title: glClearColor doesn't work
body: <p>I started sdl and opengl course. i have one problem when i try to change background this function doesn't give any results. i use MSVS and Win8.1.
  I was trying use various options with parameters. i always have black background. Any ideas what i could do wrong?</p>
  
  <pre><code>#include &lt;SDL.h&gt;
  #include &lt;SDL_opengles2.h&gt;
  #include &lt;GLES3/gl3.h&gt;
  #include &lt;cstdio&gt;
  #include &lt;cstdlib&gt;
  
  const unsigned int DISP_WIDTH = 800;
  const unsigned int DISP_HEIGHT = 600;
  
  int SDL_main(int argc, char *args[]) {
  // ##### FIXME! #####
  SDL_Window *window = NULL;
  SDL_GLContext context = NULL;
  
  if (SDL_Init(SDL_INIT_VIDEO) &lt; 0) {
      SDL_Log("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());
      return 10;
  }
  
  atexit(SDL_Quit);
  
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK,SDL_GL_CONTEXT_PROFILE_ES);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION,3);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION,0);
  
  SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
  
  window = SDL_CreateWindow("Tut", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, DISP_WIDTH, DISP_HEIGHT, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
  
  if (!window) {
      SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Error","Couldn't create the main window",NULL);
      return EXIT_FAILURE;
  }
  
  context = SDL_GL_CreateContext(window);
  
  if (!context) {
      SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Error", "Couldn't create an OpenGl context", NULL);
      return EXIT_FAILURE;
  }
  
  glClearColor(0.5F, 0.0F, 1.0F, 0.5F);   // this function changes the color
  glClear(GL_COLOR_BUFFER_BIT);
  
  SDL_GL_SwapWindow(window);
  bool quit = false;
  
  while (!quit) {
      SDL_Event event;
      if (SDL_WaitEvent(&amp;event) != 0) {
          if (event.type == SDL_QUIT) {
              quit = true;
          }
      }
  
  }
  
  return EXIT_SUCCESS;
  </code></pre>
  
  <p>}</p>