[webkit-changes] [WebKit/WebKit] 1c37e9: [css-conditional] Support CSSConditionRule.supports

[Kiet Ho]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 1c37e97a7554ca065853b97e368e0360de153650
      
https://github.com/WebKit/WebKit/commit/1c37e97a7554ca065853b97e368e0360de153650
  Author: Kiet Ho <kiet...@apple.com>
  Date:   2026-08-17 (Mon, 17 Aug 2026)

  Changed paths:
    M 
LayoutTests/imported/w3c/web-platform-tests/css/css-conditional/at-supports-matches-expected.txt
    M 
LayoutTests/imported/w3c/web-platform-tests/css/css-conditional/idlharness-expected.txt
    M Source/WebCore/css/CSSSupportsRule.cpp
    M Source/WebCore/css/CSSSupportsRule.h
    M Source/WebCore/css/CSSSupportsRule.idl

  Log Message:
  -----------
  [css-conditional] Support CSSConditionRule.supports
rdar://184943650
https://bugs.webkit.org/show_bug.cgi?id=321808

Reviewed by Tim Nguyen.

CSSWG resolves in 2022 [1] to add CSSConditionRule.supports, which returns
whether the supports query in @supports is supported or not. In WebKit,
CSSConditionRule wraps StyleRuleSupports, and it exposes the supported status
via conditionIsSupported(), so it's straightforward to expose it to CSSOM.

[1]: https://github.com/w3c/csswg-drafts/issues/4240#issuecomment-1196983719

Tests: 
imported/w3c/web-platform-tests/css/css-conditional/at-supports-matches.html
       imported/w3c/web-platform-tests/css/css-conditional/idlharness.html

* 
LayoutTests/imported/w3c/web-platform-tests/css/css-conditional/at-supports-matches-expected.txt:
* 
LayoutTests/imported/w3c/web-platform-tests/css/css-conditional/idlharness-expected.txt:
* Source/WebCore/css/CSSSupportsRule.cpp:
(WebCore::CSSSupportsRule::matches const):
* Source/WebCore/css/CSSSupportsRule.h:
* Source/WebCore/css/CSSSupportsRule.idl:

Canonical link: https://commits.webkit.org/319302@main



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