[SDL] Problem with WM_USER

[Albert Fernández Marsal]

Albert Fernández Marsal <afmarsal <at> cirsa.com> writes:

> 
> Hi all,
> 
> I have to integrate a third party dll into my sdl application on a Win32 
> platform. The dll polls for a resource and, to notify that something 
> happended, it sends a WM_USER to a previously provided window handler. This 
> handler cannot be the SDL window handler (I tried to, but it doesn't work). 
> So, I created a window via CreateWindow API call. I have to run a 
PeekMessage 
> loop over that window so it can process the messages, but it seems to 
conflict 
> with the SDL_PollEvent loop that I run elsewhere.
> 
> The scenario is as follows (the calls are not sintactically correct, but 
they 
> can be understood) :
> 
> Main thread (my app):
>  while( true )
>  {
>   SDL_PollEvent( ev )
>   if( ev.type >= SDL_USEREVENT )
>    SDL_PushEvent( ev );
>  }
> 
> Secondary thread (my app):
>  hdl = CreateWindow('',0,0,0,0,0,0,0,0,0); // fake window
>  Register3rdPartyDll( hdl );
>  while( true )
>  {
>    // loop for processing the fake window event queue
>   if( PeekMessage( hdl, WM_USER ) // only processing WM_USER event
>   {
>    translatemsg;
>    dispatchmsg;
>   }
>  }
> 
> 3rd party dll:
>  register custom Window Proc for the fake window.
>  Run a thread for polling the resource and post WM_USER to the fake window 
if 
> smthg happened
>  The custom window proc calls my code through a callback when WM_USER is 
> processed.
> 
> The problem is that I get a Memory Exception inside the 3rd party dll in my 
> main thread when I call the SDL_PollEvent.
> 
> Since the SDL_Event struct defines the event type as a UInt8 and WM_USER is 
> 0x0400 (out of range of a uint8 type), i cannot figure out how to bypass the 
> WM_USER from inside the SDL_PollEvent loop.
> 
> Thank you very much for your help.
> 
> ALBERT
> 


Ok, after some tests, there's no problem with the events. I tried a simple 
program with 2 threads:

1st:
while( true )
{
 sdl_pollevent;
 sdl_updaterects;
}

2nd:
while( true )
{
 process events for fake window;
}

and it works, so forget about the last problem. But something keeps the 3rd 
party dll from working. The call to sdl_pollevent provokes a memory exeption 
in the 3rd party dll. May it be related to the fact that both calls are in 
separate dll's loaded by my main app? Maybe the window proc can't be reached 
when consuming events?

Thank you.

ALBERT