Add gizmo handles for spline points

Source/Editor/SceneGraph/Actors/SplineNode.cs

@@ -1,6 +1,8 @@
 // Copyright (c) 2012-2021 Wojciech Figat. All rights reserved.
 
+using System;
 using FlaxEngine;
+using FlaxEngine.Json;
 
 namespace FlaxEditor.SceneGraph.Actors
 {
@@ -10,10 +12,78 @@ namespace FlaxEditor.SceneGraph.Actors
     [HideInEditor]
     public sealed class SplineNode : ActorNode
     {
+        private sealed class SplinePointNode : ActorChildNode<SplineNode>
+        {
+            public SplinePointNode(SplineNode actor, Guid id, int index)
+            : base(actor, id, index)
+            {
+            }
+
+            public override bool CanBeSelectedDirectly => true;
+
+            public override Transform Transform
+            {
+                get
+                {
+                    var actor = (Spline)_actor.Actor;
+                    return actor.GetSplineTransform(Index);
+                }
+                set
+                {
+                    var actor = (Spline)_actor.Actor;
+                    actor.SetSplineTransform(Index, value);
+                }
+            }
+
+            public override bool RayCastSelf(ref RayCastData ray, out float distance, out Vector3 normal)
+            {
+                var actor = (Spline)_actor.Actor;
+                var pos = actor.GetSplinePoint(Index);
+                normal = -ray.Ray.Direction;
+                return new BoundingSphere(pos, 5.0f).Intersects(ref ray.Ray, out distance);
+            }
+        }
+
         /// <inheritdoc />
         public SplineNode(Actor actor)
         : base(actor)
         {
+            OnUpdate();
+            FlaxEngine.Scripting.Update += OnUpdate;
+        }
+
+        private unsafe void OnUpdate()
+        {
+            // Sync spline points with gizmo handles
+            var actor = (Spline)Actor;
+            var dstCount = actor.SplinePointsCount;
+            if (dstCount > 1 && actor.IsLoop)
+                dstCount--; // The last point is the same as the first one for loop mode
+            var srcCount = ActorChildNodes?.Count ?? 0;
+            if (dstCount != srcCount)
+            {
+                // Remove unused points
+                while (srcCount > dstCount)
+                    ActorChildNodes[srcCount-- - 1].Dispose();
+
+                // Add new points
+                var id = ID;
+                var g = (JsonSerializer.GuidInterop*)&id;
+                g->D += (uint)srcCount;
+                while (srcCount < dstCount)
+                {
+                    g->D += 1;
+                    AddChildNode(new SplinePointNode(this, id, srcCount++));
+                }
+            }
+        }
+
+        /// <inheritdoc />
+        public override void OnDispose()
+        {
+            FlaxEngine.Scripting.Update -= OnUpdate;
+
+            base.OnDispose();
         }
     }
 }