Maps a chart point to a pixel position within the grid based on the
        rulers.
        
        :param      x | <variant>
                    y | <variant>
        
        :return     <QPointF>

def mapFromChart( self, x, y ):
        """
        Maps a chart point to a pixel position within the grid based on the
        rulers.
        
        :param      x | <variant>
                    y | <variant>
        
        :return     <QPointF>
        """
        grid      = self.gridRect()
        hruler    = self.horizontalRuler()
        vruler    = self.verticalRuler()
        
        xperc     = hruler.percentAt(x)
        yperc     = vruler.percentAt(y)
        
        xoffset   = grid.width() * xperc
        yoffset   = grid.height() * yperc
        
        xpos      = grid.left() + xoffset
        ypos      = grid.bottom() - yoffset
        
        return QPointF(xpos, ypos)