where it is not appropriate. If mainprog->jmpbuf is used by setjmp,
then png_longjmp cannot be used.
Reversed patch to remove error handler when the jmp_buf is stored in the
main program structure, not the png_struct.
The error handler is needed because the default handler in libpng will
always use the jmp_buf in the library control structure; this is never
set. The gregbook code is a useful example because, even though it
uses setjmp/longjmp, it shows how error handling can be implemented
using control mechanisms not directly supported by libpng. The
technique will work correctly with mechanisms such as Microsoft
Structure Exceptions or C++ exceptions (compiler willing - note that gcc
does not by default support interworking of C and C++ error handling.)
options. This makes the installed pnglibconf.h more readable but causes no
other change. The intention is that users of libpng will find it
easier to understand if an API they need is missing.
The macro was documented with two arguments (name,ordinal), however
the symbol checking .dfn files assumed five arguments. The five
argument form seems more useful so it is changed to that.
For Windows/x86 platforms only:
__stdcall is no longer needed for Visual Basic, so libpng-1.5.0 uses
__cdecl throughout (both API functions and callbacks) on Windows/x86
platforms.
This allows the functions
to read and write ints to be disabled independently of PNG_USE_READ_MACROS,
which allows libpng to be built with the functions even though the default
is to use the macros - this allows applications to choose at app build
time whether or not to use macros (previously impossible because the
functions weren't in the default build.)
contrib/pngminim project to pngerror.c, for use when warnings or
errors are disabled via PNG_NO_WARN or PNG_NO_ERROR_TEXT, to avoid
storing unneeded error/warning text.
In all prior versions of libpng most configuration options
controlled by compiler #defines had to be repeated by the
application code that used libpng. This patch changes this
so that compilation options that can only be changed at build
time are frozen in the build. Options that are compiler
dependent (and those that are system dependent) are evaluated
each time - pngconf.h holds these. Options that can be changed
per-file in the application are in png.h. Frozen options are
in the new installed header file pnglconf.h
