Change window close/deallocation to match upstream

src/ai/ai_gui.cpp

@@ -98,10 +98,11 @@ struct AIConfigWindow : public Window {
 		this->OnInvalidateData(0);
 	}
 
-	~AIConfigWindow()
+	void Close() override
 	{
 		CloseWindowByClass(WC_SCRIPT_LIST);
 		CloseWindowByClass(WC_SCRIPT_SETTINGS);
+		this->Window::Close();
 	}
 
 	void SetStringParameters(int widget) const override
@@ -247,7 +248,7 @@ struct AIConfigWindow : public Window {
 				break;
 
 			case WID_AIC_CLOSE:
-				delete this;
+				this->Close();
 				break;
 
 			case WID_AIC_CONTENT_DOWNLOAD:

src/airport_gui.cpp

@@ -78,10 +78,11 @@ struct BuildAirToolbarWindow : Window {
 		this->last_user_action = WIDGET_LIST_END;
 	}
 
-	~BuildAirToolbarWindow()
+	void Close() override
 	{
 		if (this->IsWidgetLowered(WID_AT_AIRPORT)) SetViewportCatchmentStation(nullptr, true);
 		if (_settings_client.gui.link_terraform_toolbar) CloseWindowById(WC_SCEN_LAND_GEN, 0, false);
+		this->Window::Close();
 	}
 
 	/**
@@ -278,9 +279,10 @@ public:
 		if (selectFirstAirport) this->SelectFirstAvailableAirport(true);
 	}
 
-	virtual ~BuildAirportWindow()
+	void Close() override
 	{
 		CloseWindowById(WC_SELECT_STATION, 0);
+		this->PickerWindowBase::Close();
 	}
 
 	void SetStringParameters(int widget) const override

src/bootstrap_gui.cpp

@@ -91,9 +91,10 @@ public:
 		this->InitNested(1);
 	}
 
-	~BootstrapErrorWindow()
+	void Close() override
 	{
 		_exit_game = true;
+		this->Window::Close();
 	}
 
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
@@ -148,12 +149,13 @@ public:
 	{
 	}
 
-	~BootstrapContentDownloadStatusWindow()
+	void Close() override
 	{
 		/* If we are not set to exit the game, it means the bootstrap failed. */
 		if (!_exit_game) {
 			new BootstrapErrorWindow();
 		}
+		this->BaseNetworkContentDownloadStatusWindow::Close();
 	}
 
 	void OnDownloadComplete(ContentID cid) override
@@ -166,7 +168,7 @@ public:
 
 		/* _exit_game is used to break out of the outer video driver's MainLoop. */
 		_exit_game = true;
-		delete this;
+		this->Close();
 	}
 };
 
@@ -205,9 +207,10 @@ public:
 	}
 
 	/** Stop listening to the content client events. */
-	~BootstrapAskForDownloadWindow()
+	void Close() override
 	{
 		_network_content_client.RemoveCallback(this);
+		this->Window::Close();
 	}
 
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
@@ -268,7 +271,7 @@ public:
 		/* And once the meta data is received, start downloading it. */
 		_network_content_client.Select(ci->id);
 		new BootstrapContentDownloadStatusWindow();
-		delete this;
+		this->Close();
 	}
 };
 

src/bridge_gui.cpp

@@ -185,11 +185,15 @@ public:
 
 	~BuildBridgeWindow()
 	{
-		this->last_sorting = this->bridges->GetListing();
-
 		delete bridges;
 	}
 
+	void Close() override
+	{
+		this->last_sorting = this->bridges->GetListing();
+		this->Window::Close();
+	}
+
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
 	{
 		switch (widget) {
@@ -266,7 +270,7 @@ public:
 		if (i < 9 && i < this->bridges->size()) {
 			/* Build the requested bridge */
 			this->BuildBridge(i);
-			delete this;
+			this->Close();
 			return ES_HANDLED;
 		}
 		return ES_NOT_HANDLED;
@@ -280,7 +284,7 @@ public:
 				auto it = this->vscroll->GetScrolledItemFromWidget(*this->bridges, pt.y, this, WID_BBS_BRIDGE_LIST);
 				if (it != this->bridges->end()) {
 					this->BuildBridge(it - this->bridges->begin());
-					delete this;
+					this->Close();
 				}
 				break;
 			}

src/company_gui.cpp

@@ -1689,7 +1689,7 @@ public:
 
 			/* Cancel button */
 			case WID_SCMF_CANCEL:
-				delete this;
+				this->Close();
 				break;
 
 			/* Load button */
@@ -2895,12 +2895,13 @@ struct BuyCompanyWindow : Window {
 		this->company_value = hostile_takeover ? CalculateHostileTakeoverValue(c) : c->bankrupt_value;
 	}
 
-	~BuyCompanyWindow()
+	void Close() override
 	{
 		const Company *c = Company::GetIfValid((CompanyID)this->window_number);
 		if (!this->hostile_takeover && c != nullptr && HasBit(c->bankrupt_asked, this->owner) && _current_company == this->owner) {
 			EnqueueDoCommandP(NewCommandContainerBasic(0, this->window_number, 0, CMD_DECLINE_BUY_COMPANY | CMD_NO_SHIFT_ESTIMATE));
 		}
+		this->Window::Close();
 	}
 
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
@@ -2952,7 +2953,7 @@ struct BuyCompanyWindow : Window {
 	{
 		switch (widget) {
 			case WID_BC_NO:
-				delete this;
+				this->Close();
 				break;
 
 			case WID_BC_YES:

src/console_gui.cpp

@@ -133,10 +133,11 @@ struct IConsoleWindow : Window
 		this->line_offset = GetStringBoundingBox("] ").width + WidgetDimensions::scaled.frametext.left;
 	}
 
-	~IConsoleWindow()
+	void Close() override
 	{
 		_iconsole_mode = ICONSOLE_CLOSED;
 		VideoDriver::GetInstance()->EditBoxLostFocus();
+		this->Window::Close();
 	}
 
 	/**
@@ -345,7 +346,7 @@ struct IConsoleWindow : Window
 		VideoDriver::GetInstance()->EditBoxGainedFocus();
 	}
 
-	void OnFocusLost(Window *newly_focused_window) override
+	void OnFocusLost(bool closing, Window *newly_focused_window) override
 	{
 		VideoDriver::GetInstance()->EditBoxLostFocus();
 	}

src/date_gui.cpp

@@ -155,7 +155,7 @@ struct SetDateWindow : Window {
 				if (this->callback != nullptr) {
 					this->callback(this, DateToScaledDateTicks(ConvertYMDToDate(this->date.year, this->date.month, this->date.day)));
 				}
-				delete this;
+				this->Close();
 				break;
 		}
 	}
@@ -271,7 +271,7 @@ struct SetMinutesWindow : SetDateWindow
 				if (this->callback != nullptr) {
 					this->callback(this, ((DateTicks)minutes - _settings_time.clock_offset) * (DateTicksScaled)_settings_time.ticks_per_minute);
 				}
-				delete this;
+				this->Close();
 				break;
 		}
 	}

src/departures_gui.cpp

@@ -289,7 +289,7 @@ public:
 
 	virtual ~DeparturesWindow()
 	{
-		this->DeleteDeparturesList(departures);
+		this->DeleteDeparturesList(this->departures);
 		this->DeleteDeparturesList(this->arrivals);
 	}
 

src/depot_gui.cpp

@@ -296,11 +296,12 @@ struct DepotWindow : Window {
 		OrderBackup::Reset();
 	}
 
-	~DepotWindow()
+	void Close() override
 	{
 		CloseWindowById(WC_BUILD_VEHICLE, this->window_number);
 		CloseWindowById(GetWindowClassForVehicleType(this->type), VehicleListIdentifier(VL_DEPOT_LIST, this->type, this->owner, this->GetDepotIndex()).Pack(), false);
 		OrderBackup::Reset(this->window_number);
+		this->Window::Close();
 	}
 
 	/**

src/dock_gui.cpp

@@ -106,10 +106,11 @@ struct BuildDocksToolbarWindow : Window {
 		if (_settings_client.gui.link_terraform_toolbar) ShowTerraformToolbar(this);
 	}
 
-	~BuildDocksToolbarWindow()
+	void Close() override
 	{
 		if (_game_mode == GM_NORMAL && this->IsWidgetLowered(WID_DT_STATION)) SetViewportCatchmentStation(nullptr, true);
 		if (_settings_client.gui.link_terraform_toolbar) CloseWindowById(WC_SCEN_LAND_GEN, 0, false);
+		this->Window::Close();
 	}
 
 	/**
@@ -425,9 +426,10 @@ public:
 		this->LowerWidget(_settings_client.gui.station_show_coverage + BDSW_LT_OFF);
 	}
 
-	virtual ~BuildDocksStationWindow()
+	void Close() override
 	{
 		CloseWindowById(WC_SELECT_STATION, 0);
+		this->PickerWindowBase::Close();
 	}
 
 	void OnPaint() override

src/engine_gui.cpp

@@ -128,7 +128,7 @@ struct EnginePreviewWindow : Window {
 				DoCommandP(0, this->window_number, 0, CMD_WANT_ENGINE_PREVIEW);
 				FALLTHROUGH;
 			case WID_EP_NO:
-				if (!_shift_pressed) delete this;
+				if (!_shift_pressed) this->Close();
 				break;
 		}
 	}
@@ -138,7 +138,7 @@ struct EnginePreviewWindow : Window {
 		if (!gui_scope) return;
 
 		EngineID engine = this->window_number;
-		if (Engine::Get(engine)->preview_company != _local_company) delete this;
+		if (Engine::Get(engine)->preview_company != _local_company) this->Close();
 	}
 };
 

src/error_gui.cpp

@@ -262,7 +262,7 @@ public:
 	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		/* If company gets shut down, while displaying an error about it, remove the error message. */
-		if (this->face != INVALID_COMPANY && !Company::IsValidID(this->face)) delete this;
+		if (this->face != INVALID_COMPANY && !Company::IsValidID(this->face)) this->Close();
 	}
 
 	void SetStringParameters(int widget) const override
@@ -316,20 +316,21 @@ public:
 	void OnMouseLoop() override
 	{
 		/* Disallow closing the window too easily, if timeout is disabled */
-		if (_right_button_down && !this->display_timer.HasElapsed()) delete this;
+		if (_right_button_down && !this->display_timer.HasElapsed()) this->Close();
 	}
 
 	void OnRealtimeTick(uint delta_ms) override
 	{
 		if (this->display_timer.CountElapsed(delta_ms) == 0) return;
 
-		delete this;
+		this->Close();
 	}
 
-	~ErrmsgWindow()
+	void Close() override
 	{
 		SetRedErrorSquare(INVALID_TILE);
 		if (_window_system_initialized) ShowFirstError();
+		this->Window::Close();
 	}
 
 	/**
@@ -372,7 +373,7 @@ void UnshowCriticalError()
 	if (_window_system_initialized && w != nullptr) {
 		if (w->IsCritical()) _error_list.push_front(*w);
 		_window_system_initialized = false;
-		delete w;
+		w->Close();
 	}
 }
 
@@ -426,18 +427,20 @@ void ShowErrorMessage(StringID summary_msg, StringID detailed_msg, WarningLevel
 	data.CopyOutDParams();
 
 	ErrmsgWindow *w = (ErrmsgWindow*)FindWindowById(WC_ERRMSG, 0);
-	if (w != nullptr && w->IsCritical()) {
+	if (w != nullptr) {
-		/* A critical error is currently shown. */
+		if (w->IsCritical()) {
-		if (wl == WL_CRITICAL) {
+			/* A critical error is currently shown. */
-			/* Push another critical error in the queue of errors,
+			if (wl == WL_CRITICAL) {
-			 * but do not put other errors in the queue. */
+				/* Push another critical error in the queue of errors,
-			_error_list.push_back(data);
+				 * but do not put other errors in the queue. */
+				_error_list.push_back(data);
+			}
+			return;
 		}
-	} else {
+		/* A non-critical error was shown. */
-		/* Nothing or a non-critical error was shown. */
+		w->Close();
-		delete w;
-		new ErrmsgWindow(data);
 	}
+	new ErrmsgWindow(data);
 }
 
 
@@ -448,7 +451,7 @@ void ShowErrorMessage(StringID summary_msg, StringID detailed_msg, WarningLevel
 bool HideActiveErrorMessage() {
 	ErrmsgWindow *w = (ErrmsgWindow*)FindWindowById(WC_ERRMSG, 0);
 	if (w == nullptr) return false;
-	delete w;
+	w->Close();
 	return true;
 }
 

src/fios_gui.cpp

@@ -408,12 +408,13 @@ public:
 		}
 	}
 
-	virtual ~SaveLoadWindow()
+	void Close() override
 	{
 		/* pause is only used in single-player, non-editor mode, non menu mode */
 		if (!_networking && _game_mode != GM_EDITOR && _game_mode != GM_MENU) {
 			DoCommandP(0, PM_PAUSED_SAVELOAD, 0, CMD_PAUSE);
 		}
+		this->Window::Close();
 	}
 
 	void DrawWidget(const Rect &r, int widget) const override
@@ -641,12 +642,12 @@ public:
 				_file_to_saveload.Set(*this->selected);
 
 				if (this->abstract_filetype == FT_HEIGHTMAP) {
-					delete this;
+					this->Close();
 					ShowHeightmapLoad();
 				} else if (!_load_check_data.HasNewGrfs() || _load_check_data.grf_compatibility != GLC_NOT_FOUND || _settings_client.gui.UserIsAllowedToChangeNewGRFs()) {
 					_switch_mode = (_game_mode == GM_EDITOR) ? SM_LOAD_SCENARIO : SM_LOAD_GAME;
 					ClearErrorMessages();
-					delete this;
+					this->Close();
 				}
 				break;
 			}
@@ -704,7 +705,7 @@ public:
 							assert(this->abstract_filetype == FT_HEIGHTMAP);
 							_file_to_saveload.Set(*file);
 
-							delete this;
+							this->Close();
 							ShowHeightmapLoad();
 						}
 					}
@@ -757,7 +758,7 @@ public:
 	EventState OnKeyPress(WChar key, uint16 keycode) override
 	{
 		if (keycode == WKC_ESC) {
-			delete this;
+			this->Close();
 			return ES_HANDLED;
 		}
 

src/game/game_gui.cpp

@@ -111,10 +111,11 @@ struct GSConfigWindow : public Window {
 		this->RebuildVisibleSettings();
 	}
 
-	~GSConfigWindow()
+	void Close() override
 	{
 		HideDropDownMenu(this);
 		CloseWindowByClass(WC_SCRIPT_LIST);
+		this->Window::Close();
 	}
 
 	/**
@@ -354,7 +355,7 @@ struct GSConfigWindow : public Window {
 			}
 
 			case WID_GSC_ACCEPT:
-				delete this;
+				this->Close();
 				break;
 
 			case WID_GSC_RESET:

src/goal_gui.cpp

@@ -375,17 +375,17 @@ struct GoalQuestionWindow : public Window {
 		switch (widget) {
 			case WID_GQ_BUTTON_1:
 				DoCommandP(0, this->window_number, this->button[0], CMD_GOAL_QUESTION_ANSWER);
-				delete this;
+				this->Close();
 				break;
 
 			case WID_GQ_BUTTON_2:
 				DoCommandP(0, this->window_number, this->button[1], CMD_GOAL_QUESTION_ANSWER);
-				delete this;
+				this->Close();
 				break;
 
 			case WID_GQ_BUTTON_3:
 				DoCommandP(0, this->window_number, this->button[2], CMD_GOAL_QUESTION_ANSWER);
-				delete this;
+				this->Close();
 				break;
 		}
 	}

src/group_gui.cpp

@@ -447,9 +447,10 @@ public:
 		this->owner = vli.company;
 	}
 
-	~VehicleGroupWindow()
+	void Close() override
 	{
 		*this->sorting = this->vehgroups.GetListing();
+		this->Window::Close();
 	}
 
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override

src/highscore_gui.cpp

@@ -64,7 +64,7 @@ struct EndGameHighScoreBaseWindow : Window {
 
 	void OnClick(Point pt, int widget, int click_count) override
 	{
-		delete this;
+		this->Close();
 	}
 
 	EventState OnKeyPress(WChar key, uint16 keycode) override
@@ -79,7 +79,7 @@ struct EndGameHighScoreBaseWindow : Window {
 			case WKC_RETURN:
 			case WKC_ESC:
 			case WKC_SPACE:
-				delete this;
+				this->Close();
 				return ES_HANDLED;
 
 			default:
@@ -122,10 +122,11 @@ struct EndGameWindow : EndGameHighScoreBaseWindow {
 		MarkWholeScreenDirty();
 	}
 
-	~EndGameWindow()
+	void Close() override
 	{
 		if (!_networking) DoCommandP(0, PM_PAUSED_NORMAL, 0, CMD_PAUSE); // unpause
 		if (_game_mode != GM_MENU) ShowHighscoreTable(this->window_number, this->rank);
+		this->EndGameHighScoreBaseWindow::Close();
 	}
 
 	void OnPaint() override
@@ -169,11 +170,13 @@ struct HighScoreWindow : EndGameHighScoreBaseWindow {
 		this->rank = ranking;
 	}
 
-	~HighScoreWindow()
+	void Close() override
 	{
 		if (_game_mode != GM_MENU) ShowVitalWindows();
 
 		if (!_networking && !this->game_paused_by_player) DoCommandP(0, PM_PAUSED_NORMAL, 0, CMD_PAUSE); // unpause
+
+		this->EndGameHighScoreBaseWindow::Close();
 	}
 
 	void OnPaint() override

src/industry_gui.cpp

@@ -1638,9 +1638,10 @@ public:
 		this->industry_editbox.cancel_button = QueryString::ACTION_CLEAR;
 	}
 
-	~IndustryDirectoryWindow()
+	void Close() override
 	{
 		this->last_sorting = this->industries.GetListing();
+		this->Window::Close();
 	}
 
 	void OnInit() override

src/linkgraph/linkgraph_gui.cpp

@@ -903,7 +903,7 @@ void LinkGraphLegendWindow::OnClick(Point pt, int widget, int click_count)
 void LinkGraphLegendWindow::OnInvalidateData(int data, bool gui_scope)
 {
 	if (this->num_cargo != _sorted_cargo_specs.size()) {
-		delete this;
+		this->Close();
 		return;
 	}
 

src/misc_gui.cpp

@@ -799,15 +799,15 @@ struct TooltipsWindow : public Window
 	{
 		/* Always close tooltips when the cursor is not in our window. */
 		if (!_cursor.in_window || this->delete_next_mouse_loop) {
-			delete this;
+			this->Close();
 			return;
 		}
 
 		/* We can show tooltips while dragging tools. These are shown as long as
 		 * we are dragging the tool. Normal tooltips work with hover or rmb. */
 		switch (this->close_cond) {
-			case TCC_RIGHT_CLICK: if (!_right_button_down) delete this; break;
+			case TCC_RIGHT_CLICK: if (!_right_button_down) this->Close();; break;
-			case TCC_HOVER: if (!_mouse_hovering) delete this; break;
+			case TCC_HOVER: if (!_mouse_hovering) this->Close();; break;
 			case TCC_NONE: break;
 			case TCC_NEXT_LOOP: this->delete_next_mouse_loop = true; break;
 
@@ -815,7 +815,7 @@ struct TooltipsWindow : public Window
 				if (_settings_client.gui.hover_delay_ms == 0) {
 					if (!_right_button_down) this->delete_next_mouse_loop = true;
 				} else if (!_mouse_hovering) {
-					delete this;
+					this->Close();
 					break;
 				}
 				if (this->viewport_virtual_left != this->parent->viewport->virtual_left ||
@@ -826,7 +826,7 @@ struct TooltipsWindow : public Window
 
 			case TCC_EXIT_VIEWPORT: {
 				Window *w = FindWindowFromPt(_cursor.pos.x, _cursor.pos.y);
-				if (w == nullptr || IsPtInWindowViewport(w, _cursor.pos.x, _cursor.pos.y) == nullptr) delete this;
+				if (w == nullptr || IsPtInWindowViewport(w, _cursor.pos.x, _cursor.pos.y) == nullptr) this->Close();
 				break;
 			}
 		}
@@ -1134,18 +1134,19 @@ struct QueryStringWindow : public Window
 				FALLTHROUGH;
 
 			case WID_QS_CANCEL:
-				delete this;
+				this->Close();
 				break;
 		}
 	}
 
-	~QueryStringWindow()
+	void Close() override
 	{
 		if (!this->editbox.handled && this->parent != nullptr) {
 			Window *parent = this->parent;
-			this->parent = nullptr; // so parent doesn't try to delete us again
+			this->parent = nullptr; // so parent doesn't try to close us again
 			parent->OnQueryTextFinished(nullptr);
 		}
+		this->Window::Close();
 	}
 };
 
@@ -1227,9 +1228,10 @@ struct QueryWindow : public Window {
 		this->InitNested(WN_CONFIRM_POPUP_QUERY);
 	}
 
-	~QueryWindow()
+	void Close() override
 	{
 		if (this->proc != nullptr) this->proc(this->parent, false);
+		this->Window::Close();
 	}
 
 	void FindWindowPlacementAndResize(int def_width, int def_height) override
@@ -1292,7 +1294,7 @@ struct QueryWindow : public Window {
 				Window *parent = this->parent;
 				/* Prevent the destructor calling the callback function */
 				this->proc = nullptr;
-				delete this;
+				this->Close();
 				if (proc != nullptr) {
 					proc(parent, true);
 					proc = nullptr;
@@ -1300,7 +1302,7 @@ struct QueryWindow : public Window {
 				break;
 			}
 			case WID_Q_NO:
-				delete this;
+				this->Close();
 				break;
 		}
 	}
@@ -1318,7 +1320,7 @@ struct QueryWindow : public Window {
 				FALLTHROUGH;
 
 			case WKC_ESC:
-				delete this;
+				this->Close();
 				return ES_HANDLED;
 		}
 		return ES_NOT_HANDLED;
@@ -1350,13 +1352,13 @@ static WindowDesc _query_desc(
 
 static void RemoveExistingQueryWindow(Window *parent, QueryCallbackProc *callback)
 {
-	for (const Window *w : Window::IterateFromBack()) {
+	for (Window *w : Window::IterateFromBack()) {
 		if (w->window_class != WC_CONFIRM_POPUP_QUERY) continue;
 
-		const QueryWindow *qw = (const QueryWindow *)w;
+		QueryWindow *qw = (QueryWindow *)w;
 		if (qw->parent != parent || qw->proc != callback) continue;
 
-		delete qw;
+		qw->Close();
 		break;
 	}
 }
@@ -1424,10 +1426,11 @@ struct ModifierKeyToggleWindow : Window {
 		this->UpdateButtons();
 	}
 
-	~ModifierKeyToggleWindow()
+	void Close() override
 	{
 		_invert_shift = false;
 		_invert_ctrl = false;
+		this->Window::Close();
 	}
 
 	void UpdateButtons()

src/network/network_chat_gui.cpp

@@ -314,9 +314,10 @@ struct NetworkChatWindow : public Window {
 		PositionNetworkChatWindow(this);
 	}
 
-	~NetworkChatWindow()
+	void Close() override
 	{
 		InvalidateWindowData(WC_NEWS_WINDOW, 0, 0);
+		this->Window::Close();
 	}
 
 	void FindWindowPlacementAndResize(int def_width, int def_height) override
@@ -470,7 +471,7 @@ struct NetworkChatWindow : public Window {
 				FALLTHROUGH;
 
 			case WID_NC_CLOSE: /* Cancel */
-				delete this;
+				this->Close();
 				break;
 		}
 	}
@@ -497,7 +498,7 @@ struct NetworkChatWindow : public Window {
 	 */
 	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
-		if (data == this->dest) delete this;
+		if (data == this->dest) this->Close();
 	}
 };
 

src/network/network_content_gui.cpp

@@ -109,9 +109,10 @@ BaseNetworkContentDownloadStatusWindow::BaseNetworkContentDownloadStatusWindow(W
 	this->InitNested(WN_NETWORK_STATUS_WINDOW_CONTENT_DOWNLOAD);
 }
 
-BaseNetworkContentDownloadStatusWindow::~BaseNetworkContentDownloadStatusWindow()
+void BaseNetworkContentDownloadStatusWindow::Close()
 {
 	_network_content_client.RemoveCallback(this);
+	this->Window::Close();
 }
 
 void BaseNetworkContentDownloadStatusWindow::UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize)
@@ -200,8 +201,7 @@ public:
 		this->parent = FindWindowById(WC_NETWORK_WINDOW, WN_NETWORK_WINDOW_CONTENT_LIST);
 	}
 
-	/** Free whatever we've allocated */
+	void Close() override
-	~NetworkContentDownloadStatusWindow()
 	{
 		TarScanner::Mode mode = TarScanner::NONE;
 		for (auto ctype : this->receivedTypes) {
@@ -282,6 +282,8 @@ public:
 
 		/* Always invalidate the download window; tell it we are going to be gone */
 		InvalidateWindowData(WC_NETWORK_WINDOW, WN_NETWORK_WINDOW_CONTENT_LIST, 2);
+
+		this->BaseNetworkContentDownloadStatusWindow::Close();
 	}
 
 	void OnClick(Point pt, int widget, int click_count) override
@@ -289,7 +291,7 @@ public:
 		if (widget == WID_NCDS_CANCELOK) {
 			if (this->downloaded_bytes != this->total_bytes) {
 				_network_content_client.CloseConnection();
-				delete this;
+				this->Close();
 			} else {
 				/* If downloading succeeded, close the online content window. This will close
 				 * the current window as well. */
@@ -572,10 +574,10 @@ public:
 		this->InvalidateData();
 	}
 
-	/** Free everything we allocated */
+	void Close() override
-	~NetworkContentListWindow()
 	{
 		_network_content_client.RemoveCallback(this);
+		this->Window::Close();
 	}
 
 	void OnInit() override
@@ -852,7 +854,7 @@ public:
 				break;
 
 			case WID_NCL_CANCEL:
-				delete this;
+				this->Close();
 				break;
 
 			case WID_NCL_OPEN_URL:
@@ -955,7 +957,7 @@ public:
 	{
 		if (!success) {
 			ShowErrorMessage(STR_CONTENT_ERROR_COULD_NOT_CONNECT, INVALID_STRING_ID, WL_ERROR);
-			delete this;
+			this->Close();
 			return;
 		}
 

src/network/network_content_gui.h

@@ -32,11 +32,7 @@ public:
 	 */
 	BaseNetworkContentDownloadStatusWindow(WindowDesc *desc);
 
-	/**
+	void Close() override;
-	 * Free everything associated with this window.
-	 */
-	~BaseNetworkContentDownloadStatusWindow();
-
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override;
 	void DrawWidget(const Rect &r, int widget) const override;
 	void OnDownloadProgress(const ContentInfo *ci, int bytes) override;

src/network/network_gui.cpp

@@ -523,9 +523,10 @@ public:
 		this->servers.ForceRebuild();
 	}
 
-	~NetworkGameWindow()
+	void Close() override
 	{
 		this->last_sorting = this->servers.GetListing();
+		this->Window::Close();
 	}
 
 	void OnInit() override
@@ -2378,7 +2379,7 @@ struct NetworkCompanyPasswordWindow : public Window {
 				FALLTHROUGH;
 
 			case WID_NCP_CANCEL:
-				delete this;
+				this->Close();
 				break;
 
 			case WID_NCP_SAVE_AS_DEFAULT_PASSWORD:
@@ -2485,18 +2486,18 @@ struct NetworkAskRelayWindow : public Window {
 		switch (widget) {
 			case WID_NAR_NO:
 				_network_coordinator_client.ConnectFailure(this->token, 0);
-				delete this;
+				this->Close();
 				break;
 
 			case WID_NAR_YES_ONCE:
 				_network_coordinator_client.StartTurnConnection(this->token);
-				delete this;
+				this->Close();
 				break;
 
 			case WID_NAR_YES_ALWAYS:
 				_settings_client.network.use_relay_service = URS_ALLOW;
 				_network_coordinator_client.StartTurnConnection(this->token);
-				delete this;
+				this->Close();
 				break;
 		}
 	}

src/newgrf_gui.cpp

@@ -184,9 +184,10 @@ struct NewGRFParametersWindow : public Window {
 		this->InvalidateData();
 	}
 
-	~NewGRFParametersWindow()
+	void Close() override
 	{
 		HideDropDownMenu(this);
+		this->Window::Close();
 	}
 
 	/**
@@ -449,7 +450,7 @@ struct NewGRFParametersWindow : public Window {
 				break;
 
 			case WID_NP_ACCEPT:
-				delete this;
+				this->Close();
 				break;
 		}
 	}
@@ -686,7 +687,7 @@ struct NewGRFWindow : public Window, NewGRFScanCallback {
 		this->OnInvalidateData(GOID_NEWGRF_CURRENT_LOADED);
 	}
 
-	~NewGRFWindow()
+	void Close() override
 	{
 		CloseWindowByClass(WC_GRF_PARAMETERS);
 		CloseWindowByClass(WC_TEXTFILE);
@@ -699,6 +700,11 @@ struct NewGRFWindow : public Window, NewGRFScanCallback {
 			PostCheckNewGRFLoadWarnings();
 		}
 
+		this->Window::Close();
+	}
+
+	~NewGRFWindow()
+	{
 		/* Remove the temporary copy of grf-list used in window */
 		ClearGRFConfigList(&this->actives);
 	}
@@ -2121,10 +2127,6 @@ struct SavePresetWindow : public Window {
 		if (initial_text != nullptr) this->presetname_editbox.text.Assign(initial_text);
 	}
 
-	~SavePresetWindow()
-	{
-	}
-
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
 	{
 		switch (widget) {
@@ -2181,13 +2183,13 @@ struct SavePresetWindow : public Window {
 			}
 
 			case WID_SVP_CANCEL:
-				delete this;
+				this->Close();
 				break;
 
 			case WID_SVP_SAVE: {
 				Window *w = FindWindowById(WC_GAME_OPTIONS, WN_GAME_OPTIONS_NEWGRF_STATE);
 				if (w != nullptr && !StrEmpty(this->presetname_editbox.text.buf)) w->OnQueryTextFinished(this->presetname_editbox.text.buf);
-				delete this;
+				this->Close();
 				break;
 			}
 		}

src/news_gui.cpp

@@ -485,7 +485,7 @@ struct NewsWindow : Window {
 		switch (widget) {
 			case WID_N_CLOSEBOX:
 				NewsWindow::duration = 0;
-				delete this;
+				this->Close();
 				_forced_news = nullptr;
 				break;
 
@@ -1054,7 +1054,7 @@ static void ShowNewsMessage(const NewsItem *ni)
 bool HideActiveNewsMessage() {
 	NewsWindow *w = (NewsWindow*)FindWindowById(WC_NEWS_WINDOW, 0);
 	if (w == nullptr) return false;
-	delete w;
+	w->Close();
 	return true;
 }
 

src/openttd.cpp

@@ -528,7 +528,7 @@ static void LoadIntroGame(bool load_newgrfs = true)
 {
 	UnshowCriticalError();
 	for (Window *w : Window::IterateFromFront()) {
-		delete w;
+		w->Close();
 	}
 
 	_game_mode = GM_MENU;

src/order_gui.cpp

@@ -179,11 +179,12 @@ public:
 		this->owner = v->owner;
 	}
 
-	~CargoTypeOrdersWindow()
+	void Close() override
 	{
 		if (!FocusWindowById(WC_VEHICLE_ORDERS, this->window_number)) {
 			MarkDirtyFocusedRoutePaths(this->vehicle);
 		}
+		this->Window::Close();
 	}
 
 	virtual void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
@@ -229,11 +230,11 @@ public:
 	virtual void OnClick(Point pt, int widget, int click_count) override
 	{
 		if (!this->CheckOrderStillValid()) {
-			delete this;
+			this->Close();
 			return;
 		}
 		if (widget == WID_CTO_CLOSEBTN) {
-			delete this;
+			this->Close();
 		} else if (WID_CTO_CARGO_DROPDOWN_FIRST <= widget && widget <= WID_CTO_CARGO_DROPDOWN_LAST) {
 			const CargoSpec *cs = _sorted_cargo_specs[widget - WID_CTO_CARGO_DROPDOWN_FIRST];
 			const CargoID cargo_id = cs->Index();
@@ -247,7 +248,7 @@ public:
 	virtual void OnDropdownSelect(int widget, int action_type) override
 	{
 		if (!this->CheckOrderStillValid()) {
-			delete this;
+			this->Close();
 			return;
 		}
 		ModifyOrderFlags mof = (this->variant == CTOWV_LOAD) ? MOF_CARGO_TYPE_LOAD : MOF_CARGO_TYPE_UNLOAD;
@@ -301,7 +302,7 @@ public:
 		}
 	}
 
-	virtual void OnFocusLost(Window *newly_focused_window) override
+	virtual void OnFocusLost(bool closing, Window *newly_focused_window) override
 	{
 		if (HasFocusedVehicleChanged(this->window_number, newly_focused_window)) {
 			MarkDirtyFocusedRoutePaths(this->vehicle);
@@ -316,7 +317,7 @@ public:
 	virtual void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!this->CheckOrderStillValid()) {
-			delete this;
+			this->Close();
 			return;
 		}
 		if (gui_scope) {
@@ -1900,13 +1901,14 @@ public:
 		this->OnInvalidateData(VIWD_MODIFY_ORDERS);
 	}
 
-	~OrdersWindow()
+	void Close() override
 	{
 		CloseWindowById(WC_VEHICLE_CARGO_TYPE_LOAD_ORDERS, this->window_number, false);
 		CloseWindowById(WC_VEHICLE_CARGO_TYPE_UNLOAD_ORDERS, this->window_number, false);
 		if (!FocusWindowById(WC_VEHICLE_VIEW, this->window_number)) {
 			MarkDirtyFocusedRoutePaths(this->vehicle);
 		}
+		this->GeneralVehicleWindow::Close();
 	}
 
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
@@ -3575,7 +3577,7 @@ public:
 		}
 	}
 
-	virtual void OnFocusLost(Window *newly_focused_window) override
+	virtual void OnFocusLost(bool closing, Window *newly_focused_window) override
 	{
 		if (HasFocusedVehicleChanged(this->window_number, newly_focused_window)) {
 			MarkDirtyFocusedRoutePaths(this->vehicle);

src/osk_gui.cpp

@@ -165,7 +165,7 @@ struct OskWindow : public Window {
 						return;
 					}
 				}
-				delete this;
+				this->Close();
 				break;
 
 			case WID_OSK_CANCEL:
@@ -177,7 +177,7 @@ struct OskWindow : public Window {
 					qs->text.Assign(this->orig_str.c_str());
 					qs->text.MovePos(WKC_END);
 					this->OnEditboxChanged(WID_OSK_TEXT);
-					delete this;
+					this->Close();
 				}
 				break;
 		}
@@ -197,10 +197,10 @@ struct OskWindow : public Window {
 		this->parent->SetWidgetDirty(this->text_btn);
 	}
 
-	void OnFocusLost(Window *newly_focused_window) override
+	void OnFocusLost(bool closing, Window *newly_focused_window) override
 	{
 		VideoDriver::GetInstance()->EditBoxLostFocus();
-		delete this;
+		if (!closing) this->Close();
 	}
 };
 

src/plans_gui.cpp

@@ -98,13 +98,14 @@ struct PlansWindow : Window {
 		RebuildList();
 	}
 
-	~PlansWindow()
+	void Close() override
 	{
 		this->list.clear();
 		if (_current_plan) {
 			_current_plan->SetFocus(false);
 			_current_plan = nullptr;
 		}
+		this->Window::Close();
 	}
 
 	virtual void OnClick(Point pt, int widget, int click_count) override

src/rail_gui.cpp

@@ -515,12 +515,13 @@ struct BuildRailToolbarWindow : Window {
 		if (_settings_client.gui.link_terraform_toolbar) ShowTerraformToolbar(this);
 	}
 
-	~BuildRailToolbarWindow()
+	void Close() override
 	{
 		if (this->IsWidgetLowered(WID_RAT_BUILD_STATION)) SetViewportCatchmentStation(nullptr, true);
 		if (this->IsWidgetLowered(WID_RAT_BUILD_WAYPOINT)) SetViewportCatchmentWaypoint(nullptr, true);
 		if (_settings_client.gui.link_terraform_toolbar) CloseWindowById(WC_SCEN_LAND_GEN, 0, false);
 		CloseWindowById(WC_SELECT_STATION, 0);
+		this->Window::Close();
 	}
 
 	/**
@@ -1249,9 +1250,10 @@ public:
 		this->InvalidateData();
 	}
 
-	virtual ~BuildRailStationWindow()
+	void Close() override
 	{
 		CloseWindowById(WC_SELECT_STATION, 0);
+		this->PickerWindowBase::Close();
 	}
 
 	/** Sort station classes by StationClassID. */
@@ -1979,11 +1981,12 @@ public:
 		this->OnInvalidateData();
 	}
 
-	~BuildSignalWindow()
+	void Close() override
 	{
 		_convert_signal_button = false;
 		_trace_restrict_button = false;
 		_program_signal_button = false;
+		this->PickerWindowBase::Close();
 	}
 
 	void OnInit() override
@@ -2516,9 +2519,10 @@ struct BuildRailWaypointWindow : PickerWindowBase {
 		}
 	}
 
-	virtual ~BuildRailWaypointWindow()
+	void Close() override
 	{
 		CloseWindowById(WC_SELECT_STATION, 0);
+		this->PickerWindowBase::Close();
 	}
 
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override

src/road_gui.cpp

@@ -377,12 +377,13 @@ struct BuildRoadToolbarWindow : Window {
 		if (_settings_client.gui.link_terraform_toolbar) ShowTerraformToolbar(this);
 	}
 
-	~BuildRoadToolbarWindow()
+	void Close() override
 	{
 		if (_game_mode == GM_NORMAL && (this->IsWidgetLowered(WID_ROT_BUS_STATION) || this->IsWidgetLowered(WID_ROT_TRUCK_STATION))) SetViewportCatchmentStation(nullptr, true);
 		if (_game_mode == GM_NORMAL && this->IsWidgetLowered(WID_ROT_BUILD_WAYPOINT)) SetViewportCatchmentWaypoint(nullptr, true);
 		if (_settings_client.gui.link_terraform_toolbar) CloseWindowById(WC_SCEN_LAND_GEN, 0, false);
 		CloseWindowById(WC_SELECT_STATION, 0);
+		this->Window::Close();
 	}
 
 	/**
@@ -1377,9 +1378,10 @@ public:
 		}
 	}
 
-	virtual ~BuildRoadStationWindow()
+	void Close() override
 	{
 		CloseWindowById(WC_SELECT_STATION, 0);
+		this->PickerWindowBase::Close();
 	}
 
 	/** Sort classes by RoadStopClassID. */
@@ -2035,9 +2037,10 @@ struct BuildRoadWaypointWindow : PickerWindowBase {
 		}
 	}
 
-	virtual ~BuildRoadWaypointWindow()
+	void Close() override
 	{
 		CloseWindowById(WC_SELECT_STATION, 0);
+		this->PickerWindowBase::Close();
 	}
 
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
@@ -2395,7 +2398,7 @@ static BuildRoadToolbarWindow *GetRoadToolbarWindowForRoadStop(const RoadStopSpe
 	if (w != nullptr) {
 		if (spec != nullptr && ((HasBit(spec->flags, RSF_BUILD_MENU_ROAD_ONLY) && !RoadTypeIsRoad(_cur_roadtype)) ||
 				(HasBit(spec->flags, RSF_BUILD_MENU_TRAM_ONLY) && !RoadTypeIsTram(_cur_roadtype)))) {
-			delete w;
+			w->Close();
 		} else {
 			return w;
 		}

src/schdispatch_gui.cpp

@@ -210,11 +210,12 @@ struct SchdispatchWindow : GeneralVehicleWindow {
 		this->AutoSelectSchedule();
 	}
 
-	~SchdispatchWindow()
+	void Close() override
 	{
 		if (!FocusWindowById(WC_VEHICLE_VIEW, this->window_number)) {
 			MarkDirtyFocusedRoutePaths(this->vehicle);
 		}
+		this->GeneralVehicleWindow::Close();
 	}
 
 	uint base_width;
@@ -1169,7 +1170,7 @@ struct ScheduledDispatchAddSlotsWindow : Window {
 
 			case WID_SCHDISPATCH_ADD_SLOT_ADD_BUTTON:
 				static_cast<SchdispatchWindow *>(this->parent)->AddMultipleDepartureSlots(this->start, this->step, this->end);
-				delete this;
+				this->Close();
 				break;
 		}
 	}

src/script/script_gui.cpp

@@ -201,7 +201,7 @@ struct ScriptListWindow : public Window {
 					this->SetDirty();
 					if (click_count > 1) {
 						this->ChangeScript();
-						delete this;
+						this->Close();
 					}
 				}
 				break;
@@ -209,12 +209,12 @@ struct ScriptListWindow : public Window {
 
 			case WID_SCRL_ACCEPT: {
 				this->ChangeScript();
-				delete this;
+				this->Close();
 				break;
 			}
 
 			case WID_SCRL_CANCEL:
-				delete this;
+				this->Close();
 				break;
 		}
 	}
@@ -232,7 +232,7 @@ struct ScriptListWindow : public Window {
 	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (_game_mode == GM_NORMAL && Company::IsValidID(this->slot)) {
-			delete this;
+			this->Close();
 			return;
 		}
 
@@ -325,9 +325,10 @@ struct ScriptSettingsWindow : public Window {
 		this->RebuildVisibleSettings();
 	}
 
-	~ScriptSettingsWindow()
+	void Close() override
 	{
 		HideDropDownMenu(this);
+		this->Window::Close();
 	}
 
 	/**
@@ -520,7 +521,7 @@ struct ScriptSettingsWindow : public Window {
 			}
 
 			case WID_SCRS_ACCEPT:
-				delete this;
+				this->Close();
 				break;
 
 			case WID_SCRS_RESET:
@@ -660,7 +661,7 @@ struct ScriptTextfileWindow : public TextfileWindow {
 	{
 		const char *textfile = GetConfig(slot)->GetTextfile(file_type, slot);
 		if (textfile == nullptr) {
-			delete this;
+			this->Close();
 		} else {
 			this->LoadTextfile(textfile, (slot == OWNER_DEITY) ? GAME_DIR : AI_DIR);
 		}

src/settings_gui.cpp

@@ -197,11 +197,12 @@ struct GameOptionsWindow : Window {
 		if constexpr (!NetworkSurveyHandler::IsSurveyPossible()) this->GetWidget<NWidgetStacked>(WID_GO_SURVEY_SEL)->SetDisplayedPlane(SZSP_NONE);
 	}
 
-	~GameOptionsWindow()
+	void Close() override
 	{
 		CloseWindowById(WC_CUSTOM_CURRENCY, 0);
 		CloseWindowByClass(WC_TEXTFILE);
 		if (this->reload) _switch_mode = SM_MENU;
+		this->Window::Close();
 	}
 
 	/**

src/signs_gui.cpp

@@ -527,7 +527,7 @@ struct SignWindow : Window, SignList {
 				FALLTHROUGH;
 
 			case WID_QES_CANCEL:
-				delete this;
+				this->Close();
 				break;
 		}
 	}
@@ -596,5 +596,5 @@ void DeleteRenameSignWindow(SignID sign)
 {
 	SignWindow *w = dynamic_cast<SignWindow *>(FindWindowById(WC_QUERY_STRING, WN_QUERY_STRING_SIGN));
 
-	if (w != nullptr && w->cur_sign == sign) delete w;
+	if (w != nullptr && w->cur_sign == sign) w->Close();
 }

src/smallmap_gui.cpp

@@ -1086,7 +1086,12 @@ SmallMapWindow::SmallMapWindow(WindowDesc *desc, int window_number) : Window(des
 SmallMapWindow::~SmallMapWindow()
 {
 	delete this->overlay;
+}
+
+/* virtual */ void SmallMapWindow::Close()
+{
 	this->BreakIndustryChainLink();
+	this->Window::Close();
 }
 
 /**

src/smallmap_gui.h

@@ -207,6 +207,7 @@ public:
 	void SmallMapCenterOnCurrentPos();
 	Point GetStationMiddle(const Station *st) const;
 
+	void Close() override;
 	void SetStringParameters(int widget) const override;
 	void OnInit() override;
 	void OnPaint() override;

src/station_gui.cpp

@@ -480,9 +480,10 @@ public:
 		this->GetWidget<NWidgetCore>(WID_STL_SORTDROPBTN)->widget_data = this->sorter_names[this->stations.SortType()];
 	}
 
-	~CompanyStationsWindow()
+	void Close() override
 	{
 		this->last_sorting = this->stations.GetListing();
+		this->Window::Close();
 	}
 
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
@@ -1435,7 +1436,7 @@ struct StationViewWindow : public Window {
 		ZoningStationWindowOpenClose(Station::Get(window_number));
 	}
 
-	~StationViewWindow()
+	void Close() override
 	{
 		ZoningStationWindowOpenClose(Station::Get(window_number));
 		CloseWindowById(WC_TRAINS_LIST,   VehicleListIdentifier(VL_STATION_LIST, VEH_TRAIN,    this->owner, this->window_number).Pack(), false);
@@ -1444,6 +1445,7 @@ struct StationViewWindow : public Window {
 		CloseWindowById(WC_AIRCRAFT_LIST, VehicleListIdentifier(VL_STATION_LIST, VEH_AIRCRAFT, this->owner, this->window_number).Pack(), false);
 
 		SetViewportCatchmentStation(Station::Get(this->window_number), false);
+		this->Window::Close();
 	}
 
 	void OnInit() override
@@ -2545,11 +2547,12 @@ struct SelectStationWindow : Window {
 		_thd.freeze = true;
 	}
 
-	~SelectStationWindow()
+	void Close() override
 	{
 		SetViewportCatchmentStation(nullptr, true);
 
 		_thd.freeze = false;
+		this->Window::Close();
 	}
 
 	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
@@ -2684,7 +2687,7 @@ static bool StationJoinerNeeded(const CommandContainer &cmd, TileArea ta)
 	Window *selection_window = FindWindowById(WC_SELECT_STATION, 0);
 	if (selection_window != nullptr) {
 		/* Abort current distant-join and start new one */
-		delete selection_window;
+		selection_window->Close();
 		UpdateTileSelection();
 	}
 
@@ -3097,7 +3100,7 @@ public:
 	void OnMouseLoop() override
 	{
 		if (!_cursor.in_window || !(_settings_client.gui.hover_delay_ms == 0 ? _right_button_down : _mouse_hovering)) {
-			delete this;
+			this->Close();
 		}
 	}
 };

src/tbtr_template_gui_create.cpp

@@ -166,7 +166,7 @@ public:
 		UpdateButtonState();
 	}
 
-	~TemplateCreateWindow()
+	void Close() override
 	{
 		if (virtual_train != nullptr) {
 			DoCommandP(0, virtual_train->index, 0, CMD_DELETE_VIRTUAL_TRAIN);
@@ -177,6 +177,7 @@ public:
 		*create_window_open = false;
 		CloseWindowById(WC_BUILD_VIRTUAL_TRAIN, this->window_number);
 		InvalidateWindowClassesData(WC_TEMPLATEGUI_MAIN);
+		this->Window::Close();
 	}
 
 	void SetVirtualTrain(Train* const train)
@@ -208,7 +209,7 @@ public:
 
 		if (this->template_index != INVALID_VEHICLE) {
 			if (TemplateVehicle::GetIfValid(this->template_index) == nullptr) {
-				delete this;
+				this->Close();
 				return;
 			}
 		}
@@ -244,11 +245,11 @@ public:
 				} else if (this->template_index != INVALID_VEHICLE) {
 					DoCommandP(0, this->template_index, 0, CMD_DELETE_TEMPLATE_VEHICLE);
 				}
-				delete this;
+				this->Close();
 				break;
 			}
 			case TCW_CANCEL: {
-				delete this;
+				this->Close();
 				break;
 			}
 			case TCW_REFIT: {

src/tbtr_template_gui_main.cpp

@@ -255,8 +255,9 @@ public:
 		this->BuildTemplateGuiList();
 	}
 
-	~TemplateReplaceWindow() {
+	void Close() override {
 		CloseWindowById(WC_CREATE_TEMPLATE, this->window_number);
+		this->Window::Close();
 	}
 
 	virtual void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override

src/terraform_gui.cpp

@@ -213,10 +213,6 @@ struct TerraformToolbarWindow : Window {
 		this->last_user_action = WIDGET_LIST_END;
 	}
 
-	~TerraformToolbarWindow()
-	{
-	}
-
 	void OnInit() override
 	{
 		/* Don't show the place object button when there are no objects to place. */

src/timetable_gui.cpp

@@ -370,11 +370,12 @@ struct TimetableWindow : GeneralVehicleWindow {
 		this->owner = this->vehicle->owner;
 	}
 
-	~TimetableWindow()
+	void Close() override
 	{
 		if (!FocusWindowById(WC_VEHICLE_VIEW, this->window_number)) {
 			MarkDirtyFocusedRoutePaths(this->vehicle);
 		}
+		this->GeneralVehicleWindow::Close();
 	}
 
 	/**
@@ -1165,7 +1166,7 @@ struct TimetableWindow : GeneralVehicleWindow {
 		}
 	}
 
-	virtual void OnFocusLost(Window *newly_focused_window) override
+	virtual void OnFocusLost(bool closing, Window *newly_focused_window) override
 	{
 		if (HasFocusedVehicleChanged(this->window_number, newly_focused_window)) {
 			MarkDirtyFocusedRoutePaths(this->vehicle);

src/town_gui.cpp

@@ -534,9 +534,10 @@ public:
 		nvp->InitializeViewport(this, this->town->xy, ScaleZoomGUI(ZOOM_LVL_TOWN));
 	}
 
-	~TownViewWindow()
+	void Close() override
 	{
 		SetViewportCatchmentTown(Town::Get(this->window_number), false);
+		this->Window::Close();
 	}
 
 	void SetStringParameters(int widget) const override
@@ -2116,7 +2117,7 @@ struct SelectTownWindow : Window {
 		DoCommandP(&this->cmd);
 
 		/* Close the window */
-		delete this;
+		this->Close();
 	}
 
 	virtual void OnResize()

src/tracerestrict_gui.cpp

@@ -1780,7 +1780,7 @@ public:
 		this->ReloadProgramme();
 	}
 
-	~TraceRestrictWindow()
+	void Close() override
 	{
 		extern const TraceRestrictProgram *_viewport_highlight_tracerestrict_program;
 		if (_viewport_highlight_tracerestrict_program != nullptr) {
@@ -1789,6 +1789,7 @@ public:
 				SetViewportCatchmentTraceRestrictProgram(prog, false);
 			}
 		}
+		this->Window::Close();
 	}
 
 	virtual void OnClick(Point pt, int widget, int click_count) override
@@ -3844,9 +3845,10 @@ public:
 		this->owner = vli.company;
 	}
 
-	~TraceRestrictSlotWindow()
+	void Close() override
 	{
 		*this->sorting = this->vehgroups.GetListing();
+		this->Window::Close();
 	}
 
 	virtual void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override

src/vehicle_gui.cpp

@@ -906,7 +906,7 @@ struct RefitWindow : public Window {
 		this->SetWidgetDisabledState(WID_VR_REFIT, this->sel[0] < 0);
 	}
 
-	~RefitWindow()
+	void Close() override
 	{
 		if (this->window_number != INVALID_VEHICLE) {
 			if (!FocusWindowById(WC_VEHICLE_VIEW, this->window_number)) {
@@ -916,6 +916,7 @@ struct RefitWindow : public Window {
 				}
 			}
 		}
+		this->Window::Close();
 	}
 
 	void OnFocus(Window *previously_focused_window) override
@@ -928,7 +929,7 @@ struct RefitWindow : public Window {
 		}
 	}
 
-	void OnFocusLost(Window *newly_focused_window) override
+	void OnFocusLost(bool closing, Window *newly_focused_window) override
 	{
 		if (HasFocusedVehicleChanged(this->window_number, newly_focused_window)) {
 			if (this->window_number != INVALID_VEHICLE) {
@@ -1350,10 +1351,10 @@ struct RefitWindow : public Window {
 						bool delete_window = this->selected_vehicle == v->index && this->num_vehicles == UINT8_MAX;
 						if (DoCommandP(v->tile, this->selected_vehicle, this->cargo->cargo | this->cargo->subtype << 8 | this->num_vehicles << 16 | this->is_virtual_train << 31,
 								GetCmdRefitVeh(v)) && delete_window) {
-							delete this;
+							this->Close();
 						}
 					} else {
-						if (DoCommandP(v->tile, v->index, this->cargo->cargo | this->cargo->subtype << 8 | this->order << 16, CMD_ORDER_REFIT)) delete this;
+						if (DoCommandP(v->tile, v->index, this->cargo->cargo | this->cargo->subtype << 8 | this->order << 16, CMD_ORDER_REFIT)) this->Close();
 					}
 				}
 				break;
@@ -2262,10 +2263,11 @@ public:
 		if (this->vli.company != OWNER_NONE) this->owner = this->vli.company;
 	}
 
-	~VehicleListWindow()
+	void Close() override
 	{
 		*this->sorting = this->vehgroups.GetListing();
 		this->RefreshRouteOverlay();
+		this->Window::Close();
 	}
 
 	virtual void OnFocus(Window *previously_focused_window) override
@@ -2273,7 +2275,7 @@ public:
 		this->RefreshRouteOverlay();
 	}
 
-	virtual void OnFocusLost(Window *newly_focused_window) override
+	virtual void OnFocusLost(bool closing, Window *newly_focused_window) override
 	{
 		this->RefreshRouteOverlay();
 	}
@@ -2671,7 +2673,7 @@ public:
 			/* This needs to be done in command-scope to enforce rebuilding before resorting invalid data */
 			this->vehgroups.ForceRebuild();
 			if (this->vli.type == VL_SHARED_ORDERS && !_settings_client.gui.enable_single_veh_shared_order_gui && this->vehicles.size() == 1) {
-				delete this;
+				this->Close();
 				return;
 			}
 		} else {
@@ -2885,7 +2887,7 @@ struct VehicleDetailsWindow : Window {
 		if (v->type == VEH_TRAIN && _shift_pressed) this->tab = TDW_TAB_TOTALS;
 	}
 
-	~VehicleDetailsWindow()
+	void Close() override
 	{
 		if (this->window_number != INVALID_VEHICLE) {
 			if (!FocusWindowById(WC_VEHICLE_VIEW, this->window_number)) {
@@ -2895,6 +2897,7 @@ struct VehicleDetailsWindow : Window {
 				}
 			}
 		}
+		this->Window::Close();
 	}
 
 	/**
@@ -3401,7 +3404,7 @@ struct VehicleDetailsWindow : Window {
 		}
 	}
 
-	virtual void OnFocusLost(Window *newly_focused_window) override
+	virtual void OnFocusLost(bool closing, Window *newly_focused_window) override
 	{
 		if (HasFocusedVehicleChanged(this->window_number, newly_focused_window)) {
 			if (this->window_number != INVALID_VEHICLE) {
@@ -3676,7 +3679,7 @@ public:
 		this->UpdateButtonStatus();
 	}
 
-	~VehicleViewWindow()
+	void Close() override
 	{
 		if (this->window_number != INVALID_VEHICLE) {
 			const Vehicle *v = Vehicle::Get(this->window_number);
@@ -3690,6 +3693,8 @@ public:
 		if (this->fixed_route_overlay_active) {
 			RemoveFixedViewportRoutePath(this->window_number);
 		}
+
+		this->Window::Close();
 	}
 
 	virtual void OnFocus(Window *previously_focused_window) override
@@ -3702,7 +3707,7 @@ public:
 		}
 	}
 
-	virtual void OnFocusLost(Window *newly_focused_window) override
+	virtual void OnFocusLost(bool closing, Window *newly_focused_window) override
 	{
 		if (HasFocusedVehicleChanged(this->window_number, newly_focused_window)) {
 			if (this->window_number != INVALID_VEHICLE) {

src/waypoint_gui.cpp

@@ -106,11 +106,11 @@ public:
 		this->OnInvalidateData(0);
 	}
 
-	~WaypointWindow()
+	void Close() override
 	{
 		CloseWindowById(GetWindowClassForVehicleType(this->vt), VehicleListIdentifier(VL_STATION_LIST, this->vt, this->owner, this->window_number).Pack(), false);
-
 		SetViewportCatchmentWaypoint(Waypoint::Get(this->window_number), false);
+		this->Window::Close();
 	}
 
 	void SetStringParameters(int widget) const override

src/widgets/dropdown.cpp

@@ -179,12 +179,12 @@ struct DropdownWindow : Window {
 		this->scrolling_timer  = GUITimer(MILLISECONDS_PER_TICK);
 	}
 
-	~DropdownWindow()
+	void Close() override
 	{
 		/* Make the dropdown "invisible", so it doesn't affect new window placement.
 		 * Also mark it dirty in case the callback deals with the screen. (e.g. screenshots). */
-		this->window_class = WC_INVALID;
 		this->SetDirty();
+		this->Window::Close();
 
 		Window *w2 = FindWindowById(this->parent_wnd_class, this->parent_wnd_num);
 		if (w2 != nullptr) {
@@ -291,7 +291,7 @@ struct DropdownWindow : Window {
 	{
 		Window *w2 = FindWindowById(this->parent_wnd_class, this->parent_wnd_num);
 		if (w2 == nullptr) {
-			delete this;
+			this->Close();
 			return;
 		}
 
@@ -302,7 +302,7 @@ struct DropdownWindow : Window {
 			this->SetDirty();
 
 			w2->OnDropdownSelect(this->parent_button, this->selected_index);
-			delete this;
+			this->Close();
 			return;
 		}
 
@@ -312,7 +312,7 @@ struct DropdownWindow : Window {
 			if (!_left_button_clicked) {
 				this->drag_mode = false;
 				if (!this->GetDropDownItem(item)) {
-					if (this->instant_close) delete this;
+					if (this->instant_close) this->Close();
 					return;
 				}
 				this->click_delay = 2;
@@ -345,11 +345,11 @@ struct DropdownWindow : Window {
 		}
 	}
 
-	virtual void OnFocusLost(Window *newly_focused_window)
+	virtual void OnFocusLost(bool closing, Window *newly_focused_window)
 	{
 		if (this->sync_parent_focus & DDSF_LOST_FOCUS) {
 			Window *parent = FindWindowById(this->parent_wnd_class, this->parent_wnd_num);
-			if (parent) parent->OnFocusLost(newly_focused_window);
+			if (parent) parent->OnFocusLost(false, newly_focused_window);
 		}
 	}
 };

src/window.cpp

@@ -58,11 +58,11 @@ static Window *_mouseover_last_w = nullptr; ///< Window of the last OnMouseOver
 static Window *_last_scroll_window = nullptr; ///< Window of the last scroll event.
 
 /** List of windows opened at the screen sorted from the front. */
-WindowBase *_z_front_window = nullptr;
+Window *_z_front_window = nullptr;
 /** List of windows opened at the screen sorted from the back. */
-WindowBase *_z_back_window  = nullptr;
+Window *_z_back_window  = nullptr;
 /** List of windows in an arbitrary order, that is not instantaneously changed by bringing windows to the front. */
-WindowBase *_first_window  = nullptr;
+Window *_first_window  = nullptr;
 
 /** If false, highlight is white, otherwise the by the widget defined colour. */
 bool _window_highlight_colour = false;
@@ -470,7 +470,7 @@ void SetFocusedWindow(Window *w)
 	_focused_window = w;
 
 	/* So we can inform it that it lost focus */
-	if (old_focused != nullptr) old_focused->OnFocusLost(w);
+	if (old_focused != nullptr) old_focused->OnFocusLost(false, w);
 	if (_focused_window != nullptr) _focused_window->OnFocus(old_focused);
 }
 
@@ -561,7 +561,7 @@ void Window::OnFocus(Window *previously_focused_window)
 /**
  * Called when window loses focus
  */
-void Window::OnFocusLost(Window *newly_focused_window)
+void Window::OnFocusLost(bool closing, Window *newly_focused_window)
 {
 	if (this->nested_focus != nullptr && this->nested_focus->type == WWT_EDITBOX) VideoDriver::GetInstance()->EditBoxLostFocus();
 }
@@ -747,7 +747,7 @@ static void DispatchLeftClickEvent(Window *w, int x, int y, int click_count)
 		}
 
 		case WWT_CLOSEBOX: // 'X'
-			delete w;
+			w->Close();
 			return;
 
 		case WWT_CAPTION: // 'Title bar'
@@ -835,7 +835,7 @@ static void DispatchRightClickEvent(Window *w, int x, int y)
 
 	/* Right-click close is enabled and there is a closebox */
 	if (_settings_client.gui.right_mouse_wnd_close && (w->window_desc->flags & WDF_NO_CLOSE) == 0) {
-		delete w;
+		w->Close();
 	} 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, nullptr, TCC_RIGHT_CLICK);
 	}
@@ -1120,15 +1120,15 @@ void Window::CloseChildWindows(WindowClass wc) const
 {
 	Window *child = FindChildWindow(this, wc);
 	while (child != nullptr) {
-		delete child;
+		child->Close();
 		child = FindChildWindow(this, wc);
 	}
 }
 
 /**
- * Remove window and all its child windows from the window stack.
+ * Hide the window and all its child windows, and mark them for a later deletion.
  */
-Window::~Window()
+void Window::Close()
 {
 	if (_thd.window_class == this->window_class &&
 			_thd.window_number == this->window_number) {
@@ -1147,33 +1147,27 @@ Window::~Window()
 	/* Make sure we don't try to access this window as the focused window when it doesn't exist anymore. */
 	if (_focused_window == this) {
 		_focused_window = nullptr;
-		this->OnFocusLost(nullptr);
+		this->OnFocusLost(true, nullptr);
 	}
 
 	this->CloseChildWindows();
 
-	if (this->viewport != nullptr) DeleteWindowViewport(this);
-
 	this->SetDirtyAsBlocks();
 
+	this->window_class = WC_INVALID;
+}
+
+/**
+ * Remove window and all its child windows from the window stack.
+ */
+Window::~Window()
+{
+	assert(this->window_class == WC_INVALID);
+
+	if (this->viewport != nullptr) DeleteWindowViewport(this);
+
 	free(this->nested_array); // Contents is released through deletion of #nested_root.
 	delete this->nested_root;
-
-	/*
-	 * Make fairly sure that this is written, and not "optimized" away.
-	 * The delete operator is overwritten to not delete it; the deletion
-	 * happens at a later moment in time after the window has been
-	 * removed from the list of windows to prevent issues with items
-	 * being removed during the iteration as not one but more windows
-	 * may be removed by a single call to ~Window by means of the
-	 * CloseChildWindows function.
-	 */
-	const_cast<volatile WindowClass &>(this->window_class) = WC_INVALID;
-}
-
-void Window::Close()
-{
-	if (this->window_class != WC_INVALID) delete this;
 }
 
 /**
@@ -1232,7 +1226,7 @@ void CloseWindowById(WindowClass cls, WindowNumber number, bool force)
 {
 	Window *w = FindWindowById(cls, number);
 	if (w != nullptr && (force || (w->flags & WF_STICKY) == 0)) {
-		delete w;
+		w->Close();
 	}
 }
 
@@ -1247,9 +1241,9 @@ void CloseAllWindowsById(WindowClass cls, WindowNumber number, bool force)
 	if (cls < WC_END && !_present_window_types[cls]) return;
 
 	/* Note: the container remains stable, even when deleting windows. */
-	for (Window *w : Window::IterateUnordered()) {
+	for (Window *w : Window::Iterate()) {
 		if (w->window_class == cls && w->window_number == number && (force || (w->flags & WF_STICKY) == 0)) {
-			delete w;
+			w->Close();
 		}
 	}
 }
@@ -1263,9 +1257,9 @@ void CloseWindowByClass(WindowClass cls)
 	if (cls < WC_END && !_present_window_types[cls]) return;
 
 	/* Note: the container remains stable, even when deleting windows. */
-	for (Window *w : Window::IterateUnordered()) {
+	for (Window *w : Window::Iterate()) {
 		if (w->window_class == cls) {
-			delete w;
+			w->Close();
 		}
 	}
 }
@@ -1279,9 +1273,9 @@ void CloseWindowByClass(WindowClass cls)
 void DeleteCompanyWindows(CompanyID id)
 {
 	/* Note: the container remains stable, even when deleting windows. */
-	for (Window *w : Window::IterateUnordered()) {
+	for (Window *w : Window::Iterate()) {
 		if (w->owner == id) {
-			delete w;
+			w->Close();
 		}
 	}
 
@@ -1458,7 +1452,7 @@ static void AddWindowToZOrdering(Window *w)
 		w->z_front = w->z_back = nullptr;
 	} else {
 		/* Search down the z-ordering for its location. */
-		WindowBase *v = _z_front_window;
+		Window *v = _z_front_window;
 		uint last_z_priority = UINT_MAX;
 		(void)last_z_priority; // Unused without asserts
 		while (v != nullptr && (v->window_class == WC_INVALID || GetWindowZPriority(v->window_class) > GetWindowZPriority(w->window_class))) {
@@ -1498,7 +1492,7 @@ static void AddWindowToZOrdering(Window *w)
  * Removes a window from the z-ordering.
  * @param w Window to remove
  */
-static void RemoveWindowFromZOrdering(WindowBase *w)
+static void RemoveWindowFromZOrdering(Window *w)
 {
 	if (w->z_front == nullptr) {
 		dbg_assert(_z_front_window == w);
@@ -2003,13 +1997,8 @@ void UnInitWindowSystem()
 {
 	UnshowCriticalError();
 
-	for (Window *w : Window::IterateUnordered()) delete w;
+	for (Window *w : Window::Iterate()) w->Close();
-
+	Window::DeleteClosedWindows();
-	for (WindowBase *w = _z_front_window; w != nullptr; /* nothing */) {
-		WindowBase *to_del = w;
-		w = w->z_back;
-		free(to_del);
-	}
 
 	_z_front_window = nullptr;
 	_z_back_window = nullptr;
@@ -3237,7 +3226,37 @@ static void CheckSoftLimit()
 		if (deletable_count <= _settings_client.gui.window_soft_limit) break;
 
 		assert(last_deletable != nullptr);
-		delete last_deletable;
+		last_deletable->Close();
+	}
+}
+
+/**
+ * Delete all closed windows.
+ */
+/* static */ void Window::DeleteClosedWindows()
+{
+	bool reset_window_nexts = false;
+	_present_window_types.reset();
+
+	/* Do the actual free of the deleted windows. */
+	for (Window *v = _z_front_window; v != nullptr; /* nothing */) {
+		Window *w = v;
+		v = v->z_back;
+
+		if (w->window_class < WC_END) _present_window_types.set(w->window_class);
+
+		if (w->window_class != WC_INVALID) continue;
+
+		RemoveWindowFromZOrdering(w);
+		delete w;
+		reset_window_nexts = true;
+	}
+
+	if (reset_window_nexts) {
+		_first_window = _z_front_window;
+		for (Window *w = _z_front_window; w != nullptr; w = w->z_back) {
+			w->next_window = w->z_back;
+		}
 	}
 }
 
@@ -3252,30 +3271,7 @@ void InputLoop()
 
 	CheckSoftLimit();
 
-	bool reset_window_nexts = false;
+	Window::DeleteClosedWindows();
-
-	_present_window_types.reset();
-
-	/* Do the actual free of the deleted windows. */
-	for (WindowBase *v = _z_front_window; v != nullptr; /* nothing */) {
-		WindowBase *w = v;
-		v = v->z_back;
-
-		if (w->window_class < WC_END) _present_window_types.set(w->window_class);
-
-		if (w->window_class != WC_INVALID) continue;
-
-		RemoveWindowFromZOrdering(w);
-		free(w);
-		reset_window_nexts = true;
-	}
-
-	if (reset_window_nexts) {
-		_first_window = _z_front_window;
-		for (WindowBase *w = _z_front_window; w != nullptr; w = w->z_back) {
-			w->next_window = w->z_back;
-		}
-	}
 
 	if (_input_events_this_tick != 0) {
 		/* The input loop is called only once per GameLoop() - so we can clear the counter here */
@@ -3541,11 +3537,11 @@ void CallWindowGameTickEvent()
 void CloseNonVitalWindows()
 {
 	/* Note: the container remains stable, even when deleting windows. */
-	for (Window *w : Window::IterateUnordered()) {
+	for (Window *w : Window::Iterate()) {
 		if ((w->window_desc->flags & WDF_NO_CLOSE) == 0 &&
 				(w->flags & WF_STICKY) == 0) { // do not delete windows which are 'pinned'
 
-			delete w;
+			w->Close();
 		}
 	}
 }
@@ -3560,9 +3556,9 @@ void CloseNonVitalWindows()
 void CloseAllNonVitalWindows()
 {
 	/* Note: the container remains stable, even when closing windows. */
-	for (Window *w : Window::IterateUnordered()) {
+	for (Window *w : Window::Iterate()) {
 		if ((w->window_desc->flags & WDF_NO_CLOSE) == 0) {
-			delete w;
+			w->Close();
 		}
 	}
 }
@@ -3585,9 +3581,9 @@ void DeleteAllMessages()
 void CloseConstructionWindows()
 {
 	/* Note: the container remains stable, even when deleting windows. */
-	for (const Window *w : Window::IterateUnordered()) {
+	for (Window *w : Window::Iterate()) {
 		if (w->window_desc->flags & WDF_CONSTRUCTION) {
-			delete w;
+			w->Close();
 		}
 	}
 }
@@ -3598,9 +3594,9 @@ void CloseConstructionWindows()
 void CloseNetworkClientWindows()
 {
 	/* Note: the container remains stable, even when deleting windows. */
-	for (const Window *w : Window::IterateUnordered()) {
+	for (Window *w : Window::Iterate()) {
 		if (w->window_desc->flags & WDF_NETWORK) {
-			delete w;
+			w->Close();
 		}
 	}
 }
@@ -3807,14 +3803,13 @@ void RelocateAllWindows(int neww, int newh)
 }
 
 /**
- * Destructor of the base class PickerWindowBase
+ * Hide the window and all its child windows, and mark them for a later deletion.
- * Main utility is to stop the base Window destructor from triggering
+ * Always call ResetObjectToPlace() when closing a PickerWindow.
- * a free while the child will already be free, in this case by the ResetObjectToPlace().
  */
-PickerWindowBase::~PickerWindowBase()
+void PickerWindowBase::Close()
 {
-	this->window_class = WC_INVALID; // stop the ancestor from freeing the already (to be) child
 	ResetObjectToPlace();
+	this->Window::Close();
 }
 
 char *DumpWindowInfo(char *b, const char *last, const Window *w)

src/window_gui.h

@@ -77,9 +77,9 @@ static inline void DrawFrameRect(const Rect &r, Colours colour, FrameFlags flags
 void DrawCaption(const Rect &r, Colours colour, Owner owner, TextColour text_colour, StringID str, StringAlignment align, FontSize fs);
 
 /* window.cpp */
-extern WindowBase *_z_front_window;
+extern Window *_z_front_window;
-extern WindowBase *_z_back_window;
+extern Window *_z_back_window;
-extern WindowBase *_first_window;
+extern Window *_first_window;
 extern Window *_focused_window;
 
 inline uint64 GetWindowUpdateNumber()
@@ -233,51 +233,27 @@ enum TooltipCloseCondition {
 	TCC_EXIT_VIEWPORT,
 };
 
-struct WindowBase {
-	WindowBase *z_front;             ///< The window in front of us in z-order.
-	WindowBase *z_back;              ///< The window behind us in z-order.
-	WindowBase *next_window;         ///< The next window in arbitrary iteration order.
-	WindowClass window_class;        ///< Window class
-
-	virtual ~WindowBase() {}
-
-	/**
-	 * Memory allocator for a single class instance.
-	 * @param size the amount of bytes to allocate.
-	 * @return the given amounts of bytes zeroed.
-	 */
-	inline void *operator new(size_t size) { return CallocT<byte>(size); }
-
-protected:
-	WindowBase() {}
-
-private:
-	/**
-	 * Memory allocator for an array of class instances.
-	 * @param size the amount of bytes to allocate.
-	 * @return the given amounts of bytes zeroed.
-	 */
-	inline void *operator new[](size_t size) { NOT_REACHED(); }
-
-	/**
-	 * Memory release for a single class instance.
-	 * @param ptr  the memory to free.
-	 */
-	inline void operator delete(void *ptr) { NOT_REACHED(); }
-
-	/**
-	 * Memory release for an array of class instances.
-	 * @param ptr  the memory to free.
-	 */
-	inline void operator delete[](void *ptr) { NOT_REACHED(); }
-};
-
 typedef std::vector<const Vehicle *> VehicleList;
 
 /**
  * Data structure for an opened window
  */
-struct Window : WindowBase {
+struct Window : ZeroedMemoryAllocator {
+	Window *z_front;             ///< The window in front of us in z-order.
+	Window *z_back;              ///< The window behind us in z-order.
+	Window *next_window;         ///< The next window in arbitrary iteration order.
+	WindowClass window_class;        ///< Window class
+
+private:
+	/**
+	 * Helper allocation function to disallow something.
+	 * Don't allow arrays; arrays of Windows are pointless as you need
+	 * to destruct them all at the same time too, which is kinda hard.
+	 * @param size the amount of space not to allocate
+	 */
+	inline void *operator new[](size_t size) { NOT_REACHED(); }
+	inline void operator delete[](void *ptr) { NOT_REACHED(); }
+
 protected:
 	void InitializeData(WindowNumber window_number);
 	void InitializePositionSize(int x, int y, int min_width, int min_height);
@@ -285,32 +261,13 @@ protected:
 
 	std::vector<int> scheduled_invalidation_data;  ///< Data of scheduled OnInvalidateData() calls.
 
+	virtual ~Window();
+
 public:
 	Window(WindowDesc *desc);
 
-	virtual ~Window();
-
 	virtual void Close();
-
+	static void DeleteClosedWindows();
-	/**
-	 * Helper allocation function to disallow something.
-	 * Don't allow arrays; arrays of Windows are pointless as you need
-	 * to destruct them all at the same time too, which is kinda hard.
-	 * @param size the amount of space not to allocate
-	 */
-	inline void *operator new[](size_t size)
-	{
-		NOT_REACHED();
-	}
-
-	/**
-	 * Helper allocation function to disallow something.
-	 * Don't free the window directly; it corrupts the linked list when iterating
-	 * @param ptr the pointer not to free
-	 */
-	inline void operator delete(void *ptr)
-	{
-	}
 
 	WindowDesc *window_desc;    ///< Window description
 	WindowFlags flags;          ///< Window flags
@@ -601,7 +558,7 @@ public:
 
 	virtual void OnFocus(Window *previously_focused_window);
 
-	virtual void OnFocusLost(Window *newly_focused_window);
+	virtual void OnFocusLost(bool closing, Window *newly_focused_window);
 
 	/**
 	 * A key has been pressed.
@@ -845,7 +802,7 @@ public:
 	virtual void ShowNewGRFInspectWindow() const { NOT_REACHED(); }
 
 	template<class T>
-	using window_base_t = std::conditional_t<std::is_const<T>{}, WindowBase const, WindowBase>;
+	using window_type = std::conditional_t<std::is_const<T>{}, Window const, Window>;
 
 	enum IterationMode {
 		IM_FROM_FRONT,
@@ -866,7 +823,7 @@ public:
 		typedef size_t difference_type;
 		typedef std::forward_iterator_tag iterator_category;
 
-		explicit WindowIterator(window_base_t<T> *start) : w(start)
+		explicit WindowIterator(window_type<T> *start) : w(start)
 		{
 			this->Validate();
 		}
@@ -877,7 +834,7 @@ public:
 		WindowIterator & operator++() { this->Next(); this->Validate(); return *this; }
 
 	private:
-		window_base_t<T> *w;
+		window_type<T> *w;
 		void Validate() { while (this->w != nullptr && this->w->window_class == WC_INVALID) this->Next(); }
 
 		void Next()
@@ -901,16 +858,16 @@ public:
 	/**
 	 * Iterable ensemble of all valid Windows
 	 * @tparam T Type of the class/struct that is going to be iterated
-	 * @tparam Tfront Wether we iterate from front
+	 * @tparam Tmode Iteration mode
 	 */
 	template <class T, IterationMode Tmode>
-	struct Iterate {
+	struct IterateCommon {
-		Iterate(window_base_t<T> *from) : from(from) {}
+		IterateCommon(window_type<T> *from) : from(from) {}
 		WindowIterator<T, Tmode> begin() { return WindowIterator<T, Tmode>(this->from); }
 		WindowIterator<T, Tmode> end() { return WindowIterator<T, Tmode>(nullptr); }
 		bool empty() { return this->begin() == this->end(); }
 	private:
-		window_base_t<T> *from;
+		window_type<T> *from;
 	};
 
 	/**
@@ -920,7 +877,7 @@ public:
 	 * @return an iterable ensemble of all valid Window
 	 */
 	template <class T = Window>
-	static Iterate<T, IM_FROM_BACK> IterateFromBack(window_base_t<T> *from = _z_back_window) { return Iterate<T, IM_FROM_BACK>(from); }
+	static IterateCommon<T, IM_FROM_BACK> IterateFromBack(window_type<T> *from = _z_back_window) { return IterateCommon<T, IM_FROM_BACK>(from); }
 
 	/**
 	 * Returns an iterable ensemble of all valid Window from front to back
@@ -929,7 +886,7 @@ public:
 	 * @return an iterable ensemble of all valid Window
 	 */
 	template <class T = Window>
-	static Iterate<T, IM_FROM_FRONT> IterateFromFront(window_base_t<T> *from = _z_front_window) { return Iterate<T, IM_FROM_FRONT>(from); }
+	static IterateCommon<T, IM_FROM_FRONT> IterateFromFront(window_type<T> *from = _z_front_window) { return IterateCommon<T, IM_FROM_FRONT>(from); }
 
 	/**
 	 * Returns an iterable ensemble of all valid Window in an arbitrary order which is safe to use when deleting
@@ -938,7 +895,7 @@ public:
 	 * @return an iterable ensemble of all valid Window
 	 */
 	template <class T = Window>
-	static Iterate<T, IM_ARBITRARY> IterateUnordered(window_base_t<T> *from = _first_window) { return Iterate<T, IM_ARBITRARY>(from); }
+	static IterateCommon<T, IM_ARBITRARY> Iterate(window_type<T> *from = _first_window) { return IterateCommon<T, IM_ARBITRARY>(from); }
 };
 
 /**
@@ -1001,7 +958,7 @@ public:
 		this->parent = parent;
 	}
 
-	virtual ~PickerWindowBase();
+	void Close() override;
 };
 
 Window *BringWindowToFrontById(WindowClass cls, WindowNumber number);