Generic editor for Reorderable lists

#if UNITY_EDITOR

        internal virtual Rect GUIDrawElement(Rect rect, SerializedProperty serializedProperty, bool isActive, bool isFocused)
        {
            if (serializedProperty == null)
            {
                EditorGUI.HelpBox(rect, "SerializedProperty was null!", MessageType.Error);
                return rect;
            }
            serializedProperty = serializedProperty.Copy();
            int startingDepth = serializedProperty.depth;
            var currentRect = new Rect(rect.x, rect.y, rect.width, EditorGUIUtility.singleLineHeight);
            EditorGUI.LabelField(currentRect, serializedProperty.boxedValue.GetType().Name);
            var first = true;
            while (serializedProperty.NextVisible(EnterChildren(serializedProperty, first)) && serializedProperty.depth > startingDepth)
            {
                first = false;
                currentRect = currentRect.MoveDownFor(EditorGUI.GetPropertyHeight(serializedProperty));
                if (serializedProperty.propertyType == SerializedPropertyType.Generic && !serializedProperty.isArray)
                    currentRect = currentRect.CutFromTop(EditorGUIUtility.singleLineHeight)[0];
                EditorGUI.indentLevel = serializedProperty.depth;
                EditorGUI.PropertyField(currentRect, serializedProperty);
            }
            return currentRect;

            static bool EnterChildren(SerializedProperty serializedProperty, bool first)
            {
                return first || (
                    serializedProperty.propertyType == SerializedPropertyType.Generic
                    && !serializedProperty.isArray
                    && serializedProperty.isExpanded
                    );
            }
        }

        internal virtual float GUIElementHeight(SerializedProperty serializedProperty)
        {
            serializedProperty = serializedProperty.Copy();
            int startingDepth = serializedProperty.depth;
            float height = EditorGUIUtility.singleLineHeight * 2;
            var first = true;
            while (serializedProperty.NextVisible(first) && serializedProperty.depth > startingDepth)
            {
                first = false;
                height += EditorGUI.GetPropertyHeight(serializedProperty);
            }
            return height;
        }
#endif