Copying arbitrary text to a clipboard

[Ari Pollak <ari debian org>]

Hi, I'm trying to find a way to copy arbitrary text to the X clipboard, 
which isn't actually present in any widget; specifically, a URL not 
actually shown in a GtkTextView, but which I'd like copied to the 
clipboard when an event occurs. Any ideas of a simple way to do this? I 
haven't found any example code which accomplishes this using standard 
GTK2 mechanisms.