From 3d4fd1eeaed2b902fd12d907feccab66296029d1 Mon Sep 17 00:00:00 2001
From: Rune Lillesveen <futhark@chromium.org>
Date: Tue, 6 Aug 2024 12:43:46 +0200
Subject: [PATCH] [css-conditional-5] Container queries use the flat tree #5984

Per resolution in:

https://github.com/w3c/csswg-drafts/issues/5984#issuecomment-2112977366
---
 css-conditional-5/Overview.bs | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/css-conditional-5/Overview.bs b/css-conditional-5/Overview.bs
index d5bf0c75fed2..01dc61782259 100644
--- a/css-conditional-5/Overview.bs
+++ b/css-conditional-5/Overview.bs
@@ -354,7 +354,7 @@ Container Queries</h2>
 	for [=container size queries=] by specifying
 	the additional query types using the 'container-type' property
 	(or the 'container' [=shorthand=]).
-	Style rules applying to a [=query container=]’s <a>shadow-including descendants</a>
+	Style rules applying to a [=query container=]’s [=flat tree=] descendants
 	can be conditioned by querying against it,
 	using the ''@container'' [=conditional group rule=].
 
@@ -384,30 +384,25 @@ Container Queries</h2>
 		will each respond to their own container context.
 	</div>
 
-	For selectors with pseudo elements, query containers can be established by
-	the <a>shadow-including inclusive ancestors</a> of the <a>ultimate
-	originating element</a>.
+	For the ''::part()'' and ''::slotted()'' <a>pseudo-element</a> selectors,
+	which represent real elements in the DOM tree, query containers can be
+	established by [=flat tree=] ancestors of those elements.
+	For other <a>pseudo-element</a>s, query containers can be established by
+	inclusive [=flat tree=] ancestors of their <a>originating element</a>.
 
 	<div class=note>
 		It follows that:
 
-		* Pseudo elements themselves can not be query containers
 		* ''::before'', ''::after'', ''::marker'', and ''::backdrop'' query their
 			originating elements
 		* ''::first-letter'' and ''::first-line'' query their originating elements,
 			even if the <a>fictional tag sequence</a> may push the
 			<code>::first-line</code> past other elements for the purpose of
 			inheritance and rendering
-		* Multiple pseudo elements do not allow pseudo elements to be query
-			containers for other pseudo elements. E.g., the host, but not the
-			<code>::part()</code>, can be the query container for
-			<code>::before</code> in <code>host::part()::before</code>. Similarly,
-			<code>::before</code> can not be the query container for the
-			<code>::marker</code> in <code>div::before::marker</code>
 		* ''::slotted()'' selectors can query containers inside the shadow tree,
 			including the slot itself
-		* ''::part()'' selectors can query its originating host, but not internal
-			query containers inside the shadow tree
+		* ''::slotted()::before'' selectors can query the slotted shadow host child
+		* ''::part()'' selectors can query containers inside the shadow tree
 		* ''::placeholder'' and ''::file-selector-button'' can query the input
 			element, but do not expose any internal containers if the input element is
 			implemented using a shadow tree