use new syntax for connecting to backend signals that enforces explicit connection scope, plus a few other related matters

git-svn-id: svn://localhost/ardour2/branches/3.0@6376 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 171 insertions, 0 deletions

diff --git a/libs/pbd/pbd/signals.h b/libs/pbd/pbd/signals.h
new file mode 100644
index 0000000000..4ddd72eba8
--- /dev/null
+++ b/libs/pbd/pbd/signals.h
@@ -0,0 +1,171 @@
+/*
+    Copyright (C) 2009 Paul Davis 
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#ifndef __pbd_signals_h__
+#define __pbd_signals_h__
+
+#include <list>
+#include <glibmm/thread.h>
+#include <boost/signals2.hpp>
+#include <boost/noncopyable.hpp>
+
+namespace PBD {
+
+typedef boost::signals2::connection UnscopedConnection;
+typedef boost::signals2::connection Connection;
+typedef boost::signals2::scoped_connection ScopedConnection;
+
+class ScopedConnectionList  : public boost::noncopyable
+{
+  public:
+	ScopedConnectionList();
+	~ScopedConnectionList ();
+	
+	void add_connection (const UnscopedConnection& c);
+	void drop_connections ();
+
+	template<typename S> void scoped_connect (S& sig, const typename S::slot_function_type& sf) {
+		add_connection (sig.connect (sf));
+	}
+
+  private:
+	/* this class is not copyable */
+	ScopedConnectionList(const ScopedConnectionList&) {}
+
+	/* this lock is shared by all instances of a ScopedConnectionList.
+	   We do not want one mutex per list, and since we only need the lock
+	   when adding or dropping connections, which are generally occuring
+	   in object creation and UI operations, the contention on this 
+	   lock is low and not of significant consequence. Even though
+	   boost::signals2 is thread-safe, this additional list of
+	   scoped connections needs to be protected in 2 cases:
+
+	   (1) (unlikely) we make a connection involving a callback on the
+	       same object from 2 threads. (wouldn't that just be appalling 
+	       programming style?)
+	     
+	   (2) where we are dropping connections in one thread and adding
+	       one from another.
+	 */
+
+	static Glib::StaticMutex _lock;
+
+	typedef std::list<ScopedConnection*> ConnectionList;
+	ConnectionList _list;
+};
+
+template<typename R>
+class Signal0 {
+public:
+    Signal0 () {}
+    typedef boost::signals2::signal<R()> SignalType;
+
+    void connect (ScopedConnectionList& clist, 
+		  const typename SignalType::slot_function_type& slot) {
+	    clist.add_connection (_signal.connect (slot));
+    }
+    
+    void connect (Connection& c, 
+		  const typename SignalType::slot_function_type& slot) {
+	    c = _signal.connect (slot);
+    }
+    
+    typename SignalType::result_type operator()() {
+	    return _signal ();
+    }
+    
+private:
+    SignalType _signal;
+};
+
+template<typename R, typename A>
+class Signal1 {
+public:
+    Signal1 () {}
+    typedef boost::signals2::signal<R(A)> SignalType;
+
+    void connect (ScopedConnectionList& clist, 
+		  const typename SignalType::slot_function_type& slot) {
+	    clist.add_connection (_signal.connect (slot));
+    }
+
+    void connect (Connection& c, 
+		  const typename SignalType::slot_function_type& slot) {
+	    c = _signal.connect (slot);
+    }
+    
+    typename SignalType::result_type operator()(A arg1) {
+	    return _signal (arg1);
+    }
+    
+private:
+    SignalType _signal;
+};
+
+template<typename R, typename A1, typename A2>
+class Signal2 {
+public:
+    Signal2 () {}
+    typedef boost::signals2::signal<R(A1, A2)> SignalType;
+
+    void connect (ScopedConnectionList& clist, 
+		  const typename SignalType::slot_function_type& slot) {
+	    clist.add_connection (_signal.connect (slot));
+    }
+    
+    void connect (Connection& c, 
+		  const typename SignalType::slot_function_type& slot) {
+	    c = _signal.connect (slot);
+    }
+    
+    typename SignalType::result_type operator()(A1 arg1, A2 arg2) {
+	    return _signal (arg1, arg2);
+    }
+    
+private:
+    SignalType _signal;
+};
+
+template<typename R, typename A1, typename A2, typename A3>
+class Signal3 {
+public:
+    Signal3 () {}
+    typedef boost::signals2::signal<R(A1,A2,A3)> SignalType;
+
+    void connect (ScopedConnectionList& clist, 
+		  const typename SignalType::slot_function_type& slot) {
+	    clist.add_connection (_signal.connect (slot));
+    }
+    
+    void connect (Connection& c, 
+		  const typename SignalType::slot_function_type& slot) {
+	    c = _signal.connect (slot);
+    }
+    
+    typename SignalType::result_type operator()(A1 arg1, A2 arg2, A3 arg3) {
+	    return _signal (arg1, arg2, arg3);
+    }
+    
+private:
+    SignalType _signal;
+};
+
+} /* namespace */
+
+#endif /* __pbd_signals_h__ */