gtkada and timeouts

[tonyg <tonythegair@gmail.com>]

I've written a function called update_screen which always returns a
value of true and sets various values in the 'main_screen' access
record. This is part of the code from glade/gate which I have modified
to include a timeout

with Gtk; use Gtk;
with Gtk; use Gtk;
with Gtk.Main; use Gtk.Main;
with Gtk.Widget; use Gtk.Widget;
with Main_Screen_Pkg; use Main_Screen_Pkg;
with Main_Control; use Main_Control;
procedure Main_Screen is
   Main_Screen : Main_Screen_Access;
        Timeout_Id : Timeout_Handler_id ;
   package Data_Timeout is new Gtk.Main.Timeout (Main_Screen_Access);

begin
   Gtk.Main.Set_Locale;
   Gtk.Main.Init;
   Gtk_New (Main_Screen);
   Show_All (Main_Screen);
   Gtk.Main.Main;
   -- my addition -- the timer
   Timeout_Id := Data_Timeout.Add (100, Update_Screen'Access,
Main_Screen);

end Main_Screen;

Sadly the timeout is never called, Can anyone cast some light on this?