[macOS extend-to-title] Add scene/project name to the editor title, fix incorrect window button position/order when system primary language is RTL.

doc/classes/DisplayServer.xml

@@ -1548,6 +1548,8 @@
 		</constant>
 		<constant name="WINDOW_EVENT_DPI_CHANGE" value="6" enum="WindowEvent">
 		</constant>
+		<constant name="WINDOW_EVENT_TITLEBAR_CHANGE" value="7" enum="WindowEvent">
+		</constant>
 		<constant name="VSYNC_DISABLED" value="0" enum="VSyncMode">
 			No vertical synchronization, which means the engine will display frames as fast as possible (tearing may be visible).
 		</constant>

doc/classes/Window.xml

@@ -455,6 +455,11 @@
 				Emitted when the [constant NOTIFICATION_THEME_CHANGED] notification is sent.
 			</description>
 		</signal>
+		<signal name="titlebar_changed">
+			<description>
+				Emitted when window title bar decorations are changed, e.g., macOS window enter/exit full screen mode, or extend-to-title flag is changed.
+			</description>
+		</signal>
 		<signal name="visibility_changed">
 			<description>
 				Emitted when [Window] is made visible or disappears.

editor/editor_node.cpp

@@ -429,7 +429,7 @@ void EditorNode::_version_control_menu_option(int p_idx) {
 
 void EditorNode::_update_title() {
 	const String appname = ProjectSettings::get_singleton()->get("application/config/name");
-	String title = (appname.is_empty() ? TTR("Unnamed Project") : appname) + String(" - ") + VERSION_NAME;
+	String title = (appname.is_empty() ? TTR("Unnamed Project") : appname);
 	const String edited = editor_data.get_edited_scene_root() ? editor_data.get_edited_scene_root()->get_scene_file_path() : String();
 	if (!edited.is_empty()) {
 		// Display the edited scene name before the program name so that it can be seen in the OS task bar.
@@ -439,8 +439,10 @@ void EditorNode::_update_title() {
 		// Display the "modified" mark before anything else so that it can always be seen in the OS task bar.
 		title = vformat("(*) %s", title);
 	}
-
-	DisplayServer::get_singleton()->window_set_title(title);
+	DisplayServer::get_singleton()->window_set_title(title + String(" - ") + VERSION_NAME);
+	if (project_title) {
+		project_title->set_text(title);
+	}
 }
 
 void EditorNode::shortcut_input(const Ref<InputEvent> &p_event) {
@@ -659,6 +661,12 @@ void EditorNode::_notification(int p_what) {
 		case NOTIFICATION_ENTER_TREE: {
 			Engine::get_singleton()->set_editor_hint(true);
 
+			Window *window = static_cast<Window *>(get_tree()->get_root());
+			if (window) {
+				// Handle macOS fullscreen and extend-to-title changes.
+				window->connect("titlebar_changed", callable_mp(this, &EditorNode::_titlebar_resized));
+			}
+
 			OS::get_singleton()->set_low_processor_usage_mode_sleep_usec(int(EDITOR_GET("interface/editor/low_processor_mode_sleep_usec")));
 			get_tree()->get_root()->set_as_audio_listener_3d(false);
 			get_tree()->get_root()->set_as_audio_listener_2d(false);
@@ -713,6 +721,8 @@ void EditorNode::_notification(int p_what) {
 				ProjectSettings::get_singleton()->save();
 			}
 
+			_titlebar_resized();
+
 			/* DO NOT LOAD SCENES HERE, WAIT FOR FILE SCANNING AND REIMPORT TO COMPLETE */
 		} break;
 
@@ -1170,6 +1180,18 @@ void EditorNode::_reload_project_settings() {
 void EditorNode::_vp_resized() {
 }
 
+void EditorNode::_titlebar_resized() {
+	const Size2 &margin = DisplayServer::get_singleton()->window_get_safe_title_margins(DisplayServer::MAIN_WINDOW_ID);
+	if (left_menu_spacer) {
+		int w = (gui_base->is_layout_rtl()) ? margin.y : margin.x;
+		left_menu_spacer->set_custom_minimum_size(Size2(w, 0));
+	}
+	if (right_menu_spacer) {
+		int w = (gui_base->is_layout_rtl()) ? margin.x : margin.y;
+		right_menu_spacer->set_custom_minimum_size(Size2(w, 0));
+	}
+}
+
 void EditorNode::_version_button_pressed() {
 	DisplayServer::get_singleton()->clipboard_set(version_btn->get_meta(META_TEXT_TO_COPY));
 }
@@ -3390,7 +3412,7 @@ void EditorNode::add_editor_plugin(EditorPlugin *p_editor, bool p_config_changed
 		tb->add_theme_font_size_override("font_size", singleton->gui_base->get_theme_font_size(SNAME("main_button_font_size"), SNAME("EditorFonts")));
 
 		singleton->main_editor_buttons.push_back(tb);
-		singleton->main_editor_button_vb->add_child(tb);
+		singleton->main_editor_button_hb->add_child(tb);
 		singleton->editor_table.push_back(p_editor);
 
 		singleton->distraction_free->move_to_front();
@@ -6590,14 +6612,14 @@ EditorNode::EditorNode() {
 
 	if (can_expand) {
 		// Add spacer to avoid other controls under window minimize/maximize/close buttons (left side).
-		Control *menu_spacer = memnew(Control);
-		menu_spacer->set_mouse_filter(Control::MOUSE_FILTER_PASS);
-		menu_spacer->set_custom_minimum_size(Size2(DisplayServer::get_singleton()->window_get_safe_title_margins(DisplayServer::MAIN_WINDOW_ID).x, 0));
-		menu_hb->add_child(menu_spacer);
+		left_menu_spacer = memnew(Control);
+		left_menu_spacer->set_mouse_filter(Control::MOUSE_FILTER_PASS);
+		menu_hb->add_child(left_menu_spacer);
 	}
 
 	main_menu = memnew(MenuBar);
 	menu_hb->add_child(main_menu);
+
 	main_menu->add_theme_style_override("hover", gui_base->get_theme_stylebox(SNAME("MenuHover"), SNAME("EditorStyles")));
 	main_menu->set_flat(true);
 	main_menu->set_start_index(0); // Main menu, add to the start of global menu.
@@ -6766,22 +6788,30 @@ EditorNode::EditorNode() {
 	project_menu->add_shortcut(ED_GET_SHORTCUT("editor/quit_to_project_list"), RUN_PROJECT_MANAGER, true);
 
 	// Spacer to center 2D / 3D / Script buttons.
-	Control *left_spacer = memnew(Control);
+	HBoxContainer *left_spacer = memnew(HBoxContainer);
 	left_spacer->set_mouse_filter(Control::MOUSE_FILTER_PASS);
+	left_spacer->set_h_size_flags(Control::SIZE_EXPAND_FILL);
 	menu_hb->add_child(left_spacer);
 
-	menu_hb->add_spacer();
+	if (can_expand && global_menu) {
+		project_title = memnew(Label);
+		project_title->add_theme_font_override("font", gui_base->get_theme_font(SNAME("bold"), SNAME("EditorFonts")));
+		project_title->add_theme_font_size_override("font_size", gui_base->get_theme_font_size(SNAME("bold_size"), SNAME("EditorFonts")));
+		project_title->set_focus_mode(Control::FOCUS_NONE);
+		project_title->set_text_overrun_behavior(TextServer::OVERRUN_TRIM_ELLIPSIS);
+		project_title->set_vertical_alignment(VERTICAL_ALIGNMENT_CENTER);
+		project_title->set_h_size_flags(Control::SIZE_EXPAND_FILL);
+		left_spacer->add_child(project_title);
+	}
 
-	main_editor_button_vb = memnew(HBoxContainer);
-	menu_hb->add_child(main_editor_button_vb);
+	main_editor_button_hb = memnew(HBoxContainer);
+	menu_hb->add_child(main_editor_button_hb);
 
 	// Options are added and handled by DebuggerEditorPlugin.
 	debug_menu = memnew(PopupMenu);
 	debug_menu->set_name(TTR("Debug"));
 	main_menu->add_child(debug_menu);
 
-	menu_hb->add_spacer();
-
 	settings_menu = memnew(PopupMenu);
 	settings_menu->set_name(TTR("Editor"));
 	main_menu->add_child(settings_menu);
@@ -6855,6 +6885,7 @@ EditorNode::EditorNode() {
 	// Spacer to center 2D / 3D / Script buttons.
 	Control *right_spacer = memnew(Control);
 	right_spacer->set_mouse_filter(Control::MOUSE_FILTER_PASS);
+	right_spacer->set_h_size_flags(Control::SIZE_EXPAND_FILL);
 	menu_hb->add_child(right_spacer);
 
 	launch_pad = memnew(PanelContainer);
@@ -6965,10 +6996,9 @@ EditorNode::EditorNode() {
 
 	if (can_expand) {
 		// Add spacer to avoid other controls under the window minimize/maximize/close buttons (right side).
-		Control *menu_spacer = memnew(Control);
-		menu_spacer->set_mouse_filter(Control::MOUSE_FILTER_PASS);
-		menu_spacer->set_custom_minimum_size(Size2(DisplayServer::get_singleton()->window_get_safe_title_margins(DisplayServer::MAIN_WINDOW_ID).y, 0));
-		menu_hb->add_child(menu_spacer);
+		right_menu_spacer = memnew(Control);
+		right_menu_spacer->set_mouse_filter(Control::MOUSE_FILTER_PASS);
+		menu_hb->add_child(right_menu_spacer);
 	}
 
 	String current_renderer = GLOBAL_GET("rendering/renderer/rendering_method");
@@ -7523,9 +7553,9 @@ EditorNode::EditorNode() {
 	screenshot_timer->set_owner(get_owner());
 
 	// Adjust spacers to center 2D / 3D / Script buttons.
-	int max_w = MAX(launch_pad_hb->get_minimum_size().x + right_menu_hb->get_minimum_size().x, main_menu->get_minimum_size().x);
+	int max_w = MAX(launch_pad->get_minimum_size().x + right_menu_hb->get_minimum_size().x, main_menu->get_minimum_size().x);
 	left_spacer->set_custom_minimum_size(Size2(MAX(0, max_w - main_menu->get_minimum_size().x), 0));
-	right_spacer->set_custom_minimum_size(Size2(MAX(0, max_w - launch_pad_hb->get_minimum_size().x - right_menu_hb->get_minimum_size().x), 0));
+	right_spacer->set_custom_minimum_size(Size2(MAX(0, max_w - launch_pad->get_minimum_size().x - right_menu_hb->get_minimum_size().x), 0));
 
 	// Extend menu bar to window title.
 	if (can_expand) {

editor/editor_node.h

@@ -322,6 +322,9 @@ private:
 	HBoxContainer *bottom_hb = nullptr;
 	Control *vp_base = nullptr;
 
+	Label *project_title = nullptr;
+	Control *left_menu_spacer = nullptr;
+	Control *right_menu_spacer = nullptr;
 	EditorTitleBar *menu_hb = nullptr;
 	VBoxContainer *main_screen_vbox = nullptr;
 	MenuBar *main_menu = nullptr;
@@ -397,7 +400,7 @@ private:
 	String current_path;
 	MenuButton *update_spinner = nullptr;
 
-	HBoxContainer *main_editor_button_vb = nullptr;
+	HBoxContainer *main_editor_button_hb = nullptr;
 	Vector<Button *> main_editor_buttons;
 	Vector<EditorPlugin *> editor_table;
 
@@ -560,6 +563,7 @@ private:
 	void _close_messages();
 	void _show_messages();
 	void _vp_resized();
+	void _titlebar_resized();
 	void _version_button_pressed();
 
 	int _save_external_resources();

platform/macos/display_server_macos.mm

@@ -2664,21 +2664,17 @@ Vector2i DisplayServerMacOS::window_get_safe_title_margins(WindowID p_window) co
 	ERR_FAIL_COND_V(!windows.has(p_window), Vector2i());
 	const WindowData &wd = windows[p_window];
 
-	float max_x = 0.f;
-	NSButton *cb = [wd.window_object standardWindowButton:NSWindowCloseButton];
-	if (cb) {
-		max_x = MAX(max_x, [cb frame].origin.x + [cb frame].size.width);
-	}
-	NSButton *mb = [wd.window_object standardWindowButton:NSWindowMiniaturizeButton];
-	if (mb) {
-		max_x = MAX(max_x, [mb frame].origin.x + [mb frame].size.width);
-	}
-	NSButton *zb = [wd.window_object standardWindowButton:NSWindowZoomButton];
-	if (zb) {
-		max_x = MAX(max_x, [zb frame].origin.x + [zb frame].size.width);
+	if (!wd.window_button_view) {
+		return Vector2i();
 	}
 
-	return Vector2i(max_x * screen_get_max_scale(), 0);
+	float max_x = wd.wb_offset.x + [wd.window_button_view frame].size.width;
+
+	if ([wd.window_object windowTitlebarLayoutDirection] == NSUserInterfaceLayoutDirectionRightToLeft) {
+		return Vector2i(0, max_x * screen_get_max_scale());
+	} else {
+		return Vector2i(max_x * screen_get_max_scale(), 0);
+	}
 }
 
 void DisplayServerMacOS::window_set_custom_window_buttons(WindowData &p_wd, bool p_enabled) {
@@ -2687,7 +2683,11 @@ void DisplayServerMacOS::window_set_custom_window_buttons(WindowData &p_wd, bool
 		p_wd.window_button_view = nil;
 	}
 	if (p_enabled) {
-		float window_buttons_spacing = NSMinX([[p_wd.window_object standardWindowButton:NSWindowMiniaturizeButton] frame]) - NSMinX([[p_wd.window_object standardWindowButton:NSWindowCloseButton] frame]);
+		float cb_frame = NSMinX([[p_wd.window_object standardWindowButton:NSWindowCloseButton] frame]);
+		float mb_frame = NSMinX([[p_wd.window_object standardWindowButton:NSWindowMiniaturizeButton] frame]);
+		bool is_rtl = ([p_wd.window_object windowTitlebarLayoutDirection] == NSUserInterfaceLayoutDirectionRightToLeft);
+
+		float window_buttons_spacing = (is_rtl) ? (cb_frame - mb_frame) : (mb_frame - cb_frame);
 
 		[p_wd.window_object setTitleVisibility:NSWindowTitleHidden];
 		[[p_wd.window_object standardWindowButton:NSWindowZoomButton] setHidden:YES];
@@ -2695,7 +2695,7 @@ void DisplayServerMacOS::window_set_custom_window_buttons(WindowData &p_wd, bool
 		[[p_wd.window_object standardWindowButton:NSWindowCloseButton] setHidden:YES];
 
 		p_wd.window_button_view = [[GodotButtonView alloc] initWithFrame:NSZeroRect];
-		[p_wd.window_button_view initButtons:window_buttons_spacing offset:NSMakePoint(p_wd.wb_offset.x, p_wd.wb_offset.y)];
+		[p_wd.window_button_view initButtons:window_buttons_spacing offset:NSMakePoint(p_wd.wb_offset.x, p_wd.wb_offset.y) rtl:is_rtl];
 		[p_wd.window_view addSubview:p_wd.window_button_view];
 	} else {
 		[p_wd.window_object setTitleVisibility:NSWindowTitleVisible];
@@ -2741,6 +2741,7 @@ void DisplayServerMacOS::window_set_flag(WindowFlags p_flag, bool p_enabled, Win
 				}
 			}
 			[wd.window_object setFrame:rect display:YES];
+			send_window_event(wd, DisplayServerMacOS::WINDOW_EVENT_TITLEBAR_CHANGE);
 		} break;
 		case WINDOW_FLAG_BORDERLESS: {
 			// OrderOut prevents a lose focus bug with the window.

platform/macos/godot_button_view.h

@@ -41,9 +41,10 @@
 	NSPoint offset;
 	CGFloat spacing;
 	bool mouse_in_group;
+	bool rtl;
 }
 
-- (void)initButtons:(CGFloat)button_spacing offset:(NSPoint)button_offset;
+- (void)initButtons:(CGFloat)button_spacing offset:(NSPoint)button_offset rtl:(bool)is_rtl;
 - (void)displayButtons;
 
 @end

platform/macos/godot_button_view.mm

@@ -39,15 +39,17 @@
 	offset = NSMakePoint(8, 8);
 	spacing = 20;
 	mouse_in_group = false;
+	rtl = false;
 
 	return self;
 }
 
-- (void)initButtons:(CGFloat)button_spacing offset:(NSPoint)button_offset {
+- (void)initButtons:(CGFloat)button_spacing offset:(NSPoint)button_offset rtl:(bool)is_rtl {
 	spacing = button_spacing;
+	rtl = is_rtl;
 
 	NSButton *close_button = [NSWindow standardWindowButton:NSWindowCloseButton forStyleMask:NSWindowStyleMaskTitled];
-	[close_button setFrameOrigin:NSMakePoint(0, 0)];
+	[close_button setFrameOrigin:NSMakePoint(rtl ? spacing * 2 : 0, 0)];
 	[self addSubview:close_button];
 
 	NSButton *miniaturize_button = [NSWindow standardWindowButton:NSWindowMiniaturizeButton forStyleMask:NSWindowStyleMaskTitled];
@@ -55,13 +57,17 @@
 	[self addSubview:miniaturize_button];
 
 	NSButton *zoom_button = [NSWindow standardWindowButton:NSWindowZoomButton forStyleMask:NSWindowStyleMaskTitled];
-	[zoom_button setFrameOrigin:NSMakePoint(spacing * 2, 0)];
+	[zoom_button setFrameOrigin:NSMakePoint(rtl ? 0 : spacing * 2, 0)];
 	[self addSubview:zoom_button];
 
 	offset.y = button_offset.y - zoom_button.frame.size.height / 2;
 	offset.x = button_offset.x - zoom_button.frame.size.width / 2;
 
-	[self setFrameSize:NSMakeSize(zoom_button.frame.origin.x + zoom_button.frame.size.width, zoom_button.frame.size.height)];
+	if (rtl) {
+		[self setFrameSize:NSMakeSize(close_button.frame.origin.x + close_button.frame.size.width, close_button.frame.size.height)];
+	} else {
+		[self setFrameSize:NSMakeSize(zoom_button.frame.origin.x + zoom_button.frame.size.width, zoom_button.frame.size.height)];
+	}
 	[self displayButtons];
 }
 
@@ -70,8 +76,13 @@
 		return;
 	}
 
-	[self setAutoresizingMask:NSViewMaxXMargin | NSViewMinYMargin];
-	[self setFrameOrigin:NSMakePoint(offset.x, self.window.frame.size.height - self.frame.size.height - offset.y)];
+	if (rtl) {
+		[self setAutoresizingMask:NSViewMinXMargin | NSViewMinYMargin];
+		[self setFrameOrigin:NSMakePoint(self.window.frame.size.width - self.frame.size.width - offset.x, self.window.frame.size.height - self.frame.size.height - offset.y)];
+	} else {
+		[self setAutoresizingMask:NSViewMaxXMargin | NSViewMinYMargin];
+		[self setFrameOrigin:NSMakePoint(offset.x, self.window.frame.size.height - self.frame.size.height - offset.y)];
+	}
 }
 
 - (BOOL)_mouseInGroup:(NSButton *)button {

platform/macos/godot_window.h

@@ -38,9 +38,11 @@
 
 @interface GodotWindow : NSWindow {
 	DisplayServer::WindowID window_id;
+	NSTimeInterval anim_duration;
 }
 
 - (void)setWindowID:(DisplayServer::WindowID)wid;
+- (void)setAnimDuration:(NSTimeInterval)duration;
 
 @end
 

platform/macos/godot_window.mm

@@ -37,9 +37,22 @@
 - (id)init {
 	self = [super init];
 	window_id = DisplayServer::INVALID_WINDOW_ID;
+	anim_duration = -1.0f;
 	return self;
 }
 
+- (void)setAnimDuration:(NSTimeInterval)duration {
+	anim_duration = duration;
+}
+
+- (NSTimeInterval)animationResizeTime:(NSRect)newFrame {
+	if (anim_duration > 0) {
+		return anim_duration;
+	} else {
+		return [super animationResizeTime:newFrame];
+	}
+}
+
 - (void)setWindowID:(DisplayServerMacOS::WindowID)wid {
 	window_id = wid;
 }

platform/macos/godot_window_delegate.h

@@ -38,6 +38,8 @@
 
 @interface GodotWindowDelegate : NSObject <NSWindowDelegate> {
 	DisplayServer::WindowID window_id;
+	NSRect old_frame;
+	NSWindowStyleMask old_style_mask;
 }
 
 - (void)setWindowID:(DisplayServer::WindowID)wid;

platform/macos/godot_window_delegate.mm

@@ -32,6 +32,7 @@
 
 #include "display_server_macos.h"
 #include "godot_button_view.h"
+#include "godot_window.h"
 
 @implementation GodotWindowDelegate
 
@@ -69,6 +70,26 @@
 	ds->window_destroy(window_id);
 }
 
+- (NSArray<NSWindow *> *)customWindowsToEnterFullScreenForWindow:(NSWindow *)window {
+	DisplayServerMacOS *ds = (DisplayServerMacOS *)DisplayServer::get_singleton();
+	if (!ds || !ds->has_window(window_id)) {
+		return nullptr;
+	}
+
+	old_frame = [window frame];
+	old_style_mask = [window styleMask];
+
+	NSMutableArray<NSWindow *> *windows = [[NSMutableArray alloc] init];
+	[windows addObject:window];
+
+	return windows;
+}
+
+- (void)window:(NSWindow *)window startCustomAnimationToEnterFullScreenWithDuration:(NSTimeInterval)duration {
+	[(GodotWindow *)window setAnimDuration:duration];
+	[window setFrame:[[window screen] frame] display:YES animate:YES];
+}
+
 - (void)windowDidEnterFullScreen:(NSNotification *)notification {
 	DisplayServerMacOS *ds = (DisplayServerMacOS *)DisplayServer::get_singleton();
 	if (!ds || !ds->has_window(window_id)) {
@@ -81,6 +102,7 @@
 	// Reset window size limits.
 	[wd.window_object setContentMinSize:NSMakeSize(0, 0)];
 	[wd.window_object setContentMaxSize:NSMakeSize(FLT_MAX, FLT_MAX)];
+	[(GodotWindow *)wd.window_object setAnimDuration:-1.0f];
 
 	// Reset custom window buttons.
 	if ([wd.window_object styleMask] & NSWindowStyleMaskFullSizeContentView) {
@@ -89,6 +111,33 @@
 
 	// Force window resize event.
 	[self windowDidResize:notification];
+	ds->send_window_event(wd, DisplayServerMacOS::WINDOW_EVENT_TITLEBAR_CHANGE);
+}
+
+- (NSArray<NSWindow *> *)customWindowsToExitFullScreenForWindow:(NSWindow *)window {
+	DisplayServerMacOS *ds = (DisplayServerMacOS *)DisplayServer::get_singleton();
+	if (!ds || !ds->has_window(window_id)) {
+		return nullptr;
+	}
+
+	DisplayServerMacOS::WindowData &wd = ds->get_window(window_id);
+
+	// Restore custom window buttons.
+	if ([wd.window_object styleMask] & NSWindowStyleMaskFullSizeContentView) {
+		ds->window_set_custom_window_buttons(wd, true);
+	}
+
+	ds->send_window_event(wd, DisplayServerMacOS::WINDOW_EVENT_TITLEBAR_CHANGE);
+
+	NSMutableArray<NSWindow *> *windows = [[NSMutableArray alloc] init];
+	[windows addObject:wd.window_object];
+	return windows;
+}
+
+- (void)window:(NSWindow *)window startCustomAnimationToExitFullScreenWithDuration:(NSTimeInterval)duration {
+	[(GodotWindow *)window setAnimDuration:duration];
+	[window setStyleMask:old_style_mask];
+	[window setFrame:old_frame display:YES animate:YES];
 }
 
 - (void)windowDidExitFullScreen:(NSNotification *)notification {
@@ -100,6 +149,8 @@
 	DisplayServerMacOS::WindowData &wd = ds->get_window(window_id);
 	wd.fullscreen = false;
 
+	[(GodotWindow *)wd.window_object setAnimDuration:-1.0f];
+
 	// Set window size limits.
 	const float scale = ds->screen_get_max_scale();
 	if (wd.min_size != Size2i()) {
@@ -111,11 +162,6 @@
 		[wd.window_object setContentMaxSize:NSMakeSize(size.x, size.y)];
 	}
 
-	// Restore custom window buttons.
-	if ([wd.window_object styleMask] & NSWindowStyleMaskFullSizeContentView) {
-		ds->window_set_custom_window_buttons(wd, true);
-	}
-
 	// Restore resizability state.
 	if (wd.resize_disabled) {
 		[wd.window_object setStyleMask:[wd.window_object styleMask] & ~NSWindowStyleMaskResizable];

scene/main/window.cpp

@@ -389,6 +389,9 @@ void Window::_event_callback(DisplayServer::WindowEvent p_event) {
 			_propagate_window_notification(this, NOTIFICATION_WM_DPI_CHANGE);
 			emit_signal(SNAME("dpi_changed"));
 		} break;
+		case DisplayServer::WINDOW_EVENT_TITLEBAR_CHANGE: {
+			emit_signal(SNAME("titlebar_changed"));
+		} break;
 	}
 }
 
@@ -1782,6 +1785,7 @@ void Window::_bind_methods() {
 	ADD_SIGNAL(MethodInfo("visibility_changed"));
 	ADD_SIGNAL(MethodInfo("about_to_popup"));
 	ADD_SIGNAL(MethodInfo("theme_changed"));
+	ADD_SIGNAL(MethodInfo("titlebar_changed"));
 
 	BIND_CONSTANT(NOTIFICATION_VISIBILITY_CHANGED);
 	BIND_CONSTANT(NOTIFICATION_THEME_CHANGED);

servers/display_server.cpp

@@ -824,6 +824,7 @@ void DisplayServer::_bind_methods() {
 	BIND_ENUM_CONSTANT(WINDOW_EVENT_CLOSE_REQUEST);
 	BIND_ENUM_CONSTANT(WINDOW_EVENT_GO_BACK_REQUEST);
 	BIND_ENUM_CONSTANT(WINDOW_EVENT_DPI_CHANGE);
+	BIND_ENUM_CONSTANT(WINDOW_EVENT_TITLEBAR_CHANGE);
 
 	BIND_ENUM_CONSTANT(VSYNC_DISABLED);
 	BIND_ENUM_CONSTANT(VSYNC_ENABLED);

servers/display_server.h

@@ -336,6 +336,7 @@ public:
 		WINDOW_EVENT_CLOSE_REQUEST,
 		WINDOW_EVENT_GO_BACK_REQUEST,
 		WINDOW_EVENT_DPI_CHANGE,
+		WINDOW_EVENT_TITLEBAR_CHANGE,
 	};
 	virtual void window_set_window_event_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID) = 0;
 	virtual void window_set_input_event_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID) = 0;