[css-scoping-1][css-anchor-position-1] Define 'loose' and 'strict' tree-scoped names, to distinguish anchor-name from anchor-scope behavior. #7916 #9408 #5984

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -168,7 +168,7 @@ Values are defined as follows:
 	:: If the element generates a [=principal box=],
 		the element is an [=anchor element=],
 		with a list of [=anchor names=] as specified.
-		Each [=anchor name=] is a [=tree-scoped name=].
+		Each [=anchor name=] is a [=tree-scoped name/loosely matched=] [=tree-scoped name=].
 
 		Otherwise, the property has no effect.
 </dl>
@@ -195,6 +195,11 @@ Note: While an element is in the [=skipped contents=] of another element
 it's not an [=acceptable anchor element=],
 effectively acting as if it had no names.
 
+Note: Positioned elements in [=shadow trees=]
+can reference [=anchor names=] defined in “higher” trees.
+Currently, they cannot reference [=anchor names=]
+defined in “lower” shadow trees, though.
+
 ### Implicit Anchor Elements ### {#implicit}
 
 Some specifications can define that,
@@ -274,7 +279,7 @@ Values have the following meanings:
 		to [=anchor elements=] within this subtree.
 
 		This value only affects [=anchor names=] in the same tree scope,
-		as if it were a [=tree-scoped name=].
+		as if it were a [=tree-scoped name/strictly matched=] [=tree-scoped name=].
 		(That is, ''anchor-scope: all'' acts identically
 		to ''anchor-scope: --foo, --bar, ...'',
 		listing all relevant [=anchor names=].)
@@ -286,11 +291,9 @@ Values have the following meanings:
 		to be in scope only for this element's descendants;
 		and limits descendants to only match these [=anchor names=]
 		to [=anchor elements=] within this subtree.
-		The <<dashed-ident>> is a [=tree-scoped name=].
 
-		Note: Per [[css-scoping-1]],
-		when two [=tree-scoped names=] are compared,
-		they only match if they're from the same tree.
+		The <<dashed-ident>> represents a [=tree-scoped name/strictly matched=] [=tree-scoped name=],
+		i.e. it can only match against [=anchor names=] in the same shadow tree.[[!CSS-SCOPING-1]]
 </dl>
 
 This property has no effect on [=implicit anchor elements=].
@@ -429,8 +432,8 @@ in anchor positioning.
 			and either
 			* |possible anchor| is [=in a lower top layer=] than |positioned el|, or
 			* they both exist in the same [=top layer=],
-			 but |possible anchor| is either not [=absolutely positioned=]
-			 or occurs earlier in the [=flat tree=] order than |positioned el|
+				but |possible anchor| is either not [=absolutely positioned=]
+				or occurs earlier in the [=flat tree=] order than |positioned el|
 		* The element generating |possible anchor|'s [=containing block=]
 			(if one exists)
 			is an [=acceptable anchor element=] for |positioned el|
@@ -2142,7 +2145,7 @@ laying out later boxes cannot change this decision.
 			its [=containing block=] has changed,
 			or it no longer generates a box.
 		* Its computed value for any [=longhand property|longhand=] of 'position-try' has changed.
-		* Its computed value for any [=@position-try property=] has changed.
+		* Its computed value for any [=accepted @position-try property=] has changed.
 		* Any of the ''@position-try'' rules referenced by it
 			have been added, removed, or mutated.
 

css-scoping-1/Overview.bs

@@ -696,36 +696,56 @@ Name-Defining Constructs and Inheritance</h3>
 
 	If an at-rule or property defines a name that other CSS constructs can refer to it by,
 	such as a ''@font-face'' '@font-face/font-family!!descriptor' name
-	or an ''@keyframes'' name,
+	or an 'anchor-scope' name,
 	it must be defined as a <dfn export for=CSS>tree-scoped name</dfn>.
-	[=Tree-scoped names=] are "global" within a particular [=node tree=];
-	unless otherwise specified,
-	they're associated with the [=root=] of the [=element=] hosting the stylesheet that the at-rule or property is defined in.
-
-	Properties or descriptors that reference a "global" name,
+	[=Tree-scoped names=] are associated with
+	the [=root=] of the [=element=] hosting the stylesheet
+	that the at-rule or property is declared in.
+
+	Additionally, [=tree-scoped names=] can be <dfn export for="tree-scoped name">loosely matched</dfn> or <dfn export for="tree-scoped name">strictly matched</dfn>,
+	defaulting to [=loosely matched=] unless otherwise specified.
+	A [=loosely matched=] [=tree-scoped name=]
+	can be matched by [=tree-scoped references=]
+	(see below)
+	in the same tree or descendant trees,
+	while a [=strictly matched=] [=tree-scoped name=]
+	can only be matched by [=tree-scoped references=]
+	in the exact same tree.
+
+	Properties or descriptors that reference a [=tree-scoped name=],
 	such as the 'font-family!!property'
 	or 'animation-name' properties,
 	must define their value as a <dfn export for=CSS>tree-scoped reference</dfn>.
-	[=Tree-scoped references=] implicitly capture
+	These references implicitly capture
 	a [=node tree=] [=root=]
 	along with their specified value:
 	unless otherwise specified,
-	the [=root=] of the [=element=] hosting the stylesheet that the property or descriptor is defined in.
+	the [=root=] of the [=element=] hosting the stylesheet that the property or descriptor is declared in.
 	This [=root=] reference stays with the [=tree-scoped reference=]
 	as it is inherited.
 
-	Whenever a [=tree-scoped reference=] is dereferenced
-	to find the CSS construct it is referencing,
+	If a [=tree-scoped name=] is <dfn export for="tree-scoped name">global</dfn>
+	(such as ''@font-face'' names),
+	then when a [=tree-scoped reference=] is dereferenced to find it,
 	first search only the [=tree-scoped names=] associated with the same [=root=]
-	as the [=tree-scoped reference=] must be searched.
+	as the [=tree-scoped reference=].
 	If no relevant [=tree-scoped name=] is found,
 	and the [=root=] is a [=shadow root=],
-	then repeat this search in the [=root=]'s [=host=]'s [=node tree=].
-	(In other words, [=tree-scoped names=] "inherit" into descendant shadow trees,
+	then repeat this search in the [=root=]'s [=host=]'s [=node tree=] (recursively).
+	(In other words, global [=tree-scoped names=] “inherit” into descendant shadow trees,
 	so long as they don't define the same name themselves.)
 
+	If a [=tree-scoped name=] is <dfn export for="tree-scoped name">local</dfn> to an element
+	(such as 'anchor-name' or 'anchor-scope' values),
+	then whether a [=tree-scoped reference=] matches the [=tree-scoped name=] on a given element
+	depends on whether the [=tree-scoped name=] is [=tree-scoped name/strictly matched|strictly=] or [=tree-scoped name/loosely matched|loosely=] matched.
+	A [=tree-scoped name/strictly matched=] [=tree-scoped name=] only matches if
+	both names are associated with the same tree.
+	A [=tree-scoped name/loosely matched=] [=tree-scoped name=] also matches if
+	the [=tree-scoped name=] is associated with an ancestor tree.
+
 	If two [=tree-scoped names=] are directly compared
-	(for example, comparing an [=anchor name=] with an 'anchor-scope' ident),
+	(for example, when comparing [=computed values=]),
 	they are considered to match only if their identifiers match,
 	<em>and</em> their [=root=]s match exactly.
 	(If one has a [=root=] that's an ancestor of the other, for example,
@@ -736,6 +756,8 @@ Name-Defining Constructs and Inheritance</h3>
 		and the properties that reference them,
 		to use these concepts.
 
+		Global names include:
+
 		* ''@font-face'', referenced by 'font-family!!property'
 		* ''@font-feature-values'', referenced by 'font-family!!property'
 		* ''@keyframes'', referenced by 'animation-name'