[css-display] Add ruby values.

Author: tabatkins

css-display/Overview.bs

@@ -86,7 +86,7 @@ Setting the layout mode: the 'display-inside' property</h3>
 			If the element's computed 'display-outside' value is ''inline-level'',
 			the element is an inline element,
 			and lays out its contents using inline layout. [[!CSS21]]
-			If the element's computed 'display-outside' value is ''table-row-group'', ''table-header-group'', ''table-footer-group'', ''table-row'', ''table-column-group'', or ''table-column'',
+			If the element's computed 'display-outside' value is an <a>layout-specific display role</a>,
 			this elements acts as normal for its given 'display-outside' value.
 			Otherwise, this value computes to ''display-inside/block''.
 
@@ -105,6 +105,10 @@ Setting the layout mode: the 'display-inside' property</h3>
 		<dt><dfn>grid</dfn>
 		<dd>
 			The element lays out its contents using grid layout. [[!CSS3-GRID-LAYOUT]]
+
+		<dt><dfn>ruby</dfn>
+		<dd>
+			The element lays out its contents using ruby layout. [[!CSS3RUBY]]
 	</dl>
 
 
@@ -151,8 +155,23 @@ Interacting with the layout mode: the 'display-outside' property</h3>
 		<dd>
 			The element is an internal table element,
 			and participates in a table layout context. [[!CSS21]]
+			These values are all <a>layout-specific display roles</a>.
+
+		<dt><dfn>ruby-base</dfn>, <dfn>ruby-text</dfn>, <dfn>ruby-base-container</dfn>, <dfn>ruby-text-container</dfn>
+		<dd>
+			The element is an internal ruby element,
+			and participates in a ruby layout context. [[!CSS3RUBY]]
+			These values are all <a>layout-specific display roles</a>.
 	</dl>
 
+	Some values of 'display-outside' are specialized for particular formatting contexts,
+	and don't have meaning outside of those specific contexts.
+	These values are called <dfn title="layout-specific display role">layout-specific display roles</dfn>.
+	Generally, a <a>layout-specific display role</a> will generate wrapper boxes around itself
+	to ensure that it ends up in the correct formatting context,
+	if it's not placed in an appropriate formatting context;
+	the details of this are specified by each layout mode.
+
 	<p class='issue'>
 		Do we need special bits about some of the interactions with 'display-inside'?
 		For example, how ''display:inline-level block;'' works?