[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Long-lived Guile scripts in a mono-threaded game engine

From: Paul Emsley
Subject: Re: Long-lived Guile scripts in a mono-threaded game engine
Date: Tue, 27 May 2008 14:42:26 +0100
User-agent: Thunderbird (Macintosh/20080421)

Sylvain Beucler wrote:

On Tue, May 27, 2008 at 09:58:46AM +0200, Ludovic Courtès wrote:
Scripts last more than a single game loop. They are not basic scripts
that describe what happens in a single engine step; instead they
describe what happens in the story.

For example, a game introduction will create sprites on the screen,
move them around, make them say lines that the user can read (or pass
using [space]), etc.

That script can also change the current screen (which kills all other
scripts in the current script).

Multiple scripts can run in a single screen, but they run the one
after the other, not in parallel. The order/priority is known.

Scripting is essentially frozen during the screen refresh. This avoids
putting mutexes everywhere.

How could I do something similar with Guile? I didn't find a way to
make a guile script pause (and return to the caller).
IIUC, "scripts" are only invoked via hooks, e.g., the engine wants to
ask them to do something specific.  If that is the case, it suffices to
not invoke the script.

Surely you can implement coroutine-like behavior, either using `call/cc'
(but that is going to be prohibitively expensive), or using explicit
continuation-passing style or similar.  For instance, when a hook is
called by the engine, it would systematically return a thunk (a
zero-argument procedure) that the engine would later invoke.  Example:

  (define (my-hook action)
    (let ((stuff (do-some-computation action)))
      (lambda ()
        ;; This will be executed at some later point, when the engine
        ;; feels like invoking it.
        (do-the-remaining-computation stuff))))

Does this help?

Ok, so what I'm looking for isn't supported natively :/

Here's a sample script (very close to the C bindings, for a start):

[snip script]

Now every time we see a (say_stop), the script will pause for 2
seconds, so the player can read the text.

what is the nature of the pause? (I think that that might be important.) How do you interrupt the tight little say_stop sleep loop (if that's what it is) when you are using C bindings?

Maybe I'm missing a more simple solution?


reply via email to

[Prev in Thread] Current Thread [Next in Thread]