From a18b5398de42190e42699ac3d2e91274ef0c22db Mon Sep 17 00:00:00 2001
From: AJ Isaacs <ajisaacs27@gmail.com>
Date: Thu, 7 May 2026 06:52:14 -0400
Subject: [PATCH] fix(io): remove zero-sweep arcs during DXF import
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DXF files can contain degenerate arcs where start angle equals end angle
(zero sweep), often left as construction artifacts by CAD software.
These create spurious shapes in ShapeBuilder — e.g. SULLYS-033.dxf
showed 5 loops instead of 4 (3 cutouts + perimeter).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 OpenNest.IO/CadImporter.cs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/OpenNest.IO/CadImporter.cs b/OpenNest.IO/CadImporter.cs
index 75f049a..edf806c 100644
--- a/OpenNest.IO/CadImporter.cs
+++ b/OpenNest.IO/CadImporter.cs
@@ -27,6 +27,7 @@ namespace OpenNest.IO
             var dxf = Dxf.Import(path);
 
             RemoveDuplicateArcs(dxf.Entities);
+            RemoveZeroSweepArcs(dxf.Entities);
 
             var bends = new List<Bend>();
             if (options.DetectBends && dxf.Document != null)
@@ -156,6 +157,12 @@ namespace OpenNest.IO
             return drawing;
         }
 
+        internal static void RemoveZeroSweepArcs(List<Entity> entities)
+        {
+            entities.RemoveAll(e =>
+                e is Arc arc && arc.StartAngle.IsEqualTo(arc.EndAngle, Tolerance.ChainTolerance));
+        }
+
         internal static void RemoveDuplicateArcs(List<Entity> entities)
         {
             var circles = entities.OfType<Circle>().ToList();