[css-text-decor] Clarify note to avoid confusion such as <#160 (comment)>. Adjust wording in subsequent paragraph to help distinguish the two cases (baseline alignment vs. baseline shift). #160

fantasai · fantasai · commit 0ff76a5ed7ce · 2016-12-28T12:48:05.000+03:30
diff --git a/css-text-decor/Overview.bs b/css-text-decor/Overview.bs
@@ -73,7 +73,7 @@ Values</h3>
     <dfn><a href="https://www.w3.org/TR/css3-text/#content-language">content language</a></dfn>
     as used in this specification are defined in [[!CSS3TEXT]].
     Other terminology and concepts used in this specification are defined
-    in [[!CSS21]] and [[!CSS3-WRITING-MODES]].
+    in [[!CSS21]] and [[!CSS-WRITING-MODES-3]].
 
 <h2 id="line-decoration">
 Line Decoration: Underline, Overline, and Strike-Through</h2>
@@ -465,16 +465,30 @@ Text Underline Position: the 'text-underline-position' property</h3>
     For example, an overline positioned to a small font
     will effectively become a line-through if the element contains text in a significantly larger font-size.
     Even for underlines, if the text is not aligned to the alphabetic baseline
-    (for example, in vertical typesetting styles, text is aligned to the central baseline by default)
+    (for example, in vertical typesetting styles,
+    text is aligned by its central baseline by default [[CSS-WRITING-MODES-3]])
     an underline will cut through descendant text of a larger font-size.
+    UA consideration of descendant content will therefore result in better typography.
+
     <div class="figure">
       <p><img src="leftline-cross.png" alt="">
+         <img src="leftline-under.png" alt="">
+      <p class="caption">
+        Due to the central baseline alignment of vertical text,
+        a left-side underline on small vertical text will cut through the text
+        of a child with a larger font size.
+        The underline is not allowed to be broken,
+        but adjusting its position further to the left
+        properly accommodates all of the underlined text.
     </div>
   </div>
 
-  <p>UAs <em>must</em> adjust line positions to match the shifted metrics of <i>decorating boxes</i> positioned with 'vertical-align' [[!CSS21]]
+  <p>UAs <em>must</em> adjust line positions
+    to match the shifted metrics of <i>decorating boxes</i> shifted
+    with 'vertical-align' values other than ''vertical-align/baseline'' [[!CSS21]]
     or subscripted/superscripted via 'font-variant-position' [[!CSS3-FONTS]],
-    but <em>must not</em> adjust the line position or thickness in response to descendants of a <i>decorating box</i> that are so styled.
+    but <em>must not</em> adjust the line position or thickness
+    in response to descendants of a <i>decorating box</i> that are so styled.
     This allows superscripts and subscripts to be properly decorated
     (underlined, struck through, etc.)
     but prevents them from distorting or breaking the positioning of such decorations on their ancestors.
