[css-nav-1] Define the inside area in general

Define "inside area" in general and use that term elsewhere.

Author: Jihye Hong

css-nav-1/Overview.bs

@@ -1066,9 +1066,14 @@ including all graphical transformations, such as <a>relative positioning</a> or
 
 The <dfn>boundary box</dfn> of an object is defined as follows:
 * if the object is a point, the boundary box is that point
-* if the object is a [=box=] or [=box fragment=], the boundary box is the <a>border box</a> of that box or fragment.
+* if the object is a [=box=] or [=box fragment=], the boundary box is the <a>border box</a> of that box or fragment
 * if the object is a <a>focusable area</a> which is not an element, the boundary box is the axis-aligned the bounding box of that <a>focusable area</a>
 
+The <dfn>inside area </dfn> of an object is defined as follows:
+* if the object is a <a>scroll container</a>, its <a>optimal viewing region</a>
+* if the object is a <a>document</a>, the viewport of its <a>browsing context</a>
+* otherwise, the <a>optimal viewing region</a> of its nearest ancestor <a>scroll container</a>
+
 Issue(w3c/csswg-drafts#2324): CSS should have a term for “border box taking into account corner shaping properties like border-radius”.
 
 <div algorithm="to find focusable areas">
@@ -1087,13 +1092,9 @@ run the following steps:
     return <var>focusables</var>.
 
     Note: <var>focusables</var> may be empty
-4. Let <var>insideArea</var> be
-    * the <a>optimal viewing region</a> of <var>C</var> if <var>C</var> is a <a>scroll container</a>,
-    * the viewport of <var>C</var>'s <a for="/">browsing context</a> if <var>C</var> is a <a>Document</a>,
-    * the <a>optimal viewing region</a> of <var>C</var>'s nearest ancestor <a>scroll container</a> otherwise.
-5. Let <var>visibles</var> be the subset of items in <var>focusables</var>
+4. Let <var>visibles</var> be the subset of items in <var>focusables</var>
     whose <a>boundary box</a>
-    is at least partly within <var>insideArea</var>.
+    is at least partly within the <a>inside area</a> of <var>C</var>.
 
     <div class="advisement non-normative">
     Except for elements that are in the currently non visible part of a scroller,
@@ -1109,7 +1110,7 @@ run the following steps:
     or the <a href="https://github.com/WICG/inert"><code>inert</code></a> attribute.
     </div>
 
-6. Return <var>visibles</var>.
+5. Return <var>visibles</var>.
 
     Note: <var>visibles</var> may be empty
 
@@ -1125,25 +1126,21 @@ run the following steps:
 
 1. If <var>candidates</var> is <a spec=infra for=set>empty</a>, return <code>null</code>
 2. If <var>candidates</var> contains a single item, return that item
-3. Let <var>insideArea</var> be
-    * the <a>optimal viewing region</a> of <var>searchOrigin</var> if <var>searchOrigin</var> is a <a>scroll container</a>,
-    * the viewport if <var>searchOrigin</var> is a <a>Document</a>,
-    * the <a>optimal viewing region</a> of <var>searchOrigin</var>’s nearest ancestor <a>scroll container</a> otherwise.
-4. Let <var>insiders</var> be the subset of <var>candidates</var>
+3. Let <var>insiders</var> be the subset of <var>candidates</var>
     whose <a>boundary box</a>'s
-    * top edge is below the top edge of <var>insideArea</var> if <var>dir</var> is {{SpatialNavigationDirection/down}}
-    * bottom edge is above the bottom edge of <var>insideArea</var> if <var>dir</var> is {{SpatialNavigationDirection/up}}
-    * right edge is left of the right edge of <var>insideArea</var> if <var>dir</var> is {{SpatialNavigationDirection/left}}
-    * left edge is right of the left edge of <var>insideArea</var> if <var>dir</var> is {{SpatialNavigationDirection/right}}
+    * top edge is below the top edge of <a>inside area</a> of <var>searchOrigin</var> if <var>dir</var> is {{SpatialNavigationDirection/down}}
+    * bottom edge is above the bottom edge of <a>inside area</a> of <var>searchOrigin</var> if <var>dir</var> is {{SpatialNavigationDirection/up}}
+    * right edge is left of the right edge of <a>inside area</a> of <var>searchOrigin</var> if <var>dir</var> is {{SpatialNavigationDirection/left}}
+    * left edge is right of the left edge of <a>inside area</a> of <var>searchOrigin</var> if <var>dir</var> is {{SpatialNavigationDirection/right}}
 
     Note: this sub-setting is necessary to avoid going in the opposite direction than the one requested.
-5.
+4.
     * 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>dir</var> is {{SpatialNavigationDirection/down}}
-            * bottom edge is closest to the bottom edge of <var>insideArea</var> if <var>dir</var> is {{SpatialNavigationDirection/up}}
-            * right edge is closest to the right edge of <var>insideArea</var> if <var>dir</var> is {{SpatialNavigationDirection/left}}
-            * left edge is closest to the left edge of <var>insideArea</var> if <var>dir</var> is {{SpatialNavigationDirection/right}}
+            * top edge is closest to the top edge of <a>inside area</a> of <var>searchOrigin</var> if <var>dir</var> is {{SpatialNavigationDirection/down}}
+            * bottom edge is closest to the bottom edge of <a>inside area</a> of <var>searchOrigin</var> if <var>dir</var> is {{SpatialNavigationDirection/up}}
+            * right edge is closest to the right edge of <a>inside area</a> of <var>searchOrigin</var> if <var>dir</var> is {{SpatialNavigationDirection/left}}
+            * left edge is closest to the left edge of <a>inside area</a> of <var>searchOrigin</var> if <var>dir</var> is {{SpatialNavigationDirection/right}}
         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,