteGroup(Byte
 	uint16 groupid = buf->ReadWord();
 	if (!IsValidGroupID(groupid, "TownHouseMapSpriteGroup")) return;
 
-	if (_cur.grffile->housespec == NULL) {
+	if (_cur.grffile->housespec == nullptr) {
 		grfmsg(1, "TownHouseMapSpriteGroup: No houses defined, skipping");
 		return;
 	}
@@ -5320,7 +5320,7 @@ static void TownHouseMapSpriteGroup(Byte
 	for (uint i = 0; i < idcount; i++) {
 		HouseSpec *hs = _cur.grffile->housespec[houses[i]];
 
-		if (hs == NULL) {
+		if (hs == nullptr) {
 			grfmsg(1, "TownHouseMapSpriteGroup: House %d undefined, skipping.", houses[i]);
 			continue;
 		}
@@ -5343,7 +5343,7 @@ static void IndustryMapSpriteGroup(ByteR
 	uint16 groupid = buf->ReadWord();
 	if (!IsValidGroupID(groupid, "IndustryMapSpriteGroup")) return;
 
-	if (_cur.grffile->industryspec == NULL) {
+	if (_cur.grffile->industryspec == nullptr) {
 		grfmsg(1, "IndustryMapSpriteGroup: No industries defined, skipping");
 		return;
 	}
@@ -5351,7 +5351,7 @@ static void IndustryMapSpriteGroup(ByteR
 	for (uint i = 0; i < idcount; i++) {
 		IndustrySpec *indsp = _cur.grffile->industryspec[industries[i]];
 
-		if (indsp == NULL) {
+		if (indsp == nullptr) {
 			grfmsg(1, "IndustryMapSpriteGroup: Industry %d undefined, skipping", industries[i]);
 			continue;
 		}
@@ -5374,7 +5374,7 @@ static void IndustrytileMapSpriteGroup(B
 	uint16 groupid = buf->ReadWord();
 	if (!IsValidGroupID(groupid, "IndustrytileMapSpriteGroup")) return;
 
-	if (_cur.grffile->indtspec == NULL) {
+	if (_cur.grffile->indtspec == nullptr) {
 		grfmsg(1, "IndustrytileMapSpriteGroup: No industry tiles defined, skipping");
 		return;
 	}
@@ -5382,7 +5382,7 @@ static void IndustrytileMapSpriteGroup(B
 	for (uint i = 0; i < idcount; i++) {
 		IndustryTileSpec *indtsp = _cur.grffile->indtspec[indtiles[i]];
 
-		if (indtsp == NULL) {
+		if (indtsp == nullptr) {
 			grfmsg(1, "IndustrytileMapSpriteGroup: Industry tile %d undefined, skipping", indtiles[i]);
 			continue;
 		}
@@ -5421,7 +5421,7 @@ static void CargoMapSpriteGroup(ByteRead
 
 static void ObjectMapSpriteGroup(ByteReader *buf, uint8 idcount)
 {
-	if (_cur.grffile->objectspec == NULL) {
+	if (_cur.grffile->objectspec == nullptr) {
 		grfmsg(1, "ObjectMapSpriteGroup: No object tiles defined, skipping");
 		return;
 	}
@@ -5443,7 +5443,7 @@ static void ObjectMapSpriteGroup(ByteRea
 		for (uint i = 0; i < idcount; i++) {
 			ObjectSpec *spec = _cur.grffile->objectspec[objects[i]];
 
-			if (spec == NULL) {
+			if (spec == nullptr) {
 				grfmsg(1, "ObjectMapSpriteGroup: Object with ID 0x%02X undefined, skipping", objects[i]);
 				continue;
 			}
@@ -5458,12 +5458,12 @@ static void ObjectMapSpriteGroup(ByteRea
 	for (uint i = 0; i < idcount; i++) {
 		ObjectSpec *spec = _cur.grffile->objectspec[objects[i]];
 
-		if (spec == NULL) {
+		if (spec == nullptr) {
 			grfmsg(1, "ObjectMapSpriteGroup: Object with ID 0x%02X undefined, skipping", objects[i]);
 			continue;
 		}
 
-		if (spec->grf_prop.grffile != NULL) {
+		if (spec->grf_prop.grffile != nullptr) {
 			grfmsg(1, "ObjectMapSpriteGroup: Object with ID 0x%02X mapped multiple times, skipping", objects[i]);
 			continue;
 		}
@@ -5518,7 +5518,7 @@ static void AirportMapSpriteGroup(ByteRe
 	uint16 groupid = buf->ReadWord();
 	if (!IsValidGroupID(groupid, "AirportMapSpriteGroup")) return;
 
-	if (_cur.grffile->airportspec == NULL) {
+	if (_cur.grffile->airportspec == nullptr) {
 		grfmsg(1, "AirportMapSpriteGroup: No airports defined, skipping");
 		return;
 	}
@@ -5526,7 +5526,7 @@ static void AirportMapSpriteGroup(ByteRe
 	for (uint i = 0; i < idcount; i++) {
 		AirportSpec *as = _cur.grffile->airportspec[airports[i]];
 
-		if (as == NULL) {
+		if (as == nullptr) {
 			grfmsg(1, "AirportMapSpriteGroup: Airport %d undefined, skipping", airports[i]);
 			continue;
 		}
@@ -5549,7 +5549,7 @@ static void AirportTileMapSpriteGroup(By
 	uint16 groupid = buf->ReadWord();
 	if (!IsValidGroupID(groupid, "AirportTileMapSpriteGroup")) return;
 
-	if (_cur.grffile->airtspec == NULL) {
+	if (_cur.grffile->airtspec == nullptr) {
 		grfmsg(1, "AirportTileMapSpriteGroup: No airport tiles defined, skipping");
 		return;
 	}
@@ -5557,7 +5557,7 @@ static void AirportTileMapSpriteGroup(By
 	for (uint i = 0; i < idcount; i++) {
 		AirportTileSpec *airtsp = _cur.grffile->airtspec[airptiles[i]];
 
-		if (airtsp == NULL) {
+		if (airtsp == nullptr) {
 			grfmsg(1, "AirportTileMapSpriteGroup: Airport tile %d undefined, skipping", airptiles[i]);
 			continue;
 		}
@@ -5721,7 +5721,7 @@ static void FeatureNewName(ByteReader *b
 			case GSF_AIRCRAFT:
 				if (!generic) {
 					Engine *e = GetNewEngine(_cur.grffile, (VehicleType)feature, id, HasBit(_cur.grfconfig->flags, GCF_STATIC));
-					if (e == NULL) break;
+					if (e == nullptr) break;
 					StringID string = AddGRFString(_cur.grffile->grfid, e->index, lang, new_scheme, false, name, e->info.string_id);
 					e->info.string_id = string;
 				} else {
@@ -5737,7 +5737,7 @@ static void FeatureNewName(ByteReader *b
 
 				switch (GB(id, 8, 8)) {
 					case 0xC4: // Station class name
-						if (_cur.grffile->stations == NULL || _cur.grffile->stations[GB(id, 0, 8)] == NULL) {
+						if (_cur.grffile->stations == nullptr || _cur.grffile->stations[GB(id, 0, 8)] == nullptr) {
 							grfmsg(1, "FeatureNewName: Attempt to name undefined station 0x%X, ignoring", GB(id, 0, 8));
 						} else {
 							StationClassID cls_id = _cur.grffile->stations[GB(id, 0, 8)]->cls_id;
@@ -5746,7 +5746,7 @@ static void FeatureNewName(ByteReader *b
 						break;
 
 					case 0xC5: // Station name
-						if (_cur.grffile->stations == NULL || _cur.grffile->stations[GB(id, 0, 8)] == NULL) {
+						if (_cur.grffile->stations == nullptr || _cur.grffile->stations[GB(id, 0, 8)] == nullptr) {
 							grfmsg(1, "FeatureNewName: Attempt to name undefined station 0x%X, ignoring", GB(id, 0, 8));
 						} else {
 							_cur.grffile->stations[GB(id, 0, 8)]->name = AddGRFString(_cur.grffile->grfid, id, lang, new_scheme, false, name, STR_UNDEFINED);
@@ -5754,7 +5754,7 @@ static void FeatureNewName(ByteReader *b
 						break;
 
 					case 0xC7: // Airporttile name
-						if (_cur.grffile->airtspec == NULL || _cur.grffile->airtspec[GB(id, 0, 8)] == NULL) {
+						if (_cur.grffile->airtspec == nullptr || _cur.grffile->airtspec[GB(id, 0, 8)] == nullptr) {
 							grfmsg(1, "FeatureNewName: Attempt to name undefined airport tile 0x%X, ignoring", GB(id, 0, 8));
 						} else {
 							_cur.grffile->airtspec[GB(id, 0, 8)]->name = AddGRFString(_cur.grffile->grfid, id, lang, new_scheme, false, name, STR_UNDEFINED);
@@ -5762,7 +5762,7 @@ static void FeatureNewName(ByteReader *b
 						break;
 
 					case 0xC9: // House name
-						if (_cur.grffile->housespec == NULL || _cur.grffile->housespec[GB(id, 0, 8)] == NULL) {
+						if (_cur.grffile->housespec == nullptr || _cur.grffile->housespec[GB(id, 0, 8)] == nullptr) {
 							grfmsg(1, "FeatureNewName: Attempt to name undefined house 0x%X, ignoring.", GB(id, 0, 8));
 						} else {
 							_cur.grffile->housespec[GB(id, 0, 8)]->building_name = AddGRFString(_cur.grffile->grfid, id, lang, new_scheme, false, name, STR_UNDEFINED);
@@ -6099,7 +6099,7 @@ static uint32 GetParamVal(byte param, ui
 		}
 
 		case 0x85: // TTDPatch flags, only for bit tests
-			if (cond_val == NULL) {
+			if (cond_val == nullptr) {
 				/* Supported in Action 0x07 and 0x09, not 0x0D */
 				return 0;
 			} else {
@@ -6142,7 +6142,7 @@ static void CfgApply(ByteReader *buf)
 	size_t pos = FioGetPos();
 	uint32 num = _cur.grf_container_ver >= 2 ? FioReadDword() : FioReadWord();
 	uint8 type = FioReadByte();
-	byte *preload_sprite = NULL;
+	byte *preload_sprite = nullptr;
 
 	/* Check if the sprite is a pseudo sprite. We can't operate on real sprites. */
 	if (type == 0xFF) {
@@ -6204,7 +6204,7 @@ static void CfgApply(ByteReader *buf)
 
 		bool carry = false;
 		for (i = 0; i < param_size && offset + i < num; i++) {
-			uint32 value = GetParamVal(param_num + i / 4, NULL);
+			uint32 value = GetParamVal(param_num + i / 4, nullptr);
 			/* Reset carry flag for each iteration of the variable (only really
 			 * matters if param_size is greater than 4) */
 			if (i % 4 == 0) carry = false;
@@ -6290,12 +6290,12 @@ static void SkipIf(ByteReader *buf)
 
 		GRFConfig *c = GetGRFConfig(cond_val, mask);
 
-		if (c != NULL && HasBit(c->flags, GCF_STATIC) && !HasBit(_cur.grfconfig->flags, GCF_STATIC) && _networking) {
+		if (c != nullptr && HasBit(c->flags, GCF_STATIC) && !HasBit(_cur.grfconfig->flags, GCF_STATIC) && _networking) {
 			DisableStaticNewGRFInfluencingNonStaticNewGRFs(c);
-			c = NULL;
-		}
-
-		if (condtype != 10 && c == NULL) {
+			c = nullptr;
+		}
+
+		if (condtype != 10 && c == nullptr) {
 			grfmsg(7, "SkipIf: GRFID 0x%08X unknown, skipping test", BSWAP32(cond_val));
 			return;
 		}
@@ -6320,7 +6320,7 @@ static void SkipIf(ByteReader *buf)
 
 			case 0x0A: // GRFID is not nor will be active
 				/* This is the only condtype that doesn't get ignored if the GRFID is not found */
-				result = c == NULL || c->status == GCS_DISABLED || c->status == GCS_NOT_FOUND;
+				result = c == nullptr || c->status == GCS_DISABLED || c->status == GCS_NOT_FOUND;
 				break;
 
 			default: grfmsg(1, "SkipIf: Unsupported GRF condition type %02X. Ignoring", condtype); return;
@@ -6364,12 +6364,12 @@ static void SkipIf(ByteReader *buf)
 	 * file. The jump will always be the first matching label that follows
 	 * the current nfo_line. If no matching label is found, the first matching
 	 * label in the file is used. */
-	GRFLabel *choice = NULL;
-	for (GRFLabel *label = _cur.grffile->label; label != NULL; label = label->next) {
+	GRFLabel *choice = nullptr;
+	for (GRFLabel *label = _cur.grffile->label; label != nullptr; label = label->next) {
 		if (label->label != numsprites) continue;
 
 		/* Remember a goto before the current line */
-		if (choice == NULL) choice = label;
+		if (choice == nullptr) choice = label;
 		/* If we find a label here, this is definitely good */
 		if (label->nfo_line > _cur.nfo_line) {
 			choice = label;
@@ -6377,7 +6377,7 @@ static void SkipIf(ByteReader *buf)
 		}
 	}
 
-	if (choice != NULL) {
+	if (choice != nullptr) {
 		grfmsg(2, "SkipIf: Jumping to label 0x%0X at line %d, test was true", choice->label, choice->nfo_line);
 		FioSeekTo(choice->pos, SEEK_SET);
 		_cur.nfo_line = choice->nfo_line;
@@ -6569,7 +6569,7 @@ static void GRFLoadError(ByteReader *buf
 
 		/* Make sure we show fatal errors, instead of silly infos from before */
 		delete _cur.grfconfig->error;
-		_cur.grfconfig->error = NULL;
+		_cur.grfconfig->error = nullptr;
 	}
 
 	if (message_id >= lengthof(msgstr) && message_id != 0xFF) {
@@ -6583,7 +6583,7 @@ static void GRFLoadError(ByteReader *buf
 	}
 
 	/* For now we can only show one message per newgrf file. */
-	if (_cur.grfconfig->error != NULL) return;
+	if (_cur.grfconfig->error != nullptr) return;
 
 	GRFError *error = new GRFError(sevstr[severity]);
 
@@ -6592,7 +6592,7 @@ static void GRFLoadError(ByteReader *buf
 		if (buf->HasData()) {
 			const char *message = buf->ReadString();
 
-			error->custom_message = TranslateTTDPatchCodes(_cur.grffile->grfid, lang, true, message, NULL, SCC_RAW_STRING_POINTER);
+			error->custom_message = TranslateTTDPatchCodes(_cur.grffile->grfid, lang, true, message, nullptr, SCC_RAW_STRING_POINTER);
 		} else {
 			grfmsg(7, "GRFLoadError: No custom message supplied.");
 			error->custom_message = stredup("");
@@ -6910,11 +6910,11 @@ static void ParamSet(ByteReader *buf)
 			/* Read another GRF File's parameter */
 			const GRFFile *file = GetFileByGRFID(data);
 			GRFConfig *c = GetGRFConfig(data);
-			if (c != NULL && HasBit(c->flags, GCF_STATIC) && !HasBit(_cur.grfconfig->flags, GCF_STATIC) && _networking) {
+			if (c != nullptr && HasBit(c->flags, GCF_STATIC) && !HasBit(_cur.grfconfig->flags, GCF_STATIC) && _networking) {
 				/* Disable the read GRF if it is a static NewGRF. */
 				DisableStaticNewGRFInfluencingNonStaticNewGRFs(c);
 				src1 = 0;
-			} else if (file == NULL || c == NULL || c->status == GCS_DISABLED) {
+			} else if (file == nullptr || c == nullptr || c->status == GCS_DISABLED) {
 				src1 = 0;
 			} else if (src1 == 0xFE) {
 				src1 = c->version;
@@ -6928,8 +6928,8 @@ static void ParamSet(ByteReader *buf)
 		 * variables available in action 7, or they can be FF to use the value
 		 * of <data>.  If referring to parameters that are undefined, a value
 		 * of 0 is used instead.  */
-		src1 = (src1 == 0xFF) ? data : GetParamVal(src1, NULL);
-		src2 = (src2 == 0xFF) ? data : GetParamVal(src2, NULL);
+		src1 = (src1 == 0xFF) ? data : GetParamVal(src1, nullptr);
+		src2 = (src2 == 0xFF) ? data : GetParamVal(src2, nullptr);
 	}
 
 	uint32 res;
@@ -7115,7 +7115,7 @@ static void GRFInhibit(ByteReader *buf)
 		GRFConfig *file = GetGRFConfig(grfid);
 
 		/* Unset activation flag */
-		if (file != NULL && file != _cur.grfconfig) {
+		if (file != nullptr && file != _cur.grfconfig) {
 			grfmsg(2, "GRFInhibit: Deactivating file '%s'", file->filename);
 			GRFError *error = DisableGrf(STR_NEWGRF_ERROR_FORCEFULLY_DISABLED, file);
 			error->data = stredup(_cur.grfconfig->GetName());
@@ -7221,15 +7221,15 @@ static void DefineGotoLabel(ByteReader *
 	label->label    = nfo_label;
 	label->nfo_line = _cur.nfo_line;
 	label->pos      = FioGetPos();
-	label->next     = NULL;
+	label->next     = nullptr;
 
 	/* Set up a linked list of goto targets which we will search in an Action 0x7/0x9 */
-	if (_cur.grffile->label == NULL) {
+	if (_cur.grffile->label == nullptr) {
 		_cur.grffile->label = label;
 	} else {
 		/* Attach the label to the end of the list */
 		GRFLabel *l;
-		for (l = _cur.grffile->label; l->next != NULL; l = l->next) {}
+		for (l = _cur.grffile->label; l->next != nullptr; l = l->next) {}
 		l->next = label;
 	}
 
@@ -7247,7 +7247,7 @@ static void ImportGRFSound(SoundEntry *s
 	SoundID sound_id = FioReadWord();
 
 	file = GetFileByGRFID(grfid);
-	if (file == NULL || file->sound_offset == 0) {
+	if (file == nullptr || file->sound_offset == 0) {
 		grfmsg(1, "ImportGRFSound: Source file not available");
 		return;
 	}
@@ -7457,7 +7457,7 @@ static void TranslateGRFStrings(ByteRead
 
 	uint32 grfid = buf->ReadDWord();
 	const GRFConfig *c = GetGRFConfig(grfid);
-	if (c == NULL || (c->status != GCS_INITIALISED && c->status != GCS_ACTIVATED)) {
+	if (c == nullptr || (c->status != GCS_INITIALISED && c->status != GCS_ACTIVATED)) {
 		grfmsg(7, "TranslateGRFStrings: GRFID 0x%08x unknown, skipping action 13", BSWAP32(grfid));
 		return;
 	}
@@ -7808,7 +7808,7 @@ static bool ChangeGRFParamValueNames(Byt
 		if (val_name != _cur_parameter->value_names.End()) {
 			AddGRFTextToList(&val_name->second, langid, _cur.grfconfig->ident.grfid, false, name_string);
 		} else {
-			GRFText *list = NULL;
+			GRFText *list = nullptr;
 			AddGRFTextToList(&list, langid, _cur.grfconfig->ident.grfid, false, name_string);
 			_cur_parameter->value_names.Insert(id, list);
 		}
@@ -7851,7 +7851,7 @@ static bool HandleParameterInfo(ByteRead
 		if (id >= _cur.grfconfig->param_info.size()) {
 			_cur.grfconfig->param_info.resize(id + 1);
 		}
-		if (_cur.grfconfig->param_info[id] == NULL) {
+		if (_cur.grfconfig->param_info[id] == nullptr) {
 			_cur.grfconfig->param_info[id] = new GRFParameterInfo(id);
 		}
 		_cur_parameter = _cur.grfconfig->param_info[id];
@@ -8094,9 +8094,9 @@ static void ResetCustomStations()
 {
 	for (GRFFile * const file : _grf_files) {
 		StationSpec **&stations = file->stations;
-		if (stations == NULL) continue;
+		if (stations == nullptr) continue;
 		for (uint i = 0; i < NUM_STATIONS_PER_GRF; i++) {
-			if (stations[i] == NULL) continue;
+			if (stations[i] == nullptr) continue;
 			StationSpec *statspec = stations[i];
 
 			delete[] statspec->renderdata;
@@ -8119,7 +8119,7 @@ static void ResetCustomStations()
 
 		/* Free and reset the station data */
 		free(stations);
-		stations = NULL;
+		stations = nullptr;
 	}
 }
 
@@ -8128,13 +8128,13 @@ static void ResetCustomHouses()
 {
 	for (GRFFile * const file : _grf_files) {
 		HouseSpec **&housespec = file->housespec;
-		if (housespec == NULL) continue;
+		if (housespec == nullptr) continue;
 		for (uint i = 0; i < NUM_HOUSES_PER_GRF; i++) {
 			free(housespec[i]);
 		}
 
 		free(housespec);
-		housespec = NULL;
+		housespec = nullptr;
 	}
 }
 
@@ -8143,11 +8143,11 @@ static void ResetCustomAirports()
 {
 	for (GRFFile * const file : _grf_files) {
 		AirportSpec **aslist = file->airportspec;
-		if (aslist != NULL) {
+		if (aslist != nullptr) {
 			for (uint i = 0; i < NUM_AIRPORTS_PER_GRF; i++) {
 				AirportSpec *as = aslist[i];
 
-				if (as != NULL) {
+				if (as != nullptr) {
 					/* We need to remove the tiles layouts */
 					for (int j = 0; j < as->num_table; j++) {
 						/* remove the individual layouts */
@@ -8161,16 +8161,16 @@ static void ResetCustomAirports()
 				}
 			}
 			free(aslist);
-			file->airportspec = NULL;
+			file->airportspec = nullptr;
 		}
 
 		AirportTileSpec **&airporttilespec = file->airtspec;
-		if (airporttilespec != NULL) {
+		if (airporttilespec != nullptr) {
 			for (uint i = 0; i < NUM_AIRPORTTILES_PER_GRF; i++) {
 				free(airporttilespec[i]);
 			}
 			free(airporttilespec);
-			airporttilespec = NULL;
+			airporttilespec = nullptr;
 		}
 	}
 }
@@ -8184,10 +8184,10 @@ static void ResetCustomIndustries()
 
 		/* We are verifiying both tiles and industries specs loaded from the grf file
 		 * First, let's deal with industryspec */
-		if (industryspec != NULL) {
+		if (industryspec != nullptr) {
 			for (uint i = 0; i < NUM_INDUSTRYTYPES_PER_GRF; i++) {
 				IndustrySpec *ind = industryspec[i];
-				if (ind == NULL) continue;
+				if (ind == nullptr) continue;
 
 				/* We need to remove the sounds array */
 				if (HasBit(ind->cleanup_flag, CLEAN_RANDOMSOUNDS)) {
@@ -8201,16 +8201,16 @@ static void ResetCustomIndustries()
 			}
 
 			free(industryspec);
-			industryspec = NULL;
-		}
-
-		if (indtspec == NULL) continue;
+			industryspec = nullptr;
+		}
+
+		if (indtspec == nullptr) continue;
 		for (uint i = 0; i < NUM_INDUSTRYTILES_PER_GRF; i++) {
 			free(indtspec[i]);
 		}
 
 		free(indtspec);
-		indtspec = NULL;
+		indtspec = nullptr;
 	}
 }
 
@@ -8219,13 +8219,13 @@ static void ResetCustomObjects()
 {
 	for (GRFFile * const file : _grf_files) {
 		ObjectSpec **&objectspec = file->objectspec;
-		if (objectspec == NULL) continue;
+		if (objectspec == nullptr) continue;
 		for (uint i = 0; i < NUM_OBJECTS_PER_GRF; i++) {
 			free(objectspec[i]);
 		}
 
 		free(objectspec);
-		objectspec = NULL;
+		objectspec = nullptr;
 	}
 }
 
@@ -8237,16 +8237,16 @@ static void ResetNewGRF()
 	}
 
 	_grf_files.clear();
-	_cur.grffile   = NULL;
+	_cur.grffile   = nullptr;
 }
 
 /** Clear all NewGRF errors */
 static void ResetNewGRFErrors()
 {
-	for (GRFConfig *c = _grfconfig; c != NULL; c = c->next) {
-		if (!HasBit(c->flags, GCF_COPY) && c->error != NULL) {
+	for (GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
+		if (!HasBit(c->flags, GCF_COPY) && c->error != nullptr) {
 			delete c->error;
-			c->error = NULL;
+			c->error = nullptr;
 		}
 	}
 }
@@ -8388,7 +8388,7 @@ static void BuildCargoTranslationMap()
 static void InitNewGRFFile(const GRFConfig *config)
 {
 	GRFFile *newfile = GetFileByFilename(config->filename);
-	if (newfile != NULL) {
+	if (newfile != nullptr) {
 		/* We already loaded it once. */
 		_cur.grffile = newfile;
 		return;
@@ -8546,16 +8546,16 @@ static void CalculateRefitMasks()
 		 * cargo type. Finally disable the vehicle, if there is still no cargo. */
 		if (ei->cargo_type == CT_INVALID && ei->refit_mask != 0) {
 			/* Figure out which CTT to use for the default cargo, if it is 'first refittable'. */
-			const uint8 *cargo_map_for_first_refittable = NULL;
+			const uint8 *cargo_map_for_first_refittable = nullptr;
 			{
 				const GRFFile *file = _gted[engine].defaultcargo_grf;
-				if (file == NULL) file = e->GetGRF();
-				if (file != NULL && file->grf_version >= 8 && file->cargo_list.size() != 0) {
+				if (file == nullptr) file = e->GetGRF();
+				if (file != nullptr && file->grf_version >= 8 && file->cargo_list.size() != 0) {
 					cargo_map_for_first_refittable = file->cargo_map;
 				}
 			}
 
-			if (cargo_map_for_first_refittable != NULL) {
+			if (cargo_map_for_first_refittable != nullptr) {
 				/* Use first refittable cargo from cargo translation table */
 				byte best_local_slot = 0xFF;
 				CargoID cargo_type;
@@ -8586,7 +8586,7 @@ static void CalculateRefitMasks()
 static void FinaliseCanals()
 {
 	for (uint i = 0; i < CF_END; i++) {
-		if (_water_feature[i].grffile != NULL) {
+		if (_water_feature[i].grffile != nullptr) {
 			_water_feature[i].callback_mask = _water_feature[i].grffile->canal_local_properties[i].callback_mask;
 			_water_feature[i].flags = _water_feature[i].grffile->canal_local_properties[i].flags;
 		}
@@ -8599,7 +8599,7 @@ static void FinaliseEngineArray()
 	Engine *e;
 
 	FOR_ALL_ENGINES(e) {
-		if (e->GetGRF() == NULL) {
+		if (e->GetGRF() == nullptr) {
 			const EngineIDMapping &eid = _engine_mngr[e->index];
 			if (eid.grfid != INVALID_GRFID || eid.internal_id != eid.substitute_id) {
 				e->info.string_id = STR_NEWGRF_INVALID_ENGINE;
@@ -8611,13 +8611,13 @@ static void FinaliseEngineArray()
 		/* When the train does not set property 27 (misc flags), but it
 		 * is overridden by a NewGRF graphically we want to disable the
 		 * flipping possibility. */
-		if (e->type == VEH_TRAIN && !_gted[e->index].prop27_set && e->GetGRF() != NULL && is_custom_sprite(e->u.rail.image_index)) {
+		if (e->type == VEH_TRAIN && !_gted[e->index].prop27_set && e->GetGRF() != nullptr && is_custom_sprite(e->u.rail.image_index)) {
 			ClrBit(e->info.misc_flags, EF_RAIL_FLIPS);
 		}
 
 		/* Skip wagons, there livery is defined via the engine */
 		if (e->type != VEH_TRAIN || e->u.rail.railveh_type != RAILVEH_WAGON) {
-			LiveryScheme ls = GetEngineLiveryScheme(e->index, INVALID_ENGINE, NULL);
+			LiveryScheme ls = GetEngineLiveryScheme(e->index, INVALID_ENGINE, nullptr);
 			SetBit(_loaded_newgrf_features.used_liveries, ls);
 			/* Note: For ships and roadvehicles we assume that they cannot be refitted between passenger and freight */
 
@@ -8671,12 +8671,12 @@ static void FinaliseCargoArray()
 static bool IsHouseSpecValid(HouseSpec *hs, const HouseSpec *next1, const HouseSpec *next2, const HouseSpec *next3, const char *filename)
 {
 	if (((hs->building_flags & BUILDING_HAS_2_TILES) != 0 &&
-				(next1 == NULL || !next1->enabled || (next1->building_flags & BUILDING_HAS_1_TILE) != 0)) ||
+				(next1 == nullptr || !next1->enabled || (next1->building_flags & BUILDING_HAS_1_TILE) != 0)) ||
 			((hs->building_flags & BUILDING_HAS_4_TILES) != 0 &&
-				(next2 == NULL || !next2->enabled || (next2->building_flags & BUILDING_HAS_1_TILE) != 0 ||
-				next3 == NULL || !next3->enabled || (next3->building_flags & BUILDING_HAS_1_TILE) != 0))) {
+				(next2 == nullptr || !next2->enabled || (next2->building_flags & BUILDING_HAS_1_TILE) != 0 ||
+				next3 == nullptr || !next3->enabled || (next3->building_flags & BUILDING_HAS_1_TILE) != 0))) {
 		hs->enabled = false;
-		if (filename != NULL) DEBUG(grf, 1, "FinaliseHouseArray: %s defines house %d as multitile, but no suitable tiles follow. Disabling house.", filename, hs->grf_prop.local_id);
+		if (filename != nullptr) DEBUG(grf, 1, "FinaliseHouseArray: %s defines house %d as multitile, but no suitable tiles follow. Disabling house.", filename, hs->grf_prop.local_id);
 		return false;
 	}
 
@@ -8686,13 +8686,13 @@ static bool IsHouseSpecValid(HouseSpec *
 	if (((hs->building_flags & BUILDING_HAS_2_TILES) != 0 && next1->population != 0) ||
 			((hs->building_flags & BUILDING_HAS_4_TILES) != 0 && (next2->population != 0 || next3->population != 0))) {
 		hs->enabled = false;
-		if (filename != NULL) DEBUG(grf, 1, "FinaliseHouseArray: %s defines multitile house %d with non-zero population on additional tiles. Disabling house.", filename, hs->grf_prop.local_id);
+		if (filename != nullptr) DEBUG(grf, 1, "FinaliseHouseArray: %s defines multitile house %d with non-zero population on additional tiles. Disabling house.", filename, hs->grf_prop.local_id);
 		return false;
 	}
 
 	/* Substitute type is also used for override, and having an override with a different size causes crashes.
 	 * This check should only be done for NewGRF houses because grf_prop.subst_id is not set for original houses.*/
-	if (filename != NULL && (hs->building_flags & BUILDING_HAS_1_TILE) != (HouseSpec::Get(hs->grf_prop.subst_id)->building_flags & BUILDING_HAS_1_TILE)) {
+	if (filename != nullptr && (hs->building_flags & BUILDING_HAS_1_TILE) != (HouseSpec::Get(hs->grf_prop.subst_id)->building_flags & BUILDING_HAS_1_TILE)) {
 		hs->enabled = false;
 		DEBUG(grf, 1, "FinaliseHouseArray: %s defines house %d with different house size then it's substitute type. Disabling house.", filename, hs->grf_prop.local_id);
 		return false;
@@ -8701,7 +8701,7 @@ static bool IsHouseSpecValid(HouseSpec *
 	/* Make sure that additional parts of multitile houses are not available. */
 	if ((hs->building_flags & BUILDING_HAS_1_TILE) == 0 && (hs->building_availability & HZ_ZONALL) != 0 && (hs->building_availability & HZ_CLIMALL) != 0) {
 		hs->enabled = false;
-		if (filename != NULL) DEBUG(grf, 1, "FinaliseHouseArray: %s defines house %d without a size but marked it as available. Disabling house.", filename, hs->grf_prop.local_id);
+		if (filename != nullptr) DEBUG(grf, 1, "FinaliseHouseArray: %s defines house %d without a size but marked it as available. Disabling house.", filename, hs->grf_prop.local_id);
 		return false;
 	}
 
@@ -8720,7 +8720,7 @@ static void EnsureEarlyHouse(HouseZones 
 
 	for (int i = 0; i < NUM_HOUSES; i++) {
 		HouseSpec *hs = HouseSpec::Get(i);
-		if (hs == NULL || !hs->enabled) continue;
+		if (hs == nullptr || !hs->enabled) continue;
 		if ((hs->building_availability & bitmask) != bitmask) continue;
 		if (hs->min_year < min_year) min_year = hs->min_year;
 	}
@@ -8729,7 +8729,7 @@ static void EnsureEarlyHouse(HouseZones 
 
 	for (int i = 0; i < NUM_HOUSES; i++) {
 		HouseSpec *hs = HouseSpec::Get(i);
-		if (hs == NULL || !hs->enabled) continue;
+		if (hs == nullptr || !hs->enabled) continue;
 		if ((hs->building_availability & bitmask) != bitmask) continue;
 		if (hs->min_year == min_year) hs->min_year = 0;
 	}
@@ -8754,16 +8754,16 @@ static void FinaliseHouseArray()
 	 */
 	for (GRFFile * const file : _grf_files) {
 		HouseSpec **&housespec = file->housespec;
-		if (housespec == NULL) continue;
+		if (housespec == nullptr) continue;
 
 		for (int i = 0; i < NUM_HOUSES_PER_GRF; i++) {
 			HouseSpec *hs = housespec[i];
 
-			if (hs == NULL) continue;
-
-			const HouseSpec *next1 = (i + 1 < NUM_HOUSES_PER_GRF ? housespec[i + 1] : NULL);
-			const HouseSpec *next2 = (i + 2 < NUM_HOUSES_PER_GRF ? housespec[i + 2] : NULL);
-			const HouseSpec *next3 = (i + 3 < NUM_HOUSES_PER_GRF ? housespec[i + 3] : NULL);
+			if (hs == nullptr) continue;
+
+			const HouseSpec *next1 = (i + 1 < NUM_HOUSES_PER_GRF ? housespec[i + 1] : nullptr);
+			const HouseSpec *next2 = (i + 2 < NUM_HOUSES_PER_GRF ? housespec[i + 2] : nullptr);
+			const HouseSpec *next3 = (i + 3 < NUM_HOUSES_PER_GRF ? housespec[i + 3] : nullptr);
 
 			if (!IsHouseSpecValid(hs, next1, next2, next3, file->filename)) continue;
 
@@ -8773,13 +8773,13 @@ static void FinaliseHouseArray()
 
 	for (int i = 0; i < NUM_HOUSES; i++) {
 		HouseSpec *hs = HouseSpec::Get(i);
-		const HouseSpec *next1 = (i + 1 < NUM_HOUSES ? HouseSpec::Get(i + 1) : NULL);
-		const HouseSpec *next2 = (i + 2 < NUM_HOUSES ? HouseSpec::Get(i + 2) : NULL);
-		const HouseSpec *next3 = (i + 3 < NUM_HOUSES ? HouseSpec::Get(i + 3) : NULL);
+		const HouseSpec *next1 = (i + 1 < NUM_HOUSES ? HouseSpec::Get(i + 1) : nullptr);
+		const HouseSpec *next2 = (i + 2 < NUM_HOUSES ? HouseSpec::Get(i + 2) : nullptr);
+		const HouseSpec *next3 = (i + 3 < NUM_HOUSES ? HouseSpec::Get(i + 3) : nullptr);
 
 		/* We need to check all houses again to we are sure that multitile houses
 		 * did get consecutive IDs and none of the parts are missing. */
-		if (!IsHouseSpecValid(hs, next1, next2, next3, NULL)) {
+		if (!IsHouseSpecValid(hs, next1, next2, next3, nullptr)) {
 			/* GetHouseNorthPart checks 3 houses that are directly before
 			 * it in the house pool. If any of those houses have multi-tile
 			 * flags set it assumes it's part of a multitile house. Since
@@ -8817,11 +8817,11 @@ static void FinaliseIndustriesArray()
 	for (GRFFile * const file : _grf_files) {
 		IndustrySpec **&industryspec = file->industryspec;
 		IndustryTileSpec **&indtspec = file->indtspec;
-		if (industryspec != NULL) {
+		if (industryspec != nullptr) {
 			for (int i = 0; i < NUM_INDUSTRYTYPES_PER_GRF; i++) {
 				IndustrySpec *indsp = industryspec[i];
 
-				if (indsp != NULL && indsp->enabled) {
+				if (indsp != nullptr && indsp->enabled) {
 					StringID strid;
 					/* process the conversion of text at the end, so to be sure everything will be fine
 					 * and available.  Check if it does not return undefind marker, which is a very good sign of a
@@ -8854,10 +8854,10 @@ static void FinaliseIndustriesArray()
 			}
 		}
 
-		if (indtspec != NULL) {
+		if (indtspec != nullptr) {
 			for (int i = 0; i < NUM_INDUSTRYTILES_PER_GRF; i++) {
 				IndustryTileSpec *indtsp = indtspec[i];
-				if (indtsp != NULL) {
+				if (indtsp != nullptr) {
 					_industile_mngr.SetEntitySpec(indtsp);
 				}
 			}
@@ -8866,7 +8866,7 @@ static void FinaliseIndustriesArray()
 
 	for (uint j = 0; j < NUM_INDUSTRYTYPES; j++) {
 		IndustrySpec *indsp = &_industry_specs[j];
-		if (indsp->enabled && indsp->grf_prop.grffile != NULL) {
+		if (indsp->enabled && indsp->grf_prop.grffile != nullptr) {
 			for (uint i = 0; i < 3; i++) {
 				indsp->conflicting[i] = MapNewGRFIndustryType(indsp->conflicting[i], indsp->grf_prop.grffile->grfid);
 			}
@@ -8886,9 +8886,9 @@ static void FinaliseObjectsArray()
 {
 	for (GRFFile * const file : _grf_files) {
 		ObjectSpec **&objectspec = file->objectspec;
-		if (objectspec != NULL) {
+		if (objectspec != nullptr) {
 			for (int i = 0; i < NUM_OBJECTS_PER_GRF; i++) {
-				if (objectspec[i] != NULL && objectspec[i]->grf_prop.grffile != NULL && objectspec[i]->enabled) {
+				if (objectspec[i] != nullptr && objectspec[i]->grf_prop.grffile != nullptr && objectspec[i]->enabled) {
 					_object_mngr.SetEntitySpec(objectspec[i]);
 				}
 			}
@@ -8905,18 +8905,18 @@ static void FinaliseAirportsArray()
 {
 	for (GRFFile * const file : _grf_files) {
 		AirportSpec **&airportspec = file->airportspec;
-		if (airportspec != NULL) {
+		if (airportspec != nullptr) {
 			for (int i = 0; i < NUM_AIRPORTS_PER_GRF; i++) {
-				if (airportspec[i] != NULL && airportspec[i]->enabled) {
+				if (airportspec[i] != nullptr && airportspec[i]->enabled) {
 					_airport_mngr.SetEntitySpec(airportspec[i]);
 				}
 			}
 		}
 
 		AirportTileSpec **&airporttilespec = file->airtspec;
-		if (airporttilespec != NULL) {
+		if (airporttilespec != nullptr) {
 			for (uint i = 0; i < NUM_AIRPORTTILES_PER_GRF; i++) {
-				if (airporttilespec[i] != NULL && airporttilespec[i]->enabled) {
+				if (airporttilespec[i] != nullptr && airporttilespec[i]->enabled) {
 					_airporttile_mngr.SetEntitySpec(airporttilespec[i]);
 				}
 			}
@@ -8945,27 +8945,27 @@ static void DecodeSpecialSprite(byte *bu
 	 * is not in memory and scanning the file every time would be too expensive.
 	 * In other stages we skip action 0x10 since it's already dealt with. */
 	static const SpecialSpriteHandler handlers[][GLS_END] = {
-		/* 0x00 */ { NULL,     SafeChangeInfo, NULL,       NULL,           ReserveChangeInfo, FeatureChangeInfo, },
+		/* 0x00 */ { nullptr,     SafeChangeInfo, nullptr,       nullptr,           ReserveChangeInfo, FeatureChangeInfo, },
 		/* 0x01 */ { SkipAct1, SkipAct1,  SkipAct1,        SkipAct1,       SkipAct1,          NewSpriteSet, },
-		/* 0x02 */ { NULL,     NULL,      NULL,            NULL,           NULL,              NewSpriteGroup, },
-		/* 0x03 */ { NULL,     GRFUnsafe, NULL,            NULL,           NULL,              FeatureMapSpriteGroup, },
-		/* 0x04 */ { NULL,     NULL,      NULL,            NULL,           NULL,              FeatureNewName, },
+		/* 0x02 */ { nullptr,     nullptr,      nullptr,            nullptr,           nullptr,              NewSpriteGroup, },
+		/* 0x03 */ { nullptr,     GRFUnsafe, nullptr,            nullptr,           nullptr,              FeatureMapSpriteGroup, },
+		/* 0x04 */ { nullptr,     nullptr,      nullptr,            nullptr,           nullptr,              FeatureNewName, },
 		/* 0x05 */ { SkipAct5, SkipAct5,  SkipAct5,        SkipAct5,       SkipAct5,          GraphicsNew, },
-		/* 0x06 */ { NULL,     NULL,      NULL,            CfgApply,       CfgApply,          CfgApply, },
-		/* 0x07 */ { NULL,     NULL,      NULL,            NULL,           SkipIf,            SkipIf, },
-		/* 0x08 */ { ScanInfo, NULL,      NULL,            GRFInfo,        GRFInfo,           GRFInfo, },
-		/* 0x09 */ { NULL,     NULL,      NULL,            SkipIf,         SkipIf,            SkipIf, },
+		/* 0x06 */ { nullptr,     nullptr,      nullptr,            CfgApply,       CfgApply,          CfgApply, },
+		/* 0x07 */ { nullptr,     nullptr,      nullptr,            nullptr,           SkipIf,            SkipIf, },
+		/* 0x08 */ { ScanInfo, nullptr,      nullptr,            GRFInfo,        GRFInfo,           GRFInfo, },
+		/* 0x09 */ { nullptr,     nullptr,      nullptr,            SkipIf,         SkipIf,            SkipIf, },
 		/* 0x0A */ { SkipActA, SkipActA,  SkipActA,        SkipActA,       SkipActA,          SpriteReplace, },
-		/* 0x0B */ { NULL,     NULL,      NULL,            GRFLoadError,   GRFLoadError,      GRFLoadError, },
-		/* 0x0C */ { NULL,     NULL,      NULL,            GRFComment,     NULL,              GRFComment, },
-		/* 0x0D */ { NULL,     SafeParamSet, NULL,         ParamSet,       ParamSet,          ParamSet, },
-		/* 0x0E */ { NULL,     SafeGRFInhibit, NULL,       GRFInhibit,     GRFInhibit,        GRFInhibit, },
-		/* 0x0F */ { NULL,     GRFUnsafe, NULL,            FeatureTownName, NULL,             NULL, },
-		/* 0x10 */ { NULL,     NULL,      DefineGotoLabel, NULL,           NULL,              NULL, },
+		/* 0x0B */ { nullptr,     nullptr,      nullptr,            GRFLoadError,   GRFLoadError,      GRFLoadError, },
+		/* 0x0C */ { nullptr,     nullptr,      nullptr,            GRFComment,     nullptr,              GRFComment, },
+		/* 0x0D */ { nullptr,     SafeParamSet, nullptr,         ParamSet,       ParamSet,          ParamSet, },
+		/* 0x0E */ { nullptr,     SafeGRFInhibit, nullptr,       GRFInhibit,     GRFInhibit,        GRFInhibit, },
+		/* 0x0F */ { nullptr,     GRFUnsafe, nullptr,            FeatureTownName, nullptr,             nullptr, },
+		/* 0x10 */ { nullptr,     nullptr,      DefineGotoLabel, nullptr,           nullptr,              nullptr, },
 		/* 0x11 */ { SkipAct11,GRFUnsafe, SkipAct11,       GRFSound,       SkipAct11,         GRFSound, },
 		/* 0x12 */ { SkipAct12, SkipAct12, SkipAct12,      SkipAct12,      SkipAct12,         LoadFontGlyph, },
-		/* 0x13 */ { NULL,     NULL,      NULL,            NULL,           NULL,              TranslateGRFStrings, },
-		/* 0x14 */ { StaticGRFInfo, NULL, NULL,            NULL,           NULL,              NULL, },
+		/* 0x13 */ { nullptr,     nullptr,      nullptr,            nullptr,           nullptr,              TranslateGRFStrings, },
+		/* 0x14 */ { StaticGRFInfo, nullptr, nullptr,            nullptr,           nullptr,              nullptr, },
 	};
 
 	GRFLocation location(_cur.grfconfig->ident.grfid, _cur.nfo_line);
@@ -8996,7 +8996,7 @@ static void DecodeSpecialSprite(byte *bu
 			grfmsg(2, "DecodeSpecialSprite: Unexpected import block, skipping");
 		} else if (action >= lengthof(handlers)) {
 			grfmsg(7, "DecodeSpecialSprite: Skipping unknown action 0x%02X", action);
-		} else if (handlers[action][stage] == NULL) {
+		} else if (handlers[action][stage] == nullptr) {
 			grfmsg(7, "DecodeSpecialSprite: Skipping action 0x%02X in stage %d", action, stage);
 		} else {
 			grfmsg(7, "DecodeSpecialSprite: Handling action 0x%02X in stage %d", action, stage);
@@ -9057,7 +9057,7 @@ void LoadNewGRFFile(GRFConfig *config, u
 	 * processed once at initialization.  */
 	if (stage != GLS_FILESCAN && stage != GLS_SAFETYSCAN && stage != GLS_LABELSCAN) {
 		_cur.grffile = GetFileByFilename(filename);
-		if (_cur.grffile == NULL) usererror("File '%s' lost in cache.\n", filename);
+		if (_cur.grffile == nullptr) usererror("File '%s' lost in cache.\n", filename);
 		if (stage == GLS_RESERVE && config->status != GCS_INITIALISED) return;
 		if (stage == GLS_ACTIVATION && !HasBit(config->flags, GCF_RESERVED)) return;
 	}
@@ -9212,7 +9212,7 @@ static void FinalisePriceBaseMultipliers
 		if (override == 0) continue;
 
 		GRFFile *dest = GetFileByGRFID(override);
-		if (dest == NULL) continue;
+		if (dest == nullptr) continue;
 
 		grf_overrides[i] = find_index(_grf_files, dest);
 		assert(grf_overrides[i] >= 0);
@@ -9437,7 +9437,7 @@ void LoadNewGRF(uint load_index, uint fi
 	 * be reset, the NewGRF would remain disabled even though it should
 	 * have been enabled.
 	 */
-	for (GRFConfig *c = _grfconfig; c != NULL; c = c->next) {
+	for (GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
 		if (c->status != GCS_NOT_FOUND) c->status = GCS_UNKNOWN;
 	}
 
@@ -9449,7 +9449,7 @@ void LoadNewGRF(uint load_index, uint fi
 	for (GrfLoadingStage stage = GLS_LABELSCAN; stage <= GLS_ACTIVATION; stage++) {
 		/* Set activated grfs back to will-be-activated between reservation- and activation-stage.
 		 * This ensures that action7/9 conditions 0x06 - 0x0A work correctly. */
-		for (GRFConfig *c = _grfconfig; c != NULL; c = c->next) {
+		for (GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
 			if (c->status == GCS_ACTIVATED) c->status = GCS_INITIALISED;
 		}
 
@@ -9468,7 +9468,7 @@ void LoadNewGRF(uint load_index, uint fi
 		uint num_non_static = 0;
 
 		_cur.stage = stage;
-		for (GRFConfig *c = _grfconfig; c != NULL; c = c->next) {
+		for (GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
 			if (c->status == GCS_DISABLED || c->status == GCS_NOT_FOUND) continue;
 			if (stage > GLS_INIT && HasBit(c->flags, GCF_INIT_ONLY)) continue;
 
diff --git a/src/newgrf_airport.cpp b/src/newgrf_airport.cpp
--- a/src/newgrf_airport.cpp
+++ b/src/newgrf_airport.cpp
@@ -21,7 +21,7 @@
 
 /** Resolver for the airport scope. */
 struct AirportScopeResolver : public ScopeResolver {
-	struct Station *st; ///< Station of the airport for which the callback is run, or \c NULL for build gui.
+	struct Station *st; ///< Station of the airport for which the callback is run, or \c nullptr for build gui.
 	byte airport_id;    ///< Type of airport for which the callback is run.
 	byte layout;        ///< Layout of the airport to build.
 	TileIndex tile;     ///< Tile for the callback, only valid for airporttile callbacks.
@@ -30,7 +30,7 @@ struct AirportScopeResolver : public Sco
 	 * Constructor of the scope resolver for an airport.
 	 * @param ro Surrounding resolver.
 	 * @param tile %Tile for the callback, only valid for airporttile callbacks.
-	 * @param st %Station of the airport for which the callback is run, or \c NULL for build gui.
+	 * @param st %Station of the airport for which the callback is run, or \c nullptr for build gui.
 	 * @param airport_id Type of airport for which the callback is run.
 	 * @param layout Layout of the airport to build.
 	 */
@@ -202,14 +202,14 @@ void AirportOverrideManager::SetEntitySp
 		case 0x40: return this->layout;
 	}
 
-	if (this->st == NULL) {
+	if (this->st == nullptr) {
 		*available = false;
 		return UINT_MAX;
 	}
 
 	switch (variable) {
 		/* Get a variable from the persistent storage */
-		case 0x7C: return (this->st->airport.psa != NULL) ? this->st->airport.psa->GetValue(parameter) : 0;
+		case 0x7C: return (this->st->airport.psa != nullptr) ? this->st->airport.psa->GetValue(parameter) : 0;
 
 		case 0xF0: return this->st->facilities;
 		case 0xFA: return Clamp(this->st->build_date - DAYS_TILL_ORIGINAL_BASE_YEAR, 0, 65535);
@@ -225,12 +225,12 @@ void AirportOverrideManager::SetEntitySp
 	if (group->num_loaded > 0) return group->loaded[0];
 	if (group->num_loading > 0) return group->loading[0];
 
-	return NULL;
+	return nullptr;
 }
 
 /* virtual */ uint32 AirportScopeResolver::GetRandomBits() const
 {
-	return this->st == NULL ? 0 : this->st->random_bits;
+	return this->st == nullptr ? 0 : this->st->random_bits;
 }
 
 /**
@@ -240,14 +240,14 @@ void AirportOverrideManager::SetEntitySp
  */
 /* virtual */ void AirportScopeResolver::StorePSA(uint pos, int32 value)
 {
-	if (this->st == NULL) return;
+	if (this->st == nullptr) return;
 
-	if (this->st->airport.psa == NULL) {
+	if (this->st->airport.psa == nullptr) {
 		/* There is no need to create a storage if the value is zero. */
 		if (value == 0) return;
 
 		/* Create storage on first modification. */
-		uint32 grfid = (this->ro.grffile != NULL) ? this->ro.grffile->grfid : 0;
+		uint32 grfid = (this->ro.grffile != nullptr) ? this->ro.grffile->grfid : 0;
 		assert(PersistentStorage::CanAllocateItem());
 		this->st->airport.psa = new PersistentStorage(grfid, GSF_AIRPORTS, this->st->airport.tile);
 	}
@@ -257,7 +257,7 @@ void AirportOverrideManager::SetEntitySp
 /**
  * Constructor of the airport resolver.
  * @param tile %Tile for the callback, only valid for airporttile callbacks.
- * @param st %Station of the airport for which the callback is run, or \c NULL for build gui.
+ * @param st %Station of the airport for which the callback is run, or \c nullptr for build gui.
  * @param airport_id Type of airport for which the callback is run.
  * @param layout Layout of the airport to build.
  * @param callback Callback ID.
@@ -273,9 +273,9 @@ AirportResolverObject::AirportResolverOb
 
 SpriteID GetCustomAirportSprite(const AirportSpec *as, byte layout)
 {
-	AirportResolverObject object(INVALID_TILE, NULL, as->GetIndex(), layout);
+	AirportResolverObject object(INVALID_TILE, nullptr, as->GetIndex(), layout);
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL) return as->preview_sprite;
+	if (group == nullptr) return as->preview_sprite;
 
 	return group->GetResult();
 }
@@ -295,7 +295,7 @@ uint16 GetAirportCallback(CallbackID cal
  */
 StringID GetAirportTextCallback(const AirportSpec *as, byte layout, uint16 callback)
 {
-	AirportResolverObject object(INVALID_TILE, NULL, as->GetIndex(), layout, (CallbackID)callback);
+	AirportResolverObject object(INVALID_TILE, nullptr, as->GetIndex(), layout, (CallbackID)callback);
 	uint16 cb_res = object.ResolveCallback();
 	if (cb_res == CALLBACK_FAILED || cb_res == 0x400) return STR_UNDEFINED;
 	if (cb_res > 0x400) {
diff --git a/src/newgrf_airporttiles.cpp b/src/newgrf_airporttiles.cpp
--- a/src/newgrf_airporttiles.cpp
+++ b/src/newgrf_airporttiles.cpp
@@ -149,7 +149,7 @@ static uint32 GetAirportTileIDAtOffset(T
 		}
 	}
 	/* Not an 'old type' tile */
-	if (ats->grf_prop.spritegroup[0] != NULL) { // tile has a spritegroup ?
+	if (ats->grf_prop.spritegroup[0] != nullptr) { // tile has a spritegroup ?
 		if (ats->grf_prop.grffile->grfid == cur_grfid) { // same airport, same grf ?
 			return ats->grf_prop.local_id;
 		} else {
@@ -162,7 +162,7 @@ static uint32 GetAirportTileIDAtOffset(T
 
 /* virtual */ uint32 AirportTileScopeResolver::GetVariable(byte variable, uint32 parameter, bool *available) const
 {
-	assert(this->st != NULL);
+	assert(this->st != nullptr);
 
 	extern uint32 GetRelativePosition(TileIndex tile, TileIndex ind_tile);
 
@@ -203,14 +203,14 @@ static uint32 GetAirportTileIDAtOffset(T
 
 /* virtual */ uint32 AirportTileScopeResolver::GetRandomBits() const
 {
-	return (this->st == NULL ? 0 : this->st->random_bits) | (this->tile == INVALID_TILE ? 0 : GetStationTileRandomBits(this->tile) << 16);
+	return (this->st == nullptr ? 0 : this->st->random_bits) | (this->tile == INVALID_TILE ? 0 : GetStationTileRandomBits(this->tile) << 16);
 }
 
 /**
  * Constructor of the resolver for airport tiles.
  * @param ats Specification of the airport tiles.
  * @param tile %Tile for the callback, only valid for airporttile callbacks.
- * @param st Station of the airport for which the callback is run, or \c NULL for build gui.
+ * @param st Station of the airport for which the callback is run, or \c nullptr for build gui.
  * @param callback Callback ID.
  * @param callback_param1 First parameter (var 10) of the callback.
  * @param callback_param2 Second parameter (var 18) of the callback.
@@ -230,7 +230,7 @@ uint16 GetAirportTileCallback(CallbackID
 
 static void AirportDrawTileLayout(const TileInfo *ti, const TileLayoutSpriteGroup *group, byte colour, StationGfx gfx)
 {
-	const DrawTileSprites *dts = group->ProcessRegisters(NULL);
+	const DrawTileSprites *dts = group->ProcessRegisters(nullptr);
 
 	SpriteID image = dts->ground.sprite;
 	SpriteID pal   = dts->ground.pal;
@@ -261,7 +261,7 @@ bool DrawNewAirportTile(TileInfo *ti, St
 
 	AirportTileResolverObject object(airts, ti->tile, st);
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL || group->type != SGT_TILELAYOUT) {
+	if (group == nullptr || group->type != SGT_TILELAYOUT) {
 		return false;
 	}
 
@@ -282,7 +282,7 @@ struct AirportTileAnimationBase : public
 void AnimateAirportTile(TileIndex tile)
 {
 	const AirportTileSpec *ats = AirportTileSpec::GetByTile(tile);
-	if (ats == NULL) return;
+	if (ats == nullptr) return;
 
 	AirportTileAnimationBase::AnimateTile(ats, Station::GetByTile(tile), tile, HasBit(ats->animation_special_flags, 0));
 }
diff --git a/src/newgrf_airporttiles.h b/src/newgrf_airporttiles.h
--- a/src/newgrf_airporttiles.h
+++ b/src/newgrf_airporttiles.h
@@ -21,7 +21,7 @@
 
 /** Scope resolver for handling the tiles of an airport. */
 struct AirportTileScopeResolver : public ScopeResolver {
-	struct Station *st;  ///< %Station of the airport for which the callback is run, or \c NULL for build gui.
+	struct Station *st;  ///< %Station of the airport for which the callback is run, or \c nullptr for build gui.
 	byte airport_id;     ///< Type of airport for which the callback is run.
 	TileIndex tile;      ///< Tile for the callback, only valid for airporttile callbacks.
 
@@ -29,12 +29,12 @@ struct AirportTileScopeResolver : public
 	 * Constructor of the scope resolver specific for airport tiles.
 	 * @param ats Specification of the airport tiles.
 	 * @param tile %Tile for the callback, only valid for airporttile callbacks.
-	 * @param st Station of the airport for which the callback is run, or \c NULL for build gui.
+	 * @param st Station of the airport for which the callback is run, or \c nullptr for build gui.
 	 */
 	AirportTileScopeResolver(ResolverObject &ro, const AirportTileSpec *ats, TileIndex tile, Station *st)
 		: ScopeResolver(ro), st(st), tile(tile)
 	{
-		assert(st != NULL);
+		assert(st != nullptr);
 		this->airport_id = st->airport.type;
 	}
 
diff --git a/src/newgrf_animation_base.h b/src/newgrf_animation_base.h
--- a/src/newgrf_animation_base.h
+++ b/src/newgrf_animation_base.h
@@ -39,7 +39,7 @@ struct AnimationBase {
 	 */
 	static void AnimateTile(const Tspec *spec, Tobj *obj, TileIndex tile, bool random_animation, Textra extra_data = 0)
 	{
-		assert(spec != NULL);
+		assert(spec != nullptr);
 
 		/* Acquire the animation speed from the NewGRF. */
 		uint8 animation_speed = spec->animation.speed;
diff --git a/src/newgrf_canal.cpp b/src/newgrf_canal.cpp
--- a/src/newgrf_canal.cpp
+++ b/src/newgrf_canal.cpp
@@ -108,7 +108,7 @@ struct CanalResolverObject : public Reso
 
 /* virtual */ const SpriteGroup *CanalResolverObject::ResolveReal(const RealSpriteGroup *group) const
 {
-	if (group->num_loaded == 0) return NULL;
+	if (group->num_loaded == 0) return nullptr;
 
 	return group->loaded[0];
 }
@@ -138,7 +138,7 @@ SpriteID GetCanalSprite(CanalFeature fea
 {
 	CanalResolverObject object(feature, tile);
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL) return 0;
+	if (group == nullptr) return 0;
 
 	return group->GetResult();
 }
diff --git a/src/newgrf_cargo.cpp b/src/newgrf_cargo.cpp
--- a/src/newgrf_cargo.cpp
+++ b/src/newgrf_cargo.cpp
@@ -29,7 +29,7 @@ struct CargoResolverObject : public Reso
 	if (group->num_loaded > 0) return group->loaded[0];
 	if (group->num_loading > 0) return group->loading[0];
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -54,7 +54,7 @@ SpriteID GetCustomCargoSprite(const Carg
 {
 	CargoResolverObject object(cs);
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL) return 0;
+	if (group == nullptr) return 0;
 
 	return group->GetResult();
 }
diff --git a/src/newgrf_class_func.h b/src/newgrf_class_func.h
--- a/src/newgrf_class_func.h
+++ b/src/newgrf_class_func.h
@@ -34,7 +34,7 @@ DEFINE_NEWGRF_CLASS_METHOD(void)::ResetC
 	this->ui_count  = 0;
 
 	free(this->spec);
-	this->spec = NULL;
+	this->spec = nullptr;
 }
 
 /** Reset the classes, i.e. clear everything. */
@@ -154,7 +154,7 @@ DEFINE_NEWGRF_CLASS_METHOD(Tid)::GetUICl
 DEFINE_NEWGRF_CLASS_METHOD(const Tspec *)::GetSpec(uint index) const
 {
 	/* If the custom spec isn't defined any more, then the GRF file probably was not loaded. */
-	return index < this->GetSpecCount() ? this->spec[index] : NULL;
+	return index < this->GetSpecCount() ? this->spec[index] : nullptr;
 }
 
 /**
@@ -191,7 +191,7 @@ DEFINE_NEWGRF_CLASS_METHOD(int)::GetUIFr
  * Retrieve a spec by GRF location.
  * @param grfid    GRF ID of spec.
  * @param local_id Index within GRF file of spec.
- * @param index    Pointer to return the index of the spec in its class. If NULL then not used.
+ * @param index    Pointer to return the index of the spec in its class. If nullptr then not used.
  * @return The spec.
  */
 DEFINE_NEWGRF_CLASS_METHOD(const Tspec *)::GetByGrf(uint32 grfid, byte local_id, int *index)
@@ -201,15 +201,15 @@ DEFINE_NEWGRF_CLASS_METHOD(const Tspec *
 	for (Tid i = (Tid)0; i < Tmax; i++) {
 		for (j = 0; j < classes[i].count; j++) {
 			const Tspec *spec = classes[i].spec[j];
-			if (spec == NULL) continue;
+			if (spec == nullptr) continue;
 			if (spec->grf_prop.grffile->grfid == grfid && spec->grf_prop.local_id == local_id) {
-				if (index != NULL) *index = j;
+				if (index != nullptr) *index = j;
 				return spec;
 			}
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 #undef DEFINE_NEWGRF_CLASS_METHOD
diff --git a/src/newgrf_commons.cpp b/src/newgrf_commons.cpp
--- a/src/newgrf_commons.cpp
+++ b/src/newgrf_commons.cpp
@@ -235,9 +235,9 @@ uint16 IndustryOverrideManager::AddEntit
 		const IndustrySpec *inds = GetIndustrySpec(id);
 
 		/* This industry must be one that is not available(enabled), mostly because of climate.
-		 * And it must not already be used by a grf (grffile == NULL).
+		 * And it must not already be used by a grf (grffile == nullptr).
 		 * So reserve this slot here, as it is the chosen one */
-		if (!inds->enabled && inds->grf_prop.grffile == NULL) {
+		if (!inds->enabled && inds->grf_prop.grffile == nullptr) {
 			EntityIDMapping *map = &mapping_ID[id];
 
 			if (map->entity_id == 0 && map->grfid == 0) {
@@ -463,13 +463,13 @@ uint32 GetNearbyTileInformation(TileInde
 /**
  * Returns company information like in vehicle var 43 or station var 43.
  * @param owner Owner of the object.
- * @param l Livery of the object; NULL to use default.
+ * @param l Livery of the object; nullptr to use default.
  * @return NewGRF company information.
  */
 uint32 GetCompanyInfo(CompanyID owner, const Livery *l)
 {
-	if (l == NULL && Company::IsValidID(owner)) l = &Company::Get(owner)->livery[LS_DEFAULT];
-	return owner | (Company::IsValidAiID(owner) ? 0x10000 : 0) | (l != NULL ? (l->colour1 << 24) | (l->colour2 << 28) : 0);
+	if (l == nullptr && Company::IsValidID(owner)) l = &Company::Get(owner)->livery[LS_DEFAULT];
+	return owner | (Company::IsValidAiID(owner) ? 0x10000 : 0) | (l != nullptr ? (l->colour1 << 24) | (l->colour2 << 28) : 0);
 }
 
 /**
@@ -587,8 +587,8 @@ bool Convert8bitBooleanCallback(const GR
  */
 void NewGRFSpriteLayout::Clone(const DrawTileSeqStruct *source)
 {
-	assert(this->seq == NULL);
-	assert(source != NULL);
+	assert(this->seq == nullptr);
+	assert(source != nullptr);
 
 	size_t count = 1; // 1 for the terminator
 	const DrawTileSeqStruct *element;
@@ -607,7 +607,7 @@ void NewGRFSpriteLayout::Clone(const New
 {
 	this->Clone((const DrawTileSprites*)source);
 
-	if (source->registers != NULL) {
+	if (source->registers != nullptr) {
 		size_t count = 1; // 1 for the ground sprite
 		const DrawTileSeqStruct *element;
 		foreach_draw_tile_seq(element, source->seq) count++;
@@ -625,7 +625,7 @@ void NewGRFSpriteLayout::Clone(const New
  */
 void NewGRFSpriteLayout::Allocate(uint num_sprites)
 {
-	assert(this->seq == NULL);
+	assert(this->seq == nullptr);
 
 	DrawTileSeqStruct *sprites = CallocT<DrawTileSeqStruct>(num_sprites + 1);
 	sprites[num_sprites].MakeTerminator();
@@ -637,8 +637,8 @@ void NewGRFSpriteLayout::Allocate(uint n
  */
 void NewGRFSpriteLayout::AllocateRegisters()
 {
-	assert(this->seq != NULL);
-	assert(this->registers == NULL);
+	assert(this->seq != nullptr);
+	assert(this->registers == nullptr);
 
 	size_t count = 1; // 1 for the ground sprite
 	const DrawTileSeqStruct *element;
@@ -685,7 +685,7 @@ uint32 NewGRFSpriteLayout::PrepareLayout
 	bool ground = true;
 	foreach_draw_tile_seq(result, result_seq.data()) {
 		TileLayoutFlags flags = TLF_NOTHING;
-		if (regs != NULL) flags = regs->flags;
+		if (regs != nullptr) flags = regs->flags;
 
 		/* Record var10 value for the sprite */
 		if (HasBit(result->image.sprite, SPRITE_MODIFIER_CUSTOM_SPRITE) || (flags & TLF_SPRITE_REG_FLAGS)) {
@@ -697,7 +697,7 @@ uint32 NewGRFSpriteLayout::PrepareLayout
 		if (!(flags & TLF_SPRITE)) {
 			if (HasBit(result->image.sprite, SPRITE_MODIFIER_CUSTOM_SPRITE)) {
 				result->image.sprite += ground ? newgrf_ground_offset : newgrf_offset;
-				if (constr_stage > 0 && regs != NULL) result->image.sprite += GetConstructionStageOffset(constr_stage, regs->max_sprite_offset);
+				if (constr_stage > 0 && regs != nullptr) result->image.sprite += GetConstructionStageOffset(constr_stage, regs->max_sprite_offset);
 			} else {
 				result->image.sprite += orig_offset;
 			}
@@ -713,12 +713,12 @@ uint32 NewGRFSpriteLayout::PrepareLayout
 		if (!(flags & TLF_PALETTE)) {
 			if (HasBit(result->image.pal, SPRITE_MODIFIER_CUSTOM_SPRITE)) {
 				result->image.sprite += ground ? newgrf_ground_offset : newgrf_offset;
-				if (constr_stage > 0 && regs != NULL) result->image.sprite += GetConstructionStageOffset(constr_stage, regs->max_palette_offset);
+				if (constr_stage > 0 && regs != nullptr) result->image.sprite += GetConstructionStageOffset(constr_stage, regs->max_palette_offset);
 			}
 		}
 
 		ground = false;
-		if (regs != NULL) regs++;
+		if (regs != nullptr) regs++;
 	}
 
 	return var10_values;
@@ -739,7 +739,7 @@ void NewGRFSpriteLayout::ProcessRegister
 	bool ground = true;
 	foreach_draw_tile_seq(result, result_seq.data()) {
 		TileLayoutFlags flags = TLF_NOTHING;
-		if (regs != NULL) flags = regs->flags;
+		if (regs != nullptr) flags = regs->flags;
 
 		/* Is the sprite or bounding box affected by an action-1-2-3 chain? */
 		if (HasBit(result->image.sprite, SPRITE_MODIFIER_CUSTOM_SPRITE) || (flags & TLF_SPRITE_REG_FLAGS)) {
@@ -794,6 +794,6 @@ void NewGRFSpriteLayout::ProcessRegister
 		}
 
 		ground = false;
-		if (regs != NULL) regs++;
+		if (regs != nullptr) regs++;
 	}
 }
diff --git a/src/newgrf_commons.h b/src/newgrf_commons.h
--- a/src/newgrf_commons.h
+++ b/src/newgrf_commons.h
@@ -132,7 +132,7 @@ struct NewGRFSpriteLayout : ZeroedMemory
 	 */
 	void Clone(const DrawTileSprites *source)
 	{
-		assert(source != NULL && this != source);
+		assert(source != nullptr && this != source);
 		this->ground = source->ground;
 		this->Clone(source->seq);
 	}
@@ -151,7 +151,7 @@ struct NewGRFSpriteLayout : ZeroedMemory
 	 */
 	bool NeedsPreprocessing() const
 	{
-		return this->registers != NULL;
+		return this->registers != nullptr;
 	}
 
 	uint32 PrepareLayout(uint32 orig_offset, uint32 newgrf_ground_offset, uint32 newgrf_offset, uint constr_stage, bool separate_ground) const;
@@ -298,7 +298,7 @@ extern ObjectOverrideManager _object_mng
 uint32 GetTerrainType(TileIndex tile, TileContext context = TCX_NORMAL);
 TileIndex GetNearbyTile(byte parameter, TileIndex tile, bool signed_offsets = true, Axis axis = INVALID_AXIS);
 uint32 GetNearbyTileInformation(TileIndex tile, bool grf_version8);
-uint32 GetCompanyInfo(CompanyID owner, const struct Livery *l = NULL);
+uint32 GetCompanyInfo(CompanyID owner, const struct Livery *l = nullptr);
 CommandCost GetErrorMessageFromLocationCallbackResult(uint16 cb_res, const GRFFile *grffile, StringID default_error);
 
 void ErrorUnknownCallbackResult(uint32 grfid, uint16 cbid, uint16 cb_res);
diff --git a/src/newgrf_config.cpp b/src/newgrf_config.cpp
--- a/src/newgrf_config.cpp
+++ b/src/newgrf_config.cpp
@@ -31,7 +31,7 @@
 
 /** Create a new GRFTextWrapper. */
 GRFTextWrapper::GRFTextWrapper() :
-	text(NULL)
+	text(nullptr)
 {
 }
 
@@ -52,7 +52,7 @@ GRFConfig::GRFConfig(const char *filenam
 	url(new GRFTextWrapper()),
 	num_valid_params(lengthof(param))
 {
-	if (filename != NULL) this->filename = stredup(filename);
+	if (filename != nullptr) this->filename = stredup(filename);
 	this->name->AddRef();
 	this->info->AddRef();
 	this->url->AddRef();
@@ -80,14 +80,14 @@ GRFConfig::GRFConfig(const GRFConfig &co
 {
 	MemCpyT<uint8>(this->original_md5sum, config.original_md5sum, lengthof(this->original_md5sum));
 	MemCpyT<uint32>(this->param, config.param, lengthof(this->param));
-	if (config.filename != NULL) this->filename = stredup(config.filename);
+	if (config.filename != nullptr) this->filename = stredup(config.filename);
 	this->name->AddRef();
 	this->info->AddRef();
 	this->url->AddRef();
-	if (config.error != NULL) this->error = new GRFError(*config.error);
+	if (config.error != nullptr) this->error = new GRFError(*config.error);
 	for (uint i = 0; i < config.param_info.size(); i++) {
-		if (config.param_info[i] == NULL) {
-			this->param_info.push_back(NULL);
+		if (config.param_info[i] == nullptr) {
+			this->param_info.push_back(nullptr);
 		} else {
 			this->param_info.push_back(new GRFParameterInfo(*config.param_info[i]));
 		}
@@ -158,7 +158,7 @@ void GRFConfig::SetParameterDefaults()
 	if (!this->has_param_defaults) return;
 
 	for (uint i = 0; i < this->param_info.size(); i++) {
-		if (this->param_info[i] == NULL) continue;
+		if (this->param_info[i] == nullptr) continue;
 		this->param_info[i]->SetValue(this, this->param_info[i]->def_value);
 	}
 }
@@ -185,7 +185,7 @@ void GRFConfig::SetSuitablePalette()
 void GRFConfig::FinalizeParameterInfo()
 {
 	for (GRFParameterInfo *info : this->param_info) {
-		if (info == NULL) continue;
+		if (info == nullptr) continue;
 		info->Finalize();
 	}
 }
@@ -218,8 +218,8 @@ GRFError::GRFError(const GRFError &error
 	message(error.message),
 	severity(error.severity)
 {
-	if (error.custom_message != NULL) this->custom_message = stredup(error.custom_message);
-	if (error.data           != NULL) this->data           = stredup(error.data);
+	if (error.custom_message != nullptr) this->custom_message = stredup(error.custom_message);
+	if (error.data           != nullptr) this->data           = stredup(error.data);
 	memcpy(this->param_value, error.param_value, sizeof(this->param_value));
 }
 
@@ -234,8 +234,8 @@ GRFError::~GRFError()
  * @param nr The newgrf parameter that is changed.
  */
 GRFParameterInfo::GRFParameterInfo(uint nr) :
-	name(NULL),
-	desc(NULL),
+	name(nullptr),
+	desc(nullptr),
 	type(PTYPE_UINT_ENUM),
 	min_value(0),
 	max_value(UINT32_MAX),
@@ -331,9 +331,9 @@ void GRFParameterInfo::Finalize()
  */
 bool UpdateNewGRFConfigPalette(int32 p1)
 {
-	for (GRFConfig *c = _grfconfig_newgame; c != NULL; c = c->next) c->SetSuitablePalette();
-	for (GRFConfig *c = _grfconfig_static;  c != NULL; c = c->next) c->SetSuitablePalette();
-	for (GRFConfig *c = _all_grfs;          c != NULL; c = c->next) c->SetSuitablePalette();
+	for (GRFConfig *c = _grfconfig_newgame; c != nullptr; c = c->next) c->SetSuitablePalette();
+	for (GRFConfig *c = _grfconfig_static;  c != nullptr; c = c->next) c->SetSuitablePalette();
+	for (GRFConfig *c = _all_grfs;          c != nullptr; c = c->next) c->SetSuitablePalette();
 	return true;
 }
 
@@ -381,7 +381,7 @@ static bool CalcGRFMD5Sum(GRFConfig *con
 
 	/* open the file */
 	f = FioFOpenFile(config->filename, "rb", subdir, &size);
-	if (f == NULL) return false;
+	if (f == nullptr) return false;
 
 	long start = ftell(f);
 	size = min(size, GRFGetSizeOfDataSection(f));
@@ -441,16 +441,16 @@ bool FillGRFDetails(GRFConfig *config, b
 /**
  * Clear a GRF Config list, freeing all nodes.
  * @param config Start of the list.
- * @post \a config is set to \c NULL.
+ * @post \a config is set to \c nullptr.
  */
 void ClearGRFConfigList(GRFConfig **config)
 {
 	GRFConfig *c, *next;
-	for (c = *config; c != NULL; c = next) {
+	for (c = *config; c != nullptr; c = next) {
 		next = c->next;
 		delete c;
 	}
-	*config = NULL;
+	*config = nullptr;
 }
 
 
@@ -465,7 +465,7 @@ GRFConfig **CopyGRFConfigList(GRFConfig 
 {
 	/* Clear destination as it will be overwritten */
 	ClearGRFConfigList(dst);
-	for (; src != NULL; src = src->next) {
+	for (; src != nullptr; src = src->next) {
 		GRFConfig *c = new GRFConfig(*src);
 
 		ClrBit(c->flags, GCF_INIT_ONLY);
@@ -496,9 +496,9 @@ static void RemoveDuplicatesFromGRFConfi
 	GRFConfig *prev;
 	GRFConfig *cur;
 
-	if (list == NULL) return;
+	if (list == nullptr) return;
 
-	for (prev = list, cur = list->next; cur != NULL; prev = cur, cur = cur->next) {
+	for (prev = list, cur = list->next; cur != nullptr; prev = cur, cur = cur->next) {
 		if (cur->ident.grfid != list->ident.grfid) continue;
 
 		prev->next = cur->next;
@@ -516,7 +516,7 @@ static void RemoveDuplicatesFromGRFConfi
 void AppendStaticGRFConfigs(GRFConfig **dst)
 {
 	GRFConfig **tail = dst;
-	while (*tail != NULL) tail = &(*tail)->next;
+	while (*tail != nullptr) tail = &(*tail)->next;
 
 	CopyGRFConfigList(tail, _grfconfig_static, false);
 	RemoveDuplicatesFromGRFConfigList(*dst);
@@ -530,7 +530,7 @@ void AppendStaticGRFConfigs(GRFConfig **
 void AppendToGRFConfigList(GRFConfig **dst, GRFConfig *el)
 {
 	GRFConfig **tail = dst;
-	while (*tail != NULL) tail = &(*tail)->next;
+	while (*tail != nullptr) tail = &(*tail)->next;
 	*tail = el;
 
 	RemoveDuplicatesFromGRFConfigList(*dst);
@@ -560,15 +560,15 @@ GRFListCompatibility IsGoodGRFConfigList
 {
 	GRFListCompatibility res = GLC_ALL_GOOD;
 
-	for (GRFConfig *c = grfconfig; c != NULL; c = c->next) {
+	for (GRFConfig *c = grfconfig; c != nullptr; c = c->next) {
 		const GRFConfig *f = FindGRFConfig(c->ident.grfid, FGCM_EXACT, c->ident.md5sum);
-		if (f == NULL || HasBit(f->flags, GCF_INVALID)) {
+		if (f == nullptr || HasBit(f->flags, GCF_INVALID)) {
 			char buf[256];
 
 			/* If we have not found the exactly matching GRF try to find one with the
 			 * same grfid, as it most likely is compatible */
-			f = FindGRFConfig(c->ident.grfid, FGCM_COMPATIBLE, NULL, c->version);
-			if (f != NULL) {
+			f = FindGRFConfig(c->ident.grfid, FGCM_COMPATIBLE, nullptr, c->version);
+			if (f != nullptr) {
 				md5sumToString(buf, lastof(buf), c->ident.md5sum);
 				DEBUG(grf, 1, "NewGRF %08X (%s) not found; checksum %s. Compatibility mode on", BSWAP32(c->ident.grfid), c->filename, buf);
 				if (!HasBit(c->flags, GCF_COMPATIBLE)) {
@@ -606,14 +606,14 @@ compatible_grf:
 				c->info->Release();
 				c->info = f->name;
 				c->info->AddRef();
-				c->error = NULL;
+				c->error = nullptr;
 				c->version = f->version;
 				c->min_loadable_version = f->min_loadable_version;
 				c->num_valid_params = f->num_valid_params;
 				c->has_param_defaults = f->has_param_defaults;
 				for (uint i = 0; i < f->param_info.size(); i++) {
-					if (f->param_info[i] == NULL) {
-						c->param_info.push_back(NULL);
+					if (f->param_info[i] == nullptr) {
+						c->param_info.push_back(nullptr);
 					} else {
 						c->param_info.push_back(new GRFParameterInfo(*f->param_info[i]));
 					}
@@ -655,14 +655,14 @@ bool GRFFileScanner::AddFile(const char 
 
 	bool added = true;
 	if (FillGRFDetails(c, false)) {
-		if (_all_grfs == NULL) {
+		if (_all_grfs == nullptr) {
 			_all_grfs = c;
 		} else {
 			/* Insert file into list at a position determined by its
 			 * name, so the list is sorted as we go along */
 			GRFConfig **pd, *d;
 			bool stop = false;
-			for (pd = &_all_grfs; (d = *pd) != NULL; pd = &d->next) {
+			for (pd = &_all_grfs; (d = *pd) != nullptr; pd = &d->next) {
 				if (c->ident.grfid == d->ident.grfid && memcmp(c->ident.md5sum, d->ident.md5sum, sizeof(c->ident.md5sum)) == 0) added = false;
 				/* Because there can be multiple grfs with the same name, make sure we checked all grfs with the same name,
 				 *  before inserting the entry. So insert a new grf at the end of all grfs with the same name, instead of
@@ -687,9 +687,9 @@ bool GRFFileScanner::AddFile(const char 
 		_modal_progress_work_mutex.unlock();
 		_modal_progress_paint_mutex.lock();
 
-		const char *name = NULL;
-		if (c->name != NULL) name = GetGRFStringFromGRFText(c->name->text);
-		if (name == NULL) name = c->filename;
+		const char *name = nullptr;
+		if (c->name != nullptr) name = GetGRFStringFromGRFText(c->name->text);
+		if (name == nullptr) name = c->filename;
 		UpdateNewGRFScanStatus(this->num_scanned, name);
 
 		_modal_progress_work_mutex.lock();
@@ -736,14 +736,14 @@ void DoScanNewGRFFiles(NewGRFScanCallbac
 	uint num = GRFFileScanner::DoScan();
 
 	DEBUG(grf, 1, "Scan complete, found %d files", num);
-	if (num != 0 && _all_grfs != NULL) {
+	if (num != 0 && _all_grfs != nullptr) {
 		/* Sort the linked list using quicksort.
 		 * For that we first have to make an array, then sort and
 		 * then remake the linked list. */
 		GRFConfig **to_sort = MallocT<GRFConfig*>(num);
 
 		uint i = 0;
-		for (GRFConfig *p = _all_grfs; p != NULL; p = p->next, i++) {
+		for (GRFConfig *p = _all_grfs; p != nullptr; p = p->next, i++) {
 			to_sort[i] = p;
 		}
 		/* Number of files is not necessarily right */
@@ -754,7 +754,7 @@ void DoScanNewGRFFiles(NewGRFScanCallbac
 		for (i = 1; i < num; i++) {
 			to_sort[i - 1]->next = to_sort[i];
 		}
-		to_sort[num - 1]->next = NULL;
+		to_sort[num - 1]->next = nullptr;
 		_all_grfs = to_sort[0];
 
 		free(to_sort);
@@ -768,7 +768,7 @@ void DoScanNewGRFFiles(NewGRFScanCallbac
 	/* Yes... these are the NewGRF windows */
 	InvalidateWindowClassesData(WC_SAVELOAD, 0, true);
 	InvalidateWindowData(WC_GAME_OPTIONS, WN_GAME_OPTIONS_NEWGRF_STATE, GOID_NEWGRF_RESCANNED, true);
-	if (callback != NULL) callback->OnNewGRFsScanned();
+	if (callback != nullptr) callback->OnNewGRFsScanned();
 
 	DeleteWindowByClass(WC_MODAL_PROGRESS);
 	SetModalProgress(false);
@@ -786,14 +786,14 @@ void ScanNewGRFFiles(NewGRFScanCallback 
 	/* Only then can we really start, especially by marking the whole screen dirty. Get those other windows hidden!. */
 	MarkWholeScreenDirty();
 
-	if (!UseThreadedModelProgress() || !VideoDriver::GetInstance()->HasGUI() || !StartNewThread(NULL, "ottd:newgrf-scan", &DoScanNewGRFFiles, (NewGRFScanCallback *)callback)) { // Without the seemingly superfluous cast, strange compiler errors ensue.
+	if (!UseThreadedModelProgress() || !VideoDriver::GetInstance()->HasGUI() || !StartNewThread(nullptr, "ottd:newgrf-scan", &DoScanNewGRFFiles, (NewGRFScanCallback *)callback)) { // Without the seemingly superfluous cast, strange compiler errors ensue.
 		_modal_progress_work_mutex.unlock();
 		_modal_progress_paint_mutex.unlock();
 		DoScanNewGRFFiles(callback);
 		_modal_progress_paint_mutex.lock();
 		_modal_progress_work_mutex.lock();
 	} else {
-		UpdateNewGRFScanStatus(0, NULL);
+		UpdateNewGRFScanStatus(0, nullptr);
 	}
 }
 
@@ -803,23 +803,23 @@ void ScanNewGRFFiles(NewGRFScanCallback 
  * @param mode Restrictions for matching grfs
  * @param md5sum Expected MD5 sum
  * @param desired_version Requested version
- * @return The matching grf, if it exists in #_all_grfs, else \c NULL.
+ * @return The matching grf, if it exists in #_all_grfs, else \c nullptr.
  */
 const GRFConfig *FindGRFConfig(uint32 grfid, FindGRFConfigMode mode, const uint8 *md5sum, uint32 desired_version)
 {
-	assert((mode == FGCM_EXACT) != (md5sum == NULL));
-	const GRFConfig *best = NULL;
-	for (const GRFConfig *c = _all_grfs; c != NULL; c = c->next) {
+	assert((mode == FGCM_EXACT) != (md5sum == nullptr));
+	const GRFConfig *best = nullptr;
+	for (const GRFConfig *c = _all_grfs; c != nullptr; c = c->next) {
 		/* if md5sum is set, we look for an exact match and continue if not found */
 		if (!c->ident.HasGrfIdentifier(grfid, md5sum)) continue;
 		/* return it, if the exact same newgrf is found, or if we do not care about finding "the best" */
-		if (md5sum != NULL || mode == FGCM_ANY) return c;
+		if (md5sum != nullptr || mode == FGCM_ANY) return c;
 		/* Skip incompatible stuff, unless explicitly allowed */
 		if (mode != FGCM_NEWEST && HasBit(c->flags, GCF_INVALID)) continue;
 		/* check version compatibility */
 		if (mode == FGCM_COMPATIBLE && (c->version < desired_version || c->min_loadable_version > desired_version)) continue;
 		/* remember the newest one as "the best" */
-		if (best == NULL || c->version > best->version) best = c;
+		if (best == nullptr || c->version > best->version) best = c;
 	}
 
 	return best;
@@ -845,21 +845,21 @@ struct UnknownGRF : public GRFIdentifier
  * @param create whether to create a new GRFConfig if the GRFConfig did not
  *               exist in the fake list of GRFConfigs.
  * @return The GRFTextWrapper of the name of the GRFConfig with the given GRF ID
- *         and MD5 checksum or NULL when it does not exist and create is false.
+ *         and MD5 checksum or nullptr when it does not exist and create is false.
  *         This value must NEVER be freed by the caller.
  */
 GRFTextWrapper *FindUnknownGRFName(uint32 grfid, uint8 *md5sum, bool create)
 {
 	UnknownGRF *grf;
-	static UnknownGRF *unknown_grfs = NULL;
+	static UnknownGRF *unknown_grfs = nullptr;
 
-	for (grf = unknown_grfs; grf != NULL; grf = grf->next) {
+	for (grf = unknown_grfs; grf != nullptr; grf = grf->next) {
 		if (grf->grfid == grfid) {
 			if (memcmp(md5sum, grf->md5sum, sizeof(grf->md5sum)) == 0) return grf->name;
 		}
 	}
 
-	if (!create) return NULL;
+	if (!create) return nullptr;
 
 	grf = CallocT<UnknownGRF>(1);
 	grf->grfid = grfid;
@@ -878,17 +878,17 @@ GRFTextWrapper *FindUnknownGRFName(uint3
  * Retrieve a NewGRF from the current config by its grfid.
  * @param grfid grf to look for.
  * @param mask  GRFID mask to allow for partial matching.
- * @return The grf config, if it exists, else \c NULL.
+ * @return The grf config, if it exists, else \c nullptr.
  */
 GRFConfig *GetGRFConfig(uint32 grfid, uint32 mask)
 {
 	GRFConfig *c;
 
-	for (c = _grfconfig; c != NULL; c = c->next) {
+	for (c = _grfconfig; c != nullptr; c = c->next) {
 		if ((c->ident.grfid & mask) == (grfid & mask)) return c;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 
@@ -913,7 +913,7 @@ static const uint32 OPENTTD_GRAPHICS_BAS
 /**
  * Search a textfile file next to this NewGRF.
  * @param type The type of the textfile to search for.
- * @return The filename for the textfile, \c NULL otherwise.
+ * @return The filename for the textfile, \c nullptr otherwise.
  */
 const char *GRFConfig::GetTextfile(TextfileType type) const
 {
diff --git a/src/newgrf_config.h b/src/newgrf_config.h
--- a/src/newgrf_config.h
+++ b/src/newgrf_config.h
@@ -88,13 +88,13 @@ struct GRFIdentifier {
 	/**
 	 * Does the identification match the provided values?
 	 * @param grfid  Expected grfid.
-	 * @param md5sum Expected md5sum, may be \c NULL (in which case, do not check it).
+	 * @param md5sum Expected md5sum, may be \c nullptr (in which case, do not check it).
 	 * @return the object has the provided grfid and md5sum.
 	 */
 	inline bool HasGrfIdentifier(uint32 grfid, const uint8 *md5sum) const
 	{
 		if (this->grfid != grfid) return false;
-		if (md5sum == NULL) return true;
+		if (md5sum == nullptr) return true;
 		return memcmp(md5sum, this->md5sum, sizeof(this->md5sum)) == 0;
 	}
 };
@@ -151,7 +151,7 @@ struct GRFTextWrapper : public SimpleCou
 
 /** Information about GRF, used in the game and (part of it) in savegames */
 struct GRFConfig : ZeroedMemoryAllocator {
-	GRFConfig(const char *filename = NULL);
+	GRFConfig(const char *filename = nullptr);
 	GRFConfig(const GRFConfig &config);
 	~GRFConfig();
 
@@ -215,7 +215,7 @@ struct NewGRFScanCallback {
 size_t GRFGetSizeOfDataSection(FILE *f);
 
 void ScanNewGRFFiles(NewGRFScanCallback *callback);
-const GRFConfig *FindGRFConfig(uint32 grfid, FindGRFConfigMode mode, const uint8 *md5sum = NULL, uint32 desired_version = 0);
+const GRFConfig *FindGRFConfig(uint32 grfid, FindGRFConfigMode mode, const uint8 *md5sum = nullptr, uint32 desired_version = 0);
 GRFConfig *GetGRFConfig(uint32 grfid, uint32 mask = 0xFFFFFFFF);
 GRFConfig **CopyGRFConfigList(GRFConfig **dst, const GRFConfig *src, bool init_only);
 void AppendStaticGRFConfigs(GRFConfig **dst);
diff --git a/src/newgrf_debug_gui.cpp b/src/newgrf_debug_gui.cpp
--- a/src/newgrf_debug_gui.cpp
+++ b/src/newgrf_debug_gui.cpp
@@ -47,7 +47,7 @@
 #include "safeguards.h"
 
 /** The sprite picker. */
-NewGrfDebugSpritePicker _newgrf_debug_sprite_picker = { SPM_NONE, NULL, 0, std::vector<SpriteID>() };
+NewGrfDebugSpritePicker _newgrf_debug_sprite_picker = { SPM_NONE, nullptr, 0, std::vector<SpriteID>() };
 
 /**
  * Get the feature index related to the window number.
@@ -192,11 +192,11 @@ public:
 	 * Gets the first position of the array containing the persistent storage.
 	 * @param index Index of the item.
 	 * @param grfid Parameter for the PSA. Only required for items with parameters.
-	 * @return Pointer to the first position of the storage array or NULL if not present.
+	 * @return Pointer to the first position of the storage array or nullptr if not present.
 	 */
 	virtual const int32 *GetPSAFirstPosition(uint index, uint32 grfid) const
 	{
-		return NULL;
+		return nullptr;
 	}
 
 protected:
@@ -252,18 +252,18 @@ static inline GrfSpecFeature GetFeatureN
 /**
  * Get the NIFeature related to the window number.
  * @param window_number The window to get the NIFeature for.
- * @return the NIFeature, or NULL is there isn't one.
+ * @return the NIFeature, or nullptr is there isn't one.
  */
 static inline const NIFeature *GetFeature(uint window_number)
 {
 	GrfSpecFeature idx = GetFeatureNum(window_number);
-	return idx < GSF_FAKE_END ? _nifeatures[idx] : NULL;
+	return idx < GSF_FAKE_END ? _nifeatures[idx] : nullptr;
 }
 
 /**
  * Get the NIHelper related to the window number.
  * @param window_number The window to get the NIHelper for.
- * @pre GetFeature(window_number) != NULL
+ * @pre GetFeature(window_number) != nullptr
  * @return the NIHelper
  */
 static inline const NIHelper *GetFeatureHelper(uint window_number)
@@ -332,7 +332,7 @@ struct NewGRFInspectWindow : Window {
 			assert(this->HasChainIndex());
 			const Vehicle *v = Vehicle::Get(index);
 			v = v->Move(this->chain_index);
-			if (v != NULL) index = v->index;
+			if (v != nullptr) index = v->index;
 		}
 		return index;
 	}
@@ -348,7 +348,7 @@ struct NewGRFInspectWindow : Window {
 
 		const Vehicle *v = Vehicle::Get(::GetFeatureIndex(this->window_number));
 		v = v->Move(this->chain_index);
-		if (v == NULL) this->chain_index = 0;
+		if (v == nullptr) this->chain_index = 0;
 	}
 
 	NewGRFInspectWindow(WindowDesc *desc, WindowNumber wno) : Window(desc)
@@ -418,7 +418,7 @@ struct NewGRFInspectWindow : Window {
 				int total_width = 0;
 				int sel_start = 0;
 				int sel_end = 0;
-				for (const Vehicle *u = v->First(); u != NULL; u = u->Next()) {
+				for (const Vehicle *u = v->First(); u != nullptr; u = u->Next()) {
 					if (u == v) sel_start = total_width;
 					switch (u->type) {
 						case VEH_TRAIN: total_width += Train      ::From(u)->GetDisplayImageWidth(); break;
@@ -459,9 +459,9 @@ struct NewGRFInspectWindow : Window {
 		const void *base_spec = nih->GetSpec(index);
 
 		uint i = 0;
-		if (nif->variables != NULL) {
+		if (nif->variables != nullptr) {
 			this->DrawString(r, i++, "Variables:");
-			for (const NIVariable *niv = nif->variables; niv->name != NULL; niv++) {
+			for (const NIVariable *niv = nif->variables; niv->name != nullptr; niv++) {
 				bool avail = true;
 				uint param = HasVariableParameter(niv->var) ? NewGRFInspectWindow::var60params[GetFeatureNum(this->window_number)][niv->var - 0x60] : 0;
 				uint value = nih->Resolve(index, niv->var, param, &avail);
@@ -478,7 +478,7 @@ struct NewGRFInspectWindow : Window {
 
 		uint psa_size = nih->GetPSASize(index, this->caller_grfid);
 		const int32 *psa = nih->GetPSAFirstPosition(index, this->caller_grfid);
-		if (psa_size != 0 && psa != NULL) {
+		if (psa_size != 0 && psa != nullptr) {
 			if (nih->PSAWithParameter()) {
 				this->DrawString(r, i++, "Persistent storage [%08X]:", BSWAP32(this->caller_grfid));
 			} else {
@@ -490,9 +490,9 @@ struct NewGRFInspectWindow : Window {
 			}
 		}
 
-		if (nif->properties != NULL) {
+		if (nif->properties != nullptr) {
 			this->DrawString(r, i++, "Properties:");
-			for (const NIProperty *nip = nif->properties; nip->name != NULL; nip++) {
+			for (const NIProperty *nip = nif->properties; nip->name != nullptr; nip++) {
 				const void *ptr = (const byte *)base + nip->offset;
 				uint value;
 				switch (nip->read_size) {
@@ -523,9 +523,9 @@ struct NewGRFInspectWindow : Window {
 			}
 		}
 
-		if (nif->callbacks != NULL) {
+		if (nif->callbacks != nullptr) {
 			this->DrawString(r, i++, "Callbacks:");
-			for (const NICallback *nic = nif->callbacks; nic->name != NULL; nic++) {
+			for (const NICallback *nic = nif->callbacks; nic->name != nullptr; nic++) {
 				if (nic->cb_bit != CBM_NO_BIT) {
 					const void *ptr = (const byte *)base_spec + nic->offset;
 					uint value;
@@ -571,7 +571,7 @@ struct NewGRFInspectWindow : Window {
 				if (this->HasChainIndex()) {
 					uint index = this->GetFeatureIndex();
 					Vehicle *v = Vehicle::Get(index);
-					if (v != NULL && v->Next() != NULL) {
+					if (v != nullptr && v->Next() != nullptr) {
 						this->chain_index++;
 						this->InvalidateData();
 					}
@@ -581,14 +581,14 @@ struct NewGRFInspectWindow : Window {
 			case WID_NGRFI_MAINPANEL: {
 				/* Does this feature have variables? */
 				const NIFeature *nif  = GetFeature(this->window_number);
-				if (nif->variables == NULL) return;
+				if (nif->variables == nullptr) return;
 
 				/* Get the line, make sure it's within the boundaries. */
 				int line = this->vscroll->GetScrolledRowFromWidget(pt.y, this, WID_NGRFI_MAINPANEL, TOP_OFFSET);
 				if (line == INT_MAX) return;
 
 				/* Find the variable related to the line */
-				for (const NIVariable *niv = nif->variables; niv->name != NULL; niv++, line--) {
+				for (const NIVariable *niv = nif->variables; niv->name != nullptr; niv++, line--) {
 					if (line != 1) continue; // 1 because of the "Variables:" line
 
 					if (!HasVariableParameter(niv->var)) break;
@@ -604,7 +604,7 @@ struct NewGRFInspectWindow : Window {
 	{
 		if (StrEmpty(str)) return;
 
-		NewGRFInspectWindow::var60params[GetFeatureNum(this->window_number)][this->current_edit_param - 0x60] = strtol(str, NULL, 16);
+		NewGRFInspectWindow::var60params[GetFeatureNum(this->window_number)][this->current_edit_param - 0x60] = strtol(str, nullptr, 16);
 		this->SetDirty();
 	}
 
@@ -625,7 +625,7 @@ struct NewGRFInspectWindow : Window {
 			this->ValidateChainIndex();
 			this->SetWidgetDisabledState(WID_NGRFI_VEH_PREV, this->chain_index == 0);
 			Vehicle *v = Vehicle::Get(this->GetFeatureIndex());
-			this->SetWidgetDisabledState(WID_NGRFI_VEH_NEXT, v == NULL || v->Next() == NULL);
+			this->SetWidgetDisabledState(WID_NGRFI_VEH_NEXT, v == nullptr || v->Next() == nullptr);
 		}
 	}
 };
@@ -756,7 +756,7 @@ void DeleteNewGRFInspectWindow(GrfSpecFe
 bool IsNewGRFInspectable(GrfSpecFeature feature, uint index)
 {
 	const NIFeature *nif = GetFeature(GetInspectWindowNumber(feature, index));
-	if (nif == NULL) return false;
+	if (nif == nullptr) return false;
 	return nif->helper->IsInspectable(index);
 }
 
@@ -883,7 +883,7 @@ struct SpriteAlignerWindow : Window {
 				DrawPixelInfo *old_dpi = _cur_dpi;
 				_cur_dpi = &new_dpi;
 
-				DrawSprite(this->current_sprite, PAL_NONE, x, y, NULL, ZOOM_LVL_GUI);
+				DrawSprite(this->current_sprite, PAL_NONE, x, y, nullptr, ZOOM_LVL_GUI);
 
 				_cur_dpi = old_dpi;
 
diff --git a/src/newgrf_engine.cpp b/src/newgrf_engine.cpp
--- a/src/newgrf_engine.cpp
+++ b/src/newgrf_engine.cpp
@@ -65,7 +65,7 @@ const SpriteGroup *GetWagonOverrideSprit
 			if (wo->train_id[j] == overriding_engine) return wo->group;
 		}
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -79,7 +79,7 @@ void UnloadWagonOverrides(Engine *e)
 	}
 	free(e->overrides);
 	e->overrides_count = 0;
-	e->overrides = NULL;
+	e->overrides = nullptr;
 }
 
 
@@ -88,7 +88,7 @@ void SetCustomEngineSprites(EngineID eng
 	Engine *e = Engine::Get(engine);
 	assert(cargo < lengthof(e->grf_prop.spritegroup));
 
-	if (e->grf_prop.spritegroup[cargo] != NULL) {
+	if (e->grf_prop.spritegroup[cargo] != nullptr) {
 		grfmsg(6, "SetCustomEngineSprites: engine %d cargo %d already has group -- replacing", engine, cargo);
 	}
 	e->grf_prop.spritegroup[cargo] = group;
@@ -166,7 +166,7 @@ enum TTDPAircraftMovementStates {
 static byte MapAircraftMovementState(const Aircraft *v)
 {
 	const Station *st = GetTargetAirportIfValid(v);
-	if (st == NULL) return AMS_TTDP_FLIGHT_TO_TOWER;
+	if (st == nullptr) return AMS_TTDP_FLIGHT_TO_TOWER;
 
 	const AirportFTAClass *afc = st->airport.GetFTA();
 	uint16 amdflag = afc->MovingData(v->pos)->flag;
@@ -339,12 +339,12 @@ static byte MapAircraftMovementAction(co
 
 /* virtual */ uint32 VehicleScopeResolver::GetRandomBits() const
 {
-	return this->v == NULL ? 0 : this->v->random_bits;
+	return this->v == nullptr ? 0 : this->v->random_bits;
 }
 
 /* virtual */ uint32 VehicleScopeResolver::GetTriggers() const
 {
-	return this->v == NULL ? 0 : this->v->waiting_triggers;
+	return this->v == nullptr ? 0 : this->v->waiting_triggers;
 }
 
 
@@ -355,12 +355,12 @@ static byte MapAircraftMovementAction(co
 		case VSG_SCOPE_PARENT: return &this->parent_scope;
 		case VSG_SCOPE_RELATIVE: {
 			int32 count = GB(relative, 0, 4);
-			if (this->self_scope.v != NULL && (relative != this->cached_relative_count || count == 0)) {
+			if (this->self_scope.v != nullptr && (relative != this->cached_relative_count || count == 0)) {
 				/* Note: This caching only works as long as the VSG_SCOPE_RELATIVE cannot be used in
 				 *       VarAct2 with procedure calls. */
 				if (count == 0) count = GetRegister(0x100);
 
-				const Vehicle *v = NULL;
+				const Vehicle *v = nullptr;
 				switch (GB(relative, 6, 2)) {
 					default: NOT_REACHED();
 					case 0x00: // count back (away from the engine), starting at this vehicle
@@ -377,12 +377,12 @@ static byte MapAircraftMovementAction(co
 						const Vehicle *self = this->self_scope.v;
 						for (const Vehicle *u = self->First(); u != self; u = u->Next()) {
 							if (u->engine_type != self->engine_type) {
-								v = NULL;
+								v = nullptr;
 							} else {
-								if (v == NULL) v = u;
+								if (v == nullptr) v = u;
 							}
 						}
-						if (v == NULL) v = self;
+						if (v == nullptr) v = self;
 						break;
 					}
 				}
@@ -400,16 +400,16 @@ static byte MapAircraftMovementAction(co
  * This always uses dual company colours independent of GUI settings. So it is desync-safe.
  *
  * @param engine Engine type
- * @param v Vehicle, NULL in purchase list.
+ * @param v Vehicle, nullptr in purchase list.
  * @return Livery to use
  */
 static const Livery *LiveryHelper(EngineID engine, const Vehicle *v)
 {
 	const Livery *l;
 
-	if (v == NULL) {
-		if (!Company::IsValidID(_current_company)) return NULL;
-		l = GetEngineLivery(engine, _current_company, INVALID_ENGINE, NULL, LIT_ALL);
+	if (v == nullptr) {
+		if (!Company::IsValidID(_current_company)) return nullptr;
+		l = GetEngineLivery(engine, _current_company, INVALID_ENGINE, nullptr, LIT_ALL);
 	} else if (v->IsGroundVehicle()) {
 		l = GetEngineLivery(v->engine_type, v->owner, v->GetGroundVehicleCache()->first_engine, v, LIT_ALL);
 	} else {
@@ -437,7 +437,7 @@ static uint32 PositionHelper(const Vehic
 		if (consecutive && u->engine_type != v->engine_type) chain_before = 0;
 	}
 
-	while (u->Next() != NULL && (!consecutive || u->Next()->engine_type == v->engine_type)) {
+	while (u->Next() != nullptr && (!consecutive || u->Next()->engine_type == v->engine_type)) {
 		chain_after++;
 		u = u->Next();
 	}
@@ -480,7 +480,7 @@ static uint32 VehicleGetVariable(Vehicle
 				memset(common_cargoes, 0, sizeof(common_cargoes));
 				memset(common_subtypes, 0, sizeof(common_subtypes));
 
-				for (u = v; u != NULL; u = u->Next()) {
+				for (u = v; u != nullptr; u = u->Next()) {
 					if (v->type == VEH_TRAIN) user_def_data |= Train::From(u)->tcache.user_def_data;
 
 					/* Skip empty engines */
@@ -500,7 +500,7 @@ static uint32 VehicleGetVariable(Vehicle
 				}
 
 				/* Count subcargo types of common_cargo_type */
-				for (u = v; u != NULL; u = u->Next()) {
+				for (u = v; u != nullptr; u = u->Next()) {
 					/* Skip empty engines and engines not carrying common_cargo_type */
 					if (u->cargo_type != common_cargo_type || !u->GetEngine()->CanCarryCargo()) continue;
 
@@ -530,12 +530,12 @@ static uint32 VehicleGetVariable(Vehicle
 			 *  - For translating the cargo type we need to use the GRF which is resolving the variable, which
 			 *    is object->ro.grffile.
 			 *    In case of CBID_TRAIN_ALLOW_WAGON_ATTACH this is not the same as v->GetGRF().
-			 *  - The grffile == NULL case only happens if this function is called for default vehicles.
+			 *  - The grffile == nullptr case only happens if this function is called for default vehicles.
 			 *    And this is only done by CheckCaches().
 			 */
 			const GRFFile *grffile = object->ro.grffile;
 			uint8 common_bitnum = (common_cargo_type == CT_INVALID) ? 0xFF :
-				(grffile == NULL || grffile->grf_version < 8) ? CargoSpec::Get(common_cargo_type)->bitnum : grffile->cargo_map[common_cargo_type];
+				(grffile == nullptr || grffile->grf_version < 8) ? CargoSpec::Get(common_cargo_type)->bitnum : grffile->cargo_map[common_cargo_type];
 
 			return (v->grf_cache.consist_cargo_information & 0xFFFF00FF) | common_bitnum << 8;
 		}
@@ -557,7 +557,7 @@ static uint32 VehicleGetVariable(Vehicle
 
 				const Station *st = GetTargetAirportIfValid(Aircraft::From(v));
 
-				if (st != NULL && st->airport.tile != INVALID_TILE) {
+				if (st != nullptr && st->airport.tile != INVALID_TILE) {
 					airporttype = st->airport.GetSpec()->ttd_airport_type;
 				}
 
@@ -574,8 +574,8 @@ static uint32 VehicleGetVariable(Vehicle
 
 			const Vehicle *u_p = v->Previous();
 			const Vehicle *u_n = v->Next();
-			DirDiff f = (u_p == NULL) ?  DIRDIFF_SAME : DirDifference(u_p->direction, v->direction);
-			DirDiff b = (u_n == NULL) ?  DIRDIFF_SAME : DirDifference(v->direction, u_n->direction);
+			DirDiff f = (u_p == nullptr) ?  DIRDIFF_SAME : DirDifference(u_p->direction, v->direction);
+			DirDiff b = (u_n == nullptr) ?  DIRDIFF_SAME : DirDifference(v->direction, u_n->direction);
 			DirDiff t = ChangeDirDiff(f, b);
 
 			return ((t > DIRDIFF_REVERSE ? t | 8 : t) << 16) |
@@ -636,7 +636,7 @@ static uint32 VehicleGetVariable(Vehicle
 
 			{
 				uint count = 0;
-				for (; v != NULL; v = v->Next()) {
+				for (; v != nullptr; v = v->Next()) {
 					if (v->GetEngine()->grf_prop.local_id == parameter) count++;
 				}
 				return count;
@@ -653,7 +653,7 @@ static uint32 VehicleGetVariable(Vehicle
 					object->ro.callback == CBID_VEHICLE_START_STOP_CHECK || object->ro.callback == CBID_VEHICLE_32DAY_CALLBACK || object->ro.callback == CBID_VEHICLE_COLOUR_MAPPING ||
 					object->ro.callback == CBID_VEHICLE_SPAWN_VISUAL_EFFECT) {
 				Vehicle *u = v->Move((int32)GetRegister(0x10F));
-				if (u == NULL) return 0; // available, but zero
+				if (u == nullptr) return 0; // available, but zero
 
 				if (parameter == 0x5F) {
 					/* This seems to be the only variable that makes sense to access via var 61, but is not handled by VehicleGetVariable */
@@ -676,7 +676,7 @@ static uint32 VehicleGetVariable(Vehicle
 			if (!v->IsGroundVehicle()) return 0;
 
 			const Vehicle *u = v->Move((int8)parameter);
-			if (u == NULL) return 0;
+			if (u == nullptr) return 0;
 
 			/* Get direction difference. */
 			bool prev = (int8)parameter < 0;
@@ -810,7 +810,7 @@ static uint32 VehicleGetVariable(Vehicle
 		case 0x57: return GB(ClampToI32(v->GetDisplayProfitLastYear()),  8, 24);
 		case 0x58: return GB(ClampToI32(v->GetDisplayProfitLastYear()), 16, 16);
 		case 0x59: return GB(ClampToI32(v->GetDisplayProfitLastYear()), 24,  8);
-		case 0x5A: return v->Next() == NULL ? INVALID_VEHICLE : v->Next()->index;
+		case 0x5A: return v->Next() == nullptr ? INVALID_VEHICLE : v->Next()->index;
 		case 0x5C: return ClampToI32(v->value);
 		case 0x5D: return GB(ClampToI32(v->value),  8, 24);
 		case 0x5E: return GB(ClampToI32(v->value), 16, 16);
@@ -882,10 +882,10 @@ static uint32 VehicleGetVariable(Vehicle
 
 /* virtual */ uint32 VehicleScopeResolver::GetVariable(byte variable, uint32 parameter, bool *available) const
 {
-	if (this->v == NULL) {
+	if (this->v == nullptr) {
 		/* Vehicle does not exist, so we're in a purchase list */
 		switch (variable) {
-			case 0x43: return GetCompanyInfo(_current_company, LiveryHelper(this->self_type, NULL)); // Owner information
+			case 0x43: return GetCompanyInfo(_current_company, LiveryHelper(this->self_type, nullptr)); // Owner information
 			case 0x46: return 0;               // Motion counter
 			case 0x47: { // Vehicle cargo info
 				const Engine *e = Engine::Get(this->self_type);
@@ -919,17 +919,17 @@ static uint32 VehicleGetVariable(Vehicle
 {
 	const Vehicle *v = this->self_scope.v;
 
-	if (v == NULL) {
+	if (v == nullptr) {
 		if (group->num_loading > 0) return group->loading[0];
 		if (group->num_loaded  > 0) return group->loaded[0];
-		return NULL;
+		return nullptr;
 	}
 
 	bool in_motion = !v->First()->current_order.IsType(OT_LOADING);
 
 	uint totalsets = in_motion ? group->num_loaded : group->num_loading;
 
-	if (totalsets == 0) return NULL;
+	if (totalsets == 0) return nullptr;
 
 	uint set = (v->cargo.StoredCount() * totalsets) / max((uint16)1, v->cargo_cap);
 	set = min(set, totalsets - 1);
@@ -945,7 +945,7 @@ static uint32 VehicleGetVariable(Vehicle
 static const GRFFile *GetEngineGrfFile(EngineID engine_type)
 {
 	const Engine *e = Engine::Get(engine_type);
-	return (e != NULL) ? e->GetGRF() : NULL;
+	return (e != nullptr) ? e->GetGRF() : nullptr;
 }
 
 /**
@@ -962,14 +962,14 @@ VehicleResolverObject::VehicleResolverOb
 		CallbackID callback, uint32 callback_param1, uint32 callback_param2)
 	: ResolverObject(GetEngineGrfFile(engine_type), callback, callback_param1, callback_param2),
 	self_scope(*this, engine_type, v, info_view),
-	parent_scope(*this, engine_type, ((v != NULL) ? v->First() : v), info_view),
+	parent_scope(*this, engine_type, ((v != nullptr) ? v->First() : v), info_view),
 	relative_scope(*this, engine_type, v, info_view),
 	cached_relative_count(0)
 {
 	if (wagon_override == WO_SELF) {
 		this->root_spritegroup = GetWagonOverrideSpriteSet(engine_type, CT_DEFAULT, engine_type);
 	} else {
-		if (wagon_override != WO_NONE && v != NULL && v->IsGroundVehicle()) {
+		if (wagon_override != WO_NONE && v != nullptr && v->IsGroundVehicle()) {
 			assert(v->engine_type == engine_type); // overrides make little sense with fake scopes
 
 			/* For trains we always use cached value, except for callbacks because the override spriteset
@@ -982,11 +982,11 @@ VehicleResolverObject::VehicleResolverOb
 			}
 		}
 
-		if (this->root_spritegroup == NULL) {
+		if (this->root_spritegroup == nullptr) {
 			const Engine *e = Engine::Get(engine_type);
-			CargoID cargo = v != NULL ? v->cargo_type : CT_PURCHASE;
+			CargoID cargo = v != nullptr ? v->cargo_type : CT_PURCHASE;
 			assert(cargo < lengthof(e->grf_prop.spritegroup));
-			this->root_spritegroup = e->grf_prop.spritegroup[cargo] != NULL ? e->grf_prop.spritegroup[cargo] : e->grf_prop.spritegroup[CT_DEFAULT];
+			this->root_spritegroup = e->grf_prop.spritegroup[cargo] != nullptr ? e->grf_prop.spritegroup[cargo] : e->grf_prop.spritegroup[CT_DEFAULT];
 		}
 	}
 }
@@ -1005,7 +1005,7 @@ void GetCustomEngineSprite(EngineID engi
 		object.callback_param1 = image_type | (stack << 8);
 		const SpriteGroup *group = object.Resolve();
 		uint32 reg100 = sprite_stack ? GetRegister(0x100) : 0;
-		if (group != NULL && group->GetNumResults() != 0) {
+		if (group != nullptr && group->GetNumResults() != 0) {
 			result->seq[result->count].sprite = group->GetResult() + (direction % group->GetNumResults());
 			result->seq[result->count].pal    = GB(reg100, 0, 16); // zero means default recolouring
 			result->count++;
@@ -1025,7 +1025,7 @@ void GetRotorOverrideSprite(EngineID eng
 
 	VehicleResolverObject object(engine, v, VehicleResolverObject::WO_SELF, info_view, CBID_NO_CALLBACK);
 	result->Clear();
-	uint rotor_pos = v == NULL || info_view ? 0 : v->Next()->Next()->state;
+	uint rotor_pos = v == nullptr || info_view ? 0 : v->Next()->Next()->state;
 
 	bool sprite_stack = HasBit(e->info.misc_flags, EF_SPRITE_STACK);
 	uint max_stack = sprite_stack ? lengthof(result->seq) : 1;
@@ -1034,7 +1034,7 @@ void GetRotorOverrideSprite(EngineID eng
 		object.callback_param1 = image_type | (stack << 8);
 		const SpriteGroup *group = object.Resolve();
 		uint32 reg100 = sprite_stack ? GetRegister(0x100) : 0;
-		if (group != NULL && group->GetNumResults() != 0) {
+		if (group != nullptr && group->GetNumResults() != 0) {
 			result->seq[result->count].sprite = group->GetResult() + (rotor_pos % group->GetNumResults());
 			result->seq[result->count].pal    = GB(reg100, 0, 16); // zero means default recolouring
 			result->count++;
@@ -1052,7 +1052,7 @@ void GetRotorOverrideSprite(EngineID eng
 bool UsesWagonOverride(const Vehicle *v)
 {
 	assert(v->type == VEH_TRAIN);
-	return Train::From(v)->tcache.cached_override != NULL;
+	return Train::From(v)->tcache.cached_override != nullptr;
 }
 
 /**
@@ -1061,7 +1061,7 @@ bool UsesWagonOverride(const Vehicle *v)
  * @param param1   First parameter of the callback
  * @param param2   Second parameter of the callback
  * @param engine   Engine type of the vehicle to evaluate the callback for
- * @param v        The vehicle to evaluate the callback for, or NULL if it doesnt exist yet
+ * @param v        The vehicle to evaluate the callback for, or nullptr if it doesnt exist yet
  * @return The value the callback returned, or CALLBACK_FAILED if it failed
  */
 uint16 GetVehicleCallback(CallbackID callback, uint32 param1, uint32 param2, EngineID engine, const Vehicle *v)
@@ -1076,7 +1076,7 @@ uint16 GetVehicleCallback(CallbackID cal
  * @param param1   First parameter of the callback
  * @param param2   Second parameter of the callback
  * @param engine   Engine type of the vehicle to evaluate the callback for
- * @param v        The vehicle to evaluate the callback for, or NULL if it doesn't exist yet
+ * @param v        The vehicle to evaluate the callback for, or nullptr if it doesn't exist yet
  * @param parent   The vehicle to use for parent scope
  * @return The value the callback returned, or CALLBACK_FAILED if it failed
  */
@@ -1107,14 +1107,14 @@ uint GetEngineProperty(EngineID engine, 
 static void DoTriggerVehicle(Vehicle *v, VehicleTrigger trigger, byte base_random_bits, bool first)
 {
 	/* We can't trigger a non-existent vehicle... */
-	assert(v != NULL);
+	assert(v != nullptr);
 
 	VehicleResolverObject object(v->engine_type, v, VehicleResolverObject::WO_CACHED, false, CBID_RANDOM_TRIGGER);
 	object.waiting_triggers = v->waiting_triggers | trigger;
 	v->waiting_triggers = object.waiting_triggers; // store now for var 5F
 
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL) return;
+	if (group == nullptr) return;
 
 	/* Store remaining triggers. */
 	v->waiting_triggers = object.GetRemainingTriggers();
@@ -1142,7 +1142,7 @@ static void DoTriggerVehicle(Vehicle *v,
 			/* We now trigger the next vehicle in chain recursively.
 			 * The random bits portions may be different for each
 			 * vehicle in chain. */
-			if (v->Next() != NULL) DoTriggerVehicle(v->Next(), trigger, 0, true);
+			if (v->Next() != nullptr) DoTriggerVehicle(v->Next(), trigger, 0, true);
 			break;
 
 		case VEHICLE_TRIGGER_EMPTY:
@@ -1150,14 +1150,14 @@ static void DoTriggerVehicle(Vehicle *v,
 			 * recursively.  The random bits portions must be same
 			 * for each vehicle in chain, so we give them all
 			 * first chained vehicle's portion of random bits. */
-			if (v->Next() != NULL) DoTriggerVehicle(v->Next(), trigger, first ? new_random_bits : base_random_bits, false);
+			if (v->Next() != nullptr) DoTriggerVehicle(v->Next(), trigger, first ? new_random_bits : base_random_bits, false);
 			break;
 
 		case VEHICLE_TRIGGER_ANY_NEW_CARGO:
 			/* Now pass the trigger recursively to the next vehicle
 			 * in chain. */
 			assert(!first);
-			if (v->Next() != NULL) DoTriggerVehicle(v->Next(), VEHICLE_TRIGGER_ANY_NEW_CARGO, base_random_bits, false);
+			if (v->Next() != nullptr) DoTriggerVehicle(v->Next(), VEHICLE_TRIGGER_ANY_NEW_CARGO, base_random_bits, false);
 			break;
 
 		case VEHICLE_TRIGGER_CALLBACK_32:
diff --git a/src/newgrf_engine.h b/src/newgrf_engine.h
--- a/src/newgrf_engine.h
+++ b/src/newgrf_engine.h
@@ -81,11 +81,11 @@ void SetCustomEngineSprites(EngineID eng
 
 void GetCustomEngineSprite(EngineID engine, const Vehicle *v, Direction direction, EngineImageType image_type, VehicleSpriteSeq *result);
 #define GetCustomVehicleSprite(v, direction, image_type, result) GetCustomEngineSprite(v->engine_type, v, direction, image_type, result)
-#define GetCustomVehicleIcon(et, direction, image_type, result) GetCustomEngineSprite(et, NULL, direction, image_type, result)
+#define GetCustomVehicleIcon(et, direction, image_type, result) GetCustomEngineSprite(et, nullptr, direction, image_type, result)
 
 void GetRotorOverrideSprite(EngineID engine, const struct Aircraft *v, bool info_view, EngineImageType image_type, VehicleSpriteSeq *result);
 #define GetCustomRotorSprite(v, i, image_type, result) GetRotorOverrideSprite(v->engine_type, v, i, image_type, result)
-#define GetCustomRotorIcon(et, image_type, result) GetRotorOverrideSprite(et, NULL, true, image_type, result)
+#define GetCustomRotorIcon(et, image_type, result) GetRotorOverrideSprite(et, nullptr, true, image_type, result)
 
 /* Forward declaration of GRFFile, to avoid unnecessary inclusion of newgrf.h
  * elsewhere... */
@@ -100,7 +100,7 @@ bool UsesWagonOverride(const Vehicle *v)
 /* Handler to Evaluate callback 36. If the callback fails (i.e. most of the
  * time) orig_value is returned */
 uint GetVehicleProperty(const Vehicle *v, PropertyID property, uint orig_value);
-uint GetEngineProperty(EngineID engine, PropertyID property, uint orig_value, const Vehicle *v = NULL);
+uint GetEngineProperty(EngineID engine, PropertyID property, uint orig_value, const Vehicle *v = nullptr);
 
 enum VehicleTrigger {
 	VEHICLE_TRIGGER_NEW_CARGO     = 0x01,
diff --git a/src/newgrf_generic.cpp b/src/newgrf_generic.cpp
--- a/src/newgrf_generic.cpp
+++ b/src/newgrf_generic.cpp
@@ -140,7 +140,7 @@ void AddGenericCallback(uint8 feature, c
 
 /* virtual */ const SpriteGroup *GenericResolverObject::ResolveReal(const RealSpriteGroup *group) const
 {
-	if (group->num_loaded == 0) return NULL;
+	if (group->num_loaded == 0) return nullptr;
 
 	return group->loaded[0];
 }
@@ -150,7 +150,7 @@ void AddGenericCallback(uint8 feature, c
  * @param ai_callback Callback comes from the AI.
  * @param callback Callback ID.
  */
-GenericResolverObject::GenericResolverObject(bool ai_callback, CallbackID callback) : ResolverObject(NULL, callback), generic_scope(*this, ai_callback)
+GenericResolverObject::GenericResolverObject(bool ai_callback, CallbackID callback) : ResolverObject(nullptr, callback), generic_scope(*this, ai_callback)
 {
 }
 
@@ -162,7 +162,7 @@ GenericResolverObject::GenericResolverOb
  * @param object  pre-populated resolver object
  * @param param1_grfv7 callback_param1 for GRFs up to version 7.
  * @param param1_grfv8 callback_param1 for GRFs from version 8 on.
- * @param[out] file Optionally returns the GRFFile which made the final decision for the callback result. May be NULL if not required.
+ * @param[out] file Optionally returns the GRFFile which made the final decision for the callback result. May be nullptr if not required.
  * @return callback value if successful or CALLBACK_FAILED
  */
 static uint16 GetGenericCallbackResult(uint8 feature, ResolverObject &object, uint32 param1_grfv7, uint32 param1_grfv8, const GRFFile **file)
@@ -179,7 +179,7 @@ static uint16 GetGenericCallbackResult(u
 		if (result == CALLBACK_FAILED) continue;
 
 		/* Return NewGRF file if necessary */
-		if (file != NULL) *file = it->file;
+		if (file != nullptr) *file = it->file;
 
 		return result;
 	}
@@ -201,7 +201,7 @@ static uint16 GetGenericCallbackResult(u
  * @param event 'AI construction event' to pass to callback. (Variable 86)
  * @param count 'Construction number' to pass to callback. (Variable 87)
  * @param station_size 'Station size' to pass to callback. (Variable 88)
- * @param[out] file Optionally returns the GRFFile which made the final decision for the callback result. May be NULL if not required.
+ * @param[out] file Optionally returns the GRFFile which made the final decision for the callback result. May be nullptr if not required.
  * @return callback value if successful or CALLBACK_FAILED
  */
 uint16 GetAiPurchaseCallbackResult(uint8 feature, CargoID cargo_type, uint8 default_selection, IndustryType src_industry, IndustryType dst_industry, uint8 distance, AIConstructionEvent event, uint8 count, uint8 station_size, const GRFFile **file)
diff --git a/src/newgrf_gui.cpp b/src/newgrf_gui.cpp
--- a/src/newgrf_gui.cpp
+++ b/src/newgrf_gui.cpp
@@ -48,11 +48,11 @@ void ShowNewGRFError()
 	/* Do not show errors when entering the main screen */
 	if (_game_mode == GM_MENU) return;
 
-	for (const GRFConfig *c = _grfconfig; c != NULL; c = c->next) {
+	for (const GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
 		/* We only want to show fatal errors */
-		if (c->error == NULL || c->error->severity != STR_NEWGRF_ERROR_MSG_FATAL) continue;
+		if (c->error == nullptr || c->error->severity != STR_NEWGRF_ERROR_MSG_FATAL) continue;
 
-		SetDParam   (0, c->error->custom_message == NULL ? c->error->message : STR_JUST_RAW_STRING);
+		SetDParam   (0, c->error->custom_message == nullptr ? c->error->message : STR_JUST_RAW_STRING);
 		SetDParamStr(1, c->error->custom_message);
 		SetDParamStr(2, c->filename);
 		SetDParamStr(3, c->error->data);
@@ -66,7 +66,7 @@ void ShowNewGRFError()
 
 static void ShowNewGRFInfo(const GRFConfig *c, uint x, uint y, uint right, uint bottom, bool show_params)
 {
-	if (c->error != NULL) {
+	if (c->error != nullptr) {
 		char message[512];
 		SetDParamStr(0, c->error->custom_message); // is skipped by built-in messages
 		SetDParamStr(1, c->filename);
@@ -74,14 +74,14 @@ static void ShowNewGRFInfo(const GRFConf
 		for (uint i = 0; i < lengthof(c->error->param_value); i++) {
 			SetDParam(3 + i, c->error->param_value[i]);
 		}
-		GetString(message, c->error->custom_message == NULL ? c->error->message : STR_JUST_RAW_STRING, lastof(message));
+		GetString(message, c->error->custom_message == nullptr ? c->error->message : STR_JUST_RAW_STRING, lastof(message));
 
 		SetDParamStr(0, message);
 		y = DrawStringMultiLine(x, right, y, bottom, c->error->severity);
 	}
 
 	/* Draw filename or not if it is not known (GRF sent over internet) */
-	if (c->filename != NULL) {
+	if (c->filename != nullptr) {
 		SetDParamStr(0, c->filename);
 		y = DrawStringMultiLine(x, right, y, bottom, STR_NEWGRF_SETTINGS_FILENAME);
 	}
@@ -222,9 +222,9 @@ struct NewGRFParametersWindow : public W
 				Dimension suggestion = {500 - WD_FRAMERECT_LEFT - WD_FRAMERECT_RIGHT, (uint)FONT_HEIGHT_NORMAL * 4 + WD_TEXTPANEL_TOP + WD_TEXTPANEL_BOTTOM};
 				for (uint i = 0; i < this->grf_config->param_info.size(); i++) {
 					const GRFParameterInfo *par_info = this->grf_config->param_info[i];
-					if (par_info == NULL) continue;
+					if (par_info == nullptr) continue;
 					const char *desc = GetGRFStringFromGRFText(par_info->desc);
-					if (desc == NULL) continue;
+					if (desc == nullptr) continue;
 					Dimension d = GetStringMultiLineBoundingBox(desc, suggestion);
 					d.height += WD_TEXTPANEL_TOP + WD_TEXTPANEL_BOTTOM;
 					suggestion = maxdim(d, suggestion);
@@ -246,10 +246,10 @@ struct NewGRFParametersWindow : public W
 	void DrawWidget(const Rect &r, int widget) const override
 	{
 		if (widget == WID_NP_DESCRIPTION) {
-			const GRFParameterInfo *par_info = (this->clicked_row < this->grf_config->param_info.size()) ? this->grf_config->param_info[this->clicked_row] : NULL;
-			if (par_info == NULL) return;
+			const GRFParameterInfo *par_info = (this->clicked_row < this->grf_config->param_info.size()) ? this->grf_config->param_info[this->clicked_row] : nullptr;
+			if (par_info == nullptr) return;
 			const char *desc = GetGRFStringFromGRFText(par_info->desc);
-			if (desc == NULL) return;
+			if (desc == nullptr) return;
 			DrawStringMultiLine(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + WD_TEXTPANEL_TOP, r.bottom - WD_TEXTPANEL_BOTTOM, desc, TC_BLACK);
 			return;
 		} else if (widget != WID_NP_BACKGROUND) {
@@ -265,8 +265,8 @@ struct NewGRFParametersWindow : public W
 		int button_y_offset = (this->line_height - SETTING_BUTTON_HEIGHT) / 2;
 		int text_y_offset = (this->line_height - FONT_HEIGHT_NORMAL) / 2;
 		for (uint i = this->vscroll->GetPosition(); this->vscroll->IsVisible(i) && i < this->vscroll->GetCount(); i++) {
-			GRFParameterInfo *par_info = (i < this->grf_config->param_info.size()) ? this->grf_config->param_info[i] : NULL;
-			if (par_info == NULL) par_info = GetDummyParameterInfo(i);
+			GRFParameterInfo *par_info = (i < this->grf_config->param_info.size()) ? this->grf_config->param_info[i] : nullptr;
+			if (par_info == nullptr) par_info = GetDummyParameterInfo(i);
 			uint32 current_value = par_info->GetValue(this->grf_config);
 			bool selected = (i == this->clicked_row);
 
@@ -283,7 +283,7 @@ struct NewGRFParametersWindow : public W
 				SetDParam(3, current_value);
 				if (par_info->value_names.Contains(current_value)) {
 					const char *label = GetGRFStringFromGRFText(par_info->value_names.Find(current_value)->second);
-					if (label != NULL) {
+					if (label != nullptr) {
 						SetDParam(2, STR_JUST_RAW_STRING);
 						SetDParamStr(3, label);
 					}
@@ -291,7 +291,7 @@ struct NewGRFParametersWindow : public W
 			}
 
 			const char *name = GetGRFStringFromGRFText(par_info->name);
-			if (name != NULL) {
+			if (name != nullptr) {
 				SetDParam(0, STR_JUST_RAW_STRING);
 				SetDParamStr(1, name);
 			} else {
@@ -350,8 +350,8 @@ struct NewGRFParametersWindow : public W
 				if (_current_text_dir == TD_RTL) x = wid->current_x - 1 - x;
 				x -= 4;
 
-				GRFParameterInfo *par_info = (num < this->grf_config->param_info.size()) ? this->grf_config->param_info[num] : NULL;
-				if (par_info == NULL) par_info = GetDummyParameterInfo(num);
+				GRFParameterInfo *par_info = (num < this->grf_config->param_info.size()) ? this->grf_config->param_info[num] : nullptr;
+				if (par_info == nullptr) par_info = GetDummyParameterInfo(num);
 
 				/* One of the arrows is clicked */
 				uint32 old_val = par_info->GetValue(this->grf_config);
@@ -431,8 +431,8 @@ struct NewGRFParametersWindow : public W
 	{
 		if (StrEmpty(str)) return;
 		int32 value = atoi(str);
-		GRFParameterInfo *par_info = ((uint)this->clicked_row < this->grf_config->param_info.size()) ? this->grf_config->param_info[this->clicked_row] : NULL;
-		if (par_info == NULL) par_info = GetDummyParameterInfo(this->clicked_row);
+		GRFParameterInfo *par_info = ((uint)this->clicked_row < this->grf_config->param_info.size()) ? this->grf_config->param_info[this->clicked_row] : nullptr;
+		if (par_info == nullptr) par_info = GetDummyParameterInfo(this->clicked_row);
 		uint32 val = Clamp<uint32>(value, par_info->min_value, par_info->max_value);
 		par_info->SetValue(this->grf_config, val);
 		this->SetDirty();
@@ -441,8 +441,8 @@ struct NewGRFParametersWindow : public W
 	void OnDropdownSelect(int widget, int index) override
 	{
 		assert(this->clicked_dropdown);
-		GRFParameterInfo *par_info = ((uint)this->clicked_row < this->grf_config->param_info.size()) ? this->grf_config->param_info[this->clicked_row] : NULL;
-		if (par_info == NULL) par_info = GetDummyParameterInfo(this->clicked_row);
+		GRFParameterInfo *par_info = ((uint)this->clicked_row < this->grf_config->param_info.size()) ? this->grf_config->param_info[this->clicked_row] : nullptr;
+		if (par_info == nullptr) par_info = GetDummyParameterInfo(this->clicked_row);
 		par_info->SetValue(this->grf_config, index);
 		this->SetDirty();
 	}
@@ -574,7 +574,7 @@ typedef std::map<uint32, const GRFConfig
  */
 static void FillGrfidMap(const GRFConfig *c, GrfIdMap *grfid_map)
 {
-	while (c != NULL) {
+	while (c != nullptr) {
 		std::pair<uint32, const GRFConfig *> p(c->ident.grfid, c);
 		grfid_map->insert(p);
 		c = c->next;
@@ -598,7 +598,7 @@ struct NewGRFWindow : public Window, New
 	static GUIGRFConfigList::FilterFunction * const filter_funcs[]; ///< Filter functions of the #GUIGRFConfigList.
 
 	GUIGRFConfigList avails;    ///< Available (non-active) grfs.
-	const GRFConfig *avail_sel; ///< Currently selected available grf. \c NULL is none is selected.
+	const GRFConfig *avail_sel; ///< Currently selected available grf. \c nullptr is none is selected.
 	int avail_pos;              ///< Index of #avail_sel if existing, else \c -1.
 	StringFilter string_filter; ///< Filter for available grf.
 	QueryString filter_editbox; ///< Filter editbox;
@@ -620,10 +620,10 @@ struct NewGRFWindow : public Window, New
 
 	NewGRFWindow(WindowDesc *desc, bool editable, bool show_params, bool execute, GRFConfig **orig_list) : Window(desc), filter_editbox(EDITBOX_MAX_SIZE)
 	{
-		this->avail_sel   = NULL;
+		this->avail_sel   = nullptr;
 		this->avail_pos   = -1;
-		this->active_sel  = NULL;
-		this->actives     = NULL;
+		this->active_sel  = nullptr;
+		this->actives     = nullptr;
 		this->orig_list   = orig_list;
 		this->editable    = editable;
 		this->execute     = execute;
@@ -684,7 +684,7 @@ struct NewGRFWindow : public Window, New
 		GrfIdMap grfid_map;
 		FillGrfidMap(this->actives, &grfid_map);
 
-		for (const GRFConfig *a = _all_grfs; a != NULL; a = a->next) {
+		for (const GRFConfig *a = _all_grfs; a != nullptr; a = a->next) {
 			GrfIdMap::const_iterator iter = grfid_map.find(a->ident.grfid);
 			if (iter != grfid_map.end() && a->version > iter->second->version) return true;
 		}
@@ -697,7 +697,7 @@ struct NewGRFWindow : public Window, New
 		GrfIdMap grfid_map;
 		FillGrfidMap(this->actives, &grfid_map);
 
-		for (const GRFConfig *a = _all_grfs; a != NULL; a = a->next) {
+		for (const GRFConfig *a = _all_grfs; a != nullptr; a = a->next) {
 			GrfIdMap::iterator iter = grfid_map.find(a->ident.grfid);
 			if (iter == grfid_map.end() || iter->second->version >= a->version) continue;
 
@@ -709,7 +709,7 @@ struct NewGRFWindow : public Window, New
 			if (this->active_sel == *c) {
 				DeleteWindowByClass(WC_GRF_PARAMETERS);
 				DeleteWindowByClass(WC_TEXTFILE);
-				this->active_sel = NULL;
+				this->active_sel = nullptr;
 			}
 			delete *c;
 			*c = d;
@@ -842,7 +842,7 @@ struct NewGRFWindow : public Window, New
 				uint warning_left = rtl ? r.right - square.width - warning.width - 10 : r.left + square.width + 10;
 
 				int i = 0;
-				for (const GRFConfig *c = this->actives; c != NULL; c = c->next, i++) {
+				for (const GRFConfig *c = this->actives; c != nullptr; c = c->next, i++) {
 					if (this->vscroll->IsVisible(i)) {
 						const char *text = c->GetName();
 						bool h = (this->active_sel == c);
@@ -853,15 +853,15 @@ struct NewGRFWindow : public Window, New
 						} else if (i == this->active_over) {
 							/* Get index of current selection. */
 							int active_sel_pos = 0;
-							for (GRFConfig *c = this->actives; c != NULL && c != this->active_sel; c = c->next, active_sel_pos++) {}
+							for (GRFConfig *c = this->actives; c != nullptr && c != this->active_sel; c = c->next, active_sel_pos++) {}
 							if (active_sel_pos != this->active_over) {
 								uint top = this->active_over < active_sel_pos ? y + 1 : y + step_height - 2;
 								GfxFillRect(r.left + WD_FRAMERECT_LEFT, top - 1, r.right - WD_FRAMERECT_RIGHT, top + 1, PC_GREY);
 							}
 						}
 						DrawSprite(SPR_SQUARE, pal, square_left, y + square_offset_y);
-						if (c->error != NULL) DrawSprite(SPR_WARNING_SIGN, 0, warning_left, y + warning_offset_y);
-						uint txtoffset = c->error == NULL ? 0 : warning.width;
+						if (c->error != nullptr) DrawSprite(SPR_WARNING_SIGN, 0, warning_left, y + warning_offset_y);
+						uint txtoffset = c->error == nullptr ? 0 : warning.width;
 						DrawString(text_left + (rtl ? 0 : txtoffset), text_right - (rtl ? txtoffset : 0), y + offset_y, text, h ? TC_WHITE : TC_ORANGE);
 						y += step_height;
 					}
@@ -901,8 +901,8 @@ struct NewGRFWindow : public Window, New
 
 			case WID_NS_NEWGRF_INFO: {
 				const GRFConfig *selected = this->active_sel;
-				if (selected == NULL) selected = this->avail_sel;
-				if (selected != NULL) {
+				if (selected == nullptr) selected = this->avail_sel;
+				if (selected != nullptr) {
 					ShowNewGRFInfo(selected, r.left + WD_FRAMERECT_LEFT, r.top + WD_FRAMERECT_TOP, r.right - WD_FRAMERECT_RIGHT, r.bottom - WD_FRAMERECT_BOTTOM, this->show_params);
 				}
 				break;
@@ -913,9 +913,9 @@ struct NewGRFWindow : public Window, New
 	void OnClick(Point pt, int widget, int click_count) override
 	{
 		if (widget >= WID_NS_NEWGRF_TEXTFILE && widget < WID_NS_NEWGRF_TEXTFILE + TFT_END) {
-			if (this->active_sel == NULL && this->avail_sel == NULL) return;
+			if (this->active_sel == nullptr && this->avail_sel == nullptr) return;
 
-			ShowNewGRFTextfileWindow((TextfileType)(widget - WID_NS_NEWGRF_TEXTFILE), this->active_sel != NULL ? this->active_sel : this->avail_sel);
+			ShowNewGRFTextfileWindow((TextfileType)(widget - WID_NS_NEWGRF_TEXTFILE), this->active_sel != nullptr ? this->active_sel : this->avail_sel);
 			return;
 		}
 
@@ -936,7 +936,7 @@ struct NewGRFWindow : public Window, New
 			}
 
 			case WID_NS_OPEN_URL: {
-				const GRFConfig *c = (this->avail_sel == NULL) ? this->active_sel : this->avail_sel;
+				const GRFConfig *c = (this->avail_sel == nullptr) ? this->active_sel : this->avail_sel;
 
 				extern void OpenBrowser(const char *url);
 				OpenBrowser(c->GetURL());
@@ -944,7 +944,7 @@ struct NewGRFWindow : public Window, New
 			}
 
 			case WID_NS_PRESET_SAVE:
-				ShowSavePresetWindow((this->preset == -1) ? NULL : this->grf_presets[this->preset].c_str());
+				ShowSavePresetWindow((this->preset == -1) ? nullptr : this->grf_presets[this->preset].c_str());
 				break;
 
 			case WID_NS_PRESET_DELETE:
@@ -958,10 +958,10 @@ struct NewGRFWindow : public Window, New
 				break;
 
 			case WID_NS_MOVE_UP: { // Move GRF up
-				if (this->active_sel == NULL || !this->editable) break;
+				if (this->active_sel == nullptr || !this->editable) break;
 
 				int pos = 0;
-				for (GRFConfig **pc = &this->actives; *pc != NULL; pc = &(*pc)->next, pos++) {
+				for (GRFConfig **pc = &this->actives; *pc != nullptr; pc = &(*pc)->next, pos++) {
 					GRFConfig *c = *pc;
 					if (c->next == this->active_sel) {
 						c->next = this->active_sel->next;
@@ -977,10 +977,10 @@ struct NewGRFWindow : public Window, New
 			}
 
 			case WID_NS_MOVE_DOWN: { // Move GRF down
-				if (this->active_sel == NULL || !this->editable) break;
+				if (this->active_sel == nullptr || !this->editable) break;
 
 				int pos = 1; // Start at 1 as we swap the selected newgrf with the next one
-				for (GRFConfig **pc = &this->actives; *pc != NULL; pc = &(*pc)->next, pos++) {
+				for (GRFConfig **pc = &this->actives; *pc != nullptr; pc = &(*pc)->next, pos++) {
 					GRFConfig *c = *pc;
 					if (c == this->active_sel) {
 						*pc = c->next;
@@ -1001,19 +1001,19 @@ struct NewGRFWindow : public Window, New
 				uint i = this->vscroll->GetScrolledRowFromWidget(pt.y, this, WID_NS_FILE_LIST);
 
 				GRFConfig *c;
-				for (c = this->actives; c != NULL && i > 0; c = c->next, i--) {}
+				for (c = this->actives; c != nullptr && i > 0; c = c->next, i--) {}
 
 				if (this->active_sel != c) {
 					DeleteWindowByClass(WC_GRF_PARAMETERS);
 					DeleteWindowByClass(WC_TEXTFILE);
 				}
 				this->active_sel = c;
-				this->avail_sel = NULL;
+				this->avail_sel = nullptr;
 				this->avail_pos = -1;
 
 				this->InvalidateData();
 				if (click_count == 1) {
-					if (this->editable && this->active_sel != NULL) SetObjectToPlaceWnd(SPR_CURSOR_MOUSE, PAL_NONE, HT_DRAG, this);
+					if (this->editable && this->active_sel != nullptr) SetObjectToPlaceWnd(SPR_CURSOR_MOUSE, PAL_NONE, HT_DRAG, this);
 					break;
 				}
 				/* With double click, continue */
@@ -1021,20 +1021,20 @@ struct NewGRFWindow : public Window, New
 			}
 
 			case WID_NS_REMOVE: { // Remove GRF
-				if (this->active_sel == NULL || !this->editable) break;
+				if (this->active_sel == nullptr || !this->editable) break;
 				DeleteWindowByClass(WC_GRF_PARAMETERS);
 				DeleteWindowByClass(WC_TEXTFILE);
 
 				/* Choose the next GRF file to be the selected file. */
 				GRFConfig *newsel = this->active_sel->next;
-				for (GRFConfig **pc = &this->actives; *pc != NULL; pc = &(*pc)->next) {
+				for (GRFConfig **pc = &this->actives; *pc != nullptr; pc = &(*pc)->next) {
 					GRFConfig *c = *pc;
 					/* If the new selection is empty (i.e. we're deleting the last item
 					 * in the list, pick the file just before the selected file */
-					if (newsel == NULL && c->next == this->active_sel) newsel = c;
+					if (newsel == nullptr && c->next == this->active_sel) newsel = c;
 
 					if (c == this->active_sel) {
-						if (newsel == c) newsel = NULL;
+						if (newsel == c) newsel = nullptr;
 
 						*pc = c->next;
 						delete c;
@@ -1045,14 +1045,14 @@ struct NewGRFWindow : public Window, New
 				this->active_sel = newsel;
 				this->preset = -1;
 				this->avail_pos = -1;
-				this->avail_sel = NULL;
+				this->avail_sel = nullptr;
 				this->avails.ForceRebuild();
 				this->InvalidateData(GOID_NEWGRF_LIST_EDITED);
 				break;
 			}
 
 			case WID_NS_UPGRADE: { // Upgrade GRF.
-				if (!this->editable || this->actives == NULL) break;
+				if (!this->editable || this->actives == nullptr) break;
 				UpgradeCurrent();
 				this->InvalidateData(GOID_NEWGRF_LIST_EDITED);
 				break;
@@ -1062,7 +1062,7 @@ struct NewGRFWindow : public Window, New
 				ResetObjectToPlace();
 
 				uint i = this->vscroll2->GetScrolledRowFromWidget(pt.y, this, WID_NS_AVAIL_LIST);
-				this->active_sel = NULL;
+				this->active_sel = nullptr;
 				DeleteWindowByClass(WC_GRF_PARAMETERS);
 				if (i < this->avails.size()) {
 					if (this->avail_sel != this->avails[i]) DeleteWindowByClass(WC_TEXTFILE);
@@ -1071,7 +1071,7 @@ struct NewGRFWindow : public Window, New
 				}
 				this->InvalidateData();
 				if (click_count == 1) {
-					if (this->editable && this->avail_sel != NULL && !HasBit(this->avail_sel->flags, GCF_INVALID)) SetObjectToPlaceWnd(SPR_CURSOR_MOUSE, PAL_NONE, HT_DRAG, this);
+					if (this->editable && this->avail_sel != nullptr && !HasBit(this->avail_sel->flags, GCF_INVALID)) SetObjectToPlaceWnd(SPR_CURSOR_MOUSE, PAL_NONE, HT_DRAG, this);
 					break;
 				}
 				/* With double click, continue */
@@ -1079,7 +1079,7 @@ struct NewGRFWindow : public Window, New
 			}
 
 			case WID_NS_ADD:
-				if (this->avail_sel == NULL || !this->editable || HasBit(this->avail_sel->flags, GCF_INVALID)) break;
+				if (this->avail_sel == nullptr || !this->editable || HasBit(this->avail_sel->flags, GCF_INVALID)) break;
 
 				this->AddGRFToActive();
 				break;
@@ -1103,14 +1103,14 @@ struct NewGRFWindow : public Window, New
 
 			case WID_NS_VIEW_PARAMETERS:
 			case WID_NS_SET_PARAMETERS: { // Edit parameters
-				if (this->active_sel == NULL || !this->show_params || this->active_sel->num_valid_params == 0) break;
+				if (this->active_sel == nullptr || !this->show_params || this->active_sel->num_valid_params == 0) break;
 
 				OpenGRFParameterWindow(this->active_sel, this->editable);
 				break;
 			}
 
 			case WID_NS_TOGGLE_PALETTE:
-				if (this->active_sel != NULL && this->editable) {
+				if (this->active_sel != nullptr && this->editable) {
 					this->active_sel->palette ^= GRFP_USE_MASK;
 					this->SetDirty();
 				}
@@ -1136,8 +1136,8 @@ struct NewGRFWindow : public Window, New
 
 	void OnNewGRFsScanned() override
 	{
-		if (this->active_sel == NULL) DeleteWindowByClass(WC_TEXTFILE);
-		this->avail_sel = NULL;
+		if (this->active_sel == nullptr) DeleteWindowByClass(WC_TEXTFILE);
+		this->avail_sel = nullptr;
 		this->avail_pos = -1;
 		this->avails.ForceRebuild();
 		this->DeleteChildWindows(WC_QUERY_STRING); // Remove the parameter query window
@@ -1158,13 +1158,13 @@ struct NewGRFWindow : public Window, New
 		ResetObjectToPlace();
 		DeleteWindowByClass(WC_GRF_PARAMETERS);
 		DeleteWindowByClass(WC_TEXTFILE);
-		this->active_sel = NULL;
+		this->active_sel = nullptr;
 		this->InvalidateData(GOID_NEWGRF_PRESET_LOADED);
 	}
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
 		SaveGRFPresetToConfig(str, this->actives);
 		this->grf_presets = GetGRFPresetList();
@@ -1195,13 +1195,13 @@ struct NewGRFWindow : public Window, New
 
 			case GOID_NEWGRF_RESCANNED:
 				/* Search the list for items that are now found and mark them as such. */
-				for (GRFConfig **l = &this->actives; *l != NULL; l = &(*l)->next) {
+				for (GRFConfig **l = &this->actives; *l != nullptr; l = &(*l)->next) {
 					GRFConfig *c = *l;
 					bool compatible = HasBit(c->flags, GCF_COMPATIBLE);
 					if (c->status != GCS_NOT_FOUND && !compatible) continue;
 
 					const GRFConfig *f = FindGRFConfig(c->ident.grfid, FGCM_EXACT, compatible ? c->original_md5sum : c->ident.md5sum);
-					if (f == NULL || HasBit(f->flags, GCF_INVALID)) continue;
+					if (f == nullptr || HasBit(f->flags, GCF_INVALID)) continue;
 
 					*l = new GRFConfig(*f);
 					(*l)->next = c->next;
@@ -1221,7 +1221,7 @@ struct NewGRFWindow : public Window, New
 			case GOID_NEWGRF_PRESET_LOADED: {
 				/* Update scrollbars */
 				int i = 0;
-				for (const GRFConfig *c = this->actives; c != NULL; c = c->next, i++) {}
+				for (const GRFConfig *c = this->actives; c != nullptr; c = c->next, i++) {}
 
 				this->vscroll->SetCount(i + 1); // Reserve empty space for drag and drop handling.
 
@@ -1238,10 +1238,10 @@ struct NewGRFWindow : public Window, New
 			WID_NS_TOGGLE_PALETTE,
 			WIDGET_LIST_END
 		);
-		this->SetWidgetDisabledState(WID_NS_ADD, !this->editable || this->avail_sel == NULL || HasBit(this->avail_sel->flags, GCF_INVALID));
-		this->SetWidgetDisabledState(WID_NS_UPGRADE, !this->editable || this->actives == NULL || !this->CanUpgradeCurrent());
+		this->SetWidgetDisabledState(WID_NS_ADD, !this->editable || this->avail_sel == nullptr || HasBit(this->avail_sel->flags, GCF_INVALID));
+		this->SetWidgetDisabledState(WID_NS_UPGRADE, !this->editable || this->actives == nullptr || !this->CanUpgradeCurrent());
 
-		bool disable_all = this->active_sel == NULL || !this->editable;
+		bool disable_all = this->active_sel == nullptr || !this->editable;
 		this->SetWidgetsDisabledState(disable_all,
 			WID_NS_REMOVE,
 			WID_NS_MOVE_UP,
@@ -1249,28 +1249,28 @@ struct NewGRFWindow : public Window, New
 			WIDGET_LIST_END
 		);
 
-		const GRFConfig *c = (this->avail_sel == NULL) ? this->active_sel : this->avail_sel;
+		const GRFConfig *c = (this->avail_sel == nullptr) ? this->active_sel : this->avail_sel;
 		for (TextfileType tft = TFT_BEGIN; tft < TFT_END; tft++) {
-			this->SetWidgetDisabledState(WID_NS_NEWGRF_TEXTFILE + tft, c == NULL || c->GetTextfile(tft) == NULL);
+			this->SetWidgetDisabledState(WID_NS_NEWGRF_TEXTFILE + tft, c == nullptr || c->GetTextfile(tft) == nullptr);
 		}
-		this->SetWidgetDisabledState(WID_NS_OPEN_URL, c == NULL || StrEmpty(c->GetURL()));
+		this->SetWidgetDisabledState(WID_NS_OPEN_URL, c == nullptr || StrEmpty(c->GetURL()));
 
-		this->SetWidgetDisabledState(WID_NS_SET_PARAMETERS, !this->show_params || this->active_sel == NULL || this->active_sel->num_valid_params == 0);
-		this->SetWidgetDisabledState(WID_NS_VIEW_PARAMETERS, !this->show_params || this->active_sel == NULL || this->active_sel->num_valid_params == 0);
+		this->SetWidgetDisabledState(WID_NS_SET_PARAMETERS, !this->show_params || this->active_sel == nullptr || this->active_sel->num_valid_params == 0);
+		this->SetWidgetDisabledState(WID_NS_VIEW_PARAMETERS, !this->show_params || this->active_sel == nullptr || this->active_sel->num_valid_params == 0);
 		this->SetWidgetDisabledState(WID_NS_TOGGLE_PALETTE, disable_all ||
 				(!(_settings_client.gui.newgrf_developer_tools || _settings_client.gui.scenario_developer) && ((c->palette & GRFP_GRF_MASK) != GRFP_GRF_UNSET)));
 
 		if (!disable_all) {
 			/* All widgets are now enabled, so disable widgets we can't use */
 			if (this->active_sel == this->actives)    this->DisableWidget(WID_NS_MOVE_UP);
-			if (this->active_sel->next == NULL)       this->DisableWidget(WID_NS_MOVE_DOWN);
+			if (this->active_sel->next == nullptr)       this->DisableWidget(WID_NS_MOVE_DOWN);
 		}
 
 		this->SetWidgetDisabledState(WID_NS_PRESET_DELETE, this->preset == -1);
 
 		bool has_missing = false;
 		bool has_compatible = false;
-		for (const GRFConfig *c = this->actives; !has_missing && c != NULL; c = c->next) {
+		for (const GRFConfig *c = this->actives; !has_missing && c != nullptr; c = c->next) {
 			has_missing    |= c->status == GCS_NOT_FOUND;
 			has_compatible |= HasBit(c->flags, GCF_COMPATIBLE);
 		}
@@ -1332,7 +1332,7 @@ struct NewGRFWindow : public Window, New
 
 		if (this->avails.size() == 0) this->avail_pos = -1;
 		if (this->avail_pos >= 0) {
-			this->active_sel = NULL;
+			this->active_sel = nullptr;
 			DeleteWindowByClass(WC_GRF_PARAMETERS);
 			if (this->avail_sel != this->avails[this->avail_pos]) DeleteWindowByClass(WC_TEXTFILE);
 			this->avail_sel = this->avails[this->avail_pos];
@@ -1358,7 +1358,7 @@ struct NewGRFWindow : public Window, New
 		if (!this->editable) return;
 
 		if (widget == WID_NS_FILE_LIST) {
-			if (this->active_sel != NULL) {
+			if (this->active_sel != nullptr) {
 				/* Get pointer to the selected file in the active list. */
 				int from_pos = 0;
 				GRFConfig **from_prev;
@@ -1369,7 +1369,7 @@ struct NewGRFWindow : public Window, New
 				if (to_pos != from_pos) { // Don't move NewGRF file over itself.
 					/* Get pointer to destination position. */
 					GRFConfig **to_prev = &this->actives;
-					for (int i = from_pos < to_pos ? -1 : 0; *to_prev != NULL && i < to_pos; to_prev = &(*to_prev)->next, i++) {}
+					for (int i = from_pos < to_pos ? -1 : 0; *to_prev != nullptr && i < to_pos; to_prev = &(*to_prev)->next, i++) {}
 
 					/* Detach NewGRF file from its original position. */
 					*from_prev = this->active_sel->next;
@@ -1382,11 +1382,11 @@ struct NewGRFWindow : public Window, New
 					this->preset = -1;
 					this->InvalidateData();
 				}
-			} else if (this->avail_sel != NULL) {
+			} else if (this->avail_sel != nullptr) {
 				int to_pos = min(this->vscroll->GetScrolledRowFromWidget(pt.y, this, WID_NS_FILE_LIST), this->vscroll->GetCount() - 1);
 				this->AddGRFToActive(to_pos);
 			}
-		} else if (widget == WID_NS_AVAIL_LIST && this->active_sel != NULL) {
+		} else if (widget == WID_NS_AVAIL_LIST && this->active_sel != nullptr) {
 			/* Remove active NewGRF file by dragging it over available list. */
 			Point dummy = {-1, -1};
 			this->OnClick(dummy, WID_NS_REMOVE, 1);
@@ -1405,17 +1405,17 @@ struct NewGRFWindow : public Window, New
 	{
 		if (!this->editable) return;
 
-		if (widget == WID_NS_FILE_LIST && (this->active_sel != NULL || this->avail_sel != NULL)) {
+		if (widget == WID_NS_FILE_LIST && (this->active_sel != nullptr || this->avail_sel != nullptr)) {
 			/* An NewGRF file is dragged over the active list. */
 			int to_pos = this->vscroll->GetScrolledRowFromWidget(pt.y, this, WID_NS_FILE_LIST);
 			/* Skip the last dummy line if the source is from the active list. */
-			to_pos = min(to_pos, this->vscroll->GetCount() - (this->active_sel != NULL ? 2 : 1));
+			to_pos = min(to_pos, this->vscroll->GetCount() - (this->active_sel != nullptr ? 2 : 1));
 
 			if (to_pos != this->active_over) {
 				this->active_over = to_pos;
 				this->SetWidgetDirty(WID_NS_FILE_LIST);
 			}
-		} else if (widget == WID_NS_AVAIL_LIST && this->active_sel != NULL) {
+		} else if (widget == WID_NS_AVAIL_LIST && this->active_sel != nullptr) {
 			this->active_over = -2;
 			this->SetWidgetDirty(WID_NS_AVAIL_LIST);
 		} else if (this->active_over != -1) {
@@ -1453,9 +1453,9 @@ private:
 
 		this->avails.clear();
 
-		for (const GRFConfig *c = _all_grfs; c != NULL; c = c->next) {
+		for (const GRFConfig *c = _all_grfs; c != nullptr; c = c->next) {
 			bool found = false;
-			for (const GRFConfig *grf = this->actives; grf != NULL && !found; grf = grf->next) found = grf->ident.HasGrfIdentifier(c->ident.grfid, c->ident.md5sum);
+			for (const GRFConfig *grf = this->actives; grf != nullptr && !found; grf = grf->next) found = grf->ident.HasGrfIdentifier(c->ident.grfid, c->ident.md5sum);
 			if (found) continue;
 
 			if (_settings_client.gui.newgrf_show_old_versions) {
@@ -1480,10 +1480,10 @@ private:
 		this->avails.RebuildDone();
 		this->avails.Sort();
 
-		if (this->avail_sel != NULL) {
+		if (this->avail_sel != nullptr) {
 			this->avail_pos = find_index(this->avails, this->avail_sel);
 			if (this->avail_pos == -1) {
-				this->avail_sel = NULL;
+				this->avail_sel = nullptr;
 			}
 		}
 
@@ -1497,15 +1497,15 @@ private:
 	 */
 	bool AddGRFToActive(int ins_pos = -1)
 	{
-		if (this->avail_sel == NULL || !this->editable || HasBit(this->avail_sel->flags, GCF_INVALID)) return false;
+		if (this->avail_sel == nullptr || !this->editable || HasBit(this->avail_sel->flags, GCF_INVALID)) return false;
 
 		DeleteWindowByClass(WC_TEXTFILE);
 
 		uint count = 0;
-		GRFConfig **entry = NULL;
+		GRFConfig **entry = nullptr;
 		GRFConfig **list;
 		/* Find last entry in the list, checking for duplicate grfid on the way */
-		for (list = &this->actives; *list != NULL; list = &(*list)->next, ins_pos--) {
+		for (list = &this->actives; *list != nullptr; list = &(*list)->next, ins_pos--) {
 			if (ins_pos == 0) entry = list; // Insert position? Save.
 			if ((*list)->ident.grfid == this->avail_sel->ident.grfid) {
 				ShowErrorMessage(STR_NEWGRF_DUPLICATE_GRFID, INVALID_STRING_ID, WL_INFO);
@@ -1513,7 +1513,7 @@ private:
 			}
 			if (!HasBit((*list)->flags, GCF_STATIC)) count++;
 		}
-		if (entry == NULL) entry = list;
+		if (entry == nullptr) entry = list;
 		if (count >= NETWORK_MAX_GRF_COUNT) {
 			ShowErrorMessage(STR_NEWGRF_TOO_MANY_NEWGRFS, INVALID_STRING_ID, WL_INFO);
 			return false;
@@ -1546,7 +1546,7 @@ void ShowMissingContentWindow(const GRFC
 {
 	/* Only show the things in the current list, or everything when nothing's selected */
 	ContentVector cv;
-	for (const GRFConfig *c = list; c != NULL; c = c->next) {
+	for (const GRFConfig *c = list; c != nullptr; c = c->next) {
 		if (c->status != GCS_NOT_FOUND && !HasBit(c->flags, GCF_COMPATIBLE)) continue;
 
 		ContentInfo *ci = new ContentInfo();
@@ -1557,7 +1557,7 @@ void ShowMissingContentWindow(const GRFC
 		memcpy(ci->md5sum, HasBit(c->flags, GCF_COMPATIBLE) ? c->original_md5sum : c->ident.md5sum, sizeof(ci->md5sum));
 		cv.push_back(ci);
 	}
-	ShowNetworkContentListWindow(cv.size() == 0 ? NULL : &cv, CONTENT_TYPE_NEWGRF);
+	ShowNetworkContentListWindow(cv.size() == 0 ? nullptr : &cv, CONTENT_TYPE_NEWGRF);
 }
 
 Listing NewGRFWindow::last_sorting     = {false, 0};
@@ -1605,7 +1605,7 @@ public:
 	void SetupSmallestSize(Window *w, bool init_array) override
 	{
 		/* Copy state flag from the window. */
-		assert(dynamic_cast<NewGRFWindow *>(w) != NULL);
+		assert(dynamic_cast<NewGRFWindow *>(w) != nullptr);
 		NewGRFWindow *ngw = (NewGRFWindow *)w;
 		this->editable = ngw->editable;
 
@@ -1766,11 +1766,11 @@ public:
 
 	NWidgetCore *GetWidgetFromPos(int x, int y) override
 	{
-		if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return NULL;
+		if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return nullptr;
 
-		NWidgetCore *nw = (this->editable) ? this->avs->GetWidgetFromPos(x, y) : NULL;
-		if (nw == NULL) nw = this->acs->GetWidgetFromPos(x, y);
-		if (nw == NULL) nw = this->inf->GetWidgetFromPos(x, y);
+		NWidgetCore *nw = (this->editable) ? this->avs->GetWidgetFromPos(x, y) : nullptr;
+		if (nw == nullptr) nw = this->acs->GetWidgetFromPos(x, y);
+		if (nw == nullptr) nw = this->inf->GetWidgetFromPos(x, y);
 		return nw;
 	}
 
@@ -1912,13 +1912,13 @@ static const NWidgetPart _nested_newgrf_
 /** Construct nested container widget for managing the lists and the info panel of the NewGRF GUI. */
 NWidgetBase* NewGRFDisplay(int *biggest_index)
 {
-	NWidgetBase *avs = MakeNWidgets(_nested_newgrf_availables_widgets, lengthof(_nested_newgrf_availables_widgets), biggest_index, NULL);
+	NWidgetBase *avs = MakeNWidgets(_nested_newgrf_availables_widgets, lengthof(_nested_newgrf_availables_widgets), biggest_index, nullptr);
 
 	int biggest2;
-	NWidgetBase *acs = MakeNWidgets(_nested_newgrf_actives_widgets, lengthof(_nested_newgrf_actives_widgets), &biggest2, NULL);
+	NWidgetBase *acs = MakeNWidgets(_nested_newgrf_actives_widgets, lengthof(_nested_newgrf_actives_widgets), &biggest2, nullptr);
 	*biggest_index = max(*biggest_index, biggest2);
 
-	NWidgetBase *inf = MakeNWidgets(_nested_newgrf_infopanel_widgets, lengthof(_nested_newgrf_infopanel_widgets), &biggest2, NULL);
+	NWidgetBase *inf = MakeNWidgets(_nested_newgrf_infopanel_widgets, lengthof(_nested_newgrf_infopanel_widgets), &biggest2, nullptr);
 	*biggest_index = max(*biggest_index, biggest2);
 
 	return new NWidgetNewGRFDisplay(avs, acs, inf);
@@ -1970,9 +1970,9 @@ static void NewGRFConfirmationCallback(W
 		/* Show new, updated list */
 		GRFConfig *c;
 		int i = 0;
-		for (c = nw->actives; c != NULL && c != nw->active_sel; c = c->next, i++) {}
+		for (c = nw->actives; c != nullptr && c != nw->active_sel; c = c->next, i++) {}
 		CopyGRFConfigList(&nw->actives, *nw->orig_list, false);
-		for (c = nw->actives; c != NULL && i > 0; c = c->next, i--) {}
+		for (c = nw->actives; c != nullptr && i > 0; c = c->next, i--) {}
 		nw->active_sel = c;
 		nw->avails.ForceRebuild();
 
@@ -2039,13 +2039,13 @@ struct SavePresetWindow : public Window 
 
 	/**
 	 * Constructor of the save preset window.
-	 * @param initial_text Initial text to display in the edit box, or \c NULL.
+	 * @param initial_text Initial text to display in the edit box, or \c nullptr.
 	 */
 	SavePresetWindow(const char *initial_text) : Window(&_save_preset_desc), presetname_editbox(32)
 	{
 		this->presets = GetGRFPresetList();
 		this->selected = -1;
-		if (initial_text != NULL) {
+		if (initial_text != nullptr) {
 			for (uint i = 0; i < this->presets.size(); i++) {
 				if (this->presets[i] == initial_text) {
 					this->selected = i;
@@ -2064,7 +2064,7 @@ struct SavePresetWindow : public Window 
 
 		this->vscroll->SetCount((uint)this->presets.size());
 		this->SetFocusedWidget(WID_SVP_EDITBOX);
-		if (initial_text != NULL) this->presetname_editbox.text.Assign(initial_text);
+		if (initial_text != nullptr) this->presetname_editbox.text.Assign(initial_text);
 	}
 
 	~SavePresetWindow()
@@ -2132,7 +2132,7 @@ struct SavePresetWindow : public Window 
 
 			case WID_SVP_SAVE: {
 				Window *w = FindWindowById(WC_GAME_OPTIONS, WN_GAME_OPTIONS_NEWGRF_STATE);
-				if (w != NULL && !StrEmpty(this->presetname_editbox.text.buf)) w->OnQueryTextFinished(this->presetname_editbox.text.buf);
+				if (w != nullptr && !StrEmpty(this->presetname_editbox.text.buf)) w->OnQueryTextFinished(this->presetname_editbox.text.buf);
 				delete this;
 				break;
 			}
@@ -2147,7 +2147,7 @@ struct SavePresetWindow : public Window 
 
 /**
  * Open the window for saving a preset.
- * @param initial_text Initial text to display in the edit box, or \c NULL.
+ * @param initial_text Initial text to display in the edit box, or \c nullptr.
  */
 static void ShowSavePresetWindow(const char *initial_text)
 {
@@ -2171,7 +2171,7 @@ static const NWidgetPart _nested_scan_pr
 
 /** Description of the widgets and other settings of the window. */
 static WindowDesc _scan_progress_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_MODAL_PROGRESS, WC_NONE,
 	0,
 	_nested_scan_progress_widgets, lengthof(_nested_scan_progress_widgets)
@@ -2183,7 +2183,7 @@ struct ScanProgressWindow : public Windo
 	int scanned;     ///< The number of NewGRFs that we have seen.
 
 	/** Create the window. */
-	ScanProgressWindow() : Window(&_scan_progress_desc), last_name(NULL), scanned(0)
+	ScanProgressWindow() : Window(&_scan_progress_desc), last_name(nullptr), scanned(0)
 	{
 		this->InitNested(1);
 	}
@@ -2235,7 +2235,7 @@ struct ScanProgressWindow : public Windo
 				SetDParam(1, _settings_client.gui.last_newgrf_count);
 				DrawString(r.left, r.right, r.top, STR_NEWGRF_SCAN_STATUS, TC_FROMSTRING, SA_HOR_CENTER);
 
-				DrawString(r.left, r.right, r.top + FONT_HEIGHT_NORMAL + WD_PAR_VSEP_NORMAL, this->last_name == NULL ? "" : this->last_name, TC_BLACK, SA_HOR_CENTER);
+				DrawString(r.left, r.right, r.top + FONT_HEIGHT_NORMAL + WD_PAR_VSEP_NORMAL, this->last_name == nullptr ? "" : this->last_name, TC_BLACK, SA_HOR_CENTER);
 				break;
 		}
 	}
@@ -2248,7 +2248,7 @@ struct ScanProgressWindow : public Windo
 	void UpdateNewGRFScanStatus(uint num, const char *name)
 	{
 		free(this->last_name);
-		if (name == NULL) {
+		if (name == nullptr) {
 			char buf[256];
 			GetString(buf, STR_NEWGRF_SCAN_ARCHIVES, lastof(buf));
 			this->last_name = stredup(buf);
@@ -2270,6 +2270,6 @@ struct ScanProgressWindow : public Windo
 void UpdateNewGRFScanStatus(uint num, const char *name)
 {
 	ScanProgressWindow *w  = dynamic_cast<ScanProgressWindow *>(FindWindowByClass(WC_MODAL_PROGRESS));
-	if (w == NULL) w = new ScanProgressWindow();
+	if (w == nullptr) w = new ScanProgressWindow();
 	w->UpdateNewGRFScanStatus(num, name);
 }
diff --git a/src/newgrf_house.cpp b/src/newgrf_house.cpp
--- a/src/newgrf_house.cpp
+++ b/src/newgrf_house.cpp
@@ -34,12 +34,12 @@ HouseOverrideManager _house_mngr(NEW_HOU
 /**
  * Retrieve the grf file associated with a house.
  * @param house_id House to query.
- * @return The associated GRF file (may be \c NULL).
+ * @return The associated GRF file (may be \c nullptr).
  */
 static const GRFFile *GetHouseSpecGrf(HouseID house_id)
 {
 	const HouseSpec *hs  = HouseSpec::Get(house_id);
-	return (hs != NULL) ? hs->grf_prop.grffile : NULL;
+	return (hs != nullptr) ? hs->grf_prop.grffile : nullptr;
 }
 
 /**
@@ -190,7 +190,7 @@ static bool SearchNearbyHouseID(TileInde
 	if (IsTileType(tile, MP_HOUSE)) {
 		HouseID house = GetHouseType(tile); // tile been examined
 		const HouseSpec *hs = HouseSpec::Get(house);
-		if (hs->grf_prop.grffile != NULL) { // must be one from a grf file
+		if (hs->grf_prop.grffile != nullptr) { // must be one from a grf file
 			SearchNearbyHouseData *nbhd = (SearchNearbyHouseData *)user_data;
 
 			TileIndex north_tile = tile + GetHouseNorthPart(house); // modifies 'house'!
@@ -214,7 +214,7 @@ static bool SearchNearbyHouseClass(TileI
 	if (IsTileType(tile, MP_HOUSE)) {
 		HouseID house = GetHouseType(tile); // tile been examined
 		const HouseSpec *hs = HouseSpec::Get(house);
-		if (hs->grf_prop.grffile != NULL) { // must be one from a grf file
+		if (hs->grf_prop.grffile != nullptr) { // must be one from a grf file
 			SearchNearbyHouseData *nbhd = (SearchNearbyHouseData *)user_data;
 
 			TileIndex north_tile = tile + GetHouseNorthPart(house); // modifies 'house'!
@@ -238,7 +238,7 @@ static bool SearchNearbyHouseGRFID(TileI
 	if (IsTileType(tile, MP_HOUSE)) {
 		HouseID house = GetHouseType(tile); // tile been examined
 		const HouseSpec *hs = HouseSpec::Get(house);
-		if (hs->grf_prop.grffile != NULL) { // must be one from a grf file
+		if (hs->grf_prop.grffile != nullptr) { // must be one from a grf file
 			SearchNearbyHouseData *nbhd = (SearchNearbyHouseData *)user_data;
 
 			TileIndex north_tile = tile + GetHouseNorthPart(house); // modifies 'house'!
@@ -320,7 +320,7 @@ static uint32 GetDistanceFromNearbyHouse
 		/* Building counts for new houses with id = parameter. */
 		case 0x61: {
 			const HouseSpec *hs = HouseSpec::Get(this->house_id);
-			if (hs->grf_prop.grffile == NULL) return 0;
+			if (hs->grf_prop.grffile == nullptr) return 0;
 
 			HouseID new_house = _house_mngr.GetID(parameter, hs->grf_prop.grffile->grfid);
 			return new_house == INVALID_HOUSE_ID ? 0 : GetNumHouses(new_house, this->town);
@@ -462,7 +462,7 @@ void DrawNewHouseTile(TileInfo *ti, Hous
 	HouseResolverObject object(house_id, ti->tile, Town::GetByTile(ti->tile));
 
 	const SpriteGroup *group = object.Resolve();
-	if (group != NULL && group->type == SGT_TILELAYOUT) {
+	if (group != nullptr && group->type == SGT_TILELAYOUT) {
 		/* Limit the building stage to the number of stages supplied. */
 		const TileLayoutSpriteGroup *tlgroup = (const TileLayoutSpriteGroup *)group;
 		byte stage = GetHouseBuildingStage(ti->tile);
@@ -488,7 +488,7 @@ struct HouseAnimationBase : public Anima
 void AnimateNewHouseTile(TileIndex tile)
 {
 	const HouseSpec *hs = HouseSpec::Get(GetHouseType(tile));
-	if (hs == NULL) return;
+	if (hs == nullptr) return;
 
 	HouseAnimationBase::AnimateTile(hs, Town::GetByTile(tile), tile, HasBit(hs->extra_flags, CALLBACK_1A_RANDOM_BITS));
 }
@@ -581,14 +581,14 @@ static void DoTriggerHouse(TileIndex til
 	HouseID hid = GetHouseType(tile);
 	HouseSpec *hs = HouseSpec::Get(hid);
 
-	if (hs->grf_prop.spritegroup[0] == NULL) return;
+	if (hs->grf_prop.spritegroup[0] == nullptr) return;
 
 	HouseResolverObject object(hid, tile, Town::GetByTile(tile), CBID_RANDOM_TRIGGER);
 	object.waiting_triggers = GetHouseTriggers(tile) | trigger;
 	SetHouseTriggers(tile, object.waiting_triggers); // store now for var 5F
 
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL) return;
+	if (group == nullptr) return;
 
 	/* Store remaining triggers. */
 	SetHouseTriggers(tile, object.GetRemainingTriggers());
diff --git a/src/newgrf_industries.cpp b/src/newgrf_industries.cpp
--- a/src/newgrf_industries.cpp
+++ b/src/newgrf_industries.cpp
@@ -79,7 +79,7 @@ uint32 GetIndustryIDAtOffset(TileIndex t
 		}
 	}
 	/* Not an 'old type' tile */
-	if (indtsp->grf_prop.spritegroup[0] != NULL) { // tile has a spritegroup ?
+	if (indtsp->grf_prop.spritegroup[0] != nullptr) { // tile has a spritegroup ?
 		if (indtsp->grf_prop.grffile->grfid == cur_grfid) { // same industry, same grf ?
 			return indtsp->grf_prop.local_id;
 		} else {
@@ -202,7 +202,7 @@ static uint32 GetCountAndDistanceOfClose
 
 	const IndustrySpec *indspec = GetIndustrySpec(this->type);
 
-	if (this->industry == NULL) {
+	if (this->industry == nullptr) {
 		DEBUG(grf, 1, "Unhandled variable 0x%X (no available industry) in callback 0x%x", variable, this->ro.callback);
 
 		*available = false;
@@ -240,7 +240,7 @@ static uint32 GetCountAndDistanceOfClose
 			bool is_ai = false;
 
 			const Company *c = Company::GetIfValid(this->industry->founder);
-			if (c != NULL) {
+			if (c != nullptr) {
 				const Livery *l = &c->livery[LS_DEFAULT];
 
 				is_ai = c->is_ai;
@@ -338,7 +338,7 @@ static uint32 GetCountAndDistanceOfClose
 		}
 
 		/* Get a variable from the persistent storage */
-		case 0x7C: return (this->industry->psa != NULL) ? this->industry->psa->GetValue(parameter) : 0;
+		case 0x7C: return (this->industry->psa != nullptr) ? this->industry->psa->GetValue(parameter) : 0;
 
 		/* Industry structure access*/
 		case 0x80: return this->industry->location.tile;
@@ -411,7 +411,7 @@ static uint32 GetCountAndDistanceOfClose
 
 /* virtual */ uint32 IndustriesScopeResolver::GetRandomBits() const
 {
-	return this->industry != NULL ? this->industry->random : 0;
+	return this->industry != nullptr ? this->industry->random : 0;
 }
 
 /* virtual */ uint32 IndustriesScopeResolver::GetTriggers() const
@@ -423,13 +423,13 @@ static uint32 GetCountAndDistanceOfClose
 {
 	if (this->industry->index == INVALID_INDUSTRY) return;
 
-	if (this->industry->psa == NULL) {
+	if (this->industry->psa == nullptr) {
 		/* There is no need to create a storage if the value is zero. */
 		if (value == 0) return;
 
 		/* Create storage on first modification. */
 		const IndustrySpec *indsp = GetIndustrySpec(this->industry->type);
-		uint32 grfid = (indsp->grf_prop.grffile != NULL) ? indsp->grf_prop.grffile->grfid : 0;
+		uint32 grfid = (indsp->grf_prop.grffile != nullptr) ? indsp->grf_prop.grffile->grfid : 0;
 		assert(PersistentStorage::CanAllocateItem());
 		this->industry->psa = new PersistentStorage(grfid, GSF_INDUSTRIES, this->industry->location.tile);
 	}
@@ -445,7 +445,7 @@ static uint32 GetCountAndDistanceOfClose
 static const GRFFile *GetGrffile(IndustryType type)
 {
 	const IndustrySpec *indspec = GetIndustrySpec(type);
-	return (indspec != NULL) ? indspec->grf_prop.grffile : NULL;
+	return (indspec != nullptr) ? indspec->grf_prop.grffile : nullptr;
 }
 
 /**
@@ -462,7 +462,7 @@ IndustriesResolverObject::IndustriesReso
 		CallbackID callback, uint32 callback_param1, uint32 callback_param2)
 	: ResolverObject(GetGrffile(type), callback, callback_param1, callback_param2),
 	industries_scope(*this, tile, indus, type, random_bits),
-	town_scope(NULL)
+	town_scope(nullptr)
 {
 	this->root_spritegroup = GetIndustrySpec(type)->grf_prop.spritegroup[0];
 }
@@ -478,16 +478,16 @@ IndustriesResolverObject::~IndustriesRes
  */
 TownScopeResolver *IndustriesResolverObject::GetTown()
 {
-	if (this->town_scope == NULL) {
-		Town *t = NULL;
+	if (this->town_scope == nullptr) {
+		Town *t = nullptr;
 		bool readonly = true;
-		if (this->industries_scope.industry != NULL) {
+		if (this->industries_scope.industry != nullptr) {
 			t = this->industries_scope.industry->town;
 			readonly = this->industries_scope.industry->index == INVALID_INDUSTRY;
 		} else if (this->industries_scope.tile != INVALID_TILE) {
 			t = ClosestTownFromTile(this->industries_scope.tile, UINT_MAX);
 		}
-		if (t == NULL) return NULL;
+		if (t == nullptr) return nullptr;
 		this->town_scope = new TownScopeResolver(*this, t, readonly);
 	}
 	return this->town_scope;
@@ -533,7 +533,7 @@ CommandCost CheckIfCallBackAllowsCreatio
 	ind.town = ClosestTownFromTile(tile, UINT_MAX);
 	ind.random = initial_random_bits;
 	ind.founder = founder;
-	ind.psa = NULL;
+	ind.psa = nullptr;
 
 	IndustriesResolverObject object(tile, &ind, type, seed, CBID_INDUSTRY_LOCATION, 0, creation_type);
 	uint16 result = object.ResolveCallback();
@@ -556,7 +556,7 @@ uint32 GetIndustryProbabilityCallback(In
 	const IndustrySpec *indspec = GetIndustrySpec(type);
 
 	if (HasBit(indspec->callback_mask, CBM_IND_PROBABILITY)) {
-		uint16 res = GetIndustryCallback(CBID_INDUSTRY_PROBABILITY, 0, creation_type, NULL, type, INVALID_TILE);
+		uint16 res = GetIndustryCallback(CBID_INDUSTRY_PROBABILITY, 0, creation_type, nullptr, type, INVALID_TILE);
 		if (res != CALLBACK_FAILED) {
 			if (indspec->grf_prop.grffile->grf_version < 8) {
 				/* Disallow if result != 0 */
@@ -608,7 +608,7 @@ void IndustryProductionCallback(Industry
 
 		SB(object.callback_param2, 8, 16, loop);
 		const SpriteGroup *tgroup = object.Resolve();
-		if (tgroup == NULL || tgroup->type != SGT_INDUSTRY_PRODUCTION) break;
+		if (tgroup == nullptr || tgroup->type != SGT_INDUSTRY_PRODUCTION) break;
 		const IndustryProductionSpriteGroup *group = (const IndustryProductionSpriteGroup *)tgroup;
 
 		if (group->version == 0xFF) {
diff --git a/src/newgrf_industries.h b/src/newgrf_industries.h
--- a/src/newgrf_industries.h
+++ b/src/newgrf_industries.h
@@ -43,7 +43,7 @@ struct IndustriesScopeResolver : public 
 /** Resolver for industries. */
 struct IndustriesResolverObject : public ResolverObject {
 	IndustriesScopeResolver industries_scope; ///< Scope resolver for the industry.
-	TownScopeResolver *town_scope;            ///< Scope resolver for the associated town (if needed and available, else \c NULL).
+	TownScopeResolver *town_scope;            ///< Scope resolver for the associated town (if needed and available, else \c nullptr).
 
 	IndustriesResolverObject(TileIndex tile, Industry *indus, IndustryType type, uint32 random_bits = 0,
 			CallbackID callback = CBID_NO_CALLBACK, uint32 callback_param1 = 0, uint32 callback_param2 = 0);
@@ -57,7 +57,7 @@ struct IndustriesResolverObject : public
 			case VSG_SCOPE_SELF: return &industries_scope;
 			case VSG_SCOPE_PARENT: {
 				TownScopeResolver *tsr = this->GetTown();
-				if (tsr != NULL) return tsr;
+				if (tsr != nullptr) return tsr;
 			}
 			FALLTHROUGH;
 
diff --git a/src/newgrf_industrytiles.cpp b/src/newgrf_industrytiles.cpp
--- a/src/newgrf_industrytiles.cpp
+++ b/src/newgrf_industrytiles.cpp
@@ -80,7 +80,7 @@ uint32 GetRelativePosition(TileIndex til
 
 		/* Land info of nearby tiles */
 		case 0x60: return GetNearbyIndustryTileInformation(parameter, this->tile,
-				this->industry == NULL ? (IndustryID)INVALID_INDUSTRY : this->industry->index, true, this->ro.grffile->grf_version >= 8);
+				this->industry == nullptr ? (IndustryID)INVALID_INDUSTRY : this->industry->index, true, this->ro.grffile->grf_version >= 8);
 
 		/* Animation stage of nearby tiles */
 		case 0x61: {
@@ -103,7 +103,7 @@ uint32 GetRelativePosition(TileIndex til
 
 /* virtual */ uint32 IndustryTileScopeResolver::GetRandomBits() const
 {
-	assert(this->industry != NULL && IsValidTile(this->tile));
+	assert(this->industry != nullptr && IsValidTile(this->tile));
 	assert(this->industry->index == INVALID_INDUSTRY || IsTileType(this->tile, MP_INDUSTRY));
 
 	return (this->industry->index != INVALID_INDUSTRY) ? GetIndustryRandomBits(this->tile) : 0;
@@ -111,7 +111,7 @@ uint32 GetRelativePosition(TileIndex til
 
 /* virtual */ uint32 IndustryTileScopeResolver::GetTriggers() const
 {
-	assert(this->industry != NULL && IsValidTile(this->tile));
+	assert(this->industry != nullptr && IsValidTile(this->tile));
 	assert(this->industry->index == INVALID_INDUSTRY || IsTileType(this->tile, MP_INDUSTRY));
 	if (this->industry->index == INVALID_INDUSTRY) return 0;
 	return GetIndustryTriggers(this->tile);
@@ -125,7 +125,7 @@ uint32 GetRelativePosition(TileIndex til
 static const GRFFile *GetIndTileGrffile(IndustryGfx gfx)
 {
 	const IndustryTileSpec *its = GetIndustryTileSpec(gfx);
-	return (its != NULL) ? its->grf_prop.grffile : NULL;
+	return (its != nullptr) ? its->grf_prop.grffile : nullptr;
 }
 
 /**
@@ -171,7 +171,7 @@ static void IndustryDrawTileLayout(const
 
 uint16 GetIndustryTileCallback(CallbackID callback, uint32 param1, uint32 param2, IndustryGfx gfx_id, Industry *industry, TileIndex tile)
 {
-	assert(industry != NULL && IsValidTile(tile));
+	assert(industry != nullptr && IsValidTile(tile));
 	assert(industry->index == INVALID_INDUSTRY || IsTileType(tile, MP_INDUSTRY));
 
 	IndustryTileResolverObject object(gfx_id, tile, industry, callback, param1, param2);
@@ -194,7 +194,7 @@ bool DrawNewIndustryTile(TileInfo *ti, I
 	IndustryTileResolverObject object(gfx, ti->tile, i);
 
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL || group->type != SGT_TILELAYOUT) return false;
+	if (group == nullptr || group->type != SGT_TILELAYOUT) return false;
 
 	/* Limit the building stage to the number of stages supplied. */
 	const TileLayoutSpriteGroup *tlgroup = (const TileLayoutSpriteGroup *)group;
@@ -259,7 +259,7 @@ struct IndustryAnimationBase : public An
 void AnimateNewIndustryTile(TileIndex tile)
 {
 	const IndustryTileSpec *itspec = GetIndustryTileSpec(GetIndustryGfx(tile));
-	if (itspec == NULL) return;
+	if (itspec == nullptr) return;
 
 	IndustryAnimationBase::AnimateTile(itspec, Industry::GetByTile(tile), tile, (itspec->special_flags & INDTILE_SPECIAL_NEXTFRAME_RANDOMBITS) != 0);
 }
@@ -305,14 +305,14 @@ static void DoTriggerIndustryTile(TileIn
 	IndustryGfx gfx = GetIndustryGfx(tile);
 	const IndustryTileSpec *itspec = GetIndustryTileSpec(gfx);
 
-	if (itspec->grf_prop.spritegroup[0] == NULL) return;
+	if (itspec->grf_prop.spritegroup[0] == nullptr) return;
 
 	IndustryTileResolverObject object(gfx, tile, ind, CBID_RANDOM_TRIGGER);
 	object.waiting_triggers = GetIndustryTriggers(tile) | trigger;
 	SetIndustryTriggers(tile, object.waiting_triggers); // store now for var 5F
 
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL) return;
+	if (group == nullptr) return;
 
 	/* Store remaining triggers. */
 	SetIndustryTriggers(tile, object.GetRemainingTriggers());
@@ -335,7 +335,7 @@ static void DoTriggerIndustryTile(TileIn
  */
 static void DoReseedIndustry(Industry *ind, uint32 reseed)
 {
-	if (reseed == 0 || ind == NULL) return;
+	if (reseed == 0 || ind == nullptr) return;
 
 	uint16 random_bits = Random();
 	ind->random &= reseed;
diff --git a/src/newgrf_object.cpp b/src/newgrf_object.cpp
--- a/src/newgrf_object.cpp
+++ b/src/newgrf_object.cpp
@@ -151,7 +151,7 @@ static uint32 GetObjectIDAtOffset(TileIn
 	const ObjectSpec *spec = ObjectSpec::Get(o->type);
 
 	/* Default objects have no associated NewGRF file */
-	if (spec->grf_prop.grffile == NULL) {
+	if (spec->grf_prop.grffile == nullptr) {
 		return 0xFFFE; // Defined in another grf file
 	}
 
@@ -237,9 +237,9 @@ static uint32 GetCountAndDistanceOfClose
 {
 	/* We get the town from the object, or we calculate the closest
 	 * town if we need to when there's no object. */
-	const Town *t = NULL;
+	const Town *t = nullptr;
 
-	if (this->obj == NULL) {
+	if (this->obj == nullptr) {
 		switch (variable) {
 			/* Allow these when there's no object. */
 			case 0x41:
@@ -325,7 +325,7 @@ static uint32 GetCountAndDistanceOfClose
 		}
 
 		/* Land info of nearby tiles */
-		case 0x62: return GetNearbyObjectTileInformation(parameter, this->tile, this->obj == NULL ? INVALID_OBJECT : this->obj->index, this->ro.grffile->grf_version >= 8);
+		case 0x62: return GetNearbyObjectTileInformation(parameter, this->tile, this->obj == nullptr ? INVALID_OBJECT : this->obj->index, this->ro.grffile->grf_version >= 8);
 
 		/* Animation counter of nearby tile */
 		case 0x63: {
@@ -357,8 +357,8 @@ ObjectResolverObject::ObjectResolverObje
 		CallbackID callback, uint32 param1, uint32 param2)
 	: ResolverObject(spec->grf_prop.grffile, callback, param1, param2), object_scope(*this, obj, tile, view)
 {
-	this->town_scope = NULL;
-	this->root_spritegroup = (obj == NULL && spec->grf_prop.spritegroup[CT_PURCHASE_OBJECT] != NULL) ?
+	this->town_scope = nullptr;
+	this->root_spritegroup = (obj == nullptr && spec->grf_prop.spritegroup[CT_PURCHASE_OBJECT] != nullptr) ?
 			spec->grf_prop.spritegroup[CT_PURCHASE_OBJECT] : spec->grf_prop.spritegroup[0];
 }
 
@@ -374,15 +374,15 @@ ObjectResolverObject::~ObjectResolverObj
  */
 TownScopeResolver *ObjectResolverObject::GetTown()
 {
-	if (this->town_scope == NULL) {
+	if (this->town_scope == nullptr) {
 		Town *t;
-		if (this->object_scope.obj != NULL) {
+		if (this->object_scope.obj != nullptr) {
 			t = this->object_scope.obj->town;
 		} else {
 			t = ClosestTownFromTile(this->object_scope.tile, UINT_MAX);
 		}
-		if (t == NULL) return NULL;
-		this->town_scope = new TownScopeResolver(*this, t, this->object_scope.obj == NULL);
+		if (t == nullptr) return nullptr;
+		this->town_scope = new TownScopeResolver(*this, t, this->object_scope.obj == nullptr);
 	}
 	return this->town_scope;
 }
@@ -395,7 +395,7 @@ TownScopeResolver *ObjectResolverObject:
  * @param spec     The specification of the object / the entry point.
  * @param o        The object to call the callback for.
  * @param tile     The tile the callback is called for.
- * @param view     The view of the object (only used when o == NULL).
+ * @param view     The view of the object (only used when o == nullptr).
  * @return The result of the callback.
  */
 uint16 GetObjectCallback(CallbackID callback, uint32 param1, uint32 param2, const ObjectSpec *spec, Object *o, TileIndex tile, uint8 view)
@@ -412,7 +412,7 @@ uint16 GetObjectCallback(CallbackID call
  */
 static void DrawTileLayout(const TileInfo *ti, const TileLayoutSpriteGroup *group, const ObjectSpec *spec)
 {
-	const DrawTileSprites *dts = group->ProcessRegisters(NULL);
+	const DrawTileSprites *dts = group->ProcessRegisters(nullptr);
 	PaletteID palette = ((spec->flags & OBJECT_FLAG_2CC_COLOUR) ? SPR_2CCMAP_BASE : PALETTE_RECOLOUR_START) + Object::GetByTile(ti->tile)->colour;
 
 	SpriteID image = dts->ground.sprite;
@@ -442,7 +442,7 @@ void DrawNewObjectTile(TileInfo *ti, con
 	ObjectResolverObject object(spec, o, ti->tile);
 
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL || group->type != SGT_TILELAYOUT) return;
+	if (group == nullptr || group->type != SGT_TILELAYOUT) return;
 
 	DrawTileLayout(ti, (const TileLayoutSpriteGroup *)group, spec);
 }
@@ -456,11 +456,11 @@ void DrawNewObjectTile(TileInfo *ti, con
  */
 void DrawNewObjectTileInGUI(int x, int y, const ObjectSpec *spec, uint8 view)
 {
-	ObjectResolverObject object(spec, NULL, INVALID_TILE, view);
+	ObjectResolverObject object(spec, nullptr, INVALID_TILE, view);
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL || group->type != SGT_TILELAYOUT) return;
+	if (group == nullptr || group->type != SGT_TILELAYOUT) return;
 
-	const DrawTileSprites *dts = ((const TileLayoutSpriteGroup *)group)->ProcessRegisters(NULL);
+	const DrawTileSprites *dts = ((const TileLayoutSpriteGroup *)group)->ProcessRegisters(nullptr);
 
 	PaletteID palette;
 	if (Company::IsValidID(_local_company)) {
@@ -518,7 +518,7 @@ struct ObjectAnimationBase : public Anim
 void AnimateNewObjectTile(TileIndex tile)
 {
 	const ObjectSpec *spec = ObjectSpec::GetByTile(tile);
-	if (spec == NULL || !(spec->flags & OBJECT_FLAG_ANIMATION)) return;
+	if (spec == nullptr || !(spec->flags & OBJECT_FLAG_ANIMATION)) return;
 
 	ObjectAnimationBase::AnimateTile(spec, Object::GetByTile(tile), tile, (spec->flags & OBJECT_FLAG_ANIM_RANDOM_BITS) != 0);
 }
diff --git a/src/newgrf_object.h b/src/newgrf_object.h
--- a/src/newgrf_object.h
+++ b/src/newgrf_object.h
@@ -137,7 +137,7 @@ struct ObjectResolverObject : public Res
 
 			case VSG_SCOPE_PARENT: {
 				TownScopeResolver *tsr = this->GetTown();
-				if (tsr != NULL) return tsr;
+				if (tsr != nullptr) return tsr;
 				FALLTHROUGH;
 			}
 
diff --git a/src/newgrf_railtype.cpp b/src/newgrf_railtype.cpp
--- a/src/newgrf_railtype.cpp
+++ b/src/newgrf_railtype.cpp
@@ -44,13 +44,13 @@
 			if (IsRailDepotTile(this->tile)) return Depot::GetByTile(this->tile)->build_date;
 			return _date;
 		case 0x44: {
-			const Town *t = NULL;
+			const Town *t = nullptr;
 			if (IsRailDepotTile(this->tile)) {
 				t = Depot::GetByTile(this->tile)->town;
 			} else if (IsLevelCrossingTile(this->tile)) {
 				t = ClosestTownFromTile(this->tile, UINT_MAX);
 			}
-			return t != NULL ? GetTownRadiusGroup(t, this->tile) : HZB_TOWN_EDGE;
+			return t != nullptr ? GetTownRadiusGroup(t, this->tile) : HZB_TOWN_EDGE;
 		}
 	}
 
@@ -64,12 +64,12 @@
 {
 	if (group->num_loading > 0) return group->loading[0];
 	if (group->num_loaded  > 0) return group->loaded[0];
-	return NULL;
+	return nullptr;
 }
 
 /**
  * Resolver object for rail types.
- * @param rti Railtype. NULL in NewGRF Inspect window.
+ * @param rti Railtype. nullptr in NewGRF Inspect window.
  * @param tile %Tile containing the track. For track on a bridge this is the southern bridgehead.
  * @param context Are we resolving sprites for the upper halftile, or on a bridge?
  * @param rtsg Railpart of interest
@@ -77,9 +77,9 @@
  * @param param2 Extra parameter (second parameter of the callback, except railtypes do not have callbacks).
  */
 RailTypeResolverObject::RailTypeResolverObject(const RailtypeInfo *rti, TileIndex tile, TileContext context, RailTypeSpriteGroup rtsg, uint32 param1, uint32 param2)
-	: ResolverObject(rti != NULL ? rti->grffile[rtsg] : NULL, CBID_NO_CALLBACK, param1, param2), railtype_scope(*this, tile, context)
+	: ResolverObject(rti != nullptr ? rti->grffile[rtsg] : nullptr, CBID_NO_CALLBACK, param1, param2), railtype_scope(*this, tile, context)
 {
-	this->root_spritegroup = rti != NULL ? rti->group[rtsg] : NULL;
+	this->root_spritegroup = rti != nullptr ? rti->group[rtsg] : nullptr;
 }
 
 /**
@@ -88,18 +88,18 @@ RailTypeResolverObject::RailTypeResolver
  * @param tile The tile to get the sprite for.
  * @param rtsg The type of sprite to draw.
  * @param context Where are we drawing the tile?
- * @param[out] num_results If not NULL, return the number of sprites in the spriteset.
+ * @param[out] num_results If not nullptr, return the number of sprites in the spriteset.
  * @return The sprite to draw.
  */
 SpriteID GetCustomRailSprite(const RailtypeInfo *rti, TileIndex tile, RailTypeSpriteGroup rtsg, TileContext context, uint *num_results)
 {
 	assert(rtsg < RTSG_END);
 
-	if (rti->group[rtsg] == NULL) return 0;
+	if (rti->group[rtsg] == nullptr) return 0;
 
 	RailTypeResolverObject object(rti, tile, context, rtsg);
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL || group->GetNumResults() == 0) return 0;
+	if (group == nullptr || group->GetNumResults() == 0) return 0;
 
 	if (num_results) *num_results = group->GetNumResults();
 
@@ -118,14 +118,14 @@ SpriteID GetCustomRailSprite(const Railt
  */
 SpriteID GetCustomSignalSprite(const RailtypeInfo *rti, TileIndex tile, SignalType type, SignalVariant var, SignalState state, bool gui)
 {
-	if (rti->group[RTSG_SIGNALS] == NULL) return 0;
+	if (rti->group[RTSG_SIGNALS] == nullptr) return 0;
 
 	uint32 param1 = gui ? 0x10 : 0x00;
 	uint32 param2 = (type << 16) | (var << 8) | state;
 	RailTypeResolverObject object(rti, tile, TCX_NORMAL, RTSG_SIGNALS, param1, param2);
 
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL || group->GetNumResults() == 0) return 0;
+	if (group == nullptr || group->GetNumResults() == 0) return 0;
 
 	return group->GetResult();
 }
@@ -139,7 +139,7 @@ SpriteID GetCustomSignalSprite(const Rai
 uint8 GetReverseRailTypeTranslation(RailType railtype, const GRFFile *grffile)
 {
 	/* No rail type table present, return rail type as-is */
-	if (grffile == NULL || grffile->railtype_list.size() == 0) return railtype;
+	if (grffile == nullptr || grffile->railtype_list.size() == 0) return railtype;
 
 	/* Look for a matching rail type label in the table */
 	RailTypeLabel label = GetRailTypeInfo(railtype)->label;
diff --git a/src/newgrf_railtype.h b/src/newgrf_railtype.h
--- a/src/newgrf_railtype.h
+++ b/src/newgrf_railtype.h
@@ -53,7 +53,7 @@ struct RailTypeResolverObject : public R
 	const SpriteGroup *ResolveReal(const RealSpriteGroup *group) const override;
 };
 
-SpriteID GetCustomRailSprite(const RailtypeInfo *rti, TileIndex tile, RailTypeSpriteGroup rtsg, TileContext context = TCX_NORMAL, uint *num_results = NULL);
+SpriteID GetCustomRailSprite(const RailtypeInfo *rti, TileIndex tile, RailTypeSpriteGroup rtsg, TileContext context = TCX_NORMAL, uint *num_results = nullptr);
 SpriteID GetCustomSignalSprite(const RailtypeInfo *rti, TileIndex tile, SignalType type, SignalVariant var, SignalState state, bool gui = false);
 
 uint8 GetReverseRailTypeTranslation(RailType railtype, const GRFFile *grffile);
diff --git a/src/newgrf_sound.cpp b/src/newgrf_sound.cpp
--- a/src/newgrf_sound.cpp
+++ b/src/newgrf_sound.cpp
@@ -49,7 +49,7 @@ void InitializeSoundPool()
 
 SoundEntry *GetSound(SoundID index)
 {
-	if (index >= _sounds.size()) return NULL;
+	if (index >= _sounds.size()) return nullptr;
 	return &_sounds[index];
 }
 
@@ -173,7 +173,7 @@ SoundID GetNewGRFSoundID(const GRFFile *
 	if (sound_id < ORIGINAL_SAMPLE_COUNT) return sound_id;
 
 	sound_id -= ORIGINAL_SAMPLE_COUNT;
-	if (file == NULL || sound_id >= file->num_sounds) return INVALID_SOUND;
+	if (file == nullptr || sound_id >= file->num_sounds) return INVALID_SOUND;
 
 	return file->sound_offset  + sound_id;
 }
@@ -192,7 +192,7 @@ bool PlayVehicleSound(const Vehicle *v, 
 	uint16 callback;
 
 	/* If the engine has no GRF ID associated it can't ever play any new sounds */
-	if (file == NULL) return false;
+	if (file == nullptr) return false;
 
 	/* Check that the vehicle type uses the sound effect callback */
 	if (!HasBit(EngInfo(v->engine_type)->callback_mask, CBM_VEHICLE_SOUND_EFFECT)) return false;
diff --git a/src/newgrf_spritegroup.cpp b/src/newgrf_spritegroup.cpp
--- a/src/newgrf_spritegroup.cpp
+++ b/src/newgrf_spritegroup.cpp
@@ -26,7 +26,7 @@ TemporaryStorageArray<int32, 0x110> _tem
 /**
  * ResolverObject (re)entry point.
  * This cannot be made a call to a virtual function because virtual functions
- * do not like NULL and checking for NULL *everywhere* is more cumbersome than
+ * do not like nullptr and checking for nullptr *everywhere* is more cumbersome than
  * this little helper function.
  * @param group the group to resolve for
  * @param object information needed to resolve the group
@@ -35,7 +35,7 @@ TemporaryStorageArray<int32, 0x110> _tem
  */
 /* static */ const SpriteGroup *SpriteGroup::Resolve(const SpriteGroup *group, ResolverObject &object, bool top_level)
 {
-	if (group == NULL) return NULL;
+	if (group == nullptr) return nullptr;
 	if (top_level) {
 		_temp_store.ClearChanges();
 	}
@@ -73,7 +73,7 @@ static inline uint32 GetVariable(const R
 		case 0x7D: return _temp_store.GetValue(parameter);
 
 		case 0x7F:
-			if (object.grffile == NULL) return 0;
+			if (object.grffile == nullptr) return 0;
 			return object.grffile->GetParam(parameter);
 
 		default:
@@ -130,7 +130,7 @@ static inline uint32 GetVariable(const R
  */
 /* virtual */ const SpriteGroup *ResolverObject::ResolveReal(const RealSpriteGroup *group) const
 {
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -207,7 +207,7 @@ const SpriteGroup *DeterministicSpriteGr
 		bool available = true;
 		if (adjust->variable == 0x7E) {
 			const SpriteGroup *subgroup = SpriteGroup::Resolve(adjust->subroutine, object, false);
-			if (subgroup == NULL) {
+			if (subgroup == nullptr) {
 				value = CALLBACK_FAILED;
 			} else {
 				value = subgroup->GetCallbackResult();
@@ -293,24 +293,24 @@ const SpriteGroup *RealSpriteGroup::Reso
  * Process registers and the construction stage into the sprite layout.
  * The passed construction stage might get reset to zero, if it gets incorporated into the layout
  * during the preprocessing.
- * @param[in,out] stage Construction stage (0-3), or NULL if not applicable.
+ * @param[in,out] stage Construction stage (0-3), or nullptr if not applicable.
  * @return sprite layout to draw.
  */
 const DrawTileSprites *TileLayoutSpriteGroup::ProcessRegisters(uint8 *stage) const
 {
 	if (!this->dts.NeedsPreprocessing()) {
-		if (stage != NULL && this->dts.consistent_max_offset > 0) *stage = GetConstructionStageOffset(*stage, this->dts.consistent_max_offset);
+		if (stage != nullptr && this->dts.consistent_max_offset > 0) *stage = GetConstructionStageOffset(*stage, this->dts.consistent_max_offset);
 		return &this->dts;
 	}
 
 	static DrawTileSprites result;
-	uint8 actual_stage = stage != NULL ? *stage : 0;
+	uint8 actual_stage = stage != nullptr ? *stage : 0;
 	this->dts.PrepareLayout(0, 0, 0, actual_stage, false);
 	this->dts.ProcessRegisters(0, 0, false);
 	result.seq = this->dts.GetLayout(&result.ground);
 
 	/* Stage has been processed by PrepareLayout(), set it to zero. */
-	if (stage != NULL) *stage = 0;
+	if (stage != nullptr) *stage = 0;
 
 	return &result;
 }
diff --git a/src/newgrf_spritegroup.h b/src/newgrf_spritegroup.h
--- a/src/newgrf_spritegroup.h
+++ b/src/newgrf_spritegroup.h
@@ -316,13 +316,13 @@ struct ScopeResolver {
 struct ResolverObject {
 	/**
 	 * Resolver constructor.
-	 * @param grffile NewGRF file associated with the object (or \c NULL if none).
+	 * @param grffile NewGRF file associated with the object (or \c nullptr if none).
 	 * @param callback Callback code being resolved (default value is #CBID_NO_CALLBACK).
 	 * @param callback_param1 First parameter (var 10) of the callback (only used when \a callback is also set).
 	 * @param callback_param2 Second parameter (var 18) of the callback (only used when \a callback is also set).
 	 */
 	ResolverObject(const GRFFile *grffile, CallbackID callback = CBID_NO_CALLBACK, uint32 callback_param1 = 0, uint32 callback_param2 = 0)
-		: default_scope(*this), callback(callback), callback_param1(callback_param1), callback_param2(callback_param2), grffile(grffile), root_spritegroup(NULL)
+		: default_scope(*this), callback(callback), callback_param1(callback_param1), callback_param2(callback_param2), grffile(grffile), root_spritegroup(nullptr)
 	{
 		this->ResetState();
 	}
@@ -360,7 +360,7 @@ struct ResolverObject {
 	uint16 ResolveCallback()
 	{
 		const SpriteGroup *result = Resolve();
-		return result != NULL ? result->GetCallbackResult() : CALLBACK_FAILED;
+		return result != nullptr ? result->GetCallbackResult() : CALLBACK_FAILED;
 	}
 
 	virtual const SpriteGroup *ResolveReal(const RealSpriteGroup *group) const;
diff --git a/src/newgrf_station.cpp b/src/newgrf_station.cpp
--- a/src/newgrf_station.cpp
+++ b/src/newgrf_station.cpp
@@ -35,11 +35,11 @@ template <typename Tspec, typename Tid, 
 	/* Set up initial data */
 	classes[0].global_id = 'DFLT';
 	classes[0].name = STR_STATION_CLASS_DFLT;
-	classes[0].Insert(NULL);
+	classes[0].Insert(nullptr);
 
 	classes[1].global_id = 'WAYP';
 	classes[1].name = STR_STATION_CLASS_WAYP;
-	classes[1].Insert(NULL);
+	classes[1].Insert(nullptr);
 }
 
 template <typename Tspec, typename Tid, Tid Tmax>
@@ -225,13 +225,13 @@ static uint32 GetRailContinuationInfo(Ti
 /* Station Resolver Functions */
 /* virtual */ uint32 StationScopeResolver::GetRandomBits() const
 {
-	return (this->st == NULL ? 0 : this->st->random_bits) | (this->tile == INVALID_TILE ? 0 : GetStationTileRandomBits(this->tile) << 16);
+	return (this->st == nullptr ? 0 : this->st->random_bits) | (this->tile == INVALID_TILE ? 0 : GetStationTileRandomBits(this->tile) << 16);
 }
 
 
 /* virtual */ uint32 StationScopeResolver::GetTriggers() const
 {
-	return this->st == NULL ? 0 : this->st->waiting_triggers;
+	return this->st == nullptr ? 0 : this->st->waiting_triggers;
 }
 
 
@@ -257,22 +257,22 @@ static struct {
  */
 TownScopeResolver *StationResolverObject::GetTown()
 {
-	if (this->town_scope == NULL) {
-		Town *t = NULL;
-		if (this->station_scope.st != NULL) {
+	if (this->town_scope == nullptr) {
+		Town *t = nullptr;
+		if (this->station_scope.st != nullptr) {
 			t = this->station_scope.st->town;
 		} else if (this->station_scope.tile != INVALID_TILE) {
 			t = ClosestTownFromTile(this->station_scope.tile, UINT_MAX);
 		}
-		if (t == NULL) return NULL;
-		this->town_scope = new TownScopeResolver(*this, t, this->station_scope.st == NULL);
+		if (t == nullptr) return nullptr;
+		this->town_scope = new TownScopeResolver(*this, t, this->station_scope.st == nullptr);
 	}
 	return this->town_scope;
 }
 
 /* virtual */ uint32 StationScopeResolver::GetVariable(byte variable, uint32 parameter, bool *available) const
 {
-	if (this->st == NULL) {
+	if (this->st == nullptr) {
 		/* Station does not exist, so we're in a purchase list or the land slope check callback. */
 		switch (variable) {
 			case 0x40:
@@ -396,8 +396,8 @@ uint32 Station::GetNewGRFVariable(const 
 
 		case 0x8A: return this->had_vehicle_of_type;
 		case 0xF1: return (this->airport.tile != INVALID_TILE) ? this->airport.GetSpec()->ttd_airport_type : ATP_TTDP_LARGE;
-		case 0xF2: return (this->truck_stops != NULL) ? this->truck_stops->status : 0;
-		case 0xF3: return (this->bus_stops != NULL)   ? this->bus_stops->status   : 0;
+		case 0xF2: return (this->truck_stops != nullptr) ? this->truck_stops->status : 0;
+		case 0xF3: return (this->bus_stops != nullptr)   ? this->bus_stops->status   : 0;
 		case 0xF6: return this->airport.flags;
 		case 0xF7: return GB(this->airport.flags, 8, 8);
 	}
@@ -486,7 +486,7 @@ uint32 Waypoint::GetNewGRFVariable(const
 
 /* virtual */ const SpriteGroup *StationResolverObject::ResolveReal(const RealSpriteGroup *group) const
 {
-	if (this->station_scope.st == NULL || this->station_scope.statspec->cls_id == STAT_CLASS_WAYP) {
+	if (this->station_scope.st == nullptr || this->station_scope.statspec->cls_id == STAT_CLASS_WAYP) {
 		return group->loading[0];
 	}
 
@@ -541,14 +541,14 @@ uint32 Waypoint::GetNewGRFVariable(const
 StationResolverObject::StationResolverObject(const StationSpec *statspec, BaseStation *st, TileIndex tile,
 		CallbackID callback, uint32 callback_param1, uint32 callback_param2)
 	: ResolverObject(statspec->grf_prop.grffile, callback, callback_param1, callback_param2),
-	station_scope(*this, statspec, st, tile), town_scope(NULL)
+	station_scope(*this, statspec, st, tile), town_scope(nullptr)
 {
 	/* Invalidate all cached vars */
 	_svc.valid = 0;
 
 	CargoID ctype = CT_DEFAULT_NA;
 
-	if (this->station_scope.st == NULL) {
+	if (this->station_scope.st == nullptr) {
 		/* No station, so we are in a purchase list */
 		ctype = CT_PURCHASE;
 	} else if (Station::IsExpected(this->station_scope.st)) {
@@ -556,7 +556,7 @@ StationResolverObject::StationResolverOb
 		/* Pick the first cargo that we have waiting */
 		const CargoSpec *cs;
 		FOR_ALL_CARGOSPECS(cs) {
-			if (this->station_scope.statspec->grf_prop.spritegroup[cs->Index()] != NULL &&
+			if (this->station_scope.statspec->grf_prop.spritegroup[cs->Index()] != nullptr &&
 					st->goods[cs->Index()].cargo.TotalCount() > 0) {
 				ctype = cs->Index();
 				break;
@@ -564,7 +564,7 @@ StationResolverObject::StationResolverOb
 		}
 	}
 
-	if (this->station_scope.statspec->grf_prop.spritegroup[ctype] == NULL) {
+	if (this->station_scope.statspec->grf_prop.spritegroup[ctype] == nullptr) {
 		ctype = CT_DEFAULT;
 	}
 
@@ -581,7 +581,7 @@ StationResolverObject::~StationResolverO
 /**
  * Resolve sprites for drawing a station tile.
  * @param statspec Station spec
- * @param st Station (NULL in GUI)
+ * @param st Station (nullptr in GUI)
  * @param tile Station tile being drawn (INVALID_TILE in GUI)
  * @param var10 Value to put in variable 10; normally 0; 1 when resolving the groundsprite and SSF_SEPARATE_GROUND is set.
  * @return First sprite of the Action 1 spriteset to use, minus an offset of 0x42D to accommodate for weird NewGRF specs.
@@ -590,7 +590,7 @@ SpriteID GetCustomStationRelocation(cons
 {
 	StationResolverObject object(statspec, st, tile, CBID_NO_CALLBACK, var10);
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL || group->type != SGT_RESULT) return 0;
+	if (group == nullptr || group->type != SGT_RESULT) return 0;
 	return group->GetResult() - 0x42D;
 }
 
@@ -609,7 +609,7 @@ SpriteID GetCustomStationFoundationReloc
 	StationResolverObject object(statspec, st, tile, CBID_NO_CALLBACK, 2, layout | (edge_info << 16));
 
 	const SpriteGroup *group = object.Resolve();
-	if (group == NULL || group->type != SGT_RESULT) return 0;
+	if (group == nullptr || group->type != SGT_RESULT) return 0;
 
 	/* Note: SpriteGroup::Resolve zeroes all registers, so register 0x100 is initialised to 0. (compatibility) */
 	return group->GetResult() + GetRegister(0x100);
@@ -637,7 +637,7 @@ CommandCost PerformStationTileSlopeCheck
 	TileIndexDiff diff = cur_tile - north_tile;
 	Slope slope = GetTileSlope(cur_tile);
 
-	StationResolverObject object(statspec, NULL, cur_tile, CBID_STATION_LAND_SLOPE_CHECK,
+	StationResolverObject object(statspec, nullptr, cur_tile, CBID_STATION_LAND_SLOPE_CHECK,
 			(slope << 4) | (slope ^ (axis == AXIS_Y && HasBit(slope, CORNER_W) != HasBit(slope, CORNER_E) ? SLOPE_EW : 0)),
 			(numtracks << 24) | (plat_len << 16) | (axis == AXIS_Y ? TileX(diff) << 8 | TileY(diff) : TileY(diff) << 8 | TileX(diff)));
 	object.station_scope.axis = axis;
@@ -664,10 +664,10 @@ int AllocateSpecToStation(const StationS
 {
 	uint i;
 
-	if (statspec == NULL || st == NULL) return 0;
+	if (statspec == nullptr || st == nullptr) return 0;
 
 	for (i = 1; i < st->num_specs && i < NUM_STATIONSSPECS_PER_STATION; i++) {
-		if (st->speclist[i].spec == NULL && st->speclist[i].grfid == 0) break;
+		if (st->speclist[i].spec == nullptr && st->speclist[i].grfid == 0) break;
 	}
 
 	if (i == NUM_STATIONSSPECS_PER_STATION) {
@@ -690,7 +690,7 @@ int AllocateSpecToStation(const StationS
 
 			if (st->num_specs == 2) {
 				/* Initial allocation */
-				st->speclist[0].spec     = NULL;
+				st->speclist[0].spec     = nullptr;
 				st->speclist[0].grfid    = 0;
 				st->speclist[0].localidx = 0;
 			}
@@ -727,7 +727,7 @@ void DeallocateSpecFromStation(BaseStati
 	}
 
 	/* This specindex is no longer in use, so deallocate it */
-	st->speclist[specindex].spec     = NULL;
+	st->speclist[specindex].spec     = nullptr;
 	st->speclist[specindex].grfid    = 0;
 	st->speclist[specindex].localidx = 0;
 
@@ -740,7 +740,7 @@ void DeallocateSpecFromStation(BaseStati
 		} else {
 			free(st->speclist);
 			st->num_specs = 0;
-			st->speclist  = NULL;
+			st->speclist  = nullptr;
 			st->cached_anim_triggers = 0;
 			st->cached_cargo_triggers = 0;
 			return;
@@ -762,42 +762,42 @@ void DeallocateSpecFromStation(BaseStati
  */
 bool DrawStationTile(int x, int y, RailType railtype, Axis axis, StationClassID sclass, uint station)
 {
-	const DrawTileSprites *sprites = NULL;
+	const DrawTileSprites *sprites = nullptr;
 	const RailtypeInfo *rti = GetRailTypeInfo(railtype);
 	PaletteID palette = COMPANY_SPRITE_COLOUR(_local_company);
 	uint tile = 2;
 
 	const StationSpec *statspec = StationClass::Get(sclass)->GetSpec(station);
-	if (statspec == NULL) return false;
+	if (statspec == nullptr) return false;
 
 	if (HasBit(statspec->callback_mask, CBM_STATION_SPRITE_LAYOUT)) {
-		uint16 callback = GetStationCallback(CBID_STATION_SPRITE_LAYOUT, 0x2110000, 0, statspec, NULL, INVALID_TILE);
+		uint16 callback = GetStationCallback(CBID_STATION_SPRITE_LAYOUT, 0x2110000, 0, statspec, nullptr, INVALID_TILE);
 		if (callback != CALLBACK_FAILED) tile = callback;
 	}
 
 	uint32 total_offset = rti->GetRailtypeSpriteOffset();
 	uint32 relocation = 0;
 	uint32 ground_relocation = 0;
-	const NewGRFSpriteLayout *layout = NULL;
+	const NewGRFSpriteLayout *layout = nullptr;
 	DrawTileSprites tmp_rail_layout;
 
-	if (statspec->renderdata == NULL) {
+	if (statspec->renderdata == nullptr) {
 		sprites = GetStationTileLayout(STATION_RAIL, tile + axis);
 	} else {
 		layout = &statspec->renderdata[(tile < statspec->tiles) ? tile + axis : (uint)axis];
 		if (!layout->NeedsPreprocessing()) {
 			sprites = layout;
-			layout = NULL;
+			layout = nullptr;
 		}
 	}
 
-	if (layout != NULL) {
+	if (layout != nullptr) {
 		/* Sprite layout which needs preprocessing */
 		bool separate_ground = HasBit(statspec->flags, SSF_SEPARATE_GROUND);
 		uint32 var10_values = layout->PrepareLayout(total_offset, rti->fallback_railtype, 0, 0, separate_ground);
 		uint8 var10;
 		FOR_EACH_SET_BIT(var10, var10_values) {
-			uint32 var10_relocation = GetCustomStationRelocation(statspec, NULL, INVALID_TILE, var10);
+			uint32 var10_relocation = GetCustomStationRelocation(statspec, nullptr, INVALID_TILE, var10);
 			layout->ProcessRegisters(var10, var10_relocation, separate_ground);
 		}
 
@@ -806,9 +806,9 @@ bool DrawStationTile(int x, int y, RailT
 		total_offset = 0;
 	} else {
 		/* Simple sprite layout */
-		ground_relocation = relocation = GetCustomStationRelocation(statspec, NULL, INVALID_TILE, 0);
+		ground_relocation = relocation = GetCustomStationRelocation(statspec, nullptr, INVALID_TILE, 0);
 		if (HasBit(sprites->ground.sprite, SPRITE_MODIFIER_CUSTOM_SPRITE)) {
-			ground_relocation = GetCustomStationRelocation(statspec, NULL, INVALID_TILE, 1);
+			ground_relocation = GetCustomStationRelocation(statspec, nullptr, INVALID_TILE, 1);
 		}
 		ground_relocation += rti->fallback_railtype;
 	}
@@ -816,7 +816,7 @@ bool DrawStationTile(int x, int y, RailT
 	SpriteID image = sprites->ground.sprite;
 	PaletteID pal = sprites->ground.pal;
 	RailTrackOffset overlay_offset;
-	if (rti->UsesOverlay() && SplitGroundSpriteForOverlay(NULL, &image, &overlay_offset)) {
+	if (rti->UsesOverlay() && SplitGroundSpriteForOverlay(nullptr, &image, &overlay_offset)) {
 		SpriteID ground = GetCustomRailSprite(rti, INVALID_TILE, RTSG_GROUND);
 		DrawSprite(image, PAL_NONE, x, y);
 		DrawSprite(ground + overlay_offset, PAL_NONE, x, y);
@@ -834,11 +834,11 @@ bool DrawStationTile(int x, int y, RailT
 
 const StationSpec *GetStationSpec(TileIndex t)
 {
-	if (!IsCustomStationSpecIndex(t)) return NULL;
+	if (!IsCustomStationSpecIndex(t)) return nullptr;
 
 	const BaseStation *st = BaseStation::GetByTile(t);
 	uint specindex = GetCustomStationSpecIndex(t);
-	return specindex < st->num_specs ? st->speclist[specindex].spec : NULL;
+	return specindex < st->num_specs ? st->speclist[specindex].spec : nullptr;
 }
 
 
@@ -852,7 +852,7 @@ bool IsStationTileBlocked(TileIndex tile
 {
 	const StationSpec *statspec = GetStationSpec(tile);
 
-	return statspec != NULL && HasBit(statspec->blocked, GetStationGfx(tile));
+	return statspec != nullptr && HasBit(statspec->blocked, GetStationGfx(tile));
 }
 
 /**
@@ -866,7 +866,7 @@ bool CanStationTileHavePylons(TileIndex 
 	const StationSpec *statspec = GetStationSpec(tile);
 	uint gfx = GetStationGfx(tile);
 	/* Default stations do not draw pylons under roofs (gfx >= 4) */
-	return statspec != NULL ? HasBit(statspec->pylons, gfx) : gfx < 4;
+	return statspec != nullptr ? HasBit(statspec->pylons, gfx) : gfx < 4;
 }
 
 /**
@@ -878,7 +878,7 @@ bool CanStationTileHavePylons(TileIndex 
 bool CanStationTileHaveWires(TileIndex tile)
 {
 	const StationSpec *statspec = GetStationSpec(tile);
-	return statspec == NULL || !HasBit(statspec->wires, GetStationGfx(tile));
+	return statspec == nullptr || !HasBit(statspec->wires, GetStationGfx(tile));
 }
 
 /** Wrapper for animation control, see GetStationCallback. */
@@ -899,7 +899,7 @@ struct StationAnimationBase : public Ani
 void AnimateStationTile(TileIndex tile)
 {
 	const StationSpec *ss = GetStationSpec(tile);
-	if (ss == NULL) return;
+	if (ss == nullptr) return;
 
 	StationAnimationBase::AnimateTile(ss, BaseStation::GetByTile(tile), tile, HasBit(ss->flags, SSF_CB141_RANDOM_BITS));
 }
@@ -912,7 +912,7 @@ void TriggerStationAnimation(BaseStation
 	};
 
 	/* Get Station if it wasn't supplied */
-	if (st == NULL) st = BaseStation::GetByTile(tile);
+	if (st == nullptr) st = BaseStation::GetByTile(tile);
 
 	/* Check the cached animation trigger bitmask to see if we need
 	 * to bother with any further processing. */
@@ -925,7 +925,7 @@ void TriggerStationAnimation(BaseStation
 	TILE_AREA_LOOP(tile, area) {
 		if (st->TileBelongsToRailStation(tile)) {
 			const StationSpec *ss = GetStationSpec(tile);
-			if (ss != NULL && HasBit(ss->animation.triggers, trigger)) {
+			if (ss != nullptr && HasBit(ss->animation.triggers, trigger)) {
 				CargoID cargo;
 				if (cargo_type == CT_INVALID) {
 					cargo = CT_INVALID;
@@ -953,7 +953,7 @@ void TriggerStationRandomisation(Station
 	};
 
 	/* Get Station if it wasn't supplied */
-	if (st == NULL) st = Station::GetByTile(tile);
+	if (st == nullptr) st = Station::GetByTile(tile);
 
 	/* Check the cached cargo trigger bitmask to see if we need
 	 * to bother with any further processing. */
@@ -981,7 +981,7 @@ void TriggerStationRandomisation(Station
 	TILE_AREA_LOOP(tile, area) {
 		if (st->TileBelongsToRailStation(tile)) {
 			const StationSpec *ss = GetStationSpec(tile);
-			if (ss == NULL) continue;
+			if (ss == nullptr) continue;
 
 			/* Cargo taken "will only be triggered if all of those
 			 * cargo types have no more cargo waiting." */
@@ -994,7 +994,7 @@ void TriggerStationRandomisation(Station
 				object.waiting_triggers = st->waiting_triggers;
 
 				const SpriteGroup *group = object.Resolve();
-				if (group == NULL) continue;
+				if (group == nullptr) continue;
 
 				used_triggers |= object.used_triggers;
 
@@ -1036,7 +1036,7 @@ void StationUpdateCachedTriggers(BaseSta
 	 * of this station. */
 	for (uint i = 0; i < st->num_specs; i++) {
 		const StationSpec *ss = st->speclist[i].spec;
-		if (ss != NULL) {
+		if (ss != nullptr) {
 			st->cached_anim_triggers |= ss->animation.triggers;
 			st->cached_cargo_triggers |= ss->cargo_triggers;
 		}
diff --git a/src/newgrf_station.h b/src/newgrf_station.h
--- a/src/newgrf_station.h
+++ b/src/newgrf_station.h
@@ -67,7 +67,7 @@ struct StationResolverObject : public Re
 
 			case VSG_SCOPE_PARENT: {
 				TownScopeResolver *tsr = this->GetTown();
-				if (tsr != NULL) return tsr;
+				if (tsr != nullptr) return tsr;
 				FALLTHROUGH;
 			}
 
diff --git a/src/newgrf_storage.h b/src/newgrf_storage.h
--- a/src/newgrf_storage.h
+++ b/src/newgrf_storage.h
@@ -70,7 +70,7 @@ struct PersistentStorageArray : BasePers
 	TYPE *prev_storage; ///< Memory to store "old" states so we can revert them on the performance of test cases for commands etc.
 
 	/** Simply construct the array */
-	PersistentStorageArray() : prev_storage(NULL)
+	PersistentStorageArray() : prev_storage(nullptr)
 	{
 		memset(this->storage, 0, sizeof(this->storage));
 	}
@@ -105,8 +105,8 @@ struct PersistentStorageArray : BasePers
 
 		/* We do not have made a backup; lets do so */
 		if (AreChangesPersistent()) {
-			assert(this->prev_storage == NULL);
-		} else if (this->prev_storage == NULL) {
+			assert(this->prev_storage == nullptr);
+		} else if (this->prev_storage == nullptr) {
 			this->prev_storage = MallocT<TYPE>(SIZE);
 			memcpy(this->prev_storage, this->storage, sizeof(this->storage));
 
@@ -133,10 +133,10 @@ struct PersistentStorageArray : BasePers
 
 	void ClearChanges()
 	{
-		if (this->prev_storage != NULL) {
+		if (this->prev_storage != nullptr) {
 			memcpy(this->storage, this->prev_storage, sizeof(this->storage));
 			free(this->prev_storage);
-			this->prev_storage = NULL;
+			this->prev_storage = nullptr;
 		}
 	}
 };
diff --git a/src/newgrf_text.cpp b/src/newgrf_text.cpp
--- a/src/newgrf_text.cpp
+++ b/src/newgrf_text.cpp
@@ -115,7 +115,7 @@ private:
 	 * @param text_   The text to store in this GRFText.
 	 * @param len_    The length of the text to store.
 	 */
-	GRFText(byte langid_, const char *text_, size_t len_) : next(NULL), len(len_), langid(langid_)
+	GRFText(byte langid_, const char *text_, size_t len_) : next(nullptr), len(len_), langid(langid_)
 	{
 		/* We need to use memcpy instead of strcpy due to
 		 * the possibility of "choice lists" and therefore
@@ -232,7 +232,7 @@ struct UnmappedChoiceList : ZeroedMemory
 		}
 
 		char *d = old_d;
-		if (lm == NULL) {
+		if (lm == nullptr) {
 			/* In case there is no mapping, just ignore everything but the default.
 			 * A probable cause for this happening is when the language file has
 			 * been removed by the user and as such no mapping could be made. */
@@ -342,7 +342,7 @@ char *TranslateTTDPatchCodes(uint32 grfi
 	size_t len = Utf8Decode(&c, str);
 
 	/* Helper variable for a possible (string) mapping. */
-	UnmappedChoiceList *mapping = NULL;
+	UnmappedChoiceList *mapping = nullptr;
 
 	if (c == NFO_UTF8_IDENTIFIER) {
 		unicode = true;
@@ -461,7 +461,7 @@ char *TranslateTTDPatchCodes(uint32 grfi
 						if (str[0] == '\0') goto string_end;
 						const LanguageMap *lm = LanguageMap::GetLanguageMap(grfid, language_id);
 						int index = *str++;
-						int mapped = lm != NULL ? lm->GetMapping(index, code == 0x0E) : -1;
+						int mapped = lm != nullptr ? lm->GetMapping(index, code == 0x0E) : -1;
 						if (mapped >= 0) {
 							d += Utf8Encode(d, code == 0x0E ? SCC_GENDER_INDEX : SCC_SET_CASE);
 							d += Utf8Encode(d, code == 0x0E ? mapped : mapped + 1);
@@ -472,7 +472,7 @@ char *TranslateTTDPatchCodes(uint32 grfi
 					case 0x10:
 					case 0x11:
 						if (str[0] == '\0') goto string_end;
-						if (mapping == NULL) {
+						if (mapping == nullptr) {
 							if (code == 0x10) str++; // Skip the index
 							grfmsg(1, "choice list %s marker found when not expected", code == 0x10 ? "next" : "default");
 							break;
@@ -490,7 +490,7 @@ char *TranslateTTDPatchCodes(uint32 grfi
 						break;
 
 					case 0x12:
-						if (mapping == NULL) {
+						if (mapping == nullptr) {
 							grfmsg(1, "choice list end marker found when not expected");
 						} else {
 							/* Terminate the previous string. */
@@ -499,7 +499,7 @@ char *TranslateTTDPatchCodes(uint32 grfi
 							/* Now we can start flushing everything and clean everything up. */
 							d = mapping->Flush(LanguageMap::GetLanguageMap(grfid, language_id));
 							delete mapping;
-							mapping = NULL;
+							mapping = nullptr;
 						}
 						break;
 
@@ -507,7 +507,7 @@ char *TranslateTTDPatchCodes(uint32 grfi
 					case 0x14:
 					case 0x15:
 						if (str[0] == '\0') goto string_end;
-						if (mapping != NULL) {
+						if (mapping != nullptr) {
 							grfmsg(1, "choice lists can't be stacked, it's going to get messy now...");
 							if (code != 0x14) str++;
 						} else {
@@ -559,13 +559,13 @@ char *TranslateTTDPatchCodes(uint32 grfi
 	}
 
 string_end:
-	if (mapping != NULL) {
+	if (mapping != nullptr) {
 		grfmsg(1, "choice list was incomplete, the whole list is ignored");
 		delete mapping;
 	}
 
 	*d = '\0';
-	if (olen != NULL) *olen = d - tmp + 1;
+	if (olen != nullptr) *olen = d - tmp + 1;
 	tmp = ReallocT(tmp, d - tmp + 1);
 	return tmp;
 }
@@ -580,7 +580,7 @@ void AddGRFTextToList(GRFText **list, GR
 	GRFText **ptext, *text;
 
 	/* Loop through all languages and see if we can replace a string */
-	for (ptext = list; (text = *ptext) != NULL; ptext = &text->next) {
+	for (ptext = list; (text = *ptext) != nullptr; ptext = &text->next) {
 		if (text->langid == text_to_add->langid) {
 			text_to_add->next = text->next;
 			*ptext = text_to_add;
@@ -630,9 +630,9 @@ void AddGRFTextToList(struct GRFText **l
  */
 GRFText *DuplicateGRFText(GRFText *orig)
 {
-	GRFText *newtext = NULL;
+	GRFText *newtext = nullptr;
 	GRFText **ptext = &newtext;
-	for (; orig != NULL; orig = orig->next) {
+	for (; orig != nullptr; orig = orig->next) {
 		*ptext = GRFText::Copy(orig);
 		ptext = &(*ptext)->next;
 	}
@@ -684,7 +684,7 @@ StringID AddGRFString(uint32 grfid, uint
 	/* If we didn't find our stringid and grfid in the list, allocate a new id */
 	if (id == _num_grf_texts) _num_grf_texts++;
 
-	if (_grf_text[id].textholder == NULL) {
+	if (_grf_text[id].textholder == nullptr) {
 		_grf_text[id].grfid      = grfid;
 		_grf_text[id].stringid   = stringid;
 		_grf_text[id].def_string = def_string;
@@ -715,20 +715,20 @@ StringID GetGRFStringID(uint32 grfid, St
  * Get a C-string from a GRFText-list. If there is a translation for the
  * current language it is returned, otherwise the default translation
  * is returned. If there is neither a default nor a translation for the
- * current language NULL is returned.
+ * current language nullptr is returned.
  * @param text The GRFText to get the string from.
  */
 const char *GetGRFStringFromGRFText(const GRFText *text)
 {
-	const char *default_text = NULL;
+	const char *default_text = nullptr;
 
 	/* Search the list of lang-strings of this stringid for current lang */
-	for (; text != NULL; text = text->next) {
+	for (; text != nullptr; text = text->next) {
 		if (text->langid == _currentLangID) return text->text;
 
 		/* If the current string is English or American, set it as the
 		 * fallback language if the specific language isn't available. */
-		if (text->langid == GRFLX_UNSPECIFIED || (default_text == NULL && (text->langid == GRFLX_ENGLISH || text->langid == GRFLX_AMERICAN))) {
+		if (text->langid == GRFLX_UNSPECIFIED || (default_text == nullptr && (text->langid == GRFLX_ENGLISH || text->langid == GRFLX_AMERICAN))) {
 			default_text = text->text;
 		}
 	}
@@ -744,7 +744,7 @@ const char *GetGRFStringPtr(uint16 strin
 	assert(_grf_text[stringid].grfid != 0);
 
 	const char *str = GetGRFStringFromGRFText(_grf_text[stringid].textholder);
-	if (str != NULL) return str;
+	if (str != nullptr) return str;
 
 	/* Use the default string ID if the fallback string isn't available */
 	return GetStringPtr(_grf_text[stringid].def_string);
@@ -783,7 +783,7 @@ bool CheckGrfLangID(byte lang_id, byte g
  */
 void CleanUpGRFText(GRFText *grftext)
 {
-	while (grftext != NULL) {
+	while (grftext != nullptr) {
 		GRFText *grftext2 = grftext->next;
 		delete grftext;
 		grftext = grftext2;
@@ -802,7 +802,7 @@ void CleanUpStrings()
 		CleanUpGRFText(_grf_text[id].textholder);
 		_grf_text[id].grfid      = 0;
 		_grf_text[id].stringid   = 0;
-		_grf_text[id].textholder = NULL;
+		_grf_text[id].textholder = nullptr;
 	}
 
 	_num_grf_texts = 0;
@@ -814,7 +814,7 @@ struct TextRefStack {
 	const GRFFile *grffile;
 	bool used;
 
-	TextRefStack() : position(0), grffile(NULL), used(false) {}
+	TextRefStack() : position(0), grffile(nullptr), used(false) {}
 
 	TextRefStack(const TextRefStack &stack) :
 		position(stack.position),
@@ -872,7 +872,7 @@ struct TextRefStack {
 
 	void ResetStack(const GRFFile *grffile)
 	{
-		assert(grffile != NULL);
+		assert(grffile != nullptr);
 		this->position = 0;
 		this->grffile = grffile;
 		this->used = true;
@@ -928,7 +928,7 @@ void RestoreTextRefStackBackup(struct Te
  *
  * @param grffile the NewGRF providing the stack data
  * @param numEntries number of entries to copy from the registers
- * @param values values to copy onto the stack; if NULL the temporary NewGRF registers will be used instead
+ * @param values values to copy onto the stack; if nullptr the temporary NewGRF registers will be used instead
  */
 void StartTextRefStackUsage(const GRFFile *grffile, byte numEntries, const uint32 *values)
 {
@@ -938,7 +938,7 @@ void StartTextRefStackUsage(const GRFFil
 
 	byte *p = _newgrf_textrefstack.stack;
 	for (uint i = 0; i < numEntries; i++) {
-		uint32 value = values != NULL ? values[i] : _temp_store.GetValue(0x100 + i);
+		uint32 value = values != nullptr ? values[i] : _temp_store.GetValue(0x100 + i);
 		for (uint j = 0; j < 32; j += 8) {
 			*p = GB(value, j, 8);
 			p++;
diff --git a/src/newgrf_text.h b/src/newgrf_text.h
--- a/src/newgrf_text.h
+++ b/src/newgrf_text.h
@@ -26,7 +26,7 @@ const char *GetGRFStringFromGRFText(cons
 const char *GetGRFStringPtr(uint16 stringid);
 void CleanUpStrings();
 void SetCurrentGrfLangID(byte language_id);
-char *TranslateTTDPatchCodes(uint32 grfid, uint8 language_id, bool allow_newlines, const char *str, int *olen = NULL, StringControlCode byte80 = SCC_NEWGRF_PRINT_WORD_STRING_ID);
+char *TranslateTTDPatchCodes(uint32 grfid, uint8 language_id, bool allow_newlines, const char *str, int *olen = nullptr, StringControlCode byte80 = SCC_NEWGRF_PRINT_WORD_STRING_ID);
 struct GRFText *DuplicateGRFText(struct GRFText *orig);
 void AddGRFTextToList(struct GRFText **list, struct GRFText *text_to_add);
 void AddGRFTextToList(struct GRFText **list, byte langid, uint32 grfid, bool allow_newlines, const char *text_to_add);
@@ -35,7 +35,7 @@ void CleanUpGRFText(struct GRFText *grft
 
 bool CheckGrfLangID(byte lang_id, byte grf_version);
 
-void StartTextRefStackUsage(const GRFFile *grffile, byte numEntries, const uint32 *values = NULL);
+void StartTextRefStackUsage(const GRFFile *grffile, byte numEntries, const uint32 *values = nullptr);
 void StopTextRefStackUsage();
 void RewindTextRefStack();
 bool UsingNewGRFTextStack();
diff --git a/src/newgrf_town.cpp b/src/newgrf_town.cpp
--- a/src/newgrf_town.cpp
+++ b/src/newgrf_town.cpp
@@ -33,7 +33,7 @@
 			/* Check the persistent storage for the GrfID stored in register 100h. */
 			uint32 grfid = GetRegister(0x100);
 			if (grfid == 0xFFFFFFFF) {
-				if (this->ro.grffile == NULL) return 0;
+				if (this->ro.grffile == nullptr) return 0;
 				grfid = this->ro.grffile->grfid;
 			}
 
@@ -123,9 +123,9 @@
 {
 	if (this->readonly) return;
 
-	assert(this->t != NULL);
+	assert(this->t != nullptr);
 	/* We can't store anything if the caller has no #GRFFile. */
-	if (this->ro.grffile == NULL) return;
+	if (this->ro.grffile == nullptr) return;
 
 	/* Check the persistent storage for the GrfID stored in register 100h. */
 	uint32 grfid = GetRegister(0x100);
diff --git a/src/newgrf_townname.cpp b/src/newgrf_townname.cpp
--- a/src/newgrf_townname.cpp
+++ b/src/newgrf_townname.cpp
@@ -21,21 +21,21 @@
 
 #include "safeguards.h"
 
-static GRFTownName *_grf_townnames = NULL;
+static GRFTownName *_grf_townnames = nullptr;
 
 GRFTownName *GetGRFTownName(uint32 grfid)
 {
 	GRFTownName *t = _grf_townnames;
-	for (; t != NULL; t = t->next) {
+	for (; t != nullptr; t = t->next) {
 		if (t->grfid == grfid) return t;
 	}
-	return NULL;
+	return nullptr;
 }
 
 GRFTownName *AddGRFTownName(uint32 grfid)
 {
 	GRFTownName *t = GetGRFTownName(grfid);
-	if (t == NULL) {
+	if (t == nullptr) {
 		t = CallocT<GRFTownName>(1);
 		t->grfid = grfid;
 		t->next = _grf_townnames;
@@ -47,9 +47,9 @@ GRFTownName *AddGRFTownName(uint32 grfid
 void DelGRFTownName(uint32 grfid)
 {
 	GRFTownName *t = _grf_townnames;
-	GRFTownName *p = NULL;
-	for (;t != NULL; p = t, t = t->next) if (t->grfid == grfid) break;
-	if (t != NULL) {
+	GRFTownName *p = nullptr;
+	for (;t != nullptr; p = t, t = t->next) if (t->grfid == grfid) break;
+	if (t != nullptr) {
 		for (int i = 0; i < 128; i++) {
 			for (int j = 0; j < t->nbparts[i]; j++) {
 				for (int k = 0; k < t->partlist[i][j].partcount; k++) {
@@ -59,7 +59,7 @@ void DelGRFTownName(uint32 grfid)
 			}
 			free(t->partlist[i]);
 		}
-		if (p != NULL) {
+		if (p != nullptr) {
 			p->next = t->next;
 		} else {
 			_grf_townnames = t->next;
@@ -70,7 +70,7 @@ void DelGRFTownName(uint32 grfid)
 
 static char *RandomPart(char *buf, GRFTownName *t, uint32 seed, byte id, const char *last)
 {
-	assert(t != NULL);
+	assert(t != nullptr);
 	for (int i = 0; i < t->nbparts[id]; i++) {
 		byte count = t->partlist[id][i].bitcount;
 		uint16 maxprob = t->partlist[id][i].maxprob;
@@ -93,7 +93,7 @@ static char *RandomPart(char *buf, GRFTo
 char *GRFTownNameGenerate(char *buf, uint32 grfid, uint16 gen, uint32 seed, const char *last)
 {
 	strecpy(buf, "", last);
-	for (GRFTownName *t = _grf_townnames; t != NULL; t = t->next) {
+	for (GRFTownName *t = _grf_townnames; t != nullptr; t = t->next) {
 		if (t->grfid == grfid) {
 			assert(gen < t->nb_gen);
 			buf = RandomPart(buf, t, seed, t->id[gen], last);
@@ -106,9 +106,9 @@ char *GRFTownNameGenerate(char *buf, uin
 StringID *GetGRFTownNameList()
 {
 	int nb_names = 0, n = 0;
-	for (GRFTownName *t = _grf_townnames; t != NULL; t = t->next) nb_names += t->nb_gen;
+	for (GRFTownName *t = _grf_townnames; t != nullptr; t = t->next) nb_names += t->nb_gen;
 	StringID *list = MallocT<StringID>(nb_names + 1);
-	for (GRFTownName *t = _grf_townnames; t != NULL; t = t->next) {
+	for (GRFTownName *t = _grf_townnames; t != nullptr; t = t->next) {
 		for (int j = 0; j < t->nb_gen; j++) list[n++] = t->name[j];
 	}
 	list[n] = INVALID_STRING_ID;
@@ -117,12 +117,12 @@ StringID *GetGRFTownNameList()
 
 void CleanUpGRFTownNames()
 {
-	while (_grf_townnames != NULL) DelGRFTownName(_grf_townnames->grfid);
+	while (_grf_townnames != nullptr) DelGRFTownName(_grf_townnames->grfid);
 }
 
 uint32 GetGRFTownNameId(int gen)
 {
-	for (GRFTownName *t = _grf_townnames; t != NULL; t = t->next) {
+	for (GRFTownName *t = _grf_townnames; t != nullptr; t = t->next) {
 		if (gen < t->nb_gen) return t->grfid;
 		gen -= t->nb_gen;
 	}
@@ -132,7 +132,7 @@ uint32 GetGRFTownNameId(int gen)
 
 uint16 GetGRFTownNameType(int gen)
 {
-	for (GRFTownName *t = _grf_townnames; t != NULL; t = t->next) {
+	for (GRFTownName *t = _grf_townnames; t != nullptr; t = t->next) {
 		if (gen < t->nb_gen) return gen;
 		gen -= t->nb_gen;
 	}
diff --git a/src/news_func.h b/src/news_func.h
--- a/src/news_func.h
+++ b/src/news_func.h
@@ -17,7 +17,7 @@
 #include "station_type.h"
 #include "industry_type.h"
 
-void AddNewsItem(StringID string, NewsType type, NewsFlag flags, NewsReferenceType reftype1 = NR_NONE, uint32 ref1 = UINT32_MAX, NewsReferenceType reftype2 = NR_NONE, uint32 ref2 = UINT32_MAX, void *free_data = NULL);
+void AddNewsItem(StringID string, NewsType type, NewsFlag flags, NewsReferenceType reftype1 = NR_NONE, uint32 ref1 = UINT32_MAX, NewsReferenceType reftype2 = NR_NONE, uint32 ref2 = UINT32_MAX, void *free_data = nullptr);
 
 static inline void AddCompanyNewsItem(StringID string, CompanyNewsInformation *cni)
 {
@@ -44,7 +44,7 @@ static inline void AddVehicleAdviceNewsI
 	AddNewsItem(string, NT_ADVICE, NF_INCOLOUR | NF_SMALL | NF_VEHICLE_PARAM0, NR_VEHICLE, vehicle);
 }
 
-static inline void AddTileNewsItem(StringID string, NewsType type, TileIndex tile, void *free_data = NULL)
+static inline void AddTileNewsItem(StringID string, NewsType type, TileIndex tile, void *free_data = nullptr)
 {
 	AddNewsItem(string, type, NF_NO_TRANSPARENT | NF_SHADE | NF_THIN, NR_TILE, tile, NR_NONE, UINT32_MAX, free_data);
 }
diff --git a/src/news_gui.cpp b/src/news_gui.cpp
--- a/src/news_gui.cpp
+++ b/src/news_gui.cpp
@@ -41,23 +41,23 @@
 
 #include "safeguards.h"
 
-const NewsItem *_statusbar_news_item = NULL;
+const NewsItem *_statusbar_news_item = nullptr;
 
 static uint MIN_NEWS_AMOUNT = 30;      ///< preferred minimum amount of news messages
 static uint _total_news = 0;           ///< current number of news items
-NewsItem *_oldest_news = NULL;         ///< head of news items queue
-static NewsItem *_latest_news = NULL;  ///< tail of news items queue
+NewsItem *_oldest_news = nullptr;         ///< head of news items queue
+static NewsItem *_latest_news = nullptr;  ///< tail of news items queue
 
 /**
  * Forced news item.
  * Users can force an item by accessing the history or "last message".
  * If the message being shown was forced by the user, a pointer is stored
- * in _forced_news. Otherwise, \a _forced_news variable is NULL.
+ * in _forced_news. Otherwise, \a _forced_news variable is nullptr.
  */
-static const NewsItem *_forced_news = NULL;       ///< item the user has asked for
+static const NewsItem *_forced_news = nullptr;       ///< item the user has asked for
 
 /** Current news item (last item shown regularly). */
-static const NewsItem *_current_news = NULL;
+static const NewsItem *_current_news = nullptr;
 
 
 /**
@@ -93,7 +93,7 @@ static const NWidgetPart _nested_normal_
 };
 
 static WindowDesc _normal_news_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_NEWS_WINDOW, WC_NONE,
 	0,
 	_nested_normal_news_widgets, lengthof(_nested_normal_news_widgets)
@@ -120,7 +120,7 @@ static const NWidgetPart _nested_vehicle
 };
 
 static WindowDesc _vehicle_news_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_NEWS_WINDOW, WC_NONE,
 	0,
 	_nested_vehicle_news_widgets, lengthof(_nested_vehicle_news_widgets)
@@ -148,7 +148,7 @@ static const NWidgetPart _nested_company
 };
 
 static WindowDesc _company_news_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_NEWS_WINDOW, WC_NONE,
 	0,
 	_nested_company_news_widgets, lengthof(_nested_company_news_widgets)
@@ -171,7 +171,7 @@ static const NWidgetPart _nested_thin_ne
 };
 
 static WindowDesc _thin_news_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_NEWS_WINDOW, WC_NONE,
 	0,
 	_nested_thin_news_widgets, lengthof(_nested_thin_news_widgets)
@@ -195,7 +195,7 @@ static const NWidgetPart _nested_small_n
 };
 
 static WindowDesc _small_news_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_NEWS_WINDOW, WC_NONE,
 	0,
 	_nested_small_news_widgets, lengthof(_nested_small_news_widgets)
@@ -251,8 +251,8 @@ NewsDisplay NewsTypeData::GetDisplay() c
 {
 	uint index;
 	const SettingDesc *sd = GetSettingFromName(this->name, &index);
-	assert(sd != NULL);
-	void *ptr = GetVariableAddress(NULL, &sd->save);
+	assert(sd != nullptr);
+	void *ptr = GetVariableAddress(nullptr, &sd->save);
 	return (NewsDisplay)ReadValue(ptr, sd->save.conv);
 }
 
@@ -269,7 +269,7 @@ struct NewsWindow : Window {
 	{
 		NewsWindow::duration = 16650;
 		const Window *w = FindWindowByClass(WC_SEND_NETWORK_MSG);
-		this->chat_height = (w != NULL) ? w->height : 0;
+		this->chat_height = (w != nullptr) ? w->height : 0;
 		this->status_height = FindWindowById(WC_STATUS_BAR, 0)->height;
 
 		this->flags |= WF_DISABLE_VP_SCROLL;
@@ -285,7 +285,7 @@ struct NewsWindow : Window {
 
 		/* Initialize viewport if it exists. */
 		NWidgetViewport *nvp = this->GetWidget<NWidgetViewport>(WID_N_VIEWPORT);
-		if (nvp != NULL) {
+		if (nvp != nullptr) {
 			nvp->InitializeViewport(this, ni->reftype1 == NR_VEHICLE ? 0x80000000 | ni->ref1 : GetReferenceTile(ni->reftype1, ni->ref1), ZOOM_LVL_NEWS);
 			if (this->ni->flags & NF_NO_TRANSPARENT) nvp->disp_flags |= ND_NO_TRANSPARENCY;
 			if ((this->ni->flags & NF_INCOLOUR) == 0) {
@@ -433,7 +433,7 @@ struct NewsWindow : Window {
 			case WID_N_CLOSEBOX:
 				NewsWindow::duration = 0;
 				delete this;
-				_forced_news = NULL;
+				_forced_news = nullptr;
 				break;
 
 			case WID_N_CAPTION:
@@ -515,7 +515,7 @@ private:
 
 		int mintop = min(newtop, this->top);
 		int maxtop = max(newtop, this->top);
-		if (this->viewport != NULL) this->viewport->top += newtop - this->top;
+		if (this->viewport != nullptr) this->viewport->top += newtop - this->top;
 		this->top = newtop;
 
 		SetDirtyBlocks(this->left, mintop, this->left + this->width, maxtop + this->height);
@@ -572,18 +572,18 @@ static void ShowTicker(const NewsItem *n
 /** Initialize the news-items data structures */
 void InitNewsItemStructs()
 {
-	for (NewsItem *ni = _oldest_news; ni != NULL; ) {
+	for (NewsItem *ni = _oldest_news; ni != nullptr; ) {
 		NewsItem *next = ni->next;
 		delete ni;
 		ni = next;
 	}
 
 	_total_news = 0;
-	_oldest_news = NULL;
-	_latest_news = NULL;
-	_forced_news = NULL;
-	_current_news = NULL;
-	_statusbar_news_item = NULL;
+	_oldest_news = nullptr;
+	_latest_news = nullptr;
+	_forced_news = nullptr;
+	_current_news = nullptr;
+	_statusbar_news_item = nullptr;
 	NewsWindow::duration = 0;
 }
 
@@ -593,15 +593,15 @@ void InitNewsItemStructs()
  */
 static bool ReadyForNextItem()
 {
-	const NewsItem *ni = _forced_news == NULL ? _current_news : _forced_news;
-	if (ni == NULL) return true;
+	const NewsItem *ni = _forced_news == nullptr ? _current_news : _forced_news;
+	if (ni == nullptr) return true;
 
 	/* Ticker message
 	 * Check if the status bar message is still being displayed? */
 	if (IsNewsTickerShown()) return false;
 
 	/* neither newsticker nor newspaper are running */
-	return (NewsWindow::duration <= 0 || FindWindowById(WC_NEWS_WINDOW, 0) == NULL);
+	return (NewsWindow::duration <= 0 || FindWindowById(WC_NEWS_WINDOW, 0) == nullptr);
 }
 
 /** Move to the next news item */
@@ -609,12 +609,12 @@ static void MoveToNextItem()
 {
 	InvalidateWindowData(WC_STATUS_BAR, 0, SBI_NEWS_DELETED); // invalidate the statusbar
 	DeleteWindowById(WC_NEWS_WINDOW, 0); // close the newspapers window if shown
-	_forced_news = NULL;
-	_statusbar_news_item = NULL;
+	_forced_news = nullptr;
+	_statusbar_news_item = nullptr;
 
 	/* if we're not at the last item, then move on */
 	if (_current_news != _latest_news) {
-		_current_news = (_current_news == NULL) ? _oldest_news : _current_news->next;
+		_current_news = (_current_news == nullptr) ? _oldest_news : _current_news->next;
 		const NewsItem *ni = _current_news;
 		const NewsType type = ni->type;
 
@@ -674,16 +674,16 @@ void AddNewsItem(StringID string, NewsTy
 	CopyOutDParam(ni->params, 0, lengthof(ni->params));
 
 	if (_total_news++ == 0) {
-		assert(_oldest_news == NULL);
+		assert(_oldest_news == nullptr);
 		_oldest_news = ni;
-		ni->prev = NULL;
+		ni->prev = nullptr;
 	} else {
-		assert(_latest_news->next == NULL);
+		assert(_latest_news->next == nullptr);
 		_latest_news->next = ni;
 		ni->prev = _latest_news;
 	}
 
-	ni->next = NULL;
+	ni->next = nullptr;
 	_latest_news = ni;
 
 	SetWindowDirty(WC_MESSAGE_HISTORY, 0);
@@ -757,14 +757,14 @@ CommandCost CmdCustomNewsItem(TileIndex 
 static void DeleteNewsItem(NewsItem *ni)
 {
 	/* Delete the news from the news queue. */
-	if (ni->prev != NULL) {
+	if (ni->prev != nullptr) {
 		ni->prev->next = ni->next;
 	} else {
 		assert(_oldest_news == ni);
 		_oldest_news = ni->next;
 	}
 
-	if (ni->next != NULL) {
+	if (ni->next != nullptr) {
 		ni->next->prev = ni->prev;
 	} else {
 		assert(_latest_news == ni);
@@ -798,7 +798,7 @@ void DeleteVehicleNews(VehicleID vid, St
 {
 	NewsItem *ni = _oldest_news;
 
-	while (ni != NULL) {
+	while (ni != nullptr) {
 		NewsItem *next = ni->next;
 		if (((ni->reftype1 == NR_VEHICLE && ni->ref1 == vid) || (ni->reftype2 == NR_VEHICLE && ni->ref2 == vid)) &&
 				(news == INVALID_STRING_ID || ni->string_id == news)) {
@@ -817,7 +817,7 @@ void DeleteStationNews(StationID sid)
 {
 	NewsItem *ni = _oldest_news;
 
-	while (ni != NULL) {
+	while (ni != nullptr) {
 		NewsItem *next = ni->next;
 		if ((ni->reftype1 == NR_STATION && ni->ref1 == sid) || (ni->reftype2 == NR_STATION && ni->ref2 == sid)) {
 			DeleteNewsItem(ni);
@@ -834,7 +834,7 @@ void DeleteIndustryNews(IndustryID iid)
 {
 	NewsItem *ni = _oldest_news;
 
-	while (ni != NULL) {
+	while (ni != nullptr) {
 		NewsItem *next = ni->next;
 		if ((ni->reftype1 == NR_INDUSTRY && ni->ref1 == iid) || (ni->reftype2 == NR_INDUSTRY && ni->ref2 == iid)) {
 			DeleteNewsItem(ni);
@@ -850,7 +850,7 @@ void DeleteInvalidEngineNews()
 {
 	NewsItem *ni = _oldest_news;
 
-	while (ni != NULL) {
+	while (ni != nullptr) {
 		NewsItem *next = ni->next;
 		if ((ni->reftype1 == NR_ENGINE && (!Engine::IsValidID(ni->ref1) || !Engine::Get(ni->ref1)->IsEnabled())) ||
 				(ni->reftype2 == NR_ENGINE && (!Engine::IsValidID(ni->ref2) || !Engine::Get(ni->ref2)->IsEnabled()))) {
@@ -863,7 +863,7 @@ void DeleteInvalidEngineNews()
 static void RemoveOldNewsItems()
 {
 	NewsItem *next;
-	for (NewsItem *cur = _oldest_news; _total_news > MIN_NEWS_AMOUNT && cur != NULL; cur = next) {
+	for (NewsItem *cur = _oldest_news; _total_news > MIN_NEWS_AMOUNT && cur != nullptr; cur = next) {
 		next = cur->next;
 		if (_date - _news_type_data[cur->type].age * _settings_client.gui.news_message_timeout > cur->date) DeleteNewsItem(cur);
 	}
@@ -877,7 +877,7 @@ static void RemoveOldNewsItems()
  */
 void ChangeVehicleNews(VehicleID from_index, VehicleID to_index)
 {
-	for (NewsItem *ni = _oldest_news; ni != NULL; ni = ni->next) {
+	for (NewsItem *ni = _oldest_news; ni != nullptr; ni = ni->next) {
 		if (ni->reftype1 == NR_VEHICLE && ni->ref1 == from_index) ni->ref1 = to_index;
 		if (ni->reftype2 == NR_VEHICLE && ni->ref2 == from_index) ni->ref2 = to_index;
 		if (ni->flags & NF_VEHICLE_PARAM0 && ni->params[0] == from_index) ni->params[0] = to_index;
@@ -892,7 +892,7 @@ void NewsLoop()
 	/* There is no status bar, so no reason to show news;
 	 * especially important with the end game screen when
 	 * there is no status bar but possible news. */
-	if (FindWindowById(WC_STATUS_BAR, 0) == NULL) return;
+	if (FindWindowById(WC_STATUS_BAR, 0) == nullptr) return;
 
 	static byte _last_clean_month = 0;
 
@@ -915,7 +915,7 @@ static void ShowNewsMessage(const NewsIt
 	/* setup forced news item */
 	_forced_news = ni;
 
-	if (_forced_news != NULL) {
+	if (_forced_news != nullptr) {
 		DeleteWindowById(WC_NEWS_WINDOW, 0);
 		ShowNewspaper(ni);
 	}
@@ -924,19 +924,19 @@ static void ShowNewsMessage(const NewsIt
 /** Show previous news item */
 void ShowLastNewsMessage()
 {
-	const NewsItem *ni = NULL;
+	const NewsItem *ni = nullptr;
 	if (_total_news == 0) {
 		return;
-	} else if (_forced_news == NULL) {
+	} else if (_forced_news == nullptr) {
 		/* Not forced any news yet, show the current one, unless a news window is
 		 * open (which can only be the current one), then show the previous item */
-		if (_current_news == NULL) {
+		if (_current_news == nullptr) {
 			/* No news were shown yet resp. the last shown one was already deleted.
 			 * Threat this as if _forced_news reached _oldest_news; so, wrap around and start anew with the latest. */
 			ni = _latest_news;
 		} else {
 			const Window *w = FindWindowById(WC_NEWS_WINDOW, 0);
-			ni = (w == NULL || (_current_news == _oldest_news)) ? _current_news : _current_news->prev;
+			ni = (w == nullptr || (_current_news == _oldest_news)) ? _current_news : _current_news->prev;
 		}
 	} else if (_forced_news == _oldest_news) {
 		/* We have reached the oldest news, start anew with the latest */
@@ -953,7 +953,7 @@ void ShowLastNewsMessage()
 		}
 
 		ni = ni->prev;
-		if (ni == NULL) {
+		if (ni == nullptr) {
 			if (wrap) break;
 			/* We have reached the oldest news, start anew with the latest */
 			ni = _latest_news;
@@ -1054,7 +1054,7 @@ struct MessageHistoryWindow : Window {
 		NewsItem *ni = _latest_news;
 		for (int n = this->vscroll->GetPosition(); n > 0; n--) {
 			ni = ni->prev;
-			if (ni == NULL) return;
+			if (ni == nullptr) return;
 		}
 
 		/* Fill the widget with news items. */
@@ -1072,7 +1072,7 @@ struct MessageHistoryWindow : Window {
 			y += this->line_height;
 
 			ni = ni->prev;
-			if (ni == NULL) return;
+			if (ni == nullptr) return;
 		}
 	}
 
@@ -1091,11 +1091,11 @@ struct MessageHistoryWindow : Window {
 	{
 		if (widget == WID_MH_BACKGROUND) {
 			NewsItem *ni = _latest_news;
-			if (ni == NULL) return;
+			if (ni == nullptr) return;
 
 			for (int n = this->vscroll->GetScrolledRowFromWidget(pt.y, this, WID_MH_BACKGROUND, WD_FRAMERECT_TOP, this->line_height); n > 0; n--) {
 				ni = ni->prev;
-				if (ni == NULL) return;
+				if (ni == nullptr) return;
 			}
 
 			ShowNewsMessage(ni);
diff --git a/src/news_type.h b/src/news_type.h
--- a/src/news_type.h
+++ b/src/news_type.h
@@ -155,7 +155,7 @@ struct CompanyNewsInformation {
 	uint32 face; ///< The face of the president
 	byte colour; ///< The colour related to the company
 
-	void FillData(const struct Company *c, const struct Company *other = NULL);
+	void FillData(const struct Company *c, const struct Company *other = nullptr);
 };
 
 #endif /* NEWS_TYPE_H */
diff --git a/src/object.h b/src/object.h
--- a/src/object.h
+++ b/src/object.h
@@ -18,7 +18,7 @@
 
 void UpdateCompanyHQ(TileIndex tile, uint score);
 
-void BuildObject(ObjectType type, TileIndex tile, CompanyID owner = OWNER_NONE, struct Town *town = NULL, uint8 view = 0);
+void BuildObject(ObjectType type, TileIndex tile, CompanyID owner = OWNER_NONE, struct Town *town = nullptr, uint8 view = 0);
 
 void ShowBuildObjectPicker();
 
diff --git a/src/object_cmd.cpp b/src/object_cmd.cpp
--- a/src/object_cmd.cpp
+++ b/src/object_cmd.cpp
@@ -90,7 +90,7 @@ void BuildObject(ObjectType type, TileIn
 	Object *o = new Object();
 	o->type          = type;
 	o->location      = ta;
-	o->town          = town == NULL ? CalcClosestTownFromTile(tile) : town;
+	o->town          = town == nullptr ? CalcClosestTownFromTile(tile) : town;
 	o->build_date    = _date;
 	o->view          = view;
 
@@ -114,7 +114,7 @@ void BuildObject(ObjectType type, TileIn
 		}
 	}
 
-	assert(o->town != NULL);
+	assert(o->town != nullptr);
 
 	TILE_AREA_LOOP(t, ta) {
 		WaterClass wc = (IsWaterTile(t) ? GetWaterClass(t) : WATER_CLASS_INVALID);
@@ -263,7 +263,7 @@ CommandCost CmdBuildObject(TileIndex til
 			uint16 callback = CALLBACK_FAILED;
 			if (HasBit(spec->callback_mask, CBM_OBJ_SLOPE_CHECK)) {
 				TileIndex diff = t - tile;
-				callback = GetObjectCallback(CBID_OBJECT_LAND_SLOPE_CHECK, GetTileSlope(t), TileY(diff) << 4 | TileX(diff), spec, NULL, t, view);
+				callback = GetObjectCallback(CBID_OBJECT_LAND_SLOPE_CHECK, GetTileSlope(t), TileY(diff) << 4 | TileX(diff), spec, nullptr, t, view);
 			}
 
 			if (callback == CALLBACK_FAILED) {
@@ -342,7 +342,7 @@ CommandCost CmdBuildObject(TileIndex til
 	}
 
 	if (flags & DC_EXEC) {
-		BuildObject(type, tile, _current_company, NULL, view);
+		BuildObject(type, tile, _current_company, nullptr, view);
 
 		/* Make sure the HQ starts at the right size. */
 		if (type == OBJECT_HQ) UpdateCompanyHQ(tile, hq_score);
@@ -366,7 +366,7 @@ static void DrawTile_Object(TileInfo *ti
 	if ((spec->flags & OBJECT_FLAG_HAS_NO_FOUNDATION) == 0) DrawFoundation(ti, GetFoundation_Object(ti->tile, ti->tileh));
 
 	if (type < NEW_OBJECT_OFFSET) {
-		const DrawTileSprites *dts = NULL;
+		const DrawTileSprites *dts = nullptr;
 		Owner to = GetTileOwner(ti->tile);
 		PaletteID palette = to == OWNER_NONE ? PAL_NONE : COMPANY_SPRITE_COLOUR(to);
 
@@ -447,7 +447,7 @@ std::vector<ClearedObjectArea> _cleared_
 /**
  * Find the entry in _cleared_object_areas which occupies a certain tile.
  * @param tile Tile of interest
- * @return Occupying entry, or NULL if none
+ * @return Occupying entry, or nullptr if none
  */
 ClearedObjectArea *FindClearedObject(TileIndex tile)
 {
@@ -457,7 +457,7 @@ ClearedObjectArea *FindClearedObject(Til
 		if (coa.area.Intersects(ta)) return &coa;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 static CommandCost ClearTile_Object(TileIndex tile, DoCommandFlag flags)
@@ -567,7 +567,7 @@ static void GetTileDesc_Object(TileIndex
 	td->owner[0] = GetTileOwner(tile);
 	td->build_date = Object::GetByTile(tile)->build_date;
 
-	if (spec->grf_prop.grffile != NULL) {
+	if (spec->grf_prop.grffile != nullptr) {
 		td->grf = GetGRFConfig(spec->grf_prop.grffile->grfid)->GetName();
 	}
 }
@@ -694,7 +694,7 @@ static bool TryBuildTransmitter()
 	int h;
 	if (IsTileType(tile, MP_CLEAR) && IsTileFlat(tile, &h) && h >= 4 && !IsBridgeAbove(tile)) {
 		TileIndex t = tile;
-		if (CircularTileSearch(&t, 9, HasTransmitter, NULL)) return false;
+		if (CircularTileSearch(&t, 9, HasTransmitter, nullptr)) return false;
 
 		BuildObject(OBJECT_TRANSMITTER, tile);
 		return true;
@@ -754,7 +754,7 @@ void GenerateObjects()
 
 				default:
 					uint8 view = RandomRange(spec->views);
-					if (CmdBuildObject(RandomTile(), DC_EXEC | DC_AUTO | DC_NO_TEST_TOWN_RATING | DC_NO_MODIFY_TOWN_RATING, i, view, NULL).Succeeded()) amount--;
+					if (CmdBuildObject(RandomTile(), DC_EXEC | DC_AUTO | DC_NO_TEST_TOWN_RATING | DC_NO_MODIFY_TOWN_RATING, i, view, nullptr).Succeeded()) amount--;
 					break;
 			}
 		}
@@ -840,8 +840,8 @@ extern const TileTypeProcs _tile_type_ob
 	AnimateTile_Object,          // animate_tile_proc
 	TileLoop_Object,             // tile_loop_proc
 	ChangeTileOwner_Object,      // change_tile_owner_proc
-	NULL,                        // add_produced_cargo_proc
-	NULL,                        // vehicle_enter_tile_proc
+	nullptr,                        // add_produced_cargo_proc
+	nullptr,                        // vehicle_enter_tile_proc
 	GetFoundation_Object,        // get_foundation_proc
 	TerraformTile_Object,        // terraform_tile_proc
 };
diff --git a/src/object_gui.cpp b/src/object_gui.cpp
--- a/src/object_gui.cpp
+++ b/src/object_gui.cpp
@@ -104,13 +104,13 @@ public:
 		switch (widget) {
 			case WID_BO_OBJECT_NAME: {
 				const ObjectSpec *spec = ObjectClass::Get(_selected_object_class)->GetSpec(_selected_object_index);
-				SetDParam(0, spec != NULL ? spec->name : STR_EMPTY);
+				SetDParam(0, spec != nullptr ? spec->name : STR_EMPTY);
 				break;
 			}
 
 			case WID_BO_OBJECT_SIZE: {
 				const ObjectSpec *spec = ObjectClass::Get(_selected_object_class)->GetSpec(_selected_object_index);
-				int size = spec == NULL ? 0 : spec->size;
+				int size = spec == nullptr ? 0 : spec->size;
 				SetDParam(0, GB(size, HasBit(_selected_object_view, 0) ? 4 : 0, 4));
 				SetDParam(1, GB(size, HasBit(_selected_object_view, 0) ? 0 : 4, 4));
 				break;
@@ -145,7 +145,7 @@ public:
 			case WID_BO_OBJECT_MATRIX: {
 				/* Get the right amount of buttons based on the current spec. */
 				const ObjectSpec *spec = ObjectClass::Get(_selected_object_class)->GetSpec(_selected_object_index);
-				if (spec != NULL) {
+				if (spec != nullptr) {
 					if (spec->views >= 2) size->width  += resize->width;
 					if (spec->views >= 4) size->height += resize->height;
 				}
@@ -185,7 +185,7 @@ public:
 
 				/* Get the right size for the single widget based on the current spec. */
 				const ObjectSpec *spec = ObjectClass::Get(_selected_object_class)->GetSpec(_selected_object_index);
-				if (spec != NULL) {
+				if (spec != nullptr) {
 					if (spec->views >= 2) size->width  = size->width  / 2 - 1;
 					if (spec->views >= 4) size->height = size->height / 2 - 1;
 				}
@@ -229,7 +229,7 @@ public:
 
 			case WID_BO_OBJECT_SPRITE: {
 				const ObjectSpec *spec = ObjectClass::Get(_selected_object_class)->GetSpec(_selected_object_index);
-				if (spec == NULL) break;
+				if (spec == nullptr) break;
 
 				/* Height of the selection matrix.
 				 * Depending on the number of views, the matrix has a 1x1, 1x2, 2x1 or 2x2 layout. To make the previews
@@ -243,7 +243,7 @@ public:
 				if (FillDrawPixelInfo(&tmp_dpi, r.left, r.top, r.right - r.left + 1, r.bottom - r.top + 1)) {
 					DrawPixelInfo *old_dpi = _cur_dpi;
 					_cur_dpi = &tmp_dpi;
-					if (spec->grf_prop.grffile == NULL) {
+					if (spec->grf_prop.grffile == nullptr) {
 						extern const DrawTileSprites _objects[];
 						const DrawTileSprites *dts = &_objects[spec->grf_prop.local_id];
 						DrawOrigTileSeqInGUI((r.right - r.left) / 2 - 1, (r.bottom - r.top + matrix_height / 2) / 2 - OBJECT_MARGIN - ScaleGUITrad(TILE_PIXELS), dts, PAL_NONE);
@@ -260,7 +260,7 @@ public:
 				int obj_index = objclass->GetIndexFromUI(GB(widget, 16, 16));
 				if (obj_index < 0) break;
 				const ObjectSpec *spec = objclass->GetSpec(obj_index);
-				if (spec == NULL) break;
+				if (spec == nullptr) break;
 
 				if (!spec->IsAvailable()) {
 					GfxFillRect(r.left + 1, r.top + 1, r.right - 1, r.bottom - 1, PC_BLACK, FILLRECT_CHECKER);
@@ -270,7 +270,7 @@ public:
 				if (FillDrawPixelInfo(&tmp_dpi, r.left + 1, r.top, (r.right - 1) - (r.left + 1) + 1, r.bottom - r.top + 1)) {
 					DrawPixelInfo *old_dpi = _cur_dpi;
 					_cur_dpi = &tmp_dpi;
-					if (spec->grf_prop.grffile == NULL) {
+					if (spec->grf_prop.grffile == nullptr) {
 						extern const DrawTileSprites _objects[];
 						const DrawTileSprites *dts = &_objects[spec->grf_prop.local_id];
 						DrawOrigTileSeqInGUI((r.right - r.left) / 2 - 1, r.bottom - r.top - OBJECT_MARGIN - ScaleGUITrad(TILE_PIXELS), dts, PAL_NONE);
@@ -285,11 +285,11 @@ public:
 
 			case WID_BO_INFO: {
 				const ObjectSpec *spec = ObjectClass::Get(_selected_object_class)->GetSpec(_selected_object_index);
-				if (spec == NULL) break;
+				if (spec == nullptr) break;
 
 				/* Get the extra message for the GUI */
 				if (HasBit(spec->callback_mask, CBM_OBJ_FUND_MORE_TEXT)) {
-					uint16 callback_res = GetObjectCallback(CBID_OBJECT_FUND_MORE_TEXT, 0, 0, spec, NULL, INVALID_TILE, _selected_object_view);
+					uint16 callback_res = GetObjectCallback(CBID_OBJECT_FUND_MORE_TEXT, 0, 0, spec, nullptr, INVALID_TILE, _selected_object_view);
 					if (callback_res != CALLBACK_FAILED && callback_res != 0x400) {
 						if (callback_res > 0x400) {
 							ErrorUnknownCallbackResult(spec->grf_prop.grffile->grfid, CBID_OBJECT_FUND_MORE_TEXT, callback_res);
diff --git a/src/openttd.cpp b/src/openttd.cpp
--- a/src/openttd.cpp
+++ b/src/openttd.cpp
@@ -99,7 +99,7 @@ void CDECL usererror(const char *s, ...)
 	va_end(va);
 
 	ShowOSErrorBox(buf, false);
-	if (VideoDriver::GetInstance() != NULL) VideoDriver::GetInstance()->Stop();
+	if (VideoDriver::GetInstance() != nullptr) VideoDriver::GetInstance()->Stop();
 
 	exit(1);
 }
@@ -118,7 +118,7 @@ void CDECL error(const char *s, ...)
 	vseprintf(buf, lastof(buf), s, va);
 	va_end(va);
 
-	if (VideoDriver::GetInstance() == NULL || VideoDriver::GetInstance()->HasGUI()) {
+	if (VideoDriver::GetInstance() == nullptr || VideoDriver::GetInstance()->HasGUI()) {
 		ShowOSErrorBox(buf, true);
 	}
 
@@ -242,7 +242,7 @@ static void WriteSavegameInfo(const char
 
 	p = strecpy(p, "NewGRFs:\n", lastof(buf));
 	if (_load_check_data.HasNewGrfs()) {
-		for (GRFConfig *c = _load_check_data.grfconfig; c != NULL; c = c->next) {
+		for (GRFConfig *c = _load_check_data.grfconfig; c != nullptr; c = c->next) {
 			char md5sum[33];
 			md5sumToString(md5sum, lastof(md5sum), HasBit(c->flags, GCF_COMPATIBLE) ? c->original_md5sum : c->ident.md5sum);
 			p += seprintf(p, lastof(buf), "%08X %s %s\n", c->ident.grfid, md5sum, c->filename);
@@ -268,13 +268,13 @@ static void WriteSavegameInfo(const char
 static void ParseResolution(Dimension *res, const char *s)
 {
 	const char *t = strchr(s, 'x');
-	if (t == NULL) {
+	if (t == nullptr) {
 		ShowInfoF("Invalid resolution '%s'", s);
 		return;
 	}
 
-	res->width  = max(strtoul(s, NULL, 0), 64UL);
-	res->height = max(strtoul(t + 1, NULL, 0), 64UL);
+	res->width  = max(strtoul(s, nullptr, 0), 64UL);
+	res->height = max(strtoul(t + 1, nullptr, 0), 64UL);
 }
 
 
@@ -347,11 +347,11 @@ static void LoadIntroGame(bool load_newg
 void MakeNewgameSettingsLive()
 {
 	for (CompanyID c = COMPANY_FIRST; c < MAX_COMPANIES; c++) {
-		if (_settings_game.ai_config[c] != NULL) {
+		if (_settings_game.ai_config[c] != nullptr) {
 			delete _settings_game.ai_config[c];
 		}
 	}
-	if (_settings_game.game_config != NULL) {
+	if (_settings_game.game_config != nullptr) {
 		delete _settings_game.game_config;
 	}
 
@@ -361,16 +361,16 @@ void MakeNewgameSettingsLive()
 	_old_vds = _settings_client.company.vehicle;
 
 	for (CompanyID c = COMPANY_FIRST; c < MAX_COMPANIES; c++) {
-		_settings_game.ai_config[c] = NULL;
-		if (_settings_newgame.ai_config[c] != NULL) {
+		_settings_game.ai_config[c] = nullptr;
+		if (_settings_newgame.ai_config[c] != nullptr) {
 			_settings_game.ai_config[c] = new AIConfig(_settings_newgame.ai_config[c]);
 			if (!AIConfig::GetConfig(c, AIConfig::SSS_FORCE_GAME)->HasScript()) {
-				AIConfig::GetConfig(c, AIConfig::SSS_FORCE_GAME)->Change(NULL);
+				AIConfig::GetConfig(c, AIConfig::SSS_FORCE_GAME)->Change(nullptr);
 			}
 		}
 	}
-	_settings_game.game_config = NULL;
-	if (_settings_newgame.game_config != NULL) {
+	_settings_game.game_config = nullptr;
+	if (_settings_newgame.game_config != nullptr) {
 		_settings_game.game_config = new GameConfig(_settings_newgame.game_config);
 	}
 }
@@ -390,7 +390,7 @@ struct AfterNewGRFScan : NewGRFScanCallb
 	uint32 generation_seed;            ///< Seed for the new game.
 	char *dedicated_host;              ///< Hostname for the dedicated server.
 	uint16 dedicated_port;             ///< Port for the dedicated server.
-	char *network_conn;                ///< Information about the server to connect to, or NULL.
+	char *network_conn;                ///< Information about the server to connect to, or nullptr.
 	const char *join_server_password;  ///< The password to join the server with.
 	const char *join_company_password; ///< The password to join the company with.
 	bool *save_config_ptr;             ///< The pointer to the save config setting.
@@ -403,8 +403,8 @@ struct AfterNewGRFScan : NewGRFScanCallb
 	 */
 	AfterNewGRFScan(bool *save_config_ptr) :
 			startyear(INVALID_YEAR), generation_seed(GENERATE_NEW_SEED),
-			dedicated_host(NULL), dedicated_port(0), network_conn(NULL),
-			join_server_password(NULL), join_company_password(NULL),
+			dedicated_host(nullptr), dedicated_port(0), network_conn(nullptr),
+			join_server_password(nullptr), join_company_password(nullptr),
 			save_config_ptr(save_config_ptr), save_config(true)
 	{
 		/* Visual C++ 2015 fails compiling this line (AfterNewGRFScan::generation_seed undefined symbol)
@@ -444,7 +444,7 @@ struct AfterNewGRFScan : NewGRFScanCallb
 		if (startyear != INVALID_YEAR) _settings_newgame.game_creation.starting_year = startyear;
 		if (generation_seed != GENERATE_NEW_SEED) _settings_newgame.game_creation.generation_seed = generation_seed;
 
-		if (dedicated_host != NULL) {
+		if (dedicated_host != nullptr) {
 			_network_bind_list.clear();
 			_network_bind_list.emplace_back(dedicated_host);
 		}
@@ -458,15 +458,15 @@ struct AfterNewGRFScan : NewGRFScanCallb
 		/* Make sure _settings is filled with _settings_newgame if we switch to a game directly */
 		if (_switch_mode != SM_NONE) MakeNewgameSettingsLive();
 
-		if (_network_available && network_conn != NULL) {
-			const char *port = NULL;
-			const char *company = NULL;
+		if (_network_available && network_conn != nullptr) {
+			const char *port = nullptr;
+			const char *company = nullptr;
 			uint16 rport = NETWORK_DEFAULT_PORT;
 			CompanyID join_as = COMPANY_NEW_COMPANY;
 
 			ParseConnectionString(&company, &port, network_conn);
 
-			if (company != NULL) {
+			if (company != nullptr) {
 				join_as = (CompanyID)atoi(company);
 
 				if (join_as != COMPANY_SPECTATOR) {
@@ -477,7 +477,7 @@ struct AfterNewGRFScan : NewGRFScanCallb
 					}
 				}
 			}
-			if (port != NULL) rport = atoi(port);
+			if (port != nullptr) rport = atoi(port);
 
 			LoadIntroGame();
 			_switch_mode = SM_NONE;
@@ -531,19 +531,19 @@ static const OptionData _options[] = {
  */
 int openttd_main(int argc, char *argv[])
 {
-	char *musicdriver = NULL;
-	char *sounddriver = NULL;
-	char *videodriver = NULL;
-	char *blitter = NULL;
-	char *graphics_set = NULL;
-	char *sounds_set = NULL;
-	char *music_set = NULL;
+	char *musicdriver = nullptr;
+	char *sounddriver = nullptr;
+	char *videodriver = nullptr;
+	char *blitter = nullptr;
+	char *graphics_set = nullptr;
+	char *sounds_set = nullptr;
+	char *music_set = nullptr;
 	Dimension resolution = {0, 0};
 	/* AfterNewGRFScan sets save_config to true after scanning completed. */
 	bool save_config = false;
 	AfterNewGRFScan *scanner = new AfterNewGRFScan(&save_config);
 	bool dedicated = false;
-	char *debuglog_conn = NULL;
+	char *debuglog_conn = nullptr;
 
 	extern bool _dedicated_forks;
 	_dedicated_forks = false;
@@ -553,7 +553,7 @@ int openttd_main(int argc, char *argv[])
 
 	_game_mode = GM_MENU;
 	_switch_mode = SM_MENU;
-	_config_file = NULL;
+	_config_file = nullptr;
 
 	GetOptData mgo(argc - 1, argv + 1, _options);
 	int ret = 0;
@@ -579,19 +579,19 @@ int openttd_main(int argc, char *argv[])
 			blitter = stredup("null");
 			dedicated = true;
 			SetDebugString("net=6");
-			if (mgo.opt != NULL) {
+			if (mgo.opt != nullptr) {
 				/* Use the existing method for parsing (openttd -n).
 				 * However, we do ignore the #company part. */
-				const char *temp = NULL;
-				const char *port = NULL;
+				const char *temp = nullptr;
+				const char *port = nullptr;
 				ParseConnectionString(&temp, &port, mgo.opt);
 				if (!StrEmpty(mgo.opt)) scanner->dedicated_host = mgo.opt;
-				if (port != NULL) scanner->dedicated_port = atoi(port);
+				if (port != nullptr) scanner->dedicated_port = atoi(port);
 			}
 			break;
 		case 'f': _dedicated_forks = true; break;
 		case 'n':
-			scanner->network_conn = mgo.opt; // optional IP parameter, NULL if unset
+			scanner->network_conn = mgo.opt; // optional IP parameter, nullptr if unset
 			break;
 		case 'l':
 			debuglog_conn = mgo.opt;
@@ -608,12 +608,12 @@ int openttd_main(int argc, char *argv[])
 #if defined(_WIN32)
 				CreateConsole();
 #endif
-				if (mgo.opt != NULL) SetDebugString(mgo.opt);
+				if (mgo.opt != nullptr) SetDebugString(mgo.opt);
 				break;
 			}
 		case 'e': _switch_mode = (_switch_mode == SM_LOAD_GAME || _switch_mode == SM_LOAD_SCENARIO ? SM_LOAD_SCENARIO : SM_EDITOR); break;
 		case 'g':
-			if (mgo.opt != NULL) {
+			if (mgo.opt != nullptr) {
 				_file_to_saveload.SetName(mgo.opt);
 				bool is_scenario = _switch_mode == SM_EDITOR || _switch_mode == SM_LOAD_SCENARIO;
 				_switch_mode = is_scenario ? SM_LOAD_SCENARIO : SM_LOAD_GAME;
@@ -621,8 +621,8 @@ int openttd_main(int argc, char *argv[])
 
 				/* if the file doesn't exist or it is not a valid savegame, let the saveload code show an error */
 				const char *t = strrchr(_file_to_saveload.name, '.');
-				if (t != NULL) {
-					FiosType ft = FiosGetSavegameListCallback(SLO_LOAD, _file_to_saveload.name, t, NULL, NULL);
+				if (t != nullptr) {
+					FiosType ft = FiosGetSavegameListCallback(SLO_LOAD, _file_to_saveload.name, t, nullptr, nullptr);
 					if (ft != FIOS_TYPE_INVALID) _file_to_saveload.SetMode(ft);
 				}
 
@@ -663,7 +663,7 @@ int openttd_main(int argc, char *argv[])
 
 			goto exit_noshutdown;
 		}
-		case 'G': scanner->generation_seed = strtoul(mgo.opt, NULL, 10); break;
+		case 'G': scanner->generation_seed = strtoul(mgo.opt, nullptr, 10); break;
 		case 'c': free(_config_file); _config_file = stredup(mgo.opt); break;
 		case 'x': scanner->save_config = false; break;
 		case 'h':
@@ -729,10 +729,10 @@ int openttd_main(int argc, char *argv[])
 	InitWindowSystem();
 
 	BaseGraphics::FindSets();
-	if (graphics_set == NULL && BaseGraphics::ini_set != NULL) graphics_set = stredup(BaseGraphics::ini_set);
+	if (graphics_set == nullptr && BaseGraphics::ini_set != nullptr) graphics_set = stredup(BaseGraphics::ini_set);
 	if (!BaseGraphics::SetSet(graphics_set)) {
 		if (!StrEmpty(graphics_set)) {
-			BaseGraphics::SetSet(NULL);
+			BaseGraphics::SetSet(nullptr);
 
 			ErrorMessageData msg(STR_CONFIG_ERROR, STR_CONFIG_ERROR_INVALID_BASE_GRAPHICS_NOT_FOUND);
 			msg.SetDParamStr(0, graphics_set);
@@ -745,7 +745,7 @@ int openttd_main(int argc, char *argv[])
 	GfxInitPalettes();
 
 	DEBUG(misc, 1, "Loading blitter...");
-	if (blitter == NULL && _ini_blitter != NULL) blitter = stredup(_ini_blitter);
+	if (blitter == nullptr && _ini_blitter != nullptr) blitter = stredup(_ini_blitter);
 	_blitter_autodetected = StrEmpty(blitter);
 	/* Activate the initial blitter.
 	 * This is only some initial guess, after NewGRFs have been loaded SwitchNewGRFBlitter may switch to a different one.
@@ -754,9 +754,9 @@ int openttd_main(int argc, char *argv[])
 	 *  - Use 8bpp blitter otherwise.
 	 */
 	if (!_blitter_autodetected ||
-			(_support8bpp != S8BPP_NONE && (BaseGraphics::GetUsedSet() == NULL || BaseGraphics::GetUsedSet()->blitter == BLT_8BPP)) ||
-			BlitterFactory::SelectBlitter("32bpp-anim") == NULL) {
-		if (BlitterFactory::SelectBlitter(blitter) == NULL) {
+			(_support8bpp != S8BPP_NONE && (BaseGraphics::GetUsedSet() == nullptr || BaseGraphics::GetUsedSet()->blitter == BLT_8BPP)) ||
+			BlitterFactory::SelectBlitter("32bpp-anim") == nullptr) {
+		if (BlitterFactory::SelectBlitter(blitter) == nullptr) {
 			StrEmpty(blitter) ?
 				usererror("Failed to autoprobe blitter") :
 				usererror("Failed to select requested blitter '%s'; does it exist?", blitter);
@@ -764,7 +764,7 @@ int openttd_main(int argc, char *argv[])
 	}
 	free(blitter);
 
-	if (videodriver == NULL && _ini_videodriver != NULL) videodriver = stredup(_ini_videodriver);
+	if (videodriver == nullptr && _ini_videodriver != nullptr) videodriver = stredup(_ini_videodriver);
 	DriverFactoryBase::SelectDriver(videodriver, Driver::DT_VIDEO);
 	free(videodriver);
 
@@ -775,15 +775,15 @@ int openttd_main(int argc, char *argv[])
 
 	NetworkStartUp(); // initialize network-core
 
-	if (debuglog_conn != NULL && _network_available) {
-		const char *not_used = NULL;
-		const char *port = NULL;
+	if (debuglog_conn != nullptr && _network_available) {
+		const char *not_used = nullptr;
+		const char *port = nullptr;
 		uint16 rport;
 
 		rport = NETWORK_DEFAULT_DEBUGLOG_PORT;
 
 		ParseConnectionString(&not_used, &port, debuglog_conn);
-		if (port != NULL) rport = atoi(port);
+		if (port != nullptr) rport = atoi(port);
 
 		NetworkStartDebugLog(NetworkAddress(debuglog_conn, rport));
 	}
@@ -800,9 +800,9 @@ int openttd_main(int argc, char *argv[])
 	InitializeScreenshotFormats();
 
 	BaseSounds::FindSets();
-	if (sounds_set == NULL && BaseSounds::ini_set != NULL) sounds_set = stredup(BaseSounds::ini_set);
+	if (sounds_set == nullptr && BaseSounds::ini_set != nullptr) sounds_set = stredup(BaseSounds::ini_set);
 	if (!BaseSounds::SetSet(sounds_set)) {
-		if (StrEmpty(sounds_set) || !BaseSounds::SetSet(NULL)) {
+		if (StrEmpty(sounds_set) || !BaseSounds::SetSet(nullptr)) {
 			usererror("Failed to find a sounds set. Please acquire a sounds set for OpenTTD. See section 4.1 of README.md.");
 		} else {
 			ErrorMessageData msg(STR_CONFIG_ERROR, STR_CONFIG_ERROR_INVALID_BASE_SOUNDS_NOT_FOUND);
@@ -813,9 +813,9 @@ int openttd_main(int argc, char *argv[])
 	free(sounds_set);
 
 	BaseMusic::FindSets();
-	if (music_set == NULL && BaseMusic::ini_set != NULL) music_set = stredup(BaseMusic::ini_set);
+	if (music_set == nullptr && BaseMusic::ini_set != nullptr) music_set = stredup(BaseMusic::ini_set);
 	if (!BaseMusic::SetSet(music_set)) {
-		if (StrEmpty(music_set) || !BaseMusic::SetSet(NULL)) {
+		if (StrEmpty(music_set) || !BaseMusic::SetSet(nullptr)) {
 			usererror("Failed to find a music set. Please acquire a music set for OpenTTD. See section 4.1 of README.md.");
 		} else {
 			ErrorMessageData msg(STR_CONFIG_ERROR, STR_CONFIG_ERROR_INVALID_BASE_MUSIC_NOT_FOUND);
@@ -825,11 +825,11 @@ int openttd_main(int argc, char *argv[])
 	}
 	free(music_set);
 
-	if (sounddriver == NULL && _ini_sounddriver != NULL) sounddriver = stredup(_ini_sounddriver);
+	if (sounddriver == nullptr && _ini_sounddriver != nullptr) sounddriver = stredup(_ini_sounddriver);
 	DriverFactoryBase::SelectDriver(sounddriver, Driver::DT_SOUND);
 	free(sounddriver);
 
-	if (musicdriver == NULL && _ini_musicdriver != NULL) musicdriver = stredup(_ini_musicdriver);
+	if (musicdriver == nullptr && _ini_musicdriver != nullptr) musicdriver = stredup(_ini_musicdriver);
 	DriverFactoryBase::SelectDriver(musicdriver, Driver::DT_MUSIC);
 	free(musicdriver);
 
@@ -852,7 +852,7 @@ int openttd_main(int argc, char *argv[])
 
 	/* ScanNewGRFFiles now has control over the scanner. */
 	ScanNewGRFFiles(scanner);
-	scanner = NULL;
+	scanner = nullptr;
 
 	VideoDriver::GetInstance()->MainLoop();
 
@@ -897,7 +897,7 @@ exit_normal:
 	delete scanner;
 
 	extern FILE *_log_fd;
-	if (_log_fd != NULL) {
+	if (_log_fd != nullptr) {
 		fclose(_log_fd);
 	}
 
@@ -994,17 +994,17 @@ static void MakeNewEditorWorld()
  * @param fop mode of loading, always SLO_LOAD
  * @param newgm switch to this mode of loading fails due to some unknown error
  * @param subdir default directory to look for filename, set to 0 if not needed
- * @param lf Load filter to use, if NULL: use filename + subdir.
+ * @param lf Load filter to use, if nullptr: use filename + subdir.
  */
-bool SafeLoad(const char *filename, SaveLoadOperation fop, DetailedFileType dft, GameMode newgm, Subdirectory subdir, struct LoadFilter *lf = NULL)
+bool SafeLoad(const char *filename, SaveLoadOperation fop, DetailedFileType dft, GameMode newgm, Subdirectory subdir, struct LoadFilter *lf = nullptr)
 {
 	assert(fop == SLO_LOAD);
-	assert(dft == DFT_GAME_FILE || (lf == NULL && dft == DFT_OLD_GAME_FILE));
+	assert(dft == DFT_GAME_FILE || (lf == nullptr && dft == DFT_OLD_GAME_FILE));
 	GameMode ogm = _game_mode;
 
 	_game_mode = newgm;
 
-	switch (lf == NULL ? SaveOrLoad(filename, fop, dft, subdir) : LoadWithFilter(lf)) {
+	switch (lf == nullptr ? SaveOrLoad(filename, fop, dft, subdir) : LoadWithFilter(lf)) {
 		case SL_OK: return true;
 
 		case SL_REINIT:
@@ -1139,7 +1139,7 @@ void SwitchToMode(SwitchMode new_mode)
 
 		case SM_MENU: // Switch to game intro menu
 			LoadIntroGame();
-			if (BaseSounds::ini_set == NULL && BaseSounds::GetUsedSet()->fallback) {
+			if (BaseSounds::ini_set == nullptr && BaseSounds::GetUsedSet()->fallback) {
 				ShowErrorMessage(STR_WARNING_FALLBACK_SOUNDSET, INVALID_STRING_ID, WL_CRITICAL);
 				BaseSounds::ini_set = stredup(BaseSounds::GetUsedSet()->name);
 			}
@@ -1235,7 +1235,7 @@ static void CheckCaches()
 		if (v != v->First() || v->vehstatus & VS_CRASHED || !v->IsPrimaryVehicle()) continue;
 
 		uint length = 0;
-		for (const Vehicle *u = v; u != NULL; u = u->Next()) length++;
+		for (const Vehicle *u = v; u != nullptr; u = u->Next()) length++;
 
 		NewGRFCache        *grf_cache = CallocT<NewGRFCache>(length);
 		VehicleCache       *veh_cache = CallocT<VehicleCache>(length);
@@ -1243,7 +1243,7 @@ static void CheckCaches()
 		TrainCache         *tra_cache = CallocT<TrainCache>(length);
 
 		length = 0;
-		for (const Vehicle *u = v; u != NULL; u = u->Next()) {
+		for (const Vehicle *u = v; u != nullptr; u = u->Next()) {
 			FillNewGRFVehicleCache(u);
 			grf_cache[length] = u->grf_cache;
 			veh_cache[length] = u->vcache;
@@ -1270,7 +1270,7 @@ static void CheckCaches()
 		}
 
 		length = 0;
-		for (const Vehicle *u = v; u != NULL; u = u->Next()) {
+		for (const Vehicle *u = v; u != nullptr; u = u->Next()) {
 			FillNewGRFVehicleCache(u);
 			if (memcmp(&grf_cache[length], &u->grf_cache, sizeof(NewGRFCache)) != 0) {
 				DEBUG(desync, 2, "newgrf cache mismatch: type %i, vehicle %i, company %i, unit number %i, wagon %i", (int)v->type, v->index, (int)v->owner, v->unitnumber, length);
diff --git a/src/order_backup.cpp b/src/order_backup.cpp
--- a/src/order_backup.cpp
+++ b/src/order_backup.cpp
@@ -30,7 +30,7 @@ OrderBackup::~OrderBackup()
 	if (CleaningPool()) return;
 
 	Order *o = this->orders;
-	while (o != NULL) {
+	while (o != nullptr) {
 		Order *next = o->next;
 		delete o;
 		o = next;
@@ -75,11 +75,11 @@ OrderBackup::OrderBackup(const Vehicle *
 void OrderBackup::DoRestore(Vehicle *v)
 {
 	/* If we had shared orders, recover that */
-	if (this->clone != NULL) {
+	if (this->clone != nullptr) {
 		DoCommand(0, v->index | CO_SHARE << 30, this->clone->index, DC_EXEC, CMD_CLONE_ORDER);
-	} else if (this->orders != NULL && OrderList::CanAllocateItem()) {
+	} else if (this->orders != nullptr && OrderList::CanAllocateItem()) {
 		v->orders.list = new OrderList(this->orders, v);
-		this->orders = NULL;
+		this->orders = nullptr;
 		/* Make sure buoys/oil rigs are updated in the station list. */
 		InvalidateWindowClassesData(WC_STATION_LIST, 0);
 	}
@@ -206,7 +206,7 @@ CommandCost CmdClearOrderBackup(TileInde
 			/* We need to circumvent the "prevention" from this command being executed
 			 * while the game is paused, so use the internal method. Nor do we want
 			 * this command to get its cost estimated when shift is pressed. */
-			DoCommandPInternal(ob->tile, 0, user, CMD_CLEAR_ORDER_BACKUP, NULL, NULL, true, false);
+			DoCommandPInternal(ob->tile, 0, user, CMD_CLEAR_ORDER_BACKUP, nullptr, nullptr, true, false);
 		} else {
 			/* The command came from the game logic, i.e. the clearing of a tile.
 			 * In that case we have no need to actually sync this, just do it. */
@@ -230,20 +230,20 @@ CommandCost CmdClearOrderBackup(TileInde
 /**
  * Clear/update the (clone) vehicle from an order backup.
  * @param v The vehicle to clear.
- * @pre v != NULL
+ * @pre v != nullptr
  * @note If it is not possible to set another vehicle as clone
  *       "example", then this backed up order will be removed.
  */
 /* static */ void OrderBackup::ClearVehicle(const Vehicle *v)
 {
-	assert(v != NULL);
+	assert(v != nullptr);
 	OrderBackup *ob;
 	FOR_ALL_ORDER_BACKUPS(ob) {
 		if (ob->clone == v) {
 			/* Get another item in the shared list. */
 			ob->clone = (v->FirstShared() == v) ? v->NextShared() : v->FirstShared();
 			/* But if that isn't there, remove it. */
-			if (ob->clone == NULL) delete ob;
+			if (ob->clone == nullptr) delete ob;
 		}
 	}
 }
@@ -260,7 +260,7 @@ CommandCost CmdClearOrderBackup(TileInde
 {
 	OrderBackup *ob;
 	FOR_ALL_ORDER_BACKUPS(ob) {
-		for (Order *order = ob->orders; order != NULL; order = order->next) {
+		for (Order *order = ob->orders; order != nullptr; order = order->next) {
 			OrderType ot = order->GetType();
 			if (ot == OT_GOTO_DEPOT && (order->GetDepotActionType() & ODATFB_NEAREST_DEPOT) != 0) continue;
 			if (ot == OT_GOTO_DEPOT && hangar && !IsHangarTile(ob->tile)) continue; // Not an aircraft? Can't have a hangar order.
diff --git a/src/order_base.h b/src/order_base.h
--- a/src/order_base.h
+++ b/src/order_base.h
@@ -48,7 +48,7 @@ private:
 	uint16 max_speed;    ///< How fast the vehicle may go on the way to the destination.
 
 public:
-	Order *next;          ///< Pointer to next order. If NULL, end of list
+	Order *next;          ///< Pointer to next order. If nullptr, end of list
 
 	Order() : flags(0), refit_cargo(CT_NO_REFIT), max_speed(UINT16_MAX) {}
 	~Order();
@@ -268,7 +268,7 @@ private:
 public:
 	/** Default constructor producing an invalid order list. */
 	OrderList(VehicleOrderID num_orders = INVALID_VEH_ORDER_ID)
-		: first(NULL), num_orders(num_orders), num_manual_orders(0), num_vehicles(0), first_shared(NULL),
+		: first(nullptr), num_orders(num_orders), num_manual_orders(0), num_vehicles(0), first_shared(nullptr),
 		  timetable_duration(0), total_duration(0) { }
 
 	/**
@@ -303,7 +303,7 @@ public:
 	 * @param curr Order to find the next one for.
 	 * @return Next order.
 	 */
-	inline const Order *GetNext(const Order *curr) const { return (curr->next == NULL) ? this->GetFirstOrder() : curr->next; }
+	inline const Order *GetNext(const Order *curr) const { return (curr->next == nullptr) ? this->GetFirstOrder() : curr->next; }
 
 	/**
 	 * Get number of orders in the order list.
@@ -317,7 +317,7 @@ public:
 	 */
 	inline VehicleOrderID GetNumManualOrders() const { return this->num_manual_orders; }
 
-	StationIDStack GetNextStoppingStation(const Vehicle *v, const Order *first = NULL, uint hops = 0) const;
+	StationIDStack GetNextStoppingStation(const Vehicle *v, const Order *first = nullptr, uint hops = 0) const;
 	const Order *GetNextDecisionNode(const Order *next, uint hops) const;
 
 	void InsertOrderAt(Order *new_order, int index);
@@ -396,7 +396,7 @@ public:
 #define FOR_ALL_ORDERS(var) FOR_ALL_ORDERS_FROM(var, 0)
 
 
-#define FOR_VEHICLE_ORDERS(v, order) for (order = (v->orders.list == NULL) ? NULL : v->orders.list->GetFirstOrder(); order != NULL; order = order->next)
+#define FOR_VEHICLE_ORDERS(v, order) for (order = (v->orders.list == nullptr) ? nullptr : v->orders.list->GetFirstOrder(); order != nullptr; order = order->next)
 
 
 #define FOR_ALL_ORDER_LISTS_FROM(var, start) FOR_ALL_ITEMS_FROM(OrderList, orderlist_index, var, start)
diff --git a/src/order_cmd.cpp b/src/order_cmd.cpp
--- a/src/order_cmd.cpp
+++ b/src/order_cmd.cpp
@@ -53,7 +53,7 @@ Order::~Order()
 	 * the list of stations. So, we need to invalidate that window if needed. */
 	if (this->IsType(OT_GOTO_STATION) || this->IsType(OT_GOTO_WAYPOINT)) {
 		BaseStation *bs = BaseStation::GetIfValid(this->GetDestination());
-		if (bs != NULL && bs->owner == OWNER_NONE) InvalidateWindowClassesData(WC_STATION_LIST, 0);
+		if (bs != nullptr && bs->owner == OWNER_NONE) InvalidateWindowClassesData(WC_STATION_LIST, 0);
 	}
 }
 
@@ -66,7 +66,7 @@ void Order::Free()
 	this->type  = OT_NOTHING;
 	this->flags = 0;
 	this->dest  = 0;
-	this->next  = NULL;
+	this->next  = nullptr;
 }
 
 /**
@@ -237,7 +237,7 @@ Order::Order(uint32 packed)
 	this->type    = (OrderType)GB(packed,  0,  8);
 	this->flags   = GB(packed,  8,  8);
 	this->dest    = GB(packed, 16, 16);
-	this->next    = NULL;
+	this->next    = nullptr;
 	this->refit_cargo   = CT_NO_REFIT;
 	this->wait_time     = 0;
 	this->travel_time   = 0;
@@ -300,19 +300,19 @@ void OrderList::Initialize(Order *chain,
 	this->timetable_duration = 0;
 	this->total_duration = 0;
 
-	for (Order *o = this->first; o != NULL; o = o->next) {
+	for (Order *o = this->first; o != nullptr; o = o->next) {
 		++this->num_orders;
 		if (!o->IsType(OT_IMPLICIT)) ++this->num_manual_orders;
 		this->timetable_duration += o->GetTimetabledWait() + o->GetTimetabledTravel();
 		this->total_duration += o->GetWaitTime() + o->GetTravelTime();
 	}
 
-	for (Vehicle *u = this->first_shared->PreviousShared(); u != NULL; u = u->PreviousShared()) {
+	for (Vehicle *u = this->first_shared->PreviousShared(); u != nullptr; u = u->PreviousShared()) {
 		++this->num_vehicles;
 		this->first_shared = u;
 	}
 
-	for (const Vehicle *u = v->NextShared(); u != NULL; u = u->NextShared()) ++this->num_vehicles;
+	for (const Vehicle *u = v->NextShared(); u != nullptr; u = u->NextShared()) ++this->num_vehicles;
 }
 
 /**
@@ -323,13 +323,13 @@ void OrderList::Initialize(Order *chain,
 void OrderList::FreeChain(bool keep_orderlist)
 {
 	Order *next;
-	for (Order *o = this->first; o != NULL; o = next) {
+	for (Order *o = this->first; o != nullptr; o = next) {
 		next = o->next;
 		delete o;
 	}
 
 	if (keep_orderlist) {
-		this->first = NULL;
+		this->first = nullptr;
 		this->num_orders = 0;
 		this->num_manual_orders = 0;
 		this->timetable_duration = 0;
@@ -345,11 +345,11 @@ void OrderList::FreeChain(bool keep_orde
  */
 Order *OrderList::GetOrderAt(int index) const
 {
-	if (index < 0) return NULL;
+	if (index < 0) return nullptr;
 
 	Order *order = this->first;
 
-	while (order != NULL && index-- > 0) {
+	while (order != nullptr && index-- > 0) {
 		order = order->next;
 	}
 	return order;
@@ -364,11 +364,11 @@ Order *OrderList::GetOrderAt(int index) 
  *         \li a station order
  *         \li a refitting depot order
  *         \li a non-trivial conditional order
- *         \li NULL  if the vehicle won't stop anymore.
+ *         \li nullptr  if the vehicle won't stop anymore.
  */
 const Order *OrderList::GetNextDecisionNode(const Order *next, uint hops) const
 {
-	if (hops > this->GetNumOrders() || next == NULL) return NULL;
+	if (hops > this->GetNumOrders() || next == nullptr) return nullptr;
 
 	if (next->IsType(OT_CONDITIONAL)) {
 		if (next->GetConditionVariable() != OCV_UNCONDITIONALLY) return next;
@@ -381,7 +381,7 @@ const Order *OrderList::GetNextDecisionN
 	}
 
 	if (next->IsType(OT_GOTO_DEPOT)) {
-		if (next->GetDepotActionType() == ODATFB_HALT) return NULL;
+		if (next->GetDepotActionType() == ODATFB_HALT) return nullptr;
 		if (next->IsRefit()) return next;
 	}
 
@@ -395,7 +395,7 @@ const Order *OrderList::GetNextDecisionN
 /**
  * Recursively determine the next deterministic station to stop at.
  * @param v The vehicle we're looking at.
- * @param first Order to start searching at or NULL to start at cur_implicit_order_index + 1.
+ * @param first Order to start searching at or nullptr to start at cur_implicit_order_index + 1.
  * @param hops Number of orders we have already looked at.
  * @return Next stoppping station or INVALID_STATION.
  * @pre The vehicle is currently loading and v->last_station_visited is meaningful.
@@ -405,17 +405,17 @@ StationIDStack OrderList::GetNextStoppin
 {
 
 	const Order *next = first;
-	if (first == NULL) {
+	if (first == nullptr) {
 		next = this->GetOrderAt(v->cur_implicit_order_index);
-		if (next == NULL) {
+		if (next == nullptr) {
 			next = this->GetFirstOrder();
-			if (next == NULL) return INVALID_STATION;
+			if (next == nullptr) return INVALID_STATION;
 		} else {
-			/* GetNext never returns NULL if there is a valid station in the list.
+			/* GetNext never returns nullptr if there is a valid station in the list.
 			 * As the given "next" is already valid and a station in the list, we
-			 * don't have to check for NULL here. */
+			 * don't have to check for nullptr here. */
 			next = this->GetNext(next);
-			assert(next != NULL);
+			assert(next != nullptr);
 		}
 	}
 
@@ -423,16 +423,16 @@ StationIDStack OrderList::GetNextStoppin
 		next = this->GetNextDecisionNode(next, ++hops);
 
 		/* Resolve possibly nested conditionals by estimation. */
-		while (next != NULL && next->IsType(OT_CONDITIONAL)) {
+		while (next != nullptr && next->IsType(OT_CONDITIONAL)) {
 			/* We return both options of conditional orders. */
 			const Order *skip_to = this->GetNextDecisionNode(
 					this->GetOrderAt(next->GetConditionSkipToOrder()), hops);
 			const Order *advance = this->GetNextDecisionNode(
 					this->GetNext(next), hops);
-			if (advance == NULL || advance == first || skip_to == advance) {
-				next = (skip_to == first) ? NULL : skip_to;
-			} else if (skip_to == NULL || skip_to == first) {
-				next = (advance == first) ? NULL : advance;
+			if (advance == nullptr || advance == first || skip_to == advance) {
+				next = (skip_to == first) ? nullptr : skip_to;
+			} else if (skip_to == nullptr || skip_to == first) {
+				next = (advance == first) ? nullptr : advance;
 			} else {
 				StationIDStack st1 = this->GetNextStoppingStation(v, skip_to, hops);
 				StationIDStack st2 = this->GetNextStoppingStation(v, advance, hops);
@@ -443,7 +443,7 @@ StationIDStack OrderList::GetNextStoppin
 		}
 
 		/* Don't return a next stop if the vehicle has to unload everything. */
-		if (next == NULL || ((next->IsType(OT_GOTO_STATION) || next->IsType(OT_IMPLICIT)) &&
+		if (next == nullptr || ((next->IsType(OT_GOTO_STATION) || next->IsType(OT_IMPLICIT)) &&
 				next->GetDestination() == v->last_station_visited &&
 				(next->GetUnloadType() & (OUFB_TRANSFER | OUFB_UNLOAD)) != 0)) {
 			return INVALID_STATION;
@@ -460,7 +460,7 @@ StationIDStack OrderList::GetNextStoppin
  */
 void OrderList::InsertOrderAt(Order *new_order, int index)
 {
-	if (this->first == NULL) {
+	if (this->first == nullptr) {
 		this->first = new_order;
 	} else {
 		if (index == 0) {
@@ -566,7 +566,7 @@ void OrderList::RemoveVehicle(Vehicle *v
  */
 bool OrderList::IsVehicleInSharedOrdersList(const Vehicle *v) const
 {
-	for (const Vehicle *v_shared = this->first_shared; v_shared != NULL; v_shared = v_shared->NextShared()) {
+	for (const Vehicle *v_shared = this->first_shared; v_shared != nullptr; v_shared = v_shared->NextShared()) {
 		if (v_shared == v) return true;
 	}
 
@@ -581,7 +581,7 @@ bool OrderList::IsVehicleInSharedOrdersL
 int OrderList::GetPositionInSharedOrderList(const Vehicle *v) const
 {
 	int count = 0;
-	for (const Vehicle *v_shared = v->PreviousShared(); v_shared != NULL; v_shared = v_shared->PreviousShared()) count++;
+	for (const Vehicle *v_shared = v->PreviousShared(); v_shared != nullptr; v_shared = v_shared->PreviousShared()) count++;
 	return count;
 }
 
@@ -591,7 +591,7 @@ int OrderList::GetPositionInSharedOrderL
  */
 bool OrderList::IsCompleteTimetable() const
 {
-	for (Order *o = this->first; o != NULL; o = o->next) {
+	for (Order *o = this->first; o != nullptr; o = o->next) {
 		/* Implicit orders are, by definition, not timetabled. */
 		if (o->IsType(OT_IMPLICIT)) continue;
 		if (!o->IsCompletelyTimetabled()) return false;
@@ -612,7 +612,7 @@ void OrderList::DebugCheckSanity() const
 
 	DEBUG(misc, 6, "Checking OrderList %hu for sanity...", this->index);
 
-	for (const Order *o = this->first; o != NULL; o = o->next) {
+	for (const Order *o = this->first; o != nullptr; o = o->next) {
 		++check_num_orders;
 		if (!o->IsType(OT_IMPLICIT)) ++check_num_manual_orders;
 		check_timetable_duration += o->GetTimetabledWait() + o->GetTimetabledTravel();
@@ -623,7 +623,7 @@ void OrderList::DebugCheckSanity() const
 	assert(this->timetable_duration == check_timetable_duration);
 	assert(this->total_duration == check_total_duration);
 
-	for (const Vehicle *v = this->first_shared; v != NULL; v = v->NextShared()) {
+	for (const Vehicle *v = this->first_shared; v != nullptr; v = v->NextShared()) {
 		++check_num_vehicles;
 		assert(v->orders.list == this);
 	}
@@ -702,7 +702,7 @@ uint GetOrderDistance(const Order *prev,
 		conditional_depth++;
 
 		int dist1 = GetOrderDistance(prev, v->GetOrder(cur->GetConditionSkipToOrder()), v, conditional_depth);
-		int dist2 = GetOrderDistance(prev, cur->next == NULL ? v->orders.list->GetFirstOrder() : cur->next, v, conditional_depth);
+		int dist2 = GetOrderDistance(prev, cur->next == nullptr ? v->orders.list->GetFirstOrder() : cur->next, v, conditional_depth);
 		return max(dist1, dist2);
 	}
 
@@ -732,7 +732,7 @@ CommandCost CmdInsertOrder(TileIndex til
 	Order new_order(p2);
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle()) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -742,7 +742,7 @@ CommandCost CmdInsertOrder(TileIndex til
 	switch (new_order.GetType()) {
 		case OT_GOTO_STATION: {
 			const Station *st = Station::GetIfValid(new_order.GetDestination());
-			if (st == NULL) return CMD_ERROR;
+			if (st == nullptr) return CMD_ERROR;
 
 			if (st->owner != OWNER_NONE) {
 				CommandCost ret = CheckOwnership(st->owner);
@@ -750,7 +750,7 @@ CommandCost CmdInsertOrder(TileIndex til
 			}
 
 			if (!CanVehicleUseStation(v, st)) return_cmd_error(STR_ERROR_CAN_T_ADD_ORDER);
-			for (Vehicle *u = v->FirstShared(); u != NULL; u = u->NextShared()) {
+			for (Vehicle *u = v->FirstShared(); u != nullptr; u = u->NextShared()) {
 				if (!CanVehicleUseStation(u, st)) return_cmd_error(STR_ERROR_CAN_T_ADD_ORDER_SHARED);
 			}
 
@@ -789,7 +789,7 @@ CommandCost CmdInsertOrder(TileIndex til
 				if (v->type == VEH_AIRCRAFT) {
 					const Station *st = Station::GetIfValid(new_order.GetDestination());
 
-					if (st == NULL) return CMD_ERROR;
+					if (st == nullptr) return CMD_ERROR;
 
 					CommandCost ret = CheckOwnership(st->owner);
 					if (ret.Failed()) return ret;
@@ -800,7 +800,7 @@ CommandCost CmdInsertOrder(TileIndex til
 				} else {
 					const Depot *dp = Depot::GetIfValid(new_order.GetDestination());
 
-					if (dp == NULL) return CMD_ERROR;
+					if (dp == nullptr) return CMD_ERROR;
 
 					CommandCost ret = CheckOwnership(GetTileOwner(dp->xy));
 					if (ret.Failed()) return ret;
@@ -832,7 +832,7 @@ CommandCost CmdInsertOrder(TileIndex til
 
 		case OT_GOTO_WAYPOINT: {
 			const Waypoint *wp = Waypoint::GetIfValid(new_order.GetDestination());
-			if (wp == NULL) return CMD_ERROR;
+			if (wp == nullptr) return CMD_ERROR;
 
 			switch (v->type) {
 				default: return CMD_ERROR;
@@ -897,7 +897,7 @@ CommandCost CmdInsertOrder(TileIndex til
 
 	if (v->GetNumOrders() >= MAX_VEH_ORDER_ID) return_cmd_error(STR_ERROR_TOO_MANY_ORDERS);
 	if (!Order::CanAllocateItem()) return_cmd_error(STR_ERROR_NO_MORE_SPACE_FOR_ORDERS);
-	if (v->orders.list == NULL && !OrderList::CanAllocateItem()) return_cmd_error(STR_ERROR_NO_MORE_SPACE_FOR_ORDERS);
+	if (v->orders.list == nullptr && !OrderList::CanAllocateItem()) return_cmd_error(STR_ERROR_NO_MORE_SPACE_FOR_ORDERS);
 
 	if (flags & DC_EXEC) {
 		Order *new_o = new Order();
@@ -917,7 +917,7 @@ CommandCost CmdInsertOrder(TileIndex til
 void InsertOrder(Vehicle *v, Order *new_o, VehicleOrderID sel_ord)
 {
 	/* Create new order and link in list */
-	if (v->orders.list == NULL) {
+	if (v->orders.list == nullptr) {
 		v->orders.list = new OrderList(new_o, v);
 	} else {
 		v->orders.list->InsertOrderAt(new_o, sel_ord);
@@ -925,7 +925,7 @@ void InsertOrder(Vehicle *v, Order *new_
 
 	Vehicle *u = v->FirstShared();
 	DeleteOrderWarnings(u);
-	for (; u != NULL; u = u->NextShared()) {
+	for (; u != nullptr; u = u->NextShared()) {
 		assert(v->orders.list == u->orders.list);
 
 		/* If there is added an order before the current one, we need
@@ -1008,7 +1008,7 @@ CommandCost CmdDeleteOrder(TileIndex til
 
 	Vehicle *v = Vehicle::GetIfValid(veh_id);
 
-	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle()) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -1016,7 +1016,7 @@ CommandCost CmdDeleteOrder(TileIndex til
 	/* If we did not select an order, we maybe want to de-clone the orders */
 	if (sel_ord >= v->GetNumOrders()) return DecloneOrder(v, flags);
 
-	if (v->GetOrder(sel_ord) == NULL) return CMD_ERROR;
+	if (v->GetOrder(sel_ord) == nullptr) return CMD_ERROR;
 
 	if (flags & DC_EXEC) DeleteOrder(v, sel_ord);
 	return CommandCost();
@@ -1048,7 +1048,7 @@ void DeleteOrder(Vehicle *v, VehicleOrde
 
 	Vehicle *u = v->FirstShared();
 	DeleteOrderWarnings(u);
-	for (; u != NULL; u = u->NextShared()) {
+	for (; u != nullptr; u = u->NextShared()) {
 		assert(v->orders.list == u->orders.list);
 
 		if (sel_ord == u->cur_real_order_index && u->current_order.IsType(OT_LOADING)) {
@@ -1080,7 +1080,7 @@ void DeleteOrder(Vehicle *v, VehicleOrde
 
 	/* As we delete an order, the order to skip to will be 'wrong'. */
 	VehicleOrderID cur_order_id = 0;
-	Order *order = NULL;
+	Order *order = nullptr;
 	FOR_VEHICLE_ORDERS(v, order) {
 		if (order->IsType(OT_CONDITIONAL)) {
 			VehicleOrderID order_id = order->GetConditionSkipToOrder();
@@ -1114,7 +1114,7 @@ CommandCost CmdSkipToOrder(TileIndex til
 
 	Vehicle *v = Vehicle::GetIfValid(veh_id);
 
-	if (v == NULL || !v->IsPrimaryVehicle() || sel_ord == v->cur_implicit_order_index || sel_ord >= v->GetNumOrders() || v->GetNumOrders() < 2) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle() || sel_ord == v->cur_implicit_order_index || sel_ord >= v->GetNumOrders() || v->GetNumOrders() < 2) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -1155,7 +1155,7 @@ CommandCost CmdMoveOrder(TileIndex tile,
 	VehicleOrderID target_order = GB(p2, 16, 16);
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle()) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -1166,7 +1166,7 @@ CommandCost CmdMoveOrder(TileIndex tile,
 
 	Order *moving_one = v->GetOrder(moving_order);
 	/* Don't move an empty order */
-	if (moving_one == NULL) return CMD_ERROR;
+	if (moving_one == nullptr) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
 		v->orders.list->MoveOrder(moving_order, target_order);
@@ -1176,7 +1176,7 @@ CommandCost CmdMoveOrder(TileIndex tile,
 
 		DeleteOrderWarnings(u);
 
-		for (; u != NULL; u = u->NextShared()) {
+		for (; u != nullptr; u = u->NextShared()) {
 			/* Update the current order.
 			 * There are multiple ways to move orders, which result in cur_implicit_order_index
 			 * and cur_real_order_index to not longer make any sense. E.g. moving another
@@ -1262,7 +1262,7 @@ CommandCost CmdModifyOrder(TileIndex til
 	if (mof >= MOF_END) return CMD_ERROR;
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle()) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -1459,7 +1459,7 @@ CommandCost CmdModifyOrder(TileIndex til
 		/* Update the windows and full load flags, also for vehicles that share the same order list */
 		Vehicle *u = v->FirstShared();
 		DeleteOrderWarnings(u);
-		for (; u != NULL; u = u->NextShared()) {
+		for (; u != nullptr; u = u->NextShared()) {
 			/* Toggle u->current_order "Full load" flag if it changed.
 			 * However, as the same flag is used for depot orders, check
 			 * whether we are not going to a depot as there are three
@@ -1490,17 +1490,17 @@ CommandCost CmdModifyOrder(TileIndex til
  */
 static bool CheckAircraftOrderDistance(const Aircraft *v_new, const Vehicle *v_order, const Order *first)
 {
-	if (first == NULL || v_new->acache.cached_max_range == 0) return true;
+	if (first == nullptr || v_new->acache.cached_max_range == 0) return true;
 
 	/* Iterate over all orders to check the distance between all
 	 * 'goto' orders and their respective next order (of any type). */
-	for (const Order *o = first; o != NULL; o = o->next) {
+	for (const Order *o = first; o != nullptr; o = o->next) {
 		switch (o->GetType()) {
 			case OT_GOTO_STATION:
 			case OT_GOTO_DEPOT:
 			case OT_GOTO_WAYPOINT:
 				/* If we don't have a next order, we've reached the end and must check the first order instead. */
-				if (GetOrderDistance(o, o->next != NULL ? o->next : first, v_order) > v_new->acache.cached_max_range_sqr) return false;
+				if (GetOrderDistance(o, o->next != nullptr ? o->next : first, v_order) > v_new->acache.cached_max_range_sqr) return false;
 				break;
 
 			default: break;
@@ -1527,7 +1527,7 @@ CommandCost CmdCloneOrder(TileIndex tile
 	VehicleID veh_dst = GB(p1, 0, 20);
 
 	Vehicle *dst = Vehicle::GetIfValid(veh_dst);
-	if (dst == NULL || !dst->IsPrimaryVehicle()) return CMD_ERROR;
+	if (dst == nullptr || !dst->IsPrimaryVehicle()) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(dst->owner);
 	if (ret.Failed()) return ret;
@@ -1537,7 +1537,7 @@ CommandCost CmdCloneOrder(TileIndex tile
 			Vehicle *src = Vehicle::GetIfValid(veh_src);
 
 			/* Sanity checks */
-			if (src == NULL || !src->IsPrimaryVehicle() || dst->type != src->type || dst == src) return CMD_ERROR;
+			if (src == nullptr || !src->IsPrimaryVehicle() || dst->type != src->type || dst == src) return CMD_ERROR;
 
 			CommandCost ret = CheckOwnership(src->owner);
 			if (ret.Failed()) return ret;
@@ -1569,7 +1569,7 @@ CommandCost CmdCloneOrder(TileIndex tile
 				return_cmd_error(STR_ERROR_AIRCRAFT_NOT_ENOUGH_RANGE);
 			}
 
-			if (src->orders.list == NULL && !OrderList::CanAllocateItem()) {
+			if (src->orders.list == nullptr && !OrderList::CanAllocateItem()) {
 				return_cmd_error(STR_ERROR_NO_MORE_SPACE_FOR_ORDERS);
 			}
 
@@ -1596,7 +1596,7 @@ CommandCost CmdCloneOrder(TileIndex tile
 			Vehicle *src = Vehicle::GetIfValid(veh_src);
 
 			/* Sanity checks */
-			if (src == NULL || !src->IsPrimaryVehicle() || dst->type != src->type || dst == src) return CMD_ERROR;
+			if (src == nullptr || !src->IsPrimaryVehicle() || dst->type != src->type || dst == src) return CMD_ERROR;
 
 			CommandCost ret = CheckOwnership(src->owner);
 			if (ret.Failed()) return ret;
@@ -1623,7 +1623,7 @@ CommandCost CmdCloneOrder(TileIndex tile
 
 			if (flags & DC_EXEC) {
 				const Order *order;
-				Order *first = NULL;
+				Order *first = nullptr;
 				Order **order_dst;
 
 				/* If the destination vehicle had an order list, destroy the chain but keep the OrderList.
@@ -1637,10 +1637,10 @@ CommandCost CmdCloneOrder(TileIndex tile
 					(*order_dst)->AssignOrder(*order);
 					order_dst = &(*order_dst)->next;
 				}
-				if (dst->orders.list == NULL) {
+				if (dst->orders.list == nullptr) {
 					dst->orders.list = new OrderList(first, dst);
 				} else {
-					assert(dst->orders.list->GetFirstOrder() == NULL);
+					assert(dst->orders.list->GetFirstOrder() == nullptr);
 					assert(!dst->orders.list->IsShared());
 					delete dst->orders.list;
 					assert(OrderList::CanAllocateItem());
@@ -1681,13 +1681,13 @@ CommandCost CmdOrderRefit(TileIndex tile
 	if (cargo >= NUM_CARGO && cargo != CT_NO_REFIT && cargo != CT_AUTO_REFIT) return CMD_ERROR;
 
 	const Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle()) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
 
 	Order *order = v->GetOrder(order_number);
-	if (order == NULL) return CMD_ERROR;
+	if (order == nullptr) return CMD_ERROR;
 
 	/* Automatic refit cargo is only supported for goto station orders. */
 	if (cargo == CT_AUTO_REFIT && !order->IsType(OT_GOTO_STATION)) return CMD_ERROR;
@@ -1703,7 +1703,7 @@ CommandCost CmdOrderRefit(TileIndex tile
 			order->SetDepotActionType((OrderDepotActionFlags)(order->GetDepotActionType() & ~ODATFB_HALT));
 		}
 
-		for (Vehicle *u = v->FirstShared(); u != NULL; u = u->NextShared()) {
+		for (Vehicle *u = v->FirstShared(); u != nullptr; u = u->NextShared()) {
 			/* Update any possible open window of the vehicle */
 			InvalidateVehicleOrder(u, VIWD_MODIFY_ORDERS);
 
@@ -1781,7 +1781,7 @@ void CheckOrders(const Vehicle *v)
 		if (n_st < 2 && message == INVALID_STRING_ID) message = STR_NEWS_VEHICLE_HAS_TOO_FEW_ORDERS;
 
 #ifndef NDEBUG
-		if (v->orders.list != NULL) v->orders.list->DebugCheckSanity();
+		if (v->orders.list != nullptr) v->orders.list->DebugCheckSanity();
 #endif
 
 		/* We don't have a problem */
@@ -1836,7 +1836,7 @@ restart:
 				if (order->IsType(OT_IMPLICIT)) {
 					order = order->next; // DeleteOrder() invalidates current order
 					DeleteOrder(v, id);
-					if (order != NULL) goto restart;
+					if (order != nullptr) goto restart;
 					break;
 				}
 
@@ -1853,7 +1853,7 @@ restart:
 				order->MakeDummy();
 				order->SetTravelTimetabled(travel_timetabled);
 
-				for (const Vehicle *w = v->FirstShared(); w != NULL; w = w->NextShared()) {
+				for (const Vehicle *w = v->FirstShared(); w != nullptr; w = w->NextShared()) {
 					/* In GUI, simulate by removing the order and adding it back */
 					InvalidateVehicleOrder(w, id | (INVALID_VEH_ORDER_ID << 8));
 					InvalidateVehicleOrder(w, (INVALID_VEH_ORDER_ID << 8) | id);
@@ -1896,11 +1896,11 @@ void DeleteVehicleOrders(Vehicle *v, boo
 	if (v->IsOrderListShared()) {
 		/* Remove ourself from the shared order list. */
 		v->RemoveFromShared();
-		v->orders.list = NULL;
-	} else if (v->orders.list != NULL) {
+		v->orders.list = nullptr;
+	} else if (v->orders.list != nullptr) {
 		/* Remove the orders */
 		v->orders.list->FreeChain(keep_orderlist);
-		if (!keep_orderlist) v->orders.list = NULL;
+		if (!keep_orderlist) v->orders.list = nullptr;
 	}
 
 	if (reset_order_indices) {
@@ -1982,7 +1982,7 @@ VehicleOrderID ProcessConditionalOrder(c
 	uint16 value = order->GetConditionValue();
 
 	switch (order->GetConditionVariable()) {
-		case OCV_LOAD_PERCENTAGE:    skip_order = OrderConditionCompare(occ, CalcPercentVehicleFilled(v, NULL), value); break;
+		case OCV_LOAD_PERCENTAGE:    skip_order = OrderConditionCompare(occ, CalcPercentVehicleFilled(v, nullptr), value); break;
 		case OCV_RELIABILITY:        skip_order = OrderConditionCompare(occ, ToPercent16(v->reliability),       value); break;
 		case OCV_MAX_RELIABILITY:    skip_order = OrderConditionCompare(occ, ToPercent16(v->GetEngine()->reliability),   value); break;
 		case OCV_MAX_SPEED:          skip_order = OrderConditionCompare(occ, v->GetDisplayMaxSpeed() * 10 / 16, value); break;
@@ -2109,12 +2109,12 @@ bool UpdateOrderDest(Vehicle *v, const O
 
 	/* Get the current order */
 	order = v->GetOrder(v->cur_real_order_index);
-	if (order != NULL && order->IsType(OT_IMPLICIT)) {
+	if (order != nullptr && order->IsType(OT_IMPLICIT)) {
 		assert(v->GetNumManualOrders() == 0);
-		order = NULL;
+		order = nullptr;
 	}
 
-	if (order == NULL) {
+	if (order == nullptr) {
 		v->current_order.Free();
 		v->SetDestTile(0);
 		return false;
@@ -2177,13 +2177,13 @@ bool ProcessOrders(Vehicle *v)
 	v->UpdateRealOrderIndex();
 
 	const Order *order = v->GetOrder(v->cur_real_order_index);
-	if (order != NULL && order->IsType(OT_IMPLICIT)) {
+	if (order != nullptr && order->IsType(OT_IMPLICIT)) {
 		assert(v->GetNumManualOrders() == 0);
-		order = NULL;
+		order = nullptr;
 	}
 
 	/* If no order, do nothing. */
-	if (order == NULL || (v->type == VEH_AIRCRAFT && !CheckForValidOrders(v))) {
+	if (order == nullptr || (v->type == VEH_AIRCRAFT && !CheckForValidOrders(v))) {
 		if (v->type == VEH_AIRCRAFT) {
 			/* Aircraft do something vastly different here, so handle separately */
 			extern void HandleMissingAircraftOrders(Aircraft *v);
diff --git a/src/order_gui.cpp b/src/order_gui.cpp
--- a/src/order_gui.cpp
+++ b/src/order_gui.cpp
@@ -239,7 +239,7 @@ void DrawOrderString(const Vehicle *v, c
 
 	/* Check range for aircraft. */
 	if (v->type == VEH_AIRCRAFT && Aircraft::From(v)->GetRange() > 0 && order->IsGotoOrder()) {
-		const Order *next = order->next != NULL ? order->next : v->GetFirstOrder();
+		const Order *next = order->next != nullptr ? order->next : v->GetFirstOrder();
 		if (GetOrderDistance(order, next, v) > Aircraft::From(v)->acache.cached_max_range_sqr) SetDParam(8, STR_ORDER_OUT_OF_RANGE);
 	}
 
@@ -576,7 +576,7 @@ private:
 		VehicleOrderID sel_ord = this->OrderGetSel();
 		const Order *order = this->vehicle->GetOrder(sel_ord);
 
-		if (order == NULL || order->GetLoadType() == load_type) return;
+		if (order == nullptr || order->GetLoadType() == load_type) return;
 
 		if (load_type < 0) {
 			load_type = order->GetLoadType() == OLF_LOAD_IF_POSSIBLE ? OLF_FULL_LOAD_ANY : OLF_LOAD_IF_POSSIBLE;
@@ -601,7 +601,7 @@ private:
 
 		if (i < 0) {
 			const Order *order = this->vehicle->GetOrder(sel_ord);
-			if (order == NULL) return;
+			if (order == nullptr) return;
 			i = (order->GetDepotOrderType() & ODTFB_SERVICE) ? DA_ALWAYS_GO : DA_SERVICE;
 		}
 		DoCommandP(this->vehicle->tile, this->vehicle->index + (sel_ord << 20), MOF_DEPOT_ACTION | (i << 4), CMD_MODIFY_ORDER | CMD_MSG(STR_ERROR_CAN_T_MODIFY_THIS_ORDER));
@@ -613,7 +613,7 @@ private:
 	void OrderClick_NearestDepot()
 	{
 		Order order;
-		order.next = NULL;
+		order.next = nullptr;
 		order.index = 0;
 		order.MakeGoToDepot(0, ODTFB_PART_OF_ORDERS,
 				_settings_client.gui.new_nonstop && this->vehicle->IsGroundVehicle() ? ONSF_NO_STOP_AT_INTERMEDIATE_STATIONS : ONSF_STOP_EVERYWHERE);
@@ -630,7 +630,7 @@ private:
 		VehicleOrderID sel_ord = this->OrderGetSel();
 		const Order *order = this->vehicle->GetOrder(sel_ord);
 
-		if (order == NULL || order->GetUnloadType() == unload_type) return;
+		if (order == nullptr || order->GetUnloadType() == unload_type) return;
 
 		if (unload_type < 0) {
 			unload_type = order->GetUnloadType() == OUF_UNLOAD_IF_POSSIBLE ? OUFB_UNLOAD : OUF_UNLOAD_IF_POSSIBLE;
@@ -672,7 +672,7 @@ private:
 		VehicleOrderID sel_ord = this->OrderGetSel();
 		const Order *order = this->vehicle->GetOrder(sel_ord);
 
-		if (order == NULL || order->GetNonStopType() == non_stop) return;
+		if (order == nullptr || order->GetNonStopType() == non_stop) return;
 
 		/* Keypress if negative, so 'toggle' to the next */
 		if (non_stop < 0) {
@@ -760,7 +760,7 @@ private:
 	{
 		this->can_do_refit = false;
 		this->can_do_autorefit = false;
-		for (const Vehicle *w = this->vehicle; w != NULL; w = w->IsGroundVehicle() ? w->Next() : NULL) {
+		for (const Vehicle *w = this->vehicle; w != nullptr; w = w->IsGroundVehicle() ? w->Next() : nullptr) {
 			if (IsEngineRefittable(w->engine_type)) this->can_do_refit = true;
 			if (HasBit(Engine::Get(w->engine_type)->info.misc_flags, EF_AUTO_REFIT)) this->can_do_autorefit = true;
 		}
@@ -953,11 +953,11 @@ public:
 		NWidgetStacked *right_sel     = this->GetWidget<NWidgetStacked>(WID_O_SEL_TOP_RIGHT);
 		/* Ship or airplane. */
 		NWidgetStacked *row_sel = this->GetWidget<NWidgetStacked>(WID_O_SEL_TOP_ROW);
-		assert(row_sel != NULL || (train_row_sel != NULL && left_sel != NULL && middle_sel != NULL && right_sel != NULL));
+		assert(row_sel != nullptr || (train_row_sel != nullptr && left_sel != nullptr && middle_sel != nullptr && right_sel != nullptr));
 
 
-		if (order == NULL) {
-			if (row_sel != NULL) {
+		if (order == nullptr) {
+			if (row_sel != nullptr) {
 				row_sel->SetDisplayedPlane(DP_ROW_LOAD);
 			} else {
 				train_row_sel->SetDisplayedPlane(DP_GROUNDVEHICLE_ROW_NORMAL);
@@ -976,7 +976,7 @@ public:
 
 			switch (order->GetType()) {
 				case OT_GOTO_STATION:
-					if (row_sel != NULL) {
+					if (row_sel != nullptr) {
 						row_sel->SetDisplayedPlane(DP_ROW_LOAD);
 					} else {
 						train_row_sel->SetDisplayedPlane(DP_GROUNDVEHICLE_ROW_NORMAL);
@@ -998,7 +998,7 @@ public:
 					break;
 
 				case OT_GOTO_WAYPOINT:
-					if (row_sel != NULL) {
+					if (row_sel != nullptr) {
 						row_sel->SetDisplayedPlane(DP_ROW_LOAD);
 					} else {
 						train_row_sel->SetDisplayedPlane(DP_GROUNDVEHICLE_ROW_NORMAL);
@@ -1014,7 +1014,7 @@ public:
 					break;
 
 				case OT_GOTO_DEPOT:
-					if (row_sel != NULL) {
+					if (row_sel != nullptr) {
 						row_sel->SetDisplayedPlane(DP_ROW_DEPOT);
 					} else {
 						train_row_sel->SetDisplayedPlane(DP_GROUNDVEHICLE_ROW_NORMAL);
@@ -1033,7 +1033,7 @@ public:
 					break;
 
 				case OT_CONDITIONAL: {
-					if (row_sel != NULL) {
+					if (row_sel != nullptr) {
 						row_sel->SetDisplayedPlane(DP_ROW_CONDITIONAL);
 					} else {
 						train_row_sel->SetDisplayedPlane(DP_GROUNDVEHICLE_ROW_CONDITIONAL);
@@ -1048,7 +1048,7 @@ public:
 				}
 
 				default: // every other order
-					if (row_sel != NULL) {
+					if (row_sel != nullptr) {
 						row_sel->SetDisplayedPlane(DP_ROW_LOAD);
 					} else {
 						train_row_sel->SetDisplayedPlane(DP_GROUNDVEHICLE_ROW_NORMAL);
@@ -1096,7 +1096,7 @@ public:
 		const Order *order = this->vehicle->GetOrder(i);
 		/* First draw the highlighting underground if it exists. */
 		if (this->order_over != INVALID_VEH_ORDER_ID) {
-			while (order != NULL) {
+			while (order != nullptr) {
 				/* Don't draw anything if it extends past the end of the window. */
 				if (!this->vscroll->IsVisible(i)) break;
 
@@ -1121,7 +1121,7 @@ public:
 		}
 
 		/* Draw the orders. */
-		while (order != NULL) {
+		while (order != nullptr) {
 			/* Don't draw anything if it extends past the end of the window. */
 			if (!this->vscroll->IsVisible(i)) break;
 
@@ -1145,7 +1145,7 @@ public:
 				VehicleOrderID sel = this->OrderGetSel();
 				const Order *order = this->vehicle->GetOrder(sel);
 
-				if (order != NULL && order->IsType(OT_CONDITIONAL)) {
+				if (order != nullptr && order->IsType(OT_CONDITIONAL)) {
 					uint value = order->GetConditionValue();
 					if (order->GetConditionVariable() == OCV_MAX_SPEED) value = ConvertSpeedToDisplaySpeed(value);
 					SetDParam(0, value);
@@ -1167,7 +1167,7 @@ public:
 					VehicleOrderID order_id = this->GetOrderFromPt(_cursor.pos.y - this->top);
 					if (order_id != INVALID_VEH_ORDER_ID) {
 						Order order;
-						order.next = NULL;
+						order.next = nullptr;
 						order.index = 0;
 						order.MakeConditional(order_id);
 
@@ -1714,7 +1714,7 @@ void ShowOrdersWindow(const Vehicle *v)
 {
 	DeleteWindowById(WC_VEHICLE_DETAILS, v->index, false);
 	DeleteWindowById(WC_VEHICLE_TIMETABLE, v->index, false);
-	if (BringWindowToFrontById(WC_VEHICLE_ORDERS, v->index) != NULL) return;
+	if (BringWindowToFrontById(WC_VEHICLE_ORDERS, v->index) != nullptr) return;
 
 	/* Using a different WindowDescs for _local_company causes problems.
 	 * Due to this we have to close order windows in ChangeWindowOwner/DeleteCompanyWindows,
diff --git a/src/os/macosx/crashlog_osx.cpp b/src/os/macosx/crashlog_osx.cpp
--- a/src/os/macosx/crashlog_osx.cpp
+++ b/src/os/macosx/crashlog_osx.cpp
@@ -66,7 +66,7 @@ class CrashLogOSX : public CrashLog {
 				" Machine:  %s\n"
 				" Min Ver:  %d\n",
 				ver_maj, ver_min, ver_bug,
-				arch != NULL ? arch->description : "unknown",
+				arch != nullptr ? arch->description : "unknown",
 				MAC_OS_X_VERSION_MIN_REQUIRED
 		);
 	}
@@ -79,7 +79,7 @@ class CrashLogOSX : public CrashLog {
 				" Message: %s\n\n",
 				strsignal(this->signum),
 				this->signum,
-				message == NULL ? "<none>" : message
+				message == nullptr ? "<none>" : message
 		);
 	}
 
@@ -99,14 +99,14 @@ class CrashLogOSX : public CrashLog {
 		frame = (void **)__builtin_frame_address(0);
 #endif
 
-		for (int i = 0; frame != NULL && i < MAX_STACK_FRAMES; i++) {
+		for (int i = 0; frame != nullptr && i < MAX_STACK_FRAMES; i++) {
 			/* Get IP for current stack frame. */
 #if defined(__ppc__) || defined(__ppc64__)
 			void *ip = frame[2];
 #else
 			void *ip = frame[1];
 #endif
-			if (ip == NULL) break;
+			if (ip == nullptr) break;
 
 			/* Print running index. */
 			buffer += seprintf(buffer, last, " [%02d]", i);
@@ -118,7 +118,7 @@ class CrashLogOSX : public CrashLog {
 			if (dl_valid && dli.dli_fname) {
 				/* Valid image name? Extract filename from the complete path. */
 				const char *s = strrchr(dli.dli_fname, '/');
-				if (s != NULL) {
+				if (s != nullptr) {
 					fname = s + 1;
 				} else {
 					fname = dli.dli_fname;
@@ -128,13 +128,13 @@ class CrashLogOSX : public CrashLog {
 			buffer += seprintf(buffer, last, " %-20s " PRINTF_PTR, fname, (uintptr_t)ip);
 
 			/* Print function offset if information is available. */
-			if (dl_valid && dli.dli_sname != NULL && dli.dli_saddr != NULL) {
+			if (dl_valid && dli.dli_sname != nullptr && dli.dli_saddr != nullptr) {
 				/* Try to demangle a possible C++ symbol. */
 				int status = -1;
-				char *func_name = abi::__cxa_demangle(dli.dli_sname, NULL, 0, &status);
+				char *func_name = abi::__cxa_demangle(dli.dli_sname, nullptr, 0, &status);
 
 				long int offset = (intptr_t)ip - (intptr_t)dli.dli_saddr;
-				buffer += seprintf(buffer, last, " (%s + %ld)", func_name != NULL ? func_name : dli.dli_sname, offset);
+				buffer += seprintf(buffer, last, " (%s + %ld)", func_name != nullptr ? func_name : dli.dli_sname, offset);
 
 				free(func_name);
 			}
diff --git a/src/os/macosx/splash.cpp b/src/os/macosx/splash.cpp
--- a/src/os/macosx/splash.cpp
+++ b/src/os/macosx/splash.cpp
@@ -54,7 +54,7 @@ static void PNGAPI png_my_warning(png_st
 void DisplaySplashImage()
 {
 	FILE *f = FioFOpenFile(SPLASH_IMAGE_FILE, "r", BASESET_DIR);
-	if (f == NULL) return;
+	if (f == nullptr) return;
 
 	png_byte header[8];
 	fread(header, sizeof(png_byte), 8, f);
@@ -63,23 +63,23 @@ void DisplaySplashImage()
 		return;
 	}
 
-	png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, (png_voidp) NULL, png_my_error, png_my_warning);
+	png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, (png_voidp) nullptr, png_my_error, png_my_warning);
 
-	if (png_ptr == NULL) {
+	if (png_ptr == nullptr) {
 		fclose(f);
 		return;
 	}
 
 	png_infop info_ptr = png_create_info_struct(png_ptr);
-	if (info_ptr == NULL) {
-		png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
+	if (info_ptr == nullptr) {
+		png_destroy_read_struct(&png_ptr, (png_infopp)nullptr, (png_infopp)nullptr);
 		fclose(f);
 		return;
 	}
 
 	png_infop end_info = png_create_info_struct(png_ptr);
-	if (end_info == NULL) {
-		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
+	if (end_info == nullptr) {
+		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)nullptr);
 		fclose(f);
 		return;
 	}
@@ -93,7 +93,7 @@ void DisplaySplashImage()
 	png_init_io(png_ptr, f);
 	png_set_sig_bytes(png_ptr, 8);
 
-	png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
+	png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, nullptr);
 
 	uint width      = png_get_image_width(png_ptr, info_ptr);
 	uint height     = png_get_image_height(png_ptr, info_ptr);
diff --git a/src/os/macosx/string_osx.cpp b/src/os/macosx/string_osx.cpp
--- a/src/os/macosx/string_osx.cpp
+++ b/src/os/macosx/string_osx.cpp
@@ -22,7 +22,7 @@
 
 #if (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5)
 /** Cached current locale. */
-static CFLocaleRef _osx_locale = NULL;
+static CFLocaleRef _osx_locale = nullptr;
 /** CoreText cache for font information, cleared when OTTD changes fonts. */
 static CTFontRef _font_cache[FS_END];
 
@@ -125,21 +125,21 @@ static CGFloat SpriteFontGetWidth(void *
 }
 
 static CTRunDelegateCallbacks _sprite_font_callback = {
-	kCTRunDelegateCurrentVersion, NULL, NULL, NULL,
+	kCTRunDelegateCurrentVersion, nullptr, nullptr, nullptr,
 	&SpriteFontGetWidth
 };
 
 /* static */ ParagraphLayouter *CoreTextParagraphLayoutFactory::GetParagraphLayout(CharType *buff, CharType *buff_end, FontMap &fontMapping)
 {
-	if (!MacOSVersionIsAtLeast(10, 5, 0)) return NULL;
+	if (!MacOSVersionIsAtLeast(10, 5, 0)) return nullptr;
 
 	/* Can't layout an empty string. */
 	ptrdiff_t length = buff_end - buff;
-	if (length == 0) return NULL;
+	if (length == 0) return nullptr;
 
 	/* Can't layout our in-built sprite fonts. */
 	for (const auto &i : fontMapping) {
-		if (i.second->fc->IsBuiltInFont()) return NULL;
+		if (i.second->fc->IsBuiltInFont()) return nullptr;
 	}
 
 	/* Make attributed string with embedded font information. */
@@ -156,10 +156,10 @@ static CTRunDelegateCallbacks _sprite_fo
 	for (const auto &i : fontMapping) {
 		if (i.first - last == 0) continue;
 
-		if (_font_cache[i.second->fc->GetSize()] == NULL) {
+		if (_font_cache[i.second->fc->GetSize()] == nullptr) {
 			/* Cache font information. */
 			CFStringRef font_name = CFStringCreateWithCString(kCFAllocatorDefault, i.second->fc->GetFontName(), kCFStringEncodingUTF8);
-			_font_cache[i.second->fc->GetSize()] = CTFontCreateWithName(font_name, i.second->fc->GetFontSize(), NULL);
+			_font_cache[i.second->fc->GetSize()] = CTFontCreateWithName(font_name, i.second->fc->GetFontSize(), nullptr);
 			CFRelease(font_name);
 		}
 		CFAttributedStringSetAttribute(str, CFRangeMake(last, i.first - last), kCTFontAttributeName, _font_cache[i.second->fc->GetSize()]);
@@ -185,12 +185,12 @@ static CTRunDelegateCallbacks _sprite_fo
 	CTTypesetterRef typesetter = CTTypesetterCreateWithAttributedString(str);
 	CFRelease(str);
 
-	return typesetter != NULL ? new CoreTextParagraphLayout(typesetter, buff, length, fontMapping) : NULL;
+	return typesetter != nullptr ? new CoreTextParagraphLayout(typesetter, buff, length, fontMapping) : nullptr;
 }
 
 /* virtual */ std::unique_ptr<const ParagraphLayouter::Line> CoreTextParagraphLayout::NextLine(int max_width)
 {
-	if (this->cur_offset >= this->length) return NULL;
+	if (this->cur_offset >= this->length) return nullptr;
 
 	/* Get line break position, trying word breaking first and breaking somewhere if that doesn't work. */
 	CFIndex len = CTTypesetterSuggestLineBreak(this->typesetter, this->cur_offset, max_width);
@@ -200,7 +200,7 @@ static CTRunDelegateCallbacks _sprite_fo
 	CTLineRef line = CTTypesetterCreateLine(this->typesetter, CFRangeMake(this->cur_offset, len));
 	this->cur_offset += len;
 
-	return std::unique_ptr<const Line>(line != NULL ? new CoreTextLine(line, this->font_map, this->text_buffer) : NULL);
+	return std::unique_ptr<const Line>(line != nullptr ? new CoreTextLine(line, this->font_map, this->text_buffer) : nullptr);
 }
 
 CoreTextParagraphLayout::CoreTextVisualRun::CoreTextVisualRun(CTRunRef run, Font *font, const CoreTextParagraphLayoutFactory::CharType *buff) : font(font)
@@ -233,7 +233,7 @@ CoreTextParagraphLayout::CoreTextVisualR
 			this->positions[i * 2 + 1] = pts[i].y;
 		}
 	}
-	this->total_advance = (int)CTRunGetTypographicBounds(run, CFRangeMake(0, 0), NULL, NULL, NULL);
+	this->total_advance = (int)CTRunGetTypographicBounds(run, CFRangeMake(0, 0), nullptr, nullptr, nullptr);
 	this->positions[this->glyphs.size() * 2] = this->positions[0] + this->total_advance;
 }
 
@@ -271,9 +271,9 @@ int CoreTextParagraphLayout::CoreTextLin
 /** Delete CoreText font reference for a specific font size. */
 void MacOSResetScriptCache(FontSize size)
 {
-	if (_font_cache[size] != NULL) {
+	if (_font_cache[size] != nullptr) {
 		CFRelease(_font_cache[size]);
-		_font_cache[size] = NULL;
+		_font_cache[size] = nullptr;
 	}
 }
 
@@ -282,7 +282,7 @@ void MacOSSetCurrentLocaleName(const cha
 {
 	if (!MacOSVersionIsAtLeast(10, 5, 0)) return;
 
-	if (_osx_locale != NULL) CFRelease(_osx_locale);
+	if (_osx_locale != nullptr) CFRelease(_osx_locale);
 
 	CFStringRef iso = CFStringCreateWithCString(kCFAllocatorNull, iso_code, kCFStringEncodingUTF8);
 	_osx_locale = CFLocaleCreate(kCFAllocatorDefault, iso);
@@ -425,7 +425,7 @@ int MacOSStringCompare(const char *s1, c
 
 /* static */ StringIterator *OSXStringIterator::Create()
 {
-	if (!MacOSVersionIsAtLeast(10, 5, 0)) return NULL;
+	if (!MacOSVersionIsAtLeast(10, 5, 0)) return nullptr;
 
 	return new OSXStringIterator();
 }
@@ -441,11 +441,11 @@ int MacOSStringCompare(const char *s1, c
 
 /* static */ StringIterator *OSXStringIterator::Create()
 {
-	return NULL;
+	return nullptr;
 }
 
 /* static */ ParagraphLayouter *CoreTextParagraphLayoutFactory::GetParagraphLayout(CharType *buff, CharType *buff_end, FontMap &fontMapping)
 {
-	return NULL;
+	return nullptr;
 }
 #endif /* (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5) */
diff --git a/src/os/os2/os2.cpp b/src/os/os2/os2.cpp
--- a/src/os/os2/os2.cpp
+++ b/src/os/os2/os2.cpp
@@ -102,7 +102,7 @@ bool FiosGetDiskFreeSpace(const char *pa
 	struct diskfree_t free;
 	char drive = path[0] - 'A' + 1;
 
-	if (tot != NULL && _getdiskfree(drive, &free) == 0) {
+	if (tot != nullptr && _getdiskfree(drive, &free) == 0) {
 		*tot = free.avail_clusters * free.sectors_per_cluster * free.bytes_per_sector;
 		return true;
 	}
@@ -119,7 +119,7 @@ bool FiosGetDiskFreeSpace(const char *pa
 		free = (uint64)s.f_frsize * s.f_bavail;
 	}
 #endif
-	if (tot != NULL) *tot = free;
+	if (tot != nullptr) *tot = free;
 	return true;
 #endif
 }
@@ -173,7 +173,7 @@ void ShowOSErrorBox(const char *buf, boo
 
 int CDECL main(int argc, char *argv[])
 {
-	SetRandomSeed(time(NULL));
+	SetRandomSeed(time(nullptr));
 
 	/* Make sure our arguments contain only valid UTF-8 characters. */
 	for (int i = 0; i < argc; i++) ValidateString(argv[i]);
@@ -191,7 +191,7 @@ bool GetClipboardContents(char *buffer, 
 	{
 		const char *text = (const char*)WinQueryClipbrdData(hab, CF_TEXT);
 
-		if (text != NULL)
+		if (text != nullptr)
 		{
 			strecpy(buffer, text, last);
 			WinCloseClipbrd(hab);
diff --git a/src/os/unix/crashlog_unix.cpp b/src/os/unix/crashlog_unix.cpp
--- a/src/os/unix/crashlog_unix.cpp
+++ b/src/os/unix/crashlog_unix.cpp
@@ -68,7 +68,7 @@ class CrashLogUnix : public CrashLog {
 				" Message: %s\n\n",
 				strsignal(this->signum),
 				this->signum,
-				message == NULL ? "<none>" : message
+				message == nullptr ? "<none>" : message
 		);
 	}
 
diff --git a/src/os/unix/unix.cpp b/src/os/unix/unix.cpp
--- a/src/os/unix/unix.cpp
+++ b/src/os/unix/unix.cpp
@@ -84,7 +84,7 @@ bool FiosGetDiskFreeSpace(const char *pa
 	if (statvfs(path, &s) != 0) return false;
 	free = (uint64)s.f_frsize * s.f_bavail;
 #endif
-	if (tot != NULL) *tot = free;
+	if (tot != nullptr) *tot = free;
 	return true;
 }
 
@@ -130,9 +130,9 @@ static const char *GetLocalCode()
 #else
 	/* Strip locale (eg en_US.UTF-8) to only have UTF-8 */
 	const char *locale = GetCurrentLocale("LC_CTYPE");
-	if (locale != NULL) locale = strchr(locale, '.');
+	if (locale != nullptr) locale = strchr(locale, '.');
 
-	return (locale == NULL) ? "" : locale + 1;
+	return (locale == nullptr) ? "" : locale + 1;
 #endif
 }
 
@@ -158,7 +158,7 @@ static const char *convert_tofrom_fs(ico
 
 	strecpy(outbuf, name, outbuf + outlen);
 
-	iconv(convd, NULL, NULL, NULL, NULL);
+	iconv(convd, nullptr, nullptr, nullptr, nullptr);
 	if (iconv(convd, &inbuf, &inlen, &outbuf, &outlen) == (size_t)(-1)) {
 		DEBUG(misc, 0, "[iconv] error converting '%s'. Errno %d", name, errno);
 	}
@@ -246,13 +246,13 @@ int CDECL main(int argc, char *argv[])
 	cocoaSetupAutoreleasePool();
 	/* This is passed if we are launched by double-clicking */
 	if (argc >= 2 && strncmp(argv[1], "-psn", 4) == 0) {
-		argv[1] = NULL;
+		argv[1] = nullptr;
 		argc = 1;
 	}
 #endif
 	CrashLog::InitialiseCrashLog();
 
-	SetRandomSeed(time(NULL));
+	SetRandomSeed(time(nullptr));
 
 	signal(SIGPIPE, SIG_IGN);
 
@@ -282,7 +282,7 @@ void OSOpenBrowser(const char *url)
 	const char *args[3];
 	args[0] = "xdg-open";
 	args[1] = url;
-	args[2] = NULL;
+	args[2] = nullptr;
 	execvp(args[0], const_cast<char * const *>(args));
 	DEBUG(misc, 0, "Failed to open url: %s", url);
 	exit(0);
diff --git a/src/os/windows/crashlog_win.cpp b/src/os/windows/crashlog_win.cpp
--- a/src/os/windows/crashlog_win.cpp
+++ b/src/os/windows/crashlog_win.cpp
@@ -66,7 +66,7 @@ public:
 	 * A crash log is always generated when it's generated.
 	 * @param ep the data related to the exception.
 	 */
-	CrashLogWindows(EXCEPTION_POINTERS *ep = NULL) :
+	CrashLogWindows(EXCEPTION_POINTERS *ep = nullptr) :
 		ep(ep)
 	{
 		this->crashlog[0] = '\0';
@@ -81,7 +81,7 @@ public:
 	static CrashLogWindows *current;
 };
 
-/* static */ CrashLogWindows *CrashLogWindows::current = NULL;
+/* static */ CrashLogWindows *CrashLogWindows::current = nullptr;
 
 /* virtual */ char *CrashLogWindows::LogOSVersion(char *buffer, const char *last) const
 {
@@ -114,7 +114,7 @@ public:
 			" Message:   %s\n\n",
 			(int)ep->ExceptionRecord->ExceptionCode,
 			(size_t)ep->ExceptionRecord->ExceptionAddress,
-			message == NULL ? "<none>" : message
+			message == nullptr ? "<none>" : message
 	);
 }
 
@@ -156,7 +156,7 @@ static void GetFileInfo(DebugFileInfo *d
 	HANDLE file;
 	memset(dfi, 0, sizeof(*dfi));
 
-	file = CreateFile(filename, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, 0);
+	file = CreateFile(filename, GENERIC_READ, FILE_SHARE_READ, nullptr, OPEN_EXISTING, 0, 0);
 	if (file != INVALID_HANDLE_VALUE) {
 		byte buffer[1024];
 		DWORD numread;
@@ -165,7 +165,7 @@ static void GetFileInfo(DebugFileInfo *d
 		uint32 crc = (uint32)-1;
 
 		for (;;) {
-			if (ReadFile(file, buffer, sizeof(buffer), &numread, NULL) == 0 || numread == 0) {
+			if (ReadFile(file, buffer, sizeof(buffer), &numread, nullptr) == 0 || numread == 0) {
 				break;
 			}
 			filesize += numread;
@@ -174,7 +174,7 @@ static void GetFileInfo(DebugFileInfo *d
 		dfi->size = filesize;
 		dfi->crc32 = crc ^ (uint32)-1;
 
-		if (GetFileTime(file, NULL, NULL, &write_time)) {
+		if (GetFileTime(file, nullptr, nullptr, &write_time)) {
 			FileTimeToSystemTime(&write_time, &dfi->file_time);
 		}
 		CloseHandle(file);
@@ -217,7 +217,7 @@ static char *PrintModuleInfo(char *outpu
 		BOOL res;
 
 		HANDLE proc = OpenProcess(PROCESS_ALL_ACCESS, FALSE, GetCurrentProcessId());
-		if (proc != NULL) {
+		if (proc != nullptr) {
 			res = EnumProcessModules(proc, modules, sizeof(modules), &needed);
 			CloseHandle(proc);
 			if (res) {
@@ -228,7 +228,7 @@ static char *PrintModuleInfo(char *outpu
 			}
 		}
 	}
-	output = PrintModuleInfo(output, last, NULL);
+	output = PrintModuleInfo(output, last, nullptr);
 	return output + seprintf(output, last, "\n");
 }
 
@@ -362,7 +362,7 @@ char *CrashLogWindows::AppendDecodedStac
 	if (LoadLibraryList((Function*)&proc, dbg_import)) {
 		/* Initialize symbol handler. */
 		HANDLE hCur = GetCurrentProcess();
-		proc.pSymInitialize(hCur, NULL, TRUE);
+		proc.pSymInitialize(hCur, nullptr, TRUE);
 		/* Load symbols only when needed, fail silently on errors, demangle symbol names. */
 		proc.pSymSetOptions(SYMOPT_DEFERRED_LOADS | SYMOPT_FAIL_CRITICAL_ERRORS | SYMOPT_UNDNAME);
 
@@ -399,7 +399,7 @@ char *CrashLogWindows::AppendDecodedStac
 #else
 				IMAGE_FILE_MACHINE_I386,
 #endif
-				hCur, GetCurrentThread(), &frame, &ctx, NULL, proc.pSymFunctionTableAccess64, proc.pSymGetModuleBase64, NULL)) break;
+				hCur, GetCurrentThread(), &frame, &ctx, nullptr, proc.pSymFunctionTableAccess64, proc.pSymGetModuleBase64, nullptr)) break;
 
 			if (frame.AddrPC.Offset == frame.AddrReturn.Offset) {
 				buffer += seprintf(buffer, last, " <infinite loop>\n");
@@ -443,16 +443,16 @@ char *CrashLogWindows::AppendDecodedStac
 {
 	int ret = 0;
 	HMODULE dbghelp = LoadLibrary(_T("dbghelp.dll"));
-	if (dbghelp != NULL) {
+	if (dbghelp != nullptr) {
 		typedef BOOL (WINAPI *MiniDumpWriteDump_t)(HANDLE, DWORD, HANDLE,
 				MINIDUMP_TYPE,
 				CONST PMINIDUMP_EXCEPTION_INFORMATION,
 				CONST PMINIDUMP_USER_STREAM_INFORMATION,
 				CONST PMINIDUMP_CALLBACK_INFORMATION);
 		MiniDumpWriteDump_t funcMiniDumpWriteDump = (MiniDumpWriteDump_t)GetProcAddress(dbghelp, "MiniDumpWriteDump");
-		if (funcMiniDumpWriteDump != NULL) {
+		if (funcMiniDumpWriteDump != nullptr) {
 			seprintf(filename, filename_last, "%scrash.dmp", _personal_dir);
-			HANDLE file  = CreateFile(OTTD2FS(filename), GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, 0, 0);
+			HANDLE file  = CreateFile(OTTD2FS(filename), GENERIC_WRITE, 0, nullptr, CREATE_ALWAYS, 0, 0);
 			HANDLE proc  = GetCurrentProcess();
 			DWORD procid = GetCurrentProcessId();
 			MINIDUMP_EXCEPTION_INFORMATION mdei;
@@ -470,7 +470,7 @@ char *CrashLogWindows::AppendDecodedStac
 			mdei.ExceptionPointers  = ep;
 			mdei.ClientPointers     = false;
 
-			funcMiniDumpWriteDump(proc, procid, file, MiniDumpWithDataSegs, &mdei, &musi, NULL);
+			funcMiniDumpWriteDump(proc, procid, file, MiniDumpWithDataSegs, &mdei, &musi, nullptr);
 			ret = 1;
 		} else {
 			ret = -1;
@@ -488,11 +488,11 @@ static void ShowCrashlogWindow();
  * Stack pointer for use when 'starting' the crash handler.
  * Not static as gcc's inline assembly needs it that way.
  */
-void *_safe_esp = NULL;
+void *_safe_esp = nullptr;
 
 static LONG WINAPI ExceptionHandler(EXCEPTION_POINTERS *ep)
 {
-	if (CrashLogWindows::current != NULL) {
+	if (CrashLogWindows::current != nullptr) {
 		CrashLog::AfterCrashLogCleanup();
 		ExitProcess(2);
 	}
@@ -501,7 +501,7 @@ static LONG WINAPI ExceptionHandler(EXCE
 		static const TCHAR _emergency_crash[] =
 			_T("A serious fault condition occurred in the game. The game will shut down.\n")
 			_T("As you loaded an emergency savegame no crash information will be generated.\n");
-		MessageBox(NULL, _emergency_crash, _T("Fatal Application Failure"), MB_ICONERROR);
+		MessageBox(nullptr, _emergency_crash, _T("Fatal Application Failure"), MB_ICONERROR);
 		ExitProcess(3);
 	}
 
@@ -510,7 +510,7 @@ static LONG WINAPI ExceptionHandler(EXCE
 			_T("A serious fault condition occurred in the game. The game will shut down.\n")
 			_T("As you loaded an savegame for which you do not have the required NewGRFs\n")
 			_T("no crash information will be generated.\n");
-		MessageBox(NULL, _saveload_crash, _T("Fatal Application Failure"), MB_ICONERROR);
+		MessageBox(nullptr, _saveload_crash, _T("Fatal Application Failure"), MB_ICONERROR);
 		ExitProcess(3);
 	}
 
@@ -525,7 +525,7 @@ static LONG WINAPI ExceptionHandler(EXCE
 	/* Close any possible log files */
 	CloseConsoleLogIfActive();
 
-	if ((VideoDriver::GetInstance() == NULL || VideoDriver::GetInstance()->HasGUI()) && _safe_esp != NULL) {
+	if ((VideoDriver::GetInstance() == nullptr || VideoDriver::GetInstance()->HasGUI()) && _safe_esp != nullptr) {
 #ifdef _M_AMD64
 		ep->ContextRecord->Rip = (DWORD64)ShowCrashlogWindow;
 		ep->ContextRecord->Rsp = (DWORD64)_safe_esp;
@@ -542,7 +542,7 @@ static LONG WINAPI ExceptionHandler(EXCE
 
 static void CDECL CustomAbort(int signal)
 {
-	RaiseException(0xE1212012, 0, 0, NULL);
+	RaiseException(0xE1212012, 0, 0, nullptr);
 }
 
 /* static */ void CrashLog::InitialiseCrashLog()
@@ -693,5 +693,5 @@ static void ShowCrashlogWindow()
 {
 	ShowCursor(TRUE);
 	ShowWindow(GetActiveWindow(), FALSE);
-	DialogBox(GetModuleHandle(NULL), MAKEINTRESOURCE(100), NULL, CrashDialogFunc);
+	DialogBox(GetModuleHandle(nullptr), MAKEINTRESOURCE(100), nullptr, CrashDialogFunc);
 }
diff --git a/src/os/windows/string_uniscribe.cpp b/src/os/windows/string_uniscribe.cpp
--- a/src/os/windows/string_uniscribe.cpp
+++ b/src/os/windows/string_uniscribe.cpp
@@ -86,7 +86,7 @@ public:
 		int num_glyphs;
 		Font *font;
 
-		mutable int *glyph_to_char = NULL;
+		mutable int *glyph_to_char = nullptr;
 
 	public:
 		UniscribeVisualRun(const UniscribeRun &range, int x);
@@ -139,9 +139,9 @@ public:
 
 void UniscribeResetScriptCache(FontSize size)
 {
-	if (_script_cache[size] != NULL) {
+	if (_script_cache[size] != nullptr) {
 		ScriptFreeCache(&_script_cache[size]);
-		_script_cache[size] = NULL;
+		_script_cache[size] = nullptr;
 	}
 }
 
@@ -168,9 +168,9 @@ static bool UniscribeShapeRun(const Unis
 	/* The char-to-glyph array is the same size as the input. */
 	range.char_to_glyph.resize(range.len);
 
-	HDC temp_dc = NULL;
-	HFONT old_font = NULL;
-	HFONT cur_font = NULL;
+	HDC temp_dc = nullptr;
+	HFONT old_font = nullptr;
+	HFONT cur_font = nullptr;
 
 	while (true) {
 		/* Shape the text run by determining the glyphs needed for display. */
@@ -217,9 +217,9 @@ static bool UniscribeShapeRun(const Unis
 		} else if (hr == E_PENDING) {
 			/* Glyph data is not in cache, load native font. */
 			cur_font = HFontFromFont(range.font);
-			if (cur_font == NULL) return false; // Sorry, no dice.
+			if (cur_font == nullptr) return false; // Sorry, no dice.
 
-			temp_dc = CreateCompatibleDC(NULL);
+			temp_dc = CreateCompatibleDC(nullptr);
 			SetMapMode(temp_dc, MM_TEXT);
 			old_font = (HFONT)SelectObject(temp_dc, cur_font);
 		} else if (hr == USP_E_SCRIPT_NOT_IN_FONT && range.sa.eScript != SCRIPT_UNDEFINED) {
@@ -227,19 +227,19 @@ static bool UniscribeShapeRun(const Unis
 			range.sa.eScript = SCRIPT_UNDEFINED;
 		} else {
 			/* Some unknown other error. */
-			if (temp_dc != NULL) {
+			if (temp_dc != nullptr) {
 				SelectObject(temp_dc, old_font);
 				DeleteObject(cur_font);
-				ReleaseDC(NULL, temp_dc);
+				ReleaseDC(nullptr, temp_dc);
 			}
 			return false;
 		}
 	}
 
-	if (temp_dc != NULL) {
+	if (temp_dc != nullptr) {
 		SelectObject(temp_dc, old_font);
 		DeleteObject(cur_font);
-		ReleaseDC(NULL, temp_dc);
+		ReleaseDC(nullptr, temp_dc);
 	}
 
 	return true;
@@ -280,16 +280,16 @@ static std::vector<SCRIPT_ITEM> Uniscrib
 {
 	int32 length = buff_end - buff;
 	/* Can't layout an empty string. */
-	if (length == 0) return NULL;
+	if (length == 0) return nullptr;
 
 	/* Can't layout our in-built sprite fonts. */
 	for (auto const &pair : fontMapping) {
-		if (pair.second->fc->IsBuiltInFont()) return NULL;
+		if (pair.second->fc->IsBuiltInFont()) return nullptr;
 	}
 
 	/* Itemize text. */
 	std::vector<SCRIPT_ITEM> items = UniscribeItemizeString(buff, length);
-	if (items.size() == 0) return NULL;
+	if (items.size() == 0) return nullptr;
 
 	/* Build ranges from the items and the font map. A range is a run of text
 	 * that is part of a single item and formatted using a single font style. */
@@ -306,7 +306,7 @@ static std::vector<SCRIPT_ITEM> Uniscrib
 
 			/* Shape the range. */
 			if (!UniscribeShapeRun(buff, ranges.back())) {
-				return NULL;
+				return nullptr;
 			}
 
 			/* If we are at the end of the current item, advance to the next item. */
@@ -323,7 +323,7 @@ static std::vector<SCRIPT_ITEM> Uniscrib
 	std::vector<UniscribeRun>::iterator start_run = this->cur_range;
 	std::vector<UniscribeRun>::iterator last_run = this->cur_range;
 
-	if (start_run == this->ranges.end()) return NULL;
+	if (start_run == this->ranges.end()) return nullptr;
 
 	/* Add remaining width of the first run if it is a broken run. */
 	int cur_width = 0;
@@ -355,7 +355,7 @@ static std::vector<SCRIPT_ITEM> Uniscrib
 		int last_cluster = this->cur_range_offset + 1;
 		for (std::vector<UniscribeRun>::iterator r = start_run; r != last_run; r++) {
 			log_attribs.resize(r->pos - start_run->pos + r->len);
-			if (FAILED(ScriptBreak(this->text_buffer + r->pos + start_offs, r->len - start_offs, &r->sa, &log_attribs[r->pos - start_run->pos + start_offs]))) return NULL;
+			if (FAILED(ScriptBreak(this->text_buffer + r->pos + start_offs, r->len - start_offs, &r->sa, &log_attribs[r->pos - start_run->pos + start_offs]))) return nullptr;
 
 			std::vector<int> dx(r->len);
 			ScriptGetLogicalWidths(&r->sa, r->len, (int)r->glyphs.size(), &r->advances[0], &r->char_to_glyph[0], &r->vis_attribs[0], &dx[0]);
@@ -401,7 +401,7 @@ static std::vector<SCRIPT_ITEM> Uniscrib
 		bidi_level.push_back(r->sa.s.uBidiLevel);
 	}
 	std::vector<INT> vis_to_log(bidi_level.size());
-	if (FAILED(ScriptLayout((int)bidi_level.size(), &bidi_level[0], &vis_to_log[0], NULL))) return NULL;
+	if (FAILED(ScriptLayout((int)bidi_level.size(), &bidi_level[0], &vis_to_log[0], nullptr))) return nullptr;
 
 	/* Create line. */
 	std::unique_ptr<UniscribeLine> line(new UniscribeLine());
@@ -415,14 +415,14 @@ static std::vector<SCRIPT_ITEM> Uniscrib
 		if (i_run == last_run - 1 && remaing_offset < (last_run - 1)->len) {
 			run.len = remaing_offset - 1;
 
-			if (!UniscribeShapeRun(this->text_buffer, run)) return NULL;
+			if (!UniscribeShapeRun(this->text_buffer, run)) return nullptr;
 		}
 		if (i_run == start_run && this->cur_range_offset > 0) {
 			assert(run.len - this->cur_range_offset > 0);
 			run.pos += this->cur_range_offset;
 			run.len -= this->cur_range_offset;
 
-			if (!UniscribeShapeRun(this->text_buffer, run)) return NULL;
+			if (!UniscribeShapeRun(this->text_buffer, run)) return nullptr;
 		}
 
 		line->emplace_back(run, cur_pos);
@@ -490,12 +490,12 @@ UniscribeParagraphLayout::UniscribeVisua
 								  start_pos(other.start_pos), total_advance(other.total_advance), num_glyphs(other.num_glyphs), font(other.font)
 {
 	this->glyph_to_char = other.glyph_to_char;
-	other.glyph_to_char = NULL;
+	other.glyph_to_char = nullptr;
 }
 
 const int *UniscribeParagraphLayout::UniscribeVisualRun::GetGlyphToCharMap() const
 {
-	if (this->glyph_to_char == NULL) {
+	if (this->glyph_to_char == nullptr) {
 		this->glyph_to_char = CallocT<int>(this->GetGlyphCount());
 
 		/* The char to glyph array contains the first glyph index of the cluster that is associated
diff --git a/src/os/windows/win32.cpp b/src/os/windows/win32.cpp
--- a/src/os/windows/win32.cpp
+++ b/src/os/windows/win32.cpp
@@ -61,14 +61,14 @@ bool LoadLibraryList(Function proc[], co
 		HMODULE lib;
 		lib = LoadLibrary(MB_TO_WIDE(dll));
 
-		if (lib == NULL) return false;
+		if (lib == nullptr) return false;
 		for (;;) {
 			FARPROC p;
 
 			while (*dll++ != '\0') { /* Nothing */ }
 			if (*dll == '\0') break;
 			p = GetProcAddress(lib, dll);
-			if (p == NULL) return false;
+			if (p == nullptr) return false;
 			*proc++ = (Function)p;
 		}
 		dll++;
@@ -84,7 +84,7 @@ void ShowOSErrorBox(const char *buf, boo
 
 void OSOpenBrowser(const char *url)
 {
-	ShellExecute(GetActiveWindow(), _T("open"), OTTD2FS(url), NULL, NULL, SW_SHOWNORMAL);
+	ShellExecute(GetActiveWindow(), _T("open"), OTTD2FS(url), nullptr, nullptr, SW_SHOWNORMAL);
 }
 
 /* Code below for windows version of opendir/readdir/closedir copied and
@@ -142,7 +142,7 @@ DIR *opendir(const TCHAR *path)
 
 	if ((fa != INVALID_FILE_ATTRIBUTES) && (fa & FILE_ATTRIBUTE_DIRECTORY)) {
 		d = dir_calloc();
-		if (d != NULL) {
+		if (d != nullptr) {
 			TCHAR search_path[MAX_PATH];
 			bool slash = path[_tcslen(path) - 1] == '\\';
 
@@ -158,14 +158,14 @@ DIR *opendir(const TCHAR *path)
 				d->at_first_entry = true;
 			} else {
 				dir_free(d);
-				d = NULL;
+				d = nullptr;
 			}
 		} else {
 			errno = ENOMEM;
 		}
 	} else {
 		/* path not found or not a directory */
-		d = NULL;
+		d = nullptr;
 		errno = ENOENT;
 	}
 
@@ -179,11 +179,11 @@ struct dirent *readdir(DIR *d)
 
 	if (d->at_first_entry) {
 		/* the directory was empty when opened */
-		if (d->hFind == INVALID_HANDLE_VALUE) return NULL;
+		if (d->hFind == INVALID_HANDLE_VALUE) return nullptr;
 		d->at_first_entry = false;
 	} else if (!FindNextFile(d->hFind, &d->fd)) { // determine cause and bail
 		if (GetLastError() == ERROR_NO_MORE_FILES) SetLastError(prev_err);
-		return NULL;
+		return nullptr;
 	}
 
 	/* This entry has passed all checks; return information about it.
@@ -251,7 +251,7 @@ bool FiosGetDiskFreeSpace(const char *pa
 	DWORD spc, bps, nfc, tnc;
 
 	_sntprintf(root, lengthof(root), _T("%c:") _T(PATHSEP), path[0]);
-	if (tot != NULL && GetDiskFreeSpace(root, &spc, &bps, &nfc, &tnc)) {
+	if (tot != nullptr && GetDiskFreeSpace(root, &spc, &bps, &nfc, &tnc)) {
 		*tot = ((spc * bps) * (uint64)nfc);
 		retval = true;
 	}
@@ -339,9 +339,9 @@ void CreateConsole()
 	*stderr = *fdopen(2, "w" );
 #endif
 
-	setvbuf(stdin, NULL, _IONBF, 0);
-	setvbuf(stdout, NULL, _IONBF, 0);
-	setvbuf(stderr, NULL, _IONBF, 0);
+	setvbuf(stdin, nullptr, _IONBF, 0);
+	setvbuf(stdout, nullptr, _IONBF, 0);
+	setvbuf(stderr, nullptr, _IONBF, 0);
 }
 
 /** Temporary pointer to get the help message to the window */
@@ -398,7 +398,7 @@ void ShowInfo(const char *str)
 			 * ShowInfo are much shorter, or so long they need this way of displaying
 			 * them anyway. */
 			_help_msg = str;
-			DialogBox(GetModuleHandle(NULL), MAKEINTRESOURCE(101), NULL, HelpDialogFunc);
+			DialogBox(GetModuleHandle(nullptr), MAKEINTRESOURCE(101), nullptr, HelpDialogFunc);
 		} else {
 			/* We need to put the text in a separate buffer because the default
 			 * buffer in OTTD2FS might not be large enough (512 chars). */
@@ -459,28 +459,28 @@ void DetermineBasePaths(const char *exe)
 	char tmp[MAX_PATH];
 	TCHAR path[MAX_PATH];
 #ifdef WITH_PERSONAL_DIR
-	if (SUCCEEDED(OTTDSHGetFolderPath(NULL, CSIDL_PERSONAL, NULL, SHGFP_TYPE_CURRENT, path))) {
+	if (SUCCEEDED(OTTDSHGetFolderPath(nullptr, CSIDL_PERSONAL, nullptr, SHGFP_TYPE_CURRENT, path))) {
 		strecpy(tmp, FS2OTTD(path), lastof(tmp));
 		AppendPathSeparator(tmp, lastof(tmp));
 		strecat(tmp, PERSONAL_DIR, lastof(tmp));
 		AppendPathSeparator(tmp, lastof(tmp));
 		_searchpaths[SP_PERSONAL_DIR] = stredup(tmp);
 	} else {
-		_searchpaths[SP_PERSONAL_DIR] = NULL;
+		_searchpaths[SP_PERSONAL_DIR] = nullptr;
 	}
 
-	if (SUCCEEDED(OTTDSHGetFolderPath(NULL, CSIDL_COMMON_DOCUMENTS, NULL, SHGFP_TYPE_CURRENT, path))) {
+	if (SUCCEEDED(OTTDSHGetFolderPath(nullptr, CSIDL_COMMON_DOCUMENTS, nullptr, SHGFP_TYPE_CURRENT, path))) {
 		strecpy(tmp, FS2OTTD(path), lastof(tmp));
 		AppendPathSeparator(tmp, lastof(tmp));
 		strecat(tmp, PERSONAL_DIR, lastof(tmp));
 		AppendPathSeparator(tmp, lastof(tmp));
 		_searchpaths[SP_SHARED_DIR] = stredup(tmp);
 	} else {
-		_searchpaths[SP_SHARED_DIR] = NULL;
+		_searchpaths[SP_SHARED_DIR] = nullptr;
 	}
 #else
-	_searchpaths[SP_PERSONAL_DIR] = NULL;
-	_searchpaths[SP_SHARED_DIR]   = NULL;
+	_searchpaths[SP_PERSONAL_DIR] = nullptr;
+	_searchpaths[SP_SHARED_DIR]   = nullptr;
 #endif
 
 	/* Get the path to working directory of OpenTTD */
@@ -488,15 +488,15 @@ void DetermineBasePaths(const char *exe)
 	AppendPathSeparator(tmp, lastof(tmp));
 	_searchpaths[SP_WORKING_DIR] = stredup(tmp);
 
-	if (!GetModuleFileName(NULL, path, lengthof(path))) {
+	if (!GetModuleFileName(nullptr, path, lengthof(path))) {
 		DEBUG(misc, 0, "GetModuleFileName failed (%lu)\n", GetLastError());
-		_searchpaths[SP_BINARY_DIR] = NULL;
+		_searchpaths[SP_BINARY_DIR] = nullptr;
 	} else {
 		TCHAR exec_dir[MAX_PATH];
 		_tcsncpy(path, convert_to_fs(exe, path, lengthof(path)), lengthof(path));
-		if (!GetFullPathName(path, lengthof(exec_dir), exec_dir, NULL)) {
+		if (!GetFullPathName(path, lengthof(exec_dir), exec_dir, nullptr)) {
 			DEBUG(misc, 0, "GetFullPathName failed (%lu)\n", GetLastError());
-			_searchpaths[SP_BINARY_DIR] = NULL;
+			_searchpaths[SP_BINARY_DIR] = nullptr;
 		} else {
 			strecpy(tmp, convert_from_fs(exec_dir, tmp, lengthof(tmp)), lastof(tmp));
 			char *s = strrchr(tmp, PATHSEPCHAR);
@@ -505,8 +505,8 @@ void DetermineBasePaths(const char *exe)
 		}
 	}
 
-	_searchpaths[SP_INSTALLATION_DIR]       = NULL;
-	_searchpaths[SP_APPLICATION_BUNDLE_DIR] = NULL;
+	_searchpaths[SP_INSTALLATION_DIR]       = nullptr;
+	_searchpaths[SP_APPLICATION_BUNDLE_DIR] = nullptr;
 }
 
 
@@ -516,18 +516,18 @@ bool GetClipboardContents(char *buffer, 
 	const char *ptr;
 
 	if (IsClipboardFormatAvailable(CF_UNICODETEXT)) {
-		OpenClipboard(NULL);
+		OpenClipboard(nullptr);
 		cbuf = GetClipboardData(CF_UNICODETEXT);
 
 		ptr = (const char*)GlobalLock(cbuf);
-		int out_len = WideCharToMultiByte(CP_UTF8, 0, (LPCWSTR)ptr, -1, buffer, (last - buffer) + 1, NULL, NULL);
+		int out_len = WideCharToMultiByte(CP_UTF8, 0, (LPCWSTR)ptr, -1, buffer, (last - buffer) + 1, nullptr, nullptr);
 		GlobalUnlock(cbuf);
 		CloseClipboard();
 
 		if (out_len == 0) return false;
 #if !defined(UNICODE)
 	} else if (IsClipboardFormatAvailable(CF_TEXT)) {
-		OpenClipboard(NULL);
+		OpenClipboard(nullptr);
 		cbuf = GetClipboardData(CF_TEXT);
 
 		ptr = (const char*)GlobalLock(cbuf);
@@ -596,7 +596,7 @@ char *convert_from_fs(const TCHAR *name,
 	const WCHAR *wide_buf = name;
 #else
 	/* Convert string from the local codepage to UTF-16. */
-	int wide_len = MultiByteToWideChar(CP_ACP, 0, name, -1, NULL, 0);
+	int wide_len = MultiByteToWideChar(CP_ACP, 0, name, -1, nullptr, 0);
 	if (wide_len == 0) {
 		utf8_buf[0] = '\0';
 		return utf8_buf;
@@ -607,7 +607,7 @@ char *convert_from_fs(const TCHAR *name,
 #endif
 
 	/* Convert UTF-16 string to UTF-8. */
-	int len = WideCharToMultiByte(CP_UTF8, 0, wide_buf, -1, utf8_buf, (int)buflen, NULL, NULL);
+	int len = WideCharToMultiByte(CP_UTF8, 0, wide_buf, -1, utf8_buf, (int)buflen, nullptr, nullptr);
 	if (len == 0) utf8_buf[0] = '\0';
 
 	return utf8_buf;
@@ -630,7 +630,7 @@ TCHAR *convert_to_fs(const char *name, T
 	int len = MultiByteToWideChar(CP_UTF8, 0, name, -1, system_buf, (int)buflen);
 	if (len == 0) system_buf[0] = '\0';
 #else
-	int len = MultiByteToWideChar(CP_UTF8, 0, name, -1, NULL, 0);
+	int len = MultiByteToWideChar(CP_UTF8, 0, name, -1, nullptr, 0);
 	if (len == 0) {
 		system_buf[0] = '\0';
 		return system_buf;
@@ -639,7 +639,7 @@ TCHAR *convert_to_fs(const char *name, T
 	WCHAR *wide_buf = AllocaM(WCHAR, len);
 	MultiByteToWideChar(CP_UTF8, 0, name, -1, wide_buf, len);
 
-	len = WideCharToMultiByte(console_cp ? CP_OEMCP : CP_ACP, 0, wide_buf, len, system_buf, (int)buflen, NULL, NULL);
+	len = WideCharToMultiByte(console_cp ? CP_OEMCP : CP_ACP, 0, wide_buf, len, system_buf, (int)buflen, nullptr, nullptr);
 	if (len == 0) system_buf[0] = '\0';
 #endif
 
@@ -654,7 +654,7 @@ TCHAR *convert_to_fs(const char *name, T
  */
 HRESULT OTTDSHGetFolderPath(HWND hwnd, int csidl, HANDLE hToken, DWORD dwFlags, LPTSTR pszPath)
 {
-	static HRESULT (WINAPI *SHGetFolderPath)(HWND, int, HANDLE, DWORD, LPTSTR) = NULL;
+	static HRESULT (WINAPI *SHGetFolderPath)(HWND, int, HANDLE, DWORD, LPTSTR) = nullptr;
 	static bool first_time = true;
 
 	/* We only try to load the library one time; if it fails, it fails */
@@ -674,7 +674,7 @@ HRESULT OTTDSHGetFolderPath(HWND hwnd, i
 		first_time = false;
 	}
 
-	if (SHGetFolderPath != NULL) return SHGetFolderPath(hwnd, csidl, hToken, dwFlags, pszPath);
+	if (SHGetFolderPath != nullptr) return SHGetFolderPath(hwnd, csidl, hToken, dwFlags, pszPath);
 
 	/* SHGetFolderPath doesn't exist, try a more conservative approach,
 	 * eg environment variables. This is only included for legacy modes
@@ -698,7 +698,7 @@ HRESULT OTTDSHGetFolderPath(HWND hwnd, i
 				HKEY key;
 				if (RegOpenKeyEx(csidl == CSIDL_PERSONAL ? HKEY_CURRENT_USER : HKEY_LOCAL_MACHINE, REGSTR_PATH_SPECIAL_FOLDERS, 0, KEY_READ, &key) != ERROR_SUCCESS) break;
 				DWORD len = MAX_PATH;
-				ret = RegQueryValueEx(key, csidl == CSIDL_PERSONAL ? _T("Personal") : _T("Common Documents"), NULL, NULL, (LPBYTE)pszPath, &len);
+				ret = RegQueryValueEx(key, csidl == CSIDL_PERSONAL ? _T("Personal") : _T("Common Documents"), nullptr, nullptr, (LPBYTE)pszPath, &len);
 				RegCloseKey(key);
 				if (ret == ERROR_SUCCESS) return (HRESULT)0;
 				break;
@@ -718,7 +718,7 @@ const char *GetCurrentLocale(const char 
 	if (GetLocaleInfoA(LOCALE_USER_DEFAULT, LOCALE_SISO639LANGNAME, lang, lengthof(lang)) == 0 ||
 	    GetLocaleInfoA(LOCALE_USER_DEFAULT, LOCALE_SISO3166CTRYNAME, country, lengthof(country)) == 0) {
 		/* Unable to retrieve the locale. */
-		return NULL;
+		return nullptr;
 	}
 	/* Format it as 'en_us'. */
 	static char retbuf[6] = {lang[0], lang[1], '_', country[0], country[1], 0};
@@ -750,7 +750,7 @@ void Win32SetCurrentLocaleName(const cha
 int OTTDStringCompare(const char *s1, const char *s2)
 {
 	typedef int (WINAPI *PFNCOMPARESTRINGEX)(LPCWSTR, DWORD, LPCWCH, int, LPCWCH, int, LPVOID, LPVOID, LPARAM);
-	static PFNCOMPARESTRINGEX _CompareStringEx = NULL;
+	static PFNCOMPARESTRINGEX _CompareStringEx = nullptr;
 	static bool first_time = true;
 
 #ifndef SORT_DIGITSASNUMBERS
@@ -765,10 +765,10 @@ int OTTDStringCompare(const char *s1, co
 		first_time = false;
 	}
 
-	if (_CompareStringEx != NULL) {
+	if (_CompareStringEx != nullptr) {
 		/* CompareStringEx takes UTF-16 strings, even in ANSI-builds. */
-		int len_s1 = MultiByteToWideChar(CP_UTF8, 0, s1, -1, NULL, 0);
-		int len_s2 = MultiByteToWideChar(CP_UTF8, 0, s2, -1, NULL, 0);
+		int len_s1 = MultiByteToWideChar(CP_UTF8, 0, s1, -1, nullptr, 0);
+		int len_s2 = MultiByteToWideChar(CP_UTF8, 0, s2, -1, nullptr, 0);
 
 		if (len_s1 != 0 && len_s2 != 0) {
 			LPWSTR str_s1 = AllocaM(WCHAR, len_s1);
@@ -777,7 +777,7 @@ int OTTDStringCompare(const char *s1, co
 			MultiByteToWideChar(CP_UTF8, 0, s1, -1, str_s1, len_s1);
 			MultiByteToWideChar(CP_UTF8, 0, s2, -1, str_s2, len_s2);
 
-			int result = _CompareStringEx(_cur_iso_locale, LINGUISTIC_IGNORECASE | SORT_DIGITSASNUMBERS, str_s1, -1, str_s2, -1, NULL, NULL, 0);
+			int result = _CompareStringEx(_cur_iso_locale, LINGUISTIC_IGNORECASE | SORT_DIGITSASNUMBERS, str_s1, -1, str_s2, -1, nullptr, nullptr, 0);
 			if (result != 0) return result;
 		}
 	}
diff --git a/src/osk_gui.cpp b/src/osk_gui.cpp
--- a/src/osk_gui.cpp
+++ b/src/osk_gui.cpp
@@ -46,10 +46,10 @@ struct OskWindow : public Window {
 	OskWindow(WindowDesc *desc, Window *parent, int button) : Window(desc)
 	{
 		this->parent = parent;
-		assert(parent != NULL);
+		assert(parent != nullptr);
 
 		NWidgetCore *par_wid = parent->GetWidget<NWidgetCore>(button);
-		assert(par_wid != NULL);
+		assert(par_wid != nullptr);
 
 		assert(parent->querystrings.Contains(button));
 		this->qs         = parent->querystrings.Find(button)->second;
@@ -166,7 +166,7 @@ struct OskWindow : public Window {
 				break;
 
 			case WID_OSK_OK:
-				if (this->qs->orig == NULL || strcmp(this->qs->text.buf, this->qs->orig) != 0) {
+				if (this->qs->orig == nullptr || strcmp(this->qs->text.buf, this->qs->orig) != 0) {
 					/* pass information by simulating a button press on parent window */
 					if (this->qs->ok_button >= 0) {
 						this->parent->OnClick(pt, this->qs->ok_button, 1);
@@ -427,7 +427,7 @@ void ShowOnScreenKeyboard(Window *parent
 void UpdateOSKOriginalText(const Window *parent, int button)
 {
 	OskWindow *osk = dynamic_cast<OskWindow *>(FindWindowById(WC_OSK, 0));
-	if (osk == NULL || osk->parent != parent || osk->text_btn != button) return;
+	if (osk == nullptr || osk->parent != parent || osk->text_btn != button) return;
 
 	free(osk->orig_str_buf);
 	osk->orig_str_buf = stredup(osk->qs->text.buf);
@@ -444,5 +444,5 @@ void UpdateOSKOriginalText(const Window 
 bool IsOSKOpenedFor(const Window *w, int button)
 {
 	OskWindow *osk = dynamic_cast<OskWindow *>(FindWindowById(WC_OSK, 0));
-	return osk != NULL && osk->parent == w && osk->text_btn == button;
+	return osk != nullptr && osk->parent == w && osk->text_btn == button;
 }
diff --git a/src/pathfinder/follow_track.hpp b/src/pathfinder/follow_track.hpp
--- a/src/pathfinder/follow_track.hpp
+++ b/src/pathfinder/follow_track.hpp
@@ -53,27 +53,27 @@ struct CFollowTrackT
 	CPerformanceTimer  *m_pPerf;
 	RailTypes           m_railtypes;
 
-	inline CFollowTrackT(const VehicleType *v = NULL, RailTypes railtype_override = INVALID_RAILTYPES, CPerformanceTimer *pPerf = NULL)
+	inline CFollowTrackT(const VehicleType *v = nullptr, RailTypes railtype_override = INVALID_RAILTYPES, CPerformanceTimer *pPerf = nullptr)
 	{
 		Init(v, railtype_override, pPerf);
 	}
 
-	inline CFollowTrackT(Owner o, RailTypes railtype_override = INVALID_RAILTYPES, CPerformanceTimer *pPerf = NULL)
+	inline CFollowTrackT(Owner o, RailTypes railtype_override = INVALID_RAILTYPES, CPerformanceTimer *pPerf = nullptr)
 	{
-		m_veh = NULL;
+		m_veh = nullptr;
 		Init(o, railtype_override, pPerf);
 	}
 
 	inline void Init(const VehicleType *v, RailTypes railtype_override, CPerformanceTimer *pPerf)
 	{
-		assert(!IsRailTT() || (v != NULL && v->type == VEH_TRAIN));
+		assert(!IsRailTT() || (v != nullptr && v->type == VEH_TRAIN));
 		m_veh = v;
-		Init(v != NULL ? v->owner : INVALID_OWNER, IsRailTT() && railtype_override == INVALID_RAILTYPES ? Train::From(v)->compatible_railtypes : railtype_override, pPerf);
+		Init(v != nullptr ? v->owner : INVALID_OWNER, IsRailTT() && railtype_override == INVALID_RAILTYPES ? Train::From(v)->compatible_railtypes : railtype_override, pPerf);
 	}
 
 	inline void Init(Owner o, RailTypes railtype_override, CPerformanceTimer *pPerf)
 	{
-		assert(!IsRoadTT() || m_veh != NULL);
+		assert(!IsRoadTT() || m_veh != nullptr);
 		assert(!IsRailTT() || railtype_override != INVALID_RAILTYPES);
 		m_veh_owner = o;
 		m_pPerf = pPerf;
@@ -126,7 +126,7 @@ struct CFollowTrackT
 		m_err = EC_NONE;
 		assert(
 			((TrackStatusToTrackdirBits(
-				GetTileTrackStatus(m_old_tile, TT(), (IsRoadTT() && m_veh != NULL) ? RoadVehicle::From(m_veh)->compatible_roadtypes : 0)
+				GetTileTrackStatus(m_old_tile, TT(), (IsRoadTT() && m_veh != nullptr) ? RoadVehicle::From(m_veh)->compatible_roadtypes : 0)
 			) & TrackdirToTrackdirBits(m_old_td)) != 0) ||
 			(IsTram() && GetSingleTramBit(m_old_tile) != INVALID_DIAGDIR) // Disable the assertion for single tram bits
 		);
@@ -447,7 +447,7 @@ protected:
 
 public:
 	/** Helper for pathfinders - get min/max speed on the m_old_tile/m_old_td */
-	int GetSpeedLimit(int *pmin_speed = NULL) const
+	int GetSpeedLimit(int *pmin_speed = nullptr) const
 	{
 		int min_speed = 0;
 		int max_speed = INT_MAX; // no limit
@@ -465,7 +465,7 @@ public:
 		}
 
 		/* if min speed was requested, return it */
-		if (pmin_speed != NULL) *pmin_speed = min_speed;
+		if (pmin_speed != nullptr) *pmin_speed = min_speed;
 		return max_speed;
 	}
 };
diff --git a/src/pathfinder/npf/aystar.cpp b/src/pathfinder/npf/aystar.cpp
--- a/src/pathfinder/npf/aystar.cpp
+++ b/src/pathfinder/npf/aystar.cpp
@@ -32,7 +32,7 @@
 /**
  * This looks in the hash whether a node exists in the closed list.
  * @param node Node to search.
- * @return The #PathNode if it is available, else \c NULL
+ * @return The #PathNode if it is available, else \c nullptr
  */
 PathNode *AyStar::ClosedListIsInList(const AyStarNode *node)
 {
@@ -55,7 +55,7 @@ void AyStar::ClosedListAdd(const PathNod
 /**
  * Check whether a node is in the open list.
  * @param node Node to search.
- * @return If the node is available, it is returned, else \c NULL is returned.
+ * @return If the node is available, it is returned, else \c nullptr is returned.
  */
 OpenListNode *AyStar::OpenListIsInList(const AyStarNode *node)
 {
@@ -65,13 +65,13 @@ OpenListNode *AyStar::OpenListIsInList(c
 /**
  * Gets the best node from the open list.
  * It deletes the returned node from the open list.
- * @returns the best node available, or \c NULL of none is found.
+ * @returns the best node available, or \c nullptr of none is found.
  */
 OpenListNode *AyStar::OpenListPop()
 {
 	/* Return the item the Queue returns.. the best next OpenList item. */
 	OpenListNode *res = (OpenListNode*)this->openlist_queue.Pop();
-	if (res != NULL) {
+	if (res != nullptr) {
 		this->openlist_hash.DeleteValue(res->path.node.tile, res->path.node.direction);
 	}
 
@@ -105,7 +105,7 @@ void AyStar::CheckTile(AyStarNode *curre
 	OpenListNode *check;
 
 	/* Check the new node against the ClosedList */
-	if (this->ClosedListIsInList(current) != NULL) return;
+	if (this->ClosedListIsInList(current) != nullptr) return;
 
 	/* Calculate the G-value for this node */
 	new_g = this->CalculateG(this, current, parent);
@@ -131,7 +131,7 @@ void AyStar::CheckTile(AyStarNode *curre
 
 	/* Check if this item is already in the OpenList */
 	check = this->OpenListIsInList(current);
-	if (check != NULL) {
+	if (check != nullptr) {
 		uint i;
 		/* Yes, check if this g value is lower.. */
 		if (new_g > check->g) return;
@@ -167,11 +167,11 @@ int AyStar::Loop()
 	/* Get the best node from OpenList */
 	OpenListNode *current = this->OpenListPop();
 	/* If empty, drop an error */
-	if (current == NULL) return AYSTAR_EMPTY_OPENLIST;
+	if (current == nullptr) return AYSTAR_EMPTY_OPENLIST;
 
 	/* Check for end node and if found, return that code */
 	if (this->EndNodeCheck(this, current) == AYSTAR_FOUND_END_NODE && !CheckIgnoreFirstTile(&current->path)) {
-		if (this->FoundEndNode != NULL) {
+		if (this->FoundEndNode != nullptr) {
 			this->FoundEndNode(this, current);
 		}
 		free(current);
@@ -285,7 +285,7 @@ void AyStar::AddStartNode(AyStarNode *st
 	printf("[AyStar] Starting A* Algorithm from node (%d, %d, %d)\n",
 		TileX(start_node->tile), TileY(start_node->tile), start_node->direction);
 #endif
-	this->OpenListAdd(NULL, start_node, 0, g);
+	this->OpenListAdd(nullptr, start_node, 0, g);
 }
 
 /**
diff --git a/src/pathfinder/npf/npf.cpp b/src/pathfinder/npf/npf.cpp
--- a/src/pathfinder/npf/npf.cpp
+++ b/src/pathfinder/npf/npf.cpp
@@ -103,7 +103,7 @@ static inline void NPFSetFlag(AyStarNode
 
 bool CheckIgnoreFirstTile(const PathNode *node)
 {
-	return (node->parent == NULL && HasBit(node->node.user_data[NPF_NODE_FLAGS], NPF_FLAG_IGNORE_START_TILE));
+	return (node->parent == nullptr && HasBit(node->node.user_data[NPF_NODE_FLAGS], NPF_FLAG_IGNORE_START_TILE));
 }
 
 /**
@@ -192,7 +192,7 @@ static int32 NPFCalcStationOrTileHeurist
  * choice */
 static void NPFFillTrackdirChoice(AyStarNode *current, OpenListNode *parent)
 {
-	if (parent->path.parent == NULL) {
+	if (parent->path.parent == nullptr) {
 		Trackdir trackdir = current->direction;
 		/* This is a first order decision, so we'd better save the
 		 * direction we chose */
@@ -584,7 +584,7 @@ static const PathNode *FindSafePosition(
 	/* If there is no signal, reserve the whole path. */
 	PathNode *sig = path;
 
-	for (; path->parent != NULL; path = path->parent) {
+	for (; path->parent != nullptr; path = path->parent) {
 		if (IsSafeWaitingPosition(v, path->node.tile, path->node.direction, true, _settings_game.pf.forbid_90_deg)) {
 			sig = path;
 		}
@@ -625,7 +625,7 @@ static void NPFSaveTargetData(AyStar *as
 	ftd->node = current->path.node;
 	ftd->res_okay = false;
 
-	if (as->user_target != NULL && ((NPFFindStationOrTileData*)as->user_target)->reserve_path && user->type == TRANSPORT_RAIL) {
+	if (as->user_target != nullptr && ((NPFFindStationOrTileData*)as->user_target)->reserve_path && user->type == TRANSPORT_RAIL) {
 		/* Path reservation is requested. */
 		const Train *v = Train::From(((NPFFindStationOrTileData *)as->user_target)->v);
 
@@ -647,7 +647,7 @@ static void NPFSaveTargetData(AyStar *as
 			if (!IsWaitingPositionFree(v, target->node.tile, target->node.direction, _settings_game.pf.forbid_90_deg)) return;
 		}
 
-		for (const PathNode *cur = target; cur->parent != NULL; cur = cur->parent) {
+		for (const PathNode *cur = target; cur->parent != nullptr; cur = cur->parent) {
 			if (!TryReserveRailTrack(cur->node.tile, TrackdirToTrack(cur->node.direction))) {
 				/* Reservation failed, undo. */
 				ClearPathReservation(target, cur);
@@ -957,7 +957,7 @@ static void NPFFollowTrack(AyStar *aysta
 
 /*
  * Plan a route to the specified target (which is checked by target_proc),
- * from start1 and if not NULL, from start2 as well. The type of transport we
+ * from start1 and if not nullptr, from start2 as well. The type of transport we
  * are checking is in type. reverse_penalty is applied to all routes that
  * originate from the second start node.
  * When we are looking for one specific target (optionally multiple tiles), we
@@ -989,7 +989,7 @@ static NPFFoundTargetData NPFRouteIntern
 	NPFSetFlag(start1, NPF_FLAG_IGNORE_START_TILE, ignore_start_tile1);
 	NPFSetFlag(start1, NPF_FLAG_IGNORE_RESERVED, ignore_reserved);
 	_npf_aystar.AddStartNode(start1, 0);
-	if (start2 != NULL) {
+	if (start2 != nullptr) {
 		start2->user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
 		start2->user_data[NPF_NODE_FLAGS] = 0;
 		NPFSetFlag(start2, NPF_FLAG_IGNORE_START_TILE, ignore_start_tile2);
@@ -1017,10 +1017,10 @@ static NPFFoundTargetData NPFRouteIntern
 	assert(r != AYSTAR_STILL_BUSY);
 
 	if (result.best_bird_dist != 0) {
-		if (target != NULL) {
+		if (target != nullptr) {
 			DEBUG(npf, 1, "Could not find route to tile 0x%X from 0x%X.", target->dest_coords, start1->tile);
 		} else {
-			/* Assumption: target == NULL, so we are looking for a depot */
+			/* Assumption: target == nullptr, so we are looking for a depot */
 			DEBUG(npf, 1, "Could not find route to a depot from tile 0x%X.", start1->tile);
 		}
 
@@ -1041,7 +1041,7 @@ static NPFFoundTargetData NPFRouteToStat
 	start1.direction = trackdir1;
 	start2.direction = trackdir2;
 
-	return NPFRouteInternal(&start1, ignore_start_tile1, (IsValidTile(tile2) ? &start2 : NULL), ignore_start_tile2, target, NPFFindStationOrTile, NPFCalcStationOrTileHeuristic, user, 0);
+	return NPFRouteInternal(&start1, ignore_start_tile1, (IsValidTile(tile2) ? &start2 : nullptr), ignore_start_tile2, target, NPFFindStationOrTile, NPFCalcStationOrTileHeuristic, user, 0);
 }
 
 /* Will search from the given tile and direction, for a route to the given
@@ -1069,9 +1069,9 @@ static NPFFoundTargetData NPFRouteToDepo
 	start1.direction = trackdir1;
 	start2.direction = trackdir2;
 
-	/* perform a breadth first search. Target is NULL,
+	/* perform a breadth first search. Target is nullptr,
 	 * since we are just looking for any depot...*/
-	return NPFRouteInternal(&start1, ignore_start_tile1, (IsValidTile(tile2) ? &start2 : NULL), ignore_start_tile2, target, NPFFindDepot, NPFCalcZero, user, reverse_penalty, false, max_penalty);
+	return NPFRouteInternal(&start1, ignore_start_tile1, (IsValidTile(tile2) ? &start2 : nullptr), ignore_start_tile2, target, NPFFindDepot, NPFCalcZero, user, reverse_penalty, false, max_penalty);
 }
 
 void InitializeNPF()
@@ -1121,7 +1121,7 @@ FindDepotData NPFRoadVehicleFindNearestD
 	Trackdir trackdir = v->GetVehicleTrackdir();
 
 	AyStarUserData user = { v->owner, TRANSPORT_ROAD, INVALID_RAILTYPES, v->compatible_roadtypes };
-	NPFFoundTargetData ftd = NPFRouteToDepotBreadthFirstTwoWay(v->tile, trackdir, false, INVALID_TILE, INVALID_TRACKDIR, false, NULL, &user, 0, max_penalty);
+	NPFFoundTargetData ftd = NPFRouteToDepotBreadthFirstTwoWay(v->tile, trackdir, false, INVALID_TILE, INVALID_TRACKDIR, false, nullptr, &user, 0, max_penalty);
 
 	if (ftd.best_bird_dist != 0) return FindDepotData();
 
@@ -1233,10 +1233,10 @@ bool NPFTrainFindNearestSafeTile(const T
 	RailTypes railtypes = v->compatible_railtypes;
 	if (override_railtype) railtypes |= GetRailTypeInfo(v->railtype)->compatible_railtypes;
 
-	/* perform a breadth first search. Target is NULL,
+	/* perform a breadth first search. Target is nullptr,
 	 * since we are just looking for any safe tile...*/
 	AyStarUserData user = { v->owner, TRANSPORT_RAIL, railtypes, ROADTYPES_NONE };
-	return NPFRouteInternal(&start1, true, NULL, false, &fstd, NPFFindSafeTile, NPFCalcZero, &user, 0, true).res_okay;
+	return NPFRouteInternal(&start1, true, nullptr, false, &fstd, NPFFindSafeTile, NPFCalcZero, &user, 0, true).res_okay;
 }
 
 bool NPFTrainCheckReverse(const Train *v)
@@ -1269,7 +1269,7 @@ Track NPFTrainChooseTrack(const Train *v
 	AyStarUserData user = { v->owner, TRANSPORT_RAIL, v->compatible_railtypes, ROADTYPES_NONE };
 	NPFFoundTargetData ftd = NPFRouteToStationOrTile(origin.tile, origin.trackdir, true, &fstd, &user);
 
-	if (target != NULL) {
+	if (target != nullptr) {
 		target->tile = ftd.node.tile;
 		target->trackdir = (Trackdir)ftd.node.direction;
 		target->okay = ftd.res_okay;
diff --git a/src/pathfinder/npf/queue.cpp b/src/pathfinder/npf/queue.cpp
--- a/src/pathfinder/npf/queue.cpp
+++ b/src/pathfinder/npf/queue.cpp
@@ -37,7 +37,7 @@ void BinaryHeap::Clear(bool free_values)
 	uint j;
 
 	for (i = 0; i < this->blocks; i++) {
-		if (this->elements[i] == NULL) {
+		if (this->elements[i] == nullptr) {
 			/* No more allocated blocks */
 			break;
 		}
@@ -55,7 +55,7 @@ void BinaryHeap::Clear(bool free_values)
 		if (i != 0) {
 			/* Leave the first block of memory alone */
 			free(this->elements[i]);
-			this->elements[i] = NULL;
+			this->elements[i] = nullptr;
 		}
 	}
 	this->size = 0;
@@ -73,7 +73,7 @@ void BinaryHeap::Free(bool free_values)
 
 	this->Clear(free_values);
 	for (i = 0; i < this->blocks; i++) {
-		if (this->elements[i] == NULL) break;
+		if (this->elements[i] == nullptr) break;
 		free(this->elements[i]);
 	}
 	free(this->elements);
@@ -88,7 +88,7 @@ bool BinaryHeap::Push(void *item, int pr
 	if (this->size == this->max_size) return false;
 	assert(this->size < this->max_size);
 
-	if (this->elements[this->size >> BINARY_HEAP_BLOCKSIZE_BITS] == NULL) {
+	if (this->elements[this->size >> BINARY_HEAP_BLOCKSIZE_BITS] == nullptr) {
 		/* The currently allocated blocks are full, allocate a new one */
 		assert((this->size & BINARY_HEAP_BLOCKSIZE_MASK) == 0);
 		this->elements[this->size >> BINARY_HEAP_BLOCKSIZE_BITS] = MallocT<BinaryHeapNode>(BINARY_HEAP_BLOCKSIZE);
@@ -195,7 +195,7 @@ void *BinaryHeap::Pop()
 {
 	void *result;
 
-	if (this->size == 0) return NULL;
+	if (this->size == 0) return nullptr;
 
 	/* The best item is always on top, so give that as result */
 	result = this->GetElement(1).item;
@@ -264,7 +264,7 @@ void Hash::Delete(bool free_values)
 			/* Free the first value */
 			if (free_values) free(this->buckets[i].value);
 			node = this->buckets[i].next;
-			while (node != NULL) {
+			while (node != nullptr) {
 				HashNode *prev = node;
 
 				node = node->next;
@@ -296,7 +296,7 @@ void Hash::PrintStatistics() const
 			const HashNode *node;
 
 			used_buckets++;
-			for (node = &this->buckets[i]; node != NULL; node = node->next) collision++;
+			for (node = &this->buckets[i]; node != nullptr; node = node->next) collision++;
 			if (collision > max_collision) max_collision = collision;
 		}
 		if (collision >= lengthof(usage)) collision = lengthof(usage) - 1;
@@ -351,7 +351,7 @@ void Hash::Clear(bool free_values)
 			/* Free the first value */
 			if (free_values) free(this->buckets[i].value);
 			node = this->buckets[i].next;
-			while (node != NULL) {
+			while (node != nullptr) {
 				HashNode *prev = node;
 
 				node = node->next;
@@ -365,32 +365,32 @@ void Hash::Clear(bool free_values)
 
 /**
  * Finds the node that that saves this key pair. If it is not
- * found, returns NULL. If it is found, *prev is set to the
+ * found, returns nullptr. If it is found, *prev is set to the
  * node before the one found, or if the node found was the first in the bucket
- * to NULL. If it is not found, *prev is set to the last HashNode in the
- * bucket, or NULL if it is empty. prev can also be NULL, in which case it is
+ * to nullptr. If it is not found, *prev is set to the last HashNode in the
+ * bucket, or nullptr if it is empty. prev can also be nullptr, in which case it is
  * not used for output.
  */
 HashNode *Hash::FindNode(uint key1, uint key2, HashNode** prev_out) const
 {
 	uint hash = this->hash(key1, key2);
-	HashNode *result = NULL;
+	HashNode *result = nullptr;
 
 	/* Check if the bucket is empty */
 	if (!this->buckets_in_use[hash]) {
-		if (prev_out != NULL) *prev_out = NULL;
-		result = NULL;
+		if (prev_out != nullptr) *prev_out = nullptr;
+		result = nullptr;
 	/* Check the first node specially */
 	} else if (this->buckets[hash].key1 == key1 && this->buckets[hash].key2 == key2) {
 		/* Save the value */
 		result = this->buckets + hash;
-		if (prev_out != NULL) *prev_out = NULL;
+		if (prev_out != nullptr) *prev_out = nullptr;
 	/* Check all other nodes */
 	} else {
 		HashNode *prev = this->buckets + hash;
 		HashNode *node;
 
-		for (node = prev->next; node != NULL; node = node->next) {
+		for (node = prev->next; node != nullptr; node = node->next) {
 			if (node->key1 == key1 && node->key2 == key2) {
 				/* Found it */
 				result = node;
@@ -398,14 +398,14 @@ HashNode *Hash::FindNode(uint key1, uint
 			}
 			prev = node;
 		}
-		if (prev_out != NULL) *prev_out = prev;
+		if (prev_out != nullptr) *prev_out = prev;
 	}
 	return result;
 }
 
 /**
  * Deletes the value with the specified key pair from the hash and returns
- * that value. Returns NULL when the value was not present. The value returned
+ * that value. Returns nullptr when the value was not present. The value returned
  * is _not_ free()'d!
  */
 void *Hash::DeleteValue(uint key1, uint key2)
@@ -414,15 +414,15 @@ void *Hash::DeleteValue(uint key1, uint 
 	HashNode *prev; // Used as output var for below function call
 	HashNode *node = this->FindNode(key1, key2, &prev);
 
-	if (node == NULL) {
+	if (node == nullptr) {
 		/* not found */
-		result = NULL;
-	} else if (prev == NULL) {
+		result = nullptr;
+	} else if (prev == nullptr) {
 		/* It is in the first node, we can't free that one, so we free
 		 * the next one instead (if there is any)*/
 		/* Save the value */
 		result = node->value;
-		if (node->next != NULL) {
+		if (node->next != nullptr) {
 			HashNode *next = node->next;
 			/* Copy the second to the first */
 			*node = *next;
@@ -443,20 +443,20 @@ void *Hash::DeleteValue(uint key1, uint 
 		/* Free the node */
 		free(node);
 	}
-	if (result != NULL) this->size--;
+	if (result != nullptr) this->size--;
 	return result;
 }
 
 /**
  * Sets the value associated with the given key pair to the given value.
- * Returns the old value if the value was replaced, NULL when it was not yet present.
+ * Returns the old value if the value was replaced, nullptr when it was not yet present.
  */
 void *Hash::Set(uint key1, uint key2, void *value)
 {
 	HashNode *prev;
 	HashNode *node = this->FindNode(key1, key2, &prev);
 
-	if (node != NULL) {
+	if (node != nullptr) {
 		/* Found it */
 		void *result = node->value;
 
@@ -464,7 +464,7 @@ void *Hash::Set(uint key1, uint key2, vo
 		return result;
 	}
 	/* It is not yet present, let's add it */
-	if (prev == NULL) {
+	if (prev == nullptr) {
 		/* The bucket is still empty */
 		uint hash = this->hash(key1, key2);
 		this->buckets_in_use[hash] = true;
@@ -474,21 +474,21 @@ void *Hash::Set(uint key1, uint key2, vo
 		node = MallocT<HashNode>(1);
 		prev->next = node;
 	}
-	node->next = NULL;
+	node->next = nullptr;
 	node->key1 = key1;
 	node->key2 = key2;
 	node->value = value;
 	this->size++;
-	return NULL;
+	return nullptr;
 }
 
 /**
- * Gets the value associated with the given key pair, or NULL when it is not
+ * Gets the value associated with the given key pair, or nullptr when it is not
  * present.
  */
 void *Hash::Get(uint key1, uint key2) const
 {
-	HashNode *node = this->FindNode(key1, key2, NULL);
+	HashNode *node = this->FindNode(key1, key2, nullptr);
 
-	return (node != NULL) ? node->value : NULL;
+	return (node != nullptr) ? node->value : nullptr;
 }
diff --git a/src/pathfinder/pf_performance_timer.hpp b/src/pathfinder/pf_performance_timer.hpp
--- a/src/pathfinder/pf_performance_timer.hpp
+++ b/src/pathfinder/pf_performance_timer.hpp
@@ -53,7 +53,7 @@ struct CPerfStartReal
 
 	inline CPerfStartReal(CPerformanceTimer& perf) : m_pperf(&perf)
 	{
-		if (m_pperf != NULL) m_pperf->Start();
+		if (m_pperf != nullptr) m_pperf->Start();
 	}
 
 	inline ~CPerfStartReal()
@@ -63,9 +63,9 @@ struct CPerfStartReal
 
 	inline void Stop()
 	{
-		if (m_pperf != NULL) {
+		if (m_pperf != nullptr) {
 			m_pperf->Stop();
-			m_pperf = NULL;
+			m_pperf = nullptr;
 		}
 	}
 };
diff --git a/src/pathfinder/yapf/nodelist.hpp b/src/pathfinder/yapf/nodelist.hpp
--- a/src/pathfinder/yapf/nodelist.hpp
+++ b/src/pathfinder/yapf/nodelist.hpp
@@ -42,7 +42,7 @@ public:
 	/** default constructor */
 	CNodeList_HashTableT() : m_open_queue(2048)
 	{
-		m_new_node = NULL;
+		m_new_node = nullptr;
 	}
 
 	/** destructor */
@@ -65,7 +65,7 @@ public:
 	/** allocate new data item from m_arr */
 	inline Titem_ *CreateNewNode()
 	{
-		if (m_new_node == NULL) m_new_node = m_arr.AppendC();
+		if (m_new_node == nullptr) m_new_node = m_arr.AppendC();
 		return m_new_node;
 	}
 
@@ -74,7 +74,7 @@ public:
 	{
 		/* for now it is enough to invalidate m_new_node if it is our given node */
 		if (&item == m_new_node) {
-			m_new_node = NULL;
+			m_new_node = nullptr;
 		}
 		/* TODO: do we need to store best nodes found in some extra list/array? Probably not now. */
 	}
@@ -82,11 +82,11 @@ public:
 	/** insert given item as open node (into m_open and m_open_queue) */
 	inline void InsertOpenNode(Titem_ &item)
 	{
-		assert(m_closed.Find(item.GetKey()) == NULL);
+		assert(m_closed.Find(item.GetKey()) == nullptr);
 		m_open.Push(item);
 		m_open_queue.Include(&item);
 		if (&item == m_new_node) {
-			m_new_node = NULL;
+			m_new_node = nullptr;
 		}
 	}
 
@@ -96,7 +96,7 @@ public:
 		if (!m_open_queue.IsEmpty()) {
 			return m_open_queue.Begin();
 		}
-		return NULL;
+		return nullptr;
 	}
 
 	/** remove and return the best open node */
@@ -107,10 +107,10 @@ public:
 			m_open.Pop(*item);
 			return item;
 		}
-		return NULL;
+		return nullptr;
 	}
 
-	/** return the open node specified by a key or NULL if not found */
+	/** return the open node specified by a key or nullptr if not found */
 	inline Titem_ *FindOpenNode(const Key &key)
 	{
 		Titem_ *item = m_open.Find(key);
@@ -129,11 +129,11 @@ public:
 	/** close node */
 	inline void InsertClosedNode(Titem_ &item)
 	{
-		assert(m_open.Find(item.GetKey()) == NULL);
+		assert(m_open.Find(item.GetKey()) == nullptr);
 		m_closed.Push(item);
 	}
 
-	/** return the closed node specified by a key or NULL if not found */
+	/** return the closed node specified by a key or nullptr if not found */
 	inline Titem_ *FindClosedNode(const Key &key)
 	{
 		Titem_ *item = m_closed.Find(key);
diff --git a/src/pathfinder/yapf/yapf_base.hpp b/src/pathfinder/yapf/yapf_base.hpp
--- a/src/pathfinder/yapf/yapf_base.hpp
+++ b/src/pathfinder/yapf/yapf_base.hpp
@@ -81,11 +81,11 @@ public:
 public:
 	/** default constructor */
 	inline CYapfBaseT()
-		: m_pBestDestNode(NULL)
-		, m_pBestIntermediateNode(NULL)
+		: m_pBestDestNode(nullptr)
+		, m_pBestIntermediateNode(nullptr)
 		, m_settings(&_settings_game.pf.yapf)
 		, m_max_search_nodes(PfGetSettings().max_search_nodes)
-		, m_veh(NULL)
+		, m_veh(nullptr)
 		, m_stats_cost_calcs(0)
 		, m_stats_cache_hits(0)
 		, m_num_steps(0)
@@ -131,12 +131,12 @@ public:
 		for (;;) {
 			m_num_steps++;
 			Node *n = m_nodes.GetBestOpenNode();
-			if (n == NULL) {
+			if (n == nullptr) {
 				break;
 			}
 
 			/* if the best open node was worse than the best path found, we can finish */
-			if (m_pBestDestNode != NULL && m_pBestDestNode->GetCost() < n->GetCostEstimate()) {
+			if (m_pBestDestNode != nullptr && m_pBestDestNode->GetCost() < n->GetCostEstimate()) {
 				break;
 			}
 
@@ -150,7 +150,7 @@ public:
 			}
 		}
 
-		bDestFound &= (m_pBestDestNode != NULL);
+		bDestFound &= (m_pBestDestNode != nullptr);
 
 		perf.Stop();
 		if (_debug_yapf_level >= 2) {
@@ -158,7 +158,7 @@ public:
 			_total_pf_time_us += t;
 
 			if (_debug_yapf_level >= 3) {
-				UnitID veh_idx = (m_veh != NULL) ? m_veh->unitnumber : 0;
+				UnitID veh_idx = (m_veh != nullptr) ? m_veh->unitnumber : 0;
 				char ttc = Yapf().TransportTypeChar();
 				float cache_hit_ratio = (m_stats_cache_hits == 0) ? 0.0f : ((float)m_stats_cache_hits / (float)(m_stats_cache_hits + m_stats_cost_calcs) * 100.0f);
 				int cost = bDestFound ? m_pBestDestNode->m_cost : -1;
@@ -180,7 +180,7 @@ public:
 	 */
 	inline Node *GetBestNode()
 	{
-		return (m_pBestDestNode != NULL) ? m_pBestDestNode : m_pBestIntermediateNode;
+		return (m_pBestDestNode != nullptr) ? m_pBestDestNode : m_pBestIntermediateNode;
 	}
 
 	/**
@@ -198,7 +198,7 @@ public:
 	{
 		Yapf().PfNodeCacheFetch(n);
 		/* insert the new node only if it is not there */
-		if (m_nodes.FindOpenNode(n.m_key) == NULL) {
+		if (m_nodes.FindOpenNode(n.m_key) == nullptr) {
 			m_nodes.InsertOpenNode(n);
 		} else {
 			/* if we are here, it means that node is already there - how it is possible?
@@ -229,7 +229,7 @@ public:
 	 */
 	void PruneIntermediateNodeBranch()
 	{
-		while (Yapf().m_pBestIntermediateNode != NULL && (Yapf().m_pBestIntermediateNode->m_segment->m_end_segment_reason & ESRB_CHOICE_FOLLOWS) == 0) {
+		while (Yapf().m_pBestIntermediateNode != nullptr && (Yapf().m_pBestIntermediateNode->m_segment->m_end_segment_reason & ESRB_CHOICE_FOLLOWS) == 0) {
 			Yapf().m_pBestIntermediateNode = Yapf().m_pBestIntermediateNode->m_parent;
 		}
 	}
@@ -262,20 +262,20 @@ public:
 		/* detect the destination */
 		bool bDestination = Yapf().PfDetectDestination(n);
 		if (bDestination) {
-			if (m_pBestDestNode == NULL || n < *m_pBestDestNode) {
+			if (m_pBestDestNode == nullptr || n < *m_pBestDestNode) {
 				m_pBestDestNode = &n;
 			}
 			m_nodes.FoundBestNode(n);
 			return;
 		}
 
-		if (m_max_search_nodes > 0 && (m_pBestIntermediateNode == NULL || (m_pBestIntermediateNode->GetCostEstimate() - m_pBestIntermediateNode->GetCost()) > (n.GetCostEstimate() - n.GetCost()))) {
+		if (m_max_search_nodes > 0 && (m_pBestIntermediateNode == nullptr || (m_pBestIntermediateNode->GetCostEstimate() - m_pBestIntermediateNode->GetCost()) > (n.GetCostEstimate() - n.GetCost()))) {
 			m_pBestIntermediateNode = &n;
 		}
 
 		/* check new node against open list */
 		Node *openNode = m_nodes.FindOpenNode(n.GetKey());
-		if (openNode != NULL) {
+		if (openNode != nullptr) {
 			/* another node exists with the same key in the open list
 			 * is it better than new one? */
 			if (n.GetCostEstimate() < openNode->GetCostEstimate()) {
@@ -290,7 +290,7 @@ public:
 
 		/* check new node against closed list */
 		Node *closedNode = m_nodes.FindClosedNode(n.GetKey());
-		if (closedNode != NULL) {
+		if (closedNode != nullptr) {
 			/* another node exists with the same key in the closed list
 			 * is it better than new one? */
 			int node_est = n.GetCostEstimate();
diff --git a/src/pathfinder/yapf/yapf_common.hpp b/src/pathfinder/yapf/yapf_common.hpp
--- a/src/pathfinder/yapf/yapf_common.hpp
+++ b/src/pathfinder/yapf/yapf_common.hpp
@@ -46,7 +46,7 @@ public:
 		for (TrackdirBits tdb = m_orgTrackdirs; tdb != TRACKDIR_BIT_NONE; tdb = KillFirstBit(tdb)) {
 			Trackdir td = (Trackdir)FindFirstBit2x64(tdb);
 			Node &n1 = Yapf().CreateNewNode();
-			n1.Set(NULL, m_orgTile, td, is_choice);
+			n1.Set(nullptr, m_orgTile, td, is_choice);
 			Yapf().AddStartupNode(n1);
 		}
 	}
@@ -92,12 +92,12 @@ public:
 	{
 		if (m_orgTile != INVALID_TILE && m_orgTd != INVALID_TRACKDIR) {
 			Node &n1 = Yapf().CreateNewNode();
-			n1.Set(NULL, m_orgTile, m_orgTd, false);
+			n1.Set(nullptr, m_orgTile, m_orgTd, false);
 			Yapf().AddStartupNode(n1);
 		}
 		if (m_revTile != INVALID_TILE && m_revTd != INVALID_TRACKDIR) {
 			Node &n2 = Yapf().CreateNewNode();
-			n2.Set(NULL, m_revTile, m_revTd, false);
+			n2.Set(nullptr, m_revTile, m_revTd, false);
 			n2.m_cost = m_reverse_penalty;
 			Yapf().AddStartupNode(n2);
 		}
diff --git a/src/pathfinder/yapf/yapf_costcache.hpp b/src/pathfinder/yapf/yapf_costcache.hpp
--- a/src/pathfinder/yapf/yapf_costcache.hpp
+++ b/src/pathfinder/yapf/yapf_costcache.hpp
@@ -143,7 +143,7 @@ struct CSegmentCostCacheT : public CSegm
 	inline Tsegment& Get(Key &key, bool *found)
 	{
 		Tsegment *item = m_map.Find(key);
-		if (item == NULL) {
+		if (item == nullptr) {
 			*found = false;
 			item = new (m_heap.Append()) Tsegment(key);
 			m_map.Push(*item);
diff --git a/src/pathfinder/yapf/yapf_costrail.hpp b/src/pathfinder/yapf/yapf_costrail.hpp
--- a/src/pathfinder/yapf/yapf_costrail.hpp
+++ b/src/pathfinder/yapf/yapf_costrail.hpp
@@ -251,7 +251,7 @@ public:
 	{
 		int cost = 0;
 		const Train *v = Yapf().GetVehicle();
-		assert(v != NULL);
+		assert(v != nullptr);
 		assert(v->type == VEH_TRAIN);
 		assert(v->gcache.cached_total_length != 0);
 		int missing_platform_length = CeilDiv(v->gcache.cached_total_length, TILE_SIZE) - platform_length;
@@ -285,7 +285,7 @@ public:
 		CPerfStart perf_cost(Yapf().m_perf_cost);
 
 		/* Does the node have some parent node? */
-		bool has_parent = (n.m_parent != NULL);
+		bool has_parent = (n.m_parent != nullptr);
 
 		/* Do we already have a cached segment? */
 		CachedData &segment = *n.m_segment;
@@ -606,7 +606,7 @@ no_entry_cost: // jump here at the begin
 			/* Station platform-length penalty. */
 			if ((end_segment_reason & ESRB_STATION) != ESRB_NONE) {
 				const BaseStation *st = BaseStation::GetByTile(n.GetLastTile());
-				assert(st != NULL);
+				assert(st != nullptr);
 				uint platform_length = st->GetPlatformLength(n.GetLastTile(), ReverseDiagDir(TrackdirToExitdir(n.GetLastTrackdir())));
 				/* Reduce the extra cost caused by passing-station penalty (each station receives it in the segment cost). */
 				extra_cost -= Yapf().PfGetSettings().rail_station_penalty * platform_length;
@@ -624,7 +624,7 @@ no_entry_cost: // jump here at the begin
 	inline bool CanUseGlobalCache(Node &n) const
 	{
 		return !m_disable_cache
-			&& (n.m_parent != NULL)
+			&& (n.m_parent != nullptr)
 			&& (n.m_parent->m_num_signals_passed >= m_sig_look_ahead_costs.Size());
 	}
 
diff --git a/src/pathfinder/yapf/yapf_node.hpp b/src/pathfinder/yapf/yapf_node.hpp
--- a/src/pathfinder/yapf/yapf_node.hpp
+++ b/src/pathfinder/yapf/yapf_node.hpp
@@ -72,7 +72,7 @@ struct CYapfNodeT {
 	inline void Set(Node *parent, TileIndex tile, Trackdir td, bool is_choice)
 	{
 		m_key.Set(tile, td);
-		m_hash_next = NULL;
+		m_hash_next = nullptr;
 		m_parent = parent;
 		m_cost = 0;
 		m_estimate = 0;
diff --git a/src/pathfinder/yapf/yapf_node_rail.hpp b/src/pathfinder/yapf/yapf_node_rail.hpp
--- a/src/pathfinder/yapf/yapf_node_rail.hpp
+++ b/src/pathfinder/yapf/yapf_node_rail.hpp
@@ -83,7 +83,7 @@ struct CYapfRailSegment
 		, m_last_signal_tile(INVALID_TILE)
 		, m_last_signal_td(INVALID_TRACKDIR)
 		, m_end_segment_reason(ESRB_NONE)
-		, m_hash_next(NULL)
+		, m_hash_next(nullptr)
 	{}
 
 	inline const Key& GetKey() const
@@ -142,8 +142,8 @@ struct CYapfRailNodeT
 	inline void Set(CYapfRailNodeT *parent, TileIndex tile, Trackdir td, bool is_choice)
 	{
 		base::Set(parent, tile, td, is_choice);
-		m_segment = NULL;
-		if (parent == NULL) {
+		m_segment = nullptr;
+		if (parent == nullptr) {
 			m_num_signals_passed      = 0;
 			flags_u.m_inherited_flags = 0;
 			m_last_red_signal_type    = SIGTYPE_NORMAL;
@@ -169,19 +169,19 @@ struct CYapfRailNodeT
 
 	inline TileIndex GetLastTile() const
 	{
-		assert(m_segment != NULL);
+		assert(m_segment != nullptr);
 		return m_segment->m_last_tile;
 	}
 
 	inline Trackdir GetLastTrackdir() const
 	{
-		assert(m_segment != NULL);
+		assert(m_segment != nullptr);
 		return m_segment->m_last_td;
 	}
 
 	inline void SetLastTileTrackdir(TileIndex tile, Trackdir td)
 	{
-		assert(m_segment != NULL);
+		assert(m_segment != nullptr);
 		m_segment->m_last_tile = tile;
 		m_segment->m_last_td = td;
 	}
diff --git a/src/pathfinder/yapf/yapf_rail.cpp b/src/pathfinder/yapf/yapf_rail.cpp
--- a/src/pathfinder/yapf/yapf_rail.cpp
+++ b/src/pathfinder/yapf/yapf_rail.cpp
@@ -28,8 +28,8 @@ template <typename Tpf> void DumpState(T
 	pf2.DumpBase(dmp2);
 	FILE *f1 = fopen("yapf1.txt", "wt");
 	FILE *f2 = fopen("yapf2.txt", "wt");
-	assert(f1 != NULL);
-	assert(f2 != NULL);
+	assert(f1 != nullptr);
+	assert(f2 != nullptr);
 	fwrite(dmp1.m_out.Data(), 1, dmp1.m_out.Size(), f1);
 	fwrite(dmp2.m_out.Data(), 1, dmp2.m_out.Size(), f2);
 	fclose(f1);
@@ -84,7 +84,7 @@ private:
 			tile = TILE_ADD(tile, diff);
 		} while (IsCompatibleTrainStationTile(tile, start) && tile != m_origin_tile);
 
-		TriggerStationRandomisation(NULL, start, SRT_PATH_RESERVATION);
+		TriggerStationRandomisation(nullptr, start, SRT_PATH_RESERVATION);
 
 		return true;
 	}
@@ -138,7 +138,7 @@ public:
 	/** Check the node for a possible reservation target. */
 	inline void FindSafePositionOnNode(Node *node)
 	{
-		assert(node->m_parent != NULL);
+		assert(node->m_parent != nullptr);
 
 		/* We will never pass more than two signals, no need to check for a safe tile. */
 		if (node->m_parent->m_num_signals_passed >= 2) return;
@@ -154,7 +154,7 @@ public:
 		m_res_fail_tile = INVALID_TILE;
 		m_origin_tile = origin;
 
-		if (target != NULL) {
+		if (target != nullptr) {
 			target->tile = m_res_dest;
 			target->trackdir = m_res_dest_td;
 			target->okay = false;
@@ -163,7 +163,7 @@ public:
 		/* Don't bother if the target is reserved. */
 		if (!IsWaitingPositionFree(Yapf().GetVehicle(), m_res_dest, m_res_dest_td)) return false;
 
-		for (Node *node = m_res_node; node->m_parent != NULL; node = node->m_parent) {
+		for (Node *node = m_res_node; node->m_parent != nullptr; node = node->m_parent) {
 			node->IterateTiles(Yapf().GetVehicle(), Yapf(), *this, &CYapfReserveTrack<Types>::ReserveSingleTrack);
 			if (m_res_fail_tile != INVALID_TILE) {
 				/* Reservation failed, undo. */
@@ -173,13 +173,13 @@ public:
 					/* If this is the node that failed, stop at the failed tile. */
 					m_res_fail_tile = fail_node == node ? stop_tile : INVALID_TILE;
 					fail_node->IterateTiles(Yapf().GetVehicle(), Yapf(), *this, &CYapfReserveTrack<Types>::UnreserveSingleTrack);
-				} while (fail_node != node && (fail_node = fail_node->m_parent) != NULL);
+				} while (fail_node != node && (fail_node = fail_node->m_parent) != nullptr);
 
 				return false;
 			}
 		}
 
-		if (target != NULL) target->okay = true;
+		if (target != nullptr) target->okay = true;
 
 		if (Yapf().CanUseGlobalCache(*m_res_node)) {
 			YapfNotifyTrackLayoutChange(INVALID_TILE, INVALID_TRACK);
@@ -270,7 +270,7 @@ public:
 
 		/* walk through the path back to the origin */
 		Node *pNode = n;
-		while (pNode->m_parent != NULL) {
+		while (pNode->m_parent != nullptr) {
 			pNode = pNode->m_parent;
 		}
 
@@ -351,15 +351,15 @@ public:
 		this->SetReservationTarget(pNode, pNode->GetLastTile(), pNode->GetLastTrackdir());
 
 		/* Walk through the path back to the origin. */
-		Node *pPrev = NULL;
-		while (pNode->m_parent != NULL) {
+		Node *pPrev = nullptr;
+		while (pNode->m_parent != nullptr) {
 			pPrev = pNode;
 			pNode = pNode->m_parent;
 
 			this->FindSafePositionOnNode(pPrev);
 		}
 
-		return dont_reserve || this->TryReservePath(NULL, pNode->GetLastTile());
+		return dont_reserve || this->TryReservePath(nullptr, pNode->GetLastTile());
 	}
 };
 
@@ -408,7 +408,7 @@ public:
 		if (_debug_desync_level < 2) {
 			result1 = pf1.ChooseRailTrack(v, tile, enterdir, tracks, path_found, reserve_track, target);
 		} else {
-			result1 = pf1.ChooseRailTrack(v, tile, enterdir, tracks, path_found, false, NULL);
+			result1 = pf1.ChooseRailTrack(v, tile, enterdir, tracks, path_found, false, nullptr);
 			Tpf pf2;
 			pf2.DisableCache(true);
 			Trackdir result2 = pf2.ChooseRailTrack(v, tile, enterdir, tracks, path_found, reserve_track, target);
@@ -423,7 +423,7 @@ public:
 
 	inline Trackdir ChooseRailTrack(const Train *v, TileIndex tile, DiagDirection enterdir, TrackBits tracks, bool &path_found, bool reserve_track, PBSTileInfo *target)
 	{
-		if (target != NULL) target->tile = INVALID_TILE;
+		if (target != nullptr) target->tile = INVALID_TILE;
 
 		/* set origin and destination nodes */
 		PBSTileInfo origin = FollowTrainReservation(v);
@@ -436,14 +436,14 @@ public:
 		/* if path not found - return INVALID_TRACKDIR */
 		Trackdir next_trackdir = INVALID_TRACKDIR;
 		Node *pNode = Yapf().GetBestNode();
-		if (pNode != NULL) {
+		if (pNode != nullptr) {
 			/* reserve till end of path */
 			this->SetReservationTarget(pNode, pNode->GetLastTile(), pNode->GetLastTrackdir());
 
 			/* path was found or at least suggested
 			 * walk through the path back to the origin */
-			Node *pPrev = NULL;
-			while (pNode->m_parent != NULL) {
+			Node *pPrev = nullptr;
+			while (pNode->m_parent != nullptr) {
 				pPrev = pNode;
 				pNode = pNode->m_parent;
 
@@ -494,7 +494,7 @@ public:
 		/* path was found
 		 * walk through the path back to the origin */
 		Node *pNode = Yapf().GetBestNode();
-		while (pNode->m_parent != NULL) {
+		while (pNode->m_parent != nullptr) {
 			pNode = pNode->m_parent;
 		}
 
diff --git a/src/pathfinder/yapf/yapf_road.cpp b/src/pathfinder/yapf/yapf_road.cpp
--- a/src/pathfinder/yapf/yapf_road.cpp
+++ b/src/pathfinder/yapf/yapf_road.cpp
@@ -118,7 +118,7 @@ public:
 		/* start at n.m_key.m_tile / n.m_key.m_td and walk to the end of segment */
 		TileIndex tile = n.m_key.m_tile;
 		Trackdir trackdir = n.m_key.m_td;
-		int parent_cost = (n.m_parent != NULL) ? n.m_parent->m_cost : 0;
+		int parent_cost = (n.m_parent != nullptr) ? n.m_parent->m_cost : 0;
 
 		for (;;) {
 			/* base tile cost depending on distance between edges */
@@ -381,13 +381,13 @@ public:
 		/* if path not found - return INVALID_TRACKDIR */
 		Trackdir next_trackdir = INVALID_TRACKDIR;
 		Node *pNode = Yapf().GetBestNode();
-		if (pNode != NULL) {
+		if (pNode != nullptr) {
 			uint steps = 0;
-			for (Node *n = pNode; n->m_parent != NULL; n = n->m_parent) steps++;
+			for (Node *n = pNode; n->m_parent != nullptr; n = n->m_parent) steps++;
 
 			/* path was found or at least suggested
 			 * walk through the path back to its origin */
-			while (pNode->m_parent != NULL) {
+			while (pNode->m_parent != nullptr) {
 				steps--;
 				if (pNode->GetIsChoice() && steps < YAPF_ROADVEH_PATH_CACHE_SEGMENTS) {
 					TrackdirByte td;
@@ -436,7 +436,7 @@ public:
 		if (!Yapf().FindPath(v)) return dist;
 
 		Node *pNode = Yapf().GetBestNode();
-		if (pNode != NULL) {
+		if (pNode != nullptr) {
 			/* path was found
 			 * get the path cost estimate */
 			dist = pNode->GetCostEstimate();
diff --git a/src/pathfinder/yapf/yapf_ship.cpp b/src/pathfinder/yapf/yapf_ship.cpp
--- a/src/pathfinder/yapf/yapf_ship.cpp
+++ b/src/pathfinder/yapf/yapf_ship.cpp
@@ -89,13 +89,13 @@ public:
 		Trackdir next_trackdir = INVALID_TRACKDIR; // this would mean "path not found"
 
 		Node *pNode = pf.GetBestNode();
-		if (pNode != NULL) {
+		if (pNode != nullptr) {
 			uint steps = 0;
-			for (Node *n = pNode; n->m_parent != NULL; n = n->m_parent) steps++;
+			for (Node *n = pNode; n->m_parent != nullptr; n = n->m_parent) steps++;
 
 			/* walk through the path back to the origin */
-			Node *pPrevNode = NULL;
-			while (pNode->m_parent != NULL) {
+			Node *pPrevNode = nullptr;
+			while (pNode->m_parent != nullptr) {
 				steps--;
 				if (steps > 0 && steps < YAPF_SHIP_PATH_CACHE_LENGTH) {
 					TrackdirByte td;
@@ -138,11 +138,11 @@ public:
 		if (!pf.FindPath(v)) return false;
 
 		Node *pNode = pf.GetBestNode();
-		if (pNode == NULL) return false;
+		if (pNode == nullptr) return false;
 
 		/* path was found
 		 * walk through the path back to the origin */
-		while (pNode->m_parent != NULL) {
+		while (pNode->m_parent != nullptr) {
 			pNode = pNode->m_parent;
 		}
 
diff --git a/src/pbs.cpp b/src/pbs.cpp
--- a/src/pbs.cpp
+++ b/src/pbs.cpp
@@ -116,7 +116,7 @@ bool TryReserveRailTrack(TileIndex tile,
 		case MP_STATION:
 			if (HasStationRail(tile) && !HasStationReservation(tile)) {
 				SetRailStationReservation(tile, true);
-				if (trigger_stations && IsRailStation(tile)) TriggerStationRandomisation(NULL, tile, SRT_PATH_RESERVATION);
+				if (trigger_stations && IsRailStation(tile)) TriggerStationRandomisation(nullptr, tile, SRT_PATH_RESERVATION);
 				MarkTileDirtyByTile(tile); // some GRFs need redraw after reserving track
 				return true;
 			}
@@ -258,8 +258,8 @@ struct FindTrainOnTrackInfo {
 	PBSTileInfo res; ///< Information about the track.
 	Train *best;     ///< The currently "best" vehicle we have found.
 
-	/** Init the best location to NULL always! */
-	FindTrainOnTrackInfo() : best(NULL) {}
+	/** Init the best location to nullptr always! */
+	FindTrainOnTrackInfo() : best(nullptr) {}
 };
 
 /** Callback for Has/FindVehicleOnPos to find a train on a specific track. */
@@ -267,18 +267,18 @@ static Vehicle *FindTrainOnTrackEnum(Veh
 {
 	FindTrainOnTrackInfo *info = (FindTrainOnTrackInfo *)data;
 
-	if (v->type != VEH_TRAIN || (v->vehstatus & VS_CRASHED)) return NULL;
+	if (v->type != VEH_TRAIN || (v->vehstatus & VS_CRASHED)) return nullptr;
 
 	Train *t = Train::From(v);
 	if (t->track == TRACK_BIT_WORMHOLE || HasBit((TrackBits)t->track, TrackdirToTrack(info->res.trackdir))) {
 		t = t->First();
 
 		/* ALWAYS return the lowest ID (anti-desync!) */
-		if (info->best == NULL || t->index < info->best->index) info->best = t;
+		if (info->best == nullptr || t->index < info->best->index) info->best = t;
 		return t;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -300,24 +300,24 @@ PBSTileInfo FollowTrainReservation(const
 	FindTrainOnTrackInfo ftoti;
 	ftoti.res = FollowReservation(v->owner, GetRailTypeInfo(v->railtype)->compatible_railtypes, tile, trackdir);
 	ftoti.res.okay = IsSafeWaitingPosition(v, ftoti.res.tile, ftoti.res.trackdir, true, _settings_game.pf.forbid_90_deg);
-	if (train_on_res != NULL) {
+	if (train_on_res != nullptr) {
 		FindVehicleOnPos(ftoti.res.tile, &ftoti, FindTrainOnTrackEnum);
-		if (ftoti.best != NULL) *train_on_res = ftoti.best->First();
-		if (*train_on_res == NULL && IsRailStationTile(ftoti.res.tile)) {
+		if (ftoti.best != nullptr) *train_on_res = ftoti.best->First();
+		if (*train_on_res == nullptr && IsRailStationTile(ftoti.res.tile)) {
 			/* The target tile is a rail station. The track follower
 			 * has stopped on the last platform tile where we haven't
 			 * found a train. Also check all previous platform tiles
 			 * for a possible train. */
 			TileIndexDiff diff = TileOffsByDiagDir(TrackdirToExitdir(ReverseTrackdir(ftoti.res.trackdir)));
-			for (TileIndex st_tile = ftoti.res.tile + diff; *train_on_res == NULL && IsCompatibleTrainStationTile(st_tile, ftoti.res.tile); st_tile += diff) {
+			for (TileIndex st_tile = ftoti.res.tile + diff; *train_on_res == nullptr && IsCompatibleTrainStationTile(st_tile, ftoti.res.tile); st_tile += diff) {
 				FindVehicleOnPos(st_tile, &ftoti, FindTrainOnTrackEnum);
-				if (ftoti.best != NULL) *train_on_res = ftoti.best->First();
+				if (ftoti.best != nullptr) *train_on_res = ftoti.best->First();
 			}
 		}
-		if (*train_on_res == NULL && IsTileType(ftoti.res.tile, MP_TUNNELBRIDGE)) {
+		if (*train_on_res == nullptr && IsTileType(ftoti.res.tile, MP_TUNNELBRIDGE)) {
 			/* The target tile is a bridge/tunnel, also check the other end tile. */
 			FindVehicleOnPos(GetOtherTunnelBridgeEnd(ftoti.res.tile), &ftoti, FindTrainOnTrackEnum);
-			if (ftoti.best != NULL) *train_on_res = ftoti.best->First();
+			if (ftoti.best != nullptr) *train_on_res = ftoti.best->First();
 		}
 	}
 	return ftoti.res;
@@ -328,7 +328,7 @@ PBSTileInfo FollowTrainReservation(const
  *
  * @param tile A tile on the path.
  * @param track A reserved track on the tile.
- * @return The vehicle holding the reservation or NULL if the path is stray.
+ * @return The vehicle holding the reservation or nullptr if the path is stray.
  */
 Train *GetTrainForReservation(TileIndex tile, Track track)
 {
@@ -349,25 +349,25 @@ Train *GetTrainForReservation(TileIndex 
 		ftoti.res = FollowReservation(GetTileOwner(tile), rts, tile, trackdir, true);
 
 		FindVehicleOnPos(ftoti.res.tile, &ftoti, FindTrainOnTrackEnum);
-		if (ftoti.best != NULL) return ftoti.best;
+		if (ftoti.best != nullptr) return ftoti.best;
 
 		/* Special case for stations: check the whole platform for a vehicle. */
 		if (IsRailStationTile(ftoti.res.tile)) {
 			TileIndexDiff diff = TileOffsByDiagDir(TrackdirToExitdir(ReverseTrackdir(ftoti.res.trackdir)));
 			for (TileIndex st_tile = ftoti.res.tile + diff; IsCompatibleTrainStationTile(st_tile, ftoti.res.tile); st_tile += diff) {
 				FindVehicleOnPos(st_tile, &ftoti, FindTrainOnTrackEnum);
-				if (ftoti.best != NULL) return ftoti.best;
+				if (ftoti.best != nullptr) return ftoti.best;
 			}
 		}
 
 		/* Special case for bridges/tunnels: check the other end as well. */
 		if (IsTileType(ftoti.res.tile, MP_TUNNELBRIDGE)) {
 			FindVehicleOnPos(GetOtherTunnelBridgeEnd(ftoti.res.tile), &ftoti, FindTrainOnTrackEnum);
-			if (ftoti.best != NULL) return ftoti.best;
+			if (ftoti.best != nullptr) return ftoti.best;
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
diff --git a/src/pbs.h b/src/pbs.h
--- a/src/pbs.h
+++ b/src/pbs.h
@@ -44,7 +44,7 @@ struct PBSTileInfo {
 	PBSTileInfo(TileIndex _t, Trackdir _td, bool _okay) : tile(_t), trackdir(_td), okay(_okay) {}
 };
 
-PBSTileInfo FollowTrainReservation(const Train *v, Vehicle **train_on_res = NULL);
+PBSTileInfo FollowTrainReservation(const Train *v, Vehicle **train_on_res = nullptr);
 bool IsSafeWaitingPosition(const Train *v, TileIndex tile, Trackdir trackdir, bool include_line_end, bool forbid_90deg = false);
 bool IsWaitingPositionFree(const Train *v, TileIndex tile, Trackdir trackdir, bool forbid_90deg = false);
 
diff --git a/src/querystring_gui.h b/src/querystring_gui.h
--- a/src/querystring_gui.h
+++ b/src/querystring_gui.h
@@ -37,7 +37,7 @@ struct QueryString {
 	 * @param size Maximum size in bytes.
 	 * @param chars Maximum size in chars.
 	 */
-	QueryString(uint16 size, uint16 chars = UINT16_MAX) : ok_button(ACTION_NOTHING), cancel_button(ACTION_DESELECT), text(size, chars), orig(NULL)
+	QueryString(uint16 size, uint16 chars = UINT16_MAX) : ok_button(ACTION_NOTHING), cancel_button(ACTION_DESELECT), text(size, chars), orig(nullptr)
 	{
 	}
 
@@ -79,11 +79,11 @@ public:
 	/**
 	 * Get the currently marked text.
 	 * @param[out] length Length of the marked text.
-	 * @return Begining of the marked area or NULL if no text is marked.
+	 * @return Begining of the marked area or nullptr if no text is marked.
 	 */
 	const char *GetMarkedText(size_t *length) const
 	{
-		if (this->text.markend == 0) return NULL;
+		if (this->text.markend == 0) return nullptr;
 
 		*length = this->text.markend - this->text.markpos;
 		return this->text.buf + this->text.markpos;
diff --git a/src/rail.h b/src/rail.h
--- a/src/rail.h
+++ b/src/rail.h
@@ -270,7 +270,7 @@ public:
 	byte sorting_order;
 
 	/**
-	 * NewGRF providing the Action3 for the railtype. NULL if not available.
+	 * NewGRF providing the Action3 for the railtype. nullptr if not available.
 	 */
 	const GRFFile *grffile[RTSG_END];
 
@@ -281,7 +281,7 @@ public:
 
 	inline bool UsesOverlay() const
 	{
-		return this->group[RTSG_GROUND] != NULL;
+		return this->group[RTSG_GROUND] != nullptr;
 	}
 
 	/**
diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -622,7 +622,7 @@ CommandCost CmdRemoveSingleRail(TileInde
 	 * so do not call GetTileOwner(tile) in any case here */
 	Owner owner = INVALID_OWNER;
 
-	Train *v = NULL;
+	Train *v = nullptr;
 
 	switch (GetTileType(tile)) {
 		case MP_ROAD: {
@@ -643,7 +643,7 @@ CommandCost CmdRemoveSingleRail(TileInde
 			if (flags & DC_EXEC) {
 				if (HasReservedTracks(tile, trackbit)) {
 					v = GetTrainForReservation(tile, track);
-					if (v != NULL) FreeTrainTrackReservation(v);
+					if (v != nullptr) FreeTrainTrackReservation(v);
 				}
 				owner = GetTileOwner(tile);
 				Company::Get(owner)->infrastructure.rail[GetRailType(tile)] -= LEVELCROSSING_TRACKBIT_FACTOR;
@@ -681,7 +681,7 @@ CommandCost CmdRemoveSingleRail(TileInde
 			if (flags & DC_EXEC) {
 				if (HasReservedTracks(tile, trackbit)) {
 					v = GetTrainForReservation(tile, track);
-					if (v != NULL) FreeTrainTrackReservation(v);
+					if (v != nullptr) FreeTrainTrackReservation(v);
 				}
 
 				owner = GetTileOwner(tile);
@@ -736,7 +736,7 @@ CommandCost CmdRemoveSingleRail(TileInde
 			YapfNotifyTrackLayoutChange(tile, track);
 		}
 
-		if (v != NULL) TryPathReserve(v, true);
+		if (v != nullptr) TryPathReserve(v, true);
 	}
 
 	return cost;
@@ -1095,13 +1095,13 @@ CommandCost CmdBuildSingleSignal(TileInd
 	}
 
 	if (flags & DC_EXEC) {
-		Train *v = NULL;
+		Train *v = nullptr;
 		/* The new/changed signal could block our path. As this can lead to
 		 * stale reservations, we clear the path reservation here and try
 		 * to redo it later on. */
 		if (HasReservedTracks(tile, TrackToTrackBits(track))) {
 			v = GetTrainForReservation(tile, track);
-			if (v != NULL) FreeTrainTrackReservation(v);
+			if (v != nullptr) FreeTrainTrackReservation(v);
 		}
 
 		if (!HasSignals(tile)) {
@@ -1177,7 +1177,7 @@ CommandCost CmdBuildSingleSignal(TileInd
 		MarkTileDirtyByTile(tile);
 		AddTrackToSignalBuffer(tile, track, _current_company);
 		YapfNotifyTrackLayoutChange(tile, track);
-		if (v != NULL) {
+		if (v != nullptr) {
 			/* Extend the train's path if it's not stopped or loading, or not at a safe position. */
 			if (!(((v->vehstatus & VS_STOPPED) && v->cur_speed == 0) || v->current_order.IsType(OT_LOADING)) ||
 					!IsSafeWaitingPosition(v, v->tile, v->GetVehicleTrackdir(), true, _settings_game.pf.forbid_90_deg)) {
@@ -1467,13 +1467,13 @@ CommandCost CmdRemoveSingleSignal(TileIn
 
 	/* Do it? */
 	if (flags & DC_EXEC) {
-		Train *v = NULL;
+		Train *v = nullptr;
 		if (HasReservedTracks(tile, TrackToTrackBits(track))) {
 			v = GetTrainForReservation(tile, track);
 		} else if (IsPbsSignal(GetSignalType(tile, track))) {
 			/* PBS signal, might be the end of a path reservation. */
 			Trackdir td = TrackToTrackdir(track);
-			for (int i = 0; v == NULL && i < 2; i++, td = ReverseTrackdir(td)) {
+			for (int i = 0; v == nullptr && i < 2; i++, td = ReverseTrackdir(td)) {
 				/* Only test the active signal side. */
 				if (!HasSignalOnTrackdir(tile, ReverseTrackdir(td))) continue;
 				TileIndex next = TileAddByDiagDir(tile, TrackdirToExitdir(td));
@@ -1497,7 +1497,7 @@ CommandCost CmdRemoveSingleSignal(TileIn
 
 		AddTrackToSignalBuffer(tile, track, GetTileOwner(tile));
 		YapfNotifyTrackLayoutChange(tile, track);
-		if (v != NULL) TryPathReserve(v, false);
+		if (v != nullptr) TryPathReserve(v, false);
 
 		MarkTileDirtyByTile(tile);
 	}
@@ -1531,12 +1531,12 @@ CommandCost CmdRemoveSignalTrack(TileInd
 /** Update power of train under which is the railtype being converted */
 static Vehicle *UpdateTrainPowerProc(Vehicle *v, void *data)
 {
-	if (v->type != VEH_TRAIN) return NULL;
+	if (v->type != VEH_TRAIN) return nullptr;
 
 	TrainList *affected_trains = static_cast<TrainList*>(data);
 	include(*affected_trains, Train::From(v)->First());
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -1620,7 +1620,7 @@ CommandCost CmdConvertRail(TileIndex til
 				Track     track;
 				while ((track = RemoveFirstTrack(&reserved)) != INVALID_TRACK) {
 					Train *v = GetTrainForReservation(tile, track);
-					if (v != NULL && !HasPowerOnRail(v->railtype, totype)) {
+					if (v != nullptr && !HasPowerOnRail(v->railtype, totype)) {
 						/* No power on new rail type, reroute. */
 						FreeTrainTrackReservation(v);
 						vehicles_affected.push_back(v);
@@ -1702,7 +1702,7 @@ CommandCost CmdConvertRail(TileIndex til
 					Track track = DiagDirToDiagTrack(GetTunnelBridgeDirection(tile));
 					if (HasTunnelBridgeReservation(tile)) {
 						Train *v = GetTrainForReservation(tile, track);
-						if (v != NULL && !HasPowerOnRail(v->railtype, totype)) {
+						if (v != nullptr && !HasPowerOnRail(v->railtype, totype)) {
 							/* No power on new rail type, reroute. */
 							FreeTrainTrackReservation(v);
 							vehicles_affected.push_back(v);
@@ -1777,11 +1777,11 @@ static CommandCost RemoveTrainDepot(Tile
 		/* read variables before the depot is removed */
 		DiagDirection dir = GetRailDepotDirection(tile);
 		Owner owner = GetTileOwner(tile);
-		Train *v = NULL;
+		Train *v = nullptr;
 
 		if (HasDepotReservation(tile)) {
 			v = GetTrainForReservation(tile, DiagDirToDiagTrack(dir));
-			if (v != NULL) FreeTrainTrackReservation(v);
+			if (v != nullptr) FreeTrainTrackReservation(v);
 		}
 
 		Company::Get(owner)->infrastructure.rail[GetRailType(tile)]--;
@@ -1791,7 +1791,7 @@ static CommandCost RemoveTrainDepot(Tile
 		DoClearSquare(tile);
 		AddSideToSignalBuffer(tile, dir, owner);
 		YapfNotifyTrackLayoutChange(tile, DiagDirToDiagTrack(dir));
-		if (v != NULL) TryPathReserve(v, true);
+		if (v != nullptr) TryPathReserve(v, true);
 	}
 
 	return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_DEPOT_TRAIN]);
@@ -2064,7 +2064,7 @@ static const SubSprite _halftile_sub_spr
 
 static inline void DrawTrackSprite(SpriteID sprite, PaletteID pal, const TileInfo *ti, Slope s)
 {
-	DrawGroundSprite(sprite, pal, NULL, 0, (ti->tileh & s) ? -8 : 0);
+	DrawGroundSprite(sprite, pal, nullptr, 0, (ti->tileh & s) ? -8 : 0);
 }
 
 static void DrawTrackBitsOverlay(TileInfo *ti, TrackBits track, const RailtypeInfo *rti)
@@ -2258,7 +2258,7 @@ static void DrawTrackBits(TileInfo *ti, 
 
 	SpriteID image;
 	PaletteID pal = PAL_NONE;
-	const SubSprite *sub = NULL;
+	const SubSprite *sub = nullptr;
 	bool junction = false;
 
 	/* Select the sprite to use. */
@@ -2355,10 +2355,10 @@ static void DrawTrackBits(TileInfo *ti, 
 				DrawGroundSprite(_track_sloped_sprites[ti->tileh - 1] + rti->base_sprites.single_sloped - 20, PALETTE_CRASH);
 			}
 		}
-		if (pbs & TRACK_BIT_UPPER) DrawGroundSprite(rti->base_sprites.single_n, PALETTE_CRASH, NULL, 0, ti->tileh & SLOPE_N ? -(int)TILE_HEIGHT : 0);
-		if (pbs & TRACK_BIT_LOWER) DrawGroundSprite(rti->base_sprites.single_s, PALETTE_CRASH, NULL, 0, ti->tileh & SLOPE_S ? -(int)TILE_HEIGHT : 0);
-		if (pbs & TRACK_BIT_LEFT)  DrawGroundSprite(rti->base_sprites.single_w, PALETTE_CRASH, NULL, 0, ti->tileh & SLOPE_W ? -(int)TILE_HEIGHT : 0);
-		if (pbs & TRACK_BIT_RIGHT) DrawGroundSprite(rti->base_sprites.single_e, PALETTE_CRASH, NULL, 0, ti->tileh & SLOPE_E ? -(int)TILE_HEIGHT : 0);
+		if (pbs & TRACK_BIT_UPPER) DrawGroundSprite(rti->base_sprites.single_n, PALETTE_CRASH, nullptr, 0, ti->tileh & SLOPE_N ? -(int)TILE_HEIGHT : 0);
+		if (pbs & TRACK_BIT_LOWER) DrawGroundSprite(rti->base_sprites.single_s, PALETTE_CRASH, nullptr, 0, ti->tileh & SLOPE_S ? -(int)TILE_HEIGHT : 0);
+		if (pbs & TRACK_BIT_LEFT)  DrawGroundSprite(rti->base_sprites.single_w, PALETTE_CRASH, nullptr, 0, ti->tileh & SLOPE_W ? -(int)TILE_HEIGHT : 0);
+		if (pbs & TRACK_BIT_RIGHT) DrawGroundSprite(rti->base_sprites.single_e, PALETTE_CRASH, nullptr, 0, ti->tileh & SLOPE_E ? -(int)TILE_HEIGHT : 0);
 	}
 
 	if (IsValidCorner(halftile_corner)) {
@@ -2378,7 +2378,7 @@ static void DrawTrackBits(TileInfo *ti, 
 
 		if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasReservedTracks(ti->tile, CornerToTrackBits(halftile_corner))) {
 			static const byte _corner_to_track_sprite[] = {3, 1, 2, 0};
-			DrawGroundSprite(_corner_to_track_sprite[halftile_corner] + rti->base_sprites.single_n, PALETTE_CRASH, NULL, 0, -(int)TILE_HEIGHT);
+			DrawGroundSprite(_corner_to_track_sprite[halftile_corner] + rti->base_sprites.single_n, PALETTE_CRASH, nullptr, 0, -(int)TILE_HEIGHT);
 		}
 	}
 }
@@ -2958,7 +2958,7 @@ static VehicleEnterTileStatus VehicleEnt
 
 		if (fract_coord_leave == fract_coord) {
 			/* Leave the depot. */
-			if ((v = v->Next()) != NULL) {
+			if ((v = v->Next()) != nullptr) {
 				v->vehstatus &= ~VS_HIDDEN;
 				v->track = (DiagDirToAxis(dir) == AXIS_X ? TRACK_BIT_X : TRACK_BIT_Y);
 			}
@@ -2969,7 +2969,7 @@ static VehicleEnterTileStatus VehicleEnt
 		v->track = TRACK_BIT_DEPOT,
 		v->vehstatus |= VS_HIDDEN;
 		v->direction = ReverseDir(v->direction);
-		if (v->Next() == NULL) VehicleEnterDepot(v->First());
+		if (v->Next() == nullptr) VehicleEnterDepot(v->First());
 		v->tile = tile;
 
 		InvalidateWindowData(WC_VEHICLE_DEPOT, v->tile);
@@ -3034,7 +3034,7 @@ static CommandCost TestAutoslopeOnRailTi
  */
 static Vehicle *EnsureNoShipProc(Vehicle *v, void *data)
 {
-	return v->type == VEH_SHIP ? v : NULL;
+	return v->type == VEH_SHIP ? v : nullptr;
 }
 
 static CommandCost TerraformTile_Track(TileIndex tile, DoCommandFlag flags, int z_new, Slope tileh_new)
@@ -3047,7 +3047,7 @@ static CommandCost TerraformTile_Track(T
 		bool was_water = (GetRailGroundType(tile) == RAIL_GROUND_WATER && IsSlopeWithOneCornerRaised(tileh_old));
 
 		/* Allow clearing the water only if there is no ship */
-		if (was_water && HasVehicleOnPos(tile, NULL, &EnsureNoShipProc)) return_cmd_error(STR_ERROR_SHIP_IN_THE_WAY);
+		if (was_water && HasVehicleOnPos(tile, nullptr, &EnsureNoShipProc)) return_cmd_error(STR_ERROR_SHIP_IN_THE_WAY);
 
 		/* First test autoslope. However if it succeeds we still have to test the rest, because non-autoslope terraforming is cheaper. */
 		CommandCost autoslope_result = TestAutoslopeOnRailTile(tile, flags, z_old, tileh_old, z_new, tileh_new, rail_bits);
@@ -3090,14 +3090,14 @@ extern const TileTypeProcs _tile_type_ra
 	DrawTile_Track,           // draw_tile_proc
 	GetSlopePixelZ_Track,     // get_slope_z_proc
 	ClearTile_Track,          // clear_tile_proc
-	NULL,                     // add_accepted_cargo_proc
+	nullptr,                     // add_accepted_cargo_proc
 	GetTileDesc_Track,        // get_tile_desc_proc
 	GetTileTrackStatus_Track, // get_tile_track_status_proc
 	ClickTile_Track,          // click_tile_proc
-	NULL,                     // animate_tile_proc
+	nullptr,                     // animate_tile_proc
 	TileLoop_Track,           // tile_loop_proc
 	ChangeTileOwner_Track,    // change_tile_owner_proc
-	NULL,                     // add_produced_cargo_proc
+	nullptr,                     // add_produced_cargo_proc
 	VehicleEnter_Track,       // vehicle_enter_tile_proc
 	GetFoundation_Track,      // get_foundation_proc
 	TerraformTile_Track,      // terraform_tile_proc
diff --git a/src/rail_gui.cpp b/src/rail_gui.cpp
--- a/src/rail_gui.cpp
+++ b/src/rail_gui.cpp
@@ -78,9 +78,9 @@ static void ShowSignalBuilder(Window *pa
  */
 static bool IsStationAvailable(const StationSpec *statspec)
 {
-	if (statspec == NULL || !HasBit(statspec->callback_mask, CBM_STATION_AVAIL)) return true;
+	if (statspec == nullptr || !HasBit(statspec->callback_mask, CBM_STATION_AVAIL)) return true;
 
-	uint16 cb_res = GetStationCallback(CBID_STATION_AVAILABILITY, 0, 0, statspec, NULL, INVALID_TILE);
+	uint16 cb_res = GetStationCallback(CBID_STATION_AVAILABILITY, 0, 0, statspec, nullptr, INVALID_TILE);
 	if (cb_res == CALLBACK_FAILED) return true;
 
 	return Convert8bitBooleanCallback(statspec->grf_prop.grffile, CBID_STATION_AVAILABILITY, cb_res);
@@ -234,7 +234,7 @@ static void GenericPlaceSignals(TileInde
 		/* various bitstuffed elements for CmdBuildSingleSignal() */
 		uint32 p1 = track;
 
-		if (w != NULL) {
+		if (w != nullptr) {
 			/* signal GUI is used */
 			SB(p1, 3, 1, _ctrl_pressed);
 			SB(p1, 4, 1, _cur_signal_variant);
@@ -250,7 +250,7 @@ static void GenericPlaceSignals(TileInde
 		}
 
 		DoCommandP(tile, p1, 0, CMD_BUILD_SIGNALS |
-				CMD_MSG((w != NULL && _convert_signal_button) ? STR_ERROR_SIGNAL_CAN_T_CONVERT_SIGNALS_HERE : STR_ERROR_CAN_T_BUILD_SIGNALS_HERE),
+				CMD_MSG((w != nullptr && _convert_signal_button) ? STR_ERROR_SIGNAL_CAN_T_CONVERT_SIGNALS_HERE : STR_ERROR_CAN_T_BUILD_SIGNALS_HERE),
 				CcPlaySound_SPLAT_RAIL);
 	}
 }
@@ -388,7 +388,7 @@ static void HandleAutoSignalPlacement()
 
 	const Window *w = FindWindowById(WC_BUILD_SIGNAL, 0);
 
-	if (w != NULL) {
+	if (w != nullptr) {
 		/* signal GUI is used */
 		SB(p2,  3, 1, 0);
 		SB(p2,  4, 1, _cur_signal_variant);
@@ -683,7 +683,7 @@ struct BuildRailToolbarWindow : Window {
 	void OnPlaceDrag(ViewportPlaceMethod select_method, ViewportDragDropSelectionProcess select_proc, Point pt) override
 	{
 		/* no dragging if you have pressed the convert button */
-		if (FindWindowById(WC_BUILD_SIGNAL, 0) != NULL && _convert_signal_button && this->IsWidgetLowered(WID_RAT_BUILD_SIGNALS)) return;
+		if (FindWindowById(WC_BUILD_SIGNAL, 0) != nullptr && _convert_signal_button && this->IsWidgetLowered(WID_RAT_BUILD_SIGNALS)) return;
 
 		VpSelectTilesWithMethod(pt.x, pt.y, select_method);
 	}
@@ -781,7 +781,7 @@ static EventState RailToolbarGlobalHotke
 	if (_game_mode != GM_NORMAL || !CanBuildVehicleInfrastructure(VEH_TRAIN)) return ES_NOT_HANDLED;
 	extern RailType _last_built_railtype;
 	Window *w = ShowBuildRailToolbar(_last_built_railtype);
-	if (w == NULL) return ES_NOT_HANDLED;
+	if (w == nullptr) return ES_NOT_HANDLED;
 	return w->OnHotkey(hotkey);
 }
 
@@ -862,12 +862,12 @@ static WindowDesc _build_rail_desc(
  * If the terraform toolbar is linked to the toolbar, that window is also opened.
  *
  * @param railtype Rail type to open the window for
- * @return newly opened rail toolbar, or NULL if the toolbar could not be opened.
+ * @return newly opened rail toolbar, or nullptr if the toolbar could not be opened.
  */
 Window *ShowBuildRailToolbar(RailType railtype)
 {
-	if (!Company::IsValidID(_local_company)) return NULL;
-	if (!ValParamRailtype(railtype)) return NULL;
+	if (!Company::IsValidID(_local_company)) return nullptr;
+	if (!ValParamRailtype(railtype)) return nullptr;
 
 	DeleteWindowByClass(WC_BUILD_TOOLBAR);
 	_cur_railtype = railtype;
@@ -907,7 +907,7 @@ private:
 	 */
 	void CheckSelectedSize(const StationSpec *statspec)
 	{
-		if (statspec == NULL || _settings_client.gui.station_dragdrop) return;
+		if (statspec == nullptr || _settings_client.gui.station_dragdrop) return;
 
 		/* If current number of tracks is not allowed, make it as big as possible */
 		if (HasBit(statspec->disallowed_platforms, _settings_client.gui.station_numtracks - 1)) {
@@ -937,7 +937,7 @@ public:
 	BuildRailStationWindow(WindowDesc *desc, Window *parent, bool newstation) : PickerWindowBase(desc, parent)
 	{
 		this->coverage_height = 2 * FONT_HEIGHT_NORMAL + 3 * WD_PAR_VSEP_NORMAL;
-		this->vscroll = NULL;
+		this->vscroll = nullptr;
 		_railstation.newstations = newstation;
 
 		this->CreateNestedTree();
@@ -970,7 +970,7 @@ public:
 			 * type is 'selected'. */
 			_railstation.station_class = STAT_CLASS_DFLT;
 			_railstation.station_type = 0;
-			this->vscroll2 = NULL;
+			this->vscroll2 = nullptr;
 		}
 		if (newstation) {
 			_railstation.station_count = StationClass::Get(_railstation.station_class)->GetSpecCount();
@@ -999,7 +999,7 @@ public:
 	void OnPaint() override
 	{
 		bool newstations = _railstation.newstations;
-		const StationSpec *statspec = newstations ? StationClass::Get(_railstation.station_class)->GetSpec(_railstation.station_type) : NULL;
+		const StationSpec *statspec = newstations ? StationClass::Get(_railstation.station_class)->GetSpec(_railstation.station_type) : nullptr;
 
 		if (_settings_client.gui.station_dragdrop) {
 			SetTileSelectSize(1, 1);
@@ -1018,7 +1018,7 @@ public:
 
 		for (uint bits = 0; bits < 7; bits++) {
 			bool disable = bits >= _settings_game.station.station_spread;
-			if (statspec == NULL) {
+			if (statspec == nullptr) {
 				this->SetWidgetDisabledState(bits + WID_BRAS_PLATFORM_NUM_1, disable);
 				this->SetWidgetDisabledState(bits + WID_BRAS_PLATFORM_LEN_1, disable);
 			} else {
@@ -1078,7 +1078,7 @@ public:
 					StationClass *stclass = StationClass::Get(statclass);
 					for (uint16 j = 0; j < stclass->GetSpecCount(); j++) {
 						const StationSpec *statspec = stclass->GetSpec(j);
-						SetDParam(0, (statspec != NULL && statspec->name != 0) ? statspec->name : STR_STATION_CLASS_DFLT);
+						SetDParam(0, (statspec != nullptr && statspec->name != 0) ? statspec->name : STR_STATION_CLASS_DFLT);
 						d = maxdim(d, GetStringBoundingBox(str));
 					}
 				}
@@ -1180,7 +1180,7 @@ public:
 
 	void OnResize() override
 	{
-		if (this->vscroll != NULL) { // New stations available.
+		if (this->vscroll != nullptr) { // New stations available.
 			this->vscroll->SetCapacityFromWidget(this, WID_BRAS_NEWST_LIST);
 		}
 	}
@@ -1189,7 +1189,7 @@ public:
 	{
 		if (widget == WID_BRAS_SHOW_NEWST_TYPE) {
 			const StationSpec *statspec = StationClass::Get(_railstation.station_class)->GetSpec(_railstation.station_type);
-			SetDParam(0, (statspec != NULL && statspec->name != 0) ? statspec->name : STR_STATION_CLASS_DFLT);
+			SetDParam(0, (statspec != nullptr && statspec->name != 0) ? statspec->name : STR_STATION_CLASS_DFLT);
 		}
 	}
 
@@ -1221,8 +1221,8 @@ public:
 
 				_settings_client.gui.station_dragdrop = false;
 
-				const StationSpec *statspec = _railstation.newstations ? StationClass::Get(_railstation.station_class)->GetSpec(_railstation.station_type) : NULL;
-				if (statspec != NULL && HasBit(statspec->disallowed_lengths, _settings_client.gui.station_platlength - 1)) {
+				const StationSpec *statspec = _railstation.newstations ? StationClass::Get(_railstation.station_class)->GetSpec(_railstation.station_type) : nullptr;
+				if (statspec != nullptr && HasBit(statspec->disallowed_lengths, _settings_client.gui.station_platlength - 1)) {
 					/* The previously selected number of platforms in invalid */
 					for (uint i = 0; i < 7; i++) {
 						if (!HasBit(statspec->disallowed_lengths, i)) {
@@ -1256,8 +1256,8 @@ public:
 
 				_settings_client.gui.station_dragdrop = false;
 
-				const StationSpec *statspec = _railstation.newstations ? StationClass::Get(_railstation.station_class)->GetSpec(_railstation.station_type) : NULL;
-				if (statspec != NULL && HasBit(statspec->disallowed_platforms, _settings_client.gui.station_numtracks - 1)) {
+				const StationSpec *statspec = _railstation.newstations ? StationClass::Get(_railstation.station_class)->GetSpec(_railstation.station_type) : nullptr;
+				if (statspec != nullptr && HasBit(statspec->disallowed_platforms, _settings_client.gui.station_numtracks - 1)) {
 					/* The previously selected number of tracks in invalid */
 					for (uint i = 0; i < 7; i++) {
 						if (!HasBit(statspec->disallowed_platforms, i)) {
@@ -1282,8 +1282,8 @@ public:
 				this->ToggleWidgetLoweredState(WID_BRAS_PLATFORM_DRAG_N_DROP);
 
 				/* get the first allowed length/number of platforms */
-				const StationSpec *statspec = _railstation.newstations ? StationClass::Get(_railstation.station_class)->GetSpec(_railstation.station_type) : NULL;
-				if (statspec != NULL && HasBit(statspec->disallowed_lengths, _settings_client.gui.station_platlength - 1)) {
+				const StationSpec *statspec = _railstation.newstations ? StationClass::Get(_railstation.station_class)->GetSpec(_railstation.station_type) : nullptr;
+				if (statspec != nullptr && HasBit(statspec->disallowed_lengths, _settings_client.gui.station_platlength - 1)) {
 					for (uint i = 0; i < 7; i++) {
 						if (!HasBit(statspec->disallowed_lengths, i)) {
 							this->RaiseWidget(_settings_client.gui.station_platlength + WID_BRAS_PLATFORM_LEN_BEGIN);
@@ -1292,7 +1292,7 @@ public:
 						}
 					}
 				}
-				if (statspec != NULL && HasBit(statspec->disallowed_platforms, _settings_client.gui.station_numtracks - 1)) {
+				if (statspec != nullptr && HasBit(statspec->disallowed_platforms, _settings_client.gui.station_numtracks - 1)) {
 					for (uint i = 0; i < 7; i++) {
 						if (!HasBit(statspec->disallowed_platforms, i)) {
 							this->RaiseWidget(_settings_client.gui.station_numtracks + WID_BRAS_PLATFORM_NUM_BEGIN);
@@ -1598,7 +1598,7 @@ public:
 				/* If 'remove' button of rail build toolbar is active, disable it. */
 				if (_remove_button_clicked) {
 					Window *w = FindWindowById(WC_BUILD_TOOLBAR, TRANSPORT_RAIL);
-					if (w != NULL) ToggleRailButton_Remove(w);
+					if (w != nullptr) ToggleRailButton_Remove(w);
 				}
 
 				break;
@@ -1768,7 +1768,7 @@ static const NWidgetPart _nested_build_d
 };
 
 static WindowDesc _build_depot_desc(
-	WDP_AUTO, NULL, 0, 0,
+	WDP_AUTO, nullptr, 0, 0,
 	WC_BUILD_DEPOT, WC_BUILD_TOOLBAR,
 	WDF_CONSTRUCTION,
 	_nested_build_depot_widgets, lengthof(_nested_build_depot_widgets)
@@ -1896,7 +1896,7 @@ void ReinitGuiAfterToggleElrail(bool dis
 	if (disable && _last_built_railtype == RAILTYPE_ELECTRIC) {
 		_last_built_railtype = _cur_railtype = RAILTYPE_RAIL;
 		BuildRailToolbarWindow *w = dynamic_cast<BuildRailToolbarWindow *>(FindWindowById(WC_BUILD_TOOLBAR, TRANSPORT_RAIL));
-		if (w != NULL) w->ModifyRailType(_cur_railtype);
+		if (w != nullptr) w->ModifyRailType(_cur_railtype);
 	}
 	MarkWholeScreenDirty();
 }
@@ -1943,7 +1943,7 @@ static void SetDefaultRailGui()
 
 	_last_built_railtype = _cur_railtype = rt;
 	BuildRailToolbarWindow *w = dynamic_cast<BuildRailToolbarWindow *>(FindWindowById(WC_BUILD_TOOLBAR, TRANSPORT_RAIL));
-	if (w != NULL) w->ModifyRailType(_cur_railtype);
+	if (w != nullptr) w->ModifyRailType(_cur_railtype);
 }
 
 /**
@@ -1958,7 +1958,7 @@ bool ResetSignalVariant(int32 p)
 
 	if (new_variant != _cur_signal_variant) {
 		Window *w = FindWindowById(WC_BUILD_SIGNAL, 0);
-		if (w != NULL) {
+		if (w != nullptr) {
 			w->SetDirty();
 			w->RaiseWidget((_cur_signal_variant == SIG_ELECTRIC ? WID_BS_ELECTRIC_NORM : WID_BS_SEMAPHORE_NORM) + _cur_signal_type);
 		}
diff --git a/src/road.cpp b/src/road.cpp
--- a/src/road.cpp
+++ b/src/road.cpp
@@ -115,7 +115,7 @@ bool HasRoadTypesAvail(const CompanyID c
 		avail_roadtypes = ROADTYPES_ROAD;
 	} else {
 		Company *c = Company::GetIfValid(company);
-		if (c == NULL) return false;
+		if (c == nullptr) return false;
 		avail_roadtypes = (RoadTypes)c->avail_roadtypes | ROADTYPES_ROAD; // road is available for always for everybody
 	}
 	return (rts & ~avail_roadtypes) == 0;
diff --git a/src/road_cmd.cpp b/src/road_cmd.cpp
--- a/src/road_cmd.cpp
+++ b/src/road_cmd.cpp
@@ -136,7 +136,7 @@ CommandCost CheckAllowRemoveRoad(TileInd
 	if (_cheats.magic_bulldozer.value) return CommandCost();
 
 	Town *t = ClosestTownFromTile(tile, UINT_MAX);
-	if (t == NULL) return CommandCost();
+	if (t == nullptr) return CommandCost();
 
 	/* check if you're allowed to remove the street owned by a town
 	 * removal allowance depends on difficulty setting */
@@ -227,7 +227,7 @@ static CommandCost RemoveRoad(TileIndex 
 			cost.AddCost(len * 2 * _price[PR_CLEAR_ROAD]);
 			if (flags & DC_EXEC) {
 				Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
-				if (c != NULL) {
+				if (c != nullptr) {
 					/* A full diagonal road tile has two road bits. */
 					c->infrastructure.road[rt] -= len * 2 * TUNNELBRIDGE_TRACKBIT_FACTOR;
 					DirtyCompanyInfrastructureWindows(c->index);
@@ -258,7 +258,7 @@ static CommandCost RemoveRoad(TileIndex 
 			cost.AddCost(_price[PR_CLEAR_ROAD] * 2);
 			if (flags & DC_EXEC) {
 				Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
-				if (c != NULL) {
+				if (c != nullptr) {
 					/* A full diagonal road tile has two road bits. */
 					c->infrastructure.road[rt] -= 2;
 					DirtyCompanyInfrastructureWindows(c->index);
@@ -319,7 +319,7 @@ static CommandCost RemoveRoad(TileIndex 
 				}
 
 				Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
-				if (c != NULL) {
+				if (c != nullptr) {
 					c->infrastructure.road[rt] -= CountBits(pieces);
 					DirtyCompanyInfrastructureWindows(c->index);
 				}
@@ -333,7 +333,7 @@ static CommandCost RemoveRoad(TileIndex 
 						if (rt == ROADTYPE_ROAD && IsRoadOwner(tile, ROADTYPE_ROAD, OWNER_TOWN)) {
 							/* Update nearest-town index */
 							const Town *town = CalcClosestTownFromTile(tile);
-							SetTownIndex(tile, town == NULL ? INVALID_TOWN : town->index);
+							SetTownIndex(tile, town == nullptr ? INVALID_TOWN : town->index);
 						}
 						SetRoadBits(tile, ROAD_NONE, rt);
 						SetRoadTypes(tile, rts);
@@ -367,7 +367,7 @@ static CommandCost RemoveRoad(TileIndex 
 
 			if (flags & DC_EXEC) {
 				Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
-				if (c != NULL) {
+				if (c != nullptr) {
 					/* A full diagonal road tile has two road bits. */
 					c->infrastructure.road[rt] -= 2;
 					DirtyCompanyInfrastructureWindows(c->index);
@@ -384,7 +384,7 @@ static CommandCost RemoveRoad(TileIndex 
 					/* Update rail count for level crossings. The plain track should still be accounted
 					 * for, so only subtract the difference to the level crossing cost. */
 					c = Company::GetIfValid(GetTileOwner(tile));
-					if (c != NULL) {
+					if (c != nullptr) {
 						c->infrastructure.rail[GetRailType(tile)] -= LEVELCROSSING_TRACKBIT_FACTOR - 1;
 						DirtyCompanyInfrastructureWindows(c->index);
 					}
@@ -494,13 +494,13 @@ CommandCost CmdBuildRoad(TileIndex tile,
 	if ((Company::IsValidID(company) && p2 != 0) || (company == OWNER_TOWN && !Town::IsValidID(p2)) || (company == OWNER_DEITY && p2 != 0)) return CMD_ERROR;
 	if (company != OWNER_TOWN) {
 		const Town *town = CalcClosestTownFromTile(tile);
-		p2 = (town != NULL) ? town->index : INVALID_TOWN;
+		p2 = (town != nullptr) ? town->index : INVALID_TOWN;
 
 		if (company == OWNER_DEITY) {
 			company = OWNER_TOWN;
 
 			/* If we are not within a town, we are not owned by the town */
-			if (town == NULL || DistanceSquare(tile, town->xy) > town->cache.squared_town_zone_radius[HZB_TOWN_EDGE]) {
+			if (town == nullptr || DistanceSquare(tile, town->xy) > town->cache.squared_town_zone_radius[HZB_TOWN_EDGE]) {
 				company = OWNER_NONE;
 			}
 		}
@@ -633,7 +633,7 @@ CommandCost CmdBuildRoad(TileIndex tile,
 				YapfNotifyTrackLayoutChange(tile, railtrack);
 				/* Update company infrastructure counts. A level crossing has two road bits. */
 				Company *c = Company::GetIfValid(company);
-				if (c != NULL) {
+				if (c != nullptr) {
 					c->infrastructure.road[rt] += 2;
 					if (rt != ROADTYPE_ROAD) c->infrastructure.road[ROADTYPE_ROAD] += 2;
 					DirtyCompanyInfrastructureWindows(company);
@@ -641,7 +641,7 @@ CommandCost CmdBuildRoad(TileIndex tile,
 				/* Update rail count for level crossings. The plain track is already
 				 * counted, so only add the difference to the level crossing cost. */
 				c = Company::GetIfValid(GetTileOwner(tile));
-				if (c != NULL) {
+				if (c != nullptr) {
 					c->infrastructure.rail[GetRailType(tile)] += LEVELCROSSING_TRACKBIT_FACTOR - 1;
 					DirtyCompanyInfrastructureWindows(c->index);
 				}
@@ -783,7 +783,7 @@ do_clear:;
 
 		/* Update company infrastructure count. */
 		Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
-		if (c != NULL) {
+		if (c != nullptr) {
 			if (IsTileType(tile, MP_TUNNELBRIDGE)) num_pieces *= TUNNELBRIDGE_TRACKBIT_FACTOR;
 			c->infrastructure.road[rt] += num_pieces;
 			DirtyCompanyInfrastructureWindows(c->index);
@@ -1064,7 +1064,7 @@ static CommandCost RemoveRoadDepot(TileI
 
 	if (flags & DC_EXEC) {
 		Company *c = Company::GetIfValid(GetTileOwner(tile));
-		if (c != NULL) {
+		if (c != nullptr) {
 			/* A road depot has two road bits. */
 			c->infrastructure.road[FIND_FIRST_BIT(GetRoadTypes(tile))] -= 2;
 			DirtyCompanyInfrastructureWindows(c->index);
@@ -1449,7 +1449,7 @@ void UpdateNearestTownForRoadTiles(bool 
 			TownID tid = INVALID_TOWN;
 			if (!invalidate) {
 				const Town *town = CalcClosestTownFromTile(t);
-				if (town != NULL) tid = town->index;
+				if (town != nullptr) tid = town->index;
 			}
 			SetTownIndex(t, tid);
 		}
@@ -1522,7 +1522,7 @@ static void TileLoop_Road(TileIndex tile
 	if (!HasRoadWorks(tile)) {
 		HouseZonesBits grp = HZB_TOWN_EDGE;
 
-		if (t != NULL) {
+		if (t != nullptr) {
 			grp = GetTownRadiusGroup(t, tile);
 
 			/* Show an animation to indicate road work */
@@ -1751,7 +1751,7 @@ static VehicleEnterTileStatus VehicleEnt
 				rv->state = RVSB_IN_DEPOT;
 				rv->vehstatus |= VS_HIDDEN;
 				rv->direction = ReverseDir(rv->direction);
-				if (rv->Next() == NULL) VehicleEnterDepot(rv->First());
+				if (rv->Next() == nullptr) VehicleEnterDepot(rv->First());
 				rv->tile = tile;
 
 				InvalidateWindowData(WC_VEHICLE_DEPOT, rv->tile);
@@ -1863,14 +1863,14 @@ extern const TileTypeProcs _tile_type_ro
 	DrawTile_Road,           // draw_tile_proc
 	GetSlopePixelZ_Road,     // get_slope_z_proc
 	ClearTile_Road,          // clear_tile_proc
-	NULL,                    // add_accepted_cargo_proc
+	nullptr,                    // add_accepted_cargo_proc
 	GetTileDesc_Road,        // get_tile_desc_proc
 	GetTileTrackStatus_Road, // get_tile_track_status_proc
 	ClickTile_Road,          // click_tile_proc
-	NULL,                    // animate_tile_proc
+	nullptr,                    // animate_tile_proc
 	TileLoop_Road,           // tile_loop_proc
 	ChangeTileOwner_Road,    // change_tile_owner_proc
-	NULL,                    // add_produced_cargo_proc
+	nullptr,                    // add_produced_cargo_proc
 	VehicleEnter_Road,       // vehicle_enter_tile_proc
 	GetFoundation_Road,      // get_foundation_proc
 	TerraformTile_Road,      // terraform_tile_proc
diff --git a/src/road_gui.cpp b/src/road_gui.cpp
--- a/src/road_gui.cpp
+++ b/src/road_gui.cpp
@@ -681,7 +681,7 @@ struct BuildRoadToolbarWindow : Window {
  */
 static EventState RoadToolbarGlobalHotkeys(int hotkey)
 {
-	Window *w = NULL;
+	Window *w = nullptr;
 	switch (_game_mode) {
 		case GM_NORMAL: {
 			extern RoadType _last_built_roadtype;
@@ -697,7 +697,7 @@ static EventState RoadToolbarGlobalHotke
 			break;
 	}
 
-	if (w == NULL) return ES_NOT_HANDLED;
+	if (w == nullptr) return ES_NOT_HANDLED;
 	return w->OnHotkey(hotkey);
 }
 
@@ -804,11 +804,11 @@ static WindowDesc _build_tramway_desc(
  *
  * If the terraform toolbar is linked to the toolbar, that window is also opened.
  *
- * @return newly opened road toolbar, or NULL if the toolbar could not be opened.
+ * @return newly opened road toolbar, or nullptr if the toolbar could not be opened.
  */
 Window *ShowBuildRoadToolbar(RoadType roadtype)
 {
-	if (!Company::IsValidID(_local_company)) return NULL;
+	if (!Company::IsValidID(_local_company)) return nullptr;
 	_cur_roadtype = roadtype;
 
 	DeleteWindowByClass(WC_BUILD_TOOLBAR);
@@ -852,7 +852,7 @@ static WindowDesc _build_road_scen_desc(
 
 /**
  * Show the road building toolbar in the scenario editor.
- * @return The just opened toolbar, or \c NULL if the toolbar was already open.
+ * @return The just opened toolbar, or \c nullptr if the toolbar was already open.
  */
 Window *ShowBuildRoadScenToolbar()
 {
@@ -940,7 +940,7 @@ static const NWidgetPart _nested_build_r
 };
 
 static WindowDesc _build_road_depot_desc(
-	WDP_AUTO, NULL, 0, 0,
+	WDP_AUTO, nullptr, 0, 0,
 	WC_BUILD_DEPOT, WC_BUILD_TOOLBAR,
 	WDF_CONSTRUCTION,
 	_nested_build_road_depot_widgets, lengthof(_nested_build_road_depot_widgets)
@@ -1100,7 +1100,7 @@ static const NWidgetPart _nested_road_st
 };
 
 static WindowDesc _road_station_picker_desc(
-	WDP_AUTO, NULL, 0, 0,
+	WDP_AUTO, nullptr, 0, 0,
 	WC_BUS_STATION, WC_BUILD_TOOLBAR,
 	WDF_CONSTRUCTION,
 	_nested_road_station_picker_widgets, lengthof(_nested_road_station_picker_widgets)
@@ -1138,7 +1138,7 @@ static const NWidgetPart _nested_tram_st
 };
 
 static WindowDesc _tram_station_picker_desc(
-	WDP_AUTO, NULL, 0, 0,
+	WDP_AUTO, nullptr, 0, 0,
 	WC_BUS_STATION, WC_BUILD_TOOLBAR,
 	WDF_CONSTRUCTION,
 	_nested_tram_station_picker_widgets, lengthof(_nested_tram_station_picker_widgets)
diff --git a/src/roadstop.cpp b/src/roadstop.cpp
--- a/src/roadstop.cpp
+++ b/src/roadstop.cpp
@@ -43,7 +43,7 @@ RoadStop::~RoadStop()
  */
 RoadStop *RoadStop::GetNextRoadStop(const RoadVehicle *v) const
 {
-	for (RoadStop *rs = this->next; rs != NULL; rs = rs->next) {
+	for (RoadStop *rs = this->next; rs != nullptr; rs = rs->next) {
 		/* The vehicle cannot go to this roadstop (different roadtype) */
 		if ((GetRoadTypes(rs->xy) & v->compatible_roadtypes) == ROADTYPES_NONE) continue;
 		/* The vehicle is articulated and can therefore not go to a standard road stop. */
@@ -53,7 +53,7 @@ RoadStop *RoadStop::GetNextRoadStop(cons
 		return rs;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -63,7 +63,7 @@ RoadStop *RoadStop::GetNextRoadStop(cons
  */
 void RoadStop::MakeDriveThrough()
 {
-	assert(this->east == NULL && this->west == NULL);
+	assert(this->east == nullptr && this->west == nullptr);
 
 	RoadStopType rst = GetRoadStopType(this->xy);
 	DiagDirection dir = GetRoadStopDir(this->xy);
@@ -73,21 +73,21 @@ void RoadStop::MakeDriveThrough()
 	/* Information about the tile north of us */
 	TileIndex north_tile = this->xy - offset;
 	bool north = IsDriveThroughRoadStopContinuation(this->xy, north_tile);
-	RoadStop *rs_north = north ? RoadStop::GetByTile(north_tile, rst) : NULL;
+	RoadStop *rs_north = north ? RoadStop::GetByTile(north_tile, rst) : nullptr;
 
 	/* Information about the tile south of us */
 	TileIndex south_tile = this->xy + offset;
 	bool south = IsDriveThroughRoadStopContinuation(this->xy, south_tile);
-	RoadStop *rs_south = south ? RoadStop::GetByTile(south_tile, rst) : NULL;
+	RoadStop *rs_south = south ? RoadStop::GetByTile(south_tile, rst) : nullptr;
 
 	/* Amount of road stops that will be added to the 'northern' head */
 	int added = 1;
-	if (north && rs_north->east != NULL) { // (east != NULL) == (west != NULL)
+	if (north && rs_north->east != nullptr) { // (east != nullptr) == (west != nullptr)
 		/* There is a more northern one, so this can join them */
 		this->east = rs_north->east;
 		this->west = rs_north->west;
 
-		if (south && rs_south->east != NULL) { // (east != NULL) == (west != NULL)
+		if (south && rs_south->east != nullptr) { // (east != nullptr) == (west != nullptr)
 			/* There more southern tiles too, they must 'join' us too */
 			ClrBit(rs_south->status, RSSFB_BASE_ENTRY);
 			this->east->occupied += rs_south->east->occupied;
@@ -100,13 +100,13 @@ void RoadStop::MakeDriveThrough()
 			/* Make all 'children' of the southern tile take the new master */
 			for (; IsDriveThroughRoadStopContinuation(this->xy, south_tile); south_tile += offset) {
 				rs_south = RoadStop::GetByTile(south_tile, rst);
-				if (rs_south->east == NULL) break;
+				if (rs_south->east == nullptr) break;
 				rs_south->east = rs_north->east;
 				rs_south->west = rs_north->west;
 				added++;
 			}
 		}
-	} else if (south && rs_south->east != NULL) { // (east != NULL) == (west != NULL)
+	} else if (south && rs_south->east != nullptr) { // (east != nullptr) == (west != nullptr)
 		/* There is one to the south, but not to the north... so we become 'parent' */
 		this->east = rs_south->east;
 		this->west = rs_south->west;
@@ -131,7 +131,7 @@ void RoadStop::MakeDriveThrough()
  */
 void RoadStop::ClearDriveThrough()
 {
-	assert(this->east != NULL && this->west != NULL);
+	assert(this->east != nullptr && this->west != nullptr);
 
 	RoadStopType rst = GetRoadStopType(this->xy);
 	DiagDirection dir = GetRoadStopDir(this->xy);
@@ -141,12 +141,12 @@ void RoadStop::ClearDriveThrough()
 	/* Information about the tile north of us */
 	TileIndex north_tile = this->xy - offset;
 	bool north = IsDriveThroughRoadStopContinuation(this->xy, north_tile);
-	RoadStop *rs_north = north ? RoadStop::GetByTile(north_tile, rst) : NULL;
+	RoadStop *rs_north = north ? RoadStop::GetByTile(north_tile, rst) : nullptr;
 
 	/* Information about the tile south of us */
 	TileIndex south_tile = this->xy + offset;
 	bool south = IsDriveThroughRoadStopContinuation(this->xy, south_tile);
-	RoadStop *rs_south = south ? RoadStop::GetByTile(south_tile, rst) : NULL;
+	RoadStop *rs_south = south ? RoadStop::GetByTile(south_tile, rst) : nullptr;
 
 	/* Must only be cleared after we determined which neighbours are
 	 * part of our little entry 'queue' */
@@ -207,8 +207,8 @@ void RoadStop::ClearDriveThrough()
 
 	/* Make sure we don't get used for something 'incorrect' */
 	ClrBit(this->status, RSSFB_BASE_ENTRY);
-	this->east = NULL;
-	this->west = NULL;
+	this->east = nullptr;
+	this->west = nullptr;
 }
 
 /**
@@ -271,7 +271,7 @@ bool RoadStop::Enter(RoadVehicle *rv)
 
 	for (RoadStop *rs = st->GetPrimaryRoadStop(type);; rs = rs->next) {
 		if (rs->xy == tile) return rs;
-		assert(rs->next != NULL);
+		assert(rs->next != nullptr);
 	}
 }
 
@@ -325,25 +325,25 @@ struct RoadStopEntryRebuilderHelper {
  * Add road vehicles to the station's list if needed.
  * @param v the found vehicle
  * @param data the extra data used to make our decision
- * @return always NULL
+ * @return always nullptr
  */
 Vehicle *FindVehiclesInRoadStop(Vehicle *v, void *data)
 {
 	RoadStopEntryRebuilderHelper *rserh = (RoadStopEntryRebuilderHelper*)data;
 	/* Not a RV or not in the right direction or crashed :( */
-	if (v->type != VEH_ROAD || DirToDiagDir(v->direction) != rserh->dir || !v->IsPrimaryVehicle() || (v->vehstatus & VS_CRASHED) != 0) return NULL;
+	if (v->type != VEH_ROAD || DirToDiagDir(v->direction) != rserh->dir || !v->IsPrimaryVehicle() || (v->vehstatus & VS_CRASHED) != 0) return nullptr;
 
 	RoadVehicle *rv = RoadVehicle::From(v);
 	/* Don't add ones not in a road stop */
-	if (rv->state < RVSB_IN_ROAD_STOP) return NULL;
+	if (rv->state < RVSB_IN_ROAD_STOP) return nullptr;
 
 	/* Do not add duplicates! */
 	for (RVList::iterator it = rserh->vehicles.begin(); it != rserh->vehicles.end(); it++) {
-		if (rv == *it) return NULL;
+		if (rv == *it) return nullptr;
 	}
 
 	rserh->vehicles.push_back(rv);
-	return NULL;
+	return nullptr;
 }
 
 /**
diff --git a/src/roadveh.h b/src/roadveh.h
--- a/src/roadveh.h
+++ b/src/roadveh.h
@@ -133,7 +133,7 @@ struct RoadVehicle FINAL : public Ground
 	int GetDisplaySpeed() const { return this->gcache.last_speed / 2; }
 	int GetDisplayMaxSpeed() const { return this->vcache.cached_max_speed / 2; }
 	Money GetRunningCost() const;
-	int GetDisplayImageWidth(Point *offset = NULL) const;
+	int GetDisplayImageWidth(Point *offset = nullptr) const;
 	bool IsInDepot() const { return this->state == RVSB_IN_DEPOT; }
 	bool Tick();
 	void OnNewDay();
diff --git a/src/roadveh_cmd.cpp b/src/roadveh_cmd.cpp
--- a/src/roadveh_cmd.cpp
+++ b/src/roadveh_cmd.cpp
@@ -86,14 +86,14 @@ bool RoadVehicle::IsBus() const
 
 /**
  * Get the width of a road vehicle image in the GUI.
- * @param offset Additional offset for positioning the sprite; set to NULL if not needed
+ * @param offset Additional offset for positioning the sprite; set to nullptr if not needed
  * @return Width in pixels
  */
 int RoadVehicle::GetDisplayImageWidth(Point *offset) const
 {
 	int reference_width = ROADVEHINFO_DEFAULT_VEHICLE_WIDTH;
 
-	if (offset != NULL) {
+	if (offset != nullptr) {
 		offset->x = ScaleGUITrad(reference_width) / 2;
 		offset->y = 0;
 	}
@@ -192,7 +192,7 @@ static uint GetRoadVehLength(const RoadV
 	uint length = VEHICLE_LENGTH;
 
 	uint16 veh_len = CALLBACK_FAILED;
-	if (e->GetGRF() != NULL && e->GetGRF()->grf_version >= 8) {
+	if (e->GetGRF() != nullptr && e->GetGRF()->grf_version >= 8) {
 		/* Use callback 36 */
 		veh_len = GetVehicleProperty(v, PROP_ROADVEH_SHORTEN_FACTOR, CALLBACK_FAILED);
 		if (veh_len != CALLBACK_FAILED && veh_len >= VEHICLE_LENGTH) ErrorUnknownCallbackResult(e->GetGRFID(), CBID_VEHICLE_LENGTH, veh_len);
@@ -223,7 +223,7 @@ void RoadVehUpdateCache(RoadVehicle *v, 
 
 	v->gcache.cached_total_length = 0;
 
-	for (RoadVehicle *u = v; u != NULL; u = u->Next()) {
+	for (RoadVehicle *u = v; u != nullptr; u = u->Next()) {
 		/* Check the v->first cache. */
 		assert(u->First() == v);
 
@@ -315,7 +315,7 @@ CommandCost CmdBuildRoadVehicle(TileInde
 		v->InvalidateNewGRFCacheOfChain();
 
 		/* Call various callbacks after the whole consist has been constructed */
-		for (RoadVehicle *u = v; u != NULL; u = u->Next()) {
+		for (RoadVehicle *u = v; u != nullptr; u = u->Next()) {
 			u->cargo_cap = u->GetEngine()->DetermineCapacity(u);
 			u->refit_cap = 0;
 			v->InvalidateNewGRFCache();
@@ -350,8 +350,8 @@ bool RoadVehicle::FindClosestDepot(TileI
 	FindDepotData rfdd = FindClosestRoadDepot(this, 0);
 	if (rfdd.best_length == UINT_MAX) return false;
 
-	if (location    != NULL) *location    = rfdd.tile;
-	if (destination != NULL) *destination = GetDepotIndex(rfdd.tile);
+	if (location    != nullptr) *location    = rfdd.tile;
+	if (destination != nullptr) *destination = GetDepotIndex(rfdd.tile);
 
 	return true;
 }
@@ -368,7 +368,7 @@ bool RoadVehicle::FindClosestDepot(TileI
 CommandCost CmdTurnRoadVeh(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	RoadVehicle *v = RoadVehicle::GetIfValid(p1);
-	if (v == NULL) return CMD_ERROR;
+	if (v == nullptr) return CMD_ERROR;
 
 	if (!v->IsPrimaryVehicle()) return CMD_ERROR;
 
@@ -397,7 +397,7 @@ CommandCost CmdTurnRoadVeh(TileIndex til
 
 void RoadVehicle::MarkDirty()
 {
-	for (RoadVehicle *v = this; v != NULL; v = v->Next()) {
+	for (RoadVehicle *v = this; v != nullptr; v = v->Next()) {
 		v->colourmap = PAL_NONE;
 		v->UpdateViewport(true, false);
 	}
@@ -440,7 +440,7 @@ inline int RoadVehicle::GetCurrentMaxSpe
 	int max_speed = this->vcache.cached_max_speed;
 
 	/* Limit speed to 50% while reversing, 75% in curves. */
-	for (const RoadVehicle *u = this; u != NULL; u = u->Next()) {
+	for (const RoadVehicle *u = this; u != nullptr; u = u->Next()) {
 		if (_settings_game.vehicle.roadveh_acceleration_model == AM_REALISTIC) {
 			if (this->state <= RVSB_TRACKDIR_MASK && IsReversingRoadTrackdir((Trackdir)this->state)) {
 				max_speed = this->vcache.cached_max_speed / 2;
@@ -467,8 +467,8 @@ static void DeleteLastRoadVeh(RoadVehicl
 {
 	RoadVehicle *first = v->First();
 	Vehicle *u = v;
-	for (; v->Next() != NULL; v = v->Next()) u = v;
-	u->SetNext(NULL);
+	for (; v->Next() != nullptr; v = v->Next()) u = v;
+	u->SetNext(nullptr);
 	v->last_station_visited = first->last_station_visited; // for PreDestructor
 
 	/* Only leave the road stop when we're really gone. */
@@ -488,7 +488,7 @@ static void RoadVehSetRandomDirection(Ro
 
 		v->direction = ChangeDir(v->direction, delta[r & 3]);
 		v->UpdateViewport(true, true);
-	} while ((v = v->Next()) != NULL);
+	} while ((v = v->Next()) != nullptr);
 }
 
 /**
@@ -504,7 +504,7 @@ static bool RoadVehIsCrashed(RoadVehicle
 	} else if (v->crashed_ctr <= 45) {
 		if ((v->tick_counter & 7) == 0) RoadVehSetRandomDirection(v);
 	} else if (v->crashed_ctr >= 2220 && !(v->tick_counter & 0x1F)) {
-		bool ret = v->Next() != NULL;
+		bool ret = v->Next() != nullptr;
 		DeleteLastRoadVeh(v);
 		return ret;
 	}
@@ -516,7 +516,7 @@ static bool RoadVehIsCrashed(RoadVehicle
  * Check routine whether a road and a train vehicle have collided.
  * @param v    %Train vehicle to test.
  * @param data Road vehicle to test.
- * @return %Train vehicle if the vehicles collided, else \c NULL.
+ * @return %Train vehicle if the vehicles collided, else \c nullptr.
  */
 static Vehicle *EnumCheckRoadVehCrashTrain(Vehicle *v, void *data)
 {
@@ -525,7 +525,7 @@ static Vehicle *EnumCheckRoadVehCrashTra
 	return (v->type == VEH_TRAIN &&
 			abs(v->z_pos - u->z_pos) <= 6 &&
 			abs(v->x_pos - u->x_pos) <= 4 &&
-			abs(v->y_pos - u->y_pos) <= 4) ? v : NULL;
+			abs(v->y_pos - u->y_pos) <= 4) ? v : nullptr;
 }
 
 uint RoadVehicle::Crash(bool flooded)
@@ -564,7 +564,7 @@ static void RoadVehCrash(RoadVehicle *v)
 
 static bool RoadVehCheckTrainCrash(RoadVehicle *v)
 {
-	for (RoadVehicle *u = v; u != NULL; u = u->Next()) {
+	for (RoadVehicle *u = v; u != nullptr; u = u->Next()) {
 		if (u->state == RVSB_WORMHOLE) continue;
 
 		TileIndex tile = u->tile;
@@ -641,7 +641,7 @@ static Vehicle *EnumCheckRoadVehClose(Ve
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 static RoadVehicle *RoadVehFindCloseTo(RoadVehicle *v, int x, int y, Direction dir, bool update_blocked_ctr = true)
@@ -649,7 +649,7 @@ static RoadVehicle *RoadVehFindCloseTo(R
 	RoadVehFindData rvf;
 	RoadVehicle *front = v->First();
 
-	if (front->reverse_ctr != 0) return NULL;
+	if (front->reverse_ctr != 0) return nullptr;
 
 	rvf.x = x;
 	rvf.y = y;
@@ -670,10 +670,10 @@ static RoadVehicle *RoadVehFindCloseTo(R
 	 * It can be disabled. */
 	if (rvf.best_diff == UINT_MAX) {
 		front->blocked_ctr = 0;
-		return NULL;
+		return nullptr;
 	}
 
-	if (update_blocked_ctr && ++front->blocked_ctr > 1480) return NULL;
+	if (update_blocked_ctr && ++front->blocked_ctr > 1480) return nullptr;
 
 	return RoadVehicle::From(rvf.best);
 }
@@ -772,7 +772,7 @@ static Vehicle *EnumFindVehBlockingOvert
 {
 	const OvertakeData *od = (OvertakeData*)data;
 
-	return (v->type == VEH_ROAD && v->First() == v && v != od->u && v != od->v) ? v : NULL;
+	return (v->type == VEH_ROAD && v->First() == v && v != od->u && v != od->v) ? v : nullptr;
 }
 
 /**
@@ -1006,7 +1006,7 @@ struct RoadDriveEntry {
 static bool RoadVehLeaveDepot(RoadVehicle *v, bool first)
 {
 	/* Don't leave unless v and following wagons are in the depot. */
-	for (const RoadVehicle *u = v; u != NULL; u = u->Next()) {
+	for (const RoadVehicle *u = v; u != nullptr; u = u->Next()) {
 		if (u->state != RVSB_IN_DEPOT || u->tile != v->tile) return false;
 	}
 
@@ -1026,7 +1026,7 @@ static bool RoadVehLeaveDepot(RoadVehicl
 			return true;
 		}
 
-		if (RoadVehFindCloseTo(v, x, y, v->direction, false) != NULL) return true;
+		if (RoadVehFindCloseTo(v, x, y, v->direction, false) != nullptr) return true;
 
 		VehicleServiceInDepot(v);
 
@@ -1161,7 +1161,7 @@ bool IndividualRoadVehicleController(Roa
 
 		if (v->IsFrontEngine()) {
 			const Vehicle *u = RoadVehFindCloseTo(v, gp.x, gp.y, v->direction);
-			if (u != NULL) {
+			if (u != nullptr) {
 				v->cur_speed = u->First()->cur_speed;
 				return false;
 			}
@@ -1225,7 +1225,7 @@ again:
 					case TRACKDIR_RVREV_SW: needed = ROAD_NE; break;
 					case TRACKDIR_RVREV_NW: needed = ROAD_SE; break;
 				}
-				if ((v->Previous() != NULL && v->Previous()->tile == tile) ||
+				if ((v->Previous() != nullptr && v->Previous()->tile == tile) ||
 						(v->IsFrontEngine() && IsNormalRoadTile(tile) && !HasRoadWorks(tile) &&
 							(needed & GetRoadBits(tile, ROADTYPE_TRAM)) != ROAD_NONE)) {
 					/*
@@ -1274,7 +1274,7 @@ again:
 		Direction new_dir = RoadVehGetSlidingDirection(v, x, y);
 		if (v->IsFrontEngine()) {
 			Vehicle *u = RoadVehFindCloseTo(v, x, y, new_dir);
-			if (u != NULL) {
+			if (u != nullptr) {
 				v->cur_speed = u->First()->cur_speed;
 				return false;
 			}
@@ -1376,7 +1376,7 @@ again:
 		int y = TileY(v->tile) * TILE_SIZE + rdp[turn_around_start_frame].y;
 
 		Direction new_dir = RoadVehGetSlidingDirection(v, x, y);
-		if (v->IsFrontEngine() && RoadVehFindCloseTo(v, x, y, new_dir) != NULL) return false;
+		if (v->IsFrontEngine() && RoadVehFindCloseTo(v, x, y, new_dir) != nullptr) return false;
 
 		uint32 r = VehicleEnterTile(v, v->tile, x, y);
 		if (HasBit(r, VETS_CANNOT_ENTER)) {
@@ -1402,7 +1402,7 @@ again:
 	/* This vehicle is not in a wormhole and it hasn't entered a new tile. If
 	 * it's on a depot tile, check if it's time to activate the next vehicle in
 	 * the chain yet. */
-	if (v->Next() != NULL && IsRoadDepotTile(v->tile)) {
+	if (v->Next() != nullptr && IsRoadDepotTile(v->tile)) {
 		if (v->frame == v->gcache.cached_veh_length + RVC_DEPOT_START_FRAME) {
 			RoadVehLeaveDepot(v->Next(), false);
 		}
@@ -1419,7 +1419,7 @@ again:
 		 * Check for another vehicle to overtake */
 		RoadVehicle *u = RoadVehFindCloseTo(v, x, y, new_dir);
 
-		if (u != NULL) {
+		if (u != nullptr) {
 			u = u->First();
 			/* There is a vehicle in front overtake it if possible */
 			if (v->overtaking == 0) RoadVehCheckOvertake(v, u);
@@ -1569,7 +1569,7 @@ static bool RoadVehController(RoadVehicl
 		j -= adv_spd;
 
 		RoadVehicle *u = v;
-		for (RoadVehicle *prev = NULL; u != NULL; prev = u, u = u->Next()) {
+		for (RoadVehicle *prev = nullptr; u != nullptr; prev = u, u = u->Next()) {
 			if (!IndividualRoadVehicleController(u, prev)) {
 				blocked = true;
 				break;
@@ -1586,7 +1586,7 @@ static bool RoadVehController(RoadVehicl
 
 	v->SetLastSpeed();
 
-	for (RoadVehicle *u = v; u != NULL; u = u->Next()) {
+	for (RoadVehicle *u = v; u != nullptr; u = u->Next()) {
 		if ((u->vehstatus & VS_HIDDEN) != 0) continue;
 
 		u->UpdateViewport(false, false);
diff --git a/src/roadveh_gui.cpp b/src/roadveh_gui.cpp
--- a/src/roadveh_gui.cpp
+++ b/src/roadveh_gui.cpp
@@ -47,7 +47,7 @@ void DrawRoadVehDetails(const Vehicle *v
 
 		memset(subtype_text, 0, sizeof(subtype_text));
 
-		for (const Vehicle *u = v; u != NULL; u = u->Next()) {
+		for (const Vehicle *u = v; u != nullptr; u = u->Next()) {
 			max_cargo[u->cargo_type] += u->cargo_cap;
 			if (u->cargo_cap > 0) {
 				StringID text = GetCargoSubtypeText(u);
@@ -80,7 +80,7 @@ void DrawRoadVehDetails(const Vehicle *v
 
 		DrawString(left, right, y + FONT_HEIGHT_NORMAL + y_offset, capacity, TC_BLUE);
 
-		for (const Vehicle *u = v; u != NULL; u = u->Next()) {
+		for (const Vehicle *u = v; u != nullptr; u = u->Next()) {
 			if (u->cargo_cap == 0) continue;
 
 			str = STR_VEHICLE_DETAILS_CARGO_EMPTY;
@@ -143,7 +143,7 @@ void DrawRoadVehImage(const Vehicle *v, 
 	_cur_dpi = &tmp_dpi;
 
 	int px = rtl ? max_width + skip : -skip;
-	for (; u != NULL && (rtl ? px > 0 : px < max_width); u = u->Next()) {
+	for (; u != nullptr && (rtl ? px > 0 : px < max_width); u = u->Next()) {
 		Point offset;
 		int width = u->GetDisplayImageWidth(&offset);
 
diff --git a/src/safeguards.h b/src/safeguards.h
--- a/src/safeguards.h
+++ b/src/safeguards.h
@@ -12,7 +12,7 @@
  *
  * Unsafe methods are, for example, strndup and strncpy because they may leave the
  * string without a null termination, but also strdup and strndup because they can
- * return NULL and then all strdups would need to be guarded against that instead
+ * return nullptr and then all strdups would need to be guarded against that instead
  * of using the current MallocT/ReallocT/CallocT technique of just giving the user
  * an error that too much memory was used instead of spreading that code though
  * the whole code base.
diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -263,14 +263,14 @@ static void InitializeWindowsAndCaches()
 	/* Identify owners of persistent storage arrays */
 	Industry *i;
 	FOR_ALL_INDUSTRIES(i) {
-		if (i->psa != NULL) {
+		if (i->psa != nullptr) {
 			i->psa->feature = GSF_INDUSTRIES;
 			i->psa->tile = i->location.tile;
 		}
 	}
 	Station *s;
 	FOR_ALL_STATIONS(s) {
-		if (s->airport.psa != NULL) {
+		if (s->airport.psa != nullptr) {
 			s->airport.psa->feature = GSF_AIRPORTS;
 			s->airport.psa->tile = s->airport.tile;
 		}
@@ -303,9 +303,9 @@ static void InitializeWindowsAndCaches()
 }
 
 typedef void (CDECL *SignalHandlerPointer)(int);
-static SignalHandlerPointer _prev_segfault = NULL;
-static SignalHandlerPointer _prev_abort    = NULL;
-static SignalHandlerPointer _prev_fpe      = NULL;
+static SignalHandlerPointer _prev_segfault = nullptr;
+static SignalHandlerPointer _prev_abort    = nullptr;
+static SignalHandlerPointer _prev_fpe      = nullptr;
 
 static void CDECL HandleSavegameLoadCrash(int signum);
 
@@ -375,7 +375,7 @@ static void CDECL HandleSavegameLoadCras
 	char *p = buffer;
 	p += seprintf(p, lastof(buffer), "Loading your savegame caused OpenTTD to crash.\n");
 
-	for (const GRFConfig *c = _grfconfig; !_saveload_crash_with_missing_newgrfs && c != NULL; c = c->next) {
+	for (const GRFConfig *c = _grfconfig; !_saveload_crash_with_missing_newgrfs && c != nullptr; c = c->next) {
 		_saveload_crash_with_missing_newgrfs = HasBit(c->flags, GCF_COMPATIBLE) || c->status == GCS_NOT_FOUND;
 	}
 
@@ -393,7 +393,7 @@ static void CDECL HandleSavegameLoadCras
 			"Please load the savegame with the appropriate NewGRFs installed.\n"
 			"The missing/compatible NewGRFs are:\n");
 
-		for (const GRFConfig *c = _grfconfig; c != NULL; c = c->next) {
+		for (const GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
 			if (HasBit(c->flags, GCF_COMPATIBLE)) {
 				const GRFIdentifier *replaced = GetOverriddenIdentifier(c);
 				char buf[40];
@@ -414,14 +414,14 @@ static void CDECL HandleSavegameLoadCras
 
 	ShowInfo(buffer);
 
-	SignalHandlerPointer call = NULL;
+	SignalHandlerPointer call = nullptr;
 	switch (signum) {
 		case SIGSEGV: call = _prev_segfault; break;
 		case SIGABRT: call = _prev_abort; break;
 		case SIGFPE:  call = _prev_fpe; break;
 		default: NOT_REACHED();
 	}
-	if (call != NULL) call(signum);
+	if (call != nullptr) call(signum);
 }
 
 /**
@@ -434,7 +434,7 @@ static void FixOwnerOfRailTrack(TileInde
 	assert(!Company::IsValidID(GetTileOwner(t)) && (IsLevelCrossingTile(t) || IsPlainRailTile(t)));
 
 	/* remove leftover rail piece from crossing (from very old savegames) */
-	Train *v = NULL, *w;
+	Train *v = nullptr, *w;
 	FOR_ALL_TRAINS(w) {
 		if (w->tile == t) {
 			v = w;
@@ -442,7 +442,7 @@ static void FixOwnerOfRailTrack(TileInde
 		}
 	}
 
-	if (v != NULL) {
+	if (v != nullptr) {
 		/* when there is a train on crossing (it could happen in TTD), set owner of crossing to train owner */
 		SetTileOwner(t, v->owner);
 		return;
@@ -631,22 +631,22 @@ bool AfterLoadGame()
 		Company *c;
 		FOR_ALL_COMPANIES(c) {
 			c->name = CopyFromOldName(c->name_1);
-			if (c->name != NULL) c->name_1 = STR_SV_UNNAMED;
+			if (c->name != nullptr) c->name_1 = STR_SV_UNNAMED;
 			c->president_name = CopyFromOldName(c->president_name_1);
-			if (c->president_name != NULL) c->president_name_1 = SPECSTR_PRESIDENT_NAME;
+			if (c->president_name != nullptr) c->president_name_1 = SPECSTR_PRESIDENT_NAME;
 		}
 
 		Station *st;
 		FOR_ALL_STATIONS(st) {
 			st->name = CopyFromOldName(st->string_id);
 			/* generating new name would be too much work for little effect, use the station name fallback */
-			if (st->name != NULL) st->string_id = STR_SV_STNAME_FALLBACK;
+			if (st->name != nullptr) st->string_id = STR_SV_STNAME_FALLBACK;
 		}
 
 		Town *t;
 		FOR_ALL_TOWNS(t) {
 			t->name = CopyFromOldName(t->townnametype);
-			if (t->name != NULL) t->townnametype = SPECSTR_TOWNNAME_START + _settings_game.game_creation.town_name;
+			if (t->name != nullptr) t->townnametype = SPECSTR_TOWNNAME_START + _settings_game.game_creation.town_name;
 		}
 	}
 
@@ -676,7 +676,7 @@ bool AfterLoadGame()
 
 	/* Check if all NewGRFs are present, we are very strict in MP mode */
 	GRFListCompatibility gcf_res = IsGoodGRFConfigList(_grfconfig);
-	for (GRFConfig *c = _grfconfig; c != NULL; c = c->next) {
+	for (GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
 		if (c->status == GCS_NOT_FOUND) {
 			GamelogGRFRemove(c->ident.grfid);
 		} else if (HasBit(c->flags, GCF_COMPATIBLE)) {
@@ -787,7 +787,7 @@ bool AfterLoadGame()
 	{
 		Company *c;
 		FOR_ALL_COMPANIES(c) {
-			if (c->is_ai && c->ai_instance == NULL) AI::StartNew(c->index);
+			if (c->is_ai && c->ai_instance == nullptr) AI::StartNew(c->index);
 		}
 	}
 
@@ -987,7 +987,7 @@ bool AfterLoadGame()
 	if (IsSavegameVersionBefore(SLV_16)) {
 		Company *c;
 		FOR_ALL_COMPANIES(c) {
-			c->engine_renew_list            = NULL;
+			c->engine_renew_list            = nullptr;
 			c->settings.engine_renew        = false;
 			c->settings.engine_renew_months = 6;
 			c->settings.engine_renew_money  = 100000;
@@ -1000,7 +1000,7 @@ bool AfterLoadGame()
 		 * companies are 'invalid'.
 		 */
 		c = Company::GetIfValid(COMPANY_FIRST);
-		if (!_network_dedicated && c != NULL) {
+		if (!_network_dedicated && c != nullptr) {
 			c->settings = _settings_client.company;
 		}
 	}
@@ -1104,7 +1104,7 @@ bool AfterLoadGame()
 					}
 					if (!IsRoadDepot(t) && !HasTownOwnedRoad(t)) {
 						const Town *town = CalcClosestTownFromTile(t);
-						if (town != NULL) SetTownIndex(t, town->index);
+						if (town != nullptr) SetTownIndex(t, town->index);
 					}
 					_m[t].m4 = 0;
 					break;
@@ -1711,9 +1711,9 @@ bool AfterLoadGame()
 
 		Vehicle *v;
 		FOR_ALL_VEHICLES(v) {
-			if (v->orders.list != NULL && v->orders.list->GetFirstOrder() != NULL && v->orders.list->GetFirstOrder()->IsType(OT_NOTHING)) {
+			if (v->orders.list != nullptr && v->orders.list->GetFirstOrder() != nullptr && v->orders.list->GetFirstOrder()->IsType(OT_NOTHING)) {
 				v->orders.list->FreeChain();
-				v->orders.list = NULL;
+				v->orders.list = nullptr;
 			}
 
 			v->current_order.ConvertFromOldSavegame();
@@ -2165,7 +2165,7 @@ bool AfterLoadGame()
 		FOR_ALL_DISASTERVEHICLES(v) {
 			if (v->subtype == 2 /* ST_SMALL_UFO */ && v->current_order.GetDestination() != 0) {
 				const Vehicle *u = Vehicle::GetIfValid(v->dest_tile);
-				if (u == NULL || u->type != VEH_ROAD || !RoadVehicle::From(u)->IsFrontEngine()) {
+				if (u == nullptr || u->type != VEH_ROAD || !RoadVehicle::From(u)->IsFrontEngine()) {
 					delete v;
 				}
 			}
@@ -2186,7 +2186,7 @@ bool AfterLoadGame()
 				assert_compile(CargoPaymentPool::MAX_SIZE == VehiclePool::MAX_SIZE);
 				assert(CargoPayment::CanAllocateItem());
 				Vehicle *v = *iter;
-				if (v->cargo_payment == NULL) v->cargo_payment = new CargoPayment(v);
+				if (v->cargo_payment == nullptr) v->cargo_payment = new CargoPayment(v);
 			}
 		}
 	}
@@ -2199,7 +2199,7 @@ bool AfterLoadGame()
 
 		for (auto tile = _animated_tiles.begin(); tile < _animated_tiles.end(); /* Nothing */) {
 			/* Remove if tile is not animated */
-			bool remove = _tile_type_procs[GetTileType(*tile)]->animate_tile_proc == NULL;
+			bool remove = _tile_type_procs[GetTileType(*tile)]->animate_tile_proc == nullptr;
 
 			/* and remove if duplicate */
 			for (auto j = _animated_tiles.begin(); !remove && j < tile; j++) {
@@ -2271,7 +2271,7 @@ bool AfterLoadGame()
 						/* Town -> Town */
 						const Station *ss = Station::GetIfValid(s->src);
 						const Station *sd = Station::GetIfValid(s->dst);
-						if (ss != NULL && sd != NULL && ss->owner == sd->owner &&
+						if (ss != nullptr && sd != nullptr && ss->owner == sd->owner &&
 								Company::IsValidID(ss->owner)) {
 							s->src_type = s->dst_type = ST_TOWN;
 							s->src = ss->town->index;
@@ -2438,13 +2438,13 @@ bool AfterLoadGame()
 		FOR_ALL_AIRCRAFT(v) {
 			if (!v->IsNormalAircraft()) continue;
 			Station *st = GetTargetAirportIfValid(v);
-			if (st == NULL && v->state != FLYING) {
+			if (st == nullptr && v->state != FLYING) {
 				v->state = FLYING;
 				UpdateAircraftCache(v);
 				AircraftNextAirportPos_and_Order(v);
 				/* get aircraft back on running altitude */
 				if ((v->vehstatus & VS_CRASHED) == 0) {
-					GetAircraftFlightLevelBounds(v, &v->z_pos, NULL);
+					GetAircraftFlightLevelBounds(v, &v->z_pos, nullptr);
 					SetAircraftPosition(v, v->x_pos, v->y_pos, GetAircraftFlightLevel(v));
 				}
 			}
@@ -2506,11 +2506,11 @@ bool AfterLoadGame()
 		 * order they have in the pool. */
 		Waypoint *wp;
 		FOR_ALL_WAYPOINTS(wp) {
-			if (wp->name != NULL) wp->town_cn = UINT16_MAX;
+			if (wp->name != nullptr) wp->town_cn = UINT16_MAX;
 		}
 
 		FOR_ALL_WAYPOINTS(wp) {
-			if (wp->name != NULL) MakeDefaultName(wp);
+			if (wp->name != nullptr) MakeDefaultName(wp);
 		}
 	}
 
@@ -2742,7 +2742,7 @@ bool AfterLoadGame()
 		if (!IsSavegameVersionBefore(SLV_76)) {
 			Industry *ind;
 			FOR_ALL_INDUSTRIES(ind) {
-				assert(ind->psa != NULL);
+				assert(ind->psa != nullptr);
 
 				/* Check if the old storage was empty. */
 				bool is_empty = true;
@@ -2757,7 +2757,7 @@ bool AfterLoadGame()
 					ind->psa->grfid = _industry_mngr.GetGRFID(ind->type);
 				} else {
 					delete ind->psa;
-					ind->psa = NULL;
+					ind->psa = nullptr;
 				}
 			}
 		}
@@ -2766,7 +2766,7 @@ bool AfterLoadGame()
 			Station *st;
 			FOR_ALL_STATIONS(st) {
 				if (!(st->facilities & FACIL_AIRPORT)) continue;
-				assert(st->airport.psa != NULL);
+				assert(st->airport.psa != nullptr);
 
 				/* Check if the old storage was empty. */
 				bool is_empty = true;
@@ -2781,7 +2781,7 @@ bool AfterLoadGame()
 					st->airport.psa->grfid = _airport_mngr.GetGRFID(st->airport.type);
 				} else {
 					delete st->airport.psa;
-					st->airport.psa = NULL;
+					st->airport.psa = nullptr;
 
 				}
 			}
@@ -2821,12 +2821,12 @@ bool AfterLoadGame()
 			/* Set the default cargo requirement for town growth */
 			switch (_settings_game.game_creation.landscape) {
 				case LT_ARCTIC:
-					if (FindFirstCargoWithTownEffect(TE_FOOD) != NULL) t->goal[TE_FOOD] = TOWN_GROWTH_WINTER;
+					if (FindFirstCargoWithTownEffect(TE_FOOD) != nullptr) t->goal[TE_FOOD] = TOWN_GROWTH_WINTER;
 					break;
 
 				case LT_TROPIC:
-					if (FindFirstCargoWithTownEffect(TE_FOOD) != NULL) t->goal[TE_FOOD] = TOWN_GROWTH_DESERT;
-					if (FindFirstCargoWithTownEffect(TE_WATER) != NULL) t->goal[TE_WATER] = TOWN_GROWTH_DESERT;
+					if (FindFirstCargoWithTownEffect(TE_FOOD) != nullptr) t->goal[TE_FOOD] = TOWN_GROWTH_DESERT;
+					if (FindFirstCargoWithTownEffect(TE_WATER) != nullptr) t->goal[TE_WATER] = TOWN_GROWTH_DESERT;
 					break;
 			}
 		}
@@ -2946,7 +2946,7 @@ bool AfterLoadGame()
 			TileIndex prev_tile = v->tile;
 			uint prev_tile_skip = 0;
 			uint cur_skip = 0;
-			for (RoadVehicle *u = v; u != NULL; u = u->Next()) {
+			for (RoadVehicle *u = v; u != nullptr; u = u->Next()) {
 				if (u->tile != prev_tile) {
 					prev_tile_skip = cur_skip;
 					prev_tile = u->tile;
@@ -2980,7 +2980,7 @@ bool AfterLoadGame()
 			}
 			while (cur_skip > skip_frames[0]) {
 				RoadVehicle *u = v;
-				RoadVehicle *prev = NULL;
+				RoadVehicle *prev = nullptr;
 				for (uint sf : skip_frames) {
 					extern bool IndividualRoadVehicleController(RoadVehicle *v, const RoadVehicle *prev);
 					if (sf >= cur_skip) IndividualRoadVehicleController(u, prev);
@@ -3111,7 +3111,7 @@ bool AfterLoadGame()
 	} else {
 		/* Link neutral station back to industry, as this is not saved. */
 		Industry *ind;
-		FOR_ALL_INDUSTRIES(ind) if (ind->neutral_station != NULL) ind->neutral_station->industry = ind;
+		FOR_ALL_INDUSTRIES(ind) if (ind->neutral_station != nullptr) ind->neutral_station->industry = ind;
 	}
 
 	if (IsSavegameVersionBefore(SLV_TREES_WATER_CLASS)) {
diff --git a/src/saveload/ai_sl.cpp b/src/saveload/ai_sl.cpp
--- a/src/saveload/ai_sl.cpp
+++ b/src/saveload/ai_sl.cpp
@@ -53,7 +53,7 @@ static void SaveReal_AIPL(int *index_ptr
 	_ai_saveload_settings[0] = '\0';
 	config->SettingsToString(_ai_saveload_settings, lastof(_ai_saveload_settings));
 
-	SlObject(NULL, _ai_company);
+	SlObject(nullptr, _ai_company);
 	/* If the AI was active, store his data too */
 	if (Company::IsValidAiID(index)) AI::Save(index);
 }
@@ -62,7 +62,7 @@ static void Load_AIPL()
 {
 	/* Free all current data */
 	for (CompanyID c = COMPANY_FIRST; c < MAX_COMPANIES; c++) {
-		AIConfig::GetConfig(c, AIConfig::SSS_FORCE_GAME)->Change(NULL);
+		AIConfig::GetConfig(c, AIConfig::SSS_FORCE_GAME)->Change(nullptr);
 	}
 
 	CompanyID index;
@@ -71,7 +71,7 @@ static void Load_AIPL()
 
 		_ai_saveload_is_random = 0;
 		_ai_saveload_version = -1;
-		SlObject(NULL, _ai_company);
+		SlObject(nullptr, _ai_company);
 
 		if (_networking && !_network_server) {
 			if (Company::IsValidAiID(index)) AIInstance::LoadEmpty();
@@ -81,7 +81,7 @@ static void Load_AIPL()
 		AIConfig *config = AIConfig::GetConfig(index, AIConfig::SSS_FORCE_GAME);
 		if (StrEmpty(_ai_saveload_name)) {
 			/* A random AI. */
-			config->Change(NULL, -1, false, true);
+			config->Change(nullptr, -1, false, true);
 		} else {
 			config->Change(_ai_saveload_name, _ai_saveload_version, false, _ai_saveload_is_random);
 			if (!config->HasScript()) {
@@ -125,5 +125,5 @@ static void Save_AIPL()
 }
 
 extern const ChunkHandler _ai_chunk_handlers[] = {
-	{ 'AIPL', Save_AIPL, Load_AIPL, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'AIPL', Save_AIPL, Load_AIPL, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/airport_sl.cpp b/src/saveload/airport_sl.cpp
--- a/src/saveload/airport_sl.cpp
+++ b/src/saveload/airport_sl.cpp
@@ -37,6 +37,6 @@ static void Load_ATID()
 }
 
 extern const ChunkHandler _airport_chunk_handlers[] = {
-	{ 'ATID', Save_ATID, Load_ATID, NULL, NULL, CH_ARRAY },
-	{ 'APID', Save_APID, Load_APID, NULL, NULL, CH_ARRAY | CH_LAST },
+	{ 'ATID', Save_ATID, Load_ATID, nullptr, nullptr, CH_ARRAY },
+	{ 'APID', Save_APID, Load_APID, nullptr, nullptr, CH_ARRAY | CH_LAST },
 };
diff --git a/src/saveload/animated_tile_sl.cpp b/src/saveload/animated_tile_sl.cpp
--- a/src/saveload/animated_tile_sl.cpp
+++ b/src/saveload/animated_tile_sl.cpp
@@ -58,5 +58,5 @@ static void Load_ANIT()
  * the animated tile table.
  */
 extern const ChunkHandler _animated_tile_chunk_handlers[] = {
-	{ 'ANIT', Save_ANIT, Load_ANIT, NULL, NULL, CH_RIFF | CH_LAST},
+	{ 'ANIT', Save_ANIT, Load_ANIT, nullptr, nullptr, CH_RIFF | CH_LAST},
 };
diff --git a/src/saveload/autoreplace_sl.cpp b/src/saveload/autoreplace_sl.cpp
--- a/src/saveload/autoreplace_sl.cpp
+++ b/src/saveload/autoreplace_sl.cpp
@@ -63,5 +63,5 @@ static void Ptrs_ERNW()
 }
 
 extern const ChunkHandler _autoreplace_chunk_handlers[] = {
-	{ 'ERNW', Save_ERNW, Load_ERNW, Ptrs_ERNW, NULL, CH_ARRAY | CH_LAST},
+	{ 'ERNW', Save_ERNW, Load_ERNW, Ptrs_ERNW, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/cargomonitor_sl.cpp b/src/saveload/cargomonitor_sl.cpp
--- a/src/saveload/cargomonitor_sl.cpp
+++ b/src/saveload/cargomonitor_sl.cpp
@@ -121,6 +121,6 @@ static void LoadPickup()
 
 /** Chunk definition of the cargomonitoring maps. */
 extern const ChunkHandler _cargomonitor_chunk_handlers[] = {
-	{ 'CMDL', SaveDelivery, LoadDelivery, NULL, NULL, CH_ARRAY},
-	{ 'CMPU', SavePickup,   LoadPickup,   NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'CMDL', SaveDelivery, LoadDelivery, nullptr, nullptr, CH_ARRAY},
+	{ 'CMPU', SavePickup,   LoadPickup,   nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/cargopacket_sl.cpp b/src/saveload/cargopacket_sl.cpp
--- a/src/saveload/cargopacket_sl.cpp
+++ b/src/saveload/cargopacket_sl.cpp
@@ -139,5 +139,5 @@ static void Load_CAPA()
 
 /** Chunk handlers related to cargo packets. */
 extern const ChunkHandler _cargopacket_chunk_handlers[] = {
-	{ 'CAPA', Save_CAPA, Load_CAPA, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'CAPA', Save_CAPA, Load_CAPA, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/cheat_sl.cpp b/src/saveload/cheat_sl.cpp
--- a/src/saveload/cheat_sl.cpp
+++ b/src/saveload/cheat_sl.cpp
@@ -51,5 +51,5 @@ static void Load_CHTS()
 
 /** Chunk handlers related to cheats. */
 extern const ChunkHandler _cheat_chunk_handlers[] = {
-	{ 'CHTS', Save_CHTS, Load_CHTS, NULL, NULL, CH_RIFF | CH_LAST},
+	{ 'CHTS', Save_CHTS, Load_CHTS, nullptr, nullptr, CH_RIFF | CH_LAST},
 };
diff --git a/src/saveload/company_sl.cpp b/src/saveload/company_sl.cpp
--- a/src/saveload/company_sl.cpp
+++ b/src/saveload/company_sl.cpp
@@ -111,7 +111,7 @@ void AfterLoadCompanyStats()
 		switch (GetTileType(tile)) {
 			case MP_RAILWAY:
 				c = Company::GetIfValid(GetTileOwner(tile));
-				if (c != NULL) {
+				if (c != nullptr) {
 					uint pieces = 1;
 					if (IsPlainRail(tile)) {
 						TrackBits bits = GetTrackBits(tile);
@@ -127,7 +127,7 @@ void AfterLoadCompanyStats()
 			case MP_ROAD: {
 				if (IsLevelCrossing(tile)) {
 					c = Company::GetIfValid(GetTileOwner(tile));
-					if (c != NULL) c->infrastructure.rail[GetRailType(tile)] += LEVELCROSSING_TRACKBIT_FACTOR;
+					if (c != nullptr) c->infrastructure.rail[GetRailType(tile)] += LEVELCROSSING_TRACKBIT_FACTOR;
 				}
 
 				/* Iterate all present road types as each can have a different owner. */
@@ -135,19 +135,19 @@ void AfterLoadCompanyStats()
 				FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
 					c = Company::GetIfValid(IsRoadDepot(tile) ? GetTileOwner(tile) : GetRoadOwner(tile, rt));
 					/* A level crossings and depots have two road bits. */
-					if (c != NULL) c->infrastructure.road[rt] += IsNormalRoad(tile) ? CountBits(GetRoadBits(tile, rt)) : 2;
+					if (c != nullptr) c->infrastructure.road[rt] += IsNormalRoad(tile) ? CountBits(GetRoadBits(tile, rt)) : 2;
 				}
 				break;
 			}
 
 			case MP_STATION:
 				c = Company::GetIfValid(GetTileOwner(tile));
-				if (c != NULL && GetStationType(tile) != STATION_AIRPORT && !IsBuoy(tile)) c->infrastructure.station++;
+				if (c != nullptr && GetStationType(tile) != STATION_AIRPORT && !IsBuoy(tile)) c->infrastructure.station++;
 
 				switch (GetStationType(tile)) {
 					case STATION_RAIL:
 					case STATION_WAYPOINT:
-						if (c != NULL && !IsStationTileBlocked(tile)) c->infrastructure.rail[GetRailType(tile)]++;
+						if (c != nullptr && !IsStationTileBlocked(tile)) c->infrastructure.rail[GetRailType(tile)]++;
 						break;
 
 					case STATION_BUS:
@@ -156,7 +156,7 @@ void AfterLoadCompanyStats()
 						RoadType rt;
 						FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
 							c = Company::GetIfValid(GetRoadOwner(tile, rt));
-							if (c != NULL) c->infrastructure.road[rt] += 2; // A road stop has two road bits.
+							if (c != nullptr) c->infrastructure.road[rt] += 2; // A road stop has two road bits.
 						}
 						break;
 					}
@@ -164,7 +164,7 @@ void AfterLoadCompanyStats()
 					case STATION_DOCK:
 					case STATION_BUOY:
 						if (GetWaterClass(tile) == WATER_CLASS_CANAL) {
-							if (c != NULL) c->infrastructure.water++;
+							if (c != nullptr) c->infrastructure.water++;
 						}
 						break;
 
@@ -176,7 +176,7 @@ void AfterLoadCompanyStats()
 			case MP_WATER:
 				if (IsShipDepot(tile) || IsLock(tile)) {
 					c = Company::GetIfValid(GetTileOwner(tile));
-					if (c != NULL) {
+					if (c != nullptr) {
 						if (IsShipDepot(tile)) c->infrastructure.water += LOCK_DEPOT_TILE_FACTOR;
 						if (IsLock(tile) && GetLockPart(tile) == LOCK_PART_MIDDLE) {
 							/* The middle tile specifies the owner of the lock. */
@@ -190,7 +190,7 @@ void AfterLoadCompanyStats()
 			case MP_OBJECT:
 				if (GetWaterClass(tile) == WATER_CLASS_CANAL) {
 					c = Company::GetIfValid(GetTileOwner(tile));
-					if (c != NULL) c->infrastructure.water++;
+					if (c != nullptr) c->infrastructure.water++;
 				}
 				break;
 
@@ -205,7 +205,7 @@ void AfterLoadCompanyStats()
 					switch (GetTunnelBridgeTransportType(tile)) {
 						case TRANSPORT_RAIL:
 							c = Company::GetIfValid(GetTileOwner(tile));
-							if (c != NULL) c->infrastructure.rail[GetRailType(tile)] += len;
+							if (c != nullptr) c->infrastructure.rail[GetRailType(tile)] += len;
 							break;
 
 						case TRANSPORT_ROAD: {
@@ -213,14 +213,14 @@ void AfterLoadCompanyStats()
 							RoadType rt;
 							FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
 								c = Company::GetIfValid(GetRoadOwner(tile, rt));
-								if (c != NULL) c->infrastructure.road[rt] += len * 2; // A full diagonal road has two road bits.
+								if (c != nullptr) c->infrastructure.road[rt] += len * 2; // A full diagonal road has two road bits.
 							}
 							break;
 						}
 
 						case TRANSPORT_WATER:
 							c = Company::GetIfValid(GetTileOwner(tile));
-							if (c != NULL) c->infrastructure.water += len;
+							if (c != nullptr) c->infrastructure.water += len;
 							break;
 
 						default:
@@ -414,7 +414,7 @@ static void SaveLoad_PLYR_common(Company
 	int i;
 
 	SlObject(cprops, _company_desc);
-	if (c != NULL) {
+	if (c != nullptr) {
 		SlObject(c, _company_settings_desc);
 	} else {
 		char nothing;
@@ -444,7 +444,7 @@ static void SaveLoad_PLYR_common(Company
 	/* Write each livery entry. */
 	int num_liveries = IsSavegameVersionBefore(SLV_63) ? LS_END - 4 : (IsSavegameVersionBefore(SLV_85) ? LS_END - 2: LS_END);
 	bool update_in_use = IsSavegameVersionBefore(SLV_GROUP_LIVERIES);
-	if (c != NULL) {
+	if (c != nullptr) {
 		for (i = 0; i < num_liveries; i++) {
 			SlObject(&c->livery[i], _company_livery_desc);
 			if (update_in_use && i != LS_DEFAULT) {
@@ -507,7 +507,7 @@ static void Check_PLYR()
 	int index;
 	while ((index = SlIterateArray()) != -1) {
 		CompanyProperties *cprops = new CompanyProperties();
-		SaveLoad_PLYR_common(NULL, cprops);
+		SaveLoad_PLYR_common(nullptr, cprops);
 
 		/* We do not load old custom names */
 		if (IsSavegameVersionBefore(SLV_84)) {
@@ -520,7 +520,7 @@ static void Check_PLYR()
 			}
 		}
 
-		if (cprops->name == NULL && !IsInsideMM(cprops->name_1, SPECSTR_COMPANY_NAME_START, SPECSTR_COMPANY_NAME_LAST + 1) &&
+		if (cprops->name == nullptr && !IsInsideMM(cprops->name_1, SPECSTR_COMPANY_NAME_START, SPECSTR_COMPANY_NAME_LAST + 1) &&
 				cprops->name_1 != STR_GAME_SAVELOAD_NOT_AVAILABLE && cprops->name_1 != STR_SV_UNNAMED &&
 				cprops->name_1 != SPECSTR_ANDCO_NAME && cprops->name_1 != SPECSTR_PRESIDENT_NAME &&
 				cprops->name_1 != SPECSTR_SILLY_NAME) {
diff --git a/src/saveload/depot_sl.cpp b/src/saveload/depot_sl.cpp
--- a/src/saveload/depot_sl.cpp
+++ b/src/saveload/depot_sl.cpp
@@ -64,5 +64,5 @@ static void Ptrs_DEPT()
 }
 
 extern const ChunkHandler _depot_chunk_handlers[] = {
-	{ 'DEPT', Save_DEPT, Load_DEPT, Ptrs_DEPT, NULL, CH_ARRAY | CH_LAST},
+	{ 'DEPT', Save_DEPT, Load_DEPT, Ptrs_DEPT, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/economy_sl.cpp b/src/saveload/economy_sl.cpp
--- a/src/saveload/economy_sl.cpp
+++ b/src/saveload/economy_sl.cpp
@@ -22,8 +22,8 @@ static void Load_PRIC()
 {
 	/* Old games store 49 base prices, very old games store them as int32 */
 	int vt = IsSavegameVersionBefore(SLV_65) ? SLE_FILE_I32 : SLE_FILE_I64;
-	SlArray(NULL, 49, vt | SLE_VAR_NULL);
-	SlArray(NULL, 49, SLE_FILE_U16 | SLE_VAR_NULL);
+	SlArray(nullptr, 49, vt | SLE_VAR_NULL);
+	SlArray(nullptr, 49, SLE_FILE_U16 | SLE_VAR_NULL);
 }
 
 /** Cargo payment rates in pre 126 savegames */
@@ -31,8 +31,8 @@ static void Load_CAPR()
 {
 	uint num_cargo = IsSavegameVersionBefore(SLV_55) ? 12 : IsSavegameVersionBefore(SLV_EXTEND_CARGOTYPES) ? 32 : NUM_CARGO;
 	int vt = IsSavegameVersionBefore(SLV_65) ? SLE_FILE_I32 : SLE_FILE_I64;
-	SlArray(NULL, num_cargo, vt | SLE_VAR_NULL);
-	SlArray(NULL, num_cargo, SLE_FILE_U16 | SLE_VAR_NULL);
+	SlArray(nullptr, num_cargo, vt | SLE_VAR_NULL);
+	SlArray(nullptr, num_cargo, SLE_FILE_U16 | SLE_VAR_NULL);
 }
 
 static const SaveLoad _economy_desc[] = {
@@ -101,8 +101,8 @@ static void Ptrs_CAPY()
 
 
 extern const ChunkHandler _economy_chunk_handlers[] = {
-	{ 'CAPY', Save_CAPY,     Load_CAPY,     Ptrs_CAPY, NULL, CH_ARRAY},
-	{ 'PRIC', NULL,          Load_PRIC,     NULL,      NULL, CH_RIFF | CH_AUTO_LENGTH},
-	{ 'CAPR', NULL,          Load_CAPR,     NULL,      NULL, CH_RIFF | CH_AUTO_LENGTH},
-	{ 'ECMY', Save_ECMY,     Load_ECMY,     NULL,      NULL, CH_RIFF | CH_LAST},
+	{ 'CAPY', Save_CAPY,     Load_CAPY,     Ptrs_CAPY, nullptr, CH_ARRAY},
+	{ 'PRIC', nullptr,          Load_PRIC,     nullptr,      nullptr, CH_RIFF | CH_AUTO_LENGTH},
+	{ 'CAPR', nullptr,          Load_CAPR,     nullptr,      nullptr, CH_RIFF | CH_AUTO_LENGTH},
+	{ 'ECMY', Save_ECMY,     Load_ECMY,     nullptr,      nullptr, CH_RIFF | CH_LAST},
 };
diff --git a/src/saveload/engine_sl.cpp b/src/saveload/engine_sl.cpp
--- a/src/saveload/engine_sl.cpp
+++ b/src/saveload/engine_sl.cpp
@@ -68,7 +68,7 @@ static Engine* CallocEngine()
  */
 static void FreeEngine(Engine *e)
 {
-	if (e != NULL) {
+	if (e != nullptr) {
 		e->~Engine();
 		free(e);
 	}
@@ -141,7 +141,7 @@ void CopyTempEngineData()
 		e->preview_wait        = se->preview_wait;
 		e->company_avail       = se->company_avail;
 		e->company_hidden      = se->company_hidden;
-		if (se->name != NULL) e->name = stredup(se->name);
+		if (se->name != nullptr) e->name = stredup(se->name);
 	}
 
 	/* Get rid of temporary data */
@@ -197,7 +197,7 @@ static void Load_EIDS()
 }
 
 extern const ChunkHandler _engine_chunk_handlers[] = {
-	{ 'EIDS', Save_EIDS, Load_EIDS, NULL, NULL, CH_ARRAY          },
-	{ 'ENGN', Save_ENGN, Load_ENGN, NULL, NULL, CH_ARRAY          },
-	{ 'ENGS', NULL,      Load_ENGS, NULL, NULL, CH_RIFF | CH_LAST },
+	{ 'EIDS', Save_EIDS, Load_EIDS, nullptr, nullptr, CH_ARRAY          },
+	{ 'ENGN', Save_ENGN, Load_ENGN, nullptr, nullptr, CH_ARRAY          },
+	{ 'ENGS', nullptr,      Load_ENGS, nullptr, nullptr, CH_RIFF | CH_LAST },
 };
diff --git a/src/saveload/game_sl.cpp b/src/saveload/game_sl.cpp
--- a/src/saveload/game_sl.cpp
+++ b/src/saveload/game_sl.cpp
@@ -52,19 +52,19 @@ static void SaveReal_GSDT(int *index_ptr
 	_game_saveload_settings[0] = '\0';
 	config->SettingsToString(_game_saveload_settings, lastof(_game_saveload_settings));
 
-	SlObject(NULL, _game_script);
+	SlObject(nullptr, _game_script);
 	Game::Save();
 }
 
 static void Load_GSDT()
 {
 	/* Free all current data */
-	GameConfig::GetConfig(GameConfig::SSS_FORCE_GAME)->Change(NULL);
+	GameConfig::GetConfig(GameConfig::SSS_FORCE_GAME)->Change(nullptr);
 
 	if ((CompanyID)SlIterateArray() == (CompanyID)-1) return;
 
 	_game_saveload_version = -1;
-	SlObject(NULL, _game_script);
+	SlObject(nullptr, _game_script);
 
 	if (_networking && !_network_server) {
 		GameInstance::LoadEmpty();
@@ -110,7 +110,7 @@ static void Load_GSDT()
 static void Save_GSDT()
 {
 	SlSetArrayIndex(0);
-	SlAutolength((AutolengthProc *)SaveReal_GSDT, NULL);
+	SlAutolength((AutolengthProc *)SaveReal_GSDT, nullptr);
 }
 
 extern GameStrings *_current_data;
@@ -134,10 +134,10 @@ static void SaveReal_GSTR(const Language
 	_game_saveload_string  = ls->language;
 	_game_saveload_strings = (uint)ls->lines.size();
 
-	SlObject(NULL, _game_language_header);
+	SlObject(nullptr, _game_language_header);
 	for (const auto &i : ls->lines) {
 		_game_saveload_string = i.c_str();
-		SlObject(NULL, _game_language_string);
+		SlObject(nullptr, _game_language_string);
 	}
 }
 
@@ -147,22 +147,22 @@ static void Load_GSTR()
 	_current_data = new GameStrings();
 
 	while (SlIterateArray() != -1) {
-		_game_saveload_string = NULL;
-		SlObject(NULL, _game_language_header);
+		_game_saveload_string = nullptr;
+		SlObject(nullptr, _game_language_header);
 
-		std::unique_ptr<LanguageStrings> ls(new LanguageStrings(_game_saveload_string != NULL ? _game_saveload_string : ""));
+		std::unique_ptr<LanguageStrings> ls(new LanguageStrings(_game_saveload_string != nullptr ? _game_saveload_string : ""));
 		for (uint i = 0; i < _game_saveload_strings; i++) {
-			SlObject(NULL, _game_language_string);
-			ls->lines.emplace_back(_game_saveload_string != NULL ? _game_saveload_string : "");
+			SlObject(nullptr, _game_language_string);
+			ls->lines.emplace_back(_game_saveload_string != nullptr ? _game_saveload_string : "");
 		}
 
 		_current_data->raw_strings.push_back(std::move(ls));
 	}
 
-	/* If there were no strings in the savegame, set GameStrings to NULL */
+	/* If there were no strings in the savegame, set GameStrings to nullptr */
 	if (_current_data->raw_strings.size() == 0) {
 		delete _current_data;
-		_current_data = NULL;
+		_current_data = nullptr;
 		return;
 	}
 
@@ -172,7 +172,7 @@ static void Load_GSTR()
 
 static void Save_GSTR()
 {
-	if (_current_data == NULL) return;
+	if (_current_data == nullptr) return;
 
 	for (uint i = 0; i < _current_data->raw_strings.size(); i++) {
 		SlSetArrayIndex(i);
@@ -181,6 +181,6 @@ static void Save_GSTR()
 }
 
 extern const ChunkHandler _game_chunk_handlers[] = {
-	{ 'GSTR', Save_GSTR, Load_GSTR, NULL, NULL, CH_ARRAY },
-	{ 'GSDT', Save_GSDT, Load_GSDT, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'GSTR', Save_GSTR, Load_GSTR, nullptr, nullptr, CH_ARRAY },
+	{ 'GSDT', Save_GSDT, Load_GSDT, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/gamelog_sl.cpp b/src/saveload/gamelog_sl.cpp
--- a/src/saveload/gamelog_sl.cpp
+++ b/src/saveload/gamelog_sl.cpp
@@ -106,7 +106,7 @@ assert_compile(lengthof(_glog_desc) == G
 
 static void Load_GLOG_common(LoggedAction *&gamelog_action, uint &gamelog_actions)
 {
-	assert(gamelog_action == NULL);
+	assert(gamelog_action == nullptr);
 	assert(gamelog_actions == 0);
 
 	GamelogActionType at;
@@ -117,7 +117,7 @@ static void Load_GLOG_common(LoggedActio
 		la->at = at;
 
 		SlObject(la, _glog_action_desc); // has to be saved after 'DATE'!
-		la->change = NULL;
+		la->change = nullptr;
 		la->changes = 0;
 
 		GamelogChangeType ct;
@@ -125,7 +125,7 @@ static void Load_GLOG_common(LoggedActio
 			la->change = ReallocT(la->change, la->changes + 1);
 
 			LoggedChange *lc = &la->change[la->changes++];
-			/* for SLE_STR, pointer has to be valid! so make it NULL */
+			/* for SLE_STR, pointer has to be valid! so make it nullptr */
 			memset(lc, 0, sizeof(*lc));
 			lc->ct = ct;
 
@@ -179,5 +179,5 @@ static void Check_GLOG()
 }
 
 extern const ChunkHandler _gamelog_chunk_handlers[] = {
-	{ 'GLOG', Save_GLOG, Load_GLOG, NULL, Check_GLOG, CH_RIFF | CH_LAST }
+	{ 'GLOG', Save_GLOG, Load_GLOG, nullptr, Check_GLOG, CH_RIFF | CH_LAST }
 };
diff --git a/src/saveload/goal_sl.cpp b/src/saveload/goal_sl.cpp
--- a/src/saveload/goal_sl.cpp
+++ b/src/saveload/goal_sl.cpp
@@ -45,5 +45,5 @@ static void Load_GOAL()
 }
 
 extern const ChunkHandler _goal_chunk_handlers[] = {
-	{ 'GOAL', Save_GOAL, Load_GOAL, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'GOAL', Save_GOAL, Load_GOAL, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/group_sl.cpp b/src/saveload/group_sl.cpp
--- a/src/saveload/group_sl.cpp
+++ b/src/saveload/group_sl.cpp
@@ -61,5 +61,5 @@ static void Load_GRPS()
 }
 
 extern const ChunkHandler _group_chunk_handlers[] = {
-	{ 'GRPS', Save_GRPS, Load_GRPS, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'GRPS', Save_GRPS, Load_GRPS, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/industry_sl.cpp b/src/saveload/industry_sl.cpp
--- a/src/saveload/industry_sl.cpp
+++ b/src/saveload/industry_sl.cpp
@@ -183,9 +183,9 @@ static void Load_ITBL()
 }
 
 extern const ChunkHandler _industry_chunk_handlers[] = {
-	{ 'INDY', Save_INDY,     Load_INDY,     Ptrs_INDY, NULL, CH_ARRAY},
-	{ 'IIDS', Save_IIDS,     Load_IIDS,     NULL,      NULL, CH_ARRAY},
-	{ 'TIDS', Save_TIDS,     Load_TIDS,     NULL,      NULL, CH_ARRAY},
-	{ 'IBLD', LoadSave_IBLD, LoadSave_IBLD, NULL,      NULL, CH_RIFF},
-	{ 'ITBL', Save_ITBL,     Load_ITBL,     NULL,      NULL, CH_ARRAY | CH_LAST},
+	{ 'INDY', Save_INDY,     Load_INDY,     Ptrs_INDY, nullptr, CH_ARRAY},
+	{ 'IIDS', Save_IIDS,     Load_IIDS,     nullptr,      nullptr, CH_ARRAY},
+	{ 'TIDS', Save_TIDS,     Load_TIDS,     nullptr,      nullptr, CH_ARRAY},
+	{ 'IBLD', LoadSave_IBLD, LoadSave_IBLD, nullptr,      nullptr, CH_RIFF},
+	{ 'ITBL', Save_ITBL,     Load_ITBL,     nullptr,      nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/labelmaps_sl.cpp b/src/saveload/labelmaps_sl.cpp
--- a/src/saveload/labelmaps_sl.cpp
+++ b/src/saveload/labelmaps_sl.cpp
@@ -119,6 +119,6 @@ static void Load_RAIL()
 }
 
 extern const ChunkHandler _labelmaps_chunk_handlers[] = {
-	{ 'RAIL', Save_RAIL, Load_RAIL, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'RAIL', Save_RAIL, Load_RAIL, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
 
diff --git a/src/saveload/linkgraph_sl.cpp b/src/saveload/linkgraph_sl.cpp
--- a/src/saveload/linkgraph_sl.cpp
+++ b/src/saveload/linkgraph_sl.cpp
@@ -64,7 +64,7 @@ const SaveLoad *GetLinkGraphJobDesc()
 		int setting = 0;
 		const SettingDesc *desc = GetSettingDescription(setting);
 		while (desc->save.cmd != SL_END) {
-			if (desc->desc.name != NULL && strncmp(desc->desc.name, prefix, prefixlen) == 0) {
+			if (desc->desc.name != nullptr && strncmp(desc->desc.name, prefix, prefixlen) == 0) {
 				SaveLoad sl = desc->save;
 				char *&address = reinterpret_cast<char *&>(sl.address);
 				address -= offset_gamesettings;
@@ -290,7 +290,7 @@ static void Ptrs_LGRS()
 }
 
 extern const ChunkHandler _linkgraph_chunk_handlers[] = {
-	{ 'LGRP', Save_LGRP, Load_LGRP, NULL,      NULL, CH_ARRAY },
-	{ 'LGRJ', Save_LGRJ, Load_LGRJ, NULL,      NULL, CH_ARRAY },
-	{ 'LGRS', Save_LGRS, Load_LGRS, Ptrs_LGRS, NULL, CH_LAST  }
+	{ 'LGRP', Save_LGRP, Load_LGRP, nullptr,      nullptr, CH_ARRAY },
+	{ 'LGRJ', Save_LGRJ, Load_LGRJ, nullptr,      nullptr, CH_ARRAY },
+	{ 'LGRS', Save_LGRS, Load_LGRS, Ptrs_LGRS, nullptr, CH_LAST  }
 };
diff --git a/src/saveload/map_sl.cpp b/src/saveload/map_sl.cpp
--- a/src/saveload/map_sl.cpp
+++ b/src/saveload/map_sl.cpp
@@ -297,15 +297,15 @@ static void Save_MAP8()
 
 
 extern const ChunkHandler _map_chunk_handlers[] = {
-	{ 'MAPS', Save_MAPS, Load_MAPS, NULL, Check_MAPS, CH_RIFF },
-	{ 'MAPT', Save_MAPT, Load_MAPT, NULL, NULL,       CH_RIFF },
-	{ 'MAPH', Save_MAPH, Load_MAPH, NULL, NULL,       CH_RIFF },
-	{ 'MAPO', Save_MAP1, Load_MAP1, NULL, NULL,       CH_RIFF },
-	{ 'MAP2', Save_MAP2, Load_MAP2, NULL, NULL,       CH_RIFF },
-	{ 'M3LO', Save_MAP3, Load_MAP3, NULL, NULL,       CH_RIFF },
-	{ 'M3HI', Save_MAP4, Load_MAP4, NULL, NULL,       CH_RIFF },
-	{ 'MAP5', Save_MAP5, Load_MAP5, NULL, NULL,       CH_RIFF },
-	{ 'MAPE', Save_MAP6, Load_MAP6, NULL, NULL,       CH_RIFF },
-	{ 'MAP7', Save_MAP7, Load_MAP7, NULL, NULL,       CH_RIFF },
-	{ 'MAP8', Save_MAP8, Load_MAP8, NULL, NULL,       CH_RIFF | CH_LAST },
+	{ 'MAPS', Save_MAPS, Load_MAPS, nullptr, Check_MAPS, CH_RIFF },
+	{ 'MAPT', Save_MAPT, Load_MAPT, nullptr, nullptr,       CH_RIFF },
+	{ 'MAPH', Save_MAPH, Load_MAPH, nullptr, nullptr,       CH_RIFF },
+	{ 'MAPO', Save_MAP1, Load_MAP1, nullptr, nullptr,       CH_RIFF },
+	{ 'MAP2', Save_MAP2, Load_MAP2, nullptr, nullptr,       CH_RIFF },
+	{ 'M3LO', Save_MAP3, Load_MAP3, nullptr, nullptr,       CH_RIFF },
+	{ 'M3HI', Save_MAP4, Load_MAP4, nullptr, nullptr,       CH_RIFF },
+	{ 'MAP5', Save_MAP5, Load_MAP5, nullptr, nullptr,       CH_RIFF },
+	{ 'MAPE', Save_MAP6, Load_MAP6, nullptr, nullptr,       CH_RIFF },
+	{ 'MAP7', Save_MAP7, Load_MAP7, nullptr, nullptr,       CH_RIFF },
+	{ 'MAP8', Save_MAP8, Load_MAP8, nullptr, nullptr,       CH_RIFF | CH_LAST },
 };
diff --git a/src/saveload/misc_sl.cpp b/src/saveload/misc_sl.cpp
--- a/src/saveload/misc_sl.cpp
+++ b/src/saveload/misc_sl.cpp
@@ -36,7 +36,7 @@ void SaveViewportBeforeSaveGame()
 {
 	const Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
 
-	if (w != NULL) {
+	if (w != nullptr) {
 		_saved_scrollpos_x = w->viewport->scrollpos_x;
 		_saved_scrollpos_y = w->viewport->scrollpos_y;
 		_saved_scrollpos_zoom = w->viewport->zoom;
@@ -151,6 +151,6 @@ static void SaveLoad_VIEW()
 }
 
 extern const ChunkHandler _misc_chunk_handlers[] = {
-	{ 'DATE', SaveLoad_DATE, SaveLoad_DATE, NULL, Check_DATE, CH_RIFF},
-	{ 'VIEW', SaveLoad_VIEW, SaveLoad_VIEW, NULL, NULL,       CH_RIFF | CH_LAST},
+	{ 'DATE', SaveLoad_DATE, SaveLoad_DATE, nullptr, Check_DATE, CH_RIFF},
+	{ 'VIEW', SaveLoad_VIEW, SaveLoad_VIEW, nullptr, nullptr,       CH_RIFF | CH_LAST},
 };
diff --git a/src/saveload/newgrf_sl.cpp b/src/saveload/newgrf_sl.cpp
--- a/src/saveload/newgrf_sl.cpp
+++ b/src/saveload/newgrf_sl.cpp
@@ -73,7 +73,7 @@ static void Save_NGRF()
 {
 	int index = 0;
 
-	for (GRFConfig *c = _grfconfig; c != NULL; c = c->next) {
+	for (GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
 		if (HasBit(c->flags, GCF_STATIC)) continue;
 		SlSetArrayIndex(index++);
 		SlObject(c, _grfconfig_desc);
@@ -98,7 +98,7 @@ static void Load_NGRF()
 
 	if (_game_mode == GM_MENU) {
 		/* Intro game must not have NewGRF. */
-		if (_grfconfig != NULL) SlErrorCorrupt("The intro game must not use NewGRF");
+		if (_grfconfig != nullptr) SlErrorCorrupt("The intro game must not use NewGRF");
 
 		/* Activate intro NewGRFs (townnames) */
 		ResetGRFConfig(false);
@@ -114,5 +114,5 @@ static void Check_NGRF()
 }
 
 extern const ChunkHandler _newgrf_chunk_handlers[] = {
-	{ 'NGRF', Save_NGRF, Load_NGRF, NULL, Check_NGRF, CH_ARRAY | CH_LAST }
+	{ 'NGRF', Save_NGRF, Load_NGRF, nullptr, Check_NGRF, CH_ARRAY | CH_LAST }
 };
diff --git a/src/saveload/object_sl.cpp b/src/saveload/object_sl.cpp
--- a/src/saveload/object_sl.cpp
+++ b/src/saveload/object_sl.cpp
@@ -74,6 +74,6 @@ static void Load_OBID()
 }
 
 extern const ChunkHandler _object_chunk_handlers[] = {
-	{ 'OBID', Save_OBID, Load_OBID, NULL,      NULL, CH_ARRAY },
-	{ 'OBJS', Save_OBJS, Load_OBJS, Ptrs_OBJS, NULL, CH_ARRAY | CH_LAST},
+	{ 'OBID', Save_OBID, Load_OBID, nullptr,      nullptr, CH_ARRAY },
+	{ 'OBJS', Save_OBJS, Load_OBJS, Ptrs_OBJS, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/oldloader.cpp b/src/saveload/oldloader.cpp
--- a/src/saveload/oldloader.cpp
+++ b/src/saveload/oldloader.cpp
@@ -154,11 +154,11 @@ bool LoadChunk(LoadgameState *ls, void *
 					default: NOT_REACHED();
 				}
 
-				/* When both pointers are NULL, we are just skipping data */
-				if (base_ptr == NULL && chunk->ptr == NULL) continue;
+				/* When both pointers are nullptr, we are just skipping data */
+				if (base_ptr == nullptr && chunk->ptr == nullptr) continue;
 
 				/* Writing to the var: bits 8 to 15 have the VAR type */
-				if (chunk->ptr == NULL) ptr = base_ptr + chunk->offset;
+				if (chunk->ptr == nullptr) ptr = base_ptr + chunk->offset;
 
 				/* Write the data */
 				switch (GetOldChunkVarType(chunk->type)) {
@@ -174,7 +174,7 @@ bool LoadChunk(LoadgameState *ls, void *
 				}
 
 				/* Increase pointer base for arrays when looping */
-				if (chunk->amount > 1 && chunk->ptr != NULL) ptr += CalcOldVarLen(chunk->type);
+				if (chunk->amount > 1 && chunk->ptr != nullptr) ptr += CalcOldVarLen(chunk->type);
 			}
 		}
 	}
@@ -259,7 +259,7 @@ static SavegameType DetermineOldSavegame
 		}
 	}
 
-	if (title != NULL) {
+	if (title != nullptr) {
 		switch (type) {
 			case SGT_TTO: title = strecpy(title, "(TTO) ", last);    break;
 			case SGT_TTD: title = strecpy(title, "(TTD) ", last);    break;
@@ -284,14 +284,14 @@ bool LoadOldSaveGame(const char *file)
 	/* Open file */
 	ls.file = FioFOpenFile(file, "rb", NO_DIRECTORY);
 
-	if (ls.file == NULL) {
+	if (ls.file == nullptr) {
 		DEBUG(oldloader, 0, "Cannot open file '%s'", file);
 		return false;
 	}
 
-	SavegameType type = DetermineOldSavegameType(ls.file, NULL, NULL);
+	SavegameType type = DetermineOldSavegameType(ls.file, nullptr, nullptr);
 
-	LoadOldMainProc *proc = NULL;
+	LoadOldMainProc *proc = nullptr;
 
 	switch (type) {
 		case SGT_TTO: proc = &LoadTTOMain; break;
@@ -303,7 +303,7 @@ bool LoadOldSaveGame(const char *file)
 
 	bool game_loaded;
 	try {
-		game_loaded = proc != NULL && proc(&ls);
+		game_loaded = proc != nullptr && proc(&ls);
 	} catch (...) {
 		game_loaded = false;
 	}
@@ -323,7 +323,7 @@ void GetOldSaveGameName(const char *file
 {
 	FILE *f = FioFOpenFile(file, "rb", NO_DIRECTORY);
 
-	if (f == NULL) {
+	if (f == nullptr) {
 		*title = '\0';
 		return;
 	}
diff --git a/src/saveload/oldloader.h b/src/saveload/oldloader.h
--- a/src/saveload/oldloader.h
+++ b/src/saveload/oldloader.h
@@ -90,7 +90,7 @@ struct OldChunks {
 	uint32 amount;       ///< Amount of fields
 
 	void *ptr;           ///< Pointer where to save the data (may only be set if offset is 0)
-	uint offset;         ///< Offset from basepointer (may only be set if ptr is NULL)
+	uint offset;         ///< Offset from basepointer (may only be set if ptr is nullptr)
 	OldChunkProc *proc;  ///< Pointer to function that is called with OC_CHUNK
 };
 
@@ -125,12 +125,12 @@ static inline uint32 ReadUint32(Loadgame
  *  - OCL_CHUNK: load another proc to load a part of the savegame, 'amount' times
  *  - OCL_ASSERT: to check if we are really at the place we expect to be.. because old savegames are too binary to be sure ;)
  */
-#define OCL_SVAR(type, base, offset)         { type,                 1,    NULL, (uint)cpp_offsetof(base, offset), NULL }
-#define OCL_VAR(type, amount, pointer)       { type,            amount, pointer,    0,                             NULL }
-#define OCL_END()                            { OC_END,               0,    NULL,    0,                             NULL }
-#define OCL_CNULL(type, amount)              { OC_NULL | type,  amount,    NULL,    0,                             NULL }
-#define OCL_CCHUNK(type, amount, proc)       { OC_CHUNK | type, amount,    NULL,    0,                             proc }
-#define OCL_ASSERT(type, size)               { OC_ASSERT | type,     1,    NULL, size,                             NULL }
+#define OCL_SVAR(type, base, offset)         { type,                 1,    nullptr, (uint)cpp_offsetof(base, offset), nullptr }
+#define OCL_VAR(type, amount, pointer)       { type,            amount, pointer,    0,                             nullptr }
+#define OCL_END()                            { OC_END,               0,    nullptr,    0,                             nullptr }
+#define OCL_CNULL(type, amount)              { OC_NULL | type,  amount,    nullptr,    0,                             nullptr }
+#define OCL_CCHUNK(type, amount, proc)       { OC_CHUNK | type, amount,    nullptr,    0,                             proc }
+#define OCL_ASSERT(type, size)               { OC_ASSERT | type,     1,    nullptr, size,                             nullptr }
 #define OCL_NULL(amount)        OCL_CNULL((OldChunkType)0, amount)
 #define OCL_CHUNK(amount, proc) OCL_CCHUNK((OldChunkType)0, amount, proc)
 
diff --git a/src/saveload/oldloader_sl.cpp b/src/saveload/oldloader_sl.cpp
--- a/src/saveload/oldloader_sl.cpp
+++ b/src/saveload/oldloader_sl.cpp
@@ -178,7 +178,7 @@ void FixOldVehicles()
 
 	FOR_ALL_VEHICLES(v) {
 		if ((size_t)v->next == 0xFFFF) {
-			v->next = NULL;
+			v->next = nullptr;
 		} else {
 			v->next = Vehicle::GetIfValid((size_t)v->next);
 		}
@@ -452,7 +452,7 @@ static bool FixTTOEngines()
 		e->preview_company = INVALID_COMPANY;
 		e->preview_asked = (CompanyMask)-1;
 		e->preview_wait = 0;
-		e->name = NULL;
+		e->name = nullptr;
 	}
 
 	return true;
@@ -621,7 +621,7 @@ static const OldChunks order_chunk[] = {
 
 static bool LoadOldOrder(LoadgameState *ls, int num)
 {
-	if (!LoadChunk(ls, NULL, order_chunk)) return false;
+	if (!LoadChunk(ls, nullptr, order_chunk)) return false;
 
 	Order *o = new (num) Order();
 	o->AssignOrder(UnpackOldOrder(_old_order));
@@ -632,7 +632,7 @@ static bool LoadOldOrder(LoadgameState *
 		/* Relink the orders to each other (in the orders for one vehicle are behind each other,
 		 * with an invalid order (OT_NOTHING) as indication that it is the last order */
 		Order *prev = Order::GetIfValid(num - 1);
-		if (prev != NULL) prev->next = o;
+		if (prev != nullptr) prev->next = o;
 	}
 
 	return true;
@@ -646,7 +646,7 @@ static bool LoadOldAnimTileList(Loadgame
 		OCL_END ()
 	};
 
-	if (!LoadChunk(ls, NULL, anim_chunk)) return false;
+	if (!LoadChunk(ls, nullptr, anim_chunk)) return false;
 
 	/* The first zero in the loaded array indicates the end of the list. */
 	for (int i = 0; i < 256; i++) {
@@ -671,7 +671,7 @@ static bool LoadOldDepot(LoadgameState *
 	if (d->xy != 0) {
 		/* In some cases, there could be depots referencing invalid town. */
 		Town *t = Town::GetIfValid(RemapTownIndex(_old_town_index));
-		if (t == NULL) t = Town::GetRandom();
+		if (t == nullptr) t = Town::GetRandom();
 		d->town = t;
 	} else {
 		delete d;
@@ -876,7 +876,7 @@ static bool LoadOldCompanyYearly(Loadgam
 		if (_savegame_type == SGT_TTO && i == 6) {
 			_old_yearly = 0; // property maintenance
 		} else {
-			if (!LoadChunk(ls, NULL, _company_yearly_chunk)) return false;
+			if (!LoadChunk(ls, nullptr, _company_yearly_chunk)) return false;
 		}
 
 		c->yearly_expenses[num][i] = _old_yearly;
@@ -1106,8 +1106,8 @@ static bool LoadOldVehicleUnion(Loadgame
 	uint temp = ls->total_read;
 	bool res;
 
-	if (v == NULL) {
-		res = LoadChunk(ls, NULL, vehicle_empty_chunk);
+	if (v == nullptr) {
+		res = LoadChunk(ls, nullptr, vehicle_empty_chunk);
 	} else {
 		switch (v->type) {
 			default: SlErrorCorrupt("Invalid vehicle type");
@@ -1240,7 +1240,7 @@ bool LoadOldVehicle(LoadgameState *ls, i
 			uint type = ReadByte(ls);
 			switch (type) {
 				default: return false;
-				case 0x00 /* VEH_INVALID  */: v = NULL;                                        break;
+				case 0x00 /* VEH_INVALID  */: v = nullptr;                                        break;
 				case 0x25 /* MONORAIL     */:
 				case 0x20 /* VEH_TRAIN    */: v = new (_current_vehicle_id) Train();           break;
 				case 0x21 /* VEH_ROAD     */: v = new (_current_vehicle_id) RoadVehicle();     break;
@@ -1251,7 +1251,7 @@ bool LoadOldVehicle(LoadgameState *ls, i
 			}
 
 			if (!LoadChunk(ls, v, vehicle_chunk)) return false;
-			if (v == NULL) continue;
+			if (v == nullptr) continue;
 			v->refit_cap = v->cargo_cap;
 
 			SpriteID sprite = v->sprite_seq.seq[0].sprite;
@@ -1318,7 +1318,7 @@ bool LoadOldVehicle(LoadgameState *ls, i
 			/* Read the vehicle type and allocate the right vehicle */
 			switch (ReadByte(ls)) {
 				default: SlErrorCorrupt("Invalid vehicle type");
-				case 0x00 /* VEH_INVALID */: v = NULL;                                        break;
+				case 0x00 /* VEH_INVALID */: v = nullptr;                                        break;
 				case 0x10 /* VEH_TRAIN   */: v = new (_current_vehicle_id) Train();           break;
 				case 0x11 /* VEH_ROAD    */: v = new (_current_vehicle_id) RoadVehicle();     break;
 				case 0x12 /* VEH_SHIP    */: v = new (_current_vehicle_id) Ship();            break;
@@ -1328,7 +1328,7 @@ bool LoadOldVehicle(LoadgameState *ls, i
 			}
 
 			if (!LoadChunk(ls, v, vehicle_chunk)) return false;
-			if (v == NULL) continue;
+			if (v == nullptr) continue;
 
 			_old_vehicle_names[_current_vehicle_id] = RemapOldStringID(_old_string_id);
 
@@ -1756,9 +1756,9 @@ bool LoadTTDMain(LoadgameState *ls)
 	/* Load the biggest chunk */
 	SmallStackSafeStackAlloc<byte, OLD_MAP_SIZE * 2> map3;
 	_old_map3 = map3.data;
-	_old_vehicle_names = NULL;
+	_old_vehicle_names = nullptr;
 	try {
-		if (!LoadChunk(ls, NULL, main_chunk)) {
+		if (!LoadChunk(ls, nullptr, main_chunk)) {
 			DEBUG(oldloader, 0, "Loading failed");
 			free(_old_vehicle_names);
 			return false;
@@ -1803,7 +1803,7 @@ bool LoadTTOMain(LoadgameState *ls)
 	_old_vehicle_names = vehnames.data;
 
 	/* Load the biggest chunk */
-	if (!LoadChunk(ls, NULL, main_chunk)) {
+	if (!LoadChunk(ls, nullptr, main_chunk)) {
 		DEBUG(oldloader, 0, "Loading failed");
 		return false;
 	}
diff --git a/src/saveload/order_sl.cpp b/src/saveload/order_sl.cpp
--- a/src/saveload/order_sl.cpp
+++ b/src/saveload/order_sl.cpp
@@ -178,7 +178,7 @@ static void Load_ORDR()
 			/* The orders were built like this:
 			 * While the order is valid, set the previous will get its next pointer set */
 			Order *prev = Order::GetIfValid(order_index - 1);
-			if (prev != NULL) prev->next = o;
+			if (prev != nullptr) prev->next = o;
 		}
 	} else {
 		int index;
@@ -306,7 +306,7 @@ static void Ptrs_BKOR()
 }
 
 extern const ChunkHandler _order_chunk_handlers[] = {
-	{ 'BKOR', Save_BKOR, Load_BKOR, Ptrs_BKOR, NULL, CH_ARRAY},
-	{ 'ORDR', Save_ORDR, Load_ORDR, Ptrs_ORDR, NULL, CH_ARRAY},
-	{ 'ORDL', Save_ORDL, Load_ORDL, Ptrs_ORDL, NULL, CH_ARRAY | CH_LAST},
+	{ 'BKOR', Save_BKOR, Load_BKOR, Ptrs_BKOR, nullptr, CH_ARRAY},
+	{ 'ORDR', Save_ORDR, Load_ORDR, Ptrs_ORDR, nullptr, CH_ARRAY},
+	{ 'ORDL', Save_ORDL, Load_ORDL, Ptrs_ORDL, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/saveload.cpp b/src/saveload/saveload.cpp
--- a/src/saveload/saveload.cpp
+++ b/src/saveload/saveload.cpp
@@ -95,7 +95,7 @@ struct ReadBuffer {
 	 * Initialise our variables.
 	 * @param reader The filter to actually read data.
 	 */
-	ReadBuffer(LoadFilter *reader) : bufp(NULL), bufe(NULL), reader(reader), read(0)
+	ReadBuffer(LoadFilter *reader) : bufp(nullptr), bufe(nullptr), reader(reader), read(0)
 	{
 	}
 
@@ -131,7 +131,7 @@ struct MemoryDumper {
 	byte *bufe;                 ///< End of the buffer we write to.
 
 	/** Initialise our variables. */
-	MemoryDumper() : buf(NULL), bufe(NULL)
+	MemoryDumper() : buf(nullptr), bufe(nullptr)
 	{
 	}
 
@@ -247,7 +247,7 @@ extern const ChunkHandler _airport_chunk
 extern const ChunkHandler _object_chunk_handlers[];
 extern const ChunkHandler _persistent_storage_chunk_handlers[];
 
-/** Array of all chunks in a savegame, \c NULL terminated. */
+/** Array of all chunks in a savegame, \c nullptr terminated. */
 static const ChunkHandler * const _chunk_handlers[] = {
 	_gamelog_chunk_handlers,
 	_map_chunk_handlers,
@@ -282,7 +282,7 @@ static const ChunkHandler * const _chunk
 	_airport_chunk_handlers,
 	_object_chunk_handlers,
 	_persistent_storage_chunk_handlers,
-	NULL,
+	nullptr,
 };
 
 /**
@@ -290,10 +290,10 @@ static const ChunkHandler * const _chunk
  * @param ch the chunk handler iterator
  */
 #define FOR_ALL_CHUNK_HANDLERS(ch) \
-	for (const ChunkHandler * const *chsc = _chunk_handlers; *chsc != NULL; chsc++) \
-		for (const ChunkHandler *ch = *chsc; ch != NULL; ch = (ch->flags & CH_LAST) ? NULL : ch + 1)
-
-/** Null all pointers (convert index -> NULL) */
+	for (const ChunkHandler * const *chsc = _chunk_handlers; *chsc != nullptr; chsc++) \
+		for (const ChunkHandler *ch = *chsc; ch != nullptr; ch = (ch->flags & CH_LAST) ? nullptr : ch + 1)
+
+/** Null all pointers (convert index -> nullptr) */
 static void SlNullPointers()
 {
 	_sl.action = SLA_NULL;
@@ -306,7 +306,7 @@ static void SlNullPointers()
 	DEBUG(sl, 1, "Nulling pointers");
 
 	FOR_ALL_CHUNK_HANDLERS(ch) {
-		if (ch->ptrs_proc != NULL) {
+		if (ch->ptrs_proc != nullptr) {
 			DEBUG(sl, 2, "Nulling pointers for %c%c%c%c", ch->id >> 24, ch->id >> 16, ch->id >> 8, ch->id);
 			ch->ptrs_proc();
 		}
@@ -331,14 +331,14 @@ void NORETURN SlError(StringID string, c
 	if (_sl.action == SLA_LOAD_CHECK) {
 		_load_check_data.error = string;
 		free(_load_check_data.error_data);
-		_load_check_data.error_data = (extra_msg == NULL) ? NULL : stredup(extra_msg);
+		_load_check_data.error_data = (extra_msg == nullptr) ? nullptr : stredup(extra_msg);
 	} else {
 		_sl.error_str = string;
 		free(_sl.extra_msg);
-		_sl.extra_msg = (extra_msg == NULL) ? NULL : stredup(extra_msg);
+		_sl.extra_msg = (extra_msg == nullptr) ? nullptr : stredup(extra_msg);
 	}
 
-	/* We have to NULL all pointers here; we might be in a state where
+	/* We have to nullptr all pointers here; we might be in a state where
 	 * the pointers are actually filled with indices, which means that
 	 * when we access them during cleaning the pool dereferences of
 	 * those indices will be made with segmentation faults as result. */
@@ -389,7 +389,7 @@ static std::thread _save_thread;        
 static void SetAsyncSaveFinish(AsyncSaveFinishProc proc)
 {
 	if (_exit_game) return;
-	while (_async_save_finish.load(std::memory_order_acquire) != NULL) CSleep(10);
+	while (_async_save_finish.load(std::memory_order_acquire) != nullptr) CSleep(10);
 
 	_async_save_finish.store(proc, std::memory_order_release);
 }
@@ -399,8 +399,8 @@ static void SetAsyncSaveFinish(AsyncSave
  */
 void ProcessAsyncSaveFinish()
 {
-	AsyncSaveFinishProc proc = _async_save_finish.exchange(NULL, std::memory_order_acq_rel);
-	if (proc == NULL) return;
+	AsyncSaveFinishProc proc = _async_save_finish.exchange(nullptr, std::memory_order_acq_rel);
+	if (proc == nullptr) return;
 
 	proc();
 
@@ -863,7 +863,7 @@ static void SlSaveLoadConv(void *ptr, Va
  */
 static inline size_t SlCalcNetStringLen(const char *ptr, size_t length)
 {
-	if (ptr == NULL) return 0;
+	if (ptr == nullptr) return 0;
 	return min(strlen(ptr), length - 1);
 }
 
@@ -948,7 +948,7 @@ static void SlString(void *ptr, size_t l
 				case SLE_VAR_STRQ: // Malloc'd string, free previous incarnation, and allocate
 					free(*(char **)ptr);
 					if (len == 0) {
-						*(char **)ptr = NULL;
+						*(char **)ptr = nullptr;
 						return;
 					} else {
 						*(char **)ptr = MallocT<char>(len + 1); // terminating '\0'
@@ -1043,7 +1043,7 @@ void SlArray(void *array, size_t length,
  * Pointers cannot be saved to a savegame, so this functions gets
  * the index of the item, and if not available, it hussles with
  * pointers (looks really bad :()
- * Remember that a NULL item has value 0, and all
+ * Remember that a nullptr item has value 0, and all
  * indices have +1, so vehicle 0 is saved as index 1.
  * @param obj The object that we want to get the index of
  * @param rt SLRefType type of the object the index is being sought of
@@ -1053,7 +1053,7 @@ static size_t ReferenceToInt(const void 
 {
 	assert(_sl.action == SLA_SAVE);
 
-	if (obj == NULL) return 0;
+	if (obj == nullptr) return 0;
 
 	switch (rt) {
 		case REF_VEHICLE_OLD: // Old vehicles we save as new ones
@@ -1076,7 +1076,7 @@ static size_t ReferenceToInt(const void 
  * Pointers cannot be loaded from a savegame, so this function
  * gets the index from the savegame and returns the appropriate
  * pointer from the already loaded base.
- * Remember that an index of 0 is a NULL pointer so all indices
+ * Remember that an index of 0 is a nullptr pointer so all indices
  * are +1 so vehicle 0 is saved as 1.
  * @param index The index that is being converted to a pointer
  * @param rt SLRefType type of the object the pointer is sought of
@@ -1094,8 +1094,8 @@ static void *IntToReference(size_t index
 		rt = REF_VEHICLE;
 	}
 
-	/* No need to look up NULL pointers, just return immediately */
-	if (index == (rt == REF_VEHICLE_OLD ? 0xFFFF : 0)) return NULL;
+	/* No need to look up nullptr pointers, just return immediately */
+	if (index == (rt == REF_VEHICLE_OLD ? 0xFFFF : 0)) return nullptr;
 
 	/* Correct index. Old vehicles were saved differently:
 	 * invalid vehicle was 0xFFFF, now we use 0x0000 for everything invalid. */
@@ -1109,7 +1109,7 @@ static void *IntToReference(size_t index
 		case REF_ORDER:
 			if (Order::IsValidID(index)) return Order::Get(index);
 			/* in old versions, invalid order was used to mark end of order list */
-			if (IsSavegameVersionBefore(SLV_5, 2)) return NULL;
+			if (IsSavegameVersionBefore(SLV_5, 2)) return nullptr;
 			SlErrorCorrupt("Referencing invalid Order");
 
 		case REF_VEHICLE_OLD:
@@ -1499,7 +1499,7 @@ bool SlObjectMember(void *ptr, const Sav
 							*(void **)ptr = IntToReference(*(size_t *)ptr, (SLRefType)conv);
 							break;
 						case SLA_NULL:
-							*(void **)ptr = NULL;
+							*(void **)ptr = nullptr;
 							break;
 						default: NOT_REACHED();
 					}
@@ -1565,7 +1565,7 @@ void SlObject(void *object, const SaveLo
  */
 void SlGlobList(const SaveLoadGlobVarList *sldg)
 {
-	SlObject(NULL, (const SaveLoad*)sldg);
+	SlObject(nullptr, (const SaveLoad*)sldg);
 }
 
 /**
@@ -1637,7 +1637,7 @@ static void SlLoadChunk(const ChunkHandl
 
 /**
  * Load a chunk of data for checking savegames.
- * If the chunkhandler is NULL, the chunk is skipped.
+ * If the chunkhandler is nullptr, the chunk is skipped.
  * @param ch The chunkhandler that will be used for the operation
  */
 static void SlLoadCheckChunk(const ChunkHandler *ch)
@@ -1708,7 +1708,7 @@ static inline void SlStubSaveProc2(void 
  */
 static void SlStubSaveProc()
 {
-	SlAutolength(SlStubSaveProc2, NULL);
+	SlAutolength(SlStubSaveProc2, nullptr);
 }
 
 /**
@@ -1721,7 +1721,7 @@ static void SlSaveChunk(const ChunkHandl
 	ChunkSaveLoadProc *proc = ch->save_proc;
 
 	/* Don't save any chunk information if there is no save handler. */
-	if (proc == NULL) return;
+	if (proc == nullptr) return;
 
 	SlWriteUint32(ch->id);
 	DEBUG(sl, 2, "Saving chunk %c%c%c%c", ch->id >> 24, ch->id >> 16, ch->id >> 8, ch->id);
@@ -1773,7 +1773,7 @@ static void SlSaveChunks()
 static const ChunkHandler *SlFindChunkHandler(uint32 id)
 {
 	FOR_ALL_CHUNK_HANDLERS(ch) if (ch->id == id) return ch;
-	return NULL;
+	return nullptr;
 }
 
 /** Load all chunks */
@@ -1786,7 +1786,7 @@ static void SlLoadChunks()
 		DEBUG(sl, 2, "Loading chunk %c%c%c%c", id >> 24, id >> 16, id >> 8, id);
 
 		ch = SlFindChunkHandler(id);
-		if (ch == NULL) SlErrorCorrupt("Unknown chunk type");
+		if (ch == nullptr) SlErrorCorrupt("Unknown chunk type");
 		SlLoadChunk(ch);
 	}
 }
@@ -1801,7 +1801,7 @@ static void SlLoadCheckChunks()
 		DEBUG(sl, 2, "Loading chunk %c%c%c%c", id >> 24, id >> 16, id >> 8, id);
 
 		ch = SlFindChunkHandler(id);
-		if (ch == NULL) SlErrorCorrupt("Unknown chunk type");
+		if (ch == nullptr) SlErrorCorrupt("Unknown chunk type");
 		SlLoadCheckChunk(ch);
 	}
 }
@@ -1814,7 +1814,7 @@ static void SlFixPointers()
 	DEBUG(sl, 1, "Fixing pointers");
 
 	FOR_ALL_CHUNK_HANDLERS(ch) {
-		if (ch->ptrs_proc != NULL) {
+		if (ch->ptrs_proc != nullptr) {
 			DEBUG(sl, 2, "Fixing pointers for %c%c%c%c", ch->id >> 24, ch->id >> 16, ch->id >> 8, ch->id);
 			ch->ptrs_proc();
 		}
@@ -1835,24 +1835,24 @@ struct FileReader : LoadFilter {
 	 * Create the file reader, so it reads from a specific file.
 	 * @param file The file to read from.
 	 */
-	FileReader(FILE *file) : LoadFilter(NULL), file(file), begin(ftell(file))
+	FileReader(FILE *file) : LoadFilter(nullptr), file(file), begin(ftell(file))
 	{
 	}
 
 	/** Make sure everything is cleaned up. */
 	~FileReader()
 	{
-		if (this->file != NULL) fclose(this->file);
-		this->file = NULL;
+		if (this->file != nullptr) fclose(this->file);
+		this->file = nullptr;
 
 		/* Make sure we don't double free. */
-		_sl.sf = NULL;
+		_sl.sf = nullptr;
 	}
 
 	size_t Read(byte *buf, size_t size) override
 	{
 		/* We're in the process of shutting down, i.e. in "failure" mode. */
-		if (this->file == NULL) return 0;
+		if (this->file == nullptr) return 0;
 
 		return fread(buf, 1, size, this->file);
 	}
@@ -1874,7 +1874,7 @@ struct FileWriter : SaveFilter {
 	 * Create the file writer, so it writes to a specific file.
 	 * @param file The file to write to.
 	 */
-	FileWriter(FILE *file) : SaveFilter(NULL), file(file)
+	FileWriter(FILE *file) : SaveFilter(nullptr), file(file)
 	{
 	}
 
@@ -1884,21 +1884,21 @@ struct FileWriter : SaveFilter {
 		this->Finish();
 
 		/* Make sure we don't double free. */
-		_sl.sf = NULL;
+		_sl.sf = nullptr;
 	}
 
 	void Write(byte *buf, size_t size) override
 	{
 		/* We're in the process of shutting down, i.e. in "failure" mode. */
-		if (this->file == NULL) return;
+		if (this->file == nullptr) return;
 
 		if (fwrite(buf, 1, size, this->file) != size) SlError(STR_GAME_SAVELOAD_ERROR_FILE_NOT_WRITEABLE);
 	}
 
 	void Finish() override
 	{
-		if (this->file != NULL) fclose(this->file);
-		this->file = NULL;
+		if (this->file != nullptr) fclose(this->file);
+		this->file = nullptr;
 	}
 };
 
@@ -1953,7 +1953,7 @@ struct LZOLoadFilter : LoadFilter {
 		if (tmp[0] != lzo_adler32(0, out, size + sizeof(uint32))) SlErrorCorrupt("Bad checksum");
 
 		/* Decompress */
-		int ret = lzo1x_decompress_safe(out + sizeof(uint32) * 1, size, buf, &len, NULL);
+		int ret = lzo1x_decompress_safe(out + sizeof(uint32) * 1, size, buf, &len, nullptr);
 		if (ret != LZO_E_OK) SlError(STR_GAME_SAVELOAD_ERROR_FILE_NOT_READABLE);
 		return len;
 	}
@@ -2147,7 +2147,7 @@ struct ZlibSaveFilter : SaveFilter {
 
 	void Finish() override
 	{
-		this->WriteLoop(NULL, 0, Z_FINISH);
+		this->WriteLoop(nullptr, 0, Z_FINISH);
 		this->chain->Finish();
 	}
 };
@@ -2266,7 +2266,7 @@ struct LZMASaveFilter : SaveFilter {
 
 	void Finish() override
 	{
-		this->WriteLoop(NULL, 0, LZMA_FINISH);
+		this->WriteLoop(nullptr, 0, LZMA_FINISH);
 		this->chain->Finish();
 	}
 };
@@ -2296,7 +2296,7 @@ static const SaveLoadFormat _saveload_fo
 	/* Roughly 75% larger than zlib level 6 at only ~7% of the CPU usage. */
 	{"lzo",    TO_BE32X('OTTD'), CreateLoadFilter<LZOLoadFilter>,    CreateSaveFilter<LZOSaveFilter>,    0, 0, 0},
 #else
-	{"lzo",    TO_BE32X('OTTD'), NULL,                               NULL,                               0, 0, 0},
+	{"lzo",    TO_BE32X('OTTD'), nullptr,                               nullptr,                               0, 0, 0},
 #endif
 	/* Roughly 5 times larger at only 1% of the CPU usage over zlib level 6. */
 	{"none",   TO_BE32X('OTTN'), CreateLoadFilter<NoCompLoadFilter>, CreateSaveFilter<NoCompSaveFilter>, 0, 0, 0},
@@ -2306,7 +2306,7 @@ static const SaveLoadFormat _saveload_fo
 	 * 1 is "only" 3 times as fast. Level 0 results in uncompressed savegames at about 8 times the cost of "none". */
 	{"zlib",   TO_BE32X('OTTZ'), CreateLoadFilter<ZlibLoadFilter>,   CreateSaveFilter<ZlibSaveFilter>,   0, 6, 9},
 #else
-	{"zlib",   TO_BE32X('OTTZ'), NULL,                               NULL,                               0, 0, 0},
+	{"zlib",   TO_BE32X('OTTZ'), nullptr,                               nullptr,                               0, 0, 0},
 #endif
 #if defined(WITH_LIBLZMA)
 	/* Level 2 compression is speed wise as fast as zlib level 6 compression (old default), but results in ~10% smaller saves.
@@ -2316,14 +2316,14 @@ static const SaveLoadFormat _saveload_fo
 	 * It's OTTX and not e.g. OTTL because liblzma is part of xz-utils and .tar.xz is preferred over .tar.lzma. */
 	{"lzma",   TO_BE32X('OTTX'), CreateLoadFilter<LZMALoadFilter>,   CreateSaveFilter<LZMASaveFilter>,   0, 2, 9},
 #else
-	{"lzma",   TO_BE32X('OTTX'), NULL,                               NULL,                               0, 0, 0},
+	{"lzma",   TO_BE32X('OTTX'), nullptr,                               nullptr,                               0, 0, 0},
 #endif
 };
 
 /**
  * Return the savegameformat of the game. Whether it was created with ZLIB compression
  * uncompressed, or another type
- * @param s Name of the savegame format. If NULL it picks the first available one
+ * @param s Name of the savegame format. If nullptr it picks the first available one
  * @param compression_level Output for telling what compression level we want.
  * @return Pointer to SaveLoadFormat struct giving all characteristics of this type of savegame
  */
@@ -2337,12 +2337,12 @@ static const SaveLoadFormat *GetSavegame
 	if (!StrEmpty(s)) {
 		/* Get the ":..." of the compression level out of the way */
 		char *complevel = strrchr(s, ':');
-		if (complevel != NULL) *complevel = '\0';
+		if (complevel != nullptr) *complevel = '\0';
 
 		for (const SaveLoadFormat *slf = &_saveload_formats[0]; slf != endof(_saveload_formats); slf++) {
-			if (slf->init_write != NULL && strcmp(s, slf->name) == 0) {
+			if (slf->init_write != nullptr && strcmp(s, slf->name) == 0) {
 				*compression_level = slf->default_compression;
-				if (complevel != NULL) {
+				if (complevel != nullptr) {
 					/* There is a compression level in the string.
 					 * First restore the : we removed to do proper name matching,
 					 * then move the the begin of the actual version. */
@@ -2368,7 +2368,7 @@ static const SaveLoadFormat *GetSavegame
 		ShowErrorMessage(STR_CONFIG_ERROR, STR_CONFIG_ERROR_INVALID_SAVEGAME_COMPRESSION_ALGORITHM, WL_CRITICAL);
 
 		/* Restore the string by adding the : back */
-		if (complevel != NULL) *complevel = ':';
+		if (complevel != nullptr) *complevel = ':';
 	}
 	*compression_level = def->default_compression;
 	return def;
@@ -2385,16 +2385,16 @@ extern bool LoadOldSaveGame(const char *
 static inline void ClearSaveLoadState()
 {
 	delete _sl.dumper;
-	_sl.dumper = NULL;
+	_sl.dumper = nullptr;
 
 	delete _sl.sf;
-	_sl.sf = NULL;
+	_sl.sf = nullptr;
 
 	delete _sl.reader;
-	_sl.reader = NULL;
+	_sl.reader = nullptr;
 
 	delete _sl.lf;
-	_sl.lf = NULL;
+	_sl.lf = nullptr;
 }
 
 /**
@@ -2614,7 +2614,7 @@ static SaveOrLoadResult DoLoad(LoadFilte
 	}
 
 	/* loader for this savegame type is not implemented? */
-	if (fmt->init_load == NULL) {
+	if (fmt->init_load == nullptr) {
 		char err_str[64];
 		seprintf(err_str, lastof(err_str), "Loader for '%s' is not available.", fmt->name);
 		SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_INTERNAL_ERROR, err_str);
@@ -2769,11 +2769,11 @@ SaveOrLoadResult SaveOrLoad(const char *
 		FILE *fh = (fop == SLO_SAVE) ? FioFOpenFile(filename, "wb", sb) : FioFOpenFile(filename, "rb", sb);
 
 		/* Make it a little easier to load savegames from the console */
-		if (fh == NULL && fop != SLO_SAVE) fh = FioFOpenFile(filename, "rb", SAVE_DIR);
-		if (fh == NULL && fop != SLO_SAVE) fh = FioFOpenFile(filename, "rb", BASE_DIR);
-		if (fh == NULL && fop != SLO_SAVE) fh = FioFOpenFile(filename, "rb", SCENARIO_DIR);
-
-		if (fh == NULL) {
+		if (fh == nullptr && fop != SLO_SAVE) fh = FioFOpenFile(filename, "rb", SAVE_DIR);
+		if (fh == nullptr && fop != SLO_SAVE) fh = FioFOpenFile(filename, "rb", BASE_DIR);
+		if (fh == nullptr && fop != SLO_SAVE) fh = FioFOpenFile(filename, "rb", SCENARIO_DIR);
+
+		if (fh == nullptr) {
 			SlError(fop == SLO_SAVE ? STR_GAME_SAVELOAD_ERROR_FILE_NOT_WRITEABLE : STR_GAME_SAVELOAD_ERROR_FILE_NOT_READABLE);
 		}
 
diff --git a/src/saveload/saveload.h b/src/saveload/saveload.h
--- a/src/saveload/saveload.h
+++ b/src/saveload/saveload.h
@@ -641,11 +641,11 @@ typedef SaveLoad SaveLoadGlobVarList;
 /** Translate values ingame to different values in the savegame and vv. */
 #define SLE_WRITEBYTE(base, variable) SLE_GENERAL(SL_WRITEBYTE, base, variable, 0, 0, SL_MIN_VERSION, SL_MAX_VERSION)
 
-#define SLE_VEH_INCLUDE() {false, SL_VEH_INCLUDE, 0, 0, SL_MIN_VERSION, SL_MAX_VERSION, NULL, 0}
-#define SLE_ST_INCLUDE() {false, SL_ST_INCLUDE, 0, 0, SL_MIN_VERSION, SL_MAX_VERSION, NULL, 0}
+#define SLE_VEH_INCLUDE() {false, SL_VEH_INCLUDE, 0, 0, SL_MIN_VERSION, SL_MAX_VERSION, nullptr, 0}
+#define SLE_ST_INCLUDE() {false, SL_ST_INCLUDE, 0, 0, SL_MIN_VERSION, SL_MAX_VERSION, nullptr, 0}
 
 /** End marker of a struct/class save or load. */
-#define SLE_END() {false, SL_END, 0, 0, SL_MIN_VERSION, SL_MIN_VERSION, NULL, 0}
+#define SLE_END() {false, SL_END, 0, 0, SL_MIN_VERSION, SL_MIN_VERSION, nullptr, 0}
 
 /**
  * Storage of global simple variables, references (pointers), and arrays.
@@ -746,10 +746,10 @@ typedef SaveLoad SaveLoadGlobVarList;
  * @param from   First savegame version that has the empty space.
  * @param to     Last savegame version that has the empty space.
  */
-#define SLEG_CONDNULL(length, from, to) {true, SL_ARR, SLE_FILE_U8 | SLE_VAR_NULL | SLF_NOT_IN_CONFIG, length, from, to, (void*)NULL}
+#define SLEG_CONDNULL(length, from, to) {true, SL_ARR, SLE_FILE_U8 | SLE_VAR_NULL | SLF_NOT_IN_CONFIG, length, from, to, (void*)nullptr}
 
 /** End marker of global variables save or load. */
-#define SLEG_END() {true, SL_END, 0, 0, SL_MIN_VERSION, SL_MIN_VERSION, NULL, 0}
+#define SLEG_END() {true, SL_END, 0, 0, SL_MIN_VERSION, SL_MIN_VERSION, nullptr, 0}
 
 /**
  * Checks whether the savegame is below \a major.\a minor.
@@ -813,13 +813,13 @@ static inline bool IsNumericType(VarType
 
 /**
  * Get the address of the variable. Which one to pick depends on the object
- * pointer. If it is NULL we are dealing with global variables so the address
+ * pointer. If it is nullptr we are dealing with global variables so the address
  * is taken. If non-null only the offset is stored in the union and we need
  * to add this to the address of the object
  */
 static inline void *GetVariableAddress(const void *object, const SaveLoad *sld)
 {
-	return const_cast<byte *>((const byte*)(sld->global ? NULL : object) + (ptrdiff_t)sld->address);
+	return const_cast<byte *>((const byte*)(sld->global ? nullptr : object) + (ptrdiff_t)sld->address);
 }
 
 int64 ReadValue(const void *ptr, VarType conv);
@@ -841,7 +841,7 @@ void SlGlobList(const SaveLoadGlobVarLis
 void SlArray(void *array, size_t length, VarType conv);
 void SlObject(void *object, const SaveLoad *sld);
 bool SlObjectMember(void *object, const SaveLoad *sld);
-void NORETURN SlError(StringID string, const char *extra_msg = NULL);
+void NORETURN SlError(StringID string, const char *extra_msg = nullptr);
 void NORETURN SlErrorCorrupt(const char *msg);
 void NORETURN SlErrorCorruptFmt(const char *format, ...);
 
diff --git a/src/saveload/saveload_filter.h b/src/saveload/saveload_filter.h
--- a/src/saveload/saveload_filter.h
+++ b/src/saveload/saveload_filter.h
@@ -89,7 +89,7 @@ struct SaveFilter {
 	 */
 	virtual void Finish()
 	{
-		if (this->chain != NULL) this->chain->Finish();
+		if (this->chain != nullptr) this->chain->Finish();
 	}
 };
 
diff --git a/src/saveload/signs_sl.cpp b/src/saveload/signs_sl.cpp
--- a/src/saveload/signs_sl.cpp
+++ b/src/saveload/signs_sl.cpp
@@ -68,5 +68,5 @@ static void Load_SIGN()
 
 /** Chunk handlers related to signs. */
 extern const ChunkHandler _sign_chunk_handlers[] = {
-	{ 'SIGN', Save_SIGN, Load_SIGN, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'SIGN', Save_SIGN, Load_SIGN, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/station_sl.cpp b/src/saveload/station_sl.cpp
--- a/src/saveload/station_sl.cpp
+++ b/src/saveload/station_sl.cpp
@@ -47,7 +47,7 @@ void MoveBuoysToWaypoints()
 		VehicleType vt = ol->GetFirstSharedVehicle()->type;
 		if (vt != VEH_SHIP && vt != VEH_TRAIN) continue;
 
-		for (Order *o = ol->GetFirstOrder(); o != NULL; o = o->next) UpdateWaypointOrder(o);
+		for (Order *o = ol->GetFirstOrder(); o != nullptr; o = o->next) UpdateWaypointOrder(o);
 	}
 
 	Vehicle *v;
@@ -68,7 +68,7 @@ void MoveBuoysToWaypoints()
 		Town *town         = st->town;
 		StringID string_id = st->string_id;
 		char *name         = st->name;
-		st->name           = NULL;
+		st->name           = nullptr;
 		Date build_date    = st->build_date;
 		/* TTDPatch could use "buoys with rail station" for rail waypoints */
 		bool train         = st->train_station.tile != INVALID_TILE;
@@ -116,13 +116,13 @@ void AfterLoadStations()
 		for (uint i = 0; i < st->num_specs; i++) {
 			if (st->speclist[i].grfid == 0) continue;
 
-			st->speclist[i].spec = StationClass::GetByGrf(st->speclist[i].grfid, st->speclist[i].localidx, NULL);
+			st->speclist[i].spec = StationClass::GetByGrf(st->speclist[i].grfid, st->speclist[i].localidx, nullptr);
 		}
 
 		if (Station::IsExpected(st)) {
 			Station *sta = Station::From(st);
-			for (const RoadStop *rs = sta->bus_stops; rs != NULL; rs = rs->next) sta->bus_station.Add(rs->xy);
-			for (const RoadStop *rs = sta->truck_stops; rs != NULL; rs = rs->next) sta->truck_station.Add(rs->xy);
+			for (const RoadStop *rs = sta->bus_stops; rs != nullptr; rs = rs->next) sta->bus_station.Add(rs->xy);
+			for (const RoadStop *rs = sta->truck_stops; rs != nullptr; rs = rs->next) sta->truck_station.Add(rs->xy);
 		}
 
 		StationUpdateCachedTriggers(st);
@@ -544,11 +544,11 @@ static void Load_STNN()
 			for (CargoID i = 0; i < num_cargo; i++) {
 				SlObject(&st->goods[i], GetGoodsDesc());
 				FlowSaveLoad flow;
-				FlowStat *fs = NULL;
+				FlowStat *fs = nullptr;
 				StationID prev_source = INVALID_STATION;
 				for (uint32 j = 0; j < _num_flows; ++j) {
 					SlObject(&flow, _flow_desc);
-					if (fs == NULL || prev_source != flow.source) {
+					if (fs == nullptr || prev_source != flow.source) {
 						fs = &(st->goods[i].flows.insert(std::make_pair(flow.source, FlowStat(flow.via, flow.share, flow.restricted))).first->second);
 					} else {
 						fs->AppendShare(flow.via, flow.share, flow.restricted);
@@ -638,7 +638,7 @@ static void Ptrs_ROADSTOP()
 }
 
 extern const ChunkHandler _station_chunk_handlers[] = {
-	{ 'STNS', NULL,          Load_STNS,     Ptrs_STNS,     NULL, CH_ARRAY },
-	{ 'STNN', Save_STNN,     Load_STNN,     Ptrs_STNN,     NULL, CH_ARRAY },
-	{ 'ROAD', Save_ROADSTOP, Load_ROADSTOP, Ptrs_ROADSTOP, NULL, CH_ARRAY | CH_LAST},
+	{ 'STNS', nullptr,          Load_STNS,     Ptrs_STNS,     nullptr, CH_ARRAY },
+	{ 'STNN', Save_STNN,     Load_STNN,     Ptrs_STNN,     nullptr, CH_ARRAY },
+	{ 'ROAD', Save_ROADSTOP, Load_ROADSTOP, Ptrs_ROADSTOP, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/storage_sl.cpp b/src/saveload/storage_sl.cpp
--- a/src/saveload/storage_sl.cpp
+++ b/src/saveload/storage_sl.cpp
@@ -50,5 +50,5 @@ static void Save_PSAC()
 
 /** Chunk handler for persistent storages. */
 extern const ChunkHandler _persistent_storage_chunk_handlers[] = {
-	{ 'PSAC', Save_PSAC, Load_PSAC, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'PSAC', Save_PSAC, Load_PSAC, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/story_sl.cpp b/src/saveload/story_sl.cpp
--- a/src/saveload/story_sl.cpp
+++ b/src/saveload/story_sl.cpp
@@ -102,6 +102,6 @@ static void Load_STORY_PAGE()
 }
 
 extern const ChunkHandler _story_page_chunk_handlers[] = {
-	{ 'STPE', Save_STORY_PAGE_ELEMENT, Load_STORY_PAGE_ELEMENT, NULL, NULL, CH_ARRAY},
-	{ 'STPA', Save_STORY_PAGE, Load_STORY_PAGE, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'STPE', Save_STORY_PAGE_ELEMENT, Load_STORY_PAGE_ELEMENT, nullptr, nullptr, CH_ARRAY},
+	{ 'STPA', Save_STORY_PAGE, Load_STORY_PAGE, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/strings_sl.cpp b/src/saveload/strings_sl.cpp
--- a/src/saveload/strings_sl.cpp
+++ b/src/saveload/strings_sl.cpp
@@ -49,7 +49,7 @@ StringID RemapOldStringID(StringID s)
 }
 
 /** Location to load the old names to. */
-char *_old_name_array = NULL;
+char *_old_name_array = nullptr;
 
 /**
  * Copy and convert old custom names to UTF-8.
@@ -61,7 +61,7 @@ char *_old_name_array = NULL;
 char *CopyFromOldName(StringID id)
 {
 	/* Is this name an (old) custom name? */
-	if (GetStringTab(id) != TEXT_TAB_OLD_CUSTOM) return NULL;
+	if (GetStringTab(id) != TEXT_TAB_OLD_CUSTOM) return nullptr;
 
 	if (IsSavegameVersionBefore(SLV_37)) {
 		/* Allow for expansion when converted to UTF-8. */
@@ -109,7 +109,7 @@ char *CopyFromOldName(StringID id)
 void ResetOldNames()
 {
 	free(_old_name_array);
-	_old_name_array = NULL;
+	_old_name_array = nullptr;
 }
 
 /**
@@ -140,5 +140,5 @@ static void Load_NAME()
 
 /** Chunk handlers related to strings. */
 extern const ChunkHandler _name_chunk_handlers[] = {
-	{ 'NAME', NULL, Load_NAME, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'NAME', nullptr, Load_NAME, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/subsidy_sl.cpp b/src/saveload/subsidy_sl.cpp
--- a/src/saveload/subsidy_sl.cpp
+++ b/src/saveload/subsidy_sl.cpp
@@ -48,5 +48,5 @@ static void Load_SUBS()
 }
 
 extern const ChunkHandler _subsidy_chunk_handlers[] = {
-	{ 'SUBS', Save_SUBS, Load_SUBS, NULL, NULL, CH_ARRAY | CH_LAST},
+	{ 'SUBS', Save_SUBS, Load_SUBS, nullptr, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/town_sl.cpp b/src/saveload/town_sl.cpp
--- a/src/saveload/town_sl.cpp
+++ b/src/saveload/town_sl.cpp
@@ -321,6 +321,6 @@ static void Ptrs_TOWN()
 
 /** Chunk handler for towns. */
 extern const ChunkHandler _town_chunk_handlers[] = {
-	{ 'HIDS', Save_HIDS, Load_HIDS,      NULL, NULL, CH_ARRAY },
-	{ 'CITY', Save_TOWN, Load_TOWN, Ptrs_TOWN, NULL, CH_ARRAY | CH_LAST},
+	{ 'HIDS', Save_HIDS, Load_HIDS,      nullptr, nullptr, CH_ARRAY },
+	{ 'CITY', Save_TOWN, Load_TOWN, Ptrs_TOWN, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/vehicle_sl.cpp b/src/saveload/vehicle_sl.cpp
--- a/src/saveload/vehicle_sl.cpp
+++ b/src/saveload/vehicle_sl.cpp
@@ -36,7 +36,7 @@ void ConnectMultiheadedTrains()
 	Train *v;
 
 	FOR_ALL_TRAINS(v) {
-		v->other_multiheaded_part = NULL;
+		v->other_multiheaded_part = nullptr;
 	}
 
 	FOR_ALL_TRAINS(v) {
@@ -56,8 +56,8 @@ void ConnectMultiheadedTrains()
 
 			bool sequential_matching = v->IsFrontEngine();
 
-			for (Train *u = v; u != NULL; u = u->GetNextVehicle()) {
-				if (u->other_multiheaded_part != NULL) continue; // we already linked this one
+			for (Train *u = v; u != nullptr; u = u->GetNextVehicle()) {
+				if (u->other_multiheaded_part != nullptr) continue; // we already linked this one
 
 				if (u->IsMultiheaded()) {
 					if (!u->IsEngine()) {
@@ -70,8 +70,8 @@ void ConnectMultiheadedTrains()
 					EngineID eid = u->engine_type;
 					Train *w;
 					if (sequential_matching) {
-						for (w = u->GetNextVehicle(); w != NULL; w = w->GetNextVehicle()) {
-							if (w->engine_type != eid || w->other_multiheaded_part != NULL || !w->IsMultiheaded()) continue;
+						for (w = u->GetNextVehicle(); w != nullptr; w = w->GetNextVehicle()) {
+							if (w->engine_type != eid || w->other_multiheaded_part != nullptr || !w->IsMultiheaded()) continue;
 
 							/* we found a car to partner with this engine. Now we will make sure it face the right way */
 							if (w->IsEngine()) {
@@ -82,8 +82,8 @@ void ConnectMultiheadedTrains()
 						}
 					} else {
 						uint stack_pos = 0;
-						for (w = u->GetNextVehicle(); w != NULL; w = w->GetNextVehicle()) {
-							if (w->engine_type != eid || w->other_multiheaded_part != NULL || !w->IsMultiheaded()) continue;
+						for (w = u->GetNextVehicle(); w != nullptr; w = w->GetNextVehicle()) {
+							if (w->engine_type != eid || w->other_multiheaded_part != nullptr || !w->IsMultiheaded()) continue;
 
 							if (w->IsEngine()) {
 								stack_pos++;
@@ -94,7 +94,7 @@ void ConnectMultiheadedTrains()
 						}
 					}
 
-					if (w != NULL) {
+					if (w != nullptr) {
 						w->other_multiheaded_part = u;
 						u->other_multiheaded_part = w;
 					} else {
@@ -118,7 +118,7 @@ void ConvertOldMultiheadToNew()
 
 	FOR_ALL_TRAINS(t) {
 		if (HasBit(t->subtype, 7) && ((t->subtype & ~0x80) == 0 || (t->subtype & ~0x80) == 4)) {
-			for (Train *u = t; u != NULL; u = u->Next()) {
+			for (Train *u = t; u != nullptr; u = u->Next()) {
 				const RailVehicleInfo *rvi = RailVehInfo(u->engine_type);
 
 				ClrBit(u->subtype, 7);
@@ -200,7 +200,7 @@ void UpdateOldAircraft()
 			if (a->subtype == AIR_HELICOPTER) a->Next()->Next()->cur_speed = 32;
 
 			/* set new position x,y,z */
-			GetAircraftFlightLevelBounds(a, &a->z_pos, NULL);
+			GetAircraftFlightLevelBounds(a, &a->z_pos, nullptr);
 			SetAircraftPosition(a, gp.x, gp.y, GetAircraftFlightLevel(a));
 		}
 	}
@@ -252,11 +252,11 @@ void AfterLoadVehicles(bool part_of_load
 
 	FOR_ALL_VEHICLES(v) {
 		/* Reinstate the previous pointer */
-		if (v->Next() != NULL) v->Next()->previous = v;
-		if (v->NextShared() != NULL) v->NextShared()->previous_shared = v;
+		if (v->Next() != nullptr) v->Next()->previous = v;
+		if (v->NextShared() != nullptr) v->NextShared()->previous_shared = v;
 
 		if (part_of_load) v->fill_percent_te_id = INVALID_TE_ID;
-		v->first = NULL;
+		v->first = nullptr;
 		if (v->IsGroundVehicle()) v->GetGroundVehicleCache()->first_engine = INVALID_ENGINE;
 	}
 
@@ -272,9 +272,9 @@ void AfterLoadVehicles(bool part_of_load
 		std::map<Order*, OrderList*> mapping;
 
 		FOR_ALL_VEHICLES(v) {
-			if (v->orders.old != NULL) {
+			if (v->orders.old != nullptr) {
 				if (IsSavegameVersionBefore(SLV_105)) { // Pre-105 didn't save an OrderList
-					if (mapping[v->orders.old] == NULL) {
+					if (mapping[v->orders.old] == nullptr) {
 						/* This adds the whole shared vehicle chain for case b */
 
 						/* Creating an OrderList here is safe because the number of vehicles
@@ -290,7 +290,7 @@ void AfterLoadVehicles(bool part_of_load
 						}
 					}
 				} else { // OrderList was saved as such, only recalculate not saved values
-					if (v->PreviousShared() == NULL) {
+					if (v->PreviousShared() == nullptr) {
 						v->orders.list->Initialize(v->orders.list->first, v);
 					}
 				}
@@ -300,8 +300,8 @@ void AfterLoadVehicles(bool part_of_load
 
 	FOR_ALL_VEHICLES(v) {
 		/* Fill the first pointers */
-		if (v->Previous() == NULL) {
-			for (Vehicle *u = v; u != NULL; u = u->Next()) {
+		if (v->Previous() == nullptr) {
+			for (Vehicle *u = v; u != nullptr; u = u->Next()) {
 				u->first = v;
 			}
 		}
@@ -311,12 +311,12 @@ void AfterLoadVehicles(bool part_of_load
 		if (IsSavegameVersionBefore(SLV_105)) {
 			/* Before 105 there was no order for shared orders, thus it messed up horribly */
 			FOR_ALL_VEHICLES(v) {
-				if (v->First() != v || v->orders.list != NULL || v->previous_shared != NULL || v->next_shared == NULL) continue;
+				if (v->First() != v || v->orders.list != nullptr || v->previous_shared != nullptr || v->next_shared == nullptr) continue;
 
 				/* As above, allocating OrderList here is safe. */
 				assert(OrderList::CanAllocateItem());
-				v->orders.list = new OrderList(NULL, v);
-				for (Vehicle *u = v; u != NULL; u = u->next_shared) {
+				v->orders.list = new OrderList(nullptr, v);
+				for (Vehicle *u = v; u != nullptr; u = u->next_shared) {
 					u->orders.list = v->orders.list;
 				}
 			}
@@ -392,9 +392,9 @@ void AfterLoadVehicles(bool part_of_load
 	CheckValidVehicles();
 
 	FOR_ALL_VEHICLES(v) {
-		assert(v->first != NULL);
+		assert(v->first != nullptr);
 
-		v->trip_occupancy = CalcPercentVehicleFilled(v, NULL);
+		v->trip_occupancy = CalcPercentVehicleFilled(v, nullptr);
 
 		switch (v->type) {
 			case VEH_TRAIN: {
@@ -502,7 +502,7 @@ void FixupTrainLengths()
 			/* The vehicle center is now more to the front depending on vehicle length,
 			 * so we need to move all vehicles forward to cover the difference to the
 			 * old center, otherwise wagon spacing in trains would be broken upon load. */
-			for (Train *u = Train::From(v); u != NULL; u = u->Next()) {
+			for (Train *u = Train::From(v); u != nullptr; u = u->Next()) {
 				if (u->track == TRACK_BIT_DEPOT || (u->vehstatus & VS_CRASHED)) continue;
 
 				Train *next = u->Next();
@@ -514,7 +514,7 @@ void FixupTrainLengths()
 					if (!TrainController(u, next, false)) break;
 				}
 
-				if (next != NULL && done < diff && u->IsFrontEngine()) {
+				if (next != nullptr && done < diff && u->IsFrontEngine()) {
 					/* Pulling the front vehicle forwards failed, we either encountered a dead-end
 					 * or a red signal. To fix this, we try to move the whole train the required
 					 * space backwards and re-do the fix up of the front vehicle. */
@@ -530,14 +530,14 @@ void FixupTrainLengths()
 
 					/* We moved the first vehicle which is now the last. Move it back to the
 					 * original position as we will fix up the last vehicle later in the loop. */
-					for (int i = 0; i < done; i++) TrainController(u->Last(), NULL);
+					for (int i = 0; i < done; i++) TrainController(u->Last(), nullptr);
 
 					/* Move the train backwards to get space for the first vehicle. As the stopping
 					 * distance from a line end is rounded up, move the train one unit more to cater
 					 * for front vehicles with odd lengths. */
 					int moved;
 					for (moved = 0; moved < diff + 1; moved++) {
-						if (!TrainController(u, NULL, false)) break;
+						if (!TrainController(u, nullptr, false)) break;
 					}
 
 					/* Swap start<>end, start+1<>end-1, ... again. */
@@ -556,17 +556,17 @@ void FixupTrainLengths()
 
 					/* We moved one unit more backwards than needed for even-length front vehicles,
 					 * try to move that unit forward again. We don't care if this step fails. */
-					TrainController(u, NULL, false);
+					TrainController(u, nullptr, false);
 				}
 
 				/* If the next wagon is still in a depot, check if it shouldn't be outside already. */
-				if (next != NULL && next->track == TRACK_BIT_DEPOT) {
+				if (next != nullptr && next->track == TRACK_BIT_DEPOT) {
 					int d = TicksToLeaveDepot(u);
 					if (d <= 0) {
 						/* Next vehicle should have left the depot already, show it and pull forward. */
 						next->vehstatus &= ~VS_HIDDEN;
 						next->track = TrackToTrackBits(GetRailDepotTrack(next->tile));
-						for (int i = 0; i >= d; i--) TrainController(next, NULL);
+						for (int i = 0; i >= d; i--) TrainController(next, nullptr);
 					}
 				}
 			}
@@ -960,5 +960,5 @@ static void Ptrs_VEHS()
 }
 
 extern const ChunkHandler _veh_chunk_handlers[] = {
-	{ 'VEHS', Save_VEHS, Load_VEHS, Ptrs_VEHS, NULL, CH_SPARSE_ARRAY | CH_LAST},
+	{ 'VEHS', Save_VEHS, Load_VEHS, Ptrs_VEHS, nullptr, CH_SPARSE_ARRAY | CH_LAST},
 };
diff --git a/src/saveload/waypoint_sl.cpp b/src/saveload/waypoint_sl.cpp
--- a/src/saveload/waypoint_sl.cpp
+++ b/src/saveload/waypoint_sl.cpp
@@ -88,7 +88,7 @@ void MoveWaypointsToBaseStations()
 			StationClass* stclass = StationClass::Get(STAT_CLASS_WAYP);
 			for (uint i = 0; i < stclass->GetSpecCount(); i++) {
 				const StationSpec *statspec = stclass->GetSpec(i);
-				if (statspec != NULL && statspec->grf_prop.grffile->grfid == wp.grfid && statspec->grf_prop.local_id == wp.localidx) {
+				if (statspec != nullptr && statspec->grf_prop.grffile->grfid == wp.grfid && statspec->grf_prop.local_id == wp.localidx) {
 					wp.spec = statspec;
 					break;
 				}
@@ -122,7 +122,7 @@ void MoveWaypointsToBaseStations()
 
 			SetRailStationReservation(t, reserved);
 
-			if (wp.spec != NULL) {
+			if (wp.spec != nullptr) {
 				SetCustomStationSpecIndex(t, AllocateSpecToStation(wp.spec, new_wp, true));
 			}
 			new_wp->rect.BeforeAddTile(t, StationRect::ADD_FORCE);
@@ -136,7 +136,7 @@ void MoveWaypointsToBaseStations()
 	FOR_ALL_ORDER_LISTS(ol) {
 		if (ol->GetFirstSharedVehicle()->type != VEH_TRAIN) continue;
 
-		for (Order *o = ol->GetFirstOrder(); o != NULL; o = o->next) UpdateWaypointOrder(o);
+		for (Order *o = ol->GetFirstOrder(); o != nullptr; o = o->next) UpdateWaypointOrder(o);
 	}
 
 	Vehicle *v;
@@ -199,10 +199,10 @@ static void Ptrs_WAYP()
 			/* Only for versions 12 .. 122 */
 			if (!Town::IsValidID(wp.town_index)) {
 				/* Upon a corrupted waypoint we'll likely get here. The next step will be to
-				 * loop over all Ptrs procs to NULL the pointers. However, we don't know
-				 * whether we're in the NULL or "normal" Ptrs proc. So just clear the list
+				 * loop over all Ptrs procs to nullptr the pointers. However, we don't know
+				 * whether we're in the nullptr or "normal" Ptrs proc. So just clear the list
 				 * of old waypoints we constructed and then this waypoint (and the other
-				 * possibly corrupt ones) will not be queried in the NULL Ptrs proc run. */
+				 * possibly corrupt ones) will not be queried in the nullptr Ptrs proc run. */
 				_old_waypoints.clear();
 				SlErrorCorrupt("Referencing invalid Town");
 			}
@@ -215,5 +215,5 @@ static void Ptrs_WAYP()
 }
 
 extern const ChunkHandler _waypoint_chunk_handlers[] = {
-	{ 'CHKP', NULL, Load_WAYP, Ptrs_WAYP, NULL, CH_ARRAY | CH_LAST},
+	{ 'CHKP', nullptr, Load_WAYP, Ptrs_WAYP, nullptr, CH_ARRAY | CH_LAST},
 };
diff --git a/src/screenshot.cpp b/src/screenshot.cpp
--- a/src/screenshot.cpp
+++ b/src/screenshot.cpp
@@ -120,7 +120,7 @@ static bool MakeBMPImage(const char *nam
 	}
 
 	FILE *f = fopen(name, "wb");
-	if (f == NULL) return false;
+	if (f == nullptr) return false;
 
 	/* Each scanline must be aligned on a 32bit boundary */
 	uint bytewidth = Align(w * bpp, 4); // bytes per line in file
@@ -268,18 +268,18 @@ static bool MakePNGImage(const char *nam
 	if (pixelformat != 8 && pixelformat != 32) return false;
 
 	f = fopen(name, "wb");
-	if (f == NULL) return false;
+	if (f == nullptr) return false;
 
 	png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, const_cast<char *>(name), png_my_error, png_my_warning);
 
-	if (png_ptr == NULL) {
+	if (png_ptr == nullptr) {
 		fclose(f);
 		return false;
 	}
 
 	info_ptr = png_create_info_struct(png_ptr);
-	if (info_ptr == NULL) {
-		png_destroy_write_struct(&png_ptr, (png_infopp)NULL);
+	if (info_ptr == nullptr) {
+		png_destroy_write_struct(&png_ptr, (png_infopp)nullptr);
 		fclose(f);
 		return false;
 	}
@@ -311,7 +311,7 @@ static bool MakePNGImage(const char *nam
 	char *p = buf;
 	p += seprintf(p, lastof(buf), "Graphics set: %s (%u)\n", BaseGraphics::GetUsedSet()->name, BaseGraphics::GetUsedSet()->version);
 	p = strecpy(p, "NewGRFs:\n", lastof(buf));
-	for (const GRFConfig *c = _game_mode == GM_MENU ? NULL : _grfconfig; c != NULL; c = c->next) {
+	for (const GRFConfig *c = _game_mode == GM_MENU ? nullptr : _grfconfig; c != nullptr; c = c->next) {
 		p += seprintf(p, lastof(buf), "%08X ", BSWAP32(c->ident.grfid));
 		p = md5sumToString(p, lastof(buf), c->ident.md5sum);
 		p += seprintf(p, lastof(buf), " %s\n", c->filename);
@@ -319,7 +319,7 @@ static bool MakePNGImage(const char *nam
 	p = strecpy(p, "\nCompanies:\n", lastof(buf));
 	const Company *c;
 	FOR_ALL_COMPANIES(c) {
-		if (c->ai_info == NULL) {
+		if (c->ai_info == nullptr) {
 			p += seprintf(p, lastof(buf), "%2i: Human\n", (int)c->index);
 		} else {
 			p += seprintf(p, lastof(buf), "%2i: %s (v%d)\n", (int)c->index, c->ai_info->GetName(), c->ai_info->GetVersion());
@@ -447,7 +447,7 @@ static bool MakePCXImage(const char *nam
 	if (pixelformat != 8 || w == 0) return false;
 
 	f = fopen(name, "wb");
-	if (f == NULL) return false;
+	if (f == nullptr) return false;
 
 	memset(&pcx, 0, sizeof(pcx));
 
@@ -701,7 +701,7 @@ static const char *MakeScreenshotName(co
 static bool MakeSmallScreenshot(bool crashlog)
 {
 	const ScreenshotFormat *sf = _screenshot_formats + _cur_screenshot_format;
-	return sf->proc(MakeScreenshotName(SCREENSHOT_NAME, sf->extension, crashlog), CurrentScreenCallback, NULL, _screen.width, _screen.height,
+	return sf->proc(MakeScreenshotName(SCREENSHOT_NAME, sf->extension, crashlog), CurrentScreenCallback, nullptr, _screen.width, _screen.height,
 			BlitterFactory::GetCurrentBlitter()->GetScreenDepth(), _cur_palette.palette);
 }
 
@@ -743,7 +743,7 @@ void SetupScreenshotViewport(ScreenshotT
 	vp->top = 0;
 	vp->width  = UnScaleByZoom(vp->virtual_width,  vp->zoom);
 	vp->height = UnScaleByZoom(vp->virtual_height, vp->zoom);
-	vp->overlay = NULL;
+	vp->overlay = nullptr;
 }
 
 /**
@@ -800,7 +800,7 @@ bool MakeHeightmapScreenshot(const char 
 		palette[i].b = i;
 	}
 	const ScreenshotFormat *sf = _screenshot_formats + _cur_screenshot_format;
-	return sf->proc(filename, HeightmapCallback, NULL, MapSizeX(), MapSizeY(), 8, palette);
+	return sf->proc(filename, HeightmapCallback, nullptr, MapSizeX(), MapSizeY(), 8, palette);
 }
 
 /**
@@ -821,7 +821,7 @@ bool MakeScreenshot(ScreenshotType t, co
 	}
 
 	_screenshot_name[0] = '\0';
-	if (name != NULL) strecpy(_screenshot_name, name, lastof(_screenshot_name));
+	if (name != nullptr) strecpy(_screenshot_name, name, lastof(_screenshot_name));
 
 	bool ret;
 	switch (t) {
diff --git a/src/script/api/script_basestation.cpp b/src/script/api/script_basestation.cpp
--- a/src/script/api/script_basestation.cpp
+++ b/src/script/api/script_basestation.cpp
@@ -22,12 +22,12 @@
 /* static */ bool ScriptBaseStation::IsValidBaseStation(StationID station_id)
 {
 	const BaseStation *st = ::BaseStation::GetIfValid(station_id);
-	return st != NULL && (st->owner == ScriptObject::GetCompany() || ScriptObject::GetCompany() == OWNER_DEITY || st->owner == OWNER_NONE);
+	return st != nullptr && (st->owner == ScriptObject::GetCompany() || ScriptObject::GetCompany() == OWNER_DEITY || st->owner == OWNER_NONE);
 }
 
 /* static */ char *ScriptBaseStation::GetName(StationID station_id)
 {
-	if (!IsValidBaseStation(station_id)) return NULL;
+	if (!IsValidBaseStation(station_id)) return nullptr;
 
 	::SetDParam(0, station_id);
 	return GetString(::Station::IsValidID(station_id) ? STR_STATION_NAME : STR_WAYPOINT_NAME);
@@ -39,7 +39,7 @@
 
 	EnforcePrecondition(false, ScriptObject::GetCompany() != OWNER_DEITY);
 	EnforcePrecondition(false, IsValidBaseStation(station_id));
-	EnforcePrecondition(false, name != NULL);
+	EnforcePrecondition(false, name != nullptr);
 	const char *text = name->GetDecodedText();
 	EnforcePreconditionEncodedText(false, text);
 	EnforcePreconditionCustomError(false, ::Utf8StringLength(text) < MAX_LENGTH_STATION_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
diff --git a/src/script/api/script_basestation.hpp b/src/script/api/script_basestation.hpp
--- a/src/script/api/script_basestation.hpp
+++ b/src/script/api/script_basestation.hpp
@@ -52,7 +52,7 @@ public:
 	 * @param station_id The basestation to set the name of.
 	 * @param name The new name of the station (can be either a raw string, or a ScriptText object).
 	 * @pre IsValidBaseStation(station_id).
-	 * @pre name != NULL && len(name) != 0.
+	 * @pre name != nullptr && len(name) != 0.
 	 * @game @pre Valid ScriptCompanyMode active in scope.
 	 * @exception ScriptError::ERR_NAME_IS_NOT_UNIQUE
 	 * @return True if the name was changed.
diff --git a/src/script/api/script_bridge.cpp b/src/script/api/script_bridge.cpp
--- a/src/script/api/script_bridge.cpp
+++ b/src/script/api/script_bridge.cpp
@@ -102,7 +102,7 @@ static void _DoCommandReturnBuildBridge1
 
 	ScriptObject::SetCallbackVariable(0, start);
 	ScriptObject::SetCallbackVariable(1, end);
-	return ScriptObject::DoCommand(end, start, type | bridge_id, CMD_BUILD_BRIDGE, NULL, &::_DoCommandReturnBuildBridge1);
+	return ScriptObject::DoCommand(end, start, type | bridge_id, CMD_BUILD_BRIDGE, nullptr, &::_DoCommandReturnBuildBridge1);
 }
 
 /* static */ bool ScriptBridge::_BuildBridgeRoad1()
@@ -114,7 +114,7 @@ static void _DoCommandReturnBuildBridge1
 	DiagDirection dir_1 = ::DiagdirBetweenTiles(end, start);
 	DiagDirection dir_2 = ::ReverseDiagDir(dir_1);
 
-	return ScriptObject::DoCommand(start + ::TileOffsByDiagDir(dir_1), ::DiagDirToRoadBits(dir_2) | (ScriptObject::GetRoadType() << 4), 0, CMD_BUILD_ROAD, NULL, &::_DoCommandReturnBuildBridge2);
+	return ScriptObject::DoCommand(start + ::TileOffsByDiagDir(dir_1), ::DiagDirToRoadBits(dir_2) | (ScriptObject::GetRoadType() << 4), 0, CMD_BUILD_ROAD, nullptr, &::_DoCommandReturnBuildBridge2);
 }
 
 /* static */ bool ScriptBridge::_BuildBridgeRoad2()
@@ -138,8 +138,8 @@ static void _DoCommandReturnBuildBridge1
 
 /* static */ char *ScriptBridge::GetName(BridgeID bridge_id, ScriptVehicle::VehicleType vehicle_type)
 {
-	EnforcePrecondition(NULL, vehicle_type == ScriptVehicle::VT_ROAD || vehicle_type == ScriptVehicle::VT_RAIL || vehicle_type == ScriptVehicle::VT_WATER);
-	if (!IsValidBridge(bridge_id)) return NULL;
+	EnforcePrecondition(nullptr, vehicle_type == ScriptVehicle::VT_ROAD || vehicle_type == ScriptVehicle::VT_RAIL || vehicle_type == ScriptVehicle::VT_WATER);
+	if (!IsValidBridge(bridge_id)) return nullptr;
 
 	return GetString(vehicle_type == ScriptVehicle::VT_WATER ? STR_LAI_BRIDGE_DESCRIPTION_AQUEDUCT : ::GetBridgeSpec(bridge_id)->transport_name[vehicle_type]);
 }
diff --git a/src/script/api/script_cargo.cpp b/src/script/api/script_cargo.cpp
--- a/src/script/api/script_cargo.cpp
+++ b/src/script/api/script_cargo.cpp
@@ -29,7 +29,7 @@
 
 /* static */ char *ScriptCargo::GetCargoLabel(CargoID cargo_type)
 {
-	if (!IsValidCargo(cargo_type)) return NULL;
+	if (!IsValidCargo(cargo_type)) return nullptr;
 	const CargoSpec *cargo = ::CargoSpec::Get(cargo_type);
 
 	/* cargo->label is a uint32 packing a 4 character non-terminated string,
diff --git a/src/script/api/script_client.cpp b/src/script/api/script_client.cpp
--- a/src/script/api/script_client.cpp
+++ b/src/script/api/script_client.cpp
@@ -20,37 +20,37 @@
  * Finds NetworkClientInfo given client-identifier,
  *  is used by other methods to resolve client-identifier.
  * @param client The client to get info structure for
- * @return A pointer to corresponding CI struct or NULL when not found.
+ * @return A pointer to corresponding CI struct or nullptr when not found.
  */
 static NetworkClientInfo *FindClientInfo(ScriptClient::ClientID client)
 {
-	if (client == ScriptClient::CLIENT_INVALID) return NULL;
-	if (!_networking) return NULL;
+	if (client == ScriptClient::CLIENT_INVALID) return nullptr;
+	if (!_networking) return nullptr;
 	return NetworkClientInfo::GetByClientID((::ClientID)client);
 }
 
 /* static */ ScriptClient::ClientID ScriptClient::ResolveClientID(ScriptClient::ClientID client)
 {
-	return (FindClientInfo(client) == NULL ? ScriptClient::CLIENT_INVALID : client);
+	return (FindClientInfo(client) == nullptr ? ScriptClient::CLIENT_INVALID : client);
 }
 
 /* static */ char *ScriptClient::GetName(ScriptClient::ClientID client)
 {
 	NetworkClientInfo *ci = FindClientInfo(client);
-	if (ci == NULL) return NULL;
+	if (ci == nullptr) return nullptr;
 	return stredup(ci->client_name);
 }
 
 /* static */ ScriptCompany::CompanyID ScriptClient::GetCompany(ScriptClient::ClientID client)
 {
 	NetworkClientInfo *ci = FindClientInfo(client);
-	if (ci == NULL) return ScriptCompany::COMPANY_INVALID;
+	if (ci == nullptr) return ScriptCompany::COMPANY_INVALID;
 	return (ScriptCompany::CompanyID)ci->client_playas;
 }
 
 /* static */ ScriptDate::Date ScriptClient::GetJoinDate(ScriptClient::ClientID client)
 {
 	NetworkClientInfo *ci = FindClientInfo(client);
-	if (ci == NULL) return ScriptDate::DATE_INVALID;
+	if (ci == nullptr) return ScriptDate::DATE_INVALID;
 	return (ScriptDate::Date)ci->join_date;
 }
diff --git a/src/script/api/script_company.cpp b/src/script/api/script_company.cpp
--- a/src/script/api/script_company.cpp
+++ b/src/script/api/script_company.cpp
@@ -45,7 +45,7 @@
 {
 	CCountedPtr<Text> counter(name);
 
-	EnforcePrecondition(false, name != NULL);
+	EnforcePrecondition(false, name != nullptr);
 	const char *text = name->GetDecodedText();
 	EnforcePreconditionEncodedText(false, text);
 	EnforcePreconditionCustomError(false, ::Utf8StringLength(text) < MAX_LENGTH_COMPANY_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
@@ -56,7 +56,7 @@
 /* static */ char *ScriptCompany::GetName(ScriptCompany::CompanyID company)
 {
 	company = ResolveCompanyID(company);
-	if (company == COMPANY_INVALID) return NULL;
+	if (company == COMPANY_INVALID) return nullptr;
 
 	::SetDParam(0, company);
 	return GetString(STR_COMPANY_NAME);
@@ -66,7 +66,7 @@
 {
 	CCountedPtr<Text> counter(name);
 
-	EnforcePrecondition(false, name != NULL);
+	EnforcePrecondition(false, name != nullptr);
 	const char *text = name->GetDecodedText();
 	EnforcePreconditionEncodedText(false, text);
 	EnforcePreconditionCustomError(false, ::Utf8StringLength(text) < MAX_LENGTH_PRESIDENT_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
@@ -312,7 +312,7 @@
 	if ((::LiveryScheme)scheme < LS_BEGIN || (::LiveryScheme)scheme >= LS_END) return COLOUR_INVALID;
 
 	const Company *c = ::Company::GetIfValid(_current_company);
-	if (c == NULL) return COLOUR_INVALID;
+	if (c == nullptr) return COLOUR_INVALID;
 
 	return (ScriptCompany::Colours)c->livery[scheme].colour1;
 }
@@ -322,7 +322,7 @@
 	if ((::LiveryScheme)scheme < LS_BEGIN || (::LiveryScheme)scheme >= LS_END) return COLOUR_INVALID;
 
 	const Company *c = ::Company::GetIfValid(_current_company);
-	if (c == NULL) return COLOUR_INVALID;
+	if (c == nullptr) return COLOUR_INVALID;
 
 	return (ScriptCompany::Colours)c->livery[scheme].colour2;
 }
diff --git a/src/script/api/script_company.hpp b/src/script/api/script_company.hpp
--- a/src/script/api/script_company.hpp
+++ b/src/script/api/script_company.hpp
@@ -139,7 +139,7 @@ public:
 	/**
 	 * Set the name of your company.
 	 * @param name The new name of the company (can be either a raw string, or a ScriptText object).
-	 * @pre name != NULL && len(name) != 0.
+	 * @pre name != nullptr && len(name) != 0.
 	 * @exception ScriptError::ERR_NAME_IS_NOT_UNIQUE
 	 * @return True if the name was changed.
 	 */
@@ -156,7 +156,7 @@ public:
 	/**
 	 * Set the name of your president.
 	 * @param name The new name of the president (can be either a raw string, or a ScriptText object).
-	 * @pre name != NULL && len(name) != 0.
+	 * @pre name != nullptr && len(name) != 0.
 	 * @exception ScriptError::ERR_NAME_IS_NOT_UNIQUE
 	 * @return True if the name was changed.
 	 */
diff --git a/src/script/api/script_controller.cpp b/src/script/api/script_controller.cpp
--- a/src/script/api/script_controller.cpp
+++ b/src/script/api/script_controller.cpp
@@ -43,7 +43,7 @@
 		ticks = 1;
 	}
 
-	throw Script_Suspend(ticks, NULL);
+	throw Script_Suspend(ticks, nullptr);
 }
 
 /* static */ void ScriptController::Break(const char* message)
@@ -119,7 +119,7 @@ ScriptController::~ScriptController()
 	strtolower(library_name);
 
 	ScriptInfo *lib = ScriptObject::GetActiveInstance()->FindLibrary(library, version);
-	if (lib == NULL) {
+	if (lib == nullptr) {
 		char error[1024];
 		seprintf(error, lastof(error), "couldn't find library '%s' with version %d", library, version);
 		throw sq_throwerror(vm, error);
diff --git a/src/script/api/script_engine.cpp b/src/script/api/script_engine.cpp
--- a/src/script/api/script_engine.cpp
+++ b/src/script/api/script_engine.cpp
@@ -25,7 +25,7 @@
 /* static */ bool ScriptEngine::IsValidEngine(EngineID engine_id)
 {
 	const Engine *e = ::Engine::GetIfValid(engine_id);
-	if (e == NULL || !e->IsEnabled()) return false;
+	if (e == nullptr || !e->IsEnabled()) return false;
 
 	/* AIs have only access to engines they can purchase or still have in use.
 	 * Deity has access to all engined that will be or were available ever. */
@@ -36,12 +36,12 @@
 /* static */ bool ScriptEngine::IsBuildable(EngineID engine_id)
 {
 	const Engine *e = ::Engine::GetIfValid(engine_id);
-	return e != NULL && ::IsEngineBuildable(engine_id, e->type, ScriptObject::GetCompany());
+	return e != nullptr && ::IsEngineBuildable(engine_id, e->type, ScriptObject::GetCompany());
 }
 
 /* static */ char *ScriptEngine::GetName(EngineID engine_id)
 {
-	if (!IsValidEngine(engine_id)) return NULL;
+	if (!IsValidEngine(engine_id)) return nullptr;
 
 	::SetDParam(0, engine_id);
 	return GetString(STR_ENGINE_NAME);
diff --git a/src/script/api/script_error.hpp b/src/script/api/script_error.hpp
--- a/src/script/api/script_error.hpp
+++ b/src/script/api/script_error.hpp
@@ -44,7 +44,7 @@
  * @param string The string that is checked.
  */
 #define EnforcePreconditionEncodedText(returnval, string)   \
-	if ((string) == NULL) { \
+	if ((string) == nullptr) { \
 		ScriptObject::SetLastError(ScriptError::ERR_PRECONDITION_TOO_MANY_PARAMETERS); \
 		return returnval; \
 	} \
diff --git a/src/script/api/script_event.cpp b/src/script/api/script_event.cpp
--- a/src/script/api/script_event.cpp
+++ b/src/script/api/script_event.cpp
@@ -23,7 +23,7 @@ struct ScriptEventData {
 
 /* static */ void ScriptEventController::CreateEventPointer()
 {
-	assert(ScriptObject::GetEventPointer() == NULL);
+	assert(ScriptObject::GetEventPointer() == nullptr);
 
 	ScriptObject::GetEventPointer() = new ScriptEventData();
 }
@@ -45,7 +45,7 @@ struct ScriptEventData {
 
 /* static */ bool ScriptEventController::IsEventWaiting()
 {
-	if (ScriptObject::GetEventPointer() == NULL) ScriptEventController::CreateEventPointer();
+	if (ScriptObject::GetEventPointer() == nullptr) ScriptEventController::CreateEventPointer();
 	ScriptEventData *data = (ScriptEventData *)ScriptObject::GetEventPointer();
 
 	return !data->stack.empty();
@@ -53,10 +53,10 @@ struct ScriptEventData {
 
 /* static */ ScriptEvent *ScriptEventController::GetNextEvent()
 {
-	if (ScriptObject::GetEventPointer() == NULL) ScriptEventController::CreateEventPointer();
+	if (ScriptObject::GetEventPointer() == nullptr) ScriptEventController::CreateEventPointer();
 	ScriptEventData *data = (ScriptEventData *)ScriptObject::GetEventPointer();
 
-	if (data->stack.empty()) return NULL;
+	if (data->stack.empty()) return nullptr;
 
 	ScriptEvent *e = data->stack.front();
 	data->stack.pop();
@@ -65,7 +65,7 @@ struct ScriptEventData {
 
 /* static */ void ScriptEventController::InsertEvent(ScriptEvent *event)
 {
-	if (ScriptObject::GetEventPointer() == NULL) ScriptEventController::CreateEventPointer();
+	if (ScriptObject::GetEventPointer() == nullptr) ScriptEventController::CreateEventPointer();
 	ScriptEventData *data = (ScriptEventData *)ScriptObject::GetEventPointer();
 
 	event->AddRef();
diff --git a/src/script/api/script_event_types.cpp b/src/script/api/script_event_types.cpp
--- a/src/script/api/script_event_types.cpp
+++ b/src/script/api/script_event_types.cpp
@@ -25,12 +25,12 @@
 bool ScriptEventEnginePreview::IsEngineValid() const
 {
 	const Engine *e = ::Engine::GetIfValid(this->engine);
-	return e != NULL && e->IsEnabled();
+	return e != nullptr && e->IsEnabled();
 }
 
 char *ScriptEventEnginePreview::GetName()
 {
-	if (!this->IsEngineValid()) return NULL;
+	if (!this->IsEngineValid()) return nullptr;
 
 	::SetDParam(0, this->engine);
 	return GetString(STR_ENGINE_NAME);
@@ -132,13 +132,13 @@ ScriptEventAdminPort::~ScriptEventAdminP
 }
 
 #define SKIP_EMPTY(p) while (*(p) == ' ' || *(p) == '\n' || *(p) == '\r') (p)++;
-#define RETURN_ERROR(stack) { ScriptLog::Error("Received invalid JSON data from AdminPort."); if (stack != 0) sq_pop(vm, stack); return NULL; }
+#define RETURN_ERROR(stack) { ScriptLog::Error("Received invalid JSON data from AdminPort."); if (stack != 0) sq_pop(vm, stack); return nullptr; }
 
 SQInteger ScriptEventAdminPort::GetObject(HSQUIRRELVM vm)
 {
 	char *p = this->json;
 
-	if (this->ReadTable(vm, p) == NULL) {
+	if (this->ReadTable(vm, p) == nullptr) {
 		sq_pushnull(vm);
 		return 1;
 	}
@@ -189,18 +189,18 @@ char *ScriptEventAdminPort::ReadTable(HS
 		if (*p++ != '"') RETURN_ERROR(1);
 
 		p = ReadString(vm, p);
-		if (p == NULL) {
+		if (p == nullptr) {
 			sq_pop(vm, 1);
-			return NULL;
+			return nullptr;
 		}
 
 		SKIP_EMPTY(p);
 		if (*p++ != ':') RETURN_ERROR(2);
 
 		p = this->ReadValue(vm, p);
-		if (p == NULL) {
+		if (p == nullptr) {
 			sq_pop(vm, 2);
-			return NULL;
+			return nullptr;
 		}
 
 		sq_rawset(vm, -3);
@@ -241,7 +241,7 @@ char *ScriptEventAdminPort::ReadValue(HS
 		case '"': {
 			/* String */
 			p = ReadString(vm, ++p);
-			if (p == NULL) return NULL;
+			if (p == nullptr) return nullptr;
 
 			break;
 		}
@@ -249,7 +249,7 @@ char *ScriptEventAdminPort::ReadValue(HS
 		case '{': {
 			/* Table */
 			p = this->ReadTable(vm, p);
-			if (p == NULL) return NULL;
+			if (p == nullptr) return nullptr;
 
 			break;
 		}
@@ -268,9 +268,9 @@ char *ScriptEventAdminPort::ReadValue(HS
 
 			while (*p++ != ']') {
 				p = this->ReadValue(vm, p);
-				if (p == NULL) {
+				if (p == nullptr) {
 					sq_pop(vm, 1);
-					return NULL;
+					return nullptr;
 				}
 				sq_arrayappend(vm, -2);
 
diff --git a/src/script/api/script_gamesettings.cpp b/src/script/api/script_gamesettings.cpp
--- a/src/script/api/script_gamesettings.cpp
+++ b/src/script/api/script_gamesettings.cpp
@@ -21,7 +21,7 @@
 {
 	uint i;
 	const SettingDesc *sd = GetSettingFromName(setting, &i);
-	return sd != NULL && sd->desc.cmd != SDT_STRING;
+	return sd != nullptr && sd->desc.cmd != SDT_STRING;
 }
 
 /* static */ int32 ScriptGameSettings::GetValue(const char *setting)
diff --git a/src/script/api/script_goal.cpp b/src/script/api/script_goal.cpp
--- a/src/script/api/script_goal.cpp
+++ b/src/script/api/script_goal.cpp
@@ -34,14 +34,14 @@
 	CCountedPtr<Text> counter(goal);
 
 	EnforcePrecondition(GOAL_INVALID, ScriptObject::GetCompany() == OWNER_DEITY);
-	EnforcePrecondition(GOAL_INVALID, goal != NULL);
+	EnforcePrecondition(GOAL_INVALID, goal != nullptr);
 	const char *text = goal->GetEncodedText();
 	EnforcePreconditionEncodedText(GOAL_INVALID, text);
 	EnforcePrecondition(GOAL_INVALID, company == ScriptCompany::COMPANY_INVALID || ScriptCompany::ResolveCompanyID(company) != ScriptCompany::COMPANY_INVALID);
 
 	uint8 c = company;
 	if (company == ScriptCompany::COMPANY_INVALID) c = INVALID_COMPANY;
-	StoryPage *story_page = NULL;
+	StoryPage *story_page = nullptr;
 	if (type == GT_STORY_PAGE && ScriptStoryPage::IsValidStoryPage((ScriptStoryPage::StoryPageID)destination)) story_page = ::StoryPage::Get((ScriptStoryPage::StoryPageID)destination);
 
 	EnforcePrecondition(GOAL_INVALID, (type == GT_NONE && destination == 0) ||
@@ -49,7 +49,7 @@
 			(type == GT_INDUSTRY && ScriptIndustry::IsValidIndustry(destination)) ||
 			(type == GT_TOWN && ScriptTown::IsValidTown(destination)) ||
 			(type == GT_COMPANY && ScriptCompany::ResolveCompanyID((ScriptCompany::CompanyID)destination) != ScriptCompany::COMPANY_INVALID) ||
-			(type == GT_STORY_PAGE && story_page != NULL && (c == INVALID_COMPANY ? story_page->company == INVALID_COMPANY : story_page->company == INVALID_COMPANY || story_page->company == c)));
+			(type == GT_STORY_PAGE && story_page != nullptr && (c == INVALID_COMPANY ? story_page->company == INVALID_COMPANY : story_page->company == INVALID_COMPANY || story_page->company == c)));
 
 	if (!ScriptObject::DoCommand(0, type | (c << 8), destination, CMD_CREATE_GOAL, text, &ScriptInstance::DoCommandReturnGoalID)) return GOAL_INVALID;
 
@@ -71,7 +71,7 @@
 
 	EnforcePrecondition(false, IsValidGoal(goal_id));
 	EnforcePrecondition(false, ScriptObject::GetCompany() == OWNER_DEITY);
-	EnforcePrecondition(false, goal != NULL);
+	EnforcePrecondition(false, goal != nullptr);
 	EnforcePrecondition(false, !StrEmpty(goal->GetEncodedText()));
 
 	return ScriptObject::DoCommand(0, goal_id, 0, CMD_SET_GOAL_TEXT, goal->GetEncodedText());
@@ -85,11 +85,11 @@
 	EnforcePrecondition(false, ScriptObject::GetCompany() == OWNER_DEITY);
 
 	/* Ensure null as used for emtpy string. */
-	if (progress != NULL && StrEmpty(progress->GetEncodedText())) {
-		progress = NULL;
+	if (progress != nullptr && StrEmpty(progress->GetEncodedText())) {
+		progress = nullptr;
 	}
 
-	return ScriptObject::DoCommand(0, goal_id, 0, CMD_SET_GOAL_PROGRESS, progress != NULL ? progress->GetEncodedText() : NULL);
+	return ScriptObject::DoCommand(0, goal_id, 0, CMD_SET_GOAL_PROGRESS, progress != nullptr ? progress->GetEncodedText() : nullptr);
 }
 
 /* static */ bool ScriptGoal::SetCompleted(GoalID goal_id, bool completed)
@@ -106,7 +106,7 @@
 	EnforcePrecondition(false, ScriptObject::GetCompany() == OWNER_DEITY);
 
 	Goal *g = Goal::Get(goal_id);
-	return g != NULL && g->completed;
+	return g != nullptr && g->completed;
 }
 
 /* static */ bool ScriptGoal::DoQuestion(uint16 uniqueid, uint8 target, bool is_client, Text *question, QuestionType type, int buttons)
@@ -114,7 +114,7 @@
 	CCountedPtr<Text> counter(question);
 
 	EnforcePrecondition(false, ScriptObject::GetCompany() == OWNER_DEITY);
-	EnforcePrecondition(false, question != NULL);
+	EnforcePrecondition(false, question != nullptr);
 	const char *text = question->GetEncodedText();
 	EnforcePreconditionEncodedText(false, text);
 	EnforcePrecondition(false, CountBits(buttons) >= 1 && CountBits(buttons) <= 3);
diff --git a/src/script/api/script_goal.hpp b/src/script/api/script_goal.hpp
--- a/src/script/api/script_goal.hpp
+++ b/src/script/api/script_goal.hpp
@@ -99,7 +99,7 @@ public:
 	 * @param destination The destination of the \a type type.
 	 * @return The new GoalID, or GOAL_INVALID if it failed.
 	 * @pre No ScriptCompanyMode may be in scope.
-	 * @pre goal != NULL && len(goal) != 0.
+	 * @pre goal != nullptr && len(goal) != 0.
 	 * @pre company == COMPANY_INVALID || ResolveCompanyID(company) != COMPANY_INVALID.
 	 * @pre if type is GT_STORY_PAGE, the company of the goal and the company of the story page need to match:
 	 *       \li Global goals can only reference global story pages.
@@ -122,7 +122,7 @@ public:
 	 * @param goal The new goal text (can be either a raw string, or a ScriptText object).
 	 * @return True if the action succeeded.
 	 * @pre No ScriptCompanyMode may be in scope.
-	 * @pre goal != NULL && len(goal) != 0.
+	 * @pre goal != nullptr && len(goal) != 0.
 	 * @pre IsValidGoal(goal_id).
 	 */
 	static bool SetText(GoalID goal_id, Text *goal);
@@ -133,7 +133,7 @@ public:
 	 * the progress string short.
 	 * @param goal_id The goal to update.
 	 * @param progress The new progress text for the goal (can be either a raw string,
-	 * or a ScriptText object). To clear the progress string you can pass NULL or an
+	 * or a ScriptText object). To clear the progress string you can pass nullptr or an
 	 * empty string.
 	 * @return True if the action succeeded.
 	 * @pre No ScriptCompanyMode may be in scope.
@@ -169,7 +169,7 @@ public:
 	 * @param buttons Any combinations (at least 1, up to 3) of buttons defined in QuestionButton. Like BUTTON_YES + BUTTON_NO.
 	 * @return True if the action succeeded.
 	 * @pre No ScriptCompanyMode may be in scope.
-	 * @pre question != NULL && len(question) != 0.
+	 * @pre question != nullptr && len(question) != 0.
 	 * @pre company == COMPANY_INVALID || ResolveCompanyID(company) != COMPANY_INVALID.
 	 * @pre CountBits(buttons) >= 1 && CountBits(buttons) <= 3.
 	 * @note Replies to the question are given by you via the event ScriptEvent_GoalQuestionAnswer.
@@ -187,7 +187,7 @@ public:
 	 * @return True if the action succeeded.
 	 * @pre No ScriptCompanyMode may be in scope.
 	 * @pre ScriptGame::IsMultiplayer()
-	 * @pre question != NULL && len(question) != 0.
+	 * @pre question != nullptr && len(question) != 0.
 	 * @pre ResolveClientID(client) != CLIENT_INVALID.
 	 * @pre CountBits(buttons) >= 1 && CountBits(buttons) <= 3.
 	 * @note Replies to the question are given by you via the event ScriptEvent_GoalQuestionAnswer.
diff --git a/src/script/api/script_group.cpp b/src/script/api/script_group.cpp
--- a/src/script/api/script_group.cpp
+++ b/src/script/api/script_group.cpp
@@ -25,12 +25,12 @@
 /* static */ bool ScriptGroup::IsValidGroup(GroupID group_id)
 {
 	const Group *g = ::Group::GetIfValid(group_id);
-	return g != NULL && g->owner == ScriptObject::GetCompany();
+	return g != nullptr && g->owner == ScriptObject::GetCompany();
 }
 
 /* static */ ScriptGroup::GroupID ScriptGroup::CreateGroup(ScriptVehicle::VehicleType vehicle_type, GroupID parent_group_id)
 {
-	if (!ScriptObject::DoCommand(0, (::VehicleType)vehicle_type, parent_group_id, CMD_CREATE_GROUP, NULL, &ScriptInstance::DoCommandReturnGroupID)) return GROUP_INVALID;
+	if (!ScriptObject::DoCommand(0, (::VehicleType)vehicle_type, parent_group_id, CMD_CREATE_GROUP, nullptr, &ScriptInstance::DoCommandReturnGroupID)) return GROUP_INVALID;
 
 	/* In case of test-mode, we return GroupID 0 */
 	return (ScriptGroup::GroupID)0;
@@ -55,7 +55,7 @@
 	CCountedPtr<Text> counter(name);
 
 	EnforcePrecondition(false, IsValidGroup(group_id));
-	EnforcePrecondition(false, name != NULL);
+	EnforcePrecondition(false, name != nullptr);
 	const char *text = name->GetDecodedText();
 	EnforcePreconditionEncodedText(false, text);
 	EnforcePreconditionCustomError(false, ::Utf8StringLength(text) < MAX_LENGTH_GROUP_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
@@ -65,7 +65,7 @@
 
 /* static */ char *ScriptGroup::GetName(GroupID group_id)
 {
-	if (!IsValidGroup(group_id)) return NULL;
+	if (!IsValidGroup(group_id)) return nullptr;
 
 	::SetDParam(0, group_id);
 	return GetString(STR_GROUP_NAME);
diff --git a/src/script/api/script_group.hpp b/src/script/api/script_group.hpp
--- a/src/script/api/script_group.hpp
+++ b/src/script/api/script_group.hpp
@@ -71,7 +71,7 @@ public:
 	 * @param group_id The group to set the name for.
 	 * @param name The name for the group (can be either a raw string, or a ScriptText object).
 	 * @pre IsValidGroup(group_id).
-	 * @pre name != NULL && len(name) != 0
+	 * @pre name != nullptr && len(name) != 0
 	 * @exception ScriptError::ERR_NAME_IS_NOT_UNIQUE
 	 * @return True if and only if the name was changed.
 	 */
diff --git a/src/script/api/script_industry.cpp b/src/script/api/script_industry.cpp
--- a/src/script/api/script_industry.cpp
+++ b/src/script/api/script_industry.cpp
@@ -39,7 +39,7 @@
 
 /* static */ char *ScriptIndustry::GetName(IndustryID industry_id)
 {
-	if (!IsValidIndustry(industry_id)) return NULL;
+	if (!IsValidIndustry(industry_id)) return nullptr;
 
 	::SetDParam(0, industry_id);
 	return GetString(STR_INDUSTRY_NAME);
diff --git a/src/script/api/script_industrytype.cpp b/src/script/api/script_industrytype.cpp
--- a/src/script/api/script_industrytype.cpp
+++ b/src/script/api/script_industrytype.cpp
@@ -59,14 +59,14 @@
 
 /* static */ char *ScriptIndustryType::GetName(IndustryType industry_type)
 {
-	if (!IsValidIndustryType(industry_type)) return NULL;
+	if (!IsValidIndustryType(industry_type)) return nullptr;
 
 	return GetString(::GetIndustrySpec(industry_type)->name);
 }
 
 /* static */ ScriptList *ScriptIndustryType::GetProducedCargo(IndustryType industry_type)
 {
-	if (!IsValidIndustryType(industry_type)) return NULL;
+	if (!IsValidIndustryType(industry_type)) return nullptr;
 
 	const IndustrySpec *ins = ::GetIndustrySpec(industry_type);
 
@@ -80,7 +80,7 @@
 
 /* static */ ScriptList *ScriptIndustryType::GetAcceptedCargo(IndustryType industry_type)
 {
-	if (!IsValidIndustryType(industry_type)) return NULL;
+	if (!IsValidIndustryType(industry_type)) return nullptr;
 
 	const IndustrySpec *ins = ::GetIndustrySpec(industry_type);
 
diff --git a/src/script/api/script_list.cpp b/src/script/api/script_list.cpp
--- a/src/script/api/script_list.cpp
+++ b/src/script/api/script_list.cpp
@@ -109,7 +109,7 @@ public:
 
 	void End()
 	{
-		this->bucket_list = NULL;
+		this->bucket_list = nullptr;
 		this->has_no_more_items = true;
 		this->item_next = 0;
 	}
@@ -119,7 +119,7 @@ public:
 	 */
 	void FindNext()
 	{
-		if (this->bucket_list == NULL) {
+		if (this->bucket_list == nullptr) {
 			this->has_no_more_items = true;
 			return;
 		}
@@ -128,7 +128,7 @@ public:
 		if (this->bucket_list_iter == this->bucket_list->end()) {
 			this->bucket_iter++;
 			if (this->bucket_iter == this->list->buckets.end()) {
-				this->bucket_list = NULL;
+				this->bucket_list = nullptr;
 				return;
 			}
 			this->bucket_list = &(*this->bucket_iter).second;
@@ -203,7 +203,7 @@ public:
 
 	void End()
 	{
-		this->bucket_list = NULL;
+		this->bucket_list = nullptr;
 		this->has_no_more_items = true;
 		this->item_next = 0;
 	}
@@ -213,14 +213,14 @@ public:
 	 */
 	void FindNext()
 	{
-		if (this->bucket_list == NULL) {
+		if (this->bucket_list == nullptr) {
 			this->has_no_more_items = true;
 			return;
 		}
 
 		if (this->bucket_list_iter == this->bucket_list->begin()) {
 			if (this->bucket_iter == this->list->buckets.begin()) {
-				this->bucket_list = NULL;
+				this->bucket_list = nullptr;
 				return;
 			}
 			this->bucket_iter--;
diff --git a/src/script/api/script_list.hpp b/src/script/api/script_list.hpp
--- a/src/script/api/script_list.hpp
+++ b/src/script/api/script_list.hpp
@@ -198,7 +198,7 @@ public:
 	/**
 	 * Remove everything that is in the given list from this list (same item index that is).
 	 * @param list the list of items to remove.
-	 * @pre list != NULL
+	 * @pre list != nullptr
 	 */
 	void RemoveList(ScriptList *list);
 
@@ -242,7 +242,7 @@ public:
 	/**
 	 * Keeps everything that is in the given list from this list (same item index that is).
 	 * @param list the list of items to keep.
-	 * @pre list != NULL
+	 * @pre list != nullptr
 	 */
 	void KeepList(ScriptList *list);
 
diff --git a/src/script/api/script_log.cpp b/src/script/api/script_log.cpp
--- a/src/script/api/script_log.cpp
+++ b/src/script/api/script_log.cpp
@@ -35,7 +35,7 @@
 
 /* static */ void ScriptLog::Log(ScriptLog::ScriptLogType level, const char *message)
 {
-	if (ScriptObject::GetLogPointer() == NULL) {
+	if (ScriptObject::GetLogPointer() == nullptr) {
 		ScriptObject::GetLogPointer() = new LogData();
 		LogData *log = (LogData *)ScriptObject::GetLogPointer();
 
@@ -59,7 +59,7 @@
 
 	/* Cut string after first \n */
 	char *p;
-	while ((p = strchr(log->lines[log->pos], '\n')) != NULL) {
+	while ((p = strchr(log->lines[log->pos], '\n')) != nullptr) {
 		*p = '\0';
 		break;
 	}
diff --git a/src/script/api/script_marine.cpp b/src/script/api/script_marine.cpp
--- a/src/script/api/script_marine.cpp
+++ b/src/script/api/script_marine.cpp
@@ -166,9 +166,9 @@
 /* static */ Money ScriptMarine::GetBuildCost(BuildType build_type)
 {
 	switch (build_type) {
-		case BT_DOCK:  return ::GetPrice(PR_BUILD_STATION_DOCK, 1, NULL);
-		case BT_DEPOT: return ::GetPrice(PR_BUILD_DEPOT_SHIP, 1, NULL);
-		case BT_BUOY:  return ::GetPrice(PR_BUILD_WAYPOINT_BUOY, 1, NULL);
+		case BT_DOCK:  return ::GetPrice(PR_BUILD_STATION_DOCK, 1, nullptr);
+		case BT_DEPOT: return ::GetPrice(PR_BUILD_DEPOT_SHIP, 1, nullptr);
+		case BT_BUOY:  return ::GetPrice(PR_BUILD_WAYPOINT_BUOY, 1, nullptr);
 		default: return -1;
 	}
 }
diff --git a/src/script/api/script_news.cpp b/src/script/api/script_news.cpp
--- a/src/script/api/script_news.cpp
+++ b/src/script/api/script_news.cpp
@@ -25,7 +25,7 @@
 {
 	CCountedPtr<Text> counter(text);
 
-	EnforcePrecondition(false, text != NULL);
+	EnforcePrecondition(false, text != nullptr);
 	const char *encoded = text->GetEncodedText();
 	EnforcePreconditionEncodedText(false, encoded);
 	EnforcePrecondition(false, type == NT_ECONOMY || type == NT_SUBSIDIES || type == NT_GENERAL);
diff --git a/src/script/api/script_news.hpp b/src/script/api/script_news.hpp
--- a/src/script/api/script_news.hpp
+++ b/src/script/api/script_news.hpp
@@ -61,7 +61,7 @@ public:
 	 *  - For #NR_TOWN this parameter should be a valid townID (ScriptTown::IsValidTown).
 	 * @return True if the action succeeded.
 	 * @pre type must be #NT_ECONOMY, #NT_SUBSIDIES, or #NT_GENERAL.
-	 * @pre text != NULL.
+	 * @pre text != nullptr.
 	 * @pre company == COMPANY_INVALID || ResolveCompanyID(company) != COMPANY_INVALID.
 	 * @pre The \a reference condition must be fulfilled.
 	 */
diff --git a/src/script/api/script_object.cpp b/src/script/api/script_object.cpp
--- a/src/script/api/script_object.cpp
+++ b/src/script/api/script_object.cpp
@@ -36,7 +36,7 @@ static ScriptStorage *GetStorage()
 }
 
 
-/* static */ ScriptInstance *ScriptObject::ActiveInstance::active = NULL;
+/* static */ ScriptInstance *ScriptObject::ActiveInstance::active = nullptr;
 
 ScriptObject::ActiveInstance::ActiveInstance(ScriptInstance *instance)
 {
@@ -51,7 +51,7 @@ ScriptObject::ActiveInstance::~ActiveIns
 
 /* static */ ScriptInstance *ScriptObject::GetActiveInstance()
 {
-	assert(ScriptObject::ActiveInstance::active != NULL);
+	assert(ScriptObject::ActiveInstance::active != nullptr);
 	return ScriptObject::ActiveInstance::active;
 }
 
@@ -296,16 +296,16 @@ ScriptObject::ActiveInstance::~ActiveIns
 	}
 
 	/* Set the default callback to return a true/false result of the DoCommand */
-	if (callback == NULL) callback = &ScriptInstance::DoCommandReturn;
+	if (callback == nullptr) callback = &ScriptInstance::DoCommandReturn;
 
 	/* Are we only interested in the estimate costs? */
-	bool estimate_only = GetDoCommandMode() != NULL && !GetDoCommandMode()();
+	bool estimate_only = GetDoCommandMode() != nullptr && !GetDoCommandMode()();
 
 	/* Only set p2 when the command does not come from the network. */
 	if (GetCommandFlags(cmd) & CMD_CLIENT_ID && p2 == 0) p2 = UINT32_MAX;
 
 	/* Try to perform the command. */
-	CommandCost res = ::DoCommandPInternal(tile, p1, p2, cmd, (_networking && !_generating_world) ? ScriptObject::GetActiveInstance()->GetDoCommandCallback() : NULL, text, false, estimate_only);
+	CommandCost res = ::DoCommandPInternal(tile, p1, p2, cmd, (_networking && !_generating_world) ? ScriptObject::GetActiveInstance()->GetDoCommandCallback() : nullptr, text, false, estimate_only);
 
 	/* We failed; set the error and bail out */
 	if (res.Failed()) {
@@ -328,7 +328,7 @@ ScriptObject::ActiveInstance::~ActiveIns
 
 	if (_generating_world) {
 		IncreaseDoCommandCosts(res.GetCost());
-		if (callback != NULL) {
+		if (callback != nullptr) {
 			/* Insert return value into to stack and throw a control code that
 			 * the return value in the stack should be used. */
 			callback(GetActiveInstance());
diff --git a/src/script/api/script_object.hpp b/src/script/api/script_object.hpp
--- a/src/script/api/script_object.hpp
+++ b/src/script/api/script_object.hpp
@@ -69,7 +69,7 @@ protected:
 	/**
 	 * Executes a raw DoCommand for the script.
 	 */
-	static bool DoCommand(TileIndex tile, uint32 p1, uint32 p2, uint cmd, const char *text = NULL, Script_SuspendCallbackProc *callback = NULL);
+	static bool DoCommand(TileIndex tile, uint32 p1, uint32 p2, uint cmd, const char *text = nullptr, Script_SuspendCallbackProc *callback = nullptr);
 
 	/**
 	 * Sets the DoCommand costs counter to a value.
diff --git a/src/script/api/script_order.cpp b/src/script/api/script_order.cpp
--- a/src/script/api/script_order.cpp
+++ b/src/script/api/script_order.cpp
@@ -66,7 +66,7 @@ static const Order *ResolveOrder(Vehicle
 		const Order *order = &v->current_order;
 		if (order->GetType() == OT_GOTO_DEPOT && !(order->GetDepotOrderType() & ODTFB_PART_OF_ORDERS)) return order;
 		order_position = ScriptOrder::ResolveOrderPosition(vehicle_id, order_position);
-		if (order_position == ScriptOrder::ORDER_INVALID) return NULL;
+		if (order_position == ScriptOrder::ORDER_INVALID) return nullptr;
 	}
 	const Order *order = v->GetFirstOrder();
 	while (order->GetType() == OT_IMPLICIT) order = order->next;
@@ -108,7 +108,7 @@ static int ScriptOrderPositionToRealOrde
 	if (!IsValidVehicleOrder(vehicle_id, order_position)) return false;
 
 	const Order *order = ::ResolveOrder(vehicle_id, order_position);
-	return order != NULL && order->GetType() == OT_GOTO_STATION;
+	return order != nullptr && order->GetType() == OT_GOTO_STATION;
 }
 
 /* static */ bool ScriptOrder::IsGotoDepotOrder(VehicleID vehicle_id, OrderPosition order_position)
@@ -116,7 +116,7 @@ static int ScriptOrderPositionToRealOrde
 	if (!IsValidVehicleOrder(vehicle_id, order_position)) return false;
 
 	const Order *order = ::ResolveOrder(vehicle_id, order_position);
-	return order != NULL && order->GetType() == OT_GOTO_DEPOT;
+	return order != nullptr && order->GetType() == OT_GOTO_DEPOT;
 }
 
 /* static */ bool ScriptOrder::IsGotoWaypointOrder(VehicleID vehicle_id, OrderPosition order_position)
@@ -124,7 +124,7 @@ static int ScriptOrderPositionToRealOrde
 	if (!IsValidVehicleOrder(vehicle_id, order_position)) return false;
 
 	const Order *order = ::ResolveOrder(vehicle_id, order_position);
-	return order != NULL && order->GetType() == OT_GOTO_WAYPOINT;
+	return order != nullptr && order->GetType() == OT_GOTO_WAYPOINT;
 }
 
 /* static */ bool ScriptOrder::IsConditionalOrder(VehicleID vehicle_id, OrderPosition order_position)
@@ -150,7 +150,7 @@ static int ScriptOrderPositionToRealOrde
 	if (!IsValidVehicleOrder(vehicle_id, order_position)) return false;
 
 	const Order *order = ::ResolveOrder(vehicle_id, order_position);
-	return order != NULL && order->IsRefit();
+	return order != nullptr && order->IsRefit();
 }
 
 /* static */ bool ScriptOrder::IsCurrentOrderPartOfOrderList(VehicleID vehicle_id)
@@ -240,7 +240,7 @@ static int ScriptOrderPositionToRealOrde
 	if (!IsValidVehicleOrder(vehicle_id, order_position)) return INVALID_TILE;
 
 	const Order *order = ::ResolveOrder(vehicle_id, order_position);
-	if (order == NULL || order->GetType() == OT_CONDITIONAL) return INVALID_TILE;
+	if (order == nullptr || order->GetType() == OT_CONDITIONAL) return INVALID_TILE;
 	const Vehicle *v = ::Vehicle::Get(vehicle_id);
 
 	switch (order->GetType()) {
@@ -263,9 +263,9 @@ static int ScriptOrderPositionToRealOrde
 				}
 			} else if (st->dock_tile != INVALID_TILE) {
 				return st->dock_tile;
-			} else if (st->bus_stops != NULL) {
+			} else if (st->bus_stops != nullptr) {
 				return st->bus_stops->xy;
-			} else if (st->truck_stops != NULL) {
+			} else if (st->truck_stops != nullptr) {
 				return st->truck_stops->xy;
 			} else if (st->airport.tile != INVALID_TILE) {
 				TILE_AREA_LOOP(tile, st->airport) {
@@ -294,7 +294,7 @@ static int ScriptOrderPositionToRealOrde
 	if (!IsValidVehicleOrder(vehicle_id, order_position)) return OF_INVALID;
 
 	const Order *order = ::ResolveOrder(vehicle_id, order_position);
-	if (order == NULL || order->GetType() == OT_CONDITIONAL || order->GetType() == OT_DUMMY) return OF_INVALID;
+	if (order == nullptr || order->GetType() == OT_CONDITIONAL || order->GetType() == OT_DUMMY) return OF_INVALID;
 
 	ScriptOrderFlags order_flags = OF_NONE;
 	order_flags |= (ScriptOrderFlags)order->GetNonStopType();
@@ -586,7 +586,7 @@ static void _DoCommandReturnSetOrderFlag
 	EnforcePrecondition(false, (order_flags & OF_GOTO_NEAREST_DEPOT) == (current & OF_GOTO_NEAREST_DEPOT));
 
 	if ((current & OF_NON_STOP_FLAGS) != (order_flags & OF_NON_STOP_FLAGS)) {
-		return ScriptObject::DoCommand(0, vehicle_id | (order_pos << 20), (order_flags & OF_NON_STOP_FLAGS) << 4 | MOF_NON_STOP, CMD_MODIFY_ORDER, NULL, &::_DoCommandReturnSetOrderFlags);
+		return ScriptObject::DoCommand(0, vehicle_id | (order_pos << 20), (order_flags & OF_NON_STOP_FLAGS) << 4 | MOF_NON_STOP, CMD_MODIFY_ORDER, nullptr, &::_DoCommandReturnSetOrderFlags);
 	}
 
 	switch (order->GetType()) {
@@ -595,16 +595,16 @@ static void _DoCommandReturnSetOrderFlag
 				uint data = DA_ALWAYS_GO;
 				if (order_flags & OF_SERVICE_IF_NEEDED) data = DA_SERVICE;
 				if (order_flags & OF_STOP_IN_DEPOT) data = DA_STOP;
-				return ScriptObject::DoCommand(0, vehicle_id | (order_pos << 20), (data << 4) | MOF_DEPOT_ACTION, CMD_MODIFY_ORDER, NULL, &::_DoCommandReturnSetOrderFlags);
+				return ScriptObject::DoCommand(0, vehicle_id | (order_pos << 20), (data << 4) | MOF_DEPOT_ACTION, CMD_MODIFY_ORDER, nullptr, &::_DoCommandReturnSetOrderFlags);
 			}
 			break;
 
 		case OT_GOTO_STATION:
 			if ((current & OF_UNLOAD_FLAGS) != (order_flags & OF_UNLOAD_FLAGS)) {
-				return ScriptObject::DoCommand(0, vehicle_id | (order_pos << 20), (order_flags & OF_UNLOAD_FLAGS) << 2 | MOF_UNLOAD, CMD_MODIFY_ORDER, NULL, &::_DoCommandReturnSetOrderFlags);
+				return ScriptObject::DoCommand(0, vehicle_id | (order_pos << 20), (order_flags & OF_UNLOAD_FLAGS) << 2 | MOF_UNLOAD, CMD_MODIFY_ORDER, nullptr, &::_DoCommandReturnSetOrderFlags);
 			}
 			if ((current & OF_LOAD_FLAGS) != (order_flags & OF_LOAD_FLAGS)) {
-				return ScriptObject::DoCommand(0, vehicle_id | (order_pos << 20), (order_flags & OF_LOAD_FLAGS) >> 1 | MOF_LOAD, CMD_MODIFY_ORDER, NULL, &::_DoCommandReturnSetOrderFlags);
+				return ScriptObject::DoCommand(0, vehicle_id | (order_pos << 20), (order_flags & OF_LOAD_FLAGS) >> 1 | MOF_LOAD, CMD_MODIFY_ORDER, nullptr, &::_DoCommandReturnSetOrderFlags);
 			}
 			break;
 
diff --git a/src/script/api/script_rail.cpp b/src/script/api/script_rail.cpp
--- a/src/script/api/script_rail.cpp
+++ b/src/script/api/script_rail.cpp
@@ -25,7 +25,7 @@
 
 /* static */ char *ScriptRail::GetName(RailType rail_type)
 {
-	if (!IsRailTypeAvailable(rail_type)) return NULL;
+	if (!IsRailTypeAvailable(rail_type)) return nullptr;
 
 	return GetString(GetRailTypeInfo((::RailType)rail_type)->strings.menu_text);
 }
@@ -185,7 +185,7 @@
 	if (res != CALLBACK_FAILED) {
 		int index = 0;
 		const StationSpec *spec = StationClass::GetByGrf(file->grfid, res, &index);
-		if (spec == NULL) {
+		if (spec == nullptr) {
 			DEBUG(grf, 1, "%s returned an invalid station ID for 'AI construction/purchase selection (18)' callback", file->filename);
 		} else {
 			/* We might have gotten an usable station spec. Try to build it, but if it fails we'll fall back to the original station. */
@@ -487,10 +487,10 @@ static bool IsValidSignalType(int signal
 
 	switch (build_type) {
 		case BT_TRACK:    return ::RailBuildCost((::RailType)railtype);
-		case BT_SIGNAL:   return ::GetPrice(PR_BUILD_SIGNALS, 1, NULL);
-		case BT_DEPOT:    return ::GetPrice(PR_BUILD_DEPOT_TRAIN, 1, NULL);
-		case BT_STATION:  return ::GetPrice(PR_BUILD_STATION_RAIL, 1, NULL) + ::GetPrice(PR_BUILD_STATION_RAIL_LENGTH, 1, NULL);
-		case BT_WAYPOINT: return ::GetPrice(PR_BUILD_WAYPOINT_RAIL, 1, NULL);
+		case BT_SIGNAL:   return ::GetPrice(PR_BUILD_SIGNALS, 1, nullptr);
+		case BT_DEPOT:    return ::GetPrice(PR_BUILD_DEPOT_TRAIN, 1, nullptr);
+		case BT_STATION:  return ::GetPrice(PR_BUILD_STATION_RAIL, 1, nullptr) + ::GetPrice(PR_BUILD_STATION_RAIL_LENGTH, 1, nullptr);
+		case BT_WAYPOINT: return ::GetPrice(PR_BUILD_WAYPOINT_RAIL, 1, nullptr);
 		default: return -1;
 	}
 }
diff --git a/src/script/api/script_road.cpp b/src/script/api/script_road.cpp
--- a/src/script/api/script_road.cpp
+++ b/src/script/api/script_road.cpp
@@ -588,10 +588,10 @@ static bool NeighbourHasReachableRoad(::
 	if (!ScriptRoad::IsRoadTypeAvailable(roadtype)) return -1;
 
 	switch (build_type) {
-		case BT_ROAD:       return ::GetPrice(PR_BUILD_ROAD, 1, NULL);
-		case BT_DEPOT:      return ::GetPrice(PR_BUILD_DEPOT_ROAD, 1, NULL);
-		case BT_BUS_STOP:   return ::GetPrice(PR_BUILD_STATION_BUS, 1, NULL);
-		case BT_TRUCK_STOP: return ::GetPrice(PR_BUILD_STATION_TRUCK, 1, NULL);
+		case BT_ROAD:       return ::GetPrice(PR_BUILD_ROAD, 1, nullptr);
+		case BT_DEPOT:      return ::GetPrice(PR_BUILD_DEPOT_ROAD, 1, nullptr);
+		case BT_BUS_STOP:   return ::GetPrice(PR_BUILD_STATION_BUS, 1, nullptr);
+		case BT_TRUCK_STOP: return ::GetPrice(PR_BUILD_STATION_TRUCK, 1, nullptr);
 		default: return -1;
 	}
 }
diff --git a/src/script/api/script_sign.cpp b/src/script/api/script_sign.cpp
--- a/src/script/api/script_sign.cpp
+++ b/src/script/api/script_sign.cpp
@@ -23,7 +23,7 @@
 /* static */ bool ScriptSign::IsValidSign(SignID sign_id)
 {
 	const Sign *si = ::Sign::GetIfValid(sign_id);
-	return si != NULL && (si->owner == ScriptObject::GetCompany() || si->owner == OWNER_DEITY);
+	return si != nullptr && (si->owner == ScriptObject::GetCompany() || si->owner == OWNER_DEITY);
 }
 
 /* static */ ScriptCompany::CompanyID ScriptSign::GetOwner(SignID sign_id)
@@ -38,7 +38,7 @@
 	CCountedPtr<Text> counter(name);
 
 	EnforcePrecondition(false, IsValidSign(sign_id));
-	EnforcePrecondition(false, name != NULL);
+	EnforcePrecondition(false, name != nullptr);
 	const char *text = name->GetDecodedText();
 	EnforcePreconditionEncodedText(false, text);
 	EnforcePreconditionCustomError(false, ::Utf8StringLength(text) < MAX_LENGTH_SIGN_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
@@ -48,7 +48,7 @@
 
 /* static */ char *ScriptSign::GetName(SignID sign_id)
 {
-	if (!IsValidSign(sign_id)) return NULL;
+	if (!IsValidSign(sign_id)) return nullptr;
 
 	::SetDParam(0, sign_id);
 	return GetString(STR_SIGN_NAME);
@@ -73,7 +73,7 @@
 	CCountedPtr<Text> counter(name);
 
 	EnforcePrecondition(INVALID_SIGN, ::IsValidTile(location));
-	EnforcePrecondition(INVALID_SIGN, name != NULL);
+	EnforcePrecondition(INVALID_SIGN, name != nullptr);
 	const char *text = name->GetDecodedText();
 	EnforcePreconditionEncodedText(INVALID_SIGN, text);
 	EnforcePreconditionCustomError(INVALID_SIGN, ::Utf8StringLength(text) < MAX_LENGTH_SIGN_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
diff --git a/src/script/api/script_sign.hpp b/src/script/api/script_sign.hpp
--- a/src/script/api/script_sign.hpp
+++ b/src/script/api/script_sign.hpp
@@ -45,7 +45,7 @@ public:
 	 * @param sign_id The sign to set the name for.
 	 * @param name The name for the sign (can be either a raw string, or a ScriptText object).
 	 * @pre IsValidSign(sign_id).
-	 * @pre name != NULL && len(name) != 0.
+	 * @pre name != nullptr && len(name) != 0.
 	 * @exception ScriptError::ERR_NAME_IS_NOT_UNIQUE
 	 * @return True if and only if the name was changed.
 	 */
@@ -81,7 +81,7 @@ public:
 	 * @param location The place to build the sign.
 	 * @param name The text to place on the sign (can be either a raw string, or a ScriptText object).
 	 * @pre ScriptMap::IsValidTile(location).
-	 * @pre name != NULL && len(name) != 0.
+	 * @pre name != nullptr && len(name) != 0.
 	 * @exception ScriptSign::ERR_SIGN_TOO_MANY_SIGNS
 	 * @return The SignID of the build sign (use IsValidSign() to check for validity).
 	 *   In test-mode it returns 0 if successful, or any other value to indicate
diff --git a/src/script/api/script_station.cpp b/src/script/api/script_station.cpp
--- a/src/script/api/script_station.cpp
+++ b/src/script/api/script_station.cpp
@@ -23,7 +23,7 @@
 /* static */ bool ScriptStation::IsValidStation(StationID station_id)
 {
 	const Station *st = ::Station::GetIfValid(station_id);
-	return st != NULL && (st->owner == ScriptObject::GetCompany() || ScriptObject::GetCompany() == OWNER_DEITY || st->owner == OWNER_NONE);
+	return st != nullptr && (st->owner == ScriptObject::GetCompany() || ScriptObject::GetCompany() == OWNER_DEITY || st->owner == OWNER_NONE);
 }
 
 /* static */ ScriptCompany::CompanyID ScriptStation::GetOwner(StationID station_id)
@@ -213,10 +213,10 @@ template<bool Tfrom, bool Tvia>
 
 	::RoadTypes r = RoadTypeToRoadTypes((::RoadType)road_type);
 
-	for (const RoadStop *rs = ::Station::Get(station_id)->GetPrimaryRoadStop(ROADSTOP_BUS); rs != NULL; rs = rs->next) {
+	for (const RoadStop *rs = ::Station::Get(station_id)->GetPrimaryRoadStop(ROADSTOP_BUS); rs != nullptr; rs = rs->next) {
 		if ((::GetRoadTypes(rs->xy) & r) != 0) return true;
 	}
-	for (const RoadStop *rs = ::Station::Get(station_id)->GetPrimaryRoadStop(ROADSTOP_TRUCK); rs != NULL; rs = rs->next) {
+	for (const RoadStop *rs = ::Station::Get(station_id)->GetPrimaryRoadStop(ROADSTOP_TRUCK); rs != nullptr; rs = rs->next) {
 		if ((::GetRoadTypes(rs->xy) & r) != 0) return true;
 	}
 
diff --git a/src/script/api/script_stationlist.cpp b/src/script/api/script_stationlist.cpp
--- a/src/script/api/script_stationlist.cpp
+++ b/src/script/api/script_stationlist.cpp
@@ -32,7 +32,7 @@ ScriptStationList_Vehicle::ScriptStation
 
 	Vehicle *v = ::Vehicle::Get(vehicle_id);
 
-	for (Order *o = v->GetFirstOrder(); o != NULL; o = o->next) {
+	for (Order *o = v->GetFirstOrder(); o != nullptr; o = o->next) {
 		if (o->IsType(OT_GOTO_STATION)) this->AddItem(o->GetDestination());
 	}
 }
@@ -120,7 +120,7 @@ private:
 
 CargoCollector::CargoCollector(ScriptStationList_Cargo *parent,
 		StationID station_id, CargoID cargo, StationID other) :
-	list(parent), ge(NULL), other_station(other), last_key(INVALID_STATION), amount(0)
+	list(parent), ge(nullptr), other_station(other), last_key(INVALID_STATION), amount(0)
 {
 	if (!ScriptStation::IsValidStation(station_id)) return;
 	if (!ScriptCargo::IsValidCargo(cargo)) return;
@@ -176,7 +176,7 @@ template<ScriptStationList_Cargo::CargoS
 void ScriptStationList_CargoWaiting::Add(StationID station_id, CargoID cargo, StationID other_station)
 {
 	CargoCollector collector(this, station_id, cargo, other_station);
-	if (collector.GE() == NULL) return;
+	if (collector.GE() == nullptr) return;
 
 	StationCargoList::ConstIterator iter = collector.GE()->cargo.Packets()->begin();
 	StationCargoList::ConstIterator end = collector.GE()->cargo.Packets()->end();
@@ -190,7 +190,7 @@ template<ScriptStationList_Cargo::CargoS
 void ScriptStationList_CargoPlanned::Add(StationID station_id, CargoID cargo, StationID other_station)
 {
 	CargoCollector collector(this, station_id, cargo, other_station);
-	if (collector.GE() == NULL) return;
+	if (collector.GE() == nullptr) return;
 
 	FlowStatMap::const_iterator iter = collector.GE()->flows.begin();
 	FlowStatMap::const_iterator end = collector.GE()->flows.end();
@@ -215,7 +215,7 @@ ScriptStationList_CargoWaitingViaByFrom:
 		StationID station_id, CargoID cargo, StationID via)
 {
 	CargoCollector collector(this, station_id, cargo, via);
-	if (collector.GE() == NULL) return;
+	if (collector.GE() == nullptr) return;
 
 	std::pair<StationCargoList::ConstIterator, StationCargoList::ConstIterator> range =
 			collector.GE()->cargo.Packets()->equal_range(via);
@@ -261,7 +261,7 @@ ScriptStationList_CargoPlannedFromByVia:
 		StationID station_id, CargoID cargo, StationID from)
 {
 	CargoCollector collector(this, station_id, cargo, from);
-	if (collector.GE() == NULL) return;
+	if (collector.GE() == nullptr) return;
 
 	FlowStatMap::const_iterator iter = collector.GE()->flows.find(from);
 	if (iter == collector.GE()->flows.end()) return;
diff --git a/src/script/api/script_story_page.cpp b/src/script/api/script_story_page.cpp
--- a/src/script/api/script_story_page.cpp
+++ b/src/script/api/script_story_page.cpp
@@ -48,7 +48,7 @@
 		c,
 		0,
 		CMD_CREATE_STORY_PAGE,
-		title != NULL? title->GetEncodedText() : NULL,
+		title != nullptr? title->GetEncodedText() : nullptr,
 		&ScriptInstance::DoCommandReturnStoryPageID)) return STORY_PAGE_INVALID;
 
 	/* In case of test-mode, we return StoryPageID 0 */
@@ -61,7 +61,7 @@
 
 	EnforcePrecondition(STORY_PAGE_ELEMENT_INVALID, ScriptObject::GetCompany() == OWNER_DEITY);
 	EnforcePrecondition(STORY_PAGE_ELEMENT_INVALID, IsValidStoryPage(story_page_id));
-	EnforcePrecondition(STORY_PAGE_ELEMENT_INVALID, (type != SPET_TEXT && type != SPET_LOCATION) || (text != NULL && !StrEmpty(text->GetEncodedText())));
+	EnforcePrecondition(STORY_PAGE_ELEMENT_INVALID, (type != SPET_TEXT && type != SPET_LOCATION) || (text != nullptr && !StrEmpty(text->GetEncodedText())));
 	EnforcePrecondition(STORY_PAGE_ELEMENT_INVALID, type != SPET_LOCATION || ::IsValidTile(reference));
 	EnforcePrecondition(STORY_PAGE_ELEMENT_INVALID, type != SPET_GOAL || ScriptGoal::IsValidGoal((ScriptGoal::GoalID)reference));
 	EnforcePrecondition(STORY_PAGE_ELEMENT_INVALID, type != SPET_GOAL || !(StoryPage::Get(story_page_id)->company == INVALID_COMPANY && Goal::Get(reference)->company != INVALID_COMPANY));
@@ -70,7 +70,7 @@
 			story_page_id + (type << 16),
 			type == SPET_GOAL ? reference : 0,
 			CMD_CREATE_STORY_PAGE_ELEMENT,
-			type == SPET_TEXT || type == SPET_LOCATION ? text->GetEncodedText() : NULL,
+			type == SPET_TEXT || type == SPET_LOCATION ? text->GetEncodedText() : nullptr,
 			&ScriptInstance::DoCommandReturnStoryPageElementID)) return STORY_PAGE_ELEMENT_INVALID;
 
 	/* In case of test-mode, we return StoryPageElementID 0 */
@@ -88,7 +88,7 @@
 	StoryPage *p = StoryPage::Get(pe->page);
 	::StoryPageElementType type = pe->type;
 
-	EnforcePrecondition(false, (type != ::SPET_TEXT && type != ::SPET_LOCATION) || (text != NULL && !StrEmpty(text->GetEncodedText())));
+	EnforcePrecondition(false, (type != ::SPET_TEXT && type != ::SPET_LOCATION) || (text != nullptr && !StrEmpty(text->GetEncodedText())));
 	EnforcePrecondition(false, type != ::SPET_LOCATION || ::IsValidTile(reference));
 	EnforcePrecondition(false, type != ::SPET_GOAL || ScriptGoal::IsValidGoal((ScriptGoal::GoalID)reference));
 	EnforcePrecondition(false, type != ::SPET_GOAL || !(p->company == INVALID_COMPANY && Goal::Get(reference)->company != INVALID_COMPANY));
@@ -97,7 +97,7 @@
 			story_page_element_id,
 			type == ::SPET_GOAL ? reference : 0,
 			CMD_UPDATE_STORY_PAGE_ELEMENT,
-			type == ::SPET_TEXT || type == ::SPET_LOCATION ? text->GetEncodedText() : NULL);
+			type == ::SPET_TEXT || type == ::SPET_LOCATION ? text->GetEncodedText() : nullptr);
 }
 
 /* static */ uint32 ScriptStoryPage::GetPageSortValue(StoryPageID story_page_id)
@@ -121,7 +121,7 @@
 	EnforcePrecondition(false, IsValidStoryPage(story_page_id));
 	EnforcePrecondition(false, ScriptObject::GetCompany() == OWNER_DEITY);
 
-	return ScriptObject::DoCommand(0, story_page_id, 0, CMD_SET_STORY_PAGE_TITLE, title != NULL? title->GetEncodedText() : NULL);
+	return ScriptObject::DoCommand(0, story_page_id, 0, CMD_SET_STORY_PAGE_TITLE, title != nullptr? title->GetEncodedText() : nullptr);
 }
 
 /* static */ ScriptCompany::CompanyID ScriptStoryPage::GetCompany(StoryPageID story_page_id)
@@ -147,7 +147,7 @@
 	EnforcePrecondition(false, IsValidStoryPage(story_page_id));
 	EnforcePrecondition(false, ScriptObject::GetCompany() == OWNER_DEITY);
 
-	return ScriptObject::DoCommand(0, story_page_id, date, CMD_SET_STORY_PAGE_DATE, NULL);
+	return ScriptObject::DoCommand(0, story_page_id, date, CMD_SET_STORY_PAGE_DATE, nullptr);
 }
 
 
diff --git a/src/script/api/script_story_page.hpp b/src/script/api/script_story_page.hpp
--- a/src/script/api/script_story_page.hpp
+++ b/src/script/api/script_story_page.hpp
@@ -97,7 +97,7 @@ public:
 	 * @return The new StoryPageElementID, or STORY_PAGE_ELEMENT_INVALID if it failed.
 	 * @pre No ScriptCompanyMode may be in scope.
 	 * @pre IsValidStoryPage(story_page).
-	 * @pre (type != SPET_TEXT && type != SPET_LOCATION) || (text != NULL && len(text) != 0).
+	 * @pre (type != SPET_TEXT && type != SPET_LOCATION) || (text != nullptr && len(text) != 0).
 	 * @pre type != SPET_LOCATION || ScriptMap::IsValidTile(reference).
 	 * @pre type != SPET_GOAL || ScriptGoal::IsValidGoal(reference).
 	 * @pre if type is SPET_GOAL and story_page is a global page, then referenced goal must be global.
@@ -112,7 +112,7 @@ public:
 	 * @return True if the action succeeded.
 	 * @pre No ScriptCompanyMode may be in scope.
 	 * @pre IsValidStoryPage(story_page).
-	 * @pre (type != SPET_TEXT && type != SPET_LOCATION) || (text != NULL && len(text) != 0).
+	 * @pre (type != SPET_TEXT && type != SPET_LOCATION) || (text != nullptr && len(text) != 0).
 	 * @pre type != SPET_LOCATION || ScriptMap::IsValidTile(reference).
 	 * @pre type != SPET_GOAL || ScriptGoal::IsValidGoal(reference).
 	 * @pre if type is SPET_GOAL and story_page is a global page, then referenced goal must be global.
diff --git a/src/script/api/script_text.cpp b/src/script/api/script_text.cpp
--- a/src/script/api/script_text.cpp
+++ b/src/script/api/script_text.cpp
@@ -63,7 +63,7 @@ ScriptText::~ScriptText()
 {
 	for (int i = 0; i < SCRIPT_TEXT_MAX_PARAMETERS; i++) {
 		free(this->params[i]);
-		if (this->paramt[i] != NULL) this->paramt[i]->Release();
+		if (this->paramt[i] != nullptr) this->paramt[i]->Release();
 	}
 }
 
@@ -72,11 +72,11 @@ SQInteger ScriptText::_SetParam(int para
 	if (parameter >= SCRIPT_TEXT_MAX_PARAMETERS) return SQ_ERROR;
 
 	free(this->params[parameter]);
-	if (this->paramt[parameter] != NULL) this->paramt[parameter]->Release();
+	if (this->paramt[parameter] != nullptr) this->paramt[parameter]->Release();
 
 	this->parami[parameter] = 0;
-	this->params[parameter] = NULL;
-	this->paramt[parameter] = NULL;
+	this->params[parameter] = nullptr;
+	this->paramt[parameter] = nullptr;
 
 	switch (sq_gettype(vm, -1)) {
 		case OT_STRING: {
@@ -97,7 +97,7 @@ SQInteger ScriptText::_SetParam(int para
 		}
 
 		case OT_INSTANCE: {
-			SQUserPointer real_instance = NULL;
+			SQUserPointer real_instance = nullptr;
 			HSQOBJECT instance;
 
 			sq_getstackobj(vm, -1, &instance);
@@ -112,7 +112,7 @@ SQInteger ScriptText::_SetParam(int para
 
 			/* Get the 'real' instance of this class */
 			sq_getinstanceup(vm, -1, &real_instance, 0);
-			if (real_instance == NULL) return SQ_ERROR;
+			if (real_instance == nullptr) return SQ_ERROR;
 
 			ScriptText *value = static_cast<ScriptText *>(real_instance);
 			value->AddRef();
@@ -183,7 +183,7 @@ const char *ScriptText::GetEncodedText()
 	static char buf[1024];
 	int param_count = 0;
 	this->_GetEncodedText(buf, lastof(buf), param_count);
-	return (param_count > SCRIPT_TEXT_MAX_PARAMETERS) ? NULL : buf;
+	return (param_count > SCRIPT_TEXT_MAX_PARAMETERS) ? nullptr : buf;
 }
 
 char *ScriptText::_GetEncodedText(char *p, char *lastofp, int &param_count)
@@ -191,12 +191,12 @@ char *ScriptText::_GetEncodedText(char *
 	p += Utf8Encode(p, SCC_ENCODED);
 	p += seprintf(p, lastofp, "%X", this->string);
 	for (int i = 0; i < this->paramc; i++) {
-		if (this->params[i] != NULL) {
+		if (this->params[i] != nullptr) {
 			p += seprintf(p, lastofp, ":\"%s\"", this->params[i]);
 			param_count++;
 			continue;
 		}
-		if (this->paramt[i] != NULL) {
+		if (this->paramt[i] != nullptr) {
 			p += seprintf(p, lastofp, ":");
 			p = this->paramt[i]->_GetEncodedText(p, lastofp, param_count);
 			continue;
@@ -211,7 +211,7 @@ char *ScriptText::_GetEncodedText(char *
 const char *Text::GetDecodedText()
 {
 	const char *encoded_text = this->GetEncodedText();
-	if (encoded_text == NULL) return NULL;
+	if (encoded_text == nullptr) return nullptr;
 
 	static char buf[1024];
 	::SetDParamStr(0, encoded_text);
diff --git a/src/script/api/script_text.hpp b/src/script/api/script_text.hpp
--- a/src/script/api/script_text.hpp
+++ b/src/script/api/script_text.hpp
@@ -23,14 +23,14 @@ class Text : public ScriptObject {
 public:
 	/**
 	 * Convert a ScriptText to a normal string.
-	 * @return A string (in a static buffer), or NULL.
+	 * @return A string (in a static buffer), or nullptr.
 	 * @api -all
 	 */
 	virtual const char *GetEncodedText() = 0;
 
 	/**
 	 * Convert a #ScriptText into a decoded normal string.
-	 * @return A string (in a static buffer), or NULL.
+	 * @return A string (in a static buffer), or nullptr.
 	 * @api -all
 	 */
 	const char *GetDecodedText();
diff --git a/src/script/api/script_tile.cpp b/src/script/api/script_tile.cpp
--- a/src/script/api/script_tile.cpp
+++ b/src/script/api/script_tile.cpp
@@ -292,7 +292,7 @@
 	if (!::IsValidTile(tile)) return INVALID_TOWN;
 
 	Town *town = ::ClosestTownFromTile(tile, _settings_game.economy.dist_local_authority);
-	if (town == NULL) return INVALID_TOWN;
+	if (town == nullptr) return INVALID_TOWN;
 
 	return town->index;
 }
@@ -302,7 +302,7 @@
 	if (!::IsValidTile(tile)) return INVALID_TOWN;
 
 	Town *town = ::ClosestTownFromTile(tile, UINT_MAX);
-	if (town == NULL) return INVALID_TOWN;
+	if (town == nullptr) return INVALID_TOWN;
 
 	return town->index;
 }
@@ -310,14 +310,14 @@
 /* static */ Money ScriptTile::GetBuildCost(BuildType build_type)
 {
 	switch (build_type) {
-		case BT_FOUNDATION:   return ::GetPrice(PR_BUILD_FOUNDATION, 1, NULL);
-		case BT_TERRAFORM:    return ::GetPrice(PR_TERRAFORM, 1, NULL);
-		case BT_BUILD_TREES:  return ::GetPrice(PR_BUILD_TREES, 1, NULL);
-		case BT_CLEAR_GRASS:  return ::GetPrice(PR_CLEAR_GRASS, 1, NULL);
-		case BT_CLEAR_ROUGH:  return ::GetPrice(PR_CLEAR_ROUGH, 1, NULL);
-		case BT_CLEAR_ROCKY:  return ::GetPrice(PR_CLEAR_ROCKS, 1, NULL);
-		case BT_CLEAR_FIELDS: return ::GetPrice(PR_CLEAR_FIELDS, 1, NULL);
-		case BT_CLEAR_HOUSE:  return ::GetPrice(PR_CLEAR_HOUSE, 1, NULL);
+		case BT_FOUNDATION:   return ::GetPrice(PR_BUILD_FOUNDATION, 1, nullptr);
+		case BT_TERRAFORM:    return ::GetPrice(PR_TERRAFORM, 1, nullptr);
+		case BT_BUILD_TREES:  return ::GetPrice(PR_BUILD_TREES, 1, nullptr);
+		case BT_CLEAR_GRASS:  return ::GetPrice(PR_CLEAR_GRASS, 1, nullptr);
+		case BT_CLEAR_ROUGH:  return ::GetPrice(PR_CLEAR_ROUGH, 1, nullptr);
+		case BT_CLEAR_ROCKY:  return ::GetPrice(PR_CLEAR_ROCKS, 1, nullptr);
+		case BT_CLEAR_FIELDS: return ::GetPrice(PR_CLEAR_FIELDS, 1, nullptr);
+		case BT_CLEAR_HOUSE:  return ::GetPrice(PR_CLEAR_HOUSE, 1, nullptr);
 		default: return -1;
 	}
 }
diff --git a/src/script/api/script_town.cpp b/src/script/api/script_town.cpp
--- a/src/script/api/script_town.cpp
+++ b/src/script/api/script_town.cpp
@@ -35,7 +35,7 @@
 
 /* static */ char *ScriptTown::GetName(TownID town_id)
 {
-	if (!IsValidTown(town_id)) return NULL;
+	if (!IsValidTown(town_id)) return nullptr;
 
 	::SetDParam(0, town_id);
 	return GetString(STR_TOWN_NAME);
@@ -45,8 +45,8 @@
 {
 	CCountedPtr<Text> counter(name);
 
-	const char *text = NULL;
-	if (name != NULL) {
+	const char *text = nullptr;
+	if (name != nullptr) {
 		text = name->GetDecodedText();
 		EnforcePreconditionEncodedText(false, text);
 		EnforcePreconditionCustomError(false, ::Utf8StringLength(text) < MAX_LENGTH_TOWN_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
@@ -60,7 +60,7 @@
 {
 	CCountedPtr<Text> counter(text);
 
-	EnforcePrecondition(false, text != NULL);
+	EnforcePrecondition(false, text != nullptr);
 	const char *encoded_text = text->GetEncodedText();
 	EnforcePreconditionEncodedText(false, encoded_text);
 	EnforcePrecondition(false, IsValidTown(town_id));
@@ -257,7 +257,7 @@
 	if (ScriptObject::GetCompany() == OWNER_DEITY) return false;
 	if (!IsValidTown(town_id)) return false;
 
-	return HasBit(::GetMaskOfTownActions(NULL, ScriptObject::GetCompany(), ::Town::Get(town_id)), town_action);
+	return HasBit(::GetMaskOfTownActions(nullptr, ScriptObject::GetCompany(), ::Town::Get(town_id)), town_action);
 }
 
 /* static */ bool ScriptTown::PerformTownAction(TownID town_id, TownAction town_action)
@@ -293,8 +293,8 @@
 		layout = (RoadLayout) (byte)_settings_game.economy.town_layout;
 	}
 
-	const char *text = NULL;
-	if (name != NULL) {
+	const char *text = nullptr;
+	if (name != nullptr) {
 		text = name->GetDecodedText();
 		EnforcePreconditionEncodedText(false, text);
 		EnforcePreconditionCustomError(false, ::Utf8StringLength(text) < MAX_LENGTH_TOWN_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
diff --git a/src/script/api/script_town.hpp b/src/script/api/script_town.hpp
--- a/src/script/api/script_town.hpp
+++ b/src/script/api/script_town.hpp
@@ -148,7 +148,7 @@ public:
 	/**
 	 * Rename a town.
 	 * @param town_id The town to rename
-	 * @param name The new name of the town. If NULL or an empty string is passed, the town name will be reset to the default name.
+	 * @param name The new name of the town. If nullptr or an empty string is passed, the town name will be reset to the default name.
 	 * @pre IsValidTown(town_id).
 	 * @return True if the action succeeded.
 	 * @api -ai
@@ -402,7 +402,7 @@ public:
 	 * @param size The town size of the new town.
 	 * @param city True if the new town should be a city.
 	 * @param layout The town layout of the new town.
-	 * @param name The name of the new town. Pass NULL to use a random town name.
+	 * @param name The name of the new town. Pass nullptr to use a random town name.
 	 * @game @pre no company mode in scope || ScriptSettings.GetValue("economy.found_town") != 0.
 	 * @ai @pre ScriptSettings.GetValue("economy.found_town") != 0.
 	 * @game @pre no company mode in scope || size != TOWN_SIZE_LARGE.
diff --git a/src/script/api/script_tunnel.cpp b/src/script/api/script_tunnel.cpp
--- a/src/script/api/script_tunnel.cpp
+++ b/src/script/api/script_tunnel.cpp
@@ -102,7 +102,7 @@ static void _DoCommandReturnBuildTunnel1
 	}
 
 	ScriptObject::SetCallbackVariable(0, start);
-	return ScriptObject::DoCommand(start, type, 0, CMD_BUILD_TUNNEL, NULL, &::_DoCommandReturnBuildTunnel1);
+	return ScriptObject::DoCommand(start, type, 0, CMD_BUILD_TUNNEL, nullptr, &::_DoCommandReturnBuildTunnel1);
 }
 
 /* static */ bool ScriptTunnel::_BuildTunnelRoad1()
@@ -114,7 +114,7 @@ static void _DoCommandReturnBuildTunnel1
 	DiagDirection dir_1 = ::DiagdirBetweenTiles(end, start);
 	DiagDirection dir_2 = ::ReverseDiagDir(dir_1);
 
-	return ScriptObject::DoCommand(start + ::TileOffsByDiagDir(dir_1), ::DiagDirToRoadBits(dir_2) | (ScriptObject::GetRoadType() << 4), 0, CMD_BUILD_ROAD, NULL, &::_DoCommandReturnBuildTunnel2);
+	return ScriptObject::DoCommand(start + ::TileOffsByDiagDir(dir_1), ::DiagDirToRoadBits(dir_2) | (ScriptObject::GetRoadType() << 4), 0, CMD_BUILD_ROAD, nullptr, &::_DoCommandReturnBuildTunnel2);
 }
 
 /* static */ bool ScriptTunnel::_BuildTunnelRoad2()
diff --git a/src/script/api/script_vehicle.cpp b/src/script/api/script_vehicle.cpp
--- a/src/script/api/script_vehicle.cpp
+++ b/src/script/api/script_vehicle.cpp
@@ -29,7 +29,7 @@
 /* static */ bool ScriptVehicle::IsValidVehicle(VehicleID vehicle_id)
 {
 	const Vehicle *v = ::Vehicle::GetIfValid(vehicle_id);
-	return v != NULL && (v->owner == ScriptObject::GetCompany() || ScriptObject::GetCompany() == OWNER_DEITY) && (v->IsPrimaryVehicle() || (v->type == VEH_TRAIN && ::Train::From(v)->IsFreeWagon()));
+	return v != nullptr && (v->owner == ScriptObject::GetCompany() || ScriptObject::GetCompany() == OWNER_DEITY) && (v->IsPrimaryVehicle() || (v->type == VEH_TRAIN && ::Train::From(v)->IsFreeWagon()));
 }
 
 /* static */ ScriptCompany::CompanyID ScriptVehicle::GetOwner(VehicleID vehicle_id)
@@ -46,8 +46,8 @@
 	int num = 1;
 
 	const Train *v = ::Train::GetIfValid(vehicle_id);
-	if (v != NULL) {
-		while ((v = v->GetNextUnit()) != NULL) num++;
+	if (v != nullptr) {
+		while ((v = v->GetNextUnit()) != nullptr) num++;
 	}
 
 	return num;
@@ -71,7 +71,7 @@
 
 	EnforcePreconditionCustomError(VEHICLE_INVALID, !ScriptGameSettings::IsDisabledVehicleType((ScriptVehicle::VehicleType)type), ScriptVehicle::ERR_VEHICLE_BUILD_DISABLED);
 
-	if (!ScriptObject::DoCommand(depot, engine_id | (cargo << 24), 0, ::GetCmdBuildVeh(type), NULL, &ScriptInstance::DoCommandReturnVehicleID)) return VEHICLE_INVALID;
+	if (!ScriptObject::DoCommand(depot, engine_id | (cargo << 24), 0, ::GetCmdBuildVeh(type), nullptr, &ScriptInstance::DoCommandReturnVehicleID)) return VEHICLE_INVALID;
 
 	/* In case of test-mode, we return VehicleID 0 */
 	return 0;
@@ -104,7 +104,7 @@
 	EnforcePrecondition(false, ScriptObject::GetCompany() != OWNER_DEITY);
 	EnforcePrecondition(false, IsValidVehicle(vehicle_id));
 
-	if (!ScriptObject::DoCommand(depot, vehicle_id, share_orders, CMD_CLONE_VEHICLE, NULL, &ScriptInstance::DoCommandReturnVehicleID)) return VEHICLE_INVALID;
+	if (!ScriptObject::DoCommand(depot, vehicle_id, share_orders, CMD_CLONE_VEHICLE, nullptr, &ScriptInstance::DoCommandReturnVehicleID)) return VEHICLE_INVALID;
 
 	/* In case of test-mode, we return VehicleID 0 */
 	return 0;
@@ -120,13 +120,13 @@
 
 	const Train *v = ::Train::Get(source_vehicle_id);
 	while (source_wagon-- > 0) v = v->GetNextUnit();
-	const Train *w = NULL;
+	const Train *w = nullptr;
 	if (dest_vehicle_id != -1) {
 		w = ::Train::Get(dest_vehicle_id);
 		while (dest_wagon-- > 0) w = w->GetNextUnit();
 	}
 
-	return ScriptObject::DoCommand(0, v->index | (move_attached_wagons ? 1 : 0) << 20, w == NULL ? ::INVALID_VEHICLE : w->index, CMD_MOVE_RAIL_VEHICLE);
+	return ScriptObject::DoCommand(0, v->index | (move_attached_wagons ? 1 : 0) << 20, w == nullptr ? ::INVALID_VEHICLE : w->index, CMD_MOVE_RAIL_VEHICLE);
 }
 
 /* static */ bool ScriptVehicle::MoveWagon(VehicleID source_vehicle_id, int source_wagon, int dest_vehicle_id, int dest_wagon)
@@ -243,7 +243,7 @@
 
 	EnforcePrecondition(false, ScriptObject::GetCompany() != OWNER_DEITY);
 	EnforcePrecondition(false, IsValidVehicle(vehicle_id));
-	EnforcePrecondition(false, name != NULL);
+	EnforcePrecondition(false, name != nullptr);
 	const char *text = name->GetDecodedText();
 	EnforcePreconditionEncodedText(false, text);
 	EnforcePreconditionCustomError(false, ::Utf8StringLength(text) < MAX_LENGTH_VEHICLE_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
@@ -293,7 +293,7 @@
 
 /* static */ char *ScriptVehicle::GetName(VehicleID vehicle_id)
 {
-	if (!IsValidVehicle(vehicle_id)) return NULL;
+	if (!IsValidVehicle(vehicle_id)) return nullptr;
 
 	::SetDParam(0, vehicle_id);
 	return GetString(STR_VEHICLE_NAME);
@@ -410,7 +410,7 @@
 	if (!ScriptCargo::IsValidCargo(cargo)) return -1;
 
 	uint32 amount = 0;
-	for (const Vehicle *v = ::Vehicle::Get(vehicle_id); v != NULL; v = v->Next()) {
+	for (const Vehicle *v = ::Vehicle::Get(vehicle_id); v != nullptr; v = v->Next()) {
 		if (v->cargo_type == cargo) amount += v->cargo_cap;
 	}
 
@@ -423,7 +423,7 @@
 	if (!ScriptCargo::IsValidCargo(cargo)) return -1;
 
 	uint32 amount = 0;
-	for (const Vehicle *v = ::Vehicle::Get(vehicle_id); v != NULL; v = v->Next()) {
+	for (const Vehicle *v = ::Vehicle::Get(vehicle_id); v != nullptr; v = v->Next()) {
 		if (v->cargo_type == cargo) amount += v->cargo.StoredCount();
 	}
 
@@ -455,7 +455,7 @@
 	if (!IsValidVehicle(vehicle_id)) return false;
 
 	Vehicle *v = ::Vehicle::Get(vehicle_id);
-	return v->orders.list != NULL && v->orders.list->GetNumVehicles() > 1;
+	return v->orders.list != nullptr && v->orders.list->GetNumVehicles() > 1;
 }
 
 /* static */ int ScriptVehicle::GetReliability(VehicleID vehicle_id)
diff --git a/src/script/api/script_vehicle.hpp b/src/script/api/script_vehicle.hpp
--- a/src/script/api/script_vehicle.hpp
+++ b/src/script/api/script_vehicle.hpp
@@ -115,7 +115,7 @@ public:
 	 * @param vehicle_id The vehicle to set the name for.
 	 * @param name The name for the vehicle (can be either a raw string, or a ScriptText object).
 	 * @pre IsValidVehicle(vehicle_id).
-	 * @pre name != NULL && len(name) != 0.
+	 * @pre name != nullptr && len(name) != 0.
 	 * @game @pre Valid ScriptCompanyMode active in scope.
 	 * @exception ScriptError::ERR_NAME_IS_NOT_UNIQUE
 	 * @return True if and only if the name was changed.
diff --git a/src/script/api/script_vehiclelist.cpp b/src/script/api/script_vehiclelist.cpp
--- a/src/script/api/script_vehiclelist.cpp
+++ b/src/script/api/script_vehiclelist.cpp
@@ -101,7 +101,7 @@ ScriptVehicleList_SharedOrders::ScriptVe
 {
 	if (!ScriptVehicle::IsValidVehicle(vehicle_id)) return;
 
-	for (const Vehicle *v = Vehicle::Get(vehicle_id)->FirstShared(); v != NULL; v = v->NextShared()) {
+	for (const Vehicle *v = Vehicle::Get(vehicle_id)->FirstShared(); v != nullptr; v = v->NextShared()) {
 		this->AddItem(v->index);
 	}
 }
diff --git a/src/script/api/script_waypoint.cpp b/src/script/api/script_waypoint.cpp
--- a/src/script/api/script_waypoint.cpp
+++ b/src/script/api/script_waypoint.cpp
@@ -20,7 +20,7 @@
 /* static */ bool ScriptWaypoint::IsValidWaypoint(StationID waypoint_id)
 {
 	const Waypoint *wp = ::Waypoint::GetIfValid(waypoint_id);
-	return wp != NULL && (wp->owner == ScriptObject::GetCompany() || ScriptObject::GetCompany() == OWNER_DEITY || wp->owner == OWNER_NONE);
+	return wp != nullptr && (wp->owner == ScriptObject::GetCompany() || ScriptObject::GetCompany() == OWNER_DEITY || wp->owner == OWNER_NONE);
 }
 
 /* static */ StationID ScriptWaypoint::GetWaypointID(TileIndex tile)
diff --git a/src/script/api/script_waypointlist.cpp b/src/script/api/script_waypointlist.cpp
--- a/src/script/api/script_waypointlist.cpp
+++ b/src/script/api/script_waypointlist.cpp
@@ -32,7 +32,7 @@ ScriptWaypointList_Vehicle::ScriptWaypoi
 
 	const Vehicle *v = ::Vehicle::Get(vehicle_id);
 
-	for (const Order *o = v->GetFirstOrder(); o != NULL; o = o->next) {
+	for (const Order *o = v->GetFirstOrder(); o != nullptr; o = o->next) {
 		if (o->IsType(OT_GOTO_WAYPOINT)) this->AddItem(o->GetDestination());
 	}
 }
diff --git a/src/script/api/script_window.cpp b/src/script/api/script_window.cpp
--- a/src/script/api/script_window.cpp
+++ b/src/script/api/script_window.cpp
@@ -34,10 +34,10 @@
 	if (ScriptGame::IsMultiplayer()) return false;
 
 	if (number == NUMBER_ALL) {
-		return (FindWindowByClass((::WindowClass)window) != NULL);
+		return (FindWindowByClass((::WindowClass)window) != nullptr);
 	}
 
-	return FindWindowById((::WindowClass)window, number) != NULL;
+	return FindWindowById((::WindowClass)window, number) != nullptr;
 }
 
 /* static */ void ScriptWindow::Highlight(WindowClass window, uint32 number, uint8 widget, TextColour colour)
@@ -56,6 +56,6 @@
 	}
 
 	const NWidgetBase *wid = w->GetWidget<NWidgetBase>(widget);
-	if (wid == NULL) return;
+	if (wid == nullptr) return;
 	w->SetWidgetHighlight(widget, (::TextColour)colour);
 }
diff --git a/src/script/script_config.cpp b/src/script/script_config.cpp
--- a/src/script/script_config.cpp
+++ b/src/script/script_config.cpp
@@ -21,17 +21,17 @@
 void ScriptConfig::Change(const char *name, int version, bool force_exact_match, bool is_random)
 {
 	free(this->name);
-	this->name = (name == NULL) ? NULL : stredup(name);
-	this->info = (name == NULL) ? NULL : this->FindInfo(this->name, version, force_exact_match);
-	this->version = (info == NULL) ? -1 : info->GetVersion();
+	this->name = (name == nullptr) ? nullptr : stredup(name);
+	this->info = (name == nullptr) ? nullptr : this->FindInfo(this->name, version, force_exact_match);
+	this->version = (info == nullptr) ? -1 : info->GetVersion();
 	this->is_random = is_random;
-	if (this->config_list != NULL) delete this->config_list;
-	this->config_list = (info == NULL) ? NULL : new ScriptConfigItemList();
-	if (this->config_list != NULL) this->PushExtraConfigList();
+	if (this->config_list != nullptr) delete this->config_list;
+	this->config_list = (info == nullptr) ? nullptr : new ScriptConfigItemList();
+	if (this->config_list != nullptr) this->PushExtraConfigList();
 
 	this->ClearConfigList();
 
-	if (_game_mode == GM_NORMAL && this->info != NULL) {
+	if (_game_mode == GM_NORMAL && this->info != nullptr) {
 		/* If we're in an existing game and the Script is changed, set all settings
 		 *  for the Script that have the random flag to a random value. */
 		for (ScriptConfigItemList::const_iterator it = this->info->GetConfigList()->begin(); it != this->info->GetConfigList()->end(); it++) {
@@ -45,10 +45,10 @@ void ScriptConfig::Change(const char *na
 
 ScriptConfig::ScriptConfig(const ScriptConfig *config)
 {
-	this->name = (config->name == NULL) ? NULL : stredup(config->name);
+	this->name = (config->name == nullptr) ? nullptr : stredup(config->name);
 	this->info = config->info;
 	this->version = config->version;
-	this->config_list = NULL;
+	this->config_list = nullptr;
 	this->is_random = config->is_random;
 
 	for (SettingValueList::const_iterator it = config->settings.begin(); it != config->settings.end(); it++) {
@@ -61,7 +61,7 @@ ScriptConfig::~ScriptConfig()
 {
 	free(this->name);
 	this->ResetSettings();
-	if (this->config_list != NULL) delete this->config_list;
+	if (this->config_list != nullptr) delete this->config_list;
 }
 
 ScriptInfo *ScriptConfig::GetInfo() const
@@ -71,8 +71,8 @@ ScriptInfo *ScriptConfig::GetInfo() cons
 
 const ScriptConfigItemList *ScriptConfig::GetConfigList()
 {
-	if (this->info != NULL) return this->info->GetConfigList();
-	if (this->config_list == NULL) {
+	if (this->info != nullptr) return this->info->GetConfigList();
+	if (this->config_list == nullptr) {
 		this->config_list = new ScriptConfigItemList();
 		this->PushExtraConfigList();
 	}
@@ -106,10 +106,10 @@ int ScriptConfig::GetSetting(const char 
 void ScriptConfig::SetSetting(const char *name, int value)
 {
 	/* You can only set Script specific settings if an Script is selected. */
-	if (this->info == NULL) return;
+	if (this->info == nullptr) return;
 
 	const ScriptConfigItem *config_item = this->info->GetConfigItem(name);
-	if (config_item == NULL) return;
+	if (config_item == nullptr) return;
 
 	value = Clamp(value, config_item->min_value, config_item->max_value);
 
@@ -140,7 +140,7 @@ void ScriptConfig::AddRandomDeviation()
 
 bool ScriptConfig::HasScript() const
 {
-	return this->info != NULL;
+	return this->info != nullptr;
 }
 
 bool ScriptConfig::IsRandom() const
@@ -163,18 +163,18 @@ void ScriptConfig::StringToSettings(cons
 	char *value_copy = stredup(value);
 	char *s = value_copy;
 
-	while (s != NULL) {
+	while (s != nullptr) {
 		/* Analyze the string ('name=value,name=value\0') */
 		char *item_name = s;
 		s = strchr(s, '=');
-		if (s == NULL) break;
+		if (s == nullptr) break;
 		if (*s == '\0') break;
 		*s = '\0';
 		s++;
 
 		char *item_value = s;
 		s = strchr(s, ',');
-		if (s != NULL) {
+		if (s != nullptr) {
 			*s = '\0';
 			s++;
 		}
@@ -209,7 +209,7 @@ void ScriptConfig::SettingsToString(char
 
 const char *ScriptConfig::GetTextfile(TextfileType type, CompanyID slot) const
 {
-	if (slot == INVALID_COMPANY || this->GetInfo() == NULL) return NULL;
+	if (slot == INVALID_COMPANY || this->GetInfo() == nullptr) return nullptr;
 
 	return ::GetTextfile(type, (slot == OWNER_DEITY) ? GAME_DIR : AI_DIR, this->GetInfo()->GetMainScript());
 }
diff --git a/src/script/script_config.hpp b/src/script/script_config.hpp
--- a/src/script/script_config.hpp
+++ b/src/script/script_config.hpp
@@ -61,10 +61,10 @@ protected:
 
 public:
 	ScriptConfig() :
-		name(NULL),
+		name(nullptr),
 		version(-1),
-		info(NULL),
-		config_list(NULL),
+		info(nullptr),
+		config_list(nullptr),
 		is_random(false)
 	{}
 
@@ -178,7 +178,7 @@ public:
 	 * Search a textfile file next to this script.
 	 * @param type The type of the textfile to search for.
 	 * @param slot #CompanyID to check status of.
-	 * @return The filename for the textfile, \c NULL otherwise.
+	 * @return The filename for the textfile, \c nullptr otherwise.
 	 */
 	const char *GetTextfile(TextfileType type, CompanyID slot) const;
 
diff --git a/src/script/script_info.cpp b/src/script/script_info.cpp
--- a/src/script/script_info.cpp
+++ b/src/script/script_info.cpp
@@ -25,7 +25,7 @@ ScriptInfo::~ScriptInfo()
 	for (ScriptConfigItemList::iterator it = this->config_list.begin(); it != this->config_list.end(); it++) {
 		free((*it).name);
 		free((*it).description);
-		if (it->labels != NULL) {
+		if (it->labels != nullptr) {
 			for (auto &lbl_map : *(*it).labels) {
 				free(lbl_map.second);
 			}
@@ -85,7 +85,7 @@ bool ScriptInfo::CheckMethod(const char 
 	/* Get location information of the scanner */
 	info->main_script = stredup(info->scanner->GetMainScript());
 	const char *tar_name = info->scanner->GetTarFile();
-	if (tar_name != NULL) info->tar_file = stredup(tar_name);
+	if (tar_name != nullptr) info->tar_file = stredup(tar_name);
 
 	/* Cache the data the info file gives us. */
 	if (!info->engine->CallStringMethodStrdup(*info->SQ_instance, "GetAuthor", &info->author, MAX_GET_OPS)) return SQ_ERROR;
@@ -111,7 +111,7 @@ bool ScriptInfo::CheckMethod(const char 
 
 bool ScriptInfo::GetSettings()
 {
-	return this->engine->CallMethod(*this->SQ_instance, "GetSettings", NULL, MAX_GET_SETTING_OPS);
+	return this->engine->CallMethod(*this->SQ_instance, "GetSettings", nullptr, MAX_GET_SETTING_OPS);
 }
 
 SQInteger ScriptInfo::AddSetting(HSQUIRRELVM vm)
@@ -138,8 +138,8 @@ SQInteger ScriptInfo::AddSetting(HSQUIRR
 
 			/* Don't allow '=' and ',' in configure setting names, as we need those
 			 *  2 chars to nicely store the settings as a string. */
-			while ((s = strchr(name, '=')) != NULL) *s = '_';
-			while ((s = strchr(name, ',')) != NULL) *s = '_';
+			while ((s = strchr(name, '=')) != nullptr) *s = '_';
+			while ((s = strchr(name, ',')) != nullptr) *s = '_';
 			config.name = name;
 			items |= 0x001;
 		} else if (strcmp(key, "description") == 0) {
@@ -233,18 +233,18 @@ SQInteger ScriptInfo::AddLabels(HSQUIRRE
 	if (SQ_FAILED(sq_getstring(vm, -2, &setting_name))) return SQ_ERROR;
 	ValidateString(setting_name);
 
-	ScriptConfigItem *config = NULL;
+	ScriptConfigItem *config = nullptr;
 	for (ScriptConfigItemList::iterator it = this->config_list.begin(); it != this->config_list.end(); it++) {
 		if (strcmp((*it).name, setting_name) == 0) config = &(*it);
 	}
 
-	if (config == NULL) {
+	if (config == nullptr) {
 		char error[1024];
 		seprintf(error, lastof(error), "Trying to add labels for non-defined setting '%s'", setting_name);
 		this->engine->ThrowError(error);
 		return SQ_ERROR;
 	}
-	if (config->labels != NULL) return SQ_ERROR;
+	if (config->labels != nullptr) return SQ_ERROR;
 
 	config->labels = new LabelMapping;
 
@@ -289,7 +289,7 @@ const ScriptConfigItem *ScriptInfo::GetC
 	for (ScriptConfigItemList::const_iterator it = this->config_list.begin(); it != this->config_list.end(); it++) {
 		if (strcmp((*it).name, name) == 0) return &(*it);
 	}
-	return NULL;
+	return nullptr;
 }
 
 int ScriptInfo::GetSettingDefaultValue(const char *name) const
diff --git a/src/script/script_info.hpp b/src/script/script_info.hpp
--- a/src/script/script_info.hpp
+++ b/src/script/script_info.hpp
@@ -32,19 +32,19 @@ static const int MAX_GET_SETTING_OPS    
 class ScriptInfo : public SimpleCountedObject {
 public:
 	ScriptInfo() :
-		engine(NULL),
-		SQ_instance(NULL),
-		main_script(NULL),
-		tar_file(NULL),
-		author(NULL),
-		name(NULL),
-		short_name(NULL),
-		description(NULL),
-		date(NULL),
-		instance_name(NULL),
+		engine(nullptr),
+		SQ_instance(nullptr),
+		main_script(nullptr),
+		tar_file(nullptr),
+		author(nullptr),
+		name(nullptr),
+		short_name(nullptr),
+		description(nullptr),
+		date(nullptr),
+		instance_name(nullptr),
 		version(0),
-		url(NULL),
-		scanner(NULL)
+		url(nullptr),
+		scanner(nullptr)
 	{}
 	~ScriptInfo();
 
diff --git a/src/script/script_info_dummy.cpp b/src/script/script_info_dummy.cpp
--- a/src/script/script_info_dummy.cpp
+++ b/src/script/script_info_dummy.cpp
@@ -86,11 +86,11 @@ void Script_CreateDummy(HSQUIRRELVM vm, 
 	char *p = safe_error_message;
 	do {
 		newline = strchr(p, '\n');
-		if (newline != NULL) *newline = '\0';
+		if (newline != nullptr) *newline = '\0';
 
 		dp += seprintf(dp, lastof(dummy_script), "    %sLog.Error(\"%s\");\n", type, p);
 		p = newline + 1;
-	} while (newline != NULL);
+	} while (newline != nullptr);
 
 	strecpy(dp, "  }\n}\n", lastof(dummy_script));
 
diff --git a/src/script/script_instance.cpp b/src/script/script_instance.cpp
--- a/src/script/script_instance.cpp
+++ b/src/script/script_instance.cpp
@@ -34,8 +34,8 @@
 ScriptStorage::~ScriptStorage()
 {
 	/* Free our pointers */
-	if (event_data != NULL) ScriptEventController::FreeEventPointer();
-	if (log_data != NULL) ScriptLog::FreeLogPointer();
+	if (event_data != nullptr) ScriptEventController::FreeEventPointer();
+	if (log_data != nullptr) ScriptLog::FreeLogPointer();
 }
 
 /**
@@ -50,17 +50,17 @@ static void PrintFunc(bool error_msg, co
 }
 
 ScriptInstance::ScriptInstance(const char *APIName) :
-	engine(NULL),
-	versionAPI(NULL),
-	controller(NULL),
-	storage(NULL),
-	instance(NULL),
+	engine(nullptr),
+	versionAPI(nullptr),
+	controller(nullptr),
+	storage(nullptr),
+	instance(nullptr),
 	is_started(false),
 	is_dead(false),
 	is_save_data_on_stack(false),
 	suspend(0),
 	is_paused(false),
-	callback(NULL)
+	callback(nullptr)
 {
 	this->storage = new ScriptStorage();
 	this->engine  = new Squirrel(APIName);
@@ -135,8 +135,8 @@ ScriptInstance::~ScriptInstance()
 {
 	ScriptObject::ActiveInstance active(this);
 
-	if (instance != NULL) this->engine->ReleaseObject(this->instance);
-	if (engine != NULL) delete this->engine;
+	if (instance != nullptr) this->engine->ReleaseObject(this->instance);
+	if (engine != nullptr) delete this->engine;
 	delete this->storage;
 	delete this->controller;
 	free(this->instance);
@@ -153,10 +153,10 @@ void ScriptInstance::Died()
 	DEBUG(script, 0, "The script died unexpectedly.");
 	this->is_dead = true;
 
-	if (this->instance != NULL) this->engine->ReleaseObject(this->instance);
+	if (this->instance != nullptr) this->engine->ReleaseObject(this->instance);
 	delete this->engine;
-	this->instance = NULL;
-	this->engine = NULL;
+	this->instance = nullptr;
+	this->engine = nullptr;
 }
 
 void ScriptInstance::GameLoop()
@@ -179,7 +179,7 @@ void ScriptInstance::GameLoop()
 	_current_company = ScriptObject::GetCompany();
 
 	/* If there is a callback to call, call that first */
-	if (this->callback != NULL) {
+	if (this->callback != nullptr) {
 		if (this->is_save_data_on_stack) {
 			sq_poptop(this->engine->GetVM());
 			this->is_save_data_on_stack = false;
@@ -195,7 +195,7 @@ void ScriptInstance::GameLoop()
 	}
 
 	this->suspend  = 0;
-	this->callback = NULL;
+	this->callback = nullptr;
 
 	if (!this->is_started) {
 		try {
@@ -351,7 +351,7 @@ static const SaveLoad _script_byte[] = {
 		case OT_INTEGER: {
 			if (!test) {
 				_script_sl_byte = SQSL_INT;
-				SlObject(NULL, _script_byte);
+				SlObject(nullptr, _script_byte);
 			}
 			SQInteger res;
 			sq_getinteger(vm, index, &res);
@@ -365,7 +365,7 @@ static const SaveLoad _script_byte[] = {
 		case OT_STRING: {
 			if (!test) {
 				_script_sl_byte = SQSL_STRING;
-				SlObject(NULL, _script_byte);
+				SlObject(nullptr, _script_byte);
 			}
 			const SQChar *buf;
 			sq_getstring(vm, index, &buf);
@@ -376,7 +376,7 @@ static const SaveLoad _script_byte[] = {
 			}
 			if (!test) {
 				_script_sl_byte = (byte)len;
-				SlObject(NULL, _script_byte);
+				SlObject(nullptr, _script_byte);
 				SlArray(const_cast<char *>(buf), len, SLE_CHAR);
 			}
 			return true;
@@ -385,7 +385,7 @@ static const SaveLoad _script_byte[] = {
 		case OT_ARRAY: {
 			if (!test) {
 				_script_sl_byte = SQSL_ARRAY;
-				SlObject(NULL, _script_byte);
+				SlObject(nullptr, _script_byte);
 			}
 			sq_pushnull(vm);
 			while (SQ_SUCCEEDED(sq_next(vm, index - 1))) {
@@ -400,7 +400,7 @@ static const SaveLoad _script_byte[] = {
 			sq_pop(vm, 1);
 			if (!test) {
 				_script_sl_byte = SQSL_ARRAY_TABLE_END;
-				SlObject(NULL, _script_byte);
+				SlObject(nullptr, _script_byte);
 			}
 			return true;
 		}
@@ -408,7 +408,7 @@ static const SaveLoad _script_byte[] = {
 		case OT_TABLE: {
 			if (!test) {
 				_script_sl_byte = SQSL_TABLE;
-				SlObject(NULL, _script_byte);
+				SlObject(nullptr, _script_byte);
 			}
 			sq_pushnull(vm);
 			while (SQ_SUCCEEDED(sq_next(vm, index - 1))) {
@@ -423,7 +423,7 @@ static const SaveLoad _script_byte[] = {
 			sq_pop(vm, 1);
 			if (!test) {
 				_script_sl_byte = SQSL_ARRAY_TABLE_END;
-				SlObject(NULL, _script_byte);
+				SlObject(nullptr, _script_byte);
 			}
 			return true;
 		}
@@ -431,13 +431,13 @@ static const SaveLoad _script_byte[] = {
 		case OT_BOOL: {
 			if (!test) {
 				_script_sl_byte = SQSL_BOOL;
-				SlObject(NULL, _script_byte);
+				SlObject(nullptr, _script_byte);
 			}
 			SQBool res;
 			sq_getbool(vm, index, &res);
 			if (!test) {
 				_script_sl_byte = res ? 1 : 0;
-				SlObject(NULL, _script_byte);
+				SlObject(nullptr, _script_byte);
 			}
 			return true;
 		}
@@ -445,7 +445,7 @@ static const SaveLoad _script_byte[] = {
 		case OT_NULL: {
 			if (!test) {
 				_script_sl_byte = SQSL_NULL;
-				SlObject(NULL, _script_byte);
+				SlObject(nullptr, _script_byte);
 			}
 			return true;
 		}
@@ -459,7 +459,7 @@ static const SaveLoad _script_byte[] = {
 /* static */ void ScriptInstance::SaveEmpty()
 {
 	_script_sl_byte = 0;
-	SlObject(NULL, _script_byte);
+	SlObject(nullptr, _script_byte);
 }
 
 void ScriptInstance::Save()
@@ -467,7 +467,7 @@ void ScriptInstance::Save()
 	ScriptObject::ActiveInstance active(this);
 
 	/* Don't save data if the script didn't start yet or if it crashed. */
-	if (this->engine == NULL || this->engine->HasScriptCrashed()) {
+	if (this->engine == nullptr || this->engine->HasScriptCrashed()) {
 		SaveEmpty();
 		return;
 	}
@@ -475,7 +475,7 @@ void ScriptInstance::Save()
 	HSQUIRRELVM vm = this->engine->GetVM();
 	if (this->is_save_data_on_stack) {
 		_script_sl_byte = 1;
-		SlObject(NULL, _script_byte);
+		SlObject(nullptr, _script_byte);
 		/* Save the data that was just loaded. */
 		SaveObject(vm, -1, SQUIRREL_MAX_DEPTH, false);
 	} else if (!this->is_started) {
@@ -518,7 +518,7 @@ void ScriptInstance::Save()
 		sq_pushobject(vm, savedata);
 		if (SaveObject(vm, -1, SQUIRREL_MAX_DEPTH, true)) {
 			_script_sl_byte = 1;
-			SlObject(NULL, _script_byte);
+			SlObject(nullptr, _script_byte);
 			SaveObject(vm, -1, SQUIRREL_MAX_DEPTH, false);
 			this->is_save_data_on_stack = true;
 		} else {
@@ -528,7 +528,7 @@ void ScriptInstance::Save()
 	} else {
 		ScriptLog::Warning("Save function is not implemented");
 		_script_sl_byte = 0;
-		SlObject(NULL, _script_byte);
+		SlObject(nullptr, _script_byte);
 	}
 }
 
@@ -553,50 +553,50 @@ bool ScriptInstance::IsPaused()
 
 /* static */ bool ScriptInstance::LoadObjects(HSQUIRRELVM vm)
 {
-	SlObject(NULL, _script_byte);
+	SlObject(nullptr, _script_byte);
 	switch (_script_sl_byte) {
 		case SQSL_INT: {
 			int value;
 			SlArray(&value, 1, SLE_INT32);
-			if (vm != NULL) sq_pushinteger(vm, (SQInteger)value);
+			if (vm != nullptr) sq_pushinteger(vm, (SQInteger)value);
 			return true;
 		}
 
 		case SQSL_STRING: {
-			SlObject(NULL, _script_byte);
+			SlObject(nullptr, _script_byte);
 			static char buf[256];
 			SlArray(buf, _script_sl_byte, SLE_CHAR);
-			if (vm != NULL) sq_pushstring(vm, buf, -1);
+			if (vm != nullptr) sq_pushstring(vm, buf, -1);
 			return true;
 		}
 
 		case SQSL_ARRAY: {
-			if (vm != NULL) sq_newarray(vm, 0);
+			if (vm != nullptr) sq_newarray(vm, 0);
 			while (LoadObjects(vm)) {
-				if (vm != NULL) sq_arrayappend(vm, -2);
+				if (vm != nullptr) sq_arrayappend(vm, -2);
 				/* The value is popped from the stack by squirrel. */
 			}
 			return true;
 		}
 
 		case SQSL_TABLE: {
-			if (vm != NULL) sq_newtable(vm);
+			if (vm != nullptr) sq_newtable(vm);
 			while (LoadObjects(vm)) {
 				LoadObjects(vm);
-				if (vm != NULL) sq_rawset(vm, -3);
+				if (vm != nullptr) sq_rawset(vm, -3);
 				/* The key (-2) and value (-1) are popped from the stack by squirrel. */
 			}
 			return true;
 		}
 
 		case SQSL_BOOL: {
-			SlObject(NULL, _script_byte);
-			if (vm != NULL) sq_pushbool(vm, (SQBool)(_script_sl_byte != 0));
+			SlObject(nullptr, _script_byte);
+			if (vm != nullptr) sq_pushbool(vm, (SQBool)(_script_sl_byte != 0));
 			return true;
 		}
 
 		case SQSL_NULL: {
-			if (vm != NULL) sq_pushnull(vm);
+			if (vm != nullptr) sq_pushnull(vm);
 			return true;
 		}
 
@@ -610,24 +610,24 @@ bool ScriptInstance::IsPaused()
 
 /* static */ void ScriptInstance::LoadEmpty()
 {
-	SlObject(NULL, _script_byte);
+	SlObject(nullptr, _script_byte);
 	/* Check if there was anything saved at all. */
 	if (_script_sl_byte == 0) return;
 
-	LoadObjects(NULL);
+	LoadObjects(nullptr);
 }
 
 void ScriptInstance::Load(int version)
 {
 	ScriptObject::ActiveInstance active(this);
 
-	if (this->engine == NULL || version == -1) {
+	if (this->engine == nullptr || version == -1) {
 		LoadEmpty();
 		return;
 	}
 	HSQUIRRELVM vm = this->engine->GetVM();
 
-	SlObject(NULL, _script_byte);
+	SlObject(nullptr, _script_byte);
 	/* Check if there was anything saved at all. */
 	if (_script_sl_byte == 0) return;
 
diff --git a/src/script/script_instance.hpp b/src/script/script_instance.hpp
--- a/src/script/script_instance.hpp
+++ b/src/script/script_instance.hpp
@@ -52,7 +52,7 @@ public:
 	 * Find a library.
 	 * @param library The library name to find.
 	 * @param version The version the library should have.
-	 * @return The library if found, NULL otherwise.
+	 * @return The library if found, nullptr otherwise.
 	 */
 	virtual class ScriptInfo *FindLibrary(const char *library, int version) = 0;
 
diff --git a/src/script/script_scanner.cpp b/src/script/script_scanner.cpp
--- a/src/script/script_scanner.cpp
+++ b/src/script/script_scanner.cpp
@@ -28,19 +28,19 @@ bool ScriptScanner::AddFile(const char *
 {
 	free(this->main_script);
 	this->main_script = stredup(filename);
-	if (this->main_script == NULL) return false;
+	if (this->main_script == nullptr) return false;
 
 	free(this->tar_file);
-	if (tar_filename != NULL) {
+	if (tar_filename != nullptr) {
 		this->tar_file = stredup(tar_filename);
-		if (this->tar_file == NULL) return false;
+		if (this->tar_file == nullptr) return false;
 	} else {
-		this->tar_file = NULL;
+		this->tar_file = nullptr;
 	}
 
 	const char *end = this->main_script + strlen(this->main_script) + 1;
 	char *p = strrchr(this->main_script, PATHSEPCHAR);
-	if (p == NULL) {
+	if (p == nullptr) {
 		p = this->main_script;
 	} else {
 		/* Skip over the path separator character. We don't need that. */
@@ -58,9 +58,9 @@ bool ScriptScanner::AddFile(const char *
 }
 
 ScriptScanner::ScriptScanner() :
-	engine(NULL),
-	main_script(NULL),
-	tar_file(NULL)
+	engine(nullptr),
+	main_script(nullptr),
+	tar_file(nullptr)
 {
 }
 
@@ -203,7 +203,7 @@ struct ScriptFileChecksumCreator : FileS
 
 		/* Open the file ... */
 		FILE *f = FioFOpenFile(filename, "rb", this->dir, &size);
-		if (f == NULL) return false;
+		if (f == nullptr) return false;
 
 		/* ... calculate md5sum... */
 		while ((len = fread(buffer, 1, (size > sizeof(buffer)) ? sizeof(buffer) : size, f)) != 0 && size != 0) {
@@ -241,7 +241,7 @@ static bool IsSameScript(const ContentIn
 	ScriptFileChecksumCreator checksum(dir);
 	const char *tar_filename = info->GetTarFile();
 	TarList::iterator iter;
-	if (tar_filename != NULL && (iter = _tar_list[dir].find(tar_filename)) != _tar_list[dir].end()) {
+	if (tar_filename != nullptr && (iter = _tar_list[dir].find(tar_filename)) != _tar_list[dir].end()) {
 		/* The main script is in a tar file, so find all files that
 		 * are in the same tar and add them to the MD5 checksumming. */
 		TarFileList::iterator tar;
@@ -251,7 +251,7 @@ static bool IsSameScript(const ContentIn
 
 			/* Check the extension. */
 			const char *ext = strrchr(tar->first.c_str(), '.');
-			if (ext == NULL || strcasecmp(ext, ".nut") != 0) continue;
+			if (ext == nullptr || strcasecmp(ext, ".nut") != 0) continue;
 
 			checksum.AddFile(tar->first.c_str(), 0, tar_filename);
 		}
@@ -281,5 +281,5 @@ const char *ScriptScanner::FindMainScrip
 	for (ScriptInfoList::iterator it = this->info_list.begin(); it != this->info_list.end(); it++) {
 		if (IsSameScript(ci, md5sum, (*it).second, this->GetDirectory())) return (*it).second->GetMainScript();
 	}
-	return NULL;
+	return nullptr;
 }
diff --git a/src/script/script_scanner.hpp b/src/script/script_scanner.hpp
--- a/src/script/script_scanner.hpp
+++ b/src/script/script_scanner.hpp
@@ -73,7 +73,7 @@ public:
 	 * Find a script of a #ContentInfo
 	 * @param ci The information to compare to.
 	 * @param md5sum Whether to check the MD5 checksum.
-	 * @return A filename of a file of the content, else \c NULL.
+	 * @return A filename of a file of the content, else \c nullptr.
 	 */
 	const char *FindMainScript(const ContentInfo *ci, bool md5sum);
 
diff --git a/src/script/script_storage.hpp b/src/script/script_storage.hpp
--- a/src/script/script_storage.hpp
+++ b/src/script/script_storage.hpp
@@ -63,8 +63,8 @@ private:
 
 public:
 	ScriptStorage() :
-		mode              (NULL),
-		mode_instance     (NULL),
+		mode              (nullptr),
+		mode_instance     (nullptr),
 		root_company      (INVALID_OWNER),
 		company           (INVALID_OWNER),
 		delay             (1),
@@ -82,8 +82,8 @@ public:
 		/* calback_value (can't be set) */
 		road_type         (INVALID_ROADTYPE),
 		rail_type         (INVALID_RAILTYPE),
-		event_data        (NULL),
-		log_data          (NULL)
+		event_data        (nullptr),
+		log_data          (nullptr)
 	{ }
 
 	~ScriptStorage();
diff --git a/src/script/squirrel.cpp b/src/script/squirrel.cpp
--- a/src/script/squirrel.cpp
+++ b/src/script/squirrel.cpp
@@ -31,7 +31,7 @@ void Squirrel::CompileError(HSQUIRRELVM 
 	Squirrel *engine = (Squirrel *)sq_getforeignptr(vm);
 	engine->crashed = true;
 	SQPrintFunc *func = engine->print_func;
-	if (func == NULL) {
+	if (func == nullptr) {
 		DEBUG(misc, 0, "[Squirrel] Compile error: %s", buf);
 	} else {
 		(*func)(true, buf);
@@ -49,7 +49,7 @@ void Squirrel::ErrorPrintFunc(HSQUIRRELV
 
 	/* Check if we have a custom print function */
 	SQPrintFunc *func = ((Squirrel *)sq_getforeignptr(vm))->print_func;
-	if (func == NULL) {
+	if (func == nullptr) {
 		fprintf(stderr, "%s", buf);
 	} else {
 		(*func)(true, buf);
@@ -67,7 +67,7 @@ void Squirrel::RunError(HSQUIRRELVM vm, 
 	seprintf(buf, lastof(buf), "Your script made an error: %s\n", error);
 	Squirrel *engine = (Squirrel *)sq_getforeignptr(vm);
 	SQPrintFunc *func = engine->print_func;
-	if (func == NULL) {
+	if (func == nullptr) {
 		fprintf(stderr, "%s", buf);
 	} else {
 		(*func)(true, buf);
@@ -106,7 +106,7 @@ void Squirrel::PrintFunc(HSQUIRRELVM vm,
 
 	/* Check if we have a custom print function */
 	SQPrintFunc *func = ((Squirrel *)sq_getforeignptr(vm))->print_func;
-	if (func == NULL) {
+	if (func == nullptr) {
 		printf("%s", buf);
 	} else {
 		(*func)(false, buf);
@@ -234,8 +234,8 @@ bool Squirrel::CallMethod(HSQOBJECT inst
 	}
 	/* Call the method */
 	sq_pushobject(this->vm, instance);
-	if (SQ_FAILED(sq_call(this->vm, 1, ret == NULL ? SQFalse : SQTrue, SQTrue, suspend))) return false;
-	if (ret != NULL) sq_getstackobj(vm, -1, ret);
+	if (SQ_FAILED(sq_call(this->vm, 1, ret == nullptr ? SQFalse : SQTrue, SQTrue, suspend))) return false;
+	if (ret != nullptr) sq_getstackobj(vm, -1, ret);
 	/* Reset the top, but don't do so for the script main function, as we need
 	 *  a correct stack when resuming. */
 	if (suspend == -1 || !this->IsSuspended()) sq_settop(this->vm, top);
@@ -305,7 +305,7 @@ bool Squirrel::CallBoolMethod(HSQOBJECT 
 		return false;
 	}
 
-	if (instance != NULL) {
+	if (instance != nullptr) {
 		/* Find our instance */
 		sq_getstackobj(vm, -1, instance);
 		/* Add a reference to it, so it survives for ever */
@@ -316,16 +316,16 @@ bool Squirrel::CallBoolMethod(HSQOBJECT 
 
 	/* Store it in the class */
 	sq_setinstanceup(vm, -1, real_instance);
-	if (release_hook != NULL) sq_setreleasehook(vm, -1, release_hook);
+	if (release_hook != nullptr) sq_setreleasehook(vm, -1, release_hook);
 
-	if (instance != NULL) sq_settop(vm, oldtop);
+	if (instance != nullptr) sq_settop(vm, oldtop);
 
 	return true;
 }
 
 bool Squirrel::CreateClassInstance(const char *class_name, void *real_instance, HSQOBJECT *instance)
 {
-	return Squirrel::CreateClassInstanceVM(this->vm, class_name, real_instance, instance, NULL);
+	return Squirrel::CreateClassInstanceVM(this->vm, class_name, real_instance, instance, nullptr);
 }
 
 Squirrel::Squirrel(const char *APIName) :
@@ -336,8 +336,8 @@ Squirrel::Squirrel(const char *APIName) 
 
 void Squirrel::Initialize()
 {
-	this->global_pointer = NULL;
-	this->print_func = NULL;
+	this->global_pointer = nullptr;
+	this->print_func = nullptr;
 	this->crashed = false;
 	this->overdrawn_ops = 0;
 	this->vm = sq_open(1024);
@@ -436,15 +436,15 @@ SQRESULT Squirrel::LoadFile(HSQUIRRELVM 
 	size_t size;
 	if (strncmp(this->GetAPIName(), "AI", 2) == 0) {
 		file = FioFOpenFile(filename, "rb", AI_DIR, &size);
-		if (file == NULL) file = FioFOpenFile(filename, "rb", AI_LIBRARY_DIR, &size);
+		if (file == nullptr) file = FioFOpenFile(filename, "rb", AI_LIBRARY_DIR, &size);
 	} else if (strncmp(this->GetAPIName(), "GS", 2) == 0) {
 		file = FioFOpenFile(filename, "rb", GAME_DIR, &size);
-		if (file == NULL) file = FioFOpenFile(filename, "rb", GAME_LIBRARY_DIR, &size);
+		if (file == nullptr) file = FioFOpenFile(filename, "rb", GAME_LIBRARY_DIR, &size);
 	} else {
 		NOT_REACHED();
 	}
 
-	if (file == NULL) {
+	if (file == nullptr) {
 		return sq_throwerror(vm, "cannot open the file");
 	}
 	unsigned short bom = 0;
diff --git a/src/script/squirrel.hpp b/src/script/squirrel.hpp
--- a/src/script/squirrel.hpp
+++ b/src/script/squirrel.hpp
@@ -26,7 +26,7 @@ private:
 
 	HSQUIRRELVM vm;          ///< The VirtualMachine instance for squirrel
 	void *global_pointer;    ///< Can be set by who ever initializes Squirrel
-	SQPrintFunc *print_func; ///< Points to either NULL, or a custom print handler
+	SQPrintFunc *print_func; ///< Points to either nullptr, or a custom print handler
 	bool crashed;            ///< True if the squirrel script made an error.
 	int overdrawn_ops;       ///< The amount of operations we have overdrawn.
 	const char *APIName;     ///< Name of the API used for this squirrel.
@@ -93,7 +93,7 @@ public:
 	 * Adds a function to the stack. Depending on the current state this means
 	 *  either a method or a global function.
 	 */
-	void AddMethod(const char *method_name, SQFUNCTION proc, uint nparam = 0, const char *params = NULL, void *userdata = NULL, int size = 0);
+	void AddMethod(const char *method_name, SQFUNCTION proc, uint nparam = 0, const char *params = nullptr, void *userdata = nullptr, int size = 0);
 
 	/**
 	 * Adds a const to the stack. Depending on the current state this means
@@ -155,7 +155,7 @@ public:
 	 * @return False if the script crashed or returned a wrong type.
 	 */
 	bool CallMethod(HSQOBJECT instance, const char *method_name, HSQOBJECT *ret, int suspend);
-	bool CallMethod(HSQOBJECT instance, const char *method_name, int suspend) { return this->CallMethod(instance, method_name, NULL, suspend); }
+	bool CallMethod(HSQOBJECT instance, const char *method_name, int suspend) { return this->CallMethod(instance, method_name, nullptr, suspend); }
 	bool CallStringMethodStrdup(HSQOBJECT instance, const char *method_name, const char **res, int suspend);
 	bool CallIntegerMethod(HSQOBJECT instance, const char *method_name, int *res, int suspend);
 	bool CallBoolMethod(HSQOBJECT instance, const char *method_name, bool *res, int suspend);
diff --git a/src/script/squirrel_class.hpp b/src/script/squirrel_class.hpp
--- a/src/script/squirrel_class.hpp
+++ b/src/script/squirrel_class.hpp
@@ -35,7 +35,7 @@ public:
 	void DefSQMethod(Squirrel *engine, Func function_proc, const char *function_name)
 	{
 		using namespace SQConvert;
-		engine->AddMethod(function_name, DefSQNonStaticCallback<CL, Func, ST>, 0, NULL, &function_proc, sizeof(function_proc));
+		engine->AddMethod(function_name, DefSQNonStaticCallback<CL, Func, ST>, 0, nullptr, &function_proc, sizeof(function_proc));
 	}
 
 	/**
@@ -45,7 +45,7 @@ public:
 	void DefSQAdvancedMethod(Squirrel *engine, Func function_proc, const char *function_name)
 	{
 		using namespace SQConvert;
-		engine->AddMethod(function_name, DefSQAdvancedNonStaticCallback<CL, Func, ST>, 0, NULL, &function_proc, sizeof(function_proc));
+		engine->AddMethod(function_name, DefSQAdvancedNonStaticCallback<CL, Func, ST>, 0, nullptr, &function_proc, sizeof(function_proc));
 	}
 
 	/**
@@ -68,7 +68,7 @@ public:
 	void DefSQStaticMethod(Squirrel *engine, Func function_proc, const char *function_name)
 	{
 		using namespace SQConvert;
-		engine->AddMethod(function_name, DefSQStaticCallback<CL, Func>, 0, NULL, &function_proc, sizeof(function_proc));
+		engine->AddMethod(function_name, DefSQStaticCallback<CL, Func>, 0, nullptr, &function_proc, sizeof(function_proc));
 	}
 
 	/**
@@ -78,7 +78,7 @@ public:
 	void DefSQAdvancedStaticMethod(Squirrel *engine, Func function_proc, const char *function_name)
 	{
 		using namespace SQConvert;
-		engine->AddMethod(function_name, DefSQAdvancedStaticCallback<CL, Func>, 0, NULL, &function_proc, sizeof(function_proc));
+		engine->AddMethod(function_name, DefSQAdvancedStaticCallback<CL, Func>, 0, nullptr, &function_proc, sizeof(function_proc));
 	}
 
 	/**
@@ -120,7 +120,7 @@ public:
 	void AddSQAdvancedConstructor(Squirrel *engine)
 	{
 		using namespace SQConvert;
-		engine->AddMethod("constructor", DefSQAdvancedConstructorCallback<CL>, 0, NULL);
+		engine->AddMethod("constructor", DefSQAdvancedConstructorCallback<CL>, 0, nullptr);
 	}
 
 	void PostRegister(Squirrel *engine)
diff --git a/src/script/squirrel_helper.hpp b/src/script/squirrel_helper.hpp
--- a/src/script/squirrel_helper.hpp
+++ b/src/script/squirrel_helper.hpp
@@ -88,8 +88,8 @@ namespace SQConvert {
 	template <> inline int Return<int64>       (HSQUIRRELVM vm, int64 res)       { sq_pushinteger(vm, res); return 1; }
 	template <> inline int Return<Money>       (HSQUIRRELVM vm, Money res)       { sq_pushinteger(vm, res); return 1; }
 	template <> inline int Return<bool>        (HSQUIRRELVM vm, bool res)        { sq_pushbool   (vm, res); return 1; }
-	template <> inline int Return<char *>      (HSQUIRRELVM vm, char *res)       { if (res == NULL) sq_pushnull(vm); else { sq_pushstring(vm, res, -1); free(res); } return 1; }
-	template <> inline int Return<const char *>(HSQUIRRELVM vm, const char *res) { if (res == NULL) sq_pushnull(vm); else { sq_pushstring(vm, res, -1); } return 1; }
+	template <> inline int Return<char *>      (HSQUIRRELVM vm, char *res)       { if (res == nullptr) sq_pushnull(vm); else { sq_pushstring(vm, res, -1); free(res); } return 1; }
+	template <> inline int Return<const char *>(HSQUIRRELVM vm, const char *res) { if (res == nullptr) sq_pushnull(vm); else { sq_pushstring(vm, res, -1); } return 1; }
 	template <> inline int Return<void *>      (HSQUIRRELVM vm, void *res)       { sq_pushuserpointer(vm, res); return 1; }
 	template <> inline int Return<HSQOBJECT>   (HSQUIRRELVM vm, HSQOBJECT res)   { sq_pushobject(vm, res); return 1; }
 
@@ -739,8 +739,8 @@ namespace SQConvert {
 	{
 		/* Find the amount of params we got */
 		int nparam = sq_gettop(vm);
-		SQUserPointer ptr = NULL;
-		SQUserPointer real_instance = NULL;
+		SQUserPointer ptr = nullptr;
+		SQUserPointer real_instance = nullptr;
 		HSQOBJECT instance;
 
 		/* Get the 'SQ' instance of this class */
@@ -759,7 +759,7 @@ namespace SQConvert {
 		sq_getinstanceup(vm, 1, &real_instance, 0);
 		/* Get the real function pointer */
 		sq_getuserdata(vm, nparam, &ptr, 0);
-		if (real_instance == NULL) return sq_throwerror(vm, "couldn't detect real instance of class for non-static call");
+		if (real_instance == nullptr) return sq_throwerror(vm, "couldn't detect real instance of class for non-static call");
 		/* Remove the userdata from the stack */
 		sq_pop(vm, 1);
 
@@ -781,8 +781,8 @@ namespace SQConvert {
 	{
 		/* Find the amount of params we got */
 		int nparam = sq_gettop(vm);
-		SQUserPointer ptr = NULL;
-		SQUserPointer real_instance = NULL;
+		SQUserPointer ptr = nullptr;
+		SQUserPointer real_instance = nullptr;
 		HSQOBJECT instance;
 
 		/* Get the 'SQ' instance of this class */
@@ -801,7 +801,7 @@ namespace SQConvert {
 		sq_getinstanceup(vm, 1, &real_instance, 0);
 		/* Get the real function pointer */
 		sq_getuserdata(vm, nparam, &ptr, 0);
-		if (real_instance == NULL) return sq_throwerror(vm, "couldn't detect real instance of class for non-static call");
+		if (real_instance == nullptr) return sq_throwerror(vm, "couldn't detect real instance of class for non-static call");
 		/* Remove the userdata from the stack */
 		sq_pop(vm, 1);
 
@@ -819,14 +819,14 @@ namespace SQConvert {
 	{
 		/* Find the amount of params we got */
 		int nparam = sq_gettop(vm);
-		SQUserPointer ptr = NULL;
+		SQUserPointer ptr = nullptr;
 
 		/* Get the real function pointer */
 		sq_getuserdata(vm, nparam, &ptr, 0);
 
 		try {
 			/* Delegate it to a template that can handle this specific function */
-			return HelperT<Tmethod>::SQCall((Tcls *)NULL, *(Tmethod *)ptr, vm);
+			return HelperT<Tmethod>::SQCall((Tcls *)nullptr, *(Tmethod *)ptr, vm);
 		} catch (SQInteger e) {
 			return e;
 		}
@@ -843,7 +843,7 @@ namespace SQConvert {
 	{
 		/* Find the amount of params we got */
 		int nparam = sq_gettop(vm);
-		SQUserPointer ptr = NULL;
+		SQUserPointer ptr = nullptr;
 
 		/* Get the real function pointer */
 		sq_getuserdata(vm, nparam, &ptr, 0);
@@ -862,7 +862,7 @@ namespace SQConvert {
 	static SQInteger DefSQDestructorCallback(SQUserPointer p, SQInteger size)
 	{
 		/* Remove the real instance too */
-		if (p != NULL) ((Tcls *)p)->Release();
+		if (p != nullptr) ((Tcls *)p)->Release();
 		return 0;
 	}
 
@@ -876,7 +876,7 @@ namespace SQConvert {
 	{
 		try {
 			/* Create the real instance */
-			Tcls *instance = HelperT<Tmethod>::SQConstruct((Tcls *)NULL, (Tmethod)NULL, vm);
+			Tcls *instance = HelperT<Tmethod>::SQConstruct((Tcls *)nullptr, (Tmethod)nullptr, vm);
 			sq_setinstanceup(vm, -Tnparam, instance);
 			sq_setreleasehook(vm, -Tnparam, DefSQDestructorCallback<Tcls>);
 			instance->AddRef();
diff --git a/src/script/squirrel_std.cpp b/src/script/squirrel_std.cpp
--- a/src/script/squirrel_std.cpp
+++ b/src/script/squirrel_std.cpp
@@ -51,7 +51,7 @@ SQInteger SquirrelStd::require(HSQUIRREL
 	/* Get the script-name of the current file, so we can work relative from it */
 	SQStackInfos si;
 	sq_stackinfos(vm, 1, &si);
-	if (si.source == NULL) {
+	if (si.source == nullptr) {
 		DEBUG(misc, 0, "[squirrel] Couldn't detect the script-name of the 'require'-caller; this should never happen!");
 		return SQ_ERROR;
 	}
@@ -60,7 +60,7 @@ SQInteger SquirrelStd::require(HSQUIRREL
 	strecpy(path, si.source, lastof(path));
 	/* Keep the dir, remove the rest */
 	SQChar *s = strrchr(path, PATHSEPCHAR);
-	if (s != NULL) {
+	if (s != nullptr) {
 		/* Keep the PATHSEPCHAR there, remove the rest */
 		s++;
 		*s = '\0';
diff --git a/src/settings.cpp b/src/settings.cpp
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -96,7 +96,7 @@ static const char * const _list_group_na
 	"newgrf",
 	"servers",
 	"server_bind_addresses",
-	NULL
+	nullptr
 };
 
 /**
@@ -114,7 +114,7 @@ static size_t LookupOneOfMany(const char
 	if (onelen == 0) onelen = strlen(one);
 
 	/* check if it's an integer */
-	if (*one >= '0' && *one <= '9') return strtoul(one, NULL, 0);
+	if (*one >= '0' && *one <= '9') return strtoul(one, nullptr, 0);
 
 	idx = 0;
 	for (;;) {
@@ -218,7 +218,7 @@ static bool LoadIntList(const char *str,
 	int items[64];
 	int i, nitems;
 
-	if (str == NULL) {
+	if (str == nullptr) {
 		memset(items, 0, sizeof(items));
 		nitems = nelems;
 	} else {
@@ -348,7 +348,7 @@ static void MakeManyOfMany(char *buf, co
  */
 static const void *StringToVal(const SettingDescBase *desc, const char *orig_str)
 {
-	const char *str = orig_str == NULL ? "" : orig_str;
+	const char *str = orig_str == nullptr ? "" : orig_str;
 
 	switch (desc->cmd) {
 		case SDT_NUMX: {
@@ -373,7 +373,7 @@ static const void *StringToVal(const Set
 			size_t r = LookupOneOfMany(desc->many, str);
 			/* if the first attempt of conversion from string to the appropriate value fails,
 			 * look if we have defined a converter from old value to new value. */
-			if (r == (size_t)-1 && desc->proc_cnvt != NULL) r = desc->proc_cnvt(str);
+			if (r == (size_t)-1 && desc->proc_cnvt != nullptr) r = desc->proc_cnvt(str);
 			if (r != (size_t)-1) return (void*)r; // and here goes converted value
 
 			ErrorMessageData msg(STR_CONFIG_ERROR, STR_CONFIG_ERROR_INVALID_VALUE);
@@ -409,7 +409,7 @@ static const void *StringToVal(const Set
 		default: break;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -508,7 +508,7 @@ static void IniLoadSettings(IniFile *ini
 
 		/* For settings.xx.yy load the settings from [xx] yy = ? */
 		s = strchr(sdb->name, '.');
-		if (s != NULL) {
+		if (s != nullptr) {
 			group = ini->GetGroup(sdb->name, s - sdb->name);
 			s++;
 		} else {
@@ -517,19 +517,19 @@ static void IniLoadSettings(IniFile *ini
 		}
 
 		item = group->GetItem(s, false);
-		if (item == NULL && group != group_def) {
+		if (item == nullptr && group != group_def) {
 			/* For settings.xx.yy load the settings from [settingss] yy = ? in case the previous
 			 * did not exist (e.g. loading old config files with a [settings] section */
 			item = group_def->GetItem(s, false);
 		}
-		if (item == NULL) {
+		if (item == nullptr) {
 			/* For settings.xx.zz.yy load the settings from [zz] yy = ? in case the previous
 			 * did not exist (e.g. loading old config files with a [yapf] section */
 			const char *sc = strchr(s, '.');
-			if (sc != NULL) item = ini->GetGroup(s, sc - s)->GetItem(sc + 1, false);
+			if (sc != nullptr) item = ini->GetGroup(s, sc - s)->GetItem(sc + 1, false);
 		}
 
-		p = (item == NULL) ? sdb->def : StringToVal(sdb, item->value);
+		p = (item == nullptr) ? sdb->def : StringToVal(sdb, item->value);
 		ptr = GetVariableAddress(object, sld);
 
 		switch (sdb->cmd) {
@@ -544,16 +544,16 @@ static void IniLoadSettings(IniFile *ini
 				switch (GetVarMemType(sld->conv)) {
 					case SLE_VAR_STRB:
 					case SLE_VAR_STRBQ:
-						if (p != NULL) strecpy((char*)ptr, (const char*)p, (char*)ptr + sld->length - 1);
+						if (p != nullptr) strecpy((char*)ptr, (const char*)p, (char*)ptr + sld->length - 1);
 						break;
 
 					case SLE_VAR_STR:
 					case SLE_VAR_STRQ:
 						free(*(char**)ptr);
-						*(char**)ptr = p == NULL ? NULL : stredup((const char*)p);
+						*(char**)ptr = p == nullptr ? nullptr : stredup((const char*)p);
 						break;
 
-					case SLE_VAR_CHAR: if (p != NULL) *(char *)ptr = *(const char *)p; break;
+					case SLE_VAR_CHAR: if (p != nullptr) *(char *)ptr = *(const char *)p; break;
 
 					default: NOT_REACHED();
 				}
@@ -567,7 +567,7 @@ static void IniLoadSettings(IniFile *ini
 
 					/* Use default */
 					LoadIntList((const char*)sdb->def, ptr, sld->length, GetVarMemType(sld->conv));
-				} else if (sd->desc.proc_cnvt != NULL) {
+				} else if (sd->desc.proc_cnvt != nullptr) {
 					sd->desc.proc_cnvt((const char*)p);
 				}
 				break;
@@ -591,7 +591,7 @@ static void IniLoadSettings(IniFile *ini
  */
 static void IniSaveSettings(IniFile *ini, const SettingDesc *sd, const char *grpname, void *object)
 {
-	IniGroup *group_def = NULL, *group;
+	IniGroup *group_def = nullptr, *group;
 	IniItem *item;
 	char buf[512];
 	const char *s;
@@ -608,11 +608,11 @@ static void IniSaveSettings(IniFile *ini
 
 		/* XXX - wtf is this?? (group override?) */
 		s = strchr(sdb->name, '.');
-		if (s != NULL) {
+		if (s != nullptr) {
 			group = ini->GetGroup(sdb->name, s - sdb->name);
 			s++;
 		} else {
-			if (group_def == NULL) group_def = ini->GetGroup(grpname);
+			if (group_def == nullptr) group_def = ini->GetGroup(grpname);
 			s = sdb->name;
 			group = group_def;
 		}
@@ -620,7 +620,7 @@ static void IniSaveSettings(IniFile *ini
 		item = group->GetItem(s, true);
 		ptr = GetVariableAddress(object, sld);
 
-		if (item->value != NULL) {
+		if (item->value != nullptr) {
 			/* check if the value is the same as the old value */
 			const void *p = StringToVal(sdb, item->value);
 
@@ -633,7 +633,7 @@ static void IniSaveSettings(IniFile *ini
 				case SDT_MANYOFMANY:
 					switch (GetVarMemType(sld->conv)) {
 						case SLE_VAR_BL:
-							if (*(bool*)ptr == (p != NULL)) continue;
+							if (*(bool*)ptr == (p != nullptr)) continue;
 							break;
 
 						case SLE_VAR_I8:
@@ -684,7 +684,7 @@ static void IniSaveSettings(IniFile *ini
 					case SLE_VAR_STR:  strecpy(buf, *(char**)ptr, lastof(buf)); break;
 
 					case SLE_VAR_STRQ:
-						if (*(char**)ptr == NULL) {
+						if (*(char**)ptr == nullptr) {
 							buf[0] = '\0';
 						} else {
 							seprintf(buf, lastof(buf), "\"%s\"", *(char**)ptr);
@@ -711,7 +711,7 @@ static void IniSaveSettings(IniFile *ini
 
 /**
  * Loads all items from a 'grpname' section into a list
- * The list parameter can be a NULL pointer, in this case nothing will be
+ * The list parameter can be a nullptr pointer, in this case nothing will be
  * saved and a callback function should be defined that will take over the
  * list-handling and store the data itself somewhere.
  * @param ini IniFile handle to the ini file with the source data
@@ -722,18 +722,18 @@ static void IniLoadSettingList(IniFile *
 {
 	IniGroup *group = ini->GetGroup(grpname);
 
-	if (group == NULL) return;
+	if (group == nullptr) return;
 
 	list.clear();
 
-	for (const IniItem *item = group->item; item != NULL; item = item->next) {
-		if (item->name != NULL) list.emplace_back(item->name);
+	for (const IniItem *item = group->item; item != nullptr; item = item->next) {
+		if (item->name != nullptr) list.emplace_back(item->name);
 	}
 }
 
 /**
  * Saves all items from a list into the 'grpname' section
- * The list parameter can be a NULL pointer, in this case a callback function
+ * The list parameter can be a nullptr pointer, in this case a callback function
  * should be defined that will provide the source data to be saved.
  * @param ini IniFile handle to the ini file where the destination data is saved
  * @param grpname character string identifying the section-header of the ini file
@@ -744,7 +744,7 @@ static void IniSaveSettingList(IniFile *
 {
 	IniGroup *group = ini->GetGroup(grpname);
 
-	if (group == NULL) return;
+	if (group == nullptr) return;
 	group->Clear();
 
 	for (const auto &iter : list) {
@@ -805,7 +805,7 @@ SettingType SettingDesc::GetType() const
 /** Reposition the main toolbar as the setting changed. */
 static bool v_PositionMainToolbar(int32 p1)
 {
-	if (_game_mode != GM_MENU) PositionMainToolbar(NULL);
+	if (_game_mode != GM_MENU) PositionMainToolbar(nullptr);
 	return true;
 }
 
@@ -813,9 +813,9 @@ static bool v_PositionMainToolbar(int32 
 static bool v_PositionStatusbar(int32 p1)
 {
 	if (_game_mode != GM_MENU) {
-		PositionStatusbar(NULL);
-		PositionNewsMessage(NULL);
-		PositionNetworkChatWindow(NULL);
+		PositionStatusbar(nullptr);
+		PositionNewsMessage(nullptr);
+		PositionNetworkChatWindow(nullptr);
 	}
 	return true;
 }
@@ -1416,14 +1416,14 @@ static void AILoadConfig(IniFile *ini, c
 
 	/* Clean any configured AI */
 	for (CompanyID c = COMPANY_FIRST; c < MAX_COMPANIES; c++) {
-		AIConfig::GetConfig(c, AIConfig::SSS_FORCE_NEWGAME)->Change(NULL);
+		AIConfig::GetConfig(c, AIConfig::SSS_FORCE_NEWGAME)->Change(nullptr);
 	}
 
 	/* If no group exists, return */
-	if (group == NULL) return;
+	if (group == nullptr) return;
 
 	CompanyID c = COMPANY_FIRST;
-	for (item = group->item; c < MAX_COMPANIES && item != NULL; c++, item = item->next) {
+	for (item = group->item; c < MAX_COMPANIES && item != nullptr; c++, item = item->next) {
 		AIConfig *config = AIConfig::GetConfig(c, AIConfig::SSS_FORCE_NEWGAME);
 
 		config->Change(item->name);
@@ -1433,7 +1433,7 @@ static void AILoadConfig(IniFile *ini, c
 				continue;
 			}
 		}
-		if (item->value != NULL) config->StringToSettings(item->value);
+		if (item->value != nullptr) config->StringToSettings(item->value);
 	}
 }
 
@@ -1443,13 +1443,13 @@ static void GameLoadConfig(IniFile *ini,
 	IniItem *item;
 
 	/* Clean any configured GameScript */
-	GameConfig::GetConfig(GameConfig::SSS_FORCE_NEWGAME)->Change(NULL);
+	GameConfig::GetConfig(GameConfig::SSS_FORCE_NEWGAME)->Change(nullptr);
 
 	/* If no group exists, return */
-	if (group == NULL) return;
+	if (group == nullptr) return;
 
 	item = group->item;
-	if (item == NULL) return;
+	if (item == nullptr) return;
 
 	GameConfig *config = GameConfig::GetConfig(AIConfig::SSS_FORCE_NEWGAME);
 
@@ -1460,7 +1460,7 @@ static void GameLoadConfig(IniFile *ini,
 			return;
 		}
 	}
-	if (item->value != NULL) config->StringToSettings(item->value);
+	if (item->value != nullptr) config->StringToSettings(item->value);
 }
 
 /**
@@ -1507,13 +1507,13 @@ static GRFConfig *GRFLoadConfig(IniFile 
 {
 	IniGroup *group = ini->GetGroup(grpname);
 	IniItem *item;
-	GRFConfig *first = NULL;
+	GRFConfig *first = nullptr;
 	GRFConfig **curr = &first;
 
-	if (group == NULL) return NULL;
+	if (group == nullptr) return nullptr;
 
-	for (item = group->item; item != NULL; item = item->next) {
-		GRFConfig *c = NULL;
+	for (item = group->item; item != nullptr; item = item->next) {
+		GRFConfig *c = nullptr;
 
 		uint8 grfid_buf[4], md5sum[16];
 		char *filename = item->name;
@@ -1530,14 +1530,14 @@ static GRFConfig *GRFLoadConfig(IniFile 
 			uint32 grfid = grfid_buf[0] | (grfid_buf[1] << 8) | (grfid_buf[2] << 16) | (grfid_buf[3] << 24);
 			if (has_md5sum) {
 				const GRFConfig *s = FindGRFConfig(grfid, FGCM_EXACT, md5sum);
-				if (s != NULL) c = new GRFConfig(*s);
+				if (s != nullptr) c = new GRFConfig(*s);
 			}
-			if (c == NULL && !FioCheckFileExists(filename, NEWGRF_DIR)) {
+			if (c == nullptr && !FioCheckFileExists(filename, NEWGRF_DIR)) {
 				const GRFConfig *s = FindGRFConfig(grfid, FGCM_NEWEST_VALID);
-				if (s != NULL) c = new GRFConfig(*s);
+				if (s != nullptr) c = new GRFConfig(*s);
 			}
 		}
-		if (c == NULL) c = new GRFConfig(filename);
+		if (c == nullptr) c = new GRFConfig(filename);
 
 		/* Parse parameters */
 		if (!StrEmpty(item->value)) {
@@ -1572,7 +1572,7 @@ static GRFConfig *GRFLoadConfig(IniFile 
 
 		/* Check for duplicate GRFID (will also check for duplicate filenames) */
 		bool duplicate = false;
-		for (const GRFConfig *gc = first; gc != NULL; gc = gc->next) {
+		for (const GRFConfig *gc = first; gc != nullptr; gc = gc->next) {
 			if (gc->ident.grfid == c->ident.grfid) {
 				SetDParamStr(0, c->filename);
 				SetDParamStr(1, gc->filename);
@@ -1601,7 +1601,7 @@ static void AISaveConfig(IniFile *ini, c
 {
 	IniGroup *group = ini->GetGroup(grpname);
 
-	if (group == NULL) return;
+	if (group == nullptr) return;
 	group->Clear();
 
 	for (CompanyID c = COMPANY_FIRST; c < MAX_COMPANIES; c++) {
@@ -1625,7 +1625,7 @@ static void GameSaveConfig(IniFile *ini,
 {
 	IniGroup *group = ini->GetGroup(grpname);
 
-	if (group == NULL) return;
+	if (group == nullptr) return;
 	group->Clear();
 
 	GameConfig *config = GameConfig::GetConfig(AIConfig::SSS_FORCE_NEWGAME);
@@ -1671,7 +1671,7 @@ static void GRFSaveConfig(IniFile *ini, 
 	IniGroup *group = ini->GetGroup(grpname);
 	const GRFConfig *c;
 
-	for (c = list; c != NULL; c = c->next) {
+	for (c = list; c != nullptr; c = c->next) {
 		/* Hex grfid (4 bytes in nibbles), "|", hex md5sum (16 bytes in nibbles), "|", file system path. */
 		char key[4 * 2 + 1 + 16 * 2 + 1 + MAX_PATH];
 		char params[512];
@@ -1688,9 +1688,9 @@ static void GRFSaveConfig(IniFile *ini, 
 static void HandleSettingDescs(IniFile *ini, SettingDescProc *proc, SettingDescProcList *proc_list, bool basic_settings = true, bool other_settings = true)
 {
 	if (basic_settings) {
-		proc(ini, (const SettingDesc*)_misc_settings,    "misc",  NULL);
+		proc(ini, (const SettingDesc*)_misc_settings,    "misc",  nullptr);
 #if defined(_WIN32) && !defined(DEDICATED)
-		proc(ini, (const SettingDesc*)_win32_settings,   "win32", NULL);
+		proc(ini, (const SettingDesc*)_win32_settings,   "win32", nullptr);
 #endif /* _WIN32 */
 	}
 
@@ -1739,7 +1739,7 @@ void LoadFromConfig(bool minimal)
 		/* Display sheduled errors */
 		extern void ScheduleErrorMessage(ErrorList &datas);
 		ScheduleErrorMessage(_settings_error_list);
-		if (FindWindowById(WC_ERRMSG, 0) == NULL) ShowFirstError();
+		if (FindWindowById(WC_ERRMSG, 0) == nullptr) ShowFirstError();
 	}
 
 	delete ini;
@@ -1774,7 +1774,7 @@ StringList GetGRFPresetList()
 	StringList list;
 
 	std::unique_ptr<IniFile> ini(IniLoadConfig());
-	for (IniGroup *group = ini->group; group != NULL; group = group->next) {
+	for (IniGroup *group = ini->group; group != nullptr; group = group->next) {
 		if (strncmp(group->name, "preset-", 7) == 0) {
 			list.emplace_back(group->name + 7);
 		}
@@ -1838,7 +1838,7 @@ void DeleteGRFPresetFromConfig(const cha
 
 const SettingDesc *GetSettingDescription(uint index)
 {
-	if (index >= lengthof(_settings)) return NULL;
+	if (index >= lengthof(_settings)) return nullptr;
 	return &_settings[index];
 }
 
@@ -1857,7 +1857,7 @@ CommandCost CmdChangeSetting(TileIndex t
 {
 	const SettingDesc *sd = GetSettingDescription(p1);
 
-	if (sd == NULL) return CMD_ERROR;
+	if (sd == nullptr) return CMD_ERROR;
 	if (!SlIsObjectCurrentlyValid(sd->save.version_from, sd->save.version_to)) return CMD_ERROR;
 
 	if (!sd->IsEditable(true)) return CMD_ERROR;
@@ -1873,7 +1873,7 @@ CommandCost CmdChangeSetting(TileIndex t
 
 		if (oldval == newval) return CommandCost();
 
-		if (sd->desc.proc != NULL && !sd->desc.proc(newval)) {
+		if (sd->desc.proc != nullptr && !sd->desc.proc(newval)) {
 			WriteValue(var, sd->save.conv, (int64)oldval);
 			return CommandCost();
 		}
@@ -1916,7 +1916,7 @@ CommandCost CmdChangeCompanySetting(Tile
 
 		if (oldval == newval) return CommandCost();
 
-		if (sd->desc.proc != NULL && !sd->desc.proc(newval)) {
+		if (sd->desc.proc != nullptr && !sd->desc.proc(newval)) {
 			WriteValue(var, sd->save.conv, (int64)oldval);
 			return CommandCost();
 		}
@@ -1949,7 +1949,7 @@ bool SetSettingValue(uint index, int32 v
 			void *var2 = GetVariableAddress(&_settings_newgame, &sd->save);
 			Write_ValidateSetting(var2, sd, value);
 		}
-		if (sd->desc.proc != NULL) sd->desc.proc((int32)ReadValue(var, sd->save.conv));
+		if (sd->desc.proc != nullptr) sd->desc.proc((int32)ReadValue(var, sd->save.conv));
 
 		SetWindowClassesDirty(WC_GAME_OPTIONS);
 
@@ -1983,7 +1983,7 @@ void SetCompanySetting(uint index, int32
 	} else {
 		void *var = GetVariableAddress(&_settings_client.company, &sd->save);
 		Write_ValidateSetting(var, sd, value);
-		if (sd->desc.proc != NULL) sd->desc.proc((int32)ReadValue(var, sd->save.conv));
+		if (sd->desc.proc != nullptr) sd->desc.proc((int32)ReadValue(var, sd->save.conv));
 	}
 }
 
@@ -2012,7 +2012,7 @@ void SyncCompanySettings()
 		const void *new_var = GetVariableAddress(&_settings_client.company, &sd->save);
 		uint32 old_value = (uint32)ReadValue(old_var, sd->save.conv);
 		uint32 new_value = (uint32)ReadValue(new_var, sd->save.conv);
-		if (old_value != new_value) NetworkSendCommand(0, i, new_value, CMD_CHANGE_COMPANY_SETTING, NULL, NULL, _local_company);
+		if (old_value != new_value) NetworkSendCommand(0, i, new_value, CMD_CHANGE_COMPANY_SETTING, nullptr, nullptr, _local_company);
 	}
 }
 
@@ -2025,7 +2025,7 @@ uint GetCompanySettingIndex(const char *
 {
 	uint i;
 	const SettingDesc *sd = GetSettingFromName(name, &i);
-	assert(sd != NULL && (sd->desc.flags & SGF_PER_COMPANY) != 0);
+	assert(sd != nullptr && (sd->desc.flags & SGF_PER_COMPANY) != 0);
 	return i;
 }
 
@@ -2044,12 +2044,12 @@ bool SetSettingValue(uint index, const c
 	if (GetVarMemType(sd->save.conv) == SLE_VAR_STRQ) {
 		char **var = (char**)GetVariableAddress((_game_mode == GM_MENU || force_newgame) ? &_settings_newgame : &_settings_game, &sd->save);
 		free(*var);
-		*var = strcmp(value, "(null)") == 0 ? NULL : stredup(value);
+		*var = strcmp(value, "(null)") == 0 ? nullptr : stredup(value);
 	} else {
-		char *var = (char*)GetVariableAddress(NULL, &sd->save);
+		char *var = (char*)GetVariableAddress(nullptr, &sd->save);
 		strecpy(var, value, &var[sd->save.length - 1]);
 	}
-	if (sd->desc.proc != NULL) sd->desc.proc(0);
+	if (sd->desc.proc != nullptr) sd->desc.proc(0);
 
 	return true;
 }
@@ -2059,7 +2059,7 @@ bool SetSettingValue(uint index, const c
  * @param name  Name of the setting to return a setting description of
  * @param i     Pointer to an integer that will contain the index of the setting after the call, if it is successful.
  * @return Pointer to the setting description of setting \a name if it can be found,
- *         \c NULL indicates failure to obtain the description
+ *         \c nullptr indicates failure to obtain the description
  */
 const SettingDesc *GetSettingFromName(const char *name, uint *i)
 {
@@ -2075,7 +2075,7 @@ const SettingDesc *GetSettingFromName(co
 	for (*i = 0, sd = _settings; sd->save.cmd != SL_END; sd++, (*i)++) {
 		if (!SlIsObjectCurrentlyValid(sd->save.version_from, sd->save.version_to)) continue;
 		const char *short_name = strchr(sd->desc.name, '.');
-		if (short_name != NULL) {
+		if (short_name != nullptr) {
 			short_name++;
 			if (strcmp(short_name, name) == 0) return sd;
 		}
@@ -2088,7 +2088,7 @@ const SettingDesc *GetSettingFromName(co
 		if (strcmp(sd->desc.name, name) == 0) return sd;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /* Those 2 functions need to be here, else we have to make some stuff non-static
@@ -2098,7 +2098,7 @@ void IConsoleSetSetting(const char *name
 	uint index;
 	const SettingDesc *sd = GetSettingFromName(name, &index);
 
-	if (sd == NULL) {
+	if (sd == nullptr) {
 		IConsolePrintF(CC_WARNING, "'%s' is an unknown setting.", name);
 		return;
 	}
@@ -2131,7 +2131,7 @@ void IConsoleSetSetting(const char *name
 {
 	uint index;
 	const SettingDesc *sd = GetSettingFromName(name, &index);
-	assert(sd != NULL);
+	assert(sd != nullptr);
 	SetSettingValue(index, value);
 }
 
@@ -2147,7 +2147,7 @@ void IConsoleGetSetting(const char *name
 	const SettingDesc *sd = GetSettingFromName(name, &index);
 	const void *ptr;
 
-	if (sd == NULL) {
+	if (sd == nullptr) {
 		IConsolePrintF(CC_WARNING, "'%s' is an unknown setting.", name);
 		return;
 	}
@@ -2171,7 +2171,7 @@ void IConsoleGetSetting(const char *name
 /**
  * List all settings and their value to the console
  *
- * @param prefilter  If not \c NULL, only list settings with names that begin with \a prefilter prefix
+ * @param prefilter  If not \c nullptr, only list settings with names that begin with \a prefilter prefix
  */
 void IConsoleListSettings(const char *prefilter)
 {
@@ -2179,7 +2179,7 @@ void IConsoleListSettings(const char *pr
 
 	for (const SettingDesc *sd = _settings; sd->save.cmd != SL_END; sd++) {
 		if (!SlIsObjectCurrentlyValid(sd->save.version_from, sd->save.version_to)) continue;
-		if (prefilter != NULL && strstr(sd->desc.name, prefilter) == NULL) continue;
+		if (prefilter != nullptr && strstr(sd->desc.name, prefilter) == nullptr) continue;
 		char value[80];
 		const void *ptr = GetVariableAddress(&GetGameSettings(), &sd->save);
 
@@ -2199,7 +2199,7 @@ void IConsoleListSettings(const char *pr
 /**
  * Save and load handler for settings
  * @param osd SettingDesc struct containing all information
- * @param object can be either NULL in which case we load global variables or
+ * @param object can be either nullptr in which case we load global variables or
  * a pointer to a struct which is getting saved
  */
 static void LoadSettings(const SettingDesc *osd, void *object)
@@ -2216,7 +2216,7 @@ static void LoadSettings(const SettingDe
 /**
  * Save and load handler for settings
  * @param sd SettingDesc struct containing all information
- * @param object can be either NULL in which case we load global variables or
+ * @param object can be either nullptr in which case we load global variables or
  * a pointer to a struct which is getting saved
  */
 static void SaveSettings(const SettingDesc *sd, void *object)
@@ -2265,8 +2265,8 @@ static void Save_PATS()
 }
 
 extern const ChunkHandler _setting_chunk_handlers[] = {
-	{ 'OPTS', NULL,      Load_OPTS, NULL, NULL,       CH_RIFF},
-	{ 'PATS', Save_PATS, Load_PATS, NULL, Check_PATS, CH_RIFF | CH_LAST},
+	{ 'OPTS', nullptr,      Load_OPTS, nullptr, nullptr,       CH_RIFF},
+	{ 'PATS', Save_PATS, Load_PATS, nullptr, Check_PATS, CH_RIFF | CH_LAST},
 };
 
 static bool IsSignedVarMemType(VarType vt)
diff --git a/src/settings_gui.cpp b/src/settings_gui.cpp
--- a/src/settings_gui.cpp
+++ b/src/settings_gui.cpp
@@ -73,7 +73,7 @@ static const StringID _font_zoom_dropdow
 };
 
 int _nb_orig_names = SPECSTR_TOWNNAME_LAST - SPECSTR_TOWNNAME_START + 1; ///< Number of original town names.
-static StringID *_grf_names = NULL; ///< Pointer to town names defined by NewGRFs.
+static StringID *_grf_names = nullptr; ///< Pointer to town names defined by NewGRFs.
 static int _nb_grf_names = 0;       ///< Number of town names defined by NewGRFs.
 
 static Dimension _circle_size; ///< Dimension of the circle +/- icon. This is here as not all users are within the class of the settings window.
@@ -198,7 +198,7 @@ struct GameOptionsWindow : Window {
 	 * Build the dropdown list for a specific widget.
 	 * @param widget         Widget to build list for
 	 * @param selected_index Currently selected item
-	 * @return the built dropdown list, or NULL if the widget has no dropdown menu.
+	 * @return the built dropdown list, or nullptr if the widget has no dropdown menu.
 	 */
 	DropDownList BuildDropDownList(int widget, int *selected_index) const
 	{
@@ -436,19 +436,19 @@ struct GameOptionsWindow : Window {
 	void OnClick(Point pt, int widget, int click_count) override
 	{
 		if (widget >= WID_GO_BASE_GRF_TEXTFILE && widget < WID_GO_BASE_GRF_TEXTFILE + TFT_END) {
-			if (BaseGraphics::GetUsedSet() == NULL) return;
+			if (BaseGraphics::GetUsedSet() == nullptr) return;
 
 			ShowBaseSetTextfileWindow((TextfileType)(widget - WID_GO_BASE_GRF_TEXTFILE), BaseGraphics::GetUsedSet(), STR_CONTENT_TYPE_BASE_GRAPHICS);
 			return;
 		}
 		if (widget >= WID_GO_BASE_SFX_TEXTFILE && widget < WID_GO_BASE_SFX_TEXTFILE + TFT_END) {
-			if (BaseSounds::GetUsedSet() == NULL) return;
+			if (BaseSounds::GetUsedSet() == nullptr) return;
 
 			ShowBaseSetTextfileWindow((TextfileType)(widget - WID_GO_BASE_SFX_TEXTFILE), BaseSounds::GetUsedSet(), STR_CONTENT_TYPE_BASE_SOUNDS);
 			return;
 		}
 		if (widget >= WID_GO_BASE_MUSIC_TEXTFILE && widget < WID_GO_BASE_MUSIC_TEXTFILE + TFT_END) {
-			if (BaseMusic::GetUsedSet() == NULL) return;
+			if (BaseMusic::GetUsedSet() == nullptr) return;
 
 			ShowBaseSetTextfileWindow((TextfileType)(widget - WID_GO_BASE_MUSIC_TEXTFILE), BaseMusic::GetUsedSet(), STR_CONTENT_TYPE_BASE_MUSIC);
 			return;
@@ -508,7 +508,7 @@ struct GameOptionsWindow : Window {
 			case WID_GO_ROADSIDE_DROPDOWN: // Road side
 				if (this->opt->vehicle.road_side != index) { // only change if setting changed
 					uint i;
-					if (GetSettingFromName("vehicle.road_side", &i) == NULL) NOT_REACHED();
+					if (GetSettingFromName("vehicle.road_side", &i) == nullptr) NOT_REACHED();
 					SetSettingValue(i, index);
 					MarkWholeScreenDirty();
 				}
@@ -584,9 +584,9 @@ struct GameOptionsWindow : Window {
 		this->GetWidget<NWidgetCore>(WID_GO_BASE_GRF_STATUS)->SetDataTip(missing_files ? STR_EMPTY : STR_GAME_OPTIONS_BASE_GRF_STATUS, STR_NULL);
 
 		for (TextfileType tft = TFT_BEGIN; tft < TFT_END; tft++) {
-			this->SetWidgetDisabledState(WID_GO_BASE_GRF_TEXTFILE + tft, BaseGraphics::GetUsedSet() == NULL || BaseGraphics::GetUsedSet()->GetTextfile(tft) == NULL);
-			this->SetWidgetDisabledState(WID_GO_BASE_SFX_TEXTFILE + tft, BaseSounds::GetUsedSet() == NULL || BaseSounds::GetUsedSet()->GetTextfile(tft) == NULL);
-			this->SetWidgetDisabledState(WID_GO_BASE_MUSIC_TEXTFILE + tft, BaseMusic::GetUsedSet() == NULL || BaseMusic::GetUsedSet()->GetTextfile(tft) == NULL);
+			this->SetWidgetDisabledState(WID_GO_BASE_GRF_TEXTFILE + tft, BaseGraphics::GetUsedSet() == nullptr || BaseGraphics::GetUsedSet()->GetTextfile(tft) == nullptr);
+			this->SetWidgetDisabledState(WID_GO_BASE_SFX_TEXTFILE + tft, BaseSounds::GetUsedSet() == nullptr || BaseSounds::GetUsedSet()->GetTextfile(tft) == nullptr);
+			this->SetWidgetDisabledState(WID_GO_BASE_MUSIC_TEXTFILE + tft, BaseMusic::GetUsedSet() == nullptr || BaseMusic::GetUsedSet()->GetTextfile(tft) == nullptr);
 		}
 
 		missing_files = BaseMusic::GetUsedSet()->GetNumInvalid() == 0;
@@ -879,14 +879,14 @@ bool BaseSettingEntry::IsVisible(const B
  * Find setting entry at row \a row_num
  * @param row_num Index of entry to return
  * @param cur_row Current row number
- * @return The requested setting entry or \c NULL if it not found (folded or filtered)
+ * @return The requested setting entry or \c nullptr if it not found (folded or filtered)
  */
 BaseSettingEntry *BaseSettingEntry::FindEntry(uint row_num, uint *cur_row)
 {
-	if (this->IsFiltered()) return NULL;
+	if (this->IsFiltered()) return nullptr;
 	if (row_num == *cur_row) return this;
 	(*cur_row)++;
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -961,7 +961,7 @@ uint BaseSettingEntry::Draw(GameSettings
 SettingEntry::SettingEntry(const char *name)
 {
 	this->name = name;
-	this->setting = NULL;
+	this->setting = nullptr;
 	this->index = 0;
 }
 
@@ -973,7 +973,7 @@ void SettingEntry::Init(byte level)
 {
 	BaseSettingEntry::Init(level);
 	this->setting = GetSettingFromName(this->name, &this->index);
-	assert(this->setting != NULL);
+	assert(this->setting != nullptr);
 }
 
 /**
@@ -1253,14 +1253,14 @@ uint SettingsContainer::Length() const
  * Find the setting entry at row number \a row_num
  * @param row_num Index of entry to return
  * @param cur_row Variable used for keeping track of the current row number. Should point to memory initialized to \c 0 when first called.
- * @return The requested setting entry or \c NULL if it does not exist
+ * @return The requested setting entry or \c nullptr if it does not exist
  */
 BaseSettingEntry *SettingsContainer::FindEntry(uint row_num, uint *cur_row)
 {
-	BaseSettingEntry *pe = NULL;
+	BaseSettingEntry *pe = nullptr;
 	for (EntryVector::iterator it = this->entries.begin(); it != this->entries.end(); ++it) {
 		pe = (*it)->FindEntry(row_num, cur_row);
-		if (pe != NULL) {
+		if (pe != nullptr) {
 			break;
 		}
 	}
@@ -1416,14 +1416,14 @@ uint SettingsPage::Length() const
  * Find setting entry at row \a row_num
  * @param row_num Index of entry to return
  * @param cur_row Current row number
- * @return The requested setting entry or \c NULL if it not found (folded or filtered)
+ * @return The requested setting entry or \c nullptr if it not found (folded or filtered)
  */
 BaseSettingEntry *SettingsPage::FindEntry(uint row_num, uint *cur_row)
 {
-	if (this->IsFiltered()) return NULL;
+	if (this->IsFiltered()) return nullptr;
 	if (row_num == *cur_row) return this;
 	(*cur_row)++;
-	if (this->folded) return NULL;
+	if (this->folded) return nullptr;
 
 	return SettingsContainer::FindEntry(row_num, cur_row);
 }
@@ -1479,9 +1479,9 @@ void SettingsPage::DrawSetting(GameSetti
 /** Construct settings tree */
 static SettingsContainer &GetSettingsTree()
 {
-	static SettingsContainer *main = NULL;
+	static SettingsContainer *main = nullptr;
 
-	if (main == NULL)
+	if (main == nullptr)
 	{
 		/* Build up the dynamic settings-array only once per OpenTTD session */
 		main = new SettingsContainer();
@@ -1801,10 +1801,10 @@ struct GameSettingsWindow : Window {
 
 	static GameSettings *settings_ptr; ///< Pointer to the game settings being displayed and modified.
 
-	SettingEntry *valuewindow_entry;   ///< If non-NULL, pointer to setting for which a value-entering window has been opened.
-	SettingEntry *clicked_entry;       ///< If non-NULL, pointer to a clicked numeric setting (with a depressed left or right button).
-	SettingEntry *last_clicked;        ///< If non-NULL, pointer to the last clicked setting.
-	SettingEntry *valuedropdown_entry; ///< If non-NULL, pointer to the value for which a dropdown window is currently opened.
+	SettingEntry *valuewindow_entry;   ///< If non-nullptr, pointer to setting for which a value-entering window has been opened.
+	SettingEntry *clicked_entry;       ///< If non-nullptr, pointer to a clicked numeric setting (with a depressed left or right button).
+	SettingEntry *last_clicked;        ///< If non-nullptr, pointer to the last clicked setting.
+	SettingEntry *valuedropdown_entry; ///< If non-nullptr, pointer to the value for which a dropdown window is currently opened.
 	bool closing_dropdown;             ///< True, if the dropdown list is currently closing.
 
 	SettingFilter filter;              ///< Filter for the list.
@@ -1828,10 +1828,10 @@ struct GameSettingsWindow : Window {
 		_circle_size = maxdim(GetSpriteSize(SPR_CIRCLE_FOLDED), GetSpriteSize(SPR_CIRCLE_UNFOLDED));
 		GetSettingsTree().FoldAll(); // Close all sub-pages
 
-		this->valuewindow_entry = NULL; // No setting entry for which a entry window is opened
-		this->clicked_entry = NULL; // No numeric setting buttons are depressed
-		this->last_clicked = NULL;
-		this->valuedropdown_entry = NULL;
+		this->valuewindow_entry = nullptr; // No setting entry for which a entry window is opened
+		this->clicked_entry = nullptr; // No numeric setting buttons are depressed
+		this->last_clicked = nullptr;
+		this->valuedropdown_entry = nullptr;
 		this->closing_dropdown = false;
 		this->manually_changed_folding = false;
 
@@ -1885,9 +1885,9 @@ struct GameSettingsWindow : Window {
 	{
 		if (this->closing_dropdown) {
 			this->closing_dropdown = false;
-			assert(this->valuedropdown_entry != NULL);
+			assert(this->valuedropdown_entry != nullptr);
 			this->valuedropdown_entry->SetButtons(0);
-			this->valuedropdown_entry = NULL;
+			this->valuedropdown_entry = nullptr;
 		}
 
 		/* Reserve the correct number of lines for the 'some search results are hidden' notice in the central settings display panel. */
@@ -1977,7 +1977,7 @@ struct GameSettingsWindow : Window {
 			}
 
 			case WID_GS_HELP_TEXT:
-				if (this->last_clicked != NULL) {
+				if (this->last_clicked != nullptr) {
 					const SettingDesc *sd = this->last_clicked->setting;
 
 					int y = r.top;
@@ -2006,7 +2006,7 @@ struct GameSettingsWindow : Window {
 
 	/**
 	 * Set the entry that should have its help text displayed, and mark the window dirty so it gets repainted.
-	 * @param pe Setting to display help text of, use \c NULL to stop displaying help of the currently displayed setting.
+	 * @param pe Setting to display help text of, use \c nullptr to stop displaying help of the currently displayed setting.
 	 */
 	void SetDisplayedHelpText(SettingEntry *pe)
 	{
@@ -2055,14 +2055,14 @@ struct GameSettingsWindow : Window {
 		uint cur_row = 0;
 		BaseSettingEntry *clicked_entry = GetSettingsTree().FindEntry(btn, &cur_row);
 
-		if (clicked_entry == NULL) return;  // Clicked below the last setting of the page
+		if (clicked_entry == nullptr) return;  // Clicked below the last setting of the page
 
 		int x = (_current_text_dir == TD_RTL ? this->width - 1 - pt.x : pt.x) - SETTINGTREE_LEFT_OFFSET - (clicked_entry->level + 1) * LEVEL_WIDTH;  // Shift x coordinate
 		if (x < 0) return;  // Clicked left of the entry
 
 		SettingsPage *clicked_page = dynamic_cast<SettingsPage*>(clicked_entry);
-		if (clicked_page != NULL) {
-			this->SetDisplayedHelpText(NULL);
+		if (clicked_page != nullptr) {
+			this->SetDisplayedHelpText(nullptr);
 			clicked_page->folded = !clicked_page->folded; // Flip 'folded'-ness of the sub-page
 
 			this->manually_changed_folding = true;
@@ -2072,7 +2072,7 @@ struct GameSettingsWindow : Window {
 		}
 
 		SettingEntry *pe = dynamic_cast<SettingEntry*>(clicked_entry);
-		assert(pe != NULL);
+		assert(pe != nullptr);
 		const SettingDesc *sd = pe->setting;
 
 		/* return if action is only active in network, or only settable by server */
@@ -2094,9 +2094,9 @@ struct GameSettingsWindow : Window {
 				HideDropDownMenu(this);
 				this->closing_dropdown = false;
 				this->valuedropdown_entry->SetButtons(0);
-				this->valuedropdown_entry = NULL;
+				this->valuedropdown_entry = nullptr;
 			} else {
-				if (this->valuedropdown_entry != NULL) this->valuedropdown_entry->SetButtons(0);
+				if (this->valuedropdown_entry != nullptr) this->valuedropdown_entry->SetButtons(0);
 				this->closing_dropdown = false;
 
 				const NWidgetBase *wid = this->GetWidget<NWidgetBase>(WID_GS_OPTIONSPANEL);
@@ -2161,7 +2161,7 @@ struct GameSettingsWindow : Window {
 
 					/* Set up scroller timeout for numeric values */
 					if (value != oldvalue) {
-						if (this->clicked_entry != NULL) { // Release previous buttons if any
+						if (this->clicked_entry != nullptr) { // Release previous buttons if any
 							this->clicked_entry->SetButtons(0);
 						}
 						this->clicked_entry = pe;
@@ -2199,9 +2199,9 @@ struct GameSettingsWindow : Window {
 
 	void OnTimeout() override
 	{
-		if (this->clicked_entry != NULL) { // On timeout, release any depressed buttons
+		if (this->clicked_entry != nullptr) { // On timeout, release any depressed buttons
 			this->clicked_entry->SetButtons(0);
-			this->clicked_entry = NULL;
+			this->clicked_entry = nullptr;
 			this->SetDirty();
 		}
 	}
@@ -2209,9 +2209,9 @@ struct GameSettingsWindow : Window {
 	void OnQueryTextFinished(char *str) override
 	{
 		/* The user pressed cancel */
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
-		assert(this->valuewindow_entry != NULL);
+		assert(this->valuewindow_entry != nullptr);
 		const SettingDesc *sd = this->valuewindow_entry->setting;
 
 		int32 value;
@@ -2260,7 +2260,7 @@ struct GameSettingsWindow : Window {
 			default:
 				if (widget < 0) {
 					/* Deal with drop down boxes on the panel. */
-					assert(this->valuedropdown_entry != NULL);
+					assert(this->valuedropdown_entry != nullptr);
 					const SettingDesc *sd = this->valuedropdown_entry->setting;
 					assert(sd->desc.flags & SGF_MULTISTRING);
 
@@ -2289,7 +2289,7 @@ struct GameSettingsWindow : Window {
 			 * the same dropdown button was clicked again, and then not open the dropdown again.
 			 * So, we only remember that it was closed, and process it on the next OnPaint, which is
 			 * after OnClick. */
-			assert(this->valuedropdown_entry != NULL);
+			assert(this->valuedropdown_entry != nullptr);
 			this->closing_dropdown = true;
 			this->SetDirty();
 		}
@@ -2314,8 +2314,8 @@ struct GameSettingsWindow : Window {
 		}
 		this->vscroll->SetCount(GetSettingsTree().Length() + this->warn_lines);
 
-		if (this->last_clicked != NULL && !GetSettingsTree().IsVisible(this->last_clicked)) {
-			this->SetDisplayedHelpText(NULL);
+		if (this->last_clicked != nullptr && !GetSettingsTree().IsVisible(this->last_clicked)) {
+			this->SetDisplayedHelpText(nullptr);
 		}
 
 		bool all_folded = true;
@@ -2344,7 +2344,7 @@ struct GameSettingsWindow : Window {
 	}
 };
 
-GameSettings *GameSettingsWindow::settings_ptr = NULL;
+GameSettings *GameSettingsWindow::settings_ptr = nullptr;
 
 static const NWidgetPart _nested_settings_selection_widgets[] = {
 	NWidget(NWID_HORIZONTAL),
@@ -2603,7 +2603,7 @@ struct CustomCurrencyWindow : Window {
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
 		switch (this->query_widget) {
 			case WID_CC_RATE:
@@ -2680,7 +2680,7 @@ static const NWidgetPart _nested_cust_cu
 };
 
 static WindowDesc _cust_currency_desc(
-	WDP_CENTER, NULL, 0, 0,
+	WDP_CENTER, nullptr, 0, 0,
 	WC_CUSTOM_CURRENCY, WC_NONE,
 	0,
 	_nested_cust_currency_widgets, lengthof(_nested_cust_currency_widgets)
diff --git a/src/settingsgen/settingsgen.cpp b/src/settingsgen/settingsgen.cpp
--- a/src/settingsgen/settingsgen.cpp
+++ b/src/settingsgen/settingsgen.cpp
@@ -160,10 +160,10 @@ private:
 struct SettingsIniFile : IniLoadFile {
 	/**
 	 * Construct a new ini loader.
-	 * @param list_group_names A \c NULL terminated list with group names that should be loaded as lists instead of variables. @see IGT_LIST
-	 * @param seq_group_names  A \c NULL terminated list with group names that should be loaded as lists of names. @see IGT_SEQUENCE
+	 * @param list_group_names A \c nullptr terminated list with group names that should be loaded as lists instead of variables. @see IGT_LIST
+	 * @param seq_group_names  A \c nullptr terminated list with group names that should be loaded as lists of names. @see IGT_SEQUENCE
 	 */
-	SettingsIniFile(const char * const *list_group_names = NULL, const char * const *seq_group_names = NULL) :
+	SettingsIniFile(const char * const *list_group_names = nullptr, const char * const *seq_group_names = nullptr) :
 			IniLoadFile(list_group_names, seq_group_names)
 	{
 	}
@@ -173,7 +173,7 @@ struct SettingsIniFile : IniLoadFile {
 		/* Open the text file in binary mode to prevent end-of-line translations
 		 * done by ftell() and friends, as defined by K&R. */
 		FILE *in = fopen(filename, "rb");
-		if (in == NULL) return NULL;
+		if (in == nullptr) return nullptr;
 
 		fseek(in, 0L, SEEK_END);
 		*size = ftell(in);
@@ -202,9 +202,9 @@ static const char *DEFAULTS_GROUP_NAME  
  */
 static IniLoadFile *LoadIniFile(const char *filename)
 {
-	static const char * const seq_groups[] = {PREAMBLE_GROUP_NAME, POSTAMBLE_GROUP_NAME, NULL};
+	static const char * const seq_groups[] = {PREAMBLE_GROUP_NAME, POSTAMBLE_GROUP_NAME, nullptr};
 
-	IniLoadFile *ini = new SettingsIniFile(NULL, seq_groups);
+	IniLoadFile *ini = new SettingsIniFile(nullptr, seq_groups);
 	ini->LoadFromDisk(filename, NO_DIRECTORY);
 	return ini;
 }
@@ -217,8 +217,8 @@ static IniLoadFile *LoadIniFile(const ch
 static void DumpGroup(IniLoadFile *ifile, const char * const group_name)
 {
 	IniGroup *grp = ifile->GetGroup(group_name, 0, false);
-	if (grp != NULL && grp->type == IGT_SEQUENCE) {
-		for (IniItem *item = grp->item; item != NULL; item = item->next) {
+	if (grp != nullptr && grp->type == IGT_SEQUENCE) {
+		for (IniItem *item = grp->item; item != nullptr; item = item->next) {
 			if (item->name) {
 				_stored_output.Add(item->name);
 				_stored_output.Add("\n", 1);
@@ -231,14 +231,14 @@ static void DumpGroup(IniLoadFile *ifile
  * Find the value of a template variable.
  * @param name Name of the item to find.
  * @param grp  Group currently being expanded (searched first).
- * @param defaults Fallback group to search, \c NULL skips the search.
- * @return Text of the item if found, else \c NULL.
+ * @param defaults Fallback group to search, \c nullptr skips the search.
+ * @return Text of the item if found, else \c nullptr.
  */
 static const char *FindItemValue(const char *name, IniGroup *grp, IniGroup *defaults)
 {
 	IniItem *item = grp->GetItem(name, false);
-	if (item == NULL && defaults != NULL) item = defaults->GetItem(name, false);
-	if (item == NULL || item->value == NULL) return NULL;
+	if (item == nullptr && defaults != nullptr) item = defaults->GetItem(name, false);
+	if (item == nullptr || item->value == nullptr) return nullptr;
 	return item->value;
 }
 
@@ -249,30 +249,30 @@ static const char *FindItemValue(const c
 static void DumpSections(IniLoadFile *ifile)
 {
 	static const int MAX_VAR_LENGTH = 64;
-	static const char * const special_group_names[] = {PREAMBLE_GROUP_NAME, POSTAMBLE_GROUP_NAME, DEFAULTS_GROUP_NAME, TEMPLATES_GROUP_NAME, NULL};
+	static const char * const special_group_names[] = {PREAMBLE_GROUP_NAME, POSTAMBLE_GROUP_NAME, DEFAULTS_GROUP_NAME, TEMPLATES_GROUP_NAME, nullptr};
 
 	IniGroup *default_grp = ifile->GetGroup(DEFAULTS_GROUP_NAME, 0, false);
 	IniGroup *templates_grp  = ifile->GetGroup(TEMPLATES_GROUP_NAME, 0, false);
-	if (templates_grp == NULL) return;
+	if (templates_grp == nullptr) return;
 
 	/* Output every group, using its name as template name. */
-	for (IniGroup *grp = ifile->group; grp != NULL; grp = grp->next) {
+	for (IniGroup *grp = ifile->group; grp != nullptr; grp = grp->next) {
 		const char * const *sgn;
-		for (sgn = special_group_names; *sgn != NULL; sgn++) if (strcmp(grp->name, *sgn) == 0) break;
-		if (*sgn != NULL) continue;
+		for (sgn = special_group_names; *sgn != nullptr; sgn++) if (strcmp(grp->name, *sgn) == 0) break;
+		if (*sgn != nullptr) continue;
 
 		IniItem *template_item = templates_grp->GetItem(grp->name, false); // Find template value.
-		if (template_item == NULL || template_item->value == NULL) {
+		if (template_item == nullptr || template_item->value == nullptr) {
 			fprintf(stderr, "settingsgen: Warning: Cannot find template %s\n", grp->name);
 			continue;
 		}
 
 		/* Prefix with #if/#ifdef/#ifndef */
-		static const char * const pp_lines[] = {"if", "ifdef", "ifndef", NULL};
+		static const char * const pp_lines[] = {"if", "ifdef", "ifndef", nullptr};
 		int count = 0;
-		for (const char * const *name = pp_lines; *name != NULL; name++) {
+		for (const char * const *name = pp_lines; *name != nullptr; name++) {
 			const char *condition = FindItemValue(*name, grp, default_grp);
-			if (condition != NULL) {
+			if (condition != nullptr) {
 				_stored_output.Add("#", 1);
 				_stored_output.Add(*name);
 				_stored_output.Add(" ", 1);
@@ -311,7 +311,7 @@ static void DumpSections(IniLoadFile *if
 			if (i > 0) {
 				/* Find the text to output. */
 				const char *valitem = FindItemValue(variable, grp, default_grp);
-				if (valitem != NULL) _stored_output.Add(valitem);
+				if (valitem != nullptr) _stored_output.Add(valitem);
 			} else {
 				_stored_output.Add("$", 1);
 			}
@@ -331,10 +331,10 @@ static void DumpSections(IniLoadFile *if
  */
 static void CopyFile(const char *fname, FILE *out_fp)
 {
-	if (fname == NULL) return;
+	if (fname == nullptr) return;
 
 	FILE *in_fp = fopen(fname, "r");
-	if (in_fp == NULL) {
+	if (in_fp == nullptr) {
 		fprintf(stderr, "settingsgen: Warning: Cannot open file %s for copying\n", fname);
 		return;
 	}
@@ -361,10 +361,10 @@ static void CopyFile(const char *fname, 
 static bool CompareFiles(const char *n1, const char *n2)
 {
 	FILE *f2 = fopen(n2, "rb");
-	if (f2 == NULL) return false;
+	if (f2 == nullptr) return false;
 
 	FILE *f1 = fopen(n1, "rb");
-	if (f1 == NULL) {
+	if (f1 == nullptr) {
 		fclose(f2);
 		error("can't open %s", n1);
 	}
@@ -392,7 +392,7 @@ static bool CompareFiles(const char *n1,
 static const OptionData _opts[] = {
 	  GETOPT_NOVAL(     'v', "--version"),
 	  GETOPT_NOVAL(     'h', "--help"),
-	GETOPT_GENERAL('h', '?', NULL, ODF_NO_VALUE),
+	GETOPT_GENERAL('h', '?', nullptr, ODF_NO_VALUE),
 	  GETOPT_VALUE(     'o', "--output"),
 	  GETOPT_VALUE(     'b', "--before"),
 	  GETOPT_VALUE(     'a', "--after"),
@@ -435,9 +435,9 @@ static void ProcessIniFile(const char *f
  */
 int CDECL main(int argc, char *argv[])
 {
-	const char *output_file = NULL;
-	const char *before_file = NULL;
-	const char *after_file = NULL;
+	const char *output_file = nullptr;
+	const char *before_file = nullptr;
+	const char *after_file = nullptr;
 
 	GetOptData mgo(argc - 1, argv + 1, _opts);
 	for (;;) {
@@ -483,7 +483,7 @@ int CDECL main(int argc, char *argv[])
 	for (int i = 0; i < mgo.numleft; i++) ProcessIniFile(mgo.argv[i]);
 
 	/* Write output. */
-	if (output_file == NULL) {
+	if (output_file == nullptr) {
 		CopyFile(before_file, stdout);
 		_stored_output.Write(stdout);
 		CopyFile(after_file, stdout);
@@ -491,7 +491,7 @@ int CDECL main(int argc, char *argv[])
 		static const char * const tmp_output = "tmp2.xxx";
 
 		FILE *fp = fopen(tmp_output, "w");
-		if (fp == NULL) {
+		if (fp == nullptr) {
 			fprintf(stderr, "settingsgen: Warning: Cannot open file %s\n", tmp_output);
 			return 1;
 		}
diff --git a/src/ship_cmd.cpp b/src/ship_cmd.cpp
--- a/src/ship_cmd.cpp
+++ b/src/ship_cmd.cpp
@@ -145,7 +145,7 @@ static const Depot *FindClosestShipDepot
 {
 	/* Find the closest depot */
 	const Depot *depot;
-	const Depot *best_depot = NULL;
+	const Depot *best_depot = nullptr;
 	/* If we don't have a maximum distance, i.e. distance = 0,
 	 * we want to find any depot so the best distance of no
 	 * depot must be more than any correct distance. On the
@@ -184,7 +184,7 @@ static void CheckIfShipNeedsService(Vehi
 
 	const Depot *depot = FindClosestShipDepot(v, max_distance);
 
-	if (depot == NULL) {
+	if (depot == nullptr) {
 		if (v->current_order.IsType(OT_GOTO_DEPOT)) {
 			v->current_order.MakeDummy();
 			SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
@@ -333,7 +333,7 @@ void Ship::UpdateDeltaXY()
  */
 static Vehicle *EnsureNoVisibleShipProc(Vehicle *v, void *data)
 {
-	return v->type == VEH_SHIP && (v->vehstatus & VS_HIDDEN) == 0 ? v : NULL;
+	return v->type == VEH_SHIP && (v->vehstatus & VS_HIDDEN) == 0 ? v : nullptr;
 }
 
 static bool CheckShipLeaveDepot(Ship *v)
@@ -352,7 +352,7 @@ static bool CheckShipLeaveDepot(Ship *v)
 
 	/* Don't leave depot if another vehicle is already entering/leaving */
 	/* This helps avoid CPU load if many ships are set to start at the same time */
-	if (HasVehicleOnPos(v->tile, NULL, &EnsureNoVisibleShipProc)) return true;
+	if (HasVehicleOnPos(v->tile, nullptr, &EnsureNoVisibleShipProc)) return true;
 
 	TileIndex tile = v->tile;
 	Axis axis = GetShipDepotAxis(tile);
@@ -869,10 +869,10 @@ bool Ship::FindClosestDepot(TileIndex *l
 {
 	const Depot *depot = FindClosestShipDepot(this, 0);
 
-	if (depot == NULL) return false;
+	if (depot == nullptr) return false;
 
-	if (location    != NULL) *location    = depot->xy;
-	if (destination != NULL) *destination = depot->index;
+	if (location    != nullptr) *location    = depot->xy;
+	if (destination != nullptr) *destination = depot->index;
 
 	return true;
 }
diff --git a/src/signal.cpp b/src/signal.cpp
--- a/src/signal.cpp
+++ b/src/signal.cpp
@@ -192,7 +192,7 @@ static SmallSet<DiagDirection, SIG_GLOB_
 /** Check whether there is a train on rail, not in a depot */
 static Vehicle *TrainOnTileEnum(Vehicle *v, void *)
 {
-	if (v->type != VEH_TRAIN || Train::From(v)->track == TRACK_BIT_DEPOT) return NULL;
+	if (v->type != VEH_TRAIN || Train::From(v)->track == TRACK_BIT_DEPOT) return nullptr;
 
 	return v;
 }
@@ -283,13 +283,13 @@ static SigFlags ExploreSegment(Owner own
 
 				if (IsRailDepot(tile)) {
 					if (enterdir == INVALID_DIAGDIR) { // from 'inside' - train just entered or left the depot
-						if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, NULL, &TrainOnTileEnum)) flags |= SF_TRAIN;
+						if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags |= SF_TRAIN;
 						exitdir = GetRailDepotDirection(tile);
 						tile += TileOffsByDiagDir(exitdir);
 						enterdir = ReverseDiagDir(exitdir);
 						break;
 					} else if (enterdir == GetRailDepotDirection(tile)) { // entered a depot
-						if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, NULL, &TrainOnTileEnum)) flags |= SF_TRAIN;
+						if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags |= SF_TRAIN;
 						continue;
 					} else {
 						continue;
@@ -306,7 +306,7 @@ static SigFlags ExploreSegment(Owner own
 					if (!(flags & SF_TRAIN) && EnsureNoTrainOnTrackBits(tile, tracks).Failed()) flags |= SF_TRAIN;
 				} else {
 					if (tracks_masked == TRACK_BIT_NONE) continue; // no incidating track
-					if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, NULL, &TrainOnTileEnum)) flags |= SF_TRAIN;
+					if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags |= SF_TRAIN;
 				}
 
 				if (HasSignals(tile)) { // there is exactly one track - not zero, because there is exit from this tile
@@ -358,7 +358,7 @@ static SigFlags ExploreSegment(Owner own
 				if (DiagDirToAxis(enterdir) != GetRailStationAxis(tile)) continue; // different axis
 				if (IsStationTileBlocked(tile)) continue; // 'eye-candy' station tile
 
-				if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, NULL, &TrainOnTileEnum)) flags |= SF_TRAIN;
+				if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags |= SF_TRAIN;
 				tile += TileOffsByDiagDir(exitdir);
 				break;
 
@@ -367,7 +367,7 @@ static SigFlags ExploreSegment(Owner own
 				if (GetTileOwner(tile) != owner) continue;
 				if (DiagDirToAxis(enterdir) == GetCrossingRoadAxis(tile)) continue; // different axis
 
-				if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, NULL, &TrainOnTileEnum)) flags |= SF_TRAIN;
+				if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags |= SF_TRAIN;
 				tile += TileOffsByDiagDir(exitdir);
 				break;
 
@@ -377,13 +377,13 @@ static SigFlags ExploreSegment(Owner own
 				DiagDirection dir = GetTunnelBridgeDirection(tile);
 
 				if (enterdir == INVALID_DIAGDIR) { // incoming from the wormhole
-					if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, NULL, &TrainOnTileEnum)) flags |= SF_TRAIN;
+					if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags |= SF_TRAIN;
 					enterdir = dir;
 					exitdir = ReverseDiagDir(dir);
 					tile += TileOffsByDiagDir(exitdir); // just skip to next tile
 				} else { // NOT incoming from the wormhole!
 					if (ReverseDiagDir(enterdir) != dir) continue;
-					if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, NULL, &TrainOnTileEnum)) flags |= SF_TRAIN;
+					if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags |= SF_TRAIN;
 					tile = GetOtherTunnelBridgeEnd(tile); // just skip to exit tile
 					enterdir = INVALID_DIAGDIR;
 					exitdir = INVALID_DIAGDIR;
diff --git a/src/signs_cmd.cpp b/src/signs_cmd.cpp
--- a/src/signs_cmd.cpp
+++ b/src/signs_cmd.cpp
@@ -81,7 +81,7 @@ CommandCost CmdPlaceSign(TileIndex tile,
 CommandCost CmdRenameSign(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Sign *si = Sign::GetIfValid(p1);
-	if (si == NULL) return CMD_ERROR;
+	if (si == nullptr) return CMD_ERROR;
 	if (si->owner == OWNER_DEITY && _current_company != OWNER_DEITY && _game_mode != GM_EDITOR) return CMD_ERROR;
 
 	/* Rename the signs when empty, otherwise remove it */
diff --git a/src/signs_gui.cpp b/src/signs_gui.cpp
--- a/src/signs_gui.cpp
+++ b/src/signs_gui.cpp
@@ -45,7 +45,7 @@ struct SignList {
 
 	StringFilter string_filter;                                       ///< The match string to be used when the GUIList is (re)-sorted.
 	static bool match_case;                                           ///< Should case sensitive matching be used?
-	static char default_name[64];                                     ///< Default sign name, used if Sign::name is NULL.
+	static char default_name[64];                                     ///< Default sign name, used if Sign::name is nullptr.
 
 	/**
 	 * Creates a SignList with filtering disabled by default.
@@ -81,8 +81,8 @@ struct SignList {
 		const char *a_name = (*a)->name;
 		const char *b_name = (*b)->name;
 
-		if (a_name == NULL) a_name = SignList::default_name;
-		if (b_name == NULL) b_name = SignList::default_name;
+		if (a_name == nullptr) a_name = SignList::default_name;
+		if (b_name == nullptr) b_name = SignList::default_name;
 
 		int r = strnatcmp(a_name, b_name); // Sort by name (natural sorting).
 
@@ -100,7 +100,7 @@ struct SignList {
 		/* Same performance benefit as above for sorting. */
 		const char *a_name = (*a)->name;
 
-		if (a_name == NULL) a_name = SignList::default_name;
+		if (a_name == nullptr) a_name = SignList::default_name;
 
 		filter.ResetState();
 		filter.AddLine(a_name);
@@ -168,7 +168,7 @@ struct SignListWindow : Window, SignList
 
 	void OnInit() override
 	{
-		/* Default sign name, used if Sign::name is NULL. */
+		/* Default sign name, used if Sign::name is nullptr. */
 		GetString(SignList::default_name, STR_DEFAULT_SIGN_NAME, lastof(SignList::default_name));
 		this->signs.ForceResort();
 		this->SortSignsList();
@@ -352,7 +352,7 @@ static EventState SignListGlobalHotkeys(
 {
 	if (_game_mode == GM_MENU) return ES_NOT_HANDLED;
 	Window *w = ShowSignList();
-	if (w == NULL) return ES_NOT_HANDLED;
+	if (w == nullptr) return ES_NOT_HANDLED;
 	return w->OnHotkey(hotkey);
 }
 
@@ -402,7 +402,7 @@ static WindowDesc _sign_list_desc(
 /**
  * Open the sign list window
  *
- * @return newly opened sign list window, or NULL if the window could not be opened.
+ * @return newly opened sign list window, or nullptr if the window could not be opened.
  */
 Window *ShowSignList()
 {
@@ -418,7 +418,7 @@ Window *ShowSignList()
 static bool RenameSign(SignID index, const char *text)
 {
 	bool remove = StrEmpty(text);
-	DoCommandP(0, index, 0, CMD_RENAME_SIGN | (StrEmpty(text) ? CMD_MSG(STR_ERROR_CAN_T_DELETE_SIGN) : CMD_MSG(STR_ERROR_CAN_T_CHANGE_SIGN_NAME)), NULL, text);
+	DoCommandP(0, index, 0, CMD_RENAME_SIGN | (StrEmpty(text) ? CMD_MSG(STR_ERROR_CAN_T_DELETE_SIGN) : CMD_MSG(STR_ERROR_CAN_T_CHANGE_SIGN_NAME)), nullptr, text);
 	return remove;
 }
 
@@ -442,7 +442,7 @@ struct SignWindow : Window, SignList {
 	void UpdateSignEditWindow(const Sign *si)
 	{
 		/* Display an empty string when the sign hasn't been edited yet */
-		if (si->name != NULL) {
+		if (si->name != nullptr) {
 			SetDParam(0, si->index);
 			this->name_editbox.text.Assign(STR_SIGN_NAME);
 		} else {
@@ -559,7 +559,7 @@ static WindowDesc _query_sign_edit_desc(
 void HandleClickOnSign(const Sign *si)
 {
 	if (_ctrl_pressed && (si->owner == _local_company || (si->owner == OWNER_DEITY && _game_mode == GM_EDITOR))) {
-		RenameSign(si->index, NULL);
+		RenameSign(si->index, nullptr);
 		return;
 	}
 	ShowRenameSignWindow(si);
@@ -585,5 +585,5 @@ void DeleteRenameSignWindow(SignID sign)
 {
 	SignWindow *w = dynamic_cast<SignWindow *>(FindWindowById(WC_QUERY_STRING, WN_QUERY_STRING_SIGN));
 
-	if (w != NULL && w->cur_sign == sign) delete w;
+	if (w != nullptr && w->cur_sign == sign) delete w;
 }
diff --git a/src/smallmap_gui.cpp b/src/smallmap_gui.cpp
--- a/src/smallmap_gui.cpp
+++ b/src/smallmap_gui.cpp
@@ -272,9 +272,9 @@ struct SmallMapColourScheme {
 
 /** Available colour schemes for height maps. */
 static SmallMapColourScheme _heightmap_schemes[] = {
-	{NULL, _green_map_heights,      lengthof(_green_map_heights),      MKCOLOUR_XXXX(0x54)}, ///< Green colour scheme.
-	{NULL, _dark_green_map_heights, lengthof(_dark_green_map_heights), MKCOLOUR_XXXX(0x62)}, ///< Dark green colour scheme.
-	{NULL, _violet_map_heights,     lengthof(_violet_map_heights),     MKCOLOUR_XXXX(0x81)}, ///< Violet colour scheme.
+	{nullptr, _green_map_heights,      lengthof(_green_map_heights),      MKCOLOUR_XXXX(0x54)}, ///< Green colour scheme.
+	{nullptr, _dark_green_map_heights, lengthof(_dark_green_map_heights), MKCOLOUR_XXXX(0x62)}, ///< Dark green colour scheme.
+	{nullptr, _violet_map_heights,     lengthof(_violet_map_heights),     MKCOLOUR_XXXX(0x81)}, ///< Violet colour scheme.
 };
 
 /**
@@ -283,7 +283,7 @@ static SmallMapColourScheme _heightmap_s
 void BuildLandLegend()
 {
 	/* The smallmap window has never been initialized, so no need to change the legend. */
-	if (_heightmap_schemes[0].height_colours == NULL) return;
+	if (_heightmap_schemes[0].height_colours == nullptr) return;
 
 	/*
 	 * The general idea of this function is to fill the legend with an appropriate evenly spaced
@@ -1071,7 +1071,7 @@ SmallMapWindow::SmallMapWindow(WindowDes
 
 	this->SetupWidgetData();
 
-	this->SetZoomLevel(ZLC_INITIALIZE, NULL);
+	this->SetZoomLevel(ZLC_INITIALIZE, nullptr);
 	this->SmallMapCenterOnCurrentPos();
 	this->SetOverlayCargoMask();
 }
@@ -1474,7 +1474,7 @@ int SmallMapWindow::GetPositionOnLegend(
 
 		case WID_SM_ENABLE_ALL:
 		case WID_SM_DISABLE_ALL: {
-			LegendAndColour *tbl = NULL;
+			LegendAndColour *tbl = nullptr;
 			switch (this->map_type) {
 				case SMT_INDUSTRY:
 					tbl = _legend_from_industries;
@@ -1682,7 +1682,7 @@ class NWidgetSmallmapDisplay : public NW
 public:
 	NWidgetSmallmapDisplay() : NWidgetContainer(NWID_VERTICAL)
 	{
-		this->smallmap_window = NULL;
+		this->smallmap_window = nullptr;
 	}
 
 	void SetupSmallestSize(Window *w, bool init_array) override
@@ -1694,7 +1694,7 @@ public:
 		bar->SetupSmallestSize(w, init_array);
 
 		this->smallmap_window = dynamic_cast<SmallMapWindow *>(w);
-		assert(this->smallmap_window != NULL);
+		assert(this->smallmap_window != nullptr);
 		this->smallest_x = max(display->smallest_x, bar->smallest_x + smallmap_window->GetMinLegendWidth());
 		this->smallest_y = display->smallest_y + max(bar->smallest_y, smallmap_window->GetLegendHeight(smallmap_window->min_number_of_columns));
 		this->fill_x = max(display->fill_x, bar->fill_x);
@@ -1729,17 +1729,17 @@ public:
 
 	NWidgetCore *GetWidgetFromPos(int x, int y) override
 	{
-		if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return NULL;
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return nullptr;
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			NWidgetCore *widget = child_wid->GetWidgetFromPos(x, y);
-			if (widget != NULL) return widget;
+			if (widget != nullptr) return widget;
 		}
-		return NULL;
+		return nullptr;
 	}
 
 	void Draw(const Window *w) override
 	{
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) child_wid->Draw(w);
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) child_wid->Draw(w);
 	}
 };
 
@@ -1862,7 +1862,7 @@ bool ScrollMainWindowTo(int x, int y, in
 	if (res) return res;
 
 	SmallMapWindow *w = dynamic_cast<SmallMapWindow*>(FindWindowById(WC_SMALLMAP, 0));
-	if (w != NULL) w->SmallMapCenterOnCurrentPos();
+	if (w != nullptr) w->SmallMapCenterOnCurrentPos();
 
 	return res;
 }
diff --git a/src/sortlist_type.h b/src/sortlist_type.h
--- a/src/sortlist_type.h
+++ b/src/sortlist_type.h
@@ -81,8 +81,8 @@ protected:
 
 public:
 	GUIList() :
-		sort_func_list(NULL),
-		filter_func_list(NULL),
+		sort_func_list(nullptr),
+		filter_func_list(nullptr),
 		flags(VL_FIRST_SORT),
 		sort_type(0),
 		filter_type(0),
@@ -296,7 +296,7 @@ public:
 	 */
 	bool Sort()
 	{
-		assert(this->sort_func_list != NULL);
+		assert(this->sort_func_list != nullptr);
 		return this->Sort(this->sort_func_list[this->sort_type]);
 	}
 
@@ -367,7 +367,7 @@ public:
 	 */
 	bool Filter(F filter_data)
 	{
-		if (this->filter_func_list == NULL) return false;
+		if (this->filter_func_list == nullptr) return false;
 		return this->Filter(this->filter_func_list[this->filter_type], filter_data);
 	}
 
diff --git a/src/sound.cpp b/src/sound.cpp
--- a/src/sound.cpp
+++ b/src/sound.cpp
@@ -30,7 +30,7 @@ static void OpenBankFile(const char *fil
 	memset(_original_sounds, 0, sizeof(_original_sounds));
 
 	/* If there is no sound file (nosound set), don't load anything */
-	if (filename == NULL) return;
+	if (filename == nullptr) return;
 
 	FioOpenFile(SOUND_SLOT, filename, BASESET_DIR);
 	size_t pos = FioGetPos();
@@ -110,7 +110,7 @@ static void OpenBankFile(const char *fil
 
 static bool SetBankSource(MixerChannel *mc, const SoundEntry *sound)
 {
-	assert(sound != NULL);
+	assert(sound != nullptr);
 
 	/* Check for valid sound size. */
 	if (sound->file_size == 0 || sound->file_size > ((size_t)-1) - 2) return false;
@@ -162,7 +162,7 @@ static void StartSound(SoundID sound_id,
 	if (volume == 0) return;
 
 	SoundEntry *sound = GetSound(sound_id);
-	if (sound == NULL) return;
+	if (sound == nullptr) return;
 
 	/* NewGRF sound that wasn't loaded yet? */
 	if (sound->rate == 0 && sound->file_slot != 0) {
@@ -177,7 +177,7 @@ static void StartSound(SoundID sound_id,
 	if (sound->rate == 0) return;
 
 	MixerChannel *mc = MxAllocateChannel();
-	if (mc == NULL) return;
+	if (mc == nullptr) return;
 
 	if (!SetBankSource(mc, sound)) return;
 
@@ -244,7 +244,7 @@ static void SndPlayScreenCoordFx(SoundID
 	FOR_ALL_WINDOWS_FROM_BACK(w) {
 		const ViewPort *vp = w->viewport;
 
-		if (vp != NULL &&
+		if (vp != nullptr &&
 				left < vp->virtual_left + vp->virtual_width && right > vp->virtual_left &&
 				top < vp->virtual_top + vp->virtual_height && bottom > vp->virtual_top) {
 			int screen_x = (left + right) / 2 - vp->virtual_left;
@@ -304,14 +304,14 @@ template <class Tbase_set>
 template <class Tbase_set>
 /* static */ bool BaseMedia<Tbase_set>::DetermineBestSet()
 {
-	if (BaseMedia<Tbase_set>::used_set != NULL) return true;
+	if (BaseMedia<Tbase_set>::used_set != nullptr) return true;
 
-	const Tbase_set *best = NULL;
-	for (const Tbase_set *c = BaseMedia<Tbase_set>::available_sets; c != NULL; c = c->next) {
+	const Tbase_set *best = nullptr;
+	for (const Tbase_set *c = BaseMedia<Tbase_set>::available_sets; c != nullptr; c = c->next) {
 		/* Skip unusable sets */
 		if (c->GetNumMissing() != 0) continue;
 
-		if (best == NULL ||
+		if (best == nullptr ||
 				(best->fallback && !c->fallback) ||
 				best->valid_files < c->valid_files ||
 				(best->valid_files == c->valid_files &&
@@ -321,6 +321,6 @@ template <class Tbase_set>
 	}
 
 	BaseMedia<Tbase_set>::used_set = best;
-	return BaseMedia<Tbase_set>::used_set != NULL;
+	return BaseMedia<Tbase_set>::used_set != nullptr;
 }
 
diff --git a/src/sound/allegro_s.cpp b/src/sound/allegro_s.cpp
--- a/src/sound/allegro_s.cpp
+++ b/src/sound/allegro_s.cpp
@@ -22,18 +22,18 @@
 
 static FSoundDriver_Allegro iFSoundDriver_Allegro;
 /** The stream we are writing too */
-static AUDIOSTREAM *_stream = NULL;
+static AUDIOSTREAM *_stream = nullptr;
 /** The number of samples in the buffer */
 static int _buffer_size;
 
 void SoundDriver_Allegro::MainLoop()
 {
 	/* We haven't opened a stream yet */
-	if (_stream == NULL) return;
+	if (_stream == nullptr) return;
 
 	void *data = get_audio_stream_buffer(_stream);
 	/* We don't have to fill the stream yet */
-	if (data == NULL) return;
+	if (data == nullptr) return;
 
 	/* Mix the samples */
 	MxMixSamples(data, _buffer_size);
@@ -54,14 +54,14 @@ extern int _allegro_instance_count;
 
 const char *SoundDriver_Allegro::Start(const char * const *parm)
 {
-	if (_allegro_instance_count == 0 && install_allegro(SYSTEM_AUTODETECT, &errno, NULL)) {
+	if (_allegro_instance_count == 0 && install_allegro(SYSTEM_AUTODETECT, &errno, nullptr)) {
 		DEBUG(driver, 0, "allegro: install_allegro failed '%s'", allegro_error);
 		return "Failed to set up Allegro";
 	}
 	_allegro_instance_count++;
 
 	/* Initialise the sound */
-	if (install_sound(DIGI_AUTODETECT, MIDI_AUTODETECT, NULL) != 0) {
+	if (install_sound(DIGI_AUTODETECT, MIDI_AUTODETECT, nullptr) != 0) {
 		DEBUG(driver, 0, "allegro: install_sound failed '%s'", allegro_error);
 		return "Failed to set up Allegro sound";
 	}
@@ -76,14 +76,14 @@ const char *SoundDriver_Allegro::Start(c
 	_buffer_size = GetDriverParamInt(parm, "samples", 1024) * hz / 11025;
 	_stream = play_audio_stream(_buffer_size, 16, true, hz, 255, 128);
 	MxInitialize(hz);
-	return NULL;
+	return nullptr;
 }
 
 void SoundDriver_Allegro::Stop()
 {
-	if (_stream != NULL) {
+	if (_stream != nullptr) {
 		stop_audio_stream(_stream);
-		_stream = NULL;
+		_stream = nullptr;
 	}
 	remove_sound();
 
diff --git a/src/sound/cocoa_s.cpp b/src/sound/cocoa_s.cpp
--- a/src/sound/cocoa_s.cpp
+++ b/src/sound/cocoa_s.cpp
@@ -80,9 +80,9 @@ const char *SoundDriver_Cocoa::Start(con
 		desc.componentFlags = 0;
 		desc.componentFlagsMask = 0;
 
-		AudioComponent comp = AudioComponentFindNext (NULL, &desc);
-		if (comp == NULL) {
-			return "cocoa_s: Failed to start CoreAudio: AudioComponentFindNext returned NULL";
+		AudioComponent comp = AudioComponentFindNext (nullptr, &desc);
+		if (comp == nullptr) {
+			return "cocoa_s: Failed to start CoreAudio: AudioComponentFindNext returned nullptr";
 		}
 
 		/* Open & initialize the default output audio unit */
@@ -101,9 +101,9 @@ const char *SoundDriver_Cocoa::Start(con
 		desc.componentFlags = 0;
 		desc.componentFlagsMask = 0;
 
-		Component comp = FindNextComponent (NULL, &desc);
-		if (comp == NULL) {
-			return "cocoa_s: Failed to start CoreAudio: FindNextComponent returned NULL";
+		Component comp = FindNextComponent (nullptr, &desc);
+		if (comp == nullptr) {
+			return "cocoa_s: Failed to start CoreAudio: FindNextComponent returned nullptr";
 		}
 
 		/* Open & initialize the default output audio unit */
@@ -126,7 +126,7 @@ const char *SoundDriver_Cocoa::Start(con
 
 	/* Set the audio callback */
 	callback.inputProc = audioCallback;
-	callback.inputProcRefCon = NULL;
+	callback.inputProcRefCon = nullptr;
 	if (AudioUnitSetProperty(_outputAudioUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Input, 0, &callback, sizeof(callback)) != noErr) {
 		return "cocoa_s: Failed to start CoreAudio: AudioUnitSetProperty (kAudioUnitProperty_SetRenderCallback)";
 	}
@@ -137,7 +137,7 @@ const char *SoundDriver_Cocoa::Start(con
 	}
 
 	/* We're running! */
-	return NULL;
+	return nullptr;
 }
 
 
diff --git a/src/sound/null_s.h b/src/sound/null_s.h
--- a/src/sound/null_s.h
+++ b/src/sound/null_s.h
@@ -17,7 +17,7 @@
 /** Implementation of the null sound driver. */
 class SoundDriver_Null : public SoundDriver {
 public:
-	const char *Start(const char * const *param) override { return NULL; }
+	const char *Start(const char * const *param) override { return nullptr; }
 
 	void Stop() override { }
 	const char *GetName() const override { return "null"; }
diff --git a/src/sound/sdl_s.cpp b/src/sound/sdl_s.cpp
--- a/src/sound/sdl_s.cpp
+++ b/src/sound/sdl_s.cpp
@@ -54,7 +54,7 @@ const char *SoundDriver_SDL::Start(const
 	MxInitialize(spec.freq);
 	SDL_OpenAudio(&spec, &spec);
 	SDL_PauseAudio(0);
-	return NULL;
+	return nullptr;
 }
 
 void SoundDriver_SDL::Stop()
diff --git a/src/sound/win32_s.cpp b/src/sound/win32_s.cpp
--- a/src/sound/win32_s.cpp
+++ b/src/sound/win32_s.cpp
@@ -50,12 +50,12 @@ static DWORD WINAPI SoundThread(LPVOID a
 			if ((hdr->dwFlags & WHDR_INQUEUE) != 0) continue;
 			MxMixSamples(hdr->lpData, hdr->dwBufferLength / 4);
 			if (waveOutWrite(_waveout, hdr, sizeof(WAVEHDR)) != MMSYSERR_NOERROR) {
-				MessageBox(NULL, _T("Sounds are disabled until restart."), _T("waveOutWrite failed"), MB_ICONINFORMATION);
+				MessageBox(nullptr, _T("Sounds are disabled until restart."), _T("waveOutWrite failed"), MB_ICONINFORMATION);
 				return 0;
 			}
 		}
 		WaitForSingleObject(_event, INFINITE);
-	} while (_waveout != NULL);
+	} while (_waveout != nullptr);
 
 	return 0;
 }
@@ -75,7 +75,7 @@ const char *SoundDriver_Win32::Start(con
 	_bufsize = min(_bufsize, UINT16_MAX);
 
 	try {
-		if (NULL == (_event = CreateEvent(NULL, FALSE, FALSE, NULL))) throw "Failed to create event";
+		if (nullptr == (_event = CreateEvent(nullptr, FALSE, FALSE, nullptr))) throw "Failed to create event";
 
 		if (waveOutOpen(&_waveout, WAVE_MAPPER, &wfex, (DWORD_PTR)_event, 0, CALLBACK_EVENT) != MMSYSERR_NOERROR) throw "waveOutOpen failed";
 
@@ -84,13 +84,13 @@ const char *SoundDriver_Win32::Start(con
 		PrepareHeader(&_wave_hdr[0]);
 		PrepareHeader(&_wave_hdr[1]);
 
-		if (NULL == (_thread = CreateThread(NULL, 8192, SoundThread, 0, 0, &_threadId))) throw "Failed to create thread";
+		if (nullptr == (_thread = CreateThread(nullptr, 8192, SoundThread, 0, 0, &_threadId))) throw "Failed to create thread";
 	} catch (const char *error) {
 		this->Stop();
 		return error;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 void SoundDriver_Win32::Stop()
@@ -98,7 +98,7 @@ void SoundDriver_Win32::Stop()
 	HWAVEOUT waveout = _waveout;
 
 	/* Stop the sound thread. */
-	_waveout = NULL;
+	_waveout = nullptr;
 	SetEvent(_event);
 	WaitForSingleObject(_thread, INFINITE);
 
diff --git a/src/sound/xaudio2_s.cpp b/src/sound/xaudio2_s.cpp
--- a/src/sound/xaudio2_s.cpp
+++ b/src/sound/xaudio2_s.cpp
@@ -125,7 +125,7 @@ static StreamingVoiceContext* _voice_con
 * Initialises the XAudio2 driver.
 *
 * @param parm Driver parameters.
-* @return An error message if unsuccessful, or NULL otherwise.
+* @return An error message if unsuccessful, or nullptr otherwise.
 *
 */
 const char *SoundDriver_XAudio2::Start(const char * const *parm)
@@ -140,7 +140,7 @@ const char *SoundDriver_XAudio2::Start(c
 
 	_xaudio_dll_handle = LoadLibraryA(XAUDIO2_DLL_A);
 
-	if (_xaudio_dll_handle == NULL)
+	if (_xaudio_dll_handle == nullptr)
 	{
 		CoUninitialize();
 
@@ -150,7 +150,7 @@ const char *SoundDriver_XAudio2::Start(c
 
 	API_XAudio2Create xAudio2Create = (API_XAudio2Create) GetProcAddress(_xaudio_dll_handle, "XAudio2Create");
 
-	if (xAudio2Create == NULL)
+	if (xAudio2Create == nullptr)
 	{
 		FreeLibrary(_xaudio_dll_handle);
 		CoUninitialize();
@@ -248,7 +248,7 @@ const char *SoundDriver_XAudio2::Start(c
 		return "Failed to submit the first audio buffer";
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
diff --git a/src/sprite.cpp b/src/sprite.cpp
--- a/src/sprite.cpp
+++ b/src/sprite.cpp
@@ -75,7 +75,7 @@ void DrawCommonTileSeq(const TileInfo *t
 					SetBit(image, PALETTE_MODIFIER_TRANSPARENT);
 					pal = PALETTE_TO_TRANSPARENT;
 				}
-				DrawGroundSprite(image, pal, NULL, offs_x, offs_y);
+				DrawGroundSprite(image, pal, nullptr, offs_x, offs_y);
 			}
 		}
 	}
diff --git a/src/spritecache.cpp b/src/spritecache.cpp
--- a/src/spritecache.cpp
+++ b/src/spritecache.cpp
@@ -44,7 +44,7 @@ struct SpriteCache {
 
 
 static uint _spritecache_items = 0;
-static SpriteCache *_spritecache = NULL;
+static SpriteCache *_spritecache = nullptr;
 
 
 static inline SpriteCache *GetSpriteCache(uint index)
@@ -424,7 +424,7 @@ static void *ReadSprite(const SpriteCach
 	}
 
 	if (sprite_avail == 0) {
-		if (sprite_type == ST_MAPGEN) return NULL;
+		if (sprite_type == ST_MAPGEN) return nullptr;
 		if (id == SPR_IMG_QUERY) usererror("Okay... something went horribly wrong. I couldn't load the fallback sprite. What should I do?");
 		return (void*)GetRawSprite(SPR_IMG_QUERY, ST_NORMAL, allocator);
 	}
@@ -535,7 +535,7 @@ bool LoadNextSprite(int load_index, byte
 	byte grf_type = FioReadByte();
 
 	SpriteType type;
-	void *data = NULL;
+	void *data = nullptr;
 	if (grf_type == 0xFF) {
 		/* Some NewGRF files have "empty" pseudo-sprites which are 1
 		 * byte long. Catch these so the sprites won't be displayed. */
@@ -595,7 +595,7 @@ void DupSprite(SpriteID old_spr, SpriteI
 
 	scnew->file_slot = scold->file_slot;
 	scnew->file_pos = scold->file_pos;
-	scnew->ptr = NULL;
+	scnew->ptr = nullptr;
 	scnew->id = scold->id;
 	scnew->type = scold->type;
 	scnew->warned = false;
@@ -643,7 +643,7 @@ void IncreaseSpriteLRU()
 
 		for (i = 0; i != _spritecache_items; i++) {
 			SpriteCache *sc = GetSpriteCache(i);
-			if (sc->ptr != NULL) {
+			if (sc->ptr != nullptr) {
 				if (sc->lru >= 0) {
 					sc->lru = -1;
 				} else if (sc->lru != -32768) {
@@ -715,7 +715,7 @@ static void DeleteEntryFromSpriteCache(u
 	MemBlock *s = (MemBlock*)GetSpriteCache(item)->ptr - 1;
 	assert(!(s->size & S_FREE_MASK));
 	s->size |= S_FREE_MASK;
-	GetSpriteCache(item)->ptr = NULL;
+	GetSpriteCache(item)->ptr = nullptr;
 
 	/* And coalesce adjacent free blocks */
 	for (s = _spritecache_ptr; s->size != 0; s = NextBlock(s)) {
@@ -737,7 +737,7 @@ static void DeleteEntryFromSpriteCache()
 	cur_lru = 0xffff;
 	for (SpriteID i = 0; i != _spritecache_items; i++) {
 		SpriteCache *sc = GetSpriteCache(i);
-		if (sc->type != ST_RECOLOUR && sc->ptr != NULL && sc->lru < cur_lru) {
+		if (sc->type != ST_RECOLOUR && sc->ptr != nullptr && sc->lru < cur_lru) {
 			cur_lru = sc->lru;
 			best = i;
 		}
@@ -807,7 +807,7 @@ static void *HandleInvalidSpriteRequest(
 
 	SpriteType available = sc->type;
 	if (requested == ST_FONT && available == ST_NORMAL) {
-		if (sc->ptr == NULL) sc->type = ST_FONT;
+		if (sc->ptr == nullptr) sc->type = ST_FONT;
 		return GetRawSprite(sprite, sc->type, allocator);
 	}
 
@@ -837,7 +837,7 @@ static void *HandleInvalidSpriteRequest(
  * If the sprite is not available or of wrong type, a fallback sprite is returned.
  * @param sprite Sprite to read.
  * @param type Expected sprite type.
- * @param allocator Allocator function to use. Set to NULL to use the usual sprite cache.
+ * @param allocator Allocator function to use. Set to nullptr to use the usual sprite cache.
  * @return Sprite raw data
  */
 void *GetRawSprite(SpriteID sprite, SpriteType type, AllocatorProc *allocator)
@@ -856,14 +856,14 @@ void *GetRawSprite(SpriteID sprite, Spri
 
 	if (sc->type != type) return HandleInvalidSpriteRequest(sprite, type, sc, allocator);
 
-	if (allocator == NULL) {
+	if (allocator == nullptr) {
 		/* Load sprite into/from spritecache */
 
 		/* Update LRU */
 		sc->lru = ++_sprite_lru_counter;
 
 		/* Load the sprite, if it is not loaded, yet */
-		if (sc->ptr == NULL) sc->ptr = ReadSprite(sc, sprite, type, AllocSprite);
+		if (sc->ptr == nullptr) sc->ptr = ReadSprite(sc, sprite, type, AllocSprite);
 
 		return sc->ptr;
 	} else {
@@ -882,7 +882,7 @@ static void GfxInitSpriteCache()
 	/* Remember 'target_size' from the previous allocation attempt, so we do not try to reach the target_size multiple times in case of failure. */
 	static uint last_alloc_attempt = 0;
 
-	if (_spritecache_ptr == NULL || (_allocated_sprite_cache_size != target_size && target_size != last_alloc_attempt)) {
+	if (_spritecache_ptr == nullptr || (_allocated_sprite_cache_size != target_size && target_size != last_alloc_attempt)) {
 		delete[] reinterpret_cast<byte *>(_spritecache_ptr);
 
 		last_alloc_attempt = target_size;
@@ -893,10 +893,10 @@ static void GfxInitSpriteCache()
 				/* Try to allocate 50% more to make sure we do not allocate almost all available. */
 				_spritecache_ptr = reinterpret_cast<MemBlock *>(new byte[_allocated_sprite_cache_size + _allocated_sprite_cache_size / 2]);
 			} catch (std::bad_alloc &) {
-				_spritecache_ptr = NULL;
+				_spritecache_ptr = nullptr;
 			}
 
-			if (_spritecache_ptr != NULL) {
+			if (_spritecache_ptr != nullptr) {
 				/* Allocation succeeded, but we wanted less. */
 				delete[] reinterpret_cast<byte *>(_spritecache_ptr);
 				_spritecache_ptr = reinterpret_cast<MemBlock *>(new byte[_allocated_sprite_cache_size]);
@@ -906,7 +906,7 @@ static void GfxInitSpriteCache()
 				/* Try again to allocate half. */
 				_allocated_sprite_cache_size >>= 1;
 			}
-		} while (_spritecache_ptr == NULL);
+		} while (_spritecache_ptr == nullptr);
 
 		if (_allocated_sprite_cache_size != target_size) {
 			DEBUG(misc, 0, "Not enough memory to allocate %d MiB of spritecache. Spritecache was reduced to %d MiB.", target_size / 1024 / 1024, _allocated_sprite_cache_size / 1024 / 1024);
@@ -931,7 +931,7 @@ void GfxInitSpriteMem()
 	/* Reset the spritecache 'pool' */
 	free(_spritecache);
 	_spritecache_items = 0;
-	_spritecache = NULL;
+	_spritecache = nullptr;
 
 	_compact_cache_counter = 0;
 }
@@ -945,7 +945,7 @@ void GfxClearSpriteCache()
 	/* Clear sprite ptr for all cached items */
 	for (uint i = 0; i != _spritecache_items; i++) {
 		SpriteCache *sc = GetSpriteCache(i);
-		if (sc->type != ST_RECOLOUR && sc->ptr != NULL) DeleteEntryFromSpriteCache(i);
+		if (sc->type != ST_RECOLOUR && sc->ptr != nullptr) DeleteEntryFromSpriteCache(i);
 	}
 }
 
diff --git a/src/spritecache.h b/src/spritecache.h
--- a/src/spritecache.h
+++ b/src/spritecache.h
@@ -27,7 +27,7 @@ extern uint _sprite_cache_size;
 
 typedef void *AllocatorProc(size_t size);
 
-void *GetRawSprite(SpriteID sprite, SpriteType type, AllocatorProc *allocator = NULL);
+void *GetRawSprite(SpriteID sprite, SpriteType type, AllocatorProc *allocator = nullptr);
 bool SpriteExists(SpriteID sprite);
 
 SpriteType GetSpriteType(SpriteID sprite);
diff --git a/src/station.cpp b/src/station.cpp
--- a/src/station.cpp
+++ b/src/station.cpp
@@ -108,7 +108,7 @@ Station::~Station()
 
 	for (CargoID c = 0; c < NUM_CARGO; ++c) {
 		LinkGraph *lg = LinkGraph::GetIfValid(this->goods[c].link_graph);
-		if (lg == NULL) continue;
+		if (lg == nullptr) continue;
 
 		for (NodeID node = 0; node < lg->Size(); ++node) {
 			Station *st = Station::Get((*lg)[node].Station());
@@ -187,7 +187,7 @@ RoadStop *Station::GetPrimaryRoadStop(co
 {
 	RoadStop *rs = this->GetPrimaryRoadStop(v->IsBus() ? ROADSTOP_BUS : ROADSTOP_TRUCK);
 
-	for (; rs != NULL; rs = rs->next) {
+	for (; rs != nullptr; rs = rs->next) {
 		/* The vehicle cannot go to this roadstop (different roadtype) */
 		if ((GetRoadTypes(rs->xy) & v->compatible_roadtypes) == ROADTYPES_NONE) continue;
 		/* The vehicle is articulated and can therefore not go to a standard road stop. */
@@ -326,13 +326,13 @@ uint Station::GetCatchmentRadius() const
 	uint ret = CA_NONE;
 
 	if (_settings_game.station.modified_catchment) {
-		if (this->bus_stops          != NULL)         ret = max<uint>(ret, CA_BUS);
-		if (this->truck_stops        != NULL)         ret = max<uint>(ret, CA_TRUCK);
+		if (this->bus_stops          != nullptr)         ret = max<uint>(ret, CA_BUS);
+		if (this->truck_stops        != nullptr)         ret = max<uint>(ret, CA_TRUCK);
 		if (this->train_station.tile != INVALID_TILE) ret = max<uint>(ret, CA_TRAIN);
 		if (this->dock_tile          != INVALID_TILE) ret = max<uint>(ret, CA_DOCK);
 		if (this->airport.tile       != INVALID_TILE) ret = max<uint>(ret, this->airport.GetSpec()->catchment);
 	} else {
-		if (this->bus_stops != NULL || this->truck_stops != NULL || this->train_station.tile != INVALID_TILE || this->dock_tile != INVALID_TILE || this->airport.tile != INVALID_TILE) {
+		if (this->bus_stops != nullptr || this->truck_stops != nullptr || this->train_station.tile != INVALID_TILE || this->dock_tile != INVALID_TILE || this->airport.tile != INVALID_TILE) {
 			ret = CA_UNMODIFIED;
 		}
 	}
@@ -423,7 +423,7 @@ void Station::RecomputeCatchment()
 	}
 	this->catchment_tiles.Initialize(GetCatchmentRect());
 
-	if (!_settings_game.station.serve_neutral_industries && this->industry != NULL) {
+	if (!_settings_game.station.serve_neutral_industries && this->industry != nullptr) {
 		/* Station is associated with an industry, so we only need to deliver to that industry. */
 		TILE_AREA_LOOP(tile, this->industry->location) {
 			if (IsTileType(tile, MP_INDUSTRY) && GetIndustryIndex(tile) == this->industry->index) {
@@ -464,7 +464,7 @@ void Station::RecomputeCatchment()
 			Industry *i = Industry::GetByTile(tile);
 
 			/* Ignore industry if it has a neutral station. It already can't be this station. */
-			if (!_settings_game.station.serve_neutral_industries && i->neutral_station != NULL) continue;
+			if (!_settings_game.station.serve_neutral_industries && i->neutral_station != nullptr) continue;
 
 			i->stations_near.insert(this);
 
diff --git a/src/station_cmd.cpp b/src/station_cmd.cpp
--- a/src/station_cmd.cpp
+++ b/src/station_cmd.cpp
@@ -117,7 +117,7 @@ CommandCost GetStationAround(TileArea ta
 			}
 		}
 	}
-	*st = (closest_station == INVALID_STATION) ? NULL : T::Get(closest_station);
+	*st = (closest_station == INVALID_STATION) ? nullptr : T::Get(closest_station);
 	return CommandCost();
 }
 
@@ -356,13 +356,13 @@ static StringID GenerateStationName(Stat
 /**
  * Find the closest deleted station of the current company
  * @param tile the tile to search from.
- * @return the closest station or NULL if too far.
+ * @return the closest station or nullptr if too far.
  */
 static Station *GetClosestDeletedStation(TileIndex tile)
 {
 	uint threshold = 8;
 
-	Station *best_station = NULL;
+	Station *best_station = nullptr;
 	ForAllStationsRadius(tile, threshold, [&](Station *st) {
 		if (!st->IsInUse() && st->owner == _current_company) {
 			uint cur_dist = DistanceManhattan(tile, st->xy);
@@ -370,7 +370,7 @@ static Station *GetClosestDeletedStation
 			if (cur_dist < threshold) {
 				threshold = cur_dist;
 				best_station = st;
-			} else if (cur_dist == threshold && best_station != NULL) {
+			} else if (cur_dist == threshold && best_station != nullptr) {
 				/* In case of a tie, lowest station ID wins */
 				if (st->index < best_station->index) best_station = st;
 			}
@@ -528,7 +528,7 @@ CargoArray GetProductionAroundTiles(Tile
 	for (IndustryID industry : industries) {
 		const Industry *i = Industry::Get(industry);
 		/* Skip industry with neutral station */
-		if (i->neutral_station != NULL && !_settings_game.station.serve_neutral_industries) continue;
+		if (i->neutral_station != nullptr && !_settings_game.station.serve_neutral_industries) continue;
 
 		for (uint j = 0; j < lengthof(i->produced_cargo); j++) {
 			CargoID cargo = i->produced_cargo[j];
@@ -545,13 +545,13 @@ CargoArray GetProductionAroundTiles(Tile
  * @param w X extent of area
  * @param h Y extent of area
  * @param rad Search radius in addition to given area
- * @param always_accepted bitmask of cargo accepted by houses and headquarters; can be NULL
- * @param ind Industry associated with neutral station (e.g. oil rig) or NULL
+ * @param always_accepted bitmask of cargo accepted by houses and headquarters; can be nullptr
+ * @param ind Industry associated with neutral station (e.g. oil rig) or nullptr
  */
 CargoArray GetAcceptanceAroundTiles(TileIndex tile, int w, int h, int rad, CargoTypes *always_accepted)
 {
 	CargoArray acceptance;
-	if (always_accepted != NULL) *always_accepted = 0;
+	if (always_accepted != nullptr) *always_accepted = 0;
 
 	int x = TileX(tile);
 	int y = TileY(tile);
@@ -573,7 +573,7 @@ CargoArray GetAcceptanceAroundTiles(Tile
 			TileIndex tile = TileXY(xc, yc);
 
 			/* Ignore industry if it has a neutral station. */
-			if (!_settings_game.station.serve_neutral_industries && IsTileType(tile, MP_INDUSTRY) && Industry::GetByTile(tile)->neutral_station != NULL) continue;
+			if (!_settings_game.station.serve_neutral_industries && IsTileType(tile, MP_INDUSTRY) && Industry::GetByTile(tile)->neutral_station != nullptr) continue;
 
 			AddAcceptedCargo(tile, acceptance, always_accepted);
 		}
@@ -585,12 +585,12 @@ CargoArray GetAcceptanceAroundTiles(Tile
 /**
  * Get the acceptance of cargoes around the station in.
  * @param st Station to get acceptance of.
- * @param always_accepted bitmask of cargo accepted by houses and headquarters; can be NULL
+ * @param always_accepted bitmask of cargo accepted by houses and headquarters; can be nullptr
  */
 static CargoArray GetAcceptanceAroundStation(const Station *st, CargoTypes *always_accepted)
 {
 	CargoArray acceptance;
-	if (always_accepted != NULL) *always_accepted = 0;
+	if (always_accepted != nullptr) *always_accepted = 0;
 
 	BitmapTileIterator it(st->catchment_tiles);
 	for (TileIndex tile = it; tile != INVALID_TILE; tile = ++it) {
@@ -712,9 +712,9 @@ static void UpdateStationSignCoord(BaseS
 static CommandCost BuildStationPart(Station **st, DoCommandFlag flags, bool reuse, TileArea area, StationNaming name_class)
 {
 	/* Find a deleted station close to us */
-	if (*st == NULL && reuse) *st = GetClosestDeletedStation(area.tile);
-
-	if (*st != NULL) {
+	if (*st == nullptr && reuse) *st = GetClosestDeletedStation(area.tile);
+
+	if (*st != nullptr) {
 		if ((*st)->owner != _current_company) {
 			return_cmd_error(CMD_ERROR);
 		}
@@ -894,7 +894,7 @@ static CommandCost CheckFlatLandRailStat
 	uint invalid_dirs = 5 << axis;
 
 	const StationSpec *statspec = StationClass::Get(spec_class)->GetSpec(spec_index);
-	bool slope_cb = statspec != NULL && HasBit(statspec->callback_mask, CBM_STATION_SLOPE_CHECK);
+	bool slope_cb = statspec != nullptr && HasBit(statspec->callback_mask, CBM_STATION_SLOPE_CHECK);
 
 	TILE_AREA_LOOP(tile_cur, tile_area) {
 		CommandCost ret = CheckBuildableTile(tile_cur, invalid_dirs, allowed_z, false);
@@ -910,7 +910,7 @@ static CommandCost CheckFlatLandRailStat
 		/* if station is set, then we have special handling to allow building on top of already existing stations.
 		 * so station points to INVALID_STATION if we can build on any station.
 		 * Or it points to a station if we're only allowed to build on exactly that station. */
-		if (station != NULL && IsTileType(tile_cur, MP_STATION)) {
+		if (station != nullptr && IsTileType(tile_cur, MP_STATION)) {
 			if (!IsRailStation(tile_cur)) {
 				return ClearTile_Station(tile_cur, DC_AUTO); // get error message
 			} else {
@@ -941,7 +941,7 @@ static CommandCost CheckFlatLandRailStat
 					/* Check for trains having a reservation for this tile. */
 					if (HasBit(GetRailReservationTrackBits(tile_cur), track)) {
 						Train *v = GetTrainForReservation(tile_cur, track);
-						if (v != NULL) {
+						if (v != nullptr) {
 							affected_vehicles.push_back(v);
 						}
 					}
@@ -986,7 +986,7 @@ static CommandCost CheckFlatLandRoadStop
 		/* If station is set, then we have special handling to allow building on top of already existing stations.
 		 * Station points to INVALID_STATION if we can build on any station.
 		 * Or it points to a station if we're only allowed to build on exactly that station. */
-		if (station != NULL && IsTileType(cur_tile, MP_STATION)) {
+		if (station != nullptr && IsTileType(cur_tile, MP_STATION)) {
 			if (!IsRoadStop(cur_tile)) {
 				return ClearTile_Station(cur_tile, DC_AUTO); // Get error message.
 			} else {
@@ -1125,7 +1125,7 @@ static inline byte *CreateMulti(byte *la
  */
 void GetStationLayout(byte *layout, int numtracks, int plat_len, const StationSpec *statspec)
 {
-	if (statspec != NULL && statspec->lengths >= plat_len &&
+	if (statspec != nullptr && statspec->lengths >= plat_len &&
 			statspec->platforms[plat_len - 1] >= numtracks &&
 			statspec->layouts[plat_len - 1][numtracks - 1]) {
 		/* Custom layout defined, follow it. */
@@ -1161,7 +1161,7 @@ void GetStationLayout(byte *layout, int 
 template <class T, StringID error_message>
 CommandCost FindJoiningBaseStation(StationID existing_station, StationID station_to_join, bool adjacent, TileArea ta, T **st)
 {
-	assert(*st == NULL);
+	assert(*st == nullptr);
 	bool check_surrounding = true;
 
 	if (_settings_game.station.adjacent_stations) {
@@ -1174,7 +1174,7 @@ CommandCost FindJoiningBaseStation(Stati
 				/* Extend the current station, and don't check whether it will
 				 * be near any other stations. */
 				*st = T::GetIfValid(existing_station);
-				check_surrounding = (*st == NULL);
+				check_surrounding = (*st == nullptr);
 			}
 		} else {
 			/* There's no station here. Don't check the tiles surrounding this
@@ -1190,7 +1190,7 @@ CommandCost FindJoiningBaseStation(Stati
 	}
 
 	/* Distant join */
-	if (*st == NULL && station_to_join != INVALID_STATION) *st = T::GetIfValid(station_to_join);
+	if (*st == nullptr && station_to_join != INVALID_STATION) *st = T::GetIfValid(station_to_join);
 
 	return CommandCost();
 }
@@ -1318,14 +1318,14 @@ CommandCost CmdBuildRailStation(TileInde
 	cost.AddCost((numtracks * _price[PR_BUILD_STATION_RAIL] + _price[PR_BUILD_STATION_RAIL_LENGTH]) * plat_len);
 	cost.AddCost(numtracks * plat_len * RailBuildCost(rt));
 
-	Station *st = NULL;
+	Station *st = nullptr;
 	ret = FindJoiningStation(est, station_to_join, adjacent, new_location, &st);
 	if (ret.Failed()) return ret;
 
 	ret = BuildStationPart(&st, flags, reuse, new_location, STATIONNAMING_RAIL);
 	if (ret.Failed()) return ret;
 
-	if (st != NULL && st->train_station.tile != INVALID_TILE) {
+	if (st != nullptr && st->train_station.tile != INVALID_TILE) {
 		CommandCost ret = CanExpandRailStation(st, new_location, axis);
 		if (ret.Failed()) return ret;
 	}
@@ -1335,7 +1335,7 @@ CommandCost CmdBuildRailStation(TileInde
 	int specindex = AllocateSpecToStation(statspec, st, (flags & DC_EXEC) != 0);
 	if (specindex == -1) return_cmd_error(STR_ERROR_TOO_MANY_STATION_SPECS);
 
-	if (statspec != NULL) {
+	if (statspec != nullptr) {
 		/* Perform NewStation checks */
 
 		/* Check if the station size is permitted */
@@ -1345,7 +1345,7 @@ CommandCost CmdBuildRailStation(TileInde
 
 		/* Check if the station is buildable */
 		if (HasBit(statspec->callback_mask, CBM_STATION_AVAIL)) {
-			uint16 cb_res = GetStationCallback(CBID_STATION_AVAILABILITY, 0, 0, statspec, NULL, INVALID_TILE);
+			uint16 cb_res = GetStationCallback(CBID_STATION_AVAILABILITY, 0, 0, statspec, nullptr, INVALID_TILE);
 			if (cb_res != CALLBACK_FAILED && !Convert8bitBooleanCallback(statspec->grf_prop.grffile, CBID_STATION_AVAILABILITY, cb_res)) return CMD_ERROR;
 		}
 	}
@@ -1361,7 +1361,7 @@ CommandCost CmdBuildRailStation(TileInde
 
 		st->rect.BeforeAddRect(tile_org, w_org, h_org, StationRect::ADD_TRY);
 
-		if (statspec != NULL) {
+		if (statspec != nullptr) {
 			/* Include this station spec's animation trigger bitmask
 			 * in the station's cached copy. */
 			st->cached_anim_triggers |= statspec->animation.triggers;
@@ -1385,7 +1385,7 @@ CommandCost CmdBuildRailStation(TileInde
 				if (IsRailStationTile(tile) && HasStationReservation(tile)) {
 					/* Check for trains having a reservation for this tile. */
 					Train *v = GetTrainForReservation(tile, AxisToTrack(GetRailStationAxis(tile)));
-					if (v != NULL) {
+					if (v != nullptr) {
 						affected_vehicles.push_back(v);
 						FreeTrainReservation(v);
 					}
@@ -1411,12 +1411,12 @@ CommandCost CmdBuildRailStation(TileInde
 				if (!IsStationTileBlocked(tile)) c->infrastructure.rail[rt]++;
 				c->infrastructure.station++;
 
-				if (statspec != NULL) {
+				if (statspec != nullptr) {
 					/* Use a fixed axis for GetPlatformInfo as our platforms / numtracks are always the right way around */
 					uint32 platinfo = GetPlatformInfo(AXIS_X, GetStationGfx(tile), plat_len, numtracks_orig, plat_len - w, numtracks_orig - numtracks, false);
 
 					/* As the station is not yet completely finished, the station does not yet exist. */
-					uint16 callback = GetStationCallback(CBID_STATION_TILE_LAYOUT, platinfo, 0, statspec, NULL, tile);
+					uint16 callback = GetStationCallback(CBID_STATION_TILE_LAYOUT, platinfo, 0, statspec, nullptr, tile);
 					if (callback != CALLBACK_FAILED) {
 						if (callback < 8) {
 							SetStationGfx(tile, (callback & ~1) + axis);
@@ -1569,7 +1569,7 @@ CommandCost RemoveFromRailBaseStation(Ti
 
 		/* Check ownership of station */
 		T *st = T::GetByTile(tile);
-		if (st == NULL) continue;
+		if (st == nullptr) continue;
 
 		if (_current_company != OWNER_WATER) {
 			CommandCost ret = CheckOwnership(st->owner);
@@ -1592,11 +1592,11 @@ CommandCost RemoveFromRailBaseStation(Ti
 			Track track = GetRailStationTrack(tile);
 			Owner owner = GetTileOwner(tile);
 			RailType rt = GetRailType(tile);
-			Train *v = NULL;
+			Train *v = nullptr;
 
 			if (HasStationReservation(tile)) {
 				v = GetTrainForReservation(tile, track);
-				if (v != NULL) FreeTrainReservation(v);
+				if (v != nullptr) FreeTrainReservation(v);
 			}
 
 			bool build_rail = keep_rail && !IsStationTileBlocked(tile);
@@ -1616,7 +1616,7 @@ CommandCost RemoveFromRailBaseStation(Ti
 
 			include(affected_stations, st);
 
-			if (v != NULL) RestoreTrainReservation(v);
+			if (v != nullptr) RestoreTrainReservation(v);
 		}
 	}
 
@@ -1784,13 +1784,13 @@ static RoadStop **FindRoadStopSpot(bool 
 {
 	RoadStop **primary_stop = (truck_station) ? &st->truck_stops : &st->bus_stops;
 
-	if (*primary_stop == NULL) {
+	if (*primary_stop == nullptr) {
 		/* we have no roadstop of the type yet, so write a "primary stop" */
 		return primary_stop;
 	} else {
 		/* there are stops already, so append to the end of the list */
 		RoadStop *stop = *primary_stop;
-		while (stop->next != NULL) stop = stop->next;
+		while (stop->next != nullptr) stop = stop->next;
 		return &stop->next;
 	}
 }
@@ -1878,7 +1878,7 @@ CommandCost CmdBuildRoadStop(TileIndex t
 	if (ret.Failed()) return ret;
 	cost.AddCost(ret);
 
-	Station *st = NULL;
+	Station *st = nullptr;
 	ret = FindJoiningRoadStop(est, station_to_join, HasBit(p2, 5), roadstop_area, &st);
 	if (ret.Failed()) return ret;
 
@@ -1922,7 +1922,7 @@ CommandCost CmdBuildRoadStop(TileIndex t
 				RoadType rt;
 				FOR_EACH_SET_ROADTYPE(rt, cur_rts | rts) {
 					Company *c = Company::GetIfValid(rt == ROADTYPE_ROAD ? road_owner : tram_owner);
-					if (c != NULL) {
+					if (c != nullptr) {
 						c->infrastructure.road[rt] += 2 - (IsNormalRoadTile(cur_tile) && HasBit(cur_rts, rt) ? CountBits(GetRoadBits(cur_tile, rt)) : 0);
 						DirtyCompanyInfrastructureWindows(c->index);
 					}
@@ -1941,7 +1941,7 @@ CommandCost CmdBuildRoadStop(TileIndex t
 		}
 	}
 
-	if (st != NULL) {
+	if (st != nullptr) {
 		st->AfterStationTileSetChange(true, type ? STATION_TRUCK: STATION_BUS);
 	}
 	return cost;
@@ -1961,7 +1961,7 @@ static Vehicle *ClearRoadStopStatusEnum(
 		if (HasBit(rv->state, RVS_IN_DT_ROAD_STOP)) rv->state &= RVSB_ROAD_STOP_TRACKDIR_MASK;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 
@@ -1992,12 +1992,12 @@ static CommandCost RemoveRoadStop(TileIn
 		cur_stop = RoadStop::GetByTile(tile, ROADSTOP_BUS);
 	}
 
-	assert(cur_stop != NULL);
+	assert(cur_stop != nullptr);
 
 	/* don't do the check for drive-through road stops when company bankrupts */
 	if (IsDriveThroughStopTile(tile) && (flags & DC_BANKRUPT)) {
 		/* remove the 'going through road stop' status from all vehicles on that tile */
-		if (flags & DC_EXEC) FindVehicleOnPos(tile, NULL, &ClearRoadStopStatusEnum);
+		if (flags & DC_EXEC) FindVehicleOnPos(tile, nullptr, &ClearRoadStopStatusEnum);
 	} else {
 		CommandCost ret = EnsureNoVehicleOnGround(tile);
 		if (ret.Failed()) return ret;
@@ -2008,7 +2008,7 @@ static CommandCost RemoveRoadStop(TileIn
 			/* removed the first stop in the list */
 			*primary_stop = cur_stop->next;
 			/* removed the only stop? */
-			if (*primary_stop == NULL) {
+			if (*primary_stop == nullptr) {
 				st->facilities &= (is_truck ? ~FACIL_TRUCK_STOP : ~FACIL_BUS_STOP);
 			}
 		} else {
@@ -2022,7 +2022,7 @@ static CommandCost RemoveRoadStop(TileIn
 		RoadType rt;
 		FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
 			Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
-			if (c != NULL) {
+			if (c != nullptr) {
 				c->infrastructure.road[rt] -= 2;
 				DirtyCompanyInfrastructureWindows(c->index);
 			}
@@ -2055,10 +2055,10 @@ static CommandCost RemoveRoadStop(TileIn
 		/* Update the tile area of the truck/bus stop */
 		if (is_truck) {
 			st->truck_station.Clear();
-			for (const RoadStop *rs = st->truck_stops; rs != NULL; rs = rs->next) st->truck_station.Add(rs->xy);
+			for (const RoadStop *rs = st->truck_stops; rs != nullptr; rs = rs->next) st->truck_station.Add(rs->xy);
 		} else {
 			st->bus_station.Clear();
-			for (const RoadStop *rs = st->bus_stops; rs != NULL; rs = rs->next) st->bus_station.Add(rs->xy);
+			for (const RoadStop *rs = st->bus_stops; rs != nullptr; rs = rs->next) st->bus_station.Add(rs->xy);
 		}
 	}
 
@@ -2131,7 +2131,7 @@ CommandCost CmdRemoveRoadStop(TileIndex 
 			RoadType rt;
 			FOR_EACH_SET_ROADTYPE(rt, rts) {
 				Company *c = Company::GetIfValid(GetRoadOwner(cur_tile, rt));
-				if (c != NULL) {
+				if (c != nullptr) {
 					c->infrastructure.road[rt] += CountBits(road_bits);
 					DirtyCompanyInfrastructureWindows(c->index);
 				}
@@ -2198,7 +2198,7 @@ uint8 GetAirportNoiseLevelForDistance(co
  */
 Town *AirportGetNearestTown(const AirportSpec *as, const TileIterator &it, uint &mindist)
 {
-	Town *t, *nearest = NULL;
+	Town *t, *nearest = nullptr;
 	uint add = as->size_x + as->size_y - 2; // GetMinimalAirportDistanceToTile can differ from DistanceManhattan by this much
 	mindist = UINT_MAX - add; // prevent overflow
 	FOR_ALL_TOWNS(t) {
@@ -2291,7 +2291,7 @@ CommandCost CmdBuildAirport(TileIndex ti
 
 	/* Check if local auth would allow a new airport */
 	StringID authority_refuse_message = STR_NULL;
-	Town *authority_refuse_town = NULL;
+	Town *authority_refuse_town = nullptr;
 
 	if (_settings_game.economy.station_noise_level) {
 		/* do not allow to build a new airport if this raise the town noise over the maximum allowed by town */
@@ -2317,17 +2317,17 @@ CommandCost CmdBuildAirport(TileIndex ti
 		return_cmd_error(authority_refuse_message);
 	}
 
-	Station *st = NULL;
+	Station *st = nullptr;
 	ret = FindJoiningStation(INVALID_STATION, station_to_join, HasBit(p2, 0), airport_area, &st);
 	if (ret.Failed()) return ret;
 
 	/* Distant join */
-	if (st == NULL && distant_join) st = Station::GetIfValid(station_to_join);
+	if (st == nullptr && distant_join) st = Station::GetIfValid(station_to_join);
 
 	ret = BuildStationPart(&st, flags, reuse, airport_area, (GetAirport(airport_type)->flags & AirportFTAClass::AIRPLANES) ? STATIONNAMING_AIRPORT : STATIONNAMING_HELIPORT);
 	if (ret.Failed()) return ret;
 
-	if (st != NULL && st->airport.tile != INVALID_TILE) {
+	if (st != nullptr && st->airport.tile != INVALID_TILE) {
 		return_cmd_error(STR_ERROR_TOO_CLOSE_TO_ANOTHER_AIRPORT);
 	}
 
@@ -2571,17 +2571,17 @@ CommandCost CmdBuildDock(TileIndex tile,
 			_dock_w_chk[direction], _dock_h_chk[direction]);
 
 	/* middle */
-	Station *st = NULL;
+	Station *st = nullptr;
 	ret = FindJoiningStation(INVALID_STATION, station_to_join, HasBit(p1, 0), dock_area, &st);
 	if (ret.Failed()) return ret;
 
 	/* Distant join */
-	if (st == NULL && distant_join) st = Station::GetIfValid(station_to_join);
+	if (st == nullptr && distant_join) st = Station::GetIfValid(station_to_join);
 
 	ret = BuildStationPart(&st, flags, reuse, dock_area, STATIONNAMING_DOCK);
 	if (ret.Failed()) return ret;
 
-	if (st != NULL && st->dock_tile != INVALID_TILE) return_cmd_error(STR_ERROR_TOO_CLOSE_TO_ANOTHER_DOCK);
+	if (st != nullptr && st->dock_tile != INVALID_TILE) return_cmd_error(STR_ERROR_TOO_CLOSE_TO_ANOTHER_DOCK);
 
 	if (flags & DC_EXEC) {
 		st->dock_tile = tile;
@@ -2671,7 +2671,7 @@ const DrawTileSprites *GetStationTileLay
  * Check whether a sprite is a track sprite, which can be replaced by a non-track ground sprite and a rail overlay.
  * If the ground sprite is suitable, \a ground is replaced with the new non-track ground sprite, and \a overlay_offset
  * is set to the overlay to draw.
- * @param         ti             Positional info for the tile to decide snowyness etc. May be NULL.
+ * @param         ti             Positional info for the tile to decide snowyness etc. May be nullptr.
  * @param[in,out] ground         Groundsprite to draw.
  * @param[out]    overlay_offset Overlay to draw.
  * @return true if overlay can be drawn.
@@ -2712,7 +2712,7 @@ bool SplitGroundSpriteForOverlay(const T
 			return false;
 	}
 
-	if (ti != NULL) {
+	if (ti != nullptr) {
 		/* Decide snow/desert from tile */
 		switch (_settings_game.game_creation.landscape) {
 			case LT_ARCTIC:
@@ -2734,16 +2734,16 @@ bool SplitGroundSpriteForOverlay(const T
 
 static void DrawTile_Station(TileInfo *ti)
 {
-	const NewGRFSpriteLayout *layout = NULL;
+	const NewGRFSpriteLayout *layout = nullptr;
 	DrawTileSprites tmp_rail_layout;
-	const DrawTileSprites *t = NULL;
+	const DrawTileSprites *t = nullptr;
 	RoadTypes roadtypes;
 	int32 total_offset;
-	const RailtypeInfo *rti = NULL;
+	const RailtypeInfo *rti = nullptr;
 	uint32 relocation = 0;
 	uint32 ground_relocation = 0;
-	BaseStation *st = NULL;
-	const StationSpec *statspec = NULL;
+	BaseStation *st = nullptr;
+	const StationSpec *statspec = nullptr;
 	uint tile_layout = 0;
 
 	if (HasStationRail(ti->tile)) {
@@ -2756,7 +2756,7 @@ static void DrawTile_Station(TileInfo *t
 			st = BaseStation::GetByTile(ti->tile);
 			statspec = st->speclist[GetCustomStationSpecIndex(ti->tile)].spec;
 
-			if (statspec != NULL) {
+			if (statspec != nullptr) {
 				tile_layout = GetStationGfx(ti->tile);
 
 				if (HasBit(statspec->callback_mask, CBM_STATION_SPRITE_LAYOUT)) {
@@ -2765,11 +2765,11 @@ static void DrawTile_Station(TileInfo *t
 				}
 
 				/* Ensure the chosen tile layout is valid for this custom station */
-				if (statspec->renderdata != NULL) {
+				if (statspec->renderdata != nullptr) {
 					layout = &statspec->renderdata[tile_layout < statspec->tiles ? tile_layout : (uint)GetRailStationAxis(ti->tile)];
 					if (!layout->NeedsPreprocessing()) {
 						t = layout;
-						layout = NULL;
+						layout = nullptr;
 					}
 				}
 			}
@@ -2784,7 +2784,7 @@ static void DrawTile_Station(TileInfo *t
 		gfx = GetAirportGfx(ti->tile);
 		if (gfx >= NEW_AIRPORTTILE_OFFSET) {
 			const AirportTileSpec *ats = AirportTileSpec::Get(gfx);
-			if (ats->grf_prop.spritegroup[0] != NULL && DrawNewAirportTile(ti, Station::GetByTile(ti->tile), gfx, ats)) {
+			if (ats->grf_prop.spritegroup[0] != nullptr && DrawNewAirportTile(ti, Station::GetByTile(ti->tile), gfx, ats)) {
 				return;
 			}
 			/* No sprite group (or no valid one) found, meaning no graphics associated.
@@ -2821,11 +2821,11 @@ static void DrawTile_Station(TileInfo *t
 		palette = PALETTE_TO_GREY;
 	}
 
-	if (layout == NULL && (t == NULL || t->seq == NULL)) t = GetStationTileLayout(GetStationType(ti->tile), gfx);
+	if (layout == nullptr && (t == nullptr || t->seq == nullptr)) t = GetStationTileLayout(GetStationType(ti->tile), gfx);
 
 	/* don't show foundation for docks */
 	if (ti->tileh != SLOPE_FLAT && !IsDock(ti->tile)) {
-		if (statspec != NULL && HasBit(statspec->flags, SSF_CUSTOM_FOUNDATIONS)) {
+		if (statspec != nullptr && HasBit(statspec->flags, SSF_CUSTOM_FOUNDATIONS)) {
 			/* Station has custom foundations.
 			 * Check whether the foundation continues beyond the tile's upper sides. */
 			uint edge_info = 0;
@@ -2912,7 +2912,7 @@ draw_default_foundation:
 			}
 		}
 	} else {
-		if (layout != NULL) {
+		if (layout != nullptr) {
 			/* Sprite layout which needs preprocessing */
 			bool separate_ground = HasBit(statspec->flags, SSF_SEPARATE_GROUND);
 			uint32 var10_values = layout->PrepareLayout(total_offset, rti->fallback_railtype, 0, 0, separate_ground);
@@ -2924,7 +2924,7 @@ draw_default_foundation:
 			tmp_rail_layout.seq = layout->GetLayout(&tmp_rail_layout.ground);
 			t = &tmp_rail_layout;
 			total_offset = 0;
-		} else if (statspec != NULL) {
+		} else if (statspec != nullptr) {
 			/* Simple sprite layout */
 			ground_relocation = relocation = GetCustomStationRelocation(statspec, st, ti->tile, 0);
 			if (HasBit(statspec->flags, SSF_SEPARATE_GROUND)) {
@@ -2936,7 +2936,7 @@ draw_default_foundation:
 		SpriteID image = t->ground.sprite;
 		PaletteID pal  = t->ground.pal;
 		RailTrackOffset overlay_offset;
-		if (rti != NULL && rti->UsesOverlay() && SplitGroundSpriteForOverlay(ti, &image, &overlay_offset)) {
+		if (rti != nullptr && rti->UsesOverlay() && SplitGroundSpriteForOverlay(ti, &image, &overlay_offset)) {
 			SpriteID ground = GetCustomRailSprite(rti, ti->tile, RTSG_GROUND);
 			DrawGroundSprite(image, PAL_NONE);
 			DrawGroundSprite(ground + overlay_offset, PAL_NONE);
@@ -2979,7 +2979,7 @@ void StationPickerDrawSprite(int x, int 
 	int32 total_offset = 0;
 	PaletteID pal = COMPANY_SPRITE_COLOUR(_local_company);
 	const DrawTileSprites *t = GetStationTileLayout(st, image);
-	const RailtypeInfo *rti = NULL;
+	const RailtypeInfo *rti = nullptr;
 
 	if (railtype != INVALID_RAILTYPE) {
 		rti = GetRailTypeInfo(railtype);
@@ -2988,7 +2988,7 @@ void StationPickerDrawSprite(int x, int 
 
 	SpriteID img = t->ground.sprite;
 	RailTrackOffset overlay_offset;
-	if (rti != NULL && rti->UsesOverlay() && SplitGroundSpriteForOverlay(NULL, &img, &overlay_offset)) {
+	if (rti != nullptr && rti->UsesOverlay() && SplitGroundSpriteForOverlay(nullptr, &img, &overlay_offset)) {
 		SpriteID ground = GetCustomRailSprite(rti, INVALID_TILE, RTSG_GROUND);
 		DrawSprite(img, PAL_NONE, x, y);
 		DrawSprite(ground + overlay_offset, PAL_NONE, x, y);
@@ -3044,11 +3044,11 @@ static void GetTileDesc_Station(TileInde
 	if (HasStationTileRail(tile)) {
 		const StationSpec *spec = GetStationSpec(tile);
 
-		if (spec != NULL) {
+		if (spec != nullptr) {
 			td->station_class = StationClass::Get(spec->cls_id)->name;
 			td->station_name  = spec->name;
 
-			if (spec->grf_prop.grffile != NULL) {
+			if (spec->grf_prop.grffile != nullptr) {
 				const GRFConfig *gc = GetGRFConfig(spec->grf_prop.grffile->grfid);
 				td->grf = gc->GetName();
 			}
@@ -3067,10 +3067,10 @@ static void GetTileDesc_Station(TileInde
 		const AirportTileSpec *ats = AirportTileSpec::GetByTile(tile);
 		td->airport_tile_name = ats->name;
 
-		if (as->grf_prop.grffile != NULL) {
+		if (as->grf_prop.grffile != nullptr) {
 			const GRFConfig *gc = GetGRFConfig(as->grf_prop.grffile->grfid);
 			td->grf = gc->GetName();
-		} else if (ats->grf_prop.grffile != NULL) {
+		} else if (ats->grf_prop.grffile != nullptr) {
 			const GRFConfig *gc = GetGRFConfig(ats->grf_prop.grffile->grfid);
 			td->grf = gc->GetName();
 		}
@@ -3090,7 +3090,7 @@ static void GetTileDesc_Station(TileInde
 			const IndustrySpec *is = GetIndustrySpec(i->type);
 			td->owner[0] = i->owner;
 			str = is->name;
-			if (is->grf_prop.grffile != NULL) td->grf = GetGRFConfig(is->grf_prop.grffile->grfid)->GetName();
+			if (is->grf_prop.grffile != nullptr) td->grf = GetGRFConfig(is->grf_prop.grffile->grfid)->GetName();
 			break;
 		}
 		case STATION_DOCK:     str = STR_LAI_STATION_DESCRIPTION_SHIP_DOCK; break;
@@ -3315,7 +3315,7 @@ static void TruncateCargo(const CargoSpe
 	ge->cargo.Truncate(amount, &waiting_per_source);
 	for (StationCargoAmountMap::iterator i(waiting_per_source.begin()); i != waiting_per_source.end(); ++i) {
 		Station *source_station = Station::GetIfValid(i->first);
-		if (source_station == NULL) continue;
+		if (source_station == nullptr) continue;
 
 		GoodsEntry &source_ge = source_station->goods[cs->Index()];
 		source_ge.max_waiting_cargo = max(source_ge.max_waiting_cargo, i->second);
@@ -3494,7 +3494,7 @@ void RerouteCargo(Station *st, CargoID c
 
 	/* Reroute cargo staged to be transferred. */
 	for (std::list<Vehicle *>::iterator it(st->loading_vehicles.begin()); it != st->loading_vehicles.end(); ++it) {
-		for (Vehicle *v = *it; v != NULL; v = v->Next()) {
+		for (Vehicle *v = *it; v != nullptr; v = v->Next()) {
 			if (v->cargo_type != c) continue;
 			v->cargo.Reroute(UINT_MAX, &v->cargo, avoid, avoid2, &ge);
 		}
@@ -3515,7 +3515,7 @@ void DeleteStaleLinks(Station *from)
 		const bool auto_distributed = (_settings_game.linkgraph.GetDistributionType(c) != DT_MANUAL);
 		GoodsEntry &ge = from->goods[c];
 		LinkGraph *lg = LinkGraph::GetIfValid(ge.link_graph);
-		if (lg == NULL) continue;
+		if (lg == nullptr) continue;
 		Node node = (*lg)[ge.node];
 		for (EdgeIterator it(node.Begin()); it != node.End();) {
 			Edge edge = it->second;
@@ -3535,7 +3535,7 @@ void DeleteStaleLinks(Station *from)
 					FOR_ALL_ORDER_LISTS(l) {
 						bool found_from = false;
 						bool found_to = false;
-						for (Order *order = l->GetFirstOrder(); order != NULL; order = order->next) {
+						for (Order *order = l->GetFirstOrder(); order != nullptr; order = order->next) {
 							if (!order->IsType(OT_GOTO_STATION) && !order->IsType(OT_IMPLICIT)) continue;
 							if (order->GetDestination() == from->index) {
 								found_from = true;
@@ -3606,7 +3606,7 @@ void IncreaseStats(Station *st, CargoID 
 	GoodsEntry &ge1 = st->goods[cargo];
 	Station *st2 = Station::Get(next_station_id);
 	GoodsEntry &ge2 = st2->goods[cargo];
-	LinkGraph *lg = NULL;
+	LinkGraph *lg = nullptr;
 	if (ge1.link_graph == INVALID_LINK_GRAPH) {
 		if (ge2.link_graph == INVALID_LINK_GRAPH) {
 			if (LinkGraph::CanAllocateItem()) {
@@ -3642,7 +3642,7 @@ void IncreaseStats(Station *st, CargoID 
 			}
 		}
 	}
-	if (lg != NULL) {
+	if (lg != nullptr) {
 		(*lg)[ge1.node].UpdateEdge(ge2.node, capacity, usage, mode);
 	}
 }
@@ -3655,7 +3655,7 @@ void IncreaseStats(Station *st, CargoID 
  */
 void IncreaseStats(Station *st, const Vehicle *front, StationID next_station_id)
 {
-	for (const Vehicle *v = front; v != NULL; v = v->Next()) {
+	for (const Vehicle *v = front; v != nullptr; v = v->Next()) {
 		if (v->refit_cap > 0) {
 			/* The cargo count can indeed be higher than the refit_cap if
 			 * wagons have been auto-replaced and subsequently auto-
@@ -3752,7 +3752,7 @@ static uint UpdateStationWaiting(Station
 
 	StationID next = ge.GetVia(st->index);
 	ge.cargo.Append(new CargoPacket(st->index, st->xy, amount, source_type, source_id), next);
-	LinkGraph *lg = NULL;
+	LinkGraph *lg = nullptr;
 	if (ge.link_graph == INVALID_LINK_GRAPH) {
 		if (LinkGraph::CanAllocateItem()) {
 			lg = new LinkGraph(type);
@@ -3765,7 +3765,7 @@ static uint UpdateStationWaiting(Station
 	} else {
 		lg = LinkGraph::Get(ge.link_graph);
 	}
-	if (lg != NULL) (*lg)[ge.node].UpdateSupply(amount);
+	if (lg != nullptr) (*lg)[ge.node].UpdateSupply(amount);
 
 	if (!ge.HasRating()) {
 		InvalidateWindowData(WC_STATION_LIST, st->index);
@@ -3786,7 +3786,7 @@ static bool IsUniqueStationName(const ch
 	const Station *st;
 
 	FOR_ALL_STATIONS(st) {
-		if (st->name != NULL && strcmp(st->name, name) == 0) return false;
+		if (st->name != nullptr && strcmp(st->name, name) == 0) return false;
 	}
 
 	return true;
@@ -3804,7 +3804,7 @@ static bool IsUniqueStationName(const ch
 CommandCost CmdRenameStation(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Station *st = Station::GetIfValid(p1);
-	if (st == NULL) return CMD_ERROR;
+	if (st == nullptr) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(st->owner);
 	if (ret.Failed()) return ret;
@@ -3818,7 +3818,7 @@ CommandCost CmdRenameStation(TileIndex t
 
 	if (flags & DC_EXEC) {
 		free(st->name);
-		st->name = reset ? NULL : stredup(text);
+		st->name = reset ? nullptr : stredup(text);
 
 		st->UpdateVirtCoord();
 		InvalidateWindowData(WC_STATION_LIST, st->owner, 1);
@@ -3873,10 +3873,10 @@ void FindStationsAroundTiles(const TileA
 
 	for (StationID stationid : seen_stations) {
 		Station *st = Station::GetIfValid(stationid);
-		if (st == NULL) continue; /* Waypoint */
+		if (st == nullptr) continue; /* Waypoint */
 
 		/* Check if station is attached to an industry */
-		if (!_settings_game.station.serve_neutral_industries && st->industry != NULL) continue;
+		if (!_settings_game.station.serve_neutral_industries && st->industry != nullptr) continue;
 
 		/* Test if the tile is within the station's catchment */
 		TILE_AREA_LOOP(tile, location) {
@@ -3906,8 +3906,8 @@ uint MoveGoodsToStation(CargoID type, ui
 	/* Return if nothing to do. Also the rounding below fails for 0. */
 	if (amount == 0) return 0;
 
-	Station *st1 = NULL;   // Station with best rating
-	Station *st2 = NULL;   // Second best station
+	Station *st1 = nullptr;   // Station with best rating
+	Station *st2 = nullptr;   // Second best station
 	uint best_rating1 = 0; // rating of st1
 	uint best_rating2 = 0; // rating of st2
 
@@ -3926,28 +3926,28 @@ uint MoveGoodsToStation(CargoID type, ui
 		}
 
 		/* This station can be used, add it to st1/st2 */
-		if (st1 == NULL || st->goods[type].rating >= best_rating1) {
+		if (st1 == nullptr || st->goods[type].rating >= best_rating1) {
 			st2 = st1; best_rating2 = best_rating1; st1 = st; best_rating1 = st->goods[type].rating;
-		} else if (st2 == NULL || st->goods[type].rating >= best_rating2) {
+		} else if (st2 == nullptr || st->goods[type].rating >= best_rating2) {
 			st2 = st; best_rating2 = st->goods[type].rating;
 		}
 	}
 
 	/* no stations around at all? */
-	if (st1 == NULL) return 0;
+	if (st1 == nullptr) return 0;
 
 	/* From now we'll calculate with fractal cargo amounts.
 	 * First determine how much cargo we really have. */
 	amount *= best_rating1 + 1;
 
-	if (st2 == NULL) {
+	if (st2 == nullptr) {
 		/* only one station around */
 		return UpdateStationWaiting(st1, type, amount, source_type, source_id);
 	}
 
 	/* several stations around, the best two (highest rating) are in st1 and st2 */
-	assert(st1 != NULL);
-	assert(st2 != NULL);
+	assert(st1 != nullptr);
+	assert(st2 != nullptr);
 	assert(best_rating1 != 0 || best_rating2 != 0);
 
 	/* Then determine the amount the worst station gets. We do it this way as the
@@ -4598,14 +4598,14 @@ extern const TileTypeProcs _tile_type_st
 	DrawTile_Station,           // draw_tile_proc
 	GetSlopePixelZ_Station,     // get_slope_z_proc
 	ClearTile_Station,          // clear_tile_proc
-	NULL,                       // add_accepted_cargo_proc
+	nullptr,                       // add_accepted_cargo_proc
 	GetTileDesc_Station,        // get_tile_desc_proc
 	GetTileTrackStatus_Station, // get_tile_track_status_proc
 	ClickTile_Station,          // click_tile_proc
 	AnimateTile_Station,        // animate_tile_proc
 	TileLoop_Station,           // tile_loop_proc
 	ChangeTileOwner_Station,    // change_tile_owner_proc
-	NULL,                       // add_produced_cargo_proc
+	nullptr,                       // add_produced_cargo_proc
 	VehicleEnter_Station,       // vehicle_enter_tile_proc
 	GetFoundation_Station,      // get_foundation_proc
 	TerraformTile_Station,      // terraform_tile_proc
diff --git a/src/station_func.h b/src/station_func.h
--- a/src/station_func.h
+++ b/src/station_func.h
@@ -29,7 +29,7 @@ void ShowStationViewWindow(StationID sta
 void UpdateAllStationVirtCoords();
 
 CargoArray GetProductionAroundTiles(TileIndex tile, int w, int h, int rad);
-CargoArray GetAcceptanceAroundTiles(TileIndex tile, int w, int h, int rad, CargoTypes *always_accepted = NULL);
+CargoArray GetAcceptanceAroundTiles(TileIndex tile, int w, int h, int rad, CargoTypes *always_accepted = nullptr);
 
 void UpdateStationAcceptance(Station *st, bool show_msg);
 
diff --git a/src/station_gui.cpp b/src/station_gui.cpp
--- a/src/station_gui.cpp
+++ b/src/station_gui.cpp
@@ -296,7 +296,7 @@ protected:
 		if (!this->stations.Sort()) return;
 
 		/* Reset name sorter sort cache */
-		this->last_station = NULL;
+		this->last_station = nullptr;
 
 		/* Set the modified widget dirty */
 		this->SetWidgetDirty(WID_STL_LIST);
@@ -655,7 +655,7 @@ byte CompanyStationsWindow::facilities =
 bool CompanyStationsWindow::include_empty = true;
 const CargoTypes CompanyStationsWindow::cargo_filter_max = ALL_CARGOTYPES;
 CargoTypes CompanyStationsWindow::cargo_filter = ALL_CARGOTYPES;
-const Station *CompanyStationsWindow::last_station = NULL;
+const Station *CompanyStationsWindow::last_station = nullptr;
 
 /* Available station sorting functions */
 GUIStationList::SortFunction * const CompanyStationsWindow::sorter_funcs[] = {
@@ -903,9 +903,9 @@ public:
 	}
 
 	/**
-	 * Retrieve a child for the given station. Return NULL if it doesn't exist.
+	 * Retrieve a child for the given station. Return nullptr if it doesn't exist.
 	 * @param station ID of the station the child we're looking for is associated with.
-	 * @return a child entry for the given station or NULL.
+	 * @return a child entry for the given station or nullptr.
 	 */
 	CargoDataEntry *Retrieve(StationID station) const
 	{
@@ -914,9 +914,9 @@ public:
 	}
 
 	/**
-	 * Retrieve a child for the given cargo. Return NULL if it doesn't exist.
+	 * Retrieve a child for the given cargo. Return nullptr if it doesn't exist.
 	 * @param cargo ID of the cargo the child we're looking for is associated with.
-	 * @return a child entry for the given cargo or NULL.
+	 * @return a child entry for the given cargo or nullptr.
 	 */
 	CargoDataEntry *Retrieve(CargoID cargo) const
 	{
@@ -1001,7 +1001,7 @@ private:
 };
 
 CargoDataEntry::CargoDataEntry() :
-	parent(NULL),
+	parent(nullptr),
 	station(INVALID_STATION),
 	num_children(0),
 	count(0),
@@ -1025,19 +1025,19 @@ CargoDataEntry::CargoDataEntry(StationID
 {}
 
 CargoDataEntry::CargoDataEntry(StationID station) :
-	parent(NULL),
+	parent(nullptr),
 	station(station),
 	num_children(0),
 	count(0),
-	children(NULL)
+	children(nullptr)
 {}
 
 CargoDataEntry::CargoDataEntry(CargoID cargo) :
-	parent(NULL),
+	parent(nullptr),
 	cargo(cargo),
 	num_children(0),
 	count(0),
-	children(NULL)
+	children(nullptr)
 {}
 
 CargoDataEntry::~CargoDataEntry()
@@ -1051,14 +1051,14 @@ CargoDataEntry::~CargoDataEntry()
  */
 void CargoDataEntry::Clear()
 {
-	if (this->children != NULL) {
+	if (this->children != nullptr) {
 		for (CargoDataSet::iterator i = this->children->begin(); i != this->children->end(); ++i) {
 			assert(*i != this);
 			delete *i;
 		}
 		this->children->clear();
 	}
-	if (this->parent != NULL) this->parent->count -= this->count;
+	if (this->parent != nullptr) this->parent->count -= this->count;
 	this->count = 0;
 	this->num_children = 0;
 }
@@ -1107,7 +1107,7 @@ CargoDataEntry *CargoDataEntry::InsertOr
 void CargoDataEntry::Update(uint count)
 {
 	this->count += count;
-	if (this->parent != NULL) this->parent->Update(count);
+	if (this->parent != nullptr) this->parent->Update(count);
 }
 
 /**
@@ -1116,7 +1116,7 @@ void CargoDataEntry::Update(uint count)
 void CargoDataEntry::IncrementSize()
 {
 	 ++this->num_children;
-	 if (this->parent != NULL) this->parent->IncrementSize();
+	 if (this->parent != nullptr) this->parent->IncrementSize();
 }
 
 void CargoDataEntry::Resort(CargoSortType type, SortOrder order)
@@ -1129,7 +1129,7 @@ void CargoDataEntry::Resort(CargoSortTyp
 CargoDataEntry *CargoDataEntry::Retrieve(CargoDataSet::iterator i) const
 {
 	if (i == this->children->end()) {
-		return NULL;
+		return nullptr;
 	} else {
 		assert(this->children->value_comp().GetSortType() != ST_COUNT);
 		return *i;
@@ -1330,7 +1330,7 @@ struct StationViewWindow : public Window
 		if (count == 0) return;
 		bool auto_distributed = _settings_game.linkgraph.GetDistributionType(cargo) != DT_MANUAL;
 		const CargoDataEntry *expand = &this->expanded_rows;
-		for (int i = 0; i < NUM_COLUMNS && expand != NULL; ++i) {
+		for (int i = 0; i < NUM_COLUMNS && expand != nullptr; ++i) {
 			switch (groupings[i]) {
 				case GR_CARGO:
 					assert(i == 0);
@@ -1571,13 +1571,13 @@ struct StationViewWindow : public Window
 			StationID next = it.GetKey();
 
 			const CargoDataEntry *source_entry = source_dest->Retrieve(cp->SourceStation());
-			if (source_entry == NULL) {
+			if (source_entry == nullptr) {
 				this->ShowCargo(cargo, i, cp->SourceStation(), next, INVALID_STATION, cp->Count());
 				continue;
 			}
 
 			const CargoDataEntry *via_entry = source_entry->Retrieve(next);
-			if (via_entry == NULL) {
+			if (via_entry == nullptr) {
 				this->ShowCargo(cargo, i, cp->SourceStation(), next, INVALID_STATION, cp->Count());
 				continue;
 			}
@@ -1600,7 +1600,7 @@ struct StationViewWindow : public Window
 	{
 		for (CargoID i = 0; i < NUM_CARGO; i++) {
 
-			if (this->cached_destinations.Retrieve(i) == NULL) {
+			if (this->cached_destinations.Retrieve(i) == nullptr) {
 				this->RecalcDestinations(i);
 			}
 
@@ -1620,13 +1620,13 @@ struct StationViewWindow : public Window
 	{
 		std::list<StationID> stations;
 		const CargoDataEntry *parent = data->GetParent();
-		if (parent->GetParent() == NULL) {
+		if (parent->GetParent() == nullptr) {
 			this->displayed_rows.push_back(RowDisplay(&this->expanded_rows, data->GetCargo()));
 			return;
 		}
 
 		StationID next = data->GetStation();
-		while (parent->GetParent()->GetParent() != NULL) {
+		while (parent->GetParent()->GetParent() != nullptr) {
 			stations.push_back(parent->GetStation());
 			parent = parent->GetParent();
 		}
@@ -1764,7 +1764,7 @@ struct StationViewWindow : public Window
 				DrawString(text_left, text_right, y, str);
 
 				if (column < NUM_COLUMNS - 1) {
-					const char *sym = NULL;
+					const char *sym = nullptr;
 					if (cd->GetNumChildren() > 0) {
 						sym = "-";
 					} else if (auto_distributed && str != STR_STATION_VIEW_RESERVED) {
@@ -1832,7 +1832,7 @@ struct StationViewWindow : public Window
 
 			const LinkGraph *lg = LinkGraph::GetIfValid(ge->link_graph);
 			SetDParam(0, cs->name);
-			SetDParam(1, lg != NULL ? lg->Monthly((*lg)[ge->node].Supply()) : 0);
+			SetDParam(1, lg != nullptr ? lg->Monthly((*lg)[ge->node].Supply()) : 0);
 			SetDParam(2, STR_CARGO_RATING_APPALLING + (ge->rating >> 5));
 			SetDParam(3, ToPercent8(ge->rating));
 			DrawString(r.left + WD_FRAMERECT_LEFT + 6, r.right - WD_FRAMERECT_RIGHT - 6, y, STR_STATION_VIEW_CARGO_SUPPLY_RATING);
@@ -1849,7 +1849,7 @@ struct StationViewWindow : public Window
 	template<class Tid>
 	void HandleCargoWaitingClick(CargoDataEntry *filter, Tid next)
 	{
-		if (filter->Retrieve(next) != NULL) {
+		if (filter->Retrieve(next) != nullptr) {
 			filter->Remove(next);
 		} else {
 			filter->InsertOrRetrieve(next);
@@ -2048,9 +2048,9 @@ struct StationViewWindow : public Window
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
-		DoCommandP(0, this->window_number, 0, CMD_RENAME_STATION | CMD_MSG(STR_ERROR_CAN_T_RENAME_STATION), NULL, str);
+		DoCommandP(0, this->window_number, 0, CMD_RENAME_STATION | CMD_MSG(STR_ERROR_CAN_T_RENAME_STATION), nullptr, str);
 	}
 
 	void OnResize() override
@@ -2201,13 +2201,13 @@ static const T *FindStationsNearby(TileA
 	/* Only search tiles where we have a chance to stay within the station spread.
 	 * The complete check needs to be done in the callback as we don't know the
 	 * extent of the found station, yet. */
-	if (distant_join && min(ta.w, ta.h) >= _settings_game.station.station_spread) return NULL;
+	if (distant_join && min(ta.w, ta.h) >= _settings_game.station.station_spread) return nullptr;
 	uint max_dist = distant_join ? _settings_game.station.station_spread - min(ta.w, ta.h) : 1;
 
 	TileIndex tile = TileAddByDir(ctx.tile, DIR_N);
 	CircularTileSearch(&tile, max_dist, ta.w, ta.h, AddNearbyStation<T>, &ctx);
 
-	return NULL;
+	return nullptr;
 }
 
 static const NWidgetPart _nested_select_station_widgets[] = {
@@ -2360,7 +2360,7 @@ static bool StationJoinerNeeded(const Co
 	/* If a window is already opened and we didn't ctrl-click,
 	 * return true (i.e. just flash the old window) */
 	Window *selection_window = FindWindowById(WC_SELECT_STATION, 0);
-	if (selection_window != NULL) {
+	if (selection_window != nullptr) {
 		/* Abort current distant-join and start new one */
 		delete selection_window;
 		UpdateTileSelection();
@@ -2376,7 +2376,7 @@ static bool StationJoinerNeeded(const Co
 	 * If adjacent-stations is disabled and we are building next to a station, do not show the selection window.
 	 * but join the other station immediately. */
 	const T *st = FindStationsNearby<T>(ta, false);
-	return st == NULL && (_settings_game.station.adjacent_stations || _stations_nearby_list.size() == 0);
+	return st == nullptr && (_settings_game.station.adjacent_stations || _stations_nearby_list.size() == 0);
 }
 
 /**
diff --git a/src/statusbar_gui.cpp b/src/statusbar_gui.cpp
--- a/src/statusbar_gui.cpp
+++ b/src/statusbar_gui.cpp
@@ -149,7 +149,7 @@ struct StatusBarWindow : Window {
 			case WID_S_RIGHT: {
 				/* Draw company money, if any */
 				const Company *c = Company::GetIfValid(_local_company);
-				if (c != NULL) {
+				if (c != nullptr) {
 					SetDParam(0, c->money);
 					DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + WD_FRAMERECT_TOP, STR_COMPANY_MONEY, TC_FROMSTRING, SA_HOR_CENTER);
 				}
@@ -164,7 +164,7 @@ struct StatusBarWindow : Window {
 					DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + WD_FRAMERECT_TOP, STR_STATUSBAR_AUTOSAVE, TC_FROMSTRING, SA_HOR_CENTER);
 				} else if (_pause_mode != PM_UNPAUSED) {
 					DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + WD_FRAMERECT_TOP, STR_STATUSBAR_PAUSED, TC_FROMSTRING, SA_HOR_CENTER);
-				} else if (this->ticker_scroll < TICKER_STOP && FindWindowById(WC_NEWS_WINDOW, 0) == NULL && _statusbar_news_item != NULL && _statusbar_news_item->string_id != 0) {
+				} else if (this->ticker_scroll < TICKER_STOP && FindWindowById(WC_NEWS_WINDOW, 0) == nullptr && _statusbar_news_item != nullptr && _statusbar_news_item->string_id != 0) {
 					/* Draw the scrolling news text */
 					if (!DrawScrollingStatusText(_statusbar_news_item, this->ticker_scroll, r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, r.top + WD_FRAMERECT_TOP, r.bottom)) {
 						InvalidateWindowData(WC_STATUS_BAR, 0, SBI_NEWS_DELETED);
@@ -248,7 +248,7 @@ static const NWidgetPart _nested_main_st
 };
 
 static WindowDesc _main_status_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_STATUS_BAR, WC_NONE,
 	WDF_NO_FOCUS,
 	_nested_main_status_widgets, lengthof(_nested_main_status_widgets)
@@ -260,7 +260,7 @@ static WindowDesc _main_status_desc(
 bool IsNewsTickerShown()
 {
 	const StatusBarWindow *w = dynamic_cast<StatusBarWindow*>(FindWindowById(WC_STATUS_BAR, 0));
-	return w != NULL && w->ticker_scroll < StatusBarWindow::TICKER_STOP;
+	return w != nullptr && w->ticker_scroll < StatusBarWindow::TICKER_STOP;
 }
 
 /**
diff --git a/src/story.cpp b/src/story.cpp
--- a/src/story.cpp
+++ b/src/story.cpp
@@ -124,7 +124,7 @@ CommandCost CmdCreateStoryPage(TileIndex
 		s->date = _date;
 		s->company = company;
 		if (StrEmpty(text)) {
-			s->title = NULL;
+			s->title = nullptr;
 		} else {
 			s->title = stredup(text);
 		}
@@ -241,7 +241,7 @@ CommandCost CmdSetStoryPageTitle(TileInd
 		StoryPage *p = StoryPage::Get(page_id);
 		free(p->title);
 		if (StrEmpty(text)) {
-			p->title = NULL;
+			p->title = nullptr;
 		} else {
 			p->title = stredup(text);
 		}
diff --git a/src/story_base.h b/src/story_base.h
--- a/src/story_base.h
+++ b/src/story_base.h
@@ -58,7 +58,7 @@ struct StoryPageElement : StoryPageEleme
 	inline StoryPageElement() { }
 
 	/**
-	 * (Empty) destructor has to be defined else operator delete might be called with NULL parameter
+	 * (Empty) destructor has to be defined else operator delete might be called with nullptr parameter
 	 */
 	inline ~StoryPageElement() { free(this->text); }
 };
@@ -80,7 +80,7 @@ struct StoryPage : StoryPagePool::PoolIt
 	inline StoryPage() { }
 
 	/**
-	 * (Empty) destructor has to be defined else operator delete might be called with NULL parameter
+	 * (Empty) destructor has to be defined else operator delete might be called with nullptr parameter
 	 */
 	inline ~StoryPage()
 	{
diff --git a/src/story_gui.cpp b/src/story_gui.cpp
--- a/src/story_gui.cpp
+++ b/src/story_gui.cpp
@@ -81,7 +81,7 @@ protected:
 			this->story_page_elements.clear();
 
 			const StoryPage *p = GetSelPage();
-			if (p != NULL) {
+			if (p != nullptr) {
 				const StoryPageElement *pe;
 				FOR_ALL_STORY_PAGE_ELEMENTS(pe) {
 					if (pe->page == p->index) {
@@ -115,11 +115,11 @@ protected:
 
 	/**
 	 * Get instance of selected page.
-	 * @return Instance of selected page or NULL if no page is selected.
+	 * @return Instance of selected page or nullptr if no page is selected.
 	 */
 	StoryPage *GetSelPage() const
 	{
-		if (!_story_page_pool.IsValidID(selected_page_id)) return NULL;
+		if (!_story_page_pool.IsValidID(selected_page_id)) return nullptr;
 		return _story_page_pool.Get(selected_page_id);
 	}
 
@@ -170,7 +170,7 @@ protected:
 	{
 		/* Generate generic title if selected page have no custom title. */
 		StoryPage *page = this->GetSelPage();
-		if (page != NULL && page->title == NULL) {
+		if (page != nullptr && page->title == nullptr) {
 			SetDParam(0, GetSelPageNum() + 1);
 			GetString(selected_generic_title, STR_STORY_BOOK_GENERIC_PAGE_ITEM, lastof(selected_generic_title));
 		}
@@ -193,10 +193,10 @@ protected:
 
 		/* Find the last available page which is previous to the current selected page. */
 		const StoryPage *last_available;
-		last_available = NULL;
+		last_available = nullptr;
 		for (const StoryPage *p : this->story_pages) {
 			if (p->index == this->selected_page_id) {
-				if (last_available == NULL) return; // No previous page available.
+				if (last_available == nullptr) return; // No previous page available.
 				this->SetSelectedPage(last_available->index);
 				return;
 			}
@@ -234,8 +234,8 @@ protected:
 		uint16 page_num = 1;
 		for (const StoryPage *p : this->story_pages) {
 			bool current_page = p->index == this->selected_page_id;
-			DropDownListStringItem *item = NULL;
-			if (p->title != NULL) {
+			DropDownListStringItem *item = nullptr;
+			if (p->title != nullptr) {
 				item = new DropDownListCharStringItem(p->title, p->index, current_page);
 			} else {
 				/* No custom title => use a generic page title with page number. */
@@ -270,12 +270,12 @@ protected:
 	uint GetHeadHeight(int max_width) const
 	{
 		StoryPage *page = this->GetSelPage();
-		if (page == NULL) return 0;
+		if (page == nullptr) return 0;
 		int height = 0;
 
 		/* Title lines */
 		height += FONT_HEIGHT_NORMAL; // Date always use exactly one line.
-		SetDParamStr(0, page->title != NULL ? page->title : this->selected_generic_title);
+		SetDParamStr(0, page->title != nullptr ? page->title : this->selected_generic_title);
 		height += GetStringHeight(STR_STORY_BOOK_TITLE, max_width);
 
 		return height;
@@ -292,7 +292,7 @@ protected:
 		switch (pe.type) {
 			case SPET_GOAL: {
 				Goal *g = Goal::Get((GoalID) pe.referenced_id);
-				if (g == NULL) return SPR_IMG_GOAL_BROKEN_REF;
+				if (g == nullptr) return SPR_IMG_GOAL_BROKEN_REF;
 				return g->completed ? SPR_IMG_GOAL_COMPLETED : SPR_IMG_GOAL;
 			}
 			case SPET_LOCATION:
@@ -336,7 +336,7 @@ protected:
 	uint GetContentHeight()
 	{
 		StoryPage *page = this->GetSelPage();
-		if (page == NULL) return 0;
+		if (page == nullptr) return 0;
 		int max_width = GetAvailablePageContentWidth();
 		uint element_vertical_dist = FONT_HEIGHT_NORMAL;
 
@@ -458,7 +458,7 @@ public:
 		switch (widget) {
 			case WID_SB_SEL_PAGE: {
 				StoryPage *page = this->GetSelPage();
-				SetDParamStr(0, page != NULL && page->title != NULL ? page->title : this->selected_generic_title);
+				SetDParamStr(0, page != nullptr && page->title != nullptr ? page->title : this->selected_generic_title);
 				break;
 			}
 			case WID_SB_CAPTION:
@@ -492,7 +492,7 @@ public:
 		if (widget != WID_SB_PAGE_PANEL) return;
 
 		StoryPage *page = this->GetSelPage();
-		if (page == NULL) return;
+		if (page == nullptr) return;
 
 		const int x = r.left + WD_FRAMETEXT_LEFT;
 		const int y = r.top + WD_FRAMETEXT_TOP;
@@ -518,7 +518,7 @@ public:
 		y_offset += line_height;
 
 		/* Title */
-		SetDParamStr(0, page->title != NULL ? page->title : this->selected_generic_title);
+		SetDParamStr(0, page->title != nullptr ? page->title : this->selected_generic_title);
 		y_offset = DrawStringMultiLine(0, right - x, y_offset, bottom - y, STR_STORY_BOOK_TITLE, TC_BLACK, SA_TOP | SA_HOR_CENTER);
 
 		/* Page elements */
@@ -533,8 +533,8 @@ public:
 
 				case SPET_GOAL: {
 					Goal *g = Goal::Get((GoalID) pe->referenced_id);
-					StringID string_id = g == NULL ? STR_STORY_BOOK_INVALID_GOAL_REF : STR_JUST_RAW_STRING;
-					if (g != NULL) SetDParamStr(0, g->text);
+					StringID string_id = g == nullptr ? STR_STORY_BOOK_INVALID_GOAL_REF : STR_JUST_RAW_STRING;
+					if (g != nullptr) SetDParamStr(0, g->text);
 					DrawActionElement(y_offset, right - x, line_height, GetPageElementSprite(*pe), string_id);
 					break;
 				}
@@ -567,7 +567,7 @@ public:
 				for (uint16 i = 0; i < this->story_pages.size(); i++) {
 					const StoryPage *s = this->story_pages[i];
 
-					if (s->title != NULL) {
+					if (s->title != nullptr) {
 						SetDParamStr(0, s->title);
 					} else {
 						SetDParamStr(0, this->selected_generic_title);
diff --git a/src/strgen/strgen.cpp b/src/strgen/strgen.cpp
--- a/src/strgen/strgen.cpp
+++ b/src/strgen/strgen.cpp
@@ -106,7 +106,7 @@ struct FileStringReader : StringReader {
 			StringReader(data, file, master, translation)
 	{
 		this->fh = fopen(file, "rb");
-		if (this->fh == NULL) error("Could not open %s", file);
+		if (this->fh == nullptr) error("Could not open %s", file);
 	}
 
 	/** Free/close the file. */
@@ -135,7 +135,7 @@ struct FileStringReader : StringReader {
 void FileStringReader::HandlePragma(char *str)
 {
 	if (!memcmp(str, "id ", 3)) {
-		this->data.next_string_id = strtoul(str + 3, NULL, 0);
+		this->data.next_string_id = strtoul(str + 3, nullptr, 0);
 	} else if (!memcmp(str, "name ", 5)) {
 		strecpy(_lang.name, str + 5, lastof(_lang.name));
 	} else if (!memcmp(str, "ownname ", 8)) {
@@ -161,14 +161,14 @@ void FileStringReader::HandlePragma(char
 		strecpy(_lang.digit_decimal_separator, strcmp(str, "{NBSP}") == 0 ? NBSP : str, lastof(_lang.digit_decimal_separator));
 	} else if (!memcmp(str, "winlangid ", 10)) {
 		const char *buf = str + 10;
-		long langid = strtol(buf, NULL, 16);
+		long langid = strtol(buf, nullptr, 16);
 		if (langid > (long)UINT16_MAX || langid < 0) {
 			error("Invalid winlangid %s", buf);
 		}
 		_lang.winlangid = (uint16)langid;
 	} else if (!memcmp(str, "grflangid ", 10)) {
 		const char *buf = str + 10;
-		long langid = strtol(buf, NULL, 16);
+		long langid = strtol(buf, nullptr, 16);
 		if (langid >= 0x7F || langid < 0) {
 			error("Invalid grflangid %s", buf);
 		}
@@ -180,7 +180,7 @@ void FileStringReader::HandlePragma(char
 		for (;;) {
 			const char *s = ParseWord(&buf);
 
-			if (s == NULL) break;
+			if (s == nullptr) break;
 			if (_lang.num_genders >= MAX_NUM_GENDERS) error("Too many genders, max %d", MAX_NUM_GENDERS);
 			strecpy(_lang.genders[_lang.num_genders], s, lastof(_lang.genders[_lang.num_genders]));
 			_lang.num_genders++;
@@ -192,7 +192,7 @@ void FileStringReader::HandlePragma(char
 		for (;;) {
 			const char *s = ParseWord(&buf);
 
-			if (s == NULL) break;
+			if (s == nullptr) break;
 			if (_lang.num_cases >= MAX_NUM_CASES) error("Too many cases, max %d", MAX_NUM_CASES);
 			strecpy(_lang.cases[_lang.num_cases], s, lastof(_lang.cases[_lang.num_cases]));
 			_lang.num_cases++;
@@ -205,10 +205,10 @@ void FileStringReader::HandlePragma(char
 bool CompareFiles(const char *n1, const char *n2)
 {
 	FILE *f2 = fopen(n2, "rb");
-	if (f2 == NULL) return false;
+	if (f2 == nullptr) return false;
 
 	FILE *f1 = fopen(n1, "rb");
-	if (f1 == NULL) {
+	if (f1 == nullptr) {
 		fclose(f2);
 		error("can't open %s", n1);
 	}
@@ -246,7 +246,7 @@ struct FileWriter {
 		this->filename = stredup(filename);
 		this->fh = fopen(this->filename, "wb");
 
-		if (this->fh == NULL) {
+		if (this->fh == nullptr) {
 			error("Could not open %s", this->filename);
 		}
 	}
@@ -255,14 +255,14 @@ struct FileWriter {
 	void Finalise()
 	{
 		fclose(this->fh);
-		this->fh = NULL;
+		this->fh = nullptr;
 	}
 
 	/** Make sure the file is closed. */
 	virtual ~FileWriter()
 	{
 		/* If we weren't closed an exception was thrown, so remove the temporary file. */
-		if (fh != NULL) {
+		if (fh != nullptr) {
 			fclose(this->fh);
 			unlink(this->filename);
 		}
@@ -418,7 +418,7 @@ static const OptionData _opts[] = {
 	  GETOPT_NOVAL(     't',  "--todo"),
 	  GETOPT_NOVAL(     'w',  "--warning"),
 	  GETOPT_NOVAL(     'h',  "--help"),
-	GETOPT_GENERAL('h', '?',  NULL,               ODF_NO_VALUE),
+	GETOPT_GENERAL('h', '?',  nullptr,               ODF_NO_VALUE),
 	  GETOPT_VALUE(     's',  "--source_dir"),
 	  GETOPT_VALUE(     'd',  "--dest_dir"),
 	GETOPT_END(),
@@ -428,7 +428,7 @@ int CDECL main(int argc, char *argv[])
 {
 	char pathbuf[MAX_PATH];
 	const char *src_dir = ".";
-	const char *dest_dir = NULL;
+	const char *dest_dir = nullptr;
 
 	GetOptData mgo(argc - 1, argv + 1, _opts);
 	for (;;) {
@@ -512,7 +512,7 @@ int CDECL main(int argc, char *argv[])
 		}
 	}
 
-	if (dest_dir == NULL) dest_dir = src_dir; // if dest_dir is not specified, it equals src_dir
+	if (dest_dir == nullptr) dest_dir = src_dir; // if dest_dir is not specified, it equals src_dir
 
 	try {
 		/* strgen has two modes of operation. If no (free) arguments are passed
@@ -551,17 +551,17 @@ int CDECL main(int argc, char *argv[])
 
 				const char *translation = replace_pathsep(mgo.argv[i]);
 				const char *file = strrchr(translation, PATHSEPCHAR);
-				FileStringReader translation_reader(data, translation, false, file == NULL || strcmp(file + 1, "english.txt") != 0);
+				FileStringReader translation_reader(data, translation, false, file == nullptr || strcmp(file + 1, "english.txt") != 0);
 				translation_reader.ParseFile(); // target file
 				if (_errors != 0) return 1;
 
 				/* get the targetfile, strip any directories and append to destination path */
 				r = strrchr(mgo.argv[i], PATHSEPCHAR);
-				mkpath(pathbuf, lastof(pathbuf), dest_dir, (r != NULL) ? &r[1] : mgo.argv[i]);
+				mkpath(pathbuf, lastof(pathbuf), dest_dir, (r != nullptr) ? &r[1] : mgo.argv[i]);
 
 				/* rename the .txt (input-extension) to .lng */
 				r = strrchr(pathbuf, '.');
-				if (r == NULL || strcmp(r, ".txt") != 0) r = strchr(pathbuf, '\0');
+				if (r == nullptr || strcmp(r, ".txt") != 0) r = strchr(pathbuf, '\0');
 				strecpy(r, ".lng", lastof(pathbuf));
 
 				LanguageFileWriter writer(pathbuf);
diff --git a/src/strgen/strgen.h b/src/strgen/strgen.h
--- a/src/strgen/strgen.h
+++ b/src/strgen/strgen.h
@@ -73,7 +73,7 @@ struct StringReader {
 	 * Read a single line from the source of strings.
 	 * @param buffer The buffer to read the data in to.
 	 * @param last   The last element in the buffer.
-	 * @return The buffer, or NULL if at the end of the file.
+	 * @return The buffer, or nullptr if at the end of the file.
 	 */
 	virtual char *ReadLine(char *buffer, const char *last) = 0;
 
diff --git a/src/strgen/strgen_base.cpp b/src/strgen/strgen_base.cpp
--- a/src/strgen/strgen_base.cpp
+++ b/src/strgen/strgen_base.cpp
@@ -59,8 +59,8 @@ Case::~Case()
  * @param line    The line this string was found on.
  */
 LangString::LangString(const char *name, const char *english, int index, int line) :
-		name(stredup(name)), english(stredup(english)), translated(NULL),
-		hash_next(0), index(index), line(line), translated_case(NULL)
+		name(stredup(name)), english(stredup(english)), translated(nullptr),
+		hash_next(0), index(index), line(line), translated_case(nullptr)
 {
 }
 
@@ -77,10 +77,10 @@ LangString::~LangString()
 void LangString::FreeTranslation()
 {
 	free(this->translated);
-	this->translated = NULL;
+	this->translated = nullptr;
 
 	delete this->translated_case;
-	this->translated_case = NULL;
+	this->translated_case = nullptr;
 }
 
 /**
@@ -107,7 +107,7 @@ void StringData::FreeTranslation()
 {
 	for (size_t i = 0; i < this->max_strings; i++) {
 		LangString *ls = this->strings[i];
-		if (ls != NULL) ls->FreeTranslation();
+		if (ls != nullptr) ls->FreeTranslation();
 	}
 }
 
@@ -140,7 +140,7 @@ void StringData::Add(const char *s, Lang
 /**
  * Find a LangString based on the string name.
  * @param s The string name to search on.
- * @return The LangString or NULL if it is not known.
+ * @return The LangString or nullptr if it is not known.
  */
 LangString *StringData::Find(const char *s)
 {
@@ -152,7 +152,7 @@ LangString *StringData::Find(const char 
 		if (strcmp(ls->name, s) == 0) return ls;
 		idx = ls->hash_next;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -181,7 +181,7 @@ uint StringData::Version() const
 	for (size_t i = 0; i < this->max_strings; i++) {
 		const LangString *ls = this->strings[i];
 
-		if (ls != NULL) {
+		if (ls != nullptr) {
 			const CmdStruct *cs;
 			const char *s;
 			char buf[MAX_COMMAND_PARAM_SIZE];
@@ -194,7 +194,7 @@ uint StringData::Version() const
 			hash = this->VersionHashStr(hash, s + 1);
 
 			s = ls->english;
-			while ((cs = ParseCommandString(&s, buf, &argno, &casei)) != NULL) {
+			while ((cs = ParseCommandString(&s, buf, &argno, &casei)) != nullptr) {
 				if (cs->flags & C_DONTCOUNT) continue;
 
 				hash ^= (cs - _cmd_structs) * 0x1234567;
@@ -213,7 +213,7 @@ uint StringData::Version() const
 uint StringData::CountInUse(uint tab) const
 {
 	int i;
-	for (i = TAB_SIZE; --i >= 0;) if (this->strings[(tab * TAB_SIZE) + i] != NULL) break;
+	for (i = TAB_SIZE; --i >= 0;) if (this->strings[(tab * TAB_SIZE) + i] != nullptr) break;
 	return i + 1;
 }
 
@@ -327,7 +327,7 @@ bool ParseRelNum(char **buf, int *value,
 	} else {
 		*value = v;
 	}
-	if (offset != NULL && *end == ':') {
+	if (offset != nullptr && *end == ':') {
 		/* Take the Nth within */
 		s = end + 1;
 		*offset = strtol(s, &end, 0);
@@ -337,13 +337,13 @@ bool ParseRelNum(char **buf, int *value,
 	return true;
 }
 
-/* Parse out the next word, or NULL */
+/* Parse out the next word, or nullptr */
 char *ParseWord(char **buf)
 {
 	char *s = *buf, *r;
 
 	while (*s == ' ' || *s == '\t') s++;
-	if (*s == '\0') return NULL;
+	if (*s == '\0') return nullptr;
 
 	if (*s == '"') {
 		r = ++s;
@@ -399,8 +399,8 @@ void EmitPlural(Buffer *buffer, char *bu
 	const CmdStruct *cmd = _cur_pcs.cmd[argidx];
 	if (offset == -1) {
 		/* Use default offset */
-		if (cmd == NULL || cmd->default_plural_offset < 0) {
-			strgen_fatal("Command '%s' has no (default) plural position", cmd == NULL ? "<empty>" : cmd->cmd);
+		if (cmd == nullptr || cmd->default_plural_offset < 0) {
+			strgen_fatal("Command '%s' has no (default) plural position", cmd == nullptr ? "<empty>" : cmd->cmd);
 		}
 		offset = cmd->default_plural_offset;
 	}
@@ -408,7 +408,7 @@ void EmitPlural(Buffer *buffer, char *bu
 	/* Parse each string */
 	for (nw = 0; nw < MAX_PLURALS; nw++) {
 		words[nw] = ParseWord(&buf);
-		if (words[nw] == NULL) break;
+		if (words[nw] == nullptr) break;
 	}
 
 	if (nw == 0) {
@@ -462,13 +462,13 @@ void EmitGender(Buffer *buffer, char *bu
 		if (!ParseRelNum(&buf, &argidx, &offset)) {}
 
 		const CmdStruct *cmd = _cur_pcs.cmd[argidx];
-		if (cmd == NULL || (cmd->flags & C_GENDER) == 0) {
-			strgen_fatal("Command '%s' can't have a gender", cmd == NULL ? "<empty>" : cmd->cmd);
+		if (cmd == nullptr || (cmd->flags & C_GENDER) == 0) {
+			strgen_fatal("Command '%s' can't have a gender", cmd == nullptr ? "<empty>" : cmd->cmd);
 		}
 
 		for (nw = 0; nw < MAX_NUM_GENDERS; nw++) {
 			words[nw] = ParseWord(&buf);
-			if (words[nw] == NULL) break;
+			if (words[nw] == nullptr) break;
 		}
 		if (nw != _lang.num_genders) strgen_fatal("Bad # of arguments for gender command");
 
@@ -484,7 +484,7 @@ static const CmdStruct *FindCmd(const ch
 	for (const CmdStruct *cs = _cmd_structs; cs != endof(_cmd_structs); cs++) {
 		if (strncmp(cs->cmd, s, len) == 0 && cs->cmd[len] == '\0') return cs;
 	}
-	return NULL;
+	return nullptr;
 }
 
 static uint ResolveCaseName(const char *str, size_t len)
@@ -501,7 +501,7 @@ static uint ResolveCaseName(const char *
 }
 
 
-/* returns NULL on eof
+/* returns nullptr on eof
  * else returns command struct */
 static const CmdStruct *ParseCommandString(const char **str, char *param, int *argno, int *casei)
 {
@@ -513,7 +513,7 @@ static const CmdStruct *ParseCommandStri
 
 	/* Scan to the next command, exit if there's no next command. */
 	for (; *s != '{'; s++) {
-		if (*s == '\0') return NULL;
+		if (*s == '\0') return nullptr;
 	}
 	s++; // Skip past the {
 
@@ -532,9 +532,9 @@ static const CmdStruct *ParseCommandStri
 	} while (c != '}' && c != ' ' && c != '=' && c != '.' && c != 0);
 
 	const CmdStruct *cmd = FindCmd(start, s - start - 1);
-	if (cmd == NULL) {
+	if (cmd == nullptr) {
 		strgen_error("Undefined command '%.*s'", (int)(s - start - 1), start);
-		return NULL;
+		return nullptr;
 	}
 
 	if (c == '.') {
@@ -552,7 +552,7 @@ static const CmdStruct *ParseCommandStri
 
 	if (c == '\0') {
 		strgen_error("Missing } from command '%s'", start);
-		return NULL;
+		return nullptr;
 	}
 
 
@@ -565,7 +565,7 @@ static const CmdStruct *ParseCommandStri
 			if (c == '}') break;
 			if (c == '\0') {
 				strgen_error("Missing } from command '%s'", start);
-				return NULL;
+				return nullptr;
 			}
 			if (s - start == MAX_COMMAND_PARAM_SIZE) error("param command too long");
 			*param++ = c;
@@ -609,7 +609,7 @@ static void ExtractCommandString(ParsedC
 		/* read until next command from a. */
 		const CmdStruct *ar = ParseCommandString(&s, param, &argno, &casei);
 
-		if (ar == NULL) break;
+		if (ar == nullptr) break;
 
 		/* Sanity checking */
 		if (argno != -1 && ar->consumes == 0) strgen_fatal("Non consumer param can't have a paramindex");
@@ -617,7 +617,7 @@ static void ExtractCommandString(ParsedC
 		if (ar->consumes) {
 			if (argno != -1) argidx = argno;
 			if (argidx < 0 || (uint)argidx >= lengthof(p->cmd)) strgen_fatal("invalid param idx %d", argidx);
-			if (p->cmd[argidx] != NULL && p->cmd[argidx] != ar) strgen_fatal("duplicate param idx %d", argidx);
+			if (p->cmd[argidx] != nullptr && p->cmd[argidx] != ar) strgen_fatal("duplicate param idx %d", argidx);
 
 			p->cmd[argidx++] = ar;
 		} else if (!(ar->flags & C_DONTCOUNT)) { // Ignore some of them
@@ -632,7 +632,7 @@ static void ExtractCommandString(ParsedC
 
 static const CmdStruct *TranslateCmdForCompare(const CmdStruct *a)
 {
-	if (a == NULL) return NULL;
+	if (a == nullptr) return nullptr;
 
 	if (strcmp(a->cmd, "STRING1") == 0 ||
 			strcmp(a->cmd, "STRING2") == 0 ||
@@ -677,7 +677,7 @@ static bool CheckCommandsMatch(char *a, 
 			if (templ.pairs[i].a == lang.pairs[j].a &&
 					strcmp(templ.pairs[i].v, lang.pairs[j].v) == 0) {
 				/* it was found in both. zero it out from lang so we don't find it again */
-				lang.pairs[j].a = NULL;
+				lang.pairs[j].a = nullptr;
 				found = true;
 				break;
 			}
@@ -694,8 +694,8 @@ static bool CheckCommandsMatch(char *a, 
 	for (uint i = 0; i < lengthof(templ.cmd); i++) {
 		if (TranslateCmdForCompare(templ.cmd[i]) != lang.cmd[i]) {
 			strgen_warning("%s: Param idx #%d '%s' doesn't match with template command '%s'", name, i,
-				lang.cmd[i]  == NULL ? "<empty>" : TranslateCmdForCompare(lang.cmd[i])->cmd,
-				templ.cmd[i] == NULL ? "<empty>" : templ.cmd[i]->cmd);
+				lang.cmd[i]  == nullptr ? "<empty>" : TranslateCmdForCompare(lang.cmd[i])->cmd,
+				templ.cmd[i] == nullptr ? "<empty>" : templ.cmd[i]->cmd);
 			result = false;
 		}
 	}
@@ -714,7 +714,7 @@ void StringReader::HandleString(char *st
 	if (*str == ';' || *str == ' ' || *str == '\0') return;
 
 	char *s = strchr(str, ':');
-	if (s == NULL) {
+	if (s == nullptr) {
 		strgen_error("Line has no ':' delimiter");
 		return;
 	}
@@ -747,23 +747,23 @@ void StringReader::HandleString(char *st
 	/* Check if the string has a case..
 	 * The syntax for cases is IDENTNAME.case */
 	char *casep = strchr(str, '.');
-	if (casep != NULL) *casep++ = '\0';
+	if (casep != nullptr) *casep++ = '\0';
 
 	/* Check if this string already exists.. */
 	LangString *ent = this->data.Find(str);
 
 	if (this->master) {
-		if (casep != NULL) {
+		if (casep != nullptr) {
 			strgen_error("Cases in the base translation are not supported.");
 			return;
 		}
 
-		if (ent != NULL) {
+		if (ent != nullptr) {
 			strgen_error("String name '%s' is used multiple times", str);
 			return;
 		}
 
-		if (this->data.strings[this->data.next_string_id] != NULL) {
+		if (this->data.strings[this->data.next_string_id] != nullptr) {
 			strgen_error("String ID 0x%X for '%s' already in use by '%s'", this->data.next_string_id, str, this->data.strings[this->data.next_string_id]->name);
 			return;
 		}
@@ -771,12 +771,12 @@ void StringReader::HandleString(char *st
 		/* Allocate a new LangString */
 		this->data.Add(str, new LangString(str, s, this->data.next_string_id++, _cur_line));
 	} else {
-		if (ent == NULL) {
+		if (ent == nullptr) {
 			strgen_warning("String name '%s' does not exist in master file", str);
 			return;
 		}
 
-		if (ent->translated && casep == NULL) {
+		if (ent->translated && casep == nullptr) {
 			strgen_error("String name '%s' is used multiple times", str);
 			return;
 		}
@@ -784,7 +784,7 @@ void StringReader::HandleString(char *st
 		/* make sure that the commands match */
 		if (!CheckCommandsMatch(s, ent->english, str)) return;
 
-		if (casep != NULL) {
+		if (casep != nullptr) {
 			ent->translated_case = new Case(ResolveCaseName(casep, strlen(casep)), s, ent->translated_case);
 		} else {
 			ent->translated = stredup(s);
@@ -830,7 +830,7 @@ void StringReader::ParseFile()
 	strecpy(_lang.digit_decimal_separator, ".", lastof(_lang.digit_decimal_separator));
 
 	_cur_line = 1;
-	while (this->ReadLine(buf, lastof(buf)) != NULL) {
+	while (this->ReadLine(buf, lastof(buf)) != nullptr) {
 		rstrip(buf);
 		this->HandleString(buf);
 		_cur_line++;
@@ -845,7 +845,7 @@ void HeaderWriter::WriteHeader(const Str
 {
 	int last = 0;
 	for (size_t i = 0; i < data.max_strings; i++) {
-		if (data.strings[i] != NULL) {
+		if (data.strings[i] != nullptr) {
 			this->WriteStringID(data.strings[i]->name, (int)i);
 			last = (int)i;
 		}
@@ -862,18 +862,18 @@ static int TranslateArgumentIdx(int argi
 		strgen_fatal("invalid argidx %d", argidx);
 	}
 	const CmdStruct *cs = _cur_pcs.cmd[argidx];
-	if (cs != NULL && cs->consumes <= offset) {
+	if (cs != nullptr && cs->consumes <= offset) {
 		strgen_fatal("invalid argidx offset %d:%d", argidx, offset);
 	}
 
-	if (_cur_pcs.cmd[argidx] == NULL) {
+	if (_cur_pcs.cmd[argidx] == nullptr) {
 		strgen_fatal("no command for this argidx %d", argidx);
 	}
 
 	for (int i = sum = 0; i < argidx; i++) {
 		const CmdStruct *cs = _cur_pcs.cmd[i];
 
-		sum += (cs != NULL) ? cs->consumes : 1;
+		sum += (cs != nullptr) ? cs->consumes : 1;
 	}
 
 	return sum + offset;
@@ -901,7 +901,7 @@ static void PutCommandString(Buffer *buf
 		int argno;
 		int casei;
 		const CmdStruct *cs = ParseCommandString(&str, param, &argno, &casei);
-		if (cs == NULL) break;
+		if (cs == nullptr) break;
 
 		if (casei != -1) {
 			buffer->AppendUtf8(SCC_SET_CASE); // {SET_CASE}
@@ -918,7 +918,7 @@ static void PutCommandString(Buffer *buf
 
 			/* Output the one from the master string... it's always accurate. */
 			cs = _cur_pcs.cmd[_cur_argidx++];
-			if (cs == NULL) {
+			if (cs == nullptr) {
 				strgen_fatal("%s: No argument exists at position %d", _cur_ident, _cur_argidx - 1);
 			}
 		}
@@ -961,7 +961,7 @@ void LanguageWriter::WriteLang(const Str
 
 		for (uint j = 0; j != in_use[tab]; j++) {
 			const LangString *ls = data.strings[(tab * TAB_SIZE) + j];
-			if (ls != NULL && ls->translated == NULL) _lang.missing++;
+			if (ls != nullptr && ls->translated == nullptr) _lang.missing++;
 		}
 	}
 
@@ -980,7 +980,7 @@ void LanguageWriter::WriteLang(const Str
 			const char *cmdp;
 
 			/* For undefined strings, just set that it's an empty string */
-			if (ls == NULL) {
+			if (ls == nullptr) {
 				this->WriteLength(0);
 				continue;
 			}
@@ -989,7 +989,7 @@ void LanguageWriter::WriteLang(const Str
 			_cur_line = ls->line;
 
 			/* Produce a message if a string doesn't have a translation. */
-			if (_show_todo > 0 && ls->translated == NULL) {
+			if (_show_todo > 0 && ls->translated == nullptr) {
 				if ((_show_todo & 2) != 0) {
 					strgen_warning("'%s' is untranslated", ls->name);
 				}
@@ -1002,17 +1002,17 @@ void LanguageWriter::WriteLang(const Str
 			/* Extract the strings and stuff from the english command string */
 			ExtractCommandString(&_cur_pcs, ls->english, false);
 
-			if (ls->translated_case != NULL || ls->translated != NULL) {
+			if (ls->translated_case != nullptr || ls->translated != nullptr) {
 				casep = ls->translated_case;
 				cmdp = ls->translated;
 			} else {
-				casep = NULL;
+				casep = nullptr;
 				cmdp = ls->english;
 			}
 
 			_translated = cmdp != ls->english;
 
-			if (casep != NULL) {
+			if (casep != nullptr) {
 				const Case *c;
 				uint num;
 
@@ -1026,7 +1026,7 @@ void LanguageWriter::WriteLang(const Str
 				buffer.AppendByte(num);
 
 				/* Write each case */
-				for (c = casep; c != NULL; c = c->next) {
+				for (c = casep; c != nullptr; c = c->next) {
 					buffer.AppendByte(c->caseidx);
 					/* Make some space for the 16-bit length */
 					uint pos = (uint)buffer.size();
@@ -1042,7 +1042,7 @@ void LanguageWriter::WriteLang(const Str
 				}
 			}
 
-			if (cmdp != NULL) PutCommandString(&buffer, cmdp);
+			if (cmdp != nullptr) PutCommandString(&buffer, cmdp);
 
 			this->WriteLength((uint)buffer.size());
 			this->Write(buffer.data(), buffer.size());
diff --git a/src/string.cpp b/src/string.cpp
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -71,7 +71,7 @@ int CDECL vseprintf(char *str, const cha
  *
  * Appends the source string to the destination string with respect of the
  * terminating null-character and and the last pointer to the last element
- * in the destination buffer. If the last pointer is set to NULL no
+ * in the destination buffer. If the last pointer is set to nullptr no
  * boundary check is performed.
  *
  * @note usage: strecat(dst, src, lastof(dst));
@@ -99,7 +99,7 @@ char *strecat(char *dst, const char *src
  *
  * Copies the source string to the destination buffer with respect of the
  * terminating null-character and the last pointer to the last element in
- * the destination buffer. If the last pointer is set to NULL no boundary
+ * the destination buffer. If the last pointer is set to nullptr no boundary
  * check is performed.
  *
  * @note usage: strecpy(dst, src, lastof(dst));
@@ -131,13 +131,13 @@ char *strecpy(char *dst, const char *src
 /**
  * Create a duplicate of the given string.
  * @param s    The string to duplicate.
- * @param last The last character that is safe to duplicate. If NULL, the whole string is duplicated.
+ * @param last The last character that is safe to duplicate. If nullptr, the whole string is duplicated.
  * @note The maximum length of the resulting string might therefore be last - s + 1.
  * @return The duplicate of the string.
  */
 char *stredup(const char *s, const char *last)
 {
-	size_t len = last == NULL ? strlen(s) : ttd_strnlen(s, last - s + 1);
+	size_t len = last == nullptr ? strlen(s) : ttd_strnlen(s, last - s + 1);
 	char *tmp = CallocT<char>(len + 1);
 	memcpy(tmp, s, len);
 	return tmp;
@@ -447,7 +447,7 @@ char *md5sumToString(char *buf, const ch
  */
 size_t Utf8Decode(WChar *c, const char *s)
 {
-	assert(c != NULL);
+	assert(c != nullptr);
 
 	if (!HasBit(s[0], 7)) {
 		/* Single byte character: 0xxxxxxx */
@@ -551,7 +551,7 @@ char *strcasestr(const char *haystack, c
 		hay_len--;
 	}
 
-	return NULL;
+	return nullptr;
 }
 #endif /* DEFINE_STRCASESTR */
 
@@ -585,7 +585,7 @@ int strnatcmp(const char *s1, const char
 	}
 
 #ifdef WITH_ICU_I18N
-	if (_current_collator != NULL) {
+	if (_current_collator != nullptr) {
 		UErrorCode status = U_ZERO_ERROR;
 		int result = _current_collator->compareUTF8(s1, s2, status);
 		if (U_SUCCESS(status)) return result;
@@ -628,11 +628,11 @@ class IcuStringIterator : public StringI
 	std::vector<size_t> utf16_to_utf8; ///< Mapping from UTF-16 code point position to index in the UTF-8 source string.
 
 public:
-	IcuStringIterator() : char_itr(NULL), word_itr(NULL)
+	IcuStringIterator() : char_itr(nullptr), word_itr(nullptr)
 	{
 		UErrorCode status = U_ZERO_ERROR;
-		this->char_itr = icu::BreakIterator::createCharacterInstance(icu::Locale(_current_language != NULL ? _current_language->isocode : "en"), status);
-		this->word_itr = icu::BreakIterator::createWordInstance(icu::Locale(_current_language != NULL ? _current_language->isocode : "en"), status);
+		this->char_itr = icu::BreakIterator::createCharacterInstance(icu::Locale(_current_language != nullptr ? _current_language->isocode : "en"), status);
+		this->word_itr = icu::BreakIterator::createWordInstance(icu::Locale(_current_language != nullptr ? _current_language->isocode : "en"), status);
 
 		this->utf16_str.push_back('\0');
 		this->utf16_to_utf8.push_back(0);
@@ -779,7 +779,7 @@ class DefaultStringIterator : public Str
 	size_t cur_pos;     ///< Current iteration position.
 
 public:
-	DefaultStringIterator() : string(NULL), len(0), cur_pos(0)
+	DefaultStringIterator() : string(nullptr), len(0), cur_pos(0)
 	{
 	}
 
@@ -792,7 +792,7 @@ public:
 
 	virtual size_t SetCurPosition(size_t pos)
 	{
-		assert(this->string != NULL && pos <= this->len);
+		assert(this->string != nullptr && pos <= this->len);
 		/* Sanitize in case we get a position inside an UTF-8 sequence. */
 		while (pos > 0 && IsUtf8Part(this->string[pos])) pos--;
 		return this->cur_pos = pos;
@@ -800,7 +800,7 @@ public:
 
 	virtual size_t Next(IterType what)
 	{
-		assert(this->string != NULL);
+		assert(this->string != nullptr);
 
 		/* Already at the end? */
 		if (this->cur_pos >= this->len) return END;
@@ -838,7 +838,7 @@ public:
 
 	virtual size_t Prev(IterType what)
 	{
-		assert(this->string != NULL);
+		assert(this->string != nullptr);
 
 		/* Already at the beginning? */
 		if (this->cur_pos == 0) return END;
@@ -878,7 +878,7 @@ public:
 /* static */ StringIterator *StringIterator::Create()
 {
 	StringIterator *i = OSXStringIterator::Create();
-	if (i != NULL) return i;
+	if (i != nullptr) return i;
 
 	return new DefaultStringIterator();
 }
diff --git a/src/string_func.h b/src/string_func.h
--- a/src/string_func.h
+++ b/src/string_func.h
@@ -33,7 +33,7 @@
 
 char *strecat(char *dst, const char *src, const char *last);
 char *strecpy(char *dst, const char *src, const char *last);
-char *stredup(const char *src, const char *last = NULL);
+char *stredup(const char *src, const char *last = nullptr);
 
 int CDECL seprintf(char *str, const char *last, const char *format, ...) WARN_FORMAT(3, 4);
 int CDECL vseprintf(char *str, const char *last, const char *format, va_list ap);
@@ -54,11 +54,11 @@ bool StrValid(const char *str, const cha
  *
  * @param s The pointer to the first element of the buffer
  * @return true if the buffer starts with the terminating null-character or
- *         if the given pointer points to NULL else return false
+ *         if the given pointer points to nullptr else return false
  */
 static inline bool StrEmpty(const char *s)
 {
-	return s == NULL || s[0] == '\0';
+	return s == nullptr || s[0] == '\0';
 }
 
 /**
diff --git a/src/stringfilter.cpp b/src/stringfilter.cpp
--- a/src/stringfilter.cpp
+++ b/src/stringfilter.cpp
@@ -33,14 +33,14 @@ void StringFilter::SetFilterTerm(const c
 	this->word_matches = 0;
 	free(this->filter_buffer);
 
-	assert(str != NULL);
+	assert(str != nullptr);
 
 	char *dest = MallocT<char>(strlen(str) + 1);
 	this->filter_buffer = dest;
 
 	WChar state = STATE_WHITESPACE;
 	const char *pos = str;
-	WordState *word = NULL;
+	WordState *word = nullptr;
 	size_t len;
 	for (;; pos += len) {
 		WChar c;
@@ -48,9 +48,9 @@ void StringFilter::SetFilterTerm(const c
 
 		if (c == 0 || (state == STATE_WORD && IsWhitespace(c))) {
 			/* Finish word */
-			if (word != NULL) {
+			if (word != nullptr) {
 				*(dest++) = '\0';
-				word = NULL;
+				word = nullptr;
 			}
 			state = STATE_WHITESPACE;
 			if (c != 0) continue; else break;
@@ -75,7 +75,7 @@ void StringFilter::SetFilterTerm(const c
 		}
 
 		/* Add to word */
-		if (word == NULL) {
+		if (word == nullptr) {
 			/*C++17: word = &*/ this->word_index.push_back({dest, false});
 			word = &this->word_index.back();
 		}
@@ -106,12 +106,12 @@ void StringFilter::ResetState()
  */
 void StringFilter::AddLine(const char *str)
 {
-	if (str == NULL) return;
+	if (str == nullptr) return;
 
-	bool match_case = this->case_sensitive != NULL && *this->case_sensitive;
+	bool match_case = this->case_sensitive != nullptr && *this->case_sensitive;
 	for (WordState &ws : this->word_index) {
 		if (!ws.match) {
-			if ((match_case ? strstr(str, ws.start) : strcasestr(str, ws.start)) != NULL) {
+			if ((match_case ? strstr(str, ws.start) : strcasestr(str, ws.start)) != nullptr) {
 				ws.match = true;
 				this->word_matches++;
 			}
diff --git a/src/stringfilter_type.h b/src/stringfilter_type.h
--- a/src/stringfilter_type.h
+++ b/src/stringfilter_type.h
@@ -47,9 +47,9 @@ private:
 public:
 	/**
 	 * Constructor for filter.
-	 * @param case_sensitive Pointer to a (usually static) variable controlling the case-sensitivity. NULL means always case-insensitive.
+	 * @param case_sensitive Pointer to a (usually static) variable controlling the case-sensitivity. nullptr means always case-insensitive.
 	 */
-	StringFilter(const bool *case_sensitive = NULL) : filter_buffer(NULL), word_matches(0), case_sensitive(case_sensitive) {}
+	StringFilter(const bool *case_sensitive = nullptr) : filter_buffer(nullptr), word_matches(0), case_sensitive(case_sensitive) {}
 	~StringFilter() { free(this->filter_buffer); }
 
 	void SetFilterTerm(const char *str);
diff --git a/src/strings.cpp b/src/strings.cpp
--- a/src/strings.cpp
+++ b/src/strings.cpp
@@ -45,12 +45,12 @@
 
 char _config_language_file[MAX_PATH];             ///< The file (name) stored in the configuration.
 LanguageList _languages;                          ///< The actual list of language meta data.
-const LanguageMetadata *_current_language = NULL; ///< The currently loaded language.
+const LanguageMetadata *_current_language = nullptr; ///< The currently loaded language.
 
 TextDirection _current_text_dir; ///< Text direction of the currently selected language.
 
 #ifdef WITH_ICU_I18N
-icu::Collator *_current_collator = NULL;          ///< Collator for the language currently in use.
+icu::Collator *_current_collator = nullptr;          ///< Collator for the language currently in use.
 #endif /* WITH_ICU_I18N */
 
 static uint64 _global_string_params_data[20];     ///< Global array of string parameters. To access, use #SetDParam.
@@ -60,7 +60,7 @@ StringParameters _global_string_params(_
 /** Reset the type array. */
 void StringParameters::ClearTypeInformation()
 {
-	assert(this->type != NULL);
+	assert(this->type != nullptr);
 	MemSetT(this->type, 0, this->num_param);
 }
 
@@ -75,7 +75,7 @@ int64 StringParameters::GetInt64(WChar t
 		DEBUG(misc, 0, "Trying to read invalid string parameter");
 		return 0;
 	}
-	if (this->type != NULL) {
+	if (this->type != nullptr) {
 		if (this->type[this->offset] != 0 && this->type[this->offset] != type) {
 			DEBUG(misc, 0, "Trying to read string parameter with wrong type");
 			return 0;
@@ -172,7 +172,7 @@ void CopyOutDParam(uint64 *dst, const ch
 			strings[i] = stredup((const char *)(size_t)_global_string_params.GetParam(i));
 			dst[i] = (size_t)strings[i];
 		} else {
-			strings[i] = NULL;
+			strings[i] = nullptr;
 		}
 	}
 }
@@ -320,7 +320,7 @@ static char *FormatNumber(char *buff, in
 	for (int i = 0; i < max_digits; i++) {
 		if (i == max_digits - fractional_digits) {
 			const char *decimal_separator = _settings_game.locale.digit_decimal_separator;
-			if (decimal_separator == NULL) decimal_separator = _langpack->digit_decimal_separator;
+			if (decimal_separator == nullptr) decimal_separator = _langpack->digit_decimal_separator;
 			buff += seprintf(buff, last, "%s", decimal_separator);
 		}
 
@@ -345,7 +345,7 @@ static char *FormatNumber(char *buff, in
 static char *FormatCommaNumber(char *buff, int64 number, const char *last, int fractional_digits = 0)
 {
 	const char *separator = _settings_game.locale.digit_group_separator;
-	if (separator == NULL) separator = _langpack->digit_group_separator;
+	if (separator == nullptr) separator = _langpack->digit_group_separator;
 	return FormatNumber(buff, number, last, separator, 1, fractional_digits);
 }
 
@@ -384,7 +384,7 @@ static char *FormatBytes(char *buff, int
 	}
 
 	const char *decimal_separator = _settings_game.locale.digit_decimal_separator;
-	if (decimal_separator == NULL) decimal_separator = _langpack->digit_decimal_separator;
+	if (decimal_separator == nullptr) decimal_separator = _langpack->digit_decimal_separator;
 
 	if (number < 1024) {
 		id = 0;
@@ -478,8 +478,8 @@ static char *FormatGenericCurrency(char 
 	}
 
 	const char *separator = _settings_game.locale.digit_group_separator_currency;
-	if (separator == NULL && !StrEmpty(_currency->separator)) separator = _currency->separator;
-	if (separator == NULL) separator = _langpack->digit_group_separator_currency;
+	if (separator == nullptr && !StrEmpty(_currency->separator)) separator = _currency->separator;
+	if (separator == nullptr) separator = _langpack->digit_group_separator_currency;
 	buff = FormatNumber(buff, number, last, separator);
 	buff = strecpy(buff, multiplier, last);
 
@@ -937,7 +937,7 @@ static char *FormatString(char *buff, co
 					char buf[256];
 					bool old_sgd = _scan_for_gender_data;
 					_scan_for_gender_data = true;
-					StringParameters tmp_params(args->GetPointerToOffset(offset), args->num_param - offset, NULL);
+					StringParameters tmp_params(args->GetPointerToOffset(offset), args->num_param - offset, nullptr);
 					p = FormatString(buf, input, &tmp_params, lastof(buf));
 					_scan_for_gender_data = old_sgd;
 					*p = '\0';
@@ -1016,8 +1016,8 @@ static char *FormatString(char *buff, co
 				if (game_script && GetStringTab(str) != TEXT_TAB_GAMESCRIPT_START) break;
 				/* WARNING. It's prohibited for the included string to consume any arguments.
 				 * For included strings that consume argument, you should use STRING1, STRING2 etc.
-				 * To debug stuff you can set argv to NULL and it will tell you */
-				StringParameters tmp_params(args->GetDataPointer(), args->GetDataLeft(), NULL);
+				 * To debug stuff you can set argv to nullptr and it will tell you */
+				StringParameters tmp_params(args->GetDataPointer(), args->GetDataLeft(), nullptr);
 				buff = GetStringWithArgs(buff, str, &tmp_params, last, next_substr_case_index, game_script);
 				next_substr_case_index = 0;
 				break;
@@ -1270,9 +1270,9 @@ static char *FormatString(char *buff, co
 
 			case SCC_COMPANY_NAME: { // {COMPANY}
 				const Company *c = Company::GetIfValid(args->GetInt32());
-				if (c == NULL) break;
+				if (c == nullptr) break;
 
-				if (c->name != NULL) {
+				if (c->name != nullptr) {
 					int64 args_array[] = {(int64)(size_t)c->name};
 					StringParameters tmp_params(args_array);
 					buff = GetStringWithArgs(buff, STR_JUST_RAW_STRING, &tmp_params, last);
@@ -1307,7 +1307,7 @@ static char *FormatString(char *buff, co
 				}
 
 				const Depot *d = Depot::Get(args->GetInt32());
-				if (d->name != NULL) {
+				if (d->name != nullptr) {
 					int64 args_array[] = {(int64)(size_t)d->name};
 					StringParameters tmp_params(args_array);
 					buff = GetStringWithArgs(buff, STR_JUST_RAW_STRING, &tmp_params, last);
@@ -1321,14 +1321,14 @@ static char *FormatString(char *buff, co
 
 			case SCC_ENGINE_NAME: { // {ENGINE}
 				const Engine *e = Engine::GetIfValid(args->GetInt32(SCC_ENGINE_NAME));
-				if (e == NULL) break;
+				if (e == nullptr) break;
 
-				if (e->name != NULL && e->IsEnabled()) {
+				if (e->name != nullptr && e->IsEnabled()) {
 					int64 args_array[] = {(int64)(size_t)e->name};
 					StringParameters tmp_params(args_array);
 					buff = GetStringWithArgs(buff, STR_JUST_RAW_STRING, &tmp_params, last);
 				} else {
-					StringParameters tmp_params(NULL, 0, NULL);
+					StringParameters tmp_params(nullptr, 0, nullptr);
 					buff = GetStringWithArgs(buff, e->info.string_id, &tmp_params, last);
 				}
 				break;
@@ -1336,9 +1336,9 @@ static char *FormatString(char *buff, co
 
 			case SCC_GROUP_NAME: { // {GROUP}
 				const Group *g = Group::GetIfValid(args->GetInt32());
-				if (g == NULL) break;
+				if (g == nullptr) break;
 
-				if (g->name != NULL) {
+				if (g->name != nullptr) {
 					int64 args_array[] = {(int64)(size_t)g->name};
 					StringParameters tmp_params(args_array);
 					buff = GetStringWithArgs(buff, STR_JUST_RAW_STRING, &tmp_params, last);
@@ -1353,12 +1353,12 @@ static char *FormatString(char *buff, co
 
 			case SCC_INDUSTRY_NAME: { // {INDUSTRY}
 				const Industry *i = Industry::GetIfValid(args->GetInt32(SCC_INDUSTRY_NAME));
-				if (i == NULL) break;
+				if (i == nullptr) break;
 
 				if (_scan_for_gender_data) {
 					/* Gender is defined by the industry type.
 					 * STR_FORMAT_INDUSTRY_NAME may have the town first, so it would result in the gender of the town name */
-					StringParameters tmp_params(NULL, 0, NULL);
+					StringParameters tmp_params(nullptr, 0, nullptr);
 					buff = FormatString(buff, GetStringPtr(GetIndustrySpec(i->type)->name), &tmp_params, last, next_substr_case_index);
 				} else {
 					/* First print the town name and the industry type name. */
@@ -1373,9 +1373,9 @@ static char *FormatString(char *buff, co
 
 			case SCC_PRESIDENT_NAME: { // {PRESIDENT_NAME}
 				const Company *c = Company::GetIfValid(args->GetInt32(SCC_PRESIDENT_NAME));
-				if (c == NULL) break;
+				if (c == nullptr) break;
 
-				if (c->president_name != NULL) {
+				if (c->president_name != nullptr) {
 					int64 args_array[] = {(int64)(size_t)c->president_name};
 					StringParameters tmp_params(args_array);
 					buff = GetStringWithArgs(buff, STR_JUST_RAW_STRING, &tmp_params, last);
@@ -1391,16 +1391,16 @@ static char *FormatString(char *buff, co
 				StationID sid = args->GetInt32(SCC_STATION_NAME);
 				const Station *st = Station::GetIfValid(sid);
 
-				if (st == NULL) {
+				if (st == nullptr) {
 					/* The station doesn't exist anymore. The only place where we might
 					 * be "drawing" an invalid station is in the case of cargo that is
 					 * in transit. */
-					StringParameters tmp_params(NULL, 0, NULL);
+					StringParameters tmp_params(nullptr, 0, nullptr);
 					buff = GetStringWithArgs(buff, STR_UNKNOWN_STATION, &tmp_params, last);
 					break;
 				}
 
-				if (st->name != NULL) {
+				if (st->name != nullptr) {
 					int64 args_array[] = {(int64)(size_t)st->name};
 					StringParameters tmp_params(args_array);
 					buff = GetStringWithArgs(buff, STR_JUST_RAW_STRING, &tmp_params, last);
@@ -1428,9 +1428,9 @@ static char *FormatString(char *buff, co
 
 			case SCC_TOWN_NAME: { // {TOWN}
 				const Town *t = Town::GetIfValid(args->GetInt32(SCC_TOWN_NAME));
-				if (t == NULL) break;
+				if (t == nullptr) break;
 
-				if (t->name != NULL) {
+				if (t->name != nullptr) {
 					int64 args_array[] = {(int64)(size_t)t->name};
 					StringParameters tmp_params(args_array);
 					buff = GetStringWithArgs(buff, STR_JUST_RAW_STRING, &tmp_params, last);
@@ -1442,9 +1442,9 @@ static char *FormatString(char *buff, co
 
 			case SCC_WAYPOINT_NAME: { // {WAYPOINT}
 				Waypoint *wp = Waypoint::GetIfValid(args->GetInt32(SCC_WAYPOINT_NAME));
-				if (wp == NULL) break;
+				if (wp == nullptr) break;
 
-				if (wp->name != NULL) {
+				if (wp->name != nullptr) {
 					int64 args_array[] = {(int64)(size_t)wp->name};
 					StringParameters tmp_params(args_array);
 					buff = GetStringWithArgs(buff, STR_JUST_RAW_STRING, &tmp_params, last);
@@ -1460,9 +1460,9 @@ static char *FormatString(char *buff, co
 
 			case SCC_VEHICLE_NAME: { // {VEHICLE}
 				const Vehicle *v = Vehicle::GetIfValid(args->GetInt32(SCC_VEHICLE_NAME));
-				if (v == NULL) break;
+				if (v == nullptr) break;
 
-				if (v->name != NULL) {
+				if (v->name != nullptr) {
 					int64 args_array[] = {(int64)(size_t)v->name};
 					StringParameters tmp_params(args_array);
 					buff = GetStringWithArgs(buff, STR_JUST_RAW_STRING, &tmp_params, last);
@@ -1486,14 +1486,14 @@ static char *FormatString(char *buff, co
 
 			case SCC_SIGN_NAME: { // {SIGN}
 				const Sign *si = Sign::GetIfValid(args->GetInt32());
-				if (si == NULL) break;
+				if (si == nullptr) break;
 
-				if (si->name != NULL) {
+				if (si->name != nullptr) {
 					int64 args_array[] = {(int64)(size_t)si->name};
 					StringParameters tmp_params(args_array);
 					buff = GetStringWithArgs(buff, STR_JUST_RAW_STRING, &tmp_params, last);
 				} else {
-					StringParameters tmp_params(NULL, 0, NULL);
+					StringParameters tmp_params(nullptr, 0, nullptr);
 					buff = GetStringWithArgs(buff, STR_DEFAULT_SIGN_NAME, &tmp_params, last);
 				}
 				break;
@@ -1717,7 +1717,7 @@ bool ReadLanguagePack(const LanguageMeta
 	/* Current language pack */
 	size_t len;
 	LanguagePack *lang_pack = (LanguagePack *)ReadFileToMem(lang->file, &len, 1U << 20);
-	if (lang_pack == NULL) return false;
+	if (lang_pack == nullptr) return false;
 
 	/* End of read data (+ terminating zero added in ReadFileToMem()) */
 	const char *end = (char *)lang_pack + len + 1;
@@ -1797,20 +1797,20 @@ bool ReadLanguagePack(const LanguageMeta
 
 #ifdef WITH_ICU_I18N
 	/* Delete previous collator. */
-	if (_current_collator != NULL) {
+	if (_current_collator != nullptr) {
 		delete _current_collator;
-		_current_collator = NULL;
+		_current_collator = nullptr;
 	}
 
 	/* Create a collator instance for our current locale. */
 	UErrorCode status = U_ZERO_ERROR;
 	_current_collator = icu::Collator::createInstance(icu::Locale(_current_language->isocode), status);
 	/* Sort number substrings by their numerical value. */
-	if (_current_collator != NULL) _current_collator->setAttribute(UCOL_NUMERIC_COLLATION, UCOL_ON, status);
+	if (_current_collator != nullptr) _current_collator->setAttribute(UCOL_NUMERIC_COLLATION, UCOL_ON, status);
 	/* Avoid using the collator if it is not correctly set. */
 	if (U_FAILURE(status)) {
 		delete _current_collator;
-		_current_collator = NULL;
+		_current_collator = nullptr;
 	}
 #endif /* WITH_ICU_I18N */
 
@@ -1840,22 +1840,22 @@ bool ReadLanguagePack(const LanguageMeta
  * First check some default values, after this one we passed ourselves
  * and if none exist return the value for $LANG
  * @param param environment variable to check conditionally if default ones are not
- *        set. Pass NULL if you don't want additional checks.
- * @return return string containing current charset, or NULL if not-determinable
+ *        set. Pass nullptr if you don't want additional checks.
+ * @return return string containing current charset, or nullptr if not-determinable
  */
 const char *GetCurrentLocale(const char *param)
 {
 	const char *env;
 
 	env = getenv("LANGUAGE");
-	if (env != NULL) return env;
+	if (env != nullptr) return env;
 
 	env = getenv("LC_ALL");
-	if (env != NULL) return env;
+	if (env != nullptr) return env;
 
-	if (param != NULL) {
+	if (param != nullptr) {
 		env = getenv(param);
-		if (env != NULL) return env;
+		if (env != nullptr) return env;
 	}
 
 	return getenv("LANG");
@@ -1877,7 +1877,7 @@ int CDECL StringIDSorter(const StringID 
 /**
  * Get the language with the given NewGRF language ID.
  * @param newgrflangid NewGRF languages ID to check.
- * @return The language's metadata, or NULL if it is not known.
+ * @return The language's metadata, or nullptr if it is not known.
  */
 const LanguageMetadata *GetLanguage(byte newgrflangid)
 {
@@ -1885,7 +1885,7 @@ const LanguageMetadata *GetLanguage(byte
 		if (newgrflangid == lang.newgrflangid) return &lang;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -1897,7 +1897,7 @@ const LanguageMetadata *GetLanguage(byte
 static bool GetLanguageFileHeader(const char *file, LanguagePackHeader *hdr)
 {
 	FILE *f = fopen(file, "rb");
-	if (f == NULL) return false;
+	if (f == nullptr) return false;
 
 	size_t read = fread(hdr, sizeof(*hdr), 1, f);
 	fclose(f);
@@ -1919,14 +1919,14 @@ static bool GetLanguageFileHeader(const 
 static void GetLanguageList(const char *path)
 {
 	DIR *dir = ttd_opendir(path);
-	if (dir != NULL) {
+	if (dir != nullptr) {
 		struct dirent *dirent;
-		while ((dirent = readdir(dir)) != NULL) {
+		while ((dirent = readdir(dir)) != nullptr) {
 			const char *d_name    = FS2OTTD(dirent->d_name);
 			const char *extension = strrchr(d_name, '.');
 
 			/* Not a language file */
-			if (extension == NULL || strcmp(extension, ".lng") != 0) continue;
+			if (extension == nullptr || strcmp(extension, ".lng") != 0) continue;
 
 			LanguageMetadata lmd;
 			seprintf(lmd.file, lastof(lmd.file), "%s%s", path, d_name);
@@ -1934,7 +1934,7 @@ static void GetLanguageList(const char *
 			/* Check whether the file is of the correct version */
 			if (!GetLanguageFileHeader(lmd.file, &lmd)) {
 				DEBUG(misc, 3, "%s is not a valid language file", lmd.file);
-			} else if (GetLanguage(lmd.newgrflangid) != NULL) {
+			} else if (GetLanguage(lmd.newgrflangid) != nullptr) {
 				DEBUG(misc, 3, "%s's language ID is already known", lmd.file);
 			} else {
 				_languages.push_back(lmd);
@@ -1961,10 +1961,10 @@ void InitializeLanguagePacks()
 
 	/* Acquire the locale of the current system */
 	const char *lang = GetCurrentLocale("LC_MESSAGES");
-	if (lang == NULL) lang = "en_GB";
+	if (lang == nullptr) lang = "en_GB";
 
-	const LanguageMetadata *chosen_language   = NULL; ///< Matching the language in the configuration file or the current locale
-	const LanguageMetadata *language_fallback = NULL; ///< Using pt_PT for pt_BR locale when pt_BR is not available
+	const LanguageMetadata *chosen_language   = nullptr; ///< Matching the language in the configuration file or the current locale
+	const LanguageMetadata *language_fallback = nullptr; ///< Using pt_PT for pt_BR locale when pt_BR is not available
 	const LanguageMetadata *en_GB_fallback    = _languages.data(); ///< Fallback when no locale-matching language has been found
 
 	/* Find a proper language. */
@@ -1985,8 +1985,8 @@ void InitializeLanguagePacks()
 
 	/* We haven't found the language in the config nor the one in the locale.
 	 * Now we set it to one of the fallback languages */
-	if (chosen_language == NULL) {
-		chosen_language = (language_fallback != NULL) ? language_fallback : en_GB_fallback;
+	if (chosen_language == nullptr) {
+		chosen_language = (language_fallback != nullptr) ? language_fallback : en_GB_fallback;
 	}
 
 	if (!ReadLanguagePack(chosen_language)) usererror("Can't read language pack '%s'", chosen_language->file);
@@ -2005,7 +2005,7 @@ const char *GetCurrentLanguageIsoCode()
  * Check whether there are glyphs missing in the current language.
  * @param[out] str Pointer to an address for storing the text pointer.
  * @return If glyphs are missing, return \c true, else return \c false.
- * @post If \c true is returned and str is not NULL, *str points to a string that is found to contain at least one missing glyph.
+ * @post If \c true is returned and str is not nullptr, *str points to a string that is found to contain at least one missing glyph.
  */
 bool MissingGlyphSearcher::FindMissingGlyphs(const char **str)
 {
@@ -2017,9 +2017,9 @@ bool MissingGlyphSearcher::FindMissingGl
 	}
 
 	this->Reset();
-	for (const char *text = this->NextString(); text != NULL; text = this->NextString()) {
+	for (const char *text = this->NextString(); text != nullptr; text = this->NextString()) {
 		FontSize size = this->DefaultSize();
-		if (str != NULL) *str = text;
+		if (str != nullptr) *str = text;
 		for (WChar c = Utf8Consume(&text); c != '\0'; c = Utf8Consume(&text)) {
 			if (c >= SCC_FIRST_FONT && c <= SCC_LAST_FONT) {
 				size = (FontSize)(c - SCC_FIRST_FONT);
@@ -2050,7 +2050,7 @@ class LanguagePackGlyphSearcher : public
 
 	const char *NextString() override
 	{
-		if (this->i >= TEXT_TAB_END) return NULL;
+		if (this->i >= TEXT_TAB_END) return nullptr;
 
 		const char *ret = _langpack_offs[_langtab_start[this->i] + this->j];
 
@@ -2089,13 +2089,13 @@ class LanguagePackGlyphSearcher : public
  * been added.
  * @param base_font Whether to look at the base font as well.
  * @param searcher  The methods to use to search for strings to check.
- *                  If NULL the loaded language pack searcher is used.
+ *                  If nullptr the loaded language pack searcher is used.
  */
 void CheckForMissingGlyphs(bool base_font, MissingGlyphSearcher *searcher)
 {
 	static LanguagePackGlyphSearcher pack_searcher;
-	if (searcher == NULL) searcher = &pack_searcher;
-	bool bad_font = !base_font || searcher->FindMissingGlyphs(NULL);
+	if (searcher == nullptr) searcher = &pack_searcher;
+	bool bad_font = !base_font || searcher->FindMissingGlyphs(nullptr);
 #ifdef WITH_FREETYPE
 	if (bad_font) {
 		/* We found an unprintable character... lets try whether we can find
diff --git a/src/strings_func.h b/src/strings_func.h
--- a/src/strings_func.h
+++ b/src/strings_func.h
@@ -60,9 +60,9 @@ static inline StringID MakeStringID(Stri
 }
 
 class StringParameters {
-	StringParameters *parent; ///< If not NULL, this instance references data from this parent instance.
+	StringParameters *parent; ///< If not nullptr, this instance references data from this parent instance.
 	uint64 *data;             ///< Array with the actual data.
-	WChar *type;              ///< Array with type information about the data. Can be NULL when no type information is needed. See #StringControlCode.
+	WChar *type;              ///< Array with type information about the data. Can be nullptr when no type information is needed. See #StringControlCode.
 
 public:
 	uint offset;              ///< Current offset in the data/type arrays.
@@ -70,7 +70,7 @@ public:
 
 	/** Create a new StringParameters instance. */
 	StringParameters(uint64 *data, uint num_param, WChar *type) :
-		parent(NULL),
+		parent(nullptr),
 		data(data),
 		type(type),
 		offset(0),
@@ -80,9 +80,9 @@ public:
 	/** Create a new StringParameters instance. */
 	template <size_t Tnum_param>
 	StringParameters(int64 (&data)[Tnum_param]) :
-		parent(NULL),
+		parent(nullptr),
 		data((uint64 *)data),
-		type(NULL),
+		type(nullptr),
 		offset(0),
 		num_param(Tnum_param)
 	{
@@ -100,8 +100,8 @@ public:
 		num_param(size)
 	{
 		assert(size <= parent.GetDataLeft());
-		if (parent.type == NULL) {
-			this->type = NULL;
+		if (parent.type == nullptr) {
+			this->type = nullptr;
 		} else {
 			this->type = parent.type + parent.offset;
 		}
@@ -109,7 +109,7 @@ public:
 
 	~StringParameters()
 	{
-		if (this->parent != NULL) {
+		if (this->parent != nullptr) {
 			this->parent->offset += this->num_param;
 		}
 	}
@@ -148,7 +148,7 @@ public:
 	/** Does this instance store information about the type of the parameters. */
 	bool HasTypeInformation() const
 	{
-		return this->type != NULL;
+		return this->type != nullptr;
 	}
 
 	/** Get the type of a specific element. */
@@ -250,7 +250,7 @@ public:
 
 	/**
 	 * Get the next string to search through.
-	 * @return The next string or NULL if there is none.
+	 * @return The next string or nullptr if there is none.
 	 */
 	virtual const char *NextString() = 0;
 
@@ -281,6 +281,6 @@ public:
 	bool FindMissingGlyphs(const char **str);
 };
 
-void CheckForMissingGlyphs(bool base_font = true, MissingGlyphSearcher *search = NULL);
+void CheckForMissingGlyphs(bool base_font = true, MissingGlyphSearcher *search = nullptr);
 
 #endif /* STRINGS_FUNC_H */
diff --git a/src/subsidy.cpp b/src/subsidy.cpp
--- a/src/subsidy.cpp
+++ b/src/subsidy.cpp
@@ -376,7 +376,7 @@ bool FindSubsidyIndustryCargoRoute()
 
 	/* Select a random industry. */
 	const Industry *src_ind = Industry::GetRandom();
-	if (src_ind == NULL) return false;
+	if (src_ind == nullptr) return false;
 
 	uint trans, total;
 
@@ -441,7 +441,7 @@ bool FindSubsidyCargoDestination(CargoID
 		case ST_INDUSTRY: {
 			/* Select a random industry. */
 			const Industry *dst_ind = Industry::GetRandom();
-			if (dst_ind == NULL) return false;
+			if (dst_ind == nullptr) return false;
 
 			/* The industry must accept the cargo */
 			bool valid = std::find(dst_ind->accepts_cargo, endof(dst_ind->accepts_cargo), cid) != endof(dst_ind->accepts_cargo);
diff --git a/src/subsidy_base.h b/src/subsidy_base.h
--- a/src/subsidy_base.h
+++ b/src/subsidy_base.h
@@ -36,7 +36,7 @@ struct Subsidy : SubsidyPool::PoolItem<&
 	inline Subsidy() { }
 
 	/**
-	 * (Empty) destructor has to be defined else operator delete might be called with NULL parameter
+	 * (Empty) destructor has to be defined else operator delete might be called with nullptr parameter
 	 */
 	inline ~Subsidy() { }
 
diff --git a/src/table/airport_defaults.h b/src/table/airport_defaults.h
--- a/src/table/airport_defaults.h
+++ b/src/table/airport_defaults.h
@@ -386,7 +386,7 @@ static const Direction _default_airports
 
 /** AirportSpec definition for airports without any depot. */
 #define AS_ND(ap_name, size_x, size_y, min_year, max_year, catchment, noise, maint_cost, ttdpatch_type, class_id, name, preview) \
-	AS_GENERIC(&_airportfta_##ap_name, _tile_table_##ap_name, _default_airports_rotation, lengthof(_tile_table_##ap_name), NULL, 0, \
+	AS_GENERIC(&_airportfta_##ap_name, _tile_table_##ap_name, _default_airports_rotation, lengthof(_tile_table_##ap_name), nullptr, 0, \
 		size_x, size_y, noise, catchment, min_year, max_year, maint_cost, ttdpatch_type, class_id, name, preview, true)
 
 /** AirportSpec definition for airports with at least one depot. */
@@ -405,12 +405,12 @@ extern const AirportSpec _origin_airport
 	AS(helidepot,        2, 2,  1976, MAX_YEAR,  4,  2,  7, ATP_TTDP_SMALL,    APC_HELIPORT, STR_AIRPORT_HELIDEPOT,        SPR_AIRPORT_PREVIEW_HELIDEPOT),
 	AS(intercontinental, 9, 11, 2002, MAX_YEAR, 10, 25, 72, ATP_TTDP_LARGE,    APC_HUB,      STR_AIRPORT_INTERCONTINENTAL, SPR_AIRPORT_PREVIEW_INTERCONTINENTAL),
 	AS(helistation,      4, 2,  1980, MAX_YEAR,  4,  3, 14, ATP_TTDP_SMALL,    APC_HELIPORT, STR_AIRPORT_HELISTATION,      SPR_AIRPORT_PREVIEW_HELISTATION),
-	AS_GENERIC(&_airportfta_oilrig, NULL, _default_airports_rotation, 0, NULL, 0, 1, 1, 0, 4, 0, 0, 0, ATP_TTDP_OILRIG, APC_HELIPORT, STR_NULL, 0, false),
+	AS_GENERIC(&_airportfta_oilrig, nullptr, _default_airports_rotation, 0, nullptr, 0, 1, 1, 0, 4, 0, 0, 0, ATP_TTDP_OILRIG, APC_HELIPORT, STR_NULL, 0, false),
 };
 
 assert_compile(NEW_AIRPORT_OFFSET == lengthof(_origin_airport_specs));
 
-const AirportSpec AirportSpec::dummy = AS_GENERIC(&_airportfta_dummy, NULL, _default_airports_rotation, 0, NULL, 0, 0, 0, 0, 0, MIN_YEAR, MIN_YEAR, 0, ATP_TTDP_LARGE, APC_BEGIN, STR_NULL, 0, false);
+const AirportSpec AirportSpec::dummy = AS_GENERIC(&_airportfta_dummy, nullptr, _default_airports_rotation, 0, nullptr, 0, 0, 0, 0, 0, MIN_YEAR, MIN_YEAR, 0, ATP_TTDP_LARGE, APC_BEGIN, STR_NULL, 0, false);
 
 #undef AS
 #undef AS_ND
diff --git a/src/table/bridge_land.h b/src/table/bridge_land.h
--- a/src/table/bridge_land.h
+++ b/src/table/bridge_land.h
@@ -741,7 +741,7 @@ static const PalSpriteID * const * const
  * @param nrd description of the road bridge in query tool
  */
 #define MBR(y, mnl, mxl, p, mxs, spr, plt, dsc, nrl, nrd) \
-	{y, mnl, mxl, p, mxs, spr, plt, dsc, { nrl, nrd }, NULL, 0}
+	{y, mnl, mxl, p, mxs, spr, plt, dsc, { nrl, nrd }, nullptr, 0}
 
 const BridgeSpec _orig_bridge[] = {
 /*
diff --git a/src/table/build_industry.h b/src/table/build_industry.h
--- a/src/table/build_industry.h
+++ b/src/table/build_industry.h
@@ -1213,7 +1213,7 @@ enum IndustryTypes {
 	   industry name                           building text
 	   messages : Closure                      production up                      production down   */
 static const IndustrySpec _origin_industry_specs[NEW_INDUSTRYOFFSET] = {
-	MI(_tile_table_coal_mine,                  0, NULL,
+	MI(_tile_table_coal_mine,                  0, nullptr,
 	   210,  0xB3333333,                       2, 3, 0, 0,    8, 8, 0, 0,          1,
 	   IT_POWER_STATION,  IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_COAL,       15, CT_INVALID,       0, 5,
@@ -1223,7 +1223,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_COAL_MINE,                     STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_COAL,   STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_power_station,              0, NULL,
+	MI(_tile_table_power_station,              0, nullptr,
 	   240,  0xFFFFFFFF,                       2, 2, 0, 0,    5, 5, 0, 0,        184,
 	   IT_COAL_MINE,      IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_INVALID,     0, CT_INVALID,       0, 5,
@@ -1243,7 +1243,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_SAWMILL,                       STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_SUPPLY_PROBLEMS,      STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_forest,                     0, NULL,
+	MI(_tile_table_forest,                     0, nullptr,
 	   200,  0xBFFFFFFF,                       3, 4, 0, 0,    5, 5, 0, 0,         86,
 	   IT_SAWMILL,        IT_PAPER_MILL,       IT_INVALID,       CHECK_FOREST,
 	   CT_WOOD,       13, CT_INVALID,       0, 30,
@@ -1253,7 +1253,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_FOREST,                        STR_NEWS_INDUSTRY_PLANTED,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_FARM),
 
-	MI(_tile_table_oil_refinery,               0, NULL,
+	MI(_tile_table_oil_refinery,               0, nullptr,
 	   244,  0xFFFFFFFF,                       2, 2, 2, 0,    4, 4, 4, 0,        191,
 	   IT_OIL_RIG,        IT_INVALID,          IT_INVALID,       CHECK_REFINERY,
 	   CT_GOODS,       0, CT_INVALID,       0, 5,
@@ -1263,7 +1263,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_OIL_REFINERY,                  STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_SUPPLY_PROBLEMS,      STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_oil_rig,                    0, NULL,
+	MI(_tile_table_oil_rig,                    0, nullptr,
 	   240,  0x99999999,                       6, 0, 0, 0,    0, 0, 0, 0,        152,
 	   IT_OIL_REFINERY,   IT_INVALID,          IT_INVALID,       CHECK_OIL_RIG,
 	   CT_OIL,        15, CT_PASSENGERS,    2, 5,
@@ -1293,7 +1293,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_PRINTING_WORKS,                STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_SUPPLY_PROBLEMS,      STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_steel_mill,                 0, NULL,
+	MI(_tile_table_steel_mill,                 0, nullptr,
 	   215,  0xFFFFFFFF,                       2, 0, 0, 0,    5, 0, 0, 0,         10,
 	   IT_IRON_MINE,      IT_FACTORY,          IT_INVALID,       CHECK_NOTHING,
 	   CT_STEEL,       0, CT_INVALID,       0, 5,
@@ -1313,7 +1313,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_FARM,                          STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_FARM, STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_FARM),
 
-	MI(_tile_table_copper_mine,                0, NULL,
+	MI(_tile_table_copper_mine,                0, nullptr,
 	   205,  0xB3333333,                       0, 0, 3, 0,    0, 0, 4, 0,         10,
 	   IT_FACTORY_2,      IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_COPPER_ORE, 10, CT_INVALID,       0, 5,
@@ -1323,7 +1323,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_COPPER_ORE_MINE,               STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_oil_well,                   0, NULL,
+	MI(_tile_table_oil_well,                   0, nullptr,
 	   220,  0x99999999,                       0, 5, 3, 0,    4, 5, 5, 0,        152,
 	   IT_OIL_REFINERY,   IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_OIL,        12, CT_INVALID,       0, 5,
@@ -1333,7 +1333,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_OIL_WELLS,                     STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_OIL,   STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_bank,                       0, NULL,
+	MI(_tile_table_bank,                       0, nullptr,
 	   255,  0xA6666666,                       7, 0, 0, 0,    0, 0, 0, 0,         15,
 	   IT_BANK_TEMP,      IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_VALUABLES,   6, CT_INVALID,       0, 5,
@@ -1343,7 +1343,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_BANK,                          STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_food_process,               0, NULL,
+	MI(_tile_table_food_process,               0, nullptr,
 	   206,  0xFFFFFFFF,                       0, 2, 2, 0,    0, 3, 4, 0,         55,
 	   IT_FRUIT_PLANTATION, IT_FARM,           IT_FARM_2,        CHECK_NOTHING,
 	   CT_FOOD,        0, CT_INVALID,       0, 5,
@@ -1363,7 +1363,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_PAPER_MILL,                    STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_SUPPLY_PROBLEMS,      STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_gold_mine,                  0, NULL,
+	MI(_tile_table_gold_mine,                  0, nullptr,
 	   208,  0x99999999,                       0, 3, 0, 0,    0, 4, 0, 0,        194,
 	   IT_BANK_TROPIC_ARCTIC, IT_INVALID,      IT_INVALID,       CHECK_NOTHING,
 	   CT_GOLD,        7, CT_INVALID,       0, 5,
@@ -1373,7 +1373,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_GOLD_MINE,                     STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_bank2,                      0, NULL,
+	MI(_tile_table_bank2,                      0, nullptr,
 	   151,  0xA6666666,                       0, 3, 3, 0,    0, 6, 5, 0,         15,
 	   IT_GOLD_MINE,      IT_DIAMOND_MINE,     IT_INVALID,       CHECK_NOTHING,
 	   CT_INVALID,     0, CT_INVALID,       0, 5,
@@ -1383,7 +1383,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_BANK_TROPIC_ARCTIC,                          STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_diamond_mine,               0, NULL,
+	MI(_tile_table_diamond_mine,               0, nullptr,
 	   213,  0x99999999,                       0, 0, 3, 0,    0, 0, 4, 0,        184,
 	   IT_BANK_TROPIC_ARCTIC, IT_INVALID,      IT_INVALID,       CHECK_NOTHING,
 	   CT_DIAMONDS,    7, CT_INVALID,       0, 5,
@@ -1393,7 +1393,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_DIAMOND_MINE,                  STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_iron_mine,                  0, NULL,
+	MI(_tile_table_iron_mine,                  0, nullptr,
 	   220,  0xB3333333,                       2, 0, 0, 0,    5, 0, 0, 0,         55,
 	   IT_STEEL_MILL,     IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_IRON_ORE,   10, CT_INVALID,       0, 5,
@@ -1403,7 +1403,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_IRON_ORE_MINE,                 STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_fruit_plantation,           0, NULL,
+	MI(_tile_table_fruit_plantation,           0, nullptr,
 	   225,  0xBFFFFFFF,                       0, 0, 2, 0,    0, 0, 4, 0,         86,
 	   IT_FOOD_PROCESS,   IT_INVALID,          IT_INVALID,       CHECK_PLANTATION,
 	   CT_FRUIT,      10, CT_INVALID,       0, 15,
@@ -1413,7 +1413,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_FRUIT_PLANTATION,              STR_NEWS_INDUSTRY_PLANTED,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_FARM, STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_FARM),
 
-	MI(_tile_table_rubber_plantation,          0, NULL,
+	MI(_tile_table_rubber_plantation,          0, nullptr,
 	   218,  0xBFFFFFFF,                       0, 0, 3, 0,    0, 0, 4, 0,         39,
 	   IT_FACTORY_2,      IT_INVALID,          IT_INVALID,       CHECK_PLANTATION,
 	   CT_RUBBER,     10, CT_INVALID,       0, 15,
@@ -1423,7 +1423,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_RUBBER_PLANTATION,             STR_NEWS_INDUSTRY_PLANTED,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_FARM, STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_FARM),
 
-	MI(_tile_table_water_supply,               0, NULL,
+	MI(_tile_table_water_supply,               0, nullptr,
 	   199,  0xB3333333,                       0, 0, 3, 0,    0, 0, 4, 0,         37,
 	   IT_WATER_TOWER,    IT_INVALID,          IT_INVALID,       CHECK_WATER,
 	   CT_WATER,      12, CT_INVALID,       0, 5,
@@ -1433,7 +1433,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_WATER_SUPPLY,                  STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_water_tower,                0, NULL,
+	MI(_tile_table_water_tower,                0, nullptr,
 	   115,  0xFFFFFFFF,                       0, 0, 4, 0,    0, 0, 8, 0,        208,
 	   IT_WATER_SUPPLY,   IT_INVALID,          IT_INVALID,       CHECK_WATER,
 	   CT_INVALID,     0, CT_INVALID,       0, 5,
@@ -1453,7 +1453,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_FACTORY_2,                       STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_SUPPLY_PROBLEMS,      STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_farm2,                      0, NULL,
+	MI(_tile_table_farm2,                      0, nullptr,
 	   250,  0xD9999999,                       0, 0, 1, 0,    0, 0, 2, 0,         48,
 	   IT_FOOD_PROCESS,   IT_INVALID,          IT_INVALID,       CHECK_PLANTATION,
 	   CT_MAIZE,      11, CT_INVALID,       0, 5,
@@ -1463,7 +1463,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_FARM_2,                          STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_FARM, STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_FARM),
 
-	MI(_tile_table_lumber_mill,                0, NULL,
+	MI(_tile_table_lumber_mill,                0, nullptr,
 	   135,  0xFFFFFFFF,                       0, 0, 0, 0,    0, 0, 0, 0,        194,
 	   IT_FACTORY_2,      IT_INVALID,          IT_INVALID,       CHECK_LUMBERMILL,
 	   CT_WOOD,        0, CT_INVALID,       0, 5,
@@ -1473,7 +1473,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_LUMBER_MILL,                   STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_LACK_OF_TREES,   STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_cotton_candy,               0, NULL,
+	MI(_tile_table_cotton_candy,               0, nullptr,
 	   195,  0xBFFFFFFF,                       0, 0, 0, 3,    0, 0, 0, 5,         48,
 	   IT_CANDY_FACTORY,  IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_COTTON_CANDY, 13, CT_INVALID,    0, 30,
@@ -1483,7 +1483,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_COTTON_CANDY_FOREST,           STR_NEWS_INDUSTRY_PLANTED,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_FARM, STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_candy_factory,              0, NULL,
+	MI(_tile_table_candy_factory,              0, nullptr,
 	   206,  0xFFFFFFFF,                       0, 0, 0, 3,    0, 0, 0, 5,        174,
 	   IT_COTTON_CANDY,   IT_TOFFEE_QUARRY,    IT_SUGAR_MINE,    CHECK_NOTHING,
 	   CT_CANDY,       0, CT_INVALID,       0, 5,
@@ -1493,7 +1493,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_CANDY_FACTORY,                 STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_SUPPLY_PROBLEMS,      STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_battery_farm,               0, NULL,
+	MI(_tile_table_battery_farm,               0, nullptr,
 	   187,  0xB3333333,                       0, 0, 0, 3,    0, 0, 0, 4,         39,
 	   IT_TOY_FACTORY,    IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_BATTERIES,  11, CT_INVALID,       0, 30,
@@ -1503,7 +1503,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_BATTERY_FARM,                  STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_FARM, STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_FARM),
 
-	MI(_tile_table_cola_wells,                 0, NULL,
+	MI(_tile_table_cola_wells,                 0, nullptr,
 	   193,  0x99999999,                       0, 0, 0, 3,    0, 0, 0, 5,         55,
 	   IT_FIZZY_DRINK_FACTORY, IT_INVALID,     IT_INVALID,       CHECK_NOTHING,
 	   CT_COLA,       12, CT_INVALID,       0, 5,
@@ -1513,7 +1513,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_COLA_WELLS,                    STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_toy_shop,                   0, NULL,
+	MI(_tile_table_toy_shop,                   0, nullptr,
 	   133,  0xFFFFFFFF,                       0, 0, 0, 3,    0, 0, 0, 4,        208,
 	   IT_TOY_FACTORY,    IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_INVALID,     0, CT_INVALID,       0, 5,
@@ -1523,7 +1523,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_TOY_SHOP,                      STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_SUPPLY_PROBLEMS,      STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_toy_factory,                0, NULL,
+	MI(_tile_table_toy_factory,                0, nullptr,
 	   163,  0xFFFFFFFF,                       0, 0, 0, 3,    0, 0, 0, 5,          10,
 	   IT_PLASTIC_FOUNTAINS, IT_BATTERY_FARM,  IT_TOY_SHOP,     CHECK_NOTHING,
 	   CT_TOYS,        0, CT_INVALID,       0, 5,
@@ -1543,7 +1543,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_PLASTIC_FOUNTAINS,             STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_fizzy_drink,                0, NULL,
+	MI(_tile_table_fizzy_drink,                0, nullptr,
 	   177,  0xFFFFFFFF,                       0, 0, 0, 3,    0, 0, 0, 4,        184,
 	   IT_COLA_WELLS,     IT_BUBBLE_GENERATOR, IT_INVALID,       CHECK_NOTHING,
 	   CT_FIZZY_DRINKS, 0, CT_INVALID,      0, 5,
@@ -1553,7 +1553,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_FIZZY_DRINK_FACTORY,           STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_SUPPLY_PROBLEMS,      STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_bubble_generator,           0, NULL,
+	MI(_tile_table_bubble_generator,           0, nullptr,
 	   203,  0xB3333333,                       0, 0, 0, 3,    0, 0, 0, 5,        152,
 	   IT_FIZZY_DRINK_FACTORY, IT_INVALID,     IT_INVALID,       CHECK_BUBBLEGEN,
 	   CT_BUBBLES,    13, CT_INVALID,       0, 5,
@@ -1563,7 +1563,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_BUBBLE_GENERATOR,              STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_toffee_quarry,              0, NULL,
+	MI(_tile_table_toffee_quarry,              0, nullptr,
 	   213,  0xCCCCCCCC,                       0, 0, 0, 3,    0, 0, 0, 5,        194,
 	   IT_CANDY_FACTORY,  IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_TOFFEE,     10, CT_INVALID,       0, 5,
@@ -1573,7 +1573,7 @@ static const IndustrySpec _origin_indust
 	   STR_INDUSTRY_NAME_TOFFEE_QUARRY,                 STR_NEWS_INDUSTRY_CONSTRUCTION,
 	   STR_NEWS_INDUSTRY_CLOSURE_GENERAL,    STR_NEWS_INDUSTRY_PRODUCTION_INCREASE_GENERAL,     STR_NEWS_INDUSTRY_PRODUCTION_DECREASE_GENERAL),
 
-	MI(_tile_table_sugar_mine,                 0, NULL,
+	MI(_tile_table_sugar_mine,                 0, nullptr,
 	   210,  0xBFFFFFFF,                       0, 0, 0, 2,    0, 0, 0, 4,         15,
 	   IT_CANDY_FACTORY,  IT_INVALID,          IT_INVALID,       CHECK_NOTHING,
 	   CT_SUGAR,      11, CT_INVALID,       0, 5,
diff --git a/src/table/cargo_const.h b/src/table/cargo_const.h
--- a/src/table/cargo_const.h
+++ b/src/table/cargo_const.h
@@ -11,7 +11,7 @@
 
 /** Construction macro for a #CargoSpec structure. */
 #define MK(bt, label, c, e, f, g, h, fr, te, ks1, ks2, ks3, ks4, ks5, l, m, cmult) \
-		{bt, label, c, c, e, cmult, f, {g, h}, fr, te, 0, 0, ks1, ks2, ks3, ks4, ks5, l, m, NULL, NULL, 0}
+		{bt, label, c, c, e, cmult, f, {g, h}, fr, te, 0, 0, ks1, ks2, ks3, ks4, ks5, l, m, nullptr, nullptr, 0}
 /** Cargo types available by default. */
 static const CargoSpec _default_cargo[] = {
 	MK(  0, 'PASS', 152,  1, 3185,  0,  24, false, TE_PASSENGERS,
diff --git a/src/table/newgrf_debug_data.h b/src/table/newgrf_debug_data.h
--- a/src/table/newgrf_debug_data.h
+++ b/src/table/newgrf_debug_data.h
@@ -14,15 +14,15 @@
 
 /* Helper for filling property tables */
 #define NIP(prop, base, variable, type, name) { name, (ptrdiff_t)cpp_offsetof(base, variable), cpp_sizeof(base, variable), prop, type }
-#define NIP_END() { NULL, 0, 0, 0, 0 }
+#define NIP_END() { nullptr, 0, 0, 0, 0 }
 
 /* Helper for filling callback tables */
 #define NIC(cb_id, base, variable, bit) { #cb_id, (ptrdiff_t)cpp_offsetof(base, variable), cpp_sizeof(base, variable), bit, cb_id }
-#define NIC_END() { NULL, 0, 0, 0, 0 }
+#define NIC_END() { nullptr, 0, 0, 0, 0 }
 
 /* Helper for filling variable tables */
 #define NIV(var, name) { name, var }
-#define NIV_END() { NULL, 0 }
+#define NIV_END() { nullptr, 0 }
 
 
 /*** NewGRF Vehicles ***/
@@ -69,7 +69,7 @@ static const NIVariable _niv_vehicles[] 
 };
 
 class NIHVehicle : public NIHelper {
-	bool IsInspectable(uint index) const override        { return Vehicle::Get(index)->GetGRF() != NULL; }
+	bool IsInspectable(uint index) const override        { return Vehicle::Get(index)->GetGRF() != nullptr; }
 	uint GetParent(uint index) const override            { const Vehicle *first = Vehicle::Get(index)->First(); return GetInspectWindowNumber(GetGrfSpecFeature(first->type), first->index); }
 	const void *GetInstance(uint index)const override    { return Vehicle::Get(index); }
 	const void *GetSpec(uint index) const override       { return Vehicle::Get(index)->GetEngine(); }
@@ -85,7 +85,7 @@ class NIHVehicle : public NIHelper {
 };
 
 static const NIFeature _nif_vehicle = {
-	NULL,
+	nullptr,
 	_nic_vehicles,
 	_niv_vehicles,
 	new NIHVehicle(),
@@ -132,9 +132,9 @@ static const NIVariable _niv_stations[] 
 };
 
 class NIHStation : public NIHelper {
-	bool IsInspectable(uint index) const override        { return GetStationSpec(index) != NULL; }
+	bool IsInspectable(uint index) const override        { return GetStationSpec(index) != nullptr; }
 	uint GetParent(uint index) const override            { return GetInspectWindowNumber(GSF_FAKE_TOWNS, Station::GetByTile(index)->town->index); }
-	const void *GetInstance(uint index)const override    { return NULL; }
+	const void *GetInstance(uint index)const override    { return nullptr; }
 	const void *GetSpec(uint index) const override       { return GetStationSpec(index); }
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_STATION_NAME, GetStationIndex(index), index); }
 	uint32 GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? GetStationSpec(index)->grf_prop.grffile->grfid : 0; }
@@ -147,7 +147,7 @@ class NIHStation : public NIHelper {
 };
 
 static const NIFeature _nif_station = {
-	NULL,
+	nullptr,
 	_nic_stations,
 	_niv_stations,
 	new NIHStation(),
@@ -197,9 +197,9 @@ static const NIVariable _niv_house[] = {
 };
 
 class NIHHouse : public NIHelper {
-	bool IsInspectable(uint index) const override        { return HouseSpec::Get(GetHouseType(index))->grf_prop.grffile != NULL; }
+	bool IsInspectable(uint index) const override        { return HouseSpec::Get(GetHouseType(index))->grf_prop.grffile != nullptr; }
 	uint GetParent(uint index) const override            { return GetInspectWindowNumber(GSF_FAKE_TOWNS, GetTownIndex(index)); }
-	const void *GetInstance(uint index)const override    { return NULL; }
+	const void *GetInstance(uint index)const override    { return nullptr; }
 	const void *GetSpec(uint index) const override       { return HouseSpec::Get(GetHouseType(index)); }
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_TOWN_NAME, GetTownIndex(index), index); }
 	uint32 GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? HouseSpec::Get(GetHouseType(index))->grf_prop.grffile->grfid : 0; }
@@ -212,7 +212,7 @@ class NIHHouse : public NIHelper {
 };
 
 static const NIFeature _nif_house = {
-	NULL,
+	nullptr,
 	_nic_house,
 	_niv_house,
 	new NIHHouse(),
@@ -247,9 +247,9 @@ static const NIVariable _niv_industrytil
 };
 
 class NIHIndustryTile : public NIHelper {
-	bool IsInspectable(uint index) const override        { return GetIndustryTileSpec(GetIndustryGfx(index))->grf_prop.grffile != NULL; }
+	bool IsInspectable(uint index) const override        { return GetIndustryTileSpec(GetIndustryGfx(index))->grf_prop.grffile != nullptr; }
 	uint GetParent(uint index) const override            { return GetInspectWindowNumber(GSF_INDUSTRIES, GetIndustryIndex(index)); }
-	const void *GetInstance(uint index)const override    { return NULL; }
+	const void *GetInstance(uint index)const override    { return nullptr; }
 	const void *GetSpec(uint index) const override       { return GetIndustryTileSpec(GetIndustryGfx(index)); }
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_INDUSTRY_NAME, GetIndustryIndex(index), index); }
 	uint32 GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? GetIndustryTileSpec(GetIndustryGfx(index))->grf_prop.grffile->grfid : 0; }
@@ -262,7 +262,7 @@ class NIHIndustryTile : public NIHelper 
 };
 
 static const NIFeature _nif_industrytile = {
-	NULL,
+	nullptr,
 	_nic_industrytiles,
 	_niv_industrytiles,
 	new NIHIndustryTile(),
@@ -346,7 +346,7 @@ static const NIVariable _niv_industries[
 };
 
 class NIHIndustry : public NIHelper {
-	bool IsInspectable(uint index) const override        { return GetIndustrySpec(Industry::Get(index)->type)->grf_prop.grffile != NULL; }
+	bool IsInspectable(uint index) const override        { return GetIndustrySpec(Industry::Get(index)->type)->grf_prop.grffile != nullptr; }
 	uint GetParent(uint index) const override            { return GetInspectWindowNumber(GSF_FAKE_TOWNS, Industry::Get(index)->town->index); }
 	const void *GetInstance(uint index)const override    { return Industry::Get(index); }
 	const void *GetSpec(uint index) const override       { return GetIndustrySpec(Industry::Get(index)->type); }
@@ -365,7 +365,7 @@ class NIHIndustry : public NIHelper {
 	const int32 *GetPSAFirstPosition(uint index, uint32 grfid) const override
 	{
 		const Industry *i = (const Industry *)this->GetInstance(index);
-		if (i->psa == NULL) return NULL;
+		if (i->psa == nullptr) return nullptr;
 		return (int32 *)(&i->psa->storage);
 	}
 };
@@ -411,7 +411,7 @@ static const NIVariable _niv_objects[] =
 };
 
 class NIHObject : public NIHelper {
-	bool IsInspectable(uint index) const override        { return ObjectSpec::GetByTile(index)->grf_prop.grffile != NULL; }
+	bool IsInspectable(uint index) const override        { return ObjectSpec::GetByTile(index)->grf_prop.grffile != nullptr; }
 	uint GetParent(uint index) const override            { return GetInspectWindowNumber(GSF_FAKE_TOWNS, Object::GetByTile(index)->town->index); }
 	const void *GetInstance(uint index)const override    { return Object::GetByTile(index); }
 	const void *GetSpec(uint index) const override       { return ObjectSpec::GetByTile(index); }
@@ -426,7 +426,7 @@ class NIHObject : public NIHelper {
 };
 
 static const NIFeature _nif_object = {
-	NULL,
+	nullptr,
 	_nic_objects,
 	_niv_objects,
 	new NIHObject(),
@@ -447,8 +447,8 @@ static const NIVariable _niv_railtypes[]
 class NIHRailType : public NIHelper {
 	bool IsInspectable(uint index) const override        { return true; }
 	uint GetParent(uint index) const override            { return UINT32_MAX; }
-	const void *GetInstance(uint index)const override    { return NULL; }
-	const void *GetSpec(uint index) const override       { return NULL; }
+	const void *GetInstance(uint index)const override    { return nullptr; }
+	const void *GetSpec(uint index) const override       { return nullptr; }
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_NEWGRF_INSPECT_CAPTION_OBJECT_AT_RAIL_TYPE, INVALID_STRING_ID, index); }
 	uint32 GetGRFID(uint index) const override           { return 0; }
 
@@ -456,14 +456,14 @@ class NIHRailType : public NIHelper {
 	{
 		/* There is no unique GRFFile for the tile. Multiple GRFs can define different parts of the railtype.
 		 * However, currently the NewGRF Debug GUI does not display variables depending on the GRF (like 0x7F) anyway. */
-		RailTypeResolverObject ro(NULL, index, TCX_NORMAL, RTSG_END);
+		RailTypeResolverObject ro(nullptr, index, TCX_NORMAL, RTSG_END);
 		return ro.GetScope(VSG_SCOPE_SELF)->GetVariable(var, param, avail);
 	}
 };
 
 static const NIFeature _nif_railtype = {
-	NULL,
-	NULL,
+	nullptr,
+	nullptr,
 	_niv_railtypes,
 	new NIHRailType(),
 };
@@ -481,9 +481,9 @@ static const NICallback _nic_airporttile
 };
 
 class NIHAirportTile : public NIHelper {
-	bool IsInspectable(uint index) const override        { return AirportTileSpec::Get(GetAirportGfx(index))->grf_prop.grffile != NULL; }
+	bool IsInspectable(uint index) const override        { return AirportTileSpec::Get(GetAirportGfx(index))->grf_prop.grffile != nullptr; }
 	uint GetParent(uint index) const override            { return GetInspectWindowNumber(GSF_FAKE_TOWNS, Station::GetByTile(index)->town->index); }
-	const void *GetInstance(uint index)const override    { return NULL; }
+	const void *GetInstance(uint index)const override    { return nullptr; }
 	const void *GetSpec(uint index) const override       { return AirportTileSpec::Get(GetAirportGfx(index)); }
 	void SetStringParameters(uint index) const override  { this->SetObjectAtStringParameters(STR_STATION_NAME, GetStationIndex(index), index); }
 	uint32 GetGRFID(uint index) const override           { return (this->IsInspectable(index)) ? AirportTileSpec::Get(GetAirportGfx(index))->grf_prop.grffile->grfid : 0; }
@@ -496,7 +496,7 @@ class NIHAirportTile : public NIHelper {
 };
 
 static const NIFeature _nif_airporttile = {
-	NULL,
+	nullptr,
 	_nic_airporttiles,
 	_niv_industrytiles, // Yes, they share this (at least now)
 	new NIHAirportTile(),
@@ -522,7 +522,7 @@ class NIHTown : public NIHelper {
 	bool IsInspectable(uint index) const override        { return Town::IsValidID(index); }
 	uint GetParent(uint index) const override            { return UINT32_MAX; }
 	const void *GetInstance(uint index)const override    { return Town::Get(index); }
-	const void *GetSpec(uint index) const override       { return NULL; }
+	const void *GetSpec(uint index) const override       { return nullptr; }
 	void SetStringParameters(uint index) const override  { this->SetSimpleStringParameters(STR_TOWN_NAME, index); }
 	uint32 GetGRFID(uint index) const override           { return 0; }
 	bool PSAWithParameter() const override               { return true; }
@@ -530,7 +530,7 @@ class NIHTown : public NIHelper {
 
 	uint Resolve(uint index, uint var, uint param, bool *avail) const override
 	{
-		TownResolverObject ro(NULL, Town::Get(index), true);
+		TownResolverObject ro(nullptr, Town::Get(index), true);
 		return ro.GetScope(VSG_SCOPE_SELF)->GetVariable(var, param, avail);
 	}
 
@@ -543,13 +543,13 @@ class NIHTown : public NIHelper {
 			if ((*iter)->grfid == grfid) return (int32 *)(&(*iter)->storage[0]);
 		}
 
-		return NULL;
+		return nullptr;
 	}
 };
 
 static const NIFeature _nif_town = {
-	NULL,
-	NULL,
+	nullptr,
+	nullptr,
 	_niv_towns,
 	new NIHTown(),
 };
@@ -561,16 +561,16 @@ static const NIFeature * const _nifeatur
 	&_nif_vehicle,      // GSF_SHIPS
 	&_nif_vehicle,      // GSF_AIRCRAFT
 	&_nif_station,      // GSF_STATIONS
-	NULL,               // GSF_CANALS (no callbacks/action2 implemented)
-	NULL,               // GSF_BRIDGES (no callbacks/action2)
+	nullptr,               // GSF_CANALS (no callbacks/action2 implemented)
+	nullptr,               // GSF_BRIDGES (no callbacks/action2)
 	&_nif_house,        // GSF_HOUSES
-	NULL,               // GSF_GLOBALVAR (has no "physical" objects)
+	nullptr,               // GSF_GLOBALVAR (has no "physical" objects)
 	&_nif_industrytile, // GSF_INDUSTRYTILES
 	&_nif_industry,     // GSF_INDUSTRIES
-	NULL,               // GSF_CARGOES (has no "physical" objects)
-	NULL,               // GSF_SOUNDFX (has no "physical" objects)
-	NULL,               // GSF_AIRPORTS (feature not implemented)
-	NULL,               // GSF_SIGNALS (feature not implemented)
+	nullptr,               // GSF_CARGOES (has no "physical" objects)
+	nullptr,               // GSF_SOUNDFX (has no "physical" objects)
+	nullptr,               // GSF_AIRPORTS (feature not implemented)
+	nullptr,               // GSF_SIGNALS (feature not implemented)
 	&_nif_object,       // GSF_OBJECTS
 	&_nif_railtype,     // GSF_RAILTYPES
 	&_nif_airporttile,  // GSF_AIRPORTTILES
diff --git a/src/table/railtypes.h b/src/table/railtypes.h
--- a/src/table/railtypes.h
+++ b/src/table/railtypes.h
@@ -112,8 +112,8 @@ static const RailtypeInfo _original_rail
 		/* sort order */
 		0 << 4 | 7,
 
-		{ NULL },
-		{ NULL },
+		{ nullptr },
+		{ nullptr },
 	},
 
 	/** Electrified railway */
@@ -213,8 +213,8 @@ static const RailtypeInfo _original_rail
 		/* sort order */
 		1 << 4 | 7,
 
-		{ NULL },
-		{ NULL },
+		{ nullptr },
+		{ nullptr },
 	},
 
 	/** Monorail */
@@ -310,8 +310,8 @@ static const RailtypeInfo _original_rail
 		/* sort order */
 		2 << 4 | 7,
 
-		{ NULL },
-		{ NULL },
+		{ nullptr },
+		{ nullptr },
 	},
 
 	/** Maglev */
@@ -407,8 +407,8 @@ static const RailtypeInfo _original_rail
 		/* sort order */
 		3 << 4 | 7,
 
-		{ NULL },
-		{ NULL },
+		{ nullptr },
+		{ nullptr },
 	},
 };
 
diff --git a/src/table/roadveh_movement.h b/src/table/roadveh_movement.h
--- a/src/table/roadveh_movement.h
+++ b/src/table/roadveh_movement.h
@@ -1445,39 +1445,39 @@ static const RoadDriveEntry * const _roa
 	_roadveh_drive_data_29,
 	_roadveh_tram_turn_sw_1,
 	_roadveh_tram_turn_nw_1,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
 };
 
 static const RoadDriveEntry * const * const _road_drive_data[2] = {
diff --git a/src/table/station_land.h b/src/table/station_land.h
--- a/src/table/station_land.h
+++ b/src/table/station_land.h
@@ -789,7 +789,7 @@ static const DrawTileSeqStruct _station_
  * @param dtss  Sequence child sprites of the tile
  */
 #define TILE_SPRITE_LINE(img, dtss) { {img, PAL_NONE}, dtss },
-#define TILE_SPRITE_NULL() { {0, 0}, NULL },
+#define TILE_SPRITE_NULL() { {0, 0}, nullptr },
 
 extern const DrawTileSprites _station_display_datas_rail[] = {
 	TILE_SPRITE_LINE(SPR_RAIL_TRACK_X,               _station_display_datas_0)
diff --git a/src/tar_type.h b/src/tar_type.h
--- a/src/tar_type.h
+++ b/src/tar_type.h
@@ -25,7 +25,7 @@ struct TarListEntry {
 	/* MSVC goes copying around this struct after initialisation, so it tries
 	 * to free filename, which isn't set at that moment... but because it
 	 * initializes the variable with garbage, it's going to segfault. */
-	TarListEntry() : filename(NULL), dirname(NULL) {}
+	TarListEntry() : filename(nullptr), dirname(nullptr) {}
 	~TarListEntry() { free(this->filename); free(this->dirname); }
 };
 
diff --git a/src/terraform_cmd.cpp b/src/terraform_cmd.cpp
--- a/src/terraform_cmd.cpp
+++ b/src/terraform_cmd.cpp
@@ -278,7 +278,7 @@ CommandCost CmdTerraformLand(TileIndex t
 
 			/* Is the tile already cleared? */
 			const ClearedObjectArea *coa = FindClearedObject(tile);
-			bool indirectly_cleared = coa != NULL && coa->first_tile != tile;
+			bool indirectly_cleared = coa != nullptr && coa->first_tile != tile;
 
 			/* Check tiletype-specific things, and add extra-cost */
 			const bool curr_gen = _generating_world;
@@ -304,7 +304,7 @@ CommandCost CmdTerraformLand(TileIndex t
 	}
 
 	Company *c = Company::GetIfValid(_current_company);
-	if (c != NULL && GB(c->terraform_limit, 16, 16) < ts.tile_to_new_height.size()) {
+	if (c != nullptr && GB(c->terraform_limit, 16, 16) < ts.tile_to_new_height.size()) {
 		return_cmd_error(STR_ERROR_TERRAFORM_LIMIT_REACHED);
 	}
 
@@ -326,7 +326,7 @@ CommandCost CmdTerraformLand(TileIndex t
 			SetTileHeight(tile, (uint)height);
 		}
 
-		if (c != NULL) c->terraform_limit -= (uint32)ts.tile_to_new_height.size() << 16;
+		if (c != nullptr) c->terraform_limit -= (uint32)ts.tile_to_new_height.size() << 16;
 	}
 	return total_cost;
 }
@@ -371,7 +371,7 @@ CommandCost CmdLevelLand(TileIndex tile,
 	bool had_success = false;
 
 	const Company *c = Company::GetIfValid(_current_company);
-	int limit = (c == NULL ? INT32_MAX : GB(c->terraform_limit, 16, 16));
+	int limit = (c == nullptr ? INT32_MAX : GB(c->terraform_limit, 16, 16));
 	if (limit == 0) return_cmd_error(STR_ERROR_TERRAFORM_LIMIT_REACHED);
 
 	TileIterator *iter = HasBit(p2, 0) ? (TileIterator *)new DiagonalTileIterator(tile, p1) : new OrthogonalTileIterator(tile, p1);
diff --git a/src/terraform_gui.cpp b/src/terraform_gui.cpp
--- a/src/terraform_gui.cpp
+++ b/src/terraform_gui.cpp
@@ -293,8 +293,8 @@ struct TerraformToolbarWindow : Window {
 static EventState TerraformToolbarGlobalHotkeys(int hotkey)
 {
 	if (_game_mode != GM_NORMAL) return ES_NOT_HANDLED;
-	Window *w = ShowTerraformToolbar(NULL);
-	if (w == NULL) return ES_NOT_HANDLED;
+	Window *w = ShowTerraformToolbar(nullptr);
+	if (w == nullptr) return ES_NOT_HANDLED;
 	return w->OnHotkey(hotkey);
 }
 
@@ -353,14 +353,14 @@ static WindowDesc _terraform_desc(
 /**
  * Show the toolbar for terraforming in the game.
  * @param link The toolbar we might want to link to.
- * @return The allocated toolbar if the window was newly opened, else \c NULL.
+ * @return The allocated toolbar if the window was newly opened, else \c nullptr.
  */
 Window *ShowTerraformToolbar(Window *link)
 {
-	if (!Company::IsValidID(_local_company)) return NULL;
+	if (!Company::IsValidID(_local_company)) return nullptr;
 
 	Window *w;
-	if (link == NULL) {
+	if (link == nullptr) {
 		w = AllocateWindowDescFront<TerraformToolbarWindow>(&_terraform_desc, 0);
 		return w;
 	}
@@ -631,7 +631,7 @@ struct ScenarioEditorLandscapeGeneration
 				break;
 
 			case WID_ETT_RESET_LANDSCAPE: // Reset landscape
-				ShowQuery(STR_QUERY_RESET_LANDSCAPE_CAPTION, STR_RESET_LANDSCAPE_CONFIRMATION_TEXT, NULL, ResetLandscapeConfirmationCallback);
+				ShowQuery(STR_QUERY_RESET_LANDSCAPE_CAPTION, STR_RESET_LANDSCAPE_CONFIRMATION_TEXT, nullptr, ResetLandscapeConfirmationCallback);
 				break;
 
 			default: NOT_REACHED();
@@ -720,7 +720,7 @@ static EventState TerraformToolbarEditor
 {
 	if (_game_mode != GM_EDITOR) return ES_NOT_HANDLED;
 	Window *w = ShowEditorTerraformToolbar();
-	if (w == NULL) return ES_NOT_HANDLED;
+	if (w == nullptr) return ES_NOT_HANDLED;
 	return w->OnHotkey(hotkey);
 }
 
@@ -747,7 +747,7 @@ static WindowDesc _scen_edit_land_gen_de
 
 /**
  * Show the toolbar for terraforming in the scenario editor.
- * @return The allocated toolbar if the window was newly opened, else \c NULL.
+ * @return The allocated toolbar if the window was newly opened, else \c nullptr.
  */
 Window *ShowEditorTerraformToolbar()
 {
diff --git a/src/terraform_gui.h b/src/terraform_gui.h
--- a/src/terraform_gui.h
+++ b/src/terraform_gui.h
@@ -14,7 +14,7 @@
 
 #include "window_type.h"
 
-Window *ShowTerraformToolbar(Window *link = NULL);
+Window *ShowTerraformToolbar(Window *link = nullptr);
 Window *ShowEditorTerraformToolbar();
 
 #endif /* TERRAFORM_GUI_H */
diff --git a/src/textbuf.cpp b/src/textbuf.cpp
--- a/src/textbuf.cpp
+++ b/src/textbuf.cpp
@@ -164,18 +164,18 @@ bool Textbuf::InsertChar(WChar key)
 bool Textbuf::InsertString(const char *str, bool marked, const char *caret, const char *insert_location, const char *replacement_end)
 {
 	uint16 insertpos = (marked && this->marklength != 0) ? this->markpos : this->caretpos;
-	if (insert_location != NULL) {
+	if (insert_location != nullptr) {
 		insertpos = insert_location - this->buf;
 		if (insertpos > this->bytes) return false;
 
-		if (replacement_end != NULL) {
-			this->DeleteText(insertpos, replacement_end - this->buf, str == NULL);
+		if (replacement_end != nullptr) {
+			this->DeleteText(insertpos, replacement_end - this->buf, str == nullptr);
 		}
 	} else {
-		if (marked) this->DiscardMarkedText(str == NULL);
+		if (marked) this->DiscardMarkedText(str == nullptr);
 	}
 
-	if (str == NULL) return false;
+	if (str == nullptr) return false;
 
 	uint16 bytes = 0, chars = 0;
 	WChar c;
@@ -205,7 +205,7 @@ bool Textbuf::InsertString(const char *s
 
 	this->bytes += bytes;
 	this->chars += chars;
-	if (!marked && caret == NULL) this->caretpos += bytes;
+	if (!marked && caret == nullptr) this->caretpos += bytes;
 	assert(this->bytes <= this->max_bytes);
 	assert(this->chars <= this->max_chars);
 	this->buf[this->bytes - 1] = '\0'; // terminating zero
diff --git a/src/textbuf_type.h b/src/textbuf_type.h
--- a/src/textbuf_type.h
+++ b/src/textbuf_type.h
@@ -56,7 +56,7 @@ struct Textbuf {
 	bool InsertClipboard();
 
 	bool InsertChar(uint32 key);
-	bool InsertString(const char *str, bool marked, const char *caret = NULL, const char *insert_location = NULL, const char *replacement_end = NULL);
+	bool InsertString(const char *str, bool marked, const char *caret = nullptr, const char *insert_location = nullptr, const char *replacement_end = nullptr);
 
 	bool DeleteChar(uint16 keycode);
 	bool MovePos(uint16 keycode);
diff --git a/src/textfile_gui.cpp b/src/textfile_gui.cpp
--- a/src/textfile_gui.cpp
+++ b/src/textfile_gui.cpp
@@ -184,7 +184,7 @@ void TextfileWindow::SetupScrollbars()
 
 /* virtual */ const char *TextfileWindow::NextString()
 {
-	if (this->search_iterator >= this->lines.size()) return NULL;
+	if (this->search_iterator >= this->lines.size()) return nullptr;
 
 	return this->lines[this->search_iterator++];
 }
@@ -214,13 +214,13 @@ void TextfileWindow::SetupScrollbars()
  *              After the call, it contains the size of the uncompressed
  *              data.
  *
- * When decompressing fails, *bufp is set to NULL and *sizep to 0. The
+ * When decompressing fails, *bufp is set to nullptr and *sizep to 0. The
  * compressed buffer passed in is still freed in this case.
  */
 static void Gunzip(byte **bufp, size_t *sizep)
 {
 	static const int BLOCKSIZE  = 8192;
-	byte             *buf       = NULL;
+	byte             *buf       = nullptr;
 	size_t           alloc_size = 0;
 	z_stream         z;
 	int              res;
@@ -250,7 +250,7 @@ static void Gunzip(byte **bufp, size_t *
 		*sizep = alloc_size - z.avail_out;
 	} else {
 		/* Something went wrong */
-		*bufp = NULL;
+		*bufp = nullptr;
 		*sizep = 0;
 		free(buf);
 	}
@@ -270,13 +270,13 @@ static void Gunzip(byte **bufp, size_t *
  *              After the call, it contains the size of the uncompressed
  *              data.
  *
- * When decompressing fails, *bufp is set to NULL and *sizep to 0. The
+ * When decompressing fails, *bufp is set to nullptr and *sizep to 0. The
  * compressed buffer passed in is still freed in this case.
  */
 static void Xunzip(byte **bufp, size_t *sizep)
 {
 	static const int BLOCKSIZE  = 8192;
-	byte             *buf       = NULL;
+	byte             *buf       = nullptr;
 	size_t           alloc_size = 0;
 	lzma_stream      z = LZMA_STREAM_INIT;
 	int              res;
@@ -304,7 +304,7 @@ static void Xunzip(byte **bufp, size_t *
 		*sizep = alloc_size - z.avail_out;
 	} else {
 		/* Something went wrong */
-		*bufp = NULL;
+		*bufp = nullptr;
 		*sizep = 0;
 		free(buf);
 	}
@@ -317,14 +317,14 @@ static void Xunzip(byte **bufp, size_t *
  */
 /* virtual */ void TextfileWindow::LoadTextfile(const char *textfile, Subdirectory dir)
 {
-	if (textfile == NULL) return;
+	if (textfile == nullptr) return;
 
 	this->lines.clear();
 
 	/* Get text from file */
 	size_t filesize;
 	FILE *handle = FioFOpenFile(textfile, "rb", dir, &filesize);
-	if (handle == NULL) return;
+	if (handle == nullptr) return;
 
 	this->text = ReallocT(this->text, filesize);
 	size_t read = fread(this->text, 1, filesize, handle);
@@ -334,7 +334,7 @@ static void Xunzip(byte **bufp, size_t *
 
 #if defined(WITH_ZLIB) || defined(WITH_LIBLZMA)
 	const char *suffix = strrchr(textfile, '.');
-	if (suffix == NULL) return;
+	if (suffix == nullptr) return;
 #endif
 
 #if defined(WITH_ZLIB)
@@ -381,7 +381,7 @@ static void Xunzip(byte **bufp, size_t *
  * @param type The type of the textfile to search for.
  * @param dir The subdirectory to search in.
  * @param filename The filename of the content to look for.
- * @return The path to the textfile, \c NULL otherwise.
+ * @return The path to the textfile, \c nullptr otherwise.
  */
 const char *GetTextfile(TextfileType type, Subdirectory dir, const char *filename)
 {
@@ -394,13 +394,13 @@ const char *GetTextfile(TextfileType typ
 
 	const char *prefix = prefixes[type];
 
-	if (filename == NULL) return NULL;
+	if (filename == nullptr) return nullptr;
 
 	static char file_path[MAX_PATH];
 	strecpy(file_path, filename, lastof(file_path));
 
 	char *slash = strrchr(file_path, PATHSEPCHAR);
-	if (slash == NULL) return NULL;
+	if (slash == nullptr) return nullptr;
 
 	static const char * const exts[] = {
 		"txt",
@@ -422,5 +422,5 @@ const char *GetTextfile(TextfileType typ
 		seprintf(slash + 1, lastof(file_path), "%s.%s", prefix, exts[i]);
 		if (FioCheckFileExists(file_path, dir)) return file_path;
 	}
-	return NULL;
+	return nullptr;
 }
diff --git a/src/tgp.cpp b/src/tgp.cpp
--- a/src/tgp.cpp
+++ b/src/tgp.cpp
@@ -184,7 +184,7 @@ struct HeightMap
 };
 
 /** Global height map instance */
-static HeightMap _height_map = {NULL, 0, 0, 0, 0};
+static HeightMap _height_map = {nullptr, 0, 0, 0, 0};
 
 /** Conversion: int to height_t */
 #define I2H(i) ((i) << height_decimal_bits)
@@ -325,7 +325,7 @@ static inline bool AllocHeightMap()
 static inline void FreeHeightMap()
 {
 	free(_height_map.h);
-	_height_map.h = NULL;
+	_height_map.h = nullptr;
 }
 
 /**
@@ -349,7 +349,7 @@ static inline height_t RandomHeight(ampl
 static void HeightMapGenerate()
 {
 	/* Trying to apply noise to uninitialized height map */
-	assert(_height_map.h != NULL);
+	assert(_height_map.h != nullptr);
 
 	int start = max(MAX_TGP_FREQUENCIES - (int)min(MapLogX(), MapLogY()), 0);
 	bool first = true;
@@ -423,9 +423,9 @@ static void HeightMapGetMinMaxAvg(height
 	h_avg = (height_t)(h_accu / (_height_map.size_x * _height_map.size_y));
 
 	/* Return required results */
-	if (min_ptr != NULL) *min_ptr = h_min;
-	if (max_ptr != NULL) *max_ptr = h_max;
-	if (avg_ptr != NULL) *avg_ptr = h_avg;
+	if (min_ptr != nullptr) *min_ptr = h_min;
+	if (max_ptr != nullptr) *max_ptr = h_max;
+	if (avg_ptr != nullptr) *avg_ptr = h_avg;
 }
 
 /** Dill histogram and return pointer to its base point - to the count of zero heights */
@@ -1011,5 +1011,5 @@ void GenerateTerrainPerlin()
 	IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
 
 	FreeHeightMap();
-	GenerateWorldSetAbortCallback(NULL);
+	GenerateWorldSetAbortCallback(nullptr);
 }
diff --git a/src/thread.h b/src/thread.h
--- a/src/thread.h
+++ b/src/thread.h
@@ -40,7 +40,7 @@ void SetCurrentThreadName(const char *na
  * Start a new thread.
  * @tparam TFn Type of the function to call on the thread.
  * @tparam TArgs Type of the parameters of the thread function.
- * @param thr Pointer to a thread object; may be \c NULL if a detached thread is wanted.
+ * @param thr Pointer to a thread object; may be \c nullptr if a detached thread is wanted.
  * @param name Name of the thread.
  * @param _Fx Function to call on the thread.
  * @param _Ax Arguments for the thread function.
@@ -62,7 +62,7 @@ inline bool StartNewThread(std::thread *
 				}
 			}, name, std::forward<TFn>(_Fx), std::forward<TArgs>(_Ax)...);
 
-		if (thr != NULL) {
+		if (thr != nullptr) {
 			*thr = std::move(t);
 		} else {
 			t.detach();
diff --git a/src/tile_cmd.h b/src/tile_cmd.h
--- a/src/tile_cmd.h
+++ b/src/tile_cmd.h
@@ -168,29 +168,29 @@ void GetTileDesc(TileIndex tile, TileDes
 static inline void AddAcceptedCargo(TileIndex tile, CargoArray &acceptance, CargoTypes *always_accepted)
 {
 	AddAcceptedCargoProc *proc = _tile_type_procs[GetTileType(tile)]->add_accepted_cargo_proc;
-	if (proc == NULL) return;
-	CargoTypes dummy = 0; // use dummy bitmask so there don't need to be several 'always_accepted != NULL' checks
-	proc(tile, acceptance, always_accepted == NULL ? &dummy : always_accepted);
+	if (proc == nullptr) return;
+	CargoTypes dummy = 0; // use dummy bitmask so there don't need to be several 'always_accepted != nullptr' checks
+	proc(tile, acceptance, always_accepted == nullptr ? &dummy : always_accepted);
 }
 
 static inline void AddProducedCargo(TileIndex tile, CargoArray &produced)
 {
 	AddProducedCargoProc *proc = _tile_type_procs[GetTileType(tile)]->add_produced_cargo_proc;
-	if (proc == NULL) return;
+	if (proc == nullptr) return;
 	proc(tile, produced);
 }
 
 static inline void AnimateTile(TileIndex tile)
 {
 	AnimateTileProc *proc = _tile_type_procs[GetTileType(tile)]->animate_tile_proc;
-	assert(proc != NULL);
+	assert(proc != nullptr);
 	proc(tile);
 }
 
 static inline bool ClickTile(TileIndex tile)
 {
 	ClickTileProc *proc = _tile_type_procs[GetTileType(tile)]->click_tile_proc;
-	if (proc == NULL) return false;
+	if (proc == nullptr) return false;
 	return proc(tile);
 }
 
diff --git a/src/tile_map.cpp b/src/tile_map.cpp
--- a/src/tile_map.cpp
+++ b/src/tile_map.cpp
@@ -34,7 +34,7 @@ static Slope GetTileSlopeGivenHeight(int
 	int hmines = min(heast, hsouth);
 	int hmin = min(hminnw, hmines);
 
-	if (h != NULL) *h = hmin;
+	if (h != nullptr) *h = hmin;
 
 	int hmaxnw = max(hnorth, hwest);
 	int hmaxes = max(heast, hsouth);
@@ -55,7 +55,7 @@ static Slope GetTileSlopeGivenHeight(int
 /**
  * Return the slope of a given tile inside the map.
  * @param tile Tile to compute slope of
- * @param h    If not \c NULL, pointer to storage of z height
+ * @param h    If not \c nullptr, pointer to storage of z height
  * @return Slope of the tile, except for the HALFTILE part
  */
 Slope GetTileSlope(TileIndex tile, int *h)
@@ -78,7 +78,7 @@ Slope GetTileSlope(TileIndex tile, int *
  *
  * @param x X coordinate of the tile to compute slope of, may be ouside the map.
  * @param y Y coordinate of the tile to compute slope of, may be ouside the map.
- * @param h If not \c NULL, pointer to storage of z height.
+ * @param h If not \c nullptr, pointer to storage of z height.
  * @return Slope of the tile, except for the HALFTILE part.
  */
 Slope GetTilePixelSlopeOutsideMap(int x, int y, int *h)
@@ -89,14 +89,14 @@ Slope GetTilePixelSlopeOutsideMap(int x,
 	int hsouth = TileHeightOutsideMap(x + 1, y + 1); // S corner.
 
 	Slope s = GetTileSlopeGivenHeight(hnorth, hwest, heast, hsouth, h);
-	if (h != NULL) *h *= TILE_HEIGHT;
+	if (h != nullptr) *h *= TILE_HEIGHT;
 	return s;
 }
 
 /**
  * Check if a given tile is flat
  * @param tile Tile to check
- * @param h If not \c NULL, pointer to storage of z height (only if tile is flat)
+ * @param h If not \c nullptr, pointer to storage of z height (only if tile is flat)
  * @return Whether the tile is flat
  */
 bool IsTileFlat(TileIndex tile, int *h)
@@ -111,7 +111,7 @@ bool IsTileFlat(TileIndex tile, int *h)
 	if (TileHeight(TileXY(x1, y2)) != z) return false;
 	if (TileHeight(TileXY(x2, y2)) != z) return false;
 
-	if (h != NULL) *h = z;
+	if (h != nullptr) *h = z;
 	return true;
 }
 
diff --git a/src/tile_map.h b/src/tile_map.h
--- a/src/tile_map.h
+++ b/src/tile_map.h
@@ -267,22 +267,22 @@ static inline void SetAnimationFrame(Til
 	_me[t].m7 = frame;
 }
 
-Slope GetTileSlope(TileIndex tile, int *h = NULL);
+Slope GetTileSlope(TileIndex tile, int *h = nullptr);
 int GetTileZ(TileIndex tile);
 int GetTileMaxZ(TileIndex tile);
 
-bool IsTileFlat(TileIndex tile, int *h = NULL);
+bool IsTileFlat(TileIndex tile, int *h = nullptr);
 
 /**
  * Return the slope of a given tile
  * @param tile Tile to compute slope of
- * @param h    If not \c NULL, pointer to storage of z height
+ * @param h    If not \c nullptr, pointer to storage of z height
  * @return Slope of the tile, except for the HALFTILE part
  */
 static inline Slope GetTilePixelSlope(TileIndex tile, int *h)
 {
 	Slope s = GetTileSlope(tile, h);
-	if (h != NULL) *h *= TILE_HEIGHT;
+	if (h != nullptr) *h *= TILE_HEIGHT;
 	return s;
 }
 
diff --git a/src/tilematrix_type.hpp b/src/tilematrix_type.hpp
--- a/src/tilematrix_type.hpp
+++ b/src/tilematrix_type.hpp
@@ -69,7 +69,7 @@ public:
 
 	T *data; ///< Pointer to data array.
 
-	TileMatrix() : area(INVALID_TILE, 0, 0), data(NULL) {}
+	TileMatrix() : area(INVALID_TILE, 0, 0), data(nullptr) {}
 
 	~TileMatrix()
 	{
diff --git a/src/timetable_cmd.cpp b/src/timetable_cmd.cpp
--- a/src/timetable_cmd.cpp
+++ b/src/timetable_cmd.cpp
@@ -61,7 +61,7 @@ static void ChangeTimetable(Vehicle *v, 
 	v->orders.list->UpdateTotalDuration(total_delta);
 	v->orders.list->UpdateTimetableDuration(timetable_delta);
 
-	for (v = v->FirstShared(); v != NULL; v = v->NextShared()) {
+	for (v = v->FirstShared(); v != nullptr; v = v->NextShared()) {
 		if (v->cur_real_order_index == order_number && v->current_order.Equals(*order)) {
 			switch (mtf) {
 				case MTF_WAIT_TIME:
@@ -105,14 +105,14 @@ CommandCost CmdChangeTimetable(TileIndex
 	VehicleID veh = GB(p1, 0, 20);
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle()) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
 
 	VehicleOrderID order_number = GB(p1, 20, 8);
 	Order *order = v->GetOrder(order_number);
-	if (order == NULL || order->IsType(OT_IMPLICIT)) return CMD_ERROR;
+	if (order == nullptr || order->IsType(OT_IMPLICIT)) return CMD_ERROR;
 
 	ModifyTimetableFlags mtf = Extract<ModifyTimetableFlags, 28, 2>(p1);
 	if (mtf >= MTF_END) return CMD_ERROR;
@@ -199,7 +199,7 @@ CommandCost CmdSetVehicleOnTime(TileInde
 	VehicleID veh = GB(p1, 0, 20);
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !v->IsPrimaryVehicle() || v->orders.list == NULL) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle() || v->orders.list == nullptr) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -268,7 +268,7 @@ CommandCost CmdSetTimetableStart(TileInd
 {
 	bool timetable_all = HasBit(p1, 20);
 	Vehicle *v = Vehicle::GetIfValid(GB(p1, 0, 20));
-	if (v == NULL || !v->IsPrimaryVehicle() || v->orders.list == NULL) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle() || v->orders.list == nullptr) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -284,7 +284,7 @@ CommandCost CmdSetTimetableStart(TileInd
 		std::vector<Vehicle *> vehs;
 
 		if (timetable_all) {
-			for (Vehicle *w = v->orders.list->GetFirstSharedVehicle(); w != NULL; w = w->NextShared()) {
+			for (Vehicle *w = v->orders.list->GetFirstSharedVehicle(); w != nullptr; w = w->NextShared()) {
 				vehs.push_back(w);
 			}
 		} else {
@@ -334,7 +334,7 @@ CommandCost CmdAutofillTimetable(TileInd
 	VehicleID veh = GB(p1, 0, 20);
 
 	Vehicle *v = Vehicle::GetIfValid(veh);
-	if (v == NULL || !v->IsPrimaryVehicle() || v->orders.list == NULL) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle() || v->orders.list == nullptr) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -357,7 +357,7 @@ CommandCost CmdAutofillTimetable(TileInd
 			ClrBit(v->vehicle_flags, VF_AUTOFILL_PRES_WAIT_TIME);
 		}
 
-		for (Vehicle *v2 = v->FirstShared(); v2 != NULL; v2 = v2->NextShared()) {
+		for (Vehicle *v2 = v->FirstShared(); v2 != nullptr; v2 = v2->NextShared()) {
 			if (v2 != v) {
 				/* Stop autofilling; only one vehicle at a time can perform autofill */
 				ClrBit(v2->vehicle_flags, VF_AUTOFILL_TIMETABLE);
@@ -387,7 +387,7 @@ void UpdateVehicleTimetable(Vehicle *v, 
 	Order *real_current_order = v->GetOrder(v->cur_real_order_index);
 
 	VehicleOrderID first_manual_order = 0;
-	for (Order *o = v->GetFirstOrder(); o != NULL && o->IsType(OT_IMPLICIT); o = o->next) {
+	for (Order *o = v->GetFirstOrder(); o != nullptr && o->IsType(OT_IMPLICIT); o = o->next) {
 		++first_manual_order;
 	}
 
@@ -477,7 +477,7 @@ void UpdateVehicleTimetable(Vehicle *v, 
 		}
 	}
 
-	for (v = v->FirstShared(); v != NULL; v = v->NextShared()) {
+	for (v = v->FirstShared(); v != nullptr; v = v->NextShared()) {
 		SetWindowDirty(WC_VEHICLE_TIMETABLE, v->index);
 	}
 }
diff --git a/src/timetable_gui.cpp b/src/timetable_gui.cpp
--- a/src/timetable_gui.cpp
+++ b/src/timetable_gui.cpp
@@ -87,7 +87,7 @@ static bool CanDetermineTimeTaken(const 
  */
 static void FillTimetableArrivalDepartureTable(const Vehicle *v, VehicleOrderID start, bool travelling, TimetableArrivalDeparture *table, Ticks offset)
 {
-	assert(table != NULL);
+	assert(table != nullptr);
 	assert(v->GetNumOrders() >= 2);
 	assert(start < v->GetNumOrders());
 
@@ -122,7 +122,7 @@ static void FillTimetableArrivalDepartur
 		order = order->next;
 		if (i >= v->GetNumOrders()) {
 			i = 0;
-			assert(order == NULL);
+			assert(order == nullptr);
 			order = v->orders.list->GetFirstOrder();
 		}
 	} while (i != start);
@@ -309,9 +309,9 @@ struct TimetableWindow : Window {
 			if (selected != -1) {
 				const Order *order = v->GetOrder(((selected + 1) / 2) % v->GetNumOrders());
 				if (selected % 2 == 1) {
-					disable = order != NULL && (order->IsType(OT_CONDITIONAL) || order->IsType(OT_IMPLICIT));
+					disable = order != nullptr && (order->IsType(OT_CONDITIONAL) || order->IsType(OT_IMPLICIT));
 				} else {
-					disable = order == NULL || ((!order->IsType(OT_GOTO_STATION) || (order->GetNonStopType() & ONSF_NO_STOP_AT_DESTINATION_STATION)) && !order->IsType(OT_CONDITIONAL));
+					disable = order == nullptr || ((!order->IsType(OT_GOTO_STATION) || (order->GetNonStopType() & ONSF_NO_STOP_AT_DESTINATION_STATION)) && !order->IsType(OT_CONDITIONAL));
 				}
 			}
 			bool disable_speed = disable || selected % 2 != 1 || v->type == VEH_AIRCRAFT;
@@ -322,9 +322,9 @@ struct TimetableWindow : Window {
 			this->SetWidgetDisabledState(WID_VT_CLEAR_SPEED, disable_speed);
 			this->SetWidgetDisabledState(WID_VT_SHARED_ORDER_LIST, !v->IsOrderListShared());
 
-			this->SetWidgetDisabledState(WID_VT_START_DATE, v->orders.list == NULL);
-			this->SetWidgetDisabledState(WID_VT_RESET_LATENESS, v->orders.list == NULL);
-			this->SetWidgetDisabledState(WID_VT_AUTOFILL, v->orders.list == NULL);
+			this->SetWidgetDisabledState(WID_VT_START_DATE, v->orders.list == nullptr);
+			this->SetWidgetDisabledState(WID_VT_RESET_LATENESS, v->orders.list == nullptr);
+			this->SetWidgetDisabledState(WID_VT_AUTOFILL, v->orders.list == nullptr);
 		} else {
 			this->DisableWidget(WID_VT_START_DATE);
 			this->DisableWidget(WID_VT_CHANGE_TIME);
@@ -367,7 +367,7 @@ struct TimetableWindow : Window {
 				int middle = rtl ? r.right - WD_FRAMERECT_RIGHT - index_column_width : r.left + WD_FRAMERECT_LEFT + index_column_width;
 
 				const Order *order = v->GetOrder(order_id);
-				while (order != NULL) {
+				while (order != nullptr) {
 					/* Don't draw anything if it extends past the end of the window. */
 					if (!this->vscroll->IsVisible(i)) break;
 
@@ -424,7 +424,7 @@ struct TimetableWindow : Window {
 				 * i.e. are only shown if we can calculate all times.
 				 * Excluding order lists with only one order makes some things easier.
 				 */
-				Ticks total_time = v->orders.list != NULL ? v->orders.list->GetTimetableDurationIncomplete() : 0;
+				Ticks total_time = v->orders.list != nullptr ? v->orders.list->GetTimetableDurationIncomplete() : 0;
 				if (total_time <= 0 || v->GetNumOrders() <= 1 || !HasBit(v->vehicle_flags, VF_TIMETABLE_STARTED)) break;
 
 				TimetableArrivalDeparture *arr_dep = AllocaM(TimetableArrivalDeparture, v->GetNumOrders());
@@ -475,7 +475,7 @@ struct TimetableWindow : Window {
 			case WID_VT_SUMMARY_PANEL: {
 				int y = r.top + WD_FRAMERECT_TOP;
 
-				Ticks total_time = v->orders.list != NULL ? v->orders.list->GetTimetableDurationIncomplete() : 0;
+				Ticks total_time = v->orders.list != nullptr ? v->orders.list->GetTimetableDurationIncomplete() : 0;
 				if (total_time != 0) {
 					SetTimetableParams(0, 1, total_time);
 					DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, y, v->orders.list->IsCompleteTimetable() ? STR_TIMETABLE_TOTAL_TIME : STR_TIMETABLE_TOTAL_TIME_INCOMPLETE);
@@ -543,7 +543,7 @@ struct TimetableWindow : Window {
 				const Order *order = v->GetOrder(real);
 				StringID current = STR_EMPTY;
 
-				if (order != NULL) {
+				if (order != nullptr) {
 					uint time = (selected % 2 == 1) ? order->GetTravelTime() : order->GetWaitTime();
 					if (!_settings_client.gui.timetable_in_ticks) time /= DAY_TICKS;
 
@@ -566,7 +566,7 @@ struct TimetableWindow : Window {
 
 				StringID current = STR_EMPTY;
 				const Order *order = v->GetOrder(real);
-				if (order != NULL) {
+				if (order != nullptr) {
 					if (order->GetMaxSpeed() != UINT16_MAX) {
 						SetDParam(0, ConvertKmhishSpeedToDisplaySpeed(order->GetMaxSpeed()));
 						current = STR_JUST_INT;
@@ -616,13 +616,13 @@ struct TimetableWindow : Window {
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
 		const Vehicle *v = this->vehicle;
 
 		uint32 p1 = PackTimetableArgs(v, this->sel_index, this->query_is_speed_query);
 
-		uint64 val = StrEmpty(str) ? 0 : strtoul(str, NULL, 10);
+		uint64 val = StrEmpty(str) ? 0 : strtoul(str, nullptr, 10);
 		if (this->query_is_speed_query) {
 			val = ConvertDisplaySpeedToKmhishSpeed(val);
 		} else {
diff --git a/src/toolbar_gui.cpp b/src/toolbar_gui.cpp
--- a/src/toolbar_gui.cpp
+++ b/src/toolbar_gui.cpp
@@ -616,7 +616,7 @@ static CallBackFunction MenuClickCompany
 				if (_network_server) {
 					DoCommandP(0, CCA_NEW, _network_own_client_id, CMD_COMPANY_CTRL);
 				} else {
-					NetworkSendCommand(0, CCA_NEW, 0, CMD_COMPANY_CTRL, NULL, NULL, _local_company);
+					NetworkSendCommand(0, CCA_NEW, 0, CMD_COMPANY_CTRL, nullptr, nullptr, _local_company);
 				}
 				return CBF_NONE;
 
@@ -1055,7 +1055,7 @@ static CallBackFunction ToolbarHelpClick
 
 static void MenuClickSmallScreenshot()
 {
-	MakeScreenshot(SC_VIEWPORT, NULL);
+	MakeScreenshot(SC_VIEWPORT, nullptr);
 }
 
 /**
@@ -1065,7 +1065,7 @@ static void MenuClickSmallScreenshot()
  */
 static void ScreenshotConfirmCallback(Window *w, bool confirmed)
 {
-	if (confirmed) MakeScreenshot(_confirmed_screenshot_type, NULL);
+	if (confirmed) MakeScreenshot(_confirmed_screenshot_type, nullptr);
 }
 
 /**
@@ -1082,10 +1082,10 @@ static void MenuClickLargeWorldScreensho
 		SetDParam(0, vp.width);
 		SetDParam(1, vp.height);
 		_confirmed_screenshot_type = t;
-		ShowQuery(STR_WARNING_SCREENSHOT_SIZE_CAPTION, STR_WARNING_SCREENSHOT_SIZE_MESSAGE, NULL, ScreenshotConfirmCallback);
+		ShowQuery(STR_WARNING_SCREENSHOT_SIZE_CAPTION, STR_WARNING_SCREENSHOT_SIZE_MESSAGE, nullptr, ScreenshotConfirmCallback);
 	} else {
 		/* Less than 64M pixels, just do it */
-		MakeScreenshot(t, NULL);
+		MakeScreenshot(t, nullptr);
 	}
 }
 
@@ -1280,8 +1280,8 @@ static CallBackFunction ToolbarBtn_NULL(
 typedef CallBackFunction MenuClickedProc(int index);
 
 static MenuClickedProc * const _menu_clicked_procs[] = {
-	NULL,                 // 0
-	NULL,                 // 1
+	nullptr,                 // 0
+	nullptr,                 // 1
 	MenuClickSettings,    // 2
 	MenuClickSaveLoad,    // 3
 	MenuClickMap,         // 4
@@ -1300,7 +1300,7 @@ static MenuClickedProc * const _menu_cli
 	MenuClickShowShips,   // 17
 	MenuClickShowAir,     // 18
 	MenuClickMap,         // 19
-	NULL,                 // 20
+	nullptr,                 // 20
 	MenuClickBuildRail,   // 21
 	MenuClickBuildRoad,   // 22
 	MenuClickBuildWater,  // 23
@@ -1344,7 +1344,7 @@ public:
 
 		uint nbuttons = 0;
 		/* First initialise some variables... */
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			child_wid->SetupSmallestSize(w, init_array);
 			this->smallest_y = max(this->smallest_y, child_wid->smallest_y + child_wid->padding_top + child_wid->padding_bottom);
 			if (this->IsButton(child_wid->type)) {
@@ -1356,7 +1356,7 @@ public:
 		}
 
 		/* ... then in a second pass make sure the 'current' heights are set. Won't change ever. */
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			child_wid->current_y = this->smallest_y;
 			if (!this->IsButton(child_wid->type)) {
 				child_wid->current_x = child_wid->smallest_x;
@@ -1384,7 +1384,7 @@ public:
 
 		/* Create us ourselves a quick lookup table */
 		NWidgetBase *widgets[WID_TN_END];
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			if (child_wid->type == NWID_SPACER) continue;
 			widgets[((NWidgetCore*)child_wid)->index] = child_wid;
 		}
@@ -1403,7 +1403,7 @@ public:
 			/* If we have to give space to the spacers, do that */
 			if (spacer_space != 0) {
 				NWidgetBase *possible_spacer = rtl ? child_wid->next : child_wid->prev;
-				if (possible_spacer != NULL && possible_spacer->type == NWID_SPACER) {
+				if (possible_spacer != nullptr && possible_spacer->type == NWID_SPACER) {
 					uint add = spacer_space / (spacer_count - spacer_i);
 					position += add;
 					spacer_space -= add;
@@ -1435,7 +1435,7 @@ public:
 		GfxFillRect(this->pos_x, this->pos_y, this->pos_x + this->current_x - 1, this->pos_y + this->current_y - 1, PC_DARK_RED, FILLRECT_CHECKER);
 
 		bool rtl = _current_text_dir == TD_RTL;
-		for (NWidgetBase *child_wid = rtl ? this->tail : this->head; child_wid != NULL; child_wid = rtl ? child_wid->prev : child_wid->next) {
+		for (NWidgetBase *child_wid = rtl ? this->tail : this->head; child_wid != nullptr; child_wid = rtl ? child_wid->prev : child_wid->next) {
 			if (child_wid->type == NWID_SPACER) continue;
 			if (!this->visible[((NWidgetCore*)child_wid)->index]) continue;
 
@@ -1445,16 +1445,16 @@ public:
 
 	NWidgetCore *GetWidgetFromPos(int x, int y) override
 	{
-		if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return NULL;
+		if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return nullptr;
 
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			if (child_wid->type == NWID_SPACER) continue;
 			if (!this->visible[((NWidgetCore*)child_wid)->index]) continue;
 
 			NWidgetCore *nwid = child_wid->GetWidgetFromPos(x, y);
-			if (nwid != NULL) return nwid;
+			if (nwid != nullptr) return nwid;
 		}
-		return NULL;
+		return nullptr;
 	}
 
 	/**
@@ -1799,7 +1799,7 @@ class NWidgetScenarioToolbarContainer : 
 
 		/* Find the size of panel_widths */
 		uint i = 0;
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			if (child_wid->type == NWID_SPACER || this->IsButton(child_wid->type)) continue;
 
 			assert(i < lengthof(this->panel_widths));
@@ -2133,7 +2133,7 @@ struct MainToolbarWindow : Window {
 	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
-		if (FindWindowById(WC_MAIN_WINDOW, 0) != NULL) HandleZoomMessage(this, FindWindowById(WC_MAIN_WINDOW, 0)->viewport, WID_TN_ZOOM_IN, WID_TN_ZOOM_OUT);
+		if (FindWindowById(WC_MAIN_WINDOW, 0) != nullptr) HandleZoomMessage(this, FindWindowById(WC_MAIN_WINDOW, 0)->viewport, WID_TN_ZOOM_IN, WID_TN_ZOOM_OUT);
 	}
 
 	static HotkeyList hotkeys;
@@ -2247,7 +2247,7 @@ static const NWidgetPart _nested_toolbar
 };
 
 static WindowDesc _toolb_normal_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_MAIN_TOOLBAR, WC_NONE,
 	WDF_NO_FOCUS,
 	_nested_toolbar_normal_widgets, lengthof(_nested_toolbar_normal_widgets),
@@ -2277,15 +2277,15 @@ static ToolbarButtonProc * const _scen_t
 	ToolbarScenPlantTrees,
 	ToolbarScenPlaceSign,
 	ToolbarBtn_NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
+	nullptr,
 	ToolbarMusicClick,
-	NULL,
+	nullptr,
 	ToolbarHelpClick,
 	ToolbarSwitchClick,
 };
@@ -2479,13 +2479,13 @@ struct ScenarioEditorToolbarWindow : Win
 	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
-		if (FindWindowById(WC_MAIN_WINDOW, 0) != NULL) HandleZoomMessage(this, FindWindowById(WC_MAIN_WINDOW, 0)->viewport, WID_TE_ZOOM_IN, WID_TE_ZOOM_OUT);
+		if (FindWindowById(WC_MAIN_WINDOW, 0) != nullptr) HandleZoomMessage(this, FindWindowById(WC_MAIN_WINDOW, 0)->viewport, WID_TE_ZOOM_IN, WID_TE_ZOOM_OUT);
 	}
 
 	void OnQueryTextFinished(char *str) override
 	{
 		/* Was 'cancel' pressed? */
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
 		int32 value;
 		if (!StrEmpty(str)) {
@@ -2573,7 +2573,7 @@ static const NWidgetPart _nested_toolb_s
 };
 
 static WindowDesc _toolb_scen_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_MAIN_TOOLBAR, WC_NONE,
 	WDF_NO_FOCUS,
 	_nested_toolb_scen_widgets, lengthof(_nested_toolb_scen_widgets),
diff --git a/src/town.h b/src/town.h
--- a/src/town.h
+++ b/src/town.h
@@ -61,7 +61,7 @@ struct Town : TownPool::PoolItem<&_town_
 	uint32 townnamegrfid;
 	uint16 townnametype;
 	uint32 townnameparts;
-	char *name;                    ///< Custom town name. If NULL, the town was not renamed and uses the generated name.
+	char *name;                    ///< Custom town name. If nullptr, the town was not renamed and uses the generated name.
 
 	byte flags;                    ///< See #TownFlags.
 
@@ -233,7 +233,7 @@ template <class T>
 void MakeDefaultName(T *obj)
 {
 	/* We only want to set names if it hasn't been set before, or when we're calling from afterload. */
-	assert(obj->name == NULL || obj->town_cn == UINT16_MAX);
+	assert(obj->name == nullptr || obj->town_cn == UINT16_MAX);
 
 	obj->town = ClosestTownFromTile(obj->xy, UINT_MAX);
 
@@ -257,7 +257,7 @@ void MakeDefaultName(T *obj)
 		T *lobj = T::GetIfValid(cid);
 
 		/* check only valid waypoints... */
-		if (lobj != NULL && obj != lobj) {
+		if (lobj != nullptr && obj != lobj) {
 			/* only objects within the same city and with the same type */
 			if (lobj->town == obj->town && lobj->IsOfType(obj)) {
 				/* if lobj->town_cn < next, uint will overflow to '+inf' */
diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -163,7 +163,7 @@ void Town::PostDestructor(size_t index)
 	/* Give objects a new home! */
 	Object *o;
 	FOR_ALL_OBJECTS(o) {
-		if (o->town == NULL) o->town = CalcClosestTownFromTile(o->location.tile, UINT_MAX);
+		if (o->town == nullptr) o->town = CalcClosestTownFromTile(o->location.tile, UINT_MAX);
 	}
 }
 
@@ -182,11 +182,11 @@ void Town::InitializeLayout(TownLayout l
 
 /**
  * Return a random valid town.
- * @return random town, NULL if there are no towns
+ * @return random town, nullptr if there are no towns
  */
 /* static */ Town *Town::GetRandom()
 {
-	if (Town::GetNumItems() == 0) return NULL;
+	if (Town::GetNumItems() == 0) return nullptr;
 	int num = RandomRange((uint16)Town::GetNumItems());
 	size_t index = MAX_UVALUE(size_t);
 
@@ -259,7 +259,7 @@ static void DrawTile_Town(TileInfo *ti)
 		/* Houses don't necessarily need new graphics. If they don't have a
 		 * spritegroup associated with them, then the sprite for the substitute
 		 * house id is drawn instead. */
-		if (HouseSpec::Get(house_id)->grf_prop.spritegroup[0] != NULL) {
+		if (HouseSpec::Get(house_id)->grf_prop.spritegroup[0] != nullptr) {
 			DrawNewHouseTile(ti, house_id);
 			return;
 		} else {
@@ -316,7 +316,7 @@ static Foundation GetFoundation_Town(Til
 	 */
 	if (hid >= NEW_HOUSE_OFFSET) {
 		const HouseSpec *hs = HouseSpec::Get(hid);
-		if (hs->grf_prop.spritegroup[0] != NULL && HasBit(hs->callback_mask, CBM_HOUSE_DRAW_FOUNDATIONS)) {
+		if (hs->grf_prop.spritegroup[0] != nullptr && HasBit(hs->callback_mask, CBM_HOUSE_DRAW_FOUNDATIONS)) {
 			uint32 callback_res = GetHouseCallback(CBID_HOUSE_DRAW_FOUNDATIONS, 0, 0, hid, Town::GetByTile(tile), tile);
 			if (callback_res != CALLBACK_FAILED && !ConvertBooleanCallback(hs->grf_prop.grffile, CBID_HOUSE_DRAW_FOUNDATIONS, callback_res)) return FOUNDATION_NONE;
 		}
@@ -752,7 +752,7 @@ static void GetTileDesc_Town(TileIndex t
 		td->str = STR_LAI_TOWN_INDUSTRY_DESCRIPTION_UNDER_CONSTRUCTION;
 	}
 
-	if (hs->grf_prop.grffile != NULL) {
+	if (hs->grf_prop.grffile != nullptr) {
 		const GRFConfig *gc = GetGRFConfig(hs->grf_prop.grffile->grfid);
 		td->grf = gc->GetName();
 	}
@@ -1683,12 +1683,12 @@ static void DoCreateTown(Town *t, TileIn
 	/* Set the default cargo requirement for town growth */
 	switch (_settings_game.game_creation.landscape) {
 		case LT_ARCTIC:
-			if (FindFirstCargoWithTownEffect(TE_FOOD) != NULL) t->goal[TE_FOOD] = TOWN_GROWTH_WINTER;
+			if (FindFirstCargoWithTownEffect(TE_FOOD) != nullptr) t->goal[TE_FOOD] = TOWN_GROWTH_WINTER;
 			break;
 
 		case LT_TROPIC:
-			if (FindFirstCargoWithTownEffect(TE_FOOD) != NULL) t->goal[TE_FOOD] = TOWN_GROWTH_DESERT;
-			if (FindFirstCargoWithTownEffect(TE_WATER) != NULL) t->goal[TE_WATER] = TOWN_GROWTH_DESERT;
+			if (FindFirstCargoWithTownEffect(TE_FOOD) != nullptr) t->goal[TE_FOOD] = TOWN_GROWTH_DESERT;
+			if (FindFirstCargoWithTownEffect(TE_WATER) != nullptr) t->goal[TE_WATER] = TOWN_GROWTH_DESERT;
 			break;
 	}
 
@@ -1776,7 +1776,7 @@ static bool IsUniqueTownName(const char 
 	const Town *t;
 
 	FOR_ALL_TOWNS(t) {
-		if (t->name != NULL && strcmp(t->name, name) == 0) return false;
+		if (t->name != nullptr && strcmp(t->name, name) == 0) return false;
 	}
 
 	return true;
@@ -1857,7 +1857,7 @@ CommandCost CmdFoundTown(TileIndex tile,
 		Town *t;
 		if (random) {
 			t = CreateRandomTown(20, townnameparts, size, city, layout);
-			if (t == NULL) {
+			if (t == nullptr) {
 				cost = CommandCost(STR_ERROR_NO_SPACE_FOR_TOWN);
 			} else {
 				_new_town_id = t->index;
@@ -1869,13 +1869,13 @@ CommandCost CmdFoundTown(TileIndex tile,
 		UpdateNearestTownForRoadTiles(false);
 		old_generating_world.Restore();
 
-		if (t != NULL && !StrEmpty(text)) {
+		if (t != nullptr && !StrEmpty(text)) {
 			t->name = stredup(text);
 			t->UpdateVirtCoord();
 		}
 
 		if (_game_mode != GM_EDITOR) {
-			/* 't' can't be NULL since 'random' is false outside scenedit */
+			/* 't' can't be nullptr since 'random' is false outside scenedit */
 			assert(!random);
 
 			if (_current_company == OWNER_DEITY) {
@@ -2004,7 +2004,7 @@ static TileIndex FindNearestGoodCoastalT
 	SpotData sp = { INVALID_TILE, 0, layout };
 
 	TileIndex coast = tile;
-	if (CircularTileSearch(&coast, 40, FindNearestEmptyLand, NULL)) {
+	if (CircularTileSearch(&coast, 40, FindNearestEmptyLand, nullptr)) {
 		CircularTileSearch(&coast, 10, FindFurthestFromWater, &sp);
 		return sp.tile;
 	}
@@ -2017,7 +2017,7 @@ static Town *CreateRandomTown(uint attem
 {
 	assert(_game_mode == GM_EDITOR || _generating_world); // These are the preconditions for CMD_DELETE_TOWN
 
-	if (!Town::CanAllocateItem()) return NULL;
+	if (!Town::CanAllocateItem()) return nullptr;
 
 	do {
 		/* Generate a tile index not too close from the edge */
@@ -2054,7 +2054,7 @@ static Town *CreateRandomTown(uint attem
 		assert(Town::CanAllocateItem());
 	} while (--attempts != 0);
 
-	return NULL;
+	return nullptr;
 }
 
 static const byte _num_initial_towns[4] = {5, 11, 23, 46};  // very low, low, normal, high
@@ -2086,7 +2086,7 @@ bool GenerateTowns(TownLayout layout)
 		/* Get a unique name for the town. */
 		if (!GenerateTownName(&townnameparts, &town_names)) continue;
 		/* try 20 times to create a random-sized town for the first loop. */
-		if (CreateRandomTown(20, townnameparts, TSZ_RANDOM, city, layout) != NULL) current_number++; // If creation was successful, raise a flag.
+		if (CreateRandomTown(20, townnameparts, TSZ_RANDOM, city, layout) != nullptr) current_number++; // If creation was successful, raise a flag.
 	} while (--total);
 
 	town_names.clear();
@@ -2099,7 +2099,7 @@ bool GenerateTowns(TownLayout layout)
 	/* If current_number is still zero at this point, it means that not a single town has been created.
 	 * So give it a last try, but now more aggressive */
 	if (GenerateTownName(&townnameparts) &&
-			CreateRandomTown(10000, townnameparts, TSZ_RANDOM, _settings_game.economy.larger_towns != 0, layout) != NULL) {
+			CreateRandomTown(10000, townnameparts, TSZ_RANDOM, _settings_game.economy.larger_towns != 0, layout) != nullptr) {
 		return true;
 	}
 
@@ -2608,7 +2608,7 @@ void ClearTownHouse(Town *t, TileIndex t
 CommandCost CmdRenameTown(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Town *t = Town::GetIfValid(p1);
-	if (t == NULL) return CMD_ERROR;
+	if (t == nullptr) return CMD_ERROR;
 
 	bool reset = StrEmpty(text);
 
@@ -2619,7 +2619,7 @@ CommandCost CmdRenameTown(TileIndex tile
 
 	if (flags & DC_EXEC) {
 		free(t->name);
-		t->name = reset ? NULL : stredup(text);
+		t->name = reset ? nullptr : stredup(text);
 
 		t->UpdateVirtCoord();
 		InvalidateWindowData(WC_TOWN_DIRECTORY, 0, 1);
@@ -2639,7 +2639,7 @@ const CargoSpec *FindFirstCargoWithTownE
 	FOR_ALL_CARGOSPECS(cs) {
 		if (cs->town_effect == effect) return cs;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -2662,11 +2662,11 @@ CommandCost CmdTownCargoGoal(TileIndex t
 
 	uint16 index = GB(p1, 0, 16);
 	Town *t = Town::GetIfValid(index);
-	if (t == NULL) return CMD_ERROR;
+	if (t == nullptr) return CMD_ERROR;
 
 	/* Validate if there is a cargo which is the requested TownEffect */
 	const CargoSpec *cargo = FindFirstCargoWithTownEffect(te);
-	if (cargo == NULL) return CMD_ERROR;
+	if (cargo == nullptr) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
 		t->goal[te] = p2;
@@ -2690,11 +2690,11 @@ CommandCost CmdTownSetText(TileIndex til
 {
 	if (_current_company != OWNER_DEITY) return CMD_ERROR;
 	Town *t = Town::GetIfValid(p1);
-	if (t == NULL) return CMD_ERROR;
+	if (t == nullptr) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
 		free(t->text);
-		t->text = StrEmpty(text) ? NULL : stredup(text);
+		t->text = StrEmpty(text) ? nullptr : stredup(text);
 		InvalidateWindowData(WC_TOWN_VIEW, p1);
 	}
 
@@ -2716,7 +2716,7 @@ CommandCost CmdTownGrowthRate(TileIndex 
 	if (GB(p2, 16, 16) != 0) return CMD_ERROR;
 
 	Town *t = Town::GetIfValid(p1);
-	if (t == NULL) return CMD_ERROR;
+	if (t == nullptr) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
 		if (p2 == 0) {
@@ -2754,7 +2754,7 @@ CommandCost CmdExpandTown(TileIndex tile
 {
 	if (_game_mode != GM_EDITOR && _current_company != OWNER_DEITY) return CMD_ERROR;
 	Town *t = Town::GetIfValid(p1);
-	if (t == NULL) return CMD_ERROR;
+	if (t == nullptr) return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
 		/* The more houses, the faster we grow */
@@ -2794,7 +2794,7 @@ CommandCost CmdDeleteTown(TileIndex tile
 {
 	if (_game_mode != GM_EDITOR && !_generating_world) return CMD_ERROR;
 	Town *t = Town::GetIfValid(p1);
-	if (t == NULL) return CMD_ERROR;
+	if (t == nullptr) return CMD_ERROR;
 
 	/* Stations refer to towns. */
 	const Station *st;
@@ -2853,7 +2853,7 @@ CommandCost CmdDeleteTown(TileIndex tile
 							try_clear = true;
 						} else {
 							/* Tell to find a new town. */
-							if (flags & DC_EXEC) o->town = NULL;
+							if (flags & DC_EXEC) o->town = nullptr;
 						}
 					}
 				}
@@ -3124,7 +3124,7 @@ static TownActionProc * const _town_acti
 
 /**
  * Get a list of available actions to do at a town.
- * @param nump if not NULL add put the number of available actions in it
+ * @param nump if not nullptr add put the number of available actions in it
  * @param cid the company that is querying the town
  * @param t the town that is queried
  * @return bitmasked value of enabled actions
@@ -3167,7 +3167,7 @@ uint GetMaskOfTownActions(int *nump, Com
 		}
 	}
 
-	if (nump != NULL) *nump = num;
+	if (nump != nullptr) *nump = num;
 	return buttons;
 }
 
@@ -3185,9 +3185,9 @@ uint GetMaskOfTownActions(int *nump, Com
 CommandCost CmdDoTownAction(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Town *t = Town::GetIfValid(p1);
-	if (t == NULL || p2 >= lengthof(_town_action_proc)) return CMD_ERROR;
-
-	if (!HasBit(GetMaskOfTownActions(NULL, _current_company, t), p2)) return CMD_ERROR;
+	if (t == nullptr || p2 >= lengthof(_town_action_proc)) return CMD_ERROR;
+
+	if (!HasBit(GetMaskOfTownActions(nullptr, _current_company, t), p2)) return CMD_ERROR;
 
 	CommandCost cost(EXPENSES_OTHER, _price[PR_TOWN_ACTION] * _town_action_costs[p2] >> 8);
 
@@ -3389,7 +3389,7 @@ CommandCost CheckIfAuthorityAllowsNewSta
 	if (!Company::IsValidID(_current_company) || (flags & DC_NO_TEST_TOWN_RATING)) return CommandCost();
 
 	Town *t = ClosestTownFromTile(tile, _settings_game.economy.dist_local_authority);
-	if (t == NULL) return CommandCost();
+	if (t == nullptr) return CommandCost();
 
 	if (t->ratings[_current_company] > RATING_VERYPOOR) return CommandCost();
 
@@ -3401,25 +3401,25 @@ CommandCost CheckIfAuthorityAllowsNewSta
  * Return the town closest to the given tile within \a threshold.
  * @param tile      Starting point of the search.
  * @param threshold Biggest allowed distance to the town.
- * @return Closest town to \a tile within \a threshold, or \c NULL if there is no such town.
+ * @return Closest town to \a tile within \a threshold, or \c nullptr if there is no such town.
  *
  * @note This function only uses distance, the #ClosestTownFromTile function also takes town ownership into account.
  */
 Town *CalcClosestTownFromTile(TileIndex tile, uint threshold)
 {
-	if (Town::GetNumItems() == 0) return NULL;
+	if (Town::GetNumItems() == 0) return nullptr;
 
 	TownID tid = _town_kdtree.FindNearest(TileX(tile), TileY(tile));
 	Town *town = Town::Get(tid);
 	if (DistanceManhattan(tile, town->xy) < threshold) return town;
-	return NULL;
+	return nullptr;
 }
 
 /**
  * Return the town closest (in distance or ownership) to a given tile, within a given threshold.
  * @param tile      Starting point of the search.
  * @param threshold Biggest allowed distance to the town.
- * @return Closest town to \a tile within \a threshold, or \c NULL if there is no such town.
+ * @return Closest town to \a tile within \a threshold, or \c nullptr if there is no such town.
  *
  * @note If you only care about distance, you can use the #CalcClosestTownFromTile function.
  */
@@ -3436,13 +3436,13 @@ Town *ClosestTownFromTile(TileIndex tile
 					/* in the case we are generating "many random towns", this value may be INVALID_TOWN */
 					if (_generating_world) return CalcClosestTownFromTile(tile, threshold);
 					assert(Town::GetNumItems() == 0);
-					return NULL;
+					return nullptr;
 				}
 
 				assert(Town::IsValidID(tid));
 				Town *town = Town::Get(tid);
 
-				if (DistanceManhattan(tile, town->xy) >= threshold) town = NULL;
+				if (DistanceManhattan(tile, town->xy) >= threshold) town = nullptr;
 
 				return town;
 			}
@@ -3505,7 +3505,7 @@ static int GetRating(const Town *t)
 void ChangeTownRating(Town *t, int add, int max, DoCommandFlag flags)
 {
 	/* if magic_bulldozer cheat is active, town doesn't penalize for removing stuff */
-	if (t == NULL || (flags & DC_NO_MODIFY_TOWN_RATING) ||
+	if (t == nullptr || (flags & DC_NO_MODIFY_TOWN_RATING) ||
 			!Company::IsValidID(_current_company) ||
 			(_cheats.magic_bulldozer.value && add < 0)) {
 		return;
@@ -3542,7 +3542,7 @@ void ChangeTownRating(Town *t, int add, 
 CommandCost CheckforTownRating(DoCommandFlag flags, Town *t, TownRatingCheckType type)
 {
 	/* if magic_bulldozer cheat is active, town doesn't restrict your destructive actions */
-	if (t == NULL || !Company::IsValidID(_current_company) ||
+	if (t == nullptr || !Company::IsValidID(_current_company) ||
 			_cheats.magic_bulldozer.value || (flags & DC_NO_TEST_TOWN_RATING)) {
 		return CommandCost();
 	}
@@ -3635,12 +3635,12 @@ extern const TileTypeProcs _tile_type_to
 	AddAcceptedCargo_Town,   // add_accepted_cargo_proc
 	GetTileDesc_Town,        // get_tile_desc_proc
 	GetTileTrackStatus_Town, // get_tile_track_status_proc
-	NULL,                    // click_tile_proc
+	nullptr,                    // click_tile_proc
 	AnimateTile_Town,        // animate_tile_proc
 	TileLoop_Town,           // tile_loop_proc
 	ChangeTileOwner_Town,    // change_tile_owner_proc
 	AddProducedCargo_Town,   // add_produced_cargo_proc
-	NULL,                    // vehicle_enter_tile_proc
+	nullptr,                    // vehicle_enter_tile_proc
 	GetFoundation_Town,      // get_foundation_proc
 	TerraformTile_Town,      // terraform_tile_proc
 };
diff --git a/src/town_gui.cpp b/src/town_gui.cpp
--- a/src/town_gui.cpp
+++ b/src/town_gui.cpp
@@ -261,7 +261,7 @@ public:
 				int y = this->GetRowFromWidget(pt.y, WID_TA_COMMAND_LIST, 1, FONT_HEIGHT_NORMAL);
 				if (!IsInsideMM(y, 0, 5)) return;
 
-				y = GetNthSetBit(GetMaskOfTownActions(NULL, _local_company, this->town), y + this->vscroll->GetPosition() - 1);
+				y = GetNthSetBit(GetMaskOfTownActions(nullptr, _local_company, this->town), y + this->vscroll->GetPosition() - 1);
 				if (y >= 0) {
 					this->sel_index = y;
 					this->SetDirty();
@@ -362,7 +362,7 @@ public:
 			uint cargo_text_right = r.right - WD_FRAMERECT_RIGHT - (rtl ? 20 : 0);
 
 			const CargoSpec *cargo = FindFirstCargoWithTownEffect((TownEffect)i);
-			assert(cargo != NULL);
+			assert(cargo != nullptr);
 
 			StringID string;
 
@@ -406,7 +406,7 @@ public:
 			DrawString(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_LEFT, y += FONT_HEIGHT_NORMAL, STR_TOWN_VIEW_NOISE_IN_TOWN);
 		}
 
-		if (this->town->text != NULL) {
+		if (this->town->text != nullptr) {
 			SetDParamStr(0, this->town->text);
 			DrawStringMultiLine(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT, y += FONT_HEIGHT_NORMAL, UINT16_MAX, STR_JUST_RAW_STRING, TC_BLACK);
 		}
@@ -484,7 +484,7 @@ public:
 
 		if (_settings_game.economy.station_noise_level) aimed_height += FONT_HEIGHT_NORMAL;
 
-		if (this->town->text != NULL) {
+		if (this->town->text != nullptr) {
 			SetDParamStr(0, this->town->text);
 			aimed_height += GetStringHeight(STR_JUST_RAW_STRING, width - WD_FRAMERECT_LEFT - WD_FRAMERECT_RIGHT);
 		}
@@ -503,7 +503,7 @@ public:
 
 	void OnResize() override
 	{
-		if (this->viewport != NULL) {
+		if (this->viewport != nullptr) {
 			NWidgetViewport *nvp = this->GetWidget<NWidgetViewport>(WID_TV_VIEWPORT);
 			nvp->UpdateViewportCoordinates(this);
 
@@ -526,9 +526,9 @@ public:
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
-		DoCommandP(0, this->window_number, 0, CMD_RENAME_TOWN | CMD_MSG(STR_ERROR_CAN_T_RENAME_TOWN), NULL, str);
+		DoCommandP(0, this->window_number, 0, CMD_RENAME_TOWN | CMD_MSG(STR_ERROR_CAN_T_RENAME_TOWN), nullptr, str);
 	}
 };
 
@@ -662,7 +662,7 @@ private:
 			this->vscroll->SetCount((uint)this->towns.size()); // Update scrollbar as well.
 		}
 		/* Always sort the towns. */
-		this->last_town = NULL;
+		this->last_town = nullptr;
 		this->towns.Sort();
 		this->SetWidgetDirty(WID_TD_LIST); // Force repaint of the displayed towns.
 	}
@@ -829,7 +829,7 @@ public:
 				for (uint i = 0; i < this->towns.size(); i++) {
 					const Town *t = this->towns[i];
 
-					assert(t != NULL);
+					assert(t != nullptr);
 
 					SetDParam(0, t->index);
 					SetDParamMaxDigits(1, 8);
@@ -882,7 +882,7 @@ public:
 				if (id_v >= this->towns.size()) return; // click out of town bounds
 
 				const Town *t = this->towns[id_v];
-				assert(t != NULL);
+				assert(t != nullptr);
 				if (_ctrl_pressed) {
 					ShowExtraViewPortWindow(t->xy);
 				} else {
@@ -938,7 +938,7 @@ public:
 };
 
 Listing TownDirectoryWindow::last_sorting = {false, 0};
-const Town *TownDirectoryWindow::last_town = NULL;
+const Town *TownDirectoryWindow::last_town = nullptr;
 
 /** Names of the sorting functions. */
 const StringID TownDirectoryWindow::sorter_names[] = {
@@ -1111,7 +1111,7 @@ public:
 
 	void ExecuteFoundTownCommand(TileIndex tile, bool random, StringID errstr, CommandCallback cc)
 	{
-		const char *name = NULL;
+		const char *name = nullptr;
 
 		if (!this->townnamevalid) {
 			name = this->townname_editbox.text.buf;
diff --git a/src/townname.cpp b/src/townname.cpp
--- a/src/townname.cpp
+++ b/src/townname.cpp
@@ -31,7 +31,7 @@ TownNameParams::TownNameParams(const Tow
 		grfid(t->townnamegrfid), // by default, use supplied data
 		type(t->townnametype)
 {
-	if (t->townnamegrfid != 0 && GetGRFTownName(t->townnamegrfid) == NULL) {
+	if (t->townnamegrfid != 0 && GetGRFTownName(t->townnamegrfid) == nullptr) {
 		/* Fallback to english original */
 		this->grfid = 0;
 		this->type = SPECSTR_TOWNNAME_ENGLISH;
@@ -92,7 +92,7 @@ bool VerifyTownName(uint32 r, const Town
 	/* Check size and width */
 	if (Utf8StringLength(buf1) >= MAX_LENGTH_TOWN_NAME_CHARS) return false;
 
-	if (town_names != NULL) {
+	if (town_names != nullptr) {
 		if (town_names->find(buf1) != town_names->end()) return false;
 		town_names->insert(buf1);
 	} else {
@@ -101,7 +101,7 @@ bool VerifyTownName(uint32 r, const Town
 			/* We can't just compare the numbers since
 			 * several numbers may map to a single name. */
 			const char *buf = t->name;
-			if (buf == NULL) {
+			if (buf == nullptr) {
 				GetTownName(buf2, t, lastof(buf2));
 				buf = buf2;
 			}
@@ -504,8 +504,8 @@ static char *MakeFinnishTownName(char *b
 		char *end = buf - 1;
 		assert(end >= orig);
 		if (*end == 'i') *end = 'e';
-		if (strstr(orig, "a") != NULL || strstr(orig, "o") != NULL || strstr(orig, "u") != NULL ||
-				strstr(orig, "A") != NULL || strstr(orig, "O") != NULL || strstr(orig, "U")  != NULL) {
+		if (strstr(orig, "a") != nullptr || strstr(orig, "o") != nullptr || strstr(orig, "u") != nullptr ||
+				strstr(orig, "A") != nullptr || strstr(orig, "O") != nullptr || strstr(orig, "U")  != nullptr) {
 			buf = strecpy(buf, "la", last);
 		} else {
 			buf = strecpy(buf, "l\xC3\xA4", last);
diff --git a/src/townname_func.h b/src/townname_func.h
--- a/src/townname_func.h
+++ b/src/townname_func.h
@@ -17,7 +17,7 @@
 char *GenerateTownNameString(char *buf, const char *last, size_t lang, uint32 seed);
 char *GetTownName(char *buff, const TownNameParams *par, uint32 townnameparts, const char *last);
 char *GetTownName(char *buff, const Town *t, const char *last);
-bool VerifyTownName(uint32 r, const TownNameParams *par, TownNames *town_names = NULL);
-bool GenerateTownName(uint32 *townnameparts, TownNames *town_names = NULL);
+bool VerifyTownName(uint32 r, const TownNameParams *par, TownNames *town_names = nullptr);
+bool GenerateTownName(uint32 *townnameparts, TownNames *town_names = nullptr);
 
 #endif /* TOWNNAME_FUNC_H */
diff --git a/src/train.h b/src/train.h
--- a/src/train.h
+++ b/src/train.h
@@ -118,7 +118,7 @@ struct Train FINAL : public GroundVehicl
 	int GetDisplaySpeed() const { return this->gcache.last_speed; }
 	int GetDisplayMaxSpeed() const { return this->vcache.cached_max_speed; }
 	Money GetRunningCost() const;
-	int GetDisplayImageWidth(Point *offset = NULL) const;
+	int GetDisplayImageWidth(Point *offset = nullptr) const;
 	bool IsInDepot() const { return this->track == TRACK_BIT_DEPOT; }
 	bool Tick();
 	void OnNewDay();
@@ -146,7 +146,7 @@ struct Train FINAL : public GroundVehicl
 	inline Train *GetNextUnit() const
 	{
 		Train *v = this->GetNextVehicle();
-		if (v != NULL && v->IsRearDualheaded()) v = v->GetNextVehicle();
+		if (v != nullptr && v->IsRearDualheaded()) v = v->GetNextVehicle();
 
 		return v;
 	}
@@ -158,7 +158,7 @@ struct Train FINAL : public GroundVehicl
 	inline Train *GetPrevUnit()
 	{
 		Train *v = this->GetPrevVehicle();
-		if (v != NULL && v->IsRearDualheaded()) v = v->GetPrevVehicle();
+		if (v != nullptr && v->IsRearDualheaded()) v = v->GetPrevVehicle();
 
 		return v;
 	}
@@ -173,7 +173,7 @@ struct Train FINAL : public GroundVehicl
 		 * longer than the part after the center. This means we have to round up the
 		 * length of the next vehicle but may not round the length of the current
 		 * vehicle. */
-		return this->gcache.cached_veh_length / 2 + (this->Next() != NULL ? this->Next()->gcache.cached_veh_length + 1 : 0) / 2;
+		return this->gcache.cached_veh_length / 2 + (this->Next() != nullptr ? this->Next()->gcache.cached_veh_length + 1 : 0) / 2;
 	}
 
 protected: // These functions should not be called outside acceleration code.
diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -78,7 +78,7 @@ void CheckTrainsLengths()
 
 	FOR_ALL_TRAINS(v) {
 		if (v->First() == v && !(v->vehstatus & VS_CRASHED)) {
-			for (const Train *u = v, *w = v->Next(); w != NULL; u = w, w = w->Next()) {
+			for (const Train *u = v, *w = v->Next(); w != nullptr; u = w, w = w->Next()) {
 				if (u->track != TRACK_BIT_DEPOT) {
 					if ((w->track != TRACK_BIT_DEPOT &&
 							max(abs(u->x_pos - w->x_pos), abs(u->y_pos - w->y_pos)) != u->CalcNextVehicleOffset()) ||
@@ -119,7 +119,7 @@ void Train::ConsistChanged(ConsistChange
 
 	bool train_can_tilt = true;
 
-	for (Train *u = this; u != NULL; u = u->Next()) {
+	for (Train *u = this; u != nullptr; u = u->Next()) {
 		const RailVehicleInfo *rvi_u = RailVehInfo(u->engine_type);
 
 		/* Check the this->first cache. */
@@ -137,20 +137,20 @@ void Train::ConsistChanged(ConsistChange
 		u->InvalidateNewGRFCache();
 	}
 
-	for (Train *u = this; u != NULL; u = u->Next()) {
+	for (Train *u = this; u != nullptr; u = u->Next()) {
 		/* Update user defined data (must be done before other properties) */
 		u->tcache.user_def_data = GetVehicleProperty(u, PROP_TRAIN_USER_DATA, u->tcache.user_def_data);
 		this->InvalidateNewGRFCache();
 		u->InvalidateNewGRFCache();
 	}
 
-	for (Train *u = this; u != NULL; u = u->Next()) {
+	for (Train *u = this; u != nullptr; u = u->Next()) {
 		const Engine *e_u = u->GetEngine();
 		const RailVehicleInfo *rvi_u = &e_u->u.rail;
 
 		if (!HasBit(e_u->info.misc_flags, EF_RAIL_TILTS)) train_can_tilt = false;
 
-		/* Cache wagon override sprite group. NULL is returned if there is none */
+		/* Cache wagon override sprite group. nullptr is returned if there is none */
 		u->tcache.cached_override = GetWagonOverrideSpriteSet(u->engine_type, u->cargo_type, u->gcache.first_engine);
 
 		/* Reset colour map */
@@ -202,7 +202,7 @@ void Train::ConsistChanged(ConsistChange
 
 		/* check the vehicle length (callback) */
 		uint16 veh_len = CALLBACK_FAILED;
-		if (e_u->GetGRF() != NULL && e_u->GetGRF()->grf_version >= 8) {
+		if (e_u->GetGRF() != nullptr && e_u->GetGRF()->grf_version >= 8) {
 			/* Use callback 36 */
 			veh_len = GetVehicleProperty(u, PROP_TRAIN_SHORTEN_FACTOR, CALLBACK_FAILED);
 
@@ -316,7 +316,7 @@ int Train::GetCurveSpeedLimit() const
 	int sum = 0;
 	int pos = 0;
 	int lastpos = -1;
-	for (const Vehicle *u = this; u->Next() != NULL; u = u->Next(), pos++) {
+	for (const Vehicle *u = this; u->Next() != nullptr; u = u->Next(), pos++) {
 		Direction this_dir = u->direction;
 		Direction next_dir = u->Next()->direction;
 
@@ -400,7 +400,7 @@ int Train::GetCurrentMaxSpeed() const
 		}
 	}
 
-	for (const Train *u = this; u != NULL; u = u->Next()) {
+	for (const Train *u = this; u != nullptr; u = u->Next()) {
 		if (_settings_game.vehicle.train_acceleration_model == AM_REALISTIC && u->track == TRACK_BIT_DEPOT) {
 			max_speed = min(max_speed, 61);
 			break;
@@ -429,7 +429,7 @@ void Train::UpdateAcceleration()
 
 /**
  * Get the width of a train vehicle image in the GUI.
- * @param offset Additional offset for positioning the sprite; set to NULL if not needed
+ * @param offset Additional offset for positioning the sprite; set to nullptr if not needed
  * @return Width in pixels
  */
 int Train::GetDisplayImageWidth(Point *offset) const
@@ -438,12 +438,12 @@ int Train::GetDisplayImageWidth(Point *o
 	int vehicle_pitch = 0;
 
 	const Engine *e = this->GetEngine();
-	if (e->GetGRF() != NULL && is_custom_sprite(e->u.rail.image_index)) {
+	if (e->GetGRF() != nullptr && is_custom_sprite(e->u.rail.image_index)) {
 		reference_width = e->GetGRF()->traininfo_vehicle_width;
 		vehicle_pitch = e->GetGRF()->traininfo_vehicle_pitch;
 	}
 
-	if (offset != NULL) {
+	if (offset != nullptr) {
 		offset->x = ScaleGUITrad(reference_width) / 2;
 		offset->y = ScaleGUITrad(vehicle_pitch);
 	}
@@ -492,7 +492,7 @@ static void GetRailIcon(EngineID engine,
 	if (is_custom_sprite(spritenum)) {
 		GetCustomVehicleIcon(engine, dir, image_type, result);
 		if (result->IsValid()) {
-			if (e->GetGRF() != NULL) {
+			if (e->GetGRF() != nullptr) {
 				y += ScaleGUITrad(e->GetGRF()->traininfo_vehicle_pitch);
 			}
 			return;
@@ -805,12 +805,12 @@ static Train *FindGoodVehiclePos(const T
 			Train *t = dst;
 			while (t->engine_type == eng) {
 				t = t->Next();
-				if (t == NULL) return dst;
+				if (t == nullptr) return dst;
 			}
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /** Helper type for lists/vectors of trains */
@@ -823,7 +823,7 @@ typedef std::vector<Train *> TrainList;
  */
 static void MakeTrainBackup(TrainList &list, Train *t)
 {
-	for (; t != NULL; t = t->Next()) list.push_back(t);
+	for (; t != nullptr; t = t->Next()) list.push_back(t);
 }
 
 /**
@@ -835,14 +835,14 @@ static void RestoreTrainBackup(TrainList
 	/* No train, nothing to do. */
 	if (list.size() == 0) return;
 
-	Train *prev = NULL;
+	Train *prev = nullptr;
 	/* Iterate over the list and rebuild it. */
 	for (Train *t : list) {
-		if (prev != NULL) {
+		if (prev != nullptr) {
 			prev->SetNext(t);
-		} else if (t->Previous() != NULL) {
+		} else if (t->Previous() != nullptr) {
 			/* Make sure the head of the train is always the first in the chain. */
-			t->Previous()->SetNext(NULL);
+			t->Previous()->SetNext(nullptr);
 		}
 		prev = t;
 	}
@@ -859,10 +859,10 @@ static void RemoveFromConsist(Train *par
 
 	/* Unlink at the front, but make it point to the next
 	 * vehicle after the to be remove part. */
-	if (part->Previous() != NULL) part->Previous()->SetNext(tail->Next());
+	if (part->Previous() != nullptr) part->Previous()->SetNext(tail->Next());
 
 	/* Unlink at the back */
-	tail->SetNext(NULL);
+	tail->SetNext(nullptr);
 }
 
 /**
@@ -873,7 +873,7 @@ static void RemoveFromConsist(Train *par
 static void InsertInConsist(Train *dst, Train *chain)
 {
 	/* We do not want to add something in the middle of an articulated part. */
-	assert(dst != NULL && (dst->Next() == NULL || !dst->Next()->IsArticulatedPart()));
+	assert(dst != nullptr && (dst->Next() == nullptr || !dst->Next()->IsArticulatedPart()));
 
 	chain->Last()->SetNext(dst->Next());
 	dst->SetNext(chain);
@@ -886,12 +886,12 @@ static void InsertInConsist(Train *dst, 
  */
 static void NormaliseDualHeads(Train *t)
 {
-	for (; t != NULL; t = t->GetNextVehicle()) {
+	for (; t != nullptr; t = t->GetNextVehicle()) {
 		if (!t->IsMultiheaded() || !t->IsEngine()) continue;
 
 		/* Make sure that there are no free cars before next engine */
 		Train *u;
-		for (u = t; u->Next() != NULL && !u->Next()->IsEngine(); u = u->Next()) {}
+		for (u = t; u->Next() != nullptr && !u->Next()->IsEngine(); u = u->Next()) {}
 
 		if (u == t->other_multiheaded_part) continue;
 
@@ -909,10 +909,10 @@ static void NormaliseDualHeads(Train *t)
 static void NormaliseSubtypes(Train *chain)
 {
 	/* Nothing to do */
-	if (chain == NULL) return;
+	if (chain == nullptr) return;
 
 	/* We must be the first in the chain. */
-	assert(chain->Previous() == NULL);
+	assert(chain->Previous() == nullptr);
 
 	/* Set the appropriate bits for the first in the chain. */
 	if (chain->IsWagon()) {
@@ -923,7 +923,7 @@ static void NormaliseSubtypes(Train *cha
 	}
 
 	/* Now clear the bits for the rest of the chain */
-	for (Train *t = chain->Next(); t != NULL; t = t->Next()) {
+	for (Train *t = chain->Next(); t != nullptr; t = t->Next()) {
 		t->ClearFreeWagon();
 		t->ClearFrontEngine();
 	}
@@ -943,10 +943,10 @@ static CommandCost CheckNewTrain(Train *
 	/* Just add 'new' engines and subtract the original ones.
 	 * If that's less than or equal to 0 we can be sure we did
 	 * not add any engines (read: trains) along the way. */
-	if ((src          != NULL && src->IsEngine()          ? 1 : 0) +
-			(dst          != NULL && dst->IsEngine()          ? 1 : 0) -
-			(original_src != NULL && original_src->IsEngine() ? 1 : 0) -
-			(original_dst != NULL && original_dst->IsEngine() ? 1 : 0) <= 0) {
+	if ((src          != nullptr && src->IsEngine()          ? 1 : 0) +
+			(dst          != nullptr && dst->IsEngine()          ? 1 : 0) -
+			(original_src != nullptr && original_src->IsEngine() ? 1 : 0) -
+			(original_dst != nullptr && original_dst->IsEngine() ? 1 : 0) <= 0) {
 		return CommandCost();
 	}
 
@@ -965,7 +965,7 @@ static CommandCost CheckNewTrain(Train *
 static CommandCost CheckTrainAttachment(Train *t)
 {
 	/* No multi-part train, no need to check. */
-	if (t == NULL || t->Next() == NULL || !t->IsEngine()) return CommandCost();
+	if (t == nullptr || t->Next() == nullptr || !t->IsEngine()) return CommandCost();
 
 	/* The maximum length for a train. For each part we decrease this by one
 	 * and if the result is negative the train is simply too long. */
@@ -976,19 +976,19 @@ static CommandCost CheckTrainAttachment(
 
 	/* Break the prev -> t link so it always holds within the loop. */
 	t = t->Next();
-	prev->SetNext(NULL);
+	prev->SetNext(nullptr);
 
 	/* Make sure the cache is cleared. */
 	head->InvalidateNewGRFCache();
 
-	while (t != NULL) {
+	while (t != nullptr) {
 		allowed_len -= t->gcache.cached_veh_length;
 
 		Train *next = t->Next();
 
 		/* Unlink the to-be-added piece; it is already unlinked from the previous
 		 * part due to the fact that the prev -> t link is broken. */
-		t->SetNext(NULL);
+		t->SetNext(nullptr);
 
 		/* Don't check callback for articulated or rear dual headed parts */
 		if (!t->IsArticulatedPart() && !t->IsRearDualheaded()) {
@@ -1084,8 +1084,8 @@ static void ArrangeTrains(Train **dst_he
 	if (*src_head == *dst_head) {
 		/* If we aren't moving part(s) to a new train, we are just moving the
 		 * front back and there is not destination head. */
-		*dst_head = NULL;
-	} else if (*dst_head == NULL) {
+		*dst_head = nullptr;
+	} else if (*dst_head == nullptr) {
 		/* If we are moving to a new train the head of the move train would become
 		 * the head of the new vehicle. */
 		*dst_head = src;
@@ -1098,7 +1098,7 @@ static void ArrangeTrains(Train **dst_he
 		 * In case we are a multiheaded part we want the complete thing to come
 		 * with us, so src->GetNextUnit(), however... when we are e.g. a wagon
 		 * that is followed by a rear multihead we do not want to include that. */
-		*src_head = move_chain ? NULL :
+		*src_head = move_chain ? nullptr :
 				(src->IsMultiheaded() ? src->GetNextUnit() : src->GetNextVehicle());
 	}
 
@@ -1122,7 +1122,7 @@ static void ArrangeTrains(Train **dst_he
 static void NormaliseTrainHead(Train *head)
 {
 	/* Not much to do! */
-	if (head == NULL) return;
+	if (head == nullptr) return;
 
 	/* Tell the 'world' the train changed. */
 	head->ConsistChanged(CCF_ARRANGE);
@@ -1159,7 +1159,7 @@ CommandCost CmdMoveRailVehicle(TileIndex
 	bool move_chain = HasBit(p1, 20);
 
 	Train *src = Train::GetIfValid(s);
-	if (src == NULL) return CMD_ERROR;
+	if (src == nullptr) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(src->owner);
 	if (ret.Failed()) return ret;
@@ -1170,10 +1170,10 @@ CommandCost CmdMoveRailVehicle(TileIndex
 	/* if nothing is selected as destination, try and find a matching vehicle to drag to. */
 	Train *dst;
 	if (d == INVALID_VEHICLE) {
-		dst = src->IsEngine() ? NULL : FindGoodVehiclePos(src);
+		dst = src->IsEngine() ? nullptr : FindGoodVehiclePos(src);
 	} else {
 		dst = Train::GetIfValid(d);
-		if (dst == NULL) return CMD_ERROR;
+		if (dst == nullptr) return CMD_ERROR;
 
 		CommandCost ret = CheckOwnership(dst->owner);
 		if (ret.Failed()) return ret;
@@ -1184,7 +1184,7 @@ CommandCost CmdMoveRailVehicle(TileIndex
 
 	/* if an articulated part is being handled, deal with its parent vehicle */
 	src = src->GetFirstEnginePart();
-	if (dst != NULL) {
+	if (dst != nullptr) {
 		dst = dst->GetFirstEnginePart();
 	}
 
@@ -1194,13 +1194,13 @@ CommandCost CmdMoveRailVehicle(TileIndex
 	/* locate the head of the two chains */
 	Train *src_head = src->First();
 	Train *dst_head;
-	if (dst != NULL) {
+	if (dst != nullptr) {
 		dst_head = dst->First();
 		if (dst_head->tile != src_head->tile) return CMD_ERROR;
 		/* Now deal with articulated part of destination wagon */
 		dst = dst->GetLastEnginePart();
 	} else {
-		dst_head = NULL;
+		dst_head = nullptr;
 	}
 
 	if (src->IsRearDualheaded()) return_cmd_error(STR_ERROR_REAR_ENGINE_FOLLOW_FRONT);
@@ -1209,13 +1209,13 @@ CommandCost CmdMoveRailVehicle(TileIndex
 	if (move_chain && src_head == dst_head) return CommandCost();
 
 	/* When moving a multiheaded part to be place after itself, bail out. */
-	if (!move_chain && dst != NULL && dst->IsRearDualheaded() && src == dst->other_multiheaded_part) return CommandCost();
+	if (!move_chain && dst != nullptr && dst->IsRearDualheaded() && src == dst->other_multiheaded_part) return CommandCost();
 
 	/* Check if all vehicles in the source train are stopped inside a depot. */
 	if (!src_head->IsStoppedInDepot()) return_cmd_error(STR_ERROR_TRAINS_CAN_ONLY_BE_ALTERED_INSIDE_A_DEPOT);
 
 	/* Check if all vehicles in the destination train are stopped inside a depot. */
-	if (dst_head != NULL && !dst_head->IsStoppedInDepot()) return_cmd_error(STR_ERROR_TRAINS_CAN_ONLY_BE_ALTERED_INSIDE_A_DEPOT);
+	if (dst_head != nullptr && !dst_head->IsStoppedInDepot()) return_cmd_error(STR_ERROR_TRAINS_CAN_ONLY_BE_ALTERED_INSIDE_A_DEPOT);
 
 	/* First make a backup of the order of the trains. That way we can do
 	 * whatever we want with the order and later on easily revert. */
@@ -1229,13 +1229,13 @@ CommandCost CmdMoveRailVehicle(TileIndex
 	 * For the destination head we do not care if it is the same as the source
 	 * head because in that case it's just a copy. */
 	Train *original_src_head = src_head;
-	Train *original_dst_head = (dst_head == src_head ? NULL : dst_head);
+	Train *original_dst_head = (dst_head == src_head ? nullptr : dst_head);
 
 	/* We want this information from before the rearrangement, but execute this after the validation.
-	 * original_src_head can't be NULL; src is by definition != NULL, so src_head can't be NULL as
-	 * src->GetFirst() always yields non-NULL, so eventually original_src_head != NULL as well. */
+	 * original_src_head can't be nullptr; src is by definition != nullptr, so src_head can't be nullptr as
+	 * src->GetFirst() always yields non-nullptr, so eventually original_src_head != nullptr as well. */
 	bool original_src_head_front_engine = original_src_head->IsFrontEngine();
-	bool original_dst_head_front_engine = original_dst_head != NULL && original_dst_head->IsFrontEngine();
+	bool original_dst_head_front_engine = original_dst_head != nullptr && original_dst_head->IsFrontEngine();
 
 	/* (Re)arrange the trains in the wanted arrangement. */
 	ArrangeTrains(&dst_head, dst, &src_head, src, move_chain);
@@ -1308,8 +1308,8 @@ CommandCost CmdMoveRailVehicle(TileIndex
 		}
 
 		/* Add new heads to statistics */
-		if (src_head != NULL && src_head->IsFrontEngine()) GroupStatistics::CountVehicle(src_head, 1);
-		if (dst_head != NULL && dst_head->IsFrontEngine()) GroupStatistics::CountVehicle(dst_head, 1);
+		if (src_head != nullptr && src_head->IsFrontEngine()) GroupStatistics::CountVehicle(src_head, 1);
+		if (dst_head != nullptr && dst_head->IsFrontEngine()) GroupStatistics::CountVehicle(dst_head, 1);
 
 		/* Handle 'new engine' part of cases #1b, #2b, #3b, #4b and #5 in NormaliseTrainHead. */
 		NormaliseTrainHead(src_head);
@@ -1320,8 +1320,8 @@ CommandCost CmdMoveRailVehicle(TileIndex
 			CheckCargoCapacity(dst_head);
 		}
 
-		if (src_head != NULL) src_head->First()->MarkDirty();
-		if (dst_head != NULL) dst_head->First()->MarkDirty();
+		if (src_head != nullptr) src_head->First()->MarkDirty();
+		if (dst_head != nullptr) dst_head->First()->MarkDirty();
 
 		/* We are undoubtedly changing something in the depot and train list. */
 		InvalidateWindowData(WC_VEHICLE_DEPOT, src->tile);
@@ -1363,34 +1363,34 @@ CommandCost CmdSellRailWagon(DoCommandFl
 
 	/* We need to keep track of the new head and the head of what we're going to sell. */
 	Train *new_head = first;
-	Train *sell_head = NULL;
+	Train *sell_head = nullptr;
 
 	/* Split the train in the wanted way. */
-	ArrangeTrains(&sell_head, NULL, &new_head, v, sell_chain);
+	ArrangeTrains(&sell_head, nullptr, &new_head, v, sell_chain);
 
 	/* We don't need to validate the second train; it's going to be sold. */
-	CommandCost ret = ValidateTrains(NULL, NULL, first, new_head, (flags & DC_AUTOREPLACE) == 0);
+	CommandCost ret = ValidateTrains(nullptr, nullptr, first, new_head, (flags & DC_AUTOREPLACE) == 0);
 	if (ret.Failed()) {
 		/* Restore the train we had. */
 		RestoreTrainBackup(original);
 		return ret;
 	}
 
-	if (first->orders.list == NULL && !OrderList::CanAllocateItem()) {
+	if (first->orders.list == nullptr && !OrderList::CanAllocateItem()) {
 		/* Restore the train we had. */
 		RestoreTrainBackup(original);
 		return_cmd_error(STR_ERROR_NO_MORE_SPACE_FOR_ORDERS);
 	}
 
 	CommandCost cost(EXPENSES_NEW_VEHICLES);
-	for (Train *t = sell_head; t != NULL; t = t->Next()) cost.AddCost(-t->value);
+	for (Train *t = sell_head; t != nullptr; t = t->Next()) cost.AddCost(-t->value);
 
 	/* do it? */
 	if (flags & DC_EXEC) {
 		/* First normalise the sub types of the chain. */
 		NormaliseSubtypes(new_head);
 
-		if (v == first && v->IsEngine() && !sell_chain && new_head != NULL && new_head->IsFrontEngine()) {
+		if (v == first && v->IsEngine() && !sell_chain && new_head != nullptr && new_head->IsFrontEngine()) {
 			/* We are selling the front engine. In this case we want to
 			 * 'give' the order, unit number and such to the new head. */
 			new_head->orders.list = first->orders.list;
@@ -1618,11 +1618,11 @@ void ReverseTrainSwapVeh(Train *v, int l
 /**
  * Check if the vehicle is a train
  * @param v vehicle on tile
- * @return v if it is a train, NULL otherwise
+ * @return v if it is a train, nullptr otherwise
  */
 static Vehicle *TrainOnTileEnum(Vehicle *v, void *)
 {
-	return (v->type == VEH_TRAIN) ? v : NULL;
+	return (v->type == VEH_TRAIN) ? v : nullptr;
 }
 
 
@@ -1630,18 +1630,18 @@ static Vehicle *TrainOnTileEnum(Vehicle 
  * Checks if a train is approaching a rail-road crossing
  * @param v vehicle on tile
  * @param data tile with crossing we are testing
- * @return v if it is approaching a crossing, NULL otherwise
+ * @return v if it is approaching a crossing, nullptr otherwise
  */
 static Vehicle *TrainApproachingCrossingEnum(Vehicle *v, void *data)
 {
-	if (v->type != VEH_TRAIN || (v->vehstatus & VS_CRASHED)) return NULL;
+	if (v->type != VEH_TRAIN || (v->vehstatus & VS_CRASHED)) return nullptr;
 
 	Train *t = Train::From(v);
-	if (!t->IsFrontEngine()) return NULL;
+	if (!t->IsFrontEngine()) return nullptr;
 
 	TileIndex tile = *(TileIndex *)data;
 
-	if (TrainApproachingCrossingTile(t) != tile) return NULL;
+	if (TrainApproachingCrossingTile(t) != tile) return nullptr;
 
 	return t;
 }
@@ -1680,7 +1680,7 @@ void UpdateLevelCrossing(TileIndex tile,
 	assert(IsLevelCrossingTile(tile));
 
 	/* reserved || train on crossing || train approaching crossing */
-	bool new_state = HasCrossingReservation(tile) || HasVehicleOnPos(tile, NULL, &TrainOnTileEnum) || TrainApproachingCrossing(tile);
+	bool new_state = HasCrossingReservation(tile) || HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum) || TrainApproachingCrossing(tile);
 
 	if (new_state != IsCrossingBarred(tile)) {
 		if (new_state && sound) {
@@ -1744,23 +1744,23 @@ static void AdvanceWagonsAfterSwap(Train
 {
 	/* first of all, fix the situation when the train was entering a depot */
 	Train *dep = v; // last vehicle in front of just left depot
-	while (dep->Next() != NULL && (dep->track == TRACK_BIT_DEPOT || dep->Next()->track != TRACK_BIT_DEPOT)) {
+	while (dep->Next() != nullptr && (dep->track == TRACK_BIT_DEPOT || dep->Next()->track != TRACK_BIT_DEPOT)) {
 		dep = dep->Next(); // find first vehicle outside of a depot, with next vehicle inside a depot
 	}
 
 	Train *leave = dep->Next(); // first vehicle in a depot we are leaving now
 
-	if (leave != NULL) {
+	if (leave != nullptr) {
 		/* 'pull' next wagon out of the depot, so we won't miss it (it could stay in depot forever) */
 		int d = TicksToLeaveDepot(dep);
 
 		if (d <= 0) {
 			leave->vehstatus &= ~VS_HIDDEN; // move it out of the depot
 			leave->track = TrackToTrackBits(GetRailDepotTrack(leave->tile));
-			for (int i = 0; i >= d; i--) TrainController(leave, NULL); // maybe move it, and maybe let another wagon leave
+			for (int i = 0; i >= d; i--) TrainController(leave, nullptr); // maybe move it, and maybe let another wagon leave
 		}
 	} else {
-		dep = NULL; // no vehicle in a depot, so no vehicle leaving a depot
+		dep = nullptr; // no vehicle in a depot, so no vehicle leaving a depot
 	}
 
 	Train *base = v;
@@ -1770,7 +1770,7 @@ static void AdvanceWagonsAfterSwap(Train
 
 	/* We have to make sure all wagons that leave a depot because of train reversing are moved correctly
 	 * they have already correct spacing, so we have to make sure they are moved how they should */
-	bool nomove = (dep == NULL); // If there is no vehicle leaving a depot, limit the number of wagons moved immediately.
+	bool nomove = (dep == nullptr); // If there is no vehicle leaving a depot, limit the number of wagons moved immediately.
 
 	while (length > 2) {
 		/* we reached vehicle (originally) in front of a depot, stop now
@@ -1786,7 +1786,7 @@ static void AdvanceWagonsAfterSwap(Train
 		int differential = last->CalcNextVehicleOffset() - base->CalcNextVehicleOffset();
 
 		/* do not update images now */
-		for (int i = 0; i < differential; i++) TrainController(first, (nomove ? last->Next() : NULL));
+		for (int i = 0; i < differential; i++) TrainController(first, (nomove ? last->Next() : nullptr));
 
 		base = first; // == base->Next()
 		length -= 2;
@@ -1834,7 +1834,7 @@ void ReverseTrainDirection(Train *v)
 	v->ConsistChanged(CCF_TRACK);
 
 	/* update all images */
-	for (Train *u = v; u != NULL; u = u->Next()) u->UpdateViewport(false, false);
+	for (Train *u = v; u != nullptr; u = u->Next()) u->UpdateViewport(false, false);
 
 	/* update crossing we were approaching */
 	if (crossing != INVALID_TILE) UpdateLevelCrossing(crossing);
@@ -1893,7 +1893,7 @@ void ReverseTrainDirection(Train *v)
 CommandCost CmdReverseTrainDirection(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Train *v = Train::GetIfValid(p1);
-	if (v == NULL) return CMD_ERROR;
+	if (v == nullptr) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -1929,7 +1929,7 @@ CommandCost CmdReverseTrainDirection(Til
 			/* Properly leave the station if we are loading and won't be loading anymore */
 			if (v->current_order.IsType(OT_LOADING)) {
 				const Vehicle *last = v;
-				while (last->Next() != NULL) last = last->Next();
+				while (last->Next() != nullptr) last = last->Next();
 
 				/* not a station || different station --> leave the station */
 				if (!IsTileType(last->tile, MP_STATION) || GetStationIndex(last->tile) != GetStationIndex(v->tile)) {
@@ -1966,7 +1966,7 @@ CommandCost CmdReverseTrainDirection(Til
 CommandCost CmdForceTrainProceed(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Train *t = Train::GetIfValid(p1);
-	if (t == NULL) return CMD_ERROR;
+	if (t == nullptr) return CMD_ERROR;
 
 	if (!t->IsPrimaryVehicle()) return CMD_ERROR;
 
@@ -2013,9 +2013,9 @@ static FindDepotData FindClosestTrainDep
 
 /**
  * Locate the closest depot for this consist, and return the information to the caller.
- * @param[out] location    If not \c NULL and a depot is found, store its location in the given address.
- * @param[out] destination If not \c NULL and a depot is found, store its index in the given address.
- * @param[out] reverse     If not \c NULL and a depot is found, store reversal information in the given address.
+ * @param[out] location    If not \c nullptr and a depot is found, store its location in the given address.
+ * @param[out] destination If not \c nullptr and a depot is found, store its index in the given address.
+ * @param[out] reverse     If not \c nullptr and a depot is found, store reversal information in the given address.
  * @return A depot has been found.
  */
 bool Train::FindClosestDepot(TileIndex *location, DestinationID *destination, bool *reverse)
@@ -2023,9 +2023,9 @@ bool Train::FindClosestDepot(TileIndex *
 	FindDepotData tfdd = FindClosestTrainDepot(this, 0);
 	if (tfdd.best_length == UINT_MAX) return false;
 
-	if (location    != NULL) *location    = tfdd.tile;
-	if (destination != NULL) *destination = GetDepotIndex(tfdd.tile);
-	if (reverse     != NULL) *reverse     = tfdd.reverse;
+	if (location    != nullptr) *location    = tfdd.tile;
+	if (destination != nullptr) *destination = GetDepotIndex(tfdd.tile);
+	if (reverse     != nullptr) *reverse     = tfdd.reverse;
 
 	return true;
 }
@@ -2102,7 +2102,7 @@ static void CheckNextTrainTile(Train *v)
 				if (Rail90DegTurnDisallowed(GetTileRailType(ft.m_old_tile), GetTileRailType(ft.m_new_tile))) {
 					tracks &= ~TrackCrossesTracks(TrackdirToTrack(ft.m_old_td));
 				}
-				ChooseTrainTrack(v, ft.m_new_tile, ft.m_exitdir, tracks, false, NULL, false);
+				ChooseTrainTrack(v, ft.m_new_tile, ft.m_exitdir, tracks, false, nullptr, false);
 			}
 		}
 	}
@@ -2116,7 +2116,7 @@ static void CheckNextTrainTile(Train *v)
 static bool CheckTrainStayInDepot(Train *v)
 {
 	/* bail out if not all wagons are in the same depot or not in a depot at all */
-	for (const Train *u = v; u != NULL; u = u->Next()) {
+	for (const Train *u = v; u != nullptr; u = u->Next()) {
 		if (u->track != TRACK_BIT_DEPOT || u->tile != v->tile) return false;
 	}
 
@@ -2245,7 +2245,7 @@ void FreeTrainTrackReservation(const Tra
 	if (IsRailDepotTile(tile) && TrackdirToExitdir(td) != GetRailDepotDirection(tile)) return;
 	if (v->track == TRACK_BIT_DEPOT) {
 		/* Front engine is in a depot. We enter if some part is not in the depot. */
-		for (const Train *u = v; u != NULL; u = u->Next()) {
+		for (const Train *u = v; u != nullptr; u = u->Next()) {
 			if (u->track != TRACK_BIT_DEPOT || u->tile != v->tile) return;
 		}
 	}
@@ -2359,8 +2359,8 @@ static PBSTileInfo ExtendTrainReservatio
 			if (ft.m_tiles_skipped != 0) ft.m_new_tile -= TileOffsByDiagDir(ft.m_exitdir) * ft.m_tiles_skipped;
 
 			/* Choice found, path valid but not okay. Save info about the choice tile as well. */
-			if (new_tracks != NULL) *new_tracks = TrackdirBitsToTrackBits(ft.m_new_td_bits);
-			if (enterdir != NULL) *enterdir = ft.m_exitdir;
+			if (new_tracks != nullptr) *new_tracks = TrackdirBitsToTrackBits(ft.m_new_td_bits);
+			if (enterdir != nullptr) *enterdir = ft.m_exitdir;
 			return PBSTileInfo(ft.m_new_tile, ft.m_old_td, false);
 		}
 
@@ -2473,7 +2473,7 @@ public:
 			if (this->index >= this->v->GetNumOrders()) this->index = 0;
 
 			Order *order = this->v->GetOrder(this->index);
-			assert(order != NULL);
+			assert(order != nullptr);
 
 			switch (order->GetType()) {
 				case OT_GOTO_DEPOT:
@@ -2516,7 +2516,7 @@ static Track ChooseTrainTrack(Train *v, 
 
 	assert((tracks & ~TRACK_BIT_MASK) == 0);
 
-	if (got_reservation != NULL) *got_reservation = false;
+	if (got_reservation != nullptr) *got_reservation = false;
 
 	/* Don't use tracks here as the setting to forbid 90 deg turns might have been switched between reservation and now. */
 	TrackBits res_tracks = (TrackBits)(GetReservedTrackbits(tile) & DiagdirReachesTracks(enterdir));
@@ -2549,7 +2549,7 @@ static Track ChooseTrainTrack(Train *v, 
 		}
 		if (res_dest.okay) {
 			/* Got a valid reservation that ends at a safe target, quick exit. */
-			if (got_reservation != NULL) *got_reservation = true;
+			if (got_reservation != nullptr) *got_reservation = true;
 			if (changed_signal) MarkTileDirtyByTile(tile);
 			TryReserveRailTrack(v->tile, TrackdirToTrack(v->GetVehicleTrackdir()));
 			return best_track;
@@ -2608,7 +2608,7 @@ static Track ChooseTrainTrack(Train *v, 
 			TrackBits res = GetReservedTrackbits(tile) & DiagdirReachesTracks(enterdir);
 			best_track = FindFirstTrack(res);
 			TryReserveRailTrack(v->tile, TrackdirToTrack(v->GetVehicleTrackdir()));
-			if (got_reservation != NULL) *got_reservation = true;
+			if (got_reservation != nullptr) *got_reservation = true;
 			if (changed_signal) MarkTileDirtyByTile(tile);
 		} else {
 			FreeTrainTrackReservation(v);
@@ -2617,7 +2617,7 @@ static Track ChooseTrainTrack(Train *v, 
 		return best_track;
 	}
 
-	if (got_reservation != NULL) *got_reservation = true;
+	if (got_reservation != nullptr) *got_reservation = true;
 
 	/* Reservation target found and free, check if it is safe. */
 	while (!IsSafeWaitingPosition(v, res_dest.tile, res_dest.trackdir, true, _settings_game.pf.forbid_90_deg)) {
@@ -2640,7 +2640,7 @@ static Track ChooseTrainTrack(Train *v, 
 				/* Path found, but could not be reserved. */
 				FreeTrainTrackReservation(v);
 				if (mark_stuck) MarkTrainAsStuck(v);
-				if (got_reservation != NULL) *got_reservation = false;
+				if (got_reservation != nullptr) *got_reservation = false;
 				changed_signal = false;
 				break;
 			}
@@ -2649,7 +2649,7 @@ static Track ChooseTrainTrack(Train *v, 
 		if (!TryReserveSafeTrack(v, res_dest.tile, res_dest.trackdir, true)) {
 			FreeTrainTrackReservation(v);
 			if (mark_stuck) MarkTrainAsStuck(v);
-			if (got_reservation != NULL) *got_reservation = false;
+			if (got_reservation != nullptr) *got_reservation = false;
 			changed_signal = false;
 		}
 		break;
@@ -2688,14 +2688,14 @@ bool TryPathReserve(Train *v, bool mark_
 		}
 	}
 
-	Vehicle *other_train = NULL;
+	Vehicle *other_train = nullptr;
 	PBSTileInfo origin = FollowTrainReservation(v, &other_train);
 	/* The path we are driving on is already blocked by some other train.
 	 * This can only happen in certain situations when mixing path and
 	 * block signals or when changing tracks and/or signals.
 	 * Exit here as doing any further reservations will probably just
 	 * make matters worse. */
-	if (other_train != NULL && other_train->index != v->index) {
+	if (other_train != nullptr && other_train->index != v->index) {
 		if (mark_as_stuck) MarkTrainAsStuck(v);
 		return false;
 	}
@@ -2781,7 +2781,7 @@ void Train::MarkDirty()
 	do {
 		v->colourmap = PAL_NONE;
 		v->UpdateViewport(true, false);
-	} while ((v = v->Next()) != NULL);
+	} while ((v = v->Next()) != nullptr);
 
 	/* need to update acceleration and cached values since the goods on the train changed. */
 	this->CargoChanged();
@@ -2899,7 +2899,7 @@ static bool TrainMovedChangeSignals(Tile
 /** Tries to reserve track under whole train consist. */
 void Train::ReserveTrackUnderConsist() const
 {
-	for (const Train *u = this; u != NULL; u = u->Next()) {
+	for (const Train *u = this; u != nullptr; u = u->Next()) {
 		switch (u->track) {
 			case TRACK_BIT_WORMHOLE:
 				TryReserveRailTrack(u->tile, DiagDirToDiagTrack(GetTunnelBridgeDirection(u->tile)));
@@ -2928,7 +2928,7 @@ uint Train::Crash(bool flooded)
 		/* Remove the reserved path in front of the train if it is not stuck.
 		 * Also clear all reserved tracks the train is currently on. */
 		if (!HasBit(this->flags, VRF_TRAIN_STUCK)) FreeTrainTrackReservation(this);
-		for (const Train *v = this; v != NULL; v = v->Next()) {
+		for (const Train *v = this; v != nullptr; v = v->Next()) {
 			ClearPathReservation(v, v->tile, v->GetVehicleTrackdir());
 			if (IsTileType(v->tile, MP_TUNNELBRIDGE)) {
 				/* ClearPathReservation will not free the wormhole exit
@@ -2986,23 +2986,23 @@ struct TrainCollideChecker {
  * Collision test function.
  * @param v %Train vehicle to test collision with.
  * @param data %Train being examined.
- * @return \c NULL (always continue search)
+ * @return \c nullptr (always continue search)
  */
 static Vehicle *FindTrainCollideEnum(Vehicle *v, void *data)
 {
 	TrainCollideChecker *tcc = (TrainCollideChecker*)data;
 
 	/* not a train or in depot */
-	if (v->type != VEH_TRAIN || Train::From(v)->track == TRACK_BIT_DEPOT) return NULL;
+	if (v->type != VEH_TRAIN || Train::From(v)->track == TRACK_BIT_DEPOT) return nullptr;
 
 	/* do not crash into trains of another company. */
-	if (v->owner != tcc->v->owner) return NULL;
+	if (v->owner != tcc->v->owner) return nullptr;
 
 	/* get first vehicle now to make most usual checks faster */
 	Train *coll = Train::From(v)->First();
 
 	/* can't collide with own wagons */
-	if (coll == tcc->v) return NULL;
+	if (coll == tcc->v) return nullptr;
 
 	int x_diff = v->x_pos - tcc->v->x_pos;
 	int y_diff = v->y_pos - tcc->v->y_pos;
@@ -3012,20 +3012,20 @@ static Vehicle *FindTrainCollideEnum(Veh
 	 * Differences are shifted by 7, mapping range [-7 .. 8] into [0 .. 15]
 	 * Differences are then ORed and then we check for any higher bits */
 	uint hash = (y_diff + 7) | (x_diff + 7);
-	if (hash & ~15) return NULL;
+	if (hash & ~15) return nullptr;
 
 	/* Slower check using multiplication */
 	int min_diff = (Train::From(v)->gcache.cached_veh_length + 1) / 2 + (tcc->v->gcache.cached_veh_length + 1) / 2 - 1;
-	if (x_diff * x_diff + y_diff * y_diff > min_diff * min_diff) return NULL;
+	if (x_diff * x_diff + y_diff * y_diff > min_diff * min_diff) return nullptr;
 
 	/* Happens when there is a train under bridge next to bridge head */
-	if (abs(v->z_pos - tcc->v->z_pos) > 5) return NULL;
+	if (abs(v->z_pos - tcc->v->z_pos) > 5) return nullptr;
 
 	/* crash both trains */
 	tcc->num += TrainCrashed(tcc->v);
 	tcc->num += TrainCrashed(coll);
 
-	return NULL; // continue searching
+	return nullptr; // continue searching
 }
 
 /**
@@ -3067,15 +3067,15 @@ static bool CheckTrainCollision(Train *v
 
 static Vehicle *CheckTrainAtSignal(Vehicle *v, void *data)
 {
-	if (v->type != VEH_TRAIN || (v->vehstatus & VS_CRASHED)) return NULL;
+	if (v->type != VEH_TRAIN || (v->vehstatus & VS_CRASHED)) return nullptr;
 
 	Train *t = Train::From(v);
 	DiagDirection exitdir = *(DiagDirection *)data;
 
 	/* not front engine of a train, inside wormhole or depot, crashed */
-	if (!t->IsFrontEngine() || !(t->track & TRACK_BIT_MASK)) return NULL;
-
-	if (t->cur_speed > 5 || VehicleExitDir(t->direction, t->track) != exitdir) return NULL;
+	if (!t->IsFrontEngine() || !(t->track & TRACK_BIT_MASK)) return nullptr;
+
+	if (t->cur_speed > 5 || VehicleExitDir(t->direction, t->track) != exitdir) return nullptr;
 
 	return t;
 }
@@ -3138,7 +3138,7 @@ bool TrainController(Train *v, Vehicle *
 				TrackBits red_signals = TrackdirBitsToTrackBits(TrackStatusToRedSignals(ts) & reachable_trackdirs);
 
 				TrackBits bits = TrackdirBitsToTrackBits(trackdirbits);
-				if (Rail90DegTurnDisallowed(GetTileRailType(gp.old_tile), GetTileRailType(gp.new_tile)) && prev == NULL) {
+				if (Rail90DegTurnDisallowed(GetTileRailType(gp.old_tile), GetTileRailType(gp.new_tile)) && prev == nullptr) {
 					/* We allow wagons to make 90 deg turns, because forbid_90_deg
 					 * can be switched on halfway a turn */
 					bits &= ~TrackCrossesTracks(FindFirstTrack(v->track));
@@ -3151,10 +3151,10 @@ bool TrainController(Train *v, Vehicle *
 				if (!CheckCompatibleRail(v, gp.new_tile)) goto invalid_rail;
 
 				TrackBits chosen_track;
-				if (prev == NULL) {
+				if (prev == nullptr) {
 					/* Currently the locomotive is active. Determine which one of the
 					 * available tracks to choose */
-					chosen_track = TrackToTrackBits(ChooseTrainTrack(v, gp.new_tile, enterdir, bits, false, NULL, true));
+					chosen_track = TrackToTrackBits(ChooseTrainTrack(v, gp.new_tile, enterdir, bits, false, nullptr, true));
 					assert(chosen_track & (bits | GetReservedTrackbits(gp.new_tile)));
 
 					if (v->force_proceed != TFP_NONE && IsPlainRailTile(gp.new_tile) && HasSignals(gp.new_tile)) {
@@ -3274,7 +3274,7 @@ bool TrainController(Train *v, Vehicle *
 					}
 
 					/* Clear any track reservation when the last vehicle leaves the tile */
-					if (v->Next() == NULL) ClearPathReservation(v, v->tile, v->GetVehicleTrackdir());
+					if (v->Next() == nullptr) ClearPathReservation(v, v->tile, v->GetVehicleTrackdir());
 
 					v->tile = gp.new_tile;
 
@@ -3291,7 +3291,7 @@ bool TrainController(Train *v, Vehicle *
 				update_signals_crossing = true;
 
 				if (chosen_dir != v->direction) {
-					if (prev == NULL && _settings_game.vehicle.train_acceleration_model == AM_ORIGINAL) {
+					if (prev == nullptr && _settings_game.vehicle.train_acceleration_model == AM_ORIGINAL) {
 						const AccelerationSlowdownParams *asp = &_accel_slowdown[GetRailTypeInfo(v->railtype)->acceleration_type];
 						DirDiff diff = DirDifference(v->direction, chosen_dir);
 						v->cur_speed -= (diff == DIRDIFF_45RIGHT || diff == DIRDIFF_45LEFT ? asp->small_turn : asp->large_turn) * v->cur_speed >> 8;
@@ -3347,7 +3347,7 @@ bool TrainController(Train *v, Vehicle *
 		/* update the Z position of the vehicle */
 		int old_z = v->UpdateInclination(gp.new_tile != gp.old_tile, false);
 
-		if (prev == NULL) {
+		if (prev == nullptr) {
 			/* This is the first vehicle in the train */
 			AffectSpeedByZChange(v, old_z);
 		}
@@ -3373,7 +3373,7 @@ bool TrainController(Train *v, Vehicle *
 
 			/* Signals can only change when the first
 			 * (above) or the last vehicle moves. */
-			if (v->Next() == NULL) {
+			if (v->Next() == nullptr) {
 				TrainMovedChangeSignals(gp.old_tile, ReverseDiagDir(enterdir));
 				if (IsLevelCrossingTile(gp.old_tile)) UpdateLevelCrossing(gp.old_tile);
 			}
@@ -3389,7 +3389,7 @@ bool TrainController(Train *v, Vehicle *
 
 invalid_rail:
 	/* We've reached end of line?? */
-	if (prev != NULL) error("Disconnecting train");
+	if (prev != nullptr) error("Disconnecting train");
 
 reverse_train_direction:
 	if (reverse) {
@@ -3406,7 +3406,7 @@ reverse_train_direction:
  * Collect trackbits of all crashed train vehicles on a tile
  * @param v Vehicle passed from Find/HasVehicleOnPos()
  * @param data trackdirbits for the result
- * @return NULL to iterate over all vehicles on the tile.
+ * @return nullptr to iterate over all vehicles on the tile.
  */
 static Vehicle *CollectTrackbitsFromCrashedVehiclesEnum(Vehicle *v, void *data)
 {
@@ -3422,7 +3422,7 @@ static Vehicle *CollectTrackbitsFromCras
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -3440,8 +3440,8 @@ static void DeleteLastWagon(Train *v)
 	 * *u is then the one-before-last wagon, and *v the last
 	 * one which will physically be removed */
 	Train *u = v;
-	for (; v->Next() != NULL; v = v->Next()) u = v;
-	u->SetNext(NULL);
+	for (; v->Next() != nullptr; v = v->Next()) u = v;
+	u->SetNext(nullptr);
 
 	if (first != v) {
 		/* Recalculate cached train properties */
@@ -3460,7 +3460,7 @@ static void DeleteLastWagon(Train *v)
 	Owner owner = v->owner;
 
 	delete v;
-	v = NULL; // make sure nobody will try to read 'v' anymore
+	v = nullptr; // make sure nobody will try to read 'v' anymore
 
 	if (trackbits == TRACK_BIT_WORMHOLE) {
 		/* Vehicle is inside a wormhole, v->track contains no useful value then. */
@@ -3516,7 +3516,7 @@ static void ChangeTrainDirRandomly(Train
 				v->UpdateViewport(false, true);
 			}
 		}
-	} while ((v = v->Next()) != NULL);
+	} while ((v = v->Next()) != nullptr);
 }
 
 /**
@@ -3548,13 +3548,13 @@ static bool HandleCrashedTrain(Train *v)
 					EV_EXPLOSION_SMALL);
 				break;
 			}
-		} while ((u = u->Next()) != NULL);
+		} while ((u = u->Next()) != nullptr);
 	}
 
 	if (state <= 240 && !(v->tick_counter & 3)) ChangeTrainDirRandomly(v);
 
 	if (state >= 4440 && !(v->tick_counter & 0x1F)) {
-		bool ret = v->Next() != NULL;
+		bool ret = v->Next() != nullptr;
 		DeleteLastWagon(v);
 		return ret;
 	}
@@ -3837,7 +3837,7 @@ static bool TrainLocoHandler(Train *v, b
 		/* Loop until the train has finished moving. */
 		for (;;) {
 			j -= adv_spd;
-			TrainController(v, NULL);
+			TrainController(v, nullptr);
 			/* Don't continue to move if the train crashed. */
 			if (CheckTrainCollision(v)) break;
 			/* Determine distance to next map position */
@@ -3858,7 +3858,7 @@ static bool TrainLocoHandler(Train *v, b
 		v->SetLastSpeed();
 	}
 
-	for (Train *u = v; u != NULL; u = u->Next()) {
+	for (Train *u = v; u != nullptr; u = u->Next()) {
 		if ((u->vehstatus & VS_HIDDEN) != 0) continue;
 
 		u->UpdateViewport(false, false);
@@ -3889,7 +3889,7 @@ Money Train::GetRunningCost() const
 		if (v->IsMultiheaded()) cost_factor /= 2;
 
 		cost += GetPrice(e->u.rail.running_cost_class, cost_factor, e->GetGRF());
-	} while ((v = v->GetNextVehicle()) != NULL);
+	} while ((v = v->GetNextVehicle()) != nullptr);
 
 	return cost;
 }
diff --git a/src/train_gui.cpp b/src/train_gui.cpp
--- a/src/train_gui.cpp
+++ b/src/train_gui.cpp
@@ -33,17 +33,17 @@ void CcBuildWagon(const CommandCost &res
 	if (result.Failed()) return;
 
 	/* find a locomotive in the depot. */
-	const Vehicle *found = NULL;
+	const Vehicle *found = nullptr;
 	const Train *t;
 	FOR_ALL_TRAINS(t) {
 		if (t->IsFrontEngine() && t->tile == tile && t->IsStoppedInDepot()) {
-			if (found != NULL) return; // must be exactly one.
+			if (found != nullptr) return; // must be exactly one.
 			found = t;
 		}
 	}
 
 	/* if we found a loco, */
-	if (found != NULL) {
+	if (found != nullptr) {
 		found = found->Last();
 		/* put the new wagon at the end of the loco. */
 		DoCommandP(0, _new_vehicle_id, found->index, CMD_MOVE_RAIL_VEHICLE);
@@ -65,8 +65,8 @@ static int HighlightDragPosition(int px,
 
 	assert(selection != INVALID_VEHICLE);
 	int dragged_width = 0;
-	for (Train *t = Train::Get(selection); t != NULL; t = chain ? t->Next() : (t->HasArticulatedPart() ? t->GetNextArticulatedPart() : NULL)) {
-		dragged_width += t->GetDisplayImageWidth(NULL);
+	for (Train *t = Train::Get(selection); t != nullptr; t = chain ? t->Next() : (t->HasArticulatedPart() ? t->GetNextArticulatedPart() : nullptr)) {
+		dragged_width += t->GetDisplayImageWidth(nullptr);
 	}
 
 	int drag_hlight_left = rtl ? max(px - dragged_width + 1, 0) : px;
@@ -112,7 +112,7 @@ void DrawTrainImage(const Train *v, int 
 	bool sel_articulated = false;
 	bool dragging = (drag_dest != INVALID_VEHICLE);
 	bool drag_at_end_of_train = (drag_dest == v->index); // Head index is used to mark dragging at end of train.
-	for (; v != NULL && (rtl ? px > 0 : px < max_width); v = v->Next()) {
+	for (; v != nullptr && (rtl ? px > 0 : px < max_width); v = v->Next()) {
 		if (dragging && !drag_at_end_of_train && drag_dest == v->index) {
 			/* Highlight the drag-and-drop destination inside the train. */
 			int drag_hlight_width = HighlightDragPosition(px, max_width, selection, _cursor.vehchain);
@@ -292,7 +292,7 @@ static void GetCargoSummaryOfArticulated
 		item->capacity += v->cargo_cap;
 		item->amount += v->cargo.StoredCount();
 		if (item->source == INVALID_STATION) item->source = v->cargo.Source();
-	} while ((v = v->Next()) != NULL && v->IsArticulatedPart());
+	} while ((v = v->Next()) != nullptr && v->IsArticulatedPart());
 }
 
 /**
@@ -306,7 +306,7 @@ static uint GetLengthOfArticulatedVehicl
 
 	do {
 		length += v->GetDisplayImageWidth();
-	} while ((v = v->Next()) != NULL && v->IsArticulatedPart());
+	} while ((v = v->Next()) != nullptr && v->IsArticulatedPart());
 
 	return length;
 }
@@ -324,7 +324,7 @@ int GetTrainDetailsWndVScroll(VehicleID 
 	if (det_tab == TDW_TAB_TOTALS) { // Total cargo tab
 		CargoArray act_cargo;
 		CargoArray max_cargo;
-		for (const Vehicle *v = Vehicle::Get(veh_id); v != NULL; v = v->Next()) {
+		for (const Vehicle *v = Vehicle::Get(veh_id); v != nullptr; v = v->Next()) {
 			act_cargo[v->cargo_type] += v->cargo.StoredCount();
 			max_cargo[v->cargo_type] += v->cargo_cap;
 		}
@@ -337,7 +337,7 @@ int GetTrainDetailsWndVScroll(VehicleID 
 		}
 		num++; // needs one more because first line is description string
 	} else {
-		for (const Train *v = Train::Get(veh_id); v != NULL; v = v->GetNextVehicle()) {
+		for (const Train *v = Train::Get(veh_id); v != nullptr; v = v->GetNextVehicle()) {
 			GetCargoSummaryOfArticulatedVehicle(v, &_cargo_summary);
 			num += max(1u, (unsigned)_cargo_summary.size());
 
@@ -375,7 +375,7 @@ void DrawTrainDetails(const Train *v, in
 		bool rtl = _current_text_dir == TD_RTL;
 		Direction dir = rtl ? DIR_E : DIR_W;
 		int x = rtl ? right : left;
-		for (; v != NULL && vscroll_pos > -vscroll_cap; v = v->GetNextVehicle()) {
+		for (; v != nullptr && vscroll_pos > -vscroll_cap; v = v->GetNextVehicle()) {
 			GetCargoSummaryOfArticulatedVehicle(v, &_cargo_summary);
 
 			/* Draw sprites */
@@ -388,7 +388,7 @@ void DrawTrainDetails(const Train *v, in
 				if (vscroll_pos <= 0 && vscroll_pos > -vscroll_cap) {
 					int pitch = 0;
 					const Engine *e = Engine::Get(v->engine_type);
-					if (e->GetGRF() != NULL) {
+					if (e->GetGRF() != nullptr) {
 						pitch = ScaleGUITrad(e->GetGRF()->traininfo_vehicle_pitch);
 					}
 					PaletteID pal = (v->vehstatus & VS_CRASHED) ? PALETTE_CRASH : GetVehiclePalette(v);
@@ -399,7 +399,7 @@ void DrawTrainDetails(const Train *v, in
 				px += rtl ? -width : width;
 				dx += width;
 				u = u->Next();
-			} while (u != NULL && u->IsArticulatedPart());
+			} while (u != nullptr && u->IsArticulatedPart());
 
 			bool separate_sprite_row = (dx > (uint)ScaleGUITrad(TRAIN_DETAILS_MAX_INDENT));
 			if (separate_sprite_row) {
@@ -450,7 +450,7 @@ void DrawTrainDetails(const Train *v, in
 		CargoArray max_cargo;
 		Money feeder_share = 0;
 
-		for (const Vehicle *u = v; u != NULL; u = u->Next()) {
+		for (const Vehicle *u = v; u != nullptr; u = u->Next()) {
 			act_cargo[u->cargo_type] += u->cargo.StoredCount();
 			max_cargo[u->cargo_type] += u->cargo_cap;
 			feeder_share             += u->cargo.FeederShare();
diff --git a/src/tree_cmd.cpp b/src/tree_cmd.cpp
--- a/src/tree_cmd.cpp
+++ b/src/tree_cmd.cpp
@@ -342,8 +342,8 @@ CommandCost CmdPlantTree(TileIndex tile,
 	/* Check the tree type within the current climate */
 	if (tree_to_plant != TREE_INVALID && !IsInsideBS(tree_to_plant, _tree_base_by_landscape[_settings_game.game_creation.landscape], _tree_count_by_landscape[_settings_game.game_creation.landscape])) return CMD_ERROR;
 
-	Company *c = (_game_mode != GM_EDITOR) ? Company::GetIfValid(_current_company) : NULL;
-	int limit = (c == NULL ? INT32_MAX : GB(c->tree_limit, 16, 16));
+	Company *c = (_game_mode != GM_EDITOR) ? Company::GetIfValid(_current_company) : nullptr;
+	int limit = (c == nullptr ? INT32_MAX : GB(c->tree_limit, 16, 16));
 
 	TileArea ta(tile, p2);
 	TILE_AREA_LOOP(tile, ta) {
@@ -364,7 +364,7 @@ CommandCost CmdPlantTree(TileIndex tile,
 				if (flags & DC_EXEC) {
 					AddTreeCount(tile, 1);
 					MarkTileDirtyByTile(tile);
-					if (c != NULL) c->tree_limit -= 1 << 16;
+					if (c != nullptr) c->tree_limit -= 1 << 16;
 				}
 				/* 2x as expensive to add more trees to an existing tile */
 				cost.AddCost(_price[PR_BUILD_TREES] * 2);
@@ -419,7 +419,7 @@ CommandCost CmdPlantTree(TileIndex tile,
 
 				if (_game_mode != GM_EDITOR && Company::IsValidID(_current_company)) {
 					Town *t = ClosestTownFromTile(tile, _settings_game.economy.dist_local_authority);
-					if (t != NULL) ChangeTownRating(t, RATING_TREE_UP_STEP, RATING_TREE_MAXIMUM, flags);
+					if (t != nullptr) ChangeTownRating(t, RATING_TREE_UP_STEP, RATING_TREE_MAXIMUM, flags);
 				}
 
 				if (flags & DC_EXEC) {
@@ -431,7 +431,7 @@ CommandCost CmdPlantTree(TileIndex tile,
 					/* Plant full grown trees in scenario editor */
 					PlantTreesOnTile(tile, treetype, 0, _game_mode == GM_EDITOR ? 3 : 0);
 					MarkTileDirtyByTile(tile);
-					if (c != NULL) c->tree_limit -= 1 << 16;
+					if (c != nullptr) c->tree_limit -= 1 << 16;
 
 					/* When planting rainforest-trees, set tropiczone to rainforest in editor. */
 					if (_game_mode == GM_EDITOR && IsInsideMM(treetype, TREE_RAINFOREST, TREE_CACTUS)) {
@@ -552,7 +552,7 @@ static CommandCost ClearTile_Trees(TileI
 
 	if (Company::IsValidID(_current_company)) {
 		Town *t = ClosestTownFromTile(tile, _settings_game.economy.dist_local_authority);
-		if (t != NULL) ChangeTownRating(t, RATING_TREE_DOWN_STEP, RATING_TREE_MINIMUM, flags);
+		if (t != nullptr) ChangeTownRating(t, RATING_TREE_DOWN_STEP, RATING_TREE_MINIMUM, flags);
 	}
 
 	num = GetTreeCount(tile);
@@ -803,15 +803,15 @@ extern const TileTypeProcs _tile_type_tr
 	DrawTile_Trees,           // draw_tile_proc
 	GetSlopePixelZ_Trees,     // get_slope_z_proc
 	ClearTile_Trees,          // clear_tile_proc
-	NULL,                     // add_accepted_cargo_proc
+	nullptr,                     // add_accepted_cargo_proc
 	GetTileDesc_Trees,        // get_tile_desc_proc
 	GetTileTrackStatus_Trees, // get_tile_track_status_proc
-	NULL,                     // click_tile_proc
-	NULL,                     // animate_tile_proc
+	nullptr,                     // click_tile_proc
+	nullptr,                     // animate_tile_proc
 	TileLoop_Trees,           // tile_loop_proc
 	ChangeTileOwner_Trees,    // change_tile_owner_proc
-	NULL,                     // add_produced_cargo_proc
-	NULL,                     // vehicle_enter_tile_proc
+	nullptr,                     // add_produced_cargo_proc
+	nullptr,                     // vehicle_enter_tile_proc
 	GetFoundation_Trees,      // get_foundation_proc
 	TerraformTile_Trees,      // terraform_tile_proc
 };
diff --git a/src/tunnelbridge_cmd.cpp b/src/tunnelbridge_cmd.cpp
--- a/src/tunnelbridge_cmd.cpp
+++ b/src/tunnelbridge_cmd.cpp
@@ -84,7 +84,7 @@ void ResetBridges()
 {
 	/* First, free sprite table data */
 	for (BridgeType i = 0; i < MAX_BRIDGES; i++) {
-		if (_bridge[i].sprite_table != NULL) {
+		if (_bridge[i].sprite_table != nullptr) {
 			for (BridgePieces j = BRIDGE_PIECE_NORTH; j < BRIDGE_PIECE_INVALID; j++) free(_bridge[i].sprite_table[j]);
 			free(_bridge[i].sprite_table);
 		}
@@ -150,7 +150,7 @@ static inline const PalSpriteID *GetBrid
 {
 	const BridgeSpec *bridge = GetBridgeSpec(index);
 	assert(table < BRIDGE_PIECE_INVALID);
-	if (bridge->sprite_table == NULL || bridge->sprite_table[table] == NULL) {
+	if (bridge->sprite_table == nullptr || bridge->sprite_table[table] == nullptr) {
 		return _bridge_sprite_table[index][table];
 	} else {
 		return bridge->sprite_table[table];
@@ -268,7 +268,7 @@ CommandCost CmdBuildBridge(TileIndex end
 		company = OWNER_TOWN;
 
 		/* If we are not within a town, we are not owned by the town */
-		if (town == NULL || DistanceSquare(tile_start, town->xy) > town->cache.squared_town_zone_radius[HZB_TOWN_EDGE]) {
+		if (town == nullptr || DistanceSquare(tile_start, town->xy) > town->cache.squared_town_zone_radius[HZB_TOWN_EDGE]) {
 			company = OWNER_NONE;
 		}
 	}
@@ -329,7 +329,7 @@ CommandCost CmdBuildBridge(TileIndex end
 				_game_mode != GM_EDITOR) {
 			Town *t = ClosestTownFromTile(tile_start, UINT_MAX);
 
-			if (t == NULL) {
+			if (t == nullptr) {
 				return CMD_ERROR;
 			} else {
 				SetDParam(0, t->index);
@@ -479,7 +479,7 @@ CommandCost CmdBuildBridge(TileIndex end
 		switch (transport_type) {
 			case TRANSPORT_RAIL:
 				/* Add to company infrastructure count if required. */
-				if (is_new_owner && c != NULL) c->infrastructure.rail[railtype] += (bridge_len + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;
+				if (is_new_owner && c != nullptr) c->infrastructure.rail[railtype] += (bridge_len + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;
 				MakeRailBridgeRamp(tile_start, owner, bridge_type, dir,                 railtype);
 				MakeRailBridgeRamp(tile_end,   owner, bridge_type, ReverseDiagDir(dir), railtype);
 				SetTunnelBridgeReservation(tile_start, pbs_reservation);
@@ -493,7 +493,7 @@ CommandCost CmdBuildBridge(TileIndex end
 					if (HasBit(prev_roadtypes, ROADTYPE_ROAD) && GetRoadOwner(tile_start, ROADTYPE_ROAD) == OWNER_NONE) ClrBit(prev_roadtypes, ROADTYPE_ROAD);
 					if (HasBit(prev_roadtypes, ROADTYPE_TRAM) && GetRoadOwner(tile_start, ROADTYPE_TRAM) == OWNER_NONE) ClrBit(prev_roadtypes, ROADTYPE_TRAM);
 				}
-				if (c != NULL) {
+				if (c != nullptr) {
 					/* Add all new road types to the company infrastructure counter. */
 					RoadType new_rt;
 					FOR_EACH_SET_ROADTYPE(new_rt, roadtypes ^ prev_roadtypes) {
@@ -509,7 +509,7 @@ CommandCost CmdBuildBridge(TileIndex end
 			}
 
 			case TRANSPORT_WATER:
-				if (is_new_owner && c != NULL) c->infrastructure.water += (bridge_len + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;
+				if (is_new_owner && c != nullptr) c->infrastructure.water += (bridge_len + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;
 				MakeAqueductBridgeRamp(tile_start, owner, dir);
 				MakeAqueductBridgeRamp(tile_end,   owner, ReverseDiagDir(dir));
 				break;
@@ -534,7 +534,7 @@ CommandCost CmdBuildBridge(TileIndex end
 	 * and cost is computed in "bridge_gui.c". For AI, Towns this has to be of course calculated
 	 */
 	Company *c = Company::GetIfValid(company);
-	if (!(flags & DC_QUERY_COST) || (c != NULL && c->is_ai)) {
+	if (!(flags & DC_QUERY_COST) || (c != nullptr && c->is_ai)) {
 		bridge_len += 2; // begin and end tiles/ramps
 
 		switch (transport_type) {
@@ -543,7 +543,7 @@ CommandCost CmdBuildBridge(TileIndex end
 			default: break;
 		}
 
-		if (c != NULL) bridge_len = CalcBridgeLenCostFactor(bridge_len);
+		if (c != nullptr) bridge_len = CalcBridgeLenCostFactor(bridge_len);
 
 		if (transport_type != TRANSPORT_WATER) {
 			cost.AddCost((int64)bridge_len * _price[PR_BUILD_BRIDGE] * GetBridgeSpec(bridge_type)->price >> 8);
@@ -598,7 +598,7 @@ CommandCost CmdBuildTunnel(TileIndex sta
 		company = OWNER_TOWN;
 
 		/* If we are not within a town, we are not owned by the town */
-		if (town == NULL || DistanceSquare(start_tile, town->xy) > town->cache.squared_town_zone_radius[HZB_TOWN_EDGE]) {
+		if (town == nullptr || DistanceSquare(start_tile, town->xy) > town->cache.squared_town_zone_radius[HZB_TOWN_EDGE]) {
 			company = OWNER_NONE;
 		}
 	}
@@ -680,7 +680,7 @@ CommandCost CmdBuildTunnel(TileIndex sta
 		/* Mark the tile as already cleared for the terraform command.
 		 * Do this for all tiles (like trees), not only objects. */
 		ClearedObjectArea *coa = FindClearedObject(end_tile);
-		if (coa == NULL) {
+		if (coa == nullptr) {
 			/*C++17: coa = &*/ _cleared_object_areas.push_back({end_tile, TileArea(end_tile, 1, 1)});
 			coa = &_cleared_object_areas.back();
 		}
@@ -702,7 +702,7 @@ CommandCost CmdBuildTunnel(TileIndex sta
 		assert(coa >= begin && coa < begin + _cleared_object_areas.size());
 		size_t coa_index = coa - begin;
 		assert(coa_index < UINT_MAX); // more than 2**32 cleared areas would be a bug in itself
-		coa = NULL;
+		coa = nullptr;
 
 		ret = DoCommand(end_tile, end_tileh & start_tileh, 0, flags, CMD_TERRAFORM_LAND);
 		_cleared_object_areas[(uint)coa_index].first_tile = old_first_tile;
@@ -722,13 +722,13 @@ CommandCost CmdBuildTunnel(TileIndex sta
 		Company *c = Company::GetIfValid(company);
 		uint num_pieces = (tiles + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;
 		if (transport_type == TRANSPORT_RAIL) {
-			if (!IsTunnelTile(start_tile) && c != NULL) c->infrastructure.rail[railtype] += num_pieces;
+			if (!IsTunnelTile(start_tile) && c != nullptr) c->infrastructure.rail[railtype] += num_pieces;
 			MakeRailTunnel(start_tile, company, direction,                 railtype);
 			MakeRailTunnel(end_tile,   company, ReverseDiagDir(direction), railtype);
 			AddSideToSignalBuffer(start_tile, INVALID_DIAGDIR, company);
 			YapfNotifyTrackLayoutChange(start_tile, DiagDirToDiagTrack(direction));
 		} else {
-			if (c != NULL) {
+			if (c != nullptr) {
 				RoadType rt;
 				FOR_EACH_SET_ROADTYPE(rt, rts ^ (IsTunnelTile(start_tile) ? GetRoadTypes(start_tile) : ROADTYPES_NONE)) {
 					c->infrastructure.road[rt] += num_pieces * 2; // A full diagonal road has two road bits.
@@ -808,7 +808,7 @@ static CommandCost DoClearTunnel(TileInd
 
 	_build_tunnel_endtile = endtile;
 
-	Town *t = NULL;
+	Town *t = nullptr;
 	if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
 		t = ClosestTownFromTile(tile, UINT_MAX); // town penalty rating
 
@@ -833,10 +833,10 @@ static CommandCost DoClearTunnel(TileInd
 			Track track = DiagDirToDiagTrack(dir);
 			Owner owner = GetTileOwner(tile);
 
-			Train *v = NULL;
+			Train *v = nullptr;
 			if (HasTunnelBridgeReservation(tile)) {
 				v = GetTrainForReservation(tile, track);
-				if (v != NULL) FreeTrainTrackReservation(v);
+				if (v != nullptr) FreeTrainTrackReservation(v);
 			}
 
 			if (Company::IsValidID(owner)) {
@@ -854,13 +854,13 @@ static CommandCost DoClearTunnel(TileInd
 			YapfNotifyTrackLayoutChange(tile,    track);
 			YapfNotifyTrackLayoutChange(endtile, track);
 
-			if (v != NULL) TryPathReserve(v);
+			if (v != nullptr) TryPathReserve(v);
 		} else {
 			RoadType rt;
 			FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
 				/* A full diagonal road tile has two road bits. */
 				Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
-				if (c != NULL) {
+				if (c != nullptr) {
 					c->infrastructure.road[rt] -= len * 2 * TUNNELBRIDGE_TRACKBIT_FACTOR;
 					DirtyCompanyInfrastructureWindows(c->index);
 				}
@@ -893,7 +893,7 @@ static CommandCost DoClearBridge(TileInd
 	DiagDirection direction = GetTunnelBridgeDirection(tile);
 	TileIndexDiff delta = TileOffsByDiagDir(direction);
 
-	Town *t = NULL;
+	Town *t = nullptr;
 	if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
 		t = ClosestTownFromTile(tile, UINT_MAX); // town penalty rating
 
@@ -917,11 +917,11 @@ static CommandCost DoClearBridge(TileInd
 		bool rail = GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL;
 		Owner owner = GetTileOwner(tile);
 		int height = GetBridgeHeight(tile);
-		Train *v = NULL;
+		Train *v = nullptr;
 
 		if (rail && HasTunnelBridgeReservation(tile)) {
 			v = GetTrainForReservation(tile, DiagDirToDiagTrack(direction));
-			if (v != NULL) FreeTrainTrackReservation(v);
+			if (v != nullptr) FreeTrainTrackReservation(v);
 		}
 
 		/* Update company infrastructure counts. */
@@ -931,7 +931,7 @@ static CommandCost DoClearBridge(TileInd
 			RoadType rt;
 			FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
 				Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
-				if (c != NULL) {
+				if (c != nullptr) {
 					/* A full diagonal road tile has two road bits. */
 					c->infrastructure.road[rt] -= len * 2 * TUNNELBRIDGE_TRACKBIT_FACTOR;
 					DirtyCompanyInfrastructureWindows(c->index);
@@ -963,7 +963,7 @@ static CommandCost DoClearBridge(TileInd
 			YapfNotifyTrackLayoutChange(tile,    track);
 			YapfNotifyTrackLayoutChange(endtile, track);
 
-			if (v != NULL) TryPathReserve(v, true);
+			if (v != nullptr) TryPathReserve(v, true);
 		}
 	}
 
@@ -1018,7 +1018,7 @@ static int DrawPillarColumn(int z_bottom
 {
 	int cur_z;
 	for (cur_z = z_top; cur_z >= z_bottom; cur_z -= TILE_HEIGHT) {
-		DrawPillar(psid, x, y, cur_z, w, h, NULL);
+		DrawPillar(psid, x, y, cur_z, w, h, nullptr);
 	}
 	return cur_z;
 }
@@ -1906,14 +1906,14 @@ extern const TileTypeProcs _tile_type_tu
 	DrawTile_TunnelBridge,           // draw_tile_proc
 	GetSlopePixelZ_TunnelBridge,     // get_slope_z_proc
 	ClearTile_TunnelBridge,          // clear_tile_proc
-	NULL,                            // add_accepted_cargo_proc
+	nullptr,                            // add_accepted_cargo_proc
 	GetTileDesc_TunnelBridge,        // get_tile_desc_proc
 	GetTileTrackStatus_TunnelBridge, // get_tile_track_status_proc
-	NULL,                            // click_tile_proc
-	NULL,                            // animate_tile_proc
+	nullptr,                            // click_tile_proc
+	nullptr,                            // animate_tile_proc
 	TileLoop_TunnelBridge,           // tile_loop_proc
 	ChangeTileOwner_TunnelBridge,    // change_tile_owner_proc
-	NULL,                            // add_produced_cargo_proc
+	nullptr,                            // add_produced_cargo_proc
 	VehicleEnter_TunnelBridge,       // vehicle_enter_tile_proc
 	GetFoundation_TunnelBridge,      // get_foundation_proc
 	TerraformTile_TunnelBridge,      // terraform_tile_proc
diff --git a/src/vehicle.cpp b/src/vehicle.cpp
--- a/src/vehicle.cpp
+++ b/src/vehicle.cpp
@@ -163,7 +163,7 @@ bool Vehicle::NeedsAutorenewing(const Co
  */
 void VehicleServiceInDepot(Vehicle *v)
 {
-	assert(v != NULL);
+	assert(v != nullptr);
 	SetWindowDirty(WC_VEHICLE_DETAILS, v->index); // ensure that last service date and reliability are updated
 
 	do {
@@ -173,7 +173,7 @@ void VehicleServiceInDepot(Vehicle *v)
 		/* Prevent vehicles from breaking down directly after exiting the depot. */
 		v->breakdown_chance /= 4;
 		v = v->Next();
-	} while (v != NULL && v->HasEngineType());
+	} while (v != nullptr && v->HasEngineType());
 }
 
 /**
@@ -210,7 +210,7 @@ bool Vehicle::NeedsServicing() const
 	Money needed_money = c->settings.engine_renew_money;
 	if (needed_money > c->money) return false;
 
-	for (const Vehicle *v = this; v != NULL; v = (v->type == VEH_TRAIN) ? Train::From(v)->GetNextUnit() : NULL) {
+	for (const Vehicle *v = this; v != nullptr; v = (v->type == VEH_TRAIN) ? Train::From(v)->GetNextUnit() : nullptr) {
 		bool replace_when_old = false;
 		EngineID new_engine = EngineReplacementForCompany(c, v->engine_type, v->group_id, &replace_when_old);
 
@@ -261,13 +261,13 @@ bool Vehicle::NeedsAutomaticServicing() 
 uint Vehicle::Crash(bool flooded)
 {
 	assert((this->vehstatus & VS_CRASHED) == 0);
-	assert(this->Previous() == NULL); // IsPrimaryVehicle fails for free-wagon-chains
+	assert(this->Previous() == nullptr); // IsPrimaryVehicle fails for free-wagon-chains
 
 	uint pass = 0;
 	/* Stop the vehicle. */
 	if (this->IsPrimaryVehicle()) this->vehstatus |= VS_STOPPED;
 	/* crash all wagons, and count passengers */
-	for (Vehicle *v = this; v != NULL; v = v->Next()) {
+	for (Vehicle *v = this; v != nullptr; v = v->Next()) {
 		/* We do not transfer reserver cargo back, so TotalCount() instead of StoredCount() */
 		if (IsCargoInClass(v->cargo_type, CC_PASSENGERS)) pass += v->cargo.TotalCount();
 		v->vehstatus |= VS_CRASHED;
@@ -281,7 +281,7 @@ uint Vehicle::Crash(bool flooded)
 	SetWindowDirty(WC_VEHICLE_DEPOT, this->tile);
 
 	delete this->cargo_payment;
-	assert(this->cargo_payment == NULL); // cleared by ~CargoPayment
+	assert(this->cargo_payment == nullptr); // cleared by ~CargoPayment
 
 	return RandomRange(pass + 1); // Randomise deceased passengers.
 }
@@ -301,7 +301,7 @@ void ShowNewGrfVehicleError(EngineID eng
 	GRFConfig *grfconfig = GetGRFConfig(e->GetGRFID());
 
 	/* Missing GRF. Nothing useful can be done in this situation. */
-	if (grfconfig == NULL) return;
+	if (grfconfig == nullptr) return;
 
 	if (!HasBit(grfconfig->grf_bugs, bug_type)) {
 		SetBit(grfconfig->grf_bugs, bug_type);
@@ -384,16 +384,16 @@ static Vehicle *VehicleFromTileHash(int 
 	for (int y = yl; ; y = (y + (1 << HASH_BITS)) & (HASH_MASK << HASH_BITS)) {
 		for (int x = xl; ; x = (x + 1) & HASH_MASK) {
 			Vehicle *v = _vehicle_tile_hash[(x + y) & TOTAL_HASH_MASK];
-			for (; v != NULL; v = v->hash_tile_next) {
+			for (; v != nullptr; v = v->hash_tile_next) {
 				Vehicle *a = proc(v, data);
-				if (find_first && a != NULL) return a;
+				if (find_first && a != nullptr) return a;
 			}
 			if (x == xu) break;
 		}
 		if (y == yu) break;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 
@@ -442,18 +442,18 @@ void FindVehicleOnPosXY(int x, int y, vo
 
 /**
  * Checks whether a vehicle in on a specific location. It will call proc for
- * vehicles until it returns non-NULL.
+ * vehicles until it returns non-nullptr.
  * @note Use FindVehicleOnPosXY when you have the intention that all vehicles
  *       should be iterated over.
  * @param x    The X location on the map
  * @param y    The Y location on the map
  * @param data Arbitrary data passed to proc
  * @param proc The proc that determines whether a vehicle will be "found".
- * @return True if proc returned non-NULL.
+ * @return True if proc returned non-nullptr.
  */
 bool HasVehicleOnPosXY(int x, int y, void *data, VehicleFromPosProc *proc)
 {
-	return VehicleFromPosXY(x, y, data, proc, true) != NULL;
+	return VehicleFromPosXY(x, y, data, proc, true) != nullptr;
 }
 
 /**
@@ -472,14 +472,14 @@ static Vehicle *VehicleFromPos(TileIndex
 	int y = GB(TileY(tile), HASH_RES, HASH_BITS) << HASH_BITS;
 
 	Vehicle *v = _vehicle_tile_hash[(x + y) & TOTAL_HASH_MASK];
-	for (; v != NULL; v = v->hash_tile_next) {
+	for (; v != nullptr; v = v->hash_tile_next) {
 		if (v->tile != tile) continue;
 
 		Vehicle *a = proc(v, data);
-		if (find_first && a != NULL) return a;
+		if (find_first && a != nullptr) return a;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -502,31 +502,31 @@ void FindVehicleOnPos(TileIndex tile, vo
 
 /**
  * Checks whether a vehicle is on a specific location. It will call \a proc for
- * vehicles until it returns non-NULL.
+ * vehicles until it returns non-nullptr.
  * @note Use #FindVehicleOnPos when you have the intention that all vehicles
  *       should be iterated over.
  * @param tile The location on the map
  * @param data Arbitrary data passed to \a proc.
  * @param proc The \a proc that determines whether a vehicle will be "found".
- * @return True if proc returned non-NULL.
+ * @return True if proc returned non-nullptr.
  */
 bool HasVehicleOnPos(TileIndex tile, void *data, VehicleFromPosProc *proc)
 {
-	return VehicleFromPos(tile, data, proc, true) != NULL;
+	return VehicleFromPos(tile, data, proc, true) != nullptr;
 }
 
 /**
  * Callback that returns 'real' vehicles lower or at height \c *(int*)data .
  * @param v Vehicle to examine.
  * @param data Pointer to height data.
- * @return \a v if conditions are met, else \c NULL.
+ * @return \a v if conditions are met, else \c nullptr.
  */
 static Vehicle *EnsureNoVehicleProcZ(Vehicle *v, void *data)
 {
 	int z = *(int*)data;
 
-	if (v->type == VEH_DISASTER || (v->type == VEH_AIRCRAFT && v->subtype == AIR_SHADOW)) return NULL;
-	if (v->z_pos > z) return NULL;
+	if (v->type == VEH_DISASTER || (v->type == VEH_AIRCRAFT && v->subtype == AIR_SHADOW)) return nullptr;
+	if (v->z_pos > z) return nullptr;
 
 	return v;
 }
@@ -545,15 +545,15 @@ CommandCost EnsureNoVehicleOnGround(Tile
 	 * Such a message does not affect MP synchronisation.
 	 */
 	Vehicle *v = VehicleFromPos(tile, &z, &EnsureNoVehicleProcZ, true);
-	if (v != NULL) return_cmd_error(STR_ERROR_TRAIN_IN_THE_WAY + v->type);
+	if (v != nullptr) return_cmd_error(STR_ERROR_TRAIN_IN_THE_WAY + v->type);
 	return CommandCost();
 }
 
 /** Procedure called for every vehicle found in tunnel/bridge in the hash map */
 static Vehicle *GetVehicleTunnelBridgeProc(Vehicle *v, void *data)
 {
-	if (v->type != VEH_TRAIN && v->type != VEH_ROAD && v->type != VEH_SHIP) return NULL;
-	if (v == (const Vehicle *)data) return NULL;
+	if (v->type != VEH_TRAIN && v->type != VEH_ROAD && v->type != VEH_SHIP) return nullptr;
+	if (v == (const Vehicle *)data) return nullptr;
 
 	return v;
 }
@@ -572,9 +572,9 @@ CommandCost TunnelBridgeIsFree(TileIndex
 	 * Such a message does not affect MP synchronisation.
 	 */
 	Vehicle *v = VehicleFromPos(tile, const_cast<Vehicle *>(ignore), &GetVehicleTunnelBridgeProc, true);
-	if (v == NULL) v = VehicleFromPos(endtile, const_cast<Vehicle *>(ignore), &GetVehicleTunnelBridgeProc, true);
-
-	if (v != NULL) return_cmd_error(STR_ERROR_TRAIN_IN_THE_WAY + v->type);
+	if (v == nullptr) v = VehicleFromPos(endtile, const_cast<Vehicle *>(ignore), &GetVehicleTunnelBridgeProc, true);
+
+	if (v != nullptr) return_cmd_error(STR_ERROR_TRAIN_IN_THE_WAY + v->type);
 	return CommandCost();
 }
 
@@ -582,10 +582,10 @@ static Vehicle *EnsureNoTrainOnTrackProc
 {
 	TrackBits rail_bits = *(TrackBits *)data;
 
-	if (v->type != VEH_TRAIN) return NULL;
+	if (v->type != VEH_TRAIN) return nullptr;
 
 	Train *t = Train::From(v);
-	if ((t->track != rail_bits) && !TracksOverlap(t->track | rail_bits)) return NULL;
+	if ((t->track != rail_bits) && !TracksOverlap(t->track | rail_bits)) return nullptr;
 
 	return v;
 }
@@ -605,7 +605,7 @@ CommandCost EnsureNoTrainOnTrackBits(Til
 	 * Such a message does not affect MP synchronisation.
 	 */
 	Vehicle *v = VehicleFromPos(tile, &track_bits, &EnsureNoTrainOnTrackProc, true);
-	if (v != NULL) return_cmd_error(STR_ERROR_TRAIN_IN_THE_WAY + v->type);
+	if (v != nullptr) return_cmd_error(STR_ERROR_TRAIN_IN_THE_WAY + v->type);
 	return CommandCost();
 }
 
@@ -615,7 +615,7 @@ static void UpdateVehicleTileHash(Vehicl
 	Vehicle **new_hash;
 
 	if (remove) {
-		new_hash = NULL;
+		new_hash = nullptr;
 	} else {
 		int x = GB(TileX(v->tile), HASH_RES, HASH_BITS);
 		int y = GB(TileY(v->tile), HASH_RES, HASH_BITS) << HASH_BITS;
@@ -625,15 +625,15 @@ static void UpdateVehicleTileHash(Vehicl
 	if (old_hash == new_hash) return;
 
 	/* Remove from the old position in the hash table */
-	if (old_hash != NULL) {
-		if (v->hash_tile_next != NULL) v->hash_tile_next->hash_tile_prev = v->hash_tile_prev;
+	if (old_hash != nullptr) {
+		if (v->hash_tile_next != nullptr) v->hash_tile_next->hash_tile_prev = v->hash_tile_prev;
 		*v->hash_tile_prev = v->hash_tile_next;
 	}
 
 	/* Insert vehicle at beginning of the new position in the hash table */
-	if (new_hash != NULL) {
+	if (new_hash != nullptr) {
 		v->hash_tile_next = *new_hash;
-		if (v->hash_tile_next != NULL) v->hash_tile_next->hash_tile_prev = &v->hash_tile_next;
+		if (v->hash_tile_next != nullptr) v->hash_tile_next->hash_tile_prev = &v->hash_tile_next;
 		v->hash_tile_prev = new_hash;
 		*new_hash = v;
 	}
@@ -650,21 +650,21 @@ static void UpdateVehicleViewportHash(Ve
 	int old_x = v->coord.left;
 	int old_y = v->coord.top;
 
-	new_hash = (x == INVALID_COORD) ? NULL : &_vehicle_viewport_hash[GEN_HASH(x, y)];
-	old_hash = (old_x == INVALID_COORD) ? NULL : &_vehicle_viewport_hash[GEN_HASH(old_x, old_y)];
+	new_hash = (x == INVALID_COORD) ? nullptr : &_vehicle_viewport_hash[GEN_HASH(x, y)];
+	old_hash = (old_x == INVALID_COORD) ? nullptr : &_vehicle_viewport_hash[GEN_HASH(old_x, old_y)];
 
 	if (old_hash == new_hash) return;
 
 	/* remove from hash table? */
-	if (old_hash != NULL) {
-		if (v->hash_viewport_next != NULL) v->hash_viewport_next->hash_viewport_prev = v->hash_viewport_prev;
+	if (old_hash != nullptr) {
+		if (v->hash_viewport_next != nullptr) v->hash_viewport_next->hash_viewport_prev = v->hash_viewport_prev;
 		*v->hash_viewport_prev = v->hash_viewport_next;
 	}
 
 	/* insert into hash table? */
-	if (new_hash != NULL) {
+	if (new_hash != nullptr) {
 		v->hash_viewport_next = *new_hash;
-		if (v->hash_viewport_next != NULL) v->hash_viewport_next->hash_viewport_prev = &v->hash_viewport_next;
+		if (v->hash_viewport_next != nullptr) v->hash_viewport_next->hash_viewport_prev = &v->hash_viewport_next;
 		v->hash_viewport_prev = new_hash;
 		*new_hash = v;
 	}
@@ -673,7 +673,7 @@ static void UpdateVehicleViewportHash(Ve
 void ResetVehicleHash()
 {
 	Vehicle *v;
-	FOR_ALL_VEHICLES(v) { v->hash_tile_current = NULL; }
+	FOR_ALL_VEHICLES(v) { v->hash_tile_current = nullptr; }
 	memset(_vehicle_viewport_hash, 0, sizeof(_vehicle_viewport_hash));
 	memset(_vehicle_tile_hash, 0, sizeof(_vehicle_tile_hash));
 }
@@ -701,7 +701,7 @@ void InitializeVehicles()
 uint CountVehiclesInChain(const Vehicle *v)
 {
 	uint count = 0;
-	do count++; while ((v = v->Next()) != NULL);
+	do count++; while ((v = v->Next()) != nullptr);
 	return count;
 }
 
@@ -812,7 +812,7 @@ void Vehicle::PreDestructor()
 		HideFillingPercent(&this->fill_percent_te_id);
 		this->CancelReservation(INVALID_STATION, st);
 		delete this->cargo_payment;
-		assert(this->cargo_payment == NULL); // cleared by ~CargoPayment
+		assert(this->cargo_payment == nullptr); // cleared by ~CargoPayment
 	}
 
 	if (this->IsEngineCountable()) {
@@ -827,7 +827,7 @@ void Vehicle::PreDestructor()
 	if (this->type == VEH_AIRCRAFT && this->IsPrimaryVehicle()) {
 		Aircraft *a = Aircraft::From(this);
 		Station *st = GetTargetAirportIfValid(a);
-		if (st != NULL) {
+		if (st != nullptr) {
 			const AirportFTA *layout = st->airport.GetFTA()->layout;
 			CLRBITS(st->airport.flags, layout[a->previous_pos].block | layout[a->pos].block);
 		}
@@ -842,7 +842,7 @@ void Vehicle::PreDestructor()
 		}
 	}
 
-	if (this->Previous() == NULL) {
+	if (this->Previous() == nullptr) {
 		InvalidateWindowData(WC_VEHICLE_DEPOT, this->tile);
 	}
 
@@ -879,7 +879,7 @@ Vehicle::~Vehicle()
 	if (!(this->vehstatus & VS_HIDDEN)) this->MarkAllViewportsDirty();
 
 	Vehicle *v = this->Next();
-	this->SetNext(NULL);
+	this->SetNext(nullptr);
 
 	delete v;
 
@@ -918,7 +918,7 @@ static void RunVehicleDayProc()
 	/* Run the day_proc for every DAY_TICKS vehicle starting at _date_fract. */
 	for (size_t i = _date_fract; i < Vehicle::GetPoolSize(); i += DAY_TICKS) {
 		Vehicle *v = Vehicle::Get(i);
-		if (v == NULL) continue;
+		if (v == nullptr) continue;
 
 		/* Call the 32-day callback if needed */
 		if ((v->day_counter & 0x1F) == 0 && v->HasEngineType()) {
@@ -961,7 +961,7 @@ void CallVehicleTicks()
 	FOR_ALL_VEHICLES(v) {
 		/* Vehicle could be deleted in this tick */
 		if (!v->Tick()) {
-			assert(Vehicle::Get(vehicle_index) == NULL);
+			assert(Vehicle::Get(vehicle_index) == nullptr);
 			continue;
 		}
 
@@ -1142,7 +1142,7 @@ void ViewportAddVehicles(DrawPixelInfo *
 		for (int x = xl;; x = (x + GEN_HASHX_INC) & GEN_HASHX_MASK) {
 			const Vehicle *v = _vehicle_viewport_hash[x + y]; // already masked & 0xFFF
 
-			while (v != NULL) {
+			while (v != nullptr) {
 				if (!(v->vehstatus & VS_HIDDEN) &&
 						l <= v->coord.right &&
 						t <= v->coord.bottom &&
@@ -1165,14 +1165,14 @@ void ViewportAddVehicles(DrawPixelInfo *
  * @param vp Viewport clicked in.
  * @param x  X coordinate in the viewport.
  * @param y  Y coordinate in the viewport.
- * @return Closest vehicle, or \c NULL if none found.
+ * @return Closest vehicle, or \c nullptr if none found.
  */
 Vehicle *CheckClickOnVehicle(const ViewPort *vp, int x, int y)
 {
-	Vehicle *found = NULL, *v;
+	Vehicle *found = nullptr, *v;
 	uint dist, best_dist = UINT_MAX;
 
-	if ((uint)(x -= vp->left) >= (uint)vp->width || (uint)(y -= vp->top) >= (uint)vp->height) return NULL;
+	if ((uint)(x -= vp->left) >= (uint)vp->width || (uint)(y -= vp->top) >= (uint)vp->height) return nullptr;
 
 	x = ScaleByZoom(x, vp->zoom) + vp->virtual_left;
 	y = ScaleByZoom(y, vp->zoom) + vp->virtual_top;
@@ -1296,7 +1296,7 @@ bool Vehicle::HandleBreakdown()
 
 				if (!(this->vehstatus & VS_HIDDEN) && !HasBit(EngInfo(this->engine_type)->misc_flags, EF_NO_BREAKDOWN_SMOKE)) {
 					EffectVehicle *u = CreateEffectVehicleRel(this, 4, 4, 5, EV_BREAKDOWN_SMOKE);
-					if (u != NULL) u->animation_state = this->breakdown_delay * 2;
+					if (u != nullptr) u->animation_state = this->breakdown_delay * 2;
 				}
 			}
 
@@ -1347,7 +1347,7 @@ void AgeVehicle(Vehicle *v)
 	SetWindowDirty(WC_VEHICLE_DETAILS, v->index);
 
 	/* Don't warn about non-primary or not ours vehicles or vehicles that are crashed */
-	if (v->Previous() != NULL || v->owner != _local_company || (v->vehstatus & VS_CRASHED) != 0) return;
+	if (v->Previous() != nullptr || v->owner != _local_company || (v->vehstatus & VS_CRASHED) != 0) return;
 
 	const Company *c = Company::Get(v->owner);
 	/* Don't warn if a renew is active */
@@ -1389,18 +1389,18 @@ uint8 CalcPercentVehicleFilled(const Veh
 
 	bool is_loading = front->current_order.IsType(OT_LOADING);
 
-	/* The station may be NULL when the (colour) string does not need to be set. */
+	/* The station may be nullptr when the (colour) string does not need to be set. */
 	const Station *st = Station::GetIfValid(front->last_station_visited);
-	assert(colour == NULL || (st != NULL && is_loading));
+	assert(colour == nullptr || (st != nullptr && is_loading));
 
 	bool order_no_load = is_loading && (front->current_order.GetLoadType() & OLFB_NO_LOAD);
 	bool order_full_load = is_loading && (front->current_order.GetLoadType() & OLFB_FULL_LOAD);
 
 	/* Count up max and used */
-	for (const Vehicle *v = front; v != NULL; v = v->Next()) {
+	for (const Vehicle *v = front; v != nullptr; v = v->Next()) {
 		count += v->cargo.StoredCount();
 		max += v->cargo_cap;
-		if (v->cargo_cap != 0 && colour != NULL) {
+		if (v->cargo_cap != 0 && colour != nullptr) {
 			unloading += HasBit(v->vehicle_flags, VF_CARGO_UNLOADING) ? 1 : 0;
 			loading |= !order_no_load &&
 					(order_full_load || st->goods[v->cargo_type].HasRating()) &&
@@ -1409,7 +1409,7 @@ uint8 CalcPercentVehicleFilled(const Veh
 		}
 	}
 
-	if (colour != NULL) {
+	if (colour != nullptr) {
 		if (unloading == 0 && loading) {
 			*colour = STR_PERCENT_UP;
 		} else if (unloading == 0 && !loading) {
@@ -1507,7 +1507,7 @@ void VehicleEnterDepot(Vehicle *v)
 		/* Test whether we are heading for this depot. If not, do nothing.
 		 * Note: The target depot for nearest-/manual-depot-orders is only updated on junctions, but we want to accept every depot. */
 		if ((v->current_order.GetDepotOrderType() & ODTFB_PART_OF_ORDERS) &&
-				real_order != NULL && !(real_order->GetDepotActionType() & ODATFB_NEAREST_DEPOT) &&
+				real_order != nullptr && !(real_order->GetDepotActionType() & ODATFB_NEAREST_DEPOT) &&
 				(v->type == VEH_AIRCRAFT ? v->current_order.GetDestination() != GetStationIndex(v->tile) : v->dest_tile != v->tile)) {
 			/* We are heading for another depot, keep driving. */
 			return;
@@ -1688,7 +1688,7 @@ VehicleEnterTileStatus VehicleEnterTile(
  * @param type type of vehicle
  * @param owner owner of vehicles
  */
-FreeUnitIDGenerator::FreeUnitIDGenerator(VehicleType type, CompanyID owner) : cache(NULL), maxid(0), curid(0)
+FreeUnitIDGenerator::FreeUnitIDGenerator(VehicleType type, CompanyID owner) : cache(nullptr), maxid(0), curid(0)
 {
 	/* Find maximum */
 	const Vehicle *v;
@@ -1800,17 +1800,17 @@ bool CanBuildVehicleInfrastructure(Vehic
  * Determines the #LiveryScheme for a vehicle.
  * @param engine_type Engine of the vehicle.
  * @param parent_engine_type Engine of the front vehicle, #INVALID_ENGINE if vehicle is at front itself.
- * @param v the vehicle, \c NULL if in purchase list etc.
+ * @param v the vehicle, \c nullptr if in purchase list etc.
  * @return livery scheme to use.
  */
 LiveryScheme GetEngineLiveryScheme(EngineID engine_type, EngineID parent_engine_type, const Vehicle *v)
 {
-	CargoID cargo_type = v == NULL ? (CargoID)CT_INVALID : v->cargo_type;
+	CargoID cargo_type = v == nullptr ? (CargoID)CT_INVALID : v->cargo_type;
 	const Engine *e = Engine::Get(engine_type);
 	switch (e->type) {
 		default: NOT_REACHED();
 		case VEH_TRAIN:
-			if (v != NULL && parent_engine_type != INVALID_ENGINE && (UsesWagonOverride(v) || (v->IsArticulatedPart() && e->u.rail.railveh_type != RAILVEH_WAGON))) {
+			if (v != nullptr && parent_engine_type != INVALID_ENGINE && (UsesWagonOverride(v) || (v->IsArticulatedPart() && e->u.rail.railveh_type != RAILVEH_WAGON))) {
 				/* Wagonoverrides use the colour scheme of the front engine.
 				 * Articulated parts use the colour scheme of the first part. (Not supported for articulated wagons) */
 				engine_type = parent_engine_type;
@@ -1853,7 +1853,7 @@ LiveryScheme GetEngineLiveryScheme(Engin
 
 		case VEH_ROAD:
 			/* Always use the livery of the front */
-			if (v != NULL && parent_engine_type != INVALID_ENGINE) {
+			if (v != nullptr && parent_engine_type != INVALID_ENGINE) {
 				engine_type = parent_engine_type;
 				e = Engine::Get(engine_type);
 				cargo_type = v->First()->cargo_type;
@@ -1890,7 +1890,7 @@ LiveryScheme GetEngineLiveryScheme(Engin
  * @param engine_type EngineID of the vehicle
  * @param company Owner of the vehicle
  * @param parent_engine_type EngineID of the front vehicle. INVALID_VEHICLE if vehicle is at front itself.
- * @param v the vehicle. NULL if in purchase list etc.
+ * @param v the vehicle. nullptr if in purchase list etc.
  * @param livery_setting The livery settings to use for acquiring the livery information.
  * @return livery to use
  */
@@ -1900,9 +1900,9 @@ const Livery *GetEngineLivery(EngineID e
 	LiveryScheme scheme = LS_DEFAULT;
 
 	if (livery_setting == LIT_ALL || (livery_setting == LIT_COMPANY && company == _local_company)) {
-		if (v != NULL) {
+		if (v != nullptr) {
 			const Group *g = Group::GetIfValid(v->First()->group_id);
-			if (g != NULL) {
+			if (g != nullptr) {
 				/* Traverse parents until we find a livery or reach the top */
 				while (g->livery.in_use == 0 && g->parent != INVALID_GROUP) {
 					g = Group::Get(g->parent);
@@ -1925,7 +1925,7 @@ const Livery *GetEngineLivery(EngineID e
 
 static PaletteID GetEngineColourMap(EngineID engine_type, CompanyID company, EngineID parent_engine_type, const Vehicle *v)
 {
-	PaletteID map = (v != NULL) ? v->colourmap : PAL_NONE;
+	PaletteID map = (v != nullptr) ? v->colourmap : PAL_NONE;
 
 	/* Return cached value if any */
 	if (map != PAL_NONE) return map;
@@ -1943,7 +1943,7 @@ static PaletteID GetEngineColourMap(Engi
 			 * map else it's returned as-is. */
 			if (!HasBit(callback, 14)) {
 				/* Update cache */
-				if (v != NULL) const_cast<Vehicle *>(v)->colourmap = map;
+				if (v != nullptr) const_cast<Vehicle *>(v)->colourmap = map;
 				return map;
 			}
 		}
@@ -1962,7 +1962,7 @@ static PaletteID GetEngineColourMap(Engi
 	if (twocc) map += livery->colour2 * 16;
 
 	/* Update cache */
-	if (v != NULL) const_cast<Vehicle *>(v)->colourmap = map;
+	if (v != nullptr) const_cast<Vehicle *>(v)->colourmap = map;
 	return map;
 }
 
@@ -1974,7 +1974,7 @@ static PaletteID GetEngineColourMap(Engi
  */
 PaletteID GetEnginePalette(EngineID engine_type, CompanyID company)
 {
-	return GetEngineColourMap(engine_type, company, INVALID_ENGINE, NULL);
+	return GetEngineColourMap(engine_type, company, INVALID_ENGINE, nullptr);
 }
 
 /**
@@ -2008,7 +2008,7 @@ void Vehicle::DeleteUnreachedImplicitOrd
 	}
 
 	const Order *order = this->GetOrder(this->cur_implicit_order_index);
-	while (order != NULL) {
+	while (order != nullptr) {
 		if (this->cur_implicit_order_index == this->cur_real_order_index) break;
 
 		if (order->IsType(OT_IMPLICIT)) {
@@ -2022,7 +2022,7 @@ void Vehicle::DeleteUnreachedImplicitOrd
 		}
 
 		/* Wrap around */
-		if (order == NULL) {
+		if (order == nullptr) {
 			order = this->GetOrder(0);
 			this->cur_implicit_order_index = 0;
 		}
@@ -2059,12 +2059,12 @@ void Vehicle::BeginLoading()
 		 * the 'wrong' terminal when skipping orders etc. */
 		Order *in_list = this->GetOrder(this->cur_implicit_order_index);
 		if (this->IsGroundVehicle() &&
-				(in_list == NULL || !in_list->IsType(OT_IMPLICIT) ||
+				(in_list == nullptr || !in_list->IsType(OT_IMPLICIT) ||
 				in_list->GetDestination() != this->last_station_visited)) {
 			bool suppress_implicit_orders = HasBit(this->GetGroundVehicleFlags(), GVF_SUPPRESS_IMPLICIT_ORDERS);
 			/* Do not create consecutive duplicates of implicit orders */
-			Order *prev_order = this->cur_implicit_order_index > 0 ? this->GetOrder(this->cur_implicit_order_index - 1) : (this->GetNumOrders() > 1 ? this->GetLastOrder() : NULL);
-			if (prev_order == NULL ||
+			Order *prev_order = this->cur_implicit_order_index > 0 ? this->GetOrder(this->cur_implicit_order_index - 1) : (this->GetNumOrders() > 1 ? this->GetLastOrder() : nullptr);
+			if (prev_order == nullptr ||
 					(!prev_order->IsType(OT_IMPLICIT) && !prev_order->IsType(OT_GOTO_STATION)) ||
 					prev_order->GetDestination() != this->last_station_visited) {
 
@@ -2077,7 +2077,7 @@ void Vehicle::BeginLoading()
 				bool found = false;
 				while (target_index != this->cur_real_order_index || this->GetNumManualOrders() == 0) {
 					const Order *order = this->GetOrder(target_index);
-					if (order == NULL) break; // No orders.
+					if (order == nullptr) break; // No orders.
 					if (order->IsType(OT_IMPLICIT) && order->GetDestination() == this->last_station_visited) {
 						found = true;
 						break;
@@ -2113,15 +2113,15 @@ void Vehicle::BeginLoading()
 							}
 
 							/* Wrap around */
-							if (order == NULL) {
+							if (order == nullptr) {
 								order = this->GetOrder(0);
 								this->cur_implicit_order_index = 0;
 							}
-							assert(order != NULL);
+							assert(order != nullptr);
 						}
 					}
 				} else if (!suppress_implicit_orders &&
-						((this->orders.list == NULL ? OrderList::CanAllocateItem() : this->orders.list->GetNumOrders() < MAX_VEH_ORDER_ID)) &&
+						((this->orders.list == nullptr ? OrderList::CanAllocateItem() : this->orders.list->GetNumOrders() < MAX_VEH_ORDER_ID)) &&
 						Order::CanAllocateItem()) {
 					/* Insert new implicit order */
 					Order *implicit_order = new Order();
@@ -2165,7 +2165,7 @@ void Vehicle::BeginLoading()
  */
 void Vehicle::CancelReservation(StationID next, Station *st)
 {
-	for (Vehicle *v = this; v != NULL; v = v->next) {
+	for (Vehicle *v = this; v != nullptr; v = v->next) {
 		VehicleCargoList &cargo = v->cargo;
 		if (cargo.ActionCount(VehicleCargoList::MTA_LOAD) > 0) {
 			DEBUG(misc, 1, "cancelling cargo reservation");
@@ -2185,7 +2185,7 @@ void Vehicle::LeaveStation()
 	assert(this->current_order.IsType(OT_LOADING));
 
 	delete this->cargo_payment;
-	assert(this->cargo_payment == NULL); // cleared by ~CargoPayment
+	assert(this->cargo_payment == nullptr); // cleared by ~CargoPayment
 
 	/* Only update the timetable if the vehicle was supposed to stop here. */
 	if (this->current_order.GetNonStopType() != ONSF_STOP_EVERYWHERE) UpdateVehicleTimetable(this, false);
@@ -2214,7 +2214,7 @@ void Vehicle::LeaveStation()
 	st->loading_vehicles.remove(this);
 
 	HideFillingPercent(&this->fill_percent_te_id);
-	trip_occupancy = CalcPercentVehicleFilled(this, NULL);
+	trip_occupancy = CalcPercentVehicleFilled(this, nullptr);
 
 	if (this->type == VEH_TRAIN && !(this->vehstatus & VS_CRASHED)) {
 		/* Trigger station animation (trains only) */
@@ -2234,7 +2234,7 @@ void Vehicle::LeaveStation()
  */
 void Vehicle::ResetRefitCaps()
 {
-	for (Vehicle *v = this; v != NULL; v = v->Next()) v->refit_cap = v->cargo_cap;
+	for (Vehicle *v = this; v != nullptr; v = v->Next()) v->refit_cap = v->cargo_cap;
 }
 
 /**
@@ -2257,7 +2257,7 @@ void Vehicle::HandleLoading(bool mode)
 
 			/* Only advance to next order if we just loaded at the current one */
 			const Order *order = this->GetOrder(this->cur_implicit_order_index);
-			if (order == NULL ||
+			if (order == nullptr ||
 					(!order->IsType(OT_IMPLICIT) && !order->IsType(OT_GOTO_STATION)) ||
 					order->GetDestination() != this->last_station_visited) {
 				return;
@@ -2279,7 +2279,7 @@ void Vehicle::HandleLoading(bool mode)
  */
 void Vehicle::GetConsistFreeCapacities(SmallMap<CargoID, uint> &capacities) const
 {
-	for (const Vehicle *v = this; v != NULL; v = v->Next()) {
+	for (const Vehicle *v = this; v != nullptr; v = v->Next()) {
 		if (v->cargo_cap == 0) continue;
 		SmallPair<CargoID, uint> *pair = capacities.Find(v->cargo_type);
 		if (pair == capacities.End()) {
@@ -2293,7 +2293,7 @@ void Vehicle::GetConsistFreeCapacities(S
 uint Vehicle::GetConsistTotalCapacity() const
 {
 	uint result = 0;
-	for (const Vehicle *v = this; v != NULL; v = v->Next()) {
+	for (const Vehicle *v = this; v != nullptr; v = v->Next()) {
 		result += v->cargo_cap;
 	}
 	return result;
@@ -2650,34 +2650,34 @@ void Vehicle::ShowVisualEffect() const
 
 			CreateEffectVehicleRel(v, x, y, 10, evt);
 		}
-	} while ((v = v->Next()) != NULL);
+	} while ((v = v->Next()) != nullptr);
 
 	if (sound) PlayVehicleSound(this, VSE_VISUAL_EFFECT);
 }
 
 /**
  * Set the next vehicle of this vehicle.
- * @param next the next vehicle. NULL removes the next vehicle.
+ * @param next the next vehicle. nullptr removes the next vehicle.
  */
 void Vehicle::SetNext(Vehicle *next)
 {
 	assert(this != next);
 
-	if (this->next != NULL) {
+	if (this->next != nullptr) {
 		/* We had an old next vehicle. Update the first and previous pointers */
-		for (Vehicle *v = this->next; v != NULL; v = v->Next()) {
+		for (Vehicle *v = this->next; v != nullptr; v = v->Next()) {
 			v->first = this->next;
 		}
-		this->next->previous = NULL;
+		this->next->previous = nullptr;
 	}
 
 	this->next = next;
 
-	if (this->next != NULL) {
+	if (this->next != nullptr) {
 		/* A new next vehicle. Update the first and previous pointers */
-		if (this->next->previous != NULL) this->next->previous->next = NULL;
+		if (this->next->previous != nullptr) this->next->previous->next = nullptr;
 		this->next->previous = this;
-		for (Vehicle *v = this->next; v != NULL; v = v->Next()) {
+		for (Vehicle *v = this->next; v != nullptr; v = v->Next()) {
 			v->first = this->first;
 		}
 	}
@@ -2690,12 +2690,12 @@ void Vehicle::SetNext(Vehicle *next)
  */
 void Vehicle::AddToShared(Vehicle *shared_chain)
 {
-	assert(this->previous_shared == NULL && this->next_shared == NULL);
-
-	if (shared_chain->orders.list == NULL) {
-		assert(shared_chain->previous_shared == NULL);
-		assert(shared_chain->next_shared == NULL);
-		this->orders.list = shared_chain->orders.list = new OrderList(NULL, shared_chain);
+	assert(this->previous_shared == nullptr && this->next_shared == nullptr);
+
+	if (shared_chain->orders.list == nullptr) {
+		assert(shared_chain->previous_shared == nullptr);
+		assert(shared_chain->next_shared == nullptr);
+		this->orders.list = shared_chain->orders.list = new OrderList(nullptr, shared_chain);
 	}
 
 	this->next_shared     = shared_chain->next_shared;
@@ -2703,7 +2703,7 @@ void Vehicle::AddToShared(Vehicle *share
 
 	shared_chain->next_shared = this;
 
-	if (this->next_shared != NULL) this->next_shared->previous_shared = this;
+	if (this->next_shared != nullptr) this->next_shared->previous_shared = this;
 
 	shared_chain->orders.list->AddVehicle(this);
 }
@@ -2725,7 +2725,7 @@ void Vehicle::RemoveFromShared()
 		this->previous_shared->next_shared = this->NextShared();
 	}
 
-	if (this->next_shared != NULL) this->next_shared->previous_shared = this->previous_shared;
+	if (this->next_shared != nullptr) this->next_shared->previous_shared = this->previous_shared;
 
 
 	if (this->orders.list->GetNumVehicles() == 1) {
@@ -2738,8 +2738,8 @@ void Vehicle::RemoveFromShared()
 		InvalidateWindowData(GetWindowClassForVehicleType(this->type), vli.Pack(), this->FirstShared()->index | (1U << 31));
 	}
 
-	this->next_shared     = NULL;
-	this->previous_shared = NULL;
+	this->next_shared     = nullptr;
+	this->previous_shared = nullptr;
 }
 
 void VehiclesYearlyLoop()
@@ -2783,7 +2783,7 @@ void VehiclesYearlyLoop()
 bool CanVehicleUseStation(EngineID engine_type, const Station *st)
 {
 	const Engine *e = Engine::GetIfValid(engine_type);
-	assert(e != NULL);
+	assert(e != nullptr);
 
 	switch (e->type) {
 		case VEH_TRAIN:
@@ -2815,7 +2815,7 @@ bool CanVehicleUseStation(EngineID engin
  */
 bool CanVehicleUseStation(const Vehicle *v, const Station *st)
 {
-	if (v->type == VEH_ROAD) return st->GetPrimaryRoadStop(RoadVehicle::From(v)) != NULL;
+	if (v->type == VEH_ROAD) return st->GetPrimaryRoadStop(RoadVehicle::From(v)) != nullptr;
 
 	return CanVehicleUseStation(v->engine_type, st);
 }
@@ -2896,7 +2896,7 @@ void GetVehicleSet(VehicleSet &set, Vehi
 		u = u->GetFirstEnginePart();
 
 		/* Include num_vehicles vehicles, not counting articulated parts */
-		for (; u != NULL && num_vehicles > 0; num_vehicles--) {
+		for (; u != nullptr && num_vehicles > 0; num_vehicles--) {
 			do {
 				/* Include current vehicle in the selection. */
 				include(set, u->index);
@@ -2905,7 +2905,7 @@ void GetVehicleSet(VehicleSet &set, Vehi
 				if (u->IsMultiheaded()) include(set, u->other_multiheaded_part->index);
 
 				u = u->Next();
-			} while (u != NULL && u->IsArticulatedPart());
+			} while (u != nullptr && u->IsArticulatedPart());
 		}
 	}
 }
diff --git a/src/vehicle_base.h b/src/vehicle_base.h
--- a/src/vehicle_base.h
+++ b/src/vehicle_base.h
@@ -459,7 +459,7 @@ public:
 	 */
 	inline void InvalidateNewGRFCacheOfChain()
 	{
-		for (Vehicle *u = this; u != NULL; u = u->Next()) {
+		for (Vehicle *u = this; u != nullptr; u = u->Next()) {
 			u->InvalidateNewGRFCache();
 		}
 	}
@@ -576,14 +576,14 @@ public:
 	/**
 	 * Get the next vehicle of this vehicle.
 	 * @note articulated parts are also counted as vehicles.
-	 * @return the next vehicle or NULL when there isn't a next vehicle.
+	 * @return the next vehicle or nullptr when there isn't a next vehicle.
 	 */
 	inline Vehicle *Next() const { return this->next; }
 
 	/**
 	 * Get the previous vehicle of this vehicle.
 	 * @note articulated parts are also counted as vehicles.
-	 * @return the previous vehicle or NULL when there isn't a previous vehicle.
+	 * @return the previous vehicle or nullptr when there isn't a previous vehicle.
 	 */
 	inline Vehicle *Previous() const { return this->previous; }
 
@@ -600,7 +600,7 @@ public:
 	inline Vehicle *Last()
 	{
 		Vehicle *v = this;
-		while (v->Next() != NULL) v = v->Next();
+		while (v->Next() != nullptr) v = v->Next();
 		return v;
 	}
 
@@ -611,22 +611,22 @@ public:
 	inline const Vehicle *Last() const
 	{
 		const Vehicle *v = this;
-		while (v->Next() != NULL) v = v->Next();
+		while (v->Next() != nullptr) v = v->Next();
 		return v;
 	}
 
 	/**
 	 * Get the vehicle at offset \a n of this vehicle chain.
 	 * @param n Offset from the current vehicle.
-	 * @return The new vehicle or NULL if the offset is out-of-bounds.
+	 * @return The new vehicle or nullptr if the offset is out-of-bounds.
 	 */
 	inline Vehicle *Move(int n)
 	{
 		Vehicle *v = this;
 		if (n < 0) {
-			for (int i = 0; i != n && v != NULL; i--) v = v->Previous();
+			for (int i = 0; i != n && v != nullptr; i--) v = v->Previous();
 		} else {
-			for (int i = 0; i != n && v != NULL; i++) v = v->Next();
+			for (int i = 0; i != n && v != nullptr; i++) v = v->Next();
 		}
 		return v;
 	}
@@ -634,15 +634,15 @@ public:
 	/**
 	 * Get the vehicle at offset \a n of this vehicle chain.
 	 * @param n Offset from the current vehicle.
-	 * @return The new vehicle or NULL if the offset is out-of-bounds.
+	 * @return The new vehicle or nullptr if the offset is out-of-bounds.
 	 */
 	inline const Vehicle *Move(int n) const
 	{
 		const Vehicle *v = this;
 		if (n < 0) {
-			for (int i = 0; i != n && v != NULL; i--) v = v->Previous();
+			for (int i = 0; i != n && v != nullptr; i--) v = v->Previous();
 		} else {
-			for (int i = 0; i != n && v != NULL; i++) v = v->Next();
+			for (int i = 0; i != n && v != nullptr; i++) v = v->Next();
 		}
 		return v;
 	}
@@ -651,20 +651,20 @@ public:
 	 * Get the first order of the vehicles order list.
 	 * @return first order of order list.
 	 */
-	inline Order *GetFirstOrder() const { return (this->orders.list == NULL) ? NULL : this->orders.list->GetFirstOrder(); }
+	inline Order *GetFirstOrder() const { return (this->orders.list == nullptr) ? nullptr : this->orders.list->GetFirstOrder(); }
 
 	void AddToShared(Vehicle *shared_chain);
 	void RemoveFromShared();
 
 	/**
 	 * Get the next vehicle of the shared vehicle chain.
-	 * @return the next shared vehicle or NULL when there isn't a next vehicle.
+	 * @return the next shared vehicle or nullptr when there isn't a next vehicle.
 	 */
 	inline Vehicle *NextShared() const { return this->next_shared; }
 
 	/**
 	 * Get the previous vehicle of the shared vehicle chain
-	 * @return the previous shared vehicle or NULL when there isn't a previous vehicle.
+	 * @return the previous shared vehicle or nullptr when there isn't a previous vehicle.
 	 */
 	inline Vehicle *PreviousShared() const { return this->previous_shared; }
 
@@ -672,25 +672,25 @@ public:
 	 * Get the first vehicle of this vehicle chain.
 	 * @return the first vehicle of the chain.
 	 */
-	inline Vehicle *FirstShared() const { return (this->orders.list == NULL) ? this->First() : this->orders.list->GetFirstSharedVehicle(); }
+	inline Vehicle *FirstShared() const { return (this->orders.list == nullptr) ? this->First() : this->orders.list->GetFirstSharedVehicle(); }
 
 	/**
 	 * Check if we share our orders with another vehicle.
 	 * @return true if there are other vehicles sharing the same order
 	 */
-	inline bool IsOrderListShared() const { return this->orders.list != NULL && this->orders.list->IsShared(); }
+	inline bool IsOrderListShared() const { return this->orders.list != nullptr && this->orders.list->IsShared(); }
 
 	/**
 	 * Get the number of orders this vehicle has.
 	 * @return the number of orders this vehicle has.
 	 */
-	inline VehicleOrderID GetNumOrders() const { return (this->orders.list == NULL) ? 0 : this->orders.list->GetNumOrders(); }
+	inline VehicleOrderID GetNumOrders() const { return (this->orders.list == nullptr) ? 0 : this->orders.list->GetNumOrders(); }
 
 	/**
 	 * Get the number of manually added orders this vehicle has.
 	 * @return the number of manually added orders this vehicle has.
 	 */
-	inline VehicleOrderID GetNumManualOrders() const { return (this->orders.list == NULL) ? 0 : this->orders.list->GetNumManualOrders(); }
+	inline VehicleOrderID GetNumManualOrders() const { return (this->orders.list == nullptr) ? 0 : this->orders.list->GetNumManualOrders(); }
 
 	/**
 	 * Get the next station the vehicle will stop at.
@@ -698,7 +698,7 @@ public:
 	 */
 	inline StationIDStack GetNextStoppingStation() const
 	{
-		return (this->orders.list == NULL) ? INVALID_STATION : this->orders.list->GetNextStoppingStation(this);
+		return (this->orders.list == nullptr) ? INVALID_STATION : this->orders.list->GetNextStoppingStation(this);
 	}
 
 	void ResetRefitCaps();
@@ -853,22 +853,22 @@ public:
 	}
 
 	/**
-	 * Returns order 'index' of a vehicle or NULL when it doesn't exists
+	 * Returns order 'index' of a vehicle or nullptr when it doesn't exists
 	 * @param index the order to fetch
 	 * @return the found (or not) order
 	 */
 	inline Order *GetOrder(int index) const
 	{
-		return (this->orders.list == NULL) ? NULL : this->orders.list->GetOrderAt(index);
+		return (this->orders.list == nullptr) ? nullptr : this->orders.list->GetOrderAt(index);
 	}
 
 	/**
-	 * Returns the last order of a vehicle, or NULL if it doesn't exists
+	 * Returns the last order of a vehicle, or nullptr if it doesn't exists
 	 * @return last order of a vehicle, if available
 	 */
 	inline Order *GetLastOrder() const
 	{
-		return (this->orders.list == NULL) ? NULL : this->orders.list->GetLastOrder();
+		return (this->orders.list == nullptr) ? nullptr : this->orders.list->GetLastOrder();
 	}
 
 	bool IsEngineCountable() const;
@@ -900,7 +900,7 @@ public:
 	 */
 	inline bool HasArticulatedPart() const
 	{
-		return this->Next() != NULL && this->Next()->IsArticulatedPart();
+		return this->Next() != nullptr && this->Next()->IsArticulatedPart();
 	}
 
 	/**
@@ -967,7 +967,7 @@ public:
 	inline Vehicle *GetPrevVehicle() const
 	{
 		Vehicle *v = this->Previous();
-		while (v != NULL && v->IsArticulatedPart()) v = v->Previous();
+		while (v != nullptr && v->IsArticulatedPart()) v = v->Previous();
 
 		return v;
 	}
@@ -1103,7 +1103,7 @@ struct SpecializedVehicle : public Vehic
 	 */
 	static inline T *GetIfValid(size_t index)
 	{
-		return IsValidID(index) ? Get(index) : NULL;
+		return IsValidID(index) ? Get(index) : nullptr;
 	}
 
 	/**
diff --git a/src/vehicle_cmd.cpp b/src/vehicle_cmd.cpp
--- a/src/vehicle_cmd.cpp
+++ b/src/vehicle_cmd.cpp
@@ -137,7 +137,7 @@ CommandCost CmdBuildVehicle(TileIndex ti
 	SavedRandomSeeds saved_seeds;
 	if (flags != subflags) SaveRandomSeeds(&saved_seeds);
 
-	Vehicle *v = NULL;
+	Vehicle *v = nullptr;
 	switch (type) {
 		case VEH_TRAIN:    value.AddCost(CmdBuildRailVehicle(tile, subflags, e, GB(p1, 24, 8), &v)); break;
 		case VEH_ROAD:     value.AddCost(CmdBuildRoadVehicle(tile, subflags, e, GB(p1, 24, 8), &v)); break;
@@ -153,7 +153,7 @@ CommandCost CmdBuildVehicle(TileIndex ti
 		}
 
 		if (refitting) {
-			value.AddCost(CmdRefitVehicle(tile, flags, v->index, cargo, NULL));
+			value.AddCost(CmdRefitVehicle(tile, flags, v->index, cargo, nullptr));
 		} else {
 			/* Fill in non-refitted capacities */
 			_returned_refit_capacity = e->GetDisplayDefaultCapacity(&_returned_mail_refit_capacity);
@@ -207,7 +207,7 @@ CommandCost CmdSellRailWagon(DoCommandFl
 CommandCost CmdSellVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Vehicle *v = Vehicle::GetIfValid(GB(p1, 0, 20));
-	if (v == NULL) return CMD_ERROR;
+	if (v == nullptr) return CMD_ERROR;
 
 	Vehicle *front = v->First();
 
@@ -220,7 +220,7 @@ CommandCost CmdSellVehicle(TileIndex til
 
 	/* Can we actually make the order backup, i.e. are there enough orders? */
 	if (p1 & MAKE_ORDER_BACKUP_FLAG &&
-			front->orders.list != NULL &&
+			front->orders.list != nullptr &&
 			!front->orders.list->IsShared() &&
 			!Order::CanAllocateItem(front->orders.list->GetNumOrders())) {
 		/* Only happens in exceptional cases when there aren't enough orders anyhow.
@@ -244,7 +244,7 @@ CommandCost CmdSellVehicle(TileIndex til
 
 /**
  * Helper to run the refit cost callback.
- * @param v The vehicle we are refitting, can be NULL.
+ * @param v The vehicle we are refitting, can be nullptr.
  * @param engine_type Which engine to refit
  * @param new_cid Cargo type we are refitting to.
  * @param new_subtype New cargo subtype.
@@ -257,7 +257,7 @@ static int GetRefitCostFactor(const Vehi
 	const Engine *e = Engine::Get(engine_type);
 
 	/* Is this vehicle a NewGRF vehicle? */
-	if (e->GetGRF() != NULL) {
+	if (e->GetGRF() != nullptr) {
 		const CargoSpec *cs = CargoSpec::Get(new_cid);
 		uint32 param1 = (cs->classes << 16) | (new_subtype << 8) | e->GetGRF()->cargo_map[new_cid];
 
@@ -271,12 +271,12 @@ static int GetRefitCostFactor(const Vehi
 	}
 
 	*auto_refit_allowed = e->info.refit_cost == 0;
-	return (v == NULL || v->cargo_type != new_cid) ? e->info.refit_cost : 0;
+	return (v == nullptr || v->cargo_type != new_cid) ? e->info.refit_cost : 0;
 }
 
 /**
  * Learn the price of refitting a certain engine
- * @param v The vehicle we are refitting, can be NULL.
+ * @param v The vehicle we are refitting, can be nullptr.
  * @param engine_type Which engine to refit
  * @param new_cid Cargo type we are refitting to.
  * @param new_subtype New cargo subtype.
@@ -358,7 +358,7 @@ static CommandCost RefitVehicle(Vehicle 
 
 	v->InvalidateNewGRFCacheOfChain();
 	byte actual_subtype = new_subtype;
-	for (; v != NULL; v = (only_this ? NULL : v->Next())) {
+	for (; v != nullptr; v = (only_this ? nullptr : v->Next())) {
 		/* Reset actual_subtype for every new vehicle */
 		if (!v->IsArticulatedPart()) actual_subtype = new_subtype;
 
@@ -469,7 +469,7 @@ static CommandCost RefitVehicle(Vehicle 
 CommandCost CmdRefitVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Vehicle *v = Vehicle::GetIfValid(p1);
-	if (v == NULL) return CMD_ERROR;
+	if (v == nullptr) return CMD_ERROR;
 
 	/* Don't allow disasters and sparks and such to be refitted.
 	 * We cannot check for IsPrimaryVehicle as autoreplace also refits in free wagon chains. */
@@ -560,7 +560,7 @@ CommandCost CmdStartStopVehicle(TileInde
 	if ((flags & DC_AUTOREPLACE) == 0) SetBit(p2, 0);
 
 	Vehicle *v = Vehicle::GetIfValid(p1);
-	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle()) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -652,7 +652,7 @@ CommandCost CmdMassStartStopVehicle(Tile
 		if (!GenerateVehicleSortList(&list, vli)) return CMD_ERROR;
 	} else {
 		/* Get the list of vehicles in the depot */
-		BuildDepotVehicleList(vli.vtype, tile, &list, NULL);
+		BuildDepotVehicleList(vli.vtype, tile, &list, nullptr);
 	}
 
 	for (uint i = 0; i < list.size(); i++) {
@@ -751,7 +751,7 @@ static bool IsUniqueVehicleName(const ch
 	const Vehicle *v;
 
 	FOR_ALL_VEHICLES(v) {
-		if (v->name != NULL && strcmp(v->name, name) == 0) return false;
+		if (v->name != nullptr && strcmp(v->name, name) == 0) return false;
 	}
 
 	return true;
@@ -821,11 +821,11 @@ CommandCost CmdCloneVehicle(TileIndex ti
 	CommandCost total_cost(EXPENSES_NEW_VEHICLES);
 
 	Vehicle *v = Vehicle::GetIfValid(p1);
-	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle()) return CMD_ERROR;
 	Vehicle *v_front = v;
-	Vehicle *w = NULL;
-	Vehicle *w_front = NULL;
-	Vehicle *w_rear = NULL;
+	Vehicle *w = nullptr;
+	Vehicle *w_front = nullptr;
+	Vehicle *w_rear = nullptr;
 
 	/*
 	 * v_front is the front engine in the original vehicle
@@ -845,7 +845,7 @@ CommandCost CmdCloneVehicle(TileIndex ti
 		int veh_counter = 0;
 		do {
 			veh_counter++;
-		} while ((v = v->Next()) != NULL);
+		} while ((v = v->Next()) != nullptr);
 
 		if (!Vehicle::CanAllocateItem(veh_counter)) {
 			return_cmd_error(STR_ERROR_TOO_MANY_VEHICLES_IN_GAME);
@@ -873,7 +873,7 @@ CommandCost CmdCloneVehicle(TileIndex ti
 
 		if (cost.Failed()) {
 			/* Can't build a part, then sell the stuff we already made; clear up the mess */
-			if (w_front != NULL) DoCommand(w_front->tile, w_front->index | (1 << 20), 0, flags, GetCmdSellVeh(w_front));
+			if (w_front != nullptr) DoCommand(w_front->tile, w_front->index | (1 << 20), 0, flags, GetCmdSellVeh(w_front));
 			return cost;
 		}
 
@@ -906,7 +906,7 @@ CommandCost CmdCloneVehicle(TileIndex ti
 			}
 			w_rear = w; // trains needs to know the last car in the train, so they can add more in next loop
 		}
-	} while (v->type == VEH_TRAIN && (v = v->GetNextVehicle()) != NULL);
+	} while (v->type == VEH_TRAIN && (v = v->GetNextVehicle()) != nullptr);
 
 	if ((flags & DC_EXEC) && v_front->type == VEH_TRAIN) {
 		/* for trains this needs to be the front engine due to the callback function */
@@ -932,7 +932,7 @@ CommandCost CmdCloneVehicle(TileIndex ti
 	do {
 		do {
 			if (flags & DC_EXEC) {
-				assert(w != NULL);
+				assert(w != nullptr);
 
 				/* Find out what's the best sub type */
 				byte subtype = GetBestFittingSubType(v, w, v->cargo_type);
@@ -952,7 +952,7 @@ CommandCost CmdCloneVehicle(TileIndex ti
 
 				if (v->cargo_type != initial_cargo && initial_cargo != CT_INVALID) {
 					bool dummy;
-					total_cost.AddCost(GetRefitCost(NULL, v->engine_type, v->cargo_type, v->cargo_subtype, &dummy));
+					total_cost.AddCost(GetRefitCost(nullptr, v->engine_type, v->cargo_type, v->cargo_subtype, &dummy));
 				}
 			}
 
@@ -961,10 +961,10 @@ CommandCost CmdCloneVehicle(TileIndex ti
 			} else {
 				break;
 			}
-		} while (v != NULL);
+		} while (v != nullptr);
 
 		if ((flags & DC_EXEC) && v->type == VEH_TRAIN) w = w->GetNextVehicle();
-	} while (v->type == VEH_TRAIN && (v = v->GetNextVehicle()) != NULL);
+	} while (v->type == VEH_TRAIN && (v = v->GetNextVehicle()) != nullptr);
 
 	if (flags & DC_EXEC) {
 		/*
@@ -975,7 +975,7 @@ CommandCost CmdCloneVehicle(TileIndex ti
 		DoCommand(0, w_front->index | (p2 & 1 ? CO_SHARE : CO_COPY) << 30, v_front->index, flags, CMD_CLONE_ORDER);
 
 		/* Now clone the vehicle's name, if it has one. */
-		if (v_front->name != NULL) CloneVehicleName(v_front, w_front);
+		if (v_front->name != nullptr) CloneVehicleName(v_front, w_front);
 	}
 
 	/* Since we can't estimate the cost of cloning a vehicle accurately we must
@@ -1045,7 +1045,7 @@ CommandCost CmdSendVehicleToDepot(TileIn
 	}
 
 	Vehicle *v = Vehicle::GetIfValid(GB(p1, 0, 20));
-	if (v == NULL) return CMD_ERROR;
+	if (v == nullptr) return CMD_ERROR;
 	if (!v->IsPrimaryVehicle()) return CMD_ERROR;
 
 	return v->SendToDepot(flags, (DepotCommand)(p1 & DEPOT_COMMAND_MASK));
@@ -1063,7 +1063,7 @@ CommandCost CmdSendVehicleToDepot(TileIn
 CommandCost CmdRenameVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Vehicle *v = Vehicle::GetIfValid(p1);
-	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle()) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
@@ -1077,7 +1077,7 @@ CommandCost CmdRenameVehicle(TileIndex t
 
 	if (flags & DC_EXEC) {
 		free(v->name);
-		v->name = reset ? NULL : stredup(text);
+		v->name = reset ? nullptr : stredup(text);
 		InvalidateWindowClassesData(GetWindowClassForVehicleType(v->type), 1);
 		MarkWholeScreenDirty();
 	}
@@ -1101,7 +1101,7 @@ CommandCost CmdRenameVehicle(TileIndex t
 CommandCost CmdChangeServiceInt(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Vehicle *v = Vehicle::GetIfValid(p1);
-	if (v == NULL || !v->IsPrimaryVehicle()) return CMD_ERROR;
+	if (v == nullptr || !v->IsPrimaryVehicle()) return CMD_ERROR;
 
 	CommandCost ret = CheckOwnership(v->owner);
 	if (ret.Failed()) return ret;
diff --git a/src/vehicle_func.h b/src/vehicle_func.h
--- a/src/vehicle_func.h
+++ b/src/vehicle_func.h
@@ -60,7 +60,7 @@ byte GetBestFittingSubType(Vehicle *v_fr
 void ViewportAddVehicles(DrawPixelInfo *dpi);
 
 void ShowNewGrfVehicleError(EngineID engine, StringID part1, StringID part2, GRFBugs bug_type, bool critical);
-CommandCost TunnelBridgeIsFree(TileIndex tile, TileIndex endtile, const Vehicle *ignore = NULL);
+CommandCost TunnelBridgeIsFree(TileIndex tile, TileIndex endtile, const Vehicle *ignore = nullptr);
 
 void DecreaseVehicleValue(Vehicle *v);
 void CheckVehicleBreakdown(Vehicle *v);
diff --git a/src/vehicle_gui.cpp b/src/vehicle_gui.cpp
--- a/src/vehicle_gui.cpp
+++ b/src/vehicle_gui.cpp
@@ -181,14 +181,14 @@ DropDownList BaseVehicleListWindow::Buil
 }
 
 /* cached values for VehicleNameSorter to spare many GetString() calls */
-static const Vehicle *_last_vehicle[2] = { NULL, NULL };
+static const Vehicle *_last_vehicle[2] = { nullptr, nullptr };
 
 void BaseVehicleListWindow::SortVehicleList()
 {
 	if (this->vehicles.Sort()) return;
 
 	/* invalidate cached values for name sorter - vehicle names could change */
-	_last_vehicle[0] = _last_vehicle[1] = NULL;
+	_last_vehicle[0] = _last_vehicle[1] = nullptr;
 }
 
 void DepotSortList(VehicleList *list)
@@ -235,7 +235,7 @@ byte GetBestFittingSubType(Vehicle *v_fr
 	/* Create a list of subtypes used by the various parts of v_for */
 	static std::vector<StringID> subtypes;
 	subtypes.clear();
-	for (; v_from != NULL; v_from = v_from->HasArticulatedPart() ? v_from->GetNextArticulatedPart() : NULL) {
+	for (; v_from != nullptr; v_from = v_from->HasArticulatedPart() ? v_from->GetNextArticulatedPart() : nullptr) {
 		const Engine *e_from = v_from->GetEngine();
 		if (!e_from->CanCarryCargo() || !HasBit(e_from->info.callback_mask, CBM_VEHICLE_CARGO_SUFFIX)) continue;
 		include(subtypes, GetCargoSubtypeText(v_from));
@@ -245,7 +245,7 @@ byte GetBestFittingSubType(Vehicle *v_fr
 	bool success = false;
 	if (subtypes.size() > 0) {
 		/* Check whether any articulated part is refittable to 'dest_cargo_type' with a subtype listed in 'subtypes' */
-		for (Vehicle *v = v_for; v != NULL; v = v->HasArticulatedPart() ? v->GetNextArticulatedPart() : NULL) {
+		for (Vehicle *v = v_for; v != nullptr; v = v->HasArticulatedPart() ? v->GetNextArticulatedPart() : nullptr) {
 			const Engine *e = v->GetEngine();
 			if (!e->CanCarryCargo() || !HasBit(e->info.callback_mask, CBM_VEHICLE_CARGO_SUFFIX)) continue;
 			if (!HasBit(e->info.refit_mask, dest_cargo_type) && v->cargo_type != dest_cargo_type) continue;
@@ -507,7 +507,7 @@ struct RefitWindow : public Window {
 				}
 				current_index++;
 			}
-		} while (v->IsGroundVehicle() && (v = v->Next()) != NULL);
+		} while (v->IsGroundVehicle() && (v = v->Next()) != nullptr);
 	}
 
 	/**
@@ -570,10 +570,10 @@ struct RefitWindow : public Window {
 	 */
 	RefitOption *GetRefitOption()
 	{
-		if (this->sel[0] < 0) return NULL;
+		if (this->sel[0] < 0) return nullptr;
 
 		SubtypeList &l = this->list[this->sel[0]];
-		if ((uint)this->sel[1] >= l.size()) return NULL;
+		if ((uint)this->sel[1] >= l.size()) return nullptr;
 
 		return &l[this->sel[1]];
 	}
@@ -587,7 +587,7 @@ struct RefitWindow : public Window {
 		this->CreateNestedTree();
 
 		this->vscroll = this->GetScrollbar(WID_VR_SCROLLBAR);
-		this->hscroll = (v->IsGroundVehicle() ? this->GetScrollbar(WID_VR_HSCROLLBAR) : NULL);
+		this->hscroll = (v->IsGroundVehicle() ? this->GetScrollbar(WID_VR_HSCROLLBAR) : nullptr);
 		this->GetWidget<NWidgetCore>(WID_VR_SELECT_HEADER)->tool_tip = STR_REFIT_TRAIN_LIST_TOOLTIP + v->type;
 		this->GetWidget<NWidgetCore>(WID_VR_MATRIX)->tool_tip        = STR_REFIT_TRAIN_LIST_TOOLTIP + v->type;
 		NWidgetCore *nwi = this->GetWidget<NWidgetCore>(WID_VR_REFIT);
@@ -604,7 +604,7 @@ struct RefitWindow : public Window {
 
 	void OnInit() override
 	{
-		if (this->cargo != NULL) {
+		if (this->cargo != nullptr) {
 			/* Store the RefitOption currently in use. */
 			RefitOption current_refit_option = *(this->cargo);
 
@@ -612,8 +612,8 @@ struct RefitWindow : public Window {
 			this->BuildRefitList();
 			this->sel[0] = -1;
 			this->sel[1] = 0;
-			this->cargo = NULL;
-			for (uint i = 0; this->cargo == NULL && i < NUM_CARGO; i++) {
+			this->cargo = nullptr;
+			for (uint i = 0; this->cargo == nullptr && i < NUM_CARGO; i++) {
 				for (uint j = 0; j < list[i].size(); j++) {
 					if (list[i][j] == current_refit_option) {
 						this->sel[0] = i;
@@ -635,7 +635,7 @@ struct RefitWindow : public Window {
 	void OnPaint() override
 	{
 		/* Determine amount of items for scroller. */
-		if (this->hscroll != NULL) this->hscroll->SetCount(this->vehicle_width);
+		if (this->hscroll != nullptr) this->hscroll->SetCount(this->vehicle_width);
 
 		/* Calculate sprite position. */
 		NWidgetCore *vehicle_panel_display = this->GetWidget<NWidgetCore>(WID_VR_VEHICLE_PANEL_DISPLAY);
@@ -729,7 +729,7 @@ struct RefitWindow : public Window {
 			case WID_VR_VEHICLE_PANEL_DISPLAY: {
 				Vehicle *v = Vehicle::Get(this->window_number);
 				DrawVehicleImage(v, this->sprite_left + WD_FRAMERECT_LEFT, this->sprite_right - WD_FRAMERECT_RIGHT,
-					r.top + WD_FRAMERECT_TOP, INVALID_VEHICLE, EIT_IN_DETAILS, this->hscroll != NULL ? this->hscroll->GetPosition() : 0);
+					r.top + WD_FRAMERECT_TOP, INVALID_VEHICLE, EIT_IN_DETAILS, this->hscroll != nullptr ? this->hscroll->GetPosition() : 0);
 
 				/* Highlight selected vehicles. */
 				if (this->order != INVALID_VEH_ORDER_ID) break;
@@ -742,7 +742,7 @@ struct RefitWindow : public Window {
 						int left = INT32_MIN;
 						int width = 0;
 
-						for (Train *u = Train::From(v); u != NULL; u = u->Next()) {
+						for (Train *u = Train::From(v); u != nullptr; u = u->Next()) {
 							/* Start checking. */
 							const bool contained = std::find(vehicles_to_refit.begin(), vehicles_to_refit.end(), u->index) != vehicles_to_refit.end();
 							if (contained && left == INT32_MIN) {
@@ -751,8 +751,8 @@ struct RefitWindow : public Window {
 							}
 
 							/* Draw a selection. */
-							if ((!contained || u->Next() == NULL) && left != INT32_MIN) {
-								if (u->Next() == NULL && contained) {
+							if ((!contained || u->Next() == nullptr) && left != INT32_MIN) {
+								if (u->Next() == nullptr && contained) {
 									int current_width = u->GetDisplayImageWidth();
 									width += current_width;
 									x += current_width;
@@ -790,7 +790,7 @@ struct RefitWindow : public Window {
 				break;
 
 			case WID_VR_INFO:
-				if (this->cargo != NULL) {
+				if (this->cargo != nullptr) {
 					StringID string = this->GetCapacityString(this->cargo);
 					if (string != INVALID_STRING_ID) {
 						DrawStringMultiLine(r.left + WD_FRAMERECT_LEFT, r.right - WD_FRAMERECT_RIGHT,
@@ -857,7 +857,7 @@ struct RefitWindow : public Window {
 		const NWidgetCore *matrix_widget = this->GetWidget<NWidgetCore>(WID_VR_VEHICLE_PANEL_DISPLAY);
 		if (_current_text_dir == TD_RTL) click_x = matrix_widget->current_x - click_x;
 		click_x -= this->vehicle_margin;
-		if (this->hscroll != NULL) click_x += this->hscroll->GetPosition();
+		if (this->hscroll != nullptr) click_x += this->hscroll->GetPosition();
 
 		return click_x;
 	}
@@ -878,7 +878,7 @@ struct RefitWindow : public Window {
 				if (left_x >= 0) {
 					const Train *u = Train::From(v);
 					bool start_counting = false;
-					for (; u != NULL; u = u->Next()) {
+					for (; u != nullptr; u = u->Next()) {
 						int current_width = u->GetDisplayImageWidth();
 						left_x  -= current_width;
 						right_x -= current_width;
@@ -942,7 +942,7 @@ struct RefitWindow : public Window {
 			}
 
 			case WID_VR_REFIT: // refit button
-				if (this->cargo != NULL) {
+				if (this->cargo != nullptr) {
 					const Vehicle *v = Vehicle::Get(this->window_number);
 
 					if (this->order == INVALID_VEH_ORDER_ID) {
@@ -986,7 +986,7 @@ struct RefitWindow : public Window {
 	{
 		this->vehicle_width = GetVehicleWidth(Vehicle::Get(this->window_number), EIT_IN_DETAILS);
 		this->vscroll->SetCapacityFromWidget(this, WID_VR_MATRIX);
-		if (this->hscroll != NULL) this->hscroll->SetCapacityFromWidget(this, WID_VR_VEHICLE_PANEL_DISPLAY);
+		if (this->hscroll != nullptr) this->hscroll->SetCapacityFromWidget(this, WID_VR_VEHICLE_PANEL_DISPLAY);
 	}
 };
 
@@ -1137,8 +1137,8 @@ static int CDECL VehicleCargoSorter(cons
 	CargoArray diff;
 
 	/* Append the cargo of the connected waggons */
-	for (v = *a; v != NULL; v = v->Next()) diff[v->cargo_type] += v->cargo_cap;
-	for (v = *b; v != NULL; v = v->Next()) diff[v->cargo_type] -= v->cargo_cap;
+	for (v = *a; v != nullptr; v = v->Next()) diff[v->cargo_type] += v->cargo_cap;
+	for (v = *b; v != nullptr; v = v->Next()) diff[v->cargo_type] -= v->cargo_cap;
 
 	int r = 0;
 	for (CargoID i = 0; i < NUM_CARGO; i++) {
@@ -1176,8 +1176,8 @@ static int CDECL VehicleValueSorter(cons
 	const Vehicle *u;
 	Money diff = 0;
 
-	for (u = *a; u != NULL; u = u->Next()) diff += u->value;
-	for (u = *b; u != NULL; u = u->Next()) diff -= u->value;
+	for (u = *a; u != nullptr; u = u->Next()) diff += u->value;
+	for (u = *b; u != nullptr; u = u->Next()) diff -= u->value;
 
 	int r = ClampToI32(diff);
 	return (r != 0) ? r : VehicleNumberSorter(a, b);
@@ -1218,10 +1218,10 @@ void InitializeGUI()
 static inline void ChangeVehicleWindow(WindowClass window_class, VehicleID from_index, VehicleID to_index)
 {
 	Window *w = FindWindowById(window_class, from_index);
-	if (w != NULL) {
+	if (w != nullptr) {
 		/* Update window_number */
 		w->window_number = to_index;
-		if (w->viewport != NULL) w->viewport->follow_vehicle = to_index;
+		if (w->viewport != nullptr) w->viewport->follow_vehicle = to_index;
 
 		/* Update vehicle drag data */
 		if (_thd.window_class == window_class && _thd.window_number == (WindowNumber)from_index) {
@@ -1291,7 +1291,7 @@ static const NWidgetPart _nested_vehicle
 static void DrawSmallOrderList(const Vehicle *v, int left, int right, int y, VehicleOrderID start = 0)
 {
 	const Order *order = v->GetOrder(start);
-	if (order == NULL) return;
+	if (order == nullptr) return;
 
 	bool rtl = _current_text_dir == TD_RTL;
 	int l_offset = rtl ? 0 : ScaleGUITrad(6);
@@ -1312,7 +1312,7 @@ static void DrawSmallOrderList(const Veh
 
 		oid++;
 		order = order->next;
-		if (order == NULL) {
+		if (order == nullptr) {
 			order = v->orders.list->GetFirstOrder();
 			oid = 0;
 		}
@@ -1397,7 +1397,7 @@ void BaseVehicleListWindow::DrawVehicleL
 		DrawVehicleImage(v, image_left, image_right, y + FONT_HEIGHT_SMALL - 1, selected_vehicle, EIT_IN_LIST, 0);
 		DrawString(text_left, text_right, y + line_height - FONT_HEIGHT_SMALL - WD_FRAMERECT_BOTTOM - 1, STR_VEHICLE_LIST_PROFIT_THIS_YEAR_LAST_YEAR);
 
-		if (v->name != NULL) {
+		if (v->name != nullptr) {
 			/* The vehicle got a name so we will print it */
 			SetDParam(0, v->index);
 			DrawString(text_left, text_right, y, STR_TINY_BLACK_VEHICLE);
@@ -1869,7 +1869,7 @@ struct VehicleDetailsWindow : Window {
 		const Vehicle *v = Vehicle::Get(window_number);
 
 		this->CreateNestedTree();
-		this->vscroll = (v->type == VEH_TRAIN ? this->GetScrollbar(WID_VD_SCROLLBAR) : NULL);
+		this->vscroll = (v->type == VEH_TRAIN ? this->GetScrollbar(WID_VD_SCROLLBAR) : nullptr);
 		this->FinishInitNested(window_number);
 
 		this->GetWidget<NWidgetCore>(WID_VD_RENAME_VEHICLE)->tool_tip = STR_VEHICLE_DETAILS_TRAIN_RENAME + v->type;
@@ -1914,7 +1914,7 @@ struct VehicleDetailsWindow : Window {
 			/* An articulated RV has its text drawn under the sprite instead of after it, hence 15 pixels extra. */
 			desired_height = WD_FRAMERECT_TOP + ScaleGUITrad(15) + 3 * FONT_HEIGHT_NORMAL + 2 + WD_FRAMERECT_BOTTOM;
 			/* Add space for the cargo amount for each part. */
-			for (const Vehicle *u = v; u != NULL; u = u->Next()) {
+			for (const Vehicle *u = v; u != nullptr; u = u->Next()) {
 				if (u->cargo_cap != 0) desired_height += FONT_HEIGHT_NORMAL + 1;
 			}
 		} else {
@@ -2219,15 +2219,15 @@ struct VehicleDetailsWindow : Window {
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
-
-		DoCommandP(0, this->window_number, 0, CMD_RENAME_VEHICLE | CMD_MSG(STR_ERROR_CAN_T_RENAME_TRAIN + Vehicle::Get(this->window_number)->type), NULL, str);
+		if (str == nullptr) return;
+
+		DoCommandP(0, this->window_number, 0, CMD_RENAME_VEHICLE | CMD_MSG(STR_ERROR_CAN_T_RENAME_TRAIN + Vehicle::Get(this->window_number)->type), nullptr, str);
 	}
 
 	void OnResize() override
 	{
 		NWidgetCore *nwi = this->GetWidget<NWidgetCore>(WID_VD_MATRIX);
-		if (nwi != NULL) {
+		if (nwi != nullptr) {
 			this->vscroll->SetCapacityFromWidget(this, WID_VD_MATRIX);
 		}
 	}
@@ -2382,7 +2382,7 @@ void CcStartStopVehicle(const CommandCos
 	if (result.Failed()) return;
 
 	const Vehicle *v = Vehicle::GetIfValid(p1);
-	if (v == NULL || !v->IsPrimaryVehicle() || v->owner != _local_company) return;
+	if (v == nullptr || !v->IsPrimaryVehicle() || v->owner != _local_company) return;
 
 	StringID msg = (v->vehstatus & VS_STOPPED) ? STR_VEHICLE_COMMAND_STOPPED : STR_VEHICLE_COMMAND_STARTED;
 	Point pt = RemapCoords(v->x_pos, v->y_pos, v->z_pos);
@@ -2397,7 +2397,7 @@ void CcStartStopVehicle(const CommandCos
 void StartStopVehicle(const Vehicle *v, bool texteffect)
 {
 	assert(v->IsPrimaryVehicle());
-	DoCommandP(v->tile, v->index, 0, _vehicle_command_translation_table[VCT_CMD_START_STOP][v->type], texteffect ? CcStartStopVehicle : NULL);
+	DoCommandP(v->tile, v->index, 0, _vehicle_command_translation_table[VCT_CMD_START_STOP][v->type], texteffect ? CcStartStopVehicle : nullptr);
 }
 
 /** Checks whether the vehicle may be refitted at the moment.*/
@@ -2407,7 +2407,7 @@ static bool IsVehicleRefitable(const Veh
 
 	do {
 		if (IsEngineRefittable(v->engine_type)) return true;
-	} while (v->IsGroundVehicle() && (v = v->Next()) != NULL);
+	} while (v->IsGroundVehicle() && (v = v->Next()) != nullptr);
 
 	return false;
 }
@@ -2709,7 +2709,7 @@ public:
 				 * most likely already open, but is also visible in the vehicle viewport. */
 				DoCommandP(v->tile, v->index, _ctrl_pressed ? 1 : 0,
 										_vehicle_command_translation_table[VCT_CMD_CLONE_VEH][v->type],
-										_ctrl_pressed ? NULL : CcCloneVehicle);
+										_ctrl_pressed ? nullptr : CcCloneVehicle);
 				break;
 			case WID_VV_TURN_AROUND: // turn around
 				assert(v->IsGroundVehicle());
@@ -2725,7 +2725,7 @@ public:
 
 	void OnResize() override
 	{
-		if (this->viewport != NULL) {
+		if (this->viewport != nullptr) {
 			NWidgetViewport *nvp = this->GetWidget<NWidgetViewport>(WID_VV_VIEWPORT);
 			nvp->UpdateViewportCoordinates(this);
 		}
@@ -2797,7 +2797,7 @@ void ShowVehicleViewWindow(const Vehicle
  */
 bool VehicleClicked(const Vehicle *v)
 {
-	assert(v != NULL);
+	assert(v != nullptr);
 	if (!(_thd.place_mode & HT_VEHICLE)) return false;
 
 	v = v->First();
@@ -2809,7 +2809,7 @@ bool VehicleClicked(const Vehicle *v)
 void StopGlobalFollowVehicle(const Vehicle *v)
 {
 	Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
-	if (w != NULL && w->viewport->follow_vehicle == v->index) {
+	if (w != nullptr && w->viewport->follow_vehicle == v->index) {
 		ScrollMainWindowTo(v->x_pos, v->y_pos, v->z_pos, true); // lock the main view on the vehicle's last position
 		w->viewport->follow_vehicle = INVALID_VEHICLE;
 	}
@@ -2864,7 +2864,7 @@ int GetVehicleWidth(const Vehicle *v, En
 {
 	if (v->type == VEH_TRAIN || v->type == VEH_ROAD) {
 		int vehicle_width = 0;
-		for (const Vehicle *u = v; u != NULL; u = u->Next()) {
+		for (const Vehicle *u = v; u != nullptr; u = u->Next()) {
 			vehicle_width += GetSingleVehicleWidth(u, image_type);
 		}
 		return vehicle_width;
@@ -2884,7 +2884,7 @@ void SetMouseCursorVehicle(const Vehicle
 
 	_cursor.sprite_count = 0;
 	int total_width = 0;
-	for (; v != NULL; v = v->HasArticulatedPart() ? v->GetNextArticulatedPart() : NULL) {
+	for (; v != nullptr; v = v->HasArticulatedPart() ? v->GetNextArticulatedPart() : nullptr) {
 		if (total_width >= 2 * (int)VEHICLEINFO_FULL_VEHICLE_WIDTH) break;
 
 		PaletteID pal = (v->vehstatus & VS_CRASHED) ? PALETTE_CRASH : GetVehiclePalette(v);
diff --git a/src/vehiclelist.cpp b/src/vehiclelist.cpp
--- a/src/vehiclelist.cpp
+++ b/src/vehiclelist.cpp
@@ -65,13 +65,13 @@ bool VehicleListIdentifier::UnpackIfVali
  * @param type    Type of vehicle
  * @param tile    The tile the depot is located on
  * @param engines Pointer to list to add vehicles to
- * @param wagons  Pointer to list to add wagons to (can be NULL)
+ * @param wagons  Pointer to list to add wagons to (can be nullptr)
  * @param individual_wagons If true add every wagon to \a wagons which is not attached to an engine. If false only add the first wagon of every row.
  */
 void BuildDepotVehicleList(VehicleType type, TileIndex tile, VehicleList *engines, VehicleList *wagons, bool individual_wagons)
 {
 	engines->clear();
-	if (wagons != NULL && wagons != engines) wagons->clear();
+	if (wagons != nullptr && wagons != engines) wagons->clear();
 
 	const Vehicle *v;
 	FOR_ALL_VEHICLES(v) {
@@ -84,7 +84,7 @@ void BuildDepotVehicleList(VehicleType t
 				const Train *t = Train::From(v);
 				if (t->IsArticulatedPart() || t->IsRearDualheaded()) continue;
 				if (t->track != TRACK_BIT_DEPOT) continue;
-				if (wagons != NULL && t->First()->IsFreeWagon()) {
+				if (wagons != nullptr && t->First()->IsFreeWagon()) {
 					if (individual_wagons || t->IsFreeWagon()) wagons->push_back(t);
 					continue;
 				}
@@ -104,7 +104,7 @@ void BuildDepotVehicleList(VehicleType t
 	/* Ensure the lists are not wasting too much space. If the lists are fresh
 	 * (i.e. built within a command) then this will actually do nothing. */
 	engines->shrink_to_fit();
-	if (wagons != NULL && wagons != engines) wagons->shrink_to_fit();
+	if (wagons != nullptr && wagons != engines) wagons->shrink_to_fit();
 }
 
 /**
@@ -139,9 +139,9 @@ bool GenerateVehicleSortList(VehicleList
 		case VL_SHARED_ORDERS:
 			/* Add all vehicles from this vehicle's shared order list */
 			v = Vehicle::GetIfValid(vli.index);
-			if (v == NULL || v->type != vli.vtype || !v->IsPrimaryVehicle()) return false;
+			if (v == nullptr || v->type != vli.vtype || !v->IsPrimaryVehicle()) return false;
 
-			for (; v != NULL; v = v->NextShared()) {
+			for (; v != nullptr; v = v->NextShared()) {
 				list->push_back(v);
 			}
 			break;
diff --git a/src/video/allegro_v.cpp b/src/video/allegro_v.cpp
--- a/src/video/allegro_v.cpp
+++ b/src/video/allegro_v.cpp
@@ -140,7 +140,7 @@ static void GetVideoModes()
 	set_gfx_mode(_fullscreen ? GFX_AUTODETECT_FULLSCREEN : GFX_AUTODETECT_WINDOWED, 640, 480, 0, 0);
 
 	GFX_MODE_LIST *mode_list = get_gfx_mode_list(gfx_driver->id);
-	if (mode_list == NULL) {
+	if (mode_list == nullptr) {
 		memcpy(_resolutions, default_resolutions, sizeof(default_resolutions));
 		_num_resolutions = lengthof(default_resolutions);
 		return;
@@ -243,7 +243,7 @@ static bool CreateMainSurface(uint w, ui
 bool VideoDriver_Allegro::ClaimMousePointer()
 {
 	select_mouse_cursor(MOUSE_CURSOR_NONE);
-	show_mouse(NULL);
+	show_mouse(nullptr);
 	disable_hardware_cursor();
 	return true;
 }
@@ -424,7 +424,7 @@ int _allegro_instance_count = 0;
 
 const char *VideoDriver_Allegro::Start(const char * const *parm)
 {
-	if (_allegro_instance_count == 0 && install_allegro(SYSTEM_AUTODETECT, &errno, NULL)) {
+	if (_allegro_instance_count == 0 && install_allegro(SYSTEM_AUTODETECT, &errno, nullptr)) {
 		DEBUG(driver, 0, "allegro: install_allegro failed '%s'", allegro_error);
 		return "Failed to set up Allegro";
 	}
@@ -437,8 +437,8 @@ const char *VideoDriver_Allegro::Start(c
 #if defined _DEBUG
 /* Allegro replaces SEGV/ABRT signals meaning that the debugger will never
  * be triggered, so rereplace the signals and make the debugger useful. */
-	signal(SIGABRT, NULL);
-	signal(SIGSEGV, NULL);
+	signal(SIGABRT, nullptr);
+	signal(SIGSEGV, nullptr);
 #endif
 
 	GetVideoModes();
@@ -448,7 +448,7 @@ const char *VideoDriver_Allegro::Start(c
 	MarkWholeScreenDirty();
 	set_close_button_callback(HandleExitGameRequest);
 
-	return NULL;
+	return nullptr;
 }
 
 void VideoDriver_Allegro::Stop()
@@ -463,7 +463,7 @@ static uint32 GetTime()
 {
 	struct timeval tim;
 
-	gettimeofday(&tim, NULL);
+	gettimeofday(&tim, nullptr);
 	return tim.tv_usec / 1000 + tim.tv_sec * 1000;
 }
 #else
diff --git a/src/video/dedicated_v.cpp b/src/video/dedicated_v.cpp
--- a/src/video/dedicated_v.cpp
+++ b/src/video/dedicated_v.cpp
@@ -87,7 +87,7 @@ static void WINAPI CheckForConsoleInput(
 	DWORD nb;
 	HANDLE hStdin = GetStdHandle(STD_INPUT_HANDLE);
 	for (;;) {
-		ReadFile(hStdin, _win_console_thread_buffer, lengthof(_win_console_thread_buffer), &nb, NULL);
+		ReadFile(hStdin, _win_console_thread_buffer, lengthof(_win_console_thread_buffer), &nb, nullptr);
 		if (nb >= lengthof(_win_console_thread_buffer)) nb = lengthof(_win_console_thread_buffer) - 1;
 		_win_console_thread_buffer[nb] = '\0';
 
@@ -102,12 +102,12 @@ static void CreateWindowsConsoleThread()
 {
 	DWORD dwThreadId;
 	/* Create event to signal when console input is ready */
-	_hInputReady = CreateEvent(NULL, false, false, NULL);
-	_hWaitForInputHandling = CreateEvent(NULL, false, false, NULL);
-	if (_hInputReady == NULL || _hWaitForInputHandling == NULL) usererror("Cannot create console event!");
+	_hInputReady = CreateEvent(nullptr, false, false, nullptr);
+	_hWaitForInputHandling = CreateEvent(nullptr, false, false, nullptr);
+	if (_hInputReady == nullptr || _hWaitForInputHandling == nullptr) usererror("Cannot create console event!");
 
-	_hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)CheckForConsoleInput, NULL, 0, &dwThreadId);
-	if (_hThread == NULL) usererror("Cannot create console thread!");
+	_hThread = CreateThread(nullptr, 0, (LPTHREAD_START_ROUTINE)CheckForConsoleInput, nullptr, 0, &dwThreadId);
+	if (_hThread == nullptr) usererror("Cannot create console thread!");
 
 	DEBUG(driver, 2, "Windows console thread started");
 }
@@ -130,7 +130,7 @@ static void *_dedicated_video_mem;
 /* Whether a fork has been done. */
 bool _dedicated_forks;
 
-extern bool SafeLoad(const char *filename, SaveLoadOperation fop, DetailedFileType dft, GameMode newgm, Subdirectory subdir, struct LoadFilter *lf = NULL);
+extern bool SafeLoad(const char *filename, SaveLoadOperation fop, DetailedFileType dft, GameMode newgm, Subdirectory subdir, struct LoadFilter *lf = nullptr);
 
 static FVideoDriver_Dedicated iFVideoDriver_Dedicated;
 
@@ -138,7 +138,7 @@ static FVideoDriver_Dedicated iFVideoDri
 const char *VideoDriver_Dedicated::Start(const char * const *parm)
 {
 	int bpp = BlitterFactory::GetCurrentBlitter()->GetScreenDepth();
-	_dedicated_video_mem = (bpp == 0) ? NULL : MallocT<byte>(_cur_resolution.width * _cur_resolution.height * (bpp / 8));
+	_dedicated_video_mem = (bpp == 0) ? nullptr : MallocT<byte>(_cur_resolution.width * _cur_resolution.height * (bpp / 8));
 
 	_screen.width  = _screen.pitch = _cur_resolution.width;
 	_screen.height = _cur_resolution.height;
@@ -164,7 +164,7 @@ const char *VideoDriver_Dedicated::Start
 #endif
 
 	DEBUG(driver, 1, "Loading dedicated server");
-	return NULL;
+	return nullptr;
 }
 
 void VideoDriver_Dedicated::Stop()
@@ -192,14 +192,14 @@ static bool InputWaiting()
 	FD_SET(STDIN, &readfds);
 
 	/* don't care about writefds and exceptfds: */
-	return select(STDIN + 1, &readfds, NULL, NULL, &tv) > 0;
+	return select(STDIN + 1, &readfds, nullptr, nullptr, &tv) > 0;
 }
 
 static uint32 GetTime()
 {
 	struct timeval tim;
 
-	gettimeofday(&tim, NULL);
+	gettimeofday(&tim, nullptr);
 	return tim.tv_usec / 1000 + tim.tv_sec * 1000;
 }
 
@@ -226,7 +226,7 @@ static void DedicatedHandleKeyInput()
 	if (_exit_game) return;
 
 #if defined(UNIX) || defined(__OS2__)
-	if (fgets(input_line, lengthof(input_line), stdin) == NULL) return;
+	if (fgets(input_line, lengthof(input_line), stdin) == nullptr) return;
 #else
 	/* Handle console input, and signal console thread, it can accept input again */
 	assert_compile(lengthof(_win_console_thread_buffer) <= lengthof(input_line));
diff --git a/src/video/null_v.cpp b/src/video/null_v.cpp
--- a/src/video/null_v.cpp
+++ b/src/video/null_v.cpp
@@ -29,13 +29,13 @@ const char *VideoDriver_Null::Start(cons
 	this->ticks = GetDriverParamInt(parm, "ticks", 1000);
 	_screen.width  = _screen.pitch = _cur_resolution.width;
 	_screen.height = _cur_resolution.height;
-	_screen.dst_ptr = NULL;
+	_screen.dst_ptr = nullptr;
 	ScreenSizeChanged();
 
 	/* Do not render, nor blit */
 	DEBUG(misc, 1, "Forcing blitter 'null'...");
 	BlitterFactory::SelectBlitter("null");
-	return NULL;
+	return nullptr;
 }
 
 void VideoDriver_Null::Stop() { }
diff --git a/src/video/sdl_v.cpp b/src/video/sdl_v.cpp
--- a/src/video/sdl_v.cpp
+++ b/src/video/sdl_v.cpp
@@ -39,9 +39,9 @@ static bool _all_modes;
 /** Whether the drawing is/may be done in a separate thread. */
 static bool _draw_threaded;
 /** Mutex to keep the access to the shared memory controlled. */
-static std::recursive_mutex *_draw_mutex = NULL;
+static std::recursive_mutex *_draw_mutex = nullptr;
 /** Signal to draw the next frame. */
-static std::condition_variable_any *_draw_signal = NULL;
+static std::condition_variable_any *_draw_signal = nullptr;
 /** Should we keep continue drawing? */
 static volatile bool _draw_continue;
 static Palette _local_palette;
@@ -111,7 +111,7 @@ static void UpdatePalette(bool init = fa
 		 * best mapping of shadow palette colors to real palette
 		 * colors from scratch.
 		 */
-		SDL_BlitSurface(_sdl_screen, NULL, _sdl_realscreen, NULL);
+		SDL_BlitSurface(_sdl_screen, nullptr, _sdl_realscreen, nullptr);
 		SDL_UpdateRect(_sdl_realscreen, 0, 0, 0, 0);
 	}
 }
@@ -158,7 +158,7 @@ static void DrawSurfaceToScreen()
 	_num_dirty_rects = 0;
 	if (n > MAX_DIRTY_RECTS) {
 		if (_sdl_screen != _sdl_realscreen) {
-			SDL_BlitSurface(_sdl_screen, NULL, _sdl_realscreen, NULL);
+			SDL_BlitSurface(_sdl_screen, nullptr, _sdl_realscreen, nullptr);
 		}
 		SDL_UpdateRect(_sdl_realscreen, 0, 0, 0, 0);
 	} else {
@@ -204,10 +204,10 @@ static const Dimension _default_resoluti
 
 static void GetVideoModes()
 {
-	SDL_Rect **modes = SDL_ListModes(NULL, SDL_SWSURFACE | SDL_FULLSCREEN);
-	if (modes == NULL) usererror("sdl: no modes available");
+	SDL_Rect **modes = SDL_ListModes(nullptr, SDL_SWSURFACE | SDL_FULLSCREEN);
+	if (modes == nullptr) usererror("sdl: no modes available");
 
-	_all_modes = (SDL_ListModes(NULL, SDL_SWSURFACE | (_fullscreen ? SDL_FULLSCREEN : 0)) == (void*)-1);
+	_all_modes = (SDL_ListModes(nullptr, SDL_SWSURFACE | (_fullscreen ? SDL_FULLSCREEN : 0)) == (void*)-1);
 	if (modes == (void*)-1) {
 		int n = 0;
 		for (uint i = 0; i < lengthof(_default_resolutions); i++) {
@@ -278,15 +278,15 @@ bool VideoDriver_SDL::CreateMainSurface(
 	if (bpp == 0) usererror("Can't use a blitter that blits 0 bpp for normal visuals");
 
 	char icon_path[MAX_PATH];
-	if (FioFindFullPath(icon_path, lastof(icon_path), BASESET_DIR, "openttd.32.bmp") != NULL) {
+	if (FioFindFullPath(icon_path, lastof(icon_path), BASESET_DIR, "openttd.32.bmp") != nullptr) {
 		/* Give the application an icon */
 		icon = SDL_LoadBMP(icon_path);
-		if (icon != NULL) {
+		if (icon != nullptr) {
 			/* Get the colourkey, which will be magenta */
 			uint32 rgbmap = SDL_MapRGB(icon->format, 255, 0, 255);
 
 			SDL_SetColorKey(icon, SDL_SRCCOLORKEY, rgbmap);
-			SDL_WM_SetIcon(icon, NULL);
+			SDL_WM_SetIcon(icon, nullptr);
 			SDL_FreeSurface(icon);
 		}
 	}
@@ -322,9 +322,9 @@ bool VideoDriver_SDL::CreateMainSurface(
 	if (want_hwpalette) DEBUG(driver, 1, "SDL: requesting hardware palette");
 
 	/* Free any previously allocated shadow surface */
-	if (_sdl_screen != NULL && _sdl_screen != _sdl_realscreen) SDL_FreeSurface(_sdl_screen);
+	if (_sdl_screen != nullptr && _sdl_screen != _sdl_realscreen) SDL_FreeSurface(_sdl_screen);
 
-	if (_sdl_realscreen != NULL) {
+	if (_sdl_realscreen != nullptr) {
 		if (_requested_hwpalette != want_hwpalette) {
 			/* SDL (at least the X11 driver), reuses the
 			 * same window and palette settings when the bpp
@@ -349,7 +349,7 @@ bool VideoDriver_SDL::CreateMainSurface(
 
 	/* DO NOT CHANGE TO HWSURFACE, IT DOES NOT WORK */
 	newscreen = SDL_SetVideoMode(w, h, bpp, SDL_SWSURFACE | (want_hwpalette ? SDL_HWPALETTE : 0) | (_fullscreen ? SDL_FULLSCREEN : SDL_RESIZABLE));
-	if (newscreen == NULL) {
+	if (newscreen == nullptr) {
 		DEBUG(driver, 0, "SDL: Couldn't allocate a window to draw on");
 		return false;
 	}
@@ -376,7 +376,7 @@ bool VideoDriver_SDL::CreateMainSurface(
 		 */
 		DEBUG(driver, 1, "SDL: using shadow surface");
 		newscreen = SDL_CreateRGBSurface(SDL_SWSURFACE, w, h, bpp, 0, 0, 0, 0);
-		if (newscreen == NULL) {
+		if (newscreen == nullptr) {
 			DEBUG(driver, 0, "SDL: Couldn't allocate a shadow surface to draw on");
 			return false;
 		}
@@ -637,9 +637,9 @@ const char *VideoDriver_SDL::Start(const
 	MarkWholeScreenDirty();
 	SetupKeyboard();
 
-	_draw_threaded = GetDriverParam(parm, "no_threads") == NULL && GetDriverParam(parm, "no_thread") == NULL;
+	_draw_threaded = GetDriverParam(parm, "no_threads") == nullptr && GetDriverParam(parm, "no_thread") == nullptr;
 
-	return NULL;
+	return nullptr;
 }
 
 void VideoDriver_SDL::SetupKeyboard()
@@ -673,7 +673,7 @@ void VideoDriver_SDL::MainLoop()
 		/* Initialise the mutex first, because that's the thing we *need*
 		 * directly in the newly created thread. */
 		_draw_mutex = new std::recursive_mutex();
-		if (_draw_mutex == NULL) {
+		if (_draw_mutex == nullptr) {
 			_draw_threaded = false;
 		} else {
 			draw_lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
@@ -688,8 +688,8 @@ void VideoDriver_SDL::MainLoop()
 				draw_lock.release();
 				delete _draw_mutex;
 				delete _draw_signal;
-				_draw_mutex = NULL;
-				_draw_signal = NULL;
+				_draw_mutex = nullptr;
+				_draw_signal = nullptr;
 			} else {
 				/* Wait till the draw mutex has started itself. */
 				_draw_signal->wait(*_draw_mutex);
@@ -757,26 +757,26 @@ void VideoDriver_SDL::MainLoop()
 
 			/* The gameloop is the part that can run asynchronously. The rest
 			 * except sleeping can't. */
-			if (_draw_mutex != NULL) draw_lock.unlock();
+			if (_draw_mutex != nullptr) draw_lock.unlock();
 
 			GameLoop();
 
-			if (_draw_mutex != NULL) draw_lock.lock();
+			if (_draw_mutex != nullptr) draw_lock.lock();
 
 			UpdateWindows();
 			_local_palette = _cur_palette;
 		} else {
 			/* Release the thread while sleeping */
-			if (_draw_mutex != NULL) draw_lock.unlock();
+			if (_draw_mutex != nullptr) draw_lock.unlock();
 			CSleep(1);
-			if (_draw_mutex != NULL) draw_lock.lock();
+			if (_draw_mutex != nullptr) draw_lock.lock();
 
 			NetworkDrawChatMessage();
 			DrawMouseCursor();
 		}
 
 		/* End of the critical part. */
-		if (_draw_mutex != NULL && !HasModalProgress()) {
+		if (_draw_mutex != nullptr && !HasModalProgress()) {
 			_draw_signal->notify_one();
 		} else {
 			/* Oh, we didn't have threads, then just draw unthreaded */
@@ -785,7 +785,7 @@ void VideoDriver_SDL::MainLoop()
 		}
 	}
 
-	if (_draw_mutex != NULL) {
+	if (_draw_mutex != nullptr) {
 		_draw_continue = false;
 		/* Sending signal if there is no thread blocked
 		 * is very valid and results in noop */
@@ -797,15 +797,15 @@ void VideoDriver_SDL::MainLoop()
 		delete _draw_mutex;
 		delete _draw_signal;
 
-		_draw_mutex = NULL;
-		_draw_signal = NULL;
+		_draw_mutex = nullptr;
+		_draw_signal = nullptr;
 	}
 }
 
 bool VideoDriver_SDL::ChangeResolution(int w, int h)
 {
 	std::unique_lock<std::recursive_mutex> lock;
-	if (_draw_mutex != NULL) lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
+	if (_draw_mutex != nullptr) lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
 
 	return CreateMainSurface(w, h);
 }
@@ -813,7 +813,7 @@ bool VideoDriver_SDL::ChangeResolution(i
 bool VideoDriver_SDL::ToggleFullscreen(bool fullscreen)
 {
 	std::unique_lock<std::recursive_mutex> lock;
-	if (_draw_mutex != NULL) lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
+	if (_draw_mutex != nullptr) lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
 
 	_fullscreen = fullscreen;
 	GetVideoModes(); // get the list of available video modes
@@ -834,12 +834,12 @@ bool VideoDriver_SDL::AfterBlitterChange
 
 void VideoDriver_SDL::AcquireBlitterLock()
 {
-	if (_draw_mutex != NULL) _draw_mutex->lock();
+	if (_draw_mutex != nullptr) _draw_mutex->lock();
 }
 
 void VideoDriver_SDL::ReleaseBlitterLock()
 {
-	if (_draw_mutex != NULL) _draw_mutex->unlock();
+	if (_draw_mutex != nullptr) _draw_mutex->unlock();
 }
 
 #endif /* WITH_SDL */
diff --git a/src/video/win32_v.cpp b/src/video/win32_v.cpp
--- a/src/video/win32_v.cpp
+++ b/src/video/win32_v.cpp
@@ -42,7 +42,7 @@
 #endif
 
 typedef BOOL (WINAPI *PFNTRACKMOUSEEVENT)(LPTRACKMOUSEEVENT lpEventTrack);
-static PFNTRACKMOUSEEVENT _pTrackMouseEvent = NULL;
+static PFNTRACKMOUSEEVENT _pTrackMouseEvent = nullptr;
 
 static struct {
 	HWND main_wnd;
@@ -68,9 +68,9 @@ DWORD _imm_props;
 /** Whether the drawing is/may be done in a separate thread. */
 static bool _draw_threaded;
 /** Mutex to keep the access to the shared memory controlled. */
-static std::recursive_mutex *_draw_mutex = NULL;
+static std::recursive_mutex *_draw_mutex = nullptr;
 /** Signal to draw the next frame. */
-static std::condition_variable_any *_draw_signal = NULL;
+static std::condition_variable_any *_draw_signal = nullptr;
 /** Should we keep continue drawing? */
 static volatile bool _draw_continue;
 /** Local copy of the palette for use in the drawing thread. */
@@ -91,7 +91,7 @@ static void MakePalette()
 
 	}
 	_wnd.gdi_palette = CreatePalette(pal);
-	if (_wnd.gdi_palette == NULL) usererror("CreatePalette failed!\n");
+	if (_wnd.gdi_palette == nullptr) usererror("CreatePalette failed!\n");
 
 	_cur_palette.first_dirty = 0;
 	_cur_palette.count_dirty = 256;
@@ -309,7 +309,7 @@ bool VideoDriver_Win32::MakeWindow(bool 
 		}
 	} else if (_wnd.fullscreen) {
 		/* restore display? */
-		ChangeDisplaySettings(NULL, 0);
+		ChangeDisplaySettings(nullptr, 0);
 		/* restore the resolution */
 		_wnd.width = _bck_resolution.width;
 		_wnd.height = _bck_resolution.height;
@@ -336,7 +336,7 @@ bool VideoDriver_Win32::MakeWindow(bool 
 		w = r.right - r.left;
 		h = r.bottom - r.top;
 
-		if (_wnd.main_wnd != NULL) {
+		if (_wnd.main_wnd != nullptr) {
 			if (!_window_maximize) SetWindowPos(_wnd.main_wnd, 0, 0, 0, w, h, SWP_NOACTIVATE | SWP_NOOWNERZORDER | SWP_NOZORDER | SWP_NOMOVE);
 		} else {
 			int x = (GetSystemMetrics(SM_CXSCREEN) - w) / 2;
@@ -345,8 +345,8 @@ bool VideoDriver_Win32::MakeWindow(bool 
 			char window_title[64];
 			seprintf(window_title, lastof(window_title), "OpenTTD %s", _openttd_revision);
 
-			_wnd.main_wnd = CreateWindow(_T("OTTD"), MB_TO_WIDE(window_title), style, x, y, w, h, 0, 0, GetModuleHandle(NULL), 0);
-			if (_wnd.main_wnd == NULL) usererror("CreateWindow failed");
+			_wnd.main_wnd = CreateWindow(_T("OTTD"), MB_TO_WIDE(window_title), style, x, y, w, h, 0, 0, GetModuleHandle(nullptr), 0);
+			if (_wnd.main_wnd == nullptr) usererror("CreateWindow failed");
 			ShowWindow(_wnd.main_wnd, showstyle);
 		}
 	}
@@ -559,14 +559,14 @@ static LRESULT HandleIMEComposition(HWND
 	if (hIMC != NULL) {
 		if (lParam & GCS_RESULTSTR) {
 			/* Read result string from the IME. */
-			LONG len = ImmGetCompositionString(hIMC, GCS_RESULTSTR, NULL, 0); // Length is always in bytes, even in UNICODE build.
+			LONG len = ImmGetCompositionString(hIMC, GCS_RESULTSTR, nullptr, 0); // Length is always in bytes, even in UNICODE build.
 			TCHAR *str = (TCHAR *)_alloca(len + sizeof(TCHAR));
 			len = ImmGetCompositionString(hIMC, GCS_RESULTSTR, str, len);
 			str[len / sizeof(TCHAR)] = '\0';
 
 			/* Transmit text to windowing system. */
 			if (len > 0) {
-				HandleTextInput(NULL, true); // Clear marked string.
+				HandleTextInput(nullptr, true); // Clear marked string.
 				HandleTextInput(FS2OTTD(str));
 			}
 			SetCompositionPos(hwnd);
@@ -577,7 +577,7 @@ static LRESULT HandleIMEComposition(HWND
 
 		if ((lParam & GCS_COMPSTR) && DrawIMECompositionString()) {
 			/* Read composition string from the IME. */
-			LONG len = ImmGetCompositionString(hIMC, GCS_COMPSTR, NULL, 0); // Length is always in bytes, even in UNICODE build.
+			LONG len = ImmGetCompositionString(hIMC, GCS_COMPSTR, nullptr, 0); // Length is always in bytes, even in UNICODE build.
 			TCHAR *str = (TCHAR *)_alloca(len + sizeof(TCHAR));
 			len = ImmGetCompositionString(hIMC, GCS_COMPSTR, str, len);
 			str[len / sizeof(TCHAR)] = '\0';
@@ -587,7 +587,7 @@ static LRESULT HandleIMEComposition(HWND
 				convert_from_fs(str, utf8_buf, lengthof(utf8_buf));
 
 				/* Convert caret position from bytes in the input string to a position in the UTF-8 encoded string. */
-				LONG caret_bytes = ImmGetCompositionString(hIMC, GCS_CURSORPOS, NULL, 0);
+				LONG caret_bytes = ImmGetCompositionString(hIMC, GCS_CURSORPOS, nullptr, 0);
 				const char *caret = utf8_buf;
 				for (const TCHAR *c = str; *c != '\0' && *caret != '\0' && caret_bytes > 0; c++, caret_bytes--) {
 					/* Skip DBCS lead bytes or leading surrogates. */
@@ -604,7 +604,7 @@ static LRESULT HandleIMEComposition(HWND
 
 				HandleTextInput(utf8_buf, true, caret);
 			} else {
-				HandleTextInput(NULL, true);
+				HandleTextInput(nullptr, true);
 			}
 
 			lParam &= ~(GCS_COMPSTR | GCS_COMPATTR | GCS_COMPCLAUSE | GCS_CURSORPOS | GCS_DELTASTART);
@@ -622,7 +622,7 @@ static void CancelIMEComposition(HWND hw
 	if (hIMC != NULL) ImmNotifyIME(hIMC, NI_COMPOSITIONSTR, CPS_CANCEL, 0);
 	ImmReleaseContext(hwnd, hIMC);
 	/* Clear any marked string from the current edit box. */
-	HandleTextInput(NULL, true);
+	HandleTextInput(nullptr, true);
 }
 
 static LRESULT CALLBACK WndProcGdi(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
@@ -647,14 +647,14 @@ static LRESULT CALLBACK WndProcGdi(HWND 
 			break;
 
 		case WM_PAINT:
-			if (!in_sizemove && _draw_mutex != NULL && !HasModalProgress()) {
+			if (!in_sizemove && _draw_mutex != nullptr && !HasModalProgress()) {
 				/* Get the union of the old update rect and the new update rect. */
 				RECT r;
 				GetUpdateRect(hwnd, &r, FALSE);
 				UnionRect(&_wnd.update_rect, &_wnd.update_rect, &r);
 
 				/* Mark the window as updated, otherwise Windows would send more WM_PAINT messages. */
-				ValidateRect(hwnd, NULL);
+				ValidateRect(hwnd, nullptr);
 				_draw_signal->notify_one();
 			} else {
 				PAINTSTRUCT ps;
@@ -676,7 +676,7 @@ static LRESULT CALLBACK WndProcGdi(HWND 
 
 			SelectPalette(hDC, hOldPalette, TRUE);
 			ReleaseDC(hwnd, hDC);
-			if (nChanged != 0) InvalidateRect(hwnd, NULL, FALSE);
+			if (nChanged != 0) InvalidateRect(hwnd, nullptr, FALSE);
 			return 0;
 		}
 
@@ -730,7 +730,7 @@ static LRESULT CALLBACK WndProcGdi(HWND 
 			 * tracking the mouse for exiting the window */
 			if (!_cursor.in_window) {
 				_cursor.in_window = true;
-				if (_pTrackMouseEvent != NULL) {
+				if (_pTrackMouseEvent != nullptr) {
 					TRACKMOUSEEVENT tme;
 					tme.cbSize = sizeof(tme);
 					tme.dwFlags = TME_LEAVE;
@@ -783,7 +783,7 @@ static LRESULT CALLBACK WndProcGdi(HWND 
 
 		case WM_IME_ENDCOMPOSITION:
 			/* Clear any pending composition string. */
-			HandleTextInput(NULL, true);
+			HandleTextInput(nullptr, true);
 			if (DrawIMECompositionString()) return 0;
 			break;
 
@@ -831,7 +831,7 @@ static LRESULT CALLBACK WndProcGdi(HWND 
 
 			/* Silently drop all messages handled by WM_CHAR. */
 			MSG msg;
-			if (PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE)) {
+			if (PeekMessage(&msg, nullptr, 0, 0, PM_NOREMOVE)) {
 				if ((msg.message == WM_CHAR || msg.message == WM_DEADCHAR) && GB(lParam, 16, 8) == GB(msg.lParam, 16, 8)) {
 					return 0;
 				}
@@ -993,7 +993,7 @@ static LRESULT CALLBACK WndProcGdi(HWND 
 				} else if (!active && !minimized) {
 					/* Minimise the window and restore desktop */
 					ShowWindow(hwnd, SW_MINIMIZE);
-					ChangeDisplaySettings(NULL, 0);
+					ChangeDisplaySettings(nullptr, 0);
 				}
 			}
 			break;
@@ -1008,7 +1008,7 @@ static void RegisterWndClass()
 	static bool registered = false;
 
 	if (!registered) {
-		HINSTANCE hinst = GetModuleHandle(NULL);
+		HINSTANCE hinst = GetModuleHandle(nullptr);
 		WNDCLASS wnd = {
 			CS_OWNDC,
 			WndProcGdi,
@@ -1016,7 +1016,7 @@ static void RegisterWndClass()
 			0,
 			hinst,
 			LoadIcon(hinst, MAKEINTRESOURCE(100)),
-			LoadCursor(NULL, IDC_ARROW),
+			LoadCursor(nullptr, IDC_ARROW),
 			0,
 			0,
 			_T("OTTD")
@@ -1057,8 +1057,8 @@ static bool AllocateDibSection(int w, in
 	if (_wnd.dib_sect) DeleteObject(_wnd.dib_sect);
 
 	dc = GetDC(0);
-	_wnd.dib_sect = CreateDIBSection(dc, bi, DIB_RGB_COLORS, (VOID**)&_wnd.buffer_bits, NULL, 0);
-	if (_wnd.dib_sect == NULL) usererror("CreateDIBSection failed");
+	_wnd.dib_sect = CreateDIBSection(dc, bi, DIB_RGB_COLORS, (VOID**)&_wnd.buffer_bits, nullptr, 0);
+	if (_wnd.dib_sect == nullptr) usererror("CreateDIBSection failed");
 	ReleaseDC(0, dc);
 
 	_screen.width = w;
@@ -1095,7 +1095,7 @@ static void FindResolutions()
 	/* XXX - EnumDisplaySettingsW crashes with unicows.dll on Windows95
 	 * Doesn't really matter since we don't pass a string anyways, but still
 	 * a letdown */
-	for (i = 0; EnumDisplaySettingsA(NULL, i, &dm) != 0; i++) {
+	for (i = 0; EnumDisplaySettingsA(nullptr, i, &dm) != 0; i++) {
 		if (dm.dmBitsPerPel == bpp &&
 				dm.dmPelsWidth >= 640 && dm.dmPelsHeight >= 480) {
 			uint j;
@@ -1149,9 +1149,9 @@ const char *VideoDriver_Win32::Start(con
 
 	MarkWholeScreenDirty();
 
-	_draw_threaded = GetDriverParam(parm, "no_threads") == NULL && GetDriverParam(parm, "no_thread") == NULL && std::thread::hardware_concurrency() > 1;
+	_draw_threaded = GetDriverParam(parm, "no_threads") == nullptr && GetDriverParam(parm, "no_thread") == nullptr && std::thread::hardware_concurrency() > 1;
 
-	return NULL;
+	return nullptr;
 }
 
 void VideoDriver_Win32::Stop()
@@ -1160,7 +1160,7 @@ void VideoDriver_Win32::Stop()
 	DeleteObject(_wnd.dib_sect);
 	DestroyWindow(_wnd.main_wnd);
 
-	if (_wnd.fullscreen) ChangeDisplaySettings(NULL, 0);
+	if (_wnd.fullscreen) ChangeDisplaySettings(nullptr, 0);
 	MyShowCursor(true);
 }
 
@@ -1176,7 +1176,7 @@ static void CheckPaletteAnim()
 	if (_cur_palette.count_dirty == 0) return;
 
 	_local_palette = _cur_palette;
-	InvalidateRect(_wnd.main_wnd, NULL, FALSE);
+	InvalidateRect(_wnd.main_wnd, nullptr, FALSE);
 }
 
 void VideoDriver_Win32::MainLoop()
@@ -1211,8 +1211,8 @@ void VideoDriver_Win32::MainLoop()
 				draw_lock.release();
 				delete _draw_mutex;
 				delete _draw_signal;
-				_draw_mutex = NULL;
-				_draw_signal = NULL;
+				_draw_mutex = nullptr;
+				_draw_signal = nullptr;
 			} else {
 				DEBUG(driver, 1, "Threaded drawing enabled");
 				/* Wait till the draw thread has started itself. */
@@ -1227,7 +1227,7 @@ void VideoDriver_Win32::MainLoop()
 	for (;;) {
 		uint32 prev_cur_ticks = cur_ticks; // to check for wrapping
 
-		while (PeekMessage(&mesg, NULL, 0, 0, PM_REMOVE)) {
+		while (PeekMessage(&mesg, nullptr, 0, 0, PM_REMOVE)) {
 			InteractiveRandom(); // randomness
 			/* Convert key messages to char messages if we want text input. */
 			if (EditBoxInGlobalFocus()) TranslateMessage(&mesg);
@@ -1310,14 +1310,14 @@ void VideoDriver_Win32::MainLoop()
 		delete _draw_mutex;
 		delete _draw_signal;
 
-		_draw_mutex = NULL;
+		_draw_mutex = nullptr;
 	}
 }
 
 bool VideoDriver_Win32::ChangeResolution(int w, int h)
 {
 	std::unique_lock<std::recursive_mutex> lock;
-	if (_draw_mutex != NULL) lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
+	if (_draw_mutex != nullptr) lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
 
 	if (_window_maximize) ShowWindow(_wnd.main_wnd, SW_SHOWNORMAL);
 
@@ -1330,7 +1330,7 @@ bool VideoDriver_Win32::ChangeResolution
 bool VideoDriver_Win32::ToggleFullscreen(bool full_screen)
 {
 	std::unique_lock<std::recursive_mutex> lock;
-	if (_draw_mutex != NULL) lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
+	if (_draw_mutex != nullptr) lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
 
 	return this->MakeWindow(full_screen);
 }
@@ -1342,18 +1342,18 @@ bool VideoDriver_Win32::AfterBlitterChan
 
 void VideoDriver_Win32::AcquireBlitterLock()
 {
-	if (_draw_mutex != NULL) _draw_mutex->lock();
+	if (_draw_mutex != nullptr) _draw_mutex->lock();
 }
 
 void VideoDriver_Win32::ReleaseBlitterLock()
 {
-	if (_draw_mutex != NULL) _draw_mutex->unlock();
+	if (_draw_mutex != nullptr) _draw_mutex->unlock();
 }
 
 void VideoDriver_Win32::EditBoxLostFocus()
 {
 	std::unique_lock<std::recursive_mutex> lock;
-	if (_draw_mutex != NULL) lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
+	if (_draw_mutex != nullptr) lock = std::unique_lock<std::recursive_mutex>(*_draw_mutex);
 
 	CancelIMEComposition(_wnd.main_wnd);
 	SetCompositionPos(_wnd.main_wnd);
diff --git a/src/viewport.cpp b/src/viewport.cpp
--- a/src/viewport.cpp
+++ b/src/viewport.cpp
@@ -187,7 +187,7 @@ static TileInfo *_cur_ti;
 bool _draw_bounding_boxes = false;
 bool _draw_dirty_blocks = false;
 uint _dirty_block_colour = 0;
-static VpSpriteSorter _vp_sprite_sorter = NULL;
+static VpSpriteSorter _vp_sprite_sorter = nullptr;
 
 static Point MapXYZToViewport(const ViewPort *vp, int x, int y, int z)
 {
@@ -199,11 +199,11 @@ static Point MapXYZToViewport(const View
 
 void DeleteWindowViewport(Window *w)
 {
-	if (w->viewport == NULL) return;
+	if (w->viewport == nullptr) return;
 
 	delete w->viewport->overlay;
 	free(w->viewport);
-	w->viewport = NULL;
+	w->viewport = nullptr;
 }
 
 /**
@@ -221,7 +221,7 @@ void DeleteWindowViewport(Window *w)
 void InitializeWindowViewport(Window *w, int x, int y,
 	int width, int height, uint32 follow_flags, ZoomLevel zoom)
 {
-	assert(w->viewport == NULL);
+	assert(w->viewport == nullptr);
 
 	ViewportData *vp = CallocT<ViewportData>(1);
 
@@ -256,7 +256,7 @@ void InitializeWindowViewport(Window *w,
 	vp->dest_scrollpos_x = pt.x;
 	vp->dest_scrollpos_y = pt.y;
 
-	vp->overlay = NULL;
+	vp->overlay = nullptr;
 
 	w->viewport = vp;
 	vp->virtual_left = 0; // pt.x;
@@ -389,18 +389,18 @@ static void SetViewportPosition(Window *
  * @param x X coordinate of the xy position
  * @param y Y coordinate of the xy position
  * @return Pointer to the viewport if the xy position is in the viewport of the window,
- *         otherwise \c NULL is returned.
+ *         otherwise \c nullptr is returned.
  */
 ViewPort *IsPtInWindowViewport(const Window *w, int x, int y)
 {
 	ViewPort *vp = w->viewport;
 
-	if (vp != NULL &&
+	if (vp != nullptr &&
 			IsInsideMM(x, vp->left, vp->left + vp->width) &&
 			IsInsideMM(y, vp->top, vp->top + vp->height))
 		return vp;
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -436,8 +436,8 @@ static Point GetTileFromScreenXY(int x, 
 	ViewPort *vp;
 	Point pt;
 
-	if ( (w = FindWindowFromPt(x, y)) != NULL &&
-			 (vp = IsPtInWindowViewport(w, x, y)) != NULL)
+	if ( (w = FindWindowFromPt(x, y)) != nullptr &&
+			 (vp = IsPtInWindowViewport(w, x, y)) != nullptr)
 				return TranslateXYToTileCoord(vp, zoom_x, zoom_y);
 
 	pt.y = pt.x = -1;
@@ -495,7 +495,7 @@ void HandleZoomMessage(Window *w, const 
  * @param extra_offs_x Pixel X offset for the sprite position.
  * @param extra_offs_y Pixel Y offset for the sprite position.
  */
-static void AddTileSpriteToDraw(SpriteID image, PaletteID pal, int32 x, int32 y, int z, const SubSprite *sub = NULL, int extra_offs_x = 0, int extra_offs_y = 0)
+static void AddTileSpriteToDraw(SpriteID image, PaletteID pal, int32 x, int32 y, int z, const SubSprite *sub = nullptr, int extra_offs_x = 0, int extra_offs_y = 0)
 {
 	assert((image & SPRITE_MASK) < MAX_SPRITES);
 
@@ -598,8 +598,8 @@ void OffsetGroundSprite(int x, int y)
 		default: NOT_REACHED();
 	}
 
-	/* _vd.last_child == NULL if foundation sprite was clipped by the viewport bounds */
-	if (_vd.last_child != NULL) _vd.foundation[_vd.foundation_part] = (uint)_vd.parent_sprites_to_draw.size() - 1;
+	/* _vd.last_child == nullptr if foundation sprite was clipped by the viewport bounds */
+	if (_vd.last_child != nullptr) _vd.foundation[_vd.foundation_part] = (uint)_vd.parent_sprites_to_draw.size() - 1;
 
 	_vd.foundation_offset[_vd.foundation_part].x = x * ZOOM_LVL_BASE;
 	_vd.foundation_offset[_vd.foundation_part].y = y * ZOOM_LVL_BASE;
@@ -674,7 +674,7 @@ void AddSortableSpriteToDraw(SpriteID im
 		return;
 	}
 
-	_vd.last_child = NULL;
+	_vd.last_child = nullptr;
 
 	Point pt = RemapCoords(x, y, z);
 	int tmp_left, tmp_top, tmp_x = pt.x, tmp_y = pt.y;
@@ -818,7 +818,7 @@ void AddChildSpriteScreen(SpriteID image
 	assert((image & SPRITE_MASK) < MAX_SPRITES);
 
 	/* If the ParentSprite was clipped by the viewport bounds, do not draw the ChildSprites either */
-	if (_vd.last_child == NULL) return;
+	if (_vd.last_child == nullptr) return;
 
 	/* make the sprites transparent with the right palette */
 	if (transparent) {
@@ -879,7 +879,7 @@ static void DrawSelectionSprite(SpriteID
 		AddTileSpriteToDraw(image, pal, ti->x, ti->y, ti->z + z_offset);
 	} else {
 		/* draw on top of foundation */
-		AddChildSpriteToFoundation(image, pal, NULL, foundation_part, 0, -z_offset * ZOOM_LVL_BASE);
+		AddChildSpriteToFoundation(image, pal, nullptr, foundation_part, 0, -z_offset * ZOOM_LVL_BASE);
 	}
 }
 
@@ -1171,8 +1171,8 @@ static void ViewportAddLandscape()
 				_vd.foundation_part = FOUNDATION_PART_NONE;
 				_vd.foundation[0] = -1;
 				_vd.foundation[1] = -1;
-				_vd.last_foundation_child[0] = NULL;
-				_vd.last_foundation_child[1] = NULL;
+				_vd.last_foundation_child[0] = nullptr;
+				_vd.last_foundation_child[1] = nullptr;
 
 				_tile_type_procs[tile_type]->draw_tile_proc(&tile_info);
 				if (tile_info.tile != INVALID_TILE) DrawTileSelection(&tile_info);
@@ -1383,7 +1383,7 @@ void ViewportSign::MarkDirty(ZoomLevel m
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_BACK(w) {
 		ViewPort *vp = w->viewport;
-		if (vp != NULL && vp->zoom <= maxzoom) {
+		if (vp != nullptr && vp->zoom <= maxzoom) {
 			assert(vp->width != 0);
 			Rect &zl = zoomlevels[vp->zoom];
 			MarkViewportDirty(vp, zl.left, zl.top, zl.right, zl.bottom);
@@ -1568,7 +1568,7 @@ void ViewportDoDraw(const ViewPort *vp, 
 	_vd.dpi.left = left & mask;
 	_vd.dpi.top = top & mask;
 	_vd.dpi.pitch = old_dpi->pitch;
-	_vd.last_child = NULL;
+	_vd.last_child = nullptr;
 
 	int x = UnScaleByZoom(_vd.dpi.left - (vp->virtual_left & mask), vp->zoom) + vp->left;
 	int y = UnScaleByZoom(_vd.dpi.top - (vp->virtual_top & mask), vp->zoom) + vp->top;
@@ -1601,7 +1601,7 @@ void ViewportDoDraw(const ViewPort *vp, 
 	dp.height = UnScaleByZoom(dp.height, zoom);
 	_cur_dpi = &dp;
 
-	if (vp->overlay != NULL && vp->overlay->GetCargoMask() != 0 && vp->overlay->GetCompanyMask() != 0) {
+	if (vp->overlay != nullptr && vp->overlay->GetCargoMask() != 0 && vp->overlay->GetCompanyMask() != 0) {
 		/* translate to window coordinates */
 		dp.left = x;
 		dp.top = y;
@@ -1809,7 +1809,7 @@ void MarkAllViewportsDirty(int left, int
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_BACK(w) {
 		ViewPort *vp = w->viewport;
-		if (vp != NULL) {
+		if (vp != nullptr) {
 			assert(vp->width != 0);
 			MarkViewportDirty(vp, left, top, right, bottom);
 		}
@@ -1820,7 +1820,7 @@ void ConstrainAllViewportsZoom()
 {
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_FRONT(w) {
-		if (w->viewport == NULL) continue;
+		if (w->viewport == nullptr) continue;
 
 		ZoomLevel zoom = static_cast<ZoomLevel>(Clamp(w->viewport->zoom, _settings_client.gui.zoom_min, _settings_client.gui.zoom_max));
 		if (zoom != w->viewport->zoom) {
@@ -2012,9 +2012,9 @@ static bool CheckClickOnViewportSign(con
 	bool show_competitors = HasBit(_display_opt, DO_SHOW_COMPETITOR_SIGNS);
 
 	/* Topmost of each type that was hit */
-	BaseStation *st = NULL, *last_st = NULL;
-	Town *t = NULL, *last_t = NULL;
-	Sign *si = NULL, *last_si = NULL;
+	BaseStation *st = nullptr, *last_st = nullptr;
+	Town *t = nullptr, *last_t = nullptr;
+	Sign *si = nullptr, *last_si = nullptr;
 
 	/* See ViewportAddKdtreeSigns() for details on the search logic */
 	_viewport_sign_kdtree.FindContained(search_rect.left, search_rect.top, search_rect.right, search_rect.bottom, [&](const ViewportSignKdtreeItem & item) {
@@ -2052,17 +2052,17 @@ static bool CheckClickOnViewportSign(con
 	});
 
 	/* Select which hit to handle based on priority */
-	if (last_st != NULL) {
+	if (last_st != nullptr) {
 		if (Station::IsExpected(last_st)) {
 			ShowStationViewWindow(last_st->index);
 		} else {
 			ShowWaypointWindow(Waypoint::From(last_st));
 		}
 		return true;
-	} else if (last_t != NULL) {
+	} else if (last_t != nullptr) {
 		ShowTownViewWindow(last_t->index);
 		return true;
-	} else if (last_si != NULL) {
+	} else if (last_si != nullptr) {
 		HandleClickOnSign(last_si);
 		return true;
 	} else {
@@ -2209,7 +2209,7 @@ static void PlaceObject()
 	_tile_fract_coords.y = pt.y & TILE_UNIT_MASK;
 
 	w = _thd.GetCallbackWnd();
-	if (w != NULL) w->OnPlaceObject(pt, TileVirtXY(pt.x, pt.y));
+	if (w != nullptr) w->OnPlaceObject(pt, TileVirtXY(pt.x, pt.y));
 }
 
 
@@ -2218,7 +2218,7 @@ bool HandleViewportClicked(const ViewPor
 	const Vehicle *v = CheckClickOnVehicle(vp, x, y);
 
 	if (_thd.place_mode & HT_VEHICLE) {
-		if (v != NULL && VehicleClicked(v)) return true;
+		if (v != nullptr && VehicleClicked(v)) return true;
 	}
 
 	/* Vehicle placement mode already handled above. */
@@ -2230,7 +2230,7 @@ bool HandleViewportClicked(const ViewPor
 	if (CheckClickOnViewportSign(vp, x, y)) return true;
 	bool result = CheckClickOnLandscape(vp, x, y);
 
-	if (v != NULL) {
+	if (v != nullptr) {
 		DEBUG(misc, 2, "Vehicle %d (index %d) at %p", v->unitnumber, v->index, v);
 		if (IsCompanyBuildableVehicleType(v)) {
 			v = v->First();
@@ -2247,7 +2247,7 @@ bool HandleViewportClicked(const ViewPor
 
 void RebuildViewportOverlay(Window *w)
 {
-	if (w->viewport->overlay != NULL &&
+	if (w->viewport->overlay != nullptr &&
 			w->viewport->overlay->GetCompanyMask() != 0 &&
 			w->viewport->overlay->GetCargoMask() != 0) {
 		w->viewport->overlay->SetDirty();
@@ -2381,7 +2381,7 @@ bool TileHighlightData::IsDraggingDiagon
 
 /**
  * Get the window that started the current highlighting.
- * @return The window that requested the current tile highlighting, or \c NULL if not available.
+ * @return The window that requested the current tile highlighting, or \c nullptr if not available.
  */
 Window *TileHighlightData::GetCallbackWnd()
 {
@@ -3163,7 +3163,7 @@ EventState VpHandlePlaceSizingDrag()
 
 	/* stop drag mode if the window has been closed */
 	Window *w = _thd.GetCallbackWnd();
-	if (w == NULL) {
+	if (w == nullptr) {
 		ResetObjectToPlace();
 		return ES_HANDLED;
 	}
@@ -3228,7 +3228,7 @@ void SetObjectToPlace(CursorID icon, Pal
 		 * this function might in some cases reset the newly set object to
 		 * place or not properly reset the original selection. */
 		_thd.window_class = WC_INVALID;
-		if (w != NULL) {
+		if (w != nullptr) {
 			w->OnPlaceObjectAbort();
 			HideMeasurementTooltips();
 		}
@@ -3305,7 +3305,7 @@ void InitializeSpriteSorter()
 			break;
 		}
 	}
-	assert(_vp_sprite_sorter != NULL);
+	assert(_vp_sprite_sorter != nullptr);
 }
 
 /**
diff --git a/src/viewport_func.h b/src/viewport_func.h
--- a/src/viewport_func.h
+++ b/src/viewport_func.h
@@ -49,10 +49,10 @@ static inline void MaxZoomInOut(ZoomStat
 
 void OffsetGroundSprite(int x, int y);
 
-void DrawGroundSprite(SpriteID image, PaletteID pal, const SubSprite *sub = NULL, int extra_offs_x = 0, int extra_offs_y = 0);
-void DrawGroundSpriteAt(SpriteID image, PaletteID pal, int32 x, int32 y, int z, const SubSprite *sub = NULL, int extra_offs_x = 0, int extra_offs_y = 0);
-void AddSortableSpriteToDraw(SpriteID image, PaletteID pal, int x, int y, int w, int h, int dz, int z, bool transparent = false, int bb_offset_x = 0, int bb_offset_y = 0, int bb_offset_z = 0, const SubSprite *sub = NULL);
-void AddChildSpriteScreen(SpriteID image, PaletteID pal, int x, int y, bool transparent = false, const SubSprite *sub = NULL, bool scale = true);
+void DrawGroundSprite(SpriteID image, PaletteID pal, const SubSprite *sub = nullptr, int extra_offs_x = 0, int extra_offs_y = 0);
+void DrawGroundSpriteAt(SpriteID image, PaletteID pal, int32 x, int32 y, int z, const SubSprite *sub = nullptr, int extra_offs_x = 0, int extra_offs_y = 0);
+void AddSortableSpriteToDraw(SpriteID image, PaletteID pal, int x, int y, int w, int h, int dz, int z, bool transparent = false, int bb_offset_x = 0, int bb_offset_y = 0, int bb_offset_z = 0, const SubSprite *sub = nullptr);
+void AddChildSpriteScreen(SpriteID image, PaletteID pal, int x, int y, bool transparent = false, const SubSprite *sub = nullptr, bool scale = true);
 void ViewportAddString(const DrawPixelInfo *dpi, ZoomLevel small_from, const ViewportSign *sign, StringID string_normal, StringID string_small, StringID string_small_shadow, uint64 params_1, uint64 params_2 = 0, Colours colour = INVALID_COLOUR);
 
 
diff --git a/src/viewport_gui.cpp b/src/viewport_gui.cpp
--- a/src/viewport_gui.cpp
+++ b/src/viewport_gui.cpp
@@ -122,7 +122,7 @@ public:
 
 	void OnResize() override
 	{
-		if (this->viewport != NULL) {
+		if (this->viewport != nullptr) {
 			NWidgetViewport *nvp = this->GetWidget<NWidgetViewport>(WID_EV_VIEWPORT);
 			nvp->UpdateViewportCoordinates(this);
 		}
@@ -172,7 +172,7 @@ void ShowExtraViewPortWindow(TileIndex t
 	int i = 0;
 
 	/* find next free window number for extra viewport */
-	while (FindWindowById(WC_EXTRA_VIEW_PORT, i) != NULL) i++;
+	while (FindWindowById(WC_EXTRA_VIEW_PORT, i) != nullptr) i++;
 
 	new ExtraViewportWindow(&_extra_view_port_desc, i, tile);
 }
diff --git a/src/void_cmd.cpp b/src/void_cmd.cpp
--- a/src/void_cmd.cpp
+++ b/src/void_cmd.cpp
@@ -77,15 +77,15 @@ extern const TileTypeProcs _tile_type_vo
 	DrawTile_Void,            // draw_tile_proc
 	GetSlopePixelZ_Void,      // get_slope_z_proc
 	ClearTile_Void,           // clear_tile_proc
-	NULL,                     // add_accepted_cargo_proc
+	nullptr,                     // add_accepted_cargo_proc
 	GetTileDesc_Void,         // get_tile_desc_proc
 	GetTileTrackStatus_Void,  // get_tile_track_status_proc
-	NULL,                     // click_tile_proc
-	NULL,                     // animate_tile_proc
+	nullptr,                     // click_tile_proc
+	nullptr,                     // animate_tile_proc
 	TileLoop_Void,            // tile_loop_proc
 	ChangeTileOwner_Void,     // change_tile_owner_proc
-	NULL,                     // add_produced_cargo_proc
-	NULL,                     // vehicle_enter_tile_proc
+	nullptr,                     // add_produced_cargo_proc
+	nullptr,                     // vehicle_enter_tile_proc
 	GetFoundation_Void,       // get_foundation_proc
 	TerraformTile_Void,       // terraform_tile_proc
 };
diff --git a/src/water_cmd.cpp b/src/water_cmd.cpp
--- a/src/water_cmd.cpp
+++ b/src/water_cmd.cpp
@@ -168,7 +168,7 @@ void MakeWaterKeepingClass(TileIndex til
 		if (wc == WATER_CLASS_CANAL) {
 			/* If we clear the canal, we have to remove it from the infrastructure count as well. */
 			Company *c = Company::GetIfValid(o);
-			if (c != NULL) {
+			if (c != nullptr) {
 				c->infrastructure.water--;
 				DirtyCompanyInfrastructureWindows(c->index);
 			}
@@ -185,7 +185,7 @@ void MakeWaterKeepingClass(TileIndex til
 	if (wc == WATER_CLASS_SEA && z > 0) {
 		/* Update company infrastructure count. */
 		Company *c = Company::GetIfValid(o);
-		if (c != NULL) {
+		if (c != nullptr) {
 			c->infrastructure.water++;
 			DirtyCompanyInfrastructureWindows(c->index);
 		}
@@ -227,7 +227,7 @@ static CommandCost RemoveShipDepot(TileI
 		delete Depot::GetByTile(tile);
 
 		Company *c = Company::GetIfValid(GetTileOwner(tile));
-		if (c != NULL) {
+		if (c != nullptr) {
 			c->infrastructure.water -= 2 * LOCK_DEPOT_TILE_FACTOR;
 			DirtyCompanyInfrastructureWindows(c->index);
 		}
@@ -293,7 +293,7 @@ static CommandCost DoBuildLock(TileIndex
 	if (flags & DC_EXEC) {
 		/* Update company infrastructure counts. */
 		Company *c = Company::GetIfValid(_current_company);
-		if (c != NULL) {
+		if (c != nullptr) {
 			/* Counts for the water. */
 			if (!IsWaterTile(tile - delta)) c->infrastructure.water++;
 			if (!IsWaterTile(tile + delta)) c->infrastructure.water++;
@@ -338,7 +338,7 @@ static CommandCost RemoveLock(TileIndex 
 	if (flags & DC_EXEC) {
 		/* Remove middle part from company infrastructure count. */
 		Company *c = Company::GetIfValid(GetTileOwner(tile));
-		if (c != NULL) {
+		if (c != nullptr) {
 			c->infrastructure.water -= 3 * LOCK_DEPOT_TILE_FACTOR; // three parts of the lock.
 			DirtyCompanyInfrastructureWindows(c->index);
 		}
@@ -428,7 +428,7 @@ CommandCost CmdBuildCanal(TileIndex tile
 					MakeRiver(tile, Random());
 					if (_game_mode == GM_EDITOR) {
 						TileIndex tile2 = tile;
-						CircularTileSearch(&tile2, RIVER_OFFSET_DESERT_DISTANCE, RiverModifyDesertZone, NULL);
+						CircularTileSearch(&tile2, RIVER_OFFSET_DESERT_DISTANCE, RiverModifyDesertZone, nullptr);
 					}
 					break;
 
@@ -931,11 +931,11 @@ static void FloodVehicle(Vehicle *v)
  * Flood a vehicle if we are allowed to flood it, i.e. when it is on the ground.
  * @param v    The vehicle to test for flooding.
  * @param data The z of level to flood.
- * @return NULL as we always want to remove everything.
+ * @return nullptr as we always want to remove everything.
  */
 static Vehicle *FloodVehicleProc(Vehicle *v, void *data)
 {
-	if ((v->vehstatus & VS_CRASHED) != 0) return NULL;
+	if ((v->vehstatus & VS_CRASHED) != 0) return nullptr;
 
 	switch (v->type) {
 		default: break;
@@ -963,7 +963,7 @@ static Vehicle *FloodVehicleProc(Vehicle
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -1321,14 +1321,14 @@ extern const TileTypeProcs _tile_type_wa
 	DrawTile_Water,           // draw_tile_proc
 	GetSlopePixelZ_Water,     // get_slope_z_proc
 	ClearTile_Water,          // clear_tile_proc
-	NULL,                     // add_accepted_cargo_proc
+	nullptr,                     // add_accepted_cargo_proc
 	GetTileDesc_Water,        // get_tile_desc_proc
 	GetTileTrackStatus_Water, // get_tile_track_status_proc
 	ClickTile_Water,          // click_tile_proc
-	NULL,                     // animate_tile_proc
+	nullptr,                     // animate_tile_proc
 	TileLoop_Water,           // tile_loop_proc
 	ChangeTileOwner_Water,    // change_tile_owner_proc
-	NULL,                     // add_produced_cargo_proc
+	nullptr,                     // add_produced_cargo_proc
 	VehicleEnter_Water,       // vehicle_enter_tile_proc
 	GetFoundation_Water,      // get_foundation_proc
 	TerraformTile_Water,      // terraform_tile_proc
diff --git a/src/waypoint_cmd.cpp b/src/waypoint_cmd.cpp
--- a/src/waypoint_cmd.cpp
+++ b/src/waypoint_cmd.cpp
@@ -56,7 +56,7 @@ void Waypoint::UpdateVirtCoord()
  */
 static Waypoint *FindDeletedWaypointCloseTo(TileIndex tile, StringID str, CompanyID cid)
 {
-	Waypoint *wp, *best = NULL;
+	Waypoint *wp, *best = nullptr;
 	uint thres = 8;
 
 	FOR_ALL_WAYPOINTS(wp) {
@@ -108,7 +108,7 @@ static CommandCost IsValidTileForWaypoin
 	/* if waypoint is set, then we have special handling to allow building on top of already existing waypoints.
 	 * so waypoint points to INVALID_STATION if we can build on any waypoint.
 	 * Or it points to a waypoint if we're only allowed to build on exactly that waypoint. */
-	if (waypoint != NULL && IsTileType(tile, MP_STATION)) {
+	if (waypoint != nullptr && IsTileType(tile, MP_STATION)) {
 		if (!IsRailWaypoint(tile)) {
 			return ClearTile_Station(tile, DC_AUTO); // get error message
 		} else {
@@ -199,16 +199,16 @@ CommandCost CmdBuildRailWaypoint(TileInd
 		if (ret.Failed()) return ret;
 	}
 
-	Waypoint *wp = NULL;
+	Waypoint *wp = nullptr;
 	TileArea new_location(TileArea(start_tile, width, height));
 	CommandCost ret = FindJoiningWaypoint(est, station_to_join, adjacent, new_location, &wp);
 	if (ret.Failed()) return ret;
 
 	/* Check if there is an already existing, deleted, waypoint close to us that we can reuse. */
 	TileIndex center_tile = start_tile + (count / 2) * offset;
-	if (wp == NULL && reuse) wp = FindDeletedWaypointCloseTo(center_tile, STR_SV_STNAME_WAYPOINT, _current_company);
+	if (wp == nullptr && reuse) wp = FindDeletedWaypointCloseTo(center_tile, STR_SV_STNAME_WAYPOINT, _current_company);
 
-	if (wp != NULL) {
+	if (wp != nullptr) {
 		/* Reuse an existing waypoint. */
 		if (wp->owner != _current_company) return_cmd_error(STR_ERROR_TOO_CLOSE_TO_ANOTHER_WAYPOINT);
 
@@ -227,7 +227,7 @@ CommandCost CmdBuildRailWaypoint(TileInd
 
 	if (flags & DC_EXEC) {
 		bool need_sign_update = false;
-		if (wp == NULL) {
+		if (wp == nullptr) {
 			wp = new Waypoint(start_tile);
 			need_sign_update = true;
 		} else if (!wp->IsInUse()) {
@@ -246,14 +246,14 @@ CommandCost CmdBuildRailWaypoint(TileInd
 		wp->string_id = STR_SV_STNAME_WAYPOINT;
 		wp->train_station = new_location;
 
-		if (wp->town == NULL) MakeDefaultName(wp);
+		if (wp->town == nullptr) MakeDefaultName(wp);
 
 		wp->UpdateVirtCoord();
 		if (need_sign_update) _viewport_sign_kdtree.Insert(ViewportSignKdtreeItem::MakeWaypoint(wp->index));
 
 		const StationSpec *spec = StationClass::Get(spec_class)->GetSpec(spec_index);
 		byte *layout_ptr = AllocaM(byte, count);
-		if (spec == NULL) {
+		if (spec == nullptr) {
 			/* The layout must be 0 for the 'normal' waypoints by design. */
 			memset(layout_ptr, 0, count);
 		} else {
@@ -302,7 +302,7 @@ CommandCost CmdBuildBuoy(TileIndex tile,
 
 	/* Check if there is an already existing, deleted, waypoint close to us that we can reuse. */
 	Waypoint *wp = FindDeletedWaypointCloseTo(tile, STR_SV_STNAME_BUOY, OWNER_NONE);
-	if (wp == NULL && !Waypoint::CanAllocateItem()) return_cmd_error(STR_ERROR_TOO_MANY_STATIONS_LOADING);
+	if (wp == nullptr && !Waypoint::CanAllocateItem()) return_cmd_error(STR_ERROR_TOO_MANY_STATIONS_LOADING);
 
 	CommandCost cost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_WAYPOINT_BUOY]);
 	if (!IsWaterTile(tile)) {
@@ -312,7 +312,7 @@ CommandCost CmdBuildBuoy(TileIndex tile,
 	}
 
 	if (flags & DC_EXEC) {
-		if (wp == NULL) {
+		if (wp == nullptr) {
 			wp = new Waypoint(tile);
 		} else {
 			/* Move existing (recently deleted) buoy to the new location */
@@ -329,7 +329,7 @@ CommandCost CmdBuildBuoy(TileIndex tile,
 
 		wp->build_date = _date;
 
-		if (wp->town == NULL) MakeDefaultName(wp);
+		if (wp->town == nullptr) MakeDefaultName(wp);
 
 		MakeBuoy(tile, wp->index, GetWaterClass(tile));
 		MarkTileDirtyByTile(tile);
@@ -392,7 +392,7 @@ static bool IsUniqueWaypointName(const c
 	const Waypoint *wp;
 
 	FOR_ALL_WAYPOINTS(wp) {
-		if (wp->name != NULL && strcmp(wp->name, name) == 0) return false;
+		if (wp->name != nullptr && strcmp(wp->name, name) == 0) return false;
 	}
 
 	return true;
@@ -410,7 +410,7 @@ static bool IsUniqueWaypointName(const c
 CommandCost CmdRenameWaypoint(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Waypoint *wp = Waypoint::GetIfValid(p1);
-	if (wp == NULL) return CMD_ERROR;
+	if (wp == nullptr) return CMD_ERROR;
 
 	if (wp->owner != OWNER_NONE) {
 		CommandCost ret = CheckOwnership(wp->owner);
@@ -426,7 +426,7 @@ CommandCost CmdRenameWaypoint(TileIndex 
 
 	if (flags & DC_EXEC) {
 		free(wp->name);
-		wp->name = reset ? NULL : stredup(text);
+		wp->name = reset ? nullptr : stredup(text);
 
 		wp->UpdateVirtCoord();
 	}
diff --git a/src/waypoint_gui.cpp b/src/waypoint_gui.cpp
--- a/src/waypoint_gui.cpp
+++ b/src/waypoint_gui.cpp
@@ -126,7 +126,7 @@ public:
 
 	void OnResize() override
 	{
-		if (this->viewport != NULL) {
+		if (this->viewport != nullptr) {
 			NWidgetViewport *nvp = this->GetWidget<NWidgetViewport>(WID_W_VIEWPORT);
 			nvp->UpdateViewportCoordinates(this);
 			this->wp->UpdateVirtCoord();
@@ -137,9 +137,9 @@ public:
 
 	void OnQueryTextFinished(char *str) override
 	{
-		if (str == NULL) return;
+		if (str == nullptr) return;
 
-		DoCommandP(0, this->window_number, 0, CMD_RENAME_WAYPOINT | CMD_MSG(STR_ERROR_CAN_T_CHANGE_WAYPOINT_NAME), NULL, str);
+		DoCommandP(0, this->window_number, 0, CMD_RENAME_WAYPOINT | CMD_MSG(STR_ERROR_CAN_T_CHANGE_WAYPOINT_NAME), nullptr, str);
 	}
 
 };
diff --git a/src/widget.cpp b/src/widget.cpp
--- a/src/widget.cpp
+++ b/src/widget.cpp
@@ -147,7 +147,7 @@ void ScrollbarClickHandler(Window *w, NW
 		ma = nw->pos_y + nw->current_y;
 	}
 	NWidgetScrollbar *scrollbar = dynamic_cast<NWidgetScrollbar*>(nw);
-	assert(scrollbar != NULL);
+	assert(scrollbar != nullptr);
 	ScrollbarClickPositioning(w, scrollbar, x, y, mi, ma);
 }
 
@@ -162,7 +162,7 @@ void ScrollbarClickHandler(Window *w, NW
 int GetWidgetFromPos(const Window *w, int x, int y)
 {
 	NWidgetCore *nw = w->nested_root->GetWidgetFromPos(x, y);
-	return (nw != NULL) ? nw->index : -1;
+	return (nw != nullptr) ? nw->index : -1;
 }
 
 /**
@@ -613,7 +613,7 @@ void Window::DrawWidgets() const
 		extern bool _window_highlight_colour;
 		for (uint i = 0; i < this->nested_array_size; i++) {
 			const NWidgetBase *widget = this->GetWidget<NWidgetBase>(i);
-			if (widget == NULL || !widget->IsHighlighted()) continue;
+			if (widget == nullptr || !widget->IsHighlighted()) continue;
 
 			int left = widget->pos_x;
 			int top  = widget->pos_y;
@@ -639,7 +639,7 @@ void Window::DrawSortButtonState(int wid
 {
 	if (state == SBS_OFF) return;
 
-	assert(this->nested_array != NULL);
+	assert(this->nested_array != nullptr);
 	const NWidgetBase *nwid = this->GetWidget<NWidgetBase>(widget);
 
 	/* Sort button uses the same sprites as vertical scrollbar */
@@ -784,17 +784,17 @@ void NWidgetBase::SetDirty(const Window 
  * Retrieve a widget by its position.
  * @param x Horizontal position relative to the left edge of the window.
  * @param y Vertical position relative to the top edge of the window.
- * @return Returns the deepest nested widget that covers the given position, or \c NULL if no widget can be found.
+ * @return Returns the deepest nested widget that covers the given position, or \c nullptr if no widget can be found.
  */
 
 /**
  * Retrieve a widget by its type.
  * @param tp Widget type to search for.
- * @return Returns the first widget of the specified type, or \c NULL if no widget can be found.
+ * @return Returns the first widget of the specified type, or \c nullptr if no widget can be found.
  */
 NWidgetBase *NWidgetBase::GetWidgetOfType(WidgetType tp)
 {
-	return (this->type == tp) ? this : NULL;
+	return (this->type == tp) ? this : nullptr;
 }
 
 /**
@@ -904,7 +904,7 @@ void NWidgetCore::FillNestedArray(NWidge
 
 NWidgetCore *NWidgetCore::GetWidgetFromPos(int x, int y)
 {
-	return (IsInsideBS(x, this->pos_x, this->current_x) && IsInsideBS(y, this->pos_y, this->current_y)) ? this : NULL;
+	return (IsInsideBS(x, this->pos_x, this->current_x) && IsInsideBS(y, this->pos_y, this->current_y)) ? this : nullptr;
 }
 
 /**
@@ -913,28 +913,28 @@ NWidgetCore *NWidgetCore::GetWidgetFromP
  */
 NWidgetContainer::NWidgetContainer(WidgetType tp) : NWidgetBase(tp)
 {
-	this->head = NULL;
-	this->tail = NULL;
+	this->head = nullptr;
+	this->tail = nullptr;
 }
 
 NWidgetContainer::~NWidgetContainer()
 {
-	while (this->head != NULL) {
+	while (this->head != nullptr) {
 		NWidgetBase *wid = this->head->next;
 		delete this->head;
 		this->head = wid;
 	}
-	this->tail = NULL;
+	this->tail = nullptr;
 }
 
 NWidgetBase *NWidgetContainer::GetWidgetOfType(WidgetType tp)
 {
 	if (this->type == tp) return this;
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		NWidgetBase *nwid = child_wid->GetWidgetOfType(tp);
-		if (nwid != NULL) return nwid;
+		if (nwid != nullptr) return nwid;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -943,14 +943,14 @@ NWidgetBase *NWidgetContainer::GetWidget
  */
 void NWidgetContainer::Add(NWidgetBase *wid)
 {
-	assert(wid->next == NULL && wid->prev == NULL);
-
-	if (this->head == NULL) {
+	assert(wid->next == nullptr && wid->prev == nullptr);
+
+	if (this->head == nullptr) {
 		this->head = wid;
 		this->tail = wid;
 	} else {
-		assert(this->tail != NULL);
-		assert(this->tail->next == NULL);
+		assert(this->tail != nullptr);
+		assert(this->tail->next == nullptr);
 
 		this->tail->next = wid;
 		wid->prev = this->tail;
@@ -960,7 +960,7 @@ void NWidgetContainer::Add(NWidgetBase *
 
 void NWidgetContainer::FillNestedArray(NWidgetBase **array, uint length)
 {
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		child_wid->FillNestedArray(array, length);
 	}
 }
@@ -1006,11 +1006,11 @@ void NWidgetStacked::SetupSmallestSize(W
 	/* First sweep, recurse down and compute minimal size and filling. */
 	this->smallest_x = 0;
 	this->smallest_y = 0;
-	this->fill_x = (this->head != NULL) ? 1 : 0;
-	this->fill_y = (this->head != NULL) ? 1 : 0;
-	this->resize_x = (this->head != NULL) ? 1 : 0;
-	this->resize_y = (this->head != NULL) ? 1 : 0;
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	this->fill_x = (this->head != nullptr) ? 1 : 0;
+	this->fill_y = (this->head != nullptr) ? 1 : 0;
+	this->resize_x = (this->head != nullptr) ? 1 : 0;
+	this->resize_y = (this->head != nullptr) ? 1 : 0;
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		child_wid->SetupSmallestSize(w, init_array);
 
 		this->smallest_x = max(this->smallest_x, child_wid->smallest_x + child_wid->padding_left + child_wid->padding_right);
@@ -1029,7 +1029,7 @@ void NWidgetStacked::AssignSizePosition(
 
 	if (this->shown_plane >= SZSP_BEGIN) return;
 
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		uint hor_step = (sizing == ST_SMALLEST) ? 1 : child_wid->GetHorizontalStepSize(sizing);
 		uint child_width = ComputeMaxSize(child_wid->smallest_x, given_width - child_wid->padding_left - child_wid->padding_right, hor_step);
 		uint child_pos_x = (rtl ? child_wid->padding_right : child_wid->padding_left);
@@ -1053,7 +1053,7 @@ void NWidgetStacked::Draw(const Window *
 	if (this->shown_plane >= SZSP_BEGIN) return;
 
 	int plane = 0;
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; plane++, child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; plane++, child_wid = child_wid->next) {
 		if (plane == this->shown_plane) {
 			child_wid->Draw(w);
 			return;
@@ -1065,16 +1065,16 @@ void NWidgetStacked::Draw(const Window *
 
 NWidgetCore *NWidgetStacked::GetWidgetFromPos(int x, int y)
 {
-	if (this->shown_plane >= SZSP_BEGIN) return NULL;
-
-	if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return NULL;
+	if (this->shown_plane >= SZSP_BEGIN) return nullptr;
+
+	if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return nullptr;
 	int plane = 0;
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; plane++, child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; plane++, child_wid = child_wid->next) {
 		if (plane == this->shown_plane) {
 			return child_wid->GetWidgetFromPos(x, y);
 		}
 	}
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -1109,20 +1109,20 @@ void NWidgetPIPContainer::SetPIP(uint8 p
 
 void NWidgetPIPContainer::Draw(const Window *w)
 {
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		child_wid->Draw(w);
 	}
 }
 
 NWidgetCore *NWidgetPIPContainer::GetWidgetFromPos(int x, int y)
 {
-	if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return NULL;
-
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return nullptr;
+
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		NWidgetCore *nwid = child_wid->GetWidgetFromPos(x, y);
-		if (nwid != NULL) return nwid;
+		if (nwid != nullptr) return nwid;
 	}
-	return NULL;
+	return nullptr;
 }
 
 /** Horizontal container widget. */
@@ -1142,7 +1142,7 @@ void NWidgetHorizontal::SetupSmallestSiz
 	/* 1a. Forward call, collect biggest nested array index, and longest/widest child length. */
 	uint longest = 0; // Longest child found.
 	uint max_vert_fill = 0; // Biggest vertical fill step.
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		child_wid->SetupSmallestSize(w, init_array);
 		longest = max(longest, child_wid->smallest_x);
 		max_vert_fill = max(max_vert_fill, child_wid->GetVerticalStepSize(ST_SMALLEST));
@@ -1152,7 +1152,7 @@ void NWidgetHorizontal::SetupSmallestSiz
 	uint max_smallest = this->smallest_y + 3 * max_vert_fill; // Upper limit to computing smallest height.
 	uint cur_height = this->smallest_y;
 	for (;;) {
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			uint step_size = child_wid->GetVerticalStepSize(ST_SMALLEST);
 			uint child_height = child_wid->smallest_y + child_wid->padding_top + child_wid->padding_bottom;
 			if (step_size > 1 && child_height < cur_height) { // Small step sizes or already fitting children are not interesting.
@@ -1169,14 +1169,14 @@ void NWidgetHorizontal::SetupSmallestSiz
 	}
 	/* 2. For containers that must maintain equal width, extend child minimal size. */
 	if (this->flags & NC_EQUALSIZE) {
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			if (child_wid->fill_x == 1) child_wid->smallest_x = longest;
 		}
 	}
 	/* 3. Move PIP space to the children, compute smallest, fill, and resize values of the container. */
-	if (this->head != NULL) this->head->padding_left += this->pip_pre;
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
-		if (child_wid->next != NULL) {
+	if (this->head != nullptr) this->head->padding_left += this->pip_pre;
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
+		if (child_wid->next != nullptr) {
 			child_wid->padding_right += this->pip_inter;
 		} else {
 			child_wid->padding_right += this->pip_post;
@@ -1205,7 +1205,7 @@ void NWidgetHorizontal::AssignSizePositi
 	uint additional_length = given_width;
 	if (sizing == ST_SMALLEST && (this->flags & NC_EQUALSIZE)) {
 		/* For EQUALSIZE containers this does not sum to smallest_x during initialisation */
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			additional_length -= child_wid->smallest_x + child_wid->padding_right + child_wid->padding_left;
 		}
 	} else {
@@ -1230,7 +1230,7 @@ void NWidgetHorizontal::AssignSizePositi
 	 */
 	int num_changing_childs = 0; // Number of children that can change size.
 	uint biggest_stepsize = 0;
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		uint hor_step = child_wid->GetHorizontalStepSize(sizing);
 		if (hor_step > 0) {
 			num_changing_childs++;
@@ -1246,7 +1246,7 @@ void NWidgetHorizontal::AssignSizePositi
 	/* Second loop: Allocate the additional horizontal space over the resizing children, starting with the biggest resize steps. */
 	while (biggest_stepsize > 0) {
 		uint next_biggest_stepsize = 0;
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			uint hor_step = child_wid->GetHorizontalStepSize(sizing);
 			if (hor_step > biggest_stepsize) continue; // Already done
 			if (hor_step == biggest_stepsize) {
@@ -1266,7 +1266,7 @@ void NWidgetHorizontal::AssignSizePositi
 	/* Third loop: Compute position and call the child. */
 	uint position = rtl ? this->current_x : 0; // Place to put next child relative to origin of the container.
 	NWidgetBase *child_wid = this->head;
-	while (child_wid != NULL) {
+	while (child_wid != nullptr) {
 		uint child_width = child_wid->current_x;
 		uint child_x = x + (rtl ? position - child_width - child_wid->padding_left : position + child_wid->padding_left);
 		uint child_y = y + child_wid->padding_top;
@@ -1307,7 +1307,7 @@ void NWidgetVertical::SetupSmallestSize(
 	/* 1a. Forward call, collect biggest nested array index, and longest/widest child length. */
 	uint highest = 0; // Highest child found.
 	uint max_hor_fill = 0; // Biggest horizontal fill step.
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		child_wid->SetupSmallestSize(w, init_array);
 		highest = max(highest, child_wid->smallest_y);
 		max_hor_fill = max(max_hor_fill, child_wid->GetHorizontalStepSize(ST_SMALLEST));
@@ -1317,7 +1317,7 @@ void NWidgetVertical::SetupSmallestSize(
 	uint max_smallest = this->smallest_x + 3 * max_hor_fill; // Upper limit to computing smallest height.
 	uint cur_width = this->smallest_x;
 	for (;;) {
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			uint step_size = child_wid->GetHorizontalStepSize(ST_SMALLEST);
 			uint child_width = child_wid->smallest_x + child_wid->padding_left + child_wid->padding_right;
 			if (step_size > 1 && child_width < cur_width) { // Small step sizes or already fitting children are not interesting.
@@ -1334,14 +1334,14 @@ void NWidgetVertical::SetupSmallestSize(
 	}
 	/* 2. For containers that must maintain equal width, extend children minimal size. */
 	if (this->flags & NC_EQUALSIZE) {
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			if (child_wid->fill_y == 1) child_wid->smallest_y = highest;
 		}
 	}
 	/* 3. Move PIP space to the child, compute smallest, fill, and resize values of the container. */
-	if (this->head != NULL) this->head->padding_top += this->pip_pre;
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
-		if (child_wid->next != NULL) {
+	if (this->head != nullptr) this->head->padding_top += this->pip_pre;
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
+		if (child_wid->next != nullptr) {
 			child_wid->padding_bottom += this->pip_inter;
 		} else {
 			child_wid->padding_bottom += this->pip_post;
@@ -1370,7 +1370,7 @@ void NWidgetVertical::AssignSizePosition
 	uint additional_length = given_height;
 	if (sizing == ST_SMALLEST && (this->flags & NC_EQUALSIZE)) {
 		/* For EQUALSIZE containers this does not sum to smallest_y during initialisation */
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			additional_length -= child_wid->smallest_y + child_wid->padding_top + child_wid->padding_bottom;
 		}
 	} else {
@@ -1386,7 +1386,7 @@ void NWidgetVertical::AssignSizePosition
 	/* First loop: Find biggest stepsize, find number of children that want a piece of the pie, handle horizontal size for all children, handle vertical size for non-resizing child. */
 	int num_changing_childs = 0; // Number of children that can change size.
 	uint biggest_stepsize = 0;
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		uint vert_step = child_wid->GetVerticalStepSize(sizing);
 		if (vert_step > 0) {
 			num_changing_childs++;
@@ -1402,7 +1402,7 @@ void NWidgetVertical::AssignSizePosition
 	/* Second loop: Allocate the additional vertical space over the resizing children, starting with the biggest resize steps. */
 	while (biggest_stepsize > 0) {
 		uint next_biggest_stepsize = 0;
-		for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+		for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 			uint vert_step = child_wid->GetVerticalStepSize(sizing);
 			if (vert_step > biggest_stepsize) continue; // Already done
 			if (vert_step == biggest_stepsize) {
@@ -1421,7 +1421,7 @@ void NWidgetVertical::AssignSizePosition
 
 	/* Third loop: Compute position and call the child. */
 	uint position = 0; // Place to put next child relative to origin of the container.
-	for (NWidgetBase *child_wid = this->head; child_wid != NULL; child_wid = child_wid->next) {
+	for (NWidgetBase *child_wid = this->head; child_wid != nullptr; child_wid = child_wid->next) {
 		uint child_x = x + (rtl ? child_wid->padding_right : child_wid->padding_left);
 		uint child_height = child_wid->current_y;
 
@@ -1463,7 +1463,7 @@ void NWidgetSpacer::SetDirty(const Windo
 
 NWidgetCore *NWidgetSpacer::GetWidgetFromPos(int x, int y)
 {
-	return NULL;
+	return nullptr;
 }
 
 NWidgetMatrix::NWidgetMatrix() : NWidgetPIPContainer(NWID_MATRIX, NC_EQUALSIZE), index(-1), clicked(-1), count(-1)
@@ -1487,7 +1487,7 @@ void NWidgetMatrix::SetColour(Colours co
 void NWidgetMatrix::SetClicked(int clicked)
 {
 	this->clicked = clicked;
-	if (this->clicked >= 0 && this->sb != NULL && this->widgets_x != 0) {
+	if (this->clicked >= 0 && this->sb != nullptr && this->widgets_x != 0) {
 		int vpos = (this->clicked / this->widgets_x) * this->widget_h; // Vertical position of the top.
 		/* Need to scroll down -> Scroll to the bottom.
 		 * However, last entry has no 'this->pip_inter' underneath, and we must stay below this->sb->GetCount() */
@@ -1505,7 +1505,7 @@ void NWidgetMatrix::SetCount(int count)
 {
 	this->count = count;
 
-	if (this->sb == NULL || this->widgets_x == 0) return;
+	if (this->sb == nullptr || this->widgets_x == 0) return;
 
 	/* We need to get the number of pixels the matrix is high/wide.
 	 * So, determine the number of rows/columns based on the number of
@@ -1532,8 +1532,8 @@ void NWidgetMatrix::SetScrollbar(Scrollb
 
 void NWidgetMatrix::SetupSmallestSize(Window *w, bool init_array)
 {
-	assert(this->head != NULL);
-	assert(this->head->next == NULL);
+	assert(this->head != nullptr);
+	assert(this->head->next == nullptr);
 
 	if (this->index >= 0 && init_array) { // Fill w->nested_array[]
 		assert(w->nested_array_size > (uint)this->index);
@@ -1542,7 +1542,7 @@ void NWidgetMatrix::SetupSmallestSize(Wi
 
 	/* Reset the widget number. */
 	NWidgetCore *nw = dynamic_cast<NWidgetCore *>(this->head);
-	assert(nw != NULL);
+	assert(nw != nullptr);
 	SB(nw->index, 16, 16, 0);
 	this->head->SetupSmallestSize(w, init_array);
 
@@ -1594,7 +1594,7 @@ void NWidgetMatrix::FillNestedArray(NWid
 NWidgetCore *NWidgetMatrix::GetWidgetFromPos(int x, int y)
 {
 	/* Falls outside of the matrix widget. */
-	if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return NULL;
+	if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return nullptr;
 
 	int start_x, start_y, base_offs_x, base_offs_y;
 	this->GetScrollOffsets(start_x, start_y, base_offs_x, base_offs_y);
@@ -1609,10 +1609,10 @@ NWidgetCore *NWidgetMatrix::GetWidgetFro
 	int widget_row = (y - base_offs_y - (int)this->pip_pre - (int)this->pos_y) / this->widget_h;
 
 	int sub_wid = (widget_row + start_y) * this->widgets_x + start_x + widget_col;
-	if (sub_wid >= this->count) return NULL;
+	if (sub_wid >= this->count) return nullptr;
 
 	NWidgetCore *child = dynamic_cast<NWidgetCore *>(this->head);
-	assert(child != NULL);
+	assert(child != nullptr);
 	child->AssignSizePosition(ST_RESIZE,
 			this->pos_x + (rtl ? this->pip_post - widget_col * this->widget_w : this->pip_pre + widget_col * this->widget_w) + base_offs_x,
 			this->pos_y + this->pip_pre + widget_row * this->widget_h + base_offs_y,
@@ -1637,7 +1637,7 @@ NWidgetCore *NWidgetMatrix::GetWidgetFro
 
 	/* Get the appropriate offsets so we can draw the right widgets. */
 	NWidgetCore *child = dynamic_cast<NWidgetCore *>(this->head);
-	assert(child != NULL);
+	assert(child != nullptr);
 	int start_x, start_y, base_offs_x, base_offs_y;
 	this->GetScrollOffsets(start_x, start_y, base_offs_x, base_offs_y);
 
@@ -1684,7 +1684,7 @@ void NWidgetMatrix::GetScrollOffsets(int
 	base_offs_y = 0;
 	start_x = 0;
 	start_y = 0;
-	if (this->sb != NULL) {
+	if (this->sb != nullptr) {
 		if (this->sb->IsVertical()) {
 			start_y = this->sb->GetPosition() / this->widget_h;
 			base_offs_y += -this->sb->GetPosition() + start_y * this->widget_h;
@@ -1718,7 +1718,7 @@ NWidgetBackground::NWidgetBackground(Wid
 
 NWidgetBackground::~NWidgetBackground()
 {
-	if (this->child != NULL) delete this->child;
+	if (this->child != nullptr) delete this->child;
 }
 
 /**
@@ -1730,7 +1730,7 @@ NWidgetBackground::~NWidgetBackground()
  */
 void NWidgetBackground::Add(NWidgetBase *nwid)
 {
-	if (this->child == NULL) {
+	if (this->child == nullptr) {
 		this->child = new NWidgetVertical();
 	}
 	this->child->Add(nwid);
@@ -1748,7 +1748,7 @@ void NWidgetBackground::Add(NWidgetBase 
  */
 void NWidgetBackground::SetPIP(uint8 pip_pre, uint8 pip_inter, uint8 pip_post)
 {
-	if (this->child == NULL) {
+	if (this->child == nullptr) {
 		this->child = new NWidgetVertical();
 	}
 	this->child->SetPIP(pip_pre, pip_inter, pip_post);
@@ -1760,7 +1760,7 @@ void NWidgetBackground::SetupSmallestSiz
 		assert(w->nested_array_size > (uint)this->index);
 		w->nested_array[this->index] = this;
 	}
-	if (this->child != NULL) {
+	if (this->child != nullptr) {
 		this->child->SetupSmallestSize(w, init_array);
 
 		this->smallest_x = this->child->smallest_x;
@@ -1771,7 +1771,7 @@ void NWidgetBackground::SetupSmallestSiz
 		this->resize_y = this->child->resize_y;
 
 		/* Account for the size of the frame's text if that exists */
-		if (w != NULL && this->type == WWT_FRAME) {
+		if (w != nullptr && this->type == WWT_FRAME) {
 			this->child->padding_left   = WD_FRAMETEXT_LEFT;
 			this->child->padding_right  = WD_FRAMETEXT_RIGHT;
 			this->child->padding_top    = max((int)WD_FRAMETEXT_TOP, this->widget_data != STR_NULL ? FONT_HEIGHT_NORMAL + WD_FRAMETEXT_TOP / 2 : 0);
@@ -1787,7 +1787,7 @@ void NWidgetBackground::SetupSmallestSiz
 		Dimension d = {this->min_x, this->min_y};
 		Dimension fill = {this->fill_x, this->fill_y};
 		Dimension resize  = {this->resize_x, this->resize_y};
-		if (w != NULL) { // A non-NULL window pointer acts as switch to turn dynamic widget size on.
+		if (w != nullptr) { // A non-nullptr window pointer acts as switch to turn dynamic widget size on.
 			if (this->type == WWT_FRAME || this->type == WWT_INSET) {
 				if (this->index >= 0) w->SetStringParameters(this->index);
 				Dimension background = GetStringBoundingBox(this->widget_data);
@@ -1812,7 +1812,7 @@ void NWidgetBackground::AssignSizePositi
 {
 	this->StoreSizePosition(sizing, x, y, given_width, given_height);
 
-	if (this->child != NULL) {
+	if (this->child != nullptr) {
 		uint x_offset = (rtl ? this->child->padding_right : this->child->padding_left);
 		uint width = given_width - this->child->padding_right - this->child->padding_left;
 		uint height = given_height - this->child->padding_top - this->child->padding_bottom;
@@ -1823,7 +1823,7 @@ void NWidgetBackground::AssignSizePositi
 void NWidgetBackground::FillNestedArray(NWidgetBase **array, uint length)
 {
 	if (this->index >= 0 && (uint)(this->index) < length) array[this->index] = this;
-	if (this->child != NULL) this->child->FillNestedArray(array, length);
+	if (this->child != nullptr) this->child->FillNestedArray(array, length);
 }
 
 void NWidgetBackground::Draw(const Window *w)
@@ -1860,7 +1860,7 @@ void NWidgetBackground::Draw(const Windo
 	}
 
 	if (this->index >= 0) w->DrawWidget(r, this->index);
-	if (this->child != NULL) this->child->Draw(w);
+	if (this->child != nullptr) this->child->Draw(w);
 
 	if (this->IsDisabled()) {
 		GfxFillRect(r.left + 1, r.top + 1, r.right - 1, r.bottom - 1, _colour_gradient[this->colour & 0xF][2], FILLRECT_CHECKER);
@@ -1869,19 +1869,19 @@ void NWidgetBackground::Draw(const Windo
 
 NWidgetCore *NWidgetBackground::GetWidgetFromPos(int x, int y)
 {
-	NWidgetCore *nwid = NULL;
+	NWidgetCore *nwid = nullptr;
 	if (IsInsideBS(x, this->pos_x, this->current_x) && IsInsideBS(y, this->pos_y, this->current_y)) {
-		if (this->child != NULL) nwid = this->child->GetWidgetFromPos(x, y);
-		if (nwid == NULL) nwid = this;
+		if (this->child != nullptr) nwid = this->child->GetWidgetFromPos(x, y);
+		if (nwid == nullptr) nwid = this;
 	}
 	return nwid;
 }
 
 NWidgetBase *NWidgetBackground::GetWidgetOfType(WidgetType tp)
 {
-	NWidgetBase *nwid = NULL;
-	if (this->child != NULL) nwid = this->child->GetWidgetOfType(tp);
-	if (nwid == NULL && this->type == tp) nwid = this;
+	NWidgetBase *nwid = nullptr;
+	if (this->child != nullptr) nwid = this->child->GetWidgetOfType(tp);
+	if (nwid == nullptr && this->type == tp) nwid = this;
 	return nwid;
 }
 
@@ -1936,7 +1936,7 @@ void NWidgetViewport::InitializeViewport
 void NWidgetViewport::UpdateViewportCoordinates(Window *w)
 {
 	ViewPort *vp = w->viewport;
-	if (vp != NULL) {
+	if (vp != nullptr) {
 		vp->left = w->left + this->pos_x;
 		vp->top  = w->top + this->pos_y;
 		vp->width  = this->current_x;
@@ -2207,7 +2207,7 @@ void NWidgetLeaf::SetupSmallestSize(Wind
 	Dimension fill = {this->fill_x, this->fill_y};
 	Dimension resize = {this->resize_x, this->resize_y};
 	/* Get padding, and update size with the real content size if appropriate. */
-	const Dimension *padding = NULL;
+	const Dimension *padding = nullptr;
 	switch (this->type) {
 		case WWT_EMPTY: {
 			static const Dimension extra = {0, 0};
@@ -2464,7 +2464,7 @@ void NWidgetLeaf::Draw(const Window *w)
 
 		case WWT_EDITBOX: {
 			const QueryString *query = w->GetQueryString(this->index);
-			if (query != NULL) query->DrawEditBox(w, this->index);
+			if (query != nullptr) query->DrawEditBox(w, this->index);
 			break;
 		}
 
@@ -2557,30 +2557,30 @@ bool NWidgetLeaf::ButtonHit(const Point 
  * @param fill_dest Fill the composed widget with child widgets.
  * @param biggest_index Pointer to biggest nested widget index in the tree encountered so far.
  * @return Number of widget part elements used to compose the widget.
- * @pre \c biggest_index != NULL.
+ * @pre \c biggest_index != nullptr.
  */
 static int MakeNWidget(const NWidgetPart *parts, int count, NWidgetBase **dest, bool *fill_dest, int *biggest_index)
 {
 	int num_used = 0;
 
-	*dest = NULL;
+	*dest = nullptr;
 	*fill_dest = false;
 
 	while (count > num_used) {
 		switch (parts->type) {
 			case NWID_SPACER:
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				*dest = new NWidgetSpacer(0, 0);
 				break;
 
 			case NWID_HORIZONTAL:
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				*dest = new NWidgetHorizontal(parts->u.cont_flags);
 				*fill_dest = true;
 				break;
 
 			case NWID_HORIZONTAL_LTR:
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				*dest = new NWidgetHorizontalLTR(parts->u.cont_flags);
 				*fill_dest = true;
 				break;
@@ -2588,20 +2588,20 @@ static int MakeNWidget(const NWidgetPart
 			case WWT_PANEL:
 			case WWT_INSET:
 			case WWT_FRAME:
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				*dest = new NWidgetBackground(parts->type, parts->u.widget.colour, parts->u.widget.index);
 				*biggest_index = max(*biggest_index, (int)parts->u.widget.index);
 				*fill_dest = true;
 				break;
 
 			case NWID_VERTICAL:
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				*dest = new NWidgetVertical(parts->u.cont_flags);
 				*fill_dest = true;
 				break;
 
 			case NWID_MATRIX: {
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				NWidgetMatrix *nwm = new NWidgetMatrix();
 				*dest = nwm;
 				*fill_dest = true;
@@ -2612,7 +2612,7 @@ static int MakeNWidget(const NWidgetPart
 			}
 
 			case WPT_FUNCTION: {
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				/* Ensure proper functioning even when the called code simply writes its largest index. */
 				int biggest = -1;
 				*dest = parts->u.func_ptr(&biggest);
@@ -2623,7 +2623,7 @@ static int MakeNWidget(const NWidgetPart
 
 			case WPT_RESIZE: {
 				NWidgetResizeBase *nwrb = dynamic_cast<NWidgetResizeBase *>(*dest);
-				if (nwrb != NULL) {
+				if (nwrb != nullptr) {
 					assert(parts->u.xy.x >= 0 && parts->u.xy.y >= 0);
 					nwrb->SetResize(parts->u.xy.x, parts->u.xy.y);
 				}
@@ -2632,7 +2632,7 @@ static int MakeNWidget(const NWidgetPart
 
 			case WPT_MINSIZE: {
 				NWidgetResizeBase *nwrb = dynamic_cast<NWidgetResizeBase *>(*dest);
-				if (nwrb != NULL) {
+				if (nwrb != nullptr) {
 					assert(parts->u.xy.x >= 0 && parts->u.xy.y >= 0);
 					nwrb->SetMinimalSize(parts->u.xy.x, parts->u.xy.y);
 				}
@@ -2641,7 +2641,7 @@ static int MakeNWidget(const NWidgetPart
 
 			case WPT_MINTEXTLINES: {
 				NWidgetResizeBase *nwrb = dynamic_cast<NWidgetResizeBase *>(*dest);
-				if (nwrb != NULL) {
+				if (nwrb != nullptr) {
 					assert(parts->u.text_lines.size >= FS_BEGIN && parts->u.text_lines.size < FS_END);
 					nwrb->SetMinimalTextLines(parts->u.text_lines.lines, parts->u.text_lines.spacing, parts->u.text_lines.size);
 				}
@@ -2650,13 +2650,13 @@ static int MakeNWidget(const NWidgetPart
 
 			case WPT_FILL: {
 				NWidgetResizeBase *nwrb = dynamic_cast<NWidgetResizeBase *>(*dest);
-				if (nwrb != NULL) nwrb->SetFill(parts->u.xy.x, parts->u.xy.y);
+				if (nwrb != nullptr) nwrb->SetFill(parts->u.xy.x, parts->u.xy.y);
 				break;
 			}
 
 			case WPT_DATATIP: {
 				NWidgetCore *nwc = dynamic_cast<NWidgetCore *>(*dest);
-				if (nwc != NULL) {
+				if (nwc != nullptr) {
 					nwc->widget_data = parts->u.data_tip.data;
 					nwc->tool_tip = parts->u.data_tip.tooltip;
 				}
@@ -2664,21 +2664,21 @@ static int MakeNWidget(const NWidgetPart
 			}
 
 			case WPT_PADDING:
-				if (*dest != NULL) (*dest)->SetPadding(parts->u.padding.top, parts->u.padding.right, parts->u.padding.bottom, parts->u.padding.left);
+				if (*dest != nullptr) (*dest)->SetPadding(parts->u.padding.top, parts->u.padding.right, parts->u.padding.bottom, parts->u.padding.left);
 				break;
 
 			case WPT_PIPSPACE: {
 				NWidgetPIPContainer *nwc = dynamic_cast<NWidgetPIPContainer *>(*dest);
-				if (nwc != NULL) nwc->SetPIP(parts->u.pip.pre,  parts->u.pip.inter, parts->u.pip.post);
+				if (nwc != nullptr) nwc->SetPIP(parts->u.pip.pre,  parts->u.pip.inter, parts->u.pip.post);
 
 				NWidgetBackground *nwb = dynamic_cast<NWidgetBackground *>(*dest);
-				if (nwb != NULL) nwb->SetPIP(parts->u.pip.pre,  parts->u.pip.inter, parts->u.pip.post);
+				if (nwb != nullptr) nwb->SetPIP(parts->u.pip.pre,  parts->u.pip.inter, parts->u.pip.post);
 				break;
 			}
 
 			case WPT_SCROLLBAR: {
 				NWidgetCore *nwc = dynamic_cast<NWidgetCore *>(*dest);
-				if (nwc != NULL) {
+				if (nwc != nullptr) {
 					nwc->scrollbar_index = parts->u.widget.index;
 				}
 				break;
@@ -2688,20 +2688,20 @@ static int MakeNWidget(const NWidgetPart
 				return num_used;
 
 			case NWID_VIEWPORT:
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				*dest = new NWidgetViewport(parts->u.widget.index);
 				*biggest_index = max(*biggest_index, (int)parts->u.widget.index);
 				break;
 
 			case NWID_HSCROLLBAR:
 			case NWID_VSCROLLBAR:
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				*dest = new NWidgetScrollbar(parts->type, parts->u.widget.colour, parts->u.widget.index);
 				*biggest_index = max(*biggest_index, (int)parts->u.widget.index);
 				break;
 
 			case NWID_SELECTION: {
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				NWidgetStacked *nws = new NWidgetStacked();
 				*dest = nws;
 				*fill_dest = true;
@@ -2711,7 +2711,7 @@ static int MakeNWidget(const NWidgetPart
 			}
 
 			default:
-				if (*dest != NULL) return num_used;
+				if (*dest != nullptr) return num_used;
 				assert((parts->type & WWT_MASK) < WWT_LAST || (parts->type & WWT_MASK) == NWID_BUTTON_DROPDOWN);
 				*dest = new NWidgetLeaf(parts->type, parts->u.widget.colour, parts->u.widget.index, 0x0, STR_NULL);
 				*biggest_index = max(*biggest_index, (int)parts->u.widget.index);
@@ -2728,29 +2728,29 @@ static int MakeNWidget(const NWidgetPart
  * Build a nested widget tree by recursively filling containers with nested widgets read from their parts.
  * @param parts  Array with parts of the nested widgets.
  * @param count  Length of the \a parts array.
- * @param parent Pointer or container to use for storing the child widgets (*parent == NULL or *parent == container or background widget).
+ * @param parent Pointer or container to use for storing the child widgets (*parent == nullptr or *parent == container or background widget).
  * @param biggest_index Pointer to biggest nested widget index in the tree.
  * @return Number of widget part elements used to fill the container.
  * @post \c *biggest_index contains the largest widget index of the tree and \c -1 if no index is used.
  */
 static int MakeWidgetTree(const NWidgetPart *parts, int count, NWidgetBase **parent, int *biggest_index)
 {
-	/* If *parent == NULL, only the first widget is read and returned. Otherwise, *parent must point to either
+	/* If *parent == nullptr, only the first widget is read and returned. Otherwise, *parent must point to either
 	 * a #NWidgetContainer or a #NWidgetBackground object, and parts are added as much as possible. */
 	NWidgetContainer *nwid_cont = dynamic_cast<NWidgetContainer *>(*parent);
 	NWidgetBackground *nwid_parent = dynamic_cast<NWidgetBackground *>(*parent);
-	assert(*parent == NULL || (nwid_cont != NULL && nwid_parent == NULL) || (nwid_cont == NULL && nwid_parent != NULL));
+	assert(*parent == nullptr || (nwid_cont != nullptr && nwid_parent == nullptr) || (nwid_cont == nullptr && nwid_parent != nullptr));
 
 	int total_used = 0;
 	for (;;) {
-		NWidgetBase *sub_widget = NULL;
+		NWidgetBase *sub_widget = nullptr;
 		bool fill_sub = false;
 		int num_used = MakeNWidget(parts, count - total_used, &sub_widget, &fill_sub, biggest_index);
 		parts += num_used;
 		total_used += num_used;
 
 		/* Break out of loop when end reached */
-		if (sub_widget == NULL) break;
+		if (sub_widget == nullptr) break;
 
 		/* If sub-widget is a container, recursively fill that container. */
 		WidgetType tp = sub_widget->type;
@@ -2763,9 +2763,9 @@ static int MakeWidgetTree(const NWidgetP
 		}
 
 		/* Add sub_widget to parent container if available, otherwise return the widget to the caller. */
-		if (nwid_cont != NULL) nwid_cont->Add(sub_widget);
-		if (nwid_parent != NULL) nwid_parent->Add(sub_widget);
-		if (nwid_cont == NULL && nwid_parent == NULL) {
+		if (nwid_cont != nullptr) nwid_cont->Add(sub_widget);
+		if (nwid_parent != nullptr) nwid_parent->Add(sub_widget);
+		if (nwid_cont == nullptr && nwid_parent == nullptr) {
 			*parent = sub_widget;
 			return total_used;
 		}
@@ -2783,16 +2783,16 @@ static int MakeWidgetTree(const NWidgetP
  * @param parts Array with parts of the widgets.
  * @param count Length of the \a parts array.
  * @param biggest_index Pointer to biggest nested widget index collected in the tree.
- * @param container Container to add the nested widgets to. In case it is NULL a vertical container is used.
+ * @param container Container to add the nested widgets to. In case it is nullptr a vertical container is used.
  * @return Root of the nested widget tree, a vertical container containing the entire GUI.
  * @ingroup NestedWidgetParts
- * @pre \c biggest_index != NULL
+ * @pre \c biggest_index != nullptr
  * @post \c *biggest_index contains the largest widget index of the tree and \c -1 if no index is used.
  */
 NWidgetContainer *MakeNWidgets(const NWidgetPart *parts, int count, int *biggest_index, NWidgetContainer *container)
 {
 	*biggest_index = -1;
-	if (container == NULL) container = new NWidgetVertical();
+	if (container == nullptr) container = new NWidgetVertical();
 	NWidgetBase *cont_ptr = container;
 	MakeWidgetTree(parts, count, &cont_ptr, biggest_index);
 	return container;
@@ -2805,10 +2805,10 @@ NWidgetContainer *MakeNWidgets(const NWi
  * @param parts Array with parts of the widgets.
  * @param count Length of the \a parts array.
  * @param biggest_index Pointer to biggest nested widget index collected in the tree.
- * @param[out] shade_select Pointer to the inserted shade selection widget (\c NULL if not unserted).
+ * @param[out] shade_select Pointer to the inserted shade selection widget (\c nullptr if not unserted).
  * @return Root of the nested widget tree, a vertical container containing the entire GUI.
  * @ingroup NestedWidgetParts
- * @pre \c biggest_index != NULL
+ * @pre \c biggest_index != nullptr
  * @post \c *biggest_index contains the largest widget index of the tree and \c -1 if no index is used.
  */
 NWidgetContainer *MakeWindowNWidgetTree(const NWidgetPart *parts, int count, int *biggest_index, NWidgetStacked **shade_select)
@@ -2816,16 +2816,16 @@ NWidgetContainer *MakeWindowNWidgetTree(
 	*biggest_index = -1;
 
 	/* Read the first widget recursively from the array. */
-	NWidgetBase *nwid = NULL;
+	NWidgetBase *nwid = nullptr;
 	int num_used = MakeWidgetTree(parts, count, &nwid, biggest_index);
-	assert(nwid != NULL);
+	assert(nwid != nullptr);
 	parts += num_used;
 	count -= num_used;
 
 	NWidgetContainer *root = new NWidgetVertical;
 	root->Add(nwid);
 	if (count == 0) { // There is no body at all.
-		*shade_select = NULL;
+		*shade_select = nullptr;
 		return root;
 	}
 
@@ -2833,13 +2833,13 @@ NWidgetContainer *MakeWindowNWidgetTree(
 	 * If it has a shading box, silently add a shade selection widget in the tree. */
 	NWidgetHorizontal *hor_cont = dynamic_cast<NWidgetHorizontal *>(nwid);
 	NWidgetContainer *body;
-	if (hor_cont != NULL && hor_cont->GetWidgetOfType(WWT_CAPTION) != NULL && hor_cont->GetWidgetOfType(WWT_SHADEBOX) != NULL) {
+	if (hor_cont != nullptr && hor_cont->GetWidgetOfType(WWT_CAPTION) != nullptr && hor_cont->GetWidgetOfType(WWT_SHADEBOX) != nullptr) {
 		*shade_select = new NWidgetStacked;
 		root->Add(*shade_select);
 		body = new NWidgetVertical;
 		(*shade_select)->Add(body);
 	} else {
-		*shade_select = NULL;
+		*shade_select = nullptr;
 		body = root;
 	}
 
@@ -2864,8 +2864,8 @@ NWidgetContainer *MakeWindowNWidgetTree(
 NWidgetBase *MakeCompanyButtonRows(int *biggest_index, int widget_first, int widget_last, int max_length, StringID button_tooltip)
 {
 	assert(max_length >= 1);
-	NWidgetVertical *vert = NULL; // Storage for all rows.
-	NWidgetHorizontal *hor = NULL; // Storage for buttons in one row.
+	NWidgetVertical *vert = nullptr; // Storage for all rows.
+	NWidgetHorizontal *hor = nullptr; // Storage for buttons in one row.
 	int hor_length = 0;
 
 	Dimension sprite_size = GetSpriteSize(SPR_COMPANY_ICON);
@@ -2875,12 +2875,12 @@ NWidgetBase *MakeCompanyButtonRows(int *
 	for (int widnum = widget_first; widnum <= widget_last; widnum++) {
 		/* Ensure there is room in 'hor' for another button. */
 		if (hor_length == max_length) {
-			if (vert == NULL) vert = new NWidgetVertical();
+			if (vert == nullptr) vert = new NWidgetVertical();
 			vert->Add(hor);
-			hor = NULL;
+			hor = nullptr;
 			hor_length = 0;
 		}
-		if (hor == NULL) {
+		if (hor == nullptr) {
 			hor = new NWidgetHorizontal();
 			hor_length = 0;
 		}
@@ -2894,7 +2894,7 @@ NWidgetBase *MakeCompanyButtonRows(int *
 		hor_length++;
 	}
 	*biggest_index = widget_last;
-	if (vert == NULL) return hor; // All buttons fit in a single row.
+	if (vert == nullptr) return hor; // All buttons fit in a single row.
 
 	if (hor_length > 0 && hor_length < max_length) {
 		/* Last row is partial, add a spacer at the end to force all buttons to the left. */
@@ -2903,6 +2903,6 @@ NWidgetBase *MakeCompanyButtonRows(int *
 		spc->SetResize(1, 0);
 		hor->Add(spc);
 	}
-	if (hor != NULL) vert->Add(hor);
+	if (hor != nullptr) vert->Add(hor);
 	return vert;
 }
diff --git a/src/widget_type.h b/src/widget_type.h
--- a/src/widget_type.h
+++ b/src/widget_type.h
@@ -374,7 +374,7 @@ public:
 	void FillNestedArray(NWidgetBase **array, uint length) override;
 
 	/** Return whether the container is empty. */
-	inline bool IsEmpty() { return head == NULL; }
+	inline bool IsEmpty() { return head == nullptr; }
 
 	NWidgetBase *GetWidgetOfType(WidgetType tp) override;
 
@@ -544,7 +544,7 @@ public:
  */
 class NWidgetBackground : public NWidgetCore {
 public:
-	NWidgetBackground(WidgetType tp, Colours colour, int index, NWidgetPIPContainer *child = NULL);
+	NWidgetBackground(WidgetType tp, Colours colour, int index, NWidgetPIPContainer *child = nullptr);
 	~NWidgetBackground();
 
 	void Add(NWidgetBase *nwid);
diff --git a/src/widgets/dropdown.cpp b/src/widgets/dropdown.cpp
--- a/src/widgets/dropdown.cpp
+++ b/src/widgets/dropdown.cpp
@@ -115,7 +115,7 @@ static const NWidgetPart _nested_dropdow
 };
 
 static WindowDesc _dropdown_desc(
-	WDP_MANUAL, NULL, 0, 0,
+	WDP_MANUAL, nullptr, 0, 0,
 	WC_DROPDOWN_MENU, WC_NONE,
 	WDF_NO_FOCUS,
 	_nested_dropdown_menu_widgets, lengthof(_nested_dropdown_menu_widgets)
@@ -200,7 +200,7 @@ struct DropdownWindow : Window {
 		this->SetDirty();
 
 		Window *w2 = FindWindowById(this->parent_wnd_class, this->parent_wnd_num);
-		if (w2 != NULL) {
+		if (w2 != nullptr) {
 			Point pt = _cursor.pos;
 			pt.x -= w2->left;
 			pt.y -= w2->top;
@@ -304,7 +304,7 @@ struct DropdownWindow : Window {
 	virtual void OnMouseLoop()
 	{
 		Window *w2 = FindWindowById(this->parent_wnd_class, this->parent_wnd_num);
-		if (w2 == NULL) {
+		if (w2 == nullptr) {
 			delete this;
 			return;
 		}
@@ -518,7 +518,7 @@ int HideDropDownMenu(Window *pw)
 		if (w->window_class != WC_DROPDOWN_MENU) continue;
 
 		DropdownWindow *dw = dynamic_cast<DropdownWindow*>(w);
-		assert(dw != NULL);
+		assert(dw != nullptr);
 		if (pw->window_class == dw->parent_wnd_class &&
 				pw->window_number == dw->parent_wnd_num) {
 			int parent_button = dw->parent_button;
diff --git a/src/window.cpp b/src/window.cpp
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -52,13 +52,13 @@ enum ViewportAutoscrolling {
 };
 
 static Point _drag_delta; ///< delta between mouse cursor and upper left corner of dragged window
-static Window *_mouseover_last_w = NULL; ///< Window of the last OnMouseOver event.
-static Window *_last_scroll_window = NULL; ///< Window of the last scroll event.
+static Window *_mouseover_last_w = nullptr; ///< Window of the last OnMouseOver event.
+static Window *_last_scroll_window = nullptr; ///< Window of the last scroll event.
 
 /** List of windows opened at the screen sorted from the front. */
-Window *_z_front_window = NULL;
+Window *_z_front_window = nullptr;
 /** List of windows opened at the screen sorted from the back. */
-Window *_z_back_window  = NULL;
+Window *_z_back_window  = nullptr;
 
 /** If false, highlight is white, otherwise the by the widget defined colour. */
 bool _window_highlight_colour = false;
@@ -85,7 +85,7 @@ SpecialMouseMode _special_mouse_mode; //
  * List of all WindowDescs.
  * This is a pointer to ensure initialisation order with the various static WindowDesc instances.
  */
-static std::vector<WindowDesc*> *_window_descs = NULL;
+static std::vector<WindowDesc*> *_window_descs = nullptr;
 
 /** Config file to store WindowDesc */
 char *_windows_file;
@@ -108,7 +108,7 @@ WindowDesc::WindowDesc(WindowPosition de
 	default_width_trad(def_width_trad),
 	default_height_trad(def_height_trad)
 {
-	if (_window_descs == NULL) _window_descs = new std::vector<WindowDesc*>();
+	if (_window_descs == nullptr) _window_descs = new std::vector<WindowDesc*>();
 	_window_descs->push_back(this);
 }
 
@@ -145,7 +145,7 @@ void WindowDesc::LoadFromConfig()
 	IniFile *ini = new IniFile();
 	ini->LoadFromDisk(_windows_file, NO_DIRECTORY);
 	for (WindowDesc *wd : *_window_descs) {
-		if (wd->ini_key == NULL) continue;
+		if (wd->ini_key == nullptr) continue;
 		IniLoadWindowSettings(ini, wd->ini_key, wd);
 	}
 	delete ini;
@@ -156,8 +156,8 @@ void WindowDesc::LoadFromConfig()
  */
 static int CDECL DescSorter(WindowDesc * const *a, WindowDesc * const *b)
 {
-	if ((*a)->ini_key != NULL && (*b)->ini_key != NULL) return strcmp((*a)->ini_key, (*b)->ini_key);
-	return ((*b)->ini_key != NULL ? 1 : 0) - ((*a)->ini_key != NULL ? 1 : 0);
+	if ((*a)->ini_key != nullptr && (*b)->ini_key != nullptr) return strcmp((*a)->ini_key, (*b)->ini_key);
+	return ((*b)->ini_key != nullptr ? 1 : 0) - ((*a)->ini_key != nullptr ? 1 : 0);
 }
 
 /**
@@ -171,7 +171,7 @@ void WindowDesc::SaveToConfig()
 	IniFile *ini = new IniFile();
 	ini->LoadFromDisk(_windows_file, NO_DIRECTORY);
 	for (WindowDesc *wd : *_window_descs) {
-		if (wd->ini_key == NULL) continue;
+		if (wd->ini_key == nullptr) continue;
 		IniSaveWindowSettings(ini, wd->ini_key, wd);
 	}
 	ini->SaveToDisk(_windows_file);
@@ -183,7 +183,7 @@ void WindowDesc::SaveToConfig()
  */
 void Window::ApplyDefaults()
 {
-	if (this->nested_root != NULL && this->nested_root->GetWidgetOfType(WWT_STICKYBOX) != NULL) {
+	if (this->nested_root != nullptr && this->nested_root->GetWidgetOfType(WWT_STICKYBOX) != nullptr) {
 		if (this->window_desc->pref_sticky) this->flags |= WF_STICKY;
 	} else {
 		/* There is no stickybox; clear the preference in case someone tried to be funny */
@@ -215,7 +215,7 @@ void Window::DisableAllWidgetHighlight()
 {
 	for (uint i = 0; i < this->nested_array_size; i++) {
 		NWidgetBase *nwid = this->GetWidget<NWidgetBase>(i);
-		if (nwid == NULL) continue;
+		if (nwid == nullptr) continue;
 
 		if (nwid->IsHighlighted()) {
 			nwid->SetHighlighted(TC_INVALID);
@@ -236,7 +236,7 @@ void Window::SetWidgetHighlight(byte wid
 	assert(widget_index < this->nested_array_size);
 
 	NWidgetBase *nwid = this->GetWidget<NWidgetBase>(widget_index);
-	if (nwid == NULL) return;
+	if (nwid == nullptr) return;
 
 	nwid->SetHighlighted(highlighted_colour);
 	this->SetWidgetDirty(widget_index);
@@ -249,7 +249,7 @@ void Window::SetWidgetHighlight(byte wid
 		bool valid = false;
 		for (uint i = 0; i < this->nested_array_size; i++) {
 			NWidgetBase *nwid = this->GetWidget<NWidgetBase>(i);
-			if (nwid == NULL) continue;
+			if (nwid == nullptr) continue;
 			if (!nwid->IsHighlighted()) continue;
 
 			valid = true;
@@ -269,7 +269,7 @@ bool Window::IsWidgetHighlighted(byte wi
 	assert(widget_index < this->nested_array_size);
 
 	const NWidgetBase *nwid = this->GetWidget<NWidgetBase>(widget_index);
-	if (nwid == NULL) return false;
+	if (nwid == nullptr) return false;
 
 	return nwid->IsHighlighted();
 }
@@ -326,63 +326,63 @@ Scrollbar *Window::GetScrollbar(uint wid
 /**
  * Return the querystring associated to a editbox.
  * @param widnum Editbox widget index
- * @return QueryString or NULL.
+ * @return QueryString or nullptr.
  */
 const QueryString *Window::GetQueryString(uint widnum) const
 {
 	auto query = this->querystrings.Find(widnum);
-	return query != this->querystrings.end() ? query->second : NULL;
+	return query != this->querystrings.end() ? query->second : nullptr;
 }
 
 /**
  * Return the querystring associated to a editbox.
  * @param widnum Editbox widget index
- * @return QueryString or NULL.
+ * @return QueryString or nullptr.
  */
 QueryString *Window::GetQueryString(uint widnum)
 {
 	SmallMap<int, QueryString*>::Pair *query = this->querystrings.Find(widnum);
-	return query != this->querystrings.End() ? query->second : NULL;
+	return query != this->querystrings.End() ? query->second : nullptr;
 }
 
 /**
  * Get the current input text if an edit box has the focus.
- * @return The currently focused input text or NULL if no input focused.
+ * @return The currently focused input text or nullptr if no input focused.
  */
 /* virtual */ const char *Window::GetFocusedText() const
 {
-	if (this->nested_focus != NULL && this->nested_focus->type == WWT_EDITBOX) {
+	if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
 		return this->GetQueryString(this->nested_focus->index)->GetText();
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
  * Get the string at the caret if an edit box has the focus.
- * @return The text at the caret or NULL if no edit box is focused.
+ * @return The text at the caret or nullptr if no edit box is focused.
  */
 /* virtual */ const char *Window::GetCaret() const
 {
-	if (this->nested_focus != NULL && this->nested_focus->type == WWT_EDITBOX) {
+	if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
 		return this->GetQueryString(this->nested_focus->index)->GetCaret();
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
  * Get the range of the currently marked input text.
  * @param[out] length Length of the marked text.
- * @return Pointer to the start of the marked text or NULL if no text is marked.
+ * @return Pointer to the start of the marked text or nullptr if no text is marked.
  */
 /* virtual */ const char *Window::GetMarkedText(size_t *length) const
 {
-	if (this->nested_focus != NULL && this->nested_focus->type == WWT_EDITBOX) {
+	if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
 		return this->GetQueryString(this->nested_focus->index)->GetMarkedText(length);
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -391,7 +391,7 @@ QueryString *Window::GetQueryString(uint
  */
 /* virtual */ Point Window::GetCaretPosition() const
 {
-	if (this->nested_focus != NULL && this->nested_focus->type == WWT_EDITBOX) {
+	if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
 		return this->GetQueryString(this->nested_focus->index)->GetCaretPosition(this, this->nested_focus->index);
 	}
 
@@ -407,7 +407,7 @@ QueryString *Window::GetQueryString(uint
  */
 /* virtual */ Rect Window::GetTextBoundingRect(const char *from, const char *to) const
 {
-	if (this->nested_focus != NULL && this->nested_focus->type == WWT_EDITBOX) {
+	if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
 		return this->GetQueryString(this->nested_focus->index)->GetBoundingRect(this, this->nested_focus->index, from, to);
 	}
 
@@ -418,15 +418,15 @@ QueryString *Window::GetQueryString(uint
 /**
  * Get the character that is rendered at a position by the focused edit box.
  * @param pt The position to test.
- * @return Pointer to the character at the position or NULL if no character is at the position.
+ * @return Pointer to the character at the position or nullptr if no character is at the position.
  */
 /* virtual */ const char *Window::GetTextCharacterAtPosition(const Point &pt) const
 {
-	if (this->nested_focus != NULL && this->nested_focus->type == WWT_EDITBOX) {
+	if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) {
 		return this->GetQueryString(this->nested_focus->index)->GetCharAtPosition(this, this->nested_focus->index, pt);
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -438,8 +438,8 @@ void SetFocusedWindow(Window *w)
 	if (_focused_window == w) return;
 
 	/* Invalidate focused widget */
-	if (_focused_window != NULL) {
-		if (_focused_window->nested_focus != NULL) _focused_window->nested_focus->SetDirty(_focused_window);
+	if (_focused_window != nullptr) {
+		if (_focused_window->nested_focus != nullptr) _focused_window->nested_focus->SetDirty(_focused_window);
 	}
 
 	/* Remember which window was previously focused */
@@ -447,8 +447,8 @@ void SetFocusedWindow(Window *w)
 	_focused_window = w;
 
 	/* So we can inform it that it lost focus */
-	if (old_focused != NULL) old_focused->OnFocusLost();
-	if (_focused_window != NULL) _focused_window->OnFocus();
+	if (old_focused != nullptr) old_focused->OnFocusLost();
+	if (_focused_window != nullptr) _focused_window->OnFocus();
 }
 
 /**
@@ -458,12 +458,12 @@ void SetFocusedWindow(Window *w)
  */
 bool EditBoxInGlobalFocus()
 {
-	if (_focused_window == NULL) return false;
+	if (_focused_window == nullptr) return false;
 
 	/* The console does not have an edit box so a special case is needed. */
 	if (_focused_window->window_class == WC_CONSOLE) return true;
 
-	return _focused_window->nested_focus != NULL && _focused_window->nested_focus->type == WWT_EDITBOX;
+	return _focused_window->nested_focus != nullptr && _focused_window->nested_focus->type == WWT_EDITBOX;
 }
 
 /**
@@ -471,12 +471,12 @@ bool EditBoxInGlobalFocus()
  */
 void Window::UnfocusFocusedWidget()
 {
-	if (this->nested_focus != NULL) {
+	if (this->nested_focus != nullptr) {
 		if (this->nested_focus->type == WWT_EDITBOX) VideoDriver::GetInstance()->EditBoxLostFocus();
 
 		/* Repaint the widget that lost focus. A focused edit box may else leave the caret on the screen. */
 		this->nested_focus->SetDirty(this);
-		this->nested_focus = NULL;
+		this->nested_focus = nullptr;
 	}
 }
 
@@ -490,8 +490,8 @@ bool Window::SetFocusedWidget(int widget
 	/* Do nothing if widget_index is already focused, or if it wasn't a valid widget. */
 	if ((uint)widget_index >= this->nested_array_size) return false;
 
-	assert(this->nested_array[widget_index] != NULL); // Setting focus to a non-existing widget is a bad idea.
-	if (this->nested_focus != NULL) {
+	assert(this->nested_array[widget_index] != nullptr); // Setting focus to a non-existing widget is a bad idea.
+	if (this->nested_focus != nullptr) {
 		if (this->GetWidget<NWidgetCore>(widget_index) == this->nested_focus) return false;
 
 		/* Repaint the widget that lost focus. A focused edit box may else leave the caret on the screen. */
@@ -507,7 +507,7 @@ bool Window::SetFocusedWidget(int widget
  */
 void Window::OnFocusLost()
 {
-	if (this->nested_focus != NULL && this->nested_focus->type == WWT_EDITBOX) VideoDriver::GetInstance()->EditBoxLostFocus();
+	if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) VideoDriver::GetInstance()->EditBoxLostFocus();
 }
 
 /**
@@ -557,7 +557,7 @@ void CDECL Window::SetWidgetsLoweredStat
 void Window::RaiseButtons(bool autoraise)
 {
 	for (uint i = 0; i < this->nested_array_size; i++) {
-		if (this->nested_array[i] == NULL) continue;
+		if (this->nested_array[i] == nullptr) continue;
 		WidgetType type = this->nested_array[i]->type;
 		if (((type & ~WWB_PUSHBUTTON) < WWT_LAST || type == NWID_PUSHBUTTON_DROPDOWN) &&
 				(!autoraise || (type & WWB_PUSHBUTTON) || type == WWT_EDITBOX) && this->IsWidgetLowered(i)) {
@@ -567,8 +567,8 @@ void Window::RaiseButtons(bool autoraise
 	}
 
 	/* Special widgets without widget index */
-	NWidgetCore *wid = this->nested_root != NULL ? (NWidgetCore*)this->nested_root->GetWidgetOfType(WWT_DEFSIZEBOX) : NULL;
-	if (wid != NULL) {
+	NWidgetCore *wid = this->nested_root != nullptr ? (NWidgetCore*)this->nested_root->GetWidgetOfType(WWT_DEFSIZEBOX) : nullptr;
+	if (wid != nullptr) {
 		wid->SetLowered(false);
 		wid->SetDirty(this);
 	}
@@ -581,7 +581,7 @@ void Window::RaiseButtons(bool autoraise
 void Window::SetWidgetDirty(byte widget_index) const
 {
 	/* Sometimes this function is called before the window is even fully initialized */
-	if (this->nested_array == NULL) return;
+	if (this->nested_array == nullptr) return;
 
 	this->nested_array[widget_index]->SetDirty(this);
 }
@@ -596,7 +596,7 @@ EventState Window::OnHotkey(int hotkey)
 	if (hotkey < 0) return ES_NOT_HANDLED;
 
 	NWidgetCore *nw = this->GetWidget<NWidgetCore>(hotkey);
-	if (nw == NULL || nw->IsDisabled()) return ES_NOT_HANDLED;
+	if (nw == nullptr || nw->IsDisabled()) return ES_NOT_HANDLED;
 
 	if (nw->type == WWT_EDITBOX) {
 		if (this->IsShaded()) return ES_NOT_HANDLED;
@@ -636,7 +636,7 @@ static void StartWindowSizing(Window *w,
 static void DispatchLeftClickEvent(Window *w, int x, int y, int click_count)
 {
 	NWidgetCore *nw = w->nested_root->GetWidgetFromPos(x, y);
-	WidgetType widget_type = (nw != NULL) ? nw->type : WWT_EMPTY;
+	WidgetType widget_type = (nw != nullptr) ? nw->type : WWT_EMPTY;
 
 	bool focused_widget_changed = false;
 	/* If clicked on a window that previously did dot have focus */
@@ -647,7 +647,7 @@ static void DispatchLeftClickEvent(Windo
 		SetFocusedWindow(w);
 	}
 
-	if (nw == NULL) return; // exit if clicked outside of widgets
+	if (nw == nullptr) return; // exit if clicked outside of widgets
 
 	/* don't allow any interaction if the button has been disabled */
 	if (nw->IsDisabled()) return;
@@ -686,7 +686,7 @@ static void DispatchLeftClickEvent(Windo
 
 		case WWT_EDITBOX: {
 			QueryString *query = w->GetQueryString(widget_index);
-			if (query != NULL) query->ClickEditBox(w, pt, widget_index, click_count, focused_widget_changed);
+			if (query != nullptr) query->ClickEditBox(w, pt, widget_index, click_count, focused_widget_changed);
 			break;
 		}
 
@@ -768,7 +768,7 @@ static void DispatchLeftClickEvent(Windo
 static void DispatchRightClickEvent(Window *w, int x, int y)
 {
 	NWidgetCore *wid = w->nested_root->GetWidgetFromPos(x, y);
-	if (wid == NULL) return;
+	if (wid == nullptr) return;
 
 	Point pt = { x, y };
 
@@ -781,7 +781,7 @@ static void DispatchRightClickEvent(Wind
 	if (_settings_client.gui.right_mouse_wnd_close && w->nested_root->GetWidgetOfType(WWT_CLOSEBOX)) {
 		delete w;
 	} else if (_settings_client.gui.hover_delay_ms == 0 && !w->OnTooltip(pt, wid->index, TCC_RIGHT_CLICK) && wid->tool_tip != 0) {
-		GuiShowTooltips(w, wid->tool_tip, 0, NULL, TCC_RIGHT_CLICK);
+		GuiShowTooltips(w, wid->tool_tip, 0, nullptr, TCC_RIGHT_CLICK);
 	}
 }
 
@@ -796,7 +796,7 @@ static void DispatchHoverEvent(Window *w
 	NWidgetCore *wid = w->nested_root->GetWidgetFromPos(x, y);
 
 	/* No widget to handle */
-	if (wid == NULL) return;
+	if (wid == nullptr) return;
 
 	Point pt = { x, y };
 
@@ -821,7 +821,7 @@ static void DispatchHoverEvent(Window *w
  */
 static void DispatchMouseWheelEvent(Window *w, NWidgetCore *nwid, int wheel)
 {
-	if (nwid == NULL) return;
+	if (nwid == nullptr) return;
 
 	/* Using wheel on caption/shade-box shades or unshades the window. */
 	if (nwid->type == WWT_CAPTION || nwid->type == WWT_SHADEBOX) {
@@ -840,8 +840,8 @@ static void DispatchMouseWheelEvent(Wind
 	}
 
 	/* Scroll the widget attached to the scrollbar. */
-	Scrollbar *sb = (nwid->scrollbar_index >= 0 ? w->GetScrollbar(nwid->scrollbar_index) : NULL);
-	if (sb != NULL && sb->GetCount() > sb->GetCapacity()) {
+	Scrollbar *sb = (nwid->scrollbar_index >= 0 ? w->GetScrollbar(nwid->scrollbar_index) : nullptr);
+	if (sb != nullptr && sb->GetCount() > sb->GetCapacity()) {
 		sb->UpdatePosition(wheel);
 		w->SetDirty();
 	}
@@ -1014,12 +1014,12 @@ void Window::ReInit(int rx, int ry)
  */
 void Window::SetShaded(bool make_shaded)
 {
-	if (this->shade_select == NULL) return;
+	if (this->shade_select == nullptr) return;
 
 	int desired = make_shaded ? SZSP_HORIZONTAL : 0;
 	if (this->shade_select->shown_plane != desired) {
 		if (make_shaded) {
-			if (this->nested_focus != NULL) this->UnfocusFocusedWidget();
+			if (this->nested_focus != nullptr) this->UnfocusFocusedWidget();
 			this->unshaded_size.width  = this->width;
 			this->unshaded_size.height = this->height;
 			this->shade_select->SetDisplayedPlane(desired);
@@ -1037,7 +1037,7 @@ void Window::SetShaded(bool make_shaded)
  * Find the Window whose parent pointer points to this window
  * @param w parent Window to find child of
  * @param wc Window class of the window to remove; #WC_INVALID if class does not matter
- * @return a Window pointer that is the child of \a w, or \c NULL otherwise
+ * @return a Window pointer that is the child of \a w, or \c nullptr otherwise
  */
 static Window *FindChildWindow(const Window *w, WindowClass wc)
 {
@@ -1046,7 +1046,7 @@ static Window *FindChildWindow(const Win
 		if ((wc == WC_INVALID || wc == v->window_class) && v->parent == w) return v;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -1056,7 +1056,7 @@ static Window *FindChildWindow(const Win
 void Window::DeleteChildWindows(WindowClass wc) const
 {
 	Window *child = FindChildWindow(this, wc);
-	while (child != NULL) {
+	while (child != nullptr) {
 		delete child;
 		child = FindChildWindow(this, wc);
 	}
@@ -1073,20 +1073,20 @@ Window::~Window()
 	}
 
 	/* Prevent Mouseover() from resetting mouse-over coordinates on a non-existing window */
-	if (_mouseover_last_w == this) _mouseover_last_w = NULL;
+	if (_mouseover_last_w == this) _mouseover_last_w = nullptr;
 
 	/* We can't scroll the window when it's closed. */
-	if (_last_scroll_window == this) _last_scroll_window = NULL;
+	if (_last_scroll_window == this) _last_scroll_window = nullptr;
 
 	/* Make sure we don't try to access this window as the focused window when it doesn't exist anymore. */
 	if (_focused_window == this) {
 		this->OnFocusLost();
-		_focused_window = NULL;
+		_focused_window = nullptr;
 	}
 
 	this->DeleteChildWindows();
 
-	if (this->viewport != NULL) DeleteWindowViewport(this);
+	if (this->viewport != nullptr) DeleteWindowViewport(this);
 
 	this->SetDirty();
 
@@ -1109,7 +1109,7 @@ Window::~Window()
  * Find a window by its class and window number
  * @param cls Window class
  * @param number Number of the window within the window class
- * @return Pointer to the found window, or \c NULL if not available
+ * @return Pointer to the found window, or \c nullptr if not available
  */
 Window *FindWindowById(WindowClass cls, WindowNumber number)
 {
@@ -1118,14 +1118,14 @@ Window *FindWindowById(WindowClass cls, 
 		if (w->window_class == cls && w->window_number == number) return w;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
  * Find any window by its class. Useful when searching for a window that uses
  * the window number as a #WindowClass, like #WC_SEND_NETWORK_MSG.
  * @param cls Window class
- * @return Pointer to the found window, or \c NULL if not available
+ * @return Pointer to the found window, or \c nullptr if not available
  */
 Window *FindWindowByClass(WindowClass cls)
 {
@@ -1134,7 +1134,7 @@ Window *FindWindowByClass(WindowClass cl
 		if (w->window_class == cls) return w;
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -1146,7 +1146,7 @@ Window *FindWindowByClass(WindowClass cl
 void DeleteWindowById(WindowClass cls, WindowNumber number, bool force)
 {
 	Window *w = FindWindowById(cls, number);
-	if (force || w == NULL ||
+	if (force || w == nullptr ||
 			(w->flags & WF_STICKY) == 0) {
 		delete w;
 	}
@@ -1244,7 +1244,7 @@ Window *BringWindowToFrontById(WindowCla
 {
 	Window *w = FindWindowById(cls, number);
 
-	if (w != NULL) {
+	if (w != nullptr) {
 		if (w->IsShaded()) w->SetShaded(false); // Restore original window size if it was shaded.
 
 		w->SetWhiteBorder();
@@ -1357,17 +1357,17 @@ static uint GetWindowZPriority(WindowCla
  */
 static void AddWindowToZOrdering(Window *w)
 {
-	assert(w->z_front == NULL && w->z_back == NULL);
-
-	if (_z_front_window == NULL) {
+	assert(w->z_front == nullptr && w->z_back == nullptr);
+
+	if (_z_front_window == nullptr) {
 		/* It's the only window. */
 		_z_front_window = _z_back_window = w;
-		w->z_front = w->z_back = NULL;
+		w->z_front = w->z_back = nullptr;
 	} else {
 		/* Search down the z-ordering for its location. */
 		Window *v = _z_front_window;
 		uint last_z_priority = UINT_MAX;
-		while (v != NULL && (v->window_class == WC_INVALID || GetWindowZPriority(v->window_class) > GetWindowZPriority(w->window_class))) {
+		while (v != nullptr && (v->window_class == WC_INVALID || GetWindowZPriority(v->window_class) > GetWindowZPriority(w->window_class))) {
 			if (v->window_class != WC_INVALID) {
 				/* Sanity check z-ordering, while we're at it. */
 				assert(last_z_priority >= GetWindowZPriority(v->window_class));
@@ -1377,15 +1377,15 @@ static void AddWindowToZOrdering(Window 
 			v = v->z_back;
 		}
 
-		if (v == NULL) {
+		if (v == nullptr) {
 			/* It's the new back window. */
 			w->z_front = _z_back_window;
-			w->z_back = NULL;
+			w->z_back = nullptr;
 			_z_back_window->z_back = w;
 			_z_back_window = w;
 		} else if (v == _z_front_window) {
 			/* It's the new front window. */
-			w->z_front = NULL;
+			w->z_front = nullptr;
 			w->z_back = _z_front_window;
 			_z_front_window->z_front = w;
 			_z_front_window = w;
@@ -1406,21 +1406,21 @@ static void AddWindowToZOrdering(Window 
  */
 static void RemoveWindowFromZOrdering(Window *w)
 {
-	if (w->z_front == NULL) {
+	if (w->z_front == nullptr) {
 		assert(_z_front_window == w);
 		_z_front_window = w->z_back;
 	} else {
 		w->z_front->z_back = w->z_back;
 	}
 
-	if (w->z_back == NULL) {
+	if (w->z_back == nullptr) {
 		assert(_z_back_window == w);
 		_z_back_window = w->z_front;
 	} else {
 		w->z_back->z_front = w->z_front;
 	}
 
-	w->z_front = w->z_back = NULL;
+	w->z_front = w->z_back = nullptr;
 }
 
 /**
@@ -1440,8 +1440,8 @@ static void BringWindowToFront(Window *w
  * Initializes the data (except the position and initial size) of a new Window.
  * @param window_number Number being assigned to the new window
  * @return Window pointer of the newly created window
- * @pre If nested widgets are used (\a widget is \c NULL), #nested_root and #nested_array_size must be initialized.
- *      In addition, #nested_array is either \c NULL, or already initialized.
+ * @pre If nested widgets are used (\a widget is \c nullptr), #nested_root and #nested_array_size must be initialized.
+ *      In addition, #nested_array is either \c nullptr, or already initialized.
  */
 void Window::InitializeData(WindowNumber window_number)
 {
@@ -1450,12 +1450,12 @@ void Window::InitializeData(WindowNumber
 	this->SetWhiteBorder();
 	if (this->window_desc->default_pos == WDP_CENTER) this->flags |= WF_CENTERED;
 	this->owner = INVALID_OWNER;
-	this->nested_focus = NULL;
+	this->nested_focus = nullptr;
 	this->window_number = window_number;
 
 	this->OnInit();
 	/* Initialize nested widget tree. */
-	if (this->nested_array == NULL) {
+	if (this->nested_array == nullptr) {
 		this->nested_array = CallocT<NWidgetBase *>(this->nested_array_size);
 		this->nested_root->SetupSmallestSize(this, true);
 	} else {
@@ -1472,7 +1472,7 @@ void Window::InitializeData(WindowNumber
 	/* Give focus to the opened window unless a text box
 	 * of focused window has focus (so we don't interrupt typing). But if the new
 	 * window has a text box, then take focus anyway. */
-	if (!EditBoxInGlobalFocus() || this->nested_root->GetWidgetOfType(WWT_EDITBOX) != NULL) SetFocusedWindow(this);
+	if (!EditBoxInGlobalFocus() || this->nested_root->GetWidgetOfType(WWT_EDITBOX) != nullptr) SetFocusedWindow(this);
 
 	/* Insert the window into the correct location in the z-ordering. */
 	AddWindowToZOrdering(this);
@@ -1516,9 +1516,9 @@ void Window::FindWindowPlacementAndResiz
 		/* Think about the overlapping toolbars when determining the minimum window size */
 		int free_height = _screen.height;
 		const Window *wt = FindWindowById(WC_STATUS_BAR, 0);
-		if (wt != NULL) free_height -= wt->height;
+		if (wt != nullptr) free_height -= wt->height;
 		wt = FindWindowById(WC_MAIN_TOOLBAR, 0);
-		if (wt != NULL) free_height -= wt->height;
+		if (wt != nullptr) free_height -= wt->height;
 
 		int enlarge_x = max(min(def_width  - this->width,  _screen.width - this->width),  0);
 		int enlarge_y = max(min(def_height - this->height, free_height   - this->height), 0);
@@ -1542,10 +1542,10 @@ void Window::FindWindowPlacementAndResiz
 	if (nx + this->width > _screen.width) nx -= (nx + this->width - _screen.width);
 
 	const Window *wt = FindWindowById(WC_MAIN_TOOLBAR, 0);
-	ny = max(ny, (wt == NULL || this == wt || this->top == 0) ? 0 : wt->height);
+	ny = max(ny, (wt == nullptr || this == wt || this->top == 0) ? 0 : wt->height);
 	nx = max(nx, 0);
 
-	if (this->viewport != NULL) {
+	if (this->viewport != nullptr) {
 		this->viewport->left += nx - this->left;
 		this->viewport->top  += ny - this->top;
 	}
@@ -1652,7 +1652,7 @@ static Point GetAutoPlacePosition(int wi
 
 	/* First attempt, try top-left of the screen */
 	const Window *main_toolbar = FindWindowByClass(WC_MAIN_TOOLBAR);
-	const int toolbar_y =  main_toolbar != NULL ? main_toolbar->height : 0;
+	const int toolbar_y =  main_toolbar != nullptr ? main_toolbar->height : 0;
 	if (IsGoodAutoPlace1(rtl ? _screen.width - width : 0, toolbar_y, width, height, toolbar_y, pt)) return pt;
 
 	/* Second attempt, try around all existing windows.
@@ -1716,7 +1716,7 @@ restart:
 Point GetToolbarAlignedWindowPosition(int window_width)
 {
 	const Window *w = FindWindowById(WC_MAIN_TOOLBAR, 0);
-	assert(w != NULL);
+	assert(w != nullptr);
 	Point pt = { _current_text_dir == TD_RTL ? w->left : (w->left + w->width) - window_width, w->top + w->height };
 	return pt;
 }
@@ -1746,7 +1746,7 @@ static Point LocalGetWindowPlacement(con
 	int16 default_width  = max(desc->GetDefaultWidth(),  sm_width);
 	int16 default_height = max(desc->GetDefaultHeight(), sm_height);
 
-	if (desc->parent_cls != WC_NONE && (w = FindWindowById(desc->parent_cls, window_number)) != NULL) {
+	if (desc->parent_cls != WC_NONE && (w = FindWindowById(desc->parent_cls, window_number)) != nullptr) {
 		bool rtl = _current_text_dir == TD_RTL;
 		if (desc->parent_cls == WC_BUILD_TOOLBAR || desc->parent_cls == WC_SCEN_LAND_GEN) {
 			pt.x = w->left + (rtl ? w->width - default_width : 0);
@@ -1857,7 +1857,7 @@ Window::Window(WindowDesc *desc) : windo
  * at the topmost window, obviously and work our way down to the bottom
  * @param x position x to query
  * @param y position y to query
- * @return a pointer to the found window if any, NULL otherwise
+ * @return a pointer to the found window if any, nullptr otherwise
  */
 Window *FindWindowFromPt(int x, int y)
 {
@@ -1868,7 +1868,7 @@ Window *FindWindowFromPt(int x, int y)
 		}
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 /**
@@ -1878,11 +1878,11 @@ void InitWindowSystem()
 {
 	IConsoleClose();
 
-	_z_back_window = NULL;
-	_z_front_window = NULL;
-	_focused_window = NULL;
-	_mouseover_last_w = NULL;
-	_last_scroll_window = NULL;
+	_z_back_window = nullptr;
+	_z_front_window = nullptr;
+	_focused_window = nullptr;
+	_mouseover_last_w = nullptr;
+	_last_scroll_window = nullptr;
 	_scrolling_viewport = false;
 	_mouse_hovering = false;
 
@@ -1902,14 +1902,14 @@ void UnInitWindowSystem()
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_FRONT(w) delete w;
 
-	for (w = _z_front_window; w != NULL; /* nothing */) {
+	for (w = _z_front_window; w != nullptr; /* nothing */) {
 		Window *to_del = w;
 		w = w->z_back;
 		free(to_del);
 	}
 
-	_z_front_window = NULL;
-	_z_back_window = NULL;
+	_z_front_window = nullptr;
+	_z_back_window = nullptr;
 }
 
 /**
@@ -1932,7 +1932,7 @@ static void DecreaseWindowCounters()
 			/* Unclick scrollbar buttons if they are pressed. */
 			for (uint i = 0; i < w->nested_array_size; i++) {
 				NWidgetBase *nwid = w->nested_array[i];
-				if (nwid != NULL && (nwid->type == NWID_HSCROLLBAR || nwid->type == NWID_VSCROLLBAR)) {
+				if (nwid != nullptr && (nwid->type == NWID_HSCROLLBAR || nwid->type == NWID_VSCROLLBAR)) {
 					NWidgetScrollbar *sb = static_cast<NWidgetScrollbar*>(nwid);
 					if (sb->disp_flags & (ND_SCROLLBAR_UP | ND_SCROLLBAR_DOWN)) {
 						sb->disp_flags &= ~(ND_SCROLLBAR_UP | ND_SCROLLBAR_DOWN);
@@ -1966,7 +1966,7 @@ static void HandlePlacePresize()
 	if (_special_mouse_mode != WSM_PRESIZE) return;
 
 	Window *w = _thd.GetCallbackWnd();
-	if (w == NULL) return;
+	if (w == nullptr) return;
 
 	Point pt = GetTileBelowCursor();
 	if (pt.x == -1) {
@@ -1988,7 +1988,7 @@ static EventState HandleMouseDragDrop()
 	if (_left_button_down && _cursor.delta.x == 0 && _cursor.delta.y == 0) return ES_HANDLED; // Dragging, but the mouse did not move.
 
 	Window *w = _thd.GetCallbackWnd();
-	if (w != NULL) {
+	if (w != nullptr) {
 		/* Send an event in client coordinates. */
 		Point pt;
 		pt.x = _cursor.pos.x - w->left;
@@ -2010,7 +2010,7 @@ static void HandleMouseOver()
 	Window *w = FindWindowFromPt(_cursor.pos.x, _cursor.pos.y);
 
 	/* We changed window, put an OnMouseOver event to the last window */
-	if (_mouseover_last_w != NULL && _mouseover_last_w != w) {
+	if (_mouseover_last_w != nullptr && _mouseover_last_w != w) {
 		/* Reset mouse-over coordinates of previous window */
 		Point pt = { -1, -1 };
 		_mouseover_last_w->OnMouseOver(pt, 0);
@@ -2019,11 +2019,11 @@ static void HandleMouseOver()
 	/* _mouseover_last_w will get reset when the window is deleted, see DeleteWindow() */
 	_mouseover_last_w = w;
 
-	if (w != NULL) {
+	if (w != nullptr) {
 		/* send an event in client coordinates. */
 		Point pt = { _cursor.pos.x - w->left, _cursor.pos.y - w->top };
 		const NWidgetCore *widget = w->nested_root->GetWidgetFromPos(pt.x, pt.y);
-		if (widget != NULL) w->OnMouseOver(pt, widget->index);
+		if (widget != nullptr) w->OnMouseOver(pt, widget->index);
 	}
 }
 
@@ -2048,7 +2048,7 @@ enum PreventHideDirection {
  */
 static void PreventHiding(int *nx, int *ny, const Rect &rect, const Window *v, int px, PreventHideDirection dir)
 {
-	if (v == NULL) return;
+	if (v == nullptr) return;
 
 	int v_bottom = v->top + v->height;
 	int v_right = v->left + v->width;
@@ -2089,7 +2089,7 @@ static void EnsureVisibleCaption(Window 
 	/* Search for the title bar rectangle. */
 	Rect caption_rect;
 	const NWidgetBase *caption = w->nested_root->GetWidgetOfType(WWT_CAPTION);
-	if (caption != NULL) {
+	if (caption != nullptr) {
 		caption_rect.left   = caption->pos_x;
 		caption_rect.right  = caption->pos_x + caption->current_x;
 		caption_rect.top    = caption->pos_y;
@@ -2104,7 +2104,7 @@ static void EnsureVisibleCaption(Window 
 		PreventHiding(&nx, &ny, caption_rect, FindWindowById(WC_STATUS_BAR,   0), w->left, PHD_UP);
 	}
 
-	if (w->viewport != NULL) {
+	if (w->viewport != nullptr) {
 		w->viewport->left += nx - w->left;
 		w->viewport->top  += ny - w->top;
 	}
@@ -2162,7 +2162,7 @@ void ResizeWindow(Window *w, int delta_x
 int GetMainViewTop()
 {
 	Window *w = FindWindowById(WC_MAIN_TOOLBAR, 0);
-	return (w == NULL) ? 0 : w->top + w->height;
+	return (w == nullptr) ? 0 : w->top + w->height;
 }
 
 /**
@@ -2173,7 +2173,7 @@ int GetMainViewTop()
 int GetMainViewBottom()
 {
 	Window *w = FindWindowById(WC_STATUS_BAR, 0);
-	return (w == NULL) ? _screen.height : w->top;
+	return (w == nullptr) ? _screen.height : w->top;
 }
 
 static bool _dragging_window; ///< A window is being dragged or resized.
@@ -2469,12 +2469,12 @@ static EventState HandleViewportScroll()
 	/* When we don't have a last scroll window we are starting to scroll.
 	 * When the last scroll window and this are not the same we went
 	 * outside of the window and should not left-mouse scroll anymore. */
-	if (_last_scroll_window == NULL) _last_scroll_window = FindWindowFromPt(_cursor.pos.x, _cursor.pos.y);
-
-	if (_last_scroll_window == NULL || !((_settings_client.gui.scroll_mode != VSM_MAP_LMB && _right_button_down) || scrollwheel_scrolling || (_settings_client.gui.scroll_mode == VSM_MAP_LMB && _left_button_down))) {
+	if (_last_scroll_window == nullptr) _last_scroll_window = FindWindowFromPt(_cursor.pos.x, _cursor.pos.y);
+
+	if (_last_scroll_window == nullptr || !((_settings_client.gui.scroll_mode != VSM_MAP_LMB && _right_button_down) || scrollwheel_scrolling || (_settings_client.gui.scroll_mode == VSM_MAP_LMB && _left_button_down))) {
 		_cursor.fix_at = false;
 		_scrolling_viewport = false;
-		_last_scroll_window = NULL;
+		_last_scroll_window = nullptr;
 		return ES_NOT_HANDLED;
 	}
 
@@ -2581,7 +2581,7 @@ static bool MaybeBringWindowToFront(Wind
 EventState Window::HandleEditBoxKey(int wid, WChar key, uint16 keycode)
 {
 	QueryString *query = this->GetQueryString(wid);
-	if (query == NULL) return ES_NOT_HANDLED;
+	if (query == nullptr) return ES_NOT_HANDLED;
 
 	int action = QueryString::ACTION_NOTHING;
 
@@ -2685,7 +2685,7 @@ void HandleKeypress(uint keycode, WChar 
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_FRONT(w) {
 		if (w->window_class == WC_MAIN_TOOLBAR) continue;
-		if (w->window_desc->hotkeys != NULL) {
+		if (w->window_desc->hotkeys != nullptr) {
 			int hotkey = w->window_desc->hotkeys->CheckMatch(keycode);
 			if (hotkey >= 0 && w->OnHotkey(hotkey) == ES_HANDLED) return;
 		}
@@ -2694,8 +2694,8 @@ void HandleKeypress(uint keycode, WChar 
 
 	w = FindWindowById(WC_MAIN_TOOLBAR, 0);
 	/* When there is no toolbar w is null, check for that */
-	if (w != NULL) {
-		if (w->window_desc->hotkeys != NULL) {
+	if (w != nullptr) {
+		if (w->window_desc->hotkeys != nullptr) {
 			int hotkey = w->window_desc->hotkeys->CheckMatch(keycode);
 			if (hotkey >= 0 && w->OnHotkey(hotkey) == ES_HANDLED) return;
 		}
@@ -2725,7 +2725,7 @@ void HandleCtrlChanged()
 /* virtual */ void Window::InsertTextString(int wid, const char *str, bool marked, const char *caret, const char *insert_location, const char *replacement_end)
 {
 	QueryString *query = this->GetQueryString(wid);
-	if (query == NULL) return;
+	if (query == nullptr) return;
 
 	if (query->text.InsertString(str, marked, caret, insert_location, replacement_end) || marked) {
 		this->SetWidgetDirty(wid);
@@ -2767,11 +2767,11 @@ static void HandleAutoscroll()
 	int x = _cursor.pos.x;
 	int y = _cursor.pos.y;
 	Window *w = FindWindowFromPt(x, y);
-	if (w == NULL || w->flags & WF_DISABLE_VP_SCROLL) return;
+	if (w == nullptr || w->flags & WF_DISABLE_VP_SCROLL) return;
 	if (_settings_client.gui.auto_scrolling != VA_EVERY_VIEWPORT && w->window_class != WC_MAIN_WINDOW) return;
 
 	ViewPort *vp = IsPtInWindowViewport(w, x, y);
-	if (vp == NULL) return;
+	if (vp == nullptr) return;
 
 	x -= vp->left;
 	y -= vp->top;
@@ -2877,23 +2877,23 @@ static void MouseLoop(MouseClick click, 
 	int x = _cursor.pos.x;
 	int y = _cursor.pos.y;
 	Window *w = FindWindowFromPt(x, y);
-	if (w == NULL) return;
+	if (w == nullptr) return;
 
 	if (click != MC_HOVER && !MaybeBringWindowToFront(w)) return;
 	ViewPort *vp = IsPtInWindowViewport(w, x, y);
 
 	/* Don't allow any action in a viewport if either in menu or when having a modal progress window */
-	if (vp != NULL && (_game_mode == GM_MENU || HasModalProgress())) return;
+	if (vp != nullptr && (_game_mode == GM_MENU || HasModalProgress())) return;
 
 	if (mousewheel != 0) {
 		/* Send mousewheel event to window, unless we're scrolling a viewport or the map */
-		if (!scrollwheel_scrolling || (vp == NULL && w->window_class != WC_SMALLMAP)) w->OnMouseWheel(mousewheel);
+		if (!scrollwheel_scrolling || (vp == nullptr && w->window_class != WC_SMALLMAP)) w->OnMouseWheel(mousewheel);
 
 		/* Dispatch a MouseWheelEvent for widgets if it is not a viewport */
-		if (vp == NULL) DispatchMouseWheelEvent(w, w->nested_root->GetWidgetFromPos(x - w->left, y - w->top), mousewheel);
+		if (vp == nullptr) DispatchMouseWheelEvent(w, w->nested_root->GetWidgetFromPos(x - w->left, y - w->top), mousewheel);
 	}
 
-	if (vp != NULL) {
+	if (vp != nullptr) {
 		if (scrollwheel_scrolling && !(w->flags & WF_DISABLE_VP_SCROLL)) {
 			_scrolling_viewport = true;
 			_cursor.fix_at = true;
@@ -2927,7 +2927,7 @@ static void MouseLoop(MouseClick click, 
 		}
 	}
 
-	if (vp == NULL || (w->flags & WF_DISABLE_VP_SCROLL)) {
+	if (vp == nullptr || (w->flags & WF_DISABLE_VP_SCROLL)) {
 		switch (click) {
 			case MC_LEFT:
 			case MC_DOUBLE_LEFT:
@@ -2935,7 +2935,7 @@ static void MouseLoop(MouseClick click, 
 				return;
 
 			default:
-				if (!scrollwheel_scrolling || w == NULL || w->window_class != WC_SMALLMAP) break;
+				if (!scrollwheel_scrolling || w == nullptr || w->window_class != WC_SMALLMAP) break;
 				/* We try to use the scrollwheel to scroll since we didn't touch any of the buttons.
 				 * Simulate a right button click so we can get started. */
 				FALLTHROUGH;
@@ -3046,7 +3046,7 @@ static void CheckSoftLimit()
 
 	for (;;) {
 		uint deletable_count = 0;
-		Window *w, *last_deletable = NULL;
+		Window *w, *last_deletable = nullptr;
 		FOR_ALL_WINDOWS_FROM_FRONT(w) {
 			if (w->window_class == WC_MAIN_WINDOW || IsVitalWindow(w) || (w->flags & WF_STICKY)) continue;
 
@@ -3057,7 +3057,7 @@ static void CheckSoftLimit()
 		/* We've not reached the soft limit yet. */
 		if (deletable_count <= _settings_client.gui.window_soft_limit) break;
 
-		assert(last_deletable != NULL);
+		assert(last_deletable != nullptr);
 		delete last_deletable;
 	}
 }
@@ -3074,7 +3074,7 @@ void InputLoop()
 	CheckSoftLimit();
 
 	/* Do the actual free of the deleted windows. */
-	for (Window *v = _z_front_window; v != NULL; /* nothing */) {
+	for (Window *v = _z_front_window; v != nullptr; /* nothing */) {
 		Window *w = v;
 		v = v->z_back;
 
@@ -3184,7 +3184,7 @@ void UpdateWindows()
 
 	FOR_ALL_WINDOWS_FROM_BACK(w) {
 		/* Update viewport only if window is not shaded. */
-		if (w->viewport != NULL && !w->IsShaded()) UpdateViewportPosition(w);
+		if (w->viewport != nullptr && !w->IsShaded()) UpdateViewportPosition(w);
 	}
 	NetworkDrawChatMessage();
 	/* Redraw mouse cursor in case it was hidden */
@@ -3455,17 +3455,17 @@ void ReInitAllWindows()
 
 /**
  * (Re)position a window at the screen.
- * @param w       Window structure of the window, may also be \c NULL.
+ * @param w       Window structure of the window, may also be \c nullptr.
  * @param clss    The class of the window to position.
  * @param setting The actual setting used for the window's position.
  * @return X coordinate of left edge of the repositioned window.
  */
 static int PositionWindow(Window *w, WindowClass clss, int setting)
 {
-	if (w == NULL || w->window_class != clss) {
+	if (w == nullptr || w->window_class != clss) {
 		w = FindWindowById(clss, 0);
 	}
-	if (w == NULL) return 0;
+	if (w == nullptr) return 0;
 
 	int old_left = w->left;
 	switch (setting) {
@@ -3473,14 +3473,14 @@ static int PositionWindow(Window *w, Win
 		case 2:  w->left = _screen.width - w->width; break;
 		default: w->left = 0; break;
 	}
-	if (w->viewport != NULL) w->viewport->left += w->left - old_left;
+	if (w->viewport != nullptr) w->viewport->left += w->left - old_left;
 	SetDirtyBlocks(0, w->top, _screen.width, w->top + w->height); // invalidate the whole row
 	return w->left;
 }
 
 /**
  * (Re)position main toolbar window at the screen.
- * @param w Window structure of the main toolbar window, may also be \c NULL.
+ * @param w Window structure of the main toolbar window, may also be \c nullptr.
  * @return X coordinate of left edge of the repositioned toolbar window.
  */
 int PositionMainToolbar(Window *w)
@@ -3491,7 +3491,7 @@ int PositionMainToolbar(Window *w)
 
 /**
  * (Re)position statusbar window at the screen.
- * @param w Window structure of the statusbar window, may also be \c NULL.
+ * @param w Window structure of the statusbar window, may also be \c nullptr.
  * @return X coordinate of left edge of the repositioned statusbar.
  */
 int PositionStatusbar(Window *w)
@@ -3502,7 +3502,7 @@ int PositionStatusbar(Window *w)
 
 /**
  * (Re)position news message window at the screen.
- * @param w Window structure of the news message window, may also be \c NULL.
+ * @param w Window structure of the news message window, may also be \c nullptr.
  * @return X coordinate of left edge of the repositioned news message.
  */
 int PositionNewsMessage(Window *w)
@@ -3513,7 +3513,7 @@ int PositionNewsMessage(Window *w)
 
 /**
  * (Re)position network chat window at the screen.
- * @param w Window structure of the network chat window, may also be \c NULL.
+ * @param w Window structure of the network chat window, may also be \c nullptr.
  * @return X coordinate of left edge of the repositioned network chat window.
  */
 int PositionNetworkChatWindow(Window *w)
@@ -3532,7 +3532,7 @@ void ChangeVehicleViewports(VehicleID fr
 {
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_BACK(w) {
-		if (w->viewport != NULL && w->viewport->follow_vehicle == from_index) {
+		if (w->viewport != nullptr && w->viewport->follow_vehicle == from_index) {
 			w->viewport->follow_vehicle = to_index;
 			w->SetDirty();
 		}
diff --git a/src/window_gui.h b/src/window_gui.h
--- a/src/window_gui.h
+++ b/src/window_gui.h
@@ -169,14 +169,14 @@ struct WindowDesc : ZeroedMemoryAllocato
 
 	WindowDesc(WindowPosition default_pos, const char *ini_key, int16 def_width_trad, int16 def_height_trad,
 			WindowClass window_class, WindowClass parent_class, uint32 flags,
-			const NWidgetPart *nwid_parts, int16 nwid_length, HotkeyList *hotkeys = NULL);
+			const NWidgetPart *nwid_parts, int16 nwid_length, HotkeyList *hotkeys = nullptr);
 
 	~WindowDesc();
 
 	WindowPosition default_pos;    ///< Preferred position of the window. @see WindowPosition()
 	WindowClass cls;               ///< Class of the window, @see WindowClass.
 	WindowClass parent_cls;        ///< Class of the parent window. @see WindowClass
-	const char *ini_key;           ///< Key to store window defaults in openttd.cfg. \c NULL if nothing shall be stored.
+	const char *ini_key;           ///< Key to store window defaults in openttd.cfg. \c nullptr if nothing shall be stored.
 	uint32 flags;                  ///< Flags. @see WindowDefaultFlag
 	const NWidgetPart *nwid_parts; ///< Nested widget parts describing the window.
 	int16 nwid_length;             ///< Length of the #nwid_parts array.
@@ -326,12 +326,12 @@ public:
 	Owner owner;        ///< The owner of the content shown in this window. Company colour is acquired from this variable.
 
 	ViewportData *viewport;          ///< Pointer to viewport data, if present.
-	const NWidgetCore *nested_focus; ///< Currently focused nested widget, or \c NULL if no nested widget has focus.
+	const NWidgetCore *nested_focus; ///< Currently focused nested widget, or \c nullptr if no nested widget has focus.
 	SmallMap<int, QueryString*> querystrings; ///< QueryString associated to WWT_EDITBOX widgets.
 	NWidgetBase *nested_root;        ///< Root of the nested tree.
 	NWidgetBase **nested_array;      ///< Array of pointers into the tree. Do not access directly, use #Window::GetWidget() instead.
 	uint nested_array_size;          ///< Size of the nested array.
-	NWidgetStacked *shade_select;    ///< Selection widget (#NWID_SELECTION) to use for shading the window. If \c NULL, window cannot shade.
+	NWidgetStacked *shade_select;    ///< Selection widget (#NWID_SELECTION) to use for shading the window. If \c nullptr, window cannot shade.
 	Dimension unshaded_size;         ///< Last known unshaded size (only valid while shaded).
 
 	int mouse_capture_widget;        ///< Widgetindex of current mouse capture widget (e.g. dragged scrollbar). -1 if no widget has mouse capture.
@@ -394,7 +394,7 @@ public:
 	inline void SetWidgetDisabledState(byte widget_index, bool disab_stat)
 	{
 		assert(widget_index < this->nested_array_size);
-		if (this->nested_array[widget_index] != NULL) this->GetWidget<NWidgetCore>(widget_index)->SetDisabled(disab_stat);
+		if (this->nested_array[widget_index] != nullptr) this->GetWidget<NWidgetCore>(widget_index)->SetDisabled(disab_stat);
 	}
 
 	/**
@@ -433,7 +433,7 @@ public:
 	 */
 	inline bool IsWidgetFocused(byte widget_index) const
 	{
-		return this->nested_focus != NULL && this->nested_focus->index == widget_index;
+		return this->nested_focus != nullptr && this->nested_focus->index == widget_index;
 	}
 
 	/**
@@ -525,7 +525,7 @@ public:
 	/** Is window shaded currently? */
 	inline bool IsShaded() const
 	{
-		return this->shade_select != NULL && this->shade_select->shown_plane == SZSP_HORIZONTAL;
+		return this->shade_select != nullptr && this->shade_select->shown_plane == SZSP_HORIZONTAL;
 	}
 
 	void SetShaded(bool make_shaded);
@@ -734,7 +734,7 @@ public:
 
 	/**
 	 * The query window opened from this window has closed.
-	 * @param str the new value of the string, NULL if the window
+	 * @param str the new value of the string, nullptr if the window
 	 *            was cancelled or an empty string when the default
 	 *            button was pressed, i.e. StrEmpty(str).
 	 */
@@ -818,14 +818,14 @@ public:
  * Get the nested widget with number \a widnum from the nested widget tree.
  * @tparam NWID Type of the nested widget.
  * @param widnum Widget number of the widget to retrieve.
- * @return The requested widget if it is instantiated, \c NULL otherwise.
+ * @return The requested widget if it is instantiated, \c nullptr otherwise.
  */
 template <class NWID>
 inline NWID *Window::GetWidget(uint widnum)
 {
-	if (widnum >= this->nested_array_size || this->nested_array[widnum] == NULL) return NULL;
+	if (widnum >= this->nested_array_size || this->nested_array[widnum] == nullptr) return nullptr;
 	NWID *nwid = dynamic_cast<NWID *>(this->nested_array[widnum]);
-	assert(nwid != NULL);
+	assert(nwid != nullptr);
 	return nwid;
 }
 
@@ -833,7 +833,7 @@ inline NWID *Window::GetWidget(uint widn
 template <>
 inline const NWidgetBase *Window::GetWidget<NWidgetBase>(uint widnum) const
 {
-	if (widnum >= this->nested_array_size) return NULL;
+	if (widnum >= this->nested_array_size) return nullptr;
 	return this->nested_array[widnum];
 }
 
@@ -841,7 +841,7 @@ inline const NWidgetBase *Window::GetWid
  * Get the nested widget with number \a widnum from the nested widget tree.
  * @tparam NWID Type of the nested widget.
  * @param widnum Widget number of the widget to retrieve.
- * @return The requested widget if it is instantiated, \c NULL otherwise.
+ * @return The requested widget if it is instantiated, \c nullptr otherwise.
  */
 template <class NWID>
 inline const NWID *Window::GetWidget(uint widnum) const
@@ -873,26 +873,26 @@ Window *FindWindowFromPt(int x, int y);
  * @param desc The pointer to the WindowDesc to be created
  * @param window_number the window number of the new window
  * @param return_existing If set, also return the window if it already existed.
- * @return %Window pointer of the newly created window, or the existing one if \a return_existing is set, or \c NULL.
+ * @return %Window pointer of the newly created window, or the existing one if \a return_existing is set, or \c nullptr.
  */
 template <typename Wcls>
 Wcls *AllocateWindowDescFront(WindowDesc *desc, int window_number, bool return_existing = false)
 {
 	Wcls *w = static_cast<Wcls *>(BringWindowToFrontById(desc->cls, window_number));
-	if (w != NULL) return return_existing ? w : NULL;
+	if (w != nullptr) return return_existing ? w : nullptr;
 	return new Wcls(desc, window_number);
 }
 
 void RelocateAllWindows(int neww, int newh);
 
-void GuiShowTooltips(Window *parent, StringID str, uint paramcount = 0, const uint64 params[] = NULL, TooltipCloseCondition close_tooltip = TCC_HOVER);
+void GuiShowTooltips(Window *parent, StringID str, uint paramcount = 0, const uint64 params[] = nullptr, TooltipCloseCondition close_tooltip = TCC_HOVER);
 
 /* widget.cpp */
 int GetWidgetFromPos(const Window *w, int x, int y);
 
 /** Iterate over all windows */
-#define FOR_ALL_WINDOWS_FROM_BACK_FROM(w, start)  for (w = start; w != NULL; w = w->z_front) if (w->window_class != WC_INVALID)
-#define FOR_ALL_WINDOWS_FROM_FRONT_FROM(w, start) for (w = start; w != NULL; w = w->z_back) if (w->window_class != WC_INVALID)
+#define FOR_ALL_WINDOWS_FROM_BACK_FROM(w, start)  for (w = start; w != nullptr; w = w->z_front) if (w->window_class != WC_INVALID)
+#define FOR_ALL_WINDOWS_FROM_FRONT_FROM(w, start) for (w = start; w != nullptr; w = w->z_back) if (w->window_class != WC_INVALID)
 #define FOR_ALL_WINDOWS_FROM_BACK(w)  FOR_ALL_WINDOWS_FROM_BACK_FROM(w, _z_back_window)
 #define FOR_ALL_WINDOWS_FROM_FRONT(w) FOR_ALL_WINDOWS_FROM_FRONT_FROM(w, _z_front_window)