MNE-report integration with 3D viz is broken

When I do the following:

import os
import os.path as op

import numpy as np
import matplotlib.pyplot as plt

from mayavi import mlab

import mne
from mne.viz import use_3d_backend
from mne.datasets import sample

data_path = sample.data_path()
sample_dir = os.path.join(data_path, 'MEG', 'sample')
subjects_dir = os.path.join(data_path, 'subjects')

fname_stc = os.path.join(sample_dir, 'sample_audvis-meg')

stc = mne.read_source_estimate(fname_stc, subject='sample')

initial_time = 0.1

with use_3d_backend('mayavi'):
    brain = stc.plot(subjects_dir=subjects_dir, initial_time=initial_time,
                     clim=dict(kind='value', lims=[3, 6, 9]))

report = mne.Report()
report.add_figs_to_section(mlab.gcf(), 'caption')

I get:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
~/Documents/github_repos/mne-python/tutorials/source-modeling/plot_visualize_stc.py in <module>
     29 report = mne.Report()
     30 fig = mlab.gcf()
---> 31 report.add_figs_to_section(mlab.gcf(), 'caption')
     32 
     33 sfdfdfd

~/Documents/github_repos/mne-python/mne/report.py in add_figs_to_section(self, figs, captions, section, scale, image_format, comments, replace)
   1110             img_klass = self._sectionvars[section]
   1111 
-> 1112             img = _fig_to_img(fig, image_format, scale)
   1113             html = image_template.substitute(img=img, id=global_id,
   1114                                              div_klass=div_klass,

~/Documents/github_repos/mne-python/mne/report.py in _fig_to_img(fig, image_format, scale, **kwargs)
     72     elif not isinstance(fig, Figure):
     73         from .viz.backends.renderer import backend, MNE_3D_BACKEND_TESTING
---> 74         backend._check_3d_figure(figure=fig)
     75         if not MNE_3D_BACKEND_TESTING:
     76             img = backend._take_3d_screenshot(figure=fig)

~/Documents/github_repos/mne-python/mne/viz/backends/_pyvista.py in _check_3d_figure(figure)
    845 def _check_3d_figure(figure):
    846     if not isinstance(figure, _Figure):
--> 847         raise TypeError('figure must be an instance of _Figure.')
    848 
    849 

TypeError: figure must be an instance of _Figure.

The error is very cryptic. If you do set_3d_backend at the beginning of the script, it works.

Also, having the figure handle easily accessible via brain.fig for both backends and then being able to pass that into the report will be a gamechanger.

[larsoner]

Okay let’s make this PyVista experience better rather than deal with Mayavi + PyVista mixing. @GuillaumeFavelier can you advise and update docs and maybe functions in a way that would have made things less painful for @jasmainak ?

[larsoner]

Closing this as it should be taken care of as part of #9753