Function SDL_AddEventWatch 

pub unsafe extern "C" fn SDL_AddEventWatch(
    filter: SDL_EventFilter,
    userdata: *mut c_void,
) -> bool

Add a callback to be triggered when an event is added to the event queue.

filter will be called when an event happens, and its return value is ignored.

WARNING: Be very careful of what you do in the event filter function, as it may run in a different thread!

If the quit event is generated by a signal (e.g. SIGINT), it will bypass the internal queue and be delivered to the watch callback immediately, and arrive at the next event poll.

Note: the callback is called for events posted by the user through SDL_PushEvent(), but not for disabled events, nor for events by a filter callback set with SDL_SetEventFilter(), nor for events posted by the user through SDL_PeepEvents().

Parameter: filter an SDL_EventFilter function to call when an event happens. Parameter: userdata a pointer that is passed to filter. Returns: true on success or false on failure; call SDL_GetError() for more information.

Thread Safety: It is safe to call this function from any thread.

Available Since: This function is available since SDL 3.2.0.

See Also: SDL_RemoveEventWatch See Also: SDL_SetEventFilter