2040247 - (un-)applying "overflow: clip" on the root element doesn't toggle scrollbar visibility

Status: RESOLVED FIXED

(Core :: Layout: Scrolling and Overflow, defect)

Description

[oss]

Attachment: gemini-code-1779053378603.html

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/147.0.0.0 Safari/537.36

Steps to reproduce:

1. Visit the attached reproduction
2. press the button
3. Observe scrollbar staying visible

This issue is specific to Gecko - both WebKit and Blink repaint correctly.

Actual results:

Scrollbar visibility remains unchanged.

Expected results:

Scroll container state should be removed, thereby scrollbar visibility should change.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Layout: Scrolling and Overflow' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Hiroyuki Ikezoe (:hiro)]

Attachment: Bug 2040247 - Emit nsChangeHint_ScrollbarChange when the root element's overflow toggles between 'visible' and 'clip'. r?#layout-reviewers

Per the css-overflow propagation rule [1], 'visible' on the viewport is
interpreted as 'auto' and 'clip' is interpreted as 'hidden'. So dynamically
toggling the root element's overflow between 'visible' and 'clip' changes
the viewport's propagated scrollbar styles between 'auto' and 'hidden'.

[1] https://drafts.csswg.org/css-overflow/#overflow-propagation

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/9bb989d13277
https://hg.mozilla.org/integration/autoland/rev/2ff5bb79c565
Emit nsChangeHint_ScrollbarChange when the root element's overflow toggles between 'visible' and 'clip'. r=layout-reviewers,firefox-style-system-reviewers,emilio

Comment 4

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

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/59974 for changes under testing/web-platform/tests

Comment 5

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/2ff5bb79c565

Comment 6

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

Upstream PR merged by moz-wptsync-bot