private void OnUndo()
        {
            settings = ((PanelCanvas)target).Internal;

            selectedAnchoredPanel     = settings.InitialPanelsAnchored;
            selectedAnchoredPanelTabs = selectedAnchoredPanel.panel.tabs;
        }
        private void OnEnable()
        {
            settings = ((PanelCanvas)target).Internal;

            reorderableLists          = new List <ReorderableList>();
            selectedAnchoredPanel     = settings.InitialPanelsAnchored;
            selectedAnchoredPanelTabs = selectedAnchoredPanel.panel.tabs;

            panelPrefab      = serializedObject.FindProperty("panelPrefab");
            leaveFreeSpace   = serializedObject.FindProperty("leaveFreeSpace");
            minimumFreeSpace = serializedObject.FindProperty("minimumFreeSpace");
            preventDetachingLastDockedPanel = serializedObject.FindProperty("preventDetachingLastDockedPanel");
            panelResizableAreaLength        = serializedObject.FindProperty("panelResizableAreaLength");
            canvasAnchorZoneLength          = serializedObject.FindProperty("canvasAnchorZoneLength");
            panelAnchorZoneLength           = serializedObject.FindProperty("panelAnchorZoneLength");

            showIDs = EditorPrefs.GetBool(SHOW_IDS_PREF, false);

            Undo.undoRedoPerformed -= OnUndo;
            Undo.undoRedoPerformed += OnUndo;
        }