foo.c

/* setup screen framebuffer object and its texture */

struct gl_sfbo {
    GLuint fbo, tex, shader;
    bool valid;
    const char* name;
    struct gl_bind* binds;
    size_t binds_sz;
};

static void setup_sfbo(struct gl_sfbo* s, int w, int h) {
    GLuint tex = s->valid ? s->tex : ({ glGenTextures(1, &s->tex); s->tex; });
    GLuint fbo = s->valid ? s->fbo : ({ glGenFramebuffers(1, &s->fbo); s->fbo; });
    s->valid = true;
    /* bind texture and setup space */
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, w, h, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL);
    
    /* setup and bind framebuffer to texture */
    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex, 0);
    switch (glCheckFramebufferStatus(GL_FRAMEBUFFER)) {
    case GL_FRAMEBUFFER_COMPLETE: break;
    default:
        fprintf(stderr, "error in frambuffer state\n");
        abort();
    }
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}