sub make_busy($$)
{

  my($instance, $busy) = @_;

  # Create and store the cursors if we haven't done so already.

  if (! exists($instance->{busy_cursor}))
  {
    $instance->{normal_cursor} = Gtk2::Gdk::Cursor->new("left-ptr");
    $instance->{busy_cursor} = Gtk2::Gdk::Cursor->new("watch");
  }

  # Do it. Make the application bar grab the input when the window is
  # busy, that way we gobble up keyboard and mouse events that could
  # muck up the application state.

  if ($busy)
  {
    $instance->{window}->window()->
      set_cursor($instance->{busy_cursor});
    Gtk2->grab_add($instance->{appbar});
  }
  else
  {
    $instance->{window}->window()->
      set_cursor($instance->{normal_cursor});
    Gtk2->grab_remove($instance->{appbar});
  }

}