SDL: Blit to a non-visible surface

I am trying to write a method which returns an SDL_Surface*. The code I am using is:

Code:

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SDL_Surface* SDLMenu::getSurface() {
        //Create and unlock surface
        SDL_Surface* output = SDL_CreateRGBSurface(SDL_SWSURFACE, 100, 25, 32, 0, 0, 0, 0);
        SDL_UnlockSurface(output);

        SDL_FillRect(output, 0, SDL_MapRGB(output->format, 255, 0, 255));

        SDL_LockSurface(output);

        return output;
}

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The problem I have is when I call this function, the output shown is a black screen. Can anyone tell me where I'm going wrong?

Code:

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        SDLApplication app;

        SDLMenu menu = SDLMenu();
        SDL_BlitSurface(menu.getSurface(), NULL, app.getScreen(), NULL);

        SDL_Flip(app.getScreen());

        SDL_Delay(10000);

        return 0;

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Thanks,
Gary

Since your masks are all zero, it filters out any colours you're trying to put. Hence why you have black ;)

Try putting this in:

Code:

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    Uint32 rmask, gmask, bmask, amask;
    rmask = 0x000000ff;
    gmask = 0x0000ff00;
    bmask = 0x00ff0000;
    amask = 0xff000000;
   
    SDL_Surface * output = SDL_CreateRGBSurface(SDL_SWSURFACE, 100, 25, 32,
        rmask, gmask, bmask, amask);

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