+/* Change the callback */
+%perlcode %{
+sub xfer_set_callback {
+ my ($xfer, $cb) = @_;
+ if (defined $cb) {
+ my $releasing_cb = sub {
+ my ($src, $msg, $xfer) = @_;
+ my $done = $msg->{'type'} == $XMSG_DONE;
+ $src->remove() if $done;
+ $cb->(@_);
+ $cb = undef if $done; # break potential reference loop
+ };
+ $xfer->get_source()->set_callback($releasing_cb);
+ } else {
+ $xfer->get_source()->set_callback(undef);
+ }
+}
+%}
+