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[css-cascade-5] Add the revert-rule keyword #12992

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Oct 28, 2025
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[css-cascade-5] Add the revert-rule keyword #12992

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41 changes: 40 additions & 1 deletion css-cascade-5/Overview.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@ Informative Classes: ex
spec:dom; type:dfn; text:shadow tree
spec:css-color-4; type:property; text:color
spec:css-values-3; type: value; text:ex
spec:css-values-5; type: function; text:if()
spec:css-conditional-3; type:at-rule; text:@media
spec:mediaqueries-4; type:type; for:@media; text:all
spec:mediaqueries-4; type:type; text:<media-query>
Expand Down Expand Up @@ -1817,7 +1818,7 @@ Explicit Defaulting</h3>
As specified in <a href="https://www.w3.org/TR/css-values/#common-keywords">CSS Values and Units</a> [[!css-values-3]],
all CSS properties can accept these values.

The keywords ''revert'' and ''revert-layer''
The keywords ''revert'', ''revert-layer'', and ''revert-rule''
are <dfn export lt="cascade-dependent keyword">cascade-dependent keywords</dfn>;
some contexts may restrict their use
while allowing the other [=CSS-wide keywords=].
Expand Down Expand Up @@ -1954,6 +1955,42 @@ Rolling Back Cascade Layers: the ''revert-layer'' keyword</h4>
as it is for ''revert'',
and thus effectively forms its own [=cascade layer=].

<h4 id="revert-rule-keyword">
Rolling Back Rules: the ''revert-rule'' keyword</h4>

The <dfn value for=all>revert-rule</dfn> [=CSS-wide keyword=]
rolls back the cascade similar to ''revert'' and ''revert-layer'',
except it works by [=style rule=]
rather than [=cascade origin=] or [=cascade layer=].

If the <a>cascaded value</a> of a property is the ''revert-rule'' keyword,
the <a>cascaded value</a> is rolled back
such that the <a>specified value</a> is calculated
as if the current [=style rule=] had not been present at all.

<div class="example">
The ''revert-rule'' keyword can be combined with ''if()''
to conditionally ignore a declaration:

<pre class='lang-css'>
div {
border-radius: 5px;
}
.apply-sharp {
border-radius: if(style(--mode:sharp): 0px; else: revert-rule);
}
</pre>

Given an element <code>&lt;div class=apply-sharp></code>,
the above style sets ''border-radius'' to <code>0px</code>
only when the [=computed value=] of <code>--mode</code>
is <code>sharp</code>.
</pre>
</div>

The ''revert-rule'' keyword behaves like ''revert-layer''
in the [=author origin=].
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@Loirooriol Loirooriol Nov 4, 2025

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How come? It would be useless to add it if it just behaves as revert-layer.

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@andruud andruud Nov 4, 2025

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Yeah, I noticed that myself earlier today. It's just a mistake. 14a5462


<h2 id="layer-apis">Layer APIs</h2>

<h3 id="the-csslayerblockrule-interface">
Expand Down Expand Up @@ -2025,6 +2062,8 @@ Changes since the 13 Jan 2022 Candidate Recommendation Snapshot</h3>
Non-trivial changes since the <a href="CSS Cascading and Inheritance Level 5">13 January 2022 Candidate Recommendation Snapshot</a>:

<!-- to 13 Jan 2022 -->
* Added the ''revert-rule'' keyword.
(<a href="https://github.com/w3c/csswg-drafts/issues/10443">Issue 10443</a>)
* Clarify that all “aliases” of a property are reverted by ''revert''/''revert-layer''.
* Clarify that style sheets are ordered in [[final CSS style sheets]] order.
* Clarify that only ''@layer'' statement rules are ignored when checking validity of ''@import'', not empty ''@layer'' block rules.
Expand Down