[css-text-decor] Undefine text-decoration positions, since this is still an issue.

--HG--
extra : rebase_source : 070c78d35fcfd5a9ce6eca7c4c3132b0c209c979

Author: fantasai

css-text-decor/Overview.html

@@ -10,7 +10,7 @@
    rel=dcterms.rights>
   <meta content="CSS Text Decoration Module Level 3" name=dcterms.title>
   <meta content=text name=dcterms.type>
-  <meta content=2013-05-13 name=dcterms.date>
+  <meta content=2013-06-10 name=dcterms.date>
   <meta content="Elika J. Etemad" name=dcterms.creator>
   <meta content="Koji Ishii" name=dcterms.creator>
   <meta content=W3C name=dcterms.publisher>
@@ -30,13 +30,13 @@
    <h1 class=p-name>CSS Text Decoration Module Level 3</h1>
 
    <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft <span
-    class=dt-updated><span class=value-title title=20130513>13 May
+    class=dt-updated><span class=value-title title=20130610>10 June
     2013</span></span></h2>
 
    <dl>
     <dt>This version:</dt>
     <!--  
-    <dd><a class="u-url" href="http://www.w3.org/TR/2013/WD-css-text-decor-3-20130513/">http://www.w3.org/TR/2013/WD-css-text-decor-3-20130513/</a></dd>
+    <dd><a class="u-url" href="http://www.w3.org/TR/2013/WD-css-text-decor-3-20130610/">http://www.w3.org/TR/2013/WD-css-text-decor-3-20130610/</a></dd>
   -->
 
     <dd><a class=u-url
@@ -207,9 +207,6 @@ <h2 class="no-num no-toc" id=contents> Table of Contents</h2>
      <li><a href="#text-underline-position-property"><span class=secno>2.6.
       </span> Text Underline Position: the ‘<code
       class=property>text-underline-position</code>’ property</a>
-
-     <li><a href="#line-position"><span class=secno>2.7. </span> Determining
-      the Position and Thickness of Line Decorations</a>
     </ul>
 
    <li><a href="#emphasis-marks"><span class=secno>3. </span> Emphasis
@@ -1041,136 +1038,101 @@ <h3 id=text-underline-position-property><span class=secno>2.6. </span> Text
     modes, both values are treated as ‘<code class=css>under</code>’.)
   </div>
 
-  <h3 id=line-position><span class=secno>2.7. </span> Determining the
-   Position and Thickness of Line Decorations</h3>
-  <!--
+  <p>The exact position and thickness of line decorations is UA-defined in
+   this level. However, the UA must use a single thickness and position on
+   each line for the decorations deriving from a single <a
+   href="#decorating-box"><i>decorating box</i></a>. <!--
+<h3 id="line-position">
+Determining the Position and Thickness of Line Decorations</h3>
+
   <p>Since line decorations can span elements with varying font sizes and
     vertical alignments, the best position for a line decoration is not
     necessarily the ideal position dictated by the <i>decorating box</i>.
-    In determining the position of text decoration lines within a given line box,
-    user agents must consider, for each <i>decorating box</i> on that line,
-    the “ideal” positions of such line decorations of each
-    run of text decorated by that <i>decorating box</i>
-    (each <dfn>considered run</dfn>).
+    Instead, it's calculated, per line, from all text decorated by the <i>decorating box</i> on that line,
+    the <dfn>considered text</dfn>.
     However, descendants of the <i>decorating box</i>
     that are skipped due to 'text-decoration-skip',
     descendant inlines with ''text-decoration-skip: ink'',
     and any descendants that do not participate in the <i>decorating box</i>’s inline formatting context
-    are excluded from the set of <i>considered fragments</i>.
+    are excluded from the set of <i>considered text</i>.
 
   <p>
-    <dfn>Decoration-affecting text</dfn> is any text decorated by a <i>decorating box</i>
-    that can affect the size and position of the decoration;
-    descendants that are skipped due to 'text-decoration-skip',
-    descendant inlines with ''text-decoration-skip: ink'',
-    and any descendants that do not participate in the <i>decorating box</i>’s inline formatting context
-    are not <i>considered fragments</i>.
-    The position and thickness of decorations on <i>considered fragments</i> are calculated by looking at sets of <i>considered fragments</i>:
-    each set is composed of all the <i>considered fragments</i> in a single line box 
-    and decorated by the same <i>decorating box</i>.
--->
-
-  <p>Since line decorations can span elements with varying font sizes and
-   vertical alignments, the best position for a line decoration is not
-   necessarily the ideal position dictated by the <a
-   href="#decorating-box"><i>decorating box</i></a>. Instead, it's
-   calculated, per line, from all text decorated by the <a
-   href="#decorating-box"><i>decorating box</i></a> on that line, the <dfn
-   id=considered-text>considered text</dfn>. However, descendants of the <a
-   href="#decorating-box"><i>decorating box</i></a> that are skipped due to
-   ‘<a href="#text-decoration-skip"><code
-   class=property>text-decoration-skip</code></a>’, descendant inlines with
-   ‘<code class=css>text-decoration-skip: ink</code>’, and any
-   descendants that do not participate in the <a
-   href="#decorating-box"><i>decorating box</i></a>’s inline formatting
-   context are excluded from the set of <a
-   href="#considered-text"><i>considered text</i></a>.
-
-  <p> The line decoration positions are then calculated per line as follows
-   (treating <a href="#underline-left"><i>over</i>-positioned underlines</a>
-   as <i>over</i> lines and <a href="#underline-left"><i>under</i>-positioned
-   overlines</a> as <i>under</i> lines):
+    The line decoration positions are then calculated
+    per line
+    as follows
+    (treating <a href="#underline-left"><i>over</i>-positioned underlines</a> as <i>over</i> lines
+    and <a href="#underline-left"><i>under</i>-positioned overlines</a> as <i>under</i> lines):
 
   <dl>
-   <dt><a href="http://www.w3.org/TR/css-writing-modes/#over"><i>over</i></a>
-    lines
-
-   <dd> Align the line decoration with respect to the highest
-    <!-- <i>text-over</i> baseline of the considered fragments. --> <a
-    href="http://www.w3.org/TR/css-writing-modes/#over"><i>over</i></a>
-    EM-box edge of the <a href="#considered-text"><i>considered text</i></a>.
-
-   <dt><a href="#underline-alphabetic"><i>alphabetic</i></a> underlines
-
-   <dd>
-    <p>The alphabetic underline position is calculated by taking the ideal
-     offset (from the alphabetic baseline) of each run of <a
-     href="#considered-text"><i>considered text</i></a>, averaging those, and
-     then using the lowest alphabetic baseline to actually position the line.
-     (Alphabetic baselines can differ between ‘<code
-     class=css>baseline</code>’-aligned boxes if the dominant baseline is
-     non-alphabetic.) To prevent superscripts and subscripts from throwing
-     this position off-kilter, an inline with a non-initial computed ‘<code
-     class=property>vertical-align</code>’ is treated as having the ideal
-     underline position of its parent.
-
-   <dt>non-alphabetic <a
-    href="http://www.w3.org/TR/css-writing-modes/#under"><i>under</i></a>
-    lines
-
-   <dd> Position the line decoration with respect to the lowest
-    <!-- <i>text-under</i> baseline of the considered fragments. --> <a
-    href="http://www.w3.org/TR/css-writing-modes/#under"><i>under</i></a>
-    EM-box edge of the <a href="#considered-text"><i>considered text</i></a>.
-
-   <dt>line-throughs
-
-   <dd> Line-throughs essentially use the same sort of averaging as for
-    alphabetic underlines, but recompute the position when drawing across a
-    descendant with a different computed ‘<code
-    class=property>font-size</code>’. (This ensures that the text remains
-    effectively “crossed out” despite any font size changes.) For each
-    run of <a href="#considered-text"><i>considered text</i></a> with the
-    same ‘<code class=property>font-size</code>’, compute an ideal
-    position averaged from its font metrics. To prevent superscripts and
-    subscripts from throwing this position off-kilter, an inline with a
-    non-initial computed ‘<code class=property>vertical-align</code>’ is
-    treated as having the ideal underline position of its parent. Position
-    the portion of the line across each decorated fragment at that position.
-    <p class=issue> For simplicity, line-throughs should draw over each
-     element at that element's preferred/averaged position. This can produce
-     some undesirable jumpiness, but there doesn't appear to be any way to
-     avoid that which is correct in all instances, and all attempts are
-     worryingly complex. What position should line-throughts adopt over
-     elements that have a different font-size, but no <a
-     href="#considered-text"><i>considered text</i></a>?
+    <dt><a href="http://www.w3.org/TR/css-writing-modes/#over"><i>over</i></a> lines
+    <dd>
+      Align the line decoration with respect to the highest
+      <a href="http://www.w3.org/TR/css-writing-modes/#over"><i>over</i></a> EM-box edge
+      of the <i>considered text</i>.
+
+    <dt><a href="#underline-alphabetic"><i>alphabetic</i></a> underlines
+    <dd>
+      <p>The alphabetic underline position is calculated by taking
+      the ideal offset (from the alphabetic baseline) of each run of <i>considered text</i>,
+      averaging those, and then using the lowest alphabetic baseline to actually position the line.
+      (Alphabetic baselines can differ between ''baseline''-aligned boxes
+       if the dominant baseline is non-alphabetic.)
+      To prevent superscripts and subscripts from throwing this position off-kilter,
+      an inline with a non-initial computed 'vertical-align'
+      is treated as having the ideal underline position of its parent.
+
+    <dt>non-alphabetic <a href="http://www.w3.org/TR/css-writing-modes/#under"><i>under</i></a> lines
+    <dd>
+      Position the line decoration with respect to the lowest
+      <a href="http://www.w3.org/TR/css-writing-modes/#under"><i>under</i></a> EM-box edge
+      of the <i>considered text</i>.
+
+    <dt>line-throughs
+    <dd>
+      Line-throughs essentially use the same sort of averaging as for alphabetic underlines,
+      but recompute the position when drawing across a descendant with a different computed 'font-size'.
+      (This ensures that the text remains effectively “crossed out” despite any font size changes.)
+      For each run of <i>considered text</i> with the same 'font-size', 
+      compute an ideal position averaged from its font metrics.
+      To prevent superscripts and subscripts from throwing this position off-kilter,
+      an inline with a non-initial computed 'vertical-align'
+      is treated as having the ideal underline position of its parent.
+      Position the portion of the line across each decorated fragment at that position.
+
+      <p class='issue'>
+        For simplicity, line-throughs should draw over each element at that element's preferred/averaged position.
+        This can produce some undesirable jumpiness,
+        but there doesn't appear to be any way to avoid that which is correct in all instances,
+        and all attempts are worryingly complex.
+        What position should line-throughts adopt over elements that have a different font-size,
+        but no <i>considered text</i>?
   </dl>
 
-  <p> CSS does not define the thickness of line decorations. In determining
-   the thickness of text decoration lines, user agents may consider the font
-   sizes, faces, and weights of descendants to provide an appropriately
-   averaged thickness.
-
-  <div class=example>
-   <p>The following figure shows the averaging for underline:
-
-   <p><img
-    alt="In the first rendering of the underlined text '1st a'                  with 'st' as a superscript, both the '1st' and the 'a'                  are rendered in a small font. In the second rendering,                  the 'a' is rendered in a larger font. In the third, both                  '1st' and 'a' are large."
-    height=105 src=underline-averaging.gif width=326>
-
-   <p>In the three fragments of underlined text, the underline is drawn
-    consecutively lower and thicker as the ratio of large text to small text
-    increases.
-
-   <p>Using the same example, a line-through would in the second fragment,
-    instead of averaging the two font sizes, split the line-through into two
-    segments:
-
-   <p><img alt="" src=linethrough-averaging.gif>
-
-   <p>In both cases, however, the superscript, due to the vertical-alignment
-    shift, has no effect on the position of the line.
+  <p>
+    CSS does not define the thickness of line decorations.
+    In determining the thickness of text decoration lines,
+    user agents may consider the font sizes, faces, and weights of descendants
+    to provide an appropriately averaged thickness.
+
+  <div class="example">
+    <p>The following figure shows the averaging for underline:
+    <p><img alt="In the first rendering of the underlined text '1st a'
+                 with 'st' as a superscript, both the '1st' and the 'a'
+                 are rendered in a small font. In the second rendering,
+                 the 'a' is rendered in a larger font. In the third, both
+                 '1st' and 'a' are large."
+            height="105" src="underline-averaging.gif" width="326">
+    <p>In the three fragments of underlined text, the underline is drawn
+      consecutively lower and thicker as the ratio of large text to small
+      text increases.</p>
+    <p>Using the same example, a line-through would in the second fragment,
+    instead of averaging the two font sizes,
+    split the line-through into two segments:
+    <p><img alt="" src="linethrough-averaging.gif">
+    <p>In both cases, however, the superscript, due to the vertical-alignment shift,
+    has no effect on the position of the line.
   </div>
+-->
 
   <p>Some font formats (such as OpenType) can offer information about the
    appropriate position of an underline. The UA should use such information

css-text-decor/Overview.src.html

@@ -680,35 +680,15 @@ <h3 id="text-underline-position-property">
       side of the text. (In horizontal writing modes, both values are
       treated as ''under''.)</p>
   </div>
+  
+  <p>The exact position and thickness of line decorations is UA-defined in this level.
+    However, the UA must use a single thickness and position on each line
+    for the decorations deriving from a single <i>decorating box</i>.
 
+<!--
 <h3 id="line-position">
 Determining the Position and Thickness of Line Decorations</h3>
-<!--
-  <p>Since line decorations can span elements with varying font sizes and
-    vertical alignments, the best position for a line decoration is not
-    necessarily the ideal position dictated by the <i>decorating box</i>.
-    In determining the position of text decoration lines within a given line box,
-    user agents must consider, for each <i>decorating box</i> on that line,
-    the “ideal” positions of such line decorations of each
-    run of text decorated by that <i>decorating box</i>
-    (each <dfn>considered run</dfn>).
-    However, descendants of the <i>decorating box</i>
-    that are skipped due to 'text-decoration-skip',
-    descendant inlines with ''text-decoration-skip: ink'',
-    and any descendants that do not participate in the <i>decorating box</i>’s inline formatting context
-    are excluded from the set of <i>considered fragments</i>.
 
-  <p>
-    <dfn>Decoration-affecting text</dfn> is any text decorated by a <i>decorating box</i>
-    that can affect the size and position of the decoration;
-    descendants that are skipped due to 'text-decoration-skip',
-    descendant inlines with ''text-decoration-skip: ink'',
-    and any descendants that do not participate in the <i>decorating box</i>’s inline formatting context
-    are not <i>considered fragments</i>.
-    The position and thickness of decorations on <i>considered fragments</i> are calculated by looking at sets of <i>considered fragments</i>:
-    each set is composed of all the <i>considered fragments</i> in a single line box 
-    and decorated by the same <i>decorating box</i>.
--->
   <p>Since line decorations can span elements with varying font sizes and
     vertical alignments, the best position for a line decoration is not
     necessarily the ideal position dictated by the <i>decorating box</i>.
@@ -731,7 +711,6 @@ <h3 id="line-position">
     <dt><a href="http://www.w3.org/TR/css-writing-modes/#over"><i>over</i></a> lines
     <dd>
       Align the line decoration with respect to the highest
-      <!-- <i>text-over</i> baseline of the considered fragments. -->
       <a href="http://www.w3.org/TR/css-writing-modes/#over"><i>over</i></a> EM-box edge
       of the <i>considered text</i>.
 
@@ -749,7 +728,6 @@ <h3 id="line-position">
     <dt>non-alphabetic <a href="http://www.w3.org/TR/css-writing-modes/#under"><i>under</i></a> lines
     <dd>
       Position the line decoration with respect to the lowest
-      <!-- <i>text-under</i> baseline of the considered fragments. -->
       <a href="http://www.w3.org/TR/css-writing-modes/#under"><i>under</i></a> EM-box edge
       of the <i>considered text</i>.
 
@@ -798,7 +776,7 @@ <h3 id="line-position">
     <p>In both cases, however, the superscript, due to the vertical-alignment shift,
     has no effect on the position of the line.
   </div>
-
+-->
   <p>Some font formats (such as OpenType) can offer information
     about the appropriate position of an underline.
     The UA should use such information (such as the underline thickness,