Events break in jupyter notebook when calling clear_output()

[aph42]

Bug report

Bug summary

As of matplotlib version 3.3.2, calling IPython.display.clear_output() in a jupyter notebook seems to break the matplotlib figure event handler system. It seems to be a problem with the interaction between the jupyter notebook widget display system and the matplotlib event system, but reverting to matplotlib 3.3.1 corrects the issue.

Code for reproduction

In a jupyter notebook:

# Paste your code here

%matplotlib notebook

from matplotlib import pyplot as plt
import IPython
import ipywidgets as wdg

wOut = wdg.Output()

def onClick(event):
    with wOut:
        IPython.display.clear_output()
        print(event)

fig, ax = plt.subplots(1,1)
eventid = fig.canvas.mpl_connect('button_press_event', onClick)

IPython.display.display(wOut)

Actual outcome

Clicking on the plot once updates the text in the Output widget, further clicks do nothing.

Further events result in error messages from the jupyter server:

# If applicable, paste the console output here

[IPKernelApp] WARNING | No such comm: 565a2c88b5ff42b08d89aa4cecd34763

Expected outcome

Each time you click on the plot the text in the Output widget should be updated with details of the event.

This code works in version 3.3.1, but not in 3.3.2.

• Operating system: Ubuntu
• Matplotlib version: 3.3.2
• Matplotlib backend (print(matplotlib.get_backend())): nbAgg
• Python version: 3.7.9
• Jupyter version (if applicable): 6.1.4
• Other libraries: IPython 7.19.0

conda

default channel

[jklymak]

I can't get this to do anything in any version of matplotlib. The output region just say "Output()" for me no matter what version I try. Are you sure this isn't an ipython/ipywidgets/jupyter interaction problem?

[aph42]

Here is what it looks like on my system:

The text at the bottom should update at each click. As I said - the code works in 3.3.2, but not in 3.3.1, so I think something has changed on the matplotlib end of things.

[jklymak]

But did any of the other libraries change when you changed from 3.3.1 to 3.3.2? So far as I can tell the onClick event fires, but the with wOut doesn't connect... But my understanding of jupyter widgets is pretty minimal.

I'm not saying matplotlib didn't break this, but with my jupyter (6.1.6) and ipython (7.16.1) I can't reproduce the "Expected" behaviour, regardless of Matplotlib version.

[aph42]

Thanks for your efforts on this.

Here are the packages in my conda environments that I'm using at the moment:
mpl-3.3.1.packages.txt
mpl-3.3.2.packages.txt

The only differences are in the versions of matplotlib and matplotlib-base.

My first thought was that it was a jupyter/ipython issue, but starting from matplotlib 3.3.2 I have not been able to get it to work with any version of jupyter or ipython that I tried, while starting with matplotlib 3.3.1 it's worked with all versions of jupyter and ipython that i've tried. I will try now a set up with matplotlib 3.3.1, jupyter 6.1.6 and ipython 7.16.1 to see if it works for me.

I can also confirm that before the most recent update, this code was working in a range of different browsers and operating systems.

[aph42]

I've tried again with the following conda packages (including matplotlib 3.3.1, jupyter 6.1.6 and ipython 7.16.1):
mpl-3.3.2.jupyter-6.1.6.ipython.7.16.1.packages.txt

On my system (Ubuntu 20.04.1 LTS, firefox 83.0 (64-bit)), it works as expected in that clicking the plot updates the text.

[QuLogic]

Looks like #18638, which would be fixed in 3.3.3. Please try the latest version.

[aph42]

Yes - installing 3.3.3 from conda-forge fixed the problem. Thanks.