[css-writing-modes] Use box parentage instead of containing block, since in the cases where any of these rules take effect, the same output would result. Fixes #1212.

fantasai · fantasai · commit b59c4e2e1e47 · 2017-05-02T15:05:35.000-04:00
diff --git a/css-writing-modes/Overview.bs b/css-writing-modes/Overview.bs
@@ -881,12 +881,13 @@ Block Flow Direction: the 'writing-mode' property</h3>
             src="images/vertical-form.png"></p>
   </div>
 
-  <p>If a box has a different 'writing-mode' value than its containing block:
+  <p>If a box has a different 'writing-mode' value than its parent box
+    (i.e. nearest ancestor without ''display: contents''):
   <ul>
-   <li>If the box has a specified 'display' of ''display/inline'',
-     its 'display' computes to ''inline-block''. [[!CSS21]]
-   <li>If the box is a block container, then it establishes a new block
-     formatting context.
+   <li>If the box would otherwise become an in-flow box with a computed 'display' of ''inline'',
+     its 'display' computes instead to ''inline-block''.
+   <li>If the box is a block container,
+     then it establishes a new block formatting context.
    <li>More generally, if its specified <a>inner display type</a> is ''flow'',
      then its computed <a>inner display type</a> becomes ''flow-root''. [[!CSS-DISPLAY-3]]
   </ul>
