Add Alan Stearns' text explaining why 'text-justify' leaves so much to the UA and how the restrictions in CSS3 Text can be applied to simple justification algorithms as well as to TeX

fantasai · fantasai · commit 3fffea53c334 · 2012-01-19T02:52:02.000Z
diff --git a/css3-text/Overview.html b/css3-text/Overview.html
@@ -22,7 +22,7 @@
       margin :auto;
     }
   </style>
-  <link href="http://www.w3.org/StyleSheets/TR/W3C-WD.css" rel=stylesheet
+  <link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
   type="text/css">
 
  <body>
@@ -32,17 +32,17 @@
 
    <h1>CSS Text Level 3</h1>
 
-   <h2 class="no-num no-toc" id=longstatus-date>W3C Working Draft 18 January
+   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 19 January
     2012</h2>
 
    <dl>
-    <dt>This version:</dt>
-    <!--
-    <dd><a href="http://dev.w3.org/csswg/css3-text/">$Date$ (CVS $Revision$)</a>
-  -->
+    <dt>This version:
 
-    <dd><a
-     href="http://www.w3.org/TR/2012/WD-css3-text-20120118/">http://www.w3.org/TR/2012/WD-css3-text-20120118/</a>
+    <dd><a href="http://dev.w3.org/csswg/css3-text/">$Date: 2012/01/18
+     23:33:32 $ (CVS $Revision$)</a> <!--
+    <dd><a href="http://www.w3.org/TR/2012/WD-css3-text-20120119/">http://www.w3.org/TR/2012/WD-css3-text-20120119/</a></dd>
+  -->
+     
 
     <dt>Latest version:
 
@@ -2275,6 +2275,31 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
    be followed when any justification method other than &lsquo;<code
    class=property>auto</code>&rsquo; 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.
+
+   <p>For instance, a basic but fast &lsquo;<code
+    class=css>inter-word</code>&rsquo; justification algorithm might use a
+    simple greedy method for determining line breaks, then distribute space
+    using the <a href="#spacing">spacing limits provided</a>. This algorithm
+    could follow the guidelines by changing word spacing first, increasing
+    &lsquo;<a href="#letter-spacing0"><code
+    class=property>letter-spacing</code></a>&rsquo; only if &lsquo;<a
+    href="#word-spacing0"><code class=property>word-spacing</code></a>&rsquo;
+    hit a limit.
+
+   <p>A more sophisticated but slower &lsquo;<code
+    class=css>inter-word</code>&rsquo; justification algorithm might use a
+    Knuth/Plass method where spacing opportunities and spacing limits were
+    assigned weights and assessed with other line breaking considerations.
+    This algorithm could follow the guidelines by giving more weight to word
+    spacing than letter spacing.
+  </div>
+
   <p id=expansion-opportunity>CSS defines <dfn
    id=expansion-opportunities>expansion opportunities</dfn> as points where
    the justification algorithm may alter spacing within the text. These
@@ -2501,9 +2526,6 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
    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.
 
-  <p class=issue>Add example of using &lsquo;<a href="#text-justify0"><code
-   class=property>text-justify</code></a>&rsquo; with the TeX algorithm.
-
   <div class=example>
    <p>3.8 Line Adjustment in <a href="#JLREQ"
     rel=biblioentry>[JLREQ]<!--{{JLREQ}}--></a> gives an example of a set of
@@ -2708,7 +2730,8 @@ <h3 id=word-spacing><span class=secno>8.1. </span> Word Spacing: the
 <!--    -->:lang(en) { word-spacing: 100%; }</pre>
 
    <p>The following example will <em>add</em> half the the width of the
-    &ldquo;0&rdquo; glyph to word spacing character [[CSS3VALUES]]:
+    &ldquo;0&rdquo; glyph to word spacing character <a href="#CSS3VAL"
+    rel=biblioentry>[CSS3VAL]<!--{{CSS3VAL}}--></a>:
 
    <pre>p { word-spacing: 0.5ch; }</pre>
   </div>
@@ -4337,9 +4360,9 @@ <h3 id=text-shadow><span class=secno>10.3. </span> Text Shadows: the
   <p>This property accepts a comma-separated list of shadow effects to be
    applied to the text of the element. Values are interpreted as for <a
    href="http://www.w3.org/TR/css3-background/#the-box-shadow">&lsquo;<code
-   class=property>box-shadow</code>&rsquo;</a>. [[!CSS3BACKGROUND]] The
-   shadow is applied to all of the element's text as well as any text
-   decorations it specifies.
+   class=property>box-shadow</code>&rsquo;</a>. <a href="#CSS3BG"
+   rel=biblioentry>[CSS3BG]<!--{{!CSS3BG}}--></a> The shadow is applied to
+   all of the element's text as well as any text decorations it specifies.
 
   <p>The shadow effects are applied front-to-back: the first shadow is on
    top. The shadows may thus overlay each other, but they never overlay the
@@ -4685,6 +4708,16 @@ <h3 class=no-num id=informative-ref>Informative references</h3>
     </dd>
    <!---->
 
+   <dt id=CSS3VAL>[CSS3VAL]
+
+   <dd>H&#229;kon Wium Lie; Tab Atkins; Elika J. Etemad. <a
+    href="http://www.w3.org/TR/2011/WD-css3-values-20110906/"><cite>CSS
+    Values and Units Module Level 3.</cite></a> 6 September 2011. W3C Working
+    Draft. (Work in progress.) URL: <a
+    href="http://www.w3.org/TR/2011/WD-css3-values-20110906/">http://www.w3.org/TR/2011/WD-css3-values-20110906/</a>
+    </dd>
+   <!---->
+
    <dt id=JIS4051>[JIS4051]
 
    <dd><cite>Formatting rules for Japanese documents
diff --git a/css3-text/Overview.src.html b/css3-text/Overview.src.html
@@ -37,10 +37,10 @@ <h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
 
 <dl>
   <dt>This version:</dt>
-  <!--
     <dd><a href="http://dev.w3.org/csswg/css3-text/">$Date$ (CVS $Revision$)</a>
-  -->
+  <!--
     <dd><a href="http://www.w3.org/TR/[YEAR]/WD-css3-text-[CDATE]/">http://www.w3.org/TR/[YEAR]/WD-css3-text-[CDATE]/</a></dd>
+  -->
   <dt>Latest version:</dt>
     <dd><a href="http://www.w3.org/TR/css3-text/">http://www.w3.org/TR/css3-text/</a></dd>
   <dt>Latest editor's draft:</dt>
@@ -1628,6 +1628,26 @@ <h3 id="text-justify">
       be followed when any justification method other than 'auto' is
       specified.</p>
 
+    <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.
+
+      <p>For instance, a basic but fast ''inter-word'' justification algorithm
+      might use a simple greedy method for determining line breaks, then
+      distribute space using the <a href="#spacing">spacing limits provided</a>.
+      This algorithm could follow the guidelines by changing word spacing
+      first, increasing 'letter-spacing' only if 'word-spacing' hit a limit.
+
+      <p>A more sophisticated but slower ''inter-word'' justification algorithm
+      might use a Knuth/Plass method where spacing opportunities and spacing
+      limits were assigned weights and assessed with other line breaking
+      considerations. This algorithm could follow the guidelines by giving
+      more weight to word spacing than letter spacing. 
+    </div>
+
     <p id="expansion-opportunity">CSS defines <dfn>expansion opportunities</dfn>
       as points where the justification algorithm may alter spacing within
       the text. These expansion opportunities fall into priority
@@ -1803,9 +1823,6 @@ <h3 id="text-justify">
       justify the text under any method. This behavior is not controlled by
       this level of CSS.</p>
 
-    <p class="issue">Add example of using 'text-justify' with the TeX
-      algorithm.</p>
-
     <div class="example">
       <p>3.8 Line Adjustment in [[JLREQ]] gives an example of a set of rules for
         how a text formatter can justify Japanese text.
