Merge pull request #229 from Unity-Technologies/safer-callbacks

Safer callbacks

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/Interfaces/Graph/INode.cs

 
     public interface INode
     {
-        OnNodeModified onModified { get; set; }
+        void RegisterCallback(OnNodeModified callback);
+        void UnregisterCallback(OnNodeModified callback);
         void Dirty(ModificationScope scope);
         IGraph owner { get; set; }
         Guid guid { get; }

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/Nodes/AbstractMaterialNode.cs

 
         public IGraph owner { get; set; }
 
-        public OnNodeModified onModified { get; set; }
+        OnNodeModified m_OnModified;
+
+        public void RegisterCallback(OnNodeModified callback)
+        {
+            m_OnModified += callback;
+        }
+
+        public void UnregisterCallback(OnNodeModified callback)
+        {
+            m_OnModified -= callback;
+        }
-            if (onModified != null)
-                onModified(this, scope);
+            if (m_OnModified != null)
+                m_OnModified(this, scope);
         }
 
         public Guid guid

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/PreviewManager.cs

             Set(m_Identifiers, node.tempId, node.tempId);
             Set(m_RenderDatas, node.tempId, renderData);
             m_DirtyShaders.Add(node.tempId.index);
-            node.onModified += OnNodeModified;
+            node.RegisterCallback(OnNodeModified);
             if (node.RequiresTime())
                 m_TimeDependentPreviews.Add(node.tempId.index);
 
                 Object.DestroyImmediate(renderData.renderTexture, true);
 
             if (renderData.shaderData != null && renderData.shaderData.node != null)
-                renderData.shaderData.node.onModified -= OnNodeModified;
+                renderData.shaderData.node.UnregisterCallback(OnNodeModified);
         }
 
         void DestroyPreview(Identifier nodeId)

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Views/GraphEditorView.cs

 
             foreach (var node in m_Graph.removedNodes)
             {
-                node.onModified -= OnNodeChanged;
+                node.UnregisterCallback(OnNodeChanged);
                 var nodeView = m_GraphView.nodes.ToList().OfType<MaterialNodeView>().FirstOrDefault(p => p.node != null && p.node.guid == node.guid);
                 if (nodeView != null)
                 {
             var nodeView = new MaterialNodeView { userData = node };
             m_GraphView.AddElement(nodeView);
             nodeView.Initialize(node as AbstractMaterialNode, m_PreviewManager, m_EdgeConnectorListener);
-            node.onModified += OnNodeChanged;
+            node.RegisterCallback(OnNodeChanged);
             nodeView.Dirty(ChangeType.Repaint);
 
             if (m_SearchWindowProvider.nodeNeedsRepositioning && m_SearchWindowProvider.targetSlotReference.nodeGuid.Equals(node.guid))