Problem with zoom/pan in matplot NavigationToolbar

I have a problem with zoom/pan in matplot NavigationToolbar. I am
using networkx to generate graphs and it's interface to matplot to
draw it. When I use zoom/pan with the NavigationToolbar, the edges and
the labels don't resize. I don't know if this is a networkx or a
matplotlib problem. This is my source code:

import sys, os, random
from PyQt4 import QtGui, QtCore

from numpy import arange, sin, pi
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas

from matplotlib.backends.backend_qt4agg import NavigationToolbar2QTAgg
as NavigationToolbar
from matplotlib.figure import Figure
import networkx as nx

progname = os.path.basename(sys.argv[0])
progversion = "0.1"

class MyMplCanvas(FigureCanvas):
    """Ultimately, this is a QWidget (as well as a FigureCanvasAgg, etc.)."""
    def __init__(self, parent=None, width=5, height=4, dpi=100):
        fig = Figure(figsize=(width, height), dpi=dpi)

        self.axes = fig.add_subplot(111)
        # We want the axes cleared every time plot() is called



        FigureCanvas.__init__(self, fig)


    def compute_initial_figure(self):

class MyStaticMplCanvas(MyMplCanvas):
    """Simple canvas with a sine plot."""

    def __init__(self,*args,**kwargs):

    def compute_initial_figure(self):
        nodes = nx.draw_networkx_nodes(G,pos,ax=self.axes)
        print nodes
        edges = nx.draw_networkx_edges(G,pos,ax=self.axes)
        self._labels = range(len(G.nodes()))
        nx.draw_networkx_labels(G, pos, ax=self.axes,labels=labels)

    def onpick(self,event):
        print self._labels[ind]
        return True

class ApplicationWindow(QtGui.QMainWindow):
    def __init__(self):
        self.setWindowTitle("application main window")

        self.file_menu = QtGui.QMenu('&File', self)
        self.file_menu.addAction('&Quit', self.fileQuit,
                                 QtCore.Qt.CTRL + QtCore.Qt.Key_Q)

        self.help_menu = QtGui.QMenu('&Help', self)

        self.help_menu.addAction('&About', self.about)

        self.main_widget = QtGui.QWidget(self)

        l = QtGui.QVBoxLayout(self.main_widget)
        sc = MyStaticMplCanvas(self.main_widget, width=5, height=3, dpi=100)


        bar = NavigationToolbar(sc,self)

    def fileQuit(self):

    def closeEvent(self, ce):

    def about(self):
        QtGui.QMessageBox.about(self, "About %s" % progname,
u"""%(prog)s version %(version)s
Copyright \N{COPYRIGHT SIGN} 2005 Florent Rougon, 2006 Darren Dale

This program is a simple example of a Qt4 application embedding matplotlib

It may be used and modified with no restriction; raw copies as well as
modified versions may be distributed without limitation."""
% {"prog": progname, "version": progversion})

qApp = QtGui.QApplication(sys.argv)

aw = ApplicationWindow()
aw.setWindowTitle("%s" % progname)