jupyter iframe state: make it work properly

[williamstein]

In CoCalc (probably because of react-windowed, even if set with a very large window size!), when you scroll something involving iframe output off the screen, then back on the screen, the iframe is re-rendered. Of course, this resets any state. It would be much better if all iframes for a jupyter notebook were kept in the DOM somehow, so that this re-rendering doesn't happen.

I'm calling this a bug, since it's clearly the intention of Jupyter classic that the iframe state is preserved.

Relevant code: smc-webapp/jupyter/output-messages/iframe.tsx

A good python3 example that uses an iframe and has state (zoom in on part of the plot):

import plotly.graph_objects as go
go.Figure(data=go.Bar(y=[2, 3, 1]))

[williamstein]

This is even worse than I thought -- if you add a cell above a cell that is rendered using an iframe, then the iframe cell reloads.

[williamstein]

OK, I think the only way to fix this problem is to eliminate use of react-windowed for Jupyter entirely, unfortunately. This is a lot of work since everything related to scrolling has to get ret reimplemented again.

It's ironic that cocalc uses react-windowed all over the place (e.g., in file listings, etc.,) and it works great, but it doesn't 100% solve the problem for Jupyter, which was the original reason I started using react-windowed.

[williamstein]

Fixed via a8e078b and adjacent commits.