Add Message struct and remove tons of interface boilerplate

20 files changed, 485 insertions, 672 deletions

diff --git a/ingen/AtomWriter.hpp b/ingen/AtomWriter.hpp
index e7a02049..21fcb933 100644
--- a/ingen/AtomWriter.hpp
+++ b/ingen/AtomWriter.hpp
@@ -42,52 +42,26 @@ public:
 		return Raul::URI("ingen:/clients/atom_writer");
 	}
 
-	void bundle_begin();
-
-	void bundle_end();
-
-	void put(const Raul::URI&  uri,
-	         const Properties& properties,
-	         Resource::Graph   ctx = Resource::Graph::DEFAULT);
-
-	void delta(const Raul::URI&  uri,
-	           const Properties& remove,
-	           const Properties& add,
-	           Resource::Graph   ctx = Resource::Graph::DEFAULT);
-
-	void copy(const Raul::URI& old_uri,
-	          const Raul::URI& new_uri);
-
-	void move(const Raul::Path& old_path,
-	          const Raul::Path& new_path);
-
-	void del(const Raul::URI& uri);
-
-	void connect(const Raul::Path& tail,
-	             const Raul::Path& head);
-
-	void disconnect(const Raul::Path& tail,
-	                const Raul::Path& head);
-
-	void disconnect_all(const Raul::Path& graph,
-	                    const Raul::Path& path);
-
-	void set_property(const Raul::URI& subject,
-	                  const Raul::URI& predicate,
-	                  const Atom&      value,
-	                  Resource::Graph  ctx = Resource::Graph::DEFAULT);
-
-	void undo();
-
-	void redo();
-
 	void set_response_id(int32_t id);
 
-	void get(const Raul::URI& uri);
-
-	void response(int32_t id, Status status, const std::string& subject);
-
-	void error(const std::string& msg);
+	void message(const Message& message) override;
+
+	void operator()(const BundleBegin&);
+	void operator()(const BundleEnd&);
+	void operator()(const Connect&);
+	void operator()(const Copy&);
+	void operator()(const Del&);
+	void operator()(const Delta&);
+	void operator()(const Disconnect&);
+	void operator()(const DisconnectAll&);
+	void operator()(const Error&);
+	void operator()(const Get&);
+	void operator()(const Move&);
+	void operator()(const Put&);
+	void operator()(const Redo&);
+	void operator()(const Response&);
+	void operator()(const SetProperty&);
+	void operator()(const Undo&);
 
 private:
 	void forge_uri(const Raul::URI& uri);
diff --git a/ingen/Interface.hpp b/ingen/Interface.hpp
index f83cd6f2..68f21304 100644
--- a/ingen/Interface.hpp
+++ b/ingen/Interface.hpp
@@ -23,6 +23,7 @@
 
 #include <string>
 
+#include "ingen/Message.hpp"
 #include "ingen/Resource.hpp"
 #include "ingen/Status.hpp"
 #include "ingen/ingen.h"
@@ -53,66 +54,82 @@ public:
 
 	virtual void set_respondee(SPtr<Interface> respondee) {}
 
-	/** Begin a transaction.
-	 *
-	 * This does not guarantee strict atomicity, but the events in a bundle will be
-	 * considered one operation, and they will all be undone at once.
+	/** Set the ID to use to respond to the next message.
+	 * Setting the ID to 0 will disable responses.
 	 */
-	virtual void bundle_begin() = 0;
+	virtual void set_response_id(int32_t id) = 0;
 
-	/** End a transaction. */
-	virtual void bundle_end() = 0;
+	virtual void message(const Message& message) = 0;
 
-	virtual void put(const Raul::URI&  uri,
-	                 const Properties& properties,
-	                 Resource::Graph   ctx = Resource::Graph::DEFAULT) = 0;
+	inline void bundle_begin() { message(BundleBegin{}); }
 
-	virtual void delta(const Raul::URI&  uri,
-	                   const Properties& remove,
-	                   const Properties& add,
-	                   Resource::Graph   ctx = Resource::Graph::DEFAULT) = 0;
+	inline void bundle_end() { message(BundleEnd{}); }
 
-	virtual void copy(const Raul::URI& old_uri,
-	                  const Raul::URI& new_uri) = 0;
+	inline void put(const Raul::URI&  uri,
+	                const Properties& properties,
+	                Resource::Graph   ctx = Resource::Graph::DEFAULT)
+	{
+		message(Put{uri, properties, ctx});
+	}
 
-	virtual void move(const Raul::Path& old_path,
-	                  const Raul::Path& new_path) = 0;
+	inline void delta(const Raul::URI&  uri,
+	                  const Properties& remove,
+	                  const Properties& add,
+	                  Resource::Graph   ctx = Resource::Graph::DEFAULT)
+	{
+		message(Delta{uri, remove, add, ctx});
+	}
 
-	virtual void del(const Raul::URI& uri) = 0;
+	inline void copy(const Raul::URI& old_uri, const Raul::URI& new_uri)
+	{
+		message(Copy{old_uri, new_uri});
+	}
+
+	inline void move(const Raul::Path& old_path, const Raul::Path& new_path)
+	{
+		message(Move{old_path, new_path});
+	}
 
-	virtual void connect(const Raul::Path& tail,
-	                     const Raul::Path& head) = 0;
+	inline void del(const Raul::URI& uri) { message(Del{uri}); }
 
-	virtual void disconnect(const Raul::Path& tail,
-	                        const Raul::Path& head) = 0;
+	inline void connect(const Raul::Path& tail, const Raul::Path& head)
+	{
+		message(Connect{tail, head});
+	}
 
-	virtual void disconnect_all(const Raul::Path& graph,
-	                            const Raul::Path& path) = 0;
+	inline void disconnect(const Raul::Path& tail, const Raul::Path& head)
+	{
+		message(Disconnect{tail, head});
+	}
 
-	virtual void set_property(const Raul::URI& subject,
-	                          const Raul::URI& predicate,
-	                          const Atom&      value,
-	                          Resource::Graph  ctx = Resource::Graph::DEFAULT) = 0;
+	inline void disconnect_all(const Raul::Path& graph, const Raul::Path& path)
+	{
+		message(DisconnectAll{graph, path});
+	}
 
-	virtual void undo() = 0;
+	inline void set_property(const Raul::URI& subject,
+	                         const Raul::URI& predicate,
+	                         const Atom&      value,
+	                         Resource::Graph  ctx = Resource::Graph::DEFAULT)
+	{
+		message(SetProperty{subject, predicate, value, ctx});
+	}
 
-	virtual void redo() = 0;
+	inline void undo() { message(Undo{}); }
 
-	/** Set the ID to use to respond to the next message.
-	 * Setting the ID to 0 will disable responses.
-	 */
-	virtual void set_response_id(int32_t id) = 0;
+	inline void redo() { message(Redo{}); }
 
-	// Requests
-	virtual void get(const Raul::URI& uri) = 0;
+	inline void get(const Raul::URI& uri) { message(Get{uri}); }
 
-	// Response
-	virtual void response(int32_t            id,
-	                      Status             status,
-	                      const std::string& subject) = 0;
+	inline void response(int32_t            id,
+	                     Status             status,
+	                     const std::string& subject) {
+		message(Response{id, status, subject});
+	}
 
-	// Non-response error
-	virtual void error(const std::string& msg) = 0;
+	inline void error(const std::string& error_message) {
+		message(Error{error_message});
+	}
 };
 
 } // namespace Ingen
diff --git a/ingen/Message.hpp b/ingen/Message.hpp
new file mode 100644
index 00000000..d4118dcb
--- /dev/null
+++ b/ingen/Message.hpp
@@ -0,0 +1,148 @@
+/*
+  This file is part of Ingen.
+  Copyright 2007-2017 David Robillard <http://drobilla.net/>
+
+  Ingen is free software: you can redistribute it and/or modify it under the
+  terms of the GNU Affero General Public License as published by the Free
+  Software Foundation, either version 3 of the License, or any later version.
+
+  Ingen 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 Affero General Public License for details.
+
+  You should have received a copy of the GNU Affero General Public License
+  along with Ingen.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef INGEN_MESSAGE_HPP
+#define INGEN_MESSAGE_HPP
+
+#include <string>
+
+#include <boost/variant.hpp>
+
+#include "ingen/Resource.hpp"
+#include "ingen/Status.hpp"
+#include "ingen/ingen.h"
+#include "ingen/types.hpp"
+#include "raul/Path.hpp"
+
+namespace Raul {
+class Atom;
+class Path;
+class URI;
+}
+
+namespace Ingen {
+
+struct BundleBegin
+{
+};
+
+struct BundleEnd
+{
+};
+
+struct Connect
+{
+	Raul::Path tail;
+	Raul::Path head;
+};
+
+struct Copy
+{
+	Raul::URI old_uri;
+	Raul::URI new_uri;
+};
+
+struct Del
+{
+	Raul::URI uri;
+};
+
+struct Delta
+{
+	Raul::URI       uri;
+	Properties      remove;
+	Properties      add;
+	Resource::Graph ctx;
+};
+
+struct Disconnect
+{
+	Raul::Path tail;
+	Raul::Path head;
+};
+
+struct DisconnectAll
+{
+	Raul::Path graph;
+	Raul::Path path;
+};
+
+struct Error
+{
+	std::string message;
+};
+
+struct Get
+{
+	Raul::URI subject;
+};
+
+struct Move
+{
+	Raul::Path old_path;
+	Raul::Path new_path;
+};
+
+struct Put
+{
+	Raul::URI       uri;
+	Properties      properties;
+	Resource::Graph ctx;
+};
+
+struct Redo
+{
+};
+
+struct Response
+{
+	int32_t     id;
+	Status      status;
+	std::string subject;
+};
+
+struct SetProperty
+{
+	Raul::URI       subject;
+	Raul::URI       predicate;
+	Atom            value;
+	Resource::Graph ctx;
+};
+
+struct Undo
+{
+};
+
+using Message = boost::variant<BundleBegin,
+                               BundleEnd,
+                               Connect,
+                               Copy,
+                               Del,
+                               Delta,
+                               Disconnect,
+                               DisconnectAll,
+                               Error,
+                               Get,
+                               Move,
+                               Put,
+                               Redo,
+                               Response,
+                               SetProperty,
+                               Undo>;
+
+}  // namespace Ingen
+
+#endif  // INGEN_MESSAGE_HPP
diff --git a/ingen/Tee.hpp b/ingen/Tee.hpp
index 02596e03..12cccc91 100644
--- a/ingen/Tee.hpp
+++ b/ingen/Tee.hpp
@@ -54,77 +54,20 @@ public:
 		(*_sinks.begin())->set_respondee(respondee);
 	}
 
-#define BROADCAST(msg, ...) \
-	std::lock_guard<std::mutex> lock(_sinks_mutex); \
-	for (const auto& s : _sinks) { \
-		s->msg(__VA_ARGS__); \
-	}
-
-	void bundle_begin() { BROADCAST(bundle_begin); }
-	void bundle_end()   { BROADCAST(bundle_end); }
-
-	void put(const Raul::URI&  uri,
-	         const Properties& properties,
-	         Resource::Graph   ctx = Resource::Graph::DEFAULT) {
-		BROADCAST(put, uri, properties, ctx);
-	}
-
-	void delta(const Raul::URI&  uri,
-	           const Properties& remove,
-	           const Properties& add,
-	           Resource::Graph   ctx = Resource::Graph::DEFAULT) {
-		BROADCAST(delta, uri, remove, add, ctx);
-	}
-
-	void copy(const Raul::URI& old_uri,
-	          const Raul::URI& new_uri) {
-		BROADCAST(copy, old_uri, new_uri);
-	}
-
-	void move(const Raul::Path& old_path,
-	          const Raul::Path& new_path) {
-		BROADCAST(move, old_path, new_path);
-	}
-
-	void del(const Raul::URI& uri) { BROADCAST(del, uri); }
-
-	void connect(const Raul::Path& tail,
-	             const Raul::Path& head) {
-		BROADCAST(connect, tail, head);
-	}
-
-	void disconnect(const Raul::Path& tail,
-	                const Raul::Path& head) {
-		BROADCAST(disconnect, tail, head);
-	}
-
-	void disconnect_all(const Raul::Path& graph,
-	                    const Raul::Path& path) {
-		BROADCAST(disconnect_all, graph, path);
-	}
-
-	void set_property(const Raul::URI& subject,
-	                  const Raul::URI& predicate,
-	                  const Atom&      value,
-	                  Resource::Graph  ctx = Resource::Graph::DEFAULT) {
-		BROADCAST(set_property, subject, predicate, value, ctx);
+	void set_response_id(int32_t id) {
+		std::lock_guard<std::mutex> lock(_sinks_mutex);
+		for (const auto& s : _sinks) {
+			s->set_response_id(id);
+		}
 	}
 
-	void undo() { BROADCAST(undo); }
-	void redo() { BROADCAST(redo); }
-
-	void set_response_id(int32_t id) { BROADCAST(set_response_id, id); }
-
-	void get(const Raul::URI& uri) { BROADCAST(get, uri); }
-
-	void response(int32_t id, Status status, const std::string& subject) {
-		BROADCAST(response, id, status, subject);
+	void message(const Message& message) override {
+		std::lock_guard<std::mutex> lock(_sinks_mutex);
+		for (const auto& s : _sinks) {
+			s->message(message);
+		}
 	}
 
-	void error(const std::string& msg) { BROADCAST(error, msg); }
-
-#undef BROADCAST
-
 	Raul::URI    uri()   const { return Raul::URI("ingen:/tee"); }
 	const Sinks& sinks() const { return _sinks; }
 	Sinks&       sinks()       { return _sinks; }
diff --git a/ingen/client/ClientStore.hpp b/ingen/client/ClientStore.hpp
index 1887bed3..899273dc 100644
--- a/ingen/client/ClientStore.hpp
+++ b/ingen/client/ClientStore.hpp
@@ -73,43 +73,26 @@ public:
 
 	URIs& uris() { return _uris; }
 
-	void put(const Raul::URI&  uri,
-	         const Properties& properties,
-	         Resource::Graph   ctx = Resource::Graph::DEFAULT);
+	void message(const Message& msg) override;
+
+	void operator()(const BundleBegin&) {}
+	void operator()(const BundleEnd&) {}
+	void operator()(const Connect&);
+	void operator()(const Copy&);
+	void operator()(const Del&);
+	void operator()(const Delta&);
+	void operator()(const Disconnect&);
+	void operator()(const DisconnectAll&);
+	void operator()(const Error&) {}
+	void operator()(const Get&) {}
+	void operator()(const Move&);
+	void operator()(const Put&);
+	void operator()(const Redo&) {}
+	void operator()(const Response&) {}
+	void operator()(const SetProperty&);
+	void operator()(const Undo&) {}
 
-	void delta(const Raul::URI&  uri,
-	           const Properties& remove,
-	           const Properties& add,
-	           Resource::Graph   ctx = Resource::Graph::DEFAULT);
-
-	void copy(const Raul::URI& old_uri,
-	          const Raul::URI& new_uri);
-
-	void move(const Raul::Path& old_path,
-	          const Raul::Path& new_path);
-
-	void set_property(const Raul::URI& subject_path,
-	                  const Raul::URI& predicate,
-	                  const Atom&      value,
-	                  Resource::Graph  ctx = Resource::Graph::DEFAULT);
-
-	void connect(const Raul::Path& tail,
-	             const Raul::Path& head);
-
-	void disconnect(const Raul::Path& tail,
-	                const Raul::Path& head);
-
-	void disconnect_all(const Raul::Path& graph,
-	                    const Raul::Path& path);
-
-	void del(const Raul::URI& uri);
-
-	void undo() {}
-	void redo() {}
 	void set_response_id(int32_t id) {}
-	void get(const Raul::URI& uri) {}
-	void response(int32_t id, Status status, const std::string& subject) {}
-	void error(const std::string& msg) {}
 
 	INGEN_SIGNAL(new_object, void, SPtr<ObjectModel>);
 	INGEN_SIGNAL(new_plugin, void, SPtr<PluginModel>);
@@ -129,9 +112,6 @@ private:
 	SPtr<GraphModel> connection_graph(const Raul::Path& tail_path,
 	                                  const Raul::Path& head_path);
 
-	void bundle_begin() {}
-	void bundle_end()   {}
-
 	// Slots for SigClientInterface signals
 	bool attempt_connection(const Raul::Path& tail_path,
 	                        const Raul::Path& head_path);
diff --git a/ingen/client/SigClientInterface.hpp b/ingen/client/SigClientInterface.hpp
index 7e903fab..2934e8b1 100644
--- a/ingen/client/SigClientInterface.hpp
+++ b/ingen/client/SigClientInterface.hpp
@@ -48,80 +48,17 @@ public:
 
 	Raul::URI uri() const { return Raul::URI("ingen:/clients/sig"); }
 
-	INGEN_SIGNAL(response, void, int32_t, Status, std::string)
-	INGEN_SIGNAL(bundle_begin, void)
-	INGEN_SIGNAL(bundle_end, void)
-	INGEN_SIGNAL(error, void, std::string)
-	INGEN_SIGNAL(put, void, Raul::URI, Properties, Resource::Graph)
-	INGEN_SIGNAL(delta, void, Raul::URI, Properties, Properties, Resource::Graph)
-	INGEN_SIGNAL(object_copied, void, Raul::URI, Raul::URI)
-	INGEN_SIGNAL(object_moved, void, Raul::Path, Raul::Path)
-	INGEN_SIGNAL(object_deleted, void, Raul::URI)
-	INGEN_SIGNAL(connection, void, Raul::Path, Raul::Path)
-	INGEN_SIGNAL(disconnection, void, Raul::Path, Raul::Path)
-	INGEN_SIGNAL(disconnect_all, void, Raul::Path, Raul::Path)
-	INGEN_SIGNAL(property_change, void, Raul::URI, Raul::URI, Atom, Resource::Graph)
+	INGEN_SIGNAL(message, void, Message)
 
 	/** Fire pending signals.  Only does anything on derived classes (that may queue) */
 	virtual bool emit_signals() { return false; }
 
 protected:
-
-	// ClientInterface hooks that fire the above signals
-
-#define EMIT(name, ...) { _signal_ ## name (__VA_ARGS__); }
-
-	void bundle_begin()
-	{ EMIT(bundle_begin); }
-
-	void bundle_end()
-	{ EMIT(bundle_end); }
-
-	void response(int32_t id, Status status, const std::string& subject)
-	{ EMIT(response, id, status, subject); }
-
-	void error(const std::string& msg)
-	{ EMIT(error, msg); }
-
-	void put(const Raul::URI&  uri,
-	         const Properties& properties,
-	         Resource::Graph   ctx = Resource::Graph::DEFAULT)
-	{ EMIT(put, uri, properties, ctx); }
-
-	void delta(const Raul::URI&  uri,
-	           const Properties& remove,
-	           const Properties& add,
-	           Resource::Graph   ctx = Resource::Graph::DEFAULT)
-	{ EMIT(delta, uri, remove, add, ctx); }
-
-	void connect(const Raul::Path& tail, const Raul::Path& head)
-	{ EMIT(connection, tail, head); }
-
-	void del(const Raul::URI& uri)
-	{ EMIT(object_deleted, uri); }
-
-	void copy(const Raul::URI& old_uri, const Raul::URI& new_uri)
-	{ EMIT(object_copied, old_uri, new_uri); }
-
-	void move(const Raul::Path& old_path, const Raul::Path& new_path)
-	{ EMIT(object_moved, old_path, new_path); }
-
-	void disconnect(const Raul::Path& tail, const Raul::Path& head)
-	{ EMIT(disconnection, tail, head); }
-
-	void disconnect_all(const Raul::Path& graph, const Raul::Path& path)
-	{ EMIT(disconnect_all, graph, path); }
-
-	void set_property(const Raul::URI& subject,
-	                  const Raul::URI& key,
-	                  const Atom&      value,
-	                  Resource::Graph  ctx = Resource::Graph::DEFAULT)
-	{ EMIT(property_change, subject, key, value, ctx); }
-
-	void undo() {}
-	void redo() {}
 	void set_response_id(int32_t id) {}
-	void get(const Raul::URI& uri) {}
+
+	void message(const Message& msg) override {
+		_signal_message(msg);
+	}
 };
 
 } // namespace Client
diff --git a/ingen/client/ThreadedSigClientInterface.hpp b/ingen/client/ThreadedSigClientInterface.hpp
index 96c47374..8fa36c90 100644
--- a/ingen/client/ThreadedSigClientInterface.hpp
+++ b/ingen/client/ThreadedSigClientInterface.hpp
@@ -52,66 +52,15 @@ class INGEN_API ThreadedSigClientInterface : public SigClientInterface
 {
 public:
 	ThreadedSigClientInterface()
-		: response_slot(_signal_response.make_slot())
-		, error_slot(_signal_error.make_slot())
-		, put_slot(_signal_put.make_slot())
-		, connection_slot(_signal_connection.make_slot())
-		, object_deleted_slot(_signal_object_deleted.make_slot())
-		, object_moved_slot(_signal_object_moved.make_slot())
-		, object_copied_slot(_signal_object_copied.make_slot())
-		, disconnection_slot(_signal_disconnection.make_slot())
-		, disconnect_all_slot(_signal_disconnect_all.make_slot())
-		, property_change_slot(_signal_property_change.make_slot())
+		: message_slot(_signal_message.make_slot())
 	{}
 
 	virtual Raul::URI uri() const { return Raul::URI("ingen:/clients/sig_queue"); }
 
-	void bundle_begin()
-	{ push_sig(bundle_begin_slot); }
-
-	void bundle_end()
-	{ push_sig(bundle_end_slot); }
-
-	void response(int32_t id, Status status, const std::string& subject)
-	{ push_sig(sigc::bind(response_slot, id, status, subject)); }
-
-	void error(const std::string& msg)
-	{ push_sig(sigc::bind(error_slot, msg)); }
-
-	void put(const Raul::URI&  path,
-	         const Properties& properties,
-	         Resource::Graph   ctx = Resource::Graph::DEFAULT)
-	{ push_sig(sigc::bind(put_slot, path, properties, ctx)); }
-
-	void delta(const Raul::URI&  path,
-	           const Properties& remove,
-	           const Properties& add,
-	           Resource::Graph   ctx = Resource::Graph::DEFAULT)
-	{ push_sig(sigc::bind(delta_slot, path, remove, add, ctx)); }
-
-	void connect(const Raul::Path& tail, const Raul::Path& head)
-	{ push_sig(sigc::bind(connection_slot, tail, head)); }
-
-	void del(const Raul::URI& uri)
-	{ push_sig(sigc::bind(object_deleted_slot, uri)); }
-
-	void move(const Raul::Path& old_path, const Raul::Path& new_path)
-	{ push_sig(sigc::bind(object_moved_slot, old_path, new_path)); }
-
-	void copy(const Raul::URI& old_uri, const Raul::URI& new_uri)
-	{ push_sig(sigc::bind(object_copied_slot, old_uri, new_uri)); }
-
-	void disconnect(const Raul::Path& tail, const Raul::Path& head)
-	{ push_sig(sigc::bind(disconnection_slot, tail, head)); }
-
-	void disconnect_all(const Raul::Path& graph, const Raul::Path& path)
-	{ push_sig(sigc::bind(disconnect_all_slot, graph, path)); }
-
-	void set_property(const Raul::URI& subject,
-	                  const Raul::URI& key,
-	                  const Atom&      value,
-	                  Resource::Graph  ctx = Resource::Graph::DEFAULT)
-	{ push_sig(sigc::bind(property_change_slot, subject, key, value, ctx)); }
+	void message(const Message& msg) override {
+		std::lock_guard<std::mutex> lock(_mutex);
+		_sigs.push_back(sigc::bind(message_slot, msg));
+	}
 
 	/** Process all queued events - Called from GTK thread to emit signals. */
 	bool emit_signals() {
@@ -131,11 +80,6 @@ public:
 	}
 
 private:
-	void push_sig(Closure ev) {
-		std::lock_guard<std::mutex> lock(_mutex);
-		_sigs.push_back(ev);
-	}
-
 	std::mutex           _mutex;
 	std::vector<Closure> _sigs;
 
@@ -143,20 +87,7 @@ private:
 	using Path  = Raul::Path;
 	using URI   = Raul::URI;
 
-	sigc::slot<void>                                     bundle_begin_slot;
-	sigc::slot<void>                                     bundle_end_slot;
-	sigc::slot<void, int32_t, Status, std::string>       response_slot;
-	sigc::slot<void, std::string>                        error_slot;
-	sigc::slot<void, URI, URI, Raul::Symbol>             new_plugin_slot;
-	sigc::slot<void, URI, Properties, Graph>             put_slot;
-	sigc::slot<void, URI, Properties, Properties, Graph> delta_slot;
-	sigc::slot<void, Path, Path>                         connection_slot;
-	sigc::slot<void, URI>                                object_deleted_slot;
-	sigc::slot<void, Path, Path>                         object_moved_slot;
-	sigc::slot<void, URI, URI>                           object_copied_slot;
-	sigc::slot<void, Path, Path>                         disconnection_slot;
-	sigc::slot<void, Path, Path>                         disconnect_all_slot;
-	sigc::slot<void, URI, URI, Atom, Graph>              property_change_slot;
+	sigc::slot<void, Message> message_slot;
 };
 
 } // namespace Client
diff --git a/src/AtomWriter.cpp b/src/AtomWriter.cpp
index 54dcd0a2..1615630f 100644
--- a/src/AtomWriter.cpp
+++ b/src/AtomWriter.cpp
@@ -51,6 +51,8 @@
 #include <cstdlib>
 #include <string>
 
+#include <boost/variant.hpp>
+
 #include "ingen/AtomSink.hpp"
 #include "ingen/AtomWriter.hpp"
 #include "ingen/Node.hpp"
@@ -82,6 +84,12 @@ AtomWriter::finish_msg()
 	_out.clear();
 }
 
+void
+AtomWriter::message(const Message& message)
+{
+	boost::apply_visitor(*this, message);
+}
+
 /** @page protocol
  * @subsection Bundles
  *
@@ -101,7 +109,7 @@ AtomWriter::finish_msg()
  * @endcode
  */
 void
-AtomWriter::bundle_begin()
+AtomWriter::operator()(const BundleBegin&)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.ingen_BundleStart);
@@ -110,7 +118,7 @@ AtomWriter::bundle_begin()
 }
 
 void
-AtomWriter::bundle_end()
+AtomWriter::operator()(const BundleEnd&)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.ingen_BundleEnd);
@@ -206,20 +214,18 @@ AtomWriter::forge_context(Resource::Graph ctx)
  * @endcode
  */
 void
-AtomWriter::put(const Raul::URI&  uri,
-                const Properties& properties,
-                Resource::Graph   ctx)
+AtomWriter::operator()(const Put& message)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Put);
-	forge_context(ctx);
+	forge_context(message.ctx);
 	lv2_atom_forge_key(&_forge, _uris.patch_subject);
-	forge_uri(uri);
+	forge_uri(message.uri);
 	lv2_atom_forge_key(&_forge, _uris.patch_body);
 
 	LV2_Atom_Forge_Frame body;
 	lv2_atom_forge_object(&_forge, &body, 0, 0);
-	forge_properties(properties);
+	forge_properties(message.properties);
 	lv2_atom_forge_pop(&_forge, &body);
 
 	lv2_atom_forge_pop(&_forge, &msg);
@@ -253,27 +259,24 @@ AtomWriter::put(const Raul::URI&  uri,
  * @endcode
  */
 void
-AtomWriter::delta(const Raul::URI&  uri,
-                  const Properties& remove,
-                  const Properties& add,
-                  Resource::Graph   ctx)
+AtomWriter::operator()(const Delta& message)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Patch);
-	forge_context(ctx);
+	forge_context(message.ctx);
 	lv2_atom_forge_key(&_forge, _uris.patch_subject);
-	forge_uri(uri);
+	forge_uri(message.uri);
 
 	lv2_atom_forge_key(&_forge, _uris.patch_remove);
 	LV2_Atom_Forge_Frame remove_obj;
 	lv2_atom_forge_object(&_forge, &remove_obj, 0, 0);
-	forge_properties(remove);
+	forge_properties(message.remove);
 	lv2_atom_forge_pop(&_forge, &remove_obj);
 
 	lv2_atom_forge_key(&_forge, _uris.patch_add);
 	LV2_Atom_Forge_Frame add_obj;
 	lv2_atom_forge_object(&_forge, &add_obj, 0, 0);
-	forge_properties(add);
+	forge_properties(message.add);
 	lv2_atom_forge_pop(&_forge, &add_obj);
 
 	lv2_atom_forge_pop(&_forge, &msg);
@@ -304,15 +307,14 @@ AtomWriter::delta(const Raul::URI&  uri,
  * @endcode
  */
 void
-AtomWriter::copy(const Raul::URI& old_uri,
-                 const Raul::URI& new_uri)
+AtomWriter::operator()(const Copy& message)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Copy);
 	lv2_atom_forge_key(&_forge, _uris.patch_subject);
-	forge_uri(old_uri);
+	forge_uri(message.old_uri);
 	lv2_atom_forge_key(&_forge, _uris.patch_destination);
-	forge_uri(new_uri);
+	forge_uri(message.new_uri);
 	lv2_atom_forge_pop(&_forge, &msg);
 	finish_msg();
 }
@@ -334,15 +336,14 @@ AtomWriter::copy(const Raul::URI& old_uri,
  * @endcode
  */
 void
-AtomWriter::move(const Raul::Path& old_path,
-                 const Raul::Path& new_path)
+AtomWriter::operator()(const Move& message)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Move);
 	lv2_atom_forge_key(&_forge, _uris.patch_subject);
-	forge_uri(path_to_uri(old_path));
+	forge_uri(path_to_uri(message.old_path));
 	lv2_atom_forge_key(&_forge, _uris.patch_destination);
-	forge_uri(path_to_uri(new_path));
+	forge_uri(path_to_uri(message.new_path));
 	lv2_atom_forge_pop(&_forge, &msg);
 	finish_msg();
 }
@@ -363,12 +364,12 @@ AtomWriter::move(const Raul::Path& old_path,
  * @endcode
  */
 void
-AtomWriter::del(const Raul::URI& uri)
+AtomWriter::operator()(const Del& message)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Delete);
 	lv2_atom_forge_key(&_forge, _uris.patch_subject);
-	forge_uri(uri);
+	forge_uri(message.uri);
 	lv2_atom_forge_pop(&_forge, &msg);
 	finish_msg();
 }
@@ -388,21 +389,18 @@ AtomWriter::del(const Raul::URI& uri)
  * @endcode
  */
 void
-AtomWriter::set_property(const Raul::URI& subject,
-                         const Raul::URI& predicate,
-                         const Atom&      value,
-                         Resource::Graph  ctx)
+AtomWriter::operator()(const SetProperty& message)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Set);
-	forge_context(ctx);
+	forge_context(message.ctx);
 	lv2_atom_forge_key(&_forge, _uris.patch_subject);
-	forge_uri(subject);
+	forge_uri(message.subject);
 	lv2_atom_forge_key(&_forge, _uris.patch_property);
-	lv2_atom_forge_urid(&_forge, _map.map_uri(predicate.c_str()));
+	lv2_atom_forge_urid(&_forge, _map.map_uri(message.predicate.c_str()));
 	lv2_atom_forge_key(&_forge, _uris.patch_value);
-	lv2_atom_forge_atom(&_forge, value.size(), value.type());
-	lv2_atom_forge_write(&_forge, value.get_body(), value.size());
+	lv2_atom_forge_atom(&_forge, message.value.size(), message.value.type());
+	lv2_atom_forge_write(&_forge, message.value.get_body(), message.value.size());
 
 	lv2_atom_forge_pop(&_forge, &msg);
 	finish_msg();
@@ -421,7 +419,7 @@ AtomWriter::set_property(const Raul::URI& subject,
  * @endcode
  */
 void
-AtomWriter::undo()
+AtomWriter::operator()(const Undo&)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.ingen_Undo);
@@ -439,7 +437,7 @@ AtomWriter::undo()
  * @endcode
  */
 void
-AtomWriter::redo()
+AtomWriter::operator()(const Redo&)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.ingen_Redo);
@@ -460,12 +458,12 @@ AtomWriter::redo()
  * @endcode
  */
 void
-AtomWriter::get(const Raul::URI& uri)
+AtomWriter::operator()(const Get& message)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Get);
 	lv2_atom_forge_key(&_forge, _uris.patch_subject);
-	forge_uri(uri);
+	forge_uri(message.subject);
 	lv2_atom_forge_pop(&_forge, &msg);
 	finish_msg();
 }
@@ -494,15 +492,14 @@ AtomWriter::get(const Raul::URI& uri)
  * @endcode
  */
 void
-AtomWriter::connect(const Raul::Path& tail,
-                    const Raul::Path& head)
+AtomWriter::operator()(const Connect& message)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Put);
 	lv2_atom_forge_key(&_forge, _uris.patch_subject);
-	forge_uri(path_to_uri(Raul::Path::lca(tail, head)));
+	forge_uri(path_to_uri(Raul::Path::lca(message.tail, message.head)));
 	lv2_atom_forge_key(&_forge, _uris.patch_body);
-	forge_arc(tail, head);
+	forge_arc(message.tail, message.head);
 	lv2_atom_forge_pop(&_forge, &msg);
 	finish_msg();
 }
@@ -524,13 +521,12 @@ AtomWriter::connect(const Raul::Path& tail,
  * @endcode
  */
 void
-AtomWriter::disconnect(const Raul::Path& tail,
-                       const Raul::Path& head)
+AtomWriter::operator()(const Disconnect& message)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Delete);
 	lv2_atom_forge_key(&_forge, _uris.patch_body);
-	forge_arc(tail, head);
+	forge_arc(message.tail, message.head);
 	lv2_atom_forge_pop(&_forge, &msg);
 	finish_msg();
 }
@@ -554,20 +550,19 @@ AtomWriter::disconnect(const Raul::Path& tail,
  * @endcode
  */
 void
-AtomWriter::disconnect_all(const Raul::Path& graph,
-                           const Raul::Path& path)
+AtomWriter::operator()(const DisconnectAll& message)
 {
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Delete);
 
 	lv2_atom_forge_key(&_forge, _uris.patch_subject);
-	forge_uri(path_to_uri(graph));
+	forge_uri(path_to_uri(message.graph));
 
 	lv2_atom_forge_key(&_forge, _uris.patch_body);
 	LV2_Atom_Forge_Frame arc;
 	lv2_atom_forge_object(&_forge, &arc, 0, _uris.ingen_Arc);
 	lv2_atom_forge_key(&_forge, _uris.ingen_incidentTo);
-	forge_uri(path_to_uri(path));
+	forge_uri(path_to_uri(message.path));
 	lv2_atom_forge_pop(&_forge, &arc);
 
 	lv2_atom_forge_pop(&_forge, &msg);
@@ -612,28 +607,29 @@ AtomWriter::set_response_id(int32_t id)
  * following the response.
  */
 void
-AtomWriter::response(int32_t id, Status status, const std::string& subject)
+AtomWriter::operator()(const Response& response)
 {
-	if (!id) {
+	const auto& subject = response.subject;
+	if (!response.id) {
 		return;
 	}
 
 	LV2_Atom_Forge_Frame msg;
 	forge_request(&msg, _uris.patch_Response);
 	lv2_atom_forge_key(&_forge, _uris.patch_sequenceNumber);
-	lv2_atom_forge_int(&_forge, id);
+	lv2_atom_forge_int(&_forge, response.id);
 	if (!subject.empty() && Raul::URI::is_valid(subject)) {
 		lv2_atom_forge_key(&_forge, _uris.patch_subject);
 		lv2_atom_forge_uri(&_forge, subject.c_str(), subject.length());
 	}
 	lv2_atom_forge_key(&_forge, _uris.patch_body);
-	lv2_atom_forge_int(&_forge, static_cast<int>(status));
+	lv2_atom_forge_int(&_forge, static_cast<int>(response.status));
 	lv2_atom_forge_pop(&_forge, &msg);
 	finish_msg();
 }
 
 void
-AtomWriter::error(const std::string& msg)
+AtomWriter::operator()(const Error&)
 {
 }
 
diff --git a/src/client/ClientStore.cpp b/src/client/ClientStore.cpp
index a622068c..a7bd1274 100644
--- a/src/client/ClientStore.cpp
+++ b/src/client/ClientStore.cpp
@@ -14,6 +14,8 @@
   along with Ingen.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <boost/variant.hpp>
+
 #include "ingen/Log.hpp"
 #include "ingen/client/ArcModel.hpp"
 #include "ingen/client/BlockModel.hpp"
@@ -37,21 +39,10 @@ ClientStore::ClientStore(URIs&                    uris,
 	, _emitter(emitter)
 	, _plugins(new Plugins())
 {
-	if (!emitter)
-		return;
-
-#define CONNECT(signal, method) \
-	emitter->signal_##signal().connect( \
-		sigc::mem_fun(this, &ClientStore::method));
-
-	CONNECT(object_deleted, del);
-	CONNECT(object_moved, move);
-	CONNECT(put, put);
-	CONNECT(delta, delta);
-	CONNECT(connection, connect);
-	CONNECT(disconnection, disconnect);
-	CONNECT(disconnect_all, disconnect_all);
-	CONNECT(property_change, set_property);
+	if (emitter) {
+		emitter->signal_message().connect(
+			sigc::mem_fun(this, &ClientStore::message));
+	}
 }
 
 void
@@ -207,42 +198,48 @@ ClientStore::add_plugin(SPtr<PluginModel> pm)
 /* ****** Signal Handlers ******** */
 
 void
-ClientStore::del(const Raul::URI& uri)
+ClientStore::operator()(const Del& del)
 {
-	if (uri_is_path(uri)) {
-		remove_object(uri_to_path(uri));
+	if (uri_is_path(del.uri)) {
+		remove_object(uri_to_path(del.uri));
 	} else {
-		Plugins::iterator p = _plugins->find(uri);
+		Plugins::iterator p = _plugins->find(del.uri);
 		if (p != _plugins->end()) {
 			_plugins->erase(p);
-			_signal_plugin_deleted.emit(uri);
+			_signal_plugin_deleted.emit(del.uri);
 		}
 	}
 }
 
 void
-ClientStore::copy(const Raul::URI& old_uri,
-                  const Raul::URI& new_uri)
+ClientStore::operator()(const Copy&)
 {
 	_log.error("Client store copy unsupported\n");
 }
 
 void
-ClientStore::move(const Raul::Path& old_path, const Raul::Path& new_path)
+ClientStore::operator()(const Move& msg)
 {
-	const iterator top = find(old_path);
+	const iterator top = find(msg.old_path);
 	if (top != end()) {
-		rename(top, new_path);
+		rename(top, msg.new_path);
 	}
 }
 
 void
-ClientStore::put(const Raul::URI&  uri,
-                 const Properties& properties,
-                 Resource::Graph   ctx)
+ClientStore::message(const Message& msg)
+{
+	boost::apply_visitor(*this, msg);
+}
+
+void
+ClientStore::operator()(const Put& msg)
 {
 	typedef Properties::const_iterator Iterator;
 
+	const auto& uri        = msg.uri;
+	const auto& properties = msg.properties;
+
 	bool is_graph, is_block, is_port, is_output;
 	Resource::type(uris(), properties,
 	               is_graph, is_block, is_port, is_output);
@@ -340,11 +337,9 @@ ClientStore::put(const Raul::URI&  uri,
 }
 
 void
-ClientStore::delta(const Raul::URI&  uri,
-                   const Properties& remove,
-                   const Properties& add,
-                   Resource::Graph   ctx)
+ClientStore::operator()(const Delta& msg)
 {
+	const auto& uri = msg.uri;
 	if (uri == Raul::URI("ingen:/clients/this")) {
 		// Client property, which we don't store (yet?)
 		return;
@@ -360,20 +355,20 @@ ClientStore::delta(const Raul::URI&  uri,
 
 	SPtr<ObjectModel> obj = _object(path);
 	if (obj) {
-		obj->remove_properties(remove);
-		obj->add_properties(add);
+		obj->remove_properties(msg.remove);
+		obj->add_properties(msg.add);
 	} else {
-		_log.warn(fmt("Failed to find object `%1%'\n")
-		          % path.c_str());
+		_log.warn(fmt("Failed to find object `%1%'\n") % path.c_str());
 	}
 }
 
 void
-ClientStore::set_property(const Raul::URI& subject_uri,
-                          const Raul::URI& predicate,
-                          const Atom&      value,
-                          Resource::Graph  ctx)
+ClientStore::operator()(const SetProperty& msg)
 {
+	const auto& subject_uri = msg.subject;
+	const auto& predicate   = msg.predicate;
+	const auto& value       = msg.value;
+
 	if (subject_uri == Raul::URI("ingen:/engine")) {
 		_log.info(fmt("Engine property <%1%> = %2%\n")
 		          % predicate.c_str() % _uris.forge.str(value, false));
@@ -386,7 +381,7 @@ ClientStore::set_property(const Raul::URI& subject_uri,
 			   blinkenlights) but do not store the property. */
 			subject->on_property(predicate, value);
 		} else {
-			subject->set_property(predicate, value, ctx);
+			subject->set_property(predicate, value, msg.ctx);
 		}
 	} else {
 		SPtr<PluginModel> plugin = _plugin(subject_uri);
@@ -444,33 +439,30 @@ ClientStore::attempt_connection(const Raul::Path& tail_path,
 }
 
 void
-ClientStore::connect(const Raul::Path& src_path,
-                     const Raul::Path& dst_path)
+ClientStore::operator()(const Connect& msg)
 {
-	attempt_connection(src_path, dst_path);
+	attempt_connection(msg.tail, msg.head);
 }
 
 void
-ClientStore::disconnect(const Raul::Path& src_path,
-                        const Raul::Path& dst_path)
+ClientStore::operator()(const Disconnect& msg)
 {
-	SPtr<PortModel>  tail  = dynamic_ptr_cast<PortModel>(_object(src_path));
-	SPtr<PortModel>  head  = dynamic_ptr_cast<PortModel>(_object(dst_path));
-	SPtr<GraphModel> graph = connection_graph(src_path, dst_path);
+	SPtr<PortModel>  tail  = dynamic_ptr_cast<PortModel>(_object(msg.tail));
+	SPtr<PortModel>  head  = dynamic_ptr_cast<PortModel>(_object(msg.head));
+	SPtr<GraphModel> graph = connection_graph(msg.tail, msg.head);
 	if (graph)
 		graph->remove_arc(tail.get(), head.get());
 }
 
 void
-ClientStore::disconnect_all(const Raul::Path& parent_graph,
-                            const Raul::Path& path)
+ClientStore::operator()(const DisconnectAll& msg)
 {
-	SPtr<GraphModel>  graph  = dynamic_ptr_cast<GraphModel>(_object(parent_graph));
-	SPtr<ObjectModel> object = _object(path);
+	SPtr<GraphModel>  graph  = dynamic_ptr_cast<GraphModel>(_object(msg.graph));
+	SPtr<ObjectModel> object = _object(msg.path);
 
 	if (!graph || !object) {
 		_log.error(fmt("Bad disconnect all notification %1% in %2%\n")
-		           % path % parent_graph);
+		           % msg.path % msg.graph);
 		return;
 	}
 
@@ -479,8 +471,8 @@ ClientStore::disconnect_all(const Raul::Path& parent_graph,
 		SPtr<ArcModel> arc = dynamic_ptr_cast<ArcModel>(a.second);
 		if (arc->tail()->parent() == object
 		    || arc->head()->parent() == object
-		    || arc->tail()->path() == path
-		    || arc->head()->path() == path) {
+		    || arc->tail()->path() == msg.path
+		    || arc->head()->path() == msg.path) {
 			graph->remove_arc(arc->tail().get(), arc->head().get());
 		}
 	}
diff --git a/src/gui/App.cpp b/src/gui/App.cpp
index 15bdc796..789ead6d 100644
--- a/src/gui/App.cpp
+++ b/src/gui/App.cpp
@@ -180,32 +180,12 @@ App::attach(SPtr<SigClientInterface> client)
 		                                              stderr,
 		                                              ColorContext::Color::CYAN));
 
-#define DUMP_CONNECT(signal, method) \
-		client->signal_##signal().connect( \
-			sigc::mem_fun(*_dumper.get(), &StreamWriter::method));
-
-		DUMP_CONNECT(object_deleted, del);
-		DUMP_CONNECT(object_moved, move);
-		DUMP_CONNECT(put, put);
-		DUMP_CONNECT(delta, delta);
-		DUMP_CONNECT(connection, connect);
-		DUMP_CONNECT(disconnection, disconnect);
-		DUMP_CONNECT(disconnect_all, disconnect_all);
-		DUMP_CONNECT(property_change, set_property);
-
-#undef DUMP_CONNECT
+		client->signal_message().connect(
+			sigc::mem_fun(*_dumper.get(), &StreamWriter::message));
 	}
 
 	_graph_tree_window->init(*this, *_store);
-
-	_client->signal_response().connect(
-		sigc::mem_fun(this, &App::response));
-	_client->signal_error().connect(
-		sigc::mem_fun(this, &App::error_message));
-	_client->signal_put().connect(
-		sigc::mem_fun(this, &App::put));
-	_client->signal_property_change().connect(
-		sigc::mem_fun(this, &App::property_change));
+	_client->signal_message().connect(sigc::mem_fun(this, &App::message));
 }
 
 void
@@ -238,6 +218,20 @@ App::serialiser()
 }
 
 void
+App::message(const Message& msg)
+{
+	if (const Response* const r = boost::get<Response>(&msg)) {
+		response(r->id, r->status, r->subject);
+	} else if (const Error* const e = boost::get<Error>(&msg)) {
+		error_message(e->message);
+	} else if (const Put* const p = boost::get<Put>(&msg)) {
+		put(p->uri, p->properties, p->ctx);
+	} else if (const SetProperty* const s = boost::get<SetProperty>(&msg)) {
+		property_change(s->subject, s->predicate, s->value, s->ctx);
+	}
+}
+
+void
 App::response(int32_t id, Status status, const std::string& subject)
 {
 	if (status != Status::SUCCESS) {
@@ -269,7 +263,7 @@ App::set_property(const Raul::URI& subject,
 	   went as planned here and fire the signal ourselves as if the server
 	   feedback came back immediately. */
 	if (key != uris().ingen_activity) {
-		_client->signal_property_change().emit(subject, key, value, ctx);
+		_client->signal_message().emit(SetProperty{subject, key, value, ctx});
 	}
 }
 
diff --git a/src/gui/App.hpp b/src/gui/App.hpp
index 6dcab171..e226751b 100644
--- a/src/gui/App.hpp
+++ b/src/gui/App.hpp
@@ -25,6 +25,7 @@
 #include <gtkmm/window.h>
 
 #include "ingen/Atom.hpp"
+#include "ingen/Message.hpp"
 #include "ingen/Resource.hpp"
 #include "ingen/Status.hpp"
 #include "ingen/World.hpp"
@@ -141,6 +142,8 @@ public:
 protected:
 	explicit App(Ingen::World* world);
 
+	void message(const Ingen::Message& msg);
+
 	bool animate();
 	void response(int32_t id, Ingen::Status status, const std::string& subject);
 
diff --git a/src/gui/BreadCrumbs.cpp b/src/gui/BreadCrumbs.cpp
index 447b06ba..c62a1e06 100644
--- a/src/gui/BreadCrumbs.cpp
+++ b/src/gui/BreadCrumbs.cpp
@@ -33,8 +33,8 @@ BreadCrumbs::BreadCrumbs(App& app)
 	, _full_path("/")
 	, _enable_signal(true)
 {
-	app.client()->signal_object_deleted().connect(
-		sigc::mem_fun(this, &BreadCrumbs::object_destroyed));
+	app.client()->signal_message().connect(
+		sigc::mem_fun(this, &BreadCrumbs::message));
 
 	set_can_focus(false);
 }
@@ -180,6 +180,14 @@ BreadCrumbs::breadcrumb_clicked(BreadCrumb* crumb)
 }
 
 void
+BreadCrumbs::message(const Message& msg)
+{
+	if (const Del* const del = boost::get<Del>(&msg)) {
+		object_destroyed(del->uri);
+	}
+}
+
+void
 BreadCrumbs::object_destroyed(const Raul::URI& uri)
 {
 	for (auto i = _breadcrumbs.begin(); i != _breadcrumbs.end(); ++i) {
diff --git a/src/gui/BreadCrumbs.hpp b/src/gui/BreadCrumbs.hpp
index e58b2c0f..22bbd7af 100644
--- a/src/gui/BreadCrumbs.hpp
+++ b/src/gui/BreadCrumbs.hpp
@@ -103,6 +103,7 @@ private:
 
 	void breadcrumb_clicked(BreadCrumb* crumb);
 
+	void message(const Message& msg);
 	void object_destroyed(const Raul::URI& uri);
 	void object_moved(const Raul::Path& old_path, const Raul::Path& new_path);
 
diff --git a/src/gui/ConnectWindow.cpp b/src/gui/ConnectWindow.cpp
index 0b4ea298..635df134 100644
--- a/src/gui/ConnectWindow.cpp
+++ b/src/gui/ConnectWindow.cpp
@@ -19,6 +19,7 @@
 #include <sstream>
 #include <string>
 
+#include <boost/variant.hpp>
 #include <gtkmm/stock.h>
 
 #include "raul/Process.hpp"
@@ -74,6 +75,16 @@ ConnectWindow::ConnectWindow(BaseObjectType*                   cobject,
 }
 
 void
+ConnectWindow::message(const Message& msg)
+{
+	if (const Response* const r = boost::get<Response>(&msg)) {
+		ingen_response(r->id, r->status, r->subject);
+	} else if (const Error* const e = boost::get<Error>(&msg)) {
+		error(e->message);
+	}
+}
+
+void
 ConnectWindow::error(const std::string& msg)
 {
 	if (!is_visible()) {
@@ -477,8 +488,8 @@ ConnectWindow::gtk_callback()
 		}
 	} else if (_connect_stage == 1) {
 		_attached = false;
-		_app->client()->signal_response().connect(
-			sigc::mem_fun(this, &ConnectWindow::ingen_response));
+		_app->client()->signal_message().connect(
+			sigc::mem_fun(this, &ConnectWindow::message));
 
 		_ping_id = g_random_int_range(1, std::numeric_limits<int32_t>::max());
 		_app->interface()->set_response_id(_ping_id);
diff --git a/src/gui/ConnectWindow.hpp b/src/gui/ConnectWindow.hpp
index 5b68c597..560bd82b 100644
--- a/src/gui/ConnectWindow.hpp
+++ b/src/gui/ConnectWindow.hpp
@@ -58,6 +58,8 @@ public:
 private:
 	enum class Mode { CONNECT_REMOTE, LAUNCH_REMOTE, INTERNAL };
 
+	void message(const Message& message);
+
 	void error(const std::string& msg);
 
 	void ingen_response(int32_t id, Status status, const std::string& subject);
diff --git a/src/server/Broadcaster.hpp b/src/server/Broadcaster.hpp
index fd8d3996..6fcb3e4d 100644
--- a/src/server/Broadcaster.hpp
+++ b/src/server/Broadcaster.hpp
@@ -88,75 +88,18 @@ public:
 	void send_plugins(const BlockFactory::Plugins& plugin_list);
 	void send_plugins_to(Interface*, const BlockFactory::Plugins& plugin_list);
 
-#define BROADCAST(msg, ...) \
-	std::lock_guard<std::mutex> lock(_clients_mutex); \
-	for (const auto& c : _clients) { \
-		if (c != _ignore_client) { \
-			c->msg(__VA_ARGS__); \
-		} \
-	} \
-
-	void bundle_begin() { BROADCAST(bundle_begin); }
-	void bundle_end()   { BROADCAST(bundle_end); }
-
-	void put(const Raul::URI&  uri,
-	         const Properties& properties,
-	         Resource::Graph   ctx = Resource::Graph::DEFAULT) {
-		BROADCAST(put, uri, properties, ctx);
-	}
-
-	void delta(const Raul::URI&  uri,
-	           const Properties& remove,
-	           const Properties& add,
-	           Resource::Graph   ctx = Resource::Graph::DEFAULT) {
-		BROADCAST(delta, uri, remove, add, ctx);
-	}
-
-	void copy(const Raul::URI& old_uri,
-	          const Raul::URI& new_uri) {
-		BROADCAST(copy, old_uri, new_uri);
-	}
-
-	void move(const Raul::Path& old_path,
-	          const Raul::Path& new_path) {
-		BROADCAST(move, old_path, new_path);
-	}
-
-	void del(const Raul::URI& uri) {
-		BROADCAST(del, uri);
-	}
-
-	void connect(const Raul::Path& tail,
-	             const Raul::Path& head) {
-		BROADCAST(connect, tail, head);
-	}
-
-	void disconnect(const Raul::Path& tail,
-	                const Raul::Path& head) {
-		BROADCAST(disconnect, tail, head);
-	}
-
-	void disconnect_all(const Raul::Path& graph,
-	                    const Raul::Path& path) {
-		BROADCAST(disconnect_all, graph, path);
-	}
-
-	void set_property(const Raul::URI& subject,
-	                  const Raul::URI& predicate,
-	                  const Atom&      value,
-	                  Resource::Graph  ctx = Resource::Graph::DEFAULT) {
-		BROADCAST(set_property, subject, predicate, value, ctx);
+	void message(const Message& msg) override {
+		std::lock_guard<std::mutex> lock(_clients_mutex);
+		for (const auto& c : _clients) {
+			if (c != _ignore_client) {
+				c->message(msg);
+			}
+		}
 	}
 
 	Raul::URI uri() const { return Raul::URI("ingen:/broadcaster"); }
 
-	void undo() {} ///< N/A
-	void redo() {} ///< N/A
 	void set_response_id(int32_t id) {} ///< N/A
-	void get(const Raul::URI& uri) {} ///< N/A
-	void response(int32_t id, Status status, const std::string& subject) {} ///< N/A
-
-	void error(const std::string& msg) { BROADCAST(error, msg); }
 
 private:
 	friend class Transfer;
diff --git a/src/server/EventWriter.cpp b/src/server/EventWriter.cpp
index 28a8d319..56ba439c 100644
--- a/src/server/EventWriter.cpp
+++ b/src/server/EventWriter.cpp
@@ -14,6 +14,8 @@
   along with Ingen.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <boost/variant.hpp>
+
 #include "ingen/URIs.hpp"
 
 #include "Engine.hpp"
@@ -49,7 +51,13 @@ EventWriter::set_response_id(int32_t id)
 }
 
 void
-EventWriter::bundle_begin()
+EventWriter::message(const Message& msg)
+{
+	boost::apply_visitor(*this, msg);
+}
+
+void
+EventWriter::operator()(const BundleBegin&)
 {
 	_engine.enqueue_event(
 		new Events::Mark(_engine, _respondee, _request_id, now(),
@@ -58,7 +66,7 @@ EventWriter::bundle_begin()
 }
 
 void
-EventWriter::bundle_end()
+EventWriter::operator()(const BundleEnd&)
 {
 	_engine.enqueue_event(
 		new Events::Mark(_engine, _respondee, _request_id, now(),
@@ -67,102 +75,89 @@ EventWriter::bundle_end()
 }
 
 void
-EventWriter::put(const Raul::URI&      uri,
-                 const Properties&     properties,
-                 const Resource::Graph ctx)
+EventWriter::operator()(const Put& msg)
 {
 	_engine.enqueue_event(
 		new Events::Delta(_engine, _respondee, _request_id, now(),
-		                  Events::Delta::Type::PUT, ctx, uri, properties),
+		                  Events::Delta::Type::PUT, msg.ctx, msg.uri, msg.properties),
 		_event_mode);
 }
 
 void
-EventWriter::delta(const Raul::URI&      uri,
-                   const Properties&     remove,
-                   const Properties&     add,
-                   const Resource::Graph ctx)
+EventWriter::operator()(const Delta& msg)
 {
 	_engine.enqueue_event(
 		new Events::Delta(_engine, _respondee, _request_id, now(),
-		                  Events::Delta::Type::PATCH, ctx, uri, add, remove),
+		                  Events::Delta::Type::PATCH, msg.ctx, msg.uri, msg.add, msg.remove),
 		_event_mode);
 }
 
 void
-EventWriter::copy(const Raul::URI& old_uri,
-                  const Raul::URI& new_uri)
+EventWriter::operator()(const Copy& msg)
 {
 	_engine.enqueue_event(
 		new Events::Copy(_engine, _respondee, _request_id, now(),
-		                 old_uri, new_uri),
+		                 msg.old_uri, msg.new_uri),
 		_event_mode);
 }
 
 void
-EventWriter::move(const Raul::Path& old_path,
-                  const Raul::Path& new_path)
+EventWriter::operator()(const Move& msg)
 {
 	_engine.enqueue_event(
 		new Events::Move(_engine, _respondee, _request_id, now(),
-		                 old_path, new_path),
+		                 msg.old_path, msg.new_path),
 		_event_mode);
 }
 
 void
-EventWriter::del(const Raul::URI& uri)
+EventWriter::operator()(const Del& msg)
 {
 	_engine.enqueue_event(
-		new Events::Delete(_engine, _respondee, _request_id, now(), uri),
+		new Events::Delete(_engine, _respondee, _request_id, now(), msg.uri),
 		_event_mode);
 }
 
 void
-EventWriter::connect(const Raul::Path& tail_path,
-                     const Raul::Path& head_path)
+EventWriter::operator()(const Connect& msg)
 {
 	_engine.enqueue_event(
 		new Events::Connect(_engine, _respondee, _request_id, now(),
-		                    tail_path, head_path),
+		                    msg.tail, msg.head),
 		_event_mode);
 
 }
 
 void
-EventWriter::disconnect(const Raul::Path& src,
-                        const Raul::Path& dst)
+EventWriter::operator()(const Disconnect& msg)
 {
 	_engine.enqueue_event(
 		new Events::Disconnect(_engine, _respondee, _request_id, now(),
-		                       src, dst),
+		                       msg.tail, msg.head),
 		_event_mode);
 }
 
 void
-EventWriter::disconnect_all(const Raul::Path& graph,
-                            const Raul::Path& path)
+EventWriter::operator()(const DisconnectAll& msg)
 {
 	_engine.enqueue_event(
 		new Events::DisconnectAll(_engine, _respondee, _request_id, now(),
-		                          graph, path),
+		                          msg.graph, msg.path),
 		_event_mode);
 }
 
 void
-EventWriter::set_property(const Raul::URI&      uri,
-                          const Raul::URI&      predicate,
-                          const Atom&           value,
-                          const Resource::Graph ctx)
+EventWriter::operator()(const SetProperty& msg)
 {
 	_engine.enqueue_event(
 		new Events::Delta(_engine, _respondee, _request_id, now(),
-		                  Events::Delta::Type::SET, ctx,
-		                  uri, {{predicate, value}}, {}),
+		                  Events::Delta::Type::SET, msg.ctx,
+		                  msg.subject, {{msg.predicate, msg.value}}, {}),
 		_event_mode);
 }
 
 void
-EventWriter::undo()
+EventWriter::operator()(const Undo&)
 {
 	_engine.enqueue_event(
 		new Events::Undo(_engine, _respondee, _request_id, now(), false),
@@ -170,7 +165,7 @@ EventWriter::undo()
 }
 
 void
-EventWriter::redo()
+EventWriter::operator()(const Redo&)
 {
 	_engine.enqueue_event(
 		new Events::Undo(_engine, _respondee, _request_id, now(), true),
@@ -178,10 +173,10 @@ EventWriter::redo()
 }
 
 void
-EventWriter::get(const Raul::URI& uri)
+EventWriter::operator()(const Get& msg)
 {
 	_engine.enqueue_event(
-		new Events::Get(_engine, _respondee, _request_id, now(), uri),
+		new Events::Get(_engine, _respondee, _request_id, now(), msg.subject),
 		_event_mode);
 }
 
diff --git a/src/server/EventWriter.hpp b/src/server/EventWriter.hpp
index 18e98421..3a5e285e 100644
--- a/src/server/EventWriter.hpp
+++ b/src/server/EventWriter.hpp
@@ -53,54 +53,28 @@ public:
 
 	virtual void set_response_id(int32_t id);
 
-	virtual void bundle_begin();
-
-	virtual void bundle_end();
-
-	virtual void put(const Raul::URI&      path,
-	                 const Properties&     properties,
-	                 const Resource::Graph g = Resource::Graph::DEFAULT);
-
-	virtual void delta(const Raul::URI&  path,
-	                   const Properties& remove,
-	                   const Properties& add,
-	                   Resource::Graph   ctx = Resource::Graph::DEFAULT);
-
-	virtual void copy(const Raul::URI& old_uri,
-	                  const Raul::URI& new_uri);
-
-	virtual void move(const Raul::Path& old_path,
-	                  const Raul::Path& new_path);
-
-	virtual void connect(const Raul::Path& tail,
-	                     const Raul::Path& head);
-
-	virtual void disconnect(const Raul::Path& tail,
-	                        const Raul::Path& head);
-
-	virtual void set_property(const Raul::URI& subject_path,
-	                          const Raul::URI& predicate,
-	                          const Atom&      value,
-	                          Resource::Graph  ctx = Resource::Graph::DEFAULT);
-
-	virtual void del(const Raul::URI& uri);
-
-	virtual void disconnect_all(const Raul::Path& graph,
-	                            const Raul::Path& path);
-
-	virtual void undo();
-
-	virtual void redo();
-
-	virtual void get(const Raul::URI& uri);
-
-	virtual void response(int32_t id, Status status, const std::string& subject) {}  ///< N/A
-
-	virtual void error(const std::string& msg) {}  ///< N/A
+	void message(const Message& msg) override;
 
 	void        set_event_mode(Event::Mode mode) { _event_mode = mode; }
 	Event::Mode get_event_mode()                 { return _event_mode; }
 
+	void operator()(const BundleBegin&);
+	void operator()(const BundleEnd&);
+	void operator()(const Connect&);
+	void operator()(const Copy&);
+	void operator()(const Del&);
+	void operator()(const Delta&);
+	void operator()(const Disconnect&);
+	void operator()(const DisconnectAll&);
+	void operator()(const Error&) {}
+	void operator()(const Get&);
+	void operator()(const Move&);
+	void operator()(const Put&);
+	void operator()(const Redo&);
+	void operator()(const Response&) {}
+	void operator()(const SetProperty&);
+	void operator()(const Undo&);
+
 protected:
 	Engine&         _engine;
 	SPtr<Interface> _respondee;
diff --git a/tests/TestClient.hpp b/tests/TestClient.hpp
index 968e4423..90fc212b 100644
--- a/tests/TestClient.hpp
+++ b/tests/TestClient.hpp
@@ -17,6 +17,8 @@
 #ifndef INGEN_TESTCLIENT_HPP
 #define INGEN_TESTCLIENT_HPP
 
+#include <boost/variant.hpp>
+
 #include "ingen/Interface.hpp"
 
 using namespace Ingen;
@@ -29,62 +31,23 @@ public:
 
 	Raul::URI uri() const { return Raul::URI("ingen:testClient"); }
 
-	void bundle_begin() {}
-
-	void bundle_end() {}
-
-	void put(const Raul::URI&  uri,
-	         const Properties& properties,
-	         Resource::Graph   ctx = Resource::Graph::DEFAULT) {}
-
-	void delta(const Raul::URI&  uri,
-	           const Properties& remove,
-	           const Properties& add,
-	           Resource::Graph   ctx = Resource::Graph::DEFAULT) {}
-
-	void copy(const Raul::URI& old_uri,
-	          const Raul::URI& new_uri) {}
-
-	void move(const Raul::Path& old_path,
-	          const Raul::Path& new_path) {}
-
-	void del(const Raul::URI& uri) {}
-
-	void connect(const Raul::Path& tail,
-	             const Raul::Path& head) {}
-
-	void disconnect(const Raul::Path& tail,
-	                const Raul::Path& head) {}
-
-	void disconnect_all(const Raul::Path& parent_patch_path,
-	                    const Raul::Path& path) {}
-
-	void set_property(const Raul::URI& subject,
-	                  const Raul::URI& predicate,
-	                  const Atom&      value,
-	                  Resource::Graph  ctx = Resource::Graph::DEFAULT) {}
-
-	void set_response_id(int32_t id) {}
-
-	void get(const Raul::URI& uri) {}
-
-	void undo() {}
-
-	void redo() {}
-
-	void response(int32_t id, Status status, const std::string& subject) {
-		if (status != Status::SUCCESS) {
-			_log.error(fmt("error on message %1%: %2% (%3%)\n")
-			           % id % ingen_status_string(status) % subject);
+	void set_response_id(int32_t id) override {}
+
+	void message(const Message& msg) override {
+		if (const Response* const response = boost::get<Response>(&msg)) {
+			if (response->status != Status::SUCCESS) {
+				_log.error(fmt("error on message %1%: %2% (%3%)\n")
+				           % response->id
+				           % ingen_status_string(response->status)
+				           % response->subject);
+				exit(EXIT_FAILURE);
+			}
+		} else if (const Error* const error = boost::get<Error>(&msg)) {
+			_log.error(fmt("error: %1%\n") % error->message);
 			exit(EXIT_FAILURE);
 		}
 	}
 
-	void error(const std::string& msg) {
-		_log.error(fmt("error: %1%\n") % msg);
-		exit(EXIT_FAILURE);
-	}
-
 private:
 	Log& _log;
 };
diff --git a/wscript b/wscript
index bd587592..2044e25b 100644
--- a/wscript
+++ b/wscript
@@ -63,6 +63,7 @@ def configure(conf):
     conf.check_cxx(header_name='boost/intrusive/slist.hpp')
     conf.check_cxx(header_name='boost/intrusive_ptr.hpp')
     conf.check_cxx(header_name='boost/optional.hpp')
+    conf.check_cxx(header_name='boost/variant.hpp')
     conf.check_cxx(msg='Checking for thread_local keyword',
                    mandatory=False,
                    fragment='thread_local int i = 0; int main() {}',