Clarifications to alignment-related side-effects of unicode-bidi: plaintext.

--HG--
extra : rebase_source : da17abf7b6a074ae0b91ffb215162aed5537cc49

Author: fantasai

css3-text/Overview.html

@@ -32,14 +32,14 @@
 
    <h1>CSS Text Level 3</h1>
 
-   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 24 April 2012</h2>
+   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 25 April 2012</h2>
 
    <dl>
     <dt>This version:
 
     <dd><a href="http://dev.w3.org/csswg/css3-text/">$Date$ (CVS
      $Revision$)</a> <!--
-    <dd><a href="http://www.w3.org/TR/2012/WD-css3-text-20120424/">http://www.w3.org/TR/2012/WD-css3-text-20120424/</a></dd>
+    <dd><a href="http://www.w3.org/TR/2012/WD-css3-text-20120425/">http://www.w3.org/TR/2012/WD-css3-text-20120425/</a></dd>
   -->
 
 
@@ -261,7 +261,10 @@ <h2 class="no-num no-toc" id=contents> Table of Contents</h2>
      <li><a href="#text-align"><span class=secno>7.1. </span> Text Alignment:
       the &lsquo;<code class=property>text-align</code>&rsquo; property</a>
       <ul class=toc>
-       <li><a href="#character-alignment"><span class=secno>7.1.1.
+       <li><a href="#bidi-linebox"><span class=secno>7.1.1. </span>
+        Bidirectionality and Line Boxes</a>
+
+       <li><a href="#character-alignment"><span class=secno>7.1.2.
         </span>Character-based Alignment in a Table Column</a>
       </ul>
 
@@ -1994,19 +1997,23 @@ <h3 id=text-align><span class=secno>7.1. </span> Text Alignment: the
    href="http://dev.w3.org/csswg/css3-text/#white-space-rules">white space
    processing rules</a>.
 
+  <h4 id=bidi-linebox><span class=secno>7.1.1. </span> Bidirectionality and
+   Line Boxes</h4>
+
   <p>The start and end edges of a line box are determined by the inline base
-   direction of the "bidi paragraph" to which it belongs. In most cases, this
-   means using the containing block's computed &lsquo;<code
-   class=property>direction</code>&rsquo;. However if containing block has
-   &lsquo;<code class=css>unicode-bidi: plaintext</code>&rsquo; <a
-   href="#CSS3-WRITING-MODES"
+   direction of the line box. In most cases, this is given by its containing
+   block's computed &lsquo;<code class=property>direction</code>&rsquo;.
+   However if the containing block has &lsquo;<code class=css>unicode-bidi:
+   plaintext</code>&rsquo; <a href="#CSS3-WRITING-MODES"
    rel=biblioentry>[CSS3-WRITING-MODES]<!--{{!CSS3-WRITING-MODES}}--></a>,
-   the inline base direction of its line boxes will be determined by the bidi
-   paragraphs it immediately contains. In the case of an empty bidi
-   paragraph, the direction used is that of the previous bidi paragraph in
-   the containing block, or, if this is the first bidi paragraph in the
-   containing block, then the &lsquo;<code
-   class=property>direction</code>&rsquo; property is used.
+   the inline base direction must be determined by the bidi paragraphs to
+   which it belongs: that is, the bidi paragraph that is immediately
+   contained by the line box's containing block and for which the line box
+   holds content. An empty line box (i.e. one that contains no atomic inlines
+   or characters other than the line-breaking character, if any), takes its
+   inline base direction from the previous line box (if any), or, if this is
+   the first line box in the containing block, then from the &lsquo;<code
+   class=property>direction</code>&rsquo; property of the containing block.
 
   <div class=example>
    <p>In the following example, every other line is right-aligned:</p>
@@ -2021,7 +2028,12 @@ <h3 id=text-align><span class=secno>7.1. </span> Text Alignment: the
 <!-- -->&lt;/pre&gt;</pre>
   </div>
 
-  <h4 id=character-alignment><span class=secno>7.1.1. </span>Character-based
+  <p class=note>Note, this definition also affects &lsquo;<a
+   href="#text-indent0"><code class=property>text-indent</code></a>&rsquo;
+   and &lsquo;<a href="#hanging-punctuation0"><code
+   class=property>hanging-punctuation</code></a>&rsquo;.
+
+  <h4 id=character-alignment><span class=secno>7.1.2. </span>Character-based
    Alignment in a Table Column</h4>
 
   <p>When multiple cells in a column have an <a
@@ -2174,12 +2186,13 @@ <h3 id=text-align-last><span class=secno>7.2. </span> Last Line Alignment:
    &lsquo;<a href="#text-align0"><code
    class=property>text-align</code></a>&rsquo;.
 
-  <p>If &lsquo;<code class=css>auto</code>&rsquo; is specified, content on
-   the affected line is aligned per &lsquo;<a href="#text-align0"><code
-   class=property>text-align</code></a>&rsquo; unless &lsquo;<a
-   href="#text-align0"><code class=property>text-align</code></a>&rsquo; is
-   set to &lsquo;<code class=css>justify</code>&rsquo;. In this case, content
-   is justified if &lsquo;<a href="#text-justify0"><code
+  <p>If <dfn id=auto1>&lsquo;<code class=css>auto</code>&rsquo;</dfn> is
+   specified, content on the affected line is aligned per &lsquo;<a
+   href="#text-align0"><code class=property>text-align</code></a>&rsquo;
+   unless &lsquo;<a href="#text-align0"><code
+   class=property>text-align</code></a>&rsquo; is set to &lsquo;<code
+   class=css>justify</code>&rsquo;. In this case, content is justified if
+   &lsquo;<a href="#text-justify0"><code
    class=property>text-justify</code></a>&rsquo; is &lsquo;<code
    class=css>distribute</code>&rsquo; and start-aligned otherwise. All other
    values have the same meanings as in &lsquo;<a href="#text-align0"><code
@@ -2242,7 +2255,7 @@ <h3 id=text-justify><span class=secno>7.3. </span> Justification Method:
    to) also support it on inline elements. It takes the following values:
 
   <dl>
-   <dt><dfn id=auto1 title="text-justify:auto">&lsquo;<code
+   <dt><dfn id=auto2 title="text-justify:auto">&lsquo;<code
     class=css>auto</code>&rsquo;</dfn>
 
    <dd>The UA determines the justification algorithm to follow, based on a
@@ -3774,7 +3787,7 @@ <h4 id=text-underline-position><span class=secno>10.1.6. </span> Text
    Values have the following meanings:
 
   <dl>
-   <dt><dfn id=auto2>&lsquo;<code class=css>auto</code>&rsquo;</dfn>
+   <dt><dfn id=auto3>&lsquo;<code class=css>auto</code>&rsquo;</dfn>
 
    <dd>The user agent may use any algorithm to determine the underline's
     position; however it must be placed at or below the alphabetic baseline.

css3-text/Overview.src.html

@@ -1395,16 +1395,24 @@ <h3 id="text-align">
       <a href="http://dev.w3.org/csswg/css3-text/#white-space-rules">white
       space processing rules</a>.
 
-    <p>The start and end edges of a line box are determined by the inline base
-      direction of the "bidi paragraph" to which it belongs. In most cases,
-      this means using the containing block's computed 'direction'. However if
-      containing block has ''unicode-bidi: plaintext'' [[!CSS3-WRITING-MODES]],
-      the inline base direction of its line boxes will be determined by the bidi
-      paragraphs it immediately contains.
-      In the case of an empty bidi paragraph, the direction used is that of the
-      previous bidi paragraph in the containing block, or, if this is the first
-      bidi paragraph in the containing block, then the 'direction' property is
-      used.
+<h4 id=bidi-linebox>
+Bidirectionality and Line Boxes</h4>
+
+    <p>The start and end edges of a line box are determined by
+      the inline base direction of the line box.
+      In most cases, this is given by its containing block's computed 'direction'.
+      However if the containing block has ''unicode-bidi: plaintext'' [[!CSS3-WRITING-MODES]],
+      the inline base direction must be determined
+      by the bidi paragraphs to which it belongs:
+      that is, the bidi paragraph that is immediately contained by
+      the line box's containing block
+      and for which the line box holds content.
+      An empty line box
+      (i.e. one that contains no atomic inlines or
+       characters other than the line-breaking character, if any),
+      takes its inline base direction from the previous line box (if any), or,
+      if this is the first line box in the containing block,
+      then from the 'direction' property of the containing block.
 
     <div class="example">
       <p>In the following example, every other line is right-aligned:</p>
@@ -1418,6 +1426,59 @@ <h3 id="text-align">
 <!-- -->&lt;/pre&gt;</pre>
     </div>
 
+    <p class="note">Note that the inline base direction determined here
+    applies to the line box itself, and not to its contents.
+    It affects 'text-align', 'text-align-last', 'text-indent', and 'hanging-punctuation',
+    i.e. the position and alignment of its contents with respect to its edges.
+    It does not affect the formatting or ordering of its content.
+
+    <div class="example">
+      <pre>
+<!-- -->&lt;para style="direction: rtl; unicode-bidi:plaintext">
+<!-- -->&lt;quote style="unicode-bidi:plaintext">שלום!&lt;/quote>", he said.
+<!-- -->&lt;/para&gt;</pre>
+
+      <p>The result should be a left-aligned line looking like this:
+      <pre>"!&#1513;&#1500;&#1493;&#1501;", he said.</pre>
+
+      <p>The line is left-aligned
+        (despite the containing block having ''direction: rtl'')
+        because the containing block (the <code>&lt;para></code>) has ''unicode-bidi:plaintext'',
+        and the line box displays belongs to a bidi paragraph that is LTR.
+        This is because that paragraph's first character with a strong direction
+        is the LTR "h" from "he". The RTL "שלום!" does precede the "he",
+        but it sits in its own bidi-isolated paragraph that is <em>not</em>
+        immediately contained by the <code>&lt;para&gt;</code>,
+        and is thus irrelevent to the line box's alignment.
+        From from the standpoint of the bidi paragraph immediately contained
+        by the <code>&lt;para&gt;</code> containing block,
+        the <code>&lt;quote&gt;</code>'s bidi-isolated paragraph inside it is,
+        by definition, just a neutral U+FFFC character,
+        so the immediately-contained paragraph becomes LTR by virtue
+        of the "he" following it.
+    </div>
+
+    <div class="example">
+      <pre>
+<!-- -->&lt;fieldset style="direction: rtl">
+<!-- -->&lt;textarea style="unicode-bidi:plaintext">
+<!-- -->
+<!-- -->Hello!
+<!-- -->
+<!-- -->&lt;/textarea>
+<!-- -->&lt;/fieldset></pre>
+
+      <p>As expected, the "Hello!" should be displayed LTR
+        (i.e. with the exclamation mark on the right end,
+        despite the <code>&lt;textarea></code>'s ''direction:rtl'')
+        and left-aligned.
+        This makes the empty line following it left-aligned as well,
+        which means that the caret on that line should appear at its
+        left edge. The first empty line, on the other hand, should
+        be right-aligned, due to the RTL direction of its containing
+        paragraph, the <code>&lt;textarea></code>.
+    </div>
+
   <h4 id="character-alignment">Character-based Alignment in a Table Column</h4>
 
     <p>When multiple cells in a column have an <i>alignment character</i> specified,
@@ -1551,7 +1612,7 @@ <h3 id="text-align-last">
       alignment (via ''start end''), 'text-align-last' takes precedence
       over 'text-align'.
 
-    <p>If ''auto'' is specified, content on the affected line is aligned
+    <p>If <dfn>''auto''</dfn> is specified, content on the affected line is aligned
       per 'text-align' unless 'text-align' is set to ''justify''. In
       this case, content is justified if 'text-justify' is ''distribute''
       and start-aligned otherwise.