pub fn subscribe_to_window_events(&self, window: xlib::Window) {
        let mask = xlib::EnterWindowMask | xlib::FocusChangeMask | xlib::PropertyChangeMask;
        self.subscribe_to_event(window, mask);
    }
Subscribe to the wanted events of a window.
display-servers/xlib-display-server/src/xwrap/window.rs