Fix signed fractional CFF coordinates - #557
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Pull request overview
This pull request fixes parsing of CFF Type 2 signed 16.16 fixed-point coordinates by treating the integer word as signed and the fractional word as unsigned, correcting outline coordinates for affected fonts (eg. Igrunok) without changing the public API.
Changes:
- Update
SimpleBinaryReader.ReadFloatFixed1616()to interpret the fractional 16-bit word as unsigned. - Add regression tests covering fixed-point decoding and a raw charstring prefix reproducer for glyph 54 coordinate stability.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| tests/SixLabors.Fonts.Tests/Tables/Cff/CffEvaluationEngineTests.cs | Adds a fixed-point reader test and a raw Type 2 prefix regression test for CFF coordinate evaluation. |
| src/SixLabors.Fonts/Tables/Cff/SimpleBinaryReader.cs | Corrects 16.16 fixed-point parsing to use an unsigned fractional word. |
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #557 +/- ##
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Coverage 81% 81%
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Files 406 406
Lines 35672 35672
Branches 5561 5561
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+ Hits 29143 29147 +4
+ Misses 5359 5356 -3
+ Partials 1170 1169 -1
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JimBobSquarePants
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JimBobSquarePants
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@Artromskiy Thank you for the fix. this is very much appreciated.
I'll merge it now ready for the next release. A nightly package will be published following merge.
Prerequisites
Description
Fix CFF Type 2 signed 16.16 parsing: the integer word is signed, while the fractional word is unsigned. This corrects the CFF outline coordinates produced for fonts such as Igrunok.
The change includes a raw glyph 54 regression test and a fixed-point reader test. The Igrunok font itself is not redistributed.
Validation performed:
The first renderable CFF implementation already showed the mismatch; the fix corrects the fractional-word interpretation without changing the public API.