ttk.go
func ForwardKey(k Key) {
	if k.Window == nil {
		return
	}
	k.Window.KeyHandler(windower2window[k.Window], k)
}
func ForwardKey(k Key) {
	if k.Window == nil {
		return
	}
	k.Window.KeyHandler(windower2window[k.Window], k)
}
// ForwardKey must be called from the application to route key strokes to
// windows.  The life cycle of keystrokes is as follows: widgets -> global
// application context -> window.  Care must be taken in the application to not
// rely on keystrokes that widgets may use.