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[web] Anchor flt-semantics-host at 0,0 to fix WebKit semantics offset - #190486

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auto-submit[bot] merged 11 commits into
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flutter-zl:ios-web-semantics-host-offset
Sep 1, 2026
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[web] Anchor flt-semantics-host at 0,0 to fix WebKit semantics offset#190486
auto-submit[bot] merged 11 commits into
flutter:masterfrom
flutter-zl:ios-web-semantics-host-offset

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@flutter-zl flutter-zl commented Aug 4, 2026 •
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Fixes #190483.

This is the part of the fix to #129324.

Problem
On iOS every browser uses WebKit. <flt-semantics-host> is position: absolute with no left or top, so it falls back to its CSS static position. WebKit resolves that static position past the in-flow <flt-glass-pane>, so the entire semantics layer is shifted roughly one viewport off-screen. VoiceOver focus lands off-screen for every control, text-field taps miss the <input>. Blink and Gecko resolve the same static position to 0, so they are unaffected.

Fix
Set left: 0; top: 0 in StyleManager.styleSemanticsHost so the host is anchored at the view origin.

Demo
Measured on an iPhone at 430px width and devicePixelRatio 3, with semantics enabled:

  • Before, stock engine: https://flutter-demo-57-before.web.app reports 4 of 5 accessibility nodes off-screen, VoiceOver focus lands off-screen, and picking a dropdown item blanks the screen.
  • After, this fix: https://flutter-demo-57-after.web.app reports 0 of 5, VoiceOver focus lands on each control, and the dropdown works. Please note that there is a known issue that the webkit delays keyboard's pop up when voice over is enabled.

@flutter-dashboard flutter-dashboard Bot added the CICD Run CI/CD label Aug 4, 2026
@github-actions github-actions Bot added engine flutter/engine related. See also e: labels. platform-web Web applications specifically team-web Owned by Web platform team labels Aug 4, 2026
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Code Review

This pull request updates StyleManager.styleSemanticsHost to explicitly set the left and top CSS properties of the semantics host to '0'. This anchors the host at the view origin and prevents layout offsets on WebKit browsers. A corresponding test has been added to verify these style properties. There are no review comments, and I have no additional feedback to provide.

@flutter-zl
flutter-zl requested a review from mdebbar August 5, 2026 20:54
@flutter-zl flutter-zl added the autosubmit Merge PR when tree becomes green via auto submit App label Aug 10, 2026
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auto-submit Bot commented Aug 11, 2026

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autosubmit label was removed for flutter/flutter/190486, because - The status or check suite Google testing has failed. Please fix the issues identified (or deflake) before re-applying this label.

@auto-submit auto-submit Bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Aug 11, 2026
@flutter-zl flutter-zl added the autosubmit Merge PR when tree becomes green via auto submit App label Aug 11, 2026
@auto-submit auto-submit Bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Aug 11, 2026
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autosubmit label was removed for flutter/flutter/190486, because - The status or check suite Google testing has failed. Please fix the issues identified (or deflake) before re-applying this label.

@flutter-zl flutter-zl added the autosubmit Merge PR when tree becomes green via auto submit App label Aug 31, 2026
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auto-submit Bot added this pull request to the merge queue Sep 1, 2026
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@flutter-dashboard flutter-dashboard Bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Sep 1, 2026
@flutter-zl flutter-zl added the autosubmit Merge PR when tree becomes green via auto submit App label Sep 1, 2026
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auto-submit Bot added this pull request to the merge queue Sep 1, 2026
Merged via the queue into flutter:master with commit 32e7fff Sep 1, 2026
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@flutter-dashboard flutter-dashboard Bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Sep 1, 2026
This was referenced Sep 2, 2026
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auto-submit Bot pushed a commit to flutter/packages that referenced this pull request Sep 4, 2026
@engine-flutter-autoroll
Roll Flutter from 0cbd1a4be0a4 to 70797e15325e (27 revisions) (#12727)
1240bb5 
flutter/flutter@0cbd1a4...70797e1

2026-09-02 [email protected] [analysis] Upgrade package:analyzer to 14.3.0 and enable custom plugin compilation (flutter/flutter#191590)
2026-09-02 [email protected] Roll Dart SDK from d8d7869d8031 to 9a8fbde80f6c (1 revision) (flutter/flutter#192179)
2026-09-02 [email protected] Roll Skia from dec311244db4 to ae22da2e8308 (1 revision) (flutter/flutter#192177)
2026-09-02 [email protected] [tool] Migrate DoctorCommand to modular dependency injection (flutter/flutter#190758)
2026-09-02 [email protected] Roll Skia from 482b7e285244 to dec311244db4 (3 revisions) (flutter/flutter#192161)
2026-09-02 [email protected] Roll Skia from 28447e9fb8d5 to 482b7e285244 (3 revisions) (flutter/flutter#192157)
2026-09-02 [email protected] feat: Add placeholder to DecorationImage (flutter/flutter#191528)
2026-09-02 [email protected] [Android] Do not schedule engine frames on a detached FlutterJNI (flutter/flutter#191204)
2026-09-02 [email protected] Roll Skia from 3a242fb7cdb3 to 28447e9fb8d5 (1 revision) (flutter/flutter#192145)
2026-09-02 [email protected] Roll Dart SDK from 9164def35347 to d8d7869d8031 (2 revisions) (flutter/flutter#192144)
2026-09-02 [email protected] Add FadeInImageTransition.fadeInOver to fade the image in over the placeholder (flutter/flutter#186246)
2026-09-02 [email protected] Roll Skia from 63d13ec4df6d to 3a242fb7cdb3 (9 revisions) (flutter/flutter#192138)
2026-09-02 [email protected] [flutter_tools] Add --no-plugins flag and disable plugins for benchmark (flutter/flutter#192129)
2026-09-02 [email protected] [tool] Migrate ChannelCommand to modular dependency injection (flutter/flutter#190751)
2026-09-01 [email protected] Add mouseCursor to RawScrollbar (flutter/flutter#185750)
2026-09-01 [email protected] Fix self-comparison and assert typos in TestSemantics (flutter/flutter#191938)
2026-09-01 [email protected] [Linux] Wait for frames to be rendered before using them in another context (flutter/flutter#192094)
2026-09-01 [email protected] [wimp] Turn on multithreading for wimp. (flutter/flutter#191747)
2026-09-01 [email protected] Roll Skia from 3911a1fe7f7a to 63d13ec4df6d (6 revisions) (flutter/flutter#192125)
2026-09-01 [email protected] Remove the redundant flutter/shell/platform/android:robolectric_tests build target (flutter/flutter#192117)
2026-09-01 [email protected] [iOS] Preserve semantics parents after reparenting (flutter/flutter#189686)
2026-09-01 [email protected] [flutter_tools] Report preview reload timing analytics in LspPreviewDetector (flutter/flutter#192120)
2026-09-01 [email protected] [flutter_tools] Implement Templates slice and flutter create integration (flutter/flutter#191748)
2026-09-01 [email protected] Uiscene migrate add2app hosts (flutter/flutter#191847)
2026-09-01 [email protected] Roll Packages from d642322 to 7a7912f (8 revisions) (flutter/flutter#192119)
2026-09-01 [email protected] [web] Anchor flt-semantics-host at 0,0 to fix WebKit semantics offset (flutter/flutter#190486)
2026-09-01 [email protected] Replace Shell::WaitForFirstFrame with an asynchronous API that matches the Shell threading model (flutter/flutter#191841)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-packages
Please CC [email protected] on the revert to ensure that a human
is aware of the problem.

To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
@justinmc justinmc mentioned this pull request Sep 4, 2026
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This was referenced Sep 5, 2026
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Closed
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victorsanni pushed a commit to victorsanni/packages that referenced this pull request Sep 9, 2026
@engine-flutter-autoroll @victorsanni
Roll Flutter from 0cbd1a4be0a4 to 70797e15325e (27 revisions) (flutte…
2822f8e 
…r#12727)

flutter/flutter@0cbd1a4...70797e1

2026-09-02 [email protected] [analysis] Upgrade package:analyzer to 14.3.0 and enable custom plugin compilation (flutter/flutter#191590)
2026-09-02 [email protected] Roll Dart SDK from d8d7869d8031 to 9a8fbde80f6c (1 revision) (flutter/flutter#192179)
2026-09-02 [email protected] Roll Skia from dec311244db4 to ae22da2e8308 (1 revision) (flutter/flutter#192177)
2026-09-02 [email protected] [tool] Migrate DoctorCommand to modular dependency injection (flutter/flutter#190758)
2026-09-02 [email protected] Roll Skia from 482b7e285244 to dec311244db4 (3 revisions) (flutter/flutter#192161)
2026-09-02 [email protected] Roll Skia from 28447e9fb8d5 to 482b7e285244 (3 revisions) (flutter/flutter#192157)
2026-09-02 [email protected] feat: Add placeholder to DecorationImage (flutter/flutter#191528)
2026-09-02 [email protected] [Android] Do not schedule engine frames on a detached FlutterJNI (flutter/flutter#191204)
2026-09-02 [email protected] Roll Skia from 3a242fb7cdb3 to 28447e9fb8d5 (1 revision) (flutter/flutter#192145)
2026-09-02 [email protected] Roll Dart SDK from 9164def35347 to d8d7869d8031 (2 revisions) (flutter/flutter#192144)
2026-09-02 [email protected] Add FadeInImageTransition.fadeInOver to fade the image in over the placeholder (flutter/flutter#186246)
2026-09-02 [email protected] Roll Skia from 63d13ec4df6d to 3a242fb7cdb3 (9 revisions) (flutter/flutter#192138)
2026-09-02 [email protected] [flutter_tools] Add --no-plugins flag and disable plugins for benchmark (flutter/flutter#192129)
2026-09-02 [email protected] [tool] Migrate ChannelCommand to modular dependency injection (flutter/flutter#190751)
2026-09-01 [email protected] Add mouseCursor to RawScrollbar (flutter/flutter#185750)
2026-09-01 [email protected] Fix self-comparison and assert typos in TestSemantics (flutter/flutter#191938)
2026-09-01 [email protected] [Linux] Wait for frames to be rendered before using them in another context (flutter/flutter#192094)
2026-09-01 [email protected] [wimp] Turn on multithreading for wimp. (flutter/flutter#191747)
2026-09-01 [email protected] Roll Skia from 3911a1fe7f7a to 63d13ec4df6d (6 revisions) (flutter/flutter#192125)
2026-09-01 [email protected] Remove the redundant flutter/shell/platform/android:robolectric_tests build target (flutter/flutter#192117)
2026-09-01 [email protected] [iOS] Preserve semantics parents after reparenting (flutter/flutter#189686)
2026-09-01 [email protected] [flutter_tools] Report preview reload timing analytics in LspPreviewDetector (flutter/flutter#192120)
2026-09-01 [email protected] [flutter_tools] Implement Templates slice and flutter create integration (flutter/flutter#191748)
2026-09-01 [email protected] Uiscene migrate add2app hosts (flutter/flutter#191847)
2026-09-01 [email protected] Roll Packages from d642322 to 7a7912f (8 revisions) (flutter/flutter#192119)
2026-09-01 [email protected] [web] Anchor flt-semantics-host at 0,0 to fix WebKit semantics offset (flutter/flutter#190486)
2026-09-01 [email protected] Replace Shell::WaitForFirstFrame with an asynchronous API that matches the Shell threading model (flutter/flutter#191841)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-packages
Please CC [email protected] on the revert to ensure that a human
is aware of the problem.

To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
victorsanni pushed a commit to victorsanni/packages that referenced this pull request Sep 9, 2026
@engine-flutter-autoroll @victorsanni
Roll Flutter from 0cbd1a4be0a4 to 70797e15325e (27 revisions) (flutte…
2ee1685 
…r#12727)

flutter/flutter@0cbd1a4...70797e1

2026-09-02 [email protected] [analysis] Upgrade package:analyzer to 14.3.0 and enable custom plugin compilation (flutter/flutter#191590)
2026-09-02 [email protected] Roll Dart SDK from d8d7869d8031 to 9a8fbde80f6c (1 revision) (flutter/flutter#192179)
2026-09-02 [email protected] Roll Skia from dec311244db4 to ae22da2e8308 (1 revision) (flutter/flutter#192177)
2026-09-02 [email protected] [tool] Migrate DoctorCommand to modular dependency injection (flutter/flutter#190758)
2026-09-02 [email protected] Roll Skia from 482b7e285244 to dec311244db4 (3 revisions) (flutter/flutter#192161)
2026-09-02 [email protected] Roll Skia from 28447e9fb8d5 to 482b7e285244 (3 revisions) (flutter/flutter#192157)
2026-09-02 [email protected] feat: Add placeholder to DecorationImage (flutter/flutter#191528)
2026-09-02 [email protected] [Android] Do not schedule engine frames on a detached FlutterJNI (flutter/flutter#191204)
2026-09-02 [email protected] Roll Skia from 3a242fb7cdb3 to 28447e9fb8d5 (1 revision) (flutter/flutter#192145)
2026-09-02 [email protected] Roll Dart SDK from 9164def35347 to d8d7869d8031 (2 revisions) (flutter/flutter#192144)
2026-09-02 [email protected] Add FadeInImageTransition.fadeInOver to fade the image in over the placeholder (flutter/flutter#186246)
2026-09-02 [email protected] Roll Skia from 63d13ec4df6d to 3a242fb7cdb3 (9 revisions) (flutter/flutter#192138)
2026-09-02 [email protected] [flutter_tools] Add --no-plugins flag and disable plugins for benchmark (flutter/flutter#192129)
2026-09-02 [email protected] [tool] Migrate ChannelCommand to modular dependency injection (flutter/flutter#190751)
2026-09-01 [email protected] Add mouseCursor to RawScrollbar (flutter/flutter#185750)
2026-09-01 [email protected] Fix self-comparison and assert typos in TestSemantics (flutter/flutter#191938)
2026-09-01 [email protected] [Linux] Wait for frames to be rendered before using them in another context (flutter/flutter#192094)
2026-09-01 [email protected] [wimp] Turn on multithreading for wimp. (flutter/flutter#191747)
2026-09-01 [email protected] Roll Skia from 3911a1fe7f7a to 63d13ec4df6d (6 revisions) (flutter/flutter#192125)
2026-09-01 [email protected] Remove the redundant flutter/shell/platform/android:robolectric_tests build target (flutter/flutter#192117)
2026-09-01 [email protected] [iOS] Preserve semantics parents after reparenting (flutter/flutter#189686)
2026-09-01 [email protected] [flutter_tools] Report preview reload timing analytics in LspPreviewDetector (flutter/flutter#192120)
2026-09-01 [email protected] [flutter_tools] Implement Templates slice and flutter create integration (flutter/flutter#191748)
2026-09-01 [email protected] Uiscene migrate add2app hosts (flutter/flutter#191847)
2026-09-01 [email protected] Roll Packages from d642322 to 7a7912f (8 revisions) (flutter/flutter#192119)
2026-09-01 [email protected] [web] Anchor flt-semantics-host at 0,0 to fix WebKit semantics offset (flutter/flutter#190486)
2026-09-01 [email protected] Replace Shell::WaitForFirstFrame with an asynchronous API that matches the Shell threading model (flutter/flutter#191841)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-packages
Please CC [email protected] on the revert to ensure that a human
is aware of the problem.

To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
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[web] WebKit (iOS and macOS Safari) shifts the whole semantics layer off-screen when semantics is enabled, breaking VoiceOver and TextField input

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