code: func VisibleDesktopsGet(xu *xgbutil.XUtil) ([]uint, error) {
  	return xprop.PropValNums(xprop.GetProperty(xu, xu.RootWin(),
  		"_NET_VISIBLE_DESKTOPS"))
  }
docs: // _NET_VISIBLE_DESKTOPS get
  // This is not part of the EWMH spec, but is a property of my own creation.
  // It allows the window manager to report that it has multiple desktops
  // viewable at the same time. (This conflicts with other EWMH properties,
  // so I don't think this will ever be added to the official spec.)