[gtkmm] my toolbar stays flat and doesn't show my buttons inside

[cedric <cedric probesys com>]

hi !
i've passed into version 2.4 of GTKMM and the toolbars doesn't work the 
same as former versions.
So i tried that :
...
      Gtk::ToolButton* toolbutton;
       toolbutton = Gtk::manage(new Gtk::ToolButton("NEW\nCOMPANY"));
       toolbutton->signal_clicked().connect( 
sigc::ptr_fun(&collaborators::add_company));
       toolbarmod.append(*toolbutton);
 ...
and in a file included :
       Gtk::Toolbar toolbarmod;


After making the project, and executing, the toolbar "stays flat" and 
doesn't show my buttons inside.

I don't know if there is a problem of lost pointer or anything else ...
Thank u for your help...