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

So I think some of the concerns @mirisuzanne mentioned (of needing to support this condition way before `@container` works) are really an issue, but only because browsers disagree on this case:

```js
CSS.supports("not foo()")
```

That returns `true` in Firefox (as I'd expect, fwiw), but `false` in Chrome and Safari. So you can't use `@supports not container(..)` unless they implement the new thing. We should probably get interop on that. My understanding given the supports syntax in https://drafts.csswg.org/css-conditional/#typedef-supports-condition is that this is a Chromium / WebKit bug. Does it match yours @lilles?

Now with that said, in terms of fixing this, yeah, the proposal was on the lines of:

```css
@supports at-rule(<ident>)
```

To test support for an specific at-rule. @frivoal raised the concern of it being a bit footgunny in cases we extend the syntax of the at rules, so I think this was the most controversial. Then there was:

```css
@supports container(<container-expression>)
```

And:

```css
@supports media(<media-query>)
```

And these need specific definitions because `<media-query>` has a `<general-enclosed>` clause that would parse all media queries successfully (I think this is a mediaqueries-4 feature which we weren't implementing).

-- 
GitHub Notification of comment by emilio
Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/6175#issuecomment-824237638 using your GitHub account


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

Received on Wednesday, 21 April 2021 17:37:14 UTC