App-implemented event entry point for SDL_MAIN_USE_CALLBACKS apps.
Defined in <SDL3/SDL_main.h>
| appstate | an optional pointer, provided by the app in SDL_AppInit. |
| event | the new event for the app to examine. |
Returns -1 to terminate with an error, 1 to terminate with success, 0 to continue.
Apps implement this function when using SDL_MAIN_USE_CALLBACKS. If using a standard "main" function, you should not supply this.
This function is called as needed by SDL after SDL_AppInit returns 0; It is called once for each new event.
There is (currently) no guarantee about what thread this will be called from; whatever thread pushes an event onto SDL's queue will trigger this function. SDL is responsible for pumping the event queue between each call to SDL_AppIterate, so in normal operation one should only get events in a serial fashion, but be careful if you have a thread that explicitly calls SDL_PushEvent.
Events sent to this function are not owned by the app; if you need to save the data, you should copy it.
This function should not go into an infinite mainloop; it should handle the provided event appropriately and return.
The appstate parameter is an optional pointer provided by the app during SDL_AppInit(). If the app never provided a pointer, this will be NULL.
If this function returns 0, the app will continue normal operation, receiving repeated calls to SDL_AppIterate and SDL_AppEvent for the life of the program. If this function returns < 0, SDL will call SDL_AppQuit and terminate the process with an exit code that reports an error to the platform. If it returns > 0, the SDL calls SDL_AppQuit and terminates with an exit code that reports success to the platform.
This function is not thread safe.
This function is available since SDL 3.0.0.