AC_ARG_ENABLE([gui-fltk],
  [AS_HELP_STRING([--enable-gui-fltk],[Build the FLTK version of BaconGUI])],
        [FLTK="true"])

# Default is GTK version of BaConGUI
if test "$GTK" = true -o "$FLTK" = false; then
    AC_CHECK_LIB([gtk-3], [gtk_init], [GTK="true"], [], [])
	AC_SEARCH_LIBS(gtk_init, [gtk-3], [GTK="true"], [], [])
    if test "$GTK" = false; then
        AC_CHECK_LIB([gtk-x11-2.0], [gtk_init], [GTK="true"], [], [])
	    AC_SEARCH_LIBS(gtk_init, [gtk-x11-2.0], [GTK="true"], [], [])
        if test "$GTK" = false; then
            AC_MSG_NOTICE(No GTK found on this system.)
        fi
    fi
fi

# No GTK found? Then verify presence of FLTK library