# SDL_EventFilter A function pointer used for callbacks that watch the event queue. ## Header File Defined in [](https://github.com/libsdl-org/SDL/blob/main/include/SDL3/SDL_events.h) ## Syntax ```c typedef bool (SDLCALL *SDL_EventFilter)(void *userdata, SDL_Event *event); ``` ## Function Parameters | | | | ------------ | --------------------------------------------------------------------------------------------------------------------------- | | **userdata** | what was passed as `userdata` to [SDL_SetEventFilter](SDL_SetEventFilter)() or [SDL_AddEventWatch](SDL_AddEventWatch), etc. | | **event** | the event that triggered the callback. | ## Return Value Returns true to permit event to be added to the queue, and false to disallow it. When used with [SDL_AddEventWatch](SDL_AddEventWatch), the return value is ignored. ## Thread Safety SDL may call this callback at any time from any thread; the application is responsible for locking resources the callback touches that need to be protected. ## Version This datatype is available since SDL 3.2.0. ## See Also - [SDL_SetEventFilter](SDL_SetEventFilter) - [SDL_AddEventWatch](SDL_AddEventWatch) ---- [CategoryAPI](CategoryAPI), [CategoryAPIDatatype](CategoryAPIDatatype), [CategoryEvents](CategoryEvents)