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FIX: Prevent set_alpha from changing color of legend patch#22009

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QuLogic merged 1 commit intomatplotlib:mainfrom
StefRe:fix/issue21966
Dec 21, 2021
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FIX: Prevent set_alpha from changing color of legend patch#22009
QuLogic merged 1 commit intomatplotlib:mainfrom
StefRe:fix/issue21966

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@StefRe StefRe commented Dec 19, 2021

of polycollection (e.g. from fill_between) by updating original edge and face color too.

Closes #21966

PR Summary

When updating the properties of the legend patch from the PolyCollection returned by fill_between, the HandlerPolyCollection failed to set the original edge and face colors so that when later setting the alpha of the patch, its color was set to the default C0.
This was fixed by updating the original edge and face colors too.

PR Checklist

Tests and Styling

  • Has pytest style unit tests (and pytest passes).
  • Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

  • [n/a] New features are documented, with examples if plot related.
  • [n/a] New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
  • [n/a] API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
  • [n/a] Documentation is sphinx and numpydoc compliant (the docs should build without error).

@StefRe
FIX: Prevent set_alpha from changing color of legend patch
4695cfe 
of polycollection (e.g. from fill_between) by updating original
edge and face color too.
@tacaswell tacaswell added this to the v3.5.2 milestone Dec 20, 2021
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tacaswell commented Dec 20, 2021

@StefRe Do you think there something reasonable thing to search on to see if we have any other moles of this category that need to be whacked?

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StefRe commented Dec 20, 2021

@tacaswell
I tested all plot types and the custom legend types from the legend guide and they're all OK. So I'm pretty confident that there no more instances of this issue, but in the end this is just a subjective assessment, not a automatic code review.

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tacaswell commented Dec 20, 2021

It is much easier to prove a bug exists than it does not exist ;) I was thinking of a heuristiic like "skimmed all of the functions called def _update_prop that exist in the code base and they all remember to copy the original colors", but testing that it works is better 👍🏻 . Thank you for the diligence.

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StefRe commented Dec 20, 2021

@tacaswell a very rough heuristics would be looking around ...facecolor assignments and see if other ...facecolor properties (if they exist) are assigned too:

grep -r --include=*.py --exclude=test*.py -C5 -n 'facecolor = [a-zA-Z_][a-zA-Z0-9_\.]*facecolor' *.py | grep 'facecolor\|^\-'

which yields

collections.py:918:        self._original_facecolor = other._original_facecolor
collections.py-919-        self._facecolors = other._facecolors
--
legend_handler.py-789-        legend_handle._facecolor = first_color(orig_handle.get_facecolor())
legend_handler.py:791:        legend_handle._original_facecolor = orig_handle._original_facecolor
--
lines.py:1269:        self._markerfacecolor = other._markerfacecolor
lines.py-1270-        self._markerfacecoloralt = other._markerfacecoloralt
--
patches.py:257:        self._facecolor = other._facecolor
patches.py:259:        self._original_facecolor = other._original_facecolor

According to this, everything seems to be fine :).

@QuLogic QuLogic merged commit 95524e7 into matplotlib:main Dec 21, 2021
meeseeksmachine pushed a commit to meeseeksmachine/matplotlib that referenced this pull request Dec 21, 2021
@QuLogic @meeseeksmachine
Backport PR matplotlib#22009: FIX: Prevent set_alpha from changing co…
4630a4a 
…lor of legend patch
@meeseeksmachine meeseeksmachine mentioned this pull request Dec 21, 2021
Merged
@StefRe StefRe deleted the fix/issue21966 branch December 21, 2021 07:45
QuLogic added a commit that referenced this pull request Dec 21, 2021
@QuLogic
Merge pull request #22024 from meeseeksmachine/auto-backport-of-pr-22…
8c597fb 
…009-on-v3.5.x

Backport PR #22009 on branch v3.5.x (FIX: Prevent set_alpha from changing color of legend patch)
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@tacaswell tacaswell tacaswell approved these changes

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[Bug]: Regression: Setting alpha on legend handle changes patch color

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