      *  @private
      *  Vectors to store the baseline property of the rows, and
      *  the maximum ascent of the elements in each row.
+     *  
+     *  In rowBaselines, the value is stored as
+     *  [value, maxAscent] if the baseline is maxAscent:value, 
+     *  and [value, null] if the baseline is just a value.
      */
     private var rowBaselines:Vector.<Array> = null;
     private var rowMaxAscents:Vector.<Number> = null;
     
+    /**
+     *  @private
+     *  Hashtable that maps elements to their constraint
+     *  information. The mapping has type:
+     *  ILayoutElement -> ElementConstraintInfo
+     * 
+     *  This cache is always discarded after measure() or
+     *  updateDisplayList() because the constraints may have changed.
+     */
     private var constraintCache:Dictionary = null;
     
     //--------------------------------------------------------------------------

        // 1-D properties like baseline? What parts can we parameterize and
        // what parts aren't possible.
        
        if (_constraintColumns.length <= 0)
            return new Vector.<Number>();
        

        
        // Need to measure in case of explicit width and height on target.
        // Also need to reparse constraints in case of something changing.
        measureAndPositionColumnsAndRows(unscaledWidth, unscaledHeight);
        
        layoutContent(unscaledWidth, unscaledHeight);
    }
