Add window click-through support.

doc/classes/DisplayServer.xml

@@ -901,6 +901,30 @@
 			<description>
 			</description>
 		</method>
+		<method name="window_set_mouse_passthrough">
+			<return type="void">
+			</return>
+			<argument index="0" name="region" type="PackedVector2Array">
+			</argument>
+			<argument index="1" name="window_id" type="int" default="0">
+			</argument>
+			<description>
+				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).
+				[codeblock]
+				# Set region, using Path2D node.
+				DisplayServer.window_set_mouse_passthrough($Path2D.curve.get_baked_points())
+
+				# Set region, using Polygon2D node.
+				DisplayServer.window_set_mouse_passthrough($Polygon2D.polygon)
+
+				# Reset region to default.
+				DisplayServer.window_set_mouse_passthrough([])
+				[/codeblock]
+				[b]Note:[/b] On Windows, the portion of a window that lies outside the region is not drawn, while on Linux and macOS it is.
+				[b]Note:[/b] This method is implemented on Linux, macOS and Windows.
+			</description>
+		</method>
 		<method name="window_set_position">
 			<return type="void">
 			</return>

platform/linuxbsd/detect.py

@@ -35,6 +35,11 @@ def can_build():
         print("xinerama not found.. x11 disabled.")
         return False
 
+    x11_error = os.system("pkg-config xext --modversion > /dev/null ")
+    if x11_error:
+        print("xext not found.. x11 disabled.")
+        return False
+
     x11_error = os.system("pkg-config xrandr --modversion > /dev/null ")
     if x11_error:
         print("xrandr not found.. x11 disabled.")
@@ -194,6 +199,7 @@ def configure(env):
     env.ParseConfig("pkg-config x11 --cflags --libs")
     env.ParseConfig("pkg-config xcursor --cflags --libs")
     env.ParseConfig("pkg-config xinerama --cflags --libs")
+    env.ParseConfig("pkg-config xext --cflags --libs")
     env.ParseConfig("pkg-config xrandr --cflags --libs")
     env.ParseConfig("pkg-config xrender --cflags --libs")
     env.ParseConfig("pkg-config xi --cflags --libs")

platform/linuxbsd/display_server_x11.cpp

@@ -50,6 +50,7 @@
 #include <X11/Xatom.h>
 #include <X11/Xutil.h>
 #include <X11/extensions/Xinerama.h>
+#include <X11/extensions/shape.h>
 
 // ICCCM
 #define WM_NormalState 1L // window normal state
@@ -782,6 +783,38 @@ void DisplayServerX11::window_set_title(const String &p_title, WindowID p_window
 	XChangeProperty(x11_display, wd.x11_window, _net_wm_name, utf8_string, 8, PropModeReplace, (unsigned char *)p_title.utf8().get_data(), p_title.utf8().length());
 }
 
+void DisplayServerX11::window_set_mouse_passthrough(const Vector<Vector2> &p_region, WindowID p_window) {
+	_THREAD_SAFE_METHOD_
+
+	ERR_FAIL_COND(!windows.has(p_window));
+	const WindowData &wd = windows[p_window];
+
+	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) {
+			region = XCreateRegion();
+			XRectangle rect;
+			rect.x = 0;
+			rect.y = 0;
+			rect.width = window_get_real_size(p_window).x;
+			rect.height = window_get_real_size(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;
+			}
+			region = XPolygonRegion(points, p_region.size(), EvenOddRule);
+			memfree(points);
+		}
+		XShapeCombineRegion(x11_display, wd.x11_window, ShapeInput, 0, 0, region, ShapeSet);
+		XDestroyRegion(region);
+	}
+}
+
 void DisplayServerX11::window_set_rect_changed_callback(const Callable &p_callable, WindowID p_window) {
 	_THREAD_SAFE_METHOD_
 

platform/linuxbsd/display_server_x11.h

@@ -291,6 +291,8 @@ public:
 	virtual ObjectID window_get_attached_instance_id(WindowID p_window = MAIN_WINDOW_ID) const;
 
 	virtual void window_set_title(const String &p_title, WindowID p_window = MAIN_WINDOW_ID);
+	virtual void window_set_mouse_passthrough(const Vector<Vector2> &p_region, WindowID p_window = MAIN_WINDOW_ID);
+
 	virtual void window_set_rect_changed_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID);
 	virtual void window_set_window_event_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID);
 	virtual void window_set_input_event_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID);

platform/osx/display_server_osx.h

@@ -102,6 +102,8 @@ public:
 		id window_object;
 		id window_view;
 
+		Vector<Vector2> mpath;
+
 #if defined(OPENGL_ENABLED)
 		ContextGL_OSX *context_gles2 = nullptr;
 #endif
@@ -240,6 +242,7 @@ public:
 	virtual void window_set_drop_files_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID) override;
 
 	virtual void window_set_title(const String &p_title, WindowID p_window = MAIN_WINDOW_ID) override;
+	virtual void window_set_mouse_passthrough(const Vector<Vector2> &p_region, WindowID p_window = MAIN_WINDOW_ID) override;
 
 	virtual int window_get_current_screen(WindowID p_window = MAIN_WINDOW_ID) const override;
 	virtual void window_set_current_screen(int p_screen, WindowID p_window = MAIN_WINDOW_ID) override;

platform/osx/display_server_osx.mm

@@ -33,6 +33,7 @@
 #include "os_osx.h"
 
 #include "core/io/marshalls.h"
+#include "core/math/geometry_2d.h"
 #include "core/os/keyboard.h"
 #include "main/main.h"
 #include "scene/resources/texture.h"
@@ -2404,6 +2405,15 @@ void DisplayServerOSX::window_set_title(const String &p_title, WindowID p_window
 	[wd.window_object setTitle:[NSString stringWithUTF8String:p_title.utf8().get_data()]];
 }
 
+void DisplayServerOSX::window_set_mouse_passthrough(const Vector<Vector2> &p_region, WindowID p_window) {
+	_THREAD_SAFE_METHOD_
+
+	ERR_FAIL_COND(!windows.has(p_window));
+	WindowData &wd = windows[p_window];
+
+	wd.mpath = p_region;
+}
+
 void DisplayServerOSX::window_set_rect_changed_callback(const Callable &p_callable, WindowID p_window) {
 	_THREAD_SAFE_METHOD_
 
@@ -3356,6 +3366,26 @@ void DisplayServerOSX::process_events() {
 		Input::get_singleton()->flush_accumulated_events();
 	}
 
+	for (Map<WindowID, WindowData>::Element *E = windows.front(); E; E = E->next()) {
+		WindowData &wd = E->get();
+		if (wd.mpath.size() > 0) {
+			const Vector2 mpos = _get_mouse_pos(wd, [wd.window_object mouseLocationOutsideOfEventStream]);
+			if (Geometry2D::is_point_in_polygon(mpos, wd.mpath)) {
+				if ([wd.window_object ignoresMouseEvents]) {
+					[wd.window_object setIgnoresMouseEvents:NO];
+				}
+			} else {
+				if (![wd.window_object ignoresMouseEvents]) {
+					[wd.window_object setIgnoresMouseEvents:YES];
+				}
+			}
+		} else {
+			if ([wd.window_object ignoresMouseEvents]) {
+				[wd.window_object setIgnoresMouseEvents:NO];
+			}
+		}
+	}
+
 	[autoreleasePool drain];
 	autoreleasePool = [[NSAutoreleasePool alloc] init];
 }

platform/windows/display_server_windows.cpp

@@ -29,7 +29,9 @@
 /*************************************************************************/
 
 #include "display_server_windows.h"
+
 #include "core/io/marshalls.h"
+#include "core/math/geometry_2d.h"
 #include "main/main.h"
 #include "os_windows.h"
 #include "scene/resources/texture.h"
@@ -597,6 +599,36 @@ void DisplayServerWindows::window_set_title(const String &p_title, WindowID p_wi
 	SetWindowTextW(windows[p_window].hWnd, (LPCWSTR)(p_title.utf16().get_data()));
 }
 
+void DisplayServerWindows::window_set_mouse_passthrough(const Vector<Vector2> &p_region, WindowID p_window) {
+	_THREAD_SAFE_METHOD_
+
+	ERR_FAIL_COND(!windows.has(p_window));
+	windows[p_window].mpath = p_region;
+	_update_window_mouse_passthrough(p_window);
+}
+
+void DisplayServerWindows::_update_window_mouse_passthrough(WindowID p_window) {
+	if (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());
+		for (int i = 0; i < windows[p_window].mpath.size(); i++) {
+			if (windows[p_window].borderless) {
+				points[i].x = windows[p_window].mpath[i].x;
+				points[i].y = windows[p_window].mpath[i].y;
+			} else {
+				points[i].x = windows[p_window].mpath[i].x + GetSystemMetrics(SM_CXSIZEFRAME);
+				points[i].y = windows[p_window].mpath[i].y + GetSystemMetrics(SM_CYSIZEFRAME) + GetSystemMetrics(SM_CYCAPTION);
+			}
+		}
+
+		HRGN region = CreatePolygonRgn(points, windows[p_window].mpath.size(), ALTERNATE);
+		SetWindowRgn(windows[p_window].hWnd, region, TRUE);
+		DeleteObject(region);
+		memfree(points);
+	}
+}
+
 int DisplayServerWindows::window_get_current_screen(WindowID p_window) const {
 	_THREAD_SAFE_METHOD_
 
@@ -1010,6 +1042,7 @@ void DisplayServerWindows::window_set_flag(WindowFlags p_flag, bool p_enabled, W
 		case WINDOW_FLAG_BORDERLESS: {
 			wd.borderless = p_enabled;
 			_update_window_style(p_window);
+			_update_window_mouse_passthrough(p_window);
 		} break;
 		case WINDOW_FLAG_ALWAYS_ON_TOP: {
 			ERR_FAIL_COND_MSG(wd.transient_parent != INVALID_WINDOW_ID && p_enabled, "Transient windows can't become on top");

platform/windows/display_server_windows.h

@@ -323,6 +323,8 @@ private:
 		HWND hWnd;
 		//layered window
 
+		Vector<Vector2> mpath;
+
 		bool preserve_window_size = false;
 		bool pre_fs_valid = false;
 		RECT pre_fs_rect;
@@ -416,6 +418,7 @@ private:
 	void _touch_event(WindowID p_window, bool p_pressed, float p_x, float p_y, int idx);
 
 	void _update_window_style(WindowID p_window, bool p_repaint = true, bool p_maximized = false);
+	void _update_window_mouse_passthrough(WindowID p_window);
 
 	void _update_real_mouse_position(WindowID p_window);
 
@@ -477,6 +480,7 @@ public:
 	virtual void window_set_drop_files_callback(const Callable &p_callable, WindowID p_window = MAIN_WINDOW_ID);
 
 	virtual void window_set_title(const String &p_title, WindowID p_window = MAIN_WINDOW_ID);
+	virtual void window_set_mouse_passthrough(const Vector<Vector2> &p_region, WindowID p_window = MAIN_WINDOW_ID);
 
 	virtual int window_get_current_screen(WindowID p_window = MAIN_WINDOW_ID) const;
 	virtual void window_set_current_screen(int p_screen, WindowID p_window = MAIN_WINDOW_ID);

servers/display_server.cpp

@@ -194,6 +194,10 @@ void DisplayServer::delete_sub_window(WindowID p_id) {
 	ERR_FAIL_MSG("Sub-windows not supported by this display server.");
 }
 
+void DisplayServer::window_set_mouse_passthrough(const Vector<Vector2> &p_region, WindowID p_window) {
+	ERR_FAIL_MSG("Mouse passthrough not supported by this display server.");
+}
+
 void DisplayServer::window_set_ime_active(const bool p_active, WindowID p_window) {
 	WARN_PRINT("IME not supported by this display server.");
 }
@@ -412,6 +416,7 @@ void DisplayServer::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("delete_sub_window", "window_id"), &DisplayServer::delete_sub_window);
 
 	ClassDB::bind_method(D_METHOD("window_set_title", "title", "window_id"), &DisplayServer::window_set_title, DEFVAL(MAIN_WINDOW_ID));
+	ClassDB::bind_method(D_METHOD("window_set_mouse_passthrough", "region", "window_id"), &DisplayServer::window_set_mouse_passthrough, DEFVAL(MAIN_WINDOW_ID));
 
 	ClassDB::bind_method(D_METHOD("window_get_current_screen", "window_id"), &DisplayServer::window_get_current_screen, DEFVAL(MAIN_WINDOW_ID));
 	ClassDB::bind_method(D_METHOD("window_set_current_screen", "screen", "window_id"), &DisplayServer::window_set_current_screen, DEFVAL(MAIN_WINDOW_ID));

servers/display_server.h

@@ -247,6 +247,8 @@ public:
 
 	virtual void window_set_title(const String &p_title, WindowID p_window = MAIN_WINDOW_ID) = 0;
 
+	virtual void window_set_mouse_passthrough(const Vector<Vector2> &p_region, WindowID p_window = MAIN_WINDOW_ID);
+
 	virtual int window_get_current_screen(WindowID p_window = MAIN_WINDOW_ID) const = 0;
 	virtual void window_set_current_screen(int p_screen, WindowID p_window = MAIN_WINDOW_ID) = 0;