title: Pyqtgraph plotting is slow
body: <p>It seems window redraws everything each time new rect is added, although setUpdatesEnabled is set to False, for <strong><em>win</em></strong> and <strong><em>plt</em></strong>. How to disable updates?</p>
  
  <pre><code>def f(n):
      import pyqtgraph as pg
      pg.setConfigOption('background', '#a0f0ff')
      win = pg.GraphicsWindow()
      win_size = 1000
      win.setGeometry(500, 30, win_size, win_size)
      plt = win.addPlot()
      win.setUpdatesEnabled = False
      plt.setUpdatesEnabled = False
      y = range(n)
      x = range(n)
      plt.showGrid(x=True, y=True)
      empty_pen = pg.mkPen((0, 0, 0, 0))
      brush = pg.mkBrush((255, 255, 255))
      for i1 in range(n):
          for i0 in range(n):
              print("i1, i0 =", i1, i0)
              rect = pg.QtGui.QGraphicsRectItem(i0, i1, 0.5, 0.5)
              rect.setPen(empty_pen)
              rect.setBrush(brush)
              plt.addItem(rect)
      pg.QtGui.QApplication.exec_()
  
  f(40)
  </code></pre>