code: func Enqueue(xu *xgbutil.XUtil, ev xgb.Event, err xgb.Error) {
  	xu.EvqueueLck.Lock()
  	defer xu.EvqueueLck.Unlock()
  
  	xu.Evqueue = append(xu.Evqueue, xgbutil.EventOrError{
  		Event: ev,
  		Err:   err,
  	})
  }
docs: // Enqueue queues up an event read from X.
  // Note that an event read may return an error, in which case, this queue
  // entry will be an error and not an event.
  //
  //	ev, err := XUtilValue.Conn().WaitForEvent()
  //	xevent.Enqueue(XUtilValue, ev, err)
  //
  // You probably shouldn't have to enqueue events yourself. This is done
  // automatically if you're using xevent.Main{Ping} and/or xevent.Read.