Persistent loop of Matplotlib figure animation results in flickering output when run in a thread

[rht]

Description

The Mesa agent-based modeling library is looking to replace its self-hosted Tornado-based visualization server with Voilà. I have made a prototype in https://github.com/rht/mesa-examples/tree/voila. However, I encountered the flickering issue reported in #431. To summarize, it is like running the Game of Life simulation with play and stop buttons. The play and stop work, except that the display flickers.

The long-running loop: https://github.com/rht/mesa-examples/blob/99a68386226f3fe5be3953d25a84bd92f8b7065c/examples/boltzmann_wealth_model/run_voila.py#L161-L170. If I run the loop without threading or multiprocessing, it runs just fine. Each loop lasts for about 300 ms. My hypothesis is that the solutions in #431 does not apply because there is only 1 plot being constantly re-rendered, whereas in my case, I have 3 objects being constantly rerendered:

• the time series plot of the simulation
• the imshow heatmap view of the agents
• the elapsed of each step, displayed in a widgets.Output
  https://github.com/rht/mesa-examples/blob/99a68386226f3fe5be3953d25a84bd92f8b7065c/examples/boltzmann_wealth_model/run_voila.py#L154-L159

I have tried the plt.draw() as recommended in #431 (comment), but it didn't work out. I have also tried adding clear_output(wait=True), and it didn't work out.

I haven't tried on JupyterLab yet, and have been focusing to make it work with voila --no-browser --debug. I apologize in advance if this issue is not concise nor self-contained.

Context

• voila version 0.4.0
• Operating System and version: NixOS 23.05
• Browser and version: Brave v1.52.126

[rht]

I solved the problem for my use case by using widgets.Play, and thus simplifying the looping, threading, and observe situation. The flickering and out-of sync of the display is still there, but given that #431 is still open, I will close this as a duplicate of it.

[maartenbreddels]

Hi,

thanks for opening the issue, and you are right #431 is probably related. Not that this is not a Voila issue specifically, but an ipywidget problem. The long term solution is jupyter-widgets/ipywidgets#3759 I think.

In solara (when using solara-server) this will already be used (see widgetti/solara#68 )
Although I think we could create an alternative output widget with this behavior without introducing a breaking change that should also work in the Jupyter notebook and Voila.

Regards,

Maarten

[rht]

Thank you for the pointer to Solara! It's great that it is built on top if ipywidgets, and the demo looks slick.

[rht]

Context for this issue: projectmesa/mesa#1622.

[maartenbreddels]

See also jupyter-widgets/ipywidgets#2358 (comment) which means that with ipykernel 6.29.0 this mighe work (please let us know here to confirm)

[rht]

Tested on ipykernel==6.29.0 and mesa==2.1.5: the flickering is still there, except that it happens much less often, in about every ~15 s or 30 s or so. Whereas on ipykernel==6.26.0 it won't even play the animation.