SDL_CreateWindow resolution ignored in iOS (Retina screen)

Hi,

I just can’t find the reason why the width and height parameter in the SDL_CreateWindow function gets ignored if I run my SDL application on the iPhone4.

I use the following code but the device opens always in 320x480 screen mode:

Code:
SDL_Window *window = SDL_CreateWindow(0, 0, 0, 640, 960, SDL_WINDOW_OPENGL | SDL_WINDOW_BORDERLESS | SDL_WINDOW_SHOWN);

The same happens on the iPad. Did I miss anything?

Thanks for your help!