checking for gdk/gdkx.h

["Dr. Michael J. Chudobiak" <mjc avtechpulse com>]

What is the correct way to check for the presence of gdkx.h on a system? 
This doesn't work for me:

+# Checks for GDK X11 support; GDK & GTK on Mac OS X do not provide X11
+# extensions if compiled to use the Quartz backend.
+#
+HAVE_GDKX=no
+AC_CHECK_HEADER(gdk/gdkx.h,
+               [HAVE_GDKX=yes]
+               [AC_MSG_WARN(Disabling GDK/X11-dependent features.)])

It always returns "no", even on systems where it is present.

My understanding of autotools and makefiles is pretty limited...


- Mike