From 92276e8336eadafdb9aa7cabd2fa6e7da74dcfc6 Mon Sep 17 00:00:00 2001 From: Kevin Babbitt Date: Wed, 8 Oct 2025 17:12:57 -0700 Subject: [PATCH 1/3] [css-conditional-5] Spec at-rule() per CSSWG resolutions. #2463, #6966, #11116, #11117 --- css-conditional-5/Overview.bs | 51 +++++++++++++++++++++++++++++------ 1 file changed, 43 insertions(+), 8 deletions(-) diff --git a/css-conditional-5/Overview.bs b/css-conditional-5/Overview.bs index 8c983c16cb8..6d872efe6ad 100644 --- a/css-conditional-5/Overview.bs +++ b/css-conditional-5/Overview.bs @@ -114,18 +114,15 @@ Extensions to the ''@supports'' rule This level of the specification extends the <> syntax as follows: 
-		<supports-feature> = <> | <>
-							| <> | <>
+		<supports-feature> = <>
+							| <> | <>
+							| <>
+							| <>
 		<supports-font-tech-fn> = font-tech( <> )
 		<supports-font-format-fn> = font-format( <> )
+		<supports-at-rule-fn> = at-rule( <> )
- - at-supports-font-format-001.html - at-supports-font-tech-001.html - js/CSS-supports-L5.html - - : <> :: The result is true if the UA @@ -138,9 +135,24 @@ Extensions to the ''@supports'' rule supports the font format provided as an argument to the function. + : <> + :: + The result is true if the UA + supports the at-rule + provided as an argument to the function. +

Extensions to the definition of support

+

+Font techs and formats

+ + + at-supports-font-format-001.html + at-supports-font-tech-001.html + js/CSS-supports-L5.html + + A CSS processor is considered to support a font tech when it is capable of utilizing the specified [[css-fonts-4#font-tech-definitions]] @@ -152,6 +164,21 @@ Extensions to the definition of support in layout and rendering, and this format is not specified as a <>. +

+At-rules

+ + + js/supports-at-rule.html + + + A CSS processor is considered to + support an at-rule + if it would accept an [=at-rule=] beginning with the specified at-keyword + within any context. + + Note: Because ''@charset'' is not a valid [=at-rule=], + it is not considered to be supported under this definition. +

Generalized Conditional Rules: the ''@when'' rule

@@ -1812,6 +1839,14 @@ Changes since the #10544) +
  • + Extended [=supports queries=] to express [=at-rule=] capabilities + via ''at-rule()''. + (#2463, + #6966, + #11116, + #11117) +

    • From b3cff4b5752d5f667887aa00e87da6701c59729a Mon Sep 17 00:00:00 2001 From: "Tab Atkins Jr." Date: Tue, 14 Oct 2025 09:26:52 -0700 Subject: [PATCH 2/3] Update css-conditional-5/Overview.bs --- css-conditional-5/Overview.bs | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/css-conditional-5/Overview.bs b/css-conditional-5/Overview.bs index 6d872efe6ad..16a0bdfd13a 100644 --- a/css-conditional-5/Overview.bs +++ b/css-conditional-5/Overview.bs @@ -115,9 +115,9 @@ Extensions to the ''@supports'' rule

     		<supports-feature> = <>
-							| <> | <>
-							| <>
-							| <>
+		                   | <> | <>
+		                   | <>
+		                   | <>
 		<supports-font-tech-fn> = font-tech( <> )
 		<supports-font-format-fn> = font-format( <> )
 		<supports-at-rule-fn> = at-rule( <> )

From 1e7b914adfb3fcab294a65f2570d8dbbbf841833 Mon Sep 17 00:00:00 2001
From: Kevin Babbitt 
Date: Tue, 14 Oct 2025 12:28:32 -0700
Subject: [PATCH 3/3] Add to "Additions since Level 4"

---
 css-conditional-5/Overview.bs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/css-conditional-5/Overview.bs b/css-conditional-5/Overview.bs
index 16a0bdfd13a..c67440953cf 100644
--- a/css-conditional-5/Overview.bs
+++ b/css-conditional-5/Overview.bs
@@ -1884,6 +1884,8 @@ Additions since Level 4
 		
  • Added ''@when'' and ''@else''.
 		
  • Extended [=supports queries=] to express font capabilities
 			via ''font-tech()'' and ''font-format()''.
+		
  • Extended [=supports queries=] to express at-rule capabilities
+			via ''at-rule()''.
 		
  • Moved Container Queries from [[CSS-CONTAIN-3]] to this specification.
 			(See also the [[CSS-CONTAIN-3#changes]] for more information
 			on the evolution of this feature.)