x11drv: question about byte-swapping for DIBs

[Eric Frias]

I'm trying to debug a problem in which 24-bit .bmps don't display 
correctly from a winelib application on a big-endian sparc host when 
displaying on a little-endian intel PC.  In this case, the image is 
garbled, with most of the colors being wrong and a pattern of vertical 
stripes over the image.  The code passes through 
convert_888_to_0888_reverse_dst_byteswap which is what mangles the image 
data.

I looked through the other conversion functions, and it seems the 
corresponding 'src' function (convert_888_to_0888_reverse_src_byteswap) 
actually does the correct transformation.  I don't have a very good 
grasp of why the conversions are chosen, but it seemed like a likely fix 
would be to edit dib.c and make the lines in the SetImageBits functions 
that select the conversion structure look like:

#ifdef WORDS_BIGENDIAN
    const dib_conversions *convs = (bmpImage->byte_order == LSBFirst) ? 
&dib_normal : &dib_src_byteswap;
#else
    const dib_conversions *convs = (bmpImage->byte_order == LSBFirst) ? 
&dib_normal : &dib_dst_byteswap;
#endif

Doing this fixed my problem and didn't seem to cause any others, but I'm 
wondering whether this fix is correct or if I just got lucky.  Can 
someone who knows this code tell me if this makes logical sense?

(If it's correct, there probably needs to be a related patch in the 
GetImageBits functions, just going in the other direction).

Eric

[Phil Krylov]

On Wed, 19 Apr 2006 16:50:47 -0400
Eric Frias <efrias(a)syncad.com> wrote:
> I'm trying to debug a problem in which 24-bit .bmps don't display 
> correctly from a winelib application on a big-endian sparc host when 
> displaying on a little-endian intel PC.  In this case, the image is 
> garbled, with most of the colors being wrong and a pattern of vertical 
> stripes over the image.  The code passes through 
> convert_888_to_0888_reverse_dst_byteswap which is what mangles the image 
> data.

Just my 2 cents: the same bug appears in a winelib app on a big-endian PowerPC
host when displaying on the same big-endian PowerPC host, so it's probably
independent of display host.

-- Ph.

[Willie Sippel]

Am Mittwoch, 19. April 2006 22:50 schrieb Eric Frias:
> I'm trying to debug a problem in which 24-bit .bmps don't display
> correctly from a winelib application on a big-endian sparc host when
> displaying on a little-endian intel PC.  In this case, the image is
> garbled, with most of the colors being wrong and a pattern of vertical
> stripes over the image.  The code passes through
> convert_888_to_0888_reverse_dst_byteswap which is what mangles the image
> data.

Messed colors and vertical stripes? Similar to 
http://www.froq.net/mirage/mirage1.png ?

That's a standard Windows application running with regular Wine on x86, no 
Winelib or any endianess issues involved - in case the problem you see is 
similar...

-- 
Willie Sippel

  ////////  |  Tritium Studios
 //         |  ______________________________
//// ///    |  http://www.tritium-studios.com

<willie(a)froq.net>

[Phil Krylov]

On Thu, 20 Apr 2006 00:10:42 +0200
Willie Sippel <willie(a)zeitgeistmedia.net> wrote:
> Am Mittwoch, 19. April 2006 22:50 schrieb Eric Frias:
> > I'm trying to debug a problem in which 24-bit .bmps don't display
> > correctly from a winelib application on a big-endian sparc host when
> > displaying on a little-endian intel PC.  In this case, the image is
> > garbled, with most of the colors being wrong and a pattern of vertical
> > stripes over the image.  The code passes through
> > convert_888_to_0888_reverse_dst_byteswap which is what mangles the image
> > data.
>
> Messed colors and vertical stripes? Similar to 
> http://www.froq.net/mirage/mirage1.png ?

No, I get rather like this:

http://newstar.rinet.ru/~phil/Screenshot-StarLing-for-Macintosh.png

(the yellow-greenish square buttons should be light grey and clear)

-- Ph.

[Eric Frias]

Phil Krylov wrote:
> > Messed colors and vertical stripes? Similar to 
> > http://www.froq.net/mirage/mirage1.png ?
>
> No, I get rather like this:
>
> http://newstar.rinet.ru/~phil/Screenshot-StarLing-for-Macintosh.png

The StarLing image may be similar, but I think you're both looking at 
different bugs than I am... Here's the bitmap I see:
    http://www.syncad.com/wine-devel/striped-bitmap.jpg
a closeup of one of the hands in the image to show the stripes:
    http://www.syncad.com/wine-devel/striped-bitmap-closeup.jpg
here's the bitmap file I'm using:
    http://www.syncad.com/wine-devel/Sample.bmp

I've just been testing it by replacing replacing 
programs/winecfg/idb_wine.bmp with Sample.bmp, the image will be 
displayed on the 'About' tab.

Eric