Replace HoloViews widgets with Panel

[philippjfr]

Replacing HoloViews widgets with Panel widgets.

Requires holoviz/panel#543 to match the previous styling.

• Check matplotlib
• Check plotly
• Check bokeh
• Check fps works
• Check periodic works
• Check server works
• Ensure widget json data export works (especially for docs)
• Fix Notebook archive should support interactive holomaps #449
• Fixes HoloMap wrongly renders missing data  #1677
• Fixes Saving scrubber to html broken (result is slider instead) #2885
• Add tests

Closes #3868
Closes #3212
Closes #84
Closes #3027

[jonmmease]

If I merge #3837 into this branch, and use the panel version from holoviz/panel#529, I'm able to get a plotly HoloMap to update with the slider 🎉

import numpy as np
import holoviews as hv
import panel as pn
hv.extension("plotly")

frequencies = [0.5, 0.75, 1.0, 1.25]

def sine_curve(phase, freq):
    xvals = [0.1* i for i in range(100)]
    return hv.Curve((xvals, [np.sin(phase+freq*x) for x in xvals]))

curve_dict = {f:sine_curve(0,f) for f in frequencies}

hmap = hv.HoloMap(curve_dict, kdims='frequency')
hmap

I do see an error in the JS console each time the slider is moved.

But the plot does update successfully.

I was trying to get a better understanding of what the JS side is doing here, so I saved the HoloMap to a standalone HTML file with

hv.save(hmap, 'hmap_plotly.html')

But in the resulting HTML file the slider updates don't update the plot. This is also the case for the bokeh extension.

[philippjfr]

I do see an error in the JS console each time the slider is moved.

That should be fixed in bokeh 1.3.0, it's some minor bug to do with the slider tooltip.

[philippjfr]

I was trying to get a better understanding of what the JS side is doing here, so I saved the HoloMap to a standalone HTML file with

Still need to look at this, suspect save does not correctly use the panel embed features yet.

[jonmmease]

Do you think this will be a somewhat long-running branch? Would it make sense for me to PR the plotly updates into this branch?

[philippjfr]

Do you think this will be a somewhat long-running branch? Would it make sense for me to PR the plotly updates into this branch?

I think that probably makes sense. Can't say quite how long this will take and keeping the two PRs in sync seems like a pain.

[jonmmease]

Sounds good. I'll make your suggested updates in the other branch, then rebase on this and open a new PR.

[jonmmease]

Digging into the save issue a little. The resulting Bokeh state model is empty. And I think it starts with the fact that panel.select(Widget) returns empty on the panel.pane.holoviews.HoloViews object that .save(embed=True) is called on.

https://github.com/pyviz/panel/blob/b274c45252c54091dab4caf38a2b4b9a31d75c4b/panel/io/embed.py#L105-L106

panel.widgets is empty, but panel.widgets_from_dimensions(panel.object) returns the DiscreteSlider instance.

[philippjfr]

Fixed the widget saving issue.

[jonmmease]

capturing note by @philippjfr from #3851 (comment).

I think at least for the simple matplotlib case we should probably not require panel...

This got me thinking, rather than just doing this for matplotlib maybe we should have a mode that allows non-dynamic non-widget figures to be rendered by their respective backend libraries. In version 4, plotly.py has a pretty flexible rendering system and can display plots in a bunch of contexts that full-blown HoloViews can't (Colab, VSCode, etc.). And of course matplotlib works everywhere, and I believe bokeh's support is pretty wide as well.

[jbednar]

I agree; sounds like a good baseline so that people can still use most HoloViews/hvPlot functionality anywhere.

[philippjfr]

In version 4, plotly.py has a pretty flexible rendering system and can display plots in a bunch of contexts that full-blown HoloViews can't (Colab, VSCode, etc.).

Last I checked we can render in VSCode and nteract now. Colab is an issue because they iframe the cell outputs which means the extension has to be loaded for each individual cell. I'd be okay leaving that for a later PR and doing the simplest thing in this PR.

[jbednar]

Looks fabulous! I only reviewed the new code, not what was deleted, but I don't think I'll miss any of the deleted bits. Upshot:

[jlstevens]

Looks great! Very happy to see a load of nasty code (including inline JS) go away...

I have two very minor suggestions relating to the code but otherwise I am happy to merge. I suppose my only other thought is it would be good to record the sort of (hopefully minor!) changes people might expect to see the CHANGELOG/release notes...

[jlstevens]

It would be nice to have a shorted name than widget_location but I don't currently have any better suggestions...

[jlstevens]

I won't wait for appveyor to go green as it is taking a while to start and all the other tests are green. I'm very happy to see 2000+ lines of old widget code removed and to let panel handle that side of HoloViews in a more maintainable and future proof way. Merging!

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