unable to connect a handler to Gtk::FileChooserButton's "file-activated"

["Mirco \"MacSlow\"" Müller <macslow bangang de>]

Greetings everybody!

	In my program I'm using a Gtk::FileChooserButton to retrieve a filename
from the user. But connecting a signal-handler for the signal
"file-activated" doesn't cause the handler-function to be executed when
the user actually selects a different file via the
Gtk::FileChooserButton.

	Here is the setting up of the Gtk::FileChooserButton (UI loaded from
a .glade file using libglademm):

refXml->get_widget ("fileChooserButton", pFileChooserButton);
if (pFileChooserButton)
{
	pFileChooserButton->set_filename (m_strSvgFileName.c_str ());
	Gtk::FileFilter svgFilter;
	svgFilter.set_name ("SVG Drawings");
	svgFilter.add_pattern ("*.svg");
	svgFilter.add_pattern ("*.SVG");
	pFileChooserButton->add_filter (svgFilter);
	pFileChooserButton->set_filter (svgFilter);

	pFileChooserButton->signal_file_activated ().connect (sigc::ptr_fun
(on_file_activated));
}

This is what my callback looks like:

void on_file_activated ()
{
	std::cout << "file-name = "<< pFileChooserButton->get_filename()
}

I'm using gtkmm-2.8.0 and gtk+-2.8.3. What am I missing here. Other
connected signal-handlers do get properly triggered (e.g. Gtk::ComboBox,
Gtk::Entry).

Thanks in advance for your time an kind advice!

Best regards...

MacSlow
-- 
Mirco "MacSlow" M�<macslow bangang de>