     let scrollView = ContainerView(frame: CGRectZero)
 }
 
-public extension PageController {
-
-    func frameForMenuBar() -> CGRect {
+extension PageController {
+
+    public var frameForMenuBar: CGRect {
         var frame = CGRect(x: 0, y: 0, width: view.bounds.width, height: 44)
         if let frameForNavigationBar = navigationController?.navigationBar.frame {
             frame.origin.y = frameForNavigationBar.maxY

        }

        // center
        displayViewController(visibleViewController, frame: frameForCenterContentController())

        // left
        var exists = childViewControllers.filter { $0.view.include(frame: self.frameForLeftContentController()) }
        if exists.isEmpty {
            displayViewController(viewControllers[(index - 1).relative(viewControllers.count)], frame: frameForLeftContentController())
        }

        // right
        exists = childViewControllers.filter { $0.view.include(frame: self.frameForRightContentController()) }
        if exists.isEmpty {
            displayViewController(viewControllers[(index + 1).relative(viewControllers.count)], frame: frameForRightContentController())
        }
    }


        return frame
    }

    public var frameForContentController: CGRect {
        return view.bounds
    }

    var frameForLeftContentController: CGRect {
        var frame = frameForContentController
        frame.origin.x = 0
        return frame
    }

    var frameForCenterContentController: CGRect {
        var frame = frameForContentController
        frame.origin.x = frame.width
        return frame
    }

    var frameForRightContentController: CGRect {
        var frame = frameForContentController
        frame.origin.x = frame.width * 2
        return frame
    }

    func _configure() {
        automaticallyAdjustsScrollViewInsets = false

        let frame = frameForContentController
        scrollView.frame = frame
        scrollView.controller = self

        scrollView.contentSize = CGSize(width: frame.width * 3, height: frame.height)
        view.addSubview(scrollView)

        menuBar.frame = frameForMenuBar
        menuBar.controller = self
        view.addSubview(menuBar)
    }
