1625655 - New wpt failures from PR 22437: /css/css-flexbox/floated-flexitem.html

Status: NEW

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

Description

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

The following tests have untriaged failures in the CI runs for wpt PR 22437:

New Tests That Don't Pass

/css/css-flexbox/floated-flexitem.html: FAIL [Gecko-android-em-7.0-x86_64-debug-geckoview, Gecko-android-em-7.0-x86_64-opt-geckoview], PASS [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] (Chrome: PASS, Safari: PASS)

These updates will be on mozilla-central once bug 1624832 lands.

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

This bug is linked to the relevant tests by an annotation in
https://github.com/web-platform-tests/wpt-metadata. These annotations
can be edited using the wpt interop dashboard
https://jgraham.github.io/wptdash/

If this bug is split into multiple bugs, please also update the
annotations, otherwise we are unable to track which wpt issues are
already triaged. Resolving as duplicate or closing this issue should
be cause the bot to automatically update or remove the annotation.

Comment 5

[Daniel Holbert [:dholbert]]

Attachment: reftest log showing the failure on Android

This just fails on Android.

Here's a reftest log snippet for the failure, with the data URIs included etc. (suitable for reftest-analyzer)

The issue is that the green right-border of "Item 4" is 1px to the right in the reference case, as compared to the testcase.

Comment 6

[Daniel Holbert [:dholbert]]

This is probably a subtle subpixel-positioning/alignment issue, where the border barely falls on the left vs. right side of a pixel boundary and gets snapped one way or the other.

Probably a real consistency bug in Firefox/Gecko, but not worth worrying too much about right now. Seems fine to annotate it as failing on android and move on, for the time being.

Comment 7

[Daniel Holbert [:dholbert]]

BTW, I was able to reproduce this failure in a local build, in the Android emulator. I tried pruning down the test in a few ways, as a diagnostic exercise to find out where the problematic bit was, but unfortunately all of my attempts produced a test that passed. :)

I tried:

• Removing everything besides "item 4". This makes the test pass.
• Removing everything but "item 4" and one other flex item (I tried this for each other flex item). This makes the test pass.

So this likely isn't as simple as "this particular flex item is the wrong size". To hit the failure, it seems like you need to have all 4 flex items (or at least: 2 of them isn't sufficient). I'd bet this is due to some subpixel-sized characters in the text, plus some snapping/rounding that we're doing in one case but not the other, which ends up landing this final right-border just on the exact spot to trigger the inconsistency.

Comment 8

[Firefox Bug Husbandry Bot]

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.)