Collaborative editing.

[Perry E. Metzger]

Howdy!

For years now, pair programming has been of interest to loads of 
programmers, and I've done quite a bit of it myself. For a long time, 
I'd do this with Emacs by running Screen on a machine and having myself 
and whoever I was pairing with both connect up to the same Emacs 
(running in a terminal) that way.

However, it's increasingly difficult to get the full benefits of Emacs 
in ordinary terminals; there are too many things a gui can do that a 
terminal can't.

I've also discovered that many other editors (such as VSCode and Atom) 
seem to now have dedicated modes for doing collaborative editing, and 
apparently do it quite well. Indeed, many people I asked directed me to 
VSCode for this when I asked around about methods to do it for Emacs. 
(SubEthaEdit, which is now free software, also allows such things, but 
it is a much more limited editor.)

Especially with more and more working programmers doing their jobs from 
home but wanting to work with colleagues far away, it would seem like 
having truly good support for collaborative editing baked in to Emacs by 
some means would be a good idea.

I know there have been some experiments with collaborative editing modes 
in the past that were written purely in Elisp but none seem to be 
currently maintained and I'm not sure if any were actually very good to 
begin with.

Anyone have thoughts on how one could get Emacs to be a really top 
flight collaborative editing environment, especially for programmers? 
Just to be clear, one would want both programmers to be in distant 
locations, but to get essentially the same view of the file being 
edited, the same view of any UI elements like popups, and to be able to 
control the keyboard and mouse more or less simultaneously. Presumably 
one of the two Emacsen would be the primary one and the other one just a 
remote display, though other architectures are possible.

Obvious design alternatives are dealing with some sort of quite literal 
display sharing mechanism in which a VNC-like protocol is used, a 
slightly more "semantically" based display sharing protocol in which a 
remote display is sent a series of high level commands about updates, 
some sort of more literal collaborative editing in which diffs to text 
get sent back and forth (but this would not make it easy for both 
programmers to see the same view of the text, including popups etc.), 
and there are probably other places in the design space.

Perry