When to free GnomeVFSVolumeOpCallback?

[Torsten Schoenfeld <kaffeetisch gmx de>]

Aloha,

I'm in the process of wrapping the GnomeVFSDrive and GnomeVFSVolume API
for Perl (better late than never), and I'm wondering how to know when
the callbacks for

  gnome_vfs_drive_mount, _umount, _eject and
  gnome_vfs_volume_unmount, _eject

will no longer be called and can be safely freed.  From the looks of it
the code first spawns a thread which spawns an external command to do
the job and then installs an idle handler which finally calls the
callback.

One way to do it is to put a reference to every callback structure into
the GObject so that they get destroyed when the drive/volume is
finalized.  That doesn't seem optimal, though.

So, is there another way to safely free the callbacks?

TIA,
-Torsten