Modify hexbin to respect :rc:patch.linewidth

[yuzie007]

Always thank you developpers for maintaining Matplotlib!

PR Summary

Currently in hexbin, linewidths given to PolyCollection is hard-coded as 1.0. In pcolormesh and hist2d, the default value respects :rc:patch.linewidth (default: 1.0). To improve the consistency among the methods, in this very short PR I would like to suggest respecting patch.linewidth also in hexbin.

Notes

While this PR does not change the default behavior, do we need to have some additional tests?

The default linewidth in pcolormesh and hist2d may be not immediately visually noticeable because the default edgecolors value is none. (In hexbin, edgecolors defaults to face.)

The default linewidths in pcolor and tripcolor are also hard-coded but as 0.25. It may be also possible to respect :rc:patch.linewidth also in these methods, while the plot looking changes when edgecolors other than none is given.

In principle, it should be also possible to simply remove the linewidths keyword from the arguments and pass it into PolyCollection simply via **kwargs, but then we need to pop linewidths before making marginal plots and need to modify the docstring a bit also for this.

I can also later add note in doc/api/next_api_changes if this is reasonable.

PR Checklist

Documentation and Tests

• Has pytest style unit tests (and pytest passes)
• Documentation is sphinx and numpydoc compliant (the docs should build without error).
• New plotting related features are documented with examples.

Release Notes

• New features are marked with a .. versionadded:: directive in the docstring and documented in doc/users/next_whats_new/
• API changes are marked with a .. versionchanged:: directive in the docstring and documented in doc/api/next_api_changes/
• Release notes conform with instructions in next_whats_new/README.rst or next_api_changes/README.rst

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[jklymak]

This seems reasonable to me. Note that the default mpl.rcParams['patch.lineiwdth'] = 1.0 so this won't be a breaking change for most people. OTOH, if someone has set to non-default this will make a (small) change in appearance. I suspect we could get away with doing this, with an API behaviour change note.

[dstansby]

Looks good to me - would you be able to put a quick note in doc/api/next_api_changes/behaviour about this just so it's documented for users somewhere?

[oscargus]

With a change note this should be good to go in 3.8.

[yuzie007]

I am sorry for my long silence... Thank you so much developers for your kind suggestions. I have now added also a note in doc/api/next_api_changes/behaviour.

Although I was not very sure what is the best practice, I did rebase based on the latest main branch and rewrote the changes together with the note above.

[melissawm]

I believe the failures are unrelated here.

[rcomer]

Thanks for your work on this @yuzie007 and sorry it’s taken a while to review - I think it just slipped through the cracks. Congratulations on your first PR in Matplotlib! We hope to hear from you again.