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Summary:
I have a custom UICollectionViewLayout for displaying cells in a 2x2 grid in full screen. When the view first loads, UICollectionViewDelegate collectionView:willDisplayCell:forItemAtIndexPath is called for all 4 items in view. When paging to the next page of cells, the delegate method is NOT called for the focused cell under tvOS 11.

Example: If I move to the top right cell (cell #1 in my custom layout) and move to the next cell horizontally (cell #4), the delegate method is called for all other cells except cell #4. If I move to the bottom right cell (cell #3) and move horizontally to the next cell (cell #6), the delegate method is not called for cell #6.

This happens in both the simulator and on an actual Apple TV device.

This is NOT the case in tvOS 10, only tvOS 11

Steps to Reproduce:
In the attached sample project (CollectionViewTest) I have set up something very similar to my actual project - the custom layout code (CollectionViewLayout) is directly copied from my project. The currently focused cell has a white border drawn around it. Move from Cell #0 to Cell #1, then move horizontally to the next page to select Cell #4. Notice in the console output that "Will Display Cell #" is output for all cells #5, #6, and #7, but not for cell #4. When moving back to the previous cell (Cell #1) notice that "End Displaying Cell #" is again output for all cells except Cell #4.

Expected Results:
I expect the delegate method to be called for all cells.

Actual Results:
Delegate method is not called for all cells.

Version/Build:
tvOS 11 SDK (beta 6?)

Configuration:
macOS 10.12.6
Xcode 9 beta 6


Comment: Sept 29, 2017
Still present in tvOS 11 and tvOS 11.1 beta 1 using Xcode 9 and Xcode 9.1 beta 1