Why is the top layout guide moving in my iMessage extension

Question

I have an iMessage extension and I\'m having some issues with the top layout guide. I have an MSMessagesAppViewController that handles changes between presentation

Answer 1

As a workaround I use UIPresentationController, which shifts the modal view controller by topLayoutGuide.length points:

class MyViewController: MSMessagesAppViewController {

    private func presentModalViewController() {
        let imagePicker = UIImagePickerController()
        imagePicker.delegate = self
        imagePicker.sourceType = .savedPhotosAlbum

        imagePicker.modalPresentationStyle = .custom
        imagePicker.transitioningDelegate = self

        present(imagePicker, animated: true, completion: nil)
    }
}
// MARK: - UIViewControllerTransitioningDelegate
extension MyViewController: UIViewControllerTransitioningDelegate {

    func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
        let vc = PresentationController(presentedViewController: presented, presenting: presenting)
        // I really don't want to hardcode the value of topLayoutGuideLength here, but when the extension is in compact mode, topLayoutGuide.length returns 172.0.
        vc.topLayoutGuideLength = topLayoutGuide.length > 100 ? 86.0 : topLayoutGuide.length
        return vc
    }
}


class PresentationController: UIPresentationController {

    var topLayoutGuideLength: CGFloat = 0.0

    override var frameOfPresentedViewInContainerView: CGRect {
        guard let containerView = containerView else {
            return super.frameOfPresentedViewInContainerView
        }
        return CGRect(x: 0, y: topLayoutGuideLength, width: containerView.bounds.width, height: containerView.bounds.height - topLayoutGuideLength)
    }
}

The only problem is when you're calling presentModalViewController from compact mode, topLayoutGuide.length is 172.0 for unknown reason. So I had to hardcode a value for that case.