Event attributes

Hi,

I'm using matplotlib in a GTK gui canvas with the GTKAgg backend. I'm connecting a mouse click 'button_press_event' to the click function. If I choose print event.x everything works fine. However I'm after the x value in terms of the x-axis not pixels. When I try print event.xdata I get an error message. Am I making a stupid mistake or is this a bug?

Thanks

Martin

      self.canvas.connect('button_press_event',self.click)

def click(self,widget,event):
        print 'you clicked', event.xdata, event.ydata
        #print 'you clicked', event.x, event.y

Traceback (most recent call last):
  File "./dangerplotpy", line 120, in click
    print 'you clicked', event.xdata, event.ydata
AttributeError: xdata