[web] Fix SemanticsService.announce not working inside dialogs #179958
+138
−9
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
mdebbar
reviewed
Jan 6, 2026
Comment on lines
123
to
125
| Timer(announcementDelay, () { | ||
| ariaLiveElement.text = messageText; | ||
| }); |
Contributor
There was a problem hiding this comment.
I'm not sure that I fully understand this delay. I would think that when we receive a request to announce something, we should announce it immediately.
Contributor
Author
There was a problem hiding this comment.
When a user clicks a button that triggers an announcement, voiceOver immediately starts reading the button's accessible name (for example, "Announce, button"). If we set the aria-live text immediately, VoiceOver tries to announce it at the same time. VoiceOver gets confused and drops one of the announcements (usually the aria-live one).The 500ms delay gives VoiceOver time to finish reading the button label before we inject the announcement text.
Without delay:
User clicks "Announce" button
VoiceOver: "Announce, button" ← aria-live update happens here, gets dropped
(silence - announcement lost)
With delay:
User clicks "Announce" button
VoiceOver: "Announce, button"
(500ms pause)
VoiceOver: "Your announcement message"
Contributor
Author
There was a problem hiding this comment.
I did some investigation and it turns out we do not need the 500ms delay value.
Investigation: Through systematic testing with different delay values (500ms → 100ms → 50ms → 20ms → 10ms → 5ms → 1ms → 0ms), I discovered:
-
0ms (synchronous): Doesn't work - VoiceOver doesn't announce
-
Duration.zero with Timer: Works - VoiceOver announces correctly
Root Cause: VoiceOver needs the aria-live text to be set in a different event loop tick than the button click. Setting it synchronously interferes with VoiceOver's internal speech queue processing.
Fix: Use Timer(Duration.zero, ...) to defer setting the announcement text to the next event loop iteration.
This provides the minimum necessary delay.
Please check https://flutter-demo-03-after.web.app/
engine-flutter-autoroll
added a commit
to engine-flutter-autoroll/packages
that referenced
this pull request
Jan 9, 2026
engine-flutter-autoroll
added a commit
to engine-flutter-autoroll/packages
that referenced
this pull request
Jan 9, 2026
This was referenced Jan 9, 2026
engine-flutter-autoroll
added a commit
to engine-flutter-autoroll/packages
that referenced
this pull request
Jan 9, 2026
engine-flutter-autoroll
added a commit
to engine-flutter-autoroll/packages
that referenced
this pull request
Jan 9, 2026
engine-flutter-autoroll
added a commit
to engine-flutter-autoroll/packages
that referenced
this pull request
Jan 10, 2026
engine-flutter-autoroll
added a commit
to engine-flutter-autoroll/packages
that referenced
this pull request
Jan 10, 2026
engine-flutter-autoroll
added a commit
to engine-flutter-autoroll/packages
that referenced
this pull request
Jan 10, 2026
auto-submit bot
pushed a commit
to flutter/packages
that referenced
this pull request
Jan 10, 2026
Roll Flutter from 01d37bc to 73769a2 (65 revisions) flutter/flutter@01d37bc...73769a2 2026-01-10 engine-flutter-autoroll@skia.org Roll Dart SDK from 5e855c2bb3ef to 87fbfd5381b6 (1 revision) (flutter/flutter#180800) 2026-01-10 engine-flutter-autoroll@skia.org Roll Skia from b2b109f0e980 to f39cc645b1dd (2 revisions) (flutter/flutter#180796) 2026-01-10 engine-flutter-autoroll@skia.org Roll Dart SDK from b7963905e6a2 to 5e855c2bb3ef (2 revisions) (flutter/flutter#180794) 2026-01-10 ahmedsameha1@gmail.com Make sure that a CupertinoTabScaffold doesn't crash in 0x0 environment (flutter/flutter#179824) 2026-01-10 engine-flutter-autoroll@skia.org Roll Dart SDK from d25ad331b7ea to b7963905e6a2 (2 revisions) (flutter/flutter#180783) 2026-01-10 ahmedsameha1@gmail.com Make sure that a Container doesn't crash in 0x0 environment (flutter/flutter#180350) 2026-01-10 ahmedsameha1@gmail.com Make sure that an Expansible doesn't crash in 0x0 environment (flutter/flutter#180478) 2026-01-10 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Enabled some disabled impeller fragment shader dart tests (#180759)" (flutter/flutter#180785) 2026-01-09 dkwingsmt@users.noreply.github.com Merge `widget_tester_leaks_free_test.dart` into `widget_tester_test.dart` (flutter/flutter#180600) 2026-01-09 codefu@google.com fix: there are no riscv fuchsia artifacts (flutter/flutter#180779) 2026-01-09 engine-flutter-autoroll@skia.org Roll Skia from 7386219151e6 to b2b109f0e980 (1 revision) (flutter/flutter#180771) 2026-01-09 chinmaygarde@google.com Re-prioritize pipeline compile jobs and perform them eagerly instead of waiting. (flutter/flutter#180022) 2026-01-09 30870216+gaaclarke@users.noreply.github.com Enabled some disabled impeller fragment shader dart tests (flutter/flutter#180759) 2026-01-09 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from rxeg-6UB678HKJ4UQ... to 83Favz_zzMzdVuOHg... (flutter/flutter#180765) 2026-01-09 jhy03261997@gmail.com [A11y ] Add `clearSemantics`in table (flutter/flutter#180665) 2026-01-09 chinmaygarde@google.com Update CODEOWNERS to remove chinmaygarde. (flutter/flutter#180703) 2026-01-09 vhaudiquet343@hotmail.fr [ Tool ] Add support for linux riscv64 architecture (flutter/flutter#178711) 2026-01-09 engine-flutter-autoroll@skia.org Roll Skia from e9b3264ade0c to 7386219151e6 (12 revisions) (flutter/flutter#180754) 2026-01-09 engine-flutter-autoroll@skia.org Roll Dart SDK from fe2ba2c5dd50 to d25ad331b7ea (10 revisions) (flutter/flutter#180741) 2026-01-09 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Unpin google_mobile_ads (#180573)" (flutter/flutter#180761) 2026-01-09 koichi20021217@gmail.com Fix typo in dropdown_menu.dart (flutter/flutter#180172) 2026-01-09 engine-flutter-autoroll@skia.org Roll Packages from 039a026 to 51fe1d9 (1 revision) (flutter/flutter#180742) 2026-01-09 goderbauer@google.com Unpin google_mobile_ads (flutter/flutter#180573) 2026-01-09 evanwall@buffalo.edu Update flutter changelog for 3.38.6 (flutter/flutter#180708) 2026-01-08 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Fix iOS xattr removal to clear all extended attributes (#180355)" (flutter/flutter#180709) 2026-01-08 ahmedsameha1@gmail.com Make sure that an EditableText doesn't crash in 0x0 environment (flutter/flutter#180457) 2026-01-08 matt.kosarek@canonical.com Implementation of tooltip windows for win32 (flutter/flutter#179147) 2026-01-08 mdebbar@google.com [web] Don't serve files outside of project (flutter/flutter#180699) 2026-01-08 engine-flutter-autoroll@skia.org Roll Skia from 837be28dd218 to e9b3264ade0c (1 revision) (flutter/flutter#180702) 2026-01-08 sokolovskyi.konstantin@gmail.com Add new motion accessibility features to iOS. (flutter/flutter#178102) 2026-01-08 104009581+Saqib198@users.noreply.github.com Fix iOS xattr removal to clear all extended attributes (flutter/flutter#180355) 2026-01-08 bkonyi@google.com [ Widget Preview ] Move widget_preview_scaffold tests to `dev/integration_tests/widget_preview_scaffold` (flutter/flutter#180658) 2026-01-08 30870216+gaaclarke@users.noreply.github.com De-interleaves engine dart test output (flutter/flutter#180651) 2026-01-08 zhongliu88889@gmail.com [web] Fix SemanticsService.announce not working inside dialogs (flutter/flutter#179958) 2026-01-08 engine-flutter-autoroll@skia.org Roll Skia from 42233226ac56 to 837be28dd218 (2 revisions) (flutter/flutter#180693) 2026-01-08 iinozemtsev@google.com Roll Dart SDK to 3.11.0-296.2.beta (flutter/flutter#180685) 2026-01-08 116356835+AbdeMohlbi@users.noreply.github.com Improve code quality in `AndroidTouchProcessorTest.java` (flutter/flutter#180583) 2026-01-08 1961493+harryterkelsen@users.noreply.github.com Revert "Reverts "[reland] Unify canvas creation and Surface code in S…kwasm and CanvasKit (#179473)" (#180152)" (flutter/flutter#180610) 2026-01-08 engine-flutter-autoroll@skia.org Roll Skia from a0c407bce408 to 42233226ac56 (4 revisions) (flutter/flutter#180688) 2026-01-08 bkonyi@google.com [ Tool ] Fix flake in overall_experience_test.dart (flutter/flutter#180655) 2026-01-08 engine-flutter-autoroll@skia.org Roll Packages from 9705815 to 039a026 (6 revisions) (flutter/flutter#180684) 2026-01-08 104147021+MohammedTarigg@users.noreply.github.com flutter_tools: Auto-generate ExportOptions.plist for manual iOS code signing (flutter/flutter#177888) 2026-01-08 engine-flutter-autoroll@skia.org Roll Skia from 58837e160874 to a0c407bce408 (2 revisions) (flutter/flutter#180679) 2026-01-08 engine-flutter-autoroll@skia.org Roll Skia from 1e3266fdba86 to 58837e160874 (1 revision) (flutter/flutter#180677) 2026-01-08 engine-flutter-autoroll@skia.org Roll Skia from 3c47ea10638f to 1e3266fdba86 (4 revisions) (flutter/flutter#180675) 2026-01-08 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from dTvN_JVSCfGFRasvH... to rxeg-6UB678HKJ4UQ... (flutter/flutter#180673) ...
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fixes #179076
Solution
When a modal dialog is present, temporarily move the existing aria-live element inside the modal dialog before making the announcement, then move it back afterward. A small delay is also added to allow VoiceOver to finish reading the button's accessible name first.
Demo
Before (bug): https://flutter-demo-03-before.web.app
After (fix): https://flutter-demo-03-after.web.app
Testing
Enable VoiceOver (Cmd+F5 on macOS)
Open a dialog and click the "Announce" button
Verify the announcement is spoken after the button label
Next step
Filing a follow-up issue for: Adding a delay parameter to SemanticsService.announce() API for developers who need custom delays for long button labels