Fix duplicating spline

#452

Source/Editor/Modules/SceneModule.cs

@@ -22,14 +22,25 @@ namespace FlaxEditor.Modules
         /// <seealso cref="FlaxEditor.SceneGraph.RootNode" />
         public class ScenesRootNode : RootNode
         {
+            private readonly Editor _editor;
+
+            /// <inheritdoc />
+            public ScenesRootNode()
+            {
+                _editor = Editor.Instance;
+            }
+
             /// <inheritdoc />
             public override void Spawn(Actor actor, Actor parent)
             {
-                Editor.Instance.SceneEditing.Spawn(actor, parent);
+                _editor.SceneEditing.Spawn(actor, parent);
             }
 
             /// <inheritdoc />
             public override Undo Undo => Editor.Instance.Undo;
+
+            /// <inheritdoc />
+            public override List<SceneGraphNode> Selection => _editor.SceneEditing.Selection;
         }
 
         /// <summary>

Source/Editor/SceneGraph/Actors/SplineNode.cs

@@ -29,7 +29,7 @@ namespace FlaxEditor.SceneGraph.Actors
 
             public override bool CanBeSelectedDirectly => true;
 
-            public override bool CanDuplicate => true;
+            public override bool CanDuplicate => !Root?.Selection.Contains(ParentNode) ?? true;
 
             public override bool CanDelete => true;
 

Source/Editor/SceneGraph/RootNode.cs

@@ -1,6 +1,7 @@
 // Copyright (c) 2012-2021 Wojciech Figat. All rights reserved.
 
 using System;
+using System.Collections.Generic;
 using FlaxEditor.SceneGraph.Actors;
 using FlaxEngine;
 
@@ -146,5 +147,10 @@ namespace FlaxEditor.SceneGraph
         /// Gets the undo.
         /// </summary>
         public abstract Undo Undo { get; }
+
+        /// <summary>
+        /// Gets the list of selected scene graph nodes in the editor context.
+        /// </summary>
+        public abstract List<SceneGraphNode> Selection { get; }
     }
 }

Source/Editor/SceneGraph/SceneGraphNode.cs

@@ -57,7 +57,9 @@ namespace FlaxEditor.SceneGraph
         /// </summary>
         public virtual RootNode Root => ParentNode?.Root;
 
-        /// <inheritdoc />
+        /// <summary>
+        /// Gets or sets the transform of the node.
+        /// </summary>
         public abstract Transform Transform { get; set; }
 
         /// <summary>

Source/Editor/Windows/Assets/PrefabWindow.Hierarchy.cs

@@ -36,6 +36,9 @@ namespace FlaxEditor.Windows.Assets
 
             /// <inheritdoc />
             public override Undo Undo => _window.Undo;
+
+            /// <inheritdoc />
+            public override List<SceneGraphNode> Selection => _window.Selection;
         }
 
         /// <summary>