title: Notification for new NSTableView Group Row
body: <p>I'm looking to change the look of my row view when it becomes a group row, or possibly more specifically when it becomes the group row that is stuck at the top of the NSTableview.</p>
  
  <p>I wondered if there was a notification or some property that could be checked. Ideally I'd like to do some kind of animation as it gets within range of the top from one view to the next.</p>
  
  <p>I'm thinking along the lines of tracking the row views coordinates in relation to the clip view/scroll view... Would that be the approach you would take?</p>
  
  <p>Any suggestions?</p>