[Webkit-unassigned] [Bug 235400] New: Implement at-rule function for use with @supports
bugzilla-daemon at webkit.org
bugzilla-daemon at webkit.org
Thu Jan 20 05:31:03 PST 2022
https://bugs.webkit.org/show_bug.cgi?id=235400
Bug ID: 235400
Summary: Implement at-rule function for use with @supports
Product: WebKit
Version: WebKit Nightly Build
Hardware: Unspecified
OS: Unspecified
Status: NEW
Severity: Normal
Priority: P2
Component: CSS
Assignee: webkit-unassigned at lists.webkit.org
Reporter: bramus at bram.us
As per CSS WG Decision [1]: Implement at-rule function for use with @supports
Syntax:
```css
/* Just the at-rule name, which returns whether this is a recognized at-rule name at all. */
@supports(at-rule(@foo)) {
/* @foo is supported */
}
```
```css
/* An at-rule name accompanied by a descriptor declaration, which returns whether the at-rule is recognized, and the given descriptor successfully parses as part of that at-rule.*/
@supports(at-rule(@foo; desc: val)) {
/* @foo with the descriptor `desc` and value `val` is supported */
}
```
Note that there's a follow-up issue [2] to extend at-rule() with a third syntax which allows passing in an entire at-rule into at-rule().
```css
/* An entire at-rule, which returns whether or not the at-rule as a whole, when parsed as the first and only content in a fresh stylesheet, is valid or dropped. If the at-rule is valid but drops some of its contents as invalid, such as an unknown descriptor, this will still return true. */
@supports(at-rule(@foo bar {baz: qux})) {
/* The entire at-rule is supported */
}
```
It also supports
At the moment, this third syntax is still a WIP.
^[1] https://github.com/w3c/csswg-drafts/issues/2463#issuecomment-1016720310
^[2] https://github.com/w3c/csswg-drafts/issues/6966
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