Bug report

Bug summary

Before the refactor, one would set colorbar axes to be pickable with colorbar.ax.set_picker(True). Now, it is necessary to use the undocumented colorbar.ax.inner_ax.set_picker(True). Likewise, with motion notify events, MouseEvent.inaxes is not colorbar.ax under any circumstances, it always is colorbar.ax.inner_ax.

But, this is not really about events so much as the fact that Colorbar(ax).ax is ax == False and all methods of colorbar.ax are actually bound to a different object, namely colorbar.ax.inner_ax, so they are acting on surprising, hidden state (from a user's perspective).

We could work around the events issue, but I feel like there would be an ongoing stream of bug reports without a comprehensive fix. On the other hand, I definitely don't want to revert ColorbarAxes entirely because I really like the improvements that it enabled.

Code for reproduction

Please see #20471, which this issue blocks (in my opinion).

Matplotlib version

• Operating system: Win10
• Matplotlib version (import matplotlib; print(matplotlib.__version__)): master
• Matplotlib backend (print(matplotlib.get_backend())): tkagg
• Python version: 3.8.8
• Jupyter version (if applicable):
• Other libraries:

cc @jklymak