Codechange: introduce GetMainWindow() to properly account for nullptr checks

Some nullptr checks have been removed as they were not triggered with nullptr
with the null video driver and in dedicated server mode.

src/console_cmds.cpp

@@ -295,7 +295,7 @@ DEF_CONSOLE_CMD(ConZoomToLevel)
 				} else if (level > _settings_client.gui.zoom_max) {
 					IConsolePrint(CC_ERROR, "Current client settings do not allow zooming out beyond level {}.", _settings_client.gui.zoom_max);
 				} else {
-					Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+					Window *w = GetMainWindow();
 					Viewport *vp = w->viewport;
 					while (vp->zoom > level) DoZoomInOutWindow(ZOOM_IN, w);
 					while (vp->zoom < level) DoZoomInOutWindow(ZOOM_OUT, w);

src/error_gui.cpp

@@ -235,7 +235,7 @@ public:
 		int scr_bot = GetMainViewBottom() - 20;
 
 		Point pt = RemapCoords(this->position.x, this->position.y, GetSlopePixelZOutsideMap(this->position.x, this->position.y));
-		const Viewport *vp = FindWindowById(WC_MAIN_WINDOW, 0)->viewport;
+		const Viewport *vp = GetMainWindow()->viewport;
 		if (this->face == INVALID_COMPANY) {
 			/* move x pos to opposite corner */
 			pt.x = UnScaleByZoom(pt.x - vp->virtual_left, vp->zoom) + vp->left;

src/genworld.cpp

@@ -321,9 +321,7 @@ void GenerateWorld(GenWorldMode mode, uint size_x, uint size_y, bool reset_setti
 	ShowGenerateWorldProgress();
 
 	/* Centre the view on the map */
-	if (FindWindowById(WC_MAIN_WINDOW, 0) != nullptr) {
-		ScrollMainWindowToTile(TileXY(MapSizeX() / 2, MapSizeY() / 2), true);
-	}
+	ScrollMainWindowToTile(TileXY(MapSizeX() / 2, MapSizeY() / 2), true);
 
 	_GenerateWorld();
 }

src/intro_gui.cpp

@@ -222,7 +222,7 @@ struct SelectGameWindow : public Window {
 		}
 
 		IntroGameViewportCommand &vc = intro_viewport_commands[this->cur_viewport_command_index];
-		Window *mw = FindWindowByClass(WC_MAIN_WINDOW);
+		Window *mw = GetMainWindow();
 		Viewport *vp = mw->viewport;
 
 		/* Early exit if the current command hasn't elapsed and isn't animated. */

src/linkgraph/linkgraph_gui.cpp

@@ -553,7 +553,7 @@ LinkGraphLegendWindow::LinkGraphLegendWindow(WindowDesc *desc, int window_number
 {
 	this->InitNested(window_number);
 	this->InvalidateData(0);
-	this->SetOverlay(FindWindowById(WC_MAIN_WINDOW, 0)->viewport->overlay);
+	this->SetOverlay(GetMainWindow()->viewport->overlay);
 }
 
 /**

src/main_gui.cpp

@@ -157,7 +157,7 @@ void FixTitleGameZoom(int zoom_adjust)
 {
 	if (_game_mode != GM_MENU) return;
 
-	Viewport *vp = FindWindowByClass(WC_MAIN_WINDOW)->viewport;
+	Viewport *vp = GetMainWindow()->viewport;
 
 	/* Adjust the zoom in/out.
 	 * Can't simply add, since operator+ is not defined on the ZoomLevel type. */

src/misc_gui.cpp

@@ -1264,7 +1264,7 @@ static WindowDesc _query_desc(
  */
 void ShowQuery(StringID caption, StringID message, Window *parent, QueryCallbackProc *callback)
 {
-	if (parent == nullptr) parent = FindWindowById(WC_MAIN_WINDOW, 0);
+	if (parent == nullptr) parent = GetMainWindow();
 
 	for (Window *w : Window::Iterate()) {
 		if (w->window_class != WC_CONFIRM_POPUP_QUERY) continue;

src/network/network_gui.cpp

@@ -2517,6 +2517,6 @@ void ShowNetworkAskRelay(const std::string &server_connection_string, const std:
 {
 	CloseWindowByClass(WC_NETWORK_ASK_RELAY);
 
-	Window *parent = FindWindowById(WC_MAIN_WINDOW, 0);
+	Window *parent = GetMainWindow();
 	new NetworkAskRelayWindow(&_network_ask_relay_desc, parent, server_connection_string, relay_connection_string, token);
 }

src/saveload/misc_sl.cpp

@@ -34,18 +34,16 @@ ZoomLevel _saved_scrollpos_zoom;
 
 void SaveViewportBeforeSaveGame()
 {
-	const Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+	const Window *w = GetMainWindow();
 
-	if (w != nullptr) {
-		_saved_scrollpos_x = w->viewport->scrollpos_x;
-		_saved_scrollpos_y = w->viewport->scrollpos_y;
-		_saved_scrollpos_zoom = w->viewport->zoom;
-	}
+	_saved_scrollpos_x = w->viewport->scrollpos_x;
+	_saved_scrollpos_y = w->viewport->scrollpos_y;
+	_saved_scrollpos_zoom = w->viewport->zoom;
 }
 
 void ResetViewportAfterLoadGame()
 {
-	Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+	Window *w = GetMainWindow();
 
 	w->viewport->scrollpos_x = _saved_scrollpos_x;
 	w->viewport->scrollpos_y = _saved_scrollpos_y;

src/screenshot.cpp

@@ -732,7 +732,7 @@ void SetupScreenshotViewport(ScreenshotType t, Viewport *vp, uint32 width, uint3
 		case SC_CRASHLOG: {
 			assert(width == 0 && height == 0);
 
-			Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+			Window *w = GetMainWindow();
 			vp->virtual_left   = w->viewport->virtual_left;
 			vp->virtual_top    = w->viewport->virtual_top;
 			vp->virtual_width  = w->viewport->virtual_width;
@@ -776,7 +776,7 @@ void SetupScreenshotViewport(ScreenshotType t, Viewport *vp, uint32 width, uint3
 		default: {
 			vp->zoom = (t == SC_ZOOMEDIN) ? _settings_client.gui.zoom_min : ZOOM_LVL_VIEWPORT;
 
-			Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+			Window *w = GetMainWindow();
 			vp->virtual_left   = w->viewport->virtual_left;
 			vp->virtual_top    = w->viewport->virtual_top;
 

src/smallmap_gui.cpp

@@ -941,7 +941,7 @@ void SmallMapWindow::DrawTowns(const DrawPixelInfo *dpi) const
 void SmallMapWindow::DrawMapIndicators() const
 {
 	/* Find main viewport. */
-	const Viewport *vp = FindWindowById(WC_MAIN_WINDOW, 0)->viewport;
+	const Viewport *vp = GetMainWindow()->viewport;
 
 	Point upper_left_smallmap_coord  = InverseRemapCoords2(vp->virtual_left, vp->virtual_top);
 	Point lower_right_smallmap_coord = InverseRemapCoords2(vp->virtual_left + vp->virtual_width - 1, vp->virtual_top + vp->virtual_height - 1);
@@ -1433,7 +1433,7 @@ int SmallMapWindow::GetPositionOnLegend(Point pt)
 			if (click_count > 0) this->mouse_capture_widget = widget;
 
 			const NWidgetBase *wid = this->GetWidget<NWidgetBase>(WID_SM_MAP);
-			Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+			Window *w = GetMainWindow();
 			int sub;
 			pt = this->PixelToTile(pt.x - wid->pos_x, pt.y - wid->pos_y, &sub);
 			ScrollWindowTo(this->scroll_x + pt.x * TILE_SIZE, this->scroll_y + pt.y * TILE_SIZE, -1, w);
@@ -1665,7 +1665,7 @@ void SmallMapWindow::SetNewScroll(int sx, int sy, int sub)
  */
 void SmallMapWindow::SmallMapCenterOnCurrentPos()
 {
-	const Viewport *vp = FindWindowById(WC_MAIN_WINDOW, 0)->viewport;
+	const Viewport *vp = GetMainWindow()->viewport;
 	Point viewport_center = InverseRemapCoords2(vp->virtual_left + vp->virtual_width / 2, vp->virtual_top + vp->virtual_height / 2);
 
 	int sub;
@@ -1882,7 +1882,7 @@ void ShowSmallMap()
  */
 bool ScrollMainWindowTo(int x, int y, int z, bool instant)
 {
-	bool res = ScrollWindowTo(x, y, z, FindWindowById(WC_MAIN_WINDOW, 0), instant);
+	bool res = ScrollWindowTo(x, y, z, GetMainWindow(), instant);
 
 	/* If a user scrolls to a tile (via what way what so ever) and already is on
 	 * that tile (e.g.: pressed twice), move the smallmap to that location,

src/toolbar_gui.cpp

@@ -884,7 +884,7 @@ static CallBackFunction MenuClickShowAir(int index)
 
 static CallBackFunction ToolbarZoomInClick(Window *w)
 {
-	if (DoZoomInOutWindow(ZOOM_IN, FindWindowById(WC_MAIN_WINDOW, 0))) {
+	if (DoZoomInOutWindow(ZOOM_IN, GetMainWindow())) {
 		w->HandleButtonClick((_game_mode == GM_EDITOR) ? (byte)WID_TE_ZOOM_IN : (byte)WID_TN_ZOOM_IN);
 		if (_settings_client.sound.click_beep) SndPlayFx(SND_15_BEEP);
 	}
@@ -895,7 +895,7 @@ static CallBackFunction ToolbarZoomInClick(Window *w)
 
 static CallBackFunction ToolbarZoomOutClick(Window *w)
 {
-	if (DoZoomInOutWindow(ZOOM_OUT, FindWindowById(WC_MAIN_WINDOW, 0))) {
+	if (DoZoomInOutWindow(ZOOM_OUT, GetMainWindow())) {
 		w->HandleButtonClick((_game_mode == GM_EDITOR) ? (byte)WID_TE_ZOOM_OUT : (byte)WID_TN_ZOOM_OUT);
 		if (_settings_client.sound.click_beep) SndPlayFx(SND_15_BEEP);
 	}
@@ -2146,7 +2146,7 @@ struct MainToolbarWindow : Window {
 	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
-		if (FindWindowById(WC_MAIN_WINDOW, 0) != nullptr) HandleZoomMessage(this, FindWindowById(WC_MAIN_WINDOW, 0)->viewport, WID_TN_ZOOM_IN, WID_TN_ZOOM_OUT);
+		HandleZoomMessage(this, GetMainWindow()->viewport, WID_TN_ZOOM_IN, WID_TN_ZOOM_OUT);
 	}
 
 	static HotkeyList hotkeys;
@@ -2520,7 +2520,7 @@ struct ScenarioEditorToolbarWindow : Window {
 	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
-		if (FindWindowById(WC_MAIN_WINDOW, 0) != nullptr) HandleZoomMessage(this, FindWindowById(WC_MAIN_WINDOW, 0)->viewport, WID_TE_ZOOM_IN, WID_TE_ZOOM_OUT);
+		HandleZoomMessage(this, GetMainWindow()->viewport, WID_TE_ZOOM_IN, WID_TE_ZOOM_OUT);
 	}
 
 	void OnQueryTextFinished(char *str) override

src/vehicle_gui.cpp

@@ -3118,7 +3118,7 @@ public:
 				if (_ctrl_pressed) {
 					ShowExtraViewportWindow(TileVirtXY(v->x_pos, v->y_pos));
 				} else {
-					const Window *mainwindow = FindWindowById(WC_MAIN_WINDOW, 0);
+					const Window *mainwindow = GetMainWindow();
 					if (click_count > 1 && mainwindow->viewport->zoom <= ZOOM_LVL_OUT_4X) {
 						/* main window 'follows' vehicle */
 						mainwindow->viewport->follow_vehicle = v->index;
@@ -3176,9 +3176,9 @@ public:
 	{
 		/* If the hotkey is not for any widget in the UI (i.e. for honking) */
 		if (hotkey == WID_VV_HONK_HORN) {
-			const Window* mainwindow = FindWindowById(WC_MAIN_WINDOW, 0);
-			const Vehicle* v = Vehicle::Get(window_number);
-			/*Only play the sound if we're following this vehicle */
+			const Window *mainwindow = GetMainWindow();
+			const Vehicle *v = Vehicle::Get(window_number);
+			/* Only play the sound if we're following this vehicle */
 			if (mainwindow->viewport->follow_vehicle == v->index) {
 				v->PlayLeaveStationSound(true);
 			}
@@ -3342,8 +3342,8 @@ bool VehicleClicked(const GUIVehicleGroup &vehgroup)
 
 void StopGlobalFollowVehicle(const Vehicle *v)
 {
-	Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
-	if (w != nullptr && w->viewport->follow_vehicle == v->index) {
+	Window *w = GetMainWindow();
+	if (w->viewport->follow_vehicle == v->index) {
 		ScrollMainWindowTo(v->x_pos, v->y_pos, v->z_pos, true); // lock the main view on the vehicle's last position
 		w->viewport->follow_vehicle = INVALID_VEHICLE;
 	}

src/viewport_gui.cpp

@@ -63,7 +63,7 @@ public:
 		Point pt;
 		if (tile == INVALID_TILE) {
 			/* No tile? Use center of main viewport. */
-			const Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+			const Window *w = GetMainWindow();
 
 			/* center on same place as main window (zoom is maximum, no adjustment needed) */
 			pt.x = w->viewport->scrollpos_x + w->viewport->virtual_width / 2;
@@ -95,7 +95,7 @@ public:
 			case WID_EV_ZOOM_OUT: DoZoomInOutWindow(ZOOM_OUT, this); break;
 
 			case WID_EV_MAIN_TO_VIEW: { // location button (move main view to same spot as this view) 'Paste Location'
-				Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+				Window *w = GetMainWindow();
 				int x = this->viewport->scrollpos_x; // Where is the main looking at
 				int y = this->viewport->scrollpos_y;
 
@@ -107,7 +107,7 @@ public:
 			}
 
 			case WID_EV_VIEW_TO_MAIN: { // inverse location button (move this view to same spot as main view) 'Copy Location'
-				const Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+				const Window *w = GetMainWindow();
 				int x = w->viewport->scrollpos_x;
 				int y = w->viewport->scrollpos_y;
 

src/window.cpp

@@ -1178,6 +1178,18 @@ Window *FindWindowByClass(WindowClass cls)
 	return nullptr;
 }
 
+/**
+ * Get the main window, i.e. FindWindowById(WC_MAIN_WINDOW, 0).
+ * If the main window is not available, this function will trigger an assert.
+ * @return Pointer to the main window.
+ */
+Window *GetMainWindow()
+{
+	Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+	assert(w != nullptr);
+	return w;
+}
+
 /**
  * Close a window by its class and window number (if it is open).
  * @param cls Window class
@@ -2431,7 +2443,7 @@ static EventState HandleViewportScroll()
 		return ES_NOT_HANDLED;
 	}
 
-	if (_last_scroll_window == FindWindowById(WC_MAIN_WINDOW, 0) && _last_scroll_window->viewport->follow_vehicle != INVALID_VEHICLE) {
+	if (_last_scroll_window == GetMainWindow() && _last_scroll_window->viewport->follow_vehicle != INVALID_VEHICLE) {
 		/* If the main window is following a vehicle, then first let go of it! */
 		const Vehicle *veh = Vehicle::Get(_last_scroll_window->viewport->follow_vehicle);
 		ScrollMainWindowTo(veh->x_pos, veh->y_pos, veh->z_pos, true); // This also resets follow_vehicle
@@ -2776,9 +2788,7 @@ const std::chrono::milliseconds TIME_BETWEEN_DOUBLE_CLICK(500); ///< Time betwee
 static void ScrollMainViewport(int x, int y)
 {
 	if (_game_mode != GM_MENU) {
-		Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
-		assert(w);
-
+		Window *w = GetMainWindow();
 		w->viewport->dest_scrollpos_x += ScaleByZoom(x, w->viewport->zoom);
 		w->viewport->dest_scrollpos_y += ScaleByZoom(y, w->viewport->zoom);
 	}

src/window_func.h

@@ -16,6 +16,7 @@
 
 Window *FindWindowById(WindowClass cls, WindowNumber number);
 Window *FindWindowByClass(WindowClass cls);
+Window *GetMainWindow();
 void ChangeWindowOwner(Owner old_owner, Owner new_owner);
 
 void ResizeWindow(Window *w, int x, int y, bool clamp_to_screen = true);