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[css-conditional-5] Spec at-rule() per CSSWG resolutions. #2463, #6966, #11116, #11117 #12945

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Oct 15, 2025
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[css-conditional-5] Spec at-rule() per CSSWG resolutions. #2463, #6966, #11116, #11117 #12945

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[css-conditional-5] Spec at-rule() per CSSWG resolutions. #2463, #696…
kbabbitt Oct 9, 2025
b3cff4b
Update css-conditional-5/Overview.bs
tabatkins Oct 14, 2025
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Add to "Additions since Level 4"
kbabbitt Oct 14, 2025
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51 changes: 43 additions & 8 deletions css-conditional-5/Overview.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -114,18 +114,15 @@ Extensions to the ''@supports'' rule</h2>
This level of the specification extends the <<supports-feature>> syntax as follows:

<pre class="prod def" nohighlight>
<dfn>&lt;supports-feature></dfn> = <<supports-selector-fn>> | <<supports-font-tech-fn>>
| <<supports-font-format-fn>> | <<supports-decl>>
<dfn>&lt;supports-feature></dfn> = <<supports-selector-fn>>
| <<supports-font-tech-fn>> | <<supports-font-format-fn>>
| <<supports-at-rule-fn>>
| <<supports-decl>>
<dfn>&lt;supports-font-tech-fn></dfn> = font-tech( <<font-tech>> )
<dfn>&lt;supports-font-format-fn></dfn> = font-format( <<font-format>> )
<dfn>&lt;supports-at-rule-fn></dfn> = at-rule( <<at-keyword-token>> )
</pre>

<wpt>
at-supports-font-format-001.html
at-supports-font-tech-001.html
js/CSS-supports-L5.html
</wpt>

: <<supports-font-tech-fn>>
::
The result is true if the UA
Expand All @@ -138,9 +135,24 @@ Extensions to the ''@supports'' rule</h2>
<a href="#dfn-support-font-format">supports the font format</a>
provided as an argument to the function.

: <<supports-at-rule-fn>>
::
The result is true if the UA
<a href="#dfn-support-at-rule">supports the at-rule</a>
provided as an argument to the function.

<h3 id="support-definition-ext">
Extensions to the definition of support</h3>

<h4 id="support-definition-ext-fonts">
Font techs and formats</h4>

<wpt>
at-supports-font-format-001.html
at-supports-font-tech-001.html
js/CSS-supports-L5.html
</wpt>

A CSS processor is considered to
<dfn export for=CSS id="dfn-support-font-tech">support a font tech</dfn>
when it is capable of utilizing the specified [[css-fonts-4#font-tech-definitions]]
Expand All @@ -152,6 +164,21 @@ Extensions to the definition of support</h3>
in layout and rendering,
and this format is not specified as a <<string>>.

<h4 id="support-definition-at-rules">
At-rules</h4>

<wpt>
js/supports-at-rule.html
</wpt>

A CSS processor is considered to
<dfn export for=CSS id="dfn-support-at-rule">support an at-rule</dfn>
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.

<h2 id="when-rule">
Generalized Conditional Rules: the ''@when'' rule</h2>

Expand Down Expand Up @@ -1812,6 +1839,14 @@ Changes since the <a href="https://www.w3.org/TR/2024/WD-css-conditional-5-20241
Dimensional query containers no longer apply layout containment
(<a href="https://github.com/w3c/csswg-drafts/pull/10544">#10544</a>)
</li>
<li>
Extended [=supports queries=] to express [=at-rule=] capabilities
via ''at-rule()''.
(<a href="https://github.com/w3c/csswg-drafts/issues/2463">#2463</a>,
<a href="https://github.com/w3c/csswg-drafts/issues/6966">#6966</a>,
<a href="https://github.com/w3c/csswg-drafts/issues/11116">#11116</a>,
<a href="https://github.com/w3c/csswg-drafts/issues/11117">#11117</a>)
</li>
</ul>

<h3 id="changes-20240723" class="no-num">
Expand Down