             _topViewController.view.transform = CGAffineTransform(translationX: transitionPercent * _topViewController.view.bounds.width, y: 0.0)
             _formerViewController.view.transform = CGAffineTransform(translationX: -(1.0-transitionPercent) * _formerViewController.view.bounds.width / 2.0, y: 0.0)
             _topViewController.view.clipsToBounds = false
-            // _setupTransitionShadowOfViewController(_topViewController)
-            // _topViewController.view.layer.shadowOpacity = Float(1.0-transitionPercent) * Float(0.5)
             
             _transitionTabNavigationBarWithPercent(transitionPercent, transition: _transitionNavigationBarViews)
         case .cancelled: fallthrough

    fileprivate var _rootViewControllersInfo: (selectedIndex: Array<UIViewController>.Index, viewControllers: [UIViewController]) = (0, [])
    fileprivate var _viewControllersStack: [UIViewController] = []
    
    // MARK: - Overrides.
    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)

            let location = sender.location(in: view)
            let velocity = sender.velocity(in: view)
            let translation = sender.translation(in: view)

            let transitionPercent = max(0.0, location.x - _panGestureBeginsLocation.x) / view.bounds.width
            
