Local undo/redo/history in client

[brainkim]

I got the sharedb client working with a codemirror instance, but I don’t see any tools or methods on the sharedb client to store and revert/reapply local changes. Current behavior in my app makes it so that pressing ctrl-z will undo ops sent from the server. Checking to see if anyone has implemented local undo or if I have to roll it myself? :)

[gkubisa]

I have implemented it outside ShareDB based on the op and before op events only, however, I could probably port the solution to ShareDB core. I might look into doing it in a few weeks but I don't promise anything.

In case you want to roll out your own local undo/redo, here are some pointers:

• if your ot type supports invert, you can use it to generate undo operations. Otherwise you could use diff - diff the snapshots from before op and op (this is what I do).
• transform the undo/redo stacks top-down by the remote operations.
• consider composing successive operations on the undo stack.
• consider storing (and transforming) text selections on the undo/redo stack. (I'm planning to do that later but for now I set the caret at the furthest editing position on undo/redo.)

[gkubisa]

Here's a PR adding local undo/redo to ShareDB: #216.

[curran]

What is the current status of the undo/redo feature? It's a cool idea and would be great to have in ShareDB!