let get_wm_window_position_offset () =
let win = GWindow.window ~width: 0 ~height: 0 () in
win#show ();
let (x,y) = Gdk.Window.get_position win#misc#window in
win#move ~x ~y;
treat_gtk_events ();
let (x2,y2) = Gdk.Window.get_position win#misc#window in
win#destroy ();
Cam_dbg.print ~level: 3
(Printf.sprintf "get_wm_window_position_offset: offset: x=%d-%d=%d y=%d-%d=%d"
x2 x (x2-x) y2 y (y2-y));
(x2 - x, y2 - y)