SwiftUI gestures break when contained in a UIHostingController that had a layout pass in a UIKit animated transition
When a newly instantiated UIHostingController is animated as part of a UIViewControllerAnimatedTransitioning within a UINavigationController that has a call to view.layoutIfNeeded() on the UIHostingController's view, SwiftUI gestures stop being processed, resulting in an unresponsive application.
Notably, gestures for embedded UIKit UIViews are still processed correctly; the only gestures that break are those implemented in SwiftUI, e.g. the tap gesture of a Button.
This issue reproduces on iOS 15 and iOS 16 Beta 6.
From poking around under the hood, it appears that when this occurs the SwiftUI.EventBindingManager never goes into the isActive = true state when the touches begin, and the SwiftUI.UIKitGestureRecognizer does not transition to the ended state on UIGestureRecognizer.touchesEnded(…).
Some mitigations for this behavior are:
- Slightly repositioning the
UIHostingController's view onviewDidAppear(as seen in this commit 9f75a7a) - Removing and re-adding the
UIHostingController's view to the view hierarchy, but that causes other undesirable behavior.