Tooltips issue

[Germán Arias]

See:

http://youtu.be/ZCMN3-mgIaQ

No idea if this is a bug, or I'm doing something wrong. The chalkboard is a 
grid of buttons (50x50), I add the buttons with something like:

      [botonCell setBordered: NO];
      [botonCell addToolTipRect: NSMakeRect(0, 0, 50, 50)
              owner: self
           userData: nil];
      [self addSubview: botonCell];
      [botonCell release];

Is this a bad approach? Maybe I need add the visible rect at scrollview and 
then with -hitTest: get the button to display the tooltip?

PS: No idea why the video show the menu as a white rectangle. I don't use 
Terminal.app because Control-C (copy) can't stop the recording.

Germán