Re: Help with callbacks

I have been adding fprintf statements to the SDL.dll, printing out 
the values being passed to and from the Lisp callback function.

Everything checks out: SDL receives and stores the correct address 
from the callback function. The correct values are being passed back 
to the callback when it is called (using the correct types, I 
think), but still Lisp crashes.

So my question is: Has anyone used a callback in Lisp that is passed 
two parameters ? Passing a single parameter to a callback works. 
Passing two parameters doesn't seem to work.

For the event filter callback that takes a single parameter and 
therefore WORKS: here is the SDL specific code:

typedef int (*SDL_EventFilter)(const SDL_Event *event);
(PROGN 
  (EXPORT '(SDL_EVENTFILTER)) 
  (C-TYPES:DEFCTYPE SDL_EVENTFILTER (:VOID *)))

extern DECLSPEC void SDL_SetEventFilter(SDL_EventFilter filter);
(PROGN
  (EXPORT '(SDL_SETEVENTFILTER))
  (C-TYPES:DEFUN-DLL
    SDL_SETEVENTFILTER
      ((FILTER SDL_EVENTFILTER))
        :RETURN-TYPE
        :VOID
        :LIBRARY-NAME
        "SDL.dll"
        :ENTRY-NAME
        "SDL_SetEventFilter"
        :LINKAGE-TYPE
        :C)

// Setting up the callback
SDL_EventFilter SDL_EventOK = NULL;

void SDL_SetEventFilter (SDL_EventFilter filter)
{
  SDL_EventOK = filter;
}

// Fireing the callback
(*SDL_EventOK)(&event)

The Lisp code looks like this:

(ct:defun-c-callback FilterEvents ((event (:void *)))
  (if (eql SDL_MOUSEMOTION (ct:cref SDL_Event event type))
    (progn
      (fformat "Yup, mouse moved")
       0)
     1))

(SDL_SetEventFilter (ct:get-callback-procinst 'FilterEvents))


Now, for the callback that takes two parameters and DOES NOT work:

typedef Uint32 (*SDL_NewTimerCallback)(Uint32 interval, void *param);
(PROGN 
  (EXPORT '(SDL_NEWTIMERCALLBACK)) 
  (C-TYPES:DEFCTYPE SDL_NEWTIMERCALLBACK (:VOID *)))

extern DECLSPEC SDL_TimerID SDL_AddTimer(Uint32 interval, 
SDL_NewTimerCallback callback, void *param);
(PROGN
    (EXPORT '(SDL_ADDTIMER))
    (C-TYPES:DEFUN-DLL
        SDL_ADDTIMER
        ((INTERVAL UINT32)
            (CALLBACK SDL_NEWTIMERCALLBACK)
            (PARAM (:VOID *)))
        :RETURN-TYPE
        SDL_TIMERID
        :LIBRARY-NAME
        "SDL.dll"
        :ENTRY-NAME
        "SDL_AddTimer"
        :LINKAGE-TYPE
        :C)



struct _SDL_TimerID {
  Uint32 interval;
  SDL_NewTimerCallback cb;
  void *param;
  Uint32 last_alarm;
  struct _SDL_TimerID *next;
};

// Setting up the callback
SDL_TimerID SDL_AddTimer(Uint32 interval, SDL_NewTimerCallback 
callback, void *param)
{
  t = (SDL_TimerID) malloc(sizeof(struct _SDL_TimerID));
  t->interval = ROUND_RESOLUTION(interval);
  t->cb = callback;
  t->param = param;
}

// Fireing the callback
ms = t->cb(t->interval, t->param);

And the Lisp code:

(ct:defun-c-callback my-timer-func-1 ((interval Uint32) (param 
(:void *)))
    (fformat "Timer Fired, Yup.")
    (values interval))

(setf var-1 (ct:malloc (ct:sizeof :LONG)))
(setf (ct:cref (:long *) var-1 0) 1001)

(setf a-timer-1 (SDL_AddTimer 
        500 
        (ct:get-callback-procinst 'my-timer-func-1) var-1))

I just don't know.

-Luke


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