zooming and panning with blit

Hi all,

    I am just started to use matplotlib and have a question about
using blit method to animate plots. I wrote something like this to
show the initial plot (other part of the code not shown):

           ....
           l1, = p1.plot(lineout, animated=True)
           p1.set_xlabel(xlabel)
           p1.axis(data_range)
           plt.draw()
           background = canvas.copy_from_bbox(p1.bbox)
           p1.draw_artist(l1)
           canvas.blit(p1.bbox)
           ...

    This works and showes the first plot, however, zooming and panning
using the toolbar will make plot disappear (only empty background
left). So I wonder if there is a way to make zooming and panning work
with the blit method.

Thank you!

Chengkun