Intent to Ship: Keyboard-focusable scroll containers
Di Zhang
Contact emails
hu...@chromium.org, xiaoc...@chromium.org, dizh...@chromium.orgExplainer
NoneSpecification
Design docs
NoneSummary
Improves accessibility by making scroll containers focusable using sequential focus navigation. Today, the tab key doesn't focus scrollers unless tabIndex is explicitly set to 0 or more. By making scrollers focusable by default, users who can't (or don't want to) use a mouse will be able to focus clipped content using a keyboard's tab and arrow keys. This behavior is enabled only if the scroller does not contain any keyboard focusable children. This logic is necessary so we don't cause regressions for existing focusable elements that might exist within a scroller like a <textarea>.
Blink component
Blink>HTML>FocusSearch tags
tab key, keyboard focus, sequential navigationTAG review
NoneTAG review status
Not applicableRisks
Interoperability and Compatibility
This is a change in behavior, but already matches what Firefox is doing (have scroller be focusable by default). Low compatibility risk since this default behavior is only enabled if the scroller doesn't have any focusable children.
Gecko: Shipped/Shipping Chrome behavior is slightly different since we are checking if any scroller child is focusable. This is to avoid regression on existing focus sequences.
WebKit: No signal (https://bugs.webkit.org/show_bug.cgi?id=190870)
Web developers: Positive (https://twitter.com/simevidas/status/1444033718742667270)
Other signals:
Ergonomics
There are no other platform APIs this feature will be used in tandem with. It will not be hard for Chrome to maintain good performance.
Activation
It will not be challenging for developers to take advantage of this feature immediately.
Security
There are no security risks, this is a change for keyboard focusing behavior.
WebView application risks
Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?
This is not high risk for WebView.
Debuggability
This is a change to focus navigation and DevTools does not offer debugging support for this behavior.
Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?
YesIs this feature fully tested by web-platform-tests?
YesFlag name
KeyboardFocusableScrollersRequires code in //chrome?
FalseTracking bug
https://bugs.chromium.org/p/chromium/issues/detail?id=1040141Availability expectation
Firefox already implements (a variant of this). If we succeed and don't break websites, Safari is more likely to follow suit.Adoption expectation
This is a default behavior change and websites don't need to make changes.Non-OSS dependencies
Does the feature depend on any code or APIs outside the Chromium open source repository and its open-source dependencies to function?
This feature does not depend on any APIs outside the chromium open source repository.Estimated milestones
| Shipping on desktop | 114 |
| Shipping on Android | 114 |
| Shipping on WebView | 114 |
Anticipated spec changes
Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (e.g. links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (e.g., changing to naming or structure of the API in a non-backward-compatible way).
This change is not specced yet. If this succeed, we will try to get it specced.Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5231964663578624Links to previous Intent discussions
https://groups.google.com/a/chromium.org/g/blink-dev/c/Fku6784p0wI/m/3MyOMTk7BwAJ
Mike Taylor
On 4/27/23 5:28 PM, Di Zhang wrote:
Contact emails
hu...@chromium.org, xiaoc...@chromium.org, dizh...@chromium.org
Explainer
None
Specification
None
What's the reason for not having a spec? Is the idea that this is covered by this definition of a "focusable area": "the element is determined by the user agent to be focusable"
If we have multi-vendor alignment, maybe we can be more explicit
than that?
Design docs
None
Summary
Improves accessibility by making scroll containers focusable using sequential focus navigation. Today, the tab key doesn't focus scrollers unless tabIndex is explicitly set to 0 or more. By making scrollers focusable by default, users who can't (or don't want to) use a mouse will be able to focus clipped content using a keyboard's tab and arrow keys. This behavior is enabled only if the scroller does not contain any keyboard focusable children. This logic is necessary so we don't cause regressions for existing focusable elements that might exist within a scroller like a <textarea>.
Blink component
Blink>HTML>Focus
Search tags
tab key, keyboard focus, sequential navigation
TAG review
None
TAG review status
Not applicable
Risks
Interoperability and Compatibility
This is a change in behavior, but already matches what Firefox is doing (have scroller be focusable by default). Low compatibility risk since this default behavior is only enabled if the scroller doesn't have any focusable children.
Gecko: Shipped/Shipping Chrome behavior is slightly different since we are checking if any scroller child is focusable. This is to avoid regression on existing focus sequences.
WebKit: No signal (https://bugs.webkit.org/show_bug.cgi?id=190870)
Web developers: Positive (https://twitter.com/simevidas/status/1444033718742667270)
Other signals:
Ergonomics
There are no other platform APIs this feature will be used in tandem with. It will not be hard for Chrome to maintain good performance.
Activation
It will not be challenging for developers to take advantage of this feature immediately.
Security
There are no security risks, this is a change for keyboard focusing behavior.
WebView application risks
Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?
This is not high risk for WebView.
Debuggability
This is a change to focus navigation and DevTools does not offer debugging support for this behavior.
Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?
Yes
Is this feature fully tested by web-platform-tests?
Yes
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Di Zhang
Right - the spec leaves it up to the UA to determine what is a focusable area. All browsers treat this a bit differently, and have typically considered that behavior to be up to the browser. For example, Safari has a user setting that can change what types of elements become keyboard focusable. So I'm guessing there will be pushback to standardizing this behavior. However, this is also why we don't believe there's a need to change the spec for this I2S.
Similarly, the written tests for this feature's changes are passing for Chrome, but not the other UAs. I have removed that check from this feature status and will update WPT accordingly.
On 4/27/23 5:28 PM, Di Zhang wrote:
Contact emails
hu...@chromium.org, xiaochengh@chromium.org, dizhangg@chromium.org
Explainer
None
Specification
None
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Domenic Denicola
Right - the spec leaves it up to the UA to determine what is a focusable area. All browsers treat this a bit differently, and have typically considered that behavior to be up to the browser. For example, Safari has a user setting that can change what types of elements become keyboard focusable. So I'm guessing there will be pushback to standardizing this behavior. However, this is also why we don't believe there's a need to change the spec for this I2S.
Similarly, the written tests for this feature's changes are passing for Chrome, but not the other UAs. I have removed that check from this feature status and will update WPT accordingly.
On Friday, April 28, 2023 at 7:08:37 AM UTC-7 Mike Taylor wrote:
On 4/27/23 5:28 PM, Di Zhang wrote:
Contact emails
hu...@chromium.org, xiaoc...@chromium.org, dizh...@chromium.org
Explainer
None
Specification
None
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Rick Byers
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Di Zhang
Thanks Domenic, that's helpful and makes sense to me. It's perhaps whether this is a "web exposed" change or not.This sounds pretty safe to experiment with to me. Di please make sure behavior change is done behind a flag so we can 'kill switch' it if needed.Perhaps the biggest compatibility risk here is the impact on assistive technology use cases? That's not something I feel equipped to have any judgement around. Have you talked with anyone in the accessibility team about this? Do we have any data or anecdotes on sites setting tabindex:0 on scrollers? Perhaps if that's already somewhat common place then that could reduce any fear dramatically?I have a vague memory that "element is focusable" may be used in the tab highlighting algorithm. It may be worth a quick check to ensure that this doesn't cause highlights to show up when tapping on a scrollable region that has no other tap highlight candidates. I can help point you at the right code / people if desired.RickOn Mon, May 8, 2023 at 3:51 AM Domenic Denicola <dom...@chromium.org> wrote:
Speaking with my HTML Standard spec editor hat on, I think it's appropriate for Chromium to ship this without spec changes, as Di explains.Indeed, I'd be skeptical of changing the spec here. It might be worth opening an issue to discuss whether any changes are appropriate, but in general the spec is intentional about allowing each browser to make different choices on what it considers focusable, and in which ways things are focusable. So I'd anticipate no changes resulting from such an issue.
On Tue, May 2, 2023 at 4:50 AM Di Zhang <dizh...@chromium.org> wrote:
Right - the spec leaves it up to the UA to determine what is a focusable area. All browsers treat this a bit differently, and have typically considered that behavior to be up to the browser. For example, Safari has a user setting that can change what types of elements become keyboard focusable. So I'm guessing there will be pushback to standardizing this behavior. However, this is also why we don't believe there's a need to change the spec for this I2S.
Similarly, the written tests for this feature's changes are passing for Chrome, but not the other UAs. I have removed that check from this feature status and will update WPT accordingly.
On Friday, April 28, 2023 at 7:08:37 AM UTC-7 Mike Taylor wrote:
On 4/27/23 5:28 PM, Di Zhang wrote:
Contact emails
hu...@chromium.org, xiaochengh@chromium.org, dizhangg@chromium.org
Explainer
None
Specification
None
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Mike Taylor
LGTM1
Daniel Bratell
LGTM2
/Daniel
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Philip Jägenstedt
LGTM1
On 5/9/23 6:15 PM, Di Zhang wrote:
Yes, this change is flagged behind the feature KeyboardFocusableScrollers (disabled by passing `--disable-blink-features=KeyboardFocusableScrollers`).
We have looped in aleventhal@ for similar accessibility concern. Aaron is the one who implemented the Keyboard Focusable Scrollers feature on Gecko years ago.This feature (minus the "not contain any keyboard focusable children" rule) has existed in Firefox for +18 years now without any issue. Since assistive technology (for example screen readers) are using the same code for Firefox and Chrome, this should be low risk.
> I have a vague memory that "element is focusable" may be used in the tab highlighting algorithm. It may be worth a quick check to ensure that this doesn't cause highlights to show up when tapping on a scrollable region that has no other tap highlight candidates. I can help point you at the right code / people if desired.Just to clarify, when you mention "tab highlighting algorithm", do you mean showing the orange focus ring when on mobile devices? I just tried with the feature on and off. In both cases, tapping doesn't show focus (no focus ring). As for using tab navigation, I see the same behavior as on the web. If feature is on, then an orange focus ring will show on the scroller.If my understanding is wrong, please point me to the right code / people. Thank you
On Monday, May 8, 2023 at 4:00:23 AM UTC-7 Rick Byers wrote:
Thanks Domenic, that's helpful and makes sense to me. It's perhaps whether this is a "web exposed" change or not.
This sounds pretty safe to experiment with to me. Di please make sure behavior change is done behind a flag so we can 'kill switch' it if needed.
Perhaps the biggest compatibility risk here is the impact on assistive technology use cases? That's not something I feel equipped to have any judgement around. Have you talked with anyone in the accessibility team about this? Do we have any data or anecdotes on sites setting tabindex:0 on scrollers? Perhaps if that's already somewhat common place then that could reduce any fear dramatically?
I have a vague memory that "element is focusable" may be used in the tab highlighting algorithm. It may be worth a quick check to ensure that this doesn't cause highlights to show up when tapping on a scrollable region that has no other tap highlight candidates. I can help point you at the right code / people if desired.
Rick
On Mon, May 8, 2023 at 3:51 AM Domenic Denicola <dom...@chromium.org> wrote:
Speaking with my HTML Standard spec editor hat on, I think it's appropriate for Chromium to ship this without spec changes, as Di explains.
Indeed, I'd be skeptical of changing the spec here. It might be worth opening an issue to discuss whether any changes are appropriate, but in general the spec is intentional about allowing each browser to make different choices on what it considers focusable, and in which ways things are focusable. So I'd anticipate no changes resulting from such an issue.
On Tue, May 2, 2023 at 4:50 AM Di Zhang <dizh...@chromium.org> wrote:
Right - the spec leaves it up to the UA to determine what is a focusable area. All browsers treat this a bit differently, and have typically considered that behavior to be up to the browser. For example, Safari has a user setting that can change what types of elements become keyboard focusable. So I'm guessing there will be pushback to standardizing this behavior. However, this is also why we don't believe there's a need to change the spec for this I2S.
Similarly, the written tests for this feature's changes are passing for Chrome, but not the other UAs. I have removed that check from this feature status and will update WPT accordingly.
On Friday, April 28, 2023 at 7:08:37 AM UTC-7 Mike Taylor wrote:
On 4/27/23 5:28 PM, Di Zhang wrote:
Contact emails
hu...@chromium.org, xiaoc...@chromium.org, dizh...@chromium.org
Explainer
None
Specification
None
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Daniel Bratell
Make that LGTM3 from me. Good luck shipping!
/Daniel
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