How to get the effect of showDataTips on a custom renderer?

I have an AdvancedDataGrid with a custom renderer on one of the columns (that extends AdvancedDataGridItemRenderer). I'm interested in displaying the full text in the column as a tooltip when it's too short for its content. With a standard renderer I can easily achieve this effect by using showDataTips, but it doesn't work on custom renderers. I tried measuring the text width and comparing it to the column width in several ways, but I'm getting incorrect values and so far nothing worked. Here's an example:

public override function set data(value:Object):void
{
    super.data=value;
    var metrics:TextLineMetrics=getLineMetrics(0);
    if (metrics.width>this.width) toolTip=text; else toolTip="";
}

If anybody knows the solution to this issue, I'll be glad if s/he can share.

I have actually already solved it. Here's the solution if anyone else is stuck on the same issue:

public override function validateSize(recursive:Boolean=false):void
{
    super.validateSize(recursive);
    if ((AdvancedDataGrid(listData.owner).columns[listData.columnIndex].
            showDataTips)&&(textWidth>width))
        toolTip=listData.label;
    else toolTip=null;
}