diff --git a/src/graph_gui.cpp b/src/graph_gui.cpp
--- a/src/graph_gui.cpp
+++ b/src/graph_gui.cpp
@@ -56,7 +56,7 @@ struct GraphLegendWindow : Window {
 		}
 	}
 
-	virtual void DrawWidget(const Rect &r, int widget) const
+	void DrawWidget(const Rect &r, int widget) const override
 	{
 		if (!IsInsideMM(widget, WID_GL_FIRST_COMPANY, MAX_COMPANIES + WID_GL_FIRST_COMPANY)) return;
 
@@ -74,7 +74,7 @@ struct GraphLegendWindow : Window {
 		DrawString(r.left + (rtl ? (uint)WD_FRAMERECT_LEFT : (d.width + 4)), r.right - (rtl ? (d.width + 4) : (uint)WD_FRAMERECT_RIGHT), r.top + (r.bottom - r.top + 1 - FONT_HEIGHT_NORMAL) / 2, STR_COMPANY_NAME_COMPANY_NUM, HasBit(_legend_excluded_companies, cid) ? TC_BLACK : TC_WHITE);
 	}
 
-	virtual void OnClick(Point pt, int widget, int click_count)
+	void OnClick(Point pt, int widget, int click_count) override
 	{
 		if (!IsInsideMM(widget, WID_GL_FIRST_COMPANY, MAX_COMPANIES + WID_GL_FIRST_COMPANY)) return;
 
@@ -93,7 +93,7 @@ struct GraphLegendWindow : Window {
 	 * @param data Information about the changed data.
 	 * @param gui_scope Whether the call is done from GUI scope. You may not do everything when not in GUI scope. See #InvalidateWindowData() for details.
 	 */
-	virtual void OnInvalidateData(int data = 0, bool gui_scope = true)
+	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
 		if (Company::IsValidID(data)) return;
@@ -485,7 +485,7 @@ protected:
 	}
 
 public:
-	virtual void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize)
+	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
 	{
 		if (widget != this->graph_widget) return;
 
@@ -521,7 +521,7 @@ public:
 		size->height = max<uint>(size->height, size->width / 3);
 	}
 
-	virtual void DrawWidget(const Rect &r, int widget) const
+	void DrawWidget(const Rect &r, int widget) const override
 	{
 		if (widget != this->graph_widget) return;
 
@@ -533,13 +533,13 @@ public:
 		return INVALID_DATAPOINT;
 	}
 
-	virtual void OnClick(Point pt, int widget, int click_count)
+	void OnClick(Point pt, int widget, int click_count) override
 	{
 		/* Clicked on legend? */
 		if (widget == WID_CV_KEY_BUTTON) ShowGraphLegend();
 	}
 
-	virtual void OnGameTick()
+	void OnGameTick() override
 	{
 		this->UpdateStatistics(false);
 	}
@@ -549,7 +549,7 @@ public:
 	 * @param data Information about the changed data.
 	 * @param gui_scope Whether the call is done from GUI scope. You may not do everything when not in GUI scope. See #InvalidateWindowData() for details.
 	 */
-	virtual void OnInvalidateData(int data = 0, bool gui_scope = true)
+	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
 		this->UpdateStatistics(true);
@@ -621,7 +621,7 @@ struct OperatingProfitGraphWindow : Base
 		this->InitializeWindow(window_number);
 	}
 
-	virtual OverflowSafeInt64 GetGraphData(const Company *c, int j)
+	OverflowSafeInt64 GetGraphData(const Company *c, int j) override
 	{
 		return c->old_economy[j].income + c->old_economy[j].expenses;
 	}
@@ -672,7 +672,7 @@ struct IncomeGraphWindow : BaseGraphWind
 		this->InitializeWindow(window_number);
 	}
 
-	virtual OverflowSafeInt64 GetGraphData(const Company *c, int j)
+	OverflowSafeInt64 GetGraphData(const Company *c, int j) override
 	{
 		return c->old_economy[j].income;
 	}
@@ -721,7 +721,7 @@ struct DeliveredCargoGraphWindow : BaseG
 		this->InitializeWindow(window_number);
 	}
 
-	virtual OverflowSafeInt64 GetGraphData(const Company *c, int j)
+	OverflowSafeInt64 GetGraphData(const Company *c, int j) override
 	{
 		return c->old_economy[j].delivered_cargo.GetSum<OverflowSafeInt64>();
 	}
@@ -770,12 +770,12 @@ struct PerformanceHistoryGraphWindow : B
 		this->InitializeWindow(window_number);
 	}
 
-	virtual OverflowSafeInt64 GetGraphData(const Company *c, int j)
+	OverflowSafeInt64 GetGraphData(const Company *c, int j) override
 	{
 		return c->old_economy[j].performance_history;
 	}
 
-	virtual void OnClick(Point pt, int widget, int click_count)
+	void OnClick(Point pt, int widget, int click_count) override
 	{
 		if (widget == WID_PHG_DETAILED_PERFORMANCE) ShowPerformanceRatingDetail();
 		this->BaseGraphWindow::OnClick(pt, widget, click_count);
@@ -826,7 +826,7 @@ struct CompanyValueGraphWindow : BaseGra
 		this->InitializeWindow(window_number);
 	}
 
-	virtual OverflowSafeInt64 GetGraphData(const Company *c, int j)
+	OverflowSafeInt64 GetGraphData(const Company *c, int j) override
 	{
 		return c->old_economy[j].company_value;
 	}
@@ -903,7 +903,7 @@ struct PaymentRatesGraphWindow : BaseGra
 		}
 	}
 
-	virtual void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize)
+	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
 	{
 		if (widget != WID_CPR_MATRIX) {
 			BaseGraphWindow::UpdateWidgetSize(widget, size, padding, fill, resize);
@@ -926,7 +926,7 @@ struct PaymentRatesGraphWindow : BaseGra
 		resize->height = this->line_height;
 	}
 
-	virtual void DrawWidget(const Rect &r, int widget) const
+	void DrawWidget(const Rect &r, int widget) const override
 	{
 		if (widget != WID_CPR_MATRIX) {
 			BaseGraphWindow::DrawWidget(r, widget);
@@ -963,7 +963,7 @@ struct PaymentRatesGraphWindow : BaseGra
 		}
 	}
 
-	virtual void OnClick(Point pt, int widget, int click_count)
+	void OnClick(Point pt, int widget, int click_count) override
 	{
 		switch (widget) {
 			case WID_CPR_ENABLE_CARGOES:
@@ -1004,12 +1004,12 @@ struct PaymentRatesGraphWindow : BaseGra
 		}
 	}
 
-	virtual void OnResize()
+	void OnResize() override
 	{
 		this->vscroll->SetCapacityFromWidget(this, WID_CPR_MATRIX);
 	}
 
-	virtual void OnGameTick()
+	void OnGameTick() override
 	{
 		/* Override default OnGameTick */
 	}
@@ -1019,13 +1019,13 @@ struct PaymentRatesGraphWindow : BaseGra
 	 * @param data Information about the changed data.
 	 * @param gui_scope Whether the call is done from GUI scope. You may not do everything when not in GUI scope. See #InvalidateWindowData() for details.
 	 */
-	virtual void OnInvalidateData(int data = 0, bool gui_scope = true)
+	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
 		this->OnHundredthTick();
 	}
 
-	virtual void OnHundredthTick()
+	void OnHundredthTick() override
 	{
 		this->UpdateExcludedData();
 
@@ -1161,7 +1161,7 @@ public:
 		this->companies.NeedResort();
 	}
 
-	virtual void OnPaint()
+	void OnPaint() override
 	{
 		this->BuildCompanyList();
 		this->companies.Sort(&PerformanceSorter);
@@ -1169,7 +1169,7 @@ public:
 		this->DrawWidgets();
 	}
 
-	virtual void DrawWidget(const Rect &r, int widget) const
+	void DrawWidget(const Rect &r, int widget) const override
 	{
 		if (widget != WID_CL_BACKGROUND) return;
 
@@ -1197,7 +1197,7 @@ public:
 		}
 	}
 
-	virtual void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize)
+	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
 	{
 		if (widget != WID_CL_BACKGROUND) return;
 
@@ -1236,7 +1236,7 @@ public:
 	}
 
 
-	virtual void OnGameTick()
+	void OnGameTick() override
 	{
 		if (this->companies.NeedResort()) {
 			this->SetDirty();
@@ -1248,7 +1248,7 @@ public:
 	 * @param data Information about the changed data.
 	 * @param gui_scope Whether the call is done from GUI scope. You may not do everything when not in GUI scope. See #InvalidateWindowData() for details.
 	 */
-	virtual void OnInvalidateData(int data = 0, bool gui_scope = true)
+	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (data == 0) {
 			/* This needs to be done in command-scope to enforce rebuilding before resorting invalid data */
@@ -1318,7 +1318,7 @@ struct PerformanceRatingDetailWindow : W
 	uint score_detail_left;
 	uint score_detail_right;
 
-	virtual void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize)
+	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
 	{
 		switch (widget) {
 			case WID_PRD_SCORE_FIRST:
@@ -1376,7 +1376,7 @@ struct PerformanceRatingDetailWindow : W
 		}
 	}
 
-	virtual void DrawWidget(const Rect &r, int widget) const
+	void DrawWidget(const Rect &r, int widget) const override
 	{
 		/* No need to draw when there's nothing to draw */
 		if (this->company == INVALID_COMPANY) return;
@@ -1455,7 +1455,7 @@ struct PerformanceRatingDetailWindow : W
 		}
 	}
 
-	virtual void OnClick(Point pt, int widget, int click_count)
+	void OnClick(Point pt, int widget, int click_count) override
 	{
 		/* Check which button is clicked */
 		if (IsInsideMM(widget, WID_PRD_COMPANY_FIRST, WID_PRD_COMPANY_LAST + 1)) {
@@ -1469,7 +1469,7 @@ struct PerformanceRatingDetailWindow : W
 		}
 	}
 
-	virtual void OnGameTick()
+	void OnGameTick() override
 	{
 		/* Update the company score every 5 days */
 		if (--this->timeout == 0) {
@@ -1483,7 +1483,7 @@ struct PerformanceRatingDetailWindow : W
 	 * @param data the company ID of the company that is going to be removed
 	 * @param gui_scope Whether the call is done from GUI scope. You may not do everything when not in GUI scope. See #InvalidateWindowData() for details.
 	 */
-	virtual void OnInvalidateData(int data = 0, bool gui_scope = true)
+	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
 		/* Disable the companies who are not active */