1310792 - [css-grid] grid-item-content-baseline-* and grid-item-mixed-baseline-* are disabled (random) because they depend on font metrics

Status: RESOLVED FIXED

(Core :: Layout, enhancement, P5)

Description

[Daniel Holbert [:dholbert]]

Our grid baseline tests (from bug 1256429) are all marked "skip-if(!gtkWidget)" because they depend on exact font metrics, which happen to be Just Right on our linux test machines (but not on any other platforms).  This was the case when they landed, here:
https://hg.mozilla.org/mozilla-central/rev/2b4dfcc5160c9557397bcf7a366e94def8731999#l13.12

Unfortunately, the linux font metrics are no longer Just Right after we've upgraded those machines (per bug 1309086).  So in that bug, we're changing these tests from mostly-disabled to entirely-disabled.

So: we need to fix these tests to not depend so heavily on specific font metrics (or alternately, to use the Ahem font which has predictable behavior cross-platform).

Comment 1

[Daniel Holbert [:dholbert]]

(Oh, sorry -- looks like maybe they already use Ahem?  Hmm.)

Comment 2

[Mats Palmgren (inactive)]

These tests use the Ahem font, which I thought were enough to get predictable "px" offsets
to compare the baseline with across platforms, but apparently not.  I think we have
reasonable protection against regressions though as long as we run these tests on at least
one platform, because the implementation of grid baselines is all cross-platform code.
(This bug seems rather low priority for that reason.)

Comment 3

[Daniel Holbert [:dholbert]]

(In reply to Mats Palmgren (:mats) from comment #2)
> I think we have reasonable protection against regressions though as long as we run these
> tests on at least one platform,

...and as of bug 1309086, we will no longer be running them on any platforms. :-/  (because whatever made them Just Right on our linux treeherder boxes has changed in Ubuntu 16.04, apparently)

> (This bug seems rather low priority for that reason.)

...which means this is no longer low-priority (until we can get these tests passing on at least one platform again).

Comment 4

[Mats Palmgren (inactive)]

I object to that change if they still pass on Linux32.

Comment 5

[Karl Tomlinson (:karlt)]

grid-item-mixed-baseline-004.html is still passing on Ubuntu 16.04, so that is not affected by bug 1309086.  It is skip-if(!gtkWidget) due to this bug.

Comment 6

[Mats Palmgren (inactive)]

As dholbert notes in https://phabricator.services.mozilla.com/D61100:

https://web-platform-tests.org/writing-tests/ahem.html says to make sure that the font-size is a multiple of 5px.
(I think that ensures that the baseline position & other metrics (which are e.g. 20%/80% of the font-size) are exact pixel values.)

That might make these test pass.

Comment 7

[Mats Palmgren (inactive)]

Attachment: Bug 1310792 - Fix pixel rounding issues in Grid baseline reftests and convert them to WPTs. r=dholbert

Comment 8

[Mats Palmgren (inactive)]

Changing the font-sizes to use a multiple of 5px as you suggested fixed the tests btw.

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/48e885ffad1f
Fix pixel rounding issues in Grid baseline reftests and convert them to WPTs.  r=dholbert

Comment 10

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

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/21501 for changes under testing/web-platform/tests

Comment 11

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

Upstream web-platform-tests status checks passed, PR will merge once commit reaches central.

Comment 12

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/48e885ffad1f

Comment 13

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

Upstream PR merged by moz-wptsync-bot