# HG changeset patch
# User rubidium42 <rubidium@openttd.org>
# Date 2021-05-24 09:47:37
# Node ID 35330ff774a67ac737dd4de96ad9b5a2d16cfe15
# Parent  fb65768b27a1857db3aa128141b3911de3445c31

Codechange: use separate pre and post callbacks for int settings

diff --git a/src/elrail.cpp b/src/elrail.cpp
--- a/src/elrail.cpp
+++ b/src/elrail.cpp
@@ -593,9 +593,9 @@ void DrawRailCatenary(const TileInfo *ti
 	DrawRailCatenaryRailway(ti);
 }
 
-bool SettingsDisableElrail(int32 p1)
+void SettingsDisableElrail(int32 new_value)
 {
-	bool disable = (p1 != 0);
+	bool disable = (new_value != 0);
 
 	/* we will now walk through all electric train engines and change their railtypes if it is the wrong one*/
 	const RailType old_railtype = disable ? RAILTYPE_ELECTRIC : RAILTYPE_RAIL;
@@ -639,5 +639,4 @@ bool SettingsDisableElrail(int32 p1)
 	 * rails. It may have unintended consequences if that function is ever
 	 * extended, though. */
 	ReinitGuiAfterToggleElrail(disable);
-	return true;
 }
diff --git a/src/elrail_func.h b/src/elrail_func.h
--- a/src/elrail_func.h
+++ b/src/elrail_func.h
@@ -36,6 +36,6 @@ void DrawRailCatenary(const TileInfo *ti
 void DrawRailCatenaryOnTunnel(const TileInfo *ti);
 void DrawRailCatenaryOnBridge(const TileInfo *ti);
 
-bool SettingsDisableElrail(int32 p1); ///< _settings_game.disable_elrail callback
+void SettingsDisableElrail(int32 new_value); ///< _settings_game.disable_elrail callback
 
 #endif /* ELRAIL_FUNC_H */
diff --git a/src/newgrf_config.cpp b/src/newgrf_config.cpp
--- a/src/newgrf_config.cpp
+++ b/src/newgrf_config.cpp
@@ -282,15 +282,13 @@ void GRFParameterInfo::Finalize()
 /**
  * Update the palettes of the graphics from the config file.
  * Called when changing the default palette in advanced settings.
- * @param p1 Unused.
- * @return Always true.
+ * @param new_value Unused.
  */
-bool UpdateNewGRFConfigPalette(int32 p1)
+void UpdateNewGRFConfigPalette(int32 new_value)
 {
 	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;
 }
 
 /**
diff --git a/src/newgrf_config.h b/src/newgrf_config.h
--- a/src/newgrf_config.h
+++ b/src/newgrf_config.h
@@ -239,6 +239,6 @@ void ShowNewGRFSettings(bool editable, b
 GRFTextWrapper FindUnknownGRFName(uint32 grfid, uint8 *md5sum, bool create);
 
 void UpdateNewGRFScanStatus(uint num, const char *name);
-bool UpdateNewGRFConfigPalette(int32 p1 = 0);
+void UpdateNewGRFConfigPalette(int32 new_value = 0);
 
 #endif /* NEWGRF_CONFIG_H */
diff --git a/src/rail_gui.cpp b/src/rail_gui.cpp
--- a/src/rail_gui.cpp
+++ b/src/rail_gui.cpp
@@ -2130,10 +2130,9 @@ static void SetDefaultRailGui()
 /**
  * Updates the current signal variant used in the signal GUI
  * to the one adequate to current year.
- * @param p needed to be called when a setting changes
- * @return success, needed for settings
+ * @param new_value needed to be called when a setting changes
  */
-bool ResetSignalVariant(int32 p)
+void ResetSignalVariant(int32 new_value)
 {
 	SignalVariant new_variant = (_cur_year < _settings_client.gui.semaphore_build_before ? SIG_SEMAPHORE : SIG_ELECTRIC);
 
@@ -2145,8 +2144,6 @@ bool ResetSignalVariant(int32 p)
 		}
 		_cur_signal_variant = new_variant;
 	}
-
-	return true;
 }
 
 /**
diff --git a/src/rail_gui.h b/src/rail_gui.h
--- a/src/rail_gui.h
+++ b/src/rail_gui.h
@@ -15,7 +15,7 @@
 
 struct Window *ShowBuildRailToolbar(RailType railtype);
 void ReinitGuiAfterToggleElrail(bool disable);
-bool ResetSignalVariant(int32 = 0);
+void ResetSignalVariant(int32 = 0);
 void InitializeRailGUI();
 DropDownList GetRailTypeDropDownList(bool for_replacement = false, bool all_option = false);
 
diff --git a/src/settings.cpp b/src/settings.cpp
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -807,99 +807,56 @@ const StringSettingDesc *SettingDesc::As
 /* Begin - Callback Functions for the various settings. */
 
 /** Reposition the main toolbar as the setting changed. */
-static bool v_PositionMainToolbar(int32 p1)
+static void v_PositionMainToolbar(int32 new_value)
 {
 	if (_game_mode != GM_MENU) PositionMainToolbar(nullptr);
-	return true;
 }
 
 /** Reposition the statusbar as the setting changed. */
-static bool v_PositionStatusbar(int32 p1)
+static void v_PositionStatusbar(int32 new_value)
 {
 	if (_game_mode != GM_MENU) {
 		PositionStatusbar(nullptr);
 		PositionNewsMessage(nullptr);
 		PositionNetworkChatWindow(nullptr);
 	}
-	return true;
-}
-
-static bool PopulationInLabelActive(int32 p1)
-{
-	UpdateAllTownVirtCoords();
-	return true;
-}
-
-static bool RedrawScreen(int32 p1)
-{
-	MarkWholeScreenDirty();
-	return true;
 }
 
 /**
  * Redraw the smallmap after a colour scheme change.
  * @param p1 Callback parameter.
- * @return Always true.
  */
-static bool RedrawSmallmap(int32 p1)
+static void RedrawSmallmap(int32 new_value)
 {
 	BuildLandLegend();
 	BuildOwnerLegend();
 	SetWindowClassesDirty(WC_SMALLMAP);
-	return true;
 }
 
-static bool InvalidateDetailsWindow(int32 p1)
-{
-	SetWindowClassesDirty(WC_VEHICLE_DETAILS);
-	return true;
-}
-
-static bool StationSpreadChanged(int32 p1)
+static void StationSpreadChanged(int32 p1)
 {
 	InvalidateWindowData(WC_SELECT_STATION, 0);
 	InvalidateWindowData(WC_BUILD_STATION, 0);
-	return true;
 }
 
-static bool InvalidateBuildIndustryWindow(int32 p1)
+static void CloseSignalGUI(int32 new_value)
 {
-	InvalidateWindowData(WC_BUILD_INDUSTRY, 0);
-	return true;
-}
-
-static bool CloseSignalGUI(int32 p1)
-{
-	if (p1 == 0) {
+	if (new_value == 0) {
 		DeleteWindowByClass(WC_BUILD_SIGNAL);
 	}
-	return true;
 }
 
-static bool InvalidateTownViewWindow(int32 p1)
-{
-	InvalidateWindowClassesData(WC_TOWN_VIEW, p1);
-	return true;
-}
-
-static bool DeleteSelectStationWindow(int32 p1)
-{
-	DeleteWindowById(WC_SELECT_STATION, 0);
-	return true;
-}
-
-static bool UpdateConsists(int32 p1)
+static void UpdateConsists(int32 new_value)
 {
 	for (Train *t : Train::Iterate()) {
 		/* Update the consist of all trains so the maximum speed is set correctly. */
 		if (t->IsFrontEngine() || t->IsFreeWagon()) t->ConsistChanged(CCF_TRACK);
 	}
 	InvalidateWindowClassesData(WC_BUILD_VEHICLE, 0);
-	return true;
 }
 
-/* Check service intervals of vehicles, p1 is value of % or day based servicing */
-static bool CheckInterval(int32 p1)
+/* Check service intervals of vehicles, newvalue is value of % or day based servicing */
+static void UpdateServiceInterval(int32 new_value)
 {
 	bool update_vehicles;
 	VehicleDefaultSettings *vds;
@@ -911,7 +868,7 @@ static bool CheckInterval(int32 p1)
 		update_vehicles = true;
 	}
 
-	if (p1 != 0) {
+	if (new_value != 0) {
 		vds->servint_trains   = 50;
 		vds->servint_roadveh  = 50;
 		vds->servint_aircraft = 50;
@@ -928,66 +885,42 @@ static bool CheckInterval(int32 p1)
 		for (Vehicle *v : Vehicle::Iterate()) {
 			if (v->owner == _current_company && v->IsPrimaryVehicle() && !v->ServiceIntervalIsCustom()) {
 				v->SetServiceInterval(CompanyServiceInterval(c, v->type));
-				v->SetServiceIntervalIsPercent(p1 != 0);
+				v->SetServiceIntervalIsPercent(new_value != 0);
 			}
 		}
 	}
 
-	InvalidateDetailsWindow(0);
-
-	return true;
+	SetWindowClassesDirty(WC_VEHICLE_DETAILS);
 }
 
-static bool UpdateInterval(VehicleType type, int32 p1)
+static bool CanUpdateServiceInterval(VehicleType type, int32 &new_value)
 {
-	bool update_vehicles;
 	VehicleDefaultSettings *vds;
 	if (_game_mode == GM_MENU || !Company::IsValidID(_current_company)) {
 		vds = &_settings_client.company.vehicle;
-		update_vehicles = false;
 	} else {
 		vds = &Company::Get(_current_company)->settings.vehicle;
-		update_vehicles = true;
 	}
 
 	/* Test if the interval is valid */
-	uint16 interval = GetServiceIntervalClamped(p1, vds->servint_ispercent);
-	if (interval != p1) return false;
+	int32 interval = GetServiceIntervalClamped(new_value, vds->servint_ispercent);
+	return interval == new_value;
+}
 
-	if (update_vehicles) {
+static void UpdateServiceInterval(VehicleType type, int32 new_value)
+{
+	if (_game_mode != GM_MENU && Company::IsValidID(_current_company)) {
 		for (Vehicle *v : Vehicle::Iterate()) {
 			if (v->owner == _current_company && v->type == type && v->IsPrimaryVehicle() && !v->ServiceIntervalIsCustom()) {
-				v->SetServiceInterval(p1);
+				v->SetServiceInterval(new_value);
 			}
 		}
 	}
 
-	InvalidateDetailsWindow(0);
-
-	return true;
-}
-
-static bool UpdateIntervalTrains(int32 p1)
-{
-	return UpdateInterval(VEH_TRAIN, p1);
+	SetWindowClassesDirty(WC_VEHICLE_DETAILS);
 }
 
-static bool UpdateIntervalRoadVeh(int32 p1)
-{
-	return UpdateInterval(VEH_ROAD, p1);
-}
-
-static bool UpdateIntervalShips(int32 p1)
-{
-	return UpdateInterval(VEH_SHIP, p1);
-}
-
-static bool UpdateIntervalAircraft(int32 p1)
-{
-	return UpdateInterval(VEH_AIRCRAFT, p1);
-}
-
-static bool TrainAccelerationModelChanged(int32 p1)
+static void TrainAccelerationModelChanged(int32 new_value)
 {
 	for (Train *t : Train::Iterate()) {
 		if (t->IsFrontEngine()) {
@@ -1000,30 +933,24 @@ static bool TrainAccelerationModelChange
 	SetWindowClassesDirty(WC_ENGINE_PREVIEW);
 	InvalidateWindowClassesData(WC_BUILD_VEHICLE, 0);
 	SetWindowClassesDirty(WC_VEHICLE_DETAILS);
-
-	return true;
 }
 
 /**
  * This function updates the train acceleration cache after a steepness change.
- * @param p1 Callback parameter.
- * @return Always true.
+ * @param new_value Unused new value of setting.
  */
-static bool TrainSlopeSteepnessChanged(int32 p1)
+static void TrainSlopeSteepnessChanged(int32 new_value)
 {
 	for (Train *t : Train::Iterate()) {
 		if (t->IsFrontEngine()) t->CargoChanged();
 	}
-
-	return true;
 }
 
 /**
  * This function updates realistic acceleration caches when the setting "Road vehicle acceleration model" is set.
- * @param p1 Callback parameter
- * @return Always true
+ * @param new_value Unused new value of setting.
  */
-static bool RoadVehAccelerationModelChanged(int32 p1)
+static void RoadVehAccelerationModelChanged(int32 new_value)
 {
 	if (_settings_game.vehicle.roadveh_acceleration_model != AM_ORIGINAL) {
 		for (RoadVehicle *rv : RoadVehicle::Iterate()) {
@@ -1037,48 +964,29 @@ static bool RoadVehAccelerationModelChan
 	SetWindowClassesDirty(WC_ENGINE_PREVIEW);
 	InvalidateWindowClassesData(WC_BUILD_VEHICLE, 0);
 	SetWindowClassesDirty(WC_VEHICLE_DETAILS);
-
-	return true;
 }
 
 /**
  * This function updates the road vehicle acceleration cache after a steepness change.
- * @param p1 Callback parameter.
- * @return Always true.
+ * @param new_value Unused new value of setting.
  */
-static bool RoadVehSlopeSteepnessChanged(int32 p1)
+static void RoadVehSlopeSteepnessChanged(int32 new_value)
 {
 	for (RoadVehicle *rv : RoadVehicle::Iterate()) {
 		if (rv->IsFrontEngine()) rv->CargoChanged();
 	}
-
-	return true;
 }
 
-static bool DragSignalsDensityChanged(int32)
-{
-	InvalidateWindowData(WC_BUILD_SIGNAL, 0);
-
-	return true;
-}
-
-static bool TownFoundingChanged(int32 p1)
+static void TownFoundingChanged(int32 new_value)
 {
 	if (_game_mode != GM_EDITOR && _settings_game.economy.found_town == TF_FORBIDDEN) {
 		DeleteWindowById(WC_FOUND_TOWN, 0);
-		return true;
+	} else {
+		InvalidateWindowData(WC_FOUND_TOWN, 0);
 	}
-	InvalidateWindowData(WC_FOUND_TOWN, 0);
-	return true;
 }
 
-static bool InvalidateVehTimetableWindow(int32 p1)
-{
-	InvalidateWindowClassesData(WC_VEHICLE_TIMETABLE, VIWD_MODIFY_ORDERS);
-	return true;
-}
-
-static bool ZoomMinMaxChanged(int32 p1)
+static void ZoomMinMaxChanged(int32 new_value)
 {
 	extern void ConstrainAllViewportsZoom();
 	ConstrainAllViewportsZoom();
@@ -1089,81 +997,32 @@ static bool ZoomMinMaxChanged(int32 p1)
 		UpdateCursorSize();
 		LoadStringWidthTable();
 	}
-	return true;
 }
 
-static bool SpriteZoomMinChanged(int32 p1) {
+static void SpriteZoomMinChanged(int32 new_value)
+{
 	GfxClearSpriteCache();
 	/* Force all sprites to redraw at the new chosen zoom level */
 	MarkWholeScreenDirty();
-	return true;
 }
 
 /**
  * Update any possible saveload window and delete any newgrf dialogue as
  * its widget parts might change. Reinit all windows as it allows access to the
  * newgrf debug button.
- * @param p1 unused.
- * @return Always true.
+ * @param new_value unused.
  */
-static bool InvalidateNewGRFChangeWindows(int32 p1)
+static void InvalidateNewGRFChangeWindows(int32 new_value)
 {
 	InvalidateWindowClassesData(WC_SAVELOAD);
 	DeleteWindowByClass(WC_GAME_OPTIONS);
 	ReInitAllWindows(_gui_zoom_cfg);
-	return true;
 }
 
-static bool InvalidateCompanyLiveryWindow(int32 p1)
+static void InvalidateCompanyLiveryWindow(int32 new_value)
 {
 	InvalidateWindowClassesData(WC_COMPANY_COLOUR, -1);
 	ResetVehicleColourMap();
-	return RedrawScreen(p1);
-}
-
-static bool InvalidateIndustryViewWindow(int32 p1)
-{
-	InvalidateWindowClassesData(WC_INDUSTRY_VIEW);
-	return true;
-}
-
-static bool InvalidateAISettingsWindow(int32 p1)
-{
-	InvalidateWindowClassesData(WC_AI_SETTINGS);
-	return true;
-}
-
-/**
- * Update the town authority window after a town authority setting change.
- * @param p1 Unused.
- * @return Always true.
- */
-static bool RedrawTownAuthority(int32 p1)
-{
-	SetWindowClassesDirty(WC_TOWN_AUTHORITY);
-	return true;
-}
-
-/**
- * Invalidate the company infrastructure details window after a infrastructure maintenance setting change.
- * @param p1 Unused.
- * @return Always true.
- */
-static bool InvalidateCompanyInfrastructureWindow(int32 p1)
-{
-	InvalidateWindowClassesData(WC_COMPANY_INFRASTRUCTURE);
-	return true;
-}
-
-/**
- * Invalidate the company details window after the shares setting changed.
- * @param p1 Unused.
- * @return Always true.
- */
-static bool InvalidateCompanyWindow(int32 p1)
-{
-	InvalidateWindowClassesData(WC_COMPANY);
-	return true;
 }
 
 /** Checks if any settings are set to incorrect values, and sets them to correct values in that case. */
@@ -1176,7 +1035,7 @@ static void ValidateSettings()
 	}
 }
 
-static bool DifficultyNoiseChange(int32 i)
+static void DifficultyNoiseChange(int32 new_value)
 {
 	if (_game_mode == GM_NORMAL) {
 		UpdateAirportsNoise();
@@ -1184,11 +1043,9 @@ static bool DifficultyNoiseChange(int32 
 			InvalidateWindowClassesData(WC_TOWN_VIEW, 0);
 		}
 	}
-
-	return true;
 }
 
-static bool MaxNoAIsChange(int32 i)
+static void MaxNoAIsChange(int32 new_value)
 {
 	if (GetGameSettings().difficulty.max_no_competitors != 0 &&
 			AI::GetInfoList()->size() == 0 &&
@@ -1197,15 +1054,14 @@ static bool MaxNoAIsChange(int32 i)
 	}
 
 	InvalidateWindowClassesData(WC_GAME_OPTIONS, 0);
-	return true;
 }
 
 /**
  * Check whether the road side may be changed.
- * @param p1 unused
+ * @param new_value unused
  * @return true if the road side may be changed.
  */
-static bool CheckRoadSide(int p1)
+static bool CheckRoadSide(int32 &new_value)
 {
 	extern bool RoadVehiclesAreBuilt();
 	return _game_mode == GM_MENU || !RoadVehiclesAreBuilt();
@@ -1225,10 +1081,10 @@ static size_t ConvertLandscape(const cha
 	return OneOfManySettingDesc::ParseSingleValue(value, strlen(value), _old_landscape_values);
 }
 
-static bool CheckFreeformEdges(int32 p1)
+static bool CheckFreeformEdges(int32 &new_value)
 {
 	if (_game_mode == GM_MENU) return true;
-	if (p1 != 0) {
+	if (new_value != 0) {
 		for (Ship *s : Ship::Iterate()) {
 			/* Check if there is a ship on the northern border. */
 			if (TileX(s->tile) == 0 || TileY(s->tile) == 0) {
@@ -1243,8 +1099,6 @@ static bool CheckFreeformEdges(int32 p1)
 				return false;
 			}
 		}
-		for (uint x = 0; x < MapSizeX(); x++) MakeVoid(TileXY(x, 0));
-		for (uint y = 0; y < MapSizeY(); y++) MakeVoid(TileXY(0, y));
 	} else {
 		for (uint i = 0; i < MapMaxX(); i++) {
 			if (TileHeight(TileXY(i, 1)) != 0) {
@@ -1270,6 +1124,18 @@ static bool CheckFreeformEdges(int32 p1)
 				return false;
 			}
 		}
+	}
+	return true;
+}
+
+static void UpdateFreeformEdges(int32 new_value)
+{
+	if (_game_mode == GM_MENU) return;
+
+	if (new_value != 0) {
+		for (uint x = 0; x < MapSizeX(); x++) MakeVoid(TileXY(x, 0));
+		for (uint y = 0; y < MapSizeY(); y++) MakeVoid(TileXY(0, y));
+	} else {
 		/* Make tiles at the border water again. */
 		for (uint i = 0; i < MapMaxX(); i++) {
 			SetTileHeight(TileXY(i, 0), 0);
@@ -1281,14 +1147,13 @@ static bool CheckFreeformEdges(int32 p1)
 		}
 	}
 	MarkWholeScreenDirty();
-	return true;
 }
 
 /**
  * Changing the setting "allow multiple NewGRF sets" is not allowed
  * if there are vehicles.
  */
-static bool ChangeDynamicEngines(int32 p1)
+static bool CheckDynamicEngines(int32 &new_value)
 {
 	if (_game_mode == GM_MENU) return true;
 
@@ -1300,7 +1165,7 @@ static bool ChangeDynamicEngines(int32 p
 	return true;
 }
 
-static bool ChangeMaxHeightLevel(int32 p1)
+static bool CheckMaxHeightLevel(int32 &new_value)
 {
 	if (_game_mode == GM_NORMAL) return false;
 	if (_game_mode != GM_EDITOR) return true;
@@ -1308,39 +1173,33 @@ static bool ChangeMaxHeightLevel(int32 p
 	/* Check if at least one mountain on the map is higher than the new value.
 	 * If yes, disallow the change. */
 	for (TileIndex t = 0; t < MapSize(); t++) {
-		if ((int32)TileHeight(t) > p1) {
+		if ((int32)TileHeight(t) > new_value) {
 			ShowErrorMessage(STR_CONFIG_SETTING_TOO_HIGH_MOUNTAIN, INVALID_STRING_ID, WL_ERROR);
 			/* Return old, unchanged value */
 			return false;
 		}
 	}
 
-	/* The smallmap uses an index from heightlevels to colours. Trigger rebuilding it. */
-	InvalidateWindowClassesData(WC_SMALLMAP, 2);
-
 	return true;
 }
 
-static bool StationCatchmentChanged(int32 p1)
+static void StationCatchmentChanged(int32 new_value)
 {
 	Station::RecomputeCatchmentForAll();
 	MarkWholeScreenDirty();
-	return true;
 }
 
-static bool MaxVehiclesChanged(int32 p1)
+static void MaxVehiclesChanged(int32 new_value)
 {
 	InvalidateWindowClassesData(WC_BUILD_TOOLBAR);
 	MarkWholeScreenDirty();
-	return true;
 }
 
-static bool InvalidateShipPathCache(int32 p1)
+static void InvalidateShipPathCache(int32 new_value)
 {
 	for (Ship *s : Ship::Iterate()) {
 		s->path.clear();
 	}
-	return true;
 }
 
 /**
@@ -1354,12 +1213,6 @@ static bool ReplaceAsteriskWithEmptyPass
 	return true;
 }
 
-static bool UpdateClientConfigValues(int32 p1)
-{
-	UpdateClientConfigValues();
-	return true;
-}
-
 /** Update the game info, and send it to the clients when we are running as a server. */
 static void UpdateClientConfigValues()
 {
@@ -1838,17 +1691,12 @@ void DeleteGRFPresetFromConfig(const cha
 void IntSettingDesc::ChangeValue(const void *object, int32 newval) const
 {
 	int32 oldval = this->Read(object);
-
-	this->MakeValueValidAndWrite(object, newval);
-	newval = this->Read(object);
-
+	this->MakeValueValid(newval);
+	if (this->pre_check != nullptr && !this->pre_check(newval)) return;
 	if (oldval == newval) return;
 
-	if (this->proc != nullptr && !this->proc(newval)) {
-		/* The change was not allowed, so revert. */
-		this->Write(object, oldval);
-		return;
-	}
+	this->Write(object, newval);
+	if (this->post_callback != nullptr) this->post_callback(newval);
 
 	if (this->flags & SGF_NO_NETWORK) {
 		GamelogStartAction(GLAT_SETTING);
diff --git a/src/settings_internal.h b/src/settings_internal.h
--- a/src/settings_internal.h
+++ b/src/settings_internal.h
@@ -64,8 +64,6 @@ enum SettingType {
 };
 
 struct IniItem;
-typedef bool OnChange(int32 var);           ///< callback prototype on data modification
-typedef size_t OnConvert(const char *value); ///< callback prototype for conversion error
 
 /** Properties of config file settings. */
 struct SettingDesc {
@@ -125,11 +123,27 @@ struct SettingDesc {
 
 /** Base integer type, including boolean, settings. Only these are shown in the settings UI. */
 struct IntSettingDesc : SettingDesc {
+	/**
+	 * A check to be performed before the setting gets changed. The passed integer may be
+	 * changed by the check if that is important, for example to remove some unwanted bit.
+	 * The return value denotes whether the value, potentially after the changes,
+	 * is allowed to be used/set in the configuration.
+	 * @param value The prospective new value for the setting.
+	 * @return True when the setting is accepted.
+	 */
+	typedef bool PreChangeCheck(int32 &value);
+	/**
+	 * A callback to denote that a setting has been changed.
+	 * @param The new value for the setting.
+	 */
+	typedef void PostChangeCallback(int32 value);
+
 	IntSettingDesc(SaveLoad save, const char *name, SettingGuiFlag flags, bool startup, int32 def,
-		int32 min, uint32 max, int32 interval, StringID str, StringID str_help, StringID str_val,
-		SettingCategory cat, OnChange *proc) :
+			int32 min, uint32 max, int32 interval, StringID str, StringID str_help, StringID str_val,
+			SettingCategory cat, PreChangeCheck pre_check, PostChangeCallback post_callback) :
 		SettingDesc(save, name, flags, startup), def(def), min(min), max(max), interval(interval),
-		str(str), str_help(str_help), str_val(str_val), cat(cat), proc(proc) {}
+			str(str), str_help(str_help), str_val(str_val), cat(cat), pre_check(pre_check),
+			post_callback(post_callback) {}
 	virtual ~IntSettingDesc() {}
 
 	int32 def;              ///< default value given when none is present
@@ -140,7 +154,8 @@ struct IntSettingDesc : SettingDesc {
 	StringID str_help;      ///< (Translated) string with help text; gui only.
 	StringID str_val;       ///< (Translated) first string describing the value.
 	SettingCategory cat;    ///< assigned categories of the setting
-	OnChange *proc;         ///< callback procedure for when the value is changed
+	PreChangeCheck *pre_check;         ///< Callback to check for the validity of the setting.
+	PostChangeCallback *post_callback; ///< Callback when the setting has been changed.
 
 	/**
 	 * Check whether this setting is a boolean type setting.
@@ -166,8 +181,10 @@ private:
 /** Boolean setting. */
 struct BoolSettingDesc : IntSettingDesc {
 	BoolSettingDesc(SaveLoad save, const char *name, SettingGuiFlag flags, bool startup, bool def,
-		StringID str, StringID str_help, StringID str_val, SettingCategory cat, OnChange *proc) :
-		IntSettingDesc(save, name, flags, startup, def, 0, 1, 0, str, str_help, str_val, cat, proc) {}
+			StringID str, StringID str_help, StringID str_val, SettingCategory cat,
+			PreChangeCheck pre_check, PostChangeCallback post_callback) :
+		IntSettingDesc(save, name, flags, startup, def, 0, 1, 0, str, str_help, str_val, cat,
+			pre_check, post_callback) {}
 	virtual ~BoolSettingDesc() {}
 
 	bool IsBoolSetting() const override { return true; }
@@ -177,10 +194,14 @@ struct BoolSettingDesc : IntSettingDesc 
 
 /** One of many setting. */
 struct OneOfManySettingDesc : IntSettingDesc {
-	OneOfManySettingDesc(SaveLoad save, const char *name, SettingGuiFlag flags, bool startup,
-		int32 def, int32 max, StringID str, StringID str_help, StringID str_val, SettingCategory cat, OnChange *proc,
-		std::initializer_list<const char *> many, OnConvert *many_cnvt) :
-		IntSettingDesc(save, name, flags, startup, def, 0, max, 0, str, str_help, str_val, cat, proc), many_cnvt(many_cnvt)
+	typedef size_t OnConvert(const char *value); ///< callback prototype for conversion error
+
+	OneOfManySettingDesc(SaveLoad save, const char *name, SettingGuiFlag flags, bool startup, int32 def,
+			int32 max, StringID str, StringID str_help, StringID str_val, SettingCategory cat,
+			PreChangeCheck pre_check, PostChangeCallback post_callback,
+			std::initializer_list<const char *> many, OnConvert *many_cnvt) :
+		IntSettingDesc(save, name, flags, startup, def, 0, max, 0, str, str_help, str_val, cat,
+			pre_check, post_callback), many_cnvt(many_cnvt)
 	{
 		for (auto one : many) this->many.push_back(one);
 	}
@@ -200,10 +221,11 @@ struct OneOfManySettingDesc : IntSetting
 /** Many of many setting. */
 struct ManyOfManySettingDesc : OneOfManySettingDesc {
 	ManyOfManySettingDesc(SaveLoad save, const char *name, SettingGuiFlag flags, bool startup,
-		int32 def, StringID str, StringID str_help, StringID str_val, SettingCategory cat, OnChange *proc,
+		int32 def, StringID str, StringID str_help, StringID str_val, SettingCategory cat,
+		PreChangeCheck pre_check, PostChangeCallback post_callback,
 		std::initializer_list<const char *> many, OnConvert *many_cnvt) :
 		OneOfManySettingDesc(save, name, flags, startup, def, (1 << many.size()) - 1, str, str_help,
-			str_val, cat, proc, many, many_cnvt) {}
+			str_val, cat, pre_check, post_callback, many, many_cnvt) {}
 	virtual ~ManyOfManySettingDesc() {}
 
 	size_t ParseValue(const char *str) const override;
diff --git a/src/table/company_settings.ini b/src/table/company_settings.ini
--- a/src/table/company_settings.ini
+++ b/src/table/company_settings.ini
@@ -5,19 +5,16 @@
 ;
 
 [pre-amble]
-static bool CheckInterval(int32 p1);
-static bool InvalidateDetailsWindow(int32 p1);
-static bool UpdateIntervalTrains(int32 p1);
-static bool UpdateIntervalRoadVeh(int32 p1);
-static bool UpdateIntervalShips(int32 p1);
-static bool UpdateIntervalAircraft(int32 p1);
+static void UpdateServiceInterval(int32 new_value);
+static bool CanUpdateServiceInterval(VehicleType type, int32 &new_value);
+static void UpdateServiceInterval(VehicleType type, int32 new_value);
 
 static const SettingTable _company_settings{
 [post-amble]
 };
 [templates]
-SDT_BOOL = SDT_BOOL($base, $var,        $flags, $guiflags, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra, $startup),
-SDT_VAR  =  SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra, $startup),
+SDT_BOOL = SDT_BOOL($base, $var,        $flags, $guiflags, $def,                        $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
+SDT_VAR  =  SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
 
 [validation]
 SDT_VAR = static_assert($max <= MAX_$type, "Maximum value for $base.$var exceeds storage size");
@@ -29,7 +26,8 @@ interval = 0
 str      = STR_NULL
 strhelp  = STR_CONFIG_SETTING_NO_EXPLANATION_AVAILABLE_HELPTEXT
 strval   = STR_NULL
-proc     = nullptr
+pre_cb   = nullptr
+post_cb  = nullptr
 load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION
@@ -82,7 +80,7 @@ var      = vehicle.servint_ispercent
 def      = false
 str      = STR_CONFIG_SETTING_SERVINT_ISPERCENT
 strhelp  = STR_CONFIG_SETTING_SERVINT_ISPERCENT_HELPTEXT
-proc     = CheckInterval
+post_cb  = UpdateServiceInterval
 
 [SDT_VAR]
 base     = CompanySettings
@@ -95,7 +93,8 @@ max      = 800
 str      = STR_CONFIG_SETTING_SERVINT_TRAINS
 strhelp  = STR_CONFIG_SETTING_SERVINT_TRAINS_HELPTEXT
 strval   = STR_CONFIG_SETTING_SERVINT_VALUE
-proc     = UpdateIntervalTrains
+pre_cb   = [](auto new_value) { return CanUpdateServiceInterval(VEH_TRAIN, new_value); }
+post_cb  = [](auto new_value) { UpdateServiceInterval(VEH_TRAIN, new_value); }
 
 [SDT_VAR]
 base     = CompanySettings
@@ -108,7 +107,8 @@ max      = 800
 str      = STR_CONFIG_SETTING_SERVINT_ROAD_VEHICLES
 strhelp  = STR_CONFIG_SETTING_SERVINT_ROAD_VEHICLES_HELPTEXT
 strval   = STR_CONFIG_SETTING_SERVINT_VALUE
-proc     = UpdateIntervalRoadVeh
+pre_cb   = [](auto new_value) { return CanUpdateServiceInterval(VEH_ROAD, new_value); }
+post_cb  = [](auto new_value) { UpdateServiceInterval(VEH_ROAD, new_value); }
 
 [SDT_VAR]
 base     = CompanySettings
@@ -121,7 +121,8 @@ max      = 800
 str      = STR_CONFIG_SETTING_SERVINT_SHIPS
 strhelp  = STR_CONFIG_SETTING_SERVINT_SHIPS_HELPTEXT
 strval   = STR_CONFIG_SETTING_SERVINT_VALUE
-proc     = UpdateIntervalShips
+pre_cb   = [](auto new_value) { return CanUpdateServiceInterval(VEH_SHIP, new_value); }
+post_cb  = [](auto new_value) { UpdateServiceInterval(VEH_SHIP, new_value); }
 
 [SDT_VAR]
 base     = CompanySettings
@@ -134,4 +135,5 @@ max      = 800
 str      = STR_CONFIG_SETTING_SERVINT_AIRCRAFT
 strhelp  = STR_CONFIG_SETTING_SERVINT_AIRCRAFT_HELPTEXT
 strval   = STR_CONFIG_SETTING_SERVINT_VALUE
-proc     = UpdateIntervalAircraft
+pre_cb   = [](auto new_value) { return CanUpdateServiceInterval(VEH_AIRCRAFT, new_value); }
+post_cb  = [](auto new_value) { UpdateServiceInterval(VEH_AIRCRAFT, new_value); }
diff --git a/src/table/currency_settings.ini b/src/table/currency_settings.ini
--- a/src/table/currency_settings.ini
+++ b/src/table/currency_settings.ini
@@ -9,7 +9,7 @@ static const SettingTable _currency_sett
 [post-amble]
 };
 [templates]
-SDT_VAR  = SDT_VAR ($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc,             $from, $to, $cat, $extra, $startup),
+SDT_VAR  = SDT_VAR ($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
 SDT_SSTR = SDT_SSTR($base, $var, $type, $flags, $guiflags, $def,                                                 $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
 
 [validation]
@@ -22,7 +22,6 @@ interval = 0
 str      = STR_NULL
 strhelp  = STR_CONFIG_SETTING_NO_EXPLANATION_AVAILABLE_HELPTEXT
 strval   = STR_NULL
-proc     = nullptr
 pre_cb   = nullptr
 post_cb  = nullptr
 load     = nullptr
diff --git a/src/table/gameopt_settings.ini b/src/table/gameopt_settings.ini
--- a/src/table/gameopt_settings.ini
+++ b/src/table/gameopt_settings.ini
@@ -37,12 +37,12 @@ static const SettingTable _gameopt_setti
 };
 [templates]
 SDTG_LIST    =  SDTG_LIST($name,       $type, $flags, $guiflags, $var, $def, $length, $from, $to, $cat, $extra, $startup),
-SDTG_VAR     =   SDTG_VAR($name,       $type, $flags, $guiflags, $var, $def, $min, $max, $interval,        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra, $startup),
+SDTG_VAR     =   SDTG_VAR($name,       $type, $flags, $guiflags, $var, $def, $min, $max, $interval,  $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
 SDT_NULL     =   SDT_NULL(                                                   $length, $from, $to),
-SDTC_OMANY   = SDTC_OMANY(       $var, $type, $flags, $guiflags, $def,       $max, $full,            $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra, $startup),
-SDTG_OMANY   = SDTG_OMANY($name,       $type, $flags, $guiflags, $var, $def, $max, $full,            $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra, $startup),
-SDT_OMANY    =  SDT_OMANY($base, $var, $type, $flags, $guiflags, $def,       $max, $full,            $str, $strhelp, $strval, $proc, $from, $to, $load, $cat, $extra, $startup),
-SDT_VAR      =    SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max,        $interval, $str, $strhelp, $strval, $proc, $from, $to,        $cat, $extra, $startup),
+SDTC_OMANY   = SDTC_OMANY(       $var, $type, $flags, $guiflags, $def,       $max, $full,            $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
+SDTG_OMANY   = SDTG_OMANY($name,       $type, $flags, $guiflags, $var, $def, $max, $full,            $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
+SDT_OMANY    =  SDT_OMANY($base, $var, $type, $flags, $guiflags, $def,       $max, $full,            $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $load, $cat, $extra, $startup),
+SDT_VAR      =    SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max,        $interval, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
 
 [validation]
 SDTG_VAR = static_assert($max <= MAX_$type, "Maximum value for $var exceeds storage size");
@@ -58,7 +58,8 @@ interval = 0
 str      = STR_NULL
 strhelp  = STR_CONFIG_SETTING_NO_EXPLANATION_AVAILABLE_HELPTEXT
 strval   = STR_NULL
-proc     = nullptr
+pre_cb   = nullptr
+post_cb  = nullptr
 load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION
diff --git a/src/table/misc_settings.ini b/src/table/misc_settings.ini
--- a/src/table/misc_settings.ini
+++ b/src/table/misc_settings.ini
@@ -22,11 +22,11 @@ static const SettingTable _misc_settings
 };
 [templates]
 SDTG_LIST  =  SDTG_LIST($name, $type, $flags, $guiflags, $var, $def,       $length,                                                            $from, $to, $cat, $extra, $startup),
-SDTG_MMANY = SDTG_MMANY($name, $type, $flags, $guiflags, $var, $def,                        $full, $str, $strhelp, $strval, $proc,             $from, $to, $cat, $extra, $startup),
-SDTG_OMANY = SDTG_OMANY($name, $type, $flags, $guiflags, $var, $def,       $max,            $full, $str, $strhelp, $strval, $proc,             $from, $to, $cat, $extra, $startup),
+SDTG_MMANY = SDTG_MMANY($name, $type, $flags, $guiflags, $var, $def,                        $full, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
+SDTG_OMANY = SDTG_OMANY($name, $type, $flags, $guiflags, $var, $def,       $max,            $full, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
 SDTG_SSTR  =  SDTG_SSTR($name, $type, $flags, $guiflags, $var, $def,       0,                                               $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
-SDTG_BOOL  =  SDTG_BOOL($name,        $flags, $guiflags, $var, $def,                               $str, $strhelp, $strval, $proc,             $from, $to, $cat, $extra, $startup),
-SDTG_VAR   =   SDTG_VAR($name, $type, $flags, $guiflags, $var, $def, $min, $max, $interval,        $str, $strhelp, $strval, $proc,             $from, $to, $cat, $extra, $startup),
+SDTG_BOOL  =  SDTG_BOOL($name,        $flags, $guiflags, $var, $def,                               $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
+SDTG_VAR   =   SDTG_VAR($name, $type, $flags, $guiflags, $var, $def, $min, $max, $interval,        $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
 
 [validation]
 SDTG_VAR = static_assert($max <= MAX_$type, "Maximum value for $var exceeds storage size");
@@ -39,7 +39,6 @@ interval = 0
 str      = STR_NULL
 strhelp  = STR_CONFIG_SETTING_NO_EXPLANATION_AVAILABLE_HELPTEXT
 strval   = STR_NULL
-proc     = nullptr
 pre_cb   = nullptr
 post_cb  = nullptr
 load     = nullptr
diff --git a/src/table/settings.h.preamble b/src/table/settings.h.preamble
--- a/src/table/settings.h.preamble
+++ b/src/table/settings.h.preamble
@@ -58,11 +58,11 @@ static size_t ConvertLandscape(const cha
 
 /* Macros for various objects to go in the configuration file.
  * This section is for global variables */
-#define SDTG_VAR(name, type, flags, guiflags, var, def, min, max, interval, str, strhelp, strval, proc, from, to, cat, extra, startup)\
-	NSD(Int, SLEG_GENERAL(SL_VAR, var, type | flags, 1, from, to, extra), name, guiflags, startup, def, min, max, interval, str, strhelp, strval, cat, proc)
+#define SDTG_VAR(name, type, flags, guiflags, var, def, min, max, interval, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)\
+	NSD(Int, SLEG_GENERAL(SL_VAR, var, type | flags, 1, from, to, extra), name, guiflags, startup, def, min, max, interval, str, strhelp, strval, cat, pre_check, post_callback)
 
-#define SDTG_BOOL(name, flags, guiflags, var, def, str, strhelp, strval, proc, from, to, cat, extra, startup)\
-	NSD(Bool, SLEG_GENERAL(SL_VAR, var, SLE_BOOL | flags, 1, from, to, extra), name, guiflags, startup, def, str, strhelp, strval, cat, proc)
+#define SDTG_BOOL(name, flags, guiflags, var, def, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)\
+	NSD(Bool, SLEG_GENERAL(SL_VAR, var, SLE_BOOL | flags, 1, from, to, extra), name, guiflags, startup, def, str, strhelp, strval, cat, pre_check, post_callback)
 
 #define SDTG_LIST(name, type, flags, guiflags, var, def, length, from, to, cat, extra, startup)\
 	NSD(List, SLEG_GENERAL(SL_ARR, var, type | flags, length, from, to, extra), name, guiflags, startup, def)
@@ -70,22 +70,22 @@ static size_t ConvertLandscape(const cha
 #define SDTG_SSTR(name, type, flags, guiflags, var, def, max_length, pre_check, post_callback, from, to, cat, extra, startup)\
 	NSD(String, SLEG_GENERAL(SL_STDSTR, var, type | flags, sizeof(var), from, to, extra), name, guiflags, startup, def, max_length, pre_check, post_callback)
 
-#define SDTG_OMANY(name, type, flags, guiflags, var, def, max, full, str, strhelp, strval, proc, from, to, cat, extra, startup)\
-	NSD(OneOfMany, SLEG_GENERAL(SL_VAR, var, type | flags, 1, from, to, extra), name, guiflags, startup, def, max, str, strhelp, strval, cat, proc, full, nullptr)
+#define SDTG_OMANY(name, type, flags, guiflags, var, def, max, full, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)\
+	NSD(OneOfMany, SLEG_GENERAL(SL_VAR, var, type | flags, 1, from, to, extra), name, guiflags, startup, def, max, str, strhelp, strval, cat, pre_check, post_callback, full, nullptr)
 
-#define SDTG_MMANY(name, type, flags, guiflags, var, def, full, str, strhelp, strval, proc, from, to, cat, extra, startup)\
-	NSD(ManyOfMany, SLEG_GENERAL(SL_VAR, var, type | flags, 1, from, to, extra), name, guiflags, startup, def, str, strhelp, strval, cat, proc, full, nullptr)
+#define SDTG_MMANY(name, type, flags, guiflags, var, def, full, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)\
+	NSD(ManyOfMany, SLEG_GENERAL(SL_VAR, var, type | flags, 1, from, to, extra), name, guiflags, startup, def, str, strhelp, strval, cat, pre_check, post_callback, full, nullptr)
 
 #define SDTG_NULL(length, from, to)\
 	NSD(Null, SLEG_NULL(length, from, to))
 
 /* Macros for various objects to go in the configuration file.
  * This section is for structures where their various members are saved */
-#define SDT_VAR(base, var, type, flags, guiflags, def, min, max, interval, str, strhelp, strval, proc, from, to, cat, extra, startup)\
-	NSD(Int, SLE_GENERAL(SL_VAR, base, var, type | flags, 1, from, to, extra), #var, guiflags, startup, def, min, max, interval, str, strhelp, strval, cat, proc)
+#define SDT_VAR(base, var, type, flags, guiflags, def, min, max, interval, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)\
+	NSD(Int, SLE_GENERAL(SL_VAR, base, var, type | flags, 1, from, to, extra), #var, guiflags, startup, def, min, max, interval, str, strhelp, strval, cat, pre_check, post_callback)
 
-#define SDT_BOOL(base, var, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat, extra, startup)\
-	NSD(Bool, SLE_GENERAL(SL_VAR, base, var, SLE_BOOL | flags, 1, from, to, extra), #var, guiflags, startup, def, str, strhelp, strval, cat, proc)
+#define SDT_BOOL(base, var, flags, guiflags, def, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)\
+	NSD(Bool, SLE_GENERAL(SL_VAR, base, var, SLE_BOOL | flags, 1, from, to, extra), #var, guiflags, startup, def, str, strhelp, strval, cat, pre_check, post_callback)
 
 #define SDT_LIST(base, var, type, flags, guiflags, def, from, to, cat, extra, startup)\
 	NSD(List, SLE_GENERAL(SL_ARR, base, var, type | flags, lengthof(((base*)8)->var), from, to, extra), #var, guiflags, startup, def)
@@ -93,21 +93,21 @@ static size_t ConvertLandscape(const cha
 #define SDT_SSTR(base, var, type, flags, guiflags, def, pre_check, post_callback, from, to, cat, extra, startup)\
 	NSD(String, SLE_GENERAL(SL_STDSTR, base, var, type | flags, sizeof(((base*)8)->var), from, to, extra), #var, guiflags, startup, def, 0, pre_check, post_callback)
 
-#define SDT_OMANY(base, var, type, flags, guiflags, def, max, full, str, strhelp, strval, proc, from, to, load, cat, extra, startup)\
-	NSD(OneOfMany, SLE_GENERAL(SL_VAR, base, var, type | flags, 1, from, to, extra), #var, guiflags, startup, def, max, str, strhelp, strval, cat, proc, full, load)
+#define SDT_OMANY(base, var, type, flags, guiflags, def, max, full, str, strhelp, strval, pre_check, post_callback, from, to, load, cat, extra, startup)\
+	NSD(OneOfMany, SLE_GENERAL(SL_VAR, base, var, type | flags, 1, from, to, extra), #var, guiflags, startup, def, max, str, strhelp, strval, cat, pre_check, post_callback, full, load)
 
-#define SDT_MMANY(base, var, type, flags, guiflags, def, full, str, proc, strhelp, strval, from, to, cat, extra, startup)\
-	NSD(ManyOfMany, SLE_GENERAL(SL_VAR, base, var, type | flags, 1, from, to, extra), #var, guiflags, startup, def, str, strhelp, strval, cat, proc, full, nullptr)
+#define SDT_MMANY(base, var, type, flags, guiflags, def, full, str, pre_check, post_callback, strhelp, strval, from, to, cat, extra, startup)\
+	NSD(ManyOfMany, SLE_GENERAL(SL_VAR, base, var, type | flags, 1, from, to, extra), #var, guiflags, startup, def, str, strhelp, strval, cat, pre_check, post_callback, full, nullptr)
 
 #define SDT_NULL(length, from, to)\
 	NSD(Null, SLE_CONDNULL(length, from, to))
 
 
-#define SDTC_VAR(var, type, flags, guiflags, def, min, max, interval, str, strhelp, strval, proc, from, to, cat, extra, startup)\
-	SDTG_VAR(#var, type, flags, guiflags, _settings_client.var, def, min, max, interval, str, strhelp, strval, proc, from, to, cat, extra, startup)
+#define SDTC_VAR(var, type, flags, guiflags, def, min, max, interval, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)\
+	SDTG_VAR(#var, type, flags, guiflags, _settings_client.var, def, min, max, interval, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)
 
-#define SDTC_BOOL(var, flags, guiflags, def, str, strhelp, strval, proc, from, to, cat, extra, startup)\
-	SDTG_BOOL(#var, flags, guiflags, _settings_client.var, def, str, strhelp, strval, proc, from, to, cat, extra, startup)
+#define SDTC_BOOL(var, flags, guiflags, def, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)\
+	SDTG_BOOL(#var, flags, guiflags, _settings_client.var, def, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)
 
 #define SDTC_LIST(var, type, flags, guiflags, def, from, to, cat, extra, startup)\
 	SDTG_LIST(#var, type, flags, guiflags, _settings_client.var, def, lengthof(_settings_client.var), from, to, cat, extra, startup)
@@ -115,5 +115,5 @@ static size_t ConvertLandscape(const cha
 #define SDTC_SSTR(var, type, flags, guiflags, def, max_length, pre_check, post_callback, from, to, cat, extra, startup)\
 	SDTG_SSTR(#var, type, flags, guiflags, _settings_client.var, def, max_length, pre_check, post_callback, from, to, cat, extra, startup)\
 
-#define SDTC_OMANY(var, type, flags, guiflags, def, max, full, str, strhelp, strval, proc, from, to, cat, extra, startup)\
-	SDTG_OMANY(#var, type, flags, guiflags, _settings_client.var, def, max, full, str, strhelp, strval, proc, from, to, cat, extra, startup)
+#define SDTC_OMANY(var, type, flags, guiflags, def, max, full, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)\
+	SDTG_OMANY(#var, type, flags, guiflags, _settings_client.var, def, max, full, str, strhelp, strval, pre_check, post_callback, from, to, cat, extra, startup)
diff --git a/src/table/settings.ini b/src/table/settings.ini
--- a/src/table/settings.ini
+++ b/src/table/settings.ini
@@ -6,46 +6,34 @@
 
 [pre-amble]
 /* Begin - Callback Functions for the various settings */
-static bool v_PositionMainToolbar(int32 p1);
-static bool v_PositionStatusbar(int32 p1);
-static bool PopulationInLabelActive(int32 p1);
-static bool RedrawScreen(int32 p1);
-static bool RedrawSmallmap(int32 p1);
-static bool StationSpreadChanged(int32 p1);
-static bool InvalidateBuildIndustryWindow(int32 p1);
-static bool CloseSignalGUI(int32 p1);
-static bool InvalidateTownViewWindow(int32 p1);
-static bool DeleteSelectStationWindow(int32 p1);
-static bool UpdateConsists(int32 p1);
-static bool TrainAccelerationModelChanged(int32 p1);
-static bool RoadVehAccelerationModelChanged(int32 p1);
-static bool TrainSlopeSteepnessChanged(int32 p1);
-static bool RoadVehSlopeSteepnessChanged(int32 p1);
-static bool DragSignalsDensityChanged(int32);
-static bool TownFoundingChanged(int32 p1);
-static bool DifficultyNoiseChange(int32 i);
-static bool MaxNoAIsChange(int32 i);
-static bool CheckRoadSide(int p1);
-static bool ChangeMaxHeightLevel(int32 p1);
-static bool CheckFreeformEdges(int32 p1);
-static bool ChangeDynamicEngines(int32 p1);
-static bool StationCatchmentChanged(int32 p1);
-static bool InvalidateVehTimetableWindow(int32 p1);
-static bool InvalidateCompanyLiveryWindow(int32 p1);
-static bool InvalidateNewGRFChangeWindows(int32 p1);
-static bool InvalidateIndustryViewWindow(int32 p1);
-static bool InvalidateAISettingsWindow(int32 p1);
-static bool RedrawTownAuthority(int32 p1);
-static bool InvalidateCompanyInfrastructureWindow(int32 p1);
-static bool InvalidateCompanyWindow(int32 p1);
-static bool ZoomMinMaxChanged(int32 p1);
-static bool SpriteZoomMinChanged(int32 p1);
-static bool MaxVehiclesChanged(int32 p1);
-static bool InvalidateShipPathCache(int32 p1);
+static void v_PositionMainToolbar(int32 new_value);
+static void v_PositionStatusbar(int32 new_value);
+static void RedrawSmallmap(int32 new_value);
+static void StationSpreadChanged(int32 new_value);
+static void CloseSignalGUI(int32 new_value);
+static void UpdateConsists(int32 new_value);
+static void TrainAccelerationModelChanged(int32 new_value);
+static void RoadVehAccelerationModelChanged(int32 new_value);
+static void TrainSlopeSteepnessChanged(int32 new_value);
+static void RoadVehSlopeSteepnessChanged(int32 new_value);
+static void TownFoundingChanged(int32 new_value);
+static void DifficultyNoiseChange(int32 new_value);
+static void MaxNoAIsChange(int32 new_value);
+static bool CheckRoadSide(int32 &new_value);
+static bool CheckMaxHeightLevel(int32 &new_value);
+static bool CheckFreeformEdges(int32 &new_value);
+static void UpdateFreeformEdges(int32 new_value);
+static bool CheckDynamicEngines(int32 &new_value);
+static void StationCatchmentChanged(int32 new_value);
+static void InvalidateCompanyLiveryWindow(int32 new_value);
+static void InvalidateNewGRFChangeWindows(int32 new_value);
+static void ZoomMinMaxChanged(int32 new_value);
+static void SpriteZoomMinChanged(int32 new_value);
+static void MaxVehiclesChanged(int32 new_value);
+static void InvalidateShipPathCache(int32 new_value);
 
 static bool ReplaceAsteriskWithEmptyPassword(std::string &newval);
 static void UpdateClientConfigValues();
-static bool UpdateClientConfigValues(int32 p1);
 
 /* End - Callback Functions for the various settings */
 
@@ -62,18 +50,18 @@ const SettingTable _settings{
 [post-amble]
 };
 [templates]
-SDTG_BOOL  =  SDTG_BOOL($name,              $flags, $guiflags, $var, $def,                        $str, $strhelp, $strval, $proc,             $from, $to,        $cat, $extra, $startup),
-SDTG_VAR   =   SDTG_VAR($name,       $type, $flags, $guiflags, $var, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc,             $from, $to,        $cat, $extra, $startup),
-SDTG_OMANY = SDTG_OMANY($name,       $type, $flags, $guiflags, $var, $def,       $max, $full,     $str, $strhelp, $strval, $proc,             $from, $to,        $cat, $extra, $startup),
-SDTC_BOOL  =  SDTC_BOOL(       $var,        $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc,             $from, $to,        $cat, $extra, $startup),
+SDTG_BOOL  =  SDTG_BOOL($name,              $flags, $guiflags, $var, $def,                        $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
+SDTG_VAR   =   SDTG_VAR($name,       $type, $flags, $guiflags, $var, $def, $min, $max, $interval, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
+SDTG_OMANY = SDTG_OMANY($name,       $type, $flags, $guiflags, $var, $def,       $max, $full,     $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
+SDTC_BOOL  =  SDTC_BOOL(       $var,        $flags, $guiflags, $def,                              $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
 SDTC_LIST  =  SDTC_LIST(       $var, $type, $flags, $guiflags, $def,                                                                          $from, $to,        $cat, $extra, $startup),
-SDTC_OMANY = SDTC_OMANY(       $var, $type, $flags, $guiflags, $def,             $max, $full,     $str, $strhelp, $strval, $proc,             $from, $to,        $cat, $extra, $startup),
+SDTC_OMANY = SDTC_OMANY(       $var, $type, $flags, $guiflags, $def,             $max, $full,     $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
 SDTC_SSTR  =  SDTC_SSTR(       $var, $type, $flags, $guiflags, $def,             $length,                                  $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
-SDTC_VAR   =   SDTC_VAR(       $var, $type, $flags, $guiflags, $def,       $min, $max, $interval, $str, $strhelp, $strval, $proc,             $from, $to,        $cat, $extra, $startup),
-SDT_BOOL   =   SDT_BOOL($base, $var,        $flags, $guiflags, $def,                              $str, $strhelp, $strval, $proc,             $from, $to,        $cat, $extra, $startup),
-SDT_OMANY  =  SDT_OMANY($base, $var, $type, $flags, $guiflags, $def,             $max, $full,     $str, $strhelp, $strval, $proc,             $from, $to, $load, $cat, $extra, $startup),
+SDTC_VAR   =   SDTC_VAR(       $var, $type, $flags, $guiflags, $def,       $min, $max, $interval, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
+SDT_BOOL   =   SDT_BOOL($base, $var,        $flags, $guiflags, $def,                              $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
+SDT_OMANY  =  SDT_OMANY($base, $var, $type, $flags, $guiflags, $def,             $max, $full,     $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $load, $cat, $extra, $startup),
 SDT_SSTR   =   SDT_SSTR($base, $var, $type, $flags, $guiflags, $def,                                                       $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
-SDT_VAR    =    SDT_VAR($base, $var, $type, $flags, $guiflags, $def,       $min, $max, $interval, $str, $strhelp, $strval, $proc,             $from, $to,        $cat, $extra, $startup),
+SDT_VAR    =    SDT_VAR($base, $var, $type, $flags, $guiflags, $def,       $min, $max, $interval, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to,        $cat, $extra, $startup),
 SDT_NULL   =   SDT_NULL($length, $from, $to),
 
 [validation]
@@ -91,7 +79,6 @@ interval = 0
 str      = STR_NULL
 strhelp  = STR_CONFIG_SETTING_NO_EXPLANATION_AVAILABLE_HELPTEXT
 strval   = STR_NULL
-proc     = nullptr
 pre_cb   = nullptr
 post_cb  = nullptr
 load     = nullptr
@@ -114,7 +101,7 @@ def      = 0
 min      = 0
 max      = MAX_COMPANIES - 1
 interval = 1
-proc     = MaxNoAIsChange
+post_cb  = MaxNoAIsChange
 cat      = SC_BASIC
 
 [SDT_NULL]
@@ -324,7 +311,7 @@ interval = 1
 str      = STR_CONFIG_SETTING_CITY_APPROVAL
 strhelp  = STR_CONFIG_SETTING_CITY_APPROVAL_HELPTEXT
 strval   = STR_CITY_APPROVAL_PERMISSIVE
-proc     = DifficultyNoiseChange
+post_cb  = DifficultyNoiseChange
 
 [SDTG_VAR]
 name     = ""diff_level""
@@ -384,7 +371,7 @@ full     = _roadsides
 str      = STR_CONFIG_SETTING_ROAD_SIDE
 strhelp  = STR_CONFIG_SETTING_ROAD_SIDE_HELPTEXT
 strval   = STR_GAME_OPTIONS_ROAD_VEHICLES_DROPDOWN_LEFT
-proc     = CheckRoadSide
+pre_cb   = CheckRoadSide
 cat      = SC_BASIC
 
 ; Construction
@@ -402,7 +389,8 @@ interval = 1
 str      = STR_CONFIG_SETTING_MAP_HEIGHT_LIMIT
 strhelp  = STR_CONFIG_SETTING_MAP_HEIGHT_LIMIT_HELPTEXT
 strval   = STR_CONFIG_SETTING_MAP_HEIGHT_LIMIT_VALUE
-proc     = ChangeMaxHeightLevel
+pre_cb   = CheckMaxHeightLevel
+post_cb  = [](auto) { InvalidateWindowClassesData(WC_SMALLMAP, 2); }
 cat      = SC_ADVANCED
 
 [SDT_VAR]
@@ -578,7 +566,7 @@ max      = 2
 str      = STR_CONFIG_SETTING_SIGNALSIDE
 strhelp  = STR_CONFIG_SETTING_SIGNALSIDE_HELPTEXT
 strval   = STR_CONFIG_SETTING_SIGNALSIDE_LEFT
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 
 [SDT_BOOL]
@@ -602,7 +590,7 @@ interval = 1
 str      = STR_CONFIG_SETTING_TOWN_LAYOUT
 strhelp  = STR_CONFIG_SETTING_TOWN_LAYOUT_HELPTEXT
 strval   = STR_CONFIG_SETTING_TOWN_LAYOUT_DEFAULT
-proc     = TownFoundingChanged
+post_cb  = TownFoundingChanged
 
 [SDT_BOOL]
 base     = GameSettings
@@ -626,7 +614,7 @@ interval = 1
 str      = STR_CONFIG_SETTING_TOWN_FOUNDING
 strhelp  = STR_CONFIG_SETTING_TOWN_FOUNDING_HELPTEXT
 strval   = STR_CONFIG_SETTING_TOWN_FOUNDING_FORBIDDEN
-proc     = TownFoundingChanged
+post_cb  = TownFoundingChanged
 cat      = SC_BASIC
 
 [SDT_BOOL]
@@ -822,7 +810,7 @@ interval = 1
 str      = STR_CONFIG_SETTING_TRAIN_ACCELERATION_MODEL
 strhelp  = STR_CONFIG_SETTING_TRAIN_ACCELERATION_MODEL_HELPTEXT
 strval   = STR_CONFIG_SETTING_ORIGINAL
-proc     = TrainAccelerationModelChanged
+post_cb  = TrainAccelerationModelChanged
 
 [SDT_VAR]
 base     = GameSettings
@@ -837,7 +825,7 @@ interval = 1
 str      = STR_CONFIG_SETTING_ROAD_VEHICLE_ACCELERATION_MODEL
 strhelp  = STR_CONFIG_SETTING_ROAD_VEHICLE_ACCELERATION_MODEL_HELPTEXT
 strval   = STR_CONFIG_SETTING_ORIGINAL
-proc     = RoadVehAccelerationModelChanged
+post_cb  = RoadVehAccelerationModelChanged
 
 [SDT_VAR]
 base     = GameSettings
@@ -851,7 +839,7 @@ interval = 1
 str      = STR_CONFIG_SETTING_TRAIN_SLOPE_STEEPNESS
 strhelp  = STR_CONFIG_SETTING_TRAIN_SLOPE_STEEPNESS_HELPTEXT
 strval   = STR_CONFIG_SETTING_PERCENTAGE
-proc     = TrainSlopeSteepnessChanged
+post_cb  = TrainSlopeSteepnessChanged
 cat      = SC_EXPERT
 
 [SDT_VAR]
@@ -866,7 +854,7 @@ interval = 1
 str      = STR_CONFIG_SETTING_ROAD_VEHICLE_SLOPE_STEEPNESS
 strhelp  = STR_CONFIG_SETTING_ROAD_VEHICLE_SLOPE_STEEPNESS_HELPTEXT
 strval   = STR_CONFIG_SETTING_PERCENTAGE
-proc     = RoadVehSlopeSteepnessChanged
+post_cb  = RoadVehSlopeSteepnessChanged
 cat      = SC_EXPERT
 
 [SDT_BOOL]
@@ -875,7 +863,7 @@ var      = pf.forbid_90_deg
 def      = false
 str      = STR_CONFIG_SETTING_FORBID_90_DEG
 strhelp  = STR_CONFIG_SETTING_FORBID_90_DEG_HELPTEXT
-proc     = InvalidateShipPathCache
+post_cb  = InvalidateShipPathCache
 cat      = SC_EXPERT
 
 [SDT_VAR]
@@ -998,7 +986,7 @@ interval = 1
 str      = STR_CONFIG_SETTING_PATHFINDER_FOR_SHIPS
 strhelp  = STR_CONFIG_SETTING_PATHFINDER_FOR_SHIPS_HELPTEXT
 strval   = STR_CONFIG_SETTING_PATHFINDER_NPF
-proc     = InvalidateShipPathCache
+post_cb  = InvalidateShipPathCache
 cat      = SC_EXPERT
 
 [SDT_BOOL]
@@ -1019,7 +1007,7 @@ max      = 5000
 str      = STR_CONFIG_SETTING_MAX_TRAINS
 strhelp  = STR_CONFIG_SETTING_MAX_TRAINS_HELPTEXT
 strval   = STR_JUST_COMMA
-proc     = MaxVehiclesChanged
+post_cb  = MaxVehiclesChanged
 cat      = SC_BASIC
 
 [SDT_VAR]
@@ -1032,7 +1020,7 @@ max      = 5000
 str      = STR_CONFIG_SETTING_MAX_ROAD_VEHICLES
 strhelp  = STR_CONFIG_SETTING_MAX_ROAD_VEHICLES_HELPTEXT
 strval   = STR_JUST_COMMA
-proc     = MaxVehiclesChanged
+post_cb  = MaxVehiclesChanged
 cat      = SC_BASIC
 
 [SDT_VAR]
@@ -1045,7 +1033,7 @@ max      = 5000
 str      = STR_CONFIG_SETTING_MAX_AIRCRAFT
 strhelp  = STR_CONFIG_SETTING_MAX_AIRCRAFT_HELPTEXT
 strval   = STR_JUST_COMMA
-proc     = MaxVehiclesChanged
+post_cb  = MaxVehiclesChanged
 cat      = SC_BASIC
 
 [SDT_VAR]
@@ -1058,7 +1046,7 @@ max      = 5000
 str      = STR_CONFIG_SETTING_MAX_SHIPS
 strhelp  = STR_CONFIG_SETTING_MAX_SHIPS_HELPTEXT
 strval   = STR_JUST_COMMA
-proc     = MaxVehiclesChanged
+post_cb  = MaxVehiclesChanged
 cat      = SC_BASIC
 
 [SDTG_BOOL]
@@ -1122,7 +1110,7 @@ guiflags = SGF_NO_NETWORK
 def      = true
 str      = STR_CONFIG_SETTING_WAGONSPEEDLIMITS
 strhelp  = STR_CONFIG_SETTING_WAGONSPEEDLIMITS_HELPTEXT
-proc     = UpdateConsists
+post_cb  = UpdateConsists
 
 [SDT_BOOL]
 base     = GameSettings
@@ -1132,7 +1120,7 @@ guiflags = SGF_NO_NETWORK
 def      = false
 str      = STR_CONFIG_SETTING_DISABLE_ELRAILS
 strhelp  = STR_CONFIG_SETTING_DISABLE_ELRAILS_HELPTEXT
-proc     = SettingsDisableElrail
+post_cb  = SettingsDisableElrail
 cat      = SC_EXPERT
 
 [SDT_VAR]
@@ -1148,7 +1136,7 @@ interval = 1
 str      = STR_CONFIG_SETTING_FREIGHT_TRAINS
 strhelp  = STR_CONFIG_SETTING_FREIGHT_TRAINS_HELPTEXT
 strval   = STR_JUST_COMMA
-proc     = UpdateConsists
+post_cb  = UpdateConsists
 
 ; order.timetabling
 [SDT_NULL]
@@ -1175,7 +1163,7 @@ var      = vehicle.dynamic_engines
 from     = SLV_95
 guiflags = SGF_NO_NETWORK
 def      = true
-proc     = ChangeDynamicEngines
+pre_cb   = CheckDynamicEngines
 cat      = SC_EXPERT
 
 [SDT_VAR]
@@ -1238,7 +1226,7 @@ max      = 64
 str      = STR_CONFIG_SETTING_STATION_SPREAD
 strhelp  = STR_CONFIG_SETTING_STATION_SPREAD_HELPTEXT
 strval   = STR_CONFIG_SETTING_TILE_LENGTH
-proc     = StationSpreadChanged
+post_cb  = StationSpreadChanged
 cat      = SC_BASIC
 
 [SDT_BOOL]
@@ -1255,7 +1243,7 @@ var      = station.modified_catchment
 def      = true
 str      = STR_CONFIG_SETTING_CATCHMENT
 strhelp  = STR_CONFIG_SETTING_CATCHMENT_HELPTEXT
-proc     = StationCatchmentChanged
+post_cb  = StationCatchmentChanged
 cat      = SC_EXPERT
 
 [SDT_BOOL]
@@ -1265,7 +1253,7 @@ def      = true
 from     = SLV_SERVE_NEUTRAL_INDUSTRIES
 str      = STR_CONFIG_SETTING_SERVE_NEUTRAL_INDUSTRIES
 strhelp  = STR_CONFIG_SETTING_SERVE_NEUTRAL_INDUSTRIES_HELPTEXT
-proc     = StationCatchmentChanged
+post_cb  = StationCatchmentChanged
 
 [SDT_BOOL]
 base     = GameSettings
@@ -1308,7 +1296,7 @@ guiflags = SGF_NO_NETWORK
 def      = false
 str      = STR_CONFIG_SETTING_NOISE_LEVEL
 strhelp  = STR_CONFIG_SETTING_NOISE_LEVEL_HELPTEXT
-proc     = InvalidateTownViewWindow
+post_cb  = [](auto new_value) { InvalidateWindowClassesData(WC_TOWN_VIEW, new_value); }
 
 [SDT_BOOL]
 base     = GameSettings
@@ -1317,7 +1305,7 @@ from     = SLV_106
 def      = true
 str      = STR_CONFIG_SETTING_DISTANT_JOIN_STATIONS
 strhelp  = STR_CONFIG_SETTING_DISTANT_JOIN_STATIONS_HELPTEXT
-proc     = DeleteSelectStationWindow
+post_cb  = [](auto) { DeleteWindowById(WC_SELECT_STATION, 0); }
 
 ##
 [SDT_BOOL]
@@ -1340,7 +1328,7 @@ max      = 2
 str      = STR_CONFIG_SETTING_RAW_INDUSTRY_CONSTRUCTION_METHOD
 strhelp  = STR_CONFIG_SETTING_RAW_INDUSTRY_CONSTRUCTION_METHOD_HELPTEXT
 strval   = STR_CONFIG_SETTING_RAW_INDUSTRY_CONSTRUCTION_METHOD_NONE
-proc     = InvalidateBuildIndustryWindow
+post_cb  = [](auto) { InvalidateWindowData(WC_BUILD_INDUSTRY, 0); }
 cat      = SC_BASIC
 
 [SDT_VAR]
@@ -1373,7 +1361,7 @@ var      = economy.bribe
 def      = true
 str      = STR_CONFIG_SETTING_BRIBE
 strhelp  = STR_CONFIG_SETTING_BRIBE_HELPTEXT
-proc     = RedrawTownAuthority
+post_cb  = [](auto) { SetWindowClassesDirty(WC_TOWN_AUTHORITY); }
 cat      = SC_BASIC
 
 [SDT_BOOL]
@@ -1383,7 +1371,7 @@ from     = SLV_79
 def      = true
 str      = STR_CONFIG_SETTING_ALLOW_EXCLUSIVE
 strhelp  = STR_CONFIG_SETTING_ALLOW_EXCLUSIVE_HELPTEXT
-proc     = RedrawTownAuthority
+post_cb  = [](auto) { SetWindowClassesDirty(WC_TOWN_AUTHORITY); }
 cat      = SC_BASIC
 
 [SDT_BOOL]
@@ -1393,7 +1381,7 @@ from     = SLV_165
 def      = true
 str      = STR_CONFIG_SETTING_ALLOW_FUND_BUILDINGS
 strhelp  = STR_CONFIG_SETTING_ALLOW_FUND_BUILDINGS_HELPTEXT
-proc     = RedrawTownAuthority
+post_cb  = [](auto) { SetWindowClassesDirty(WC_TOWN_AUTHORITY); }
 cat      = SC_BASIC
 
 [SDT_BOOL]
@@ -1403,7 +1391,7 @@ from     = SLV_160
 def      = true
 str      = STR_CONFIG_SETTING_ALLOW_FUND_ROAD
 strhelp  = STR_CONFIG_SETTING_ALLOW_FUND_ROAD_HELPTEXT
-proc     = RedrawTownAuthority
+post_cb  = [](auto) { SetWindowClassesDirty(WC_TOWN_AUTHORITY); }
 cat      = SC_BASIC
 
 [SDT_BOOL]
@@ -1505,7 +1493,7 @@ max      = ET_END - 1
 str      = STR_CONFIG_SETTING_ECONOMY_TYPE
 strhelp  = STR_CONFIG_SETTING_ECONOMY_TYPE_HELPTEXT
 strval   = STR_CONFIG_SETTING_ECONOMY_TYPE_ORIGINAL
-proc     = InvalidateIndustryViewWindow
+post_cb  = [](auto) { InvalidateWindowClassesData(WC_INDUSTRY_VIEW); }
 cat      = SC_BASIC
 
 [SDT_BOOL]
@@ -1514,7 +1502,7 @@ var      = economy.allow_shares
 def      = false
 str      = STR_CONFIG_SETTING_ALLOW_SHARES
 strhelp  = STR_CONFIG_SETTING_ALLOW_SHARES_HELPTEXT
-proc     = InvalidateCompanyWindow
+post_cb  = [](auto) { InvalidateWindowClassesData(WC_COMPANY); }
 
 [SDT_VAR]
 base     = GameSettings
@@ -1758,7 +1746,7 @@ from     = SLV_166
 def      = false
 str      = STR_CONFIG_SETTING_INFRASTRUCTURE_MAINTENANCE
 strhelp  = STR_CONFIG_SETTING_INFRASTRUCTURE_MAINTENANCE_HELPTEXT
-proc     = InvalidateCompanyInfrastructureWindow
+post_cb  = [](auto) { InvalidateWindowClassesData(WC_COMPANY_INFRASTRUCTURE); }
 cat      = SC_BASIC
 
 ##
@@ -2427,7 +2415,8 @@ base     = GameSettings
 var      = construction.freeform_edges
 from     = SLV_111
 def      = true
-proc     = CheckFreeformEdges
+pre_cb   = CheckFreeformEdges
+post_cb  = UpdateFreeformEdges
 cat      = SC_EXPERT
 
 [SDT_VAR]
@@ -2528,7 +2517,7 @@ flags    = SLF_NO_NETWORK_SYNC
 def      = 0
 max      = CURRENCY_END - 1
 full     = _locale_currencies
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 
 [SDTG_OMANY]
@@ -2541,7 +2530,7 @@ flags    = SLF_NOT_IN_CONFIG
 def      = 1
 max      = 2
 full     = _locale_units
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 
 [SDT_OMANY]
@@ -2554,7 +2543,7 @@ guiflags = SGF_MULTISTRING
 def      = 1
 max      = 3
 full     = _locale_units
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 str      = STR_CONFIG_SETTING_LOCALISATION_UNITS_VELOCITY
 strhelp  = STR_CONFIG_SETTING_LOCALISATION_UNITS_VELOCITY_HELPTEXT
@@ -2570,7 +2559,7 @@ guiflags = SGF_MULTISTRING
 def      = 1
 max      = 2
 full     = _locale_units
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 str      = STR_CONFIG_SETTING_LOCALISATION_UNITS_POWER
 strhelp  = STR_CONFIG_SETTING_LOCALISATION_UNITS_POWER_HELPTEXT
@@ -2586,7 +2575,7 @@ guiflags = SGF_MULTISTRING
 def      = 1
 max      = 2
 full     = _locale_units
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 str      = STR_CONFIG_SETTING_LOCALISATION_UNITS_WEIGHT
 strhelp  = STR_CONFIG_SETTING_LOCALISATION_UNITS_WEIGHT_HELPTEXT
@@ -2602,7 +2591,7 @@ guiflags = SGF_MULTISTRING
 def      = 1
 max      = 2
 full     = _locale_units
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 str      = STR_CONFIG_SETTING_LOCALISATION_UNITS_VOLUME
 strhelp  = STR_CONFIG_SETTING_LOCALISATION_UNITS_VOLUME_HELPTEXT
@@ -2618,7 +2607,7 @@ guiflags = SGF_MULTISTRING
 def      = 2
 max      = 2
 full     = _locale_units
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 str      = STR_CONFIG_SETTING_LOCALISATION_UNITS_FORCE
 strhelp  = STR_CONFIG_SETTING_LOCALISATION_UNITS_FORCE_HELPTEXT
@@ -2634,7 +2623,7 @@ guiflags = SGF_MULTISTRING
 def      = 1
 max      = 2
 full     = _locale_units
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 str      = STR_CONFIG_SETTING_LOCALISATION_UNITS_HEIGHT
 strhelp  = STR_CONFIG_SETTING_LOCALISATION_UNITS_HEIGHT_HELPTEXT
@@ -2811,7 +2800,7 @@ max      = 2
 str      = STR_CONFIG_SETTING_TOOLBAR_POS
 strhelp  = STR_CONFIG_SETTING_TOOLBAR_POS_HELPTEXT
 strval   = STR_CONFIG_SETTING_HORIZONTAL_POS_LEFT
-proc     = v_PositionMainToolbar
+post_cb  = v_PositionMainToolbar
 cat      = SC_BASIC
 
 [SDTC_VAR]
@@ -2825,7 +2814,7 @@ max      = 2
 str      = STR_CONFIG_SETTING_STATUSBAR_POS
 strhelp  = STR_CONFIG_SETTING_STATUSBAR_POS_HELPTEXT
 strval   = STR_CONFIG_SETTING_HORIZONTAL_POS_LEFT
-proc     = v_PositionStatusbar
+post_cb  = v_PositionStatusbar
 cat      = SC_BASIC
 
 [SDTC_VAR]
@@ -2866,7 +2855,7 @@ max      = ZOOM_LVL_OUT_4X
 str      = STR_CONFIG_SETTING_ZOOM_MIN
 strhelp  = STR_CONFIG_SETTING_ZOOM_MIN_HELPTEXT
 strval   = STR_CONFIG_SETTING_ZOOM_LVL_MIN
-proc     = ZoomMinMaxChanged
+post_cb  = ZoomMinMaxChanged
 startup  = true
 
 [SDTC_VAR]
@@ -2880,7 +2869,7 @@ max      = ZOOM_LVL_MAX
 str      = STR_CONFIG_SETTING_ZOOM_MAX
 strhelp  = STR_CONFIG_SETTING_ZOOM_MAX_HELPTEXT
 strval   = STR_CONFIG_SETTING_ZOOM_LVL_OUT_2X
-proc     = ZoomMinMaxChanged
+post_cb  = ZoomMinMaxChanged
 startup  = true
 
 [SDTC_VAR]
@@ -2894,7 +2883,7 @@ max      = ZOOM_LVL_OUT_4X
 str      = STR_CONFIG_SETTING_SPRITE_ZOOM_MIN
 strhelp  = STR_CONFIG_SETTING_SPRITE_ZOOM_MIN_HELPTEXT
 strval   = STR_CONFIG_SETTING_SPRITE_ZOOM_LVL_MIN
-proc     = SpriteZoomMinChanged
+post_cb  = SpriteZoomMinChanged
 
 [SDTC_BOOL]
 var      = gui.population_in_label
@@ -2902,7 +2891,7 @@ flags    = SLF_NOT_IN_SAVE | SLF_NO_NETW
 def      = true
 str      = STR_CONFIG_SETTING_POPULATION_IN_LABEL
 strhelp  = STR_CONFIG_SETTING_POPULATION_IN_LABEL_HELPTEXT
-proc     = PopulationInLabelActive
+post_cb  = [](auto) { UpdateAllTownVirtCoords(); }
 
 [SDTC_BOOL]
 var      = gui.link_terraform_toolbar
@@ -2922,7 +2911,7 @@ max      = 2
 str      = STR_CONFIG_SETTING_SMALLMAP_LAND_COLOUR
 strhelp  = STR_CONFIG_SETTING_SMALLMAP_LAND_COLOUR_HELPTEXT
 strval   = STR_CONFIG_SETTING_SMALLMAP_LAND_COLOUR_GREEN
-proc     = RedrawSmallmap
+post_cb  = RedrawSmallmap
 
 [SDTC_VAR]
 var      = gui.liveries
@@ -2935,7 +2924,7 @@ max      = 2
 str      = STR_CONFIG_SETTING_LIVERIES
 strhelp  = STR_CONFIG_SETTING_LIVERIES_HELPTEXT
 strval   = STR_CONFIG_SETTING_LIVERIES_NONE
-proc     = InvalidateCompanyLiveryWindow
+post_cb  = InvalidateCompanyLiveryWindow
 
 [SDTC_VAR]
 var      = gui.starting_colour
@@ -3017,7 +3006,7 @@ flags    = SLF_NOT_IN_SAVE | SLF_NO_NETW
 def      = false
 str      = STR_CONFIG_SETTING_TIMETABLE_IN_TICKS
 strhelp  = STR_CONFIG_SETTING_TIMETABLE_IN_TICKS_HELPTEXT
-proc     = InvalidateVehTimetableWindow
+post_cb  = [](auto) { InvalidateWindowClassesData(WC_VEHICLE_TIMETABLE, VIWD_MODIFY_ORDERS); }
 cat      = SC_EXPERT
 
 [SDTC_BOOL]
@@ -3026,7 +3015,7 @@ flags    = SLF_NOT_IN_SAVE | SLF_NO_NETW
 def      = true
 str      = STR_CONFIG_SETTING_TIMETABLE_SHOW_ARRIVAL_DEPARTURE
 strhelp  = STR_CONFIG_SETTING_TIMETABLE_SHOW_ARRIVAL_DEPARTURE_HELPTEXT
-proc     = InvalidateVehTimetableWindow
+post_cb  = [](auto) { InvalidateWindowClassesData(WC_VEHICLE_TIMETABLE, VIWD_MODIFY_ORDERS); }
 
 [SDTC_BOOL]
 var      = gui.quick_goto
@@ -3047,7 +3036,7 @@ max      = 2
 str      = STR_CONFIG_SETTING_LOADING_INDICATORS
 strhelp  = STR_CONFIG_SETTING_LOADING_INDICATORS_HELPTEXT
 strval   = STR_CONFIG_SETTING_COMPANIES_OFF
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 
 [SDTC_VAR]
@@ -3069,7 +3058,7 @@ flags    = SLF_NOT_IN_SAVE | SLF_NO_NETW
 def      = true
 str      = STR_CONFIG_SETTING_ENABLE_SIGNAL_GUI
 strhelp  = STR_CONFIG_SETTING_ENABLE_SIGNAL_GUI_HELPTEXT
-proc     = CloseSignalGUI
+post_cb  = CloseSignalGUI
 cat      = SC_EXPERT
 
 [SDTC_VAR]
@@ -3095,7 +3084,7 @@ max      = 20
 str      = STR_CONFIG_SETTING_DRAG_SIGNALS_DENSITY
 strhelp  = STR_CONFIG_SETTING_DRAG_SIGNALS_DENSITY_HELPTEXT
 strval   = STR_CONFIG_SETTING_DRAG_SIGNALS_DENSITY_VALUE
-proc     = DragSignalsDensityChanged
+post_cb  = [](auto) { InvalidateWindowData(WC_BUILD_SIGNAL, 0); }
 cat      = SC_BASIC
 
 [SDTC_BOOL]
@@ -3117,7 +3106,7 @@ interval = 1
 str      = STR_CONFIG_SETTING_SEMAPHORE_BUILD_BEFORE_DATE
 strhelp  = STR_CONFIG_SETTING_SEMAPHORE_BUILD_BEFORE_DATE_HELPTEXT
 strval   = STR_JUST_INT
-proc     = ResetSignalVariant
+post_cb  = ResetSignalVariant
 
 [SDTC_BOOL]
 var      = gui.vehicle_income_warn
@@ -3213,7 +3202,7 @@ flags    = SLF_NOT_IN_SAVE | SLF_NO_NETW
 def      = true
 str      = STR_CONFIG_SETTING_SHOW_TRACK_RESERVATION
 strhelp  = STR_CONFIG_SETTING_SHOW_TRACK_RESERVATION_HELPTEXT
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_BASIC
 
 [SDTC_VAR]
@@ -3286,7 +3275,7 @@ flags    = SLF_NOT_IN_SAVE | SLF_NO_NETW
 def      = true
 str      = STR_CONFIG_SETTING_EXPENSES_LAYOUT
 strhelp  = STR_CONFIG_SETTING_EXPENSES_LAYOUT_HELPTEXT
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 
 [SDTC_VAR]
 var      = gui.station_gui_group_order
@@ -3334,7 +3323,7 @@ max      = 5
 str      = STR_CONFIG_SETTING_GRAPH_LINE_THICKNESS
 strhelp  = STR_CONFIG_SETTING_GRAPH_LINE_THICKNESS_HELPTEXT
 strval   = STR_JUST_COMMA
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 
 [SDTC_BOOL]
 var      = gui.show_newgrf_name
@@ -3342,7 +3331,7 @@ flags    = SLF_NOT_IN_SAVE | SLF_NO_NETW
 def      = false
 str      = STR_CONFIG_SETTING_SHOW_NEWGRF_NAME
 strhelp  = STR_CONFIG_SETTING_SHOW_NEWGRF_NAME_HELPTEXT
-proc     = RedrawScreen
+post_cb  = [](auto) { MarkWholeScreenDirty(); }
 cat      = SC_ADVANCED
 
 ; For the dedicated build we'll enable dates in logs by default.
@@ -3379,21 +3368,21 @@ cat      = SC_EXPERT
 var      = gui.newgrf_developer_tools
 flags    = SLF_NOT_IN_SAVE | SLF_NO_NETWORK_SYNC
 def      = false
-proc     = InvalidateNewGRFChangeWindows
+post_cb  = InvalidateNewGRFChangeWindows
 cat      = SC_EXPERT
 
 [SDTC_BOOL]
 var      = gui.ai_developer_tools
 flags    = SLF_NOT_IN_SAVE | SLF_NO_NETWORK_SYNC
 def      = false
-proc     = InvalidateAISettingsWindow
+post_cb  = [](auto) { InvalidateWindowClassesData(WC_AI_SETTINGS); }
 cat      = SC_EXPERT
 
 [SDTC_BOOL]
 var      = gui.scenario_developer
 flags    = SLF_NOT_IN_SAVE | SLF_NO_NETWORK_SYNC
 def      = false
-proc     = InvalidateNewGRFChangeWindows
+post_cb  = InvalidateNewGRFChangeWindows
 
 [SDTC_BOOL]
 var      = gui.newgrf_show_old_versions
@@ -3409,7 +3398,7 @@ guiflags = SGF_MULTISTRING
 def      = 1
 min      = 0
 max      = 1
-proc     = UpdateNewGRFConfigPalette
+post_cb  = UpdateNewGRFConfigPalette
 cat      = SC_EXPERT
 
 [SDTC_VAR]
@@ -4029,7 +4018,7 @@ guiflags = SGF_NETWORK_ONLY
 def      = 15
 min      = 1
 max      = MAX_COMPANIES
-proc     = UpdateClientConfigValues
+post_cb  = [](auto) { UpdateClientConfigValues(); }
 cat      = SC_BASIC
 
 [SDTC_VAR]
@@ -4040,7 +4029,7 @@ guiflags = SGF_NETWORK_ONLY
 def      = 25
 min      = 2
 max      = MAX_CLIENTS
-proc     = UpdateClientConfigValues
+post_cb  = [](auto) { UpdateClientConfigValues(); }
 cat      = SC_BASIC
 
 [SDTC_VAR]
@@ -4051,7 +4040,7 @@ guiflags = SGF_NETWORK_ONLY
 def      = 15
 min      = 0
 max      = MAX_CLIENTS
-proc     = UpdateClientConfigValues
+post_cb  = [](auto) { UpdateClientConfigValues(); }
 cat      = SC_BASIC
 
 [SDTC_VAR]
diff --git a/src/table/win32_settings.ini b/src/table/win32_settings.ini
--- a/src/table/win32_settings.ini
+++ b/src/table/win32_settings.ini
@@ -14,8 +14,8 @@ static const SettingTable _win32_setting
 };
 #endif /* _WIN32 */
 [templates]
-SDTG_BOOL = SDTG_BOOL($name,        $flags, $guiflags, $var, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra, $startup),
-SDTG_VAR  =  SDTG_VAR($name, $type, $flags, $guiflags, $var, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra, $startup),
+SDTG_BOOL = SDTG_BOOL($name,        $flags, $guiflags, $var, $def,                        $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
+SDTG_VAR  =  SDTG_VAR($name, $type, $flags, $guiflags, $var, $def, $min, $max, $interval, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
 
 [validation]
 SDTG_VAR = static_assert($max <= MAX_$type, "Maximum value for $var exceeds storage size");
@@ -27,7 +27,8 @@ interval = 0
 str      = STR_NULL
 strhelp  = STR_CONFIG_SETTING_NO_EXPLANATION_AVAILABLE_HELPTEXT
 strval   = STR_NULL
-proc     = nullptr
+pre_cb   = nullptr
+post_cb  = nullptr
 load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION
diff --git a/src/table/window_settings.ini b/src/table/window_settings.ini
--- a/src/table/window_settings.ini
+++ b/src/table/window_settings.ini
@@ -10,8 +10,8 @@ static const SettingTable _window_settin
 [post-amble]
 };
 [templates]
-SDT_BOOL = SDT_BOOL($base, $var,        $flags, $guiflags, $def,                        $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra, $startup),
-SDT_VAR  =  SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $proc, $from, $to, $cat, $extra, $startup),
+SDT_BOOL = SDT_BOOL($base, $var,        $flags, $guiflags, $def,                        $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
+SDT_VAR  =  SDT_VAR($base, $var, $type, $flags, $guiflags, $def, $min, $max, $interval, $str, $strhelp, $strval, $pre_cb, $post_cb, $from, $to, $cat, $extra, $startup),
 
 [validation]
 SDT_VAR = static_assert($max <= MAX_$type, "Maximum value for $base.$var exceeds storage size");
@@ -24,7 +24,8 @@ interval = 0
 str      = STR_NULL
 strhelp  = STR_CONFIG_SETTING_NO_EXPLANATION_AVAILABLE_HELPTEXT
 strval   = STR_NULL
-proc     = nullptr
+pre_cb   = nullptr
+post_cb  = nullptr
 load     = nullptr
 from     = SL_MIN_VERSION
 to       = SL_MAX_VERSION