Info Catalog tlbuild: Library modules tlbuild: zlib library

tlbuild: png library

 
 6.4.1 The 'png' library in 'libs/libpng'
 ----------------------------------------
 
 The "generic" 'png' library uses the source tree in the subdirectory
 'libpng-src/', with all modifications for TL recorded in 'TLpatches/*'.
 The 'configure.ac' fragment 'ac/withenable.ac' contains
 
      KPSE_WITH_LIB([libpng], [zlib])
 
 to specify the module name and indicate the dependency on 'zlib'.  A
 third literal argument ''tree'' would specify that the library from the
 TeX Live tree cannot be replaced by a system version.  That not being
 the case here, a second fragment 'ac/libpng.ac' contains
 
      KPSE_TRY_LIB([libpng],
                   [#include <png.h>],
                   [png_structp png; png_voidp io; png_rw_ptr fn;
      png_set_read_fn(png, io, fn);])
 
 thus providing the simple C code
 
      #include <png.h>
      int main ()
      { png_structp png; png_voidp io; png_rw_ptr fn;
        png_set_read_fn(png, io, fn);
        return 0; }
 
 which Autoconf uses to verify the usability of a system version with C
 code.  The analogous macro 'KPSE_TRY_LIBXX' would check using C++.
 These fragments are included by the 'configure.ac' at the top level of
 TL ('Build/source/configure.ac').
 
    For this library, like many other modules, a proxy build system for
 TL is used, consisting of our own 'configure.ac', 'Makefile.am',
 'include/Makefile.am'; the distributed build system is not used.
 (Consequently, a few generated files and auxiliary scripts are removed
 from the distributed source tree.)
 
    The public headers 'png.h', 'pngconf.h', and 'pnglibconf.h' are
 "installed" (as symlinks) under 'include/' in the build tree exactly as
 they are for a system version under, e.g., '/usr/include/'.
 
    The module is supplemented by the file 'm4/kpse-libpng-flags.m4' that
 defines the M4 macro 'KPSE_LIBPNG_FLAGS' used by all modules depending
 on this library in their 'configure.ac' to generate the 'make' variables
 'LIBPNG_INCLUDES' for use in 'CPPFLAGS', 'LIBPNG_LIBS' for use in
 'LDADD', 'LIBPNG_DEPEND' for use as dependencies, and 'LIBPNG_RULE' for
 the 'make' rules to rebuild the library.
 
    'm4/kpse-libpng-flags.m4' also supplies the configure option
 '--with-system-libpng', which then uses 'pkg-config' to determine the
 flags required for the system library.
 

Info Catalog tlbuild: Library modules tlbuild: zlib library