Optimize Actor::DestroyChildren

Source/Editor/Modules/SceneEditingModule.cs

@@ -711,7 +711,11 @@ namespace FlaxEditor.Modules
 
         private void OnActorChildNodesDispose(ActorNode node)
         {
+            if (Selection.Count == 0)
+                return;
+
             // TODO: cache if selection contains any actor child node and skip this loop if no need to iterate
+            // TODO: or build a hash set with selected nodes for quick O(1) checks (cached until selection changes)
 
             // Deselect child nodes
             for (int i = 0; i < node.ChildNodes.Count; i++)

Source/Editor/Modules/SceneModule.cs

@@ -3,6 +3,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using FlaxEditor.SceneGraph;
 using FlaxEditor.SceneGraph.Actors;
 using FlaxEngine;
@@ -658,6 +659,48 @@ namespace FlaxEditor.Modules
             //node?.TreeNode.OnActiveChanged();
         }
 
+        private void OnActorDestroyChildren(Actor actor)
+        {
+            // Instead of doing OnActorParentChanged for every child lets remove all of them at once from that actor
+            ActorNode node = GetActorNode(actor);
+            if (node != null)
+            {
+                if (Editor.SceneEditing.HasSthSelected)
+                {
+                    // Clear selection if one of the removed actors is selected
+                    var selection = new HashSet<Actor>();
+                    foreach (var e in Editor.SceneEditing.Selection)
+                    {
+                        if (e is ActorNode q && q.Actor)
+                            selection.Add(q.Actor);
+                    }
+                    var count = actor.ChildrenCount;
+                    for (int i = 0; i < count; i++)
+                    {
+                        var child = actor.GetChild(i);
+                        if (selection.Contains(child))
+                        {
+                            Editor.SceneEditing.Deselect();
+                            break;
+                        }
+                    }
+                }
+
+                // Remove all child nodes (upfront remove all nodes to run faster)
+                for (int i = 0; i < node.ChildNodes.Count; i++)
+                {
+                    if (node.ChildNodes[i] is ActorNode child)
+                        child.parentNode = null;
+                }
+                node.TreeNode.DisposeChildren();
+                for (int i = 0; i < node.ChildNodes.Count; i++)
+                {
+                    node.ChildNodes[i].Dispose();
+                }
+                node.ChildNodes.Clear();
+            }
+        }
+
         /// <summary>
         /// Gets the actor node.
         /// </summary>
@@ -709,6 +752,7 @@ namespace FlaxEditor.Modules
             Level.ActorOrderInParentChanged += OnActorOrderInParentChanged;
             Level.ActorNameChanged += OnActorNameChanged;
             Level.ActorActiveChanged += OnActorActiveChanged;
+            Level.ActorDestroyChildren += OnActorDestroyChildren;
         }
 
         /// <inheritdoc />
@@ -726,6 +770,7 @@ namespace FlaxEditor.Modules
             Level.ActorOrderInParentChanged -= OnActorOrderInParentChanged;
             Level.ActorNameChanged -= OnActorNameChanged;
             Level.ActorActiveChanged -= OnActorActiveChanged;
+            Level.ActorDestroyChildren -= OnActorDestroyChildren;
 
             // Cleanup graph
             Root.Dispose();

Source/Editor/SceneGraph/SceneGraphNode.cs

@@ -27,7 +27,7 @@ namespace FlaxEditor.SceneGraph
         /// <summary>
         /// The parent node.
         /// </summary>
-        protected SceneGraphNode parentNode;
+        internal SceneGraphNode parentNode;
 
         /// <summary>
         /// Gets the children list.

Source/Engine/Level/Actor.cpp

@@ -466,12 +466,71 @@ Array<Actor*> Actor::GetChildren(const MClass* type) const
 
 void Actor::DestroyChildren(float timeLeft)
 {
+    if (Children.IsEmpty())
+        return;
     PROFILE_CPU();
+
+    // Actors system doesn't support editing scene hierarchy from multiple threads
+    if (!IsInMainThread() && IsDuringPlay())
+    {
+        LOG(Error, "Editing scene hierarchy is only allowed on a main thread.");
+        return;
+    }
+
+    // Get all actors
     Array<Actor*> children = Children;
+
+    // Inform Editor beforehand
+    Level::callActorEvent(Level::ActorEventType::OnActorDestroyChildren, this, nullptr);
+
+    if (_scene && IsActiveInHierarchy())
+    {
+        // Disable children
+        for (Actor* child : children)
+        {
+            if (child->IsActiveInHierarchy())
+            {
+                child->OnDisableInHierarchy();
+            }
+        }
+    }
+
+    Level::ScenesLock.Lock();
+
+    // Remove children all at once
+    Children.Clear();
+    _isHierarchyDirty = true;
+
+    // Unlink children from scene hierarchy
+    for (Actor* child : children)
+    {
+        child->_parent = nullptr;
+        if (!_isActiveInHierarchy)
+            child->_isActive = false; // Force keep children deactivated to reduce overhead during destruction
+        if (_scene)
+            child->SetSceneInHierarchy(nullptr);
+    }
+
+    Level::ScenesLock.Unlock();
+
+    // Inform actors about this
+    for (Actor* child : children)
+    {
+        child->OnParentChanged();
+    }
+
+    // Unlink children for hierarchy
+    for (Actor* child : children)
+    {
+        //child->EndPlay();
+
+        //child->SetParent(nullptr, false, false);
+    }
+
+    // Delete objects
     const bool useGameTime = timeLeft > ZeroTolerance;
     for (Actor* child : children)
     {
-        child->SetParent(nullptr, false, false);
         child->DeleteObject(timeLeft, useGameTime);
     }
 }
@@ -1280,7 +1339,6 @@ void Actor::OnActiveChanged()
     if (wasActiveInTree != IsActiveInHierarchy())
         OnActiveInTreeChanged();
 
-    //if (GetScene())
     Level::callActorEvent(Level::ActorEventType::OnActorActiveChanged, this, nullptr);
 }
 
@@ -1311,7 +1369,6 @@ void Actor::OnActiveInTreeChanged()
 
 void Actor::OnOrderInParentChanged()
 {
-    //if (GetScene())
     Level::callActorEvent(Level::ActorEventType::OnActorOrderInParentChanged, this, nullptr);
 }
 

Source/Engine/Level/Level.cpp

@@ -263,6 +263,9 @@ Delegate<Actor*, Actor*> Level::ActorParentChanged;
 Delegate<Actor*> Level::ActorOrderInParentChanged;
 Delegate<Actor*> Level::ActorNameChanged;
 Delegate<Actor*> Level::ActorActiveChanged;
+#if USE_EDITOR
+Delegate<Actor*> Level::ActorDestroyChildren;
+#endif
 Delegate<Scene*, const Guid&> Level::SceneSaving;
 Delegate<Scene*, const Guid&> Level::SceneSaved;
 Delegate<Scene*, const Guid&> Level::SceneSaveError;
@@ -851,6 +854,11 @@ void Level::callActorEvent(ActorEventType eventType, Actor* a, Actor* b)
     case ActorEventType::OnActorActiveChanged:
         ActorActiveChanged(a);
         break;
+#if USE_EDITOR
+    case ActorEventType::OnActorDestroyChildren:
+        ActorDestroyChildren(a);
+        break;
+#endif
     }
 }
 

Source/Engine/Level/Level.h

@@ -549,7 +549,13 @@ private:
         OnActorOrderInParentChanged = 3,
         OnActorNameChanged = 4,
         OnActorActiveChanged = 5,
+#if USE_EDITOR
+        OnActorDestroyChildren = 6,
+#endif
     };
 
     static void callActorEvent(ActorEventType eventType, Actor* a, Actor* b);
+#if USE_EDITOR
+    API_EVENT(Internal) static Delegate<Actor*> ActorDestroyChildren;
+#endif
 };