Custom presentation using Auto Layout breaks on fullscreen presentation

Originator:zach
Number:rdar://47946890 Date Originated:February 10 2019, 2:54 AM
Status:Open Resolved:false
Product:iOS + SDK Product Version:Xcode Version 10.1 (10B61) / iOS 12.1.3
Classification:Other Bug Reproducible:Always
 
Area:
UIKit

Summary:

It is expected that custom `UIPresentationController` subclasses can lay out their content using Auto Layout, modulo the nuts and bolts of custom transitions or the content being driven by manual layout. Any lack of such a capability isn't documented, and DevPubs encourages it:

> Apps that use auto layout should not need to do anything because the auto layout mechanism resizes views as needed.

Adding constraints when setting up custom views in the `containerView` during `presentationTransitionWillBegin` works great.

The problem occurs when doing modal presentations on top of this custom transition. For instance, a subsequent full-screen presentation does something unexpected to move its `presentingViewController.view` into its hierarchy, which breaks any constraints.

Steps to Reproduce:

1. Download and open the attached sample project, `Layout.xcodeproj`.
2. Run the "Layout" scheme on any iOS simulator or device.
3. Tap "Show Modal".
4. Tap "Fullscreen Top Me".
5. Observer.

A video of the issue is attached.

Expected Results:

The full-screen view presents over the card view seamlessly.

The full-screen view dismisses to reveal the the card view seamlessly.

Actual Results:

The card view jumps to an unexpected position on-screen as the full-screen presentation begins.

The card view jumps again to another unexpected position on-screen as the full-screen dismissal begins.

The card view disappears entirely as the full-screen dismissal ends.

Version/Build:

Xcode Version 10.1 (10B61)

iOS 12.1.3

Configuration:

N/A

Notes:

In the attached sample project, uncomment CardPresenting.swift:37-39 for a workaround. Using `containerViewWillLayoutSubviews` felt wrong to me, as there's nothing explicit trying it to nested and presentation. If that is a fine place, or there is a better place, that should exist in the documentation.

Additionally, I suspect stealing back the view is a bad idea, but have no simple way to prevent re-activating the constraints in an invalid way. The workaround at least works as I'm expecting.

Comments

Attachments:

https://www.icloud.com/iclouddrive/0qxI_d2wKWaK--EZzdPkruegQ#Layout https://www.icloud.com/iclouddrive/0PwCUpjYpmDe_f7HA-d6kyttw#card-bad


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