class Vips::Object

def signal_connect name, handler = nil, &block
  marshal = MARSHAL_ALL[name.to_sym]
  raise Vips::Error, "unsupported signal #{name}" if marshal.nil?
  if block
    # our block as a Proc
    prc = block
  elsif handler
    # We assume the hander is a Proc (perhaps we should test)
    prc = handler
  else
    raise Vips::Error, "must supply either block or handler"
  end
  # The marshal function will make a closure with the right type signature
  # for the selected signal
  callback = marshal.call(prc)
  # we need to make sure this is not GCd while self is alive
  @references << callback
  GObject.g_signal_connect_data(self, name.to_s, callback, nil, nil, 0)
end