1854737 - Firefox fails WPT css/css-backgrounds/border-image-slice-fill-003.html (and render variants of that test quite differently from other browsers)

Status: NEW

(Core :: Graphics: WebRender, defect)

Description

[Daniel Holbert [:dholbert]]

We fail this WPT in the interop-2023-cssborderimage test set:
https://wpt.fyi/results/css/css-backgrounds/border-image-slice-fill-003.html
http://wpt.live/css/css-backgrounds/border-image-slice-fill-003.html

This was originally tracked on bug 1819485 along with the -001 and -002 tests, but I'm filing a dedicated bug since it seems like there may be distinct root causes.

I've got a broader testcase based on border-image-slice-fill-003.html here:
https://bugzilla.mozilla.org/attachment.cgi?id=9354688

See bug 1819485 comment 18 and 19 for notes there. We used to render most of the testcase the same as other browsers, but we changed in bug 1606771 to render all of the squares the same. (The part that matters for the WPT test is in the section where we always differed from other browsers, FWIW.)

Nical: as with bug 1854733, I wonder if you could take a look here?

Comment 1

[jsnkuhn]

Attempting to use border-image to slice out a portion of a sprite image to use as a repeating background since no browsers supports image(). Unfortunately this is one of the few remaining border-image bugs left from Interop 2023.

In the linked pen the last div should have the image from the top left of the sprite image as a repeated background. This works reasonably well in Safari and Chrome just not Firefox yet:
https://codepen.io/jsnkuhn/pen/vYoYBEJ?editors=1100