dnl *** X11 ***
if test "x$bc_with_x11" != "xno" ; then

    dnl find X11 libraries
    AC_PATH_XTRA
    if test "x$have_x" = "xyes" ; then
        AC_DEFINE(HAVE_X11_XLIB_H, 1, Define to 1 if you have the <X11/Xlib.h> h
    fi

    dnl add X11 libraries that link to X_LIBS
    LIBX11=""
    LIBXEXT=""
    LIBXI=""

    PRELIBS="$LIBS"
    LIBS="$PRELIBS $X_LIBS"
    AC_CHECK_LIB(X11, XCreateWindow, LIBX11="-lX11")