Add section about when to draw or not a focus ring

This section describes a set of heuristics to determine
if the currently focused element should have or not a focus ring.

source

@@ -74349,6 +74349,42 @@ END:VCARD</pre>
    <pre><code class="html">&lt;div contenteditable autofocus&gt;Edit &lt;strong>me!&lt;/strong>&lt;div></code></pre>
   </div>
 
+  <h4>Focus rings</h4>
+
+  <p>User agents should use the following heuristics in order to determine when to <dfn>indicate
+  focus</dfn>, such as by drawing a focus ring and matching <code>:focus-visible</code>, on the
+  currently focused element:</p>
+
+  <ul>
+   <li><p>If the user has expressed a preference (such as via a system preference or a browser
+   setting) to always see a visible focus indicator, <span>indicate focus</span> regardless of any
+   other factors. (Another option may be for the user agent to show its own focus indicator
+   regardless of author styles.)</p></li>
+
+   <li><p>If the currently focused element supports keyboard input (such as an input element, or any
+   other element that would trigger a virtual keyboard to be shown on focus if a physical keyboard
+   were not present), <span>indicate focus</span>.</p></li>
+
+   <li><p>If the user interacts with the page via keyboard or some other non-pointing device,
+   <span>indicate focus</span>. (This means keyboard usage may change whether focus ring is drawn
+   even if focus isn't affected).</p></li>
+
+   <li><p>If the user interacts with the page via a pointing device (mouse, touchscreen, etc.) and
+   the focused element does not support keyboard input, don't <span>indicate focus</span>.</p></li>
+
+   <li><p>If a script causes focus to be set:</p>
+
+     <ol>
+       <li><p>If the last time <span>focus update steps</span> have been run <var>focus
+       trigger</var> was "<code data-x="">click</code>", don't <span>indicate
+       focus</span>.</p></li>
+
+       <li><p>Otherwise, <span>indicate focus</span>.</p></li>
+     </ol>
+
+   </li>
+  </ul>
+
 
 
   <h3>Assigning keyboard shortcuts</h3>