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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/signals/connection.hpp" last-revision="$Date: 2006/11/03 19:45:41 $">
  <namespace name="boost">
    <namespace name="signals">
      <class name="connection">
        <!-- Models LessThanComparable and EqualityComparable -->
        <purpose>Query/disconnect a signal-slot connection.</purpose>

        <description>
          <para>The <classname>connection</classname> class represents
          a connection between a Signal and a Slot. It is a
          lightweight object that has the ability to query whether the
          signal and slot are currently connected, and to disconnect
          the signal and slot. It is always safe to query or
          disconnect a connection.</para>
        </description>

        <constructor>
          <effects><para>Sets the currently represented connection to the
          NULL connection.</para></effects>
          <postconditions><para><computeroutput>!this-><methodname>connected</methodname>()</computeroutput>.</para></postconditions>
          <throws><para>Will not throw.</para></throws>
        </constructor>

        <constructor>
          <parameter name="other"> 
            <paramtype>const <classname>connection</classname>&amp;</paramtype>
          </parameter>

          <effects><para><computeroutput>this</computeroutput> references
          the connection referenced by
          <computeroutput>other</computeroutput>.</para></effects>

          <throws><para>Will not throw.</para></throws>
        </constructor>

        <copy-assignment>
          <parameter name="other"> 
            <paramtype>const <classname>connection</classname>&amp;</paramtype>
          </parameter>

          <effects><para><computeroutput>this</computeroutput> references
          the connection referenced by
          <computeroutput>other</computeroutput>.</para></effects>

          <throws><para>Will not throw.</para></throws>
        </copy-assignment>

        <method-group name="connection management">
          <method name="disconnect" cv="const">
             <type>void</type>
             <effects><para>If
             <computeroutput>this-&gt;<methodname>connected</methodname>()</computeroutput>,
             disconnects the signal and slot referenced by this;
             otherwise, this operation is a no-op.</para></effects>

             <postconditions><para><computeroutput>!this-&gt;<methodname>connected</methodname>()</computeroutput>.</para></postconditions>
          </method>

          <method name="connected" cv="const">
            <type>bool</type>
            <returns><para><computeroutput>true</computeroutput> if this
            references a non-NULL connection that is still active
            (connected), and <computeroutput>false</computeroutput>
            otherwise.</para></returns>
            <throws><para>Will not throw.</para></throws>
          </method>
        </method-group>

        <method-group name="blocking">
          <method name="block">
            <type>void</type>
            <parameter name="should_block">
              <paramtype>bool</paramtype>
              <default>true</default>
            </parameter>
            <requires><simpara><code>connected()</code></simpara></requires>
            <postconditions><simpara><code>blocked() == should_block</code></simpara></postconditions>
            <throws><simpara>Will not throw.</simpara></throws>
          </method>
          <method name="unblock">
            <type>void</type>
            <requires><simpara><code>connected()</code></simpara></requires>
            <postconditions><simpara><code>!blocked()</code></simpara></postconditions>
            <throws><simpara>Will not throw.</simpara></throws>
          </method>
          <method name="blocked" cv="const">
            <type>bool</type>
            <returns><simpara><code>true</code> if the associated slot is either disconnected or blocked, <code>false</code> otherwise.</simpara></returns>
            <throws><simpara>Will not throw.</simpara></throws>
          </method>
        </method-group>

        <method-group name="modifiers">
          <method name="swap">
            <type>void</type>
            <parameter name="other">
              <paramtype>const <classname>connection</classname>&amp;</paramtype>
            </parameter>
            <effects><para>Swaps the connections referenced in
            <computeroutput>this</computeroutput> and
            <computeroutput>other</computeroutput>.</para></effects>
 
            <throws><para>Will not throw.</para></throws>
          </method> 
        </method-group>

        <method-group name="comparisons">
          <method name="operator==" cv="const">
            <type>bool</type>
            <parameter name="other">
              <paramtype>const <classname>connection</classname>&amp;</paramtype>
            </parameter>

            <returns><para><computeroutput>true</computeroutput> if
            <computeroutput>this</computeroutput> and
            <computeroutput>other</computeroutput> reference the same
            connection or both reference the NULL connection, and
            <computeroutput>false</computeroutput>
            otherwise.</para></returns>

            <throws><para>Will not throw.</para></throws>
          </method>

          <method name="operator&lt;" cv="const">
            <type>bool</type>
            <parameter name="other">
              <paramtype>const <classname>connection</classname>&amp;</paramtype>
            </parameter>

            <returns><para><computeroutput>true</computeroutput> if the
            connection referenced by
            <computeroutput>this</computeroutput> precedes the
            connection referenced by
            <computeroutput>other</computeroutput> based on some
            unspecified ordering, and
            <computeroutput>false</computeroutput>
            otherwise.</para></returns>

            <throws><para>Will not throw.</para></throws>
          </method>
        </method-group>

        <free-function-group name="specialized algorithms">
          <function name="swap">
            <type>void</type>
            <parameter name="x">
              <paramtype><classname>connection</classname>&amp;</paramtype>
            </parameter>
            <parameter name="y">
              <paramtype><classname>connection</classname>&amp;</paramtype>
            </parameter>

            <effects><para><computeroutput>x.swap(y)</computeroutput></para></effects>
            <throws><para>Will not throw.</para></throws>
          </function>
        </free-function-group>
      </class>

      <class name="scoped_connection">
        <inherit access="private">
          <type><classname>noncopyable</classname></type>
          <purpose>Exposition only</purpose>
        </inherit>
        <purpose>Limits a signal-slot connection lifetime to a particular scope.</purpose>

        <constructor>
          <parameter name="other"> 
            <paramtype>const <classname>connection</classname>&amp;</paramtype>
          </parameter>

          <effects><para><computeroutput>this</computeroutput> references
          the connection referenced by
          <computeroutput>other</computeroutput>.</para></effects>

          <throws><para>Will not throw.</para></throws>
        </constructor>

        <destructor>
          <effects><para>If
          <computeroutput>this-&gt;<methodname>connected</methodname>()</computeroutput>,
          disconnects the signal-slot connection.</para></effects>
        </destructor>

        <method-group name="connection management">
          <method name="disconnect" cv="const">
            <type>void</type>
             <effects><para>If
             <computeroutput>this-&gt;<methodname>connected</methodname>()</computeroutput>,
             disconnects the signal and slot referenced by this;
             otherwise, this operation is a no-op.</para></effects>

             <postconditions><para><computeroutput>!this-&gt;<methodname>connected</methodname>()</computeroutput>.</para></postconditions>
          </method>

          <method name="connected" cv="const">
            <type>bool</type>
            <returns><para><computeroutput>true</computeroutput> if this
            references a non-NULL connection that is still active
            (connected), and <computeroutput>false</computeroutput>
            otherwise.</para></returns>
            <throws><para>Will not throw.</para></throws>
          </method>
        </method-group>
      </class>
    </namespace>
  </namespace>
</header>