window - create window - opengl

  // initialize GLEW so we can make OpenGL calls. Print an error and close the window if it fails
  GLenum err = glewInit();
  if(err != GLEW_OK)
  {
    fprintf(stderr, "Error initializing GLEW.\n");
    glfwTerminate();
    return -1;
  }

  // if we see the below log statements, we've successfully attached OpenGL to the window
  // query the openGL version
  int glVersion[2] = {-1, 1};
  glGetIntegerv(GL_MAJOR_VERSION, &glVersion[0]);
  glGetIntegerv(GL_MINOR_VERSION, &glVersion[1]);

  // on error, log filepath and line number
  gl_debug(__FILE__, __LINE__);
  // print some information about our version of OpenGL.
  printf("Using OpenGL: %d.%d\n", glVersion[0], glVersion[1]);
  printf("Renderer used: %s\n", glGetString(GL_RENDERER));
  printf("Shading Language: %s\n", glGetString(GL_SHADING_LANGUAGE_VERSION));

  return 0;
}