Emitted
before
the
user
is
prompted
for
an
incoming
file-transfer.
Plugins
can
intercept
the
signal
to
auto-accept/auto-reject
the
requests.
To
auto-accept
the
file
transfer,
use
purple_xfer_request_accepted().
To
auto-reject,
set
the
status
of
the
xfer
to
PURPLE_XFER_STATUS_CANCEL_LOCAL.