[selectors] Clarify that the 'match if descendants match' user-input pseudos work on the flat tree, and work if a non-element node matches (like hovering over text).

Author: tabatkins

selectors/Overview.bs

@@ -282,8 +282,8 @@ Selectors Overview</h2>
 				<td>2
 			<tr>
 				<td><code>E:focus-ring</code>
-				<td>an E element that has user input focus, 
-					and the UA has determined that a focus ring or other indicator 
+				<td>an E element that has user input focus,
+					and the UA has determined that a focus ring or other indicator
 					should be drawn for that element
 				<td>[[#useraction-pseudos]]
 				<td>4
@@ -1989,7 +1989,10 @@ The Pointer Hover Pseudo-class: '':hover''</h3>
 	(e.g., a pen device that does not detect hovering)
 	are still conforming.
 
-	An element also matches '':hover'' if one of its <a>shadow-including descendants</a> matches '':hover''.
+	An element also matches '':hover''
+	if one of its descendants in the <a>flat tree</a>
+	(including non-element nodes, such as text nodes)
+	matches the above conditions.
 
 	Document languages may define additional ways in which an element can match '':hover''.
 	For example, [[HTML5]] defines a labeled control element as <a href="http://www.whatwg.org/html/selectors.html#selector-hover">matching <code>:hover</code></a>
@@ -2016,7 +2019,10 @@ The Activation Pseudo-class: '':active''</h3>
 	which elements can become '':active''.
 	For example, [[HTML5]] defines a <a href="http://www.whatwg.org/html/selectors.html#selector-active">list of activatable elements</a>.
 
-	An element also matches '':active'' if one of its <a>shadow-including descendants</a> matches '':active''.
+	An element also matches '':active''
+	if one of its descendants in the <a>flat tree</a>
+	(including non-element nodes, such as text nodes)
+	matches the above conditions.
 
 	Document languages may define additional ways in which an element can match '':active''.
 
@@ -2026,8 +2032,8 @@ The Activation Pseudo-class: '':active''</h3>
 <h3 id="the-focus-pseudo">
 The Input Focus Pseudo-class: '':focus''</h3>
 
-	The <dfn id='focus-pseudo'>:focus</dfn> pseudo-class applies 
-	while an element has the focus 
+	The <dfn id='focus-pseudo'>:focus</dfn> pseudo-class applies
+	while an element has the focus
 	(accepts keyboard or mouse events, or other forms of input).
 
 	There may be document language or implementation specific limits on
@@ -2046,26 +2052,26 @@ The Input Focus-Ring Pseudo-class: '':focus-ring''</h3>
 	<em>and</em> the UA determines via heuristics
 	that the focus should be specially indicated on the element
 	(typically via a "focus ring").
-	
+
 	<div class=example>
 		For example, UAs typically display focus indicators on text elements
 		<em>whenever</em> they're focused,
 		to draw attention to the fact that keyboard input will affect their contents.
-		
+
 		On the other hand, they typically only display focus indicators on buttons
 		when they were focused by a keyboard interaction
-		(such as tabbing thru the document), 
+		(such as tabbing thru the document),
 		because it's not always immediately obvious where the focus will move
 		after such an interaction,
 		but not when they were focused by more "obvious" interactions,
 		like clicking on the button with a mouse pointer.
 	</div>
-	
+
 	<div class=advisement>
 		Page authors should follow these guidelines
 		when deciding whether to use '':focus'' or '':focus-ring''
 		to style the focused state of an element:
-		
+
 		* If the element has "native" focus indicator behavior
 			(such as text fields or buttons),
 			use '':focus-ring''.
@@ -2075,7 +2081,7 @@ The Input Focus-Ring Pseudo-class: '':focus-ring''</h3>
 		* Otherwise,
 			use '':focus-ring''.
 	</div>
-	
+
 	When UAs choose to specially indicate focus on an element,
 	or whether they specially indicate focus at all,
 	is UA-dependent.
@@ -2084,12 +2090,12 @@ The Input Focus-Ring Pseudo-class: '':focus-ring''</h3>
 	or the same UA on the same OS,
 	but with different user settings,
 	can make different choices as to when an element matches '':focus-ring''.
-	
+
 	<div class=example>
 		The following guidelines are suggested heuristics
-		for choosing when to apply '':focus-ring'' 
+		for choosing when to apply '':focus-ring''
 		to elements without "native" focus ring behavior:
-		
+
 		* If the element received focus via a keyboard interaction,
 			including indirectly,
 			such as triggering a dialog
@@ -2105,7 +2111,10 @@ The Generalized Input Focus Pseudo-class: '':focus-within''</h3>
 
 	The <dfn id='focus-within-pseudo'>:focus-within</dfn> pseudo-class applies to elements for which the '':focus'' pseudo class applies.
 
-	An element also matches '':focus-within'' if one of its <a>shadow-including descendants</a> matches '':focus''.
+	An element also matches '':focus-within''
+	if one of its descendants in the <a>flat tree</a>
+	(including non-element nodes, such as text nodes)
+	matches the conditions for matching '':focus''.
 
 <h3 id="drag-pseudos">
 The Drag-and-Drop Pseudo-class: '':drop'' and '':drop()''</h3>