|  |  |  | GTK+ 3 Reference Manual |  | 
|---|
Why. 
        The region field of
        GdkEventExpose allows you to redraw
        less than the traditional GdkEventRegion.area.
      
      In early GTK+ versions, the GdkEventExpose
      structure only had an area field to
      let you determine the region that you needed to redraw. In current
      GTK+, this field still exists for compatibility and as a simple
      interface. However, there is also a region
      field which contains a fine-grained region. The
      area field is simply the bounding rectangle
      of the region.
    
      Widgets that are very expensive to re-render, such as an image
      editor, may prefer to use the
      GdkEventExpose.region field to paint
      as little as possible.  Widgets that just use a few drawing
      primitives, such as labels and buttons, may prefer to use the
      traditional GdkEventExpose.area field
      for simplicity.
    
      Regions have an internal representation that is accessible as a
      list of rectangles.  To turn the
      GdkEventExpose.region field into such
      a list, use gdk_region_get_rectangles():
    
static gboolean
my_widget_expose_event_handler (GtkWidget *widget, GdkEventExpose *event)
{
  GdkRectangle *rects;
  int n_rects;
  int i;
  gdk_region_get_rectangles (event->region, &rects, &n_rects);
  for (i = 0; i < n_rects; i++)
    {
      /* Repaint rectangle: (rects[i].x, rects[i].y),
       *                    (rects[i].width, rects[i].height)
       */
    }
  g_free (rects);
  return FALSE;
}