[SDL] Threads and SDL_PollEvent

[Pontus Pihlgren]

Hey!

I was coding away yesterday and made a multithreaded OpenGL program using SDL. 
I set up two threads, the thread where main() is called and a extra thread for 
input. The program functions well, it's drawing the 3D stuff I'm expecting and 
it receives key events as it should. But the window is not responding to 
anything, I cant move, minimize, close or resize it (I'm not sure I should be 
able to resize it though). My event polling loop looks (aproximately) like this

while(1){
   SDL_Event event;
   while( SDL_PollEvent(&event) ){
        switch(event.type){
           case SDL_KEY:
               // handle keystuff and break;
           case SDL_QUIT:
               // Handle quit event by exit()ing program.
        }
   }

Scavenging archives, documentation and testing some examples I found out that 
if I move the event loop to the main() thread (the thread that called SDL_Init 
and SDL_SetVideoMode) then the window is moveable, minimizable and closaable.

So, now everything is tiptop, but as a computer scientist student I get curious 
about the tecnical reason for this behaviour. In the docs I've read that 
SDL_PollEvent should not be called from "separate" threads... but I'm not sure 
what that means. Well, would be fun with an explanation.

Oh yeah, I'm currently coding using Visual Studio .NET under WinXP with SDL 
1.2.6, haven't tried it under Linux.

Cya Guys, Popi.