Screen readers cannot list or move focus to elements outside of the current viewport #160217
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a: accessibility
Accessibility, e.g. VoiceOver or TalkBack. (aka a11y)
customer: castaway
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r: fixed
Issue is closed as already fixed in a newer version
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Thanks for the report @jcollins-disney |
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Thanks for the update. |
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I think this may be due to insufficient cache extent, but I am not to familiar with desktop screen reader on web. assign to web team for further triage |
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Currently when using a `CustomScrollView`, screen readers cannot list or
move focus to elements that are outside the current Viewport and cache
extent because we do not create semantic nodes for these elements.
This change introduces `SliverEnsureSemantics` which ensures its sliver
child is included in the semantics tree, whether or not it is currently
visible on the screen or within the cache extent. This way screen
readers are aware the elements are there and can navigate to them /
create accessibility traversal menus with this information.
* Under the hood a new flag has been added to `RenderSliver` called
`ensureSemantics`. `RenderViewportBase` uses this in its
`visitChildrenForSemantics` to ensure a sliver is visited when creating
the semantics tree. Previously a sliver was not visited if it was not
visible or within the cache extent. `RenderViewportBase` also uses this
in `describeSemanticsClip` and `describeApproximatePaintClip` to ensure
a sliver child that wants to "ensure semantics" is not clipped out if it
is not currently visible in the viewport or outside the cache extent.
* `RenderSliverMultiBoxAdaptor.semanticBounds` now leverages its first
child as an anchor for assistive technologies to be able to reach it if
the Sliver is a child of `SliverEnsureSemantics`. If not it will still
be dropped from the semantics tree.
* `RenderProxySliver` now considers child overrides of `semanticBounds`.
On the engine side we move from using a joystick method to scroll with
`SemanticsAction.scrollUp` and `SemanticsAction.scrollDown` to using
`SemanticsAction.scrollToOffset` completely letting the browser drive
the scrolling with its current dom scroll position "scrollTop" or
"scrollLeft". This is possible by calculating the total quantity of
content under the scrollable and sizing the scroll element based on
that.
<details open><summary>Code sample</summary>
```dart
// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
/// Flutter code sample for [SliverEnsureSemantics].
void main() => runApp(const SliverEnsureSemanticsExampleApp());
class SliverEnsureSemanticsExampleApp extends StatelessWidget {
const SliverEnsureSemanticsExampleApp({super.key});
@OverRide
Widget build(BuildContext context) {
return const MaterialApp(home: SliverEnsureSemanticsExample());
}
}
class SliverEnsureSemanticsExample extends StatefulWidget {
const SliverEnsureSemanticsExample({super.key});
@OverRide
State<SliverEnsureSemanticsExample> createState() =>
_SliverEnsureSemanticsExampleState();
}
class _SliverEnsureSemanticsExampleState
extends State<SliverEnsureSemanticsExample> {
@OverRide
Widget build(BuildContext context) {
final ThemeData theme = Theme.of(context);
return Scaffold(
appBar: AppBar(
backgroundColor: theme.colorScheme.inversePrimary,
title: const Text('SliverEnsureSemantics Demo'),
),
body: Center(
child: CustomScrollView(
semanticChildCount: 106,
slivers: <Widget>[
SliverEnsureSemantics(
sliver: SliverToBoxAdapter(
child: IndexedSemantics(
index: 0,
child: Card(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Semantics(
header: true,
headingLevel: 3,
child: Text(
'Steps to reproduce',
style: theme.textTheme.headlineSmall,
),
),
const Text('Issue description'),
Semantics(
header: true,
headingLevel: 3,
child: Text(
'Expected Results',
style: theme.textTheme.headlineSmall,
),
),
Semantics(
header: true,
headingLevel: 3,
child: Text(
'Actual Results',
style: theme.textTheme.headlineSmall,
),
),
Semantics(
header: true,
headingLevel: 3,
child: Text(
'Code Sample',
style: theme.textTheme.headlineSmall,
),
),
Semantics(
header: true,
headingLevel: 3,
child: Text(
'Screenshots',
style: theme.textTheme.headlineSmall,
),
),
Semantics(
header: true,
headingLevel: 3,
child: Text(
'Logs',
style: theme.textTheme.headlineSmall,
),
),
],
),
),
),
),
),
),
SliverFixedExtentList(
itemExtent: 44.0,
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Card(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Text('Item $index'),
),
);
},
childCount: 50,
semanticIndexOffset: 1,
),
),
SliverEnsureSemantics(
sliver: SliverToBoxAdapter(
child: IndexedSemantics(
index: 51,
child: Card(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Semantics(
header: true,
child: const Text('Footer 1'),
),
),
),
),
),
),
SliverEnsureSemantics(
sliver: SliverToBoxAdapter(
child: IndexedSemantics(
index: 52,
child: Card(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Semantics(
header: true,
child: const Text('Footer 2'),
),
),
),
),
),
),
SliverEnsureSemantics(
sliver: SliverToBoxAdapter(
child: IndexedSemantics(
index: 53,
child: Semantics(link: true, child: const Text('Link #1')),
),
),
),
SliverEnsureSemantics(
sliver: SliverToBoxAdapter(
child: IndexedSemantics(
index: 54,
child: OverflowBar(
children: <Widget>[
TextButton(
onPressed: () {},
child: const Text('Button 1'),
),
TextButton(
onPressed: () {},
child: const Text('Button 2'),
),
],
),
),
),
),
SliverEnsureSemantics(
sliver: SliverToBoxAdapter(
child: IndexedSemantics(
index: 55,
child: Semantics(link: true, child: const Text('Link #2')),
),
),
),
SliverEnsureSemantics(
sliver: SliverSemanticsList(
sliver: SliverFixedExtentList(
itemExtent: 44.0,
delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
return Semantics(
role: SemanticsRole.listItem,
child: Card(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Text('Second List Item $index'),
),
),
);
},
childCount: 50,
semanticIndexOffset: 56,
),
),
),
),
SliverEnsureSemantics(
sliver: SliverToBoxAdapter(
child: IndexedSemantics(
index: 107,
child: Semantics(link: true, child: const Text('Link #3')),
),
),
),
],
),
),
);
}
}
// A sliver that assigns the role of SemanticsRole.list to its sliver child.
class SliverSemanticsList extends SingleChildRenderObjectWidget {
const SliverSemanticsList({super.key, required Widget sliver})
: super(child: sliver);
@OverRide
RenderSliverSemanticsList createRenderObject(BuildContext context) =>
RenderSliverSemanticsList();
}
class RenderSliverSemanticsList extends RenderProxySliver {
@OverRide
void describeSemanticsConfiguration(SemanticsConfiguration config) {
super.describeSemanticsConfiguration(config);
config.role = SemanticsRole.list;
}
}
```
</details>
Fixes: #160217
## Pre-launch Checklist
- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.
---------
Co-authored-by: Renzo Olivares <[email protected]>
darshankawar
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<!-- start_original_pr_link --> Reverts: #165589 <!-- end_original_pr_link --> <!-- start_initiating_author --> Initiated by: Renzo-Olivares <!-- end_initiating_author --> <!-- start_revert_reason --> Reason for reverting: breaking internal tests <!-- end_revert_reason --> <!-- start_original_pr_author --> Original PR Author: Renzo-Olivares <!-- end_original_pr_author --> <!-- start_reviewers --> Reviewed By: {Piinks} <!-- end_reviewers --> <!-- start_revert_body --> This change reverts the following previous change: Currently when using a `CustomScrollView`, screen readers cannot list or move focus to elements that are outside the current Viewport and cache extent because we do not create semantic nodes for these elements. This change introduces `SliverEnsureSemantics` which ensures its sliver child is included in the semantics tree, whether or not it is currently visible on the screen or within the cache extent. This way screen readers are aware the elements are there and can navigate to them / create accessibility traversal menus with this information. * Under the hood a new flag has been added to `RenderSliver` called `ensureSemantics`. `RenderViewportBase` uses this in its `visitChildrenForSemantics` to ensure a sliver is visited when creating the semantics tree. Previously a sliver was not visited if it was not visible or within the cache extent. `RenderViewportBase` also uses this in `describeSemanticsClip` and `describeApproximatePaintClip` to ensure a sliver child that wants to "ensure semantics" is not clipped out if it is not currently visible in the viewport or outside the cache extent. * `RenderSliverMultiBoxAdaptor.semanticBounds` now leverages its first child as an anchor for assistive technologies to be able to reach it if the Sliver is a child of `SliverEnsureSemantics`. If not it will still be dropped from the semantics tree. * `RenderProxySliver` now considers child overrides of `semanticBounds`. On the engine side we move from using a joystick method to scroll with `SemanticsAction.scrollUp` and `SemanticsAction.scrollDown` to using `SemanticsAction.scrollToOffset` completely letting the browser drive the scrolling with its current dom scroll position "scrollTop" or "scrollLeft". This is possible by calculating the total quantity of content under the scrollable and sizing the scroll element based on that. <details open><summary>Code sample</summary> ```dart // Copyright 2014 The Flutter Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. import 'package:flutter/material.dart'; import 'package:flutter/rendering.dart'; /// Flutter code sample for [SliverEnsureSemantics]. void main() => runApp(const SliverEnsureSemanticsExampleApp()); class SliverEnsureSemanticsExampleApp extends StatelessWidget { const SliverEnsureSemanticsExampleApp({super.key}); @OverRide Widget build(BuildContext context) { return const MaterialApp(home: SliverEnsureSemanticsExample()); } } class SliverEnsureSemanticsExample extends StatefulWidget { const SliverEnsureSemanticsExample({super.key}); @OverRide State<SliverEnsureSemanticsExample> createState() => _SliverEnsureSemanticsExampleState(); } class _SliverEnsureSemanticsExampleState extends State<SliverEnsureSemanticsExample> { @OverRide Widget build(BuildContext context) { final ThemeData theme = Theme.of(context); return Scaffold( appBar: AppBar( backgroundColor: theme.colorScheme.inversePrimary, title: const Text('SliverEnsureSemantics Demo'), ), body: Center( child: CustomScrollView( semanticChildCount: 106, slivers: <Widget>[ SliverEnsureSemantics( sliver: SliverToBoxAdapter( child: IndexedSemantics( index: 0, child: Card( child: Padding( padding: const EdgeInsets.all(8.0), child: Column( crossAxisAlignment: CrossAxisAlignment.start, children: <Widget>[ Semantics( header: true, headingLevel: 3, child: Text( 'Steps to reproduce', style: theme.textTheme.headlineSmall, ), ), const Text('Issue description'), Semantics( header: true, headingLevel: 3, child: Text( 'Expected Results', style: theme.textTheme.headlineSmall, ), ), Semantics( header: true, headingLevel: 3, child: Text( 'Actual Results', style: theme.textTheme.headlineSmall, ), ), Semantics( header: true, headingLevel: 3, child: Text( 'Code Sample', style: theme.textTheme.headlineSmall, ), ), Semantics( header: true, headingLevel: 3, child: Text( 'Screenshots', style: theme.textTheme.headlineSmall, ), ), Semantics( header: true, headingLevel: 3, child: Text( 'Logs', style: theme.textTheme.headlineSmall, ), ), ], ), ), ), ), ), ), SliverFixedExtentList( itemExtent: 44.0, delegate: SliverChildBuilderDelegate( (BuildContext context, int index) { return Card( child: Padding( padding: const EdgeInsets.all(8.0), child: Text('Item $index'), ), ); }, childCount: 50, semanticIndexOffset: 1, ), ), SliverEnsureSemantics( sliver: SliverToBoxAdapter( child: IndexedSemantics( index: 51, child: Card( child: Padding( padding: const EdgeInsets.all(8.0), child: Semantics( header: true, child: const Text('Footer 1'), ), ), ), ), ), ), SliverEnsureSemantics( sliver: SliverToBoxAdapter( child: IndexedSemantics( index: 52, child: Card( child: Padding( padding: const EdgeInsets.all(8.0), child: Semantics( header: true, child: const Text('Footer 2'), ), ), ), ), ), ), SliverEnsureSemantics( sliver: SliverToBoxAdapter( child: IndexedSemantics( index: 53, child: Semantics(link: true, child: const Text('Link #1')), ), ), ), SliverEnsureSemantics( sliver: SliverToBoxAdapter( child: IndexedSemantics( index: 54, child: OverflowBar( children: <Widget>[ TextButton( onPressed: () {}, child: const Text('Button 1'), ), TextButton( onPressed: () {}, child: const Text('Button 2'), ), ], ), ), ), ), SliverEnsureSemantics( sliver: SliverToBoxAdapter( child: IndexedSemantics( index: 55, child: Semantics(link: true, child: const Text('Link #2')), ), ), ), SliverEnsureSemantics( sliver: SliverSemanticsList( sliver: SliverFixedExtentList( itemExtent: 44.0, delegate: SliverChildBuilderDelegate( (BuildContext context, int index) { return Semantics( role: SemanticsRole.listItem, child: Card( child: Padding( padding: const EdgeInsets.all(8.0), child: Text('Second List Item $index'), ), ), ); }, childCount: 50, semanticIndexOffset: 56, ), ), ), ), SliverEnsureSemantics( sliver: SliverToBoxAdapter( child: IndexedSemantics( index: 107, child: Semantics(link: true, child: const Text('Link #3')), ), ), ), ], ), ), ); } } // A sliver that assigns the role of SemanticsRole.list to its sliver child. class SliverSemanticsList extends SingleChildRenderObjectWidget { const SliverSemanticsList({super.key, required Widget sliver}) : super(child: sliver); @OverRide RenderSliverSemanticsList createRenderObject(BuildContext context) => RenderSliverSemanticsList(); } class RenderSliverSemanticsList extends RenderProxySliver { @OverRide void describeSemanticsConfiguration(SemanticsConfiguration config) { super.describeSemanticsConfiguration(config); config.role = SemanticsRole.list; } } ``` </details> Fixes: #160217 ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. <!-- end_revert_body --> Co-authored-by: auto-submit[bot] <[email protected]>
|
Re-opening since #165589 was reverted. Working on a fix. |
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This reverts commit 2fc716d, and updates the cross-axis size of the `_scrollOverflowElement` to be 1px (non-zero), so it is taken into account by the scrollable elements scrollHeight. Fixes #160217 ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. --------- Co-authored-by: Renzo Olivares <[email protected]>
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Steps to reproduce
NVDA, JAWS, and VoiceOver Screen readers cannot list or move focus to elements outside of the current viewport. Any elements that have scrolled out of view or haven't yet been scrolled into view will NOT be reachable via screen reader basic keyboard commands for reading and navigating web content.
Examples:
Expected results
Actual results
Code sample
N/A
Screenshots or Video
No response
Logs
No response
Flutter Doctor output
Flutter (Channel beta, 3.27.0-0.1.pre, on macOS 14.5 23F79 darwin-arm64, locale en-US)The text was updated successfully, but these errors were encountered: