[css-text] Make control characters visible. <http://lists.w3.org/Archives/Public/www-style/2014Oct/0259.html> Also clean up some Unicode property linking.

--HG--
extra : rebase_source : 8b8831e64c46a13adba42d21ef846646f34f9343

Author: fantasai

css-text/Overview.bs

@@ -269,7 +269,7 @@ Languages and Typesetting</h4>
     In CSS, language-specific typographic tailorings
     are only applied when the content language is known (declared).
 
-  <strong class="advisement">Authors should tag their content accurately for the best typographic behavior.</strong>
+  <strong class="advisement">Authors should language-tag their content accurately for the best typographic behavior.</strong>
 
 <h2 id="transforming">
   Transforming Text</h2>
@@ -591,11 +591,17 @@ Languages and Typesetting</h4>
     See [[CSS21]] section
     <a href="http://www.w3.org/TR/CSS21/visuren.html#anonymous">9.2.2.1</a></p>
 
-  <p>Control characters (Unicode class Cc) other than tab (U+0009), line feed
-    (U+000A), and carriage return (U+000D)
-    are ignored for the purpose of rendering.
-    (As required by [[!UNICODE]],
-    unsupported Default_ignorable characters must also be ignored for rendering.)
+  <p>
+    Control characters (<i>Unicode category</i> <code>Cc</code>)
+    other than tab (U+0009), line feed (U+000A), and carriage return (U+000D)
+    must be rendered as a visible glyph
+    and otherwise treated as any other character of the Symbols (<code>S</code>) <i>general category</i> and Common <i title="Unicode script">script</i>.
+    The UA may use a glyph provided by a font specifically for the control character,
+    substitute the glyphs provided for the corresponding symbol in the Control Pictures block,
+    generate a visual representation of its codepoint value,
+    or use some other method to provide an appropriate visible glyph.
+    As required by [[!UNICODE]],
+    unsupported <code>Default_ignorable</code> characters must be ignored for rendering.
 
   <h3 id="white-space-rules">
     The White Space Processing Rules</h3>
@@ -697,8 +703,8 @@ Languages and Typesetting</h4>
         <li>If the character immediately before or immediately after the segment
           break is the zero-width space character (U+200B), then the break
           is removed, leaving behind the zero-width space.
-        <li>Otherwise, if the East Asian Width property [[!UAX11]] of both
-          the character before and after the line feed is F, W, or H (not A),
+        <li>Otherwise, if the <i>East Asian Width property</i> [[!UAX11]] of both
+          the character before and after the line feed is <code>F</code>, <code>W</code>, or <code>H</code> (not <code>A</code>),
           and neither side is Hangul, then the segment break is removed.
         <li>Otherwise, the segment break is converted to a space (U+0020).
       </ul>
@@ -1121,10 +1127,10 @@ Line Breaking Details</h3>
             &#xFF01;&nbsp;U+FF01,  &#xFF1F;&nbsp;U+FF1F
           <li>breaks before suffixes:<br>
             Characters with the Unicode Line Break property <code>PO</code>
-            and the East Asian Width property [[!UAX11]] <code>A</code>, <code>F</code>, or <code>W</code>.
+            and the <i>East Asian Width property</i> [[!UAX11]] <code>A</code>, <code>F</code>, or <code>W</code>.
           <li>breaks after prefixes:<br>
             Characters with the Unicode Line Break property <code>PR</code>
-            and the East Asian Width property [[!UAX11]] <code>A</code>, <code>F</code>, or <code>W</code>.
+            and the <i>East Asian Width property</i> [[!UAX11]] <code>A</code>, <code>F</code>, or <code>W</code>.
         </ul>
     </ul>
 
@@ -2580,22 +2586,25 @@ Appendix C: Scripts and Spacing</h2>
   <p><em>This appendix is normative.</em></p>
 
   <p>Typographic behavior varies somewhat by language, but varies drastically by writing system.
-  	This appendix categorizes some common scripts in Unicode 6.0 according to their justification and spacing behavior.
+  	This appendix categorizes some common <i title="Unicode script">scripts</i> in Unicode 6.0
+    according to their justification and spacing behavior.
   	Category descriptions are descriptive, not prescriptive;
   	the determining factor is the prioritization of <i>justification opportunities</i>.
 
   <dl>
   	<dt><dfn>block scripts</dfn></dt>
   	<dd>CJK and by extension all Wide characters (see [[!UAX11]].)
-  	  The following scripts are included: Bopomofo, Han, Hangul, Hiragana, Katakana, and Yi.
-  	  Characters of the East Asian Width property [[!UAX11]] W and F are also included,
-  	  but A are included only if the <i>content language</i> is Chinese, Korean, or Japanese.
+  	  The following <i>Unicode scripts</i> are included:
+      Bopomofo, Han, Hangul, Hiragana, Katakana, and Yi.
+  	  Characters of the <i>East Asian Width property</i> <code>W</code> and <code>F</code> are also included,
+  	  but <code>A</code> characters are included only if the <i>content language</i> is Chinese, Korean, or Japanese.
   	<dt><dfn>clustered scripts</dfn></dt>
-  	<dd>Scripts that have discrete units,
-      break only at word boundaries,
+  	<dd>Clustered scripts have discrete units
+      and break only at word boundaries,
       but do not use visible word separators.
-      They comfortably admit inter-character spacing for justification.
-  	  The following scripts are included:
+      They prioritize stretching spaces,
+      but comfortably admit inter-character spacing for justification.
+  	  The clustered scripts include, but are not limited to, the following <i>Unicode scripts</i>:
       Khmer,
       Lao,
       Myanmar,
@@ -2605,8 +2614,8 @@ Appendix C: Scripts and Spacing</h2>
       Tai Viet,
       Thai
   	<dt><dfn title="cursive script">cursive scripts</dfn>
-  	<dd>The following scripts in Unicode 6 are considered to be cursive scripts,
-      and do not admit gaps between their letters for either justification or 'letter-spacing':
+  	<dd>Cursive scripts do not admit gaps between their letters for either justification or 'letter-spacing'.
+      The following <i>Unicode scripts</i> are included:
       Arabic,
       Mandaic,
       Mongolian,
@@ -2627,17 +2636,17 @@ Characters and Properties</h2>
 
   <p>Unicode defines three codepoint-level properties that are referenced
     in CSS Text:
-  <dl>
-    <dt><a href="http://www.unicode.org/reports/tr11/#Definitions">East Asian width</a>
-    <dd>Defined in [[!UAX11]] and given as the East_Asian_Width property
+  <dl export>
+    <dt><dfn title="Unicode East Asian Width|East Asian Width property"><a href="http://www.unicode.org/reports/tr11/#Definitions">East Asian width property</a></dfn>
+    <dd>Defined in [[!UAX11]] and given as the <code>East_Asian_Width</code> property
+      in the Unicode Character Database [[!UAX44]].
+    <dt><dfn title="Unicode General Category|Unicode category|General Category"><a href="http://www.unicode.org/reports/tr44/#General_Category_Values">general category</a></dfn>
+    <dd>Defined in [[!UAX44]] and given as the <code>General_Category</code> property
       in the Unicode Character Database [[!UAX44]].
-    <dt><a href="http://www.unicode.org/reports/tr44/#General_Category_Values">General Category</a>
-    <dd>Defined in [[!UAX44]] and given as the General_Category property
+    <dt><dfn title="Unicode Script|Script property"><a href="http://www.unicode.org/reports/tr24/#Values">script property</a></dfn>
+    <dd>Defined in [[!UAX24]] and given as the <code>Script</code> property
       in the Unicode Character Database [[!UAX44]].
-    <dt><a href="http://www.unicode.org/reports/tr24/#Values">Script property</a>
-    <dd>Defined in [[!UAX24]] and given as the Script property
-      in the Unicode Character Database [[!UAX44]]. (UAs should
-      include any ScriptExtensions.txt assignments in this mapping.)
+      (UAs must include any ScriptExtensions.txt assignments in this mapping.)
   </dl>
 
   <p>Unicode defines properties for individual codepoints, but sometimes