How to set "signal_data" via Glade for glade_xml_signal_autoconnect_full

[david hagood gmail com]

I'm trying to understand using Glade + libglade to build UIs. As I
understand it, if I use the glade_xml_signal_autoconnect_full call, my
signal connect function will be called for every defined signal in the XML
tree I am processing.

One of the parameters passed to my connect functions is "signal_data",
which is defined in the libglade references as "signal_data :    the string
value of the signal data given in the XML file." There seems to be no way
to set this value via Glade-2.

How do I set this? Do I have to edit the XML outside of Glade (YUK!)?