[fovc]

Yup. Ran into the same thing.

Another Q for you if you're still around: did you have to make any changes to your algorithm for when it's running through the undo queue, or is it basically the same thing but in reverse? I found some operations could better preserve intention with some adjustments to the undo transform

[scofalik]

Oh, don't get me started on modifications we needed to do to make undo look reasonable ... :) At first, we thought that undo is the same thing as collaboration but... nope.

The crucial difference is that with undo you have a context (old document state). With collaboration, you don't. So if both users put a character at the same position, in collaboration the order of output doesn't matter (and can't be solved really). In undo it does, because a user remembers what was the order of the letters before they made a change.

[fovc]

We should compare notes some time :) Sounds like we had to solve a lot of the same issues and the dearth of info on this topic is surprising!