Fix path simplification of closed loops #21387
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Ah, I forgot there was a reason for enabling the clipping. It (along with adding a clip box) fixes an overflow in PGF, #4482. That's a long standing bug that we could revert, but as we are still waiting for NumPy wheels, I'll try again to see if I can convince Agg to draw the way we want. |
Because that is really what it checks and is for.
All the other path converters do an early return if they're disabled, which can be done here as well to drop one extra indent level.
If we ever break a path due to a NaN, then it can never be closed, as Agg will try to close it back to the last MOVETO. This would not be the initial point of the loop, but the first point after the break. So we need to emulate a CLOSEPOLY by adding a LINETO the original initial point in the path.
Otherwise, a random spurious line connecting the last clipped point with the initial point is drawn unintentionally. Fixes matplotlib#21300
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I've repurposed this to instead be fixing closed loops the right way. The original description has been updated with further details. |
tacaswell
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Oct 27, 2021
jklymak
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Oct 28, 2021
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…387-on-v3.5.x Backport PR #21387 on branch v3.5.x (Fix path simplification of closed loops)
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PR Summary
When paths are closed, if we emit a closing code, Agg will attempt to actually close the path, if it was split due to NaN removal or clipping. We do not want that to occur, since that would make phantom lines appear on any paths that are larger than the figure or have NaNs.
This fixes both NaN removal and clipping, so that if any segments are removed, the close no longer occurs and is replaced by a
LINETOinstead.There should be tests that cover all cases. The
test_simplify_curvetolerance change is because of an included NaN that caused a closed path that shouldn't have been there.Note, the first three commits are some cleanup, so this PR is a little larger looking that the fix really is. I can split that out if people prefer.
PR Checklist
pytestpasses).flake8on changed files to check).flake8-docstringsand runflake8 --docstring-convention=all).doc/users/next_whats_new/(follow instructions in README.rst there).doc/api/next_api_changes/(follow instructions in README.rst there).