Web-Facing Change PSA: Propagate Viewport overscroll-behavior from Root

[Chromestatus]

Contact emails

awogb...@google.com

Specification

https://drafts.csswg.org/css-overscroll-behavior-1

Summary

Propagate overscroll-behavior from the root instead of the body. The CSS working group resolved[0] on not propagating properties from the body to the viewport. Rather, properties of the viewport are to be propagated from the root element e.g. scroll-behavior[1], scroll-snap-type[2], scroll-padding[3]. As such, overscroll-behavior should be propagated from the root element. However, Chrome has had a longstanding issue of propagating overscroll-behavior from the body rather than the root, which deviates from the behavior of Safari(WebKit) and Firefox(Gecko). This feature intends to fix this by propagating overscroll-behavior from the root rather than the body. [0] https://github.com/w3c/csswg-drafts/issues/6079#issuecomment-816307011 [1] https://drafts.csswg.org/css-overflow/#:~:text=not%20propagated%20to%20the%20viewport [2] https://drafts.csswg.org/css-scroll-snap/#:~:text=not%20propagated%20from%20HTML%20body [3] https://drafts.csswg.org/css-scroll-snap/#:~:text=padding%20values%20are%20not%20propagated%20from%20HTML%20body

Blink component

Blink>Scroll

TAG review

None

TAG review status

Not applicable

Risks

Interoperability and Compatibility

This fixes an interop issue in which Chrome behaves differently from WebKit(Safari) and Gecko(Firefox).

Gecko: Shipped/Shipping

WebKit: Shipped/Shipping

Web developers: No signals

Other signals:

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?

None

Debuggability

None

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

Yes

Is this feature fully tested by web-platform-tests?

Yes

https://wpt.fyi/results/css/css-overscroll-behavior/overscroll-behavior-root.html?label=experimental&label=master&aligned

Flag name on about://flags

None

Finch feature name

PropagateOverscrollBehaviorFromRoot

Rollout plan

Will ship enabled for all users

Requires code in //chrome?

False

Tracking bug

https://crbug.com/41453796

Estimated milestones

Shipping on desktop	139
Shipping on Android	139
Shipping on WebView	139

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).

None

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/6210047134400512?gate=5668569165332480

This intent message was generated by Chrome Platform Status.

[David Awogbemila]

Estimated milestones

Shipping on desktop	139
Shipping on Android	139
Shipping on WebView	139

Correction: Estimated shipping milestone is 140 on all platforms.