     private var oldVisibleColumnIndices:Vector.<int> = new Vector.<int>(0);
         
     /** 
-     *  TBD: how do these vectors relate to visibleRow,ColumnIndices
+     *  TODO (hmuller): document how do these vectors relate to visibleRow,ColumnIndices
      */
     private var visibleRowBackgrounds:Vector.<IVisualElement> = new Vector.<IVisualElement>(0);
     private var visibleRowSeparators:Vector.<IVisualElement> = new Vector.<IVisualElement>(0);


                initializeItemRenderer(renderer, rowIndex, colIndex);
                
                // TBD(hmuller): if takeVisibleItemRenderer returned true, and initializeItemRenderer
                // returned false - because nothing changed - don't run prepare().
                renderer.prepare(!createdGridElement);
                
                var colWidth:Number = gridDimensions.getColumnWidth(colIndex);

    //
    //--------------------------------------------------------------------------     
    
    public function dataProviderCollectionChanged(event:CollectionEvent):void
    {
        switch (event.kind)
