     //--------------------------------------------------------------------------
 
     /**
-     *  @inheritDoc
+     *  Returns 1 if there is a viewport, 0 otherwise.
      */
     public function get numItems():int
     {

    }
    
    /**
     *  @inheritDoc
     */
    public function getItemAt(index:int):Object
    {
        if (viewport && index == 0)

    }
    
    /**
     *  Returns the 0 if the item passed in is the viewport.  
     *  Otherwise, it throws an ArgumentError.
     *
     *  @param item The item to identify.
     *
     *  @return The index position of the item to identify.
     * 
     *  @throws ArgumentError If the item is not a child of this object.
     */ 
    public function getItemIndex(item:Object):int
    {
        if (item != null && item == viewport)
