PR Summary

Currently, non-sphinx-gallery plots in the documentation (for example, from a.. plot:: directive in a docstring) produce plots that do not scale with screen size. This means that on e.g. phones, the plots get chopped off, as seen here:

Other Sphinx extensions (gallery, the inheritance diagram extension, etc) add their own custom CSS to make the images fit in the page. I copied the approach taken bysphinx.ext.graphviz to get the following result:

This became increasingly important for my GSOD work (e.g.#18544, where the API docs center around the inclusion of a "demo" figure showing the various options).

Edit: additionally, I had to fix an existing bug inplot_directive.TEMPLATE that caused Sphinx to warn (failing our tests) whenever there is both a caption and a custom class assigned to a figure.

PR Checklist

• Has pytest style unit tests (andpytest passes).
• IsFlake 8 compliant (runflake8 on changed files to check).
• [N/A] New features are documented, with examples if plot related.
• Documentation is sphinx and numpydoc compliant (the docs shouldbuild without error).
• Conforms to Matplotlib style conventions (installflake8-docstrings and runflake8 --docstring-convention=all).
• [N/A] New features have an entry indoc/users/next_whats_new/ (follow instructions in README.rst there).
• [N/A] API changes documented indoc/api/next_api_changes/ (follow instructions in README.rst there).