cmake/test/main_gui.c

#define SDL_MAIN_USE_CALLBACKS
#include <SDL3/SDL_main.h>
#include <SDL3/SDL.h>

static SDL_Window *window;

SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
{
    return SDL_APP_CONTINUE;
}

SDL_AppResult SDL_AppIterate(void *appstate)
{
    SDL_Surface *screenSurface = NULL;
    screenSurface = SDL_GetWindowSurface(window);
    SDL_FillSurfaceRect(screenSurface, NULL, SDL_MapSurfaceRGB(screenSurface, 0xff, 0xff, 0xff));
    SDL_UpdateWindowSurface(window);
    return SDL_APP_CONTINUE;
}

SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
{
    if (!SDL_Init(SDL_INIT_VIDEO)) {
        SDL_Log("Could not initialize SDL: %s", SDL_GetError());
        return SDL_APP_FAILURE;
    }
    window = SDL_CreateWindow("Hello SDL", 640, 480, 0);
    if (!window) {
        SDL_Log("could not create window: %s", SDL_GetError());
        return SDL_APP_FAILURE;
    }
    return SDL_APP_CONTINUE;
}

void SDL_AppQuit(void *appstate, SDL_AppResult result) {
    SDL_DestroyWindow(window);
}