重构并增加HitTest

Spine/Implementations/V21/Bone21.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Spine.Interfaces;
+using SpineRuntime21;
+
+namespace Spine.Implementations.V21
+{
+    internal sealed class Bone21(Bone innerObject, Bone21? parent = null) : IBone
+    {
+        private readonly Bone _o = innerObject;
+        private readonly Bone21? _parent = parent;
+
+        public Bone InnerObject => _o;
+
+        public string Name => _o.Data.Name;
+        public int Index => _o.Data.Index;
+
+        public IBone? Parent => _parent;
+        public bool Active => true; // NOTE: 3.7 及以下没有 Active 属性, 此处总是返回 true
+        public float Length => _o.Data.Length;
+        public float WorldX => _o.WorldX;
+        public float WorldY => _o.WorldY;
+        public float A => _o.M00;
+        public float B => _o.M01;
+        public float C => _o.M10;
+        public float D => _o.M11;
+
+        public override string ToString() => _o.ToString();
+    }
+}