[css-text] Improve text-justify rules.

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=2013-05-10 name=dcterms.date>
+  <meta content=2013-05-11 name=dcterms.date>
   <meta content="Elika J. Etemad" name=dcterms.creator>
   <meta content="Koji Ishii" name=dcterms.creator>
   <meta content=W3C name=dcterms.publisher>
@@ -43,12 +43,12 @@
 
    <h1>CSS Text Module Level 3</h1>
 
-   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 10 May 2013</h2>
+   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 11 May 2013</h2>
 
    <dl>
     <dt>This version:</dt>
     <!--
-    <dd><a href="http://www.w3.org/TR/2013/WD-css3-text-20130510/">http://www.w3.org/TR/2013/WD-css3-text-20130510/</a></dd>
+    <dd><a href="http://www.w3.org/TR/2013/WD-css3-text-20130511/">http://www.w3.org/TR/2013/WD-css3-text-20130511/</a></dd>
 -->
 
     <dd><a
@@ -2036,9 +2036,9 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
      for Japanese, using cursive elongation for Arabic, using ‘<code
      class=css>inter-word</code>’ for English, etc. Another possibility is
      to use a justification method that is a simple universal compromise for
-     all writing systems, such as primarily expanding <i>word separators</i>
-     along with expanding between CJK and Southeast Asian <a
-     href="#letter0"><i>letters</i></a>.
+     all writing systems, such as primarily expanding <a
+     href="#word-separator"><i>word separators</i></a> along with expanding
+     between CJK and Southeast Asian <a href="#letter0"><i>letters</i></a>.
 
     <div class=figure id=fig-text-justify-cursive>
      <p> <img
@@ -2072,9 +2072,11 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
     class=css>inter-word</code>’</dfn>
 
    <dd>Justification primarily varies the used ‘<a
-    href="#word-spacing0"><code class=property>word-spacing</code></a>’.
-    This behavior is typical for languages that separate words using spaces,
-    like English or Korean.
+    href="#word-spacing0"><code class=property>word-spacing</code></a>’;
+    the first-level <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.
     <div class=figure id=fig-text-justify-distribute>
      <p> <img alt="Extra space is equally distributed mainly to spaces."
       class=example src=text-justify-interword.png>
@@ -2099,8 +2101,11 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
     class=css>distribute</code>’</dfn>
 
    <dd>Justification primarily varies the used ‘<a
-    href="#letter-spacing0"><code class=property>letter-spacing</code></a>’
-    (excepting between <a href="#letter0"><i>letters</i></a> in <a
+    href="#letter-spacing0"><code
+    class=property>letter-spacing</code></a>’; the first-level <a
+    href="#expansion-opportunity"><i>expansion opportunities</i></a> are
+    between adjacent <a href="#character"><i>characters</i></a> (except
+    between <a href="#letter0"><i>letters</i></a> in <a
     href="#cursive-scripts"><i>cursive scripts</i></a> such as Arabic). This
     value is sometimes used in e.g. Japanese.
     <div class=figure id=fig-text-justify-distribute>
@@ -2164,35 +2169,72 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
     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 <i>word separators</i> than letter spacing.
+    weight to <a href="#word-separator"><i>word separators</i></a> than
+    letter spacing.
   </div>
 
   <p>CSS defines <dfn id=expansion-opportunity
    title="expansion opportunity">expansion opportunities</dfn> as points
-   where the justification algorithm may alter spacing within the text. These
-   <a href="#expansion-opportunity"><i>expansion opportunities</i></a> fall
-   into priority levels as defined by the justification method. Within a
-   line, expansion and compression primarily target the first-priority
-   expansion opportunities; secondary expansion opportunities may be adjusted
-   at a lower priority.
-
-  <p>Expansion and compression limits are given by the <a
-   href="#letter-spacing">letter-spacing</a> and <a
-   href="#word-spacing">word-spacing</a> properties. How any remaining space
-   is distributed once all <a href="#expansion-opportunity"><i>expansion
-   opportunities</i></a> reach their limits is up to the UA. If the inline
-   contents of a line cannot be stretched to the full width of the line box,
-   then they must be aligned as specified by the ‘<a
-   href="#text-align-last0"><code
+   where the justification algorithm may alter spacing within the text. <a
+   href="#expansion-opportunity"><i>Expansion opportunities</i></a> are
+   divided into different priority levels: within a level, all <a
+   href="#expansion-opportunity"><i>expansion opportunities</i></a> are
+   expanded or compressed by the same amount, in proportion to the <a
+   href="#expansion-opportunity"><i>expansion opportunity</i></a>’s
+   ‘<code class=property>font-size</code>’. In the case of an <a
+   href="#expansion-opportunity"><i>expansion opportunity</i></a> introduced
+   by a single <a href="#character"><i>character</i></a>, (as with ‘<a
+   href="#word-spacing0"><code class=property>word-spacing</code></a>’) the
+   ‘<code class=property>font-size</code>’ of that <a
+   href="#character"><i>character</i></a> is used; in the case of an <a
+   href="#expansion-opportunity"><i>expansion opportunity</i></a> between <a
+   href="#character"><i>characters</i></a>, (as with ‘<a
+   href="#letter-spacing0"><code class=property>letter-spacing</code></a>’)
+   the ‘<code class=property>font-size</code>’ of the innermost element
+   containing their boundary is used.
+
+  <p>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
+   class=css>distribute</code>’, as a Han <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.
+
+  <p class=example> For example, there are traditionally no <a
+   href="#expansion-opportunity"><i>expansion opportunities</i></a> between
+   consecutive EM DASH U+2014, HORIZONTAL BAR U+2015, HORIZONTAL ELLIPSIS
+   U+2026, or TWO DOT LEADER U+2025 characters <a href="#JLREQ"
+   rel=biblioentry>[JLREQ]<!--{{JLREQ}}--></a>; thus a UA might assign these
+   characters to a "never" prioritization level. As another example, certain
+   fullwidth punctuation characters are considered to contain an <a
+   href="#expansion-opportunity"><i>expansion opportunity</i></a> in
+   Japanese. The UA might therefore assign these characters to a higher
+   prioritization level than the opportunities between ideographic
+   characters.
+
+  <p>The <a href="#word-spacing">word-spacing</a> property can specify limits
+   on <a href="#expansion-opportunity"><i>expansion opportunities</i></a>
+   introduced by <a href="#word-separator"><i>word separators</i></a>. How
+   any remaining space is distributed once all <a
+   href="#expansion-opportunity"><i>expansion opportunities</i></a> reach
+   their limits is up to the UA. If the inline contents of a line cannot be
+   stretchedto the full width of the line box, then they must be aligned as
+   specified by the ‘<a href="#text-align-last0"><code
    class=property>text-align-last</code></a>’ property. (If ‘<a
    href="#text-align-last0"><code
    class=property>text-align-last</code></a>’ is ‘<code
    class=css>justify</code>’, then they must be aligned as for ‘<code
    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.)</p>
-  <!--
+   class=css>distribute</code>’, and as ‘<code class=css>start</code>’
+   otherwise.) <!--
     <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
@@ -2315,25 +2357,7 @@ <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>Characters from the Unicode Symbols (S*) and Punctuation (P*) classes
-   are generally treated the same as any <a
-   href="#letter0"><i>letter</i></a>. However, there may be additional rules
-   controlling their justification behavior due to typographic tradition.
-   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. For example, there are traditionally no <a
-   href="#expansion-opportunity"><i>expansion opportunities</i></a> between
-   consecutive EM DASH U+2014, HORIZONTAL BAR U+2015, HORIZONTAL ELLIPSIS
-   U+2026, or TWO DOT LEADER U+2025 characters <a href="#JLREQ"
-   rel=biblioentry>[JLREQ]<!--{{JLREQ}}--></a>; thus a UA might assign these
-   characters to a "never" prioritization level. As another example, certain
-   fullwidth punctuation characters are considered to contain an <a
-   href="#expansion-opportunity"><i>expansion opportunity</i></a> in
-   Japanese. The UA might therefore assign these characters to a higher
-   prioritization level than the opportunities between ideographic
-   characters. <!--
+   <!--
     <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
@@ -2543,15 +2567,17 @@ <h3 id=word-spacing><span class=secno>8.1. </span> Word Spacing: the ‘<a
    <pre>p { word-spacing: 0.5ch; }</pre>
   </div>
 
-  <p><dfn id=word-separator>Word-separator characters</dfn> include the space
-   (U+0020), the no-break space (U+00A0), the Ethiopic word space (U+1361),
-   the Aegean word separators (U+10100,U+10101), the Ugaritic word divider
-   (U+1039F), and the Phoenician Word Separator (U+1091F). If there are no
-   word-separator characters, or if the word-separating character has a zero
-   advance width (such as the zero width space U+200B) then the user agent
-   must not create an additional spacing between words. General punctuation
-   and fixed-width spaces (such as U+3000 and U+2000 through U+200A) are not
-   considered word-separator characters.
+  <p><dfn id=word-separator
+   title="word-separator character | word separator">Word-separator
+   characters</dfn> include the space (U+0020), the no-break space (U+00A0),
+   the Ethiopic word space (U+1361), the Aegean word separators
+   (U+10100,U+10101), the Ugaritic word divider (U+1039F), and the Phoenician
+   Word Separator (U+1091F). If there are no word-separator characters, or if
+   a word-separating character has a zero advance width (such as the zero
+   width space U+200B) then the user agent must not create an additional
+   spacing between words. General punctuation and fixed-width spaces (such as
+   U+3000 and U+2000 through U+200A) are not considered word-separator
+   characters.
 
   <h3 id=letter-spacing><span class=secno>8.2. </span> Tracking: the ‘<a
    href="#letter-spacing0"><code class=property>letter-spacing</code></a>’
@@ -2631,9 +2657,10 @@ <h3 id=letter-spacing><span class=secno>8.2. </span> Tracking: the ‘<a
 
   <p>Letter-spacing must not be applied at the beginning or at the end of a
    line. The total letter spacing between two adjacent <a
-   href="#character"><i>characters</i></a> (after bidi reordering) is given
-   by and rendered within the innermost element that <em>contains</em> the
-   boundary between the two <a href="#character"><i>characters</i></a>.
+   href="#character"><i>characters</i></a> (after bidi reordering) is
+   specified by and rendered within the innermost element that
+   <em>contains</em> the boundary between the two <a
+   href="#character"><i>characters</i></a>.
 
   <p>For the purpose of letter-spacing, each consecutive run of atomic
    inlines (such as image and/or inline blocks) is treated as a single <a