[SDL] SDL_gfx broken ?

[Joshua Oreman]

On 8/31/05, Michael Benfield <leftfist at mac.com> wrote:
> 
> On Aug 31, 2005, at 12:17 PM, Tyler Montbriand wrote:
> > Can you post a minimal example showing the problem?
> >
> 
> Indeed. This example should spray an orange box on the screen but the
> box comes out green because the red channel left at 0. If I make it
> opaque (by making pcolor[3] = 255), the box is orange as it should be.
> If I comment out the masks and uncomment the other set of masks, no box
> is visible, because it's the alpha channel that is left at 0. (This is
> on a big endian system. I think on a little endian system the situation
> is reversed.) What I said earlier about the *Color varieties doing
> nothing doesn't seem to be the case; I'm not sure what I was doing
> wrong then.

The *Color varieties don't take a MapRGB()'ed color.  They take a
32-bit value of the format 0xRRGGBBAA.

I think this might be the cause of your error.

> 
> Also, while I'm on the topic.. Why does the code for these drawing
> primitives do checks for endianness? Doesn't SDL_MapRGBA make that
> unnecessary? It does in my testing.

To know whether *(Uint8 *)color is RR or AA.

-- Josh

> 
> I appreciate your help.
> 
> #include<stdio.h>
> #include<SDL.h>
> #include<SDL_gfxPrimitives.h>
> 
> int main(int argc, char** argv)
> {
>    SDL_Init(SDL_INIT_VIDEO);
>    SDL_SetVideoMode(400, 400, 32, 0);
>    SDL_Surface* s = SDL_CreateRGBSurface(0, 200, 200, 32,
>                                          0xff000000, 0x00ff0000,
>                                          0x0000ff00, 0x000000ff);
>                                          //0x000000ff, 0x0000ff00,
>                                          //0x00ff0000, 0xff000000);
>    Uint32 color;
>    Uint8* pcolor = (Uint8*) &color;
>    pcolor[0] = 200; pcolor[1] = 100; pcolor[2] = 10; pcolor[3] = 254;
>    //if(boxRGBA(s, 0, 0, 199, 199, pcolor[0], pcolor[1],
>    //           pcolor[2], pcolor[3])) {
>      if(boxColor(s, 10, 10, 199, 199, color)) {
>      printf("error\n");
>    } else {
>      SDL_BlitSurface(s, 0, SDL_GetVideoSurface(), 0);
>      SDL_Flip(SDL_GetVideoSurface());
>      SDL_Event e;
>      for(;;) {
>        SDL_PollEvent(&e);
>        if(e.type == SDL_QUIT)
>          break;
>      }
>    }
> }
> 
> 
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