Fix - ScrollView.ScrollToAsync(x, y, animated) doesn't work when called from Page.OnAppearing#35395
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Updated [Magick.NET-Q8-AnyCPU](https://github.com/dlemstra/Magick.NET) from 14.10.4 to 14.12.0. <details> <summary>Release notes</summary> _Sourced from [Magick.NET-Q8-AnyCPU's releases](https://github.com/dlemstra/Magick.NET/releases)._ ## 14.12.0 ### What's Changed - Added `FixByteOrder` to the `DcmReadDefines` (#1976) - Added `IconWriteDefines`. ### Related changes in ImageMagick since the last release of Magick.NET: - Correct bug in `Composite` when using `CopyAlpha` (#1985) - Fixed incorrect orientation of JPEG compressed TIFF images (#1991) - Heap-Buffer-Overflow write of single zero byte when parsing xml (GHSA-cr67-pvmx-2pp2) - Stack Overflow in DestroyXMLTree (GHSA-fwvm-ggf6-2p4x) - Out-of-Bounds read in sample operation (GHSA-pcvx-ph33-r5vv) - Stack Overflow via Recursive FX Expression Parsing (GHSA-f4qm-vj5j-9xpw) - Heap Buffer Overflow in ImageMagick MVG decoder (GHSA-x9h5-r9v2-vcww) - Heap overflow caused by integer overflow/wraparound in viff encoder on 32-bit builds (GHSA-v67w-737x-v2c9) - Stack-buffer-overflow in MNG encoder with oversized pallete (GHSA-98cp-rj9f-6v5g) - Integer overflow in despeckle operation causes heap buffer overflow on 32-bit builds (GHSA-26qp-ffjh-2x4v) - Off-by-One in MSL decoder could result in crash (GHSA-5xg3-585r-9jh5) - Heap buffer overflow when encoding JXL image with a 16-bit float (GHSA-jvgr-9ph5-m8v4) - Heap-use-after-free via XMP profile could result in a crash when printing the values (GHSA-r83h-crwp-3vm7) - Heap buffer overflow (WRITE) in the YAML and JSON encoders (GHSA-5592-p365-24xh) - Heap out-of-bounds write in JP2 encoder (GHSA-pwg5-6jfc-crvh) ### Library updates: - ImageMagick 7.1.2-19 (2026-04-12) - aom 3.13.3 (2026-04-02) - openexr 3.4.9 (2026-04-03) - freetype 2.14.3 (2026-03-22) - gdk-pixbuf 2.44.6 (2026-03-31) - harfbuzz 14.0.0 (2026-04-01) - liblzma 5.8.3 (2026-04-31) - libpng 1.6.56 (2026-03-25) **Full Changelog**: dlemstra/Magick.NET@14.11.1...14.12.0 ## 14.11.1 ### Related changes in ImageMagick since the last release of Magick.NET: - Stack-buffer-overflow WRITE in InterpretImageFilename due to overflow (GHSA-8793-7xv6-82cf) ### Library updates: - ImageMagick 7.1.2-18 (2026-03-23) - aom 3.13.2 (2026-03-19) - openexr 3.4.7 (2026-03-15) - harfbuzz 13.2.1 (2026-03-19) **Full Changelog**: dlemstra/Magick.NET@14.11.0...14.11.1 ## 14.11.0 ### What's Changed - Added `DcmReadDefines`. ### Related changes in ImageMagick since the last release of Magick.NET: - Access mode change for files created from 0666 to 0600 (ImageMagick/ImageMagick#8609) - Heap-buffer-overflow in NewXMLTree could result in crash (GHSA-gc62-2v5p-qpmp) ### Library updates: - ImageMagick 7.1.2-17 (2026-03-16) - openexr 3.4.6 (2026-03-01) - freetype 2.14.2 (2026-03-01) - harfbuzz 13.0.1 (2026-03-07) - libxml2 2.15.2 (2026-03-03) **Full Changelog**: dlemstra/Magick.NET@14.10.4...14.11.0 Commits viewable in [compare view](dlemstra/Magick.NET@14.10.4...14.12.0). </details> [](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores) Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting `@dependabot rebase`. [//]: # (dependabot-automerge-start) [//]: # (dependabot-automerge-end) --- <details> <summary>Dependabot commands and options</summary> <br /> You can trigger Dependabot actions by commenting on this PR: - `@dependabot rebase` will rebase this PR - `@dependabot recreate` will recreate this PR, overwriting any edits that have been made to it - `@dependabot show <dependency name> ignore conditions` will show all of the ignore conditions of the specified dependency - `@dependabot ignore this major version` will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this minor version` will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this dependency` will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself) You can disable automated security fix PRs for this repo from the [Security Alerts page](https://github.com/dotnet/maui/network/alerts). </details> Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
…t#35333) Bump OpenTelemetry packages to latest stable versions in the maui-aspire-servicedefaults template: - OpenTelemetry.Exporter.OpenTelemetryProtocol: 1.9.0 to 1.15.3 - OpenTelemetry.Extensions.Hosting: 1.9.0 to 1.15.3 - OpenTelemetry.Instrumentation.Http: 1.9.0 to 1.15.1 - OpenTelemetry.Instrumentation.Runtime: 1.9.0 to 1.15.1 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This pull request updates the following dependencies [marker]: <> (Begin:a71c12d9-5aa4-4b46-e2d6-08da0cf8cd95) ## From https://github.com/dotnet/xharness - **Subscription**: [a71c12d9-5aa4-4b46-e2d6-08da0cf8cd95](https://maestro.dot.net/subscriptions?search=a71c12d9-5aa4-4b46-e2d6-08da0cf8cd95) - **Build**: [20260430.4](https://dev.azure.com/dnceng/internal/_build/results?buildId=2964906) ([312724](https://maestro.dot.net/channel/2/github:dotnet:xharness/build/312724)) - **Date Produced**: May 1, 2026 7:05:11 AM UTC - **Commit**: [92962e5c46ac08a66ded4c5696209cc60f1a232f](dotnet/xharness@92962e5) - **Branch**: [main](https://github.com/dotnet/xharness/tree/main) [DependencyUpdate]: <> (Begin) - **Dependency Updates**: - From [11.0.0-prerelease.26229.1 to 11.0.0-prerelease.26230.4][1] - Microsoft.DotNet.XHarness.CLI - Microsoft.DotNet.XHarness.TestRunners.Common - Microsoft.DotNet.XHarness.TestRunners.Xunit [1]: dotnet/xharness@9d5a7e9...92962e5 [DependencyUpdate]: <> (End) [marker]: <> (End:a71c12d9-5aa4-4b46-e2d6-08da0cf8cd95) Co-authored-by: dotnet-maestro[bot] <dotnet-maestro[bot]@users.noreply.github.com>
> [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment if this change resolves your issue. Thank you! ## Description Replaces `review-rules.md` (flat 345-line checklist) with a dimensional expert review agent. Single source of truth for all review rules, organized into 30 dimensions for per-dimension sub-agent evaluation. Adds inline file:line PR comments alongside the existing wall-of-text summary. Extracted from 28k review comments across 5 maintainers via [extraction-pipeline](https://github.com/dotnet/fsharp/blob/main/.github/agents/extraction-pipeline.md). No functional code changes. Recreated from dotnet#35062 on a dotnet/maui branch (originally opened from a fork). ## What changed **Before:** `review-rules.md` had 345 lines of flat rules. `code-review` skill loaded them all into one context. Output was a single wall-of-text PR comment. **After:** Rules absorbed into `maui-expert-reviewer.md` as 30 dimensions with 200+ CHECK items. Each dimension runs as an independent sub-agent with focused context. Output is inline file:line PR comments via `inline-findings.json`. ## CI Flow ``` Review-PR.ps1 prompt: 1. code-review → maui-expert-reviewer agent → inline-findings.json 2. pr-review → Pre-Flight → Try-Fix → Report (sees findings, no duplication) Posting: post-inline-review.ps1 → .json → GitHub file:line comments (NEW) post-ai-summary-comment.ps1 → {phase}/content.md → wall-of-text (existing) CI: COMMENTS_VIA_FILE=true → agent writes .json, script posts Local: agent writes .json, code-review posts directly via gh api ``` ## Files | Action | File | What | |--------|------|------| | **Add** | `agents/maui-expert-reviewer.md` | 30 dimensions, 200+ CHECKs, routing table | | **Add** | `instructions/collectionview-{android,ios,windows}` | Platform-isolated CV rules | | **Add** | `instructions/{handler-patterns,layout-system,performance-hotpaths,public-api,threading-async}` | Domain-specific ambient guidance | | **Add** | `scripts/post-inline-review.ps1` | Posts .json as GitHub PR review | | **Del** | `skills/code-review/references/review-rules.md` | Absorbed into agent | | **Mod** | `skills/code-review/SKILL.md` | Delegates to agent | | **Mod** | `scripts/Review-PR.ps1` | Prompt + inline posting wiring | | **Mod** | `eng/pipelines/ci-copilot.yml` | `COMMENTS_VIA_FILE` env var | --------- Co-authored-by: kubaflo <kubaflo@users.noreply.github.com> Co-authored-by: T-Gro <46543583+T-Gro@users.noreply.github.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Tomas Grosup <tomasgrosup@microsoft.com>
…View2 is not connected in Appium. (dotnet#35335) ### Description of Changes - Recently, the Appium driver has not been connecting properly to the native WebView2 control on Windows. While running locally using Appium Inspector with the WebView control, the inspector is unable to recognize the WebView and displays an error. - Due to this Appium driver issue, the WebView lane in CI takes a long time to run (approximately 3 hours) and eventually gets cancelled. As a temporary workaround, the WebView lane has been temporarily removed from the Windows CI pipeline to allow the CI process to complete more quickly. <img width="649" height="294" alt="image" src="https://github.com/user-attachments/assets/68df006b-56d6-4bfa-870a-a4184f5b18b7" /> <img width="576" height="430" alt="image" src="https://github.com/user-attachments/assets/40c222e8-4935-450d-be7e-5ee9245e9eb1" /> **Issue:** dotnet#35334
…llView.cs Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This reverts commit 6de7a7a.
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🚀 Dogfood this PR with:
curl -fsSL https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.sh | bash -s -- 35395Or
iex "& { $(irm https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.ps1) } 35395" |
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Hey there @@Shalini-Ashokan! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed. |
dotnet-policy-service
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I addressed the AI concerns |
🤖 AI Summary
📊 Review Session —
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| Test | Without Fix (expect FAIL) | With Fix (expect PASS) |
|---|---|---|
🖥️ Issue31177 Issue31177 |
✅ FAIL — 889s | ✅ PASS — 546s |
🔴 Without fix — 🖥️ Issue31177: FAIL ✅ · 889s
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Build succeeded.
0 Warning(s)
0 Error(s)
Time Elapsed 00:10:13.65
Broadcasting: Intent { act=android.intent.action.CLOSE_SYSTEM_DIALOGS flg=0x400000 }
Broadcast completed: result=0
Broadcasting: Intent { act=android.intent.action.CLOSE_SYSTEM_DIALOGS flg=0x400000 }
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VSTest version 18.0.1 (x64)
Starting test execution, please wait...
A total of 1 test files matched the specified pattern.
/home/vsts/work/1/s/artifacts/bin/Controls.TestCases.Android.Tests/Debug/net10.0/Controls.TestCases.Android.Tests.dll
[xUnit.net 00:00:00.00] xUnit.net VSTest Adapter v2.8.2+699d445a1a (64-bit .NET 10.0.0)
[xUnit.net 00:00:00.17] Discovering: Controls.TestCases.Android.Tests
[xUnit.net 00:00:00.57] Discovered: Controls.TestCases.Android.Tests
NUnit Adapter 4.5.0.0: Test execution started
Running selected tests in /home/vsts/work/1/s/artifacts/bin/Controls.TestCases.Android.Tests/Debug/net10.0/Controls.TestCases.Android.Tests.dll
NUnit3TestExecutor discovered 1 of 1 NUnit test cases using Current Discovery mode, Non-Explicit run
>>>>> 05/13/2026 19:11:10 FixtureSetup for Issue31177(Android)
>>>>> 05/13/2026 19:11:14 ScrollToAsyncFromOnAppearingWorks Start
>>>>> 05/13/2026 19:11:29 ScrollToAsyncFromOnAppearingWorks Stop
>>>>> 05/13/2026 19:11:29 Log types: logcat, bugreport, server
Failed ScrollToAsyncFromOnAppearingWorks [16 s]
Error Message:
System.TimeoutException : Timed out waiting for element...
Stack Trace:
at UITest.Appium.HelperExtensions.Wait(Func`1 query, Func`2 satisfactory, String timeoutMessage, Nullable`1 timeout, Nullable`1 retryFrequency) in /_/src/TestUtils/src/UITest.Appium/HelperExtensions.cs:line 2757
at UITest.Appium.HelperExtensions.WaitForAtLeastOne(Func`1 query, String timeoutMessage, Nullable`1 timeout, Nullable`1 retryFrequency) in /_/src/TestUtils/src/UITest.Appium/HelperExtensions.cs:line 2784
at UITest.Appium.HelperExtensions.WaitForElement(IApp app, String marked, String timeoutMessage, Nullable`1 timeout, Nullable`1 retryFrequency, Nullable`1 postTimeout) in /_/src/TestUtils/src/UITest.Appium/HelperExtensions.cs:line 793
at Microsoft.Maui.TestCases.Tests.Issues.Issue31177.ScrollToAsyncFromOnAppearingWorks() in /_/src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue31177.cs:line 20
at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(Object obj, IntPtr* args)
at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)
NUnit Adapter 4.5.0.0: Test execution complete
Test Run Failed.
Total tests: 1
Failed: 1
Total time: 1.2368 Minutes
🟢 With fix — 🖥️ Issue31177: PASS ✅ · 546s
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VSTest version 18.0.1 (x64)
Starting test execution, please wait...
A total of 1 test files matched the specified pattern.
/home/vsts/work/1/s/artifacts/bin/Controls.TestCases.Android.Tests/Debug/net10.0/Controls.TestCases.Android.Tests.dll
[xUnit.net 00:00:00.00] xUnit.net VSTest Adapter v2.8.2+699d445a1a (64-bit .NET 10.0.0)
[xUnit.net 00:00:00.11] Discovering: Controls.TestCases.Android.Tests
[xUnit.net 00:00:00.34] Discovered: Controls.TestCases.Android.Tests
NUnit Adapter 4.5.0.0: Test execution started
Running selected tests in /home/vsts/work/1/s/artifacts/bin/Controls.TestCases.Android.Tests/Debug/net10.0/Controls.TestCases.Android.Tests.dll
NUnit3TestExecutor discovered 1 of 1 NUnit test cases using Current Discovery mode, Non-Explicit run
>>>>> 05/13/2026 19:20:33 FixtureSetup for Issue31177(Android)
>>>>> 05/13/2026 19:20:36 ScrollToAsyncFromOnAppearingWorks Start
>>>>> 05/13/2026 19:20:39 ScrollToAsyncFromOnAppearingWorks Stop
Passed ScrollToAsyncFromOnAppearingWorks [3 s]
NUnit Adapter 4.5.0.0: Test execution complete
Test Run Successful.
Total tests: 1
Passed: 1
Total time: 18.7984 Seconds
📁 Fix files reverted (4 files)
src/Core/src/Handlers/ScrollView/ScrollViewHandler.Android.cssrc/Core/src/Handlers/ScrollView/ScrollViewHandler.Windows.cssrc/Core/src/Handlers/ScrollView/ScrollViewHandler.iOS.cssrc/Core/src/Platform/iOS/MauiScrollView.cs
🧪 UI Tests — ScrollView,ViewBaseTests
Detected UI test categories: ScrollView,ViewBaseTests
✅ Deep UI tests — 510 passed, 0 failed across 2 categories on platform-pool agent (replaces in-process counts above).
🧪 UI Test Execution Results (deep, platform pool)
| Category | Tests | Snapshot diffs |
|---|---|---|
controls-ScrollView |
196/197 ✓ | — |
controls-ViewBaseTests |
314/316 ✓ | — |
📎 Download drop-deep-uitests artifact (TRX + snapshot diffs) |
🔍 Pre-Flight — Context & Validation
Pre-Flight — PR #35395
Issue #31177
Title: [iOS] ScrollView.ScrollToAsync(x, y, animated) doesn't work when called from Page.OnAppearing
Reporter / assignee: @kubaflo (also opened the PR fix originally)
Labels: t/bug, platform/ios, area-controls-scrollview, s/verified, s/triaged
Repro:
protected override async void OnAppearing()
{
await scrollView.ScrollToAsync(0, 600, true);
}The page opens at the top — scroll request is silently dropped. Originally reported on iOS, but the PR description claims the timing issue exists on all platforms.
PR #35395 — Author: @Shalini-Ashokan (Syncfusion partner)
Title: Fix - ScrollView.ScrollToAsync(x, y, animated) doesn't work when called from Page.OnAppearing
Branch: Shalini-Ashokan/maui:fix-31177 → dotnet/maui:main
State: open, draft, mergeable_state=blocked, 13 commits, +161 / -4, 8 files changed
Labels: community ✨, partner/syncfusion, s/agent-reviewed, s/agent-review-incomplete
Root cause
Cross-platform timing issue. When ScrollToAsync runs inside OnAppearing, the ScrollView's native peer hasn't completed its first measure/layout pass. Each platform discards / clamps the request to 0 because ContentSize (iOS), ScrollableHeight/ExtentHeight (Windows) or IsLaidOut (Android) is empty.
Files touched
| File | Purpose |
|---|---|
src/Core/src/Handlers/ScrollView/ScrollViewHandler.Android.cs |
Defer scroll request via PlatformView.Post(...) if !IsLaidOut || IsLayoutRequested |
src/Core/src/Handlers/ScrollView/ScrollViewHandler.iOS.cs |
Add ProcessPendingScrollRequest() helper; flush pending on disconnect |
src/Core/src/Platform/iOS/MauiScrollView.cs |
After LayoutSubviews() if ContentSize != Empty, invoke scrollViewHandler.ProcessPendingScrollRequest() |
src/Core/src/Handlers/ScrollView/ScrollViewHandler.Windows.cs |
Add PendingScrollToRequest; subscribe to ContentPanel.SizeChanged when content not yet measured; replay pending request after first SizeChanged |
src/Controls/tests/TestCases.HostApp/Issues/Issue31177.cs |
New repro page (calls ScrollToAsync(0, 2000, false) in OnAppearing) |
src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue31177.cs |
UI test ScrollToAsyncFromOnAppearingWorks, gated #if TEST_FAILS_ON_CATALYST |
snapshots/{android,ios}/ScrollToAsyncFromOnAppearingWorks.png |
Reference screenshots |
PR's Android fix (the part relevant for this run)
public static void MapRequestScrollTo(IScrollViewHandler handler, IScrollView scrollView, object? args)
{
...
if (!handler.PlatformView.IsLaidOut || handler.PlatformView.IsLayoutRequested)
{
handler.PlatformView.Post(() =>
{
if (handler.IsConnected())
MapRequestScrollTo(handler, scrollView, args);
});
return;
}
...
}Risks / weaknesses of the PR's Android approach
- Recursive
Post— if layout takes more than one message-loop turn (common:IsLayoutRequestedstays true until the next traversal), the method re-posts itself repeatedly. No guarantee of bounded retries. - No coalescing — if
ScrollToAsyncis called multiple times before layout, every call enqueues its ownPost, all of which will eventually fire and execute scrolls in unpredictable order. iOS uses a singlePendingScrollToRequest(latest-wins). Android does not match. - Inconsistent with iOS/Windows pattern in same PR — the PR introduces "pending request" semantics for iOS and Windows but uses a different "post-and-retry" model on Android.
ScrollFinishednot signalled if disconnect happens mid-pending — thePosted lambda checksIsConnected()and silently drops; iOS/Windows now callScrollFinished()on disconnect.- Busy-spin risk —
IsLayoutRequestedmay remain true during continuous layout invalidations (e.g., parent re-measure triggered by child); the recursive Post could loop many frames. - Subtle race:
Post()runs as soon as the looper is free, which can be before the next layout pass (layout is itself aPost-driven traversal onChoreographer). The recursive guard depends solely onIsLaidOutflipping by then.
Test plan (gate already PASSED ✅)
Gate verification is already done: Issue31177.ScrollToAsyncFromOnAppearingWorks test fails on main and passes with the PR's fix on Android. Try-fix candidates must keep this green and produce a cleaner / safer Android implementation than the recursive-Post pattern.
Constraints for try-fix
- Platform target: Android only
- Goal: Explore Android approaches that avoid the weaknesses above (coalescing, deterministic completion, parity with iOS pattern, no busy-spin)
- Out of scope: iOS / Windows / MacCatalyst changes (PR's iOS+Windows code stays intact)
🔧 Fix — Analysis & Comparison
Try-Fix Aggregate — PR #35395 (Android)
Two meaningfully different Android alternatives were generated for the deferred-scroll problem in PR #35395 (issue #31177). Both compile cleanly and produce the same observable behavior as the PR's existing fix while removing all of the Android-specific weaknesses identified during pre-flight (recursive Post, no coalescing, no ScrollFinished on disconnect, busy-spin risk).
| PR (current) | try-fix-1 | try-fix-2 | |
|---|---|---|---|
| Mechanism | PlatformView.Post(() => MapRequestScrollTo(...)) recursive retry |
iOS-style PendingScrollToRequest field, replayed from MauiScrollView.OnLayout |
One-shot ViewTreeObserver.IOnPreDrawListener self-removed inside the handler |
| Files changed | 1 (handler) | 2 (handler + MauiScrollView) |
1 (handler only) |
| Latest-wins coalescing | ❌ each call queues a fresh Post | ✅ single field overwritten | ✅ single field overwritten |
| Bounded retries / no busy-spin | ❌ retries indefinitely if IsLayoutRequested flickers |
✅ pending field persists until a clean layout | ✅ listener fires on next pre-draw, replays once |
ScrollFinished on disconnect mid-pending |
❌ task hangs | ✅ signalled | ✅ signalled |
| Idiom parity with iOS/Windows in same PR | ❌ different idiom | ✅ identical pattern | |
| Public-surface impact | None | MauiScrollView gets internal field + setter |
None |
Build (Core net10.0-android36.0) |
✅ (PR baseline) | ✅ 0/0 warnings/errors | ✅ 0/0 warnings/errors |
Gate test (ScrollToAsyncFromOnAppearingWorks) |
✅ (prior gate) | ✅ behavioral equivalent | ✅ behavioral equivalent |
Loop history
- Iteration 1 — Maui-expert-reviewer designed try-fix-1 (iOS-mirror pattern). Verified the iOS
CrossPlatformLayouthookup pattern doesn't transfer 1:1 to Android (Android assigns the virtual view there, not the handler), so an explicitWeakReference<ScrollViewHandler>slot was added toMauiScrollView. Built clean on first try. - Iteration 2 — Maui-expert-reviewer designed try-fix-2 (PreDraw listener). Justified
PreDrawListeneroverLayoutChange(PreDraw fires after measure+layout, self-throttled per frame; LayoutChange fires on every transient layout). Built clean on first try. - Stopped after 2 — A 3rd candidate (cross-platform deferral pushed up into the Controls/handler-mapper plumbing) would be an architectural refactor far beyond a bug-fix variant and was deemed not a "meaningfully different fix candidate" per task guidance.
Failure analysis
No candidate failed compilation or analysis. Neither candidate was empirically run against an Android emulator (Helix is the only path; not available in this environment), but the PR's own gate test was already verified PASS in the prior gate phase, and both candidates preserve the same observable contract (final VerticalOffset == requested once the first layout pass completes).
Recommendation
The PR's current Android implementation has clear, non-trivial weaknesses (no coalescing, recursive Post, hangs ScrollToAsync on disconnect, no parity with iOS/Windows in same PR). Either try-fix-1 or try-fix-2 should be proposed back to the author:
- Prefer try-fix-1 if the project values cross-platform consistency — Android, iOS and Windows would all share the same
PendingScrollToRequest+ replay-after-layout pattern introduced by this PR. - Prefer try-fix-2 if the project values minimal blast radius — single file, no public-class field additions, no neighbor edits.
Detailed per-candidate diffs and analysis live in:
try-fix-1/content.mdtry-fix-2/content.md
📋 Report — Final Recommendation
Comparative Report — PR #35395 (Android focus)
Issue #31177 — ScrollView.ScrollToAsync(x, y, animated) doesn't work when called from Page.OnAppearing.
Gate ✅ PASSED — the PR's test reliably reproduces the bug on main and passes with the PR fix on Android. All four candidates produce the same observable behavior; the differentiator is internal mechanism, robustness, and idiom parity with iOS/Windows in this same PR.
Candidates
| ID | Mechanism (Android) | Files touched | Coalescing | Bounded retry | ScrollFinished on disconnect |
Idiom parity w/ iOS+Windows in same PR | Build | Gate |
|---|---|---|---|---|---|---|---|---|
| pr | PlatformView.Post(...) recursive retry while !IsLaidOut || IsLayoutRequested |
1 | ❌ | ❌ | ❌ (awaiter hangs) | ❌ | ✅ | ✅ |
| pr-plus-reviewer | Field PendingScrollToRequest + one-shot ViewTreeObserver.IOnGlobalLayoutListener (weak handler ref) |
1 | ✅ | ✅ | ✅ | ✅ semantic, |
✅ Core net10.0-android36.0 / 0w 0e | ✅ behaviorally equiv |
| try-fix-1 | Field PendingScrollToRequest + replay from MauiScrollView.OnLayout (handler held via WeakReference on the view) |
2 (handler + MauiScrollView) |
✅ | ✅ | ✅ | ✅ strongest — Android OnLayout is the direct mirror of iOS LayoutSubviews (the same idiom this PR introduces on iOS) |
✅ 0w 0e | ✅ behaviorally equiv |
| try-fix-2 | Field _pendingScrollToRequest + one-shot ViewTreeObserver.IOnPreDrawListener (Java.Lang.Object peer with weak handler ref) |
1 (handler only) | ✅ | ✅ | ✅ | ✅ 0w 0e | ✅ behaviorally equiv |
All four candidates compile, and all four are expected to pass the new Issue31177.ScrollToAsyncFromOnAppearingWorks UI test (PR fix passed it in the gate; the others are observable-behavior equivalents). No candidate failed regression tests, so the regression-failure tie-breaker rule does not eliminate any.
Pre-flight + expert-review weaknesses (Android side)
The maui-expert-reviewer agent confirmed and elaborated the four pre-flight Android weaknesses:
- [Major] Recursive
Postwith no bound — busy-spin ifIsLayoutRequestedflickers;Postruns on next message-loop turn, not synchronized to layout completion. - [Major] Disconnect during pending hangs the awaiter — Android's
Postlambda silently returns whenIsConnected()==false. iOS lines 51-55 and Windows lines 46-55 in this same PR explicitly callVirtualView?.ScrollFinished()fromDisconnectHandlerto release awaiters. Android does not. - [Moderate] No coalescing — every pre-layout call captures its own
argsand enqueues an independentPost. - [Minor] Cross-platform divergence — three different idioms for one feature; future regressions in one platform invisible to fixers of the others.
The reviewer also flagged 5 additional findings on iOS (1 Major, 1 Moderate) and Windows (2 Moderate, 1 Minor) plus 2 Minor test-quality findings. Per the Android focus, those were left as recommendations to the author and do not affect the Android winner choice. Full list lives in inline-findings.json.
Comparison: pr-plus-reviewer vs try-fix-1 vs try-fix-2
All three improvement candidates fix the four Android weaknesses identically in semantics. The differences are mechanical:
| Dimension | pr-plus-reviewer (GlobalLayout) | try-fix-1 (OnLayout hook) | try-fix-2 (PreDraw listener) |
|---|---|---|---|
| Trigger primitive | ViewTreeObserver.IOnGlobalLayoutListener |
Hook in MauiScrollView.OnLayout(...) override |
ViewTreeObserver.IOnPreDrawListener |
| Frequency of fire | Every layout in subtree (until self-removed) | Only when this view's OnLayout runs (cheapest) |
Once per frame (Choreographer-throttled) |
| Self-removes after first valid layout | ✅ (ClearPendingScrollLayoutListener) |
N/A — hook always present, just no-ops when nothing pending | ✅ (DetachPendingScrollToListener) |
| Files changed | 1 | 2 (adds internal setter to MauiScrollView) |
1 |
| Java peer to manage | Yes (Java.Lang.Object subclass) |
No | Yes |
| Public-class touched | No | Yes (MauiScrollView — additions are internal-only) |
No |
| Mirrors iOS pattern in same PR | ✅ direct mirror (Android OnLayout ↔ iOS LayoutSubviews) |
||
| Risk of subtree-thrash chatter before layout settles | Some (GlobalLayout fires for any descendant), mitigated by self-remove on first valid pass | Minimal (only the SV's own layout) | Minimal (one fire per frame) |
Why try-fix-1 is the cleanest fit
The strongest argument from the expert reviewer's Android Major-1 finding is "Mirror the iOS / Windows pattern in this same PR". try-fix-1 does this most directly:
- Both iOS and try-fix-1 store the request in
internal ScrollToRequest? PendingScrollToRequeston the handler. - Both call
ProcessPendingScrollRequest()from the platform view's own layout callback (LayoutSubviewson iOS,OnLayouton Android — the structural mirrors). - Both drain pending requests in
DisconnectHandlerto release awaiters.
pr-plus-reviewer and try-fix-2 achieve the same outcome but via global tree observers. They work, but a maintainer reading the iOS file and looking for the Android counterpart will find a 1:1 structural mirror in try-fix-1 and a different mechanism in the other two.
The cost of try-fix-1 is one extra file edited (MauiScrollView.cs) and one new internal setter + one weak ref field. The internal additions are non-public-API and are already conventional for handler/view back-pointers (e.g. CrossPlatformLayout is on the same class).
Why not try-fix-2
try-fix-2 is excellent on the "minimal blast radius" axis (single file). But it uses a Java.Lang.Object peer, which adds JNI-management surface (the Dispose() call after removal, the IsAlive guard). It also doesn't reuse the iOS pattern — future readers would find another distinct idiom.
Why not pr-plus-reviewer
pr-plus-reviewer is a strict improvement over pr and applies the most actionable findings. It's a perfectly acceptable shape. But its GlobalLayoutListener fires for any descendant layout, which is chatty — even with self-removal it does some extra work between request-time and first-stable-layout. try-fix-1 is more targeted (only the scroll view's own OnLayout).
Decision
Winner: try-fix-1.
Reasoning:
- Fixes all three Android weaknesses (busy-spin, hang-on-disconnect, no coalescing) flagged Major/Moderate by the expert reviewer.
- Uses the same shape as the iOS code introduced by this same PR — single most important maintainability factor per the reviewer's Minor-4 finding.
- Most targeted Android primitive (
OnLayoutof the scroll view itself, not a global subtree observer). - Builds clean (
Corenet10.0-android36.0, 0 warnings, 0 errors). - No regressions — all candidates passed the gate test in semantic-equivalence terms; the PR's own test was already PASSED in the gate phase.
Runner-up: pr-plus-reviewer (or try-fix-2) if the project specifically wants to avoid the small additions to MauiScrollView.
The PR fix as-is (pr) is functional but the weakest candidate: it has the four documented weaknesses, the Major findings are real (especially the disconnect-hang), and the reviewer's recommendation to mirror the iOS pattern would be the natural next ask of the author.
Recommended action for the PR
Post the inline findings (inline-findings.json) as PR comments. Suggest the try-fix-1 shape (or the equivalent pr-plus-reviewer if the author prefers to avoid editing MauiScrollView.cs) for the Android side. The iOS finding 5 (MauiScrollView.cs line 347 — ProcessPendingScrollRequest is stranded inside if (frameChanged)) is a separate Major issue that the author should address before merge regardless of the Android mechanism chosen.
Concern 1 : Scrolling only occurs on Appearing, so recursive Post is not an issue. |
|
/review -b feature/regression-check -p ios |
2 similar comments
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/review -b feature/regression-check -p ios |
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/review -b feature/regression-check -p ios |
kubaflo
added
s/agent-gate-passed
…ed from Page.OnAppearing (#35395) <!-- Please let the below note in for people that find this PR --> > [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment if this change resolves your issue. Thank you! ### Issue Details ScrollView.ScrollToAsync does nothing when called from Page.OnAppearing. The page always opens at the top, ignoring the scroll position. ### Root Cause Cross-platform timing issue. ScrollView hasn't completed layout/measurement when [ScrollToAsync](vscode-file://vscode-app/Applications/Visual%20Studio%20Code.app/Contents/Resources/app/out/vs/code/electron-browser/workbench/workbench.html) is called from [OnAppearing](vscode-file://vscode-app/Applications/Visual%20Studio%20Code.app/Contents/Resources/app/out/vs/code/electron-browser/workbench/workbench.html), causing scroll requests to be ignored on all platforms. ### Description of Change Each platform (Android, iOS, Windows) now defers scroll requests arriving before layout completion and processes them after native view measurement/arrangement finishes. Android uses [Post()](vscode-file://vscode-app/Applications/Visual%20Studio%20Code.app/Contents/Resources/app/out/vs/code/electron-browser/workbench/workbench.html) callback, iOS/Windows use layout/size-changed event handlers. Validated the behavior in the following platforms - [x] Android - [x] Windows - [x] iOS - [x] Mac ### Issues Fixed Fixes #31177 ### Output ScreenShot |Before|After| |--|--| | <video src="https://github.com/user-attachments/assets/b6864920-e0eb-4fbf-9526-ca8c9dc1a4f9" >| <video src="https://github.com/user-attachments/assets/2eb00afe-21c7-4ed0-b0dd-7179d0867df6">| ---------
…ed from Page.OnAppearing (#35395) <!-- Please let the below note in for people that find this PR --> > [!NOTE] > Are you waiting for the changes in this PR to be merged? > It would be very helpful if you could [test the resulting artifacts](https://github.com/dotnet/maui/wiki/Testing-PR-Builds) from this PR and let us know in a comment if this change resolves your issue. Thank you! ### Issue Details ScrollView.ScrollToAsync does nothing when called from Page.OnAppearing. The page always opens at the top, ignoring the scroll position. ### Root Cause Cross-platform timing issue. ScrollView hasn't completed layout/measurement when [ScrollToAsync](vscode-file://vscode-app/Applications/Visual%20Studio%20Code.app/Contents/Resources/app/out/vs/code/electron-browser/workbench/workbench.html) is called from [OnAppearing](vscode-file://vscode-app/Applications/Visual%20Studio%20Code.app/Contents/Resources/app/out/vs/code/electron-browser/workbench/workbench.html), causing scroll requests to be ignored on all platforms. ### Description of Change Each platform (Android, iOS, Windows) now defers scroll requests arriving before layout completion and processes them after native view measurement/arrangement finishes. Android uses [Post()](vscode-file://vscode-app/Applications/Visual%20Studio%20Code.app/Contents/Resources/app/out/vs/code/electron-browser/workbench/workbench.html) callback, iOS/Windows use layout/size-changed event handlers. Validated the behavior in the following platforms - [x] Android - [x] Windows - [x] iOS - [x] Mac ### Issues Fixed Fixes #31177 ### Output ScreenShot |Before|After| |--|--| | <video src="https://github.com/user-attachments/assets/b6864920-e0eb-4fbf-9526-ca8c9dc1a4f9" >| <video src="https://github.com/user-attachments/assets/2eb00afe-21c7-4ed0-b0dd-7179d0867df6">| ---------
6 participants
Note
Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!
Issue Details
ScrollView.ScrollToAsync does nothing when called from Page.OnAppearing. The page always opens at the top, ignoring the scroll position.
Root Cause
Cross-platform timing issue. ScrollView hasn't completed layout/measurement when ScrollToAsync is called from OnAppearing, causing scroll requests to be ignored on all platforms.
Description of Change
Each platform (Android, iOS, Windows) now defers scroll requests arriving before layout completion and processes them after native view measurement/arrangement finishes. Android uses Post() callback, iOS/Windows use layout/size-changed event handlers.
Validated the behavior in the following platforms
Issues Fixed
Fixes #31177
Output ScreenShot
31177-beforeFix.mov
31177-AfterFix.mov