[ttx_diff.py] only normalize contour order when contours perfectly match between fontc vs fontmake#1654
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anthrotype merged 2 commits intomainfrom Sep 25, 2025
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with underscore, not hyphen, because absl.flags is particular
Previously, ttx_diff.py would normalize contour order within each compiler's output independently, which could create misleading diffs when the contours actually differed (e.g., different starting points for all-offcurve contours). This change compares contours between fontc and fontmake first, and only normalizes the order when the contours are identical (as sets). When contours differ, they are left in their original order to make the actual differences more apparent. Fixes part of #1653
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cmyr
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One concern inline... boy do I wish we had tests for this code 😅
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Fixes part of #1653
Previously, ttx_diff.py would normalize contour order within each compiler's output independently, which could create misleading diffs when the contours actually differed (e.g., different starting points).
This change compares contours between fontc and fontmake first, and only normalizes the order of whole contours when the set of contors serialized as xml strings is identical. When contours differ, they are left in their original order to make the actual differences more apparent.
The ttx diff for Sirivennela-Regular.ufo now looks more sane and makes the different starting points more evident:
I also exposed the
--keep-directionflag to ttx_diff.py, so it gets forwarded to fontc and fontmake. I used underscore instead of hyphen because absl.flags wants that.JMM