[Matplotlib-users] segfault related to NavigationToolbar when using PySide

[TP <par...@fr...>]

Hi everybody,

The following is a small test yielding a segmentation fault with PySide, but 
not with PyQt4.

To test with PyQt4, use:
$ python example.py

To test with PySide:
$ python example.py pyside

With PySide, a segmentation fault appears as soon as the mouse cursor is 
hovering the plot area. Without the NavigationToolbar (try to comment the 
corresponding lines), the problem does not appear. It may be related to the 
display of mouse coordinates in the NavigationToolbar, because when the mouse 
is hovering the NavigationToolbar, no segfault appears.

These are the versions of Qt, PySide, and Matplotlib on my machine:
>>> from PySide import QtCore
>>> QtCore.qVersion()
'4.8.1'
>>> from PySide import __version__
>>> __version__
'1.1.0'
>>> import matplotlib
>>> matplotlib.__version__
'1.1.1rc'

Is this a bug? If yes, does any workaround exist?

Thanks in advance,

TP

###########     example.py     ############
#!/usr/bin/env python

import sys

if len(sys.argv) >= 2 and sys.argv[1] == "pyside":
    from os import environ
    environ['QT_API'] = 'pyside'

    from PySide.QtCore import *
    from PySide.QtGui import *
else:
    from PyQt4.QtCore import *
    from PyQt4.QtGui import *


from matplotlib.figure import Figure
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as 
FigureCanvas
from matplotlib.backends.backend_qt4agg import NavigationToolbar2QTAgg

class MplCanvasXY( FigureCanvas ):

    def __init__( self, title = None, xlabel = None, ylabel = None, 
parent=None ):

        self.fig = Figure()
        self.axes = self.fig.add_subplot(111)
        self.axes.grid(True)

        FigureCanvas.__init__( self, self.fig )
        self.setParent( parent )


app = QApplication( sys.argv )
d = QDialog()

vb = QVBoxLayout()
canvas = MplCanvasXY()

vb.addWidget( canvas )
navigationToolbar = NavigationToolbar2QTAgg(
        parent = canvas
        , canvas = canvas )
vb.addWidget( navigationToolbar )
d.setLayout( vb )

d.show()
sys.exit( app.exec_() )