better configure support for XFT

configure.in

@@ -10,8 +10,7 @@ dnl Check for various flavors of UNIX(r)
 dnl AC_AIX
 dnl AC_ISC_POSIX
 
-dnl TODO: do this
-dnl AC_LANG_CPLUSPLUS
+AC_LANG_CPLUSPLUS
  
 dnl Locate required external software
 AC_PROG_CC
@@ -228,19 +227,27 @@ AC_ARG_ENABLE(
   AC_MSG_RESULT([no])
 )
 
+
 AC_MSG_CHECKING([whether to have Xft support])
 AC_ARG_ENABLE(
   xft,
 [  --enable-xft            Xft (antialias) support [default=no]],
   if test x$enableval = "xyes"; then
     AC_MSG_RESULT([yes])
-	AC_DEFINE(USE_XFT, 1, "antialias support")
-	LIBS="$LIBS -lXft"
+	AC_CHECK_LIB(Xft, XftFontOpen,
+		LIBS="$LIBS -lXft"
+		XFT=true
+		AC_DEFINE(USE_XFT, 1, "antialias support"),
+	    AC_MSG_ERROR([Could not find XftFontOpen in -lXft.])
+	)
   else
     AC_MSG_RESULT([no])
+	XFT=false
   fi,
   AC_MSG_RESULT([no])
+  XFT=false
 )
+ AM_CONDITIONAL(XFT, test x$XFT = xtrue)
 
 dnl Check for Xinerama support