title: Presenting/dismissing modal view controller with custom animations does not display presenting view controller underneath
body: <p>I have implemented a view controller which provides a navigation structure similar to UINavigationController. It is using view controller containment. All view controllers are added as children.</p>
  
  <p>When I present a modal view controller from a view controller within this navigational flow, the underlying view disappears during the custom transition and the user is left viewing the Window view below.</p>
  
  <pre><code>[UIView animateWithDuration:0.35 animations:^{
  
      self.view.transform = CGAffineTransformMakeScale(0.4, 0.4);
      self.view.alpha = 0.0;
  
  } completion:^(BOOL finished) {
      [[self presentingViewController] dismissViewControllerAnimated:NO completion:nil];
  }];
  </code></pre>
  
  <p>This is a very jarring experience. Previously this animation would shrink the modal view controller's view and fade it into the presenting view controller's view underneath. As I stated before, now the user is exposed to the view of the Window (which currently has not had an color values set).</p>
  
  <p>Refering to the View Controller documentation I feel as though I have set all the right fields, however, something is incorrect.</p>
  
  <blockquote>
    <p>A view controller presents another view controller when it wants that
    view controller to perform a task. The presenting view controller is
    in charge of this behavior. It configures the presented view
    controller, receives information from it, and eventually dismisses it.
    However, while it is being presented, the presented view controller’s
    view is temporarily added to the window’s view hierarchy.</p>
  </blockquote>
  
  <p>My presenting view controller is my custom navigation controller, the presented view controller is a modal view controller that allows the user to compose a conversation.  My application's window root view controller is correctly configured to my custom navigation controller.</p>
  
  <p>I also read some more about presentation context and have configured my custom navigation controller as having definesPresentationContext as YES.</p>
  
  <blockquote>
    <p>When a view controller is presented, the portion of the screen that it
    covers is defined by a presentation context provided to it by another
    view controller. The view controller that provides the presentation
    context does not need be the same view controller that presented it.
    Figure 1-15 shows the same view controller hierarchy that is presented
    in Figure 1-14. You can see that the content view presented the view
    controller, but it did not provide the presentation context. Instead,
    the view controller was presented by the tab controller. Because of
    this, even though the presenting view controller only covers the
    portion of the screen provided to it by the tab view controller, the
    presented view controller uses the entire area owned by the tab view
    controller. Within my custom navigation controller I have not
    overriden any methods related to presentation or dismissal of view
    controllers. All of the child view controllers that are added are all
    added as childViewControllers and their views have been added to this
    custom navigation controller.</p>
  </blockquote>
  
  <ul>
  <li>Why would a custom transition show the Window's view instead of
  respecting the custom containment view controller which provides the
  presentation context? </li>
  <li>Why would the traditional transition animations    work as expected?</li>
  </ul>