bug#14820: 24.3; elisp manual: How to write good idle timer worker functions?

[Phil Sainty <psainty@orcon.net.nz>]

Thanks Greg, that sounds like good stuff in general.

Sadly it's not applicable in my case -- the processing I'm doing
is very much tied to the current running Emacs instance -- but it's
definitely good to know those packages exist for other use cases.

cheers,
-Phil


On 12/07/2013 01:39, Daimrod wrote:
> A bit of background:
> I'm GSoC student working on the XWidget branch and I wanted to add test
> to it. But I've encountered two problems while trying to write "classic"
> ERT tests. One is that since I'm working on the C side on an
> experimental branch, sometimes Emacs crashes. The second problem is that
> some tests needs to be run in a graphical Emacs. So I can't run the
> tests in batch mode to circumvent the first problem.
>
>
> I've wrote a package, emacs-parallel[1], (the API isn't very clean but
> it's good enough for my current needs) to eval some stuff in another
> Emacs process. I've been heavily inspired by emacs-async[2], but I've
> made differents choices:
> - it can start a graphical Emacs (not Batch Mode);
> - it communicates through a Unix socket instead of standard I/O stream
> (because, AFAIK, it is not possible to use them without Batch Mode);
> - you can send data from the remote process while the process isn't
> finished instead of just sending the result of the call;
> - the main entry point is a function, not a macro;
> - it tells you whether the process terminated normally, and if not, what
> happens (exit code or signal number).
> - it handles timeout (you can stop the remote instance after X seconds);
>
> I haven't wrote much doc yet (I've started it monday) so maybe
> emacs-async is a better choice (ATM) if you don't need an graphical
> Emacs or if you don't need to send data without interrupting the remote
> process.
>
> (parallel-start (lambda () (parallel-send 42) (sleep-for 3) 12)
>                  :post-exec (lambda (results _status)
>                               (message "%s" results)))
>
> (emacs-async equivalent)
> (async-start (lambda () (sleep-for 3) (list 12 42))
>               (lambda (result) (message "%s" result)))
>
> => after 3 sec it displays (12 42)
>
> However, since those packages simulate parallel/async jobs with another
> Emacs instance, you cannot execute code with side effects. Well, you
> can, but it won't have any effect in your current Emacs instance, only
> on the remote. You have to isolate the side effects and to put them in a
> function to be executed once the computation (free of side effect) is
> done (`finish-func' in `async-start' or `:post-exec' in
> `parallel-start').
>
> [1] https://github.com/daimrod/emacs-parallel.git
> [2] https://github.com/jwiegley/emacs-async.git