[css-style-attr] Parse at-rules in declarations lists, like @page.

(No such at-rule is defined yet, this is only for error handling purpose.)

Working Group resolution:
http://lists.w3.org/Archives/Public/www-style/2013May/0783.html

Author: SimonSapin

css-style-attr/Overview.html

@@ -235,9 +235,11 @@ <h2 class="no-num no-toc" id=contents>Table of contents</h2>
    <li><a href="#interpret"><span class=secno>4. </span>Cascading and
     Interpretation</a>
 
-   <li><a href="#ack"><span class=secno>5. </span>Acknowledgments</a>
+   <li><a href="#changes"><span class=secno>5. </span>Changes</a>
 
-   <li><a href="#references"><span class=secno>6. </span>References </a>
+   <li><a href="#ack"><span class=secno>6. </span>Acknowledgments</a>
+
+   <li><a href="#references"><span class=secno>7. </span>References </a>
     <ul class=toc>
      <li class=no-num><a href="#normative-references">Normative
       references</a>
@@ -325,25 +327,45 @@ <h2 id=syntax><span class=secno>3. </span>Syntax and Parsing</h2>
 
   <pre>
 declaration-list
-  : S* declaration? [ ';' S* declaration? ]*
+  : S* declaration-list-next
   ;
+
+declaration-list-next
+    : declaration [ ';' S* declaration-list-next ]?
+    | at-rule declaration-list-next
+    | /* empty */
+    ;
 </pre>
 
   <p class=note>Note that following the CSS2.1 convention, comment tokens are
    not shown in the rule above.
 
   <p>The interpreter must parse the style attribute's value using the same
    forward-compatible parsing rules that apply to parsing declaration block
-   contents in a normal CSS style sheet. See <a
+   contents in a normal CSS style sheet (see <a
    href="http://www.w3.org/TR/CSS21/syndata.html">chapter 4 of the CSS2.1
-   specification</a> for details. <a href="#CSS21"
-   rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
+   specification</a> <a href="#CSS21"
+   rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>), with the following
+   addition: when the UA expects the start of a declaration or at-rule (i.e.,
+   an IDENT token or an ATKEYWORD token) but finds an unexpected token
+   instead, that token is considered to be the first token of a malformed
+   declaration. I.e., the rule for malformed declarations, rather than
+   malformed statements, is used to determine which tokens to ignore in that
+   case.
 
   <p class=note>Note that because there is no open brace delimiting the
    declaration list in the CSS style attribute syntax, a close brace
    (<code>}</code>) in the style attribute's value does not terminate the
    style data: it is merely an invalid token.
 
+  <div class=note>
+   <p>Although the grammar allows it, no at-rule valid in style attributes is
+    define at the moment. The forward-compatible parsing rules are such that
+    a declaration following an at-rule is not ignored:
+
+   <pre>&lt;span style="@unsupported { splines: reticulating } color: green"></pre>
+  </div>
+
   <h2 id=interpret><span class=secno>4. </span>Cascading and Interpretation</h2>
 
   <p>The declarations in a style attribute apply to the element to which the
@@ -367,7 +389,17 @@ <h2 id=interpret><span class=secno>4. </span>Cascading and Interpretation</h2>
    independently and treated as a separate style rule, the ordering of which
    should be defined by the document language, else is undefined.
 
-  <h2 id=ack><span class=secno>5. </span>Acknowledgments</h2>
+  <h2 id=changes><span class=secno>5. </span>Changes</h2>
+
+  <p>Changes since the <a
+   href="http://www.w3.org/TR/2013/PR-css-style-attr-20131003/">2013-10-03
+   Proposed Recommendation</a> are:
+
+  <ul>
+   <li>Parse at-rules in declaration lists to allow future extension.
+  </ul>
+
+  <h2 id=ack><span class=secno>6. </span>Acknowledgments</h2>
 
   <p>Thanks to feedback from <span class=vcard><span class=fn>Daniel
    Glazman</span></span>, <span class=vcard><span class=fn>Ian
@@ -376,7 +408,7 @@ <h2 id=ack><span class=secno>5. </span>Acknowledgments</h2>
    class=family-name>Meyer</span></span></span>, <span class=vcard><span
    class=fn>Björn Höhrmann</span></span>.
 
-  <h2 id=references><span class=secno>6. </span>References</h2>
+  <h2 id=references><span class=secno>7. </span>References</h2>
 
   <h3 class=no-num id=normative-references>Normative references</h3>
   <!--begin-normative-->

css-style-attr/Overview.src.html

@@ -211,24 +211,43 @@ <h2 id="syntax">Syntax and Parsing</h2>
 
 <pre>
 declaration-list
-  : S* declaration? [ ';' S* declaration? ]*
+  : S* declaration-list-next
   ;
+
+declaration-list-next
+    : declaration [ ';' S* declaration-list-next ]?
+    | at-rule declaration-list-next
+    | /* empty */
+    ;
 </pre>
 
 <p class="note">Note that following the CSS2.1 convention, comment tokens
 are not shown in the rule above.
 
 <p>The interpreter must parse the style attribute's value using the
 same forward-compatible parsing rules that apply to parsing declaration block
-contents in a normal CSS style sheet. See
+contents in a normal CSS style sheet (see
 <a href="http://www.w3.org/TR/CSS21/syndata.html">chapter 4 of the CSS2.1
-specification</a> for details. [[!CSS21]]
+specification</a> [[!CSS21]]),
+with the following addition: when the UA expects the start of a declaration or at-rule
+(i.e., an IDENT token or an ATKEYWORD token) but finds an unexpected token instead,
+that token is considered to be the first token of a malformed declaration.
+I.e., the rule for malformed declarations, rather than malformed statements,
+is used to determine which tokens to ignore in that case.
 
 <p class="note">Note that because there is no open brace delimiting the
 declaration list in the CSS style attribute syntax, a close brace
 (<code>}</code>) in the style attribute's value does not terminate the
 style data: it is merely an invalid token.</p>
 
+<div class="note">
+<p>Although the grammar allows it,
+no at-rule valid in style attributes is define at the moment.
+The forward-compatible parsing rules are such that a declaration following an at-rule
+is not ignored:
+<pre>&lt;span style="@unsupported { splines: reticulating } color: green"></pre>
+</div>
+
 <h2 id="interpret">Cascading and Interpretation</h2>
 
 <p>The declarations in a style attribute apply to the element to which
@@ -250,6 +269,14 @@ <h2 id="interpret">Cascading and Interpretation</h2>
 independently and treated as a separate style rule, the ordering of which
 should be defined by the document language, else is undefined.
 
+<h2 id="changes">Changes</h2>
+
+Changes since the <a href="http://www.w3.org/TR/2013/PR-css-style-attr-20131003/">2013-10-03 Proposed Recommendation</a> are:
+
+<ul>
+  <li>Parse at-rules in declaration lists to allow future extension.
+</ul>
+
 <h2 id="ack">Acknowledgments</h2>
 
 <p>Thanks to feedback from <span class="vcard"><span class="fn">Daniel Glazman</span></span>, <span class="vcard"><span class="fn">Ian Hickson</span></span>, <span class="vcard"><span class="fn n"><span class="given-name">Eric</span> <abbr class="additional-name">A.</abbr> <span class="family-name">Meyer</span></span></span>,