code: func newWindow(X *xgbutil.XUtil, color uint32) *xwindow.Window {
  	win, err := xwindow.Generate(X)
  	if err != nil {
  		log.Fatal(err)
  	}
  
  	err = win.CreateChecked(X.RootWin(), 0, 0, 400, 400,
  		xproto.CwBackPixel|xproto.CwEventMask,
  		color, xproto.EventMaskPointerMotion)
  	if err != nil {
  		log.Fatal(err)
  	}
  
  	win.Map()
  	return win
  }
docs: // newWindow creates a new window that listens to MotionNotify events with
  // the given backgroundcolor.