connecting signal_timeout()

[Emilian Nowak <emiml wp pl>]

Hello,
I'm using gtkmm2.4, and of course I have some problem:
In on of my class called:
class SystemBar

In one of the methods of this class I'm trying to do this:
Glib::signal_timeout().connect(sigc::ptr_fun(&update_gui_info), 1234);

and this update_gui_info looks like this:
bool SystemBar::update_gui_info(void);

and I have this error:
SystemBar.cc|15| error: ISO C++ forbids taking the address of an unqualified
or parenthesized non-static member function to form a pointer to member
function.  Say '&SystemBar::update_gui_info'

If I try it like this I have:
Glib::signal_timeout().connect(sigc::ptr_fun(&SystemBar::update_gui_info),
1234);

SystemBar.cc|15| error: no matching function for call to 'ptr_fun(bool (SystemBar::*)())'

What is the correct way of connecting this timeout signal?