In my text editor (https://github.com/alefore/edge https://github.com/alefore/edge) I keep the undo/redo history always linear, which I find works pretty well.

In my text editor (https://github.com/alefore/edge https://github.com/alefore/edge) I keep the undo/redo history always linear, which I find works pretty well. So suppose the user does the following operations: • Insert "Hello" • Insert " world!" • Undo once. • Insert ", Cameron!" At this point, undo operations would gradually transform the buffer thus: "Hello, Cameron!" => "Hello" => "Hello world!" => "Hello" => "". Obviously, one can redo at any point. The undo/redo days structure don't preserve the state, just the transformations (which are reversible). The gist of it is that when you apply a modification to the buffer and the redo stack isn't empty, the redo stack gets flipped and inserted into the undo stack. If you undo a long list of transformations and then make a change, that long list is duplicated, but this hasn't been a problem in practice. In case someone finds this interesting, this is mostly implemented here: https://github.com/alefore/edge/blob/28c031230a8babe888ffe1a3be55742acdadc9d9/src/undo_state.cc#L19 https://github.com/alefore/edge/blob/28c031230a8babe888ffe1a...