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

[Eric F. <ef...@ha...>]

On 2012/07/05 11:33 PM, TP wrote:
> 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?

Yes, it's a bug, but most likely in PySide.  Mpl does not use any 
extension code specific to Qt.

Eric

>
> 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_() )
>
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