Require non-zero dash value #22569
Require non-zero dash value #22569
Conversation
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Maybe one would also like to validate the rcParams like this? No negative and at least one non-zero? Or simply go with all positive (no zeros)? |
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We can of course decide on whatever behavior we want, but note that at least cairo and svg allow zero-length "on" segments, as these will draw squares if the linecap is square and circles if the linecap is round (https://cairographics.org/manual/cairo-cairo-t.html#cairo-set-dash, https://svgwg.org/svg2-draft/paths.html#ZeroLengthSegments). |
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OK! Then I think it makes sense to still allow it (even without your insight, it can still break existing scripts if we disallow it). |
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I think the right check is that the sequence seeds to sum to 0. I suspect the hang reported by that user is because we are trying to draw a line, but only taking 0 sized steps. Having at least 1 non-zero step would fix that. |
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So negative steps are OK? If not, I do not really see the difference between checking for at least one positive value and sum != 0. |
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At least Cairo does not allow negative segments (https://cairographics.org/manual/cairo-cairo-t.html#cairo-set-dash). I suppose if they don't have it, we don't need it either. |
PR Summary
In #14498 (comment) it is mentioned that an all zero
dasheshangs.This PR introduces an exception for this case.
One may consider changing
matplotlib/lib/matplotlib/backend_bases.py
Line 925 in c57c878
I did not manage to test this properly. Code that generates exceptions in the shell does not do it in the tests. Not sure why.
PR Checklist
Tests and Styling
pytestpasses).flake8-docstringsand runflake8 --docstring-convention=all).Documentation
doc/users/next_whats_new/(follow instructions in README.rst there).doc/api/next_api_changes/(follow instructions in README.rst there).