Improve QGraphicsPathItem Performance with RemoteGraphicsView or MultiProcess

[BeJota]

Hello,

I am trying to improve the performance (plotting speed) of the following code which draws a collection of lines using QGraphicsPathItem, then updates with new data. It is a combination of examples I have found. Is there a way to improve this performance with RemoteGraphicsView or MultiProcess?

My attempts have resulted in various errors but primarily of the sort: 'RuntimeError: Internal C++ object (PySide.QtGui.QGraphicsPathItem) already deleted.'

Thank you.

# -------------------------------

import pyqtgraph as pg

import numpy as np

app = pg.mkQApp()

y = np.random.normal(size=(120,20000), scale=0.2) + np.arange(120)[:,np.newaxis]

x = np.empty((120,20000))

x[:] = np.arange(20000)[np.newaxis,:]

view = pg.GraphicsLayoutWidget()

view.show()

w1 = view.addPlot()

class MultiLine(pg.QtGui.QGraphicsPathItem):

    def __init__(self, x, y):

        """x and y are 2D arrays of shape (Nplots, Nsamples)"""

        connect = np.ones(x.shape, dtype=bool)

        connect[:,-1] = 0 # don't draw the segment between each trace

        self.path = pg.arrayToQPath(x.flatten(), y.flatten(), connect.flatten())

        pg.QtGui.QGraphicsPathItem.__init__(self, self.path)

        self.setPen(pg.mkPen('w'))

    def shape(self): # override because QGraphicsPathItem.shape is too expensive.

        return pg.QtGui.QGraphicsItem.shape(self)

    def boundingRect(self):

        return self.path.boundingRect()

now = pg.ptime.time()

lines = MultiLine(x, y)

w1.addItem(lines)

print("Plot time: %0.2f sec" % (pg.ptime.time()-now))

# --- added ----

for i in range(10):

    print(i)

    y = np.random.normal(size=(120,20000), scale=0.2) + np.arange(120)[:,np.newaxis]

    x = np.empty((120,20000))

    x[:] = np.arange(20000)[np.newaxis,:]

    newLines = MultiLine(x, y)

    # w1.addItem(newLines)

    lines.setPath(newLines.path)

    

    app.processEvents()

    

app.exec_()