Workaround for custom UIViewController animations in landscape?

Question

I have a custom animated UIViewController transition, and it seems that there is a bug in iOS that screws up the layout in landscape orientation. In the main animation method, i'm given a mix of landscape and portrait views. (In portrait the views are all portrait, so no problem.)

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext;
{
  UIViewController* toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
  UIViewController* fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
  UIView *containerView = [transitionContext containerView];

  // fromViewController.view => landscape, transform
  // toViewController.view => portrait, transform
  // containerView => portrait, no transform

  [containerView addSubview:toViewController.view];

  // ...animation... //
}

I know that the frame property is not reliable when a view has a transform - so I'm guessing this is the root of the problem. In landscape mode, the to/from viewControllers views have a 90 deg clockwise transform [0 -1 1 0]. I've tried using bounds/center to size and position the view, as well removing the transform and then reapplying it, but UIKit fights me and insists on displaying the view as portrait. Annoying!

In the screenshot, the dark grey is the UIWindow background, and the red is the added modal view controller which should cover the whole screen.

Anyone found a workaround?

Answer 1

Ok, the fix is surprisingly simple:

Set the toViewController frame to the container before adding the view to the container.

toViewController.view.frame = containerView.frame;
[containerView addSubview:toViewController.view];

Update: There is still a limitation in that you don't know the orientation of the frame. It is portrait initially, but stretched into landscape when it is displayed on screen. If you wanted to slide in the view from the right, in landscape it might slide in from the "top" (or the bottom if viewing the other landscape!)