VTK HEAD OpenGL errors

gistfile1.txt

#!/usr/bin/env python
 
import sys
import vtk
from PyQt4 import QtCore, QtGui
from vtk.qt4.QVTKRenderWindowInteractor import QVTKRenderWindowInteractor
 
class MainWindow(QtGui.QMainWindow):
 
    def __init__(self, parent = None):
        QtGui.QMainWindow.__init__(self, parent)
 
        self.frame = QtGui.QFrame()
 
        self.vl = QtGui.QVBoxLayout()
        self.vtkWidget = QVTKRenderWindowInteractor(self.frame)
        self.vl.addWidget(self.vtkWidget)
 
        self.ren = vtk.vtkRenderer()
        self.vtkWidget.GetRenderWindow().AddRenderer(self.ren)
        self.iren = self.vtkWidget.GetRenderWindow().GetInteractor()
        
        # Create source
        source = vtk.vtkSphereSource()
        source.SetCenter(0, 0, 0)
        source.SetRadius(5.0)
 
        # Create a mapper
        mapper = vtk.vtkPolyDataMapper()
        mapper.SetInputConnection(source.GetOutputPort())
 
        # Create an actor
        self.actor = vtk.vtkActor()
        self.actor.SetMapper(mapper)
 
        # Update opacity
        self.update_opacity()
 
        self.ren.AddActor(self.actor)
        
        self.ren.ResetCamera()
 
        self.frame.setLayout(self.vl)
        self.setCentralWidget(self.frame)
        
    def update_opacity(self):
        
        # Do some stuff, like changing opacity
        self.actor.GetProperty().SetOpacity(0.5)
        
        # Gives errors with VTK HEAD, but works :
        self.vtkWidget.GetRenderWindow().Render()
 
 
if __name__ == "__main__":
 
    app = QtGui.QApplication(sys.argv)
 
    window = MainWindow()
    window.show()
 
    # Put the initialize after show(), else it will segfault on Fedora
    window.iren.Start()
    window.iren.Initialize()
 
    sys.exit(app.exec_())