Port upstream earcut changes to C# (d417600) — 2026-07-02

[github-actions]

Upstream Sync Task

@Copilot please port the upstream changes listed below to C# and open a pull request.

New commits have been pushed to mapbox/earcut since the last sync.

Previous synced commit: 73e2f97
New upstream commit: d417600
Full diff: mapbox/earcut@73e2f97...d417600

Upstream commits to port

• d417600 fix refine infinite loop on near-cocircular points
• 2a4e260 small refine speedup
• cf9d047 add triangle quality stats to demo
• 9ca8502 3.2.2
• b62d887 improve refine performance
• 453e671 fix logo after refine fix
• dfc13dd 3.2.1
• 44c6a88 small refine optimizations
• 81daadc fix refine leaving some quads unflipped

What to port

Please port all upstream changes to C# and open a pull request. Follow the PORTING_GUIDE.md for language mapping conventions.

Key files to check in the upstream diff:

• src/earcut.js → port any algorithm changes to src/Earcut/Earcut.cs
• test/fixtures/*.json → copy any new/changed fixtures to test/Earcut.Tests/fixtures/
• test/expected.json → update test/Earcut.Tests/expected.json to match

After porting:

1. Run dotnet test and ensure all tests pass
2. Update PORTING_GUIDE.md if new language patterns were introduced