This is the design I also usually use for undo/redo. Actually for small interactive editors I like to go further and make it so that anytime you do anything the

This is the design I also usually use for undo/redo. Actually for small interactive editors I like to go further and make it so that anytime you do anything the program serializes its state and loads it back in. This is sometimes too costly but has unexpected reliability benefits. It makes sure your serialization code is well exercised, it ensures most of your program states are linkable/nameable, and also it's sort of like every time you do anything you're restarting the program. There's much less implicit state that can cause problems. And as a fallback if you do get the program into a bad state you can just hit undo and you're back into a good state.