[css-inline] change applies-to definition based on w3c#2184

Author: dauwhe

css-inline-3/Overview.bs

@@ -434,7 +434,7 @@ Creating Initial Letters: the 'initial-letter' property</h3>
 	Name: <dfn id="propdef-initial-letter">initial-letter</dfn>
 	Value: normal | [<<number>> <<integer>>?]
 	Initial: normal
-	Applies to: <code>::first-letter</code> pseudo-elements and inline-level first child of a block container
+	Applies to: <code>::first-letter</code> pseudo-elements and <a href="#first-most-inline-level">certain inline-level boxes</a> (see prose)
 	Inherited: no
 	Percentages: N/A
 	Media: visual
@@ -512,9 +512,55 @@ Creating Initial Letters: the 'initial-letter' property</h3>
 		The following code will create a 2-line dropped initial letter at the beginning of each paragraph:
 		<pre>p::first-letter { initial-letter: 2; }</pre>
 	</div>
-
-	The 'initial-letter' property does not apply to boxes
-	that are not positioned at the start of the line due to bidi reordering.
+	
+	<p id="first-most-inline-level">
+	To give authors more control over which characters can be styled as an <a>initial letter</a>
+	and to allow the possibility of multi-character <a>initial letters</a>
+	(such as for first word or first phrase styling),
+	the 'initial-letter' property applies not just
+	to the CSS-defined ''::first-letter'' pseudo-element,
+	but also to any
+	“first-most inline-level descendant” of a block container--
+	an inline-level box which is the first child of a block container
+	is a “first-most inline-level descendant” of that block container,
+	as is the first child of an inline box
+	that is itself a “first-most inline-level descendant” of the block container.
+	(Note, this definition is recursive.)
+	However, the 'initial-letter' property does not apply to any box
+	that is itself a descendant of an <a>initial letter box</a>.
+	It also does not apply to a box
+	that is not positioned at the start of the line due to bidi reordering.
+	
+	<div class="example">
+		For example,
+		the <code>&lt;span></code>, <code>&lt;em></code>, and <code>&lt;b></code> elements
+		in the following example are
+		"first-most inline-level descendants" of the <code>&lt;p></code>,
+		but the <code>&lt;strong></code> element
+		is not:
+		
+		<xmp>
+			<p><span><em><b>This phrase</b> is styled</em> <strong>specially</strong>. &hellip;</span>
+		</xmp>
+		
+		If we apply the following rules:
+		
+		<pre>
+			em { initial-letter: 2; }
+			b { initial-letter: 3; }
+		</pre>
+		
+		The result might be rendered as
+		
+		<pre>
+			[ADD RENDERING HERE]
+			THIS PHRASE IS STYLED specially. &hellip;
+		</pre>
+		
+		(Note that the styling on <code>&lt;b></code>
+		is ignored,
+		as it has an ancestor already styled as an <a>initial letter</a>.)
+	</div>
 
 	The 'initial-letter' property is undefined on children of <a>ruby</a> base container boxes
 	and on <a>ruby</a> container boxes.