eceivers (also called event targets or subscribers), which
  are called when the signal is "emitted."</p>
<p>Signals and slots are managed, in that signals and slots (or,
  more properly, objects that occur as part of the slots) can track
  connections and are capable of automatically disconnecting signal/slot
  connections when either is destroyed. This enables the user to make
  signal/slot connections without expending a great effort to manage the
  lifetimes of those connections with regard to the lifet