threads and gui

["Amadeus W. M." <amadeus84 cablespeed com>]

I have a gtkmm application which spawns off a non-gui WorkThread.
The WorkThread does some (heavy) computation and draws onto the gui.
I'm doing that with a Glib::Dispatcher, etc. and it works fine.

What I want to do is to block some widgets on the gui, to 
prevent the user from doing funny things to the gui while the
WorkThread thread is running. 

I can set_sensitive(0) the widgets I want, just before creating
the thread. But how do I set them back to sensitive when the
thread is done? If I put a WorkThread->join() somewhere after
the thread was created, the gui obviously doesn't get 
updated, waiting for the WorkThread. Do I need a second 
Dispatcher at the end of the WorkThread to tell the gui to set 
the widgets sensitive?