         }
     }
 
-    // MARK: ScrollView Observation
+    // MARK: - ScrollView Observation
     
     private func startObservingScrollView() {
         self.scrollView?.addObserver(self, forKeyPath: "frame", options: .New, context: &ScrollViewObservationContext)

            if currentEvent.type == .LeftMouseDown && currentEvent.clickCount > 1 {
                self.editTabButton(self.selectedButton!)
            }
            else if ...
        }
    }
    
    public func selectedItemIndex() -> Int {
        return (self.selectedButton != nil) ? self.selectedButton!.tag : -1
    }
    
    public func selectItemAtIndex(index: Int) {
        
    }
    
    // MARK: - Editing
    

        self.stopObservingScrollView()
    }
    
    // MARK: - Public Overrides

    public override func menuForEvent(event: NSEvent) -> NSMenu? {
        return nil
    }
    
    // MARK: - Data Source
    
    public func reloadTabs() {
        guard let dataSource = self.dataSource else {
