Open Bug 1625761 Opened 6 months ago Updated 5 months ago

New wpt failures from PR 22476: /css/css-flexbox/cross-axis-scrollbar.html


(Core :: Layout: Flexbox, defect, P3)





(Reporter:, Unassigned)



(Whiteboard: [wpt])

The following tests have untriaged failures in the CI runs for wpt PR 22476:

Firefox-only failures

/css/css-flexbox/cross-axis-scrollbar.html: FAIL [Gecko-linux1804-64-asan-opt, Gecko-linux1804-64-debug, Gecko-linux1804-64-opt, Gecko-linux1804-64-qr-debug, Gecko-linux1804-64-qr-opt, Gecko-windows10-64-debug, Gecko-windows10-64-opt, Gecko-windows10-64-qr-debug, Gecko-windows10-64-qr-opt, Gecko-windows7-32-debug, Gecko-windows7-32-opt, GitHub], PASS [Gecko-android-em-7.0-x86_64-debug-geckoview, Gecko-android-em-7.0-x86_64-opt-geckoview]

These updates will be on mozilla-central once bug 1625239 lands.

Note: this bug is for tracking fixing the issues and is not
owned by the wpt sync bot.

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Live version of the test on

There are two things going wrong in this test:
(1) A bug in the test -- the test is mistakenly assuming that scrollbars are opaque (the same problem as bug 1613103). The testcase has scrollbars superimposed over a red background, whereas the reference case has scrollbars superimposed over a green background. If the scrollbar "track" is transparent, then this obviously creates a rendering difference (and violates

(2) the third and fourth chunks in the first row have some slight sizing/positioning differences. These ones both have writing-mode:vertical-rl, and it's possible their differences are real Firefox bugs. At least in the third chunk, it looks like we're over-estimating the intrinsic height of the flex container (and we're sliding flex items up/down according to their "align-self" preference as a result). This seems to be due to us including the height of a horizontal scroll track, even though no such track is present (the element has overflow-x:hidden).

Priority: -- → P3

We can address issue #1 using the same solution that we used in bug 1613103 -- using a neutral background color (e.g. tan) on the scrollable element, in both the testcase and the reference case -- and adjusting the descriptive prose accordingly.

Issue #2 probably requires some debugging to sort out what's going on. (It's a somewhat subtle difference, and I'd be surprised if it affected much real-world content, so I wouldn't suggest dropping everything to look into it right now.)

See Also: → 1613103
Summary: New wpt failures from PR 22476 → New wpt failures from PR 22476: /css/css-flexbox/cross-axis-scrollbar.html:
Summary: New wpt failures from PR 22476: /css/css-flexbox/cross-axis-scrollbar.html: → New wpt failures from PR 22476: /css/css-flexbox/cross-axis-scrollbar.html
Duplicate of this bug: 1625305
Duplicate of this bug: 1625738
Duplicate of this bug: 1625656
Duplicate of this bug: 1626214

Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is P3 (Backlog,) indicating it has been triaged, the bug's Severity is being updated to S3 (normal.)

Severity: normal → S3
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