code: func GroupListStart(w *Window, num int, name string, flags WindowFlags) (GroupList, *Window) {
  	var gl GroupList
  	gl.w = w.GroupBegin(name, flags)
  	gl.num = num
  	gl.idx = -1
  	if gl.w != nil {
  		gl.scrollbary = gl.w.Scrollbar.Y
  	}
  
  	return gl, gl.w
  }
docs: // GroupListStart starts a scrollable list of <num> rows of <height> height