public static void Add(UndoStep node, bool callRedo)
 {
     if(callRedo)
         node.CallRedo();
     undoStack.Push(node);
     redoStack.Clear();
     if (OnModified != null)
         OnModified.Invoke(null, new UndoRedoEventArgs { Step = node });
 }
 public static void Add(UndoStep node)
 {
     Add(node, true);
 }