code: func WorkareaSet(xu *xgbutil.XUtil, workareas []Workarea) error {
  	rects := make([]uint, len(workareas)*4)
  	for i, workarea := range workareas {
  		rects[i*4+0] = uint(workarea.X)
  		rects[i*4+1] = uint(workarea.Y)
  		rects[i*4+2] = workarea.Width
  		rects[i*4+3] = workarea.Height
  	}
  
  	return xprop.ChangeProp32(xu, xu.RootWin(), "_NET_WORKAREA", "CARDINAL",
  		rects...)
  }
docs: // _NET_WORKAREA set