[css3-text] Revert letter-spacing to taking a single value. Make word-spacing interpret its values more sensibly. Add pictures for text-justify.

--HG--
extra : rebase_source : b52796c2a09b3494484a510d84850693568d9f99

Author: fantasai

css3-text/Overview.html

@@ -2142,20 +2142,49 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
      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
+      alt="Two lines of calligraphic Arabic end together due to a mix of compressed and swash forms."
+      class=example src=text-justify-cursive.png
+      title="Swash forms elongate the first line while a compressed contextual ligature shortens the second, allowing both to end precisely together.">
+
+     <p class=caption>An example of cursively-justified Arabic text rendered
+      by <a href="http://www.decotype.com/">Tasmeem</a>.
+    </div>
+
+    <div class=figure id=fig-text-justify-distribute>
+     <p> <img
+      alt="Extra space is partly to spaces and partly among CJK and Thai letters."
+      class=example src=text-justify-compromise.png>
+
+     <p class=caption>Mixed-script text with ‘<code class=css>text-justify:
+      auto</code>’: this interpretation uses a universal-compromise
+      justification method, expanding at spaces as well as between CJK and
+      Southeast Asian letters.
+    </div>
+
    <dt><dfn id=none1 title="text-justify:none">‘<code
     class=css>none</code>’</dfn>
 
-   <dd>Justification is disabled. <span class=note>This value is intended for
-    use in user stylesheets to improve readability or for accessibility
-    purposes.</span>
+   <dd>Justification is disabled.
+    <p class=note>This value is intended for use in user stylesheets to
+     improve readability or for accessibility purposes.
 
    <dt><dfn id=inter-word title="text-justify:inter-word">‘<code
     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. <!--
+    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>
+
+     <p class=caption>Mixed-script text with ‘<code class=css>text-justify:
+      inter-word</code>’
+    </div>
+    <!--
       <dt><dfn title="text-justify:inter-ideographic">''inter-ideograph''</dfn></dt>
         <dd>Justification primarily changes spacing at word separators and
           between characters in <a href="#block-scripts">block scripts</a>.
@@ -2175,8 +2204,16 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
     href="#letter-spacing0"><code class=property>letter-spacing</code></a>’
     (excepting 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.</dd>
-   <!--
+    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."
+      class=example src=text-justify-distribute.png>
+
+     <p class=caption>Mixed-script text with ‘<code class=css>text-justify:
+      distribute</code>’
+    </div>
+    <!--
       <dt><a name="kashida-prop"></a><a name="text-kashida-space"></a>
         <dfn title="text-justify:kashida">''kashida''</dfn></dt>
         <dd>Justification primarily stretches
@@ -2195,13 +2232,6 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
                class="example" src="text-justify-east-asia.png" height="376" width="491"></p>
         <p class="caption">Values of 'text-justify': ''inter-word'', ''auto'', and ''distribute''</p>
       </div>
-
-      <div class="figure" id="fig-text-justify-kashida">
-        <p>
-          <img alt="One possible example of rendering for Arabic justification"
-               class="example" src="text-justify-arabic.png" height="73" width="325"></p>
-        <p class="caption">One possible example of rendering for 'text-justify': ''auto''</p>
-      </div>
 -->
 
   <p>When justifying text, the user agent takes the remaining space between
@@ -2497,69 +2527,6 @@ <h2 id=spacing><span class=secno>8. </span> Spacing</h2>
    <pre>p { word-spacing: -50% 0%; }</pre>
   </div>
 
-  <p id=spacing-limits>The <dfn
-   id=ltspacing-limitsgt>&lt;spacing-limits&gt;</dfn> value type, which
-   represents optimum, minimum, and maximum spacing in ‘<a
-   href="#word-spacing0"><code class=property>word-spacing</code></a>’ and
-   ‘<a href="#letter-spacing0"><code
-   class=property>letter-spacing</code></a>’, is defined as
-
-  <pre class=prod><dfn
-   id=ltspacing-limits>&lt;spacing-limits></dfn> = [ normal | &lt;length&gt; | &lt;percentage&gt;]{1,3}</pre>
-
-  <p>If three values are specified, they represent the optimum, minimum, and
-   maximum in that order. If only two values are specified, then the first
-   represents both the optimum and the minimum, and the second represents the
-   maximum. If just one value is specified, then it represents the optimum,
-   minimum, and maximum. The values are interpreted as defined below:
-
-  <dl>
-   <dt><dfn id=normal3 title="&lt;spacing-limits&gt;:normal">‘<code
-    class=css>normal</code>’</dfn>
-
-   <dd>Specifies normal spacing as defined by the current font and/or the
-    user agent; see <a href="#normal-spacing">below</a>. A ‘<code
-    class=css>normal</code>’ optimum spacing value computes to zero.
-
-   <dt><dfn id=ltlengthgt
-    title="&lt;spacing-limits&gt;:&lt;length&gt;">‘<code
-    class=css>&lt;length&gt;</code>’</dfn>
-
-   <dd>Specifies extra spacing <em>in addition to</em> the intrinsic
-    inter-character/inter-word spacing defined by the font. Values may be
-    negative, but there may be implementation-dependent limits.
-
-   <dt><dfn id=ltpercentagegt
-    title="&lt;spacing-limits&gt;:&lt;percentage&gt;">‘<code
-    class=css>&lt;percentage&gt;</code>’</dfn>
-
-   <dd>Specifies the additional spacing as a percentage of the affected
-    character's <i>advance measure</i>. Only valid on ‘<a
-    href="#word-spacing0"><code class=property>word-spacing</code></a>’.
-  </dl>
-
-  <p>In the absence of justification the optimum spacing is be used. The text
-   justification process may alter the spacing from its optimum (see the <a
-   href="#text-justify">‘<code class=property>text-justify</code>’</a>
-   property, above) but must not violate the minimum spacing limit and should
-   also avoid exceeding the maximum. The UA may also use the difference
-   between the minimum/maximum limits and the optimum as input into a
-   weighting algorithm for justification.
-
-  <p>The minimum is treated as a hard constraint: if the maximum is less than
-   the minimum, then the used it is set to the minimum. Likewise for the
-   optimum. Similarly if the maximum is less than the optimum, then the used
-   optimum is set to the used maximum.
-
-  <p><dfn id=normal-spacing>Normal spacing</dfn>: Although ‘<code
-   class=css>normal</code>’ minimum and maximum spacing limits are
-   UA-defined, they must be defined relative to the optimum so that the
-   limits increase and decrease with changes to the optimum spacing. Normal
-   limits may also vary according to the value of the <a
-   href="#text-justify">‘<code class=property>text-justify</code>’</a>
-   property, the element's language, some measure of the amount of text on a
-   line (e.g. block width divided by font size), and/or other factors.
-
   <h3 id=word-spacing><span class=secno>8.1. </span> Word Spacing: the ‘<a
    href="#word-spacing0"><code class=property>word-spacing</code></a>’
    property</h3>
@@ -2574,7 +2541,8 @@ <h3 id=word-spacing><span class=secno>8.1. </span> Word Spacing: the ‘<a
     <tr>
      <th><a href="#values">Value</a>:
 
-     <td><a href="#spacing-limits">&lt;spacing-limits&gt;</a>
+     <td>[ normal | <var>&lt;length&gt;</var> |
+      <var>&lt;percentage&gt;</var>]{1,3}
 
     <tr>
      <th>Initial:
@@ -2609,14 +2577,60 @@ <h3 id=word-spacing><span class=secno>8.1. </span> Word Spacing: the ‘<a
       class=css>normal</code>’
   </table>
 
-  <p>This property specifies the minimum, maximum, and optimal spacing
-   between “words”.
+  <p>This property specifies the optimum, maximum, and minimum spacing
+   between “words” (in that order). Missing values are assumed to be
+   ‘<code class=css>normal</code>’. Values are interpreted as defined
+   below:
+
+  <dl>
+   <dt><dfn id=normal3 title="word-spacing:normal">‘<code
+    class=css>normal</code>’</dfn>
+
+   <dd>Specifies normal spacing as defined by the current font and/or the
+    user agent; see <a href="#normal-spacing">below</a>. A ‘<code
+    class=css>normal</code>’ optimum spacing value computes to zero.
+
+   <dt><dfn id=ltlengthgt title="word-spacing:&lt;length&gt;">‘<code
+    class=css>&lt;length&gt;</code>’</dfn>
+
+   <dd>Specifies extra spacing <em>in addition to</em> the intrinsic
+    inter-word spacing defined by the font. Values may be negative, but there
+    may be implementation-dependent limits.
+
+   <dt><dfn id=ltpercentagegt
+    title="word-spacing:&lt;percentage&gt;">‘<code
+    class=css>&lt;percentage&gt;</code>’</dfn>
+
+   <dd>Specifies the additional spacing as a percentage of the affected
+    character's <i>advance measure</i>.
+  </dl>
 
   <p>Additional spacing is applied to each word-separator character left in
    the text after the <a href="#white-space-rules">white space processing
    rules</a> have been applied, and should be applied half on each side of
    the character unless otherwise dictated by typographic tradition.
 
+  <p>In the absence of justification the optimum spacing is be used. The text
+   justification process may alter the spacing from its optimum (see the <a
+   href="#text-justify">‘<code class=property>text-justify</code>’</a>
+   property, above) but must not violate the minimum spacing limit and should
+   also avoid exceeding the maximum. The UA may also use the difference
+   between the minimum/maximum limits and the optimum as input into a
+   weighting algorithm for justification.
+
+  <p>The used optimum and maximum spacing is floored at the minimum.
+   Similarly if the maximum is less than the optimum, then the used optimum
+   is limited to the used maximum.
+
+  <p><dfn id=normal-spacing>Normal spacing</dfn>: Although ‘<code
+   class=css>normal</code>’ minimum and maximum spacing limits are
+   UA-defined, they must be defined relative to the optimum so that the
+   limits increase and decrease with changes to the optimum spacing. Normal
+   limits may also vary according to the value of the <a
+   href="#text-justify">‘<code class=property>text-justify</code>’</a>
+   property, the element's language, some measure of the amount of text on a
+   line (e.g. block width divided by font size), and/or other factors.
+
   <div class=example>
    <p>The following example will make all the spaces between words in Arabic
     be rendered as zero-width, and double the width of each space in English:
@@ -2655,7 +2669,7 @@ <h3 id=letter-spacing><span class=secno>8.2. </span> Tracking: the ‘<a
     <tr>
      <th><a href="#values">Value</a>:
 
-     <td><a href="#spacing-limits">&lt;spacing-limits&gt;</a>
+     <td>normal | <var>&lt;length&gt;</var>
 
     <tr>
      <th>Initial:
@@ -2685,13 +2699,29 @@ <h3 id=letter-spacing><span class=secno>8.2. </span> Tracking: the ‘<a
     <tr>
      <th>Computed value:
 
-     <td>an optimum, minimum, and maximum value, each consisting of either an
-      absolute length or the keyword ‘<code class=css>normal</code>’
+     <td>an optimum value each consisting of either an absolute length or the
+      keyword ‘<code class=css>normal</code>’
   </table>
 
-  <p>This property specifies the minimum, maximum, and optimal spacing
-   between <a href="#character"><i>characters</i></a>. Letter-spacing is
-   applied in addition to any word-spacing.
+  <p>This property specifies the optimal spacing between adjacent <a
+   href="#character"><i>characters</i></a>. Letter-spacing is applied in
+   addition to any word-spacing. Values have the following meanings:
+
+  <dl>
+   <dt><dfn id=normal4 title="word-spacing:normal">‘<code
+    class=css>normal</code>’</dfn>
+
+   <dd>Specifies normal spacing between <a
+    href="#character"><i>characters</i></a> as defined by the current font.
+    Typically this is zero.
+
+   <dt><dfn id=ltlengthgt0 title="word-spacing:&lt;length&gt;">‘<code
+    class=css>&lt;length&gt;</code>’</dfn>
+
+   <dd>Specifies additional spacing between <a
+    href="#character"><i>characters</i></a> Values may be negative, but there
+    may be implementation-dependent limits.
+  </dl>
 
   <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
@@ -2729,6 +2759,9 @@ <h3 id=letter-spacing><span class=secno>8.2. </span> Tracking: the ‘<a
    connections, it should not apply letter-spacing between characters of that
    script at all.
 
+  <p class=issue>Current UAs just put gaps between joined letters in cursive
+   scripts.
+
   <p>Letter-spacing ignores zero-width characters (such as those from the
    Unicode Cf category). For example, ‘<a href="#letter-spacing0"><code
    class=property>letter-spacing</code></a>’ applied to
@@ -3494,6 +3527,14 @@ <h3 class=no-num id=recent-changes> Changes from the <a
     class=css>inter-cluster</code>’, and ‘<code
     class=css>kashida</code>’ values of ‘<a href="#text-justify0"><code
     class=property>text-justify</code></a>’.
+
+   <li>Dropped minimum and maximum values in ‘<a
+    href="#letter-spacing0"><code
+    class=property>letter-spacing</code></a>’.
+
+   <li>Changed interpretation of three-value syntax in ‘<a
+    href="#word-spacing0"><code class=property>word-spacing</code></a>’ to
+    default missing values to ‘<code class=css>normal</code>’.
   </ul>
 
   <p>Significant details updated:
@@ -3742,7 +3783,7 @@ <h2 class=no-num id=appendix-g-full-property-index>Appendix G: Full
     <tr>
      <th><a class=property href="#letter-spacing0">letter-spacing</a>
 
-     <td>&lt;spacing-limits&gt;
+     <td>normal | &lt;length&gt;
 
      <td>normal
 
@@ -3908,7 +3949,7 @@ <h2 class=no-num id=appendix-g-full-property-index>Appendix G: Full
     <tr>
      <th><a class=property href="#word-spacing0">word-spacing</a>
 
-     <td>&lt;spacing-limits&gt;
+     <td>[ normal | &lt;length&gt; | &lt;percentage&gt;]{1,3}
 
      <td>normal