Added foldout UnityEventDrawers.

Author: Lachee

Editor/Utilities/UnityEventDrawer.cs

@@ -0,0 +1,130 @@
+#if UNITY_2020_1_OR_NEWER
+using UnityEditor;
+using UnityEngine;
+using UnityEngine.Events;
+using System.Reflection;
+using UnityEditorInternal;
+
+namespace Lachee.Utilities.Editor
+{
+    [CustomPropertyDrawer(typeof(UnityEventBase), true)]
+    public class UnityEventDrawer : UnityEditorInternal.UnityEventDrawer
+    {
+        #region Private Functions i steal from UnityEventDrawerer
+        private static readonly FieldInfo fi_reoderableList;
+        private static readonly FieldInfo fi_dummyEvent;
+        private static readonly FieldInfo fi_text;
+        private static readonly MethodInfo mi_RestoreState;
+        private static readonly MethodInfo mi_GetDummyEvent;
+
+        static UnityEventDrawer()
+        {
+            var T = typeof(UnityEditorInternal.UnityEventDrawer);
+            fi_reoderableList = T.GetField("m_ReorderableList", BindingFlags.NonPublic | BindingFlags.Instance);
+            fi_dummyEvent = T.GetField("m_DummyEvent", BindingFlags.NonPublic | BindingFlags.Instance);
+            fi_text = T.GetField("m_Text", BindingFlags.NonPublic | BindingFlags.Instance);
+            mi_GetDummyEvent = T.GetMethod("GetDummyEvent", BindingFlags.NonPublic | BindingFlags.Static);
+            mi_RestoreState = T.GetMethod("RestoreState", BindingFlags.NonPublic | BindingFlags.Instance);
+        }
+
+        private static UnityEventBase GetDummyEvent(SerializedProperty prop)
+            => (UnityEventBase)mi_GetDummyEvent.Invoke(null, new object[] { prop });
+
+        private ReorderableList reorderableList
+        {
+            get => (ReorderableList)fi_reoderableList.GetValue(this);
+        }
+        private UnityEventBase dummyEvent
+        {
+            get => (UnityEventBase)fi_dummyEvent.GetValue(this);
+            set => fi_dummyEvent.SetValue(this, value);
+        }
+        private string text
+        {
+            get => (string)fi_text.GetValue(this);
+            set => fi_text.SetValue(this, value);
+        }
+        private State RestoreState(SerializedProperty property)
+            => (State)mi_RestoreState.Invoke(this, new[] { property });
+        #endregion
+
+        private readonly GUIContent iconToolbarPlus = EditorGUIUtility.TrIconContent("Toolbar Plus", "Add new event listener");
+        private readonly GUIStyle headerBackground = "LODSliderBG";
+        private readonly GUIStyle preButton = "RL FooterButton";
+        private readonly Color headerColor = new Color(0.85f, 0.85f, 0.85f);
+
+        private bool? _isFolded;
+        private bool isFolded
+        {
+            get => _isFolded.GetValueOrDefault(EditorPrefs.GetBool($"com.lachee.utilities.UnityEventsFoldout", true));
+            set
+            {
+                _isFolded = value;
+                EditorPrefs.SetBool($"com.lachee.utilities.UnityEventsFoldout", value);
+            }
+        }
+
+        private float CalculateBackgroundHeight(SerializedProperty property)
+        {
+            var list = reorderableList;
+            if (list == null || list.count == 0 || isFolded)
+                return EditorGUIUtility.singleLineHeight + 2f;
+
+            return base.GetPropertyHeight(property, GUIContent.none);
+        }
+
+        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
+        {
+            RestoreState(property);
+
+            text = label.text;
+            dummyEvent = GetDummyEvent(property);
+
+            float lineHeight = EditorGUIUtility.singleLineHeight;
+
+            // Draw the folder
+            if (reorderableList.count > 0)
+            {
+                isFolded = !EditorGUI.Foldout(new Rect(position.x, position.y, position.width, lineHeight), !isFolded, GUIContent.none);
+            }
+            else
+            {
+                _isFolded = true;
+            }
+
+            // Draw the event box
+            Rect headerRect = new Rect(position.x + 2, position.y, position.width - 2, CalculateBackgroundHeight(property));
+            Rect headerLabel = new Rect(headerRect.x + 6, headerRect.y + 1, headerRect.width - 100, lineHeight);
+            Rect headerAddButton = new Rect(headerRect.x + headerRect.width - 25, headerRect.y + 2, 24, headerRect.height + 4);
+
+            // Draw the base GUI if we are unfolded
+            if (!isFolded)
+            {
+                base.OnGUI(headerRect, property, label);
+            }
+            else
+            {
+                if (Event.current.type == EventType.Repaint)
+                {
+                    GUI.backgroundColor = headerColor;
+                    headerBackground.Draw(headerRect, GUIContent.none, false, false, false, false);
+                    GUI.backgroundColor = Color.white;
+                }
+
+                DrawEventHeader(headerLabel);
+                if (GUI.Button(headerAddButton, iconToolbarPlus, preButton))
+                {
+                    isFolded = false;
+                    OnAddEvent(reorderableList);
+                }
+            }
+        }
+
+        public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
+        {
+            return CalculateBackgroundHeight(property) + 5f;
+        }
+
+    }
+}
+#endif

Editor/Utilities/UnityEventDrawer.cs.meta

@@ -1,6 +1,6 @@
 {
   "name": "com.lachee.utilities",
-  "version": "1.4.7",
+  "version": "1.5.0",
   "displayName": "Lachee's Utilities",
   "description": "Bunch of utility functionality",
   "unity": "2019.1",