Apparently this is related to the TkAgg backend -- switching to wxagg makes the warnings disappear.

attn @OceanWolf @fariza

@vnoel You should only see these warnings if you have opted in to using the new experimental tool classes and/or tool_manager class as the warning suggests, but your comments seem to indicate that you have not done this, so I find this perplexing.

By opted in, I mean either by making use of these new experimental classes directly; or in-directly by setting the toolbar rcparam to toolmanager which one can do either as a line added to your script, or to one of your matplotlibrc files. Can you double check whether you have done any of these things. Another possibility arises from the usage of another library that sets this rcParam for you, but they should not have started using classes whilst still marked as experimental.

@OceanWolf AFAIK, I do not use these experimental classes directly. I have only very little idea of what they are.

My toolbar rcparam is set to None (in ~/.config/matplotlib/matplotlibrc), as it has been for quite some time. It is however not impossible that I might have set the toolbar to toolmanager at some point in the past, but I honestly can't remember. Could that be the cause for the warnings?

As for other libraries setting the rcParam for me, I still get the warnings by running this script:

#!/usr/bin/env python
import matplotlib.pyplot as plt
plt.figure()

so I don't think other libraries could be responsible.

Ahh, I see the problem, we assumed that the toolbar rcParam set to None should still use the toolmanager but without a toolbar. An assumption we should re-evaluate. Thank you for bringing this to our attention.

Until we get this fixed, in the next bug fix release, I have three options:

1. Use the current stable toolbar, either by removing the toolbar rcParam, or changing it to toolbar2, the current stable toolbar, both methods have the same effect.

2. Use a different backend like wxagg.

3. Edit the matplotlib code in matplotlib/backends/backend_tkagg.py, changing:

   def _get_toolmanager(self):
       if rcParams['toolbar'] != 'toolbar2':

   to

   def _get_toolmanager(self):
       if rcParams['toolbar'] == 'toolmanager':