feat: `ItemCollectionTransition` by MartinZikmund · Pull Request #22960 · unoplatform/uno

MartinZikmund · 2026-04-03T08:12:06Z

GitHub Issue: closes #22904

PR Type: ✨ Feature

What is the current behavior? 🤔

Support for ItemCollectionTransition missing

What is the new behavior? 🚀

Support for ItemCollectionTransition added

PR Checklist ✅

Please check if your PR fulfills the following requirements:

📝 Commits must be following the Conventional Commits specification.
🧪 Added Runtime tests, UI tests, or a manual test sample for the changes have been added (for bug fixes / features) (if applicable)
📚 Docs have been added/updated which fit documentation template (for bug fixes / features)
🖼️ Validated PR Screenshots Compare Test Run results.
❗ Contains NO breaking changes

Other information ℹ️

Copilot

Pull request overview

This PR ports WinUI’s ItemCollectionTransition* type system into Uno, adding the core transition descriptor/progress/provider APIs plus a runtime test suite to validate expected add/remove/move transition behavior.

Changes:

Added ItemCollectionTransition, related enums, progress type, completed-event args, and the base ItemCollectionTransitionProvider implementation under UI/Xaml/Controls/Repeater/.
Updated generated stubs to defer to the new handwritten implementations.
Added runtime tests validating provider callbacks, filtering behavior, and TransitionCompleted semantics.

Reviewed changes

Copilot reviewed 7 out of 13 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
src/Uno.UI/UI/Xaml/Controls/Repeater/ItemCollectionTransitionTriggers.cs	Adds `[Flags]` triggers enum used to describe why transitions occur.
src/Uno.UI/UI/Xaml/Controls/Repeater/ItemCollectionTransitionOperation.cs	Adds operation enum (Add/Remove/Move) for transition classification.
src/Uno.UI/UI/Xaml/Controls/Repeater/ItemCollectionTransition.cs	Adds transition descriptor object + `Start()`/`HasStarted`.
src/Uno.UI/UI/Xaml/Controls/Repeater/ItemCollectionTransitionProgress.cs	Adds progress object used to signal completion back to the provider.
src/Uno.UI/UI/Xaml/Controls/Repeater/ItemCollectionTransitionCompletedEventArgs.cs	Adds event args for the provider’s `TransitionCompleted` event.
src/Uno.UI/UI/Xaml/Controls/Repeater/ItemCollectionTransitionProvider.cs	Adds provider batching logic using `CompositionTarget.Rendering` and keep-alive timers.
src/Uno.UI/Generated/3.0.0.0/Microsoft.UI.Xaml.Controls/ItemCollectionTransition*.cs	Updates generated stubs to skip members now implemented in Uno sources.
src/Uno.UI.RuntimeTests/Tests/Microsoft_UI_Xaml_Controls/Given_ItemCollectionTransitionProvider.cs	Adds runtime tests for transition provider call patterns and completion event behavior.

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morning4coffe-dev

LGTM, lets just recheck with WinUI3 source please

unodevops · 2026-04-06T10:22:04Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22960/docs/index.html

Copilot

Pull request overview

Copilot reviewed 17 out of 23 changed files in this pull request and generated 4 comments.

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unodevops · 2026-04-06T11:04:27Z

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22960/wasm-skia-net9/index.html

unodevops · 2026-04-06T11:14:00Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22960/docs/index.html

unodevops · 2026-04-16T06:45:41Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22960/docs/index.html

Copilot

Pull request overview

Copilot reviewed 17 out of 23 changed files in this pull request and generated 2 comments.

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unodevops · 2026-04-16T07:21:56Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22960/docs/index.html

unodevops · 2026-04-16T09:37:29Z

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22960/wasm-skia-net9/index.html

unodevops · 2026-04-16T09:40:25Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22960/docs/index.html

unodevops · 2026-04-16T10:45:26Z

⚠️⚠️ The build 207520 has failed on Uno.UI - CI.

…ollection # Conflicts: # src/Uno.UI/Generated/3.0.0.0/Microsoft.UI.Xaml.Controls/ItemCollectionTransition.cs # src/Uno.UI/Generated/3.0.0.0/Microsoft.UI.Xaml.Controls/ItemCollectionTransitionCompletedEventArgs.cs # src/Uno.UI/Generated/3.0.0.0/Microsoft.UI.Xaml.Controls/ItemCollectionTransitionProgress.cs Co-authored-by: MartinZikmund <1075116+MartinZikmund@users.noreply.github.com>

MartinZikmund · 2026-04-17T07:23:12Z

@copilot adjust When_Items_Changed_TransitionProvider_Receives_Correct_Calls() test, which currently fails (even on WinUI) - actual count 0, expected count 1; and adjust When_Progress_Complete_TransitionCompleted_Is_Raised() which also fails even on winui with "at least one Transition should have been started"

CLAassistant · 2026-04-17T07:31:09Z

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

✅ MartinZikmund
❌ Copilot
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

Copilot · 2026-04-17T07:31:10Z

@copilot resolve the merge conflicts in this pull request

Resolved merge conflicts in commit fc5da14. The conflicts were in 3 generated files (ItemCollectionTransition.cs, ItemCollectionTransitionCompletedEventArgs.cs, ItemCollectionTransitionProgress.cs) where master had regenerated them with [NotImplemented] stubs. Kept our versions which correctly reference the handwritten implementations via "Skipping already declared" comments. Build passes with 0 warnings/errors.

MartinZikmund · 2026-04-17T07:39:23Z

@copilot adjust When_Items_Changed_TransitionProvider_Receives_Correct_Calls() test, which currently fails (even on WinUI) - actual count 0, expected count 1; and adjust When_Progress_Complete_TransitionCompleted_Is_Raised() which also fails even on winui with "at least one Transition should have been started"

unodevops · 2026-04-17T07:52:09Z

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22960/wasm-skia-net9/index.html

unodevops · 2026-04-17T07:55:36Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22960/docs/index.html

Agent-Logs-Url: https://github.com/unoplatform/uno/sessions/f41e80f9-014b-4817-b43b-62c9272ce1dc Co-authored-by: MartinZikmund <1075116+MartinZikmund@users.noreply.github.com>

Copilot · 2026-04-17T08:14:11Z

@copilot adjust When_Items_Changed_TransitionProvider_Receives_Correct_Calls() test, which currently fails (even on WinUI) - actual count 0, expected count 1; and adjust When_Progress_Complete_Transit...

Fixed in commit 327b333. Both tests were rewritten to call QueueTransition directly (bypassing ItemsRepeater integration, which isn't wired up yet) and wait for CompositionTarget.Rendering to fire — the same frame where the provider processes its batch. This matches the pattern used in ElementAnimatorTests. Both tests now pass on Skia Desktop.

@copilot adjust When_Items_Changed_TransitionProvider_Receives_Correct_Calls() test, which currently fails (even on WinUI) - actual count 0, expected count 1; and adjust When_Progress_Complete_Transit...

Fixed in commit 327b333. Both tests rewritten to call QueueTransition directly and await CompositionTarget.Rendering instead of WaitForIdle. Verified passing on Skia Desktop.

unodevops · 2026-04-17T08:33:02Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22960/docs/index.html

unodevops · 2026-04-17T08:34:20Z

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22960/wasm-skia-net9/index.html

MartinZikmund · 2026-04-17T09:18:04Z

@copilot winui build fails with src\Uno.UI.RuntimeTests\Tests\Microsoft_UI_Xaml_Controls\Given_ItemCollectionTransitionProvider.cs(61,27): Error CS1729: 'ItemCollectionTransition' does not contain a constructor that takes 4 arguments

Either adjust test or disable it on Native winui via platform condition

Agent-Logs-Url: https://github.com/unoplatform/uno/sessions/4dc16bea-1bb7-440a-838b-10b3f444cb95 Co-authored-by: MartinZikmund <1075116+MartinZikmund@users.noreply.github.com>

Copilot · 2026-04-17T09:29:56Z

@copilot winui build fails with src\Uno.UI.RuntimeTests\Tests\Microsoft_UI_Xaml_Controls\Given_ItemCollectionTransitionProvider.cs(61,27): Error CS1729: 'ItemCollectionTransition' does not contain a c...

Fixed in commit 6a6bdb9 — wrapped both test methods and the helper class in #if HAS_UNO. The tests use internal Uno-only constructors on ItemCollectionTransition (ported from WinUI C++ internal factory methods) that don't exist on native WinUI, so they must be excluded from the Windows/WinAppSDK build.

unodevops · 2026-04-17T09:50:56Z

🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-22960/wasm-skia-net9/index.html

unodevops · 2026-04-17T09:53:51Z

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-22960/docs/index.html

Copilot AI review requested due to automatic review settings April 3, 2026 08:12

MartinZikmund self-assigned this Apr 3, 2026

MartinZikmund requested a review from morning4coffe-dev April 3, 2026 08:12

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MartinZikmund force-pushed the dev/mazi/repeater-collection branch from a51ff01 to a171406 Compare April 6, 2026 09:54

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MartinZikmund added 6 commits April 16, 2026 08:25

feat: ItemCollectionTransition

a6cbd5e

test: ItemCollectionTransition

61f14f3

chore: Improve port accuracy

b48484e

feat: Improve WinUI port skill

b4db208

chore: Disposable

c8b6309

chore: WinAppSDK build

a72a5fd

chore: Improve comment on dispose

bcc9f47

Copilot AI review requested due to automatic review settings April 16, 2026 06:51

MartinZikmund force-pushed the dev/mazi/repeater-collection branch from 8402d72 to bcc9f47 Compare April 16, 2026 06:51

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Comment thread src/Uno.UI/UI/Xaml/Controls/Repeater/ItemCollectionTransitionProvider.mux.cs

Comment thread src/Uno.UI/UI/Xaml/Controls/Repeater/ItemCollectionTransition.mux.cs Outdated

chore: Address comments

25e0ca2

Copilot started work on behalf of MartinZikmund April 17, 2026 07:19 View session

Copilot AI review requested due to automatic review settings April 17, 2026 07:31

MartinZikmund review requested due to automatic review settings April 17, 2026 07:31

Copilot finished work on behalf of MartinZikmund April 17, 2026 07:32

Copilot started work on behalf of MartinZikmund April 17, 2026 07:39 View session

test: fix failing ItemCollectionTransitionProvider runtime tests

327b333

Agent-Logs-Url: https://github.com/unoplatform/uno/sessions/f41e80f9-014b-4817-b43b-62c9272ce1dc Co-authored-by: MartinZikmund <1075116+MartinZikmund@users.noreply.github.com>

Copilot AI review requested due to automatic review settings April 17, 2026 08:13

MartinZikmund review requested due to automatic review settings April 17, 2026 08:13

Copilot finished work on behalf of MartinZikmund April 17, 2026 08:15

Copilot started work on behalf of MartinZikmund April 17, 2026 09:18 View session

test: wrap ItemCollectionTransitionProvider tests with HAS_UNO guard

6a6bdb9

Agent-Logs-Url: https://github.com/unoplatform/uno/sessions/4dc16bea-1bb7-440a-838b-10b3f444cb95 Co-authored-by: MartinZikmund <1075116+MartinZikmund@users.noreply.github.com>

Copilot AI review requested due to automatic review settings April 17, 2026 09:29

MartinZikmund review requested due to automatic review settings April 17, 2026 09:29

Copilot finished work on behalf of MartinZikmund April 17, 2026 09:30

MartinZikmund merged commit eb2838f into master Apr 17, 2026
43 checks passed

MartinZikmund deleted the dev/mazi/repeater-collection branch April 17, 2026 14:13

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MartinZikmund commented Apr 3, 2026

PR Type: ✨ Feature

What is the current behavior? 🤔

What is the new behavior? 🚀

PR Checklist ✅

Other information ℹ️

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