Add new window setting: always on top

Implemented for Windows and Linux.

core/bind/core_bind.cpp

@@ -294,6 +294,14 @@ bool _OS::is_window_maximized() const {
 	return OS::get_singleton()->is_window_maximized();
 }
 
+void _OS::set_window_always_on_top(bool p_enabled) {
+	OS::get_singleton()->set_window_always_on_top(p_enabled);
+}
+
+bool _OS::is_window_always_on_top() const {
+	return OS::get_singleton()->is_window_always_on_top();
+}
+
 void _OS::set_borderless_window(bool p_borderless) {
 	OS::get_singleton()->set_borderless_window(p_borderless);
 }
@@ -1010,6 +1018,8 @@ void _OS::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("is_window_minimized"), &_OS::is_window_minimized);
 	ClassDB::bind_method(D_METHOD("set_window_maximized", "enabled"), &_OS::set_window_maximized);
 	ClassDB::bind_method(D_METHOD("is_window_maximized"), &_OS::is_window_maximized);
+	ClassDB::bind_method(D_METHOD("set_window_always_on_top", "enabled"), &_OS::set_window_always_on_top);
+	ClassDB::bind_method(D_METHOD("is_window_always_on_top"), &_OS::is_window_always_on_top);
 	ClassDB::bind_method(D_METHOD("request_attention"), &_OS::request_attention);
 
 	ClassDB::bind_method(D_METHOD("set_borderless_window", "borderless"), &_OS::set_borderless_window);

core/bind/core_bind.h

@@ -164,6 +164,8 @@ public:
 	virtual bool is_window_minimized() const;
 	virtual void set_window_maximized(bool p_enabled);
 	virtual bool is_window_maximized() const;
+	virtual void set_window_always_on_top(bool p_enabled);
+	virtual bool is_window_always_on_top() const;
 	virtual void request_attention();
 
 	virtual void set_borderless_window(bool p_borderless);

core/os/os.h

@@ -94,15 +94,17 @@ public:
 		bool resizable;
 		bool borderless_window;
 		bool maximized;
+		bool always_on_top;
 		bool use_vsync;
 		float get_aspect() const { return (float)width / (float)height; }
-		VideoMode(int p_width = 1024, int p_height = 600, bool p_fullscreen = false, bool p_resizable = true, bool p_borderless_window = false, bool p_maximized = false, bool p_use_vsync = false) {
+		VideoMode(int p_width = 1024, int p_height = 600, bool p_fullscreen = false, bool p_resizable = true, bool p_borderless_window = false, bool p_maximized = false, bool p_always_on_top = false, bool p_use_vsync = false) {
 			width = p_width;
 			height = p_height;
 			fullscreen = p_fullscreen;
 			resizable = p_resizable;
 			borderless_window = p_borderless_window;
 			maximized = p_maximized;
+			always_on_top = p_always_on_top;
 			use_vsync = p_use_vsync;
 		}
 	};
@@ -191,6 +193,8 @@ public:
 	virtual bool is_window_minimized() const { return false; }
 	virtual void set_window_maximized(bool p_enabled) {}
 	virtual bool is_window_maximized() const { return true; }
+	virtual void set_window_always_on_top(bool p_enabled) {}
+	virtual bool is_window_always_on_top() const { return false; }
 	virtual void request_attention() {}
 
 	virtual void set_borderless_window(bool p_borderless) {}

main/main.cpp

@@ -106,6 +106,7 @@ static OS::VideoMode video_mode;
 static bool init_maximized = false;
 static bool init_windowed = false;
 static bool init_fullscreen = false;
+static bool init_always_on_top = false;
 static bool init_use_custom_pos = false;
 #ifdef DEBUG_ENABLED
 static bool debug_collisions = false;
@@ -224,6 +225,7 @@ void Main::print_help(const char *p_binary) {
 	OS::get_singleton()->print("  -f, --fullscreen                 Request fullscreen mode.\n");
 	OS::get_singleton()->print("  -m, --maximized                  Request a maximized window.\n");
 	OS::get_singleton()->print("  -w, --windowed                   Request windowed mode.\n");
+	OS::get_singleton()->print("  -t, --always-on-top              Request an always-on-top window.\n");
 	OS::get_singleton()->print("  --resolution <W>x<H>             Request window resolution.\n");
 	OS::get_singleton()->print("  --position <X>,<Y>               Request window position.\n");
 	OS::get_singleton()->print("  --low-dpi                        Force low-DPI mode (macOS and Windows only).\n");
@@ -430,6 +432,9 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 		} else if (I->get() == "-w" || I->get() == "--windowed") { // force windowed window
 
 			init_windowed = true;
+		} else if (I->get() == "-t" || I->get() == "--always-on-top") { // force always-on-top window
+
+			init_always_on_top = true;
 		} else if (I->get() == "--profiling") { // enable profiling
 
 			use_debug_profiler = true;
@@ -795,6 +800,7 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 	GLOBAL_DEF("display/window/size/resizable", true);
 	GLOBAL_DEF("display/window/size/borderless", false);
 	GLOBAL_DEF("display/window/size/fullscreen", false);
+	GLOBAL_DEF("display/window/size/always_on_top", false);
 	GLOBAL_DEF("display/window/size/test_width", 0);
 	GLOBAL_DEF("display/window/size/test_height", 0);
 
@@ -817,6 +823,7 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 		video_mode.resizable = GLOBAL_GET("display/window/size/resizable");
 		video_mode.borderless_window = GLOBAL_GET("display/window/size/borderless");
 		video_mode.fullscreen = GLOBAL_GET("display/window/size/fullscreen");
+		video_mode.always_on_top = GLOBAL_GET("display/window/size/always_on_top");
 	}
 
 	if (!force_lowdpi) {
@@ -1020,6 +1027,9 @@ Error Main::setup2(Thread::ID p_main_tid_override) {
 	} else if (init_fullscreen) {
 		OS::get_singleton()->set_window_fullscreen(true);
 	}
+	if (init_always_on_top) {
+		OS::get_singleton()->set_window_always_on_top(true);
+	}
 
 	register_server_types();
 

platform/windows/os_windows.cpp

@@ -1068,6 +1068,10 @@ Error OS_Windows::initialize(const VideoMode &p_desired, int p_video_driver, int
 		}
 	};
 
+	if (video_mode.always_on_top) {
+		SetWindowPos(hWnd, video_mode.always_on_top ? HWND_TOPMOST : HWND_NOTOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
+	}
+
 #if defined(OPENGL_ENABLED)
 	gl_context = memnew(ContextGL_Win(hWnd, true));
 	gl_context->initialize();
@@ -1601,6 +1605,19 @@ bool OS_Windows::is_window_maximized() const {
 	return maximized;
 }
 
+void OS_Windows::set_window_always_on_top(bool p_enabled) {
+	if (video_mode.always_on_top == p_enabled)
+		return;
+
+	video_mode.always_on_top = p_enabled;
+
+	_update_window_style();
+}
+
+bool OS_Windows::is_window_always_on_top() const {
+	return video_mode.always_on_top;
+}
+
 void OS_Windows::set_borderless_window(bool p_borderless) {
 	if (video_mode.borderless_window == p_borderless)
 		return;
@@ -1625,6 +1642,8 @@ void OS_Windows::_update_window_style(bool repaint) {
 		}
 	}
 
+	SetWindowPos(hWnd, video_mode.always_on_top ? HWND_TOPMOST : HWND_NOTOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
+
 	if (repaint) {
 		RECT rect;
 		GetWindowRect(hWnd, &rect);

platform/windows/os_windows.h

@@ -210,6 +210,8 @@ public:
 	virtual bool is_window_minimized() const;
 	virtual void set_window_maximized(bool p_enabled);
 	virtual bool is_window_maximized() const;
+	virtual void set_window_always_on_top(bool p_enabled);
+	virtual bool is_window_always_on_top() const;
 	virtual void request_attention();
 
 	virtual void set_borderless_window(bool p_borderless);

platform/x11/os_x11.cpp

@@ -333,6 +333,11 @@ Error OS_X11::initialize(const VideoMode &p_desired, int p_video_driver, int p_a
 		XFree(xsh);
 	}
 
+	if (current_videomode.always_on_top) {
+		current_videomode.always_on_top = false;
+		set_window_always_on_top(true);
+	}
+
 	AudioDriverManager::initialize(p_audio_driver);
 
 	ERR_FAIL_COND_V(!visual_server, ERR_UNAVAILABLE);
@@ -710,9 +715,6 @@ void OS_X11::get_fullscreen_mode_list(List<VideoMode> *p_list, int p_screen) con
 }
 
 void OS_X11::set_wm_fullscreen(bool p_enabled) {
-	if (current_videomode.fullscreen == p_enabled)
-		return;
-
 	if (p_enabled && !is_window_resizable()) {
 		// Set the window as resizable to prevent window managers to ignore the fullscreen state flag.
 		XSizeHints *xsh;
@@ -773,6 +775,22 @@ void OS_X11::set_wm_fullscreen(bool p_enabled) {
 	}
 }
 
+void OS_X11::set_wm_above(bool p_enabled) {
+	Atom wm_state = XInternAtom(x11_display, "_NET_WM_STATE", False);
+	Atom wm_above = XInternAtom(x11_display, "_NET_WM_STATE_ABOVE", False);
+
+	XClientMessageEvent xev;
+	memset(&xev, 0, sizeof(xev));
+	xev.type = ClientMessage;
+	xev.window = x11_window;
+	xev.message_type = wm_state;
+	xev.format = 32;
+	xev.data.l[0] = p_enabled ? _NET_WM_STATE_ADD : _NET_WM_STATE_REMOVE;
+	xev.data.l[1] = wm_above;
+	xev.data.l[3] = 1;
+	XSendEvent(x11_display, DefaultRootWindow(x11_display), False, SubstructureRedirectMask | SubstructureNotifyMask, (XEvent *)&xev);
+}
+
 int OS_X11::get_screen_count() const {
 	// Using Xinerama Extension
 	int event_base, error_base;
@@ -947,7 +965,19 @@ void OS_X11::set_window_size(const Size2 p_size) {
 }
 
 void OS_X11::set_window_fullscreen(bool p_enabled) {
+	if (current_videomode.fullscreen == p_enabled)
+		return;
+
+	if (p_enabled && current_videomode.always_on_top) {
+		// Fullscreen + Always-on-top requires a maximized window on some window managers (Metacity)
+		set_window_maximized(true);
+	}
 	set_wm_fullscreen(p_enabled);
+	if (!p_enabled && !current_videomode.always_on_top) {
+		// Restore
+		set_window_maximized(false);
+	}
+
 	current_videomode.fullscreen = p_enabled;
 }
 
@@ -1154,6 +1184,27 @@ bool OS_X11::is_window_maximized() const {
 	return false;
 }
 
+void OS_X11::set_window_always_on_top(bool p_enabled) {
+	if (is_window_always_on_top() == p_enabled)
+		return;
+
+	if (p_enabled && current_videomode.fullscreen) {
+		// Fullscreen + Always-on-top requires a maximized window on some window managers (Metacity)
+		set_window_maximized(true);
+	}
+	set_wm_above(p_enabled);
+	if (!p_enabled && !current_videomode.fullscreen) {
+		// Restore
+		set_window_maximized(false);
+	}
+
+	current_videomode.always_on_top = p_enabled;
+}
+
+bool OS_X11::is_window_always_on_top() const {
+	return current_videomode.always_on_top;
+}
+
 void OS_X11::set_borderless_window(bool p_borderless) {
 
 	if (current_videomode.borderless_window == p_borderless)

platform/x11/os_x11.h

@@ -178,6 +178,7 @@ class OS_X11 : public OS_Unix {
 	bool maximized;
 	//void set_wm_border(bool p_enabled);
 	void set_wm_fullscreen(bool p_enabled);
+	void set_wm_above(bool p_enabled);
 
 	typedef xrr_monitor_info *(*xrr_get_monitors_t)(Display *dpy, Window window, Bool get_active, int *nmonitors);
 	typedef void (*xrr_free_monitors_t)(xrr_monitor_info *monitors);
@@ -260,6 +261,8 @@ public:
 	virtual bool is_window_minimized() const;
 	virtual void set_window_maximized(bool p_enabled);
 	virtual bool is_window_maximized() const;
+	virtual void set_window_always_on_top(bool p_enabled);
+	virtual bool is_window_always_on_top() const;
 	virtual void request_attention();
 
 	virtual void set_borderless_window(bool p_borderless);