Updated Quadtree usage, Fixed in-edtor problems

- Quadtree can now be easily used not only for Unity's GameObjects (with appropriate code hints)
- Fixed problems with quadtree not being properly re-initialized after code changes occured

Author: dolejska-daniel

Demo/SampleScene.unity

@@ -0,0 +1,15 @@
+using Quadtree.Items;
+using UnityEngine;
+
+namespace Quadtree
+{
+    /// <inheritdoc cref="RootNode{TItem}"/>
+    [ExecuteInEditMode]
+    [AddComponentMenu("Spatial partitioning/Quadtree/Root node (for GameObjects)")]
+    public class GameObjectRootNode : RootNode<IGameObjectItem>
+    {
+        /// <inheritdoc cref="RootNode{TItem}.Rebuild"/>
+        [ContextMenu("Rebuild Quadtrees")]
+        protected new void Rebuild() => base.Rebuild();
+    }
+}

Scripts/GameObjectRootNode.cs

@@ -0,0 +1,17 @@
+using UnityEngine;
+
+namespace Quadtree.Items
+{
+    /// <summary>
+    /// Custom item interface for GameObject quadtree items.
+    /// </summary>
+    public interface IGameObjectItem : IItem
+    {
+        /// <summary>
+        /// Returns reference to corresponding game object.
+        /// </summary>
+        /// 
+        /// <returns>Game object instance.</returns>
+        GameObject GetGameObject();
+    }
+}

Scripts/GameObjectRootNode.cs.meta

@@ -3,7 +3,7 @@
 namespace Quadtree.Items
 {
     /// <summary>
-    /// 
+    /// Mandatory interface of any quadtree item.
     /// </summary>
     public interface IItem
     {
@@ -13,12 +13,5 @@ public interface IItem
         /// 
         /// <returns>Object box bounds.</returns>
         Bounds GetBounds();
-
-        /// <summary>
-        /// Returns reference to corresponding game object.
-        /// </summary>
-        /// 
-        /// <returns>Game object instance.</returns>
-        GameObject GetGameObject();
     }
 }

Scripts/Items/IGameObjectItem.cs

@@ -3,13 +3,13 @@
 namespace Quadtree.Items
 {
     /// <summary>
-    /// Boundaries of this item are determined by present <c>UnityEngine.Renderer</c> component.
+    /// Boundaries of this quadtree item are determined by present <c>UnityEngine.Renderer</c> component.
     /// </summary>
-    [ExecuteAlways]
+    [ExecuteInEditMode]
     [DisallowMultipleComponent]
     [RequireComponent(typeof(Renderer))]
     [AddComponentMenu("Spatial partitioning/Quadtree/Items/Renderer-based Item")]
-    public class RendererItem : MonoBehaviour, IItem
+    public class RendererItem : MonoBehaviour, IGameObjectItem
     {
         //==========================================================================dd==
         //  MonoBehaviour METHODS
@@ -19,20 +19,34 @@ public class RendererItem : MonoBehaviour, IItem
 
         private void Start()
         {
-            _renderer = GetComponent<Renderer>();
+            Init();
         }
-    
+
+        private void OnEnable()
+        {
+            if (_renderer == null)
+                Init();
+        }
+
         //==========================================================================dd==
         //  Quadtree ITEM METHODS
         //==========================================================================dd==
 
-        /// <inheritdoc cref="IItem"/>
+        /// <summary>
+        /// Finds and locally stores this <c>GameObject</c>'s <c>Renderer</c> component instance.
+        /// </summary>
+        private void Init()
+        {
+            _renderer = GetComponent<Renderer>();
+        }
+
+        /// <inheritdoc cref="IGameObjectItem.GetBounds"/>
         public Bounds GetBounds()
         {
             return _renderer.bounds;
         }
 
-        /// <inheritdoc cref="IItem"/>
+        /// <inheritdoc cref="IGameObjectItem.GetGameObject"/>
         public GameObject GetGameObject()
         {
             return gameObject;