code: func RootGeometry(xu *xgbutil.XUtil) xrect.Rect {
  	geom, err := RawGeometry(xu, xproto.Drawable(xu.RootWin()))
  	if err != nil {
  		panic(err)
  	}
  	return geom
  }
docs: // RootGeometry gets the geometry of the root window. It will panic on failure.