Merge pull request #16763 from RandomShaper/improve-fullscreen

Remove window decorations for fullscreen on X11

platform/x11/os_x11.cpp

@@ -730,6 +730,16 @@ 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 (p_enabled && !get_borderless_window()) {
+		// remove decorations if the window is not already borderless
+		Hints hints;
+		Atom property;
+		hints.flags = 2;
+		hints.decorations = 0;
+		property = XInternAtom(x11_display, "_MOTIF_WM_HINTS", True);
+		XChangeProperty(x11_display, x11_window, property, property, 32, PropModeReplace, (unsigned char *)&hints, 5);
+	}
+
 	if (p_enabled && !is_window_resizable()) {
 		// Set the window as resizable to prevent window managers to ignore the fullscreen state flag.
 		XSizeHints *xsh;