void loop()
{
    SDL_Event event;
    int i;
    int status;

    /* Check for events */
    ++frames;
    while (SDL_PollEvent(&event) && !done) {
        switch (event.type) {
        case SDL_WINDOWEVENT:
            switch (event.window.event) {
                case SDL_WINDOWEVENT_RESIZED:
                    for (i = 0; i < state->num_windows; ++i) {
                        if (event.window.windowID == SDL_GetWindowID(state->windows[i])) {
                            int w, h;
                            status = SDL_GL_MakeCurrent(state->windows[i], context[i]);
                            if (status) {
                                SDL_Log("SDL_GL_MakeCurrent(): %s\n", SDL_GetError());
                                break;
                            }
                            /* Change view port to the new window dimensions */
                            SDL_GL_GetDrawableSize(state->windows[i], &w, &h);
                            ctx.glViewport(0, 0, w, h);
                            state->window_w = event.window.data1;
                            state->window_h = event.window.data2;
                            /* Update window content */
                            Render(event.window.data1, event.window.data2, &datas[i]);
                            SDL_GL_SwapWindow(state->windows[i]);
                            break;
                        }
                    }
                    break;
            }
        }
        SDLTest_CommonEvent(state, &event, &done);
    }
    if (!done) {
      for (i = 0; i < state->num_windows; ++i) {
          status = SDL_GL_MakeCurrent(state->windows[i], context[i]);
          if (status) {
              SDL_Log("SDL_GL_MakeCurrent(): %s\n", SDL_GetError());

              /* Continue for next window */
              continue;
          }
          Render(state->window_w, state->window_h, &datas[i]);
          SDL_GL_SwapWindow(state->windows[i]);
      }
    }
#ifdef __EMSCRIPTEN__
    else {
        emscripten_cancel_main_loop();
    }
#endif
}
int
main(int argc, char *argv[])
{
    int fsaa, accel;
    int value;
    int i;
    SDL_DisplayMode mode;
    Uint32 then, now;
    int status;
    shader_data *data;

    /* Initialize parameters */
    fsaa = 0;
    accel = 0;

    /* Initialize test framework */
    state = SDLTest_CommonCreateState(argv, SDL_INIT_VIDEO);
    if (!state) {
        return 1;
    }
    for (i = 1; i < argc;) {
        int consumed;

        consumed = SDLTest_CommonArg(state, i);
        if (consumed == 0) {
            if (SDL_strcasecmp(argv[i], "--fsaa") == 0) {
                ++fsaa;
                consumed = 1;
            } else if (SDL_strcasecmp(argv[i], "--accel") == 0) {
                ++accel;
                consumed = 1;
            } else if (SDL_strcasecmp(argv[i], "--zdepth") == 0) {
                i++;
                if (!argv[i]) {
                    consumed = -1;
                } else {
                    depth = SDL_atoi(argv[i]);
                    consumed = 1;
                }
            } else {
                consumed = -1;
            }
        }
        if (consumed < 0) {
            SDL_Log ("Usage: %s %s [--fsaa] [--accel] [--zdepth %%d]\n", argv[0],
                    SDLTest_CommonUsage(state));
            quit(1);
        }
        i += consumed;
    }

    /* Set OpenGL parameters */
    state->window_flags |= SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_BORDERLESS | SDL_WINDOW_FULLSCREEN;
    state->gl_red_size = 5;
    state->gl_green_size = 5;
    state->gl_blue_size = 5;
    state->gl_depth_size = depth;
    state->gl_major_version = 2;
    state->gl_minor_version = 0;
    state->gl_profile_mask = SDL_GL_CONTEXT_PROFILE_ES;

    if (fsaa) {
        state->gl_multisamplebuffers=1;
        state->gl_multisamplesamples=fsaa;
    }
    if (accel) {
        state->gl_accelerated=1;
    }
    if (!SDLTest_CommonInit(state)) {
        quit(2);
        return 0;
    }

    context = SDL_calloc(state->num_windows, sizeof(context));
    if (context == NULL) {
        SDL_Log("Out of memory!\n");
        quit(2);
    }
    
    /* Create OpenGL ES contexts */
    for (i = 0; i < state->num_windows; i++) {
        context[i] = SDL_GL_CreateContext(state->windows[i]);
        if (!context[i]) {
            SDL_Log("SDL_GL_CreateContext(): %s\n", SDL_GetError());
            quit(2);
        }
    }

    /* Important: call this *after* creating the context */
    if (LoadContext(&ctx) < 0) {
        SDL_Log("Could not load GLES2 functions\n");
        quit(2);
        return 0;
    }


    if (state->render_flags & SDL_RENDERER_PRESENTVSYNC) {
        SDL_GL_SetSwapInterval(1);
    } else {
        SDL_GL_SetSwapInterval(0);
    }

    SDL_GetCurrentDisplayMode(0, &mode);
    SDL_Log("Screen bpp: %d\n", SDL_BITSPERPIXEL(mode.format));
    SDL_Log("\n");
    SDL_Log("Vendor     : %s\n", ctx.glGetString(GL_VENDOR));
    SDL_Log("Renderer   : %s\n", ctx.glGetString(GL_RENDERER));
    SDL_Log("Version    : %s\n", ctx.glGetString(GL_VERSION));
    SDL_Log("Extensions : %s\n", ctx.glGetString(GL_EXTENSIONS));
    SDL_Log("\n");

    status = SDL_GL_GetAttribute(SDL_GL_RED_SIZE, &value);
    if (!status) {
        SDL_Log("SDL_GL_RED_SIZE: requested %d, got %d\n", 5, value);
    } else {
        SDL_Log( "Failed to get SDL_GL_RED_SIZE: %s\n",
                SDL_GetError());
    }
    status = SDL_GL_GetAttribute(SDL_GL_GREEN_SIZE, &value);
    if (!status) {
        SDL_Log("SDL_GL_GREEN_SIZE: requested %d, got %d\n", 5, value);
    } else {
        SDL_Log( "Failed to get SDL_GL_GREEN_SIZE: %s\n",
                SDL_GetError());
    }
    status = SDL_GL_GetAttribute(SDL_GL_BLUE_SIZE, &value);
    if (!status) {
        SDL_Log("SDL_GL_BLUE_SIZE: requested %d, got %d\n", 5, value);
    } else {
        SDL_Log( "Failed to get SDL_GL_BLUE_SIZE: %s\n",
                SDL_GetError());
    }
    status = SDL_GL_GetAttribute(SDL_GL_DEPTH_SIZE, &value);
    if (!status) {
        SDL_Log("SDL_GL_DEPTH_SIZE: requested %d, got %d\n", depth, value);
    } else {
        SDL_Log( "Failed to get SDL_GL_DEPTH_SIZE: %s\n",
                SDL_GetError());
    }
    if (fsaa) {
        status = SDL_GL_GetAttribute(SDL_GL_MULTISAMPLEBUFFERS, &value);
        if (!status) {
            SDL_Log("SDL_GL_MULTISAMPLEBUFFERS: requested 1, got %d\n", value);
        } else {
            SDL_Log( "Failed to get SDL_GL_MULTISAMPLEBUFFERS: %s\n",
                    SDL_GetError());
        }
        status = SDL_GL_GetAttribute(SDL_GL_MULTISAMPLESAMPLES, &value);
        if (!status) {
            SDL_Log("SDL_GL_MULTISAMPLESAMPLES: requested %d, got %d\n", fsaa,
                   value);
        } else {
            SDL_Log( "Failed to get SDL_GL_MULTISAMPLESAMPLES: %s\n",
                    SDL_GetError());
        }
    }
    if (accel) {
        status = SDL_GL_GetAttribute(SDL_GL_ACCELERATED_VISUAL, &value);
        if (!status) {
            SDL_Log("SDL_GL_ACCELERATED_VISUAL: requested 1, got %d\n", value);
        } else {
            SDL_Log( "Failed to get SDL_GL_ACCELERATED_VISUAL: %s\n",
                    SDL_GetError());
        }
    }

    datas = SDL_calloc(state->num_windows, sizeof(shader_data));

    /* Set rendering settings for each context */
    for (i = 0; i < state->num_windows; ++i) {

        int w, h;
        status = SDL_GL_MakeCurrent(state->windows[i], context[i]);
        if (status) {
            SDL_Log("SDL_GL_MakeCurrent(): %s\n", SDL_GetError());

            /* Continue for next window */
            continue;
        }
        SDL_GL_GetDrawableSize(state->windows[i], &w, &h);
        ctx.glViewport(0, 0, w, h);

        data = &datas[i];
        data->angle_x = 0; data->angle_y = 0; data->angle_z = 0;

        /* Shader Initialization */
        process_shader(&data->shader_vert, _shader_vert_src, GL_VERTEX_SHADER);
        process_shader(&data->shader_frag, _shader_frag_src, GL_FRAGMENT_SHADER);

        /* Create shader_program (ready to attach shaders) */
        data->shader_program = GL_CHECK(ctx.glCreateProgram());

        /* Attach shaders and link shader_program */
        GL_CHECK(ctx.glAttachShader(data->shader_program, data->shader_vert));
        GL_CHECK(ctx.glAttachShader(data->shader_program, data->shader_frag));
        GL_CHECK(ctx.glLinkProgram(data->shader_program));

        /* Get attribute locations of non-fixed attributes like color and texture coordinates. */
        data->attr_position = GL_CHECK(ctx.glGetAttribLocation(data->shader_program, "av4position"));
        data->attr_color = GL_CHECK(ctx.glGetAttribLocation(data->shader_program, "av3color"));

        /* Get uniform locations */
        data->attr_mvp = GL_CHECK(ctx.glGetUniformLocation(data->shader_program, "mvp"));

        GL_CHECK(ctx.glUseProgram(data->shader_program));

        /* Enable attributes for position, color and texture coordinates etc. */
        GL_CHECK(ctx.glEnableVertexAttribArray(data->attr_position));
        GL_CHECK(ctx.glEnableVertexAttribArray(data->attr_color));

        /* Populate attributes for position, color and texture coordinates etc. */
        GL_CHECK(ctx.glVertexAttribPointer(data->attr_position, 3, GL_FLOAT, GL_FALSE, 0, _vertices));
        GL_CHECK(ctx.glVertexAttribPointer(data->attr_color, 3, GL_FLOAT, GL_FALSE, 0, _colors));

        GL_CHECK(ctx.glEnable(GL_CULL_FACE));
        GL_CHECK(ctx.glEnable(GL_DEPTH_TEST));
    }

    /* Main render loop */
    frames = 0;
    then = SDL_GetTicks();
    done = 0;

    while (!done) {
        loop();
    }

    /* Print out some timing information */
    now = SDL_GetTicks();

    if (now > then) {
        SDL_Log("%2.2f frames per second\n",
               ((double) frames * 1000) / (now - then));
    }

    quit(0);
    return 0;
}