Closed Bug 1520946 Opened 4 years ago Closed 4 years ago

Investigate why the WPT copy of flexbox-justify-content-horiz-001b.xhtml is failing on most platforms


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




Tracking Status
firefox66 --- fixed


(Reporter: dholbert, Assigned: dholbert)


(Blocks 1 open bug)



(1 file)

For some reason, the WPT copy of flexbox-justify-content-horiz-001b.xhtml is annotated as failing:

However, the version in our layout/reftests directory passes just fine (no fails annotations):

And interestingly, the "failing" WPT copy just started passing on "Android 7.0 x86", as of this push:

My current theory is that the "failure" is due to scrollbars (since I do see a barely-necessary scrollbar when I run the WPT version of the test locally), and I suspect it started passing on android due to one of the changes on bug 1504659 (which impacted when scrollbars appear on Android).

If my theory's correct, we could perhaps make the test pass everywhere by shrinking its contents' height slightly so that no scrollbar is ever needed. I don't immediately know how to see screenshots of the failure (./mach test [path-to-test] doesn't give me any, unfortunately), so that's why my diagnosis is just a theory at this point.

See Also: → 1520708

Ah, I think I know what's wrong here -- it looks like flexbox-justify-content-horiz-001b.xhtml and its friends all have "margin-bottom: 2px;" on their flex containers, but in -001b, the margin-bottom at the very end isn't creating scrollable overflow (perhaps because the flex container is floated?)

So there's a very slightly different page-height between the test & reference, & a different size scrollbar as a result.

All of these tests have an .ini file indicating a failure for at least one of
them right now, in the copy that lives in the WPT harness, because

  • they trigger a scrollbar in the WPT harness
  • the scrollbar is a slightly different size in the reference case vs.
    in one of the testcases, e.g. due to a tiny margin being honored (or not)
    on the final piece of content.

This patch shrinks the content a bit in these test files so that they all fit
in a 400x400 viewport and won't trigger a scrollbar. I expect this should make
them pass in the WPT harness when they make the roundtrip through our
synchronization process.

Assignee: nobody → dholbert
Pushed by
Shrink some content in various w3c-submitted flexbox tests so that they won't trigger scrollbars in WPT harness. r=TYLin
Closed: 4 years ago
Resolution: --- → FIXED
Target Milestone: --- → mozilla66
Blocks: 1521989
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