Changing application font at runtime

["Surya Kiran Gullapalli" <suryakiran gullapalli gmail com>]

Hello all,
I'm struggling to find out a way to change the application font at
runtime. By application font I mean,
the font of all the controls in the main window + font of any dialogs
it opens etc.

I'm using gtkmm and I'm trying to use this
Gtk::Window::modify_font (I'm calling this function on my main window)

How can i do that?

Thanks in advance,
Surya