code: func (win *Window) Invisible() (above, below bool) {
  	return win.LastWidgetBounds.Y < win.layout.Clip.Y, win.LastWidgetBounds.Y+win.LastWidgetBounds.H > (win.layout.Clip.Y + win.layout.Clip.H)
  }
docs: // Will return (false, false) if the last widget is visible, (true,
  // false) if it is above the visible area, (false, true) if it is
  // below the visible area