From 0a33047ad6a3f1781e05348d48fd75e56c6688bf Mon Sep 17 00:00:00 2001
From: AJ Isaacs <ajisaacs27@gmail.com>
Date: Wed, 18 Mar 2026 19:53:08 -0400
Subject: [PATCH] fix(engine): prevent FillExtents overlap and add strategy
 filter API
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FillExtents vertical copy distance was not clamped, allowing rows to be
placed overlapping each other when slide calculations returned large
values. Clamp to pairHeight + partSpacing minimum, matching FillLinear.

Also add FillStrategyRegistry.SetEnabled() to restrict which strategies
run — useful for isolating individual strategies during troubleshooting.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 OpenNest.Engine/Fill/FillExtents.cs             | 14 ++++----------
 .../Strategies/FillStrategyRegistry.cs          | 17 ++++++++++++++++-
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/OpenNest.Engine/Fill/FillExtents.cs b/OpenNest.Engine/Fill/FillExtents.cs
index ff06073..40f7dee 100644
--- a/OpenNest.Engine/Fill/FillExtents.cs
+++ b/OpenNest.Engine/Fill/FillExtents.cs
@@ -172,18 +172,12 @@ namespace OpenNest.Engine.Fill
             if (minSlide >= double.MaxValue || minSlide < 0)
                 return pairHeight + partSpacing;
 
-            // Boundaries are inflated by halfSpacing, so when inflated edges touch
-            // the actual parts have partSpacing gap. Match FillLinear's pattern:
-            // startOffset = pairHeight (no extra spacing), copyDist = height - slide.
+            // Match FillLinear.ComputeCopyDistance: copyDist = startOffset - slide,
+            // clamped so it never goes below pairHeight + partSpacing to prevent
+            // bounding-box overlap from spurious slide values.
             var copyDist = pairHeight - minSlide;
 
-            // Boundaries are inflated by halfSpacing, so the geometry-aware
-            // distance already guarantees partSpacing gap. Only fall back to
-            // bounding-box distance if the calculation produced a non-positive value.
-            if (copyDist <= Tolerance.Epsilon)
-                return pairHeight + partSpacing;
-
-            return copyDist;
+            return System.Math.Max(copyDist, pairHeight + partSpacing);
         }
 
         private static double SlideDistance(
diff --git a/OpenNest.Engine/Strategies/FillStrategyRegistry.cs b/OpenNest.Engine/Strategies/FillStrategyRegistry.cs
index 1a49604..581b4bf 100644
--- a/OpenNest.Engine/Strategies/FillStrategyRegistry.cs
+++ b/OpenNest.Engine/Strategies/FillStrategyRegistry.cs
@@ -11,6 +11,7 @@ namespace OpenNest.Engine.Strategies
     {
         private static readonly List<IFillStrategy> strategies = new();
         private static List<IFillStrategy> sorted;
+        private static HashSet<string> enabledFilter;
 
         static FillStrategyRegistry()
         {
@@ -18,7 +19,21 @@ namespace OpenNest.Engine.Strategies
         }
 
         public static IReadOnlyList<IFillStrategy> Strategies =>
-            sorted ??= strategies.OrderBy(s => s.Order).ToList();
+            sorted ??= (enabledFilter != null
+                ? strategies.Where(s => enabledFilter.Contains(s.Name)).OrderBy(s => s.Order).ToList()
+                : strategies.OrderBy(s => s.Order).ToList());
+
+        /// <summary>
+        /// Restricts the active strategies to only those whose names are listed.
+        /// Pass null to restore all strategies.
+        /// </summary>
+        public static void SetEnabled(params string[] names)
+        {
+            enabledFilter = names != null && names.Length > 0
+                ? new HashSet<string>(names, StringComparer.OrdinalIgnoreCase)
+                : null;
+            sorted = null;
+        }
 
         public static void LoadFrom(Assembly assembly)
         {