Causes @widget to become the default widget. @widget must be able to be
a default widget; typically you would ensure this yourself
by calling gtk_widget_set_can_default() with a %TRUE value.
The default widget is activated when
the user presses Enter in a window. Default widgets must be
activatable, that is, gtk_widget_activate() should affect them. Note
that #GtkEntry widgets require the “activates-default” property
set to %TRUE before they activate the default widget when Enter
is pressed and the #GtkEntry is focused.
Causes @widget to become the default widget. @widget must be able to be a default widget; typically you would ensure this yourself by calling gtk_widget_set_can_default() with a %TRUE value. The default widget is activated when the user presses Enter in a window. Default widgets must be activatable, that is, gtk_widget_activate() should affect them. Note that #GtkEntry widgets require the “activates-default” property set to %TRUE before they activate the default widget when Enter is pressed and the #GtkEntry is focused.