move DisposePtr and DisposeCPtr to NativeWrapperCPtrDisposable

com.unity.uiwidgets/Runtime/ui/compositing.cs

         }
     }
 
-    public class SceneBuilder : NativeWrapper {
-        private bool isDisposed = false;
+    public class SceneBuilder : NativeWrapperCPtrDisposable {
-        public override void DisposePtr(IntPtr ptr) {
-            if(isDisposed){
-                return;
-            }
-            isDisposed = true;
+        public override void DisposeCPtrImpl(IntPtr ptr) {
-        }
-
-        public void DisposeCPtr() {
-            if(isDisposed){
-                return;
-            }
-            isDisposed = true;
-            SceneBuilder_dispose(_ptr);
         }
 
         readonly Dictionary<EngineLayer, string> _usedLayers = new Dictionary<EngineLayer, string>();

com.unity.uiwidgets/Runtime/ui/native_bindings.cs

 
         protected NativeWrapperCPtrDisposable(IntPtr ptr) : base(ptr) {
         }
+
+        public void DisposeCPtr() {
+            DisposePtr(_ptr);
+        }
+        public override void DisposePtr(IntPtr ptr) {
+            if(isDisposed){
+                return;
+            }
+            isDisposed = true;
+            DisposeCPtrImpl(ptr); 
+        }
+
+        public abstract void DisposeCPtrImpl(IntPtr ptr);
     }
 }

com.unity.uiwidgets/Runtime/ui/painting.cs

         internal Image(IntPtr ptr) : base(ptr) {
         }
 
-        public override void DisposePtr(IntPtr ptr) {
-            if(isDisposed){
-                return;
-            }
-            isDisposed = true;
+        public override void DisposeCPtrImpl(IntPtr ptr) {
-        }
-
-        public void DisposeCPtr() {
-            if(isDisposed){
-                return;
-            }
-            isDisposed = true;
-            Image_dispose(_ptr);
         }
 
         public int width => Image_width(_ptr);
         internal FrameInfo(IntPtr ptr) : base(ptr) {
         }
 
-        public override void DisposePtr(IntPtr ptr) {
-            if (isDisposed) {
-                return;
-            }
-
-            isDisposed = true;
+        public override void DisposeCPtrImpl(IntPtr ptr) {
-        internal void DisposeCPtr() {
-            if (isDisposed) {
-                return;
-            }
-
-            isDisposed = true;
-            FrameInfo_dispose(_ptr);
-        }
 
         public TimeSpan duration => TimeSpan.FromMilliseconds(_durationMillis);
         int _durationMillis => FrameInfo_durationMillis(_ptr);
         protected EngineLayer(IntPtr ptr) : base(ptr) {
         }
 
-        public override void DisposePtr(IntPtr ptr) {
-            if(isDisposed){
-                return;
-            }
-            isDisposed = true;
+        public override void DisposeCPtrImpl(IntPtr ptr) {
-        }
-
-        internal void DisposeCPtr()
-        {
-            if(isDisposed){
-                return;
-            }
-            isDisposed = true;
-            EngineLayer_dispose(_ptr);
         }
 
         [DllImport(NativeBindings.dllName)]
         internal Picture(IntPtr ptr) : base(ptr) {
         }
 
-        public override void DisposePtr(IntPtr ptr) {
-            if(isDisposed){
-                return;
-            }
-            isDisposed = true;
+        public override void DisposeCPtrImpl(IntPtr ptr) {
-        }
-
-        public void DisposeCPtr(){
-            if(isDisposed){
-                return;
-            }
-            isDisposed = true;
-            Picture_dispose(_ptr);
         }
 
         public Future<Image> toImage(int width, int height) {