Create an empty button belonging to the specified group,
in which you can add() a widget
(e.g. a Gtk_Pixmap). If you wish to add a Gtk_Label,
you may want to
use the {Gtk_RadioButton(const string &label, Group)}
ctor directly instead.
Specify a 0 group if you want to create a new button group
Create a button belonging to the specified group, with a label inside.
You won't be able to add a widget in this button
since it already has a Gtk_Label in it.
Specify a 0 group if you want to create a new button group