button_press_event: Key presses not recognized?

Hi again,

I have another problem: I try to connect "Control + mouse drag" to some
zoom event. On mouse press, I need to check whether the Ctrol key is

import random
import sys

from PyQt4 import QtGui, QtCore
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.figure import Figure,SubplotParams

class InnerDiagramWidget(FigureCanvas):
    def __init__(self, parent):
        fig = Figure()
        FigureCanvas.__init__(self, fig)
        self.mpl_connect('button_press_event', self.on_button_press)

    def on_button_press(self, event):
        print event.key, event.button, event.xdata
        if event.key == 'control':
            print 'This should start the zoom but never happens'

a = QtGui.QApplication(sys.argv)
w = QtGui.QMainWindow()

The key returned here is always None. Why??? The API
(matplotlib.backend_bases.MouseEvent) says that it should return

$ uname -a
Linux myos #1 SMP 2009-03-31 14:50:44 +0200 x86_64 x86_64 x86_64 GNU/Linux

$ python -c "import matplotlib; print matplotlib.__version__"

I guess this is a bug in matplotlib? Can one confirm that?

Best regards