docs: def valueAt( self, point ):
          """
          Returns the X, Y value for the given point.
          
          :param      point | <QPoint>
          
          :return     (<variant> x, <variant> y)
          """
          x = point.x()
          y = point.y()
          
          hruler = self.horizontalRuler()
          vruler = self.verticalRuler()
          
          grid   = self._buildData.get('grid_rect')
          if ( not grid ):
              return (None, None)
          
          x_perc = 1 - ((grid.right() - x) / grid.width())
          y_perc = ((grid.bottom() - y) / grid.height())
          
          return (hruler.valueAt(x_perc), vruler.valueAt(y_perc))