refactor: B2Transform usage to use 'in' parameters

- Updated collision, joint, and shape functions (e.g., `b2CollideCircles`, `b2DrawDistanceJoint`) to accept `B2Transform` as `in` parameter.
- Optimized internal geometry and rendering helpers to use `in B2Transform` for better performance and read-only safety.
- Updated Samples and data structures to align with the API changes.
- This refactoring reduces unnecessary struct copying and enforces immutability for transform data in these contexts.

Author: ikpil

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

@@ -63,7 +63,7 @@ public static void DrawSolidPolygon(Draw draw, in B2Transform transform, ReadOnl
         AddPolygon(ref draw.polygons, transform, vertices, vertexCount, radius, color);
     }
 
-    public static void DrawTransform(Draw draw, B2Transform transform, float scale)
+    public static void DrawTransform(Draw draw, in B2Transform transform, float scale)
     {
         B2Vec2 p1 = transform.p;
 
@@ -103,9 +103,9 @@ public static void DrawCircle(Draw draw, B2Vec2 center, float radius, B2HexColor
         AddCircle(ref draw.hollowCircles, center, radius, color);
     }
 
-    public static void DrawSolidCircle(Draw draw, B2Transform transform, float radius, B2HexColor color)
+    public static void DrawSolidCircle(Draw draw, in B2Transform transform, float radius, B2HexColor color)
     {
-        AddSolidCircle(ref draw.circles, ref transform, radius, color);
+        AddSolidCircle(ref draw.circles, transform, radius, color);
     }
 
     public static void DrawSolidCapsule(Draw draw, B2Vec2 p1, B2Vec2 p2, float radius, B2HexColor color)

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

@@ -96,7 +96,7 @@ public static void DestroySolidCircles(GL gl, ref SolidCircleRender render)
         }
     }
 
-    public static void AddSolidCircle(ref SolidCircleRender render, ref B2Transform transform, float radius, B2HexColor color)
+    public static void AddSolidCircle(ref SolidCircleRender render, in B2Transform transform, float radius, B2HexColor color)
     {
         RGBA8 rgba = RGBA8.MakeRGBA8(color, 1.0f);
         render.circles.Add(new SolidCircleData(transform, radius, rgba));

src/Box2D.NET.Samples/Primitives/CapsuleData.cs

@@ -11,7 +11,7 @@ public struct CapsuleData
     public float length;
     public RGBA8 rgba;
 
-    public CapsuleData(B2Transform transform, float radius, float length, RGBA8 rgba)
+    public CapsuleData(in B2Transform transform, float radius, float length, RGBA8 rgba)
     {
         this.transform = transform;
         this.radius = radius;

src/Box2D.NET.Samples/Primitives/SolidCircleData.cs

@@ -10,7 +10,7 @@ public struct SolidCircleData
     public float radius;
     public RGBA8 rgba;
 
-    public SolidCircleData(B2Transform transform, float radius, RGBA8 rgba)
+    public SolidCircleData(in B2Transform transform, float radius, RGBA8 rgba)
     {
         this.transform = transform;
         this.radius = radius;

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

@@ -189,7 +189,7 @@ private B2ShapeProxy MakeProxy(ShapeType type, float radius)
         return proxy;
     }
 
-    private void DrawShape(ShapeType type, B2Transform transform, float radius, B2HexColor color)
+    private void DrawShape(ShapeType type, in B2Transform transform, float radius, B2HexColor color)
     {
         switch (type)
         {

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

@@ -164,7 +164,7 @@ B2ShapeProxy MakeProxy(ShapeType type, float radius)
         return proxy;
     }
 
-    void DrawShape(ShapeType type, ref B2Transform transform, float radius, B2HexColor color)
+    void DrawShape(ShapeType type, in B2Transform transform, float radius, B2HexColor color)
     {
         switch (type)
         {
@@ -389,8 +389,8 @@ public override void Draw()
         base.Draw();
 
         var empty = b2Transform_identity;
-        DrawShape(m_typeA, ref empty, m_radiusA, B2HexColor.b2_colorCyan);
-        DrawShape(m_typeB, ref m_transform, m_radiusB, B2HexColor.b2_colorBisque);
+        DrawShape(m_typeA, empty, m_radiusA, B2HexColor.b2_colorCyan);
+        DrawShape(m_typeB, m_transform, m_radiusB, B2HexColor.b2_colorBisque);
 
         if (m_drawSimplex)
         {

src/Box2D.NET.Samples/Samples/Issues/ShapeCastChain.cs

@@ -216,7 +216,7 @@ private bool ShapeCastSingle(ref PhysicsHitQueryResult2D outResult, B2Vec2 start
             start,
             b2MakeRot(rotation)
         );
-        B2ShapeProxy transformedShape = TransformShapeProxy(ref transform, ref shape);
+        B2ShapeProxy transformedShape = TransformShapeProxy(transform, ref shape);
 
         B2Vec2 translation = new B2Vec2(end.X - start.X, end.Y - start.Y);
         B2QueryFilter filter = new B2QueryFilter(0x1, 0x1);
@@ -252,7 +252,7 @@ private static float b2CastResult_Closest(in B2ShapeId shapeId, B2Vec2 point, B2
         return fraction;
     }
 
-    private static B2ShapeProxy TransformShapeProxy(ref B2Transform t, ref B2ShapeProxy proxy)
+    private static B2ShapeProxy TransformShapeProxy(in B2Transform t, ref B2ShapeProxy proxy)
     {
         B2ShapeProxy ret = new B2ShapeProxy();
         ret.count = proxy.count;

src/Box2D.NET/B2DistanceJoints.cs

@@ -547,7 +547,7 @@ internal static void b2SolveDistanceJoint(B2JointSim @base, B2StepContext contex
     }
 #endif
 
-        internal static void b2DrawDistanceJoint(B2DebugDraw draw, B2JointSim @base, B2Transform transformA, B2Transform transformB)
+        internal static void b2DrawDistanceJoint(B2DebugDraw draw, B2JointSim @base, in B2Transform transformA, in B2Transform transformB)
         {
             B2_ASSERT(@base.type == B2JointType.b2_distanceJoint);
 

src/Box2D.NET/B2Geometries.cs

@@ -477,7 +477,7 @@ public static B2AABB b2ComputePolygonAABB(in B2Polygon shape, in B2Transform xf)
         }
 
         /// Compute the bounding box of a transformed line segment
-        public static B2AABB b2ComputeSegmentAABB(in B2Segment shape, B2Transform xf)
+        public static B2AABB b2ComputeSegmentAABB(in B2Segment shape, in B2Transform xf)
         {
             B2Vec2 v1 = b2TransformPoint(xf, shape.point1);
             B2Vec2 v2 = b2TransformPoint(xf, shape.point2);

src/Box2D.NET/B2Joints.cs

@@ -790,7 +790,7 @@ public static B2WorldId b2Joint_GetWorld(B2JointId jointId)
         }
 
         /// Set the local frame on bodyA
-        public static void b2Joint_SetLocalFrameA(B2JointId jointId, B2Transform localFrame)
+        public static void b2Joint_SetLocalFrameA(B2JointId jointId, in B2Transform localFrame)
         {
             B2_ASSERT(b2IsValidTransform(localFrame));
 
@@ -810,7 +810,7 @@ public static B2Transform b2Joint_GetLocalFrameA(B2JointId jointId)
         }
 
         /// Set the local frame on bodyB
-        public static void b2Joint_SetLocalFrameB(B2JointId jointId, B2Transform localFrame)
+        public static void b2Joint_SetLocalFrameB(B2JointId jointId, in B2Transform localFrame)
         {
             B2_ASSERT(b2IsValidTransform(localFrame));