dnl FC_CHECK_X_LIB(LIBRARY, FUNCTION [, ACTION-IF-FOUND [,
dnl   ACTION-IF-NOT-FOUND]])
dnl
dnl This macro is intended to search for X11-related libraries.  It takes the
dnl following variables for input:
dnl   LIBS		-- prefixed to all linker lines
dnl   X_LIBS		-- prefixed to all linker lines (after LIBS)
dnl   X_EXTRA_LIBS	-- suffixed to all linker lines
dnl Thus, the trial linker line will be "$LIBS $X_LIBS -l$1 $X_EXTRA_LIBS".
dnl
dnl The following variables are output:
dnl   X_EXTRA_LIBS	-- contains "-l$1 $X_EXTRA_LIBS" if the link succeeds
dnl
dnl Thus, the intended usage of this macro is something like this:
dnl   AC_PATH_XTRA
dnl   X_LIBS="$X_LIBS $X_PRE_LIBS"
dnl	dnl Is it just me or is AC_PATH_XTRA broken?
dnl   FC_CHECK_X_LIB(X11, XOpenDisplay, , AC_MSG_ERROR("Need X11"))
dnl   FC_CHECK_X_LIB(Xext, XShapeCombineMask)
dnl     [etc.]
dnl   LIBS="$LIBS $X_LIBS $X_EXTRA_LIBS"
dnl
AC_DEFUN(FC_CHECK_X_LIB,
[AC_MSG_CHECKING([for $2 in X library -l$1])
dnl Use a cache variable name containing both the library and function name,
dnl because the test really is for library $1 defining function $2, not
dnl just for library $1.  Separate tests with the same $1 and different $2s
dnl may have different results.
ac_lib_var=`echo $1['_']$2 | sed 'y%./+-%__p_%'`
AC_CACHE_VAL(ac_cv_lib_$ac_lib_var,
[ac_save_LIBS="$LIBS"
LIBS="$LIBS $X_LIBS -l$1 $X_EXTRA_LIBS"
AC_TRY_LINK(dnl
ifelse([$2], [main], , dnl Avoid conflicting decl of main.
[/* Override any gcc2 internal prototype to avoid an error.  */
]ifelse(AC_LANG, CPLUSPLUS, [#ifdef __cplusplus
extern "C"
#endif
])dnl
[/* We use char because int might match the return type of a gcc2
    builtin and then its argument prototype would still apply.  */
char $2();
]),
	    [$2()],
	    eval "ac_cv_lib_$ac_lib_var=yes",
	    eval "ac_cv_lib_$ac_lib_var=no")
LIBS="$ac_save_LIBS"
])dnl
if eval "test \"`echo '$ac_cv_lib_'$ac_lib_var`\" = yes"; then
  AC_MSG_RESULT(yes)
  ifelse([$3], ,
[changequote(, )dnl
  ac_tr_lib=HAVE_LIB`echo $1 | sed -e 's/[^a-zA-Z0-9_]/_/g' \
    -e 'y/abcdefghijklmnopqrstuvwxyz/ABCDEFGHIJKLMNOPQRSTUVWXYZ/'`
changequote([, ])dnl
  AC_DEFINE_UNQUOTED($ac_tr_lib)
  X_EXTRA_LIBS="-l$1 $X_EXTRA_LIBS"
], [$3])
else
  AC_MSG_RESULT(no)
ifelse([$4], , , [$4
])dnl
fi
])