1902793 - Firefox fails WPT css/css-grid/alignment/self-baseline/grid-self-baseline-vertical-rl-007.html

Status: NEW

(Core :: Layout: Grid, defect)

Description

[Daniel Holbert [:dholbert]]

Firefox fails this WPT test:
wpt.fyi: https://wpt.fyi/results/css/css-grid/alignment/self-baseline/grid-self-baseline-vertical-rl-007.html

wpt.live:
http://wpt.live/css/css-grid/alignment/self-baseline/grid-self-baseline-vertical-rl-007.html
http://wpt.live/css/css-grid/alignment/self-baseline/grid-self-baseline-vertical-rl-007-ref.html

However, the failure is just an off-by-1px alignment issue in the bottom-right section of the testcase, so I suspect this isn't a real Firefox bug and the testcase probably needs fixing.

Some additional notes:

• For some reason, at a 110% zoom level (Ctrl +), we're off by substantially more than a pixel (comparing the testcase & reference case).
• Chrome is also off by varying amounts at different zoom levels; and their rendering at 200% zoom level is off in roughly the same way as our rendering is at 100% zoom.
• WebKit fails the test in a more catastrophic way, so I'm not looking at their rendering particularly much.
• The reference case seems to be doing its layout using hard-coded margin values to achieve the precise expected placement, so it's potentially a bit over-calibrated in terms of the expected layout...

Comment 1

[Daniel Holbert [:dholbert]]

One note from poking at the test: the way the test is set up, it sort-of looks like all four boxes in each gray section are being aligned collectively in some way.

But really, the top two boxes are baseline-aligned with each other, and the bottom two boxes are baseline-aligned with each other. (You can see this in both Chrome and Firefox by setting a large width on one of the items to see what happens; it only impacts the positioning of one other box.) So it's just coincidence that the aligned positions are near to the same x-coordinate.