GtkWidget::set_sensitive
void set_sensitive(bool sensitive);
Use this function to toggle whether or not the user can interact
with a widget. Setting it to false sets the
widget's state to GTK_STATE_INSENSITIVE, which
'greys out' the widget.
You might use this if, for instance, you wanted to prevent a button
from being pressed in certain situations.
Setting a container as 'insensitive' will make all that container's
children insensitive too.
