Add a function to get all relations of an accessible.

Add a default implementation for RelationTo.
Usually this should be empty and it is pointless to return
the parent-child releations in this function.
Instead we will have proper parent-child functions and also
remove this functionallity from navigate.

Having default implementations for these removes the
necessity to reimplement them to return Unrelated in
many places.

Change-Id: I13b7ad3256533681e5a0548ae15da98ca0d16b94
Reviewed-on: http://codereview.qt-project.org/4785
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Jan-Arve Sæther <jan-arve.saether@nokia.com>

src/widgets/accessible/qaccessible.cpp

@@ -822,16 +822,35 @@ const QAccessibleInterface *other, int otherChild) const
     is returned.
 
     The returned value indicates the relation of the called object to
-    the \a other object, e.g. if this object is a child of \a other
-    the return value will be \c Child.
+    the \a other object, e.g. if this object is a label for \a other
+    the return value will be \c Label.
+
+    Usually parent-child relations are not returned.
 
     The return value is a combination of the bit flags in the
     QAccessible::Relation enumeration.
 
     All objects provide this information.
 
-    \sa indexOfChild(), navigate()
+    \sa relations(), indexOfChild(), navigate()
 */
+QAccessible::Relation QAccessibleInterface::relationTo(int,
+            const QAccessibleInterface *, int) const
+{
+    return Unrelated;
+}
+
+/*!
+    Returns the meaningful relations to other widgets. Usually this will not return parent/child
+    relations, unless they are handled in a specific way such as in tree views.
+    It will typically return the labelled-by and label relations.
+
+    \sa relationTo(), navigate()
+*/
+QVector<QPair<QAccessibleInterface*, QAccessible::Relation> > QAccessibleInterface::relations() const
+{
+    return QVector<QPair<QAccessibleInterface*, Relation> >();
+}
 
 /*!
     \fn int QAccessibleInterface::childAt(int x, int y) const

src/widgets/accessible/qaccessible.h

@@ -379,7 +379,9 @@ public:
 
     // relations
     virtual Relation relationTo(int child, const QAccessibleInterface *other,
-                                int otherChild) const = 0;
+                                int otherChild) const;
+    virtual QVector<QPair<QAccessibleInterface*, Relation> > relations() const;
+
     virtual int childAt(int x, int y) const = 0;
 
     // navigation