Comment by 🐝 undefined

=> Re: "State diffing for undo?" | In: s/programming

@alice-sur-le-nuage

for this approach to work, your whole application needs to work like a pure function

I don't think so? Not everything needs to work with the undo system, ui doesn't need to (and it'd be kind of annoying if it would), project loading doesn't need to (it just replaces the whole undo list), moving around doesn't interact with it.

you can just store individual increments for every user action

And that's exactly what I'm trying to avoid doing: instead of writing a function like undo_bleh() for every bleh, I just want to write one function set_undo_point(action_name) and then call that one function every time and have it automate everything. Or a pair of functions, like start/end_undo_block() or something like that.

=> 🐝 undefined [OP]

2024-12-20 · 4 weeks ago

2 Later Comments ↓

=> 🎵 random-elephant · Dec 20 at 23:13:

I wasn't suggesting you write a function undo_action_X for every action. I was suggesting you don't need to do a full diff of two copies of your state, because every action is in itself a diff applied to your state. Whenever your state change, that's your diff. Value X changed from A to B. You can capture that if all state modifications are done via a function that then also stores the diff.

=> 🐝 undefined [OP] · Dec 21 at 04:30:

Oh ok I think I get it. So anybody that wants to modify the state, instead of doing it directly, uses an auxillary function, and it does whatever paperwork needs to be done. I've thought about that, and it seems like a pretty good solution if every action is atomic, but the way I'm doing things now is that some actions can be partially conplete if they require user input. Maybe I could convert those to be atomic, but I'm not sure if that would work for all of them.

Original Post

=> 🌒 s/programming

State diffing for undo? — Let's say I can identify all the parts of the program that need to interact with undo/redo system, and put all of them into a single contiguous chunk of memory. Then, when someone creates an undo point, I just calculate a diff over that memory, more or less. What I'm interested in is, in your experience, is there a downside to this approach? The program doesn't do any network requests or database connections (and won't, for the forseeable future). Rn I'm using a system...

=> 💬 undefined · 7 comments · 2024-12-19 · 4 weeks ago