I implemented something similar for a interactive whiteboard project once. The undo operation would simply be appended as another action that itself could be un

I implemented something similar for a interactive whiteboard project once. The undo operation would simply be appended as another action that itself could be undone by re-doing it. However, as you played with it, it became confusing because it ran counter to ingrained expected behavior of an undo/redo dual stack implementation. Eventually I implemented the classic approach.