code: func DesktopViewportSet(xu *xgbutil.XUtil, viewports []DesktopViewport) error {
  	coords := make([]uint, len(viewports)*2)
  	for i, viewport := range viewports {
  		coords[i*2] = uint(viewport.X)
  		coords[i*2+1] = uint(viewport.Y)
  	}
  
  	return xprop.ChangeProp32(xu, xu.RootWin(), "_NET_DESKTOP_VIEWPORT",
  		"CARDINAL", coords...)
  }
docs: // _NET_DESKTOP_VIEWPORT set