Re: [Sng-devel] sng 1.0.5 vs libpng 1.4

[Eric R. <es...@th...>]

James Cloos <cl...@jh...>:
> I tried to compile sng from git.  I have libpng-1.4.7 installed.
> 
> First, notwithstanding the recent commits, I had to pass
> 
>   --with-rgbtxt=/usr/share/X11/rgb.txt
> 
> to get ./configure to complete.
> 
> That is fixed by:
> 
> diff --git a/configure.in b/configure.in
> index b78df01..5dd6c4e 100644
> --- a/configure.in
> +++ b/configure.in
> @@ -44,7 +44,7 @@ if test -n "$with_rgbtxt"
>  then
>      AC_DEFINE_UNQUOTED(RGBTXT, "$with_rgbtxt", [Location of X color database])
>  else
> -    for dir in /etc/X11/ /usr/share/X11/rgb.txt /usr/X11R6/lib/X11 /usr/lib/X11 /usr/openwin/lib
> +    for dir in /etc/X11/ /usr/share/X11/ /usr/X11R6/lib/X11 /usr/lib/X11 /usr/openwin/lib
>      do
>         if test -f ${dir}/rgb.txt
>         then

That change is clearly correct.  Taken.

On the other hand...

> Second, sngd.c fails to compile with 166 deprication warnings (52 unique)
> and these errors:
> 
> :; gcc -DHAVE_CONFIG_H -I. -g -MT sngd.o -MD -MP -MF .deps/sngd.Tpo -c -o sngd.o sngd.c 2>&1 |egrep -i error
> sngd.c:797:48: error: ‘png_info’ has no member named ‘trans_values’
> sngd.c:801:15: error: ‘png_info’ has no member named ‘trans_values’
> sngd.c:802:15: error: ‘png_info’ has no member named ‘trans_values’
> sngd.c:803:15: error: ‘png_info’ has no member named ‘trans_values’
> sngd.c:807:33: error: ‘png_info’ has no member named ‘trans’
> 
> After reading libpng(3), I see that this patch is required:
> 
> diff --git a/sngd.c b/sngd.c
> index 248ac97..888d214 100644
> --- a/sngd.c
> +++ b/sngd.c
> @@ -794,17 +794,17 @@ static void dump_tRNS(FILE *fpout)
>         fprintf(fpout, "tRNS {\n");
>         switch (info_ptr->color_type) {
>         case PNG_COLOR_TYPE_GRAY:
> -           fprintf(fpout, "    gray: %u;\n", info_ptr->trans_values.gray);
> +           fprintf(fpout, "    gray: %u;\n", info_ptr->trans_color.gray);
>             break;
>         case PNG_COLOR_TYPE_RGB:
>             fprintf(fpout, "    red: %u; green: %u; blue: %u;\n",
> -                   info_ptr->trans_values.red,
> -                   info_ptr->trans_values.green,
> -                   info_ptr->trans_values.blue);
> +                   info_ptr->trans_color.red,
> +                   info_ptr->trans_color.green,
> +                   info_ptr->trans_color.blue);
>             break;
>         case PNG_COLOR_TYPE_PALETTE:
>             for (i = 0; i < info_ptr->num_trans; i++)
> -               fprintf(fpout, " %u", info_ptr->trans[i]);
> +               fprintf(fpout, " %u", info_ptr->trans_alpha[i]);
>             break;
>         case PNG_COLOR_TYPE_GRAY_ALPHA:
>         case PNG_COLOR_TYPE_RGB_ALPHA:

...this clearly relates to a libpng API change, and we need to figure out
when it happened to conditionalize the code properly.  Here's what I see
in my png.h:

#define PNG_LIBPNG_VER_MAJOR   1
#define PNG_LIBPNG_VER_MINOR   2
#define PNG_LIBPNG_VER_RELEASE 42

What do those constants look like for you?  And does the libpng Changelog
tell you when the the API break was?

What I'm thinking is that I should define TRANS_ALPHA and TRANS_COLOR
macros that are conditionally defined by version.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>