reenable minimum height for voila

[timkpaine]

Tweaks and partially reverts #2352

Currently, Perspective works great in voila except that it does not have any height::

This PR gives it a minimum height:

The sentiments in the original PR still hold, I'm looking for an alternative way to tell if specifically in voilà. but with voila-dashboards/voila#1457 we can now disambiguate and apply only in voilà

[timkpaine]

• Hoping to get https://github.com/voila-dashboards/voila/pull/1457/files in which will allow us to properly differentiate.

[timkpaine]

Not done in this PR, but we could use the same idea for notebook, which might help if/when we work in e.g. vs code: https://github.com/jupyter/notebook/blob/3b8e6736075279f80cd1e590c71a872dc5ad2c11/notebook/templates/notebooks.html#L15

[timkpaine]

needs #2596

[texodus]

Thanks for the PR! Looks good!

I will merge this as-is, but I have to ask, what is the purpose of all of these custom height overrides? Is it because we want 100% to be the default in JupyterLab's "Output View" mode? Can we just change it to be e.g.:

div.PSPContainer {
    height: 520px;
}

:not(.jp-NotebookPanel-notebook) div.PSPContainer {
    height: 100%;
}

I need to ask, because this feature has no tests, and I don't know how to build a voila app. Also, the PR has the word "reenable" in the title, as in, this feature has regressed already ...

[timkpaine]

In voila (and vs code and jupyterlab and Jupyter notebook for that matter) the output container expands to the size of its contents, so if you just set height: 100% you'll end up with a height 0 div since perspective tries to expand to fill its container and does not in-and-of-itself have a minimum height. Thus we need to give the container div some minimum height so that it displays, and 520px seemed to be a good heuristic from a UX standpoint (e.g. its pretty close to the default pandas max height when it collapses intermediate rows).

You can run a voila app with voila <notebook.ipynb> and it will run locally, I don't think it really requires tests since for all these various platforms we just need to find the container element and set a height next to the other container blocks.

Your change is fine but I think there is a reason for how we do it (though I am not aware of the reason 😄). I know we set height 98% in the viewer so we have room for that resize part (in case someone wants to make the perspective widget larger than 520px). Im ok with setting an absolute div.PSPContainer { height: 520px } but im unsure of the implications across outputs we don't know about (e.g. other than Jupyter Notebook, JupyterLab, Voilà, and VS Code, which are the 4 we've been tracking).

[texodus]

I've cherry-picked this into #2623, closing in favor of this PR.