Re: [csswg-drafts] [css-values-4] Allow an inline way to do "first value that's supported" (#5055)

> What happens if it's mixed with other things?

Parse failure.

(In your example, it's fine in the custom property, because the custom property doesn't see a `first-supported()` function, it sees a sequence of tokens. Once substituted and given meaning, it's now not the sole value in a property, and thus is a parse failure (thus IACVT).

> When does it resolve?

Parse time. This is a pure functionality substitution for just writing the property twice and using the last one that parses.

(As stated above, it's not resolved in a custom property, as only var() functions are. But once substituted, the late parse-time validation that can trigger IACVT takes over.)

> What if all values are invalid?

Parse failure.

> If it's resolved at parse time in standard properties, and all specified values are invalid, is the declaration dropped

Yes, since it's a parse failure. ^_^

> What if some value contains var()?

Then it successfully parses (so long as the `var()` itself is valid), and is used. Again, pure substitution for "write it twice".

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Received on Saturday, 16 October 2021 17:20:08 UTC