doctests run in ~19 minutes now instead of ~55 minutes. This confirms that set_environment_texture is the issue.
https://github.com/pyvista/pyvista/actions/runs/14151693064/job/39645683775?pr=7357

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.06%. Comparing base (6cafaf5) to head (bef8845).
Report is 1 commits behind head on main.

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  Coverage   96.05%   96.06%           
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  Files         149      149           
  Lines       30577    30599   +22     
  Branches     4009     4012    +3     
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+ Hits        29372    29394   +22     
  Misses        572      572           
  Partials      633      633           

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I have a working fix. I am not sure how we want to roll this out. Some options:

1. Enable this fix with an environment variable (e.g. os.environ['PYVISTA_DOWNSAMPLE_ENVIRONMENT_TEXTURE'] = 'true'). This fix is likely specific to our CI environment, so with this option we always downsample for CI purposes. We could add a github label to disable this (e.g. when building from main or for releases) but otherwise have this set true by default.
2. Add this as a keyword option for set_environment_texture, e.g. image_lighting_sampling_rate=None. This is better because it avoids managing env variables but is not ideal because then we always need to remember to set this value (e.g. image_lighting_sampling_rate=0.1 when writing new example. This may also have limited use since it's only for specific environments.

may be resetting the theme globally and setting resample_environment_texture=False as a result,

Weird, the addition from b0657c0 should be be run before and after every example.

It seems likely to me that the theme set in doc/source/conf.py never persisted throughout the whole doc build and is now being exposed in this PR. How do the themes get reset during docstring building? There is a fixture in conftest.py in pyvista/ but this will only run during doctest.

may be resetting the theme globally and setting resample_environment_texture=False as a result,

Weird, the addition from b0657c0 should be be run before and after every example.

Yes you're right, the gallery has before and after events which run reset_pyvista so the gallery is all good.

I had another look through conf.py and think maybe the plot directive is resetting the theme here:

This is a strong signal that a new documentation-build theme from #7389 may be needed here so that we can do:

- __s_p_t('document')
+ __s_p_t('doc_build')

(assuming we call the theme 'doc_build')

I had another look through conf.py and think maybe the plot directive is resetting the theme here:

So many places that the theme has to be reset. Good find.

This is a strong signal that a new documentation-build theme from #7389 may be needed here so that we can do:

Even if there is a way to do it without the documentation-building theme, it is turning out to be a nightmare to keep all these pieces in sync, so I agree that #7389 is becoming higher priority.

This is once again ready for review. The theme is now applied consistently for all document testing and building, and build time is < 2hrs, docstring tests about 25 mins.

The build is expected to fail once more to generate new cache images but otherwise this PR should be good to go.

Also, these examples are still the slowest to run in CI.

new durations from https://github.com/pyvista/pyvista/actions/runs/14184108844/job/39736183963?pr=7357#step:11:8745

====================== slowest reading durations =======================
63.921 api/examples/_autosummary/pyvista.examples.downloads.download_cubemap_space_16k
63.870 api/examples/_autosummary/pyvista.examples.downloads.download_cubemap_space_4k
62.112 api/examples/_autosummary/pyvista.examples.gltf.download_damaged_helmet
61.169 api/examples/_autosummary/pyvista.examples.downloads.download_sky_box_cube_map
60.977 api/plotting/_autosummary/pyvista.Plotter.set_environment_texture

This is much better than originally reported from #6993 (comment), but still, I wonder if we should try resample=0.05 by default instead of 0.1 ?

new sampling rate is now 1/16 (0.0625), with these new build times:

====================== slowest reading durations =======================
47.300 api/examples/dataset_gallery
45.293 api/core/_autosummary/pyvista.Texture.plot
44.820 api/examples/_autosummary/pyvista.examples.downloads.download_cubemap_space_16k
44.706 api/examples/_autosummary/pyvista.examples.downloads.download_cubemap_space_4k
43.235 api/examples/_autosummary/pyvista.examples.gltf.download_damaged_helmet

These are still among the slowest examples, but I think this is OK for now. This can also be tuned later if needed once we enable testing of the durations to enforce an upper limit.