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   Copyright (c) 2002 Douglas Gregor <doug.gregor -at- gmail.com>
  
   Distributed under the Boost Software License, Version 1.0.
   (See accompanying file LICENSE_1_0.txt or copy at
   http://www.boost.org/LICENSE_1_0.txt)
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<!DOCTYPE header PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
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<header name="boost/signal.hpp" last-revision="$Date: 2006/11/03 19:45:41 $">
  <namespace name="boost">
    <namespace name="signals">
      <enum name="connect_position">
        <enumvalue name="at_front"/>
        <enumvalue name="at_back"/>
      </enum>
    </namespace>
    <class name="signalN">
      <template>
        <template-type-parameter name="R"/>
        <template-type-parameter name="T1"/>
        <template-type-parameter name="T2"/>
        <template-varargs/>
        <template-type-parameter name="TN"/>
        <template-type-parameter name="Combiner">
          <default><classname>last_value</classname>&lt;R&gt;</default>
        </template-type-parameter>
        <template-type-parameter name="Group">
          <default>int</default>
        </template-type-parameter>
        <template-type-parameter name="GroupCompare">
          <default><classname>std::less</classname>&lt;Group&gt;</default>
        </template-type-parameter>
        <template-type-parameter name="SlotFunction">
          <default><classname>functionN</classname>&lt;R, T1, T2, ..., TN&gt;</default>
        </template-type-parameter>
      </template>
      <inherit access="public"><classname>signals::trackable</classname></inherit>
      <inherit access="private">
        <type><classname>noncopyable</classname></type>
	<purpose>Exposition only</purpose>
      </inherit>

      <purpose>Set of safe multicast callback types.</purpose>

      <description> 
        <para>The class template <classname>signalN</classname> covers
         several related classes signal0, signal1, signal2, etc.,
         where the number suffix describes the number of function
         parameters the signal and its connected slots will
         take. Instead of enumerating all classes, a single pattern
         <classname>signalN</classname> will be described, where N
         represents the number of function parameters.</para>
      </description>

      <typedef name="result_type">
        <type>typename Combiner::result_type</type>
      </typedef>
      <typedef name="combiner_type"><type>Combiner</type></typedef>
      <typedef name="group_type"><type>Group</type></typedef>
      <typedef name="group_compare_type"><type>GroupCompare</type></typedef>
      <typedef name="slot_function_type"><type>SlotFunction</type></typedef>
      <typedef name="slot_type">
        <type><classname>slot</classname>&lt;SlotFunction&gt;</type>
      </typedef>
      <typedef name="slot_result_type">
        <type><emphasis>unspecified</emphasis></type>
      </typedef>
      <typedef name="slot_call_iterator">
        <type><emphasis>unspecified</emphasis></type>
      </typedef>
      <typedef name="argument_type">
        <type>T1</type>
        <purpose>If N == 1</purpose>
      </typedef>
      <typedef name="first_argument_type">
        <type>T1</type>
        <purpose>If N == 2</purpose>
      </typedef>
      <typedef name="second_argument_type">
        <type>T2</type>
        <purpose>If N == 2</purpose>
      </typedef>
      <typedef name="arg1_type"><type>T1</type></typedef>
      <typedef name="arg2_type"><type>T2</type></typedef>
      <typedef name="..."><type/></typedef>
      <typedef name="argN_type"><type>TN</type></typedef>

      <static-constant name="arity">
        <type>int</type>
        <default>N</default>
      </static-constant>

      <constructor>
        <parameter name="combiner">
          <paramtype>const combiner_type&amp;</paramtype>
          <default>combiner_type()</default>
        </parameter>
        <parameter name="compare">
          <paramtype>const group_compare_type&amp;</paramtype>
          <default>group_compare_type()</default>
        </parameter>

        <effects><simpara>Initializes the signal to contain no slots, copies the given combiner into internal storage, and stores the given group comparison function object to compare groups.</simpara></effects>

        <postconditions><simpara><computeroutput>this-&gt;<methodname>empty</methodname>()</computeroutput></simpara></postconditions>
      </constructor>

      <destructor>
        <effects><simpara>Disconnects all slots connected to <computeroutput>*this</computeroutput>.</simpara></effects>
      </destructor>

      <method-group name="connection management">
        <overloaded-method name="connect">
          <signature>
            <type><classname>signals::connection</classname></type>
            <parameter name="slot">
              <paramtype>const slot_type&amp;</paramtype>
            </parameter>
            <parameter name="at">
              <paramtype>signals::connect_position</paramtype>
              <default>signals::at_back</default>
            </parameter>
          </signature>

          <signature>
            <type><classname>signals::connection</classname></type>
            <parameter name="group">
              <paramtype>const group_type&amp;</paramtype>
            </parameter>
            <parameter name="slot">
              <paramtype>const slot_type&amp;</paramtype>
            </parameter>
            <parameter name="at">
              <paramtype>signals::connect_position</paramtype>
              <default>signals::at_back</default>
            </parameter>
          </signature>

          <effects><simpara>Connects the signal this to the incoming
          slot. If the slot is inactive, i.e., any of the trackable
          objects bound by the slot call have been destroyed, then the
          call to connect is a no-op. If the second version of
          <computeroutput>connect</computeroutput> is invoked, the
          slot is associated with the given group. The <code>at</code>
          parameter specifies where the slot should be connected:
          <code>at_front</code> indicates that the slot will be
          connected at the front of the list or group of slots and
          <code>at_back</code> indicates that the slot will be
          connected at the back of the list or group of
          slots.</simpara></effects>

          <returns><simpara>A
          <computeroutput><classname>signals::connection</classname></computeroutput>
          object that references the newly-created connection between
          the signal and the slot; if the slot is inactive, returns a
          disconnected connection.</simpara></returns>

          <throws><simpara>This routine meets the strong exception guarantee,
          where any exception thrown will cause the slot to not be
          connected to the signal.</simpara></throws> 

          <complexity><simpara>Constant time when connecting a slot
          without a group name or logarithmic in the number of groups
          when connecting to a particular
          group.</simpara></complexity>

          <notes><simpara>It is unspecified whether connecting a slot while the
          signal is calling will result in the slot being called
          immediately.</simpara></notes>
        </overloaded-method>

        <overloaded-method name="disconnect">
          <signature>
            <type>void</type>
            <parameter name="group">
              <paramtype>const group_type&amp;</paramtype>
            </parameter>
          </signature>
          <signature>
            <template>
              <template-type-parameter name="Slot"/>
            </template>
            <type>void</type>
            <parameter name="slot">
              <paramtype>const Slot&amp;</paramtype>
            </parameter>
          </signature>

          <effects><simpara>If the parameter is (convertible to) a
          group name, any slots in the given group are
          disconnected. Otherwise, any slots equal to the given slot
          are disconnected.</simpara></effects>

          <throws><simpara>Will not throw unless a user destructor or
          equality operator <code>==</code> throws. If either throws,
          not all slots may be disconnected.</simpara></throws>

          <complexity><simpara>If a group is given, O(lg g) + k where
          g is the number of groups in the signal and k is the
          number of slots in the group. Otherwise, linear in the
          number of slots connected to the
          signal.</simpara></complexity>
        </overloaded-method>
 
        <method name="disconnect_all_slots">
          <type>void</type>
          <effects><simpara>Disconnects all slots connected to the signal.</simpara></effects>

          <postconditions><simpara><computeroutput>this-&gt;<methodname>empty</methodname>()</computeroutput>.</simpara></postconditions>

          <throws><simpara>If disconnecting a slot causes an exception to be
          thrown, not all slots may be disconnected.</simpara></throws>

          <complexity><simpara>Linear in the number of slots known to the
          signal.</simpara></complexity>

          <notes><simpara>May be called at any time within the lifetime of the
          signal, including during calls to the signal's slots.</simpara></notes>
        </method>

        <method name="empty" cv="const">
          <type>bool</type>
          <returns><simpara><computeroutput>true</computeroutput> if no slots
          are connected to the signal, and
          <computeroutput>false</computeroutput> otherwise.</simpara></returns>

          <throws><simpara>Will not throw.</simpara></throws>

          <complexity><simpara>Linear in the number of slots known to the
          signal.</simpara></complexity>

          <rationale><simpara>Slots can disconnect at any point in time,
          including while those same slots are being invoked. It is
          therefore possible that the implementation must search
          through a list of disconnected slots to determine if any
          slots are still connected.</simpara></rationale>
        </method>

        <method name="num_slots" cv="const">
          <type>std::size_t</type>
          <returns><simpara>The number of slots connected to the signal</simpara></returns>

          <throws><simpara>Will not throw.</simpara></throws>

          <complexity><simpara>Linear in the number of slots known to the
          signal.</simpara></complexity>

          <rationale><simpara>Slots can disconnect at any point in time,
          including while those same slots are being invoked. It is
          therefore possible that the implementation must search
          through a list of disconnected slots to determine how many
          slots are still connected.</simpara></rationale>
        </method>
      </method-group>

      <method-group name="invocation">
        <overloaded-method name="operator()">
          <signature>
            <type>result_type</type>
            <parameter name="a1"><paramtype>arg1_type</paramtype></parameter>
            <parameter name="a2"><paramtype>arg2_type</paramtype></parameter>
            <parameter><paramtype>...</paramtype></parameter>
            <parameter name="aN"><paramtype>argN_type</paramtype></parameter>
          </signature>
 
          <signature cv="const">
            <type>result_type</type>
            <parameter name="a1"><paramtype>arg1_type</paramtype></parameter>
            <parameter name="a2"><paramtype>arg2_type</paramtype></parameter>
            <parameter><paramtype>...</paramtype></parameter>
            <parameter name="aN"><paramtype>argN_type</paramtype></parameter>
          </signature>

          <effects><simpara>Invokes the combiner with a
          <computeroutput>slot_call_iterator</computeroutput> range
          [first, last) corresponding to the sequence of calls to the
          slots connected to signal
          <computeroutput>*this</computeroutput>. Dereferencing an
          iterator in this range causes a slot call with the given set
          of parameters <computeroutput>(a1, a2, ...,
          aN)</computeroutput>, the result of which is returned from
          the iterator dereference operation.</simpara></effects>

          <returns><simpara>The result returned by the combiner.</simpara></returns>

          <throws><simpara>If an exception is thrown by a slot call, or if the
          combiner does not dereference any slot past some given slot,
          all slots after that slot in the internal list of connected
          slots will not be invoked.</simpara></throws>

          <notes><simpara>Only the slots associated with iterators that are
          actually dereferenced will be invoked. Multiple dereferences
          of the same iterator will not result in multiple slot
          invocations, because the return value of the slot will be
          cached.</simpara>

          <simpara>The <computeroutput>const</computeroutput> version of
          the function call operator will invoke the combiner as
          <computeroutput>const</computeroutput>, whereas the
          non-<computeroutput>const</computeroutput> version will
          invoke the combiner as
          non-<computeroutput>const</computeroutput>.</simpara>

          <simpara>Calling the function call operator may invoke undefined
          behavior if no slots are connected to the signal, depending
          on the combiner used. The default combiner is well-defined
          for zero slots when the return type is void but is undefined
          when the return type is any other type (because there is no
          way to synthesize a return value).</simpara></notes>
        </overloaded-method>
      </method-group>

      <method-group name="combiner access">
        <overloaded-method name="combiner">
          <signature>
            <type>combiner_type&amp;</type>
          </signature>
          <signature cv="const">
            <type>const combiner_type&amp;</type>
          </signature>

          <returns><simpara>A reference to the stored combiner.</simpara></returns>
          <throws><simpara>Will not throw.</simpara></throws>
        </overloaded-method>
      </method-group>
    </class>

    <class name="signal">
      <template>
        <template-type-parameter name="Signature">
          <purpose>Function type R (T1, T2, ..., TN)</purpose>
        </template-type-parameter>
        <template-type-parameter name="Combiner">
          <default><classname>last_value</classname>&lt;R&gt;</default>
        </template-type-parameter>
        <template-type-parameter name="Group">
          <default>int</default>
        </template-type-parameter>
        <template-type-parameter name="GroupCompare">
          <default><classname>std::less</classname>&lt;Group&gt;</default>
        </template-type-parameter>
        <template-type-parameter name="SlotFunction">
          <default><classname>functionN</classname>&lt;Signature&gt;</default>
        </template-type-parameter>
      </template>

      <inherit access="public"><classname>signalN</classname>&lt;R, T1, T2, ..., TN, Combiner, Group, GroupCompare, SlotFunction&gt;</inherit>
      <purpose>Safe multicast callback.</purpose>

      <description>
        <para>Class template <classname>signal</classname> is a thin
        wrapper around the numbered class templates <classname
        alt="signalN">signal0</classname>, <classname
        alt="signalN">signal1</classname>, etc. It accepts a function
        type with N arguments instead of N separate arguments, and
        derives from the appropriate <classname>signalN</classname>
        instantiation.</para>
      
        <para>All functionality of this class template is in its base
        class <classname>signalN</classname>.</para>
      </description>

      <constructor>
        <parameter name="combiner">
          <paramtype>const combiner_type&amp;</paramtype>
          <default>combiner_type()</default>
        </parameter>
        <parameter name="compare">
          <paramtype>const group_compare_type&amp;</paramtype>
          <default>group_compare_type()</default>
        </parameter>

        <effects><simpara>Initializes the base class with the given combiner
        and comparison objects.</simpara></effects>
      </constructor>
    </class>
  </namespace>
</header>
