dnl @synopsis AX_CHECK_GL
dnl
dnl Check for an OpenGL implementation.  Succeeds if both GL and GLU are found.
dnl If it succeeds, the required linker flags are included in the output
dnl variable "GL_LIBS".  This macro adds the configure option
dnl "--with-apple-opengl-framework", which users can use to indicate that
dnl Apple's OpenGL framework should be used on Mac OS X.  If Apple's OpenGL
dnl framework is used, the symbol HAVE_APPLE_OPENGL_FRAMEWORK is defined.  If
dnl no OpenGL implementation is found, "no_gl" is set to "yes".
dnl
dnl @copyright (C) 2003 Braden McDaniel
dnl @license GNU GPL
dnl @version 1.4
dnl @author Braden McDaniel <address@hidden>
dnl
AC_DEFUN([AX_CHECK_GL],
[AC_REQUIRE([AC_PATH_X])dnl
AC_REQUIRE([ACX_PTHREAD])dnl

#
# There isn't a reliable way to know we should use the Apple OpenGL framework
# without a configure option.  A Mac OS X user may have installed an
# alternative GL implementation (e.g., Mesa), which may or may not depend on X.
#
AC_ARG_WITH([apple-opengl-framework],
            [AC_HELP_STRING([--with-apple-opengl-framework],
                            [use Apple OpenGL framework (Mac OS X only)])])
if test "X$with_apple_opengl_framework" = "Xyes"; then
  AC_DEFINE([HAVE_APPLE_OPENGL_FRAMEWORK], [1],
            [Use the Apple OpenGL framework.])
  GL_CFLAGS="-framework OpenGL"
else
  GL_CFLAGS="${PTHREAD_CFLAGS}"
  GL_LIBS="${PTHREAD_LIBS} -lm"

  #
  # Use x_includes and x_libraries if they have been set (presumably by
  # AC_PATH_X).
  #
  if test "X$no_x" != "Xyes"; then
    if test -n "$x_includes"; then
      GL_CFLAGS="-I${x_includes} ${GL_CFLAGS}"
    fi
    if test -n "$x_libraries"; then
      GL_LIBS="-L${x_libraries} -lX11 ${GL_LIBS}"
    fi
  fi

  AC_LANG_PUSH(C)

  AC_CHECK_HEADERS([windows.h])

  AC_CACHE_CHECK([for OpenGL library], [ax_cv_check_gl_libgl],
  [ax_cv_check_gl_libgl="no"
  ax_save_CPPFLAGS="${CPPFLAGS}"
  CPPFLAGS="${GL_CFLAGS} ${CPPFLAGS}"
  ax_save_LIBS="${LIBS}"
  LIBS=""
  ax_check_libs="-lopengl32 -lGL"
    for ax_lib in ${ax_check_libs}; do
    if test "X$CC" = "Xcl"; then
      ax_try_lib=`echo $ax_lib | sed -e 's/^-l//' -e 's/$/.lib/'`
    else
      ax_try_lib="${ax_lib}"
    fi
    LIBS="${ax_try_lib} ${GL_LIBS} ${ax_save_LIBS}"
    AC_TRY_LINK([
# if HAVE_WINDOWS_H && defined(_WIN32)
#   include <windows.h>
# endif
# include <GL/gl.h>
],
    [glBegin(0)],
    [ax_cv_check_gl_libgl="${ax_try_lib}"; break])
  done
  LIBS=${ax_save_LIBS}
  CPPFLAGS=${ax_save_CPPFLAGS}])

  if test "X${ax_cv_check_gl_libgl}" = "Xno"; then
    no_gl="yes"
  else
    GL_LIBS="${ax_cv_check_gl_libgl} ${GL_LIBS}"

    AC_CACHE_CHECK([for OpenGL Utility library], [ax_cv_check_gl_libglu],
    [ax_cv_check_gl_libglu="no"
    ax_save_CPPFLAGS="${CPPFLAGS}"
    CPPFLAGS="${GL_CFLAGS} ${CPPFLAGS}"
    ax_save_LIBS="${LIBS}"
    LIBS=""
    ax_check_libs="-lglu32 -lGLU"
    for ax_lib in ${ax_check_libs}; do
      if test "X$CC" = "Xcl"; then
        ax_try_lib=`echo $ax_lib | sed -e 's/^-l//' -e 's/$/.lib/'`
      else
        ax_try_lib="${ax_lib}"
      fi
      LIBS="${ax_try_lib} ${GL_LIBS} ${ax_save_LIBS}"
      #
      # libGLU typically links with libstdc++ on POSIX platforms. However,
      # setting the language to C++ means that test program source is named
      # "conftest.cc"; and Microsoft cl doesn't know what to do with such a
      # file.
      #
      if test "X$CXX" != "Xcl"; then
        AC_LANG_PUSH([C++])
      fi
      AC_TRY_LINK([
# if HAVE_WINDOWS_H && defined(_WIN32)
#   include <windows.h>
# endif
# include <GL/glu.h>
],
      [gluBeginCurve(0)],
      [ax_cv_check_gl_libglu="${ax_try_lib}"; break])
      if test "X$CXX" != "Xcl"; then
        AC_LANG_POP([C++])
      fi
    done
    LIBS=${ax_save_LIBS}
    CPPFLAGS=${ax_save_CPPFLAGS}])
    if test "X${ax_cv_check_gl_libglu}" = "Xno"; then
      no_gl="yes"
    else
      GL_LIBS="${ax_cv_check_gl_libglu} ${GL_LIBS}"
    fi
  fi
  AC_LANG_POP(C)
fi

AC_SUBST([GL_CFLAGS])
AC_SUBST([GL_LIBS])
])dnl