No scroll_event with Gtk3Agg Backend

Hello everyone,

so I've run into a bit of a problem while embedding a matplotlib plot
into a GTK3 application. Everything's working fine as always, except
the scroll_event seems to get stuck somewhere and my callback is never
called. The button_press_event works.

Apologies in advance if I missed something, but something somewhere
doesn't seem to be quite right. Please let me know if I need to file a
bug report?

Minimal example to demonstrate the problem: [1]
With pyplot it works just fine: [2]


[1] GTK3Agg minimal example
from gi.repository import Gtk, Gdk
from matplotlib.figure import Figure
from matplotlib.backends.backend_gtk3agg import FigureCanvasGTK3Agg as FigCanvas

def on_press(canvas, event):
  print "press!"

def on_scroll(canvas, event):
  print "scroll!"

window = Gtk.Window()
window.connect("delete-event", Gtk.main_quit)

figure = Figure(figsize=(5,4), dpi=100)
plot = figure.add_subplot(111)

canvas = FigCanvas(figure)
canvas.connect('button_press_event', on_press)
canvas.connect('scroll_event', on_scroll)


[2] pyplot minimal example
import matplotlib.pyplot as plt

fig = plt.gcf()

def on_click(event):
  print "press!"

def on_scroll(event):
  print "scroll!"

fig.canvas.mpl_connect('button_press_event', on_click)
fig.canvas.mpl_connect('scroll_event', on_scroll)