ceph/src/boost/libs/signals/doc/introduction.xml

   1 <?xml version="1.0" encoding="utf-8"?>
   2 <!DOCTYPE section PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
   3   "http://www.boost.org/tools/boostbook/dtd/boostbook.dtd">
   4 <section last-revision="$Date$">
   5
   6 <title>Introduction</title>
   7
   8 <note>
   9 <para><emphasis role="bold">Boost.Signals is no longer being actively maintained.</emphasis>
  10 Do not use Boost.Signals for new development (use
  11 <link linkend="signals2">Boost.Signals2</link>
  12 instead). If you have existing Boost.Signals-based code, it will
  13 continue to work, but consider moving to Boost.Signals2. There is
  14 <link linkend="signals2.porting">
  15 a porting guide</link> in the Signals2 documentation.</para>
  16 </note>
  17
  18 <para>The Boost.Signals library is an implementation of a managed
  19 signals and slots system. Signals represent callbacks with multiple
  20 targets, and are also called publishers or events in similar
  21 systems. Signals are connected to some set of slots, which are
  22 callback receivers (also called event targets or subscribers), which
  23 are called when the signal is "emitted."</para>
  24
  25 <para>Signals and slots are managed, in that signals and slots (or,
  26 more properly, objects that occur as part of the slots) track all
  27 connections and are capable of automatically disconnecting signal/slot
  28 connections when either is destroyed. This enables the user to make
  29 signal/slot connections without expending a great effort to manage the
  30 lifetimes of those connections with regard to the lifetimes of all
  31 objects involved.</para>
  32
  33 <para>When signals are connected to multiple slots, there is a
  34 question regarding the relationship between the return values of the
  35 slots and the return value of the signals. Boost.Signals allows the
  36 user to specify the manner in which multiple return values are
  37 combined.</para>
  38
  39 </section>