Make the focus fixup rule more explicit

* Split it into two variants: one which runs synchronously on HTML element removal, and one which runs during "update the rendering". Closes #8225.

* After this split, only the "update the rendering" variant causes the normal focus algorithms to run, and thus blur and change events to fire.

* Delete the confusing "somehow unfocused without another element being explicitly focused" sentence.

Fixes #3847. Fixes #6729.

source

@@ -1804,6 +1804,18 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
   <var>removedNode</var> and optionally <var>oldParent</var>, are defined as the following:</p>
 
   <ol>
+   <li id="node-remove-focus-fixup">
+    <p>If <var>removedNode</var>'s <span>node document</span>'s <span data-x="focused area of the
+    document">focused area</span> is <var>removedNode</var>, then set <var>removedNode</var>'s
+    <span>node document</span>'s <span data-x="focused area of the document">focused area</span> to
+    <var>removedNode</var>'s <span>node document</span>'s <span>viewport</span>.</p>
+
+    <p class="note">This does <em>not</em> perform the <span>unfocusing steps</span>,
+    <span>focusing steps</span>, or <span>focus update steps</span>, and thus no <code
+    data-x="event-blur">blur</code> or <code data-x="event-change">change</code> events are
+    fired.</p>
+   </li>
+
    <li><p>If <var>removedNode</var> is an element whose <span
    data-x="concept-element-namespace">namespace</span> is the <span>HTML namespace</span>, and this
    standard defines <span data-x="html element removing steps">HTML element removing steps</span>
@@ -59153,9 +59165,9 @@ interface <dfn interface>HTMLDialogElement</dfn> : <span>HTMLElement</span> {
 
     <p class="note" id="note-dialog-plus-focus-fixup">This will cause the <span>focused area of the
     document</span> to become <span>inert</span> (unless that currently focused area is a
-    <span>shadow-including descendant</span> of <var>subject</var>). In such cases, the <span>focus
-    fixup rule</span> will kick in and reset the <span>focused area of the document</span> to the
-    <span>viewport</span> for now. In a couple steps we will attempt to find a better candidate to
+    <span>shadow-including descendant</span> of <var>subject</var>). In such cases, the
+    <span>focused area of the document</span> will soon be <a href="#focus-fixup-rule">reset</a> to
+    the <span>viewport</span>. In a couple steps we will attempt to find a better candidate to
     focus.</p>
    </li>
 
@@ -76866,39 +76878,14 @@ partial interface <span id="NavigatorUserActivation-partial">Navigator</span> {
    </li>
   </ol>
 
-  <p>When the <span>currently focused area of a top-level traversable</span> is somehow unfocused
-  without another element being explicitly focused in its stead, the user agent must
-  <span>immediately</span> run the <span>unfocusing steps</span> for that object.</p>
-
-  <p class="note">The <span>unfocusing steps</span> do not always result in the focus changing,
-  even when applied to the <span>currently focused area of a top-level traversable</span>. For
+  <p class="note">The <span>unfocusing steps</span> do not always result in the focus changing, even
+  when applied to the <span>currently focused area of a top-level traversable</span>. For
   example, if the <span>currently focused area of a top-level traversable</span> is a
   <span>viewport</span>, then it will usually keep its focus regardless until another
   <span>focusable area</span> is explicitly focused with the <span>focusing steps</span>.</p>
 
   <hr>
 
-  <p><dfn>Focus fixup rule</dfn>: When the designated <span data-x="focused area of the
-  document">focused area of the document</span> is removed from that <code>Document</code> in some
-  way (e.g. it stops being a <span>focusable area</span>, it is removed from the DOM, it becomes
-  <span>inert</span>, etc.), designate the <code>Document</code>'s <span>viewport</span> to be the
-  new <span>focused area of the document</span>.</p>
-
-  <p class="example">For example, this might happen because an element is removed from its
-  <code>Document</code>, or has a <code data-x="attr-hidden">hidden</code> attribute added. It might
-  also happen to an <code>input</code> element when the element gets <span
-  data-x="concept-fe-disabled">disabled</span>.</p>
-
-  <p class="example">In a <code>Document</code> whose <span data-x="focused area of the
-  document">focused area</span> is a <code>button</code> element, removing, disabling, or hiding
-  that button would cause the page's new <span data-x="focused area of the document">focused
-  area</span> to be the <span>viewport</span> of the <code>Document</code>. This would, in turn,
-  be reflected through the <code
-  data-x="dom-documentorshadowroot-activeElement">activeElement</code> API as <span>the body
-  element</span>.</p>
-
-  <hr>
-
   <p>The <dfn>focus update steps</dfn>, given an <var>old chain</var>, a <var>new chain</var>, and a <var>new focus target</var> respectively, are as
   follows:</p>
 
@@ -76945,8 +76932,9 @@ partial interface <span id="NavigatorUserActivation-partial">Navigator</span> {
       named <code data-x="event-blur">blur</code> at <var>blur event target</var>, with
       <var>related blur target</var> as the related target.</p>
 
-      <p class="note">In some cases, e.g. if <var>entry</var> is an <code>area</code>
-      element's shape, a scrollable region, or a <span>viewport</span>, no event is fired.</p>
+      <p class="note" id="note-sometimes-no-blur-event">In some cases, e.g. if <var>entry</var> is
+      an <code>area</code> element's shape, a scrollable region, or a <span>viewport</span>, no
+      event is fired.</p>
      </li>
     </ol>
    </li>
@@ -99573,6 +99561,27 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
       </ol>
      </li>
 
+     <li id="focus-fixup-rule">
+      <p>For each <span>fully active</span> <code>Document</code> in <var>docs</var>, if the <span
+      data-x="focused area of the document">focused area</span> of that <code>Document</code> is no
+      longer a <span>focusable area</span>, then run the <span>focusing steps</span> for that
+      <code>Document</code>'s <span>viewport</span>.</p>
+
+      <p class="example">For example, this might happen because an element has the <code
+      data-x="attr-hidden">hidden</code> attribute added, causing it to stop <span>being
+      rendered</span>. It might also happen to an <code>input</code> element when the element gets
+      <span data-x="concept-fe-disabled">disabled</span>.</p>
+
+      <p class="note">This will <a href="#note-sometimes-no-blur-event">usually</a> fire <code
+      data-x="event-blur">blur</code> events, and possibly <code data-x="event-change">change</code>
+      events.</p>
+
+      <p class="note">In addition to this asynchronous fixup, if the <span>focused area of the
+      document</span> is removed, there is a <a href="#node-remove-focus-fixup">synchronous
+      fixup</a>. That one will <em>not</em> fire <code data-x="event-blur">blur</code> or <code
+      data-x="event-change">change</code> events.</p>
+     </li>
+
      <li><p>For each <span>fully active</span> <code>Document</code> in <var>docs</var>, <span>run
      the update intersection observations steps</span> for that <code>Document</code>, passing in
      <var>now</var> as the timestamp. <ref spec=INTERSECTIONOBSERVER></p></li>