static gboolean
button_press_cb (GtkWidget      *widget,
                 GdkEventButton *event,
		 gpointer        user_data)
{
  GdkDevice *device;
  MyWidgetPrivate *private_data;

  device = gdk_event_get_device ((GdkEvent *) event);
  private_data = MY_WIDGET (widget)->private;

  if (!private_data->grabbed_device &&
      gdk_device_grab (device, widget->window,
                   GDK_OWNERSHIP_NONE, FALSE,
		   GDK_POINTER_MOTION_MASK, NULL,
		   gdk_event_get_time ((GdkEvent *) event)) == GDK_GRAB_SUCCESS)
    {
      private_data->grabbed_device = device;
    }

  return TRUE;
}

static gboolean
key_press_cb (GtkWidget   *widget,
              GdkEventKey *event,
	      gpointer     user_data)
{
  GdkDevice *keyboard, *pointer;
  MyWidgetPrivate *private_data;

  if (event->key != GDK_Escape)
    return FALSE;

  private_data = MY_WIDGET (widget)->private;

  keyboard = gdk_event_get_device ((GdkEvent *) event);
  pointer = gdk_device_get_associated_device (keyboard);

  if (private_data->grabbed_device != NULL &&
      private_data->grabbed_device == pointer)
    {
      gdk_device_ungrab (device, gdk_event_get_time ((GdkEvent *) event));
      private_data->grabbed_device = NULL;
    }

  return TRUE;
}