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[css-sizing-4] How to handle 0 in aspect-ratio #5557
Description
https://drafts.csswg.org/css-sizing-4/#aspect-ratio
I just noticed that the spec was changed to allow a lot more values. In particular, 0 is now valid for aspect-ratio, but the spec doesn't say how to handle that. I assume it behaves as "auto" but still gets computed as specified?
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cbiesinger commentedon Sep 29, 2020
Why did you not make it compute to auto? (Also, I don't recall this entire change being discussed in the WG?)
cbiesinger commentedon Sep 29, 2020
@BorisChiou @bfgeek @tabatkins @fantasai
BorisChiou commentedon Sep 29, 2020
There is a comment about n/0 and 0/n for aspect-ratio in media query: #3757. And yes, it'd be great to address more about how to handle 0/n and n/0 in the spec.
tabatkins commentedon Sep 29, 2020
It doesn't say how to handle it because there's nothing special to do with it - it acts exactly like you'd expect, similar to values close to it. That is,
0/xacts similar to0.000000001/x, and same forx/0. Nothing wrong with zeros or infinities here; they're the same as very-small nonzero values or very-large finite values.They don't compute to auto because it would violate our 'no open ranges' restriction (giving a substantially different behavior between
0and.000000000001, potentially exposing UA-specific rounding). Also, there's no reason to, since the behavior at 0 has a simple, clean definition as the limit behavior of it approaching zero.It's just a side-effect of us changing ratios from
<integer>to<number>, which we did discuss. I'd have to dig up the issue, but it was definitely discussed in a f2f as well. When it was<integer>we could disallow zero, but as soon as you allow numbers, you have to allow zero because of no-open-ranges.tabatkins commentedon Sep 29, 2020
(See #4954 for some other discussion on this, including in particular why we defined
0/0the way we did.)[AspectRatio] Update the parsing of aspect-ratio
fantasai commentedon Oct 9, 2020
Reopened #4954 since as @cbiesinger points out, this wasn't resolved by the WG and the resolution isn't obvious.
fantasai commentedon Nov 3, 2020
RESOLVED: Treat aspect ratio of 0 or infinity as auto on Thursday 22 October 2020
fantasai commentedon Nov 5, 2020
Minutes: https://lists.w3.org/Archives/Public/www-style/2020Nov/0003.html
fantasai commentedon Nov 5, 2020
wpt: css/css-sizing/aspect-ratio/zero-or-infinity-*
tabatkins commentedon Nov 9, 2020
Fixed in 84a573d