[css-text] More tweaking of the justification section. Add section headings. Rearrange paragraphs. Etc.

--HG--
extra : rebase_source : c04bd2c0b72e6dcf08f97e3f85743269656e2420

Author: fantasai

css-text/Overview.html

@@ -10,7 +10,7 @@
    rel=dcterms.rights>
   <meta content="CSS Text Module Level 3 (CSS3 Text)" name=dcterms.title>
   <meta content=text name=dcterms.type>
-  <meta content=2013-07-12 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>
@@ -26,14 +26,6 @@
     .egbidiwsaB { background:yellow;border:2px dotted white }
     .egbidiwsbC { border:2px dotted red }
 
-    #letter-spacing-example .LS  { padding: 1px 0;
-                                   color: orange;  }
-    #letter-spacing-example .Z   { color: blue;    }
-    #letter-spacing-example .Y   { color: green;   }
-    #letter-spacing-example .P   { color: gray;
-                                   padding: 2px 0; }
-    #letter-spacing-example span { border: 1px solid; }
-
     /* Start Letter-spacing Tutorial */
     .ls-ex {
       font-size: 200%;
@@ -76,12 +68,12 @@
 
    <h1>CSS Text Module Level 3</h1>
 
-   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 12 July 2013</h2>
+   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 16 July 2013</h2>
 
    <dl>
     <dt>This version:</dt>
     <!--
-    <dd><a href="http://www.w3.org/TR/2013/WD-css3-text-20130712/">http://www.w3.org/TR/2013/WD-css3-text-20130712/</a></dd>
+    <dd><a href="http://www.w3.org/TR/2013/WD-css3-text-20130716/">http://www.w3.org/TR/2013/WD-css3-text-20130716/</a></dd>
 -->
 
     <dd><a
@@ -309,6 +301,23 @@ <h2 class="no-num no-toc" id=contents> Table of Contents</h2>
 
      <li><a href="#text-justify"><span class=secno>7.3. </span> Justification
       Method: the ‘<code class=property>text-justify</code>’ property</a>
+
+      <ul class=toc>
+       <li><a href="#expanding-text"><span class=secno>7.3.1. </span>
+        Expanding and Compressing Text</a>
+
+       <li><a href="#justify-symbols"><span class=secno>7.3.2. </span>
+        Handling Symbols and Punctuation</a>
+
+       <li><a href="#justify-limits"><span class=secno>7.3.3. </span>
+        Unexpandable Text</a>
+
+       <li><a href="#justify-cursive"><span class=secno>7.3.4. </span>
+        Cursive Scripts</a>
+
+       <li><a href="#justify-alt"><span class=secno>7.3.5. </span> Possible
+        Algorithms</a>
+      </ul>
     </ul>
 
    <li><a href="#spacing"><span class=secno>8. </span> Spacing</a>
@@ -1791,6 +1800,9 @@ <h3 id=overflow-wrap><span class=secno>6.2. </span> Overflow Wrapping: the
   <h2 id=justification><span class=secno>7. </span> Alignment and
    Justification</h2>
 
+  <p>Alignment and justification controls how inline content is distributed
+   within a line box.
+
   <h3 id=text-align><span class=secno>7.1. </span> Text Alignment: the ‘<a
    href="#text-align0"><code class=property>text-align</code></a>’ property</h3>
 
@@ -2117,12 +2129,11 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
    <dt><dfn id=inter-word title="text-justify:inter-word">‘<code
     class=css>inter-word</code>’</dfn>
 
-   <dd>Justification varies the used ‘<a href="#word-spacing0"><code
-    class=property>word-spacing</code></a>’ on the line, i.e. the primary
-    <a href="#expansion-opportunity"><i>expansion opportunities</i></a> are
-    at <a href="#word-separator"><i>word separators</i></a>. This behavior is
-    typical for languages that separate words using spaces, like English or
-    Korean.
+   <dd>Justification adjusts spacing at <a href="#word-separator"><i>word
+    separators</i></a> (effectively varying the used ‘<a
+    href="#word-spacing0"><code class=property>word-spacing</code></a>’ on
+    the line). This behavior is typical for languages that separate words
+    using spaces, like English or Korean.
     <div class=figure id=fig-text-justify-interword>
      <p> <img alt="Extra space is equally distributed mainly to spaces."
       src=text-justify-interword.png>
@@ -2146,15 +2157,11 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
    <dt><dfn id=distribute title="text-justify:distribute">‘<code
     class=css>distribute</code>’</dfn>
 
-   <dd>Justification varies the used ‘<a href="#letter-spacing0"><code
-    class=property>letter-spacing</code></a>’ on the line (except between
-    <a href="#letter0"><i>letters</i></a> in <a
-    href="#cursive-scripts"><i>cursive scripts</i></a> such as Arabic), i.e.
-    the primary <a href="#expansion-opportunity"><i>expansion
-    opportunities</i></a> are between adjacent <a
-    href="#character"><i>characters</i></a> where both <a
-    href="#character"><i>characters</i></a> in the pair are
-    non-<i>cursive</i>. This value is sometimes used in e.g. Japanese.
+   <dd>Justification adjusts spacing between each pair of adjacent <a
+    href="#character"><i>characters</i></a> (effectively varying the used
+    ‘<a href="#letter-spacing0"><code
+    class=property>letter-spacing</code></a>’ on the line). This value is
+    sometimes used in e.g. Japanese.
     <div class=figure id=fig-text-justify-distribute>
      <p> <img
       alt="Extra space is equally distributed at points between spaces and letters of all writing systems."
@@ -2184,64 +2191,49 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
       </div>
 -->
 
+  <p>The exact justification algorithm is UA-dependent; however, CSS provides
+   some general guidelines...
+
+  <h4 id=expanding-text><span class=secno>7.3.1. </span> Expanding and
+   Compressing Text</h4>
+
   <p>When justifying text, the user agent takes the remaining space between
    the ends of a line's contents and the edges of its line box, and
    distributes that space throughout its contents so that the contents
-   exactly fill the line box. If the ‘<a href="#letter-spacing0"><code
-   class=property>letter-spacing</code></a>’ and ‘<a
-   href="#word-spacing0"><code class=property>word-spacing</code></a>’
-   property values allow it, the user agent may also distribute negative
-   space, putting more content on the line than would otherwise fit under
-   normal spacing conditions. The exact justification algorithm is
-   UA-dependent; however, CSS provides some general guidelines which should
-   be followed when a justification method other than ‘<a
-   href="#auto1"><code class=property>auto</code></a>’ is specified.
-
-  <div class=note>
-   <p>The guidelines in this level of CSS do not describe a complete
-    justification algorithm. They are merely a minimum set of requirements
-    that a complete algorithm should meet. Limiting the set of requirements
-    gives UAs some latitude in choosing a justification algorithm that meets
-    their needs and desired balance of quality, speed, and complexity.
-
-   <p>For instance, a basic but fast ‘<code class=css>inter-word</code>’
-    justification algorithm might use a simple greedy method for determining
-    line breaks, then distribute leftover space. This algorithm could follow
-    the guidelines by expanding word spaces first, expanding between letters
-    only if ‘<a href="#word-spacing0"><code
-    class=property>word-spacing</code></a>’ hit a limit.
-
-   <p>A more sophisticated but slower ‘<code class=css>inter-word</code>’
-    justification algorithm might use a Knuth/Plass method where <a
-    href="#expansion-opportunity"><i>expansion opportunities</i></a> and
-    limits were assigned weights and assessed with other line breaking
-    considerations. This algorithm could follow the guidelines by giving more
-    weight to <a href="#word-separator"><i>word separators</i></a> than
-    letter spacing.
-  </div>
+   exactly fill the line box. The user agent may alternatively distribute
+   negative space, putting more content on the line than would otherwise fit
+   under normal spacing conditions.
 
   <p>An <dfn id=expansion-opportunity>expansion opportunity</dfn> is a point
-   where the justification algorithm may alter spacing within the text. The
-   UA divides <a href="#expansion-opportunity"><i>expansion
-   opportunities</i></a> into different priority levels: within a level, all
-   <a href="#expansion-opportunity"><i>expansion opportunities</i></a> are
+   where the justification algorithm may alter spacing within the text. An
+   expansion opportunity can be provided by a single <a
+   href="#character"><i>character</i></a> (such as a <i>word separator
+   character</i>), or by the juxtaposition of two <a
+   href="#character"><i>characters</i></a>. The UA divides <a
+   href="#expansion-opportunity"><i>expansion opportunities</i></a> into
+   different priority levels: within a level, all <a
+   href="#expansion-opportunity"><i>expansion opportunities</i></a> are
    expanded or compressed at the same priority.
 
+  <h4 id=justify-symbols><span class=secno>7.3.2. </span> Handling Symbols
+   and Punctuation</h4>
+
   <p>When determining <a href="#expansion-opportunity"><i>expansion
    opportunities</i></a>, characters from the Unicode Symbols (S*) and
    Punctuation (P*) classes are generally treated the same as a <a
    href="#letter0"><i>letter</i></a>: in the case of ‘<code
    class=css>inter-word</code>’, as a Latin <a
-   href="#letter0"><i>letter</i></a>, in the case of ‘<code
+   href="#letter0"><i>letter</i></a>; in the case of ‘<code
    class=css>distribute</code>’, as a Han <a
-   href="#letter0"><i>letter</i></a>, and in the case of ‘<a
+   href="#letter0"><i>letter</i></a>; and in the case of ‘<a
    href="#auto1"><code class=css>auto</code></a>’, as a <a
-   href="#letter0"><i>letter</i></a> of the dominant script. However, by
-   typographic tradition there may be additional rules controlling the
-   justification of symbols and punctuation. Therefore, the UA may reassign
-   specific characters or introduce additional levels of prioritization to
-   handle <a href="#expansion-opportunity"><i>expansion opportunities</i></a>
-   involving symbols and punctuation.
+   href="#letter0"><i>letter</i></a> of the dominant script.
+
+  <p>However, by typographic tradition there may be additional rules
+   controlling the justification of symbols and punctuation. Therefore, the
+   UA may reassign specific characters or introduce additional levels of
+   prioritization to handle <a href="#expansion-opportunity"><i>expansion
+   opportunities</i></a> involving symbols and punctuation.
 
   <p class=example> For example, there are traditionally no <a
    href="#expansion-opportunity"><i>expansion opportunities</i></a> between
@@ -2255,6 +2247,8 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
    prioritization level than the opportunities between ideographic
    characters.
 
+  <h4 id=justify-limits><span class=secno>7.3.3. </span> Unexpandable Text</h4>
+
   <p>The ‘<a href="#word-spacing0"><code
    class=property>word-spacing</code></a>’ property can specify limits on
    <a href="#expansion-opportunity"><i>expansion opportunities</i></a>
@@ -2273,7 +2267,54 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
    class=css>center</code>’ if ‘<a href="#text-justify0"><code
    class=property>text-justify</code></a>’ is ‘<code
    class=css>distribute</code>’, and as ‘<code class=css>start</code>’
-   otherwise.) <!--
+   otherwise.)
+
+  <h4 id=justify-cursive><span class=secno>7.3.4. </span> Cursive Scripts</h4>
+
+  <p>Justification <em>must not</em> introduce gaps between <a
+   href="#letter0"><i>letters</i></a> of <a
+   href="#cursive-scripts"><i>cursive scripts</i></a> such as Arabic. If it
+   is able, the UA <em>may</em> translate space distributed to <a
+   href="#expansion-opportunity"><i>expansion opportunities</i></a> within a
+   run of such <a href="#letter0"><i>letters</i></a> into some form of
+   cursive elongation for that run. It otherwise <em>must</em> assume that no
+   <a href="#expansion-opportunity"><i>expansion opportunity</i></a> exists
+   between any pair of <i>cursive script</i> <a
+   href="#letter0"><i>letters</i></a>.
+
+  <h4 id=justify-alt><span class=secno>7.3.5. </span> Possible Algorithms</h4>
+
+  <p>The UA may enable or break optional ligatures or use other font features
+   such as alternate glyphs or glyph compression to help justify the text
+   under any method. This behavior is not controlled by this level of CSS.
+
+  <div class=note>
+   <p>The guidelines in this level of CSS do not describe a complete
+    justification algorithm. They are merely a minimum set of requirements
+    that a complete algorithm should meet. Limiting the set of requirements
+    gives UAs some latitude in choosing a justification algorithm that meets
+    their needs and desired balance of quality, speed, and complexity.
+
+   <p>For instance, a basic but fast ‘<code class=css>inter-word</code>’
+    justification algorithm might use a simple greedy method for determining
+    line breaks, then distribute leftover space. This algorithm could follow
+    the guidelines by expanding word spaces first, expanding between letters
+    only if ‘<a href="#word-spacing0"><code
+    class=property>word-spacing</code></a>’ hit a limit.
+
+   <p>A more sophisticated but slower ‘<code class=css>inter-word</code>’
+    justification algorithm might use a Knuth/Plass method where <a
+    href="#expansion-opportunity"><i>expansion opportunities</i></a> and
+    limits were assigned weights and assessed with other line breaking
+    considerations. This algorithm could follow the guidelines by giving more
+    weight to <a href="#word-separator"><i>word separators</i></a> than
+    letter spacing.
+
+   <p>It's not defined whether expansion or compression is preferred, so a UA
+    may, for example, bias towards compression for CJK languages but towards
+    expansion for Western alphabetic languages.
+  </div>
+  <!--
     <p>The <i>expansion opportunity</i> priorities for values of 'text-justify'
       are given in the table below. Since justification behavior
       varies by writing system, <i>expansion opportunities</i> are organized by
@@ -2396,7 +2437,7 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
       classes.
       The default justification priority of these <i>expansion opportunities</i> is given above.
 -->
-   <!--
+  <!--
     <p id="justify-cursive">For justification of <i>cursive scripts</i>,
       words may be expanded through kashida elongation or other cursive
       expansion processes. Kashida may be applied in discrete units or
@@ -2464,10 +2505,6 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
         </ol>
       --></div>
 
-  <p>The UA may enable or break optional ligatures or use other font features
-   such as alternate glyphs or glyph compression to help justify the text
-   under any method. This behavior is not controlled by this level of CSS.
-
   <h2 id=spacing><span class=secno>8. </span> Spacing</h2>
 
   <p>CSS offers control over text spacing via the ‘<a