def METHOD_NAME(self):
    # Update grid lines based upon current grid spacing and grid size
    # First reset existing grid lines
    self.minorLines.reset()
    self.majorLines.reset()
    self.centerLines.reset()
    # Now redraw lines
    numLines = int(math.ceil(self.gridSize/self.gridSpacing))
    scaledSize = numLines * self.gridSpacing
    center = self.centerLines
    minor = self.minorLines
    major = self.majorLines
    for i in range(-numLines, numLines + 1):
        if i == 0:
            center.moveTo(i * self.gridSpacing, -scaledSize, 0)
            center.drawTo(i * self.gridSpacing, scaledSize, 0)
            center.moveTo(-scaledSize, i * self.gridSpacing, 0)
            center.drawTo(scaledSize, i * self.gridSpacing, 0)
        else:
            if (i % 5) == 0:
                major.moveTo(i * self.gridSpacing, -scaledSize, 0)
                major.drawTo(i * self.gridSpacing, scaledSize, 0)
                major.moveTo(-scaledSize, i * self.gridSpacing, 0)
                major.drawTo(scaledSize, i * self.gridSpacing, 0)
            else:
                minor.moveTo(i * self.gridSpacing, -scaledSize, 0)
                minor.drawTo(i * self.gridSpacing, scaledSize, 0)
                minor.moveTo(-scaledSize, i * self.gridSpacing, 0)
                minor.drawTo(scaledSize, i * self.gridSpacing, 0)
    center.create()
    minor.create()
    major.create()
    if self.gridBack:
        self.gridBack.setScale(scaledSize)