Add how to calculate distance if the search origin is a point

Author: Jihye Hong

css-nav-1/Overview.bs

@@ -1211,19 +1211,19 @@ follow the following steps:
 4. Let <var>insiders</var> be the subset of <var>candidates</var> items
     whose [=DOM anchor=] are descendants of <var>searchOrigin</var>
     and whose <a>boundary box</a>'s
-    * top edge is below the top edge of <var>insideArea</var> if <var>D</var> is <code>down</code>
-    * bottom edge is above the bottom edge of <var>insideArea</var> if <var>D</var> is <code>up</code>
-    * right edge is left of the right edge of <var>insideArea</var> if <var>D</var> is <code>left</code>
-    * left edge is right of the left edge of <var>insideArea</var> if <var>D</var> is <code>right</code>
+    * top edge is below the top edge of <var>insideArea</var> if <var>dir</var> is <code>down</code>
+    * bottom edge is above the bottom edge of <var>insideArea</var> if <var>dir</var> is <code>up</code>
+    * right edge is left of the right edge of <var>insideArea</var> if <var>dir</var> is <code>left</code>
+    * left edge is right of the left edge of <var>insideArea</var> if <var>dir</var> is <code>right</code>
 
     Note: this sub-setting is necessary to avoid going in the opposite direction than the one requested.
 5.
     * If <var>insiders</var> is non empty
         1. Let <var>closest subset</var> be the subset of <var>insiders</var> whose <a>boundary box</a>'s
-            * top edge is closest to the top edge of <var>insideArea</var> if <var>D</var> is <code>down</code>
-            * bottom edge is closest to the bottom edge of <var>insideArea</var> if <var>D</var> is <code>up</code>
-            * right edge is closest to the right edge of <var>insideArea</var> if <var>D</var> is <code>left</code>
-            * left edge is closest to the left edge of <var>insideArea</var> if <var>D</var> is <code>right</code>
+            * top edge is closest to the top edge of <var>insideArea</var> if <var>dir</var> is <code>down</code>
+            * bottom edge is closest to the bottom edge of <var>insideArea</var> if <var>dir</var> is <code>up</code>
+            * right edge is closest to the right edge of <var>insideArea</var> if <var>dir</var> is <code>left</code>
+            * left edge is closest to the left edge of <var>insideArea</var> if <var>dir</var> is <code>right</code>
         2. If <var>closest subset</var> contains a single item,
             return that item,
             else return the first item of <var>closest subset</var> in document order,
@@ -1236,11 +1236,13 @@ follow the following steps:
         1. Set <var>candidates</var> be the subset of its items
             whose <a>boundary box</a>'s geometric center is within the closed half plane
             whose boundary goes through the geometric center of the <var>searchOrigin</var>
-            and is perpendicular to <var>D</var>.
+            and is perpendicular to <var>dir</var>.
         2. For each <var>candidate</var> in <var>candidates</var>,
-            find the points <var>P1</var> inside the <a>boundary box</a> of <var>searchOrigin</var>
-            and <var>P2</var> inside the <a>boundary box</a> of <var>candidate</var>
-            that minimize the <var>distance</var> between these two points,
+            1. If the <var>searchOrigin</var> is an element, then find the points <var>P1</var> inside the <a>boundary box</a> 
+                of <var>searchOrigin</var> and P2 inside the boundary box of <var>candidate</var>.
+            2. Else if the <var>searchOrigin</var> is a point, then let the point <var>P1</var> be the <var>searchOrigin</var> 
+                and find the point <var>P2</var> inside the <a>boundary box</a>.
+        3. Select the <var>P1</var> and <var>P2</var> that make the smallest <var>distance</var> between those two points, 
             when <var>distance</var> is defined as follows:
 
             <dl>