Re: howto: 2 users interactively edit the same file ?

[Eli Zaretskii <eliz@gnu.org>]

> From: Tim X <timx@spamto.devnul.com>
> Date: 31 Oct 2005 19:04:16 +1100
> 
> I find it amazing this will work. The big problem is how can emacs,
> which doesn't support threads, handle simultaneous input from two
> distinct frames? I can't see how it can handle input from two
> different input devices simultaneously either.

I don't see why you cannot see that: quite simply, Emacs tries to read
from every possible input source, one after the other (that includes
any subprocesses that happen to run in some Emacs buffers, such as
compilation, Grep, spell-checker, etc.).  Emacs uses the system call
`select' or its equivalent to do that; `select' actually allows you to
set up a kind of ``poor man's threading'' in a single thread.

> The physical displaying
> of the frame on another display is easy enough to understand - this is
> a feature of X windows which emacs is able to take advantage of when
> it is built with X lib support - but coping with input from two
> sources at the same time is a very different matter. 

Not really.  Provided that you know what source each input even came
from, it's quite easy to DTRT with each one of them.