   public override func viewWillLayoutSubviews() {
     super.viewWillLayoutSubviews()
     
+    guard !scrolling else {
+      return
+    }
+    
     self.scrollView.frame = self.view.bounds
     if self.orientationIsHorizontal {
       self.scrollView.contentSize = CGSize(width: self.view.bounds.width * 3, height: self.view.bounds.height)

   - parameter startingViewController: The currently selected view controller the transition is starting from
   - parameter destinationViewController: The view controller that will be scrolled to, where the transition should end
   */
  optional func em_pageViewController(pageViewController: EMPageViewController, willStartScrollingFrom startingViewController: UIViewController, destinationViewController:UIViewController, direction: EMPageViewControllerNavigationDirection)
  
  /**
   Called whenever there has been a scroll position change in a page transition. This method is very useful if you need to know the exact progress of the page transition animation.

  
  // MARK: - Internal Callbacks
  
  private func willScrollFromViewController(startingViewController: UIViewController?, destinationViewController: UIViewController) {
    if (startingViewController != nil) {
      self.delegate?.em_pageViewController?(self, willStartScrollingFrom: startingViewController!, destinationViewController: destinationViewController)
    }
    
    destinationViewController.beginAppearanceTransition(true, animated: self.transitionAnimated)
