È possibile ricevere la notifica NSViewBoundsDidChangeNotification come indicato qui sotto
NSView *contentView = [scrollview contentView];
[contentView setPostsBoundsChangedNotifications:YES];
// a register for those notifications on the content view.
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(boundDidChange:)
name:NSViewBoundsDidChangeNotification
object:contentView];
Il metodo di notifica
- (void)boundDidChange:(NSNotification *)notification {
// get the changed content view from the notification
NSClipView *changedContentView=[notification object];
}