[css-backgrounds] Clarify background-attachment: local

Author: fantasai

css-backgrounds/Overview.html

@@ -12,7 +12,7 @@
   <meta content="CSS Backgrounds and Borders Module Level 3"
    name=dcterms.title>
   <meta content=text name=dcterms.type>
-  <meta content=2013-12-18 name=dcterms.date>
+  <meta content=2013-12-23 name=dcterms.date>
   <meta content="Bert Bos" name=dcterms.creator>
   <meta content="Elika J. Etemad" name=dcterms.creator>
   <meta content="Brad Kemper" name=dcterms.creator>
@@ -42,12 +42,12 @@
 
    <h1>CSS Backgrounds and Borders Module Level 3</h1>
 
-   <h2 class="no-num no-toc">Editor's Draft 18 December 2013</h2>
+   <h2 class="no-num no-toc">Editor's Draft 23 December 2013</h2>
 
    <dl>
     <dt>This version:
 
-    <dd><!-- <a href="http://www.w3.org/TR/2013/CR-css3-background-20131218/">http://dev.w3.org/csswg/css3-background/</a> -->
+    <dd><!-- <a href="http://www.w3.org/TR/2013/CR-css3-background-20131223/">http://dev.w3.org/csswg/css3-background/</a> -->
      <a
      href="http://dev.w3.org/csswg/css3-background/">http://dev.w3.org/csswg/css3-background/</a>
 
@@ -1018,10 +1018,14 @@ <h3 id=the-background-attachment><span class=secno>3.5. </span>Affixing
 
    <dd>The background is fixed with regard to the element's contents: if the
     element has a scrolling mechanism, the background scrolls with the
-    element's contents. In this case, the background behind the element's
-    border (if any) scrolls as well, even though the border itself does not
-    scroll with the contents. The UA may, however, treat the ‘<code
-    class=css>border-box</code>’ value of ‘<a
+    element's contents, and the <a
+    href="#background-painting-area"><i>background painting area</i></a> and
+    <a href="#background-positioning-area"><i>background positioning
+    area</i></a> are relative to the scrollable area of the element rather
+    than to the border framing them. In this case, the background behind the
+    element's border (if any) scrolls as well, even though the border itself
+    does not scroll with the contents. The UA may, however, treat the
+    ‘<code class=css>border-box</code>’ value of ‘<a
     href="#background-clip"><code
     class=property>background-clip</code></a>’ as ‘<code
     class=css>padding-box</code>’ in cases where ‘<a

css-backgrounds/Overview.src.html

@@ -598,11 +598,13 @@ <h3 id="the-background-attachment">Affixing Images: the 'background-attachment'
       element.</span>
   <dt><dfn>local</dfn></dt>
     <dd>The background is fixed with regard to the element's contents:
-      if the element has a scrolling mechanism, the background scrolls
-      with the element's contents. In this case, the background behind
-      the element's border (if any) scrolls as well, even though the
-      border itself does not scroll with the contents. The UA may,
-      however, treat the ''border-box'' value of 'background-clip' as
+      if the element has a scrolling mechanism,
+      the background scrolls with the element's contents,
+      and the <i>background painting area</i> and <i>background positioning area</i>
+      are relative to the scrollable area of the element rather than to the border framing them.
+      In this case, the background behind the element's border (if any) scrolls as well,
+      even though the  border itself does not scroll with the contents.
+      The UA may, however, treat the ''border-box'' value of 'background-clip' as
       ''padding-box'' in cases where 'background-attachment' is ''local''
       and the contents of the element scroll.</dd>
   <dt><dfn>scroll</dfn></dt>