Gdk::Display::add_client_message_filter?

[Andrew Shafer <shafer realmsys com>]

I'm trying to use Gdk::Display::add_client_message_filter to get a
signal when a window gets mapped and I'm getting hung up.

The relevant code:

Glib::ustring startup_info = Glib::ustring("_NET_STARTUP_INFO");

Gdk::Display::get_default()->add_client_message_filter(startup_info,
myclass::launch_complete, (void *)NULL);

Where my class is of the form: 

GdkFilterReturn 
myform::launch_complete(GdkXEvent *xevent, GdkEvent *event, gpointer
data)

Right now the only code in the launch_complete function is to print
"success" to the screen, but it never gets called even though I am
monitoring the X messages and see _NET_STARTUP_INFO messages being
broadcast.

Any ideas??