Gif support for Bokeh HoloMaps

[jbednar]

If I do %%output filename="tmp" holomap='gif', it works with the Matplotlib backend, but with a Bokeh backend I get Format 'gif' does not appear to be supported`. It seems like Bokeh should now be supportable, now that Bokeh provides PNG output?

Note that #2460 proposes to remove the ImageMagick gif creation that would be one way to implement this, but presumably the pillow-based support used with Matplotlib would also work here?

[philippjfr]

Yes, but without a persistent selenium session running that will be unusably slow which is why it was not implemented immediately. So it's definitely possible but probably not useful until we have a way of reusing a selenium session.

[jbednar]

Unusably slow compared to what? At the moment the alternative, which I am watching someone do right now, is to export every figure to disk one frame at a time, then manually paste them together into a gif. Surely it can't be slower than that? So I don't see why not to simply do it and then worry later about reusing a session.