docs: 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)