Polishing the processing model section

* Fix the confusing usages of 'search origin' terminology
* Add the definition of "Dispatching navbeforefocus event" and "Dispatching navnotarget event"

Author: Jihye Hong

css-nav-1/Overview.bs

@@ -22,6 +22,8 @@ spec: ui-events; urlPrefix: https://w3c.github.io/uievents/;
     type: event;
         text: keydown
         text: click
+    type: dfn;
+        text: event target
 spec: html; urlPrefix: https://html.spec.whatwg.org/multipage/;
     urlPrefix: interaction.html
         type: dfn;
@@ -691,7 +693,7 @@ For full normative details, see [[#processing-model]].
 <h4 id="event-type-navbeforefocus" class="non-normative">
 <dfn event for=NavigationEvent>navbeforefocus</dfn></h4>
 
-The <a event>navbeforefocus</a> event occurs before spatial navigation changes the focus.
+This event occurs when there is a valid result of <a>selecting the best candidate</a>.
 
 <table class="def">
     <tbody>
@@ -710,6 +712,9 @@ The <a event>navbeforefocus</a> event occurs before spatial navigation changes t
         <tr>
             <th>Attributes of the event
             <td><dl>
+                <dt>{{Event}}.{{Event/target}}
+                <dd>The element receiving focus
+
                 <dt>{{NavigationEvent}}.{{NavigationEvent/relatedTarget}}
                 <dd>The DOM anchor of the focusable area that will be focused
 
@@ -719,6 +724,14 @@ The <a event>navbeforefocus</a> event occurs before spatial navigation changes t
     </tbody>
 </table>
 
+The User Agent <dfn lt="dispatches navbeforefocus event | dispatching navbeforefocus event">dispatches <a event>navbeforefocus</a> event</dfn>
+before spatial navigation moves the focus.
+The <a>event target</a> is the element which has focus and 
+the {{NavigationEvent/relatedTarget}} is the element which is about to receive focus.
+
+If <a>navigation-override</a> is disabled in the [=node document=] of <var>eventTarget</var> for 
+the <a spec=html for="/">origin</a> of the [=active document=] of the [=top-level browsing context=], this event won't be dispatched.
+
 <div class='example'>
     This example shows the [[UI-EVENTS#event-order]] when pressing the <code class=key>ArrowRight</code>
     key.
@@ -763,7 +776,7 @@ The <a event>navbeforefocus</a> event occurs before spatial navigation changes t
 <h4 id="event-type-navnotarget" class="non-normative">
 <dfn event for=NavigationEvent>navnotarget</dfn></h4>
 
-The <a event>navnotarget</a> event occurs before going up the tree to search candidates in the
+This event occurs before going up the tree to search candidates in the
 nearest ancestor <a>spatial navigation container</a> when spatial navigation has failed to find any candidate
 within the current <a>spatial navigation container</a>,
 and in cases where the <a>spatial navigation container</a> is scrollable,
@@ -786,6 +799,9 @@ when it cannot be scrolled further.
         <tr>
             <th>Attributes of the event
             <td><dl>
+                <dt>{{Event}}.{{Event/target}}
+                <dd>The element receiving focus
+
                 <dt>{{NavigationEvent}}.{{NavigationEvent/relatedTarget}}
                 <dd>The <a>spatial navigation container</a> that was searched in.
 
@@ -795,6 +811,13 @@ when it cannot be scrolled further.
     </tbody>
 </table>
 
+The User Agent <dfn lt="dispatches navnotarget event | dispatching navnotarget event">dispatches <a event>navnotarget</a> event</dfn>
+with initializing the <a>event target</a> as the element which has focus and 
+the {{NavigationEvent/relatedTarget}} as <a>spatial navigation container</a> of the <a>event target</a>.
+
+If <a>navigation-override</a> is disabled in the [=node document=] of <var>eventTarget</var> for 
+the <a spec=html for="/">origin</a> of the [=active document=] of the [=top-level browsing context=], this event won't be dispatched.
+
 <div class='example'>
     This example shows the [[UI-EVENTS#event-order]] when pressing the <code class=key>ArrowDown</code>
     key in the situation like the following figure.
@@ -947,7 +970,6 @@ to fully define the behavior.
 Issue(w3c/csswg-drafts#3376): The following currently does not account
 for <a href="https://github.com/WICG/overscroll-behavior">the proposed overscroll-behavior specification</a>.
 
-
 <h3 id=grouping>
 Groupings of elements</h3>
 
@@ -996,15 +1018,15 @@ To run the <dfn>spatial navigation steps</dfn> in <var>direction</var>, do the f
         set <var>eventTarget</var> be <a>the body element</a> if it is not <code>null</code>
         or to the <a>document element</a> otherwise.
 4.  <ul>
-        <span class=cssapi><li>If <var>searchOrigin</var> is <a>scroll container</a>
-            and the computed value of the 'spatial-navigation-action' property on <var>searchOrigin</var> is ''spatial-navigation-action/scroll''
-            and <var>searchOrigin</var> [=can be manually scrolled=],
-            then [=directionally scroll the element=] <var>searchOrigin</var> and return.</li></span>
-        <li><span class=cssapi>Else,</span> if <var>searchOrigin</var> is either a <a>scroll container</a> or the <a>document</a>
+        <span class=cssapi><li>If <var>eventTarget</var> is <a>scroll container</a>
+            and the computed value of the 'spatial-navigation-action' property on <var>eventTarget</var> is ''spatial-navigation-action/scroll''
+            and <var>eventTarget</var> [=can be manually scrolled=],
+            then [=directionally scroll the element=] <var>eventTarget</var> and return.</li></span>
+        <li><span class=cssapi>Else,</span> if <var>eventTarget</var> is either a <a>scroll container</a> or the <a>document</a>
             1. Let <var>candidates</var> be the result of <a>finding focusable areas</a>
-                within <var>searchOrigin</var>
+                within <var>eventTarget</var>
                 with the argument <var>visibleOnly</var> set to <code>false</code>
-                <span class=cssapi>if computed value of the 'spatial-navigation-action' property on <var>searchOrigin</var>
+                <span class=cssapi>if computed value of the 'spatial-navigation-action' property on <var>eventTarget</var>
                 is ''spatial-navigation-action/focus'' or to <code>true</code> otherwise.
                 </span>
             2.  
@@ -1016,17 +1038,9 @@ To run the <dfn>spatial navigation steps</dfn> in <var>direction</var>, do the f
                     <li><span class=cssapi>Else </span>if <var>candidates</var> contains at least 1 item:
                         1. Let <var>bestCandidate</var> be the result of <a>selecting the best candidate</a>
                             within <var>candidates</var> in <var>direction</var> starting from <var>searchOrigin</var>
-                        <p class=api>
-                        2. If <a>navigation-override</a> <a>is enabled</a> in the [=node document=] of <var>eventTarget</var> for 
-                            the <a spec=html for="/">origin</a> of the [=active document=] of the [=top-level browsing context=], then
-                                <a>fire an event</a> named <a event>navbeforefocus</a> at <var>eventTarget</var> using {{NavigationEvent}} with:
-                                    <ul>
-                                        <li>{{NavigationEvent/dir}} set to <var>direction</var>
-                                        <li>{{NavigationEvent/relatedTarget}} set to <var>bestCandidate</var>
-                                        <li>the <code>bubbles</code> and <code>cancelable</code> attributes set to <code>true</code>
-                                    </ul>
-                                and return if the result is <code>false</code>.
-                        </p>
+                                <p class=api>
+                        2. <a>Dispatches navbeforefocus event</a> at <var>eventTarget</var> with <var>direction</var> and <var>bestCandidate</var>.
+                                </p>
                         3. Run the <a>focusing steps</a> for <var>bestCandidate</var> and return
                     </li>
                     <li>Else, fall back to the next step.</li>
@@ -1041,7 +1055,7 @@ To run the <dfn>spatial navigation steps</dfn> in <var>direction</var>, do the f
     <span class=cssapi>
     if computed value of the 'spatial-navigation-action' property on <var>container</var> is ''spatial-navigation-action/focus''
     or to <code>true</code> otherwise,
-    excluding <var>searchOrigin</var>
+    excluding <var>eventTarget</var>
     </span>
 7. If <var>candidates</var> is empty:
     <ul>
@@ -1050,34 +1064,22 @@ To run the <dfn>spatial navigation steps</dfn> in <var>direction</var>, do the f
             <a>directionally scroll the element</a> <var>container</var> in <var>direction</var> and return.
         </li></span>
         <span class=cssapi><li>Else,</li></span>
-            1. If <a>navigation-override</a> <a>is enabled</a> in the [=node document=] of <var>eventTarget</var> for the <a spec=html for="/">origin</a> of the [=active document=] of the [=top-level browsing context=], then
-                <span class=api><a>fire an event</a> named <a event>navnotarget</a> at <var>eventTarget</var> using {{NavigationEvent}} with:
-                * {{NavigationEvent/dir}} set to <var>direction</var>
-                * {{NavigationEvent/relatedTarget}} set to <var>container</var>
-                * the <code>bubbles</code> and <code>cancelable</code> attributes set to <code>true</code>
-
-                and return if the result is <code>false</code>.</span>
+            1. <a>Dispatches navnotarget event</a> at <var>eventTarget</var> with <var>direction</var> and <var>container</var>.
             2.
                 * If <var>container</var> is the <a>document element</a> of the <a>top-level browsing context</a>,
                     then return.
                     The User Agent may transfer focus to its own controls (if any) honouring <var>direction</var>.
                 * Else, if <var>container</var> is the <a>document element</a> of a <a>nested browsing context</a> then:
                     1. Set <var>searchOrigin</var> to <var>container</var>'s <a>browsing context container</a>
                     2. Set <var>eventTarget</var> be <var>searchOrigin</var>
-                    3. Set <var>container</var> to the nearest ancestor of <var>searchOrigin</var> that is a <a>spatial navigation container</a>.
+                    3. Set <var>container</var> to the nearest ancestor of <var>eventTarget</var> that is a <a>spatial navigation container</a>.
                     4. Return to the step labeled <i>loop</i>.
                 * Else, set <var>container</var> to its closest ancestor that is itself a <a>spatial navigation container</a>
                     and return to the step labeled <i>loop</i>.
     </ul>
 8. Let <var>bestCandidate</var> be the result of <a>selecting the best candidate</a>
-    within <var>candidates</var> in <var>direction</var> starting from <var>searchOrigin</var>.
-9. If <a>navigation-override</a> <a>is enabled</a> in the [=node document=] of <var>eventTarget</var> for the <a spec=html for="/">origin</a> of the [=active document=] of the [=top-level browsing context=], then
-    <span class=api><a>fire an event</a> named <a event>navbeforefocus</a> at <var>eventTarget</var> using {{NavigationEvent}} with:
-    * {{NavigationEvent/dir}} set to <var>direction</var>
-    * {{NavigationEvent/relatedTarget}} set to <var>bestCandidate</var>
-    * the <code>bubbles</code> and <code>cancelable</code> attributes set to <code>true</code>
-
-    and return if the result is <code>false</code>.</span>
+    within <var>candidates</var> in <var>direction</var> starting from <var>eventTarget</var>.
+9. <a>Dispatches navnotarget event</a> at <var>eventTarget</var> with <var>direction</var> and <var>bestCandidate</var>.
 10. Run the <a>focusing steps</a> for <var>bestCandidate</var> and return.
 
 </div>