gl_sdl3_callbacks.c

// gcc $(pkg-config --cflags --libs sdl3) -I${GLAD_PATH}/include gl_sdl3_callbacks.c ${GLAD_PATH}/src/gl.c
//
// Based on https://examples.libsdl.org/SDL3/renderer/01-clear/
//
#include <stdio.h>
#include <glad/gl.h>

#define SDL_MAIN_USE_CALLBACKS 1
#include <SDL3/SDL.h>
#include <SDL3/SDL_main.h>

static const GLuint WIDTH = 800, HEIGHT = 600;

static SDL_Window *window;
static SDL_Renderer *renderer;
static SDL_GLContext GLContext;

SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
{
    SDL_SetAppMetadata("GLAD SDL3 example", "1.0", "sh.glad.gen.sdl3.callbacks");

    if (!SDL_Init(SDL_INIT_VIDEO)) {
        SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
        return SDL_APP_FAILURE;
    }

    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);

    if (!SDL_CreateWindowAndRenderer("[glad] GL with SDL3 callback main", WIDTH, HEIGHT, SDL_WINDOW_RESIZABLE | SDL_WINDOW_OPENGL, &window, &renderer)) {
        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
        return SDL_APP_FAILURE;
    }

    GLContext = SDL_GL_CreateContext(window);

    int version = gladLoadGL((GLADloadfunc) SDL_GL_GetProcAddress);
    printf("GL %d.%d\n", GLAD_VERSION_MAJOR(version), GLAD_VERSION_MINOR(version));

    return SDL_APP_CONTINUE;
}

SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
{
    if (event->type == SDL_EVENT_QUIT) {
        return SDL_APP_SUCCESS;
    }

    if (event->type == SDL_EVENT_KEY_DOWN && event->key.key == SDLK_ESCAPE) {
        return SDL_APP_SUCCESS;
    }

    return SDL_APP_CONTINUE;
}

SDL_AppResult SDL_AppIterate(void *appstate)
{
    const double now = ((double)SDL_GetTicks()) / SDL_MS_PER_SECOND;

    const float red = (float) (0.5 + 0.5 * SDL_sin(now));
    const float green = (float) (0.5 + 0.5 * SDL_sin(now + SDL_PI_D * 2 / 3));
    const float blue = (float) (0.5 + 0.5 * SDL_sin(now + SDL_PI_D * 4 / 3));

    glClearColor(red, green, blue, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    SDL_GL_SwapWindow(window);

    return SDL_APP_CONTINUE;
}

void SDL_AppQuit(void *appstate, SDL_AppResult result)
{
    SDL_GL_DestroyContext(GLContext);
    /* SDL will clean up the window/renderer for us. */
}