[WIP][iOS] Horizontal CollectionView jumps to beginning

[SubhikshaSf4851]

Note

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It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment whether this change resolves your issue. Thank you!

This pull request resolves a build-breaking duplicate-method conflict between two independent CustomUICollectionViewCompositionalLayout fixes on iOS, while preserving the rotation-invalidation behavior that #32664 introduced for #32435.

Issue Details

PR #36546's fix added a ShouldInvalidateLayoutForBoundsChange(CGRect newBounds) override (with _currentSize tracking via PrepareLayout()) to CustomUICollectionViewCompositionalLayout in LayoutFactory2.cs, to stop unrelated ancestor/sibling layout passes from resetting the CollectionView's scroll position.

PR #32664 had already added a second override of the exact same method (ShouldInvalidateLayoutForBoundsChange) in the same class, to fix #32435 — text disappearing in a horizontal CollectionView after rotating the simulator, because the compositional layout's default ShouldInvalidateLayoutForBoundsChange returns false and never re-measures cells after a bounds change.

Having two overrides of the same method in the same class does not compile (CS0111: Type already defines a member with the same parameter types).

Description of Change

Removed the duplicate override:

• Removed the second ShouldInvalidateLayoutForBoundsChange(CGRect newBounds) override from CustomUICollectionViewCompositionalLayout in LayoutFactory2.cs. The _currentSize/PrepareLayout()-based override from iOS Horizontal CollectionView jumps to beginning #36546 is kept, since it already covers the "ignore same-size bounds changes" case for both scenarios.

Restored rotation invalidation via the view controller instead of the layout:

• The rotation handling was moved up to ItemsViewController2:
  • Added _isRotating and _orientationObserver fields.
  • Subscribed to UIDevice.OrientationDidChangeNotification in ViewDidLoad(), setting _isRotating = true in the DeviceOrientationChanged handler.
  • Unsubscribed the observer in Dispose(bool) to avoid leaks.
  • In ViewWillLayoutSubviews(), when _isRotating is set, explicitly call CollectionView.CollectionViewLayout.InvalidateLayout() to force cells to re-measure/re-render after the rotation completes, then reset _isRotating.

This keeps the #36546 scroll-jump fix intact (layout still returns false for same-size bounds changes) while independently guaranteeing a genuine invalidation happens after a real device rotation, without needing two competing overrides of the same UIKit method.

Why tests not added

The scroll-reset scenario from #36546 is intermittent and doesn't reproduce reliably at the same item/position, so it isn't suited to an automated test. The rotation fix for #32435 already has manual UI test coverage from #32664 (Issue32435.cs in TestCases.HostApp/TestCases.Shared.Tests), which continues to apply here.

Issues Fixed

Fixes #36546

Tested the behavior in the following platforms

• Windows
• Android
• iOS
• Mac

Before Issue Fix	After Issue Fix
BeforeFix36546.mov	AfterFix36546.mov

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.sh | bash -s -- 37307

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.ps1) } 37307"

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[dotnet-policy-service]

Hey there @@SubhikshaSf4851! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[vishnumenon2684]

/azp run maui-pr-uitests , maui-pr-devicetests

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[vishnumenon2684]

/azp run maui-pr-uitests , maui-pr-devicetests

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