[css-color-adjust-1] Per WG resolution, add forced-color-adjust:preserve-parent-color. Fixes w3c#6310

Author: tabatkins

css-color-adjust-1/Overview.bs

@@ -559,7 +559,7 @@ Opting Out of a Forced Color Palette: the 'forced-color-adjust' property {#force
 
 	<pre class=propdef>
 	Name: forced-color-adjust
-	Value: auto | none
+	Value: auto | none | preserve-parent-color
 	Initial: auto
 	Applies to: all elements and text
 	Inherited: yes
@@ -587,14 +587,31 @@ Opting Out of a Forced Color Palette: the 'forced-color-adjust' property {#force
 			and need to make changes to the UA’s default adjustments
 			to provide a more appropriate user experience
 			for those elements.
+
+		: <dfn>preserve-parent-color</dfn>
+		:: In [=forced colors mode=],
+			if the 'color' property inherits from its parent
+			(i.e. there is no [=cascaded value=]
+			or the [=cascaded value=] is ''currentColor'', ''inherit'',
+			or another keyword that inherits from the parent),
+			then it computes to the [=used value|used=] color of its parent’s 'color' value.
+
+			In all other respects, behaves the same as ''none''.
+
+			Note: This value is intended solely to get a reasonable behavior
+			from embedded SVG elements that expect to receive the outer document's text color
+			(and stay consistent with adjustments from [=forced colors mode=]),
+			while otherwise defaulting SVGs
+			to preserving their exact colors,
+			as [=forced colors mode=] can't generally be usefully applied to illustrations.
 	</dl>
 
 	In order to not break SVG content,
 	UAs are expected to add the following rules to their UA style sheet:
 
-	<pre>
+	<pre highlight=css>
 		@namespace "http://www.w3.org/2000/svg";
-		svg|svg { forced-color-adjust: none; }
+		svg|svg { forced-color-adjust: preserve-parent-color; }
 		svg|foreignObject { forced-color-adjust: auto; }
 	</pre>
 
@@ -758,6 +775,13 @@ Changes {#changes}
 			 <a href="https://github.com/w3c/csswg-drafts/issues/5987">Issue 5987</a>)
 	* Renamed 'color-adjust' to 'print-color-adjust', and re-added 'color-adjust' as an alias/shorthand.
 		(<a href="https://github.com/w3c/csswg-drafts/issues/3880">Issue 3880</a>)
+	* Added the ''preserve-parent-color'' keyword to 'forced-color-adjust'
+		and adjusted the stylesheet to use it,
+		to preserve the general "don't mess with SVG colors" behavior
+		without breaking use-cases like SVG icons
+		that want to use the inherited text color
+		<em>after</em> [=forced colors mode=] has taken effect.
+		(<a href="https://github.com/w3c/csswg-drafts/issues/6310">Issue 6310</a>)
 
 	Changes since the <a href="https://www.w3.org/TR/2020/WD-css-color-adjust-1-20200402/">2 April 2020 Working Draft</a>: