1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Frequently Asked Questions</title>
<link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
<link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset">
<link rel="up" href="../signals.html" title="Chapter 26. Boost.Signals">
<link rel="prev" href="../boost/last_value_voi_idp30143680.html" title="Class last_value<void>">
<link rel="next" href="s05.html" title="Design Overview">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td>
<td align="center"><a href="../../../index.html">Home</a></td>
<td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="../boost/last_value_voi_idp30143680.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../signals.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="s05.html"><img src="../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="idp420421104"></a>Frequently Asked Questions</h2></div></div></div>
<div class="qandaset">
<a name="idp420422128"></a><dl>
<dt>1. <a href="s04.html#idp420422384">Is Boost.Signals being actively maintained?</a>
</dt>
<dt>2. <a href="s04.html#idp420425904">Don't noncopyable signal semantics mean that a class
with a signal member will be noncopyable as well?</a>
</dt>
<dt>3. <a href="s04.html#idp420428256">Is Boost.Signals thread-safe?</a>
</dt>
<dt>4. <a href="s04.html#idp420430464">How do I get Boost.Signals to work with Qt?</a>
</dt>
</dl>
<table border="0" style="width: 100%;">
<colgroup>
<col align="left" width="1%">
<col>
</colgroup>
<tbody>
<tr class="question">
<td align="left" valign="top">
<a name="idp420422384"></a><a name="idp420422640"></a><p><b>1.</b></p>
</td>
<td align="left" valign="top"><p>Is Boost.Signals being actively maintained?</p></td>
</tr>
<tr class="answer">
<td align="left" valign="top"></td>
<td align="left" valign="top"><p>No. Please migrate to <a href="http://www.boost.org/doc/html/signals2.html" target="_top">Boost.Signals2</a>.
There is a
<a href="http://www.boost.org/doc/html/signals2/api_changes.html#signals2.porting" target="_top">porting guide</a>
in the Signals2 documentation.</p></td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="idp420425904"></a><a name="idp420426160"></a><p><b>2.</b></p>
</td>
<td align="left" valign="top"><p>Don't noncopyable signal semantics mean that a class
with a signal member will be noncopyable as well?</p></td>
</tr>
<tr class="answer">
<td align="left" valign="top"></td>
<td align="left" valign="top"><p>No. The compiler will not be able to generate a copy
constructor or copy assignment operator for your class if it
has a signal as a member, but you are free to write your own
copy constructor and/or copy assignment operator. Just don't
try to copy the signal.</p></td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="idp420428256"></a><a name="idp420428512"></a><p><b>3.</b></p>
</td>
<td align="left" valign="top"><p>Is Boost.Signals thread-safe?</p></td>
</tr>
<tr class="answer">
<td align="left" valign="top"></td>
<td align="left" valign="top"><p>No. Using Boost.Signals in a multithreaded concept is
very dangerous, and it is very likely that the results will be
less than satisfying. Boost.Signals will support thread safety
in the future.</p></td>
</tr>
<tr class="question">
<td align="left" valign="top">
<a name="idp420430464"></a><a name="idp420430720"></a><p><b>4.</b></p>
</td>
<td align="left" valign="top"><p>How do I get Boost.Signals to work with Qt?</p></td>
</tr>
<tr class="answer">
<td align="left" valign="top"></td>
<td align="left" valign="top">
<p>When building with Qt, the Moc keywords
<code class="computeroutput">signals</code> and <code class="computeroutput">slots</code> are defined using
preprocessor macros, causing programs using Boost.Signals and
Qt together to fail to compile.</p>
<p><span class="emphasis"><em>For Qt 4.1 and later</em></span>, This behavior
can be turned off in Qt on a per-project or per-file basis
with the <code class="computeroutput">no_keywords</code> option. This works with
out-of-the-box builds of Boost and Qt. You do not need to
re-configure, re-build, or duplicate existing libraries. For a
project where you want to use both Boost.Signals and Qt
Signals and Slots, the relevant part of your .pro file might
look like this:</p>
<pre class="programlisting">
CONFIG += no_keywords # so Qt won't #define any non-all-caps `keywords'
INCLUDEPATH += . /usr/local/include/boost-1_33_1/
macx:LIBS += /usr/local/lib/libboost_signals-1_33_1.a # ...your exact paths may vary
</pre>
<p>Now you can mix Boost.Signals and Qt Signals and Slots
in the same files, and even within the same class or function.
You will have to use the upper-case versions of Qt macros in
your own code. See the article <a href="http://scottcollins.net/articles/a-deeper-look-at-signals-and-slots.html" target="_top">A
Deeper Look at Signals and Slots</a> [off-site] for more
complete examples and a survey of the strengths of the two
systems.</p>
<p><span class="emphasis"><em>Older versions of Qt</em></span> did not
provide a reliable mechanism for avoiding these unfriendly,
all lower-case `keyword'-like macros. Although this is a
problem with Qt and not Boost.Signals, a user can use the two
systems together with a little extra effort. There are two
ways to do this:</p>
<p>The first way involves defining
the <code class="computeroutput">BOOST_SIGNALS_NAMESPACE</code>
macro to some other identifier (e.g., <code class="computeroutput">signalslib</code>)
when building and using the Boost.Signals library. Then the
namespace of the Boost.Signals library will be
<code class="computeroutput">boost::BOOST_SIGNALS_NAMESPACE</code> instead of
<code class="computeroutput">boost::signals</code>. To retain the original namespace
name in translation units that do not interact with Qt, you
can use a namespace alias:</p>
<pre class="programlisting">
namespace boost {
namespace signals = BOOST_SIGNALS_NAMESPACE;
}
</pre>
<p>The second way, provided by Frank Hess and improved by
Niels Dekker, involves
creating a header <code class="computeroutput">signalslib.hpp</code> that contains
the following code:</p>
<pre class="programlisting">#ifndef SIGNALSLIB_HPP_INCLUDED
#define SIGNALSLIB_HPP_INCLUDED
#if defined(signals) && defined(QOBJECTDEFS_H) && \
!defined(QT_MOC_CPP)
# undef signals
# define signals signals
#endif
#include <boost/signal.hpp>
namespace boost
{
namespace signalslib = signals;
}
#if defined(signals) && defined(QOBJECTDEFS_H) && \
!defined(QT_MOC_CPP)
# undef signals
// Restore the macro definition of "signals", as it was
// defined by Qt's <qobjectdefs.h>.
# define signals protected
#endif
#endif</pre>
<p>Use this header to include the Boost library, then refer
to it in the namespace <code class="computeroutput">boost::signalslib</code>. This
option is often
preferable to the first option because it can be used without
recompiling the Signals library binary. </p>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2001-2004 Douglas Gregor<p>Use, modification and distribution is subject to the Boost
Software License, Version 1.0. (See accompanying file
<code class="filename">LICENSE_1_0.txt</code> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="../boost/last_value_voi_idp30143680.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../signals.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="s05.html"><img src="../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
|
