Sending a hide() signal to a given widget ?

["Yann DIRSON" <ydirson linagora com>]

I would like to hide the menubar of a gtk app (namely evince - so I can
embed it in a preexisting window and pilot it from another app).

>From what I've found in the API (I'm not familiar with the Gtk API), the
GtkWidget hide() method would be what I should arrange to call.
Since it is tied to a signal I suspected I could trigger this signal from
the outside of the app, but I could not find how.

I have played with dogtail, and could browse the accessible object, and
sent a couple of click(), but hide() does not seem to be accessible from
there.

Am I just looking for something that does not exist ?