[SDL] SDL_ttf/alpha issue - sorry - typo fixed:

[David Bruce]

Sorry about the near-duplicate post - the first one had a critical typo:



Hi,

I've taken over a project that has a function (see below) that is supposed to 
return a SDL_Surface* containing text with a black outline.  The surface 
surrounding the text is supposed to be transparent.  However, the entire 
SDL_Surface comes out transparent.  I have tested having the function return 
some of the intermediate surfaces, and everything other than the "tmp" 
surfaces immediately returned by TTF_RenderUTF8_Blended() comes out 
transparent. Do I need to do something with SDL_SetAlpha() on the "tmp" 
surfaces before I blit them to the "out" surface?



#if SDL_BYTEORDER == SDL_BIG_ENDIAN
#define rmask 0xff000000
#define gmask 0x00ff0000
#define bmask 0x0000ff00
#define amask 0x000000ff
#else
#define rmask 0x000000ff
#define gmask 0x0000ff00
#define bmask 0x00ff0000
#define amask 0xff000000
#endif


SDL_Surface* black_outline(unsigned char *t, TTF_Font *font, SDL_Color *c) {
        SDL_Surface *out, *tmp, *tmp2;
        SDL_Rect dstrect;

        tmp = TTF_RenderUTF8_Blended(font, t, black);

        tmp2 = SDL_CreateRGBSurface(SDL_SWSURFACE,
                                                     (tmp->w)+5,
                                                     (tmp->h)+5,
                                                      32, 
                                                      rmask, gmask,
                                                      bmask, amask);

        out = SDL_DisplayFormatAlpha(tmp2);
        SDL_FreeSurface(tmp2);

        dstrect.w = tmp->w;
        dstrect.h = tmp->h;

        for (dstrect.x = 1; dstrect.x < 4; dstrect.x++)
          for (dstrect.y = 1; dstrect.y < 4; dstrect.y++)
            SDL_BlitSurface( tmp, NULL, out, &dstrect );

        /* NOTE: if I return "out" at this point it is transparent */

        SDL_FreeSurface(tmp);

        /* --- Put the color version of the text on top! --- */
        tmp = TTF_RenderUTF8_Blended(font, t, *c);
        dstrect.x = dstrect.y = 2;
        SDL_BlitSurface(tmp, NULL, out, &dstrect);

        SDL_FreeSurface(tmp);

        /* --- Convert to the screen format for quicker blits --- */

        tmp = SDL_DisplayFormatAlpha(out);
        SDL_FreeSurface(out);

        return tmp;
}
-- 
David Bruce