def measureSpotSizes(self, dataSet):
        for rec in dataSet:
            ## keep track of the maximum spot size and pixel size
            symbol, size, pen, brush = self.getSpotOpts(rec)
            width = 0
            pxWidth = 0
            if self.opts['pxMode']:
                pxWidth = size + pen.widthF()
            else:
                width = size
                if pen.isCosmetic():
                    pxWidth += pen.widthF()
                else:
                    width += pen.widthF()
            self._maxSpotWidth = max(self._maxSpotWidth, width)
            self._maxSpotPxWidth = max(self._maxSpotPxWidth, pxWidth)
        self.bounds = [None, None]