This is called by containers to obtain the minimum
and natural height of a widget. A widget that does not actually trade
any height for width or width for height only has to implement these
two virtual methods (#GtkWidgetClass.get_preferred_width() and
#GtkWidgetClass.get_preferred_height()).
This is called by containers to obtain the minimum and natural height of a widget. A widget that does not actually trade any height for width or width for height only has to implement these two virtual methods (#GtkWidgetClass.get_preferred_width() and #GtkWidgetClass.get_preferred_height()).