Add set semantics enabled API and wire iOS a11y bridge by chunhtai · Pull Request #161265 · flutter/flutter

chunhtai · 2025-01-07T21:37:02Z

previously the only correct way to enable semantics is that ios embedding receive signal from native OS, it call SetSemanticsEnabled to shell and then to dart to enable semantics tree generation.

If for some reason framework decide to enable semantics first, e.g. through SemanticsBinding.instance.ensureSemantics(typically due to integration test or ci that wants to test semantics), the update will be dropped in shell. Even if it later on receive signal from native OS to turn on semantics, it can't construct the complete accessibility tree in embedding because the updatesemantics sends diff update and previous updates are gone forever. It will end up in a broken state.

This pr changes so that the only source of truth will be in the framework side. When framework starts generating the the semantics tree, it will call SetSemanticsTreeEnabled through dart:ui, and the embedding needs to prepare itself to accept semantics update after receiving the message.

This however require some refactoring on iOS embedding because it will only create a11y bridge when receiving OS notification when assitive technologies turns on.

This requires three phase transition

add an empty dart:ui API setSemanticsTreeEnabled
makes framework calls the empty API.
merge this pr with actual implementation of setSemanticsTreeEnabled

I will do the android part in a separate pr

Pre-launch Checklist

I read the Contributor Guide and followed the process outlined there for submitting PRs.
I read the Tree Hygiene wiki page, which explains my responsibilities.
I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
I signed the CLA.
I listed at least one issue that this PR fixes in the description above.
I updated/added relevant documentation (doc comments with ///).
I added new tests to check the change I am making, or this PR is test-exempt.
I followed the breaking change policy and added Data Driven Fixes where supported.
All existing and new tests are passing.

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engine/src/flutter/runtime/runtime_controller.h

cbracken

@chunhtai can you add a PR description with the rationale for the change, related bug(s), etc.?

chunhtai · 2025-01-13T18:07:43Z

@chunhtai can you add a PR description with the rationale for the change, related bug(s), etc.?

sorry, forgot to add description. Done

goderbauer

LGTM for dart:ui (after doc nits are resolved)

goderbauer · 2025-02-03T23:56:18Z

engine/src/flutter/lib/ui/platform_dispatcher.dart

+  /// Informs the engine whether the framework is generating a semantics tree.
+  ///
+  /// Only framework knows when semantics tree should be generated. It uses this
+  /// method to notify the engine such event.


Maybe better:

Suggested change

/// method to notify the engine such event.

/// method to notify the engine whether the framework will generate a semantics tree.

engine/src/flutter/lib/ui/platform_dispatcher.dart

engine/src/flutter/lib/ui/window.dart

justinmc · 2025-02-26T00:05:00Z

@chunhtai heads up there are failures here if you hadn't seen.

cbracken

Just a few small nits then good to go!

engine/src/flutter/runtime/runtime_controller.h

engine/src/flutter/runtime/runtime_controller_unittests.cc

engine/src/flutter/shell/platform/darwin/ios/platform_view_ios.mm

engine/src/flutter/shell/platform/darwin/ios/platform_view_ios_test.mm

cbracken

auto-submit · 2025-03-18T23:07:17Z

autosubmit label was removed for flutter/flutter/161265, because - The status or check suite Mac_arm64 module_test_ios has failed. Please fix the issues identified (or deflake) before re-applying this label.

…er#161265)" This reverts commit 26037df.

…er/flutter#161265)

github-actions bot added platform-ios iOS applications specifically framework flutter/packages/flutter repository. See also f: labels. engine flutter/engine related. See also e: labels. platform-web Web applications specifically labels Jan 7, 2025

chunhtai mentioned this pull request Jan 8, 2025

Google test doesn't support engine changes #161323

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update

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	/// method to notify the engine such event.
	/// method to notify the engine whether the framework will generate a semantics tree.

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