From 301831e0965dd8fc60b6126caf02c43ddec195b2 Mon Sep 17 00:00:00 2001
From: AJ Isaacs <ajisaacs27@gmail.com>
Date: Fri, 3 Apr 2026 22:26:09 -0400
Subject: [PATCH] fix: correct Width/Length axis swap in best-fit slide offsets
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BuildOffsets had Width and Length swapped after the Box axis correction
in c5943e2. Horizontal pushes used Length (X) for perpendicular sweep
and Width (Y) for push start — backwards. This caused part2 to start
inside part1's footprint, producing overlapping best-fit pairs.

Added regression test that verifies no kept best-fit pairs overlap.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 .../BestFit/RotationSlideStrategy.cs          | 14 ++--
 OpenNest.Tests/BestFit/BestFitOverlapTests.cs | 70 +++++++++++++++++++
 2 files changed, 78 insertions(+), 6 deletions(-)
 create mode 100644 OpenNest.Tests/BestFit/BestFitOverlapTests.cs

diff --git a/OpenNest.Engine/BestFit/RotationSlideStrategy.cs b/OpenNest.Engine/BestFit/RotationSlideStrategy.cs
index a5706a7..7d76e16 100644
--- a/OpenNest.Engine/BestFit/RotationSlideStrategy.cs
+++ b/OpenNest.Engine/BestFit/RotationSlideStrategy.cs
@@ -89,16 +89,18 @@ namespace OpenNest.Engine.BestFit
 
                 if (isHorizontalPush)
                 {
-                    perpMin = -(bbox2.Length + spacing);
-                    perpMax = bbox1.Length + bbox2.Length + spacing;
-                    pushStartOffset = bbox1.Width + bbox2.Width + spacing * 2;
-                }
-                else
-                {
+                    // Perpendicular sweep along Y → Width; push extent along X → Length
                     perpMin = -(bbox2.Width + spacing);
                     perpMax = bbox1.Width + bbox2.Width + spacing;
                     pushStartOffset = bbox1.Length + bbox2.Length + spacing * 2;
                 }
+                else
+                {
+                    // Perpendicular sweep along X → Length; push extent along Y → Width
+                    perpMin = -(bbox2.Length + spacing);
+                    perpMax = bbox1.Length + bbox2.Length + spacing;
+                    pushStartOffset = bbox1.Width + bbox2.Width + spacing * 2;
+                }
 
                 var alignedStart = System.Math.Ceiling(perpMin / stepSize) * stepSize;
 
diff --git a/OpenNest.Tests/BestFit/BestFitOverlapTests.cs b/OpenNest.Tests/BestFit/BestFitOverlapTests.cs
new file mode 100644
index 0000000..3e5a983
--- /dev/null
+++ b/OpenNest.Tests/BestFit/BestFitOverlapTests.cs
@@ -0,0 +1,70 @@
+using OpenNest.CNC;
+using OpenNest.Converters;
+using OpenNest.Engine.BestFit;
+using OpenNest.Geometry;
+using OpenNest.IO;
+using Xunit.Abstractions;
+
+namespace OpenNest.Tests.BestFit;
+
+public class BestFitOverlapTests
+{
+    private const string DxfPath = @"C:\Users\AJ\Desktop\Templates\4526 A14 PT16.dxf";
+    private readonly ITestOutputHelper _output;
+
+    public BestFitOverlapTests(ITestOutputHelper output) => _output = output;
+
+    private static Drawing MakeRoundedRect(double w = 7.25, double h = 3.31, double r = 0.5)
+    {
+        var pgm = new Program();
+        pgm.Codes.Add(new RapidMove(new Vector(0, 0)));
+        pgm.Codes.Add(new LinearMove(new Vector(w - r, 0)));
+        pgm.Codes.Add(new ArcMove(new Vector(w, r), new Vector(w - r, r), RotationType.CW));
+        pgm.Codes.Add(new LinearMove(new Vector(w, h - r)));
+        pgm.Codes.Add(new ArcMove(new Vector(w - r, h), new Vector(w - r, h - r), RotationType.CW));
+        pgm.Codes.Add(new LinearMove(new Vector(0, h)));
+        pgm.Codes.Add(new LinearMove(new Vector(0, 0)));
+        return new Drawing("rounded-rect", pgm);
+    }
+
+    private static Drawing ImportDxf()
+    {
+        if (!File.Exists(DxfPath))
+            return null;
+
+        var importer = new DxfImporter();
+        importer.GetGeometry(DxfPath, out var geometry);
+        var pgm = ConvertGeometry.ToProgram(geometry);
+        return new Drawing("PT16", pgm);
+    }
+
+    [Fact]
+    public void KeptPairs_NoOverlap()
+    {
+        var drawing = ImportDxf() ?? MakeRoundedRect();
+        var bbox = drawing.Program.BoundingBox();
+        _output.WriteLine($"Drawing: {drawing.Name}, bbox={bbox.Length:F2} x {bbox.Width:F2}");
+
+        var finder = new BestFitFinder(120, 60);
+        var results = finder.FindBestFits(drawing);
+
+        var kept = results.Where(r => r.Keep).ToList();
+        _output.WriteLine($"Total results: {results.Count}, Kept: {kept.Count}");
+
+        var overlapping = 0;
+
+        foreach (var result in kept)
+        {
+            var parts = result.BuildParts(drawing);
+            if (parts[0].Intersects(parts[1], out var pts))
+            {
+                overlapping++;
+                _output.WriteLine($"  OVERLAP #{overlapping}: Test {result.Candidate.TestNumber} " +
+                    $"Part2Rot={OpenNest.Math.Angle.ToDegrees(result.Candidate.Part2Rotation):F1}° " +
+                    $"collision pts={pts.Count}");
+            }
+        }
+
+        Assert.Equal(0, overlapping);
+    }
+}