In the glade, for each widget on which you want to associate
an action, you will have to add a signal. This signal, to which a
callback will be linked, will run a function of the associate
script, corresponding to the widget name, with an argument.
Few callbacks do not have any output, they act directly on the
interface.
It can be useful to add user data. The widget indicated in
this data will run the callback.
FOr example, if we add in user data
a widget entry
on the signal of a button,signal clicked, callback on_entry, the function of the entry will be run with its content as argument when the button will be pressed. It can be said that the button will act as the entry.
The user data are also necessary for the callbacks that act directly on the interface.