Fix the sliding window problem in linux occur due to reparenting of t…

…he window during the decoration via tracking the parent of the window

platform/linuxbsd/x11/display_server_x11.cpp

@@ -3510,6 +3510,15 @@ void DisplayServerX11::_window_changed(XEvent *event) {
 	wd.minimized = _window_minimize_check(window_id);
 	wd.maximized = _window_maximize_check(window_id, "_NET_WM_STATE");
 
+	// Readjusting the window position if the window is being reparented by the window manager for decoration
+	Window root, parent, *children;
+	unsigned int nchildren;
+	if (XQueryTree(x11_display, wd.x11_window, &root, &parent, &children, &nchildren) && wd.parent != parent) {
+		wd.parent = parent;
+		window_set_position(wd.position, window_id);
+	}
+	XFree(children);
+
 	{
 		//the position in xconfigure is not useful here, obtain it manually
 		int x = 0, y = 0;
@@ -4994,6 +5003,7 @@ DisplayServerX11::WindowID DisplayServerX11::_create_window(WindowMode p_mode, V
 	{
 		wd.x11_window = XCreateWindow(x11_display, RootWindow(x11_display, visualInfo.screen), win_rect.position.x, win_rect.position.y, win_rect.size.width > 0 ? win_rect.size.width : 1, win_rect.size.height > 0 ? win_rect.size.height : 1, 0, visualInfo.depth, InputOutput, visualInfo.visual, valuemask, &windowAttributes);
 
+		wd.parent = RootWindow(x11_display, visualInfo.screen);
 		XSetWindowAttributes window_attributes_ime = {};
 		window_attributes_ime.event_mask = KeyPressMask | KeyReleaseMask | StructureNotifyMask | ExposureMask;
 

platform/linuxbsd/x11/display_server_x11.h

@@ -160,6 +160,7 @@ class DisplayServerX11 : public DisplayServer {
 	struct WindowData {
 		Window x11_window;
 		Window x11_xim_window;
+		Window parent;
 		::XIC xic;
 		bool ime_active = false;
 		bool ime_in_progress = false;