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When building with Qt, the Moc keywords
signals and slots are defined using
preprocessor macros, causing programs using Boost.Signals and
Qt together to fail to compile.
For Qt 4.1 and later, This behavior
can be turned off in Qt on a per-project or per-file basis
with the no_keywords 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:
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
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
Deeper Look at Signals and Slots [off-site] for more
complete examples and a survey of the strengths of the two
systems.
Older versions of Qt 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:
The first way involves defining
the BOOST_SIGNALS_NAMESPACE
macro to some other identifier (e.g., signalslib)
when building and using the Boost.Signals library. Then the
namespace of the Boost.Signals library will be
boost::BOOST_SIGNALS_NAMESPACE instead of
boost::signals. To retain the original namespace
name in translation units that do not interact with Qt, you
can use a namespace alias:
namespace boost {
namespace signals = BOOST_SIGNALS_NAMESPACE;
}
The second way, provided by Frank Hess and improved by
Niels Dekker, involves
creating a header signalslib.hpp that contains
the following code:
#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
Use this header to include the Boost library, then refer
to it in the namespace boost::signalslib. This
option is often
preferable to the first option because it can be used without
recompiling the Signals library binary.
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