(This is the documentation for SDL3, which is the current stable version. SDL2 was the previous version!)

SDL_WaitConditionTimeout

Wait until a condition variable is signaled or a certain time has passed.

Header File

Syntax

bool SDL_WaitConditionTimeout(SDL_Condition *cond,
                    SDL_Mutex *mutex, Sint32 timeoutMS);

Function Parameters

SDL_Condition *	cond	the condition variable to wait on.
SDL_Mutex *	mutex	the mutex used to coordinate thread access.
Sint32	timeoutMS	the maximum time to wait, in milliseconds, or -1 to wait indefinitely.

Return Value

(bool) Returns true if the condition variable is signaled, false if the condition is not signaled in the allotted time.

Remarks

This function unlocks the specified mutex and waits for another thread to call SDL_SignalCondition() or SDL_BroadcastCondition() on the condition variable cond, or for the specified time to elapse. Once the condition variable is signaled or the time elapsed, the mutex is re-locked and the function returns.

The mutex must be locked before calling this function. Locking the mutex recursively (more than once) is not supported and leads to undefined behavior.

Thread Safety

It is safe to call this function from any thread.

Version

This function is available since SDL 3.1.3.

Code Examples

bool condition = false;
SDL_Mutex *lock;
SDL_Condition *cond;
lock = SDL_CreateMutex();
cond = SDL_CreateCondition();

Thread_A:
    const Uint32 timeout = 1000; /* wake up every second */
    bool done = false;
    while (!done) {
        SDL_LockMutex(lock);
        while (!condition && SDL_WaitConditionTimeout(cond, lock, timeout) == 0) {
            continue;
        }
        SDL_UnlockMutex(lock);
        if (condition) {
            /* ... */
        }
        /* ... do some periodic work */
    }
Thread_B:
    SDL_LockMutex(lock);
    /* ... */
    condition = true;
    /* ... */
    SDL_SignalCondition(cond);
    SDL_UnlockMutex(lock);

SDL_DestroyCondition(cond);
SDL_DestroyMutex(lock);