[selectors] Define that the root elements when matching must have the same root. Also fix some linking errors.

Author: tabatkins

selectors/Overview.bs

@@ -24,8 +24,11 @@ At Risk: the '':drop()'' pseudo-class
 At Risk: the '':read-write'' pseudo-class
 Ignored Terms: function token, Document, DocumentFragment, math, h1, shadow tree, query(), quirks mode, button, a, span, object, p, div, q, area, link, label, input, html, em, li, ol, pre, CSS Value Definition Syntax
 Ignored Vars: identifier, extended filtering
-Link Defaults: dom-core-ls (interface) Document
 </pre>
+<pre class=link-defaults>
+spec:css-syntax-3; type:dfn; text:identifier
+</pre>
+
 <style>
 #selector-examples td:first-child {
 	white-space: nowrap;
@@ -606,7 +609,7 @@ Data Model</h3>
 	it must do so while ignoring the default namespace. [[CSS3NAMESPACE]]
 
 	<div class='example'>
-		For example, the <a>host element</a> in a <a>shadow tree</a> is <a>featureless</a>,
+		For example, the <a>shadow host</a> in a <a>shadow tree</a> is <a>featureless</a>,
 		and can't be matched by <em>any</em> <a>pseudo-class</a> except for '':host'' and '':host-context()''.)
 	</div>
 
@@ -1995,10 +1998,7 @@ The Pointer Hover Pseudo-class: '':hover''</h3>
 	(e.g., a pen device that does not detect hovering)
 	are still conforming.
 
-	The parent of an element that matches '':hover'' also matches '':hover''.
-
-	Note: When an element that is '':hover'' is in a <a>shadow tree</a>,
-	the <a>host element</a> (and its parents) are also in the '':hover'' state. (See [[css-scoping-1]])
+	An element also matches '':hover'' if one of its <a>shadow-including descendants</a> matches '':hover''.
 
 	Document languages may define additional ways in which an element can match '':hover''.
 	For example, [[HTML5]] defines a labeled control element as <a href="http://www.whatwg.org/html/selectors.html#selector-hover">matching <code>:hover</code></a>
@@ -2025,10 +2025,7 @@ The Activation Pseudo-class: '':active''</h3>
 	which elements can become '':active''.
 	For example, [[HTML5]] defines a <a href="http://www.whatwg.org/html/selectors.html#selector-active">list of activatable elements</a>.
 
-	The parent of an element that matches '':active'' also matches '':active''.
-
-	Note: When an element that is '':active'' is in a <a>shadow tree</a>,
-	the <a>host element</a> (and its parents) are also in the '':active'' state. (See [[css-scoping-1]])
+	An element also matches '':active'' if one of its <a>shadow-including descendants</a> matches '':active''.
 
 	Document languages may define additional ways in which an element can match '':active''.
 
@@ -2054,10 +2051,8 @@ The Input Focus Pseudo-class: '':focus''</h3>
 The Generalized Input Focus Pseudo-class: '':focus-within''</h3>
 
 	The <dfn id='focus-within-pseudo'>:focus-within</dfn> pseudo-class applies to elements for which the '':focus'' pseudo class applies.
-	Additionally, the ancestors of an element that matches '':focus-within'' also match '':focus-within''.
 
-	Note: When an element that is '':focus-within'' is in a <a>shadow tree</a>,
-	the <a>host element</a> (and its parents) are also in the '':focus-within'' state. (See [[css-scoping-1]])
+	An element also matches '':focus-within'' if one of its <a>shadow-including descendants</a> matches '':focus''.
 
 <h3 id="drag-pseudos">
 The Drag-and-Drop Pseudo-class: '':drop'' and '':drop()''</h3>
@@ -3153,9 +3148,12 @@ Evaluating a Selector</h3>
 	This section describes how to <dfn export>evaluate a selector</dfn> against a set of elements.
 
 	APIs using this algorithm must provide a selector,
-	and one or more root elements
-	indicating the trees that will be searched by the selector.
-	They may optionally provide:
+	and one or more <var>root elements</var>
+	indicating the <a>trees</a> that will be searched by the selector.
+	All of the <var>root elements</var> must share the same <a for=tree>root</a>,
+	or else calling this algorithm is invalid.
+
+	Callers may optionally provide:
 
 	<ul>
 		<li>
@@ -3183,14 +3181,14 @@ Evaluating a Selector</h3>
 
 	A <a>selector</a> is evaluated against some initial list of elements:
 	the <dfn export>selector match list</dfn>.
-	The <a>selector match list</a> is initially populated with the root elements
+	The <a>selector match list</a> is initially populated with the <var>root elements</var>
 	provided to the algorithm,
-	and all elements reachable from them by traversing any number of child lists.
+	and all their <a>descendants</a>.
 
 	If the selector is <a>scope-contained</a>,
 	the <a>selector match list</a> is immediately filtered
 	to contain only elements that are either the <a>scoping root</a>
-	or descendants of the <a>scoping root</a>.
+	or <a>descendants</a> of the <a>scoping root</a>.
 
 	The selector is processed from left to right in order,
 	with <a>simple selectors</a> filtering the <a>selector match list</a>,
@@ -3199,13 +3197,13 @@ Evaluating a Selector</h3>
 	then after each <a>combinator</a>
 	the <a>selector match list</a> must be filtered
 	to contain only elements that are either the <a>scoping root</a>
-	or descendants of the <a>scoping root</a>.
+	or <a>descendants</a> of the <a>scoping root</a>.
 
 	If the selector is <a>scope-filtered</a>,
 	then after the selector is finished processing,
 	the <a>selector match list</a> must be filtered
 	to contain only elements that are either the <a>scoping root</a>
-	or descendants of the <a>scoping root</a>.
+	or <a>descendants</a> of the <a>scoping root</a>.
 
 	After the selector is finished matching,
 	the <a>selector match list</a> must be filtered
@@ -3215,7 +3213,7 @@ Evaluating a Selector</h3>
 	When this process is done, the elements in the <a>selector match list</a>
 	are the elements said to match the selector.
 	If the order of elements matter,
-	they must be sorted in document order,
+	they must be sorted in <a>shadow-including tree order</a>,
 	unless otherwise specified.
 
 	<div class='example'>