     //----------------------------------
     private function invalidateTargetSizeAndDisplayList():void
     {
-        var layoutTarget:Group = target;
+        var layoutTarget:GroupBase = target;
         if (layoutTarget != null) 
         {
             layoutTarget.invalidateSize();

        if (_gap == value) 
            return;

		_gap = value;
        invalidateTargetSizeAndDisplayList();
    }


    }


    private function variableRowHeightMeasure(layoutTarget:GroupBase):void
    {
        var minWidth:Number = 0;
        var minHeight:Number = 0;
