Bug report

Bug summary

Navigation in the zoom stack using the Home, Forward, Backward buttons on the toolbar does not work after the figure is cleared with clf().

Code for reproduction

plt.plot([1,2,3])
plt.clf()
plt.plot([1,2,3])
# now click the Zoom button and try to zoom in/out on the figure. Then press Home, Forward or Back buttons on the navigation toolbar: nothing happens.

Actual outcome

The Home, Forward and Back buttons on the toolbar do not work: the zoom does not change as expected.

Expected outcome

Stepping forward and backward in the zoom stack should work as expected when pressing the navigation buttons.

Matplotlib version

• Operating system: Linux 64
• Matplotlib version: v2.0.2, v2.1.0
• Matplotlib backend (print(matplotlib.get_backend())): tried Qt5 and Tk, possibly all others are affected
• Python version: 3.6
• Jupyter version (if applicable): -
• Other libraries: -

I use conda, python3.6 and matplotlib (v2.0.2) from the default channel and matplotlib (v2.1.0) from conda-forge.