dnl
dnl AX_CHECK_GLU
dnl
dnl Check for GLU.  If GLU is found, the required preprocessor and linker flags
dnl are included in the output variables "GLU_CFLAGS" and "GLU_LIBS",
dnl respectively.  If no GLU implementation is found, "no_glu" is set to "yes".
dnl
dnl If the header "GL/glu.h" is found, "HAVE_GL_GLU_H" is defined.  If the
dnl header "OpenGL/glu.h" is found, HAVE_OPENGL_GLU_H is defined.  These
dnl preprocessor definitions may not be mutually exclusive.
dnl
dnl Some implementations (in particular, some versions of Mac OS X) are known
dnl to treat the GLU tesselator callback function type as "GLvoid (*)(...)"
dnl rather than the standard "GLvoid (*)()".  If the former condition is
dnl detected, this macro defines "HAVE_VARARGS_GLU_TESSCB".
dnl
dnl version: 2.1
dnl author: Braden McDaniel <braden@endoframe.com>
dnl
dnl This program is free software; you can redistribute it and/or modify
dnl it under the terms of the GNU General Public License as published by
dnl the Free Software Foundation; either version 2, or (at your option)
dnl any later version.
dnl
dnl This program is distributed in the hope that it will be useful,
dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
dnl GNU General Public License for more details.
dnl
dnl You should have received a copy of the GNU General Public License
dnl along with this program; if not, write to the Free Software
dnl Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
dnl 02110-1301, USA.
dnl
dnl As a special exception, the you may copy, distribute and modify the
dnl configure scripts that are the output of Autoconf when processing
dnl the Macro.  You need not follow the terms of the GNU General Public
dnl License when using or distributing such scripts.
dnl
AC_DEFUN([AX_CHECK_GLU],
[AC_REQUIRE([AX_CHECK_GL])dnl
AC_REQUIRE([AC_PROG_CXX])dnl
GLU_CFLAGS="${GL_CFLAGS}"

ax_save_CPPFLAGS="${CPPFLAGS}"
CPPFLAGS="${GL_CFLAGS} ${CPPFLAGS}"
AC_CHECK_HEADERS([GL/glu.h OpenGL/glu.h])
CPPFLAGS="${ax_save_CPPFLAGS}"

m4_define([AX_CHECK_GLU_PROGRAM],
          [AC_LANG_PROGRAM([[
# if defined(HAVE_WINDOWS_H) && defined(_WIN32)
#   include <windows.h>
# endif
# ifdef HAVE_GL_GLU_H
#   include <GL/glu.h>
# elif defined(HAVE_OPENGL_GLU_H)
#   include <OpenGL/glu.h>
# else
#   error no glu.h
# endif]],
                           [[gluBeginCurve(0)]])])

AC_CACHE_CHECK([for OpenGL Utility library], [ax_cv_check_glu_libglu],
[ax_cv_check_glu_libglu="no"
ax_save_CPPFLAGS="${CPPFLAGS}"
CPPFLAGS="${GL_CFLAGS} ${CPPFLAGS}"
ax_save_LIBS="${LIBS}"

#
# First, check for the possibility that everything we need is already in
# GL_LIBS.
#
LIBS="${GL_LIBS} ${ax_save_LIBS}"
#
# libGLU typically links with libstdc++ on POSIX platforms.
# However, setting the language to C++ means that test program
# source is named "conftest.cc"; and Microsoft cl doesn't know what
# to do with such a file.
#
AC_LANG_PUSH([C++])
AS_IF([test X$ax_compiler_ms = Xyes],
      [AC_LANG_PUSH([C])])
AC_LINK_IFELSE(
[AX_CHECK_GLU_PROGRAM],
[ax_cv_check_glu_libglu=yes],
[LIBS=""
ax_check_libs="-lglu32 -lGLU"
for ax_lib in ${ax_check_libs}; do
  AS_IF([test X$ax_compiler_ms = Xyes],
        [ax_try_lib=`echo $ax_lib | sed -e 's/^-l//' -e 's/$/.lib/'`],
        [ax_try_lib="${ax_lib}"])
  LIBS="${ax_try_lib} ${GL_LIBS} ${ax_save_LIBS}"
  AC_LINK_IFELSE([AX_CHECK_GLU_PROGRAM],
                 [ax_cv_check_glu_libglu="${ax_try_lib}"; break])
done
])
AS_IF([test X$ax_compiler_ms = Xyes],
      [AC_LANG_POP([C])])
AC_LANG_POP([C++])

LIBS=${ax_save_LIBS}
CPPFLAGS=${ax_save_CPPFLAGS}])
AS_IF([test "X$ax_cv_check_glu_libglu" = Xno],
      [no_glu=yes; GLU_CFLAGS=""; GLU_LIBS=""],
      [AS_IF([test "X$ax_cv_check_glu_libglu" = Xyes],
             [GLU_LIBS="$GL_LIBS"],
             [GLU_LIBS="${ax_cv_check_glu_libglu} ${GL_LIBS}"])])
AC_SUBST([GLU_CFLAGS])
AC_SUBST([GLU_LIBS])

#
# Some versions of Mac OS X include a broken interpretation of the GLU
# tesselation callback function signature.
#
AS_IF([test "X$ax_cv_check_glu_libglu" != Xno],
[AC_CACHE_CHECK([for varargs GLU tesselator callback function type],
                [ax_cv_varargs_glu_tesscb],
[ax_cv_varargs_glu_tesscb=no
ax_save_CFLAGS="$CFLAGS"
CFLAGS="$GL_CFLAGS $CFLAGS"
AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM([[
# ifdef HAVE_GL_GLU_H
#   include <GL/glu.h>
# else
#   include <OpenGL/glu.h>
# endif]],
                 [[GLvoid (*func)(...); gluTessCallback(0, 0, func)]])],
[ax_cv_varargs_glu_tesscb=yes])
CFLAGS="$ax_save_CFLAGS"])
AS_IF([test X$ax_cv_varargs_glu_tesscb = Xyes],
      [AC_DEFINE([HAVE_VARARGS_GLU_TESSCB], [1],
                 [Use nonstandard varargs form for the GLU tesselator callback])])])
])