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/**
* @file lllistenerwrapper.h
* @author Nat Goodspeed
* @date 2009-11-30
* @brief Introduce LLListenerWrapper template
*
* $LicenseInfo:firstyear=2009&license=viewergpl$
* Copyright (c) 2009, Linden Research, Inc.
* $/LicenseInfo$
*/
#if ! defined(LL_LLLISTENERWRAPPER_H)
#define LL_LLLISTENERWRAPPER_H
#include "llevents.h" // LLListenerWrapperBase
#include <boost/visit_each.hpp>
/**
* Template base class for coding wrappers for LLEventPump listeners.
*
* Derive your listener wrapper from LLListenerWrapper. You must use
* LLLISTENER_WRAPPER_SUBCLASS() so your subclass will play nicely with
* boost::visit_each (q.v.). That way boost::signals2 can still detect
* derivation from LLEventTrackable, and so forth.
*/
template <typename LISTENER>
class LLListenerWrapper: public LLListenerWrapperBase
{
public:
/// Wrap an arbitrary listener object
LLListenerWrapper(const LISTENER& listener):
mListener(listener)
{}
/// call
virtual bool operator()(const LLSD& event)
{
return mListener(event);
}
/// Allow boost::visit_each() to peek at our mListener.
template <class V>
void accept_visitor(V& visitor) const
{
using boost::visit_each;
visit_each(visitor, mListener, 0);
}
private:
LISTENER mListener;
};
/**
* Specialize boost::visit_each() (leveraging ADL) to peek inside an
* LLListenerWrapper<T> to traverse its LISTENER. We borrow the
* accept_visitor() pattern from boost::bind(), avoiding the need to make
* mListener public.
*/
template <class V, typename T>
void visit_each(V& visitor, const LLListenerWrapper<T>& wrapper, int)
{
wrapper.accept_visitor(visitor);
}
/// use this (sigh!) for each subclass of LLListenerWrapper<T> you write
#define LLLISTENER_WRAPPER_SUBCLASS(CLASS) \
template <class V, typename T> \
void visit_each(V& visitor, const CLASS<T>& wrapper, int) \
{ \
visit_each(visitor, static_cast<const LLListenerWrapper<T>&>(wrapper), 0); \
} \
\
/* Have to state this explicitly, rather than using LL_TEMPLATE_CONVERTIBLE, */ \
/* because the source type is itself a template. */ \
template <typename T> \
struct ll_template_cast_impl<const LLListenerWrapperBase*, const CLASS<T>*> \
{ \
const LLListenerWrapperBase* operator()(const CLASS<T>* wrapper) \
{ \
return wrapper; \
} \
}
/**
* Make an instance of a listener wrapper. Every wrapper class must be a
* template accepting a listener object of arbitrary type. In particular, the
* type of a boost::bind() expression is deliberately undocumented. So we
* can't just write Wrapper<CorrectType>(boost::bind(...)). Instead we must
* write llwrap<Wrapper>(boost::bind(...)).
*/
template <template<typename> class WRAPPER, typename T>
WRAPPER<T> llwrap(const T& listener)
{
return WRAPPER<T>(listener);
}
/**
* This LLListenerWrapper template subclass is used to report entry/exit to an
* event listener, by changing this:
* @code
* someEventPump.listen("MyClass",
* boost::bind(&MyClass::method, ptr, _1));
* @endcode
* to this:
* @code
* someEventPump.listen("MyClass",
* llwrap<LLCoutListener>(
* boost::bind(&MyClass::method, ptr, _1)));
* @endcode
*/
template <class LISTENER>
class LLCoutListener: public LLListenerWrapper<LISTENER>
{
typedef LLListenerWrapper<LISTENER> super;
public:
/// Wrap an arbitrary listener object
LLCoutListener(const LISTENER& listener):
super(listener)
{}
/// call
virtual bool operator()(const LLSD& event)
{
std::cout << "Entering listener " << *super::mName << " with " << event << std::endl;
bool handled = super::operator()(event);
std::cout << "Leaving listener " << *super::mName;
if (handled)
{
std::cout << " (handled)";
}
std::cout << std::endl;
return handled;
}
};
LLLISTENER_WRAPPER_SUBCLASS(LLCoutListener);
/**
* This LLListenerWrapper template subclass is used to log entry/exit to an
* event listener, by changing this:
* @code
* someEventPump.listen("MyClass",
* boost::bind(&MyClass::method, ptr, _1));
* @endcode
* to this:
* @code
* someEventPump.listen("MyClass",
* llwrap<LLLogListener>(
* boost::bind(&MyClass::method, ptr, _1)));
* @endcode
*/
template <class LISTENER>
class LLLogListener: public LLListenerWrapper<LISTENER>
{
typedef LLListenerWrapper<LISTENER> super;
public:
/// Wrap an arbitrary listener object
LLLogListener(const LISTENER& listener):
super(listener)
{}
/// call
virtual bool operator()(const LLSD& event)
{
LL_DEBUGS("LLLogListener") << "Entering listener " << *super::mName << " with " << event << LL_ENDL;
bool handled = super::operator()(event);
LL_DEBUGS("LLLogListener") << "Leaving listener " << *super::mName;
if (handled)
{
LL_CONT << " (handled)";
}
LL_CONT << LL_ENDL;
return handled;
}
};
LLLISTENER_WRAPPER_SUBCLASS(LLLogListener);
#endif /* ! defined(LL_LLLISTENERWRAPPER_H) */
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