Added new Signal/Slot system in FbTk

This is suppose to replace the obsolete Subject/Observer classes.
See the src/tests/testSignals.cc for basic usage.

7 files changed, 783 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 94da1ba..da15ff6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,9 @@
  (Format: Year/Month/Day)
+Changes for 1.1.2:
+*08/09/18:
+   * Added new Signal/Slot system to FbTk (Henrik)
+     This is suppose to replace the obsolete Subject/Observer classes.
+     FbTk/Signal.hh, FbTk/Slot.hh, FbTk/MemFun.hh, tests/testSignals.cc
 Changes for 1.1.1
 *08/09/14:
    * Fixed a minor pixmap resource leak (Henrik)
diff --git a/src/FbTk/Makefile.am b/src/FbTk/Makefile.am
index 0033ab9..2d2f3a2 100644
--- a/src/FbTk/Makefile.am
+++ b/src/FbTk/Makefile.am
@@ -63,6 +63,7 @@ libFbTk_a_SOURCES = App.hh App.cc Color.cc Color.hh Command.hh \
         TypeAhead.hh SearchResult.hh SearchResult.cc ITypeAheadable.hh \
         Select2nd.hh STLUtil.hh \
         CachedPixmap.hh CachedPixmap.cc \
+        Slot.hh Signal.hh MemFun.hh \
         ${xpm_SOURCE} \
         ${xft_SOURCE} \
         ${xmb_SOURCE} \
diff --git a/src/FbTk/MemFun.hh b/src/FbTk/MemFun.hh
new file mode 100644
index 0000000..4c834dd
--- /dev/null
+++ b/src/FbTk/MemFun.hh
@@ -0,0 +1,139 @@
+// MemFun.hh for FbTk, Fluxbox Toolkit
+// Copyright (c) 2008 Henrik Kinnunen (fluxgen at fluxbox dot org)
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef FBTK_MEM_FUN_HH
+#define FBTK_MEM_FUN_HH
+
+namespace FbTk {
+
+/// No argument functor
+template <typename ReturnType, typename Object>
+class MemFun0 {
+public:
+    typedef ReturnType (Object:: *Action)();
+
+    MemFun0(Object& obj, Action action):
+        m_obj(obj),
+        m_action(action) {
+    }
+
+    void operator ()() {
+        (m_obj.*m_action)();
+    }
+
+private:
+    Object& m_obj;
+    Action m_action;
+};
+
+
+template <typename ReturnType, typename Object>
+MemFun0<ReturnType, Object>
+MemFun( Object& obj, ReturnType (Object:: *action)() ) {
+    return MemFun0<ReturnType, Object>(obj, action);
+}
+
+/// One argument functor
+template <typename ReturnType, typename Object, typename Arg1>
+class MemFun1 {
+public:
+    typedef ReturnType (Object:: *Action)(Arg1);
+
+    MemFun1(Object& obj, Action action):
+        m_obj(obj),
+        m_action(action) {
+    }
+
+    void operator ()(Arg1 arg1) {
+        (m_obj.*m_action)(arg1);
+    }
+
+private:
+    Object& m_obj;
+    Action m_action;
+};
+
+/// One argument functor helper function
+template <typename ReturnType, typename Object, typename Arg1>
+MemFun1<ReturnType, Object, Arg1>
+MemFun( Object& obj, ReturnType (Object:: *action)(Arg1) ) {
+    return MemFun1<ReturnType, Object, Arg1>(obj, action);
+}
+
+/// Two argument functor
+template <typename ReturnType, typename Object, typename Arg1, typename Arg2>
+class MemFun2 {
+public:
+    typedef ReturnType (Object:: *Action)(Arg1,Arg2);
+
+    MemFun2(Object& obj, Action action):
+        m_obj(obj),
+        m_action(action) {
+    }
+    
+    void operator ()(Arg1 arg1, Arg2 arg2) {
+        (m_obj.*m_action)(arg1, arg2);
+    }
+
+private:
+    Object& m_obj;
+    Action m_action;
+};
+
+/// Two argument functor helper function
+template <typename ReturnType, typename Object, typename Arg1, typename Arg2>
+MemFun2<ReturnType, Object, Arg1, Arg2> 
+MemFun( Object& obj, ReturnType (Object:: *action)(Arg1,Arg2) ) {
+    return MemFun2<ReturnType, Object, Arg1, Arg2>(obj, action);
+}
+
+/// Three argument functor
+template <typename ReturnType, typename Object,
+          typename Arg1, typename Arg2, typename Arg3>
+class MemFun3 {
+public:
+    typedef ReturnType (Object:: *Action)(Arg1,Arg2,Arg3);
+
+    MemFun3(Object& obj, Action action):
+        m_obj(obj),
+        m_action(action) {
+    }
+
+    void operator ()(Arg1 arg1, Arg2 arg2, Arg3 arg3) {
+        (m_obj.*m_action)(arg1, arg2, arg3);
+    }
+
+private:
+    Object& m_obj;
+    Action m_action;
+};
+
+/// Three argument functor helper
+template <typename ReturnType, typename Object, typename Arg1, typename Arg2, typename Arg3>
+MemFun3<ReturnType, Object, Arg1, Arg2, Arg3>
+MemFun( Object& obj, ReturnType (Object:: *action)(Arg1, Arg2, Arg3) ) {
+    return MemFun3<ReturnType, Object, Arg1, Arg2, Arg3>(obj, action);
+}
+
+} // namespace FbTk
+
+#endif // FBTK_MEM_FUN_HH
+
diff --git a/src/FbTk/Signal.hh b/src/FbTk/Signal.hh
new file mode 100644
index 0000000..768ca90
--- /dev/null
+++ b/src/FbTk/Signal.hh
@@ -0,0 +1,218 @@
+// Signal.hh for FbTk, Fluxbox Toolkit
+// Copyright (c) 2008 Henrik Kinnunen (fluxgen at fluxbox dot org)
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef FBTK_SIGNAL_HH
+#define FBTK_SIGNAL_HH
+
+#include "Slot.hh"
+#include <list>
+#include <vector>
+
+namespace FbTk {
+
+/// \namespace Implementation details for signals, do not use anything in this namespace
+namespace SigImpl {
+
+/**
+ * Parent class for all \c Signal[0...*] classes.
+ * It handles the disconnect and holds all the slots. The connect must be
+ * handled by the child class so it can do the type checking.
+ */
+class SignalHolder {
+public:
+    /// Do not use this type outside this class
+    typedef std::list<SlotHolder> SlotList;
+
+    typedef SlotList::iterator Iterator;
+    typedef Iterator SlotID;
+    typedef SlotList::const_iterator ConstIterator;
+
+    /// Remove a specific slot \c id from this signal
+    void disconnect(SlotID slotIt) {
+        m_slots.erase( slotIt );
+    }
+
+
+    /// Removes all slots connected to this
+    void clear() {
+        m_slots.clear();
+    }
+
+protected:
+    ConstIterator begin() const { return m_slots.begin(); }
+    ConstIterator end() const { return m_slots.end(); }
+
+    Iterator begin() { return m_slots.begin(); }
+    Iterator end() { return m_slots.end(); }
+
+    /// Connect a slot to this signal. Must only be called by child classes.
+    SlotID connect(const SlotHolder& slot) {
+        return m_slots.insert(m_slots.end(), slot);
+    }
+
+private:
+    SlotList m_slots; ///< all slots connected to a signal
+};
+
+/// Signal with no argument
+template <typename ReturnType>
+class Signal0: public SignalHolder {
+public:
+    typedef Slot0<ReturnType> SlotType;
+
+    void emit() {
+        for ( Iterator it = begin(); it != end(); ++it ) {
+            static_cast<SlotType&>(*it)();
+        }
+    }
+
+    SlotID connect(const SlotType& slot) {
+        return SignalHolder::connect(slot);
+
+    }
+};
+
+/// Signal with one argument
+template <typename ReturnType, typename Arg1>
+class Signal1: public SignalHolder {
+public:
+    typedef Slot1<ReturnType, Arg1> SlotType;
+
+    void emit(Arg1 arg) {
+        for ( Iterator it = begin(); it != end(); ++it ) {
+            static_cast<SlotType&>(*it)(arg);
+        }
+    }
+
+    SlotID connect(const SlotType& slot) {
+        return SignalHolder::connect(slot);
+    }
+
+};
+
+/// Signal with two arguments
+template <typename ReturnType, typename Arg1, typename Arg2>
+class Signal2: public SignalHolder {
+public:
+    typedef Slot2<ReturnType, Arg1, Arg2> SlotType;
+
+    void emit(Arg1 arg1, Arg2 arg2) {
+        for ( Iterator it = begin(); it != end(); ++it ) {
+            static_cast<SlotType&>(*it)(arg1, arg2);
+        }
+    }
+
+    SlotID connect(const SlotType& slot) {
+        return SignalHolder::connect(slot);
+    }
+};
+
+/// Signal with three arguments
+template <typename ReturnType, typename Arg1, typename Arg2, typename Arg3>
+class Signal3: public SignalHolder {
+public:
+    typedef Slot3<ReturnType, Arg1, Arg2, Arg3> SlotType;
+
+    void emit(Arg1 arg1, Arg2 arg2, Arg3 arg3) {
+        for ( Iterator it = begin(); it != end(); ++it ) {
+            static_cast<SlotType&>(*it)(arg1, arg2, arg3);
+        }
+    }
+
+    SlotID connect(const SlotType& slot) {
+        return SignalHolder::connect(slot);
+    }
+
+};
+
+struct EmptyArg {};
+
+} // namespace SigImpl
+
+
+/// Specialization for three arguments.
+template <typename ReturnType,
+          typename Arg1 = SigImpl::EmptyArg, typename Arg2 = SigImpl::EmptyArg, typename Arg3 = SigImpl::EmptyArg >
+class Signal: public SigImpl::Signal3< ReturnType, Arg1, Arg2, Arg3 > {
+public:
+};
+
+/// Specialization for two arguments.
+template <typename ReturnType, typename Arg1, typename Arg2>
+class Signal<ReturnType, Arg1, Arg2, SigImpl::EmptyArg>: public SigImpl::Signal2< ReturnType, Arg1, Arg2 > {
+public:
+};
+
+/// Specialization for one argument.
+template <typename ReturnType, typename Arg1>
+class Signal<ReturnType, Arg1, SigImpl::EmptyArg, SigImpl::EmptyArg>: public SigImpl::Signal1< ReturnType, Arg1 > {
+public:
+};
+
+/// Specialization for no argument.
+template <typename ReturnType>
+class Signal<ReturnType, SigImpl::EmptyArg, SigImpl::EmptyArg, SigImpl::EmptyArg>: public SigImpl::Signal0< ReturnType > {
+public:
+};
+
+/**
+ * Tracks a signal during it's life time. All signals connected using \c
+ * SignalTracker::join will be erased when this instance dies.
+ */
+class SignalTracker {
+public:
+    /// Internal type, do not use.
+    typedef std::list< std::pair< SigImpl::SignalHolder*, SigImpl::SignalHolder::SlotID > > Connections;
+    typedef Connections::iterator TrackID; ///< \c ID type for join/leave.
+
+    ~SignalTracker() {
+        // disconnect all connections
+        for ( Connections::iterator conIt = m_connections.begin();
+              conIt != m_connections.end(); ) { 
+            conIt->first->disconnect( conIt->second );
+            conIt = m_connections.erase( conIt );
+        }
+    }
+
+    /// Starts tracking a signal.
+    /// @return A tracking ID ( not unique )
+    template <typename Signal, typename Functor>
+    TrackID join(Signal& sig, const Functor& functor) {
+        return 
+            m_connections.insert(m_connections.end(), 
+                                 Connections::value_type(&sig, sig.connect(functor)));
+    }
+
+    /// Leave tracking for a signal
+    /// @param id the \c id from the previous \c join 
+    void leave(TrackID id) {
+        m_connections.erase(id);
+    }
+
+private:
+    /// holds all connections to different signals and slots.
+    Connections m_connections;
+};
+
+
+} // namespace FbTk
+
+#endif // FBTK_SIGNAL_HH
diff --git a/src/FbTk/Slot.hh b/src/FbTk/Slot.hh
new file mode 100644
index 0000000..ba3cfc4
--- /dev/null
+++ b/src/FbTk/Slot.hh
@@ -0,0 +1,294 @@
+// Slot.hh for FbTk, Fluxbox Toolkit
+// Copyright (c) 2008 Henrik Kinnunen (fluxgen at fluxbox dot org)
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef FBTK_SLOT_HH
+#define FBTK_SLOT_HH
+
+namespace FbTk {
+
+/// \namespace Implementation details for signals, do not use anything in this namespace
+namespace SigImpl {
+
+class CallbackHolder;
+
+/// Placeholder type for typed callbacks
+typedef void* (*CallbackFunc)(void *);
+/// Clone function callback type for cloning typed callback holders
+typedef CallbackHolder* (*CloneFunc)(CallbackHolder*);
+/// Kill function callback type for destroying type specific information in
+/// FunctorHolder
+typedef void (*KillFunc)(CallbackHolder*);
+
+/// Holds clone, functor callback, and the kill function for FunctorHolder.
+class CallbackHolder {
+public:
+    /**
+     * @param callback The callback to call when a slot receives a signal.
+     * @param clone The callback to use for cloning a type specific instance of
+     *              this classinstance.
+     * @param kill The callback that knows how to free the memory in type
+     *             specific instance of this class.
+     */
+    CallbackHolder(CallbackFunc callback, 
+                   CloneFunc clone,
+                   KillFunc kill):
+        m_callback(callback),
+        m_kill(kill),
+        m_clone(clone) { }
+
+    ~CallbackHolder() {
+        (*m_kill)(this);
+    }
+
+    /// @return a clone of this instance
+    CallbackHolder* clone() {
+        return (*m_clone)(this);
+    }
+
+    /// \c Callback to \c Functor specific callback
+    CallbackFunc m_callback;
+    
+protected:
+
+    CallbackHolder& operator = (const CallbackHolder& other) {
+        if ( this == &other ) {
+            return *this;
+        }
+        m_callback = other.m_callback;
+        m_clone = other.m_clone;
+        m_kill = other.m_kill;
+
+        return *this;
+    }
+
+    CallbackHolder(const CallbackHolder& other) {
+        *this = other;
+    }
+
+private:
+    /// This function is called to kill this instance
+    KillFunc m_kill;
+    /// Functions that knows how to clone a specific \c Functor type
+    CloneFunc m_clone;
+};
+
+
+/// Holds the functor and creates a clone callback for \c Functor specific type
+template <typename Functor>
+class FunctorHolder: public CallbackHolder {
+public:
+    /// This type.
+    typedef FunctorHolder<Functor> Self;
+    /**
+     * @param functor The functor to be used when a signal is emitted.
+     * @param callback The callback to call when a signal is emitted.
+     */
+    FunctorHolder(const Functor& functor, CallbackFunc callback):
+        CallbackHolder(callback, &clone, &kill),
+        m_functor(functor) {
+    }
+
+    /// Specific clone for this Functor type
+    static CallbackHolder* clone(CallbackHolder* self) {
+        return new Self( static_cast<Self&>(*self));
+    }
+
+    static void kill(CallbackHolder* self) {
+        // Destroy functor
+        static_cast<Self*>( self )->m_functor.~Functor();
+    }
+
+    Functor m_functor; ///< the functor to use when a signal is emitted.
+};
+
+
+
+/// Callback with no arguments.
+template <typename Functor, typename ReturnType >
+struct Callback0 {
+    static ReturnType callback(CallbackHolder* base) {
+        static_cast< FunctorHolder<Functor>* >( base )->m_functor();
+        return ReturnType();
+    }
+
+    static CallbackFunc functionAddress() { 
+        return reinterpret_cast<CallbackFunc>(&callback);
+    }
+};
+
+/// Callback with one argument
+template <typename Functor, typename ReturnType, typename Arg1>
+struct Callback1 {
+    typedef ReturnType (Functor::* CallbackType)(CallbackHolder*, Arg1);
+
+    static ReturnType callback(CallbackHolder* base, Arg1 arg1) {
+        static_cast< FunctorHolder<Functor>* >( base )->m_functor(arg1);
+        return ReturnType();
+    }
+
+    static CallbackFunc functionAddress() { 
+        return reinterpret_cast<CallbackFunc>(&callback);
+    }
+};
+
+/// Callback with two arguments
+template <typename Functor, typename ReturnType,
+          typename Arg1, typename Arg2>
+struct Callback2 {
+    typedef ReturnType (Functor::* CallbackType)(CallbackHolder*, Arg1, Arg2);
+
+    static ReturnType callback(CallbackHolder* base, Arg1 arg1, Arg2 arg2) {
+        static_cast< FunctorHolder<Functor>* >( base )->m_functor(arg1, arg2);
+        return ReturnType();
+    }
+
+    static CallbackFunc functionAddress() { 
+        return reinterpret_cast<CallbackFunc>(&callback);
+    }
+};
+
+/// Callback with three arguments
+template <typename Functor, typename ReturnType,
+          typename Arg1, typename Arg2, typename Arg3>
+struct Callback3 {
+    typedef ReturnType (Functor::* CallbackType)(CallbackHolder*, Arg1, Arg2, Arg3);
+
+    static ReturnType callback(CallbackHolder* base, Arg1 arg1, Arg2 arg2, Arg3 arg3) {
+        static_cast< FunctorHolder<Functor>* >( base )->m_functor( arg1, arg2, arg3 );
+        return ReturnType();
+    }
+
+    static CallbackFunc functionAddress() { 
+        return reinterpret_cast<CallbackFunc>(&callback);
+    }
+};
+
+/// Holds callback holder and handles the copying of callback holders for the
+/// \c Slots.
+class SlotHolder {
+public:
+    SlotHolder(const SlotHolder& other):
+        m_holder( other.m_holder ? other.m_holder->clone() : 0 ) {
+    }
+
+    ~SlotHolder() {
+        delete m_holder;
+    }
+
+    SlotHolder& operator = (const SlotHolder& other) {
+        if ( &other == this ) {
+            return *this;
+        }
+        delete m_holder;
+        if ( other.m_holder ) {
+            m_holder = other.m_holder->clone();
+        } else {
+            m_holder = 0;
+        }
+        return *this;
+    }
+
+    SlotHolder():m_holder( 0 ) { }
+
+protected:
+    explicit SlotHolder(CallbackHolder* holder):
+        m_holder( holder ) {
+    }
+
+    CallbackHolder* m_holder;
+};
+
+/// Slot with no argument.
+template <typename ReturnType>
+class Slot0: public SlotHolder {
+public:
+    typedef ReturnType (*CallbackType)(CallbackHolder*);
+
+    template <typename Functor>
+    Slot0( const Functor& functor ):
+        SlotHolder( new FunctorHolder<Functor>
+                    (functor, Callback0<Functor, ReturnType>::functionAddress())) {
+    }
+
+    void operator()() {
+       reinterpret_cast<CallbackType>(m_holder->m_callback)( m_holder );
+    }
+};
+
+/// Slot with one argument.
+template <typename ReturnType, typename Arg1>
+class Slot1:public SlotHolder {
+public:
+    typedef ReturnType (*CallbackType)(CallbackHolder*, Arg1);
+
+    template <typename Functor>
+    Slot1( const Functor& functor ):
+        SlotHolder( new FunctorHolder<Functor>
+                    (functor, Callback1<Functor, ReturnType, Arg1>::functionAddress())){
+        
+    }
+
+    void operator()(Arg1 arg) {
+        reinterpret_cast<CallbackType>(m_holder->m_callback)(m_holder, arg);
+    }
+
+};
+
+/// Slot with two arguments
+template <typename ReturnType, typename Arg1, typename Arg2>
+class Slot2: public SlotHolder {
+public:
+    typedef ReturnType (*CallbackType)(CallbackHolder*, Arg1, Arg2);
+    template <typename Functor>
+    Slot2( const Functor& functor ):
+        SlotHolder( new FunctorHolder<Functor>
+                    (functor, Callback2<Functor, ReturnType, Arg1, Arg2>::functionAddress())){
+        
+    }
+
+    void operator()(Arg1 arg1, Arg2 arg2) {
+        reinterpret_cast<CallbackType>(m_holder->m_callback)(m_holder, arg1, arg2);
+    }
+};
+
+/// Slot with three arguments
+template <typename ReturnType, typename Arg1, typename Arg2, typename Arg3>
+class Slot3: public SlotHolder {
+public:
+    typedef ReturnType (*CallbackType)(CallbackHolder*, Arg1, Arg2, Arg3);
+    template <typename Functor>
+    Slot3( const Functor& functor ):
+        SlotHolder( new FunctorHolder<Functor>
+                    (functor, Callback3<Functor, ReturnType, Arg1, Arg2, Arg3>::functionAddress())){
+        
+    }
+
+    void operator()(Arg1 arg1, Arg2 arg2, Arg3 arg3) {
+        reinterpret_cast<CallbackType>(m_holder->m_callback)
+            ( m_holder, arg1, arg2, arg3 );
+    }
+};
+
+} // namespace SigImpl
+
+} // namespace FbTk
+
+#endif // FBTK_SLOT_H
diff --git a/src/tests/Makefile b/src/tests/Makefile
index 8d1c482..668126e 100644
--- a/src/tests/Makefile
+++ b/src/tests/Makefile
@@ -7,7 +7,8 @@ COMPILEFILE=$(CXX) -c $(CXXFLAGS)
 FONT_OBJ = ../FbTk/libFbTk.a
 COMPILE = ${CXX} ${CXXFLAGS} ${XLIBS}
 
-all: testMenu testFont testTexture movetest
+all: testMenu testFont testTexture movetest testSignals
+
 
 .cc.o:
         $(CXX) -c $(CXXFLAGS) $<
@@ -15,6 +16,9 @@ all: testMenu testFont testTexture movetest
 glxtest: ../FbTk/App.hh glxtest.cc
         ${CXX} glxtest.cc ${CXXFLAGS} ${XLIBS} -lGL -lGLU -lXpm -o glxtest
 
+testSignals: testSignals.o ../FbTk/Signal.hh ../FbTk/MemFun.hh
+        $(CXX) $(LIBS) testSignals.o -o testSignals
+
 testStringUtil: StringUtiltest.o
         $(CXX) $(LIBS) StringUtiltest.o ../FbTk/libFbTk.a -o testStringUtil
 
diff --git a/src/tests/testSignals.cc b/src/tests/testSignals.cc
new file mode 100644
index 0000000..86096bf
--- /dev/null
+++ b/src/tests/testSignals.cc
@@ -0,0 +1,121 @@
+#include <iostream>
+using namespace std;
+
+#include "../FbTk/Signal.hh"
+#include "../FbTk/MemFun.hh"
+
+#include <string>
+
+
+
+struct NoArgument {
+    void operator() () const {
+        cout << "No Argument." << endl;
+    }
+};
+
+struct OneArgument {
+    void operator ()( int value ) {
+        cout << "One argument = " << value << endl;
+    }
+};
+
+struct TwoArguments {
+    void operator ()( int value, const string& message ) {
+        cout << "Two arguments, (1) = " << value << ", (2) = " << message << endl;
+    }
+};
+
+struct ThreeArguments {
+    void operator ()( int value, const string& message, double value2 ) {
+        cout << "Two arguments, (1) = " << value << ", (2) = " << message
+             << ", (3) = " << value2 << endl;
+    }
+};
+
+struct FunctionClass {
+    FunctionClass() {
+        cout << "FunctionClass created." << endl;
+    }
+    ~FunctionClass() {
+        cout << "FunctionClass deleted." << endl;
+    }
+    void print() {
+        cout << "Printing." << endl;
+    }
+
+    void takeIt( string& str ) {
+        cout << "takeIt( " << str << ")" << endl;
+    }
+
+    void showMessage( int value, const string& message ) {
+        cout << "(" << value << "): " << message << endl;
+    }
+    void threeArgs( int value, const string& str, double pi ) {
+        cout << "(" << value << "): " << str << ", pi = " << pi << endl;
+    }
+};
+
+int main() {
+    using FbTk::Signal;
+    using FbTk::SignalTracker;
+
+    Signal<void> no_arg;
+    no_arg.connect( NoArgument() );
+
+    Signal<void, int> one_arg;
+    one_arg.connect( OneArgument() );
+
+    Signal<void, int, const string&> two_args;
+    two_args.connect( TwoArguments() );
+    
+    Signal<void, int, const string&, double> three_args;
+    three_args.connect( ThreeArguments() );
+
+    // emit test
+    no_arg.emit();
+    one_arg.emit( 10 );
+    two_args.emit( 10, "Message" );
+    three_args.emit( 10, "Three", 3.141592 );
+
+    // test signal tracker
+    {
+        cout << "---- tracker ----" << endl;
+        SignalTracker tracker;
+        // setup two new slots and track them
+        SignalTracker::TrackID id_no_arg = tracker.join( no_arg, NoArgument() );
+        SignalTracker::TrackID id_one_arg = tracker.join( one_arg, OneArgument() );
+
+        // two outputs each from these two signals
+        no_arg.emit();
+        one_arg.emit( 31 );
+
+        // stop tracking id_one_arg, which should keep the slot after this scope,
+        // the id_no_arg connection should be destroyed after this.
+        tracker.leave( id_one_arg );
+        cout << "---- tracker end ----" << endl;
+    }
+
+    // now we should have one output from no_arg and two outputs from one_arg
+    no_arg.emit();
+    one_arg.emit( 2 );
+
+    using FbTk::MemFun;
+    FunctionClass obj;
+    no_arg.clear();
+    no_arg.connect(MemFun(obj, &FunctionClass::print));
+    no_arg.emit();
+
+    string takeThis("Take this");
+    Signal<void, string&> ref_arg;
+    ref_arg.connect(MemFun(obj, &FunctionClass::takeIt));
+    ref_arg.emit( takeThis );
+
+    two_args.clear();
+    two_args.connect(MemFun(obj, &FunctionClass::showMessage));
+    two_args.emit(10, "This is a message");
+    
+    three_args.clear();
+    three_args.connect(MemFun(obj, &FunctionClass::threeArgs));
+    three_args.emit(9, "nine", 3.141592);
+}