[css-writing-modes] Require hwid/twid/qwid for OT implementations of TCY compression when they are available for all characters in the composition

Author: fantasai

css-writing-modes/Overview.html

@@ -10,7 +10,7 @@
    rel=dcterms.rights>
   <meta content="CSS Writing Modes Module Level 3" name=dcterms.title>
   <meta content=text name=dcterms.type>
-  <meta content=2013-07-10 name=dcterms.date>
+  <meta content=2013-07-16 name=dcterms.date>
   <meta content="Elika J. Etemad" name=dcterms.creator>
   <meta content="Koji Ishii" name=dcterms.creator>
   <meta content=W3C name=dcterms.publisher>
@@ -46,15 +46,15 @@
 
    <h1>CSS Writing Modes Module Level 3</h1>
 
-   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 10 July 2013</h2>
+   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 16 July 2013</h2>
 
    <dl>
     <dt>This version:
 
     <dd><a
      href="http://dev.w3.org/csswg/css3-writing-modes/">http://dev.w3.org/csswg/css3-writing-modes/</a>
      <!--
-    <dd><a href="http://www.w3.org/TR/2013/WD-css3-writing-modes-20130710/">http://dev.w3.org/csswg/css3-writing-modes/</a>
+    <dd><a href="http://www.w3.org/TR/2013/WD-css3-writing-modes-20130716/">http://dev.w3.org/csswg/css3-writing-modes/</a>
 -->
 
     <dt>Latest version:
@@ -3438,10 +3438,15 @@ <h3 id=text-combine-horizontal><span class=secno>9.1. </span>
   <p>The UA must ensure that the combined advance width of the composition
    fits within 1em by compressing the combined text if necessary. (This does
    not necessarily mean that the glyphs will fit within 1em, as some glyphs
-   are designed to draw outside their geometric boundaries.) The UA may use
-   any means to do so, including substituting half-width, third-width, and/or
-   quarter-width glyphs provided by the font or using other font features
-   designed to compress text horizontally.
+   are designed to draw outside their geometric boundaries.) OpenType
+   implementations <em>must</em> use width-specific variants
+   (<code>hwid<code>/<code>twid</code>/<code>qwid</code>) to compress text in
+   cases where those variants are available for all <a
+   href="#character"><i>characters</i></a> in the composition. Otherwise, the
+   UA may use any means to compress the text, including substituting
+   half-width, third-width, and/or quarter-width glyphs provided by the font,
+   using other font features designed to compress text horizontally, scaling
+   the text geometrically, or any combination thereof. </code></code>
 
   <div class=example>
    <p>For example, a simple OpenType-based implementation might compress the

css-writing-modes/Overview.src.html

@@ -2563,9 +2563,15 @@ <h3 id="text-combine-horizontal">
     fits within 1em by compressing the combined text if necessary.
     (This does not necessarily mean that the glyphs will fit within 1em,
     as some glyphs are designed to draw outside their geometric boundaries.)
-    The UA may use any means to do so,
-    including substituting half-width, third-width, and/or quarter-width glyphs provided by the font
-    or using other font features designed to compress text horizontally.
+    OpenType implementations <em>must</em> use width-specific variants
+    (<code>hwid<code>/<code>twid</code>/<code>qwid</code>)
+    to compress text
+    in cases where those variants are available for all <i>characters</i> in the composition.
+    Otherwise, the UA may use any means to compress the text,
+    including substituting half-width, third-width, and/or quarter-width glyphs provided by the font,
+    using other font features designed to compress text horizontally,
+    scaling the text geometrically,
+    or any combination thereof.
 
   <div class="example">
     <p>For example, a simple OpenType-based implementation might compress the text as follows: