1839401 - Issue with invalidation of scrollbar-gutter CSS property

Status: VERIFIED FIXED

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

Description

[Luke Warlow]

Steps to reproduce:

Load this WPT https://wpt.live/css/css-overflow/scrollbar-gutter-dynamic-002.html

Actual results:

Results can be seen here https://wpt.fyi/analyzer?screenshot=sha1%3Ae137eb47783ec0c399db652a8297add58f76b455&screenshot=sha1%3Ae2fe47a3a296fede5dacb9960b9e0e8008f56980

https://wpt.fyi/results/css/css-overflow/scrollbar-gutter-dynamic-002.html?label=experimental&label=master&aligned

Expected results:

This test should pass.

There seems to be an issue when an element has overflow hidden and goes from scrollbar-gutter auto to scrollbar-gutter stable both-edges (potentially other invalidations too this is just the one the test caught)

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)]

Looks like we misthink the overflow:hidden and no overflowed contents case doesn't need scrollbar-gutter: stable?

Comment 3

[Luke Warlow]

https://fiddle.jshell.net/fqkgp73u/9/show/?editor_console= - Based on this quick test script it seems when it's overflow hidden invalidating from auto to both stable OR stable both-edges is broken at least some times. (Weirdly editing through DevTools seems to work?)

Comment 4

[Ting-Yu Lin [:TYLin] (PDT, UTC-7)]

Attachment: Bug 1839401 - Get scrollbar-gutter size from theme instead of scrollbar frame.

We don't construct the vertical scrollbar frame if overflow-y is hidden in
nsHTMLScrollFrame::GetNeededAnonymousContent() [1]. However, we need it to
query the scrollbar-gutter size in ScrollReflowInput constructor [2].

[1] https://searchfox.org/mozilla-central/rev/e4afef5d3ff67781dc1377912344694f3cf3a226/layout/generic/nsGfxScrollFrame.cpp#5576-5578
[2] https://searchfox.org/mozilla-central/rev/e4afef5d3ff67781dc1377912344694f3cf3a226/layout/generic/nsGfxScrollFrame.cpp#544-546

Comment 5

[Ting-Yu Lin [:TYLin] (PDT, UTC-7)]

Attachment: Bug 1839401 - Add a helper to get non-overlay scrollbar size.

GetNondisappearingScrollbarWidth() is not used. Its last caller has been
removed in bug 1762873. So I transform it into a helper getting non-overlay
scrollbar width from theme.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5533a368b99c
Add a helper to get non-overlay scrollbar size. r=emilio
https://hg.mozilla.org/integration/autoland/rev/e8381cd51f42
Get scrollbar-gutter size from theme instead of scrollbar frame. r=emilio

Comment 7

[Noemi Erli[:noemi_erli]]

https://hg.mozilla.org/mozilla-central/rev/5533a368b99c
https://hg.mozilla.org/mozilla-central/rev/e8381cd51f42

Comment 8

[Anca Soncutean, Desktop QA]

Reproduced with Fx 116.0a1 (2023-06-20) on Windows 10.
Verified fixed with Fx 122.0a1 (2023-11-28) and Fx 121.0b4 on Windows 10.