[cu2qu] Handle degenerate case of 3 equal points #3903
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Dealing with a situation where open corner erasure is producing a cubic segment where all the points are equal, which is subsequently falling through the conversion to quadratics. This handles that situation naively, with a branch; actually improving the robustness of the numerical code is an exercise for someone else.
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i'm not sure about this patch, it's causing a bunch of other failures I need to investigate... |
How does it fail? |
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Maybe add a failing test first. |
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the test case included here fails if you run it against main. |
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I suggest the following fix: diff --git a/Lib/fontTools/cu2qu/cu2qu.py b/Lib/fontTools/cu2qu/cu2qu.py
index c0d4cf947..42c8f3983 100644
--- a/Lib/fontTools/cu2qu/cu2qu.py
+++ b/Lib/fontTools/cu2qu/cu2qu.py
@@ -273,6 +273,8 @@ def calc_intersect(a, b, c, d):
try:
h = dot(p, a - c) / dot(p, cd)
except ZeroDivisionError:
+ if a == b == c == d:
+ return a
return complex(NAN, NAN)
return c + cd * h |
anthrotype
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Aug 14, 2025
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closing in favour of #3904 |
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I'm dealing with a situation where open corner erasure is producing a cubic segment where all the points are equal, which is subsequently falling through the conversion to quadratics.
This handles that situation naively, with a branch; actually improving the robustness of the numerical code is an exercise for someone else.