(This is the legacy documentation for SDL2, the previous stable version; SDL3 is the current stable version.)

SDL_SetEventFilter

Set up a filter to process all events before they change internal state and are posted to the internal event queue.

Header File

Syntax

void SDL_SetEventFilter(SDL_EventFilter filter,
                        void *userdata);

Function Parameters

SDL_EventFilter	filter	An SDL_EventFilter function to call when an event happens.
void *	userdata	a pointer that is passed to `filter`.

Remarks

If the filter function returns 1 when called, then the event will be added to the internal queue. If it returns 0, then the event will be dropped from the queue, but the internal state will still be updated. This allows selective filtering of dynamically arriving events.

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

On platforms that support it, if the quit event is generated by an interrupt signal (e.g. pressing Ctrl-C), it will be delivered to the application at the next event poll.

There is one caveat when dealing with the SDL_QuitEvent event type. The event filter is only called when the window manager desires to close the application window. If the event filter returns 1, then the window will be closed, otherwise the window will remain open if possible.

Note: Disabled events never make it to the event filter function; see SDL_EventState().

Note: If you just want to inspect events without filtering, you should use SDL_AddEventWatch() instead.

Note: Events pushed onto the queue with SDL_PushEvent() get passed through the event filter, but events pushed onto the queue with SDL_PeepEvents() do not.

Version

This function is available since SDL 2.0.0.