El caso de Eye of Gnome
Donde sí es costoso redibujar de más

static void image_view_init (ImageView *view)
{
gtk_widget_set_double_buffered (GTK_WIDGET (view), FALSE);
}

static gboolean
image_view_expose_event (GtkWidget *widget, GdkEventExpose *event)
{
ImageView *view;
GdkRectangle *rects;
gint n_rects;
int i;

view = IMAGE_VIEW (widget);
gdk_region_get_rectangles (event->region, &rects, &n_rects);

for (i = 0; i < n_rects; i++)
image_view_paint_area (view, rects[i]);

g_free (rects);
return TRUE;
}