How do I make a gtk2+ application "swallowable"?

[Hazel Russman <hazel_russman yahoo co uk>]

Can someone please tell me how to make an application
run in "withdrawn" or "swallowable" mode so that it
can appear in the dock of certain window managers. I
have checked the gtk FAQ and the gtk Reference Guide
but have found no clear guidance, so have had to fall
back on guesswork. 

I tried using gtk_window_set_decorated to remove the
window frame and gtk_window_set_type_hint to set the
window type to GDK_WINDOW_TYPE_HINT_DOCK, but the
window still appears on the regular desktop.

What more do I need to do?


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