Fix hit-testing order in semantics by QuncCccccc · Pull Request #167522 · flutter/flutter

QuncCccccc · 2025-04-22T01:40:26Z

In updateWith() method, _replaceChildren() is called to generate _children list. _children list is used to generate the hit test order (childrenInHitTestOrder).

In _replaceChildren(), childrenIn**Inverse**PaintOrder is directly assigned to _children, so _children itself follows hit test order. So when we generate the childrenInHitTestOrder, we don't need to reverse the children again.

Screen.Recording.2025-04-21.at.6.41.37.PM.mov

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I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
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chunhtai · 2025-04-23T22:43:44Z

packages/flutter/lib/src/semantics/semantics.dart

-      for (int i = childCount - 1; i >= 0; i -= 1) {
-        childrenInHitTestOrder[i] = _children![childCount - i - 1].id;
+      for (int i = 0; i < childCount; i += 1) {
+        childrenInHitTestOrder[i] = _children![i].id;


This is surprising, does this mean we always get it wrong?

after reading the code more I think the original documentation may be wrong

_children is assigned with the childrenInInversePaintOrder in SemanticsNode.updateWith.

which is called in _buildSemanticsSubtree where the children is the same as _childrenAndElevationAdjustments order and I think by default the _childrenAndElevationAdjustments order is insertion order which will be RenderObject.visitChildForSemantics, which is the paint order.

so the the original code should be correct but just bad name.

Just an update. Talked with @chunhtai offline. It seems the hit test order was incorrect all the time. But previously when we haven't applied OverlayPortal to any widgets, if we push a new route, the items underneath the new route will be thrown away so the hit test only need to handle one "layer" of items and everything is okay. After OverlayPortal is applied to Autocomplete, the items underneath the popup still stay in the tree, and the hit test order starts show problems.

chunhtai

ＬＧＴＭ

edeetee · 2025-04-26T08:33:24Z

Thanks for the semantics fix, the attention to a11y is appreciated.

This reverts commit d9cbff2.

This reverts commit d9cbff2. Fixes #168164

…#168235) This reverts commit d9cbff2. Fixes flutter#168164

github-actions bot added framework flutter/packages/flutter repository. See also f: labels. f: material design flutter/packages/flutter/material repository. a: accessibility Accessibility, e.g. VoiceOver or TalkBack. (aka a11y) f: scrolling Viewports, list views, slivers, etc. labels Apr 22, 2025

QuncCccccc force-pushed the hit_test_order_fix branch from 2dd4595 to 252e1dd Compare April 23, 2025 01:11

QuncCccccc requested review from chunhtai and yjbanov April 23, 2025 17:33

QuncCccccc marked this pull request as ready for review April 23, 2025 17:33

chunhtai reviewed Apr 23, 2025

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QuncCccccc force-pushed the hit_test_order_fix branch from 252e1dd to 4eb6771 Compare April 24, 2025 18:09

QuncCccccc added 9 commits April 24, 2025 17:24

Fix hit-testing order in semantics

328b7a8

Update

088e457

Revert the logic change in _childrenInTraversalOrder

97c0fa0

Fix failed test

44d9048

Fix failed test

5b6e44a

Fix failed test

30322af

Fix failed test

1acef4a

Update code comment

0862f3b

Fix failed test

da4515c

QuncCccccc force-pushed the hit_test_order_fix branch from 4eb6771 to da4515c Compare April 25, 2025 00:24

chunhtai self-requested a review April 25, 2025 22:10

chunhtai approved these changes Apr 25, 2025

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QuncCccccc added the autosubmit Merge PR when tree becomes green via auto submit App label Apr 25, 2025

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Merged via the queue into flutter:master with commit d9cbff2 Apr 26, 2025
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flutter-dashboard bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Apr 26, 2025

engine-flutter-autoroll mentioned this pull request Apr 26, 2025

Roll Flutter from cfb887cd5f41 to 39d8d41a8498 (101 revisions) flutter/packages#9159

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engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Apr 26, 2025

d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

bd88906

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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justinmc mentioned this pull request May 2, 2025

DropdownButton options cannot be selected when using TalkBack on Android #168164

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Revert "Fix hit-testing order in semantics (flutter#167522)"

890dd8b

This reverts commit d9cbff2.

QuncCccccc mentioned this pull request May 2, 2025

[Web] SemanticsBinding.instance.ensureSemantics() is propagating click on overlapping widgets #163576

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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Revert "Fix hit-testing order in semantics (#167522)" (#168235)

14c45d9

This reverts commit d9cbff2. Fixes #168164

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 5, 2025

d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

38b2efe

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 5, 2025

d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

eb2c6a6

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 5, 2025

d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

698a7f6

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 5, 2025

d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

900292f

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 5, 2025

d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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ash2moon pushed a commit to ash2moon/flutter that referenced this pull request May 5, 2025

Revert "Fix hit-testing order in semantics (flutter#167522)" (flutter…

1f7f474

…#168235) This reverts commit d9cbff2. Fixes flutter#168164

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 5, 2025

d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

4097c3f

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 5, 2025

d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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QuncCccccc mentioned this pull request May 6, 2025

DropdownButton menu gets stuck in hovered state when selecting with a mouse #168096

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 6, 2025

d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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Revert "Fix hit-testing order in semantics (flutter#167522)" (flutter…

afab0ad

…#168235) This reverts commit d9cbff2. Fixes flutter#168164

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 7, 2025

d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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d9cbff2 Fix hit-testing order in semantics (flutter/flutter#167522)

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Linux web_skwasm_tests_0 is 2.00% flaky #168455

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Fix hit-testing order in semantics#167522

Fix hit-testing order in semantics#167522
auto-submit[bot] merged 9 commits intoflutter:masterfrom
QuncCccccc:hit_test_order_fix

QuncCccccc commented Apr 22, 2025 •

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