perf: Optimize core math, dynamic trees, and delegates using 'in' modifier and Span

- Updated B2MathFunction methods to pass structs (B2Vec2, B2Rot, B2Transform, etc.) by read-only reference ('in') to reduce copying overhead.
- Updated B2DynamicTrees methods to pass B2AABB by read-only reference ('in').
- Refactored b2PartitionSAH in B2DynamicTrees to use Span<B2AABB> instead of arrays for improved performance.
- Updated delegate definitions in B2Delegates (e.g., b2CustomFilterFcn, b2PreSolveFcn, DrawSolidPolygonFcn) to use 'in' parameters for structs like B2ShapeId, B2Transform, and B2Vec2.
- Adjusted related callback invocations and implementations across the project to align with these signature changes.

Author: ikpil

src/Box2D.NET.Samples/Graphics/Draws.cs

@@ -60,9 +60,9 @@ public static void DrawPolygon(Draw draw, ReadOnlySpan<B2Vec2> vertices, int ver
         }
     }
 
-    public static void DrawSolidPolygon(Draw draw, ref B2Transform transform, ReadOnlySpan<B2Vec2> vertices, int vertexCount, float radius, B2HexColor color)
+    public static void DrawSolidPolygon(Draw draw, in B2Transform transform, ReadOnlySpan<B2Vec2> vertices, int vertexCount, float radius, B2HexColor color)
     {
-        AddPolygon(ref draw.polygons, ref transform, vertices, vertexCount, radius, color);
+        AddPolygon(ref draw.polygons, transform, vertices, vertexCount, radius, color);
     }
 
     public static void DrawTransform(Draw draw, B2Transform transform, float scale)

src/Box2D.NET.Samples/Graphics/SolidPolygons.cs

@@ -112,7 +112,7 @@ public static void DestroyPolygons(GL gl, ref SolidPolygonRender render)
         }
     }
 
-    public static void AddPolygon(ref SolidPolygonRender render, ref B2Transform transform, ReadOnlySpan<B2Vec2> points, int count, float radius, B2HexColor color)
+    public static void AddPolygon(ref SolidPolygonRender render, in B2Transform transform, ReadOnlySpan<B2Vec2> points, int count, float radius, B2HexColor color)
     {
         PolygonData data = new PolygonData();
         data.transform = transform;

src/Box2D.NET.Samples/SampleContext.cs

@@ -157,49 +157,49 @@ public static void DrawPolygonFcn(ReadOnlySpan<B2Vec2> vertices, int vertexCount
         DrawPolygon(sampleContext.draw, vertices, vertexCount, color);
     }
 
-    public static void DrawSolidPolygonFcn(ref B2Transform transform, ReadOnlySpan<B2Vec2> vertices, int vertexCount, float radius, B2HexColor color, object context)
+    public static void DrawSolidPolygonFcn(in B2Transform transform, ReadOnlySpan<B2Vec2> vertices, int vertexCount, float radius, B2HexColor color, object context)
     {
         SampleContext sampleContext = (SampleContext)context;
-        DrawSolidPolygon(sampleContext.draw, ref transform, vertices, vertexCount, radius, color);
+        DrawSolidPolygon(sampleContext.draw, transform, vertices, vertexCount, radius, color);
     }
 
-    public static void DrawCircleFcn(B2Vec2 center, float radius, B2HexColor color, object context)
+    public static void DrawCircleFcn(in B2Vec2 center, float radius, B2HexColor color, object context)
     {
         SampleContext sampleContext = (SampleContext)context;
         DrawCircle(sampleContext.draw, center, radius, color);
     }
 
-    public static void DrawSolidCircleFcn(ref B2Transform transform, float radius, B2HexColor color, object context)
+    public static void DrawSolidCircleFcn(in B2Transform transform, float radius, B2HexColor color, object context)
     {
         SampleContext sampleContext = (SampleContext)(context);
         DrawSolidCircle(sampleContext.draw, transform, radius, color);
     }
 
-    public static void DrawSolidCapsuleFcn(B2Vec2 p1, B2Vec2 p2, float radius, B2HexColor color, object context)
+    public static void DrawSolidCapsuleFcn(in B2Vec2 p1, in B2Vec2 p2, float radius, B2HexColor color, object context)
     {
         SampleContext sampleContext = (SampleContext)(context);
         DrawSolidCapsule(sampleContext.draw, p1, p2, radius, color);
     }
 
-    public static void DrawLineFcn(B2Vec2 p1, B2Vec2 p2, B2HexColor color, object context)
+    public static void DrawLineFcn(in B2Vec2 p1, in B2Vec2 p2, B2HexColor color, object context)
     {
         SampleContext sampleContext = (SampleContext)(context);
         DrawLine(sampleContext.draw, p1, p2, color);
     }
 
-    public static void DrawTransformFcn(B2Transform transform, object context)
+    public static void DrawTransformFcn(in B2Transform transform, object context)
     {
         SampleContext sampleContext = (SampleContext)(context);
         DrawTransform(sampleContext.draw, transform, 1.0f);
     }
 
-    public static void DrawPointFcn(B2Vec2 p, float size, B2HexColor color, object context)
+    public static void DrawPointFcn(in B2Vec2 p, float size, B2HexColor color, object context)
     {
         SampleContext sampleContext = (SampleContext)(context);
         DrawPoint(sampleContext.draw, p, size, color);
     }
 
-    public static void DrawStringFcn(B2Vec2 p, string s, B2HexColor color, object context)
+    public static void DrawStringFcn(in B2Vec2 p, string s, B2HexColor color, object context)
     {
         SampleContext sampleContext = (SampleContext)(context);
         DrawWorldString(sampleContext.draw, sampleContext.camera, p, color, s);

src/Box2D.NET.Samples/Samples/Benchmarks/BenchmarkCast.cs

@@ -163,7 +163,7 @@ void BuildScene()
         m_minTime = 1e6f;
     }
 
-    static float CastCallback(B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
+    static float CastCallback(in B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
     {
         CastResult result = context as CastResult;
         result.point = point;
@@ -173,7 +173,7 @@ static float CastCallback(B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float
     }
 
 
-    static bool OverlapCallback(B2ShapeId shapeId, object context)
+    static bool OverlapCallback(in B2ShapeId shapeId, object context)
     {
         OverlapResult result = context as OverlapResult;
         if (result.count < 32)

src/Box2D.NET.Samples/Samples/Benchmarks/BenchmarkSensor.cs

@@ -143,7 +143,7 @@ void CreateRow(float y)
         }
     }
 
-    private bool Filter(B2ShapeId idA, B2ShapeId idB)
+    private bool Filter(in B2ShapeId idA, in B2ShapeId idB)
     {
         ShapeUserData userData = null;
         if (b2Shape_IsSensor(idA))
@@ -163,7 +163,7 @@ private bool Filter(B2ShapeId idA, B2ShapeId idB)
         return true;
     }
 
-    private static bool FilterFcn(B2ShapeId idA, B2ShapeId idB, object context)
+    private static bool FilterFcn(in B2ShapeId idA, in B2ShapeId idB, object context)
     {
         BenchmarkSensor self = context as BenchmarkSensor;
         return self.Filter(idA, idB);

src/Box2D.NET.Samples/Samples/Characters/Mover.cs

@@ -93,7 +93,7 @@ private static Sample Create(SampleContext context)
         return new Mover(context);
     }
 
-    private static float CastCallback(B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
+    private static float CastCallback(in B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
     {
         CastResult result = (CastResult)context;
         result.point = point;
@@ -497,7 +497,7 @@ public override void UpdateGui()
         ImGui.End();
     }
 
-    static bool PlaneResultFcn(B2ShapeId shapeId, ref B2PlaneResult planeResult, object context)
+    static bool PlaneResultFcn(in B2ShapeId shapeId, ref B2PlaneResult planeResult, object context)
     {
         B2_ASSERT(planeResult.hit == true);
 
@@ -521,7 +521,7 @@ static bool PlaneResultFcn(B2ShapeId shapeId, ref B2PlaneResult planeResult, obj
         return true;
     }
 
-    static bool Kick(B2ShapeId shapeId, object context)
+    static bool Kick(in B2ShapeId shapeId, object context)
     {
         Mover self = (Mover)context;
         B2BodyId bodyId = b2Shape_GetBody(shapeId);

src/Box2D.NET.Samples/Samples/Collisions/CastWorld.cs

@@ -556,7 +556,7 @@ public override void Draw()
 
 
     // This callback finds the closest hit. This is the most common callback used in games.
-    static float RayCastClosestCallback(B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
+    static float RayCastClosestCallback(in B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
     {
         CastContext rayContext = (CastContext)context;
 
@@ -584,7 +584,7 @@ static float RayCastClosestCallback(B2ShapeId shapeId, B2Vec2 point, B2Vec2 norm
     // This callback finds any hit. For this type of query we are usually just checking for obstruction,
     // so the hit data is not relevant.
     // NOTE: shape hits are not ordered, so this may not return the closest hit
-    static float RayCastAnyCallback(B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
+    static float RayCastAnyCallback(in B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
     {
         CastContext rayContext = (CastContext)context;
 
@@ -614,7 +614,7 @@ static float RayCastAnyCallback(B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal,
     // NOTE: shape hits are not ordered, so this may return hits in any order. This means that
     // if you limit the number of results, you may discard the closest hit. You can see this
     // behavior in the sample.
-    static float RayCastMultipleCallback(B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
+    static float RayCastMultipleCallback(in B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
     {
         CastContext rayContext = (CastContext)context;
 
@@ -648,7 +648,7 @@ static float RayCastMultipleCallback(B2ShapeId shapeId, B2Vec2 point, B2Vec2 nor
     }
 
     // This ray cast collects multiple hits along the ray and sorts them.
-    static float RayCastSortedCallback(B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
+    static float RayCastSortedCallback(in B2ShapeId shapeId, B2Vec2 point, B2Vec2 normal, float fraction, object context)
     {
         CastContext rayContext = (CastContext)context;
 

src/Box2D.NET.Samples/Samples/Collisions/DynamicTree.cs

@@ -58,7 +58,7 @@ static bool QueryCallback(int proxyId, ulong userData, ref DynamicTreeContext co
         return true;
     }
 
-    static float RayCallback(ref B2RayCastInput input, int proxyId, ulong userData, ref DynamicTreeContext context)
+    static float RayCallback(in B2RayCastInput input, int proxyId, ulong userData, ref DynamicTreeContext context)
     {
         DynamicTree sample = context.tree;
         Proxy proxy = sample.m_proxies[userData];

src/Box2D.NET.Samples/Samples/Collisions/OverlapWorld.cs

@@ -64,7 +64,7 @@ private static Sample Create(SampleContext context)
     }
 
 
-    static bool OverlapResultFcn(B2ShapeId shapeId, object context)
+    static bool OverlapResultFcn(in B2ShapeId shapeId, object context)
     {
         ShapeUserData userData = (ShapeUserData)b2Shape_GetUserData(shapeId);
         if (userData != null && userData.ignore)

src/Box2D.NET.Samples/Samples/Collisions/RayCast.cs

@@ -237,7 +237,7 @@ public override void Step()
             B2Vec2 translation = b2InvRotateVector(transform.q, b2Sub(m_rayEnd, m_rayStart));
             B2RayCastInput input = new B2RayCastInput(start, translation, maxFraction);
 
-            B2CastOutput localOutput = b2RayCastCircle(ref m_circle, ref input);
+            B2CastOutput localOutput = b2RayCastCircle(m_circle, ref input);
             if (localOutput.hit)
             {
                 output = localOutput;