GtkWidgetClass' expose_event function problem

["David Shultz" <mrbraz97 gmail com>]

If you look at the code below:

gtkbutton.c:


static void
gtk_button_class_init (GtkButtonClass *klass)
{
   ........

   widget_class->expose_event = gtk_button_expose;

   .....
}

static gboolean
gtk_button_expose (GtkWidget      *widget,
           GdkEventExpose *event)
{
  if (GTK_WIDGET_DRAWABLE (widget))
    {
      GtkButton *button = GTK_BUTTON (widget);
      
      _gtk_button_paint (button, &event->area,
             GTK_WIDGET_STATE (widget),
             button->depressed ? GTK_SHADOW_IN : GTK_SHADOW_OUT,
             "button", "buttondefault");
      
      (* GTK_WIDGET_CLASS
(parent_class)->expose_event) (widget, event);
<--------------------why??
    }
  
  return FALSE;
}


Why the expose_event() function of parent_class(GtkBinClass) is called?
GtkWidgetClass doesn't have an implementation of expose_event function.
We know that GtkWidgetClass' expose_event is set to gtk_button_expose
as shown above. So correct me if i'm wrong but it is basically calling
gtk_button_expose() function recursively? So the function should never
return Right? Can anyone kindly explain it? Thanks.