2036966 - [css-overscroll-1] Add an overscroll-behavior value which disables local boundary default actions

Status: RESOLVED FIXED

(Core :: Layout: Scrolling and Overflow, enhancement, P3)

Description

[Mozilla Apprentice]

Resolutions were made for csswg-drafts/#13370.

[css-overscroll-1] Add an overscroll-behavior value which disables local boundary default actions

• RESOLVED: add a chain value to the overscroll-behavior property
• RESOLVED: flackr is an editor for overscroll 1

Discussion.

Comment 1

[Botond Ballo [:botond]]

Tracking in https://mozilla-hub.atlassian.net/browse/FFXP-3766 (2026 H2 APZ WebCompat Work).

Comment 2

[Kanaru Sato [:canalun]]

Attachment: Bug 2036966 - Support an overscroll-behavior value, "chain". r?hiro

chain is defined in
https://drafts.csswg.org/css-overscroll-behavior/#propdef-overscroll-behavior .

This patch has three parts.

1. Parsing and plumbing. chain is added to the specified value in
   enum in servo and APZ, so that it is preserved through the scroll
   metadata.

2. APZ behavior. The places that consult overscroll-behavior while scrolling,
   such as AsyncPanZoomController::CallDispatchScroll() and
   OverscrollHandoffChain::FindFirstScrollable(), all reach it through
   Axis::OverscrollBehaviorAllowsHandoff() and
   Axis::OverscrollBehaviorAllowsOverscrollEffect(). The behavior change is
   therefore contained in those two methods.

3. Tests. The existing WPTs covering the handoff feature are enabled.
   Regarding overscroll-effect and swipe-to-nav, they are covered by
   new APZ mochitests.

The WPT still fails on Android. But manual testing on a device showed that handoff
and downward swipe (page refresh) behave as specified there and this looks like a
test issue. So that is left as a follow-up. Note that overscroll effect couldn't be
checked on Android due to Bug 1809969.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/afcdb0d90fc1
https://hg.mozilla.org/integration/autoland/rev/02b53e1822da
Support an overscroll-behavior value, "chain". r=hiro

Comment 4

[Silaghi Andreea]

https://hg.mozilla.org/mozilla-central/rev/02b53e1822da

Comment 5

[Sebastian Zartner [:sebo]]

Kanaru, this is probably something that should be mentioned in the release notes. So you may want to nominate it for adding.
https://wiki.mozilla.org/Release_Management/Release_Notes_Nomination

Sebastian

Comment 6

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/62445 for changes under testing/web-platform/tests

Comment 7

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot