SDL多线程
SDL线程创建: SDL_CreateThread;
SDL 线程等待: SDL_WaitThread;
SDL 互斥锁: SDL_CreateMutex / SDL_DestroyMutex;
SDL 锁定互斥: SDL_LockMutex / SDL_UnlockMutex;
SDL条件变量(信号量): SDL_CreateCond / SDL_DestroyCond;
SDL条件变量(信号量)等待/通知: SDL_CondWait / SDL_CondSignal;
SDL_CondWait暂时释放拥有的锁,并进入睡眠状态; 在别的线程中调用SDL_CondSignal后,SDL_CondWait唤醒,等到别的线程将锁释放后,SDL_CondWait所在线程重新拥有锁,可以继续往下执行;