code: func (w *Window) FocusParent(tstamp xproto.Timestamp) {
  	mode := byte(xproto.InputFocusParent)
  	err := xproto.SetInputFocusChecked(w.X.Conn(), mode, w.Id, tstamp).Check()
  	if err != nil {
  		xgbutil.Logger.Println(err)
  	}
  }
docs: // FocusParent is just like Focus, except it sets the "revert-to" mode to
  // Parent. This should be used when setting focus to a sub-window.