Re: [csswg-drafts] [css-contain] What is the migration path for Container Queries? (#6175)

@tabatkins I think it's essential that `@supports` behave different from `@media` in this case, because evaluating if new syntax is "known" or "unknown" is _the entire purpose of the at-rule_ – and in many cases "negation" is the most useful test. That is especially true with new at-rules, since they provide their own positive test, and will always require new functional syntax in `@supports`.

When we do add new functions to `@supports` itself (and I forsee several more functions on the way), we get one of two results:
1. If unknowns can't be negated (`not foo() == false`), the new syntax gives a false negative in old browsers -- there is no way to write a useful fallback
2. If unknowns _can_ be negated (`not foo() == true`), the new function works as expected everywhere, backwards-compatible in any browser that understands the basics of `@supports` -- fallbacks "just work"

I don't see how option 1 provides any useful benefit?

-- 
GitHub Notification of comment by mirisuzanne
Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/6175#issuecomment-828635999 using your GitHub account


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

Received on Wednesday, 28 April 2021 17:23:06 UTC