Non responsive ipympl with ipywidgets after updating environment

Describe the issue

I have consistently used the following workflow for fully updating my Jupyter Lab working environments:

$ rmvirtualenv my_env
$ mkvirtualenv --python=`which python` my_env
[my_env] $ pip install -r requirements.txt
[my_env] $ jupyter lab build
[my_env] $ jupyter lab

Recently however, after these steps:

1. My widgets all become non-functional. I can operate and interact with them, but the figures they control do not change at all.
2. All of the widget controls move from being above the figure they control to to below it.

Projects in virtualenvs that have not been recently updated in this way continue to work fine, and updating them reliably makes them stop working.

This occurs consistently (I have now ruined half a dozen projects confirming the pattern), and even for notebooks hosted outside my local machine (such as this one hosted on Binder). Control widgets themselves seem to work fine though (e.g., in notebooks like this one) when ipympl is not involved. I have also confirmed that the observed behavior is independent of browser and local machine (at least macOS vs iOS).

Has something about Jupyter Lab, ipywidgets, or ipympl changed recently that might be causing this?

---

Typical post update configuration:

$ jupyter --version
Selected Jupyter core packages...
IPython          : 8.4.0
ipykernel        : 6.13.1
ipywidgets       : 7.7.0
jupyter_client   : 7.3.4
jupyter_core     : 4.10.0
jupyter_server   : 1.17.1
jupyterlab       : 3.4.3
nbclient         : 0.6.4
nbconvert        : 6.5.0
nbformat         : 5.4.0
notebook         : 6.4.12
qtconsole        : not installed
traitlets        : 5.2.2

$ jupyter labextension list 
JupyterLab v3.4.3
/Users/Rax/Documents/Projects/Coding/Python/venvs/picollisions/share/jupyter/labextensions
        jupyterlab_pygments v0.2.2 enabled OK (python, jupyterlab_pygments)
        nbdime-jupyterlab v2.1.1 enabled OK
        jupyter-matplotlib v0.11.1 enabled OK
        @jupyterlab/git v0.37.1 enabled OK (python, jupyterlab-git)
        @jupyter-widgets/jupyterlab-manager v3.1.0 enabled OK (python, jupyterlab_widgets)
        @kiteco/jupyterlab-kite v2.0.2 enabled OK (python, jupyterlab_kite)

Other labextensions (built into JupyterLab)
   app dir: /Users/Rax/Documents/Projects/Coding/Python/venvs/picollisions/share/jupyter/lab

---

Typical pre update configuration:

$ jupyter --version
jupyter core     : 4.7.1
jupyter-notebook : 6.4.3
qtconsole        : not installed
ipython          : 7.26.0
ipykernel        : 6.2.0
jupyter client   : 6.1.12
jupyter lab      : 3.1.10
nbconvert        : 6.1.0
ipywidgets       : 7.6.4
nbformat         : 5.1.3
traitlets        : 5.0.5

jupyter labextension list
JupyterLab v3.1.10
/Users/Rax/Documents/Projects/Coding/Python/venvs/picollisions/share/jupyter/labextensions
        nbdime-jupyterlab v2.1.0 enabled OK
        jupyter-matplotlib v0.9.0 enabled OK
        @jupyterlab/git v0.32.2 enabled OK (python, jupyterlab-git)
        @jupyter-widgets/jupyterlab-manager v3.0.0 enabled OK (python, jupyterlab_widgets)
        @kiteco/jupyterlab-kite v2.0.2 enabled OK (python, jupyterlab_kite)

/usr/local/share/jupyter/labextensions
        jupyterlab_pygments v0.2.2 enabled OK (python, jupyterlab_pygments)

Other labextensions (built into JupyterLab)
   app dir: /Users/Rax/Documents/Projects/Coding/Python/venvs/picollisions/share/jupyter/lab

---

Typical requirements:

#...
ipywidgets                 
ipympl

jupyterlab >=3.1                
jupyterlab-git                 
jupyterlab-kite >=2.0.2        

(I’ve tried omitting Kite to see if that was the culprit. In any case it is not present in the Binder versions.)

Versions

 3.9.13 (main, May 24 2022, 21:28:44) 
[Clang 13.0.0 (clang-1300.0.29.30)]
ipympl version: 0.9.1
Selected Jupyter core packages...
IPython          : 8.4.0
ipykernel        : 6.13.1
ipywidgets       : 7.7.0
jupyter_client   : 7.3.4
jupyter_core     : 4.10.0
jupyter_server   : 1.17.1
jupyterlab       : 3.4.3
nbclient         : 0.6.4
nbconvert        : 6.5.0
nbformat         : 5.4.0
notebook         : 6.4.12
qtconsole        : not installed
traitlets        : 5.2.2
Known nbextensions:
  config dir: /Users/Rax/.jupyter/nbconfig
    notebook section
      nbdime/index  enabled 
      - Validating: OK
  config dir: /Users/Rax/Documents/Projects/Coding/Python/venvs/picollisions/etc/jupyter/nbconfig
    notebook section
      jupyter-matplotlib/extension  enabled 
      - Validating: OK
      nbdime/index  enabled 
      - Validating: OK
      jupyter-js-widgets/extension  enabled 
      - Validating: OK
  config dir: /usr/local/etc/jupyter/nbconfig
    notebook section
      nbdime/index  enabled 
      - Validating: OK
JupyterLab v3.4.3
/Users/Rax/Documents/Projects/Coding/Python/venvs/picollisions/share/jupyter/labextensions
        jupyterlab_pygments v0.2.2 enabled OK (python, jupyterlab_pygments)
        nbdime-jupyterlab v2.1.1 enabled OK
        jupyter-matplotlib v0.11.1 enabled OK
        @jupyterlab/git v0.37.1 enabled OK (python, jupyterlab-git)
        @jupyter-widgets/jupyterlab-manager v3.1.0 enabled OK (python, jupyterlab_widgets)
        @kiteco/jupyterlab-kite v2.0.2 enabled OK (python, jupyterlab_kite)

Other labextensions (built into JupyterLab)
   app dir: /Users/Rax/Documents/Projects/Coding/Python/venvs/picollisions/share/jupyter/lab

[ianhi]

@orome yup!

there is indeed a bug

I think the bug is in matplotlib 3.5.1 and 3.5.2 but will be fixed in 3.5.3+

but adding an explicit fig.canvas.draw() https://github.com/matplotlib/ipympl/issues/469#issuecomment-1151558213, right?

yes and yes

[ianhi]

@orome I believe this is something to do with the changes about when draws happen - I think between 0.8 and 0.9. The new behavior has several advantages in terms of plot persistence, but may (i’m not totally sure) be causing your problem.

Happily I think the fix is very simple. In your binder link if I add fig.canvas.draw() as the last line of plot_logisitic then it seems to work as intended. This issue aside I’d generally recommend explicit draws like this as best practice, before you were relying on a draw being triggered by something else which doesn’t come with any garuntees