Extracted NodePreviewDrawer from MaterialNodeDrawer

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Drawer/MaterialNodeDrawer.cs

 
             var previews = nodeData.elements.OfType<NodePreviewDrawData>().ToList();
 
-            if (previews.ItemsReferenceEquals(m_currentPreviewData))
-            {
-                for (int i = 0; i < previews.Count; i++)
-                {
-                    var preview = previews[i];
-                    // TODO: Need to share the texture
-                    // right now it's allocating all the time.
-                    preview.Render(new Vector2(200, 200));
-                }
-            }
-            else
+            if (!previews.ItemsReferenceEquals(m_currentPreviewData))
             {
                 m_PreviewContainer.ClearChildren();
                 m_currentPreviewData = previews;
-                    var image = preview.Render(new Vector2(200, 200));
-                    var thePreview = new Image
+                    var thePreview = new NodePreviewDrawer
-                        image = image,
+                        data = preview,
                         name = "image"
                     };
                     m_PreviewContainer.AddChild(thePreview);

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Drawer/NodePreviewDrawer.cs

+using UnityEngine;
+using UnityEngine.RMGUI;
+
+namespace UnityEditor.MaterialGraph.Drawing
+{
+    public class NodePreviewDrawer : Image
+    {
+        public NodePreviewDrawData data;
+
+        public NodePreviewDrawer() {}
+
+        public override void DoRepaint(PaintContext args)
+        {
+            image = data.Render(new Vector2(200, 200));
+            base.DoRepaint(args);
+        }
+    }
+}

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Drawer/NodePreviewDrawer.cs.meta

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