[selectors] Define proper absolutizing rules for scope-relative selectors.

Author: tabatkins

selectors/Overview.html

@@ -197,6 +197,10 @@ <h2 class="no-num no-toc" id=contents>Table of Contents</h2>
 
      <li><a href="#scoping"><span class=secno>3.3. </span> Scoped
       Selectors</a>
+      <ul class=toc>
+       <li><a href="#absolutizing"><span class=secno>3.3.1. </span>
+        Absolutizing a Scope-relative Selector</a>
+      </ul>
 
      <li><a href="#pseudo-classes"><span class=secno>3.4. </span>
       Pseudo-classes</a>
@@ -1334,10 +1338,14 @@ <h3 id=scoping><span class=secno>3.3. </span> Scoped Selectors</h3>
     href="#scope-pseudo"><code>:scope</code></a> " (the <a
     href="#scope-pseudo"><code>:scope</code></a> pseudo-class followed by a
     space) is implied at the beginning of each <a href="#complex"><i>complex
-    selector</i></a>, allowing them to begin syntactically with a <a
+    selector</i></a> that does not already contain the <a
+    href="#scope-pseudo"><code>:scope</code></a> pseudo-class. This allows
+    the selector to begin syntactically with a <a
     href="#combinator"><i>combinator</i></a>. The scoping element matches
     this implied <a href="#scope-pseudo"><code>:scope</code></a> selector,
     but does not limit which elements match.
+    <p> Scope-relative selectors must be <a href=absolutize>absolutized</a>
+     before using them for matching.
   </dl>
 
   <div class=example>
@@ -1354,6 +1362,30 @@ <h3 id=scoping><span class=secno>3.3. </span> Scoped Selectors</h3>
     href="#scope-contained"><i>scope-contained</i></a> selectors.
   </div>
 
+  <h4 id=absolutizing><span class=secno>3.3.1. </span> Absolutizing a
+   Scope-relative Selector</h4>
+
+  <p> To <dfn id=absolutize>absolutize a scope-relative selector</dfn>:
+
+  <ol>
+   <li> If the selector starts with a <a
+    href="#combinator"><i>combinator</i></a> other than the <a
+    href="#descendant-combinator"><i>descendant combinator</i></a>, prepend
+    <a href="#scope-pseudo"><code>:scope</code></a> as the initial <a
+    href="#compound"><i>compound selector</i></a>.
+
+   <li> Otherwise, if the selector does not contain any instance of the <a
+    href="#scope-pseudo"><code>:scope</code></a> pseudo-class (either at the
+    top-level or as an argument to a functional pseudo-class), prepend <a
+    href="#scope-pseudo"><code>:scope</code></a> followed by the <a
+    href="#descendant-combinator"><i>descendant combinator</i></a>.
+
+   <li> Otherwise, the selector is already absolute.
+  </ol>
+
+  <p> To <dfn id=absolutize-list>absolutize a scope-relative selector
+   list</dfn>, absolutize each scope-relative selector in the list.
+
   <h3 id=pseudo-classes><span class=secno>3.4. </span> Pseudo-classes</h3>
 
   <p>The <dfn id=pseudo-class>pseudo-class</dfn> concept is introduced to

selectors/Overview.src.html

@@ -659,10 +659,14 @@ <h3 id="scoping">
     <dd>
       With this method of scoping,
       "<code>:scope</code> " (the <code>:scope</code> pseudo-class followed by a space)
-      is implied at the beginning of each <i>complex selector</i>,
-      allowing them to begin syntactically with a <i>combinator</i>.
+      is implied at the beginning of each <i>complex selector</i>
+      that does not already contain the <code>:scope</code> pseudo-class.
+      This allows the selector to begin syntactically with a <i>combinator</i>.
       The scoping element matches this implied <code>:scope</code> selector,
       but does not limit which elements match.
+
+      <p>
+        Scope-relative selectors must be <a href="absolutize">absolutized</a> before using them for matching.
   </dl>
 
   <div class='example'>
@@ -678,6 +682,30 @@ <h3 id="scoping">
       define <i>scope-contained</i> selectors.
   </div>
 
+<h4 id='absolutizing'>
+Absolutizing a Scope-relative Selector</h4>
+
+  <p>
+    To <dfn id='absolutize'>absolutize a scope-relative selector</dfn>:
+
+  <ol>
+    <li>
+      If the selector starts with a <i>combinator</i> other than the <i>descendant combinator</i>,
+      prepend <code>:scope</code> as the initial <i>compound selector</i>.
+
+    <li>
+      Otherwise, if the selector does not contain any instance of the <code>:scope</code> pseudo-class
+      (either at the top-level or as an argument to a functional pseudo-class),
+      prepend <code>:scope</code> followed by the <i>descendant combinator</i>.
+
+    <li>
+      Otherwise, the selector is already absolute.
+  </ol>
+
+  <p>
+    To <dfn id='absolutize-list'>absolutize a scope-relative selector list</dfn>,
+    absolutize each scope-relative selector in the list.
+
 
 <h3 id="pseudo-classes">
 Pseudo-classes</h3>