Bug 258730 – Prevent counter values from over/underflowing

• Status: RESOLVED
• Resolution: FIXED
• Component: CSS

[Ahmad Saleem]

Hi Team,

While going through Blink's commits, I came across where we fail over/underflowing Layout Test on WebKit ToT:

Blink Commit: https://chromium.googlesource.com/chromium/src.git/+/e18ac62b00618f26ef125554dd8241b2aed711e9

WebKit ToT Result:

FAIL large reset does not overflow assert_array_equals: expected property 4 to be 2000000000 but got -1794967296 (expected array [500000000, 1000000000, 1500000000, 2000000000, 2000000000] got [500000000, 1000000000, 1500000000, 2000000000, -1794967296])
FAIL small reset does not underflow assert_array_equals: expected property 4 to be -2000000000 but got 1794967296 (expected array [-500000000, -1000000000, -1500000000, -2000000000, -2000000000] got [-500000000, -1000000000, -1500000000, -2000000000, 1794967296])

Just wanted to raise this bug so we can fix it.

Since Vitor and Tim were doing counter-* related fix, so tagging them.

Thanks!

[Radar WebKit Bug Importer]

<rdar://problem/111743827>

[Vitor Roriz]

I'll have a look. Thanks for reporting it.

[Vitor Roriz]

We need to clarify if it should be clamped to the max/min value of the range or if increment should be ignored in this cases. FF and Chrome do the latter, but the spec seems to suggest the former.

[Vitor Roriz]

https://github.com/w3c/csswg-drafts/issues/9029

[Vitor Roriz]

As Elika suggested, I think we can aim for compatibility here. I.E: making WebKit also ignore the counter-increment if it would overflow, but making counter-reset clamp to the valid range if it would overflow.

[Vitor Roriz]

Pull request: https://github.com/WebKit/WebKit/pull/15549

[EWS]

Committed 266817@main (a3717f099f77): <https://commits.webkit.org/266817@main>

Reviewed commits have been landed. Closing PR #15549 and removing active labels.