title: SDL2 window is transparent
body: <p>The SDL window that I created has problem : I can create a window but it's absolutely transparent , you can see through it ( not a white screen and i have no error ) . </p>
  
  <pre><code>#include &lt;SDL.h&gt;
  #include &lt;iostream&gt;
  
  int main(int argc, char *argv[])
  {
      SDL_Window *window = nullptr;
      if (SDL_Init(SDL_INIT_VIDEO) &lt; 0)
          std::cout &lt;&lt; "SDL Initialization Error : " &lt;&lt; SDL_GetError() &lt;&lt; std::endl;
      else
      {
          window = SDL_CreateWindow("SDL", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, SDL_WINDOW_SHOWN);
          if (window == NULL)
          {
              std::cout &lt;&lt; "Window creation error :" &lt;&lt; SDL_GetError() &lt;&lt; std::endl;
          }
          else
          {
              SDL_UpdateWindowSurface(window);
              SDL_Delay(2000000);
          }
      }
  
      SDL_DestroyWindow(window);
      SDL_Quit();
  
      return 0;
  }
  </code></pre>