Add blueprint transferral

osu.Game/Screens/Edit/Compose/Components/BlueprintContainer.cs

@@ -276,6 +276,13 @@ namespace osu.Game.Screens.Edit.Compose.Components
         {
         }
 
+        /// <summary>
+        /// Retrieves an item's blueprint.
+        /// </summary>
+        /// <param name="item">The item to retrieve the blueprint of.</param>
+        /// <returns>The blueprint.</returns>
+        protected SelectionBlueprint<T> GetBlueprintFor(T item) => blueprintMap[item];
+
         #endregion
 
         #region Selection

osu.Game/Screens/Edit/Compose/Components/ComposeBlueprintContainer.cs

@@ -16,6 +16,7 @@ using osu.Game.Graphics.UserInterface;
 using osu.Game.Rulesets.Edit;
 using osu.Game.Rulesets.Edit.Tools;
 using osu.Game.Rulesets.Objects;
+using osu.Game.Rulesets.Objects.Drawables;
 using osu.Game.Rulesets.Objects.Types;
 using osu.Game.Screens.Edit.Components.TernaryButtons;
 using osuTK;
@@ -73,6 +74,14 @@ namespace osu.Game.Screens.Edit.Compose.Components
             }
         }
 
+        protected override void TransferBlueprintFor(HitObject hitObject, DrawableHitObject drawableObject)
+        {
+            base.TransferBlueprintFor(hitObject, drawableObject);
+
+            var blueprint = (HitObjectSelectionBlueprint)GetBlueprintFor(hitObject);
+            blueprint.DrawableObject = drawableObject;
+        }
+
         protected override bool OnKeyDown(KeyDownEvent e)
         {
             if (e.ControlPressed)

osu.Game/Screens/Edit/Compose/Components/EditorBlueprintContainer.cs

@@ -11,6 +11,7 @@ using osu.Framework.Graphics.Containers;
 using osu.Framework.Input.Events;
 using osu.Game.Rulesets.Edit;
 using osu.Game.Rulesets.Objects;
+using osu.Game.Rulesets.Objects.Drawables;
 
 namespace osu.Game.Screens.Edit.Compose.Components
 {
@@ -65,8 +66,11 @@ namespace osu.Game.Screens.Edit.Compose.Components
                 foreach (var obj in Composer.HitObjects)
                     AddBlueprintFor(obj.HitObject);
 
-                Composer.Playfield.HitObjectUsageBegan += AddBlueprintFor;
+                var eventQueue = new HitObjectContainerEventQueue(Composer.Playfield);
-                Composer.Playfield.HitObjectUsageFinished += RemoveBlueprintFor;
+                eventQueue.HitObjectUsageBegan += AddBlueprintFor;
+                eventQueue.HitObjectUsageFinished += RemoveBlueprintFor;
+                eventQueue.HitObjectUsageTransferred += TransferBlueprintFor;
+                AddInternal(eventQueue);
             }
         }
 
@@ -100,6 +104,10 @@ namespace osu.Game.Screens.Edit.Compose.Components
             base.AddBlueprintFor(item);
         }
 
+        protected virtual void TransferBlueprintFor(HitObject hitObject, DrawableHitObject drawableObject)
+        {
+        }
+
         protected override void DragOperationCompleted()
         {
             base.DragOperationCompleted();
@@ -152,12 +160,6 @@ namespace osu.Game.Screens.Edit.Compose.Components
                 Beatmap.HitObjectAdded -= AddBlueprintFor;
                 Beatmap.HitObjectRemoved -= RemoveBlueprintFor;
             }
-
-            if (Composer != null)
-            {
-                Composer.Playfield.HitObjectUsageBegan -= AddBlueprintFor;
-                Composer.Playfield.HitObjectUsageFinished -= RemoveBlueprintFor;
-            }
         }
     }
 }

osu.Game/Screens/Edit/Compose/HitObjectContainerEventQueue.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using JetBrains.Annotations;
 using osu.Framework.Graphics;
 using osu.Game.Rulesets.Objects;
 using osu.Game.Rulesets.Objects.Drawables;
@@ -23,7 +24,7 @@ namespace osu.Game.Screens.Edit.Compose
         /// <remarks>
         /// If the ruleset uses pooled objects, this represents the time when the <see cref="HitObject"/>s become alive.
         /// </remarks>
-        public event Action<HitObject, DrawableHitObject> HitObjectUsageBegan;
+        public event Action<HitObject> HitObjectUsageBegan;
 
         /// <summary>
         /// Invoked when a <see cref="HitObject"/> becomes unused by a <see cref="DrawableHitObject"/>.
@@ -44,20 +45,12 @@ namespace osu.Game.Screens.Edit.Compose
         /// Creates a new <see cref="HitObjectContainerEventQueue"/>.
         /// </summary>
         /// <param name="playfield">The most top-level <see cref="Playfield"/>.</param>
-        public HitObjectContainerEventQueue(Playfield playfield)
+        public HitObjectContainerEventQueue([NotNull] Playfield playfield)
         {
             this.playfield = playfield;
 
-            bindPlayfieldRecursive(playfield);
+            playfield.HitObjectUsageBegan += onHitObjectUsageBegan;
-        }
+            playfield.HitObjectUsageFinished += onHitObjectUsageFinished;
-
-        private void bindPlayfieldRecursive(Playfield p)
-        {
-            p.HitObjectContainer.HitObjectUsageBegan += onHitObjectUsageBegan;
-            p.HitObjectContainer.HitObjectUsageFinished += onHitObjectUsageFinished;
-
-            foreach (var nested in p.NestedPlayfields)
-                bindPlayfieldRecursive(nested);
         }
 
         private readonly Dictionary<HitObject, int> pendingUsagesBegan = new Dictionary<HitObject, int>();
@@ -87,7 +80,7 @@ namespace osu.Game.Screens.Edit.Compose
                 else
                 {
                     // This is a new usage of the hitobject.
-                    HitObjectUsageBegan?.Invoke(hitObject, playfield.AllHitObjects.Single(d => d.HitObject == hitObject));
+                    HitObjectUsageBegan?.Invoke(hitObject);
                 }
             }
 
@@ -98,5 +91,13 @@ namespace osu.Game.Screens.Edit.Compose
             pendingUsagesBegan.Clear();
             pendingUsagesFinished.Clear();
         }
+
+        protected override void Dispose(bool isDisposing)
+        {
+            base.Dispose(isDisposing);
+
+            playfield.HitObjectUsageBegan -= onHitObjectUsageBegan;
+            playfield.HitObjectUsageFinished -= onHitObjectUsageFinished;
+        }
     }
 }