Re: Glib-Perl - GSList in a signal callback?

[Brett Kosinski <brettk frodo dyn gno org>]

> > Hmm... but how can I hook into the marshalling code to add this hack?
>
> well, that's why this idea is so dirty --- you don't.
>
> $src->signal_connect (new_file => sub {
>                 my ($object, $thing, $data) = @_;
>                 my @list = hackish_list_conversion_function ($thing);
>                 ### ^^^^^^ this is the hack ^^^^^^^^
>                 1;
>                 }, $data);
>
> because i really can't think of another way.

Hrm... I see.  Well, I suppose I could implement my own signal_connect
method for GstObject which implements the above hack if the signal is
named "new_file".  Basically, it could do something like:

sub signal_connect
{
  my ($object, $signal, $callback, $data) = @_;
  my $attached_callback = $callback;

  if ($signal =~ /^new_file$/i)
    {
      $attached_callback = sub {
        my ($object, $data) = @_;
        my @list = hackish_list_conversion_function($data);

        $callback->($object, \ list);
      };
    }

  Glib::Object::signal_connect($object, $signal, $callback, $data);
}

This would also be semi-extensible, in that if I needed to add other
bizarre exceptions, I could do it here.

> since there's no type information for GLists, you'd have to create a
> small type wrapper, probably a boxed type.  it's not much work at all,
> and is quite often done for little special cases.  unfortunately, since
> this is a signal you'd have to change the gtype at the time of the
> signal's creation, which means an API change.

Well, the above hack looks like a reasonable solution, and doesn't require
an API change... now I have to decide if it's worth it. :)

> i can't say why GLib doesn't have a GType for lists, but i can imagine
> it wouldn't be very clean --- you'd have to have the GType for the list
> itself, and then another for the items *in* the list.  and since the
> list can hold *anything*....

Yes, true, although if you're only filling the list with Glib-derived
objects, you'd be able to determine their types at runtime using the usual
methods.  Anyway, whatever the case, I think I might just use the hackish
solution above.

Brett.