SDL_AppEvent - App-implemented event entry point for SDL_MAIN_USE_CALLBACKS apps.

       This function is available since SDL 3.2.0.

       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 SDL_APP_CONTINUE.  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.  SDL itself will push events to  the
       queue on the main thread.

       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 SDL_APP_CONTINUE, 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
       SDL_APP_FAILURE, SDL will call SDL_AppQuit and terminate the process with an exit code  that  reports  an
       error  to  the platform. If it returns SDL_APP_SUCCESS, SDL calls SDL_AppQuit and terminates with an exit
       code that reports success to the platform.

appstate
              an optional pointer, provided by the app in SDL_AppInit.

       event  the new event for the app to examine.

       SDL_AppEvent - App-implemented event entry point for SDL_MAIN_USE_CALLBACKS apps.

       Returns  SDL_APP_FAILURE  to  terminate  with  an  error,  SDL_APP_SUCCESS  to  terminate  with  success,
       SDL_APP_CONTINUE to continue.

SDL_AppInit(3), SDL_AppIterate(3)

Simple Directmedia Layer                           SDL 3.2.20                                    SDL_AppEvent(3)

#include<SDL3/SDL_main.h>SDL_AppResultSDL_AppEvent(void*appstate,SDL_Event*event);

       This  function  may  get called concurrently with SDL_AppIterate() or SDL_AppQuit() for events not pushed
       from the main thread.