There are many ways for things to end up in odd states, the goal here is to detect if the the canvas has changed under us when trying to manage the state of widgets.

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Has pytest style unit tests (andpytest passes)
[N/A] Documentation is sphinx and numpydoc compliant (the docs shouldbuild without error).
[N/A] New plotting related features are documented with examples.

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[N/A] New features are marked with a.. versionadded:: directive in the docstring and documented indoc/users/next_whats_new/
[N/A] API changes are marked with a.. versionchanged:: directive in the docstring and documented indoc/api/next_api_changes/
[N/A] Release notes conform with instructions innext_whats_new/README.rst ornext_api_changes/README.rst

tacaswell added this to thev3.7.2 milestone

Mar 29, 2023

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Mar 29, 2023

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anntzer commentedMar 29, 2023

Perhaps the simpler check would beself.canvas is self.canvas.figure.canvas? Note that while figure.canvas can change (hence the introduction of _changed_canvas), I think canvas.figure does not ever change (at least in practice... it may even be possible to spec that), so the proposed check is effectively "does the figure I initially got still use the same canvas as initially?" Also none of these attributes should ever be None, AFAICT.

Alternatively, we could additionally recordself._figure = ax.figure in the constructor and checkself._figure.canvas is self.canvas; again this should sidestep the None problems?

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tacaswell commentedMar 31, 2023

Alternatively, we could additionally record self._figure = ax.figure in the constructor and check self._figure.canvas is self.canvas; again this should sidestep the None problems?

I think that would still miss the "middle removed" issue as we have references that skip generations and we should avoid adding more hard-references than we strictly need....

But I will change toself.canvas is self.canvas.figure.canvas

tacaswell force-pushed thefix_removed_widget_axes branch from54db976 to7100b57Compare

March 31, 2023 20:08

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Modulo CI, and with an optional additional comment.

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tacaswell commentedApr 3, 2023

Hmm, we are back to not being careful enough...but only an azure?!

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anntzer commentedApr 3, 2023

That's a bit fishy, but perhaps just change all theself.ax.draw_artist(artist) byartist.draw(self.canvas.get_renderer())? (which should bypass the problem of whetherself.ax.figure is None or not -- anyways, having draw_artist be an Axes method always seemed a bit weird to me (I do realize that historically we cached the renderer on the axes, but that's not really the logical place to have it)).

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Jun 13, 2023

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tacaswell force-pushed thefix_removed_widget_axes branch froma9f4c6c todb2176fCompare

July 18, 2025 00:15

github-actionsbot added topic: widgets/UI and removed status: needs rebase labels

Jul 18, 2025

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Jul 18, 2025

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Jul 18, 2025

[Bug]: fig.savefig throws error after radiobutton axes is removed#30325

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		def_clear(self,event):
		"""Internal event handler to clear the buttons."""
		ifself.ignore(event)orself.canvas.is_saving():
		ifself.ignore(event)orself.canvasisNoneorself.canvas.is_saving():

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anntzerJul 18, 2025

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Should the canvas is not None check rather go to a newAxesWidget.ignore? (def AxesWidget.ignore(self, event): return not self.active or self.canvas is None)
Then this change and the one immediately below could go away.

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timhoffmJul 18, 2025

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I agree. This belongs logically in anAxesWidget.ignore().

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I think the patch could be better, but this is also correct.

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tacaswell commentedJul 18, 2025•
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I tried putting the check inWidget.ignore which breaks for other things which is why I originally went with the checks in_clear.

Added a new method and a couple ofsuper() calls.

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lib/matplotlib/tests/test_widgets.py

Comment on lines 1762 to 1782

		deftest_parent_axes_removal():

		fig, (ax_radio,ax_checks)=plt.subplots(1,2)

		radio=widgets.RadioButtons(ax_radio, ['1','2'],0)
		checks=widgets.CheckButtons(ax_checks, ['1','2'], [True,False])

		ax_checks.remove()
		ax_radio.remove()
		withio.BytesIO()asout:
		fig.savefig(out,format='raw')

		renderer=fig._get_renderer()
		evt=DrawEvent('draw_event',fig.canvas,renderer)
		radio._clear(evt)
		checks._clear(evt)

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timhoffmJul 18, 2025

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This is obviously some kind of smoke test as it does not contain assertions. A short description would be helpful though.

I understand that removal of the buttons should not brick the figure. But what exactly are we testing with the savefig, and what with the _clear calls? (I assume there are actually two separate tests?