New inter-thread message system.

14 files changed, 496 insertions, 296 deletions

diff --git a/lv2/lv2_gui.cc b/lv2/lv2_gui.cc
index 7d9cfbf..7b56c5b 100644
--- a/lv2/lv2_gui.cc
+++ b/lv2/lv2_gui.cc
@@ -190,7 +190,7 @@ static LV2UI_Handle ui_instantiate(const struct _LV2UI_Descriptor * descriptor,
   pt->virt.run = ui_run;
   pt->virt.show = ui_show;
   pt->virt.hide = ui_hide;
-  pt->gui = new PluginGUI(pt->instance);
+  pt->gui = new PluginGUI();
   pt->gui->setWindowClosedCallback(closeHandler, pt);
 
   *widget = (LV2UI_Widget)pt;
diff --git a/plugingui/Makefile.am b/plugingui/Makefile.am
index aee2de6..fed12fc 100644
--- a/plugingui/Makefile.am
+++ b/plugingui/Makefile.am
@@ -15,7 +15,9 @@ plugingui_CFLAGS = $(plugingui_CXXFLAGS)
 plugingui_SOURCES = \
 	$(PLUGIN_GUI_SOURCES) \
 	$(top_srcdir)/src/thread.cc \
-	$(top_srcdir)/src/semaphore.cc
+	$(top_srcdir)/src/semaphore.cc \
+	$(top_srcdir)/src/mutex.cc \
+	$(top_srcdir)/src/messagehandler.cc
 
 rcgen_SOURCES = rcgen.cc
 
diff --git a/plugingui/plugingui.cc b/plugingui/plugingui.cc
index 9de7c94..a4f99d7 100644
--- a/plugingui/plugingui.cc
+++ b/plugingui/plugingui.cc
@@ -30,31 +30,10 @@
 #include <stdio.h>
 
 #include "knob.h"
-
 #include "verticalline.h"
+#include "../version.h"
 
-#ifndef STANDALONE
-#include <drumgizmo.h>
-#include "../src/configuration.h"
-#else
-#include "../src/message.h"
-class DrumGizmo {
-public:
-  bool loadkit(std::string) { return true; }
-  bool init(bool) { return true; }
-  std::string drumkitfile() { return ""; }
-  std::string midimapfile;
-  Message *receiveGUIMessage() { return NULL; }
-  Message *peekGUIMessage() { return NULL; }
-  void sendEngineMessage(Message *msg) { delete msg; }
-};
-
-namespace Conf {
-  bool enable_velocity_modifier;
-  float velocity_modifier_weight;
-  float velocity_modifier_falloff;
-};
-#endif
+#include "messagehandler.h"
 
 static void checkClick(void *ptr)
 {
@@ -63,7 +42,7 @@ static void checkClick(void *ptr)
   ChangeSettingMessage *msg =
     new ChangeSettingMessage(ChangeSettingMessage::enable_velocity_modifier,
                              gui->check->checked());
-  gui->drumgizmo->sendEngineMessage(msg);
+  msghandler.sendMessage(MSGRCV_ENGINE, msg);
 }
 
 static void knobChange(void *ptr)
@@ -73,7 +52,8 @@ static void knobChange(void *ptr)
   ChangeSettingMessage *msg =
     new ChangeSettingMessage(ChangeSettingMessage::velocity_modifier_weight,
                              gui->knob->value());
-  gui->drumgizmo->sendEngineMessage(msg);
+
+  msghandler.sendMessage(MSGRCV_ENGINE, msg);
 
 #ifdef STANDALONE
   int i = gui->knob->value() * 4;
@@ -94,7 +74,7 @@ static void knobChange2(void *ptr)
   ChangeSettingMessage *msg =
     new ChangeSettingMessage(ChangeSettingMessage::velocity_modifier_falloff,
                              gui->knob2->value());
-  gui->drumgizmo->sendEngineMessage(msg);
+  msghandler.sendMessage(MSGRCV_ENGINE, msg);
 
 #ifdef STANDALONE
   gui->progress->setProgress(gui->knob2->value());
@@ -116,16 +96,8 @@ static void selectKitFile(void *ptr, std::string filename)
 
   LoadDrumKitMessage *msg = new LoadDrumKitMessage();
   msg->drumkitfile = drumkit;
-  gui->drumgizmo->sendEngineMessage(msg);
-  /*
-  if(!gui->drumgizmo ||
-     !gui->drumgizmo->loadkit(drumkit) ||
-     !gui->drumgizmo->init(true)) {
-    gui->progress->setState(GUI::ProgressBar::red);
-  } else {
-    gui->progress->setState(GUI::ProgressBar::blue);
-  }
-  */
+
+  msghandler.sendMessage(MSGRCV_ENGINE, msg);
 }
 
 static void kitBrowseClick(void *ptr)
@@ -151,7 +123,7 @@ static void selectMapFile(void *ptr, std::string filename)
 
   LoadMidimapMessage *msg = new LoadMidimapMessage();
   msg->midimapfile = midimap;
-  gui->drumgizmo->sendEngineMessage(msg);
+  msghandler.sendMessage(MSGRCV_ENGINE, msg);
 
   /*
   if(gui->changeMidimapHandler)
@@ -180,15 +152,12 @@ void closeClick(void *ptr)
 }
 */
 
-#include "../version.h"
-
-PluginGUI::PluginGUI(DrumGizmo *drumgizmo)
+PluginGUI::PluginGUI()
+  : MessageReceiver(MSGRCV_UI)
 {
   windowClosedHandler = NULL;
   changeMidimapHandler = NULL;
 
-  this->drumgizmo = drumgizmo;
-
   window = NULL;
  
   running = true;
@@ -216,13 +185,67 @@ void PluginGUI::stopThread()
   }
 }
 
+
+void PluginGUI::handleMessage(Message *msg)
+{
+  switch(msg->type()) {
+  case Message::LoadStatus:
+    {
+      LoadStatusMessage *ls = (LoadStatusMessage*)msg;
+      progress->setProgress((float)ls->numer_of_files_loaded /
+                            (float)ls->number_of_files);
+      if(ls->numer_of_files_loaded == ls->number_of_files) {
+        progress->setState(GUI::ProgressBar::green);
+      }
+    }
+    break;
+  case Message::LoadStatusMidimap:
+    {
+      LoadStatusMessageMidimap *ls = (LoadStatusMessageMidimap*)msg;
+      progress2->setProgress(1);
+      if(ls->success) {
+        progress2->setState(GUI::ProgressBar::green);
+      } else {
+        progress2->setState(GUI::ProgressBar::red);
+      }
+    }
+    break;
+  case Message::EngineSettingsMessage:
+    {
+      EngineSettingsMessage *settings = (EngineSettingsMessage *)msg;
+      lineedit->setText(settings->drumkitfile);
+      if(settings->drumkit_loaded) {
+        progress->setProgress(1);
+        progress->setState(GUI::ProgressBar::green);
+      } else {
+        progress->setProgress(0);
+        progress->setState(GUI::ProgressBar::blue);
+      }
+      lineedit2->setText(settings->midimapfile);
+      if(settings->midimap_loaded) {
+        progress2->setProgress(1);
+        progress2->setState(GUI::ProgressBar::green);
+      } else {
+        progress2->setProgress(0);
+        progress2->setState(GUI::ProgressBar::blue);
+      }
+      check->setChecked(settings->enable_velocity_modifier);
+      knob->setValue(settings->velocity_modifier_weight);
+      knob2->setValue(settings->velocity_modifier_falloff);
+      
+    }
+  default:
+    break;
+  }
+}
+
 void PluginGUI::thread_main()
 {
   init();
 
   { // Request all engine settings
     EngineSettingsMessage *msg = new EngineSettingsMessage();
-    drumgizmo->sendEngineMessage(msg);
+    msghandler.sendMessage(MSGRCV_ENGINE, msg);
   }
 
   while(1) {
@@ -235,67 +258,7 @@ void PluginGUI::thread_main()
     if(!running) break;
 
     window->eventHandler()->processEvents();
-
-    Message *msg;
-    if((msg = drumgizmo->receiveGUIMessage()) != NULL) {
-      switch(msg->type()) {
-      case Message::LoadStatus:
-        {
-          Message *pmsg;
-          while( (pmsg = drumgizmo->peekGUIMessage()) != NULL) {
-            if(pmsg->type() != Message::LoadStatus) break;
-            delete msg;
-            msg = drumgizmo->receiveGUIMessage();
-          } 
-          LoadStatusMessage *ls = (LoadStatusMessage*)msg;
-          progress->setProgress((float)ls->numer_of_files_loaded /
-                                (float)ls->number_of_files);
-          if(ls->numer_of_files_loaded == ls->number_of_files) {
-            progress->setState(GUI::ProgressBar::green);
-          }
-        }
-        break;
-      case Message::LoadStatusMidimap:
-        {
-          LoadStatusMessageMidimap *ls = (LoadStatusMessageMidimap*)msg;
-          progress2->setProgress(1);
-          if(ls->success) {
-            progress2->setState(GUI::ProgressBar::green);
-          } else {
-            progress2->setState(GUI::ProgressBar::red);
-          }
-        }
-        break;
-      case Message::EngineSettingsMessage:
-        {
-          EngineSettingsMessage *settings = (EngineSettingsMessage *)msg;
-          lineedit->setText(settings->drumkitfile);
-          if(settings->drumkit_loaded) {
-            progress->setProgress(1);
-            progress->setState(GUI::ProgressBar::green);
-          } else {
-            progress->setProgress(0);
-            progress->setState(GUI::ProgressBar::blue);
-          }
-          lineedit2->setText(settings->midimapfile);
-          if(settings->midimap_loaded) {
-            progress2->setProgress(1);
-            progress2->setState(GUI::ProgressBar::green);
-          } else {
-            progress2->setProgress(0);
-            progress2->setState(GUI::ProgressBar::blue);
-          }
-          check->setChecked(settings->enable_velocity_modifier);
-          knob->setValue(settings->velocity_modifier_weight);
-          knob2->setValue(settings->velocity_modifier_falloff);
-      
-        }
-      default:
-        break;
-      }
-
-      delete msg;
-    }
+    handleMessages();
   }
 
   deinit();
@@ -500,6 +463,12 @@ void PluginGUI::setWindowClosedCallback(void (*handler)(void *), void *ptr)
 
 #ifdef STANDALONE
 
+class Engine : public MessageHandler {
+public:
+  void handleMessage(Message *msg) {}
+};
+
+
 void stop(void *ptr)
 {
   DEBUG(stop, "Stopping...\n");
@@ -524,7 +493,7 @@ int main()
 
   bool running = true;
 
-  PluginGUI gui(NULL);
+  PluginGUI gui;
   gui.setWindowClosedCallback(stop, &running);
 
   // gui.show();
diff --git a/plugingui/plugingui.h b/plugingui/plugingui.h
index 97e45b8..cd050de 100644
--- a/plugingui/plugingui.h
+++ b/plugingui/plugingui.h
@@ -42,11 +42,11 @@
 #include "thread.h"
 #include "semaphore.h"
 
-class DrumGizmo;
+#include "messagereceiver.h"
 
-class PluginGUI : public Thread {
+class PluginGUI : public Thread, public MessageReceiver {
 public:
-  PluginGUI(DrumGizmo *drumgizmo);
+  PluginGUI();
   ~PluginGUI();
 
   void thread_main();
@@ -60,14 +60,14 @@ public:
   void processEvents();
   void setWindowClosedCallback(void (*handler)(void *), void *ptr);
 
+  void handleMessage(Message *msg);
+
   //private:
   GUI::Window *window;
   GUI::EventHandler *eventhandler;
 
   GUI::FileBrowser *filebrowser;
 
-  DrumGizmo *drumgizmo;
-
   GUI::CheckBox *check;
   GUI::Knob *knob;
   GUI::Knob *knob2;
diff --git a/src/Makefile.am b/src/Makefile.am
index 35d052b..75c209c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -16,6 +16,8 @@ EXTRA_DIST = \
 	instrument.h \
 	instrumentparser.h \
 	message.h \
+	messagehandler.h \
+	messagereceiver.h \
 	midimapparser.h \
 	midimapper.h \
 	mutex.h \
@@ -42,6 +44,8 @@ EXTRA_DIST = \
 	events.cc \
 	instrument.cc \
 	instrumentparser.cc \
+	messagehandler.cc \
+	messagereceiver.cc \
 	midimapparser.cc \
 	midimapper.cc \
 	mutex.cc \
diff --git a/src/Makefile.am.drumgizmo b/src/Makefile.am.drumgizmo
index 428d2a7..b1ad862 100644
--- a/src/Makefile.am.drumgizmo
+++ b/src/Makefile.am.drumgizmo
@@ -11,6 +11,8 @@ DRUMGIZMO_SOURCES = \
 	$(top_srcdir)/src/events.cc \
 	$(top_srcdir)/src/instrument.cc \
 	$(top_srcdir)/src/instrumentparser.cc \
+	$(top_srcdir)/src/messagehandler.cc \
+	$(top_srcdir)/src/messagereceiver.cc \
 	$(top_srcdir)/src/midimapparser.cc \
 	$(top_srcdir)/src/midimapper.cc \
 	$(top_srcdir)/src/mutex.cc \
diff --git a/src/drumgizmo.cc b/src/drumgizmo.cc
index b6ac98f..135975d 100644
--- a/src/drumgizmo.cc
+++ b/src/drumgizmo.cc
@@ -41,7 +41,8 @@
 #include "configuration.h"
 
 DrumGizmo::DrumGizmo(AudioOutputEngine *o, AudioInputEngine *i)
-  : loader(this), oe(o), ie(i)
+  : MessageReceiver(MSGRCV_ENGINE),
+    loader(this), oe(o), ie(i)
 {
   loader.run(); // Start drumkit loader thread.
 }
@@ -59,78 +60,6 @@ DrumGizmo::~DrumGizmo()
   loader.stop();
 }
 
-/*
- * Add a message to the GUI message queue.
- */
-void DrumGizmo::sendGUIMessage(Message *msg)
-{
-  MutexAutolock l(gui_message_mutex);
-  gui_message_queue.push_back(msg);
-}
-
-/*
- * Receive message from the engine. The caller takes over the memory.
- */
-Message *DrumGizmo::receiveGUIMessage()
-{
-  MutexAutolock l(gui_message_mutex);
-  Message *msg = NULL;
-  if(gui_message_queue.size()) {
-    msg = gui_message_queue.front();
-    gui_message_queue.pop_front();
-  }
-  return msg;
-}
-
-/*
- * Receive message from the engine without removing it from the queue.
- */
-Message *DrumGizmo::peekGUIMessage()
-{
-  MutexAutolock l(gui_message_mutex);
-  Message *msg = NULL;
-  if(gui_message_queue.size()) {
-    msg = gui_message_queue.front();
-  }
-  return msg;
-}
-
-/*
- * Add a message to the GUI message queue.
- */
-void DrumGizmo::sendEngineMessage(Message *msg)
-{
-  MutexAutolock l(engine_message_mutex);
-  engine_message_queue.push_back(msg);
-}
-
-/*
- * Receive message from the engine. The caller takes over the memory.
- */
-Message *DrumGizmo::receiveEngineMessage()
-{
-  MutexAutolock l(engine_message_mutex);
-  Message *msg = NULL;
-  if(engine_message_queue.size()) {
-    msg = engine_message_queue.front();
-    engine_message_queue.pop_front();
-  }
-  return msg;
-}
-
-/*
- * Receive message from the engine without removing it from the queue.
- */
-Message *DrumGizmo::peekEngineMessage()
-{
-  MutexAutolock l(engine_message_mutex);
-  Message *msg = NULL;
-  if(engine_message_queue.size()) {
-    msg = engine_message_queue.front();
-  }
-  return msg;
-}
-
 std::string DrumGizmo::drumkitfile()
 {
   return kitfile;
@@ -181,86 +110,88 @@ bool DrumGizmo::init(bool preload)
   return true;
 }
 
-void DrumGizmo::handleEngineEvents()
+void DrumGizmo::handleMessage(Message *msg)
 {
-  Message *msg = receiveEngineMessage();
-  if(msg) {
-    DEBUG(msg, "got message.");
-    switch(msg->type()) {
-    case Message::LoadDrumKit:
-      {
-        DEBUG(msg, "got LoadDrumKitMessage message.");
-        LoadDrumKitMessage *m = (LoadDrumKitMessage*)msg;
-        loadkit(m->drumkitfile);
-        //init(true);
-      }
-      break;
-    case Message::LoadMidimap:
-      DEBUG(msg, "got LoadMidimapMessage message.");
-      if(!ie->isMidiEngine()) break;
-      {
+  DEBUG(msg, "got message.");
+  switch(msg->type()) {
+  case Message::RegisterUIMessage:
+    {
+      DEBUG(msg, "got RegisterUIMessage message.");
+      RegisterUIMessage *m = (RegisterUIMessage*)msg;
+      ui = m->messagehandler;
+    }
+    break;
+  case Message::LoadDrumKit:
+    {
+      DEBUG(msg, "got LoadDrumKitMessage message.");
+      LoadDrumKitMessage *m = (LoadDrumKitMessage*)msg;
+      loadkit(m->drumkitfile);
+      //init(true);
+    }
+    break;
+  case Message::LoadMidimap:
+    DEBUG(msg, "got LoadMidimapMessage message.");
+    if(!ie->isMidiEngine()) break;
+    {
+      AudioInputEngineMidi *aim = (AudioInputEngineMidi*)ie;
+      LoadMidimapMessage *m = (LoadMidimapMessage*)msg;
+      bool ret = aim->loadMidiMap(m->midimapfile, kit.instruments);
+      
+      LoadStatusMessageMidimap *ls = new LoadStatusMessageMidimap();
+      ls->success = ret;
+      msghandler.sendMessage(MSGRCV_UI, ls);
+    }
+    break;
+  case Message::EngineSettingsMessage:
+    {
+      DEBUG(msg, "--------------- Send: EngineSettingsMessage ------------ \n");
+      
+      bool mmap_loaded = false;
+      std::string mmapfile;
+      if(ie->isMidiEngine()) {
         AudioInputEngineMidi *aim = (AudioInputEngineMidi*)ie;
-        LoadMidimapMessage *m = (LoadMidimapMessage*)msg;
-        bool ret = aim->loadMidiMap(m->midimapfile, kit.instruments);
-        
-        LoadStatusMessageMidimap *ls = new LoadStatusMessageMidimap();
-        ls->success = ret;
-        sendGUIMessage(ls);
-      }
-      break;
-    case Message::EngineSettingsMessage:
-      {
-        DEBUG(msg, "--------------- Send: EngineSettingsMessage --------------- \n");
-
-        bool mmap_loaded = false;
-        std::string mmapfile;
-        if(ie->isMidiEngine()) {
-          AudioInputEngineMidi *aim = (AudioInputEngineMidi*)ie;
-          mmapfile = aim->midimapFile();
-          mmap_loaded = aim->isValid();
-          
-        }
-
-        EngineSettingsMessage *msg = new EngineSettingsMessage();
-        msg->midimapfile = mmapfile;
-        msg->midimap_loaded = mmap_loaded;
-        msg->drumkitfile = drumkitfile();
-        msg->drumkit_loaded = loader.isDone();
-        msg->enable_velocity_modifier = Conf::enable_velocity_modifier;
-        msg->velocity_modifier_falloff = Conf::velocity_modifier_falloff;
-        msg->velocity_modifier_weight = Conf::velocity_modifier_weight;
-        msg->enable_velocity_randomiser = Conf::enable_velocity_randomiser;
-        msg->velocity_randomiser_weight = Conf::velocity_randomiser_weight;
-        sendGUIMessage(msg);
+        mmapfile = aim->midimapFile();
+        mmap_loaded = aim->isValid();
       }
-      break;
-    case Message::ChangeSettingMessage:
-      {
-        ChangeSettingMessage *ch = (ChangeSettingMessage*)msg;
-        switch(ch->name) {
-        case ChangeSettingMessage::enable_velocity_modifier:
-          Conf::enable_velocity_modifier = ch->value;
-          break;
-        case ChangeSettingMessage::velocity_modifier_weight:
-          Conf::velocity_modifier_weight = ch->value;
-          break;
-        case ChangeSettingMessage::velocity_modifier_falloff:
-          Conf::velocity_modifier_falloff = ch->value;
-          break;
-        }
+      
+      EngineSettingsMessage *msg = new EngineSettingsMessage();
+      msg->midimapfile = mmapfile;
+      msg->midimap_loaded = mmap_loaded;
+      msg->drumkitfile = drumkitfile();
+      msg->drumkit_loaded = loader.isDone();
+      msg->enable_velocity_modifier = Conf::enable_velocity_modifier;
+      msg->velocity_modifier_falloff = Conf::velocity_modifier_falloff;
+      msg->velocity_modifier_weight = Conf::velocity_modifier_weight;
+      msg->enable_velocity_randomiser = Conf::enable_velocity_randomiser;
+      msg->velocity_randomiser_weight = Conf::velocity_randomiser_weight;
+      msghandler.sendMessage(MSGRCV_UI, msg);
+    }
+    break;
+  case Message::ChangeSettingMessage:
+    {
+      ChangeSettingMessage *ch = (ChangeSettingMessage*)msg;
+      switch(ch->name) {
+      case ChangeSettingMessage::enable_velocity_modifier:
+        Conf::enable_velocity_modifier = ch->value;
+        break;
+      case ChangeSettingMessage::velocity_modifier_weight:
+        Conf::velocity_modifier_weight = ch->value;
+        break;
+      case ChangeSettingMessage::velocity_modifier_falloff:
+        Conf::velocity_modifier_falloff = ch->value;
+        break;
       }
-      break;
-    default:
-      break;
     }
-    delete msg;
+    break;
+  default:
+    break;
   }
 }
 
 bool DrumGizmo::run(size_t pos, sample_t *samples, size_t nsamples)
 {
   // Handle engine messages, at most one in each iteration:
-  handleEngineEvents();
+  handleMessages(1);
 
   ie->pre();
   oe->pre(nsamples);
@@ -609,7 +540,7 @@ bool DrumGizmo::setConfigString(std::string cfg)
     */
     LoadDrumKitMessage *msg = new LoadDrumKitMessage();
     msg->drumkitfile = newkit;
-    sendEngineMessage(msg);
+    msghandler.sendMessage(MSGRCV_ENGINE, msg);
   }
 
   std::string newmidimap = p.value("midimapfile");
@@ -617,7 +548,7 @@ bool DrumGizmo::setConfigString(std::string cfg)
     //midimapfile = newmidimap;
     LoadMidimapMessage *msg = new LoadMidimapMessage();
     msg->midimapfile = newmidimap;
-    sendEngineMessage(msg);
+    msghandler.sendMessage(MSGRCV_ENGINE, msg);
   }
 
   return true;
diff --git a/src/drumgizmo.h b/src/drumgizmo.h
index ffb9b07..31c192c 100644
--- a/src/drumgizmo.h
+++ b/src/drumgizmo.h
@@ -43,9 +43,11 @@
 
 #include "message.h"
 
+#include "messagereceiver.h"
+
 #define MAX_NUM_CHANNELS 512
 
-class DrumGizmo {
+class DrumGizmo : public MessageReceiver {
 public:
   DrumGizmo(AudioOutputEngine *outputengine,
             AudioInputEngine *inputengine);
@@ -69,50 +71,14 @@ public:
 
   std::string kitfile;
 
-  /*
-   * Receive message from the engine. The caller takes over the memory.
-   */
-  Message *receiveGUIMessage();
-
-  /*
-   * Receive message from the engine without removing it from the queue.
-   */
-  Message *peekGUIMessage();
-
-  /*
-   * Add a message to the GUI message queue.
-   */
-  void sendEngineMessage(Message *msg);
-
-  /*
-   * Receive message from the engine. The caller takes over the memory.
-   */
-  Message *receiveEngineMessage();
-
-  /*
-   * Receive message from the engine without removing it from the queue.
-   */
-  Message *peekEngineMessage();
-
-  /*
-   * Add a message to the GUI message queue.
-   */
-  void sendGUIMessage(Message *msg);
+  void handleMessage(Message *msg);
 
 private:
-  void handleEngineEvents();
-
-  Mutex gui_message_mutex;
-  std::list<Message *> gui_message_queue;
-
-  Mutex engine_message_mutex;
-  std::list<Message *> engine_message_queue;
-
   DrumKitLoader loader;
 
   Mutex mutex;
   bool is_running;
-  
+
   AudioOutputEngine *oe;
   AudioInputEngine *ie;
 
diff --git a/src/drumkitloader.cc b/src/drumkitloader.cc
index 41b56a1..a7a8989 100644
--- a/src/drumkitloader.cc
+++ b/src/drumkitloader.cc
@@ -191,7 +191,7 @@ void DrumKitLoader::thread_main()
             ls->number_of_files = count;
             ls->numer_of_files_loaded = loaded;
             ls->current_file = af->filename;
-            drumgizmo->sendGUIMessage(ls);
+            msghandler.sendMessage(MSGRCV_UI, ls);
           
             a++;
 
diff --git a/src/message.h b/src/message.h
index 4ce65ef..d51c263 100644
--- a/src/message.h
+++ b/src/message.h
@@ -27,6 +27,10 @@
 #ifndef __DRUMGIZMO_MESSAGE_H__
 #define __DRUMGIZMO_MESSAGE_H__
 
+#include <string>
+
+class MessageHandler;
+
 class Message {
 public:
   typedef enum {
@@ -39,15 +43,24 @@ public:
     LoadMidimap, // Signal engine to load midimap.
     EngineSettingsMessage, // Request or receive engine settings.
     ChangeSettingMessage, // Update named setting in engine.
+    RegisterUIMessage, // Register new UI message handler
   } type_t;
 
+  typedef enum {
+    NormalProcessing, // Just add to the queue
+    FilterMultiple, // Ignore top message if it has the same type.
+    // SyncWait, // Block the send call until the message has been handled by the receiver.
+  } processing_mode_t;
+
   virtual ~Message() {}
   virtual type_t type() = 0;
+  virtual processing_mode_t processing_mode() { return NormalProcessing; }
 };
 
 class LoadStatusMessage : public Message {
 public:
   type_t type() { return Message::LoadStatus; }
+  processing_mode_t processing_mode() { return FilterMultiple; }
   unsigned int number_of_files;
   unsigned int numer_of_files_loaded;
   std::string current_file;
@@ -106,4 +119,10 @@ public:
   float value;
 };
 
+class RegisterUIMessage : public Message {
+public:
+  type_t type() { return Message::RegisterUIMessage; }
+  MessageHandler *messagehandler;
+};
+
 #endif/*__DRUMGIZMO_MESSAGE_H__*/
diff --git a/src/messagehandler.cc b/src/messagehandler.cc
new file mode 100644
index 0000000..a5a71f1
--- /dev/null
+++ b/src/messagehandler.cc
@@ -0,0 +1,88 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/***************************************************************************
+ *            messagehandler.cc
+ *
+ *  Fri Jun 14 20:30:43 CEST 2013
+ *  Copyright 2013 Bent Bisballe Nyeng
+ *  deva@aasimon.org
+ ****************************************************************************/
+
+/*
+ *  This file is part of DrumGizmo.
+ *
+ *  DrumGizmo 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.
+ *
+ *  DrumGizmo 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 DrumGizmo; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#include "messagehandler.h"
+
+#include <hugin.hpp>
+
+#include "messagereceiver.h"
+
+// Global messagehandler:
+MessageHandler msghandler;
+
+MessageHandler::MessageHandler()
+{
+}
+
+void MessageHandler::addReceiver(message_receiver_id_t id,
+                                 MessageReceiver *receiver)
+{
+  MutexAutolock l(mutex);
+
+  receivers[id] = receiver;
+}
+
+void MessageHandler::removeReceiver(MessageReceiver *receiver)
+{
+  MutexAutolock l(mutex);
+
+  std::map<message_receiver_id_t, MessageReceiver *>::iterator i =
+    receivers.begin();
+  while(i != receivers.end()) {
+    if(i->second == receiver) {
+      receivers.erase(i);
+      break;
+    }
+    i++;
+  }
+}
+
+bool MessageHandler::sendMessage(message_receiver_id_t id, Message* msg)
+{
+  MutexAutolock l(mutex);
+
+  if(receivers.find(id) == receivers.end()) {
+    WARN(msghandler, "Could not find id %d\n", id);
+    delete msg;
+    return false;
+  }
+
+  DEBUG(msghandler, "Sending message to id %d\n", id);
+
+  MessageReceiver *receiver = receivers[id];
+
+  if(msg->processing_mode() == Message::FilterMultiple) {
+    Message *pmsg;
+    while( (pmsg = receiver->peekMessage()) != NULL) {
+      if(pmsg->type() != Message::LoadStatus) break;
+      delete msg;
+      msg = receiver->receiveMessage();
+    }
+  }
+
+  receiver->sendMessage(msg);
+  return true;
+}
diff --git a/src/messagehandler.h b/src/messagehandler.h
new file mode 100644
index 0000000..9812777
--- /dev/null
+++ b/src/messagehandler.h
@@ -0,0 +1,66 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/***************************************************************************
+ *            messagehandler.h
+ *
+ *  Fri Jun 14 20:30:43 CEST 2013
+ *  Copyright 2013 Bent Bisballe Nyeng
+ *  deva@aasimon.org
+ ****************************************************************************/
+
+/*
+ *  This file is part of DrumGizmo.
+ *
+ *  DrumGizmo 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.
+ *
+ *  DrumGizmo 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 DrumGizmo; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#ifndef __DRUMGIZMO_MESSAGEHANDLER_H__
+#define __DRUMGIZMO_MESSAGEHANDLER_H__
+
+#include <map>
+
+#include "message.h"
+#include "mutex.h"
+
+typedef enum {
+  MSGRCV_ENGINE = 1,
+  MSGRCV_UI = 2,
+  MSGRCV_LOADER = 3,
+} message_receiver_id_t;
+
+class MessageReceiver;
+
+class MessageHandler {
+public:
+  MessageHandler();
+
+  void addReceiver(message_receiver_id_t id, MessageReceiver *receiver);
+  void removeReceiver(MessageReceiver *receiver);
+
+  /**
+   * Send Message to receiver with specified id.
+   * @return Return true if id is registered. Return false if id is not
+   * currently registered.
+   */
+  bool sendMessage(message_receiver_id_t id, Message* msg);
+
+private:
+  std::map<message_receiver_id_t, MessageReceiver *> receivers;
+
+  Mutex mutex;
+};
+
+// Global MessageHandler;
+extern MessageHandler msghandler;
+
+#endif/*__DRUMGIZMO_MESSAGEHANDLER_H__*/
diff --git a/src/messagereceiver.cc b/src/messagereceiver.cc
new file mode 100644
index 0000000..f391aad
--- /dev/null
+++ b/src/messagereceiver.cc
@@ -0,0 +1,79 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/***************************************************************************
+ *            messagereceiver.cc
+ *
+ *  Sun Jun 16 12:09:06 CEST 2013
+ *  Copyright 2013 Bent Bisballe Nyeng
+ *  deva@aasimon.org
+ ****************************************************************************/
+
+/*
+ *  This file is part of DrumGizmo.
+ *
+ *  DrumGizmo 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.
+ *
+ *  DrumGizmo 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 DrumGizmo; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#include "messagereceiver.h"
+
+#include <hugin.hpp>
+
+MessageReceiver::MessageReceiver(message_receiver_id_t id)
+{
+  msghandler.addReceiver(id, this);
+}
+
+MessageReceiver::~MessageReceiver()
+{
+  msghandler.removeReceiver(this);
+}
+
+void MessageReceiver::sendMessage(Message *msg)
+{
+  MutexAutolock l(message_mutex);
+
+  message_queue.push_back(msg);
+}
+
+Message *MessageReceiver::receiveMessage()
+{
+  MutexAutolock l(message_mutex);
+  Message *msg = NULL;
+  if(message_queue.size()) {
+    msg = message_queue.front();
+    message_queue.pop_front();
+  }
+  return msg;
+}
+
+Message *MessageReceiver::peekMessage()
+{
+  MutexAutolock l(message_mutex);
+  Message *msg = NULL;
+  if(message_queue.size()) {
+    msg = message_queue.front();
+  }
+  return msg;
+}
+
+void MessageReceiver::handleMessages(size_t max)
+{
+  bool process_all = false;
+  if(max == 0) process_all = true;
+
+  while((process_all || max--) && peekMessage()) {
+    Message *msg = receiveMessage();
+    handleMessage(msg);
+    delete msg;
+  }
+}
diff --git a/src/messagereceiver.h b/src/messagereceiver.h
new file mode 100644
index 0000000..4185f29
--- /dev/null
+++ b/src/messagereceiver.h
@@ -0,0 +1,74 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/***************************************************************************
+ *            messagereceiver.h
+ *
+ *  Sun Jun 16 12:09:06 CEST 2013
+ *  Copyright 2013 Bent Bisballe Nyeng
+ *  deva@aasimon.org
+ ****************************************************************************/
+
+/*
+ *  This file is part of DrumGizmo.
+ *
+ *  DrumGizmo 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.
+ *
+ *  DrumGizmo 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 DrumGizmo; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#ifndef __DRUMGIZMO_MESSAGERECEIVER_H__
+#define __DRUMGIZMO_MESSAGERECEIVER_H__
+
+#include <list>
+
+#include "mutex.h"
+#include "message.h"
+#include "messagehandler.h"
+
+class MessageReceiver {
+public:
+  MessageReceiver(message_receiver_id_t id);
+  ~MessageReceiver();
+
+  /**
+   * Receive message from the message queue.
+   */
+  Message *receiveMessage();
+
+  /**
+   * Receive message from the message queue without removing it.
+   */
+  Message *peekMessage();
+
+  /**
+   * Add a message to the message queue.
+   */
+  void sendMessage(Message *msg);
+
+  /**
+   * Handle messages from the event queue.
+   * @param max_number_of_events the maximum number of events to be handled in
+   * this call. 0 means all.
+   */
+  void handleMessages(size_t max_number_of_events = 0);
+
+  /**
+   * Handler to be implemented in child classes.
+   * Handles a single event.
+   */
+  virtual void handleMessage(Message *msg) = 0;
+
+private:
+  Mutex message_mutex;
+  std::list<Message *> message_queue;
+};
+
+#endif/*__DRUMGIZMO_MESSAGERECEIVER_H__*/