fix: Allow titlebars to be disabled

src/settings_gui.cpp

@@ -462,13 +462,19 @@ struct GameOptionsWindow : Window {
 				break;
 
 			case WID_GO_WINDOWS_TITLEBARS:
-				_settings_client.gui.windows_titlebars ^= _settings_client.gui.windows_titlebars;
+				_settings_client.gui.windows_titlebars = !_settings_client.gui.windows_titlebars;
+				this->SetWidgetLoweredState(WID_GO_WINDOWS_TITLEBARS, _settings_client.gui.windows_titlebars);
+				this->SetDirty();
+
 				if (_settings_client.gui.min_button == 48 && _settings_client.gui.windows_titlebars) {
 					_settings_client.gui.min_button = 40;
 				}
 				if (_settings_client.gui.min_button == 40 && !_settings_client.gui.windows_titlebars) {
 					_settings_client.gui.min_button = 48;
 				}
+
+				ReInitAllWindows(false);
+
 				break;
 
 			case WID_GO_MOUSE_CURSOR:

src/widget.cpp

@@ -2961,6 +2961,20 @@ void NWidgetLeaf::SetupSmallestSize(Window *w, bool init_array)
 	Dimension size = {this->min_x, this->min_y};
 	Dimension fill = {this->fill_x, this->fill_y};
 	Dimension resize = {this->resize_x, this->resize_y};
+
+	// Note: Disabled titlebars by reducing its elements size to zero
+	if (!_settings_client.gui.windows_titlebars && w->window_class != WC_NEWS_WINDOW &&
+		(this->type == WWT_CAPTION || this->type == WWT_STICKYBOX || this->type == WWT_SHADEBOX ||
+		this->type == WWT_DEFSIZEBOX || this->type == WWT_CLOSEBOX || this->type == WWT_DEBUGBOX)) {
+		this->sizing_type = NWST_NONE;
+		size = {0, 0};
+		fill = {0, 0};
+		resize = {0, 0};
+		if (this->type == WWT_CAPTION) {
+			fill.width = 1;
+			resize.width = 1;
+		}
+	} else {
 		switch (this->type) {
 			case WWT_EMPTY: {
 				break;
@@ -3115,6 +3129,7 @@ void NWidgetLeaf::SetupSmallestSize(Window *w, bool init_array)
 			default:
 				NOT_REACHED();
 		}
+	}
 
 	if (this->index >= 0) w->UpdateWidgetSize(this->index, &size, padding, &fill, &resize);
 

src/window.cpp

@@ -39,6 +39,7 @@
 #include "guitimer_func.h"
 #include "news_func.h"
 #include "build_confirmation_func.h"
+#include "widgets/settings_widget.h"
 
 #include "safeguards.h"
 
@@ -818,6 +819,12 @@ static void DispatchLeftClickEvent(Window *w, int x, int y, int click_count, boo
 		Game::NewEvent(new ScriptEventWindowWidgetClick((ScriptWindow::WindowClass)w->window_class, w->window_number, widget_index));
 	}
 
+	// Note: Workaround to avoid immediate toggle when titlebars are enabled.
+	if (_settings_client.gui.windows_titlebars &&
+		w->window_class == WC_GAME_OPTIONS  && widget_index == WID_GO_WINDOWS_TITLEBARS && mouse_down){
+		return;
+	}
+
 	w->OnClick(pt, widget_index, click_count);
 }
 
@@ -844,7 +851,7 @@ static void DispatchLeftButtonDownEvent(Window *w, int x, int y, int click_count
 static void DispatchLeftButtonUpEvent(Window *w, int x, int y)
 {
 	_dragging_widget = false;
-	if (_settings_client.gui.windows_titlebars || _dragging_window) return;
+	if (_dragging_window) return;
 	DispatchLeftClickEvent(w, x, y, _left_button_click_count, false);
 }