Improve text-combine: upright definition

Author: fantasai

css3-writing-modes/Overview.src.html

@@ -725,7 +725,7 @@ <h2 id="text-combine">Glyph Composition: the 'text-combine' property</h2>
       </tr>
       <tr>
         <th>Applies to:</th>
-        <td>inline elements</td>
+        <td>non-replaced inline elements</td>
       </tr>
       <tr>
         <th>Inherited:</th>
@@ -747,22 +747,28 @@ <h2 id="text-combine">Glyph Composition: the 'text-combine' property</h2>
   </table>
 
   <p>This property allows the combination of multiple characters into the
-    space of a single glyph. Values have the following meanings:</p>
+    space of a single character. For text layout purposes, e.g. bidi
+    ordering, line-breaking, emphasis marks, text-decoration, etc. the
+    resulting composition is treated as a single glyph representing the
+    Object Replacement Character U+FFFC. Values have the following
+    meanings:</p>
 
   <dl>
     <dt><dfn title="text-combine:none">none</dfn>
     <dd>No special processing.</dd>
     <dt><dfn title="text-combine:cluster">cluster</dfn>
     <dd>Display the text contents of the element in a single 1em square
-      using the Japanese "kumoji" rules. [[JISX4051]]
-      <span class="issue">This doesn't appear in the JLReq document, so
-      we can probably drop this value for now.</span>
+      using the Japanese "kumoji" rules. [[JISX4051]] The baseline of
+      the composition should be chosen to either match the baseline
+      of a typical ideographic character in the element's font, or to
+      center the composition between the content edges of its parent
+      inline box.
+      <span class="issue">This doesn't appear in the JLReq document.</span>
     </dd>
     <dt><dfn title="text-combine:upright">upright</dfn>
     <dd><p>In vertical writing mode, attempt to display the text contents
       of the element horizontally within the vertical line box, ideally
       within the space of one ideographic character (1em square), as follows:
-
     <p>If the UA has compressed glyphs available for the contents of the
       element, then it should use those glyphs to attempt sizing the
       contents to 1em square. For example, a single-digit number should
@@ -771,14 +777,12 @@ <h2 id="text-combine">Glyph Composition: the 'text-combine' property</h2>
       available, else halfwidth glyphs), etc. The glyphs are stacked
       horizontally (similar to the contents of an inline-box with a
       horizontal writing mode and a line-height of 1em) and the baseline
-      of the result chosen such that it is centered between the content
-      edges of its parent inline box.
-
+      of the resulting composition chosen such that it is centered between
+      the content edges of its parent inline box.
     <p>If the length of the element's contents exceeds the element's used
       line-height, then its contents are instead rendered as if
-      ''text-combine'' were ''none'' and ''text-orientation'' were
-      ''upright''. This fallback behavior is also triggered if the element
-      contains anything other than text.
+      ''text-combine'' were ''none''. This fallback behavior is also
+      triggered if the element contains anything other than text.
     <p>In horizontal mode this value is equivalent to ''none''.
     </dd>
   </dl>