ScatterPlotItem crashs with 7000 or more points
<p>I use pyqt5.5.1, python 3.4 (windows 32 &amp; 64 bits), numpy, pyqtgraph (tested develop git branch &amp; lastest official version)</p>

<p>Here the part of code that I use to display a scatterplot</p>

<pre><code>self.widget1 = pg.GraphicsLayoutWidget();
self.widget1.hide();

self.p1 = self.widget1.addPlot()
n = 7300
s1 = pg.ScatterPlotItem(size=10, pen=pg.mkPen(None), brush=pg.mkBrush(0, 0, 255, 120))
pos = np.random.normal(size=(2,n), scale=1e-5)
s1.setData(pos[0], pos[1])
self.p1.addItem(s1)
self.widget1.show();
</code></pre>

<p>With n = 7, or 73, 730 scatterplot works.</p>

<p>but with n = 7300 and more, it crashs python.</p>

<p>I have only this trace, just before the crash:</p>

<pre><code>QPaintDevice: Cannot destroy paint device that is being painted
R6025
- pure virtual function call
</code></pre>

<p>Could you help me to find a workaround or a fix ?</p>

<p>Thanks</p>