Re: [csswg-drafts] [css-backgrounds] Always serialize 'background-size' and `mask-size` as two values (#7802)

> In my opinion, `background-size` and `mask-size` should serialize with two values when they are identical, except if they are `auto`, while `webkit-background-size` should serialize with two values when the second is `auto` (edit) except if the first is also `auto`.

Note that we can't serialize `-webkit-background-size` and `background-size` as they're aliased.

> Seems like the assertions about what webkit does are different from the WPTs, when the mask-size or background-size is auto.
https://github.com/web-platform-tests/wpt/blob/master/css/css-masking/parsing/mask-size-valid.html#L19 asserts that auto auto serializes to auto rather than to auto auto.

Ah, there's no ambiguity in this case I think (though I could be wrong), so hence the single value. I haven't looked at this in a while tbh

-- 
GitHub Notification of comment by nt1m
Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/7802#issuecomment-3805627767 using your GitHub account


-- 
Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config

Received on Tuesday, 27 January 2026 14:44:34 UTC