Add new window setting: always on top

Implemented for Windows and Linux.

4 files changed, 78 insertions, 3 deletions

diff --git a/platform/windows/os_windows.cpp b/platform/windows/os_windows.cpp
index 4f4b225b14..fdf0efc8ae 100644
--- a/platform/windows/os_windows.cpp
+++ b/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);
diff --git a/platform/windows/os_windows.h b/platform/windows/os_windows.h
index c24e35e929..2f6d5ac601 100644
--- a/platform/windows/os_windows.h
+++ b/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);
diff --git a/platform/x11/os_x11.cpp b/platform/x11/os_x11.cpp
index e4165e2fe3..21b65b9143 100644
--- a/platform/x11/os_x11.cpp
+++ b/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)
diff --git a/platform/x11/os_x11.h b/platform/x11/os_x11.h
index f7bc0b73e0..9774dcd0d0 100644
--- a/platform/x11/os_x11.h
+++ b/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);