InterfaceRef<T> improvements

InterfaceRef.cs

@@ -8,7 +8,7 @@ namespace KBCore.Refs
     /// </summary>
     /// <typeparam name="T">Component type to find and serialize.</typeparam>
     [Serializable]
-    public class InterfaceRef<T> : ISerializableRef<T>
+    public class InterfaceRef<T> : ISerializableRef<T>, IEquatable<InterfaceRef<T>>
         where T : class
     {
 
@@ -57,5 +57,12 @@ void ISerializableRef.Clear()
             this._value = null;
             this._implementer = null;
         }
+
+        public override bool Equals(object obj) => obj is InterfaceRef<T> casted && Equals(casted);
+
+        public bool Equals(InterfaceRef<T> other)
+        {
+            return other != null && _implementer == other._implementer;
+        }
     }
 }

InterfaceRefPropertyDrawer.cs

@@ -1,8 +1,10 @@
 #if UNITY_EDITOR
 using UnityEditor;
 using UnityEngine;
+using Object = UnityEngine.Object;
 
 #if UNITY_2022_2_OR_NEWER
+using System;
 using UnityEngine.UIElements;
 using UnityEditor.UIElements;
 #endif
@@ -13,18 +15,107 @@ namespace KBCore.Refs
     public class InterfaceRefPropertyDrawer : PropertyDrawer
     {
         private const string IMPLEMENTER_PROP = "_implementer";
-        
+
 // unity 2022.2 makes UIToolkit the default for inspectors
 #if UNITY_2022_2_OR_NEWER
         public override VisualElement CreatePropertyGUI(SerializedProperty property)
         {
-            return new PropertyField(property.FindPropertyRelative(IMPLEMENTER_PROP), property.displayName);
+            var field = new PropertyField(property.FindPropertyRelative(IMPLEMENTER_PROP), property.displayName);
+            field.RegisterCallback<DragPerformEvent, SerializedProperty>(DragPerformEvent, property,
+                TrickleDown.TrickleDown);
+            field.RegisterCallback<DragUpdatedEvent, SerializedProperty>(DragUpdatedEvent, property,
+                TrickleDown.TrickleDown);
+
+            return field;
+        }
+
+        private void DragUpdatedEvent(DragUpdatedEvent evt, SerializedProperty serializedProperty)
+        {
+            evt.StopImmediatePropagation();
+            if (!TryGetDraggedComponent(serializedProperty, out _))
+            {
+                DragAndDrop.visualMode = DragAndDropVisualMode.Rejected;
+                return;
+            }
+
+            DragAndDrop.visualMode = DragAndDropVisualMode.Generic;
+        }
+
+        private void DragPerformEvent(DragPerformEvent evt, SerializedProperty serializedProperty)
+        {
+            if (!TryGetDraggedComponent(serializedProperty, out var component))
+                return;
+
+            DragAndDrop.AcceptDrag();
+
+            serializedProperty.FindPropertyRelative(IMPLEMENTER_PROP).objectReferenceValue = component;
+            serializedProperty.serializedObject.ApplyModifiedProperties();
+
+            evt.StopImmediatePropagation();
         }
+
 #endif
 
         public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
         {
-            EditorGUI.PropertyField(position, property.FindPropertyRelative(IMPLEMENTER_PROP), label, true);
+            EditorGUI.BeginProperty(position, label, property);
+
+            EditorGUI.ObjectField(position, property.FindPropertyRelative(IMPLEMENTER_PROP), label);
+            HandleIMGUIObjectDrag(position, property);
+
+            EditorGUI.EndProperty();
+        }
+
+        private void HandleIMGUIObjectDrag(Rect position, SerializedProperty property)
+        {
+            var evt = Event.current;
+
+            if ((evt.type != EventType.DragUpdated && evt.type != EventType.DragPerform) || !position.Contains(evt.mousePosition))
+                return;
+
+            evt.Use();
+
+            if (!TryGetDraggedComponent(property, out var component))
+            {
+                DragAndDrop.visualMode = DragAndDropVisualMode.Rejected;
+                return;
+            }
+
+            DragAndDrop.visualMode = DragAndDropVisualMode.Generic;
+
+            if (evt.type == EventType.DragPerform)
+            {
+                DragAndDrop.AcceptDrag();
+
+                property.FindPropertyRelative(IMPLEMENTER_PROP).objectReferenceValue = component;
+                property.serializedObject.ApplyModifiedProperties();
+
+                GUI.changed = true;
+            }
+
+            evt.Use();
+        }
+
+        private static bool TryGetDraggedComponent(SerializedProperty property, out Component component)
+        {
+            component = null;
+
+            if (DragAndDrop.objectReferences.Length != 1)
+                return false;
+
+            var targetType = ((ISerializableRef)property.boxedValue).RefType;
+            Object checkedObject = DragAndDrop.objectReferences[0];
+
+            if (checkedObject is Component draggedComponent && targetType.IsAssignableFrom(draggedComponent.GetType()))
+            {
+                component = draggedComponent;
+                return true;
+            }
+
+            if (checkedObject is GameObject go && go.TryGetComponent(targetType, out component))
+                return true;
+
+            return false;
         }
     }
 }