Add `WINDOW_FLAG_MOUSE_PASSTHROUGH` flag and enabled it for tooltips. Expose `window_set_mouse_passthrough` to `Window`.

doc/classes/DisplayServer.xml

@@ -1694,7 +1694,10 @@
 			Use [method window_get_safe_title_margins] to determine area under the title bar that is not covered by decorations.
 			[b]Note:[/b] This flag is implemented on macOS.
 		</constant>
-		<constant name="WINDOW_FLAG_MAX" value="7" enum="WindowFlags">
+		<constant name="WINDOW_FLAG_MOUSE_PASSTHROUGH" value="7" enum="WindowFlags">
+			All mouse event as passed to the underlying window of the same application.
+		</constant>
+		<constant name="WINDOW_FLAG_MAX" value="8" enum="WindowFlags">
 			Max value of the [enum WindowFlags].
 		</constant>
 		<constant name="WINDOW_EVENT_MOUSE_ENTER" value="0" enum="WindowEvent">

doc/classes/Window.xml

@@ -527,6 +527,39 @@
 			Set's the window's current mode.
 			[b]Note:[/b] Fullscreen mode is not exclusive full screen on Windows and Linux.
 		</member>
+		<member name="mouse_passthrough" type="bool" setter="set_flag" getter="get_flag" default="false">
+			If [code]true[/code], all mouse event as passed to the underlying window of the same application. See also [member mouse_passthrough_polygon].
+			[b]Note:[/b] This property is implemented on Linux (X11), macOS and Windows.
+		</member>
+		<member name="mouse_passthrough_polygon" type="PackedVector2Array" setter="set_mouse_passthrough_polygon" getter="get_mouse_passthrough_polygon" default="PackedVector2Array()">
+			Sets a polygonal region of the window which accepts mouse events. Mouse events outside the region will be passed through.
+			Passing an empty array will disable passthrough support (all mouse events will be intercepted by the window, which is the default behavior).
+			[codeblocks]
+			[gdscript]
+			# Set region, using Path2D node.
+			$Window.mouse_passthrough_polygon = $Path2D.curve.get_baked_points()
+
+			# Set region, using Polygon2D node.
+			$Window.mouse_passthrough_polygon = $Polygon2D.polygon
+
+			# Reset region to default.
+			$Window.mouse_passthrough_polygon = []
+			[/gdscript]
+			[csharp]
+			// Set region, using Path2D node.
+			GetNode&lt;Window&gt;("Window").MousePassthrough = GetNode&lt;Path2D&gt;("Path2D").Curve.GetBakedPoints();
+
+			// Set region, using Polygon2D node.
+			GetNode&lt;Window&gt;("Window").MousePassthrough = GetNode&lt;Polygon2D&gt;("Polygon2D").Polygon;
+
+			// Reset region to default.
+			GetNode&lt;Window&gt;("Window").MousePassthrough = new Vector2[] {};
+			[/csharp]
+			[/codeblocks]
+			[b]Note:[/b] This property is ignored if [member mouse_passthrough] is set to [code]true[/code].
+			[b]Note:[/b] On Windows, the portion of a window that lies outside the region is not drawn, while on Linux (X11) and macOS it is.
+			[b]Note:[/b] This property is implemented on Linux (X11), macOS and Windows.
+		</member>
 		<member name="popup_window" type="bool" setter="set_flag" getter="get_flag" default="false">
 			If [code]true[/code], the [Window] will be considered a popup. Popups are sub-windows that don't show as separate windows in system's window manager's window list and will send close request when anything is clicked outside of them (unless [member exclusive] is enabled).
 		</member>
@@ -695,7 +728,9 @@
 			Window content is expanded to the full size of the window. Unlike borderless window, the frame is left intact and can be used to resize the window, title bar is transparent, but have minimize/maximize/close buttons. Set with [member extend_to_title].
 			[b]Note:[/b] This flag is implemented on macOS.
 		</constant>
-		<constant name="FLAG_MAX" value="7" enum="Flags">
+		<constant name="FLAG_MOUSE_PASSTHROUGH" value="7" enum="Flags">
+		</constant>
+		<constant name="FLAG_MAX" value="8" enum="Flags">
 			Max value of the [enum Flags].
 		</constant>
 		<constant name="CONTENT_SCALE_MODE_DISABLED" value="0" enum="ContentScaleMode">

platform/linuxbsd/x11/display_server_x11.cpp

@@ -1420,13 +1420,22 @@ void DisplayServerX11::window_set_mouse_passthrough(const Vector<Vector2> &p_reg
 	_THREAD_SAFE_METHOD_
 
 	ERR_FAIL_COND(!windows.has(p_window));
-	const WindowData &wd = windows[p_window];
+	windows[p_window].mpath = p_region;
+	_update_window_mouse_passthrough(p_window);
+}
+
+void DisplayServerX11::_update_window_mouse_passthrough(WindowID p_window) {
+	ERR_FAIL_COND(!windows.has(p_window));
+
+	const Vector<Vector2> region_path = windows[p_window].mpath;
 
 	int event_base, error_base;
 	const Bool ext_okay = XShapeQueryExtension(x11_display, &event_base, &error_base);
 	if (ext_okay) {
 		Region region;
-		if (p_region.size() == 0) {
+		if (windows[p_window].mpass) {
+			region = XCreateRegion();
+		} else if (region_path.size() == 0) {
 			region = XCreateRegion();
 			XRectangle rect;
 			rect.x = 0;
@@ -1435,15 +1444,15 @@ void DisplayServerX11::window_set_mouse_passthrough(const Vector<Vector2> &p_reg
 			rect.height = window_get_size_with_decorations(p_window).y;
 			XUnionRectWithRegion(&rect, region, region);
 		} else {
-			XPoint *points = (XPoint *)memalloc(sizeof(XPoint) * p_region.size());
-			for (int i = 0; i < p_region.size(); i++) {
-				points[i].x = p_region[i].x;
-				points[i].y = p_region[i].y;
+			XPoint *points = (XPoint *)memalloc(sizeof(XPoint) * region_path.size());
+			for (int i = 0; i < region_path.size(); i++) {
+				points[i].x = region_path[i].x;
+				points[i].y = region_path[i].y;
 			}
-			region = XPolygonRegion(points, p_region.size(), EvenOddRule);
+			region = XPolygonRegion(points, region_path.size(), EvenOddRule);
 			memfree(points);
 		}
-		XShapeCombineRegion(x11_display, wd.x11_window, ShapeInput, 0, 0, region, ShapeSet);
+		XShapeCombineRegion(x11_display, windows[p_window].x11_window, ShapeInput, 0, 0, region, ShapeSet);
 		XDestroyRegion(region);
 	}
 }
@@ -2312,6 +2321,7 @@ void DisplayServerX11::window_set_flag(WindowFlags p_flag, bool p_enabled, Windo
 			window_set_size(window_get_size(p_window), p_window);
 
 			wd.borderless = p_enabled;
+			_update_window_mouse_passthrough(p_window);
 		} break;
 		case WINDOW_FLAG_ALWAYS_ON_TOP: {
 			ERR_FAIL_COND_MSG(wd.transient_parent != INVALID_WINDOW_ID, "Can't make a window transient if the 'on top' flag is active.");
@@ -2345,6 +2355,10 @@ void DisplayServerX11::window_set_flag(WindowFlags p_flag, bool p_enabled, Windo
 		case WINDOW_FLAG_NO_FOCUS: {
 			wd.no_focus = p_enabled;
 		} break;
+		case WINDOW_FLAG_MOUSE_PASSTHROUGH: {
+			wd.mpass = p_enabled;
+			_update_window_mouse_passthrough(p_window);
+		} break;
 		case WINDOW_FLAG_POPUP: {
 			XWindowAttributes xwa;
 			XSync(x11_display, False);
@@ -2398,6 +2412,9 @@ bool DisplayServerX11::window_get_flag(WindowFlags p_flag, WindowID p_window) co
 		case WINDOW_FLAG_NO_FOCUS: {
 			return wd.no_focus;
 		} break;
+		case WINDOW_FLAG_MOUSE_PASSTHROUGH: {
+			return wd.mpass;
+		} break;
 		case WINDOW_FLAG_POPUP: {
 			return wd.is_popup;
 		} break;

platform/linuxbsd/x11/display_server_x11.h

@@ -149,6 +149,8 @@ class DisplayServerX11 : public DisplayServer {
 		Callable input_text_callback;
 		Callable drop_files_callback;
 
+		Vector<Vector2> mpath;
+
 		WindowID transient_parent = INVALID_WINDOW_ID;
 		HashSet<WindowID> transient_children;
 
@@ -169,6 +171,7 @@ class DisplayServerX11 : public DisplayServer {
 		bool maximized = false;
 		bool is_popup = false;
 		bool layered_window = false;
+		bool mpass = false;
 
 		Rect2i parent_safe_rect;
 
@@ -245,6 +248,7 @@ class DisplayServerX11 : public DisplayServer {
 
 	Atom _process_selection_request_target(Atom p_target, Window p_requestor, Atom p_property, Atom p_selection) const;
 	void _handle_selection_request_event(XSelectionRequestEvent *p_event) const;
+	void _update_window_mouse_passthrough(WindowID p_window);
 
 	String _clipboard_get_impl(Atom p_source, Window x11_window, Atom target) const;
 	String _clipboard_get(Atom p_source, Window x11_window) const;

platform/macos/display_server_macos.h

@@ -114,6 +114,7 @@ public:
 		bool resize_disabled = false;
 		bool no_focus = false;
 		bool is_popup = false;
+		bool mpass = false;
 
 		Rect2i parent_safe_rect;
 	};

platform/macos/display_server_macos.mm

@@ -2974,6 +2974,9 @@ void DisplayServerMacOS::window_set_flag(WindowFlags p_flag, bool p_enabled, Win
 		case WINDOW_FLAG_NO_FOCUS: {
 			wd.no_focus = p_enabled;
 		} break;
+		case WINDOW_FLAG_MOUSE_PASSTHROUGH: {
+			wd.mpass = p_enabled;
+		} break;
 		case WINDOW_FLAG_POPUP: {
 			ERR_FAIL_COND_MSG(p_window == MAIN_WINDOW_ID, "Main window can't be popup.");
 			ERR_FAIL_COND_MSG([wd.window_object isVisible] && (wd.is_popup != p_enabled), "Popup flag can't changed while window is opened.");
@@ -3013,6 +3016,9 @@ bool DisplayServerMacOS::window_get_flag(WindowFlags p_flag, WindowID p_window)
 		case WINDOW_FLAG_NO_FOCUS: {
 			return wd.no_focus;
 		} break;
+		case WINDOW_FLAG_MOUSE_PASSTHROUGH: {
+			return wd.mpass;
+		} break;
 		case WINDOW_FLAG_POPUP: {
 			return wd.is_popup;
 		} break;
@@ -3487,7 +3493,11 @@ void DisplayServerMacOS::process_events() {
 
 	for (KeyValue<WindowID, WindowData> &E : windows) {
 		WindowData &wd = E.value;
-		if (wd.mpath.size() > 0) {
+		if (wd.mpass) {
+			if (![wd.window_object ignoresMouseEvents]) {
+				[wd.window_object setIgnoresMouseEvents:YES];
+			}
+		} else if (wd.mpath.size() > 0) {
 			update_mouse_pos(wd, [wd.window_object mouseLocationOutsideOfEventStream]);
 			if (Geometry2D::is_point_in_polygon(wd.mouse_pos, wd.mpath)) {
 				if ([wd.window_object ignoresMouseEvents]) {

platform/windows/display_server_windows.cpp

@@ -735,6 +735,9 @@ DisplayServer::WindowID DisplayServerWindows::create_sub_window(WindowMode p_mod
 	if (p_flags & WINDOW_FLAG_NO_FOCUS_BIT) {
 		wd.no_focus = true;
 	}
+	if (p_flags & WINDOW_FLAG_MOUSE_PASSTHROUGH_BIT) {
+		wd.mpass = true;
+	}
 	if (p_flags & WINDOW_FLAG_POPUP_BIT) {
 		wd.is_popup = true;
 	}
@@ -918,7 +921,7 @@ void DisplayServerWindows::window_set_mouse_passthrough(const Vector<Vector2> &p
 void DisplayServerWindows::_update_window_mouse_passthrough(WindowID p_window) {
 	ERR_FAIL_COND(!windows.has(p_window));
 
-	if (windows[p_window].mpath.size() == 0) {
+	if (windows[p_window].mpass || windows[p_window].mpath.size() == 0) {
 		SetWindowRgn(windows[p_window].hWnd, nullptr, TRUE);
 	} else {
 		POINT *points = (POINT *)memalloc(sizeof(POINT) * windows[p_window].mpath.size());
@@ -1499,6 +1502,10 @@ void DisplayServerWindows::window_set_flag(WindowFlags p_flag, bool p_enabled, W
 			wd.no_focus = p_enabled;
 			_update_window_style(p_window);
 		} break;
+		case WINDOW_FLAG_MOUSE_PASSTHROUGH: {
+			wd.mpass = p_enabled;
+			_update_window_mouse_passthrough(p_window);
+		} break;
 		case WINDOW_FLAG_POPUP: {
 			ERR_FAIL_COND_MSG(p_window == MAIN_WINDOW_ID, "Main window can't be popup.");
 			ERR_FAIL_COND_MSG(IsWindowVisible(wd.hWnd) && (wd.is_popup != p_enabled), "Popup flag can't changed while window is opened.");
@@ -1530,6 +1537,9 @@ bool DisplayServerWindows::window_get_flag(WindowFlags p_flag, WindowID p_window
 		case WINDOW_FLAG_NO_FOCUS: {
 			return wd.no_focus;
 		} break;
+		case WINDOW_FLAG_MOUSE_PASSTHROUGH: {
+			return wd.mpass;
+		} break;
 		case WINDOW_FLAG_POPUP: {
 			return wd.is_popup;
 		} break;
@@ -2464,6 +2474,11 @@ LRESULT DisplayServerWindows::WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARA
 
 	// Process window messages.
 	switch (uMsg) {
+		case WM_NCHITTEST: {
+			if (windows[window_id].mpass) {
+				return HTTRANSPARENT;
+			}
+		} break;
 		case WM_MOUSEACTIVATE: {
 			if (windows[window_id].no_focus) {
 				return MA_NOACTIVATEANDEAT; // Do not activate, and discard mouse messages.

platform/windows/display_server_windows.h

@@ -370,6 +370,7 @@ class DisplayServerWindows : public DisplayServer {
 		bool window_has_focus = false;
 		bool exclusive = false;
 		bool context_created = false;
+		bool mpass = false;
 
 		// Used to transfer data between events using timer.
 		WPARAM saved_wparam;

scene/main/viewport.cpp

@@ -1256,6 +1256,7 @@ void Viewport::_gui_show_tooltip() {
 	panel->set_transient(true);
 	panel->set_flag(Window::FLAG_NO_FOCUS, true);
 	panel->set_flag(Window::FLAG_POPUP, false);
+	panel->set_flag(Window::FLAG_MOUSE_PASSTHROUGH, true);
 	panel->set_wrap_controls(true);
 	panel->add_child(base_tooltip);
 	panel->gui_parent = this;

scene/main/window.cpp

@@ -489,6 +489,7 @@ void Window::_make_window() {
 	ERR_FAIL_COND(window_id == DisplayServer::INVALID_WINDOW_ID);
 	DisplayServer::get_singleton()->window_set_max_size(Size2i(), window_id);
 	DisplayServer::get_singleton()->window_set_min_size(Size2i(), window_id);
+	DisplayServer::get_singleton()->window_set_mouse_passthrough(mpath, window_id);
 	String tr_title = atr(title);
 #ifdef DEBUG_ENABLED
 	if (window_id == DisplayServer::MAIN_WINDOW_ID) {
@@ -1235,6 +1236,18 @@ DisplayServer::WindowID Window::get_window_id() const {
 	return window_id;
 }
 
+void Window::set_mouse_passthrough_polygon(const Vector<Vector2> &p_region) {
+	mpath = p_region;
+	if (window_id == DisplayServer::INVALID_WINDOW_ID) {
+		return;
+	}
+	DisplayServer::get_singleton()->window_set_mouse_passthrough(mpath, window_id);
+}
+
+Vector<Vector2> Window::get_mouse_passthrough_polygon() const {
+	return mpath;
+}
+
 void Window::set_wrap_controls(bool p_enable) {
 	wrap_controls = p_enable;
 	if (wrap_controls) {
@@ -2163,6 +2176,9 @@ void Window::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_use_font_oversampling", "enable"), &Window::set_use_font_oversampling);
 	ClassDB::bind_method(D_METHOD("is_using_font_oversampling"), &Window::is_using_font_oversampling);
 
+	ClassDB::bind_method(D_METHOD("set_mouse_passthrough_polygon", "polygon"), &Window::set_mouse_passthrough_polygon);
+	ClassDB::bind_method(D_METHOD("get_mouse_passthrough_polygon"), &Window::get_mouse_passthrough_polygon);
+
 	ClassDB::bind_method(D_METHOD("set_wrap_controls", "enable"), &Window::set_wrap_controls);
 	ClassDB::bind_method(D_METHOD("is_wrapping_controls"), &Window::is_wrapping_controls);
 	ClassDB::bind_method(D_METHOD("child_controls_changed"), &Window::child_controls_changed);
@@ -2243,6 +2259,8 @@ void Window::_bind_methods() {
 	}
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "current_screen", PROPERTY_HINT_ENUM, screen_hints), "set_current_screen", "get_current_screen");
 
+	ADD_PROPERTY(PropertyInfo(Variant::PACKED_VECTOR2_ARRAY, "mouse_passthrough_polygon"), "set_mouse_passthrough_polygon", "get_mouse_passthrough_polygon");
+
 	ADD_GROUP("Flags", "");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "visible"), "set_visible", "is_visible");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "wrap_controls"), "set_wrap_controls", "is_wrapping_controls");
@@ -2255,6 +2273,7 @@ void Window::_bind_methods() {
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "unfocusable"), "set_flag", "get_flag", FLAG_NO_FOCUS);
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "popup_window"), "set_flag", "get_flag", FLAG_POPUP);
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "extend_to_title"), "set_flag", "get_flag", FLAG_EXTEND_TO_TITLE);
+	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "mouse_passthrough"), "set_flag", "get_flag", FLAG_MOUSE_PASSTHROUGH);
 
 	ADD_GROUP("Limits", "");
 	ADD_PROPERTY(PropertyInfo(Variant::VECTOR2I, "min_size", PROPERTY_HINT_NONE, "suffix:px"), "set_min_size", "get_min_size");
@@ -2302,6 +2321,7 @@ void Window::_bind_methods() {
 	BIND_ENUM_CONSTANT(FLAG_NO_FOCUS);
 	BIND_ENUM_CONSTANT(FLAG_POPUP);
 	BIND_ENUM_CONSTANT(FLAG_EXTEND_TO_TITLE);
+	BIND_ENUM_CONSTANT(FLAG_MOUSE_PASSTHROUGH);
 	BIND_ENUM_CONSTANT(FLAG_MAX);
 
 	BIND_ENUM_CONSTANT(CONTENT_SCALE_MODE_DISABLED);

scene/main/window.h

@@ -59,6 +59,7 @@ public:
 		FLAG_NO_FOCUS = DisplayServer::WINDOW_FLAG_NO_FOCUS,
 		FLAG_POPUP = DisplayServer::WINDOW_FLAG_POPUP,
 		FLAG_EXTEND_TO_TITLE = DisplayServer::WINDOW_FLAG_EXTEND_TO_TITLE,
+		FLAG_MOUSE_PASSTHROUGH = DisplayServer::WINDOW_FLAG_MOUSE_PASSTHROUGH,
 		FLAG_MAX = DisplayServer::WINDOW_FLAG_MAX,
 	};
 
@@ -101,6 +102,7 @@ private:
 	mutable Size2i size = Size2i(DEFAULT_WINDOW_SIZE, DEFAULT_WINDOW_SIZE);
 	mutable Size2i min_size;
 	mutable Size2i max_size;
+	mutable Vector<Vector2> mpath;
 	mutable Mode mode = MODE_WINDOWED;
 	mutable bool flags[FLAG_MAX] = {};
 	bool visible = true;
@@ -281,6 +283,9 @@ public:
 	void set_use_font_oversampling(bool p_oversampling);
 	bool is_using_font_oversampling() const;
 
+	void set_mouse_passthrough_polygon(const Vector<Vector2> &p_region);
+	Vector<Vector2> get_mouse_passthrough_polygon() const;
+
 	void set_wrap_controls(bool p_enable);
 	bool is_wrapping_controls() const;
 	void child_controls_changed();

servers/display_server.cpp

@@ -848,6 +848,7 @@ void DisplayServer::_bind_methods() {
 	BIND_ENUM_CONSTANT(WINDOW_FLAG_NO_FOCUS);
 	BIND_ENUM_CONSTANT(WINDOW_FLAG_POPUP);
 	BIND_ENUM_CONSTANT(WINDOW_FLAG_EXTEND_TO_TITLE);
+	BIND_ENUM_CONSTANT(WINDOW_FLAG_MOUSE_PASSTHROUGH);
 	BIND_ENUM_CONSTANT(WINDOW_FLAG_MAX);
 
 	BIND_ENUM_CONSTANT(WINDOW_EVENT_MOUSE_ENTER);

servers/display_server.h

@@ -311,6 +311,7 @@ public:
 		WINDOW_FLAG_NO_FOCUS,
 		WINDOW_FLAG_POPUP,
 		WINDOW_FLAG_EXTEND_TO_TITLE,
+		WINDOW_FLAG_MOUSE_PASSTHROUGH,
 		WINDOW_FLAG_MAX,
 	};
 
@@ -323,6 +324,7 @@ public:
 		WINDOW_FLAG_NO_FOCUS_BIT = (1 << WINDOW_FLAG_NO_FOCUS),
 		WINDOW_FLAG_POPUP_BIT = (1 << WINDOW_FLAG_POPUP),
 		WINDOW_FLAG_EXTEND_TO_TITLE_BIT = (1 << WINDOW_FLAG_EXTEND_TO_TITLE),
+		WINDOW_FLAG_MOUSE_PASSTHROUGH_BIT = (1 << WINDOW_FLAG_MOUSE_PASSTHROUGH),
 	};
 
 	virtual WindowID create_sub_window(WindowMode p_mode, VSyncMode p_vsync_mode, uint32_t p_flags, const Rect2i &p_rect = Rect2i());