Update focus-visible guidance to match TAG feedback.

Author: robdodson

selectors-4/Overview.bs

@@ -2256,47 +2256,55 @@ The Focus-Indicated Pseudo-class: '':focus-visible''</h3>
 		like clicking on the button with a mouse pointer.
 	</div>
 
-	This pseudo-class is intended to give developers the ability to style focus
-	selectively, in order to encourage visible, usable focus styles, and
-	discourage the practice of disabling the default user agent focus style.
-
-	When UAs choose to specially indicate focus on an element,
-	or whether they specially indicate focus at all,
-	is UA-dependent.
-	Different UAs,
-	the same UA on different operating systems,
-	or the same UA on the same OS,
-	but with different user settings,
-	can make different choices as to when an element matches '':focus-visible''.
-
-	Since part of the problem is user agents' default focus indicator behaviour,
-	it is recommended that browsers implementing the `:focus-visible`
-	selector also use it in their user agent stylesheets to show the default focus
-	indicator.
-
-	<div class=note>
-		The user agent should take into account the available signals as to whether
-		the user might find focus indication useful. The result of these heuristics
-		must determine whether `:focus-visible` should match on the currently
-		focused element.
-
-		By default, if there are no signals indicating that focus should be
-		indicated, then focus SHOULD NOT be indicated on the focused element, unless
-		the user has expressed a preference for always seeing a focus ring.
-
-		The following may be considered signals:
-
-		* An element which requires the use of a keyboard, such as a text input,
-		SHOULD always have a visible focus indicator.
-		* If a user is using keyboard-based navigation by using the tab and arrow
-		keys, the focused element SHOULD be indicated. 
-		* If a user is interacting with an element via the keyboard (such as
-		incrementing or decrementing using the arrow keys, or using the spacebar to
-		activate a button) the focused element SHOULD be indicated.
-			* Note that keyboard interaction may trigger focus to be moved
-			programmatically, and this may be considered an extension of the original
-			keyboard interaction.
-
+	The goal of this selector is to explain how the browser's default focus
+	indicator behavior works in order to encourage more visible, usable focus
+	styles, and discourage the practice of disabling the default user agent focus
+	style.
+
+	For example, a `:focus` style will always be applied
+	to a focused element, regardless of _how_ it was focused. Whereas a
+	`:focus-visible` style would only be applied to an element if it matches the
+	same heuristic that the UA uses to draw its default focus indicator.
+
+	The user agent should take into account the available signals as to whether
+	the user might find focus indication useful. The result of these heuristics
+	must determine whether `:focus-visible` should match on the currently focused
+	element.
+
+	By default, if there are no signals indicating that focus should be
+	indicated, then focus should not be indicated on the focused element, unless
+	the user has expressed a preference for always seeing a focus ring.
+
+	The following may be considered signals:
+
+	* An element which requires the use of a keyboard, such as a text input,
+	should always have a visible focus indicator.
+	* If a user is using keyboard-based navigation by using the tab and arrow
+	keys, the focused element should be indicated. 
+	* If a user is interacting with an element via the keyboard (such as
+	incrementing or decrementing using the arrow keys, or using the spacebar to
+	activate a button) the focused element should be indicated.
+		* Note that keyboard interaction may trigger focus to be moved
+		programmatically, and this may be considered an extension of the original
+		keyboard interaction.
+
+	Because `:focus-visible` must match the UA's default behavior for when to show
+	a focus indicator, one way to meet this requirement would be to use
+	`:focus-visible` in the UA stylesheet itself.
+
+	<div class=advisement>
+		Page authors should follow these guidelines
+		when deciding whether to use '':focus'' or '':focus-visible''
+		to style the focused state of an element:
+
+		* If the element has “native” focus indicator behavior
+			(such as text fields or buttons),
+			use '':focus-visible''.
+		* Otherwise, if the element is emulating a text input,
+			or something else that is <em>intended</em> to receive keyboard interaction,
+			use '':focus''.
+		* Otherwise,
+			use '':focus-visible''.
 	</div>
 
 <h3 id="the-focus-within-pseudo">