# HG changeset patch
# User Sebastien Jodogne <s.jodogne@gmail.com>
# Date 1571146779 -7200
# Node ID b537002f83a9cf568fdc26a85431eecf97e2fa7d
# Parent  9d42f89b8c3cff5af187547e733614eded21a583
removing broker from deprecated classes

diff -r 9d42f89b8c3c -r b537002f83a9 Applications/Generic/NativeStoneApplicationRunner.cpp
--- a/Applications/Generic/NativeStoneApplicationRunner.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/Generic/NativeStoneApplicationRunner.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -197,7 +197,7 @@
 
       LogStatusBar statusBar;
 
-      NativeStoneApplicationContext context(broker_);
+      NativeStoneApplicationContext context;
 
       {
         // use multiple threads to execute asynchronous tasks like 
@@ -206,13 +206,12 @@
         oracle.Start();
 
         {
-          Deprecated::OracleWebService webService(
-            broker_, oracle, webServiceParameters, context);
+          Deprecated::OracleWebService webService(oracle, webServiceParameters, context);
           
           context.SetWebService(webService);
           context.SetOrthancBaseUrl(webServiceParameters.GetUrl());
 
-          Deprecated::OracleDelayedCallExecutor delayedExecutor(broker_, oracle, context);
+          Deprecated::OracleDelayedCallExecutor delayedExecutor(oracle, context);
           context.SetDelayedCallExecutor(delayedExecutor);
 
           application_.Initialize(&context, statusBar, parameters);
diff -r 9d42f89b8c3c -r b537002f83a9 Applications/Generic/NativeStoneApplicationRunner.h
--- a/Applications/Generic/NativeStoneApplicationRunner.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/Generic/NativeStoneApplicationRunner.h	Tue Oct 15 15:39:39 2019 +0200
@@ -34,14 +34,11 @@
   class NativeStoneApplicationRunner
   {
   protected:
-    MessageBroker&      broker_;
     IStoneApplication&  application_;
   public:
 
-    NativeStoneApplicationRunner(MessageBroker& broker,
-                                 IStoneApplication& application)
-      : broker_(broker),
-        application_(application)
+    NativeStoneApplicationRunner(IStoneApplication& application)
+      : application_(application)
     {
     }
     int Execute(int argc,
diff -r 9d42f89b8c3c -r b537002f83a9 Applications/Samples/SampleMainNative.cpp
--- a/Applications/Samples/SampleMainNative.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/Samples/SampleMainNative.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -26,19 +26,17 @@
 #if ORTHANC_ENABLE_QT==1
 #include "Qt/SampleQtApplicationRunner.h"
 #endif
-#include "../../Framework/Messages/MessageBroker.h"
 
 int main(int argc, char* argv[]) 
 {
-  OrthancStone::MessageBroker broker;
-  SampleApplication sampleStoneApplication(broker);
+  SampleApplication sampleStoneApplication;
 
 #if ORTHANC_ENABLE_SDL==1
-  OrthancStone::SdlStoneApplicationRunner sdlApplicationRunner(broker, sampleStoneApplication);
+  OrthancStone::SdlStoneApplicationRunner sdlApplicationRunner(sampleStoneApplication);
   return sdlApplicationRunner.Execute(argc, argv);
 #endif
 #if ORTHANC_ENABLE_QT==1
-  OrthancStone::Samples::SampleQtApplicationRunner qtAppRunner(broker, sampleStoneApplication);
+  OrthancStone::Samples::SampleQtApplicationRunner qtAppRunner(sampleStoneApplication);
   return qtAppRunner.Execute(argc, argv);
 #endif
 }
diff -r 9d42f89b8c3c -r b537002f83a9 Applications/Samples/SimpleViewerApplicationSingleFile.h
--- a/Applications/Samples/SimpleViewerApplicationSingleFile.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/Samples/SimpleViewerApplicationSingleFile.h	Tue Oct 15 15:39:39 2019 +0200
@@ -44,7 +44,7 @@
   {
     class SimpleViewerApplication :
       public SampleSingleCanvasWithButtonsApplicationBase,
-      public IObserver
+      public ObserverBase<SimpleViewerApplication>
     {
     private:
       class ThumbnailInteractor : public Deprecated::IWorldSceneInteractor
@@ -199,8 +199,8 @@
         SimpleViewerApplication&  viewerApplication_;
 
       public:
-        SimpleViewerApplicationAdapter(MessageBroker& broker, SimpleViewerApplication& application)
-          : WasmPlatformApplicationAdapter(broker, application),
+        SimpleViewerApplicationAdapter(SimpleViewerApplication& application)
+          : WasmPlatformApplicationAdapter(application),
             viewerApplication_(application)
         {
         }
@@ -258,8 +258,7 @@
       Orthanc::Font                        font_;
 
     public:
-      SimpleViewerApplication(MessageBroker& broker) :
-        IObserver(broker),
+      SimpleViewerApplication() :
         currentTool_(Tool_LineMeasure),
         mainLayout_(NULL),
         currentInstanceIndex_(0),
@@ -303,7 +302,7 @@
           thumbnailsLayout_->SetBackgroundColor(50, 50, 50);
           thumbnailsLayout_->SetVertical();
 
-          mainWidget_ = new Deprecated::SliceViewerWidget(GetBroker(), "main-viewport");
+          mainWidget_ = new Deprecated::SliceViewerWidget("main-viewport");
           //mainWidget_->RegisterObserver(*this);
 
           // hierarchy
@@ -311,7 +310,7 @@
           mainLayout_->AddWidget(mainWidget_);
 
           // sources
-          smartLoader_.reset(new Deprecated::SmartLoader(GetBroker(), context->GetOrthancApiClient()));
+          smartLoader_.reset(new Deprecated::SmartLoader(context->GetOrthancApiClient()));
           smartLoader_->SetImageQuality(Deprecated::SliceImageQuality_FullPam);
 
           mainLayout_->SetTransmitMouseOver(true);
@@ -330,7 +329,7 @@
           context->GetOrthancApiClient().GetJsonAsync(
             "/studies",
             new Callable<SimpleViewerApplication, Deprecated::OrthancApiClient::JsonResponseReadyMessage>
-            (*this, &SimpleViewerApplication::OnStudyListReceived));
+            (GetSharedObserver(), &SimpleViewerApplication::OnStudyListReceived));
         }
         else
         {
@@ -360,7 +359,7 @@
             context_->GetOrthancApiClient().GetJsonAsync(
               "/series/" + response["Series"][(int)i].asString(),
               new Callable<SimpleViewerApplication, Deprecated::OrthancApiClient::JsonResponseReadyMessage>
-              (*this, &SimpleViewerApplication::OnSeriesReceived));
+              (GetSharedObserver(), &SimpleViewerApplication::OnSeriesReceived));
           }
         }
       }
@@ -398,10 +397,10 @@
       void LoadThumbnailForSeries(const std::string& seriesId, const std::string& instanceId)
       {
         LOG(INFO) << "Loading thumbnail for series " << seriesId;
-        Deprecated::SliceViewerWidget* thumbnailWidget = new Deprecated::SliceViewerWidget(GetBroker(), "thumbnail-series-" + seriesId);
+        Deprecated::SliceViewerWidget* thumbnailWidget = new Deprecated::SliceViewerWidget("thumbnail-series-" + seriesId);
         thumbnails_.push_back(thumbnailWidget);
         thumbnailsLayout_->AddWidget(thumbnailWidget);
-        thumbnailWidget->RegisterObserverCallback(new Callable<SimpleViewerApplication, Deprecated::SliceViewerWidget::GeometryChangedMessage>(*this, &SimpleViewerApplication::OnWidgetGeometryChanged));
+        Register<Deprecated::SliceViewerWidget::GeometryChangedMessage>(*thumbnailWidget, &SimpleViewerApplication::OnWidgetGeometryChanged);
         smartLoader_->SetFrameInWidget(*thumbnailWidget, 0, instanceId, 0);
         thumbnailWidget->SetInteractor(*thumbnailInteractor_);
       }
@@ -411,7 +410,7 @@
         LOG(INFO) << "Selecting study: " << studyId;
         context_->GetOrthancApiClient().GetJsonAsync(
           "/studies/" + studyId, new Callable<SimpleViewerApplication, Deprecated::OrthancApiClient::JsonResponseReadyMessage>
-          (*this, &SimpleViewerApplication::OnStudyReceived));
+          (GetSharedObserver(), &SimpleViewerApplication::OnStudyReceived));
       }
 
       void OnWidgetGeometryChanged(const Deprecated::SliceViewerWidget::GeometryChangedMessage& message)
diff -r 9d42f89b8c3c -r b537002f83a9 Applications/Samples/SingleFrameApplication.h
--- a/Applications/Samples/SingleFrameApplication.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/Samples/SingleFrameApplication.h	Tue Oct 15 15:39:39 2019 +0200
@@ -38,7 +38,7 @@
   {
     class SingleFrameApplication :
       public SampleSingleCanvasApplicationBase,
-      public IObserver
+      public ObserverBase<SingleFrameApplication>
     {
     private:
       class Interactor : public Deprecated::IWorldSceneInteractor
@@ -202,8 +202,7 @@
       unsigned int                      slice_;
 
     public:
-      SingleFrameApplication(MessageBroker& broker) :
-        IObserver(broker),
+      SingleFrameApplication() :
         source_(NULL),
         slice_(0)
       {
@@ -243,12 +242,12 @@
         std::string instance = parameters["instance"].as<std::string>();
         int frame = parameters["frame"].as<unsigned int>();
 
-        mainWidget_ = new Deprecated::SliceViewerWidget(GetBroker(), "main-widget");
+        mainWidget_ = new Deprecated::SliceViewerWidget("main-widget");
 
-        std::auto_ptr<Deprecated::DicomSeriesVolumeSlicer> layer(new Deprecated::DicomSeriesVolumeSlicer(GetBroker(), context->GetOrthancApiClient()));
+        std::auto_ptr<Deprecated::DicomSeriesVolumeSlicer> layer(new Deprecated::DicomSeriesVolumeSlicer(context->GetOrthancApiClient()));
         source_ = layer.get();
         layer->LoadFrame(instance, frame);
-        layer->RegisterObserverCallback(new Callable<SingleFrameApplication, Deprecated::IVolumeSlicer::GeometryReadyMessage>(*this, &SingleFrameApplication::OnMainWidgetGeometryReady));
+        Register<Deprecated::IVolumeSlicer::GeometryReadyMessage>(*layer, &SingleFrameApplication::OnMainWidgetGeometryReady);
         GetMainWidget().AddLayer(layer.release());
 
         Deprecated::RenderStyle s;
diff -r 9d42f89b8c3c -r b537002f83a9 Applications/Samples/SingleFrameEditorApplication.h
--- a/Applications/Samples/SingleFrameEditorApplication.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/Samples/SingleFrameEditorApplication.h	Tue Oct 15 15:39:39 2019 +0200
@@ -53,7 +53,7 @@
   {
     class RadiographyEditorInteractor :
         public Deprecated::IWorldSceneInteractor,
-        public IObserver
+        public ObserverBase<RadiographyEditorInteractor>
     {
     private:
       enum Tool
@@ -80,8 +80,7 @@
 
 
     public:
-      RadiographyEditorInteractor(MessageBroker& broker) :
-        IObserver(broker),
+      RadiographyEditorInteractor() :
         context_(NULL),
         tool_(Tool_Move),
         maskLayer_(NULL)
@@ -310,7 +309,7 @@
           LOG(INFO) << "JSON export was successful: "
                     << snapshot.toStyledString();
 
-          boost::shared_ptr<RadiographyScene> scene(new RadiographyScene(GetBroker()));
+          boost::shared_ptr<RadiographyScene> scene(new RadiographyScene);
           RadiographySceneReader reader(*scene, context_->GetOrthancApiClient());
 
           Orthanc::FontRegistry fontRegistry;
@@ -430,12 +429,6 @@
       RadiographyMaskLayer*                 maskLayer_;
 
     public:
-      SingleFrameEditorApplication(MessageBroker& broker) :
-        IObserver(broker),
-        interactor_(broker)
-      {
-      }
-
       virtual ~SingleFrameEditorApplication()
       {
         LOG(WARNING) << "Destroying the application";
@@ -489,7 +482,7 @@
 
         fontRegistry_.AddFromResource(Orthanc::EmbeddedResources::FONT_UBUNTU_MONO_BOLD_16);
         
-        scene_.reset(new RadiographyScene(GetBroker()));
+        scene_.reset(new RadiographyScene);
         
         RadiographyLayer& dicomLayer = scene_->LoadDicomFrame(context->GetOrthancApiClient(), instance, 0, false, NULL);
         //scene_->LoadDicomFrame(instance, frame, false); //.SetPan(200, 0);
@@ -522,7 +515,7 @@
         }
         
         
-        mainWidget_ = new RadiographyWidget(GetBroker(), scene_, "main-widget");
+        mainWidget_ = new RadiographyWidget(scene_, "main-widget");
         mainWidget_->SetTransmitMouseOver(true);
         mainWidget_->SetInteractor(interactor_);
 
diff -r 9d42f89b8c3c -r b537002f83a9 Applications/Sdl/SdlEngine.cpp
--- a/Applications/Sdl/SdlEngine.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/Sdl/SdlEngine.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -99,9 +99,7 @@
 
 
   SdlEngine::SdlEngine(SdlWindow& window,
-                       NativeStoneApplicationContext& context,
-                       MessageBroker& broker) :
-    IObserver(broker),
+                       NativeStoneApplicationContext& context) :
     window_(window),
     context_(context),
     surface_(window),
diff -r 9d42f89b8c3c -r b537002f83a9 Applications/Sdl/SdlEngine.h
--- a/Applications/Sdl/SdlEngine.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/Sdl/SdlEngine.h	Tue Oct 15 15:39:39 2019 +0200
@@ -23,12 +23,13 @@
 
 #if ORTHANC_ENABLE_SDL == 1
 
+#include "../../Framework/Messages/ObserverBase.h"
+#include "../Generic/NativeStoneApplicationContext.h"
 #include "SdlCairoSurface.h"
-#include "../Generic/NativeStoneApplicationContext.h"
 
 namespace OrthancStone
 {
-  class SdlEngine : public IObserver
+  class SdlEngine : public ObserverBase<SdlEngine>
   {
   private:
     SdlWindow&                window_;
@@ -46,8 +47,7 @@
 
   public:
     SdlEngine(SdlWindow& window,
-              NativeStoneApplicationContext& context,
-              MessageBroker& broker);
+              NativeStoneApplicationContext& context);
   
     void OnViewportChanged(const Deprecated::IViewport::ViewportChangedMessage& message)
     {
diff -r 9d42f89b8c3c -r b537002f83a9 Applications/Sdl/SdlStoneApplicationRunner.cpp
--- a/Applications/Sdl/SdlStoneApplicationRunner.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/Sdl/SdlStoneApplicationRunner.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -103,14 +103,13 @@
     LOG(WARNING) << "Starting the application";
 
     SdlWindow window(title.c_str(), width_, height_, enableOpenGl_);
-    SdlEngine sdl(window, context, broker_);
+    SdlEngine sdl(window, context);
 
     {
       NativeStoneApplicationContext::GlobalMutexLocker locker(context);
 
-      locker.GetCentralViewport().RegisterObserverCallback(
-        new Callable<SdlEngine, Deprecated::IViewport::ViewportChangedMessage>
-        (sdl, &SdlEngine::OnViewportChanged));
+      sdl.Register<Deprecated::IViewport::ViewportChangedMessage>
+        (locker.GetCentralViewport(), &SdlEngine::OnViewportChanged);
 
       //context.GetCentralViewport().Register(sdl);  // (*)
     }
diff -r 9d42f89b8c3c -r b537002f83a9 Applications/Sdl/SdlStoneApplicationRunner.h
--- a/Applications/Sdl/SdlStoneApplicationRunner.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/Sdl/SdlStoneApplicationRunner.h	Tue Oct 15 15:39:39 2019 +0200
@@ -39,9 +39,8 @@
     bool          enableOpenGl_;
     
   public:
-    SdlStoneApplicationRunner(MessageBroker& broker,
-                              IStoneApplication& application) :
-      NativeStoneApplicationRunner(broker, application)
+    SdlStoneApplicationRunner(IStoneApplication& application) :
+      NativeStoneApplicationRunner(application)
     {
     }
 
diff -r 9d42f89b8c3c -r b537002f83a9 Applications/StoneApplicationContext.cpp
--- a/Applications/StoneApplicationContext.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Applications/StoneApplicationContext.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -32,7 +32,7 @@
       throw Orthanc::OrthancException(Orthanc::ErrorCode_BadSequenceOfCalls);
     }
 
-    orthanc_.reset(new Deprecated::OrthancApiClient(broker_, *webService_, orthancBaseUrl_));
+    orthanc_.reset(new Deprecated::OrthancApiClient(*webService_, orthancBaseUrl_));
   }
 
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Layers/DicomSeriesVolumeSlicer.cpp
--- a/Framework/Deprecated/Layers/DicomSeriesVolumeSlicer.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Layers/DicomSeriesVolumeSlicer.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -87,27 +87,15 @@
   }
 
 
-  DicomSeriesVolumeSlicer::DicomSeriesVolumeSlicer(OrthancStone::MessageBroker& broker,
-                                                   OrthancApiClient& orthanc) :
-    IVolumeSlicer(broker),
-    loader_(broker, orthanc),
+  DicomSeriesVolumeSlicer::DicomSeriesVolumeSlicer(OrthancApiClient& orthanc) :
+    loader_(orthanc),
     quality_(SliceImageQuality_FullPng)
   {
-    loader_.RegisterObserverCallback(
-      new OrthancStone::Callable<DicomSeriesVolumeSlicer, OrthancSlicesLoader::SliceGeometryReadyMessage>
-      (shared_from_this(), &DicomSeriesVolumeSlicer::OnSliceGeometryReady));
-
-    loader_.RegisterObserverCallback(
-      new OrthancStone::Callable<DicomSeriesVolumeSlicer, OrthancSlicesLoader::SliceGeometryErrorMessage>
-      (shared_from_this(), &DicomSeriesVolumeSlicer::OnSliceGeometryError));
-
-    loader_.RegisterObserverCallback(
-      new OrthancStone::Callable<DicomSeriesVolumeSlicer, OrthancSlicesLoader::SliceImageReadyMessage>
-        (shared_from_this(), &DicomSeriesVolumeSlicer::OnSliceImageReady));
-
-    loader_.RegisterObserverCallback(
-      new OrthancStone::Callable<DicomSeriesVolumeSlicer, OrthancSlicesLoader::SliceImageErrorMessage>
-      (shared_from_this(), &DicomSeriesVolumeSlicer::OnSliceImageError));
+    // TODO => Move this out of the constructor
+    Register<OrthancSlicesLoader::SliceGeometryReadyMessage>(loader_, &DicomSeriesVolumeSlicer::OnSliceGeometryReady);
+    Register<OrthancSlicesLoader::SliceGeometryErrorMessage>(loader_, &DicomSeriesVolumeSlicer::OnSliceGeometryError);
+    Register<OrthancSlicesLoader::SliceImageReadyMessage>(loader_, &DicomSeriesVolumeSlicer::OnSliceImageReady);
+    Register<OrthancSlicesLoader::SliceImageErrorMessage>(loader_, &DicomSeriesVolumeSlicer::OnSliceImageError);
   }
 
   
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Layers/DicomSeriesVolumeSlicer.h
--- a/Framework/Deprecated/Layers/DicomSeriesVolumeSlicer.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Layers/DicomSeriesVolumeSlicer.h	Tue Oct 15 15:39:39 2019 +0200
@@ -22,6 +22,7 @@
 #pragma once
 
 #include "IVolumeSlicer.h"
+#include "../../Messages/ObserverBase.h"
 #include "../Toolbox/IWebService.h"
 #include "../Toolbox/OrthancSlicesLoader.h"
 #include "../Toolbox/OrthancApiClient.h"
@@ -83,8 +84,7 @@
     SliceImageQuality    quality_;
 
   public:
-    DicomSeriesVolumeSlicer(OrthancStone::MessageBroker& broker,
-                            OrthancApiClient& orthanc);
+    DicomSeriesVolumeSlicer(OrthancApiClient& orthanc);
 
     void LoadSeries(const std::string& seriesId);
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Layers/DicomStructureSetSlicer.cpp
--- a/Framework/Deprecated/Layers/DicomStructureSetSlicer.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Layers/DicomStructureSetSlicer.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -141,14 +141,10 @@
   };
   
 
-  DicomStructureSetSlicer::DicomStructureSetSlicer(OrthancStone::MessageBroker& broker,
-                                                   StructureSetLoader& loader) :
-    IVolumeSlicer(broker),
+  DicomStructureSetSlicer::DicomStructureSetSlicer(StructureSetLoader& loader) :
     loader_(loader)
   {
-    loader_.RegisterObserverCallback(
-      new OrthancStone::Callable<DicomStructureSetSlicer, StructureSetLoader::ContentChangedMessage>
-      (shared_from_this(), &DicomStructureSetSlicer::OnStructureSetLoaded));
+    Register<StructureSetLoader::ContentChangedMessage>(loader_, &DicomStructureSetSlicer::OnStructureSetLoaded);
   }
 
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Layers/DicomStructureSetSlicer.h
--- a/Framework/Deprecated/Layers/DicomStructureSetSlicer.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Layers/DicomStructureSetSlicer.h	Tue Oct 15 15:39:39 2019 +0200
@@ -42,8 +42,7 @@
     }
 
   public:
-    DicomStructureSetSlicer(OrthancStone::MessageBroker& broker,
-                            StructureSetLoader& loader);
+    DicomStructureSetSlicer(StructureSetLoader& loader);
 
     virtual bool GetExtent(std::vector<OrthancStone::Vector>& points,
                            const OrthancStone::CoordinateSystem3D& viewportPlane)
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Layers/IVolumeSlicer.h
--- a/Framework/Deprecated/Layers/IVolumeSlicer.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Layers/IVolumeSlicer.h	Tue Oct 15 15:39:39 2019 +0200
@@ -122,11 +122,6 @@
     };
 
 
-    IVolumeSlicer(OrthancStone::MessageBroker& broker) :
-      IObservable(broker)
-    {
-    }
-    
     virtual ~IVolumeSlicer()
     {
     }
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/SmartLoader.cpp
--- a/Framework/Deprecated/SmartLoader.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/SmartLoader.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -21,7 +21,6 @@
 
 #include "SmartLoader.h"
 
-#include "../Messages/MessageForwarder.h"
 #include "../StoneException.h"
 #include "Core/Images/Image.h"
 #include "Core/Logging.h"
@@ -68,11 +67,6 @@
     CachedSliceStatus               status_;
 
   public:
-    CachedSlice(OrthancStone::MessageBroker& broker) :
-    IVolumeSlicer(broker)
-    {
-    }
-
     virtual ~CachedSlice()
     {
     }
@@ -106,7 +100,7 @@
 
     CachedSlice* Clone() const
     {
-      CachedSlice* output = new CachedSlice(GetBroker());
+      CachedSlice* output = new CachedSlice;
       output->sliceIndex_ = sliceIndex_;
       output->slice_.reset(slice_->Clone());
       output->image_ = image_;
@@ -119,9 +113,7 @@
   };
 
 
-  SmartLoader::SmartLoader(OrthancStone::MessageBroker& broker,  
-                           OrthancApiClient& orthancApiClient) :
-    IObservable(broker),
+  SmartLoader::SmartLoader(OrthancApiClient& orthancApiClient) :
     imageQuality_(SliceImageQuality_FullPam),
     orthancApiClient_(orthancApiClient)
   {
@@ -150,11 +142,11 @@
     }
     else
     {
-      layerSource.reset(new DicomSeriesVolumeSlicer(IObservable::GetBroker(), orthancApiClient_));
+      layerSource.reset(new DicomSeriesVolumeSlicer(orthancApiClient_));
       dynamic_cast<DicomSeriesVolumeSlicer*>(layerSource.get())->SetImageQuality(imageQuality_);
-      layerSource->RegisterObserverCallback(new OrthancStone::Callable<SmartLoader, IVolumeSlicer::GeometryReadyMessage>(shared_from_this(), &SmartLoader::OnLayerGeometryReady));
-      layerSource->RegisterObserverCallback(new OrthancStone::Callable<SmartLoader, DicomSeriesVolumeSlicer::FrameReadyMessage>(shared_from_this(), &SmartLoader::OnFrameReady));
-      layerSource->RegisterObserverCallback(new OrthancStone::Callable<SmartLoader, IVolumeSlicer::LayerReadyMessage>(shared_from_this(), &SmartLoader::OnLayerReady));
+      Register<IVolumeSlicer::GeometryReadyMessage>(*layerSource, &SmartLoader::OnLayerGeometryReady);
+      Register<DicomSeriesVolumeSlicer::FrameReadyMessage>(*layerSource, &SmartLoader::OnFrameReady);
+      Register<IVolumeSlicer::LayerReadyMessage>(*layerSource, &SmartLoader::OnLayerReady);
       dynamic_cast<DicomSeriesVolumeSlicer*>(layerSource.get())->LoadFrame(instanceId, frame);
     }
 
@@ -189,7 +181,7 @@
 
 
     // create the slice in the cache with "empty" data
-    boost::shared_ptr<CachedSlice> cachedSlice(new CachedSlice(IObservable::GetBroker()));
+    boost::shared_ptr<CachedSlice> cachedSlice(new CachedSlice);
     cachedSlice->slice_.reset(new Slice(instanceId, frame));
     cachedSlice->status_ = CachedSliceStatus_ScheduledToLoad;
     std::string sliceKeyId = instanceId + ":" + boost::lexical_cast<std::string>(frame);
@@ -198,12 +190,12 @@
 
     cachedSlices_[sliceKeyId] = boost::shared_ptr<CachedSlice>(cachedSlice);
 
-    std::auto_ptr<IVolumeSlicer> layerSource(new DicomSeriesVolumeSlicer(IObservable::GetBroker(), orthancApiClient_));
+    std::auto_ptr<IVolumeSlicer> layerSource(new DicomSeriesVolumeSlicer(orthancApiClient_));
 
     dynamic_cast<DicomSeriesVolumeSlicer*>(layerSource.get())->SetImageQuality(imageQuality_);
-    layerSource->RegisterObserverCallback(new OrthancStone::Callable<SmartLoader, IVolumeSlicer::GeometryReadyMessage>(shared_from_this(), &SmartLoader::OnLayerGeometryReady));
-    layerSource->RegisterObserverCallback(new OrthancStone::Callable<SmartLoader, DicomSeriesVolumeSlicer::FrameReadyMessage>(shared_from_this(), &SmartLoader::OnFrameReady));
-    layerSource->RegisterObserverCallback(new OrthancStone::Callable<SmartLoader, IVolumeSlicer::LayerReadyMessage>(shared_from_this(), &SmartLoader::OnLayerReady));
+    Register<IVolumeSlicer::GeometryReadyMessage>(*layerSource, &SmartLoader::OnLayerGeometryReady);
+    Register<DicomSeriesVolumeSlicer::FrameReadyMessage>(*layerSource, &SmartLoader::OnFrameReady);
+    Register<IVolumeSlicer::LayerReadyMessage>(*layerSource, &SmartLoader::OnLayerReady);
     dynamic_cast<DicomSeriesVolumeSlicer*>(layerSource.get())->LoadFrame(instanceId, frame);
 
     // keep a ref to the VolumeSlicer until the slice is fully loaded and saved to cache
@@ -234,7 +226,7 @@
 
     LOG(WARNING) << "Geometry ready: " << sliceKeyId;
 
-    boost::shared_ptr<CachedSlice> cachedSlice(new CachedSlice(IObservable::GetBroker()));
+    boost::shared_ptr<CachedSlice> cachedSlice(new CachedSlice);
     cachedSlice->slice_.reset(slice.Clone());
     cachedSlice->effectiveQuality_ = source.GetImageQuality();
     cachedSlice->status_ = CachedSliceStatus_GeometryLoaded;
@@ -255,7 +247,7 @@
 
     LOG(WARNING) << "Image ready: " << sliceKeyId;
 
-    boost::shared_ptr<CachedSlice> cachedSlice(new CachedSlice(IObservable::GetBroker()));
+    boost::shared_ptr<CachedSlice> cachedSlice(new CachedSlice);
     cachedSlice->image_.reset(Orthanc::Image::Clone(message.GetFrame()));
     cachedSlice->effectiveQuality_ = message.GetImageQuality();
     cachedSlice->slice_.reset(message.GetSlice().Clone());
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/SmartLoader.h
--- a/Framework/Deprecated/SmartLoader.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/SmartLoader.h	Tue Oct 15 15:39:39 2019 +0200
@@ -45,7 +45,7 @@
     OrthancApiClient&     orthancApiClient_;
 
   public:
-    SmartLoader(OrthancStone::MessageBroker& broker, OrthancApiClient& orthancApiClient);  // TODO: add maxPreloadStorageSizeInBytes
+    SmartLoader(OrthancApiClient& orthancApiClient);  // TODO: add maxPreloadStorageSizeInBytes
 
 //    void PreloadStudy(const std::string studyId);
 //    void PreloadSeries(const std::string seriesId);
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Toolbox/BaseWebService.h
--- a/Framework/Deprecated/Toolbox/BaseWebService.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Toolbox/BaseWebService.h	Tue Oct 15 15:39:39 2019 +0200
@@ -22,6 +22,7 @@
 #pragma once
 
 #include "IWebService.h"
+#include "../../Messages/ObserverBase.h"
 
 #include <string>
 #include <map>
@@ -90,9 +91,7 @@
     std::deque<std::string> orderedCacheKeys_;
 
   public:
-
-    BaseWebService(OrthancStone::MessageBroker& broker) :
-      IWebService(broker),
+    BaseWebService() :
       cacheEnabled_(false),
       cacheCurrentSize_(0),
       cacheMaxSize_(100*1024*1024)
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Toolbox/OrthancApiClient.cpp
--- a/Framework/Deprecated/Toolbox/OrthancApiClient.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Toolbox/OrthancApiClient.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -127,35 +127,26 @@
     {
       if (emptyHandler_.get() != NULL)
       {
-        if (broker_.IsActive(*(emptyHandler_->GetObserver())))
-        {
-          emptyHandler_->Apply(OrthancApiClient::EmptyResponseReadyMessage
-                               (message.GetUri(), userPayload_.get()));
-        }
+        emptyHandler_->Apply(OrthancApiClient::EmptyResponseReadyMessage
+                             (message.GetUri(), userPayload_.get()));
       }
       else if (binaryHandler_.get() != NULL)
       {
-        if (broker_.IsActive(*(binaryHandler_->GetObserver())))
-        {
-          binaryHandler_->Apply(OrthancApiClient::BinaryResponseReadyMessage
-                                (message.GetUri(), message.GetAnswer(),
-                                 message.GetAnswerSize(), userPayload_.get()));
-        }
+        binaryHandler_->Apply(OrthancApiClient::BinaryResponseReadyMessage
+                              (message.GetUri(), message.GetAnswer(),
+                               message.GetAnswerSize(), userPayload_.get()));
       }
       else if (jsonHandler_.get() != NULL)
       {
-        if (broker_.IsActive(*(jsonHandler_->GetObserver())))
+        Json::Value response;
+        if (MessagingToolbox::ParseJson(response, message.GetAnswer(), message.GetAnswerSize()))
         {
-          Json::Value response;
-          if (MessagingToolbox::ParseJson(response, message.GetAnswer(), message.GetAnswerSize()))
-          {
-            jsonHandler_->Apply(OrthancApiClient::JsonResponseReadyMessage
-                                (message.GetUri(), response, userPayload_.get()));
-          }
-          else
-          {
-            NotifyConversionError(message);
-          }
+          jsonHandler_->Apply(OrthancApiClient::JsonResponseReadyMessage
+                              (message.GetUri(), response, userPayload_.get()));
+        }
+        else
+        {
+          NotifyConversionError(message);
         }
       }
       else
@@ -175,11 +166,8 @@
   };
 
 
-  OrthancApiClient::OrthancApiClient(OrthancStone::MessageBroker& broker,
-                                     IWebService& web,
+  OrthancApiClient::OrthancApiClient(IWebService& web,
                                      const std::string& baseUrl) :
-    IObservable(broker),
-    IObserver(broker),
     web_(web),
     baseUrl_(baseUrl)
   {
@@ -195,11 +183,11 @@
     IWebService::HttpHeaders emptyHeaders;
     web_.GetAsync(baseUrl_ + uri,
                   emptyHeaders,
-                  new WebServicePayload(IObservable::GetBroker(), successCallback, failureCallback, payload),
+                  new WebServicePayload(successCallback, failureCallback, payload),
                   new OrthancStone::Callable<OrthancApiClient, IWebService::HttpRequestSuccessMessage>
-                  (*this, &OrthancApiClient::NotifyHttpSuccess),
+                  (GetSharedObserver(), &OrthancApiClient::NotifyHttpSuccess),
                   new OrthancStone::Callable<OrthancApiClient, IWebService::HttpRequestErrorMessage>
-                  (*this, &OrthancApiClient::NotifyHttpError));
+                  (GetSharedObserver(), &OrthancApiClient::NotifyHttpError));
   }
 
 
@@ -225,11 +213,11 @@
     // printf("GET [%s] [%s]\n", baseUrl_.c_str(), uri.c_str());
 
     web_.GetAsync(baseUrl_ + uri, headers,
-                  new WebServicePayload(IObservable::GetBroker(), successCallback, failureCallback, payload),
+                  new WebServicePayload(successCallback, failureCallback, payload),
                   new OrthancStone::Callable<OrthancApiClient, IWebService::HttpRequestSuccessMessage>
-                  (*this, &OrthancApiClient::NotifyHttpSuccess),
+                  (GetSharedObserver(), &OrthancApiClient::NotifyHttpSuccess),
                   new OrthancStone::Callable<OrthancApiClient, IWebService::HttpRequestErrorMessage>
-                  (*this, &OrthancApiClient::NotifyHttpError));
+                  (GetSharedObserver(), &OrthancApiClient::NotifyHttpError));
   }
 
   
@@ -241,11 +229,11 @@
       Orthanc::IDynamicObject* payload)
   {
     web_.PostAsync(baseUrl_ + uri, IWebService::HttpHeaders(), body,
-                   new WebServicePayload(IObservable::GetBroker(), successCallback, failureCallback, payload),
+                   new WebServicePayload(successCallback, failureCallback, payload),
                    new OrthancStone::Callable<OrthancApiClient, IWebService::HttpRequestSuccessMessage>
-                   (*this, &OrthancApiClient::NotifyHttpSuccess),
+                   (GetSharedObserver(), &OrthancApiClient::NotifyHttpSuccess),
                    new OrthancStone::Callable<OrthancApiClient, IWebService::HttpRequestErrorMessage>
-                   (*this, &OrthancApiClient::NotifyHttpError));
+                   (GetSharedObserver(), &OrthancApiClient::NotifyHttpError));
 
   }
 
@@ -264,11 +252,11 @@
       Orthanc::IDynamicObject* payload   /* takes ownership */)
   {
     web_.PostAsync(baseUrl_ + uri, IWebService::HttpHeaders(), body,
-                   new WebServicePayload(IObservable::GetBroker(), successCallback, failureCallback, payload),
+                   new WebServicePayload(successCallback, failureCallback, payload),
                    new OrthancStone::Callable<OrthancApiClient, IWebService::HttpRequestSuccessMessage>
-                   (*this, &OrthancApiClient::NotifyHttpSuccess),
+                   (GetSharedObserver(), &OrthancApiClient::NotifyHttpSuccess),
                    new OrthancStone::Callable<OrthancApiClient, IWebService::HttpRequestErrorMessage>
-                   (*this, &OrthancApiClient::NotifyHttpError));
+                   (GetSharedObserver(), &OrthancApiClient::NotifyHttpError));
   }
 
   void OrthancApiClient::PostJsonAsyncExpectJson(
@@ -311,11 +299,11 @@
       Orthanc::IDynamicObject* payload)
   {
     web_.DeleteAsync(baseUrl_ + uri, IWebService::HttpHeaders(),
-                     new WebServicePayload(IObservable::GetBroker(), successCallback, failureCallback, payload),
+                     new WebServicePayload(successCallback, failureCallback, payload),
                      new OrthancStone::Callable<OrthancApiClient, IWebService::HttpRequestSuccessMessage>
-                     (*this, &OrthancApiClient::NotifyHttpSuccess),
+                     (GetSharedObserver(), &OrthancApiClient::NotifyHttpSuccess),
                      new OrthancStone::Callable<OrthancApiClient, IWebService::HttpRequestErrorMessage>
-                     (*this, &OrthancApiClient::NotifyHttpError));
+                     (GetSharedObserver(), &OrthancApiClient::NotifyHttpError));
   }
 
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Toolbox/OrthancApiClient.h
--- a/Framework/Deprecated/Toolbox/OrthancApiClient.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Toolbox/OrthancApiClient.h	Tue Oct 15 15:39:39 2019 +0200
@@ -25,13 +25,13 @@
 #include <json/json.h>
 
 #include "IWebService.h"
-#include "../../Messages/IObservable.h"
+#include "../../Messages/ObserverBase.h"
 
 namespace Deprecated
 {
   class OrthancApiClient :
       public OrthancStone::IObservable,
-      public OrthancStone::IObserver
+      public OrthancStone::ObserverBase<OrthancApiClient>
   {
   public:
     class JsonResponseReadyMessage : public OrthancStone::IMessage
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Toolbox/OrthancSlicesLoader.cpp
--- a/Framework/Deprecated/Toolbox/OrthancSlicesLoader.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Toolbox/OrthancSlicesLoader.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -639,10 +639,7 @@
   }
   
   
-  OrthancSlicesLoader::OrthancSlicesLoader(OrthancStone::MessageBroker& broker,
-                                           OrthancApiClient& orthanc) :
-    OrthancStone::IObservable(broker),
-    OrthancStone::IObserver(broker),
+  OrthancSlicesLoader::OrthancSlicesLoader(OrthancApiClient& orthanc) :
     orthanc_(orthanc),
     state_(State_Initialization)
   {
@@ -659,8 +656,8 @@
     {
       state_ = State_LoadingGeometry;
       orthanc_.GetJsonAsync("/series/" + seriesId + "/instances-tags",
-                            new OrthancStone::Callable<OrthancSlicesLoader, OrthancApiClient::JsonResponseReadyMessage>(*this, &OrthancSlicesLoader::ParseSeriesGeometry),
-                            new OrthancStone::Callable<OrthancSlicesLoader, IWebService::HttpRequestErrorMessage>(*this, &OrthancSlicesLoader::OnGeometryError),
+                            new OrthancStone::Callable<OrthancSlicesLoader, OrthancApiClient::JsonResponseReadyMessage>(GetSharedObserver(), &OrthancSlicesLoader::ParseSeriesGeometry),
+                            new OrthancStone::Callable<OrthancSlicesLoader, IWebService::HttpRequestErrorMessage>(GetSharedObserver(), &OrthancSlicesLoader::OnGeometryError),
                             NULL);
     }
   }
@@ -678,8 +675,8 @@
       // Tag "3004-000c" is "Grid Frame Offset Vector", which is
       // mandatory to read RT DOSE, but is too long to be returned by default
       orthanc_.GetJsonAsync("/instances/" + instanceId + "/tags?ignore-length=3004-000c",
-                            new OrthancStone::Callable<OrthancSlicesLoader, OrthancApiClient::JsonResponseReadyMessage>(*this, &OrthancSlicesLoader::ParseInstanceGeometry),
-                            new OrthancStone::Callable<OrthancSlicesLoader, IWebService::HttpRequestErrorMessage>(*this, &OrthancSlicesLoader::OnGeometryError),
+                            new OrthancStone::Callable<OrthancSlicesLoader, OrthancApiClient::JsonResponseReadyMessage>(GetSharedObserver(), &OrthancSlicesLoader::ParseInstanceGeometry),
+                            new OrthancStone::Callable<OrthancSlicesLoader, IWebService::HttpRequestErrorMessage>(GetSharedObserver(), &OrthancSlicesLoader::OnGeometryError),
                             Operation::DownloadInstanceGeometry(instanceId));
     }
   }
@@ -697,8 +694,8 @@
       state_ = State_LoadingGeometry;
 
       orthanc_.GetJsonAsync("/instances/" + instanceId + "/tags",
-                            new OrthancStone::Callable<OrthancSlicesLoader, OrthancApiClient::JsonResponseReadyMessage>(*this, &OrthancSlicesLoader::ParseFrameGeometry),
-                            new OrthancStone::Callable<OrthancSlicesLoader, IWebService::HttpRequestErrorMessage>(*this, &OrthancSlicesLoader::OnGeometryError),
+                            new OrthancStone::Callable<OrthancSlicesLoader, OrthancApiClient::JsonResponseReadyMessage>(GetSharedObserver(), &OrthancSlicesLoader::ParseFrameGeometry),
+                            new OrthancStone::Callable<OrthancSlicesLoader, IWebService::HttpRequestErrorMessage>(GetSharedObserver(), &OrthancSlicesLoader::OnGeometryError),
                             Operation::DownloadFrameGeometry(instanceId, frame));
     }
   }
@@ -771,22 +768,22 @@
     }
     
     orthanc_.GetBinaryAsync(uri, "image/png",
-      new OrthancStone::Callable<OrthancSlicesLoader, 
-        OrthancApiClient::BinaryResponseReadyMessage>
-          (*this, &OrthancSlicesLoader::ParseSliceImagePng),
-      new OrthancStone::Callable<OrthancSlicesLoader, 
-        IWebService::HttpRequestErrorMessage>
-          (*this, &OrthancSlicesLoader::OnSliceImageError),
-      Operation::DownloadSliceImage(
-        static_cast<unsigned int>(index), slice, SliceImageQuality_FullPng));
-}
+                            new OrthancStone::Callable<OrthancSlicesLoader, 
+                            OrthancApiClient::BinaryResponseReadyMessage>
+                            (GetSharedObserver(), &OrthancSlicesLoader::ParseSliceImagePng),
+                            new OrthancStone::Callable<OrthancSlicesLoader, 
+                            IWebService::HttpRequestErrorMessage>
+                            (GetSharedObserver(), &OrthancSlicesLoader::OnSliceImageError),
+                            Operation::DownloadSliceImage(
+                              static_cast<unsigned int>(index), slice, SliceImageQuality_FullPng));
+  }
   
   void OrthancSlicesLoader::ScheduleSliceImagePam(const Slice& slice,
                                                   size_t index)
   {
     std::string uri = 
       ("/instances/" + slice.GetOrthancInstanceId() + "/frames/" +
-      boost::lexical_cast<std::string>(slice.GetFrame()));
+       boost::lexical_cast<std::string>(slice.GetFrame()));
 
     switch (slice.GetConverter().GetExpectedPixelFormat())
     {
@@ -807,14 +804,14 @@
     }
 
     orthanc_.GetBinaryAsync(uri, "image/x-portable-arbitrarymap",
-      new OrthancStone::Callable<OrthancSlicesLoader, 
-        OrthancApiClient::BinaryResponseReadyMessage>
-          (*this, &OrthancSlicesLoader::ParseSliceImagePam),
-      new OrthancStone::Callable<OrthancSlicesLoader, 
-        IWebService::HttpRequestErrorMessage>
-          (*this, &OrthancSlicesLoader::OnSliceImageError),
-      Operation::DownloadSliceImage(static_cast<unsigned int>(index), 
-                                    slice, SliceImageQuality_FullPam));
+                            new OrthancStone::Callable<OrthancSlicesLoader, 
+                            OrthancApiClient::BinaryResponseReadyMessage>
+                            (GetSharedObserver(), &OrthancSlicesLoader::ParseSliceImagePam),
+                            new OrthancStone::Callable<OrthancSlicesLoader, 
+                            IWebService::HttpRequestErrorMessage>
+                            (GetSharedObserver(), &OrthancSlicesLoader::OnSliceImageError),
+                            Operation::DownloadSliceImage(static_cast<unsigned int>(index), 
+                                                          slice, SliceImageQuality_FullPam));
   }
 
 
@@ -850,14 +847,14 @@
                        boost::lexical_cast<std::string>(slice.GetFrame()));
 
     orthanc_.GetJsonAsync(uri,
-      new OrthancStone::Callable<OrthancSlicesLoader, 
-        OrthancApiClient::JsonResponseReadyMessage>
-          (*this, &OrthancSlicesLoader::ParseSliceImageJpeg),
-      new OrthancStone::Callable<OrthancSlicesLoader, 
-        IWebService::HttpRequestErrorMessage>
-          (*this, &OrthancSlicesLoader::OnSliceImageError),
-        Operation::DownloadSliceImage(
-          static_cast<unsigned int>(index), slice, quality));
+                          new OrthancStone::Callable<OrthancSlicesLoader, 
+                          OrthancApiClient::JsonResponseReadyMessage>
+                          (GetSharedObserver(), &OrthancSlicesLoader::ParseSliceImageJpeg),
+                          new OrthancStone::Callable<OrthancSlicesLoader, 
+                          IWebService::HttpRequestErrorMessage>
+                          (GetSharedObserver(), &OrthancSlicesLoader::OnSliceImageError),
+                          Operation::DownloadSliceImage(
+                            static_cast<unsigned int>(index), slice, quality));
   }
   
   
@@ -891,14 +888,14 @@
       std::string uri = ("/instances/" + slice.GetOrthancInstanceId() + "/frames/" +
                          boost::lexical_cast<std::string>(slice.GetFrame()) + "/raw.gz");
       orthanc_.GetBinaryAsync(uri, IWebService::HttpHeaders(),
-        new OrthancStone::Callable<OrthancSlicesLoader, 
-          OrthancApiClient::BinaryResponseReadyMessage>
-            (*this, &OrthancSlicesLoader::ParseSliceRawImage),
-        new OrthancStone::Callable<OrthancSlicesLoader,
-          IWebService::HttpRequestErrorMessage>
-            (*this, &OrthancSlicesLoader::OnSliceImageError),
-        Operation::DownloadSliceRawImage(
-          static_cast<unsigned int>(index), slice));
+                              new OrthancStone::Callable<OrthancSlicesLoader, 
+                              OrthancApiClient::BinaryResponseReadyMessage>
+                              (GetSharedObserver(), &OrthancSlicesLoader::ParseSliceRawImage),
+                              new OrthancStone::Callable<OrthancSlicesLoader,
+                              IWebService::HttpRequestErrorMessage>
+                              (GetSharedObserver(), &OrthancSlicesLoader::OnSliceImageError),
+                              Operation::DownloadSliceRawImage(
+                                static_cast<unsigned int>(index), slice));
     }
   }
 }
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Toolbox/OrthancSlicesLoader.h
--- a/Framework/Deprecated/Toolbox/OrthancSlicesLoader.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Toolbox/OrthancSlicesLoader.h	Tue Oct 15 15:39:39 2019 +0200
@@ -22,6 +22,7 @@
 #pragma once
 
 #include "../../Messages/IObservable.h"
+#include "../../Messages/ObserverBase.h"
 #include "../../StoneEnumerations.h"
 #include "../../Toolbox/SlicesSorter.h"
 #include "IWebService.h"
@@ -33,7 +34,9 @@
 
 namespace Deprecated
 {
-  class OrthancSlicesLoader : public OrthancStone::IObservable, public OrthancStone::IObserver
+  class OrthancSlicesLoader :
+    public OrthancStone::IObservable,
+    public OrthancStone::ObserverBase<OrthancSlicesLoader>
   {
   public:
     ORTHANC_STONE_DEFINE_ORIGIN_MESSAGE(__FILE__, __LINE__, SliceGeometryReadyMessage, OrthancSlicesLoader);
@@ -183,8 +186,7 @@
     void SortAndFinalizeSlices();
     
   public:
-    OrthancSlicesLoader(OrthancStone::MessageBroker& broker,
-                        //ISliceLoaderObserver& callback,
+    OrthancSlicesLoader(//ISliceLoaderObserver& callback,
                         OrthancApiClient& orthancApi);
 
     void ScheduleLoadSeries(const std::string& seriesId);
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Volumes/StructureSetLoader.cpp
--- a/Framework/Deprecated/Volumes/StructureSetLoader.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Volumes/StructureSetLoader.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -27,10 +27,7 @@
 
 namespace Deprecated
 {
-  StructureSetLoader::StructureSetLoader(OrthancStone::MessageBroker& broker,
-                                         OrthancApiClient& orthanc) :
-    IVolumeLoader(broker),
-    IObserver(broker),
+  StructureSetLoader::StructureSetLoader(OrthancApiClient& orthanc) :
     orthanc_(orthanc)
   {
   }
@@ -60,7 +57,7 @@
          it != instances.end(); ++it)
     {
       orthanc_.PostBinaryAsyncExpectJson("/tools/lookup", *it,
-                                         new OrthancStone::Callable<StructureSetLoader, OrthancApiClient::JsonResponseReadyMessage>(*this, &StructureSetLoader::OnLookupCompleted));
+                                         new OrthancStone::Callable<StructureSetLoader, OrthancApiClient::JsonResponseReadyMessage>(GetSharedObserver(), &StructureSetLoader::OnLookupCompleted));
     }
 
     BroadcastMessage(GeometryReadyMessage(*this));
@@ -84,7 +81,7 @@
 
     const std::string& instance = lookup[0]["ID"].asString();
     orthanc_.GetJsonAsync("/instances/" + instance + "/tags",
-                          new OrthancStone::Callable<StructureSetLoader, OrthancApiClient::JsonResponseReadyMessage>(*this, &StructureSetLoader::OnReferencedSliceLoaded));
+                          new OrthancStone::Callable<StructureSetLoader, OrthancApiClient::JsonResponseReadyMessage>(GetSharedObserver(), &StructureSetLoader::OnReferencedSliceLoaded));
   }
 
   
@@ -97,7 +94,7 @@
     else
     {
       orthanc_.GetJsonAsync("/instances/" + instance + "/tags?ignore-length=3006-0050",
-                            new OrthancStone::Callable<StructureSetLoader, OrthancApiClient::JsonResponseReadyMessage>(*this, &StructureSetLoader::OnStructureSetLoaded));
+                            new OrthancStone::Callable<StructureSetLoader, OrthancApiClient::JsonResponseReadyMessage>(GetSharedObserver(), &StructureSetLoader::OnStructureSetLoaded));
     }
   }
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Volumes/StructureSetLoader.h
--- a/Framework/Deprecated/Volumes/StructureSetLoader.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Volumes/StructureSetLoader.h	Tue Oct 15 15:39:39 2019 +0200
@@ -21,6 +21,7 @@
 
 #pragma once
 
+#include "../../Messages/ObserverBase.h"
 #include "../../Toolbox/DicomStructureSet.h"
 #include "../Toolbox/OrthancApiClient.h"
 #include "IVolumeLoader.h"
@@ -29,7 +30,7 @@
 {
   class StructureSetLoader :
     public IVolumeLoader,
-    public OrthancStone::IObserver
+    public OrthancStone::ObserverBase<StructureSetLoader>
   {
   private:
     OrthancApiClient&                 orthanc_;
@@ -42,8 +43,7 @@
     void OnLookupCompleted(const OrthancApiClient::JsonResponseReadyMessage& message);
 
   public:
-    StructureSetLoader(OrthancStone::MessageBroker& broker,
-                       OrthancApiClient& orthanc);
+    StructureSetLoader(OrthancApiClient& orthanc);
 
     void ScheduleLoadInstance(const std::string& instance);
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Widgets/SliceViewerWidget.cpp
--- a/Framework/Deprecated/Widgets/SliceViewerWidget.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Widgets/SliceViewerWidget.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -364,11 +364,8 @@
   }
 
   
-  SliceViewerWidget::SliceViewerWidget(OrthancStone::MessageBroker& broker, 
-                                       const std::string& name) :
+  SliceViewerWidget::SliceViewerWidget(const std::string& name) :
     WorldSceneWidget(name),
-    IObserver(broker),
-    IObservable(broker),
     started_(false)
   {
     SetBackgroundCleared(true);
@@ -385,17 +382,13 @@
   
   void SliceViewerWidget::ObserveLayer(IVolumeSlicer& layer)
   {
-    layer.RegisterObserverCallback(new OrthancStone::Callable<SliceViewerWidget, IVolumeSlicer::GeometryReadyMessage>
-                                   (*this, &SliceViewerWidget::OnGeometryReady));
-    // currently ignore errors layer->RegisterObserverCallback(new Callable<SliceViewerWidget, IVolumeSlicer::GeometryErrorMessage>(*this, &SliceViewerWidget::...));
-    layer.RegisterObserverCallback(new OrthancStone::Callable<SliceViewerWidget, IVolumeSlicer::SliceContentChangedMessage>
-                                   (*this, &SliceViewerWidget::OnSliceChanged));
-    layer.RegisterObserverCallback(new OrthancStone::Callable<SliceViewerWidget, IVolumeSlicer::ContentChangedMessage>
-                                   (*this, &SliceViewerWidget::OnContentChanged));
-    layer.RegisterObserverCallback(new OrthancStone::Callable<SliceViewerWidget, IVolumeSlicer::LayerReadyMessage>
-                                   (*this, &SliceViewerWidget::OnLayerReady));
-    layer.RegisterObserverCallback(new OrthancStone::Callable<SliceViewerWidget, IVolumeSlicer::LayerErrorMessage>
-                                   (*this, &SliceViewerWidget::OnLayerError));
+    // currently ignoring errors of type IVolumeSlicer::GeometryErrorMessage
+
+    Register<IVolumeSlicer::GeometryReadyMessage>(layer, &SliceViewerWidget::OnGeometryReady);
+    Register<IVolumeSlicer::SliceContentChangedMessage>(layer, &SliceViewerWidget::OnSliceChanged);
+    Register<IVolumeSlicer::ContentChangedMessage>(layer, &SliceViewerWidget::OnContentChanged);
+    Register<IVolumeSlicer::LayerReadyMessage>(layer, &SliceViewerWidget::OnLayerReady);
+    Register<IVolumeSlicer::LayerErrorMessage>(layer, &SliceViewerWidget::OnLayerError);
   }
 
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Deprecated/Widgets/SliceViewerWidget.h
--- a/Framework/Deprecated/Widgets/SliceViewerWidget.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Deprecated/Widgets/SliceViewerWidget.h	Tue Oct 15 15:39:39 2019 +0200
@@ -24,7 +24,7 @@
 #include "WorldSceneWidget.h"
 #include "../Layers/IVolumeSlicer.h"
 #include "../../Toolbox/Extent2D.h"
-#include "../../Messages/IObserver.h"
+#include "../../Messages/ObserverBase.h"
 
 #include <map>
 
@@ -32,7 +32,7 @@
 {
   class SliceViewerWidget :
     public WorldSceneWidget,
-    public OrthancStone::IObserver,
+    public OrthancStone::ObserverBase<SliceViewerWidget>,
     public OrthancStone::IObservable
   {
   public:
@@ -100,8 +100,7 @@
     void ResetChangedLayers();
 
   public:
-    SliceViewerWidget(OrthancStone::MessageBroker& broker, 
-                      const std::string& name);
+    SliceViewerWidget(const std::string& name);
 
     virtual OrthancStone::Extent2D GetSceneExtent();
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyAlphaLayer.h
--- a/Framework/Radiography/RadiographyAlphaLayer.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyAlphaLayer.h	Tue Oct 15 15:39:39 2019 +0200
@@ -38,8 +38,8 @@
     float                                  foreground_;
 
   public:
-    RadiographyAlphaLayer(MessageBroker& broker, const RadiographyScene& scene) :
-      RadiographyLayer(broker, scene),
+    RadiographyAlphaLayer(const RadiographyScene& scene) :
+      RadiographyLayer(scene),
       useWindowing_(true),
       foreground_(0)
     {
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyDicomLayer.cpp
--- a/Framework/Radiography/RadiographyDicomLayer.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyDicomLayer.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -47,7 +47,8 @@
   }
 
 
-  RadiographyDicomLayer::RadiographyDicomLayer(MessageBroker& broker, const RadiographyScene& scene) : RadiographyLayer(broker, scene)
+  RadiographyDicomLayer::RadiographyDicomLayer(const RadiographyScene& scene) :
+    RadiographyLayer(scene)
   {
 
   }
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyDicomLayer.h
--- a/Framework/Radiography/RadiographyDicomLayer.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyDicomLayer.h	Tue Oct 15 15:39:39 2019 +0200
@@ -42,7 +42,7 @@
     void ApplyConverter();
 
   public:
-    RadiographyDicomLayer(MessageBroker& broker, const RadiographyScene& scene);
+    RadiographyDicomLayer(const RadiographyScene& scene);
 
     void SetInstance(const std::string& instanceId, unsigned int frame)
     {
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyLayer.cpp
--- a/Framework/Radiography/RadiographyLayer.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyLayer.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -119,8 +119,7 @@
   }
 
 
-  RadiographyLayer::RadiographyLayer(MessageBroker& broker, const RadiographyScene& scene) :
-    IObservable(broker),
+  RadiographyLayer::RadiographyLayer(const RadiographyScene& scene) :
     index_(0),
     hasSize_(false),
     width_(0),
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyLayer.h
--- a/Framework/Radiography/RadiographyLayer.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyLayer.h	Tue Oct 15 15:39:39 2019 +0200
@@ -248,7 +248,7 @@
                      double zoom);
 
   public:
-    RadiographyLayer(MessageBroker& broker, const RadiographyScene& scene);
+    RadiographyLayer(const RadiographyScene& scene);
 
     virtual ~RadiographyLayer()
     {
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyMaskLayer.h
--- a/Framework/Radiography/RadiographyMaskLayer.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyMaskLayer.h	Tue Oct 15 15:39:39 2019 +0200
@@ -40,9 +40,9 @@
 
     mutable std::auto_ptr<Orthanc::ImageAccessor>  mask_;
   public:
-    RadiographyMaskLayer(MessageBroker& broker, const RadiographyScene& scene, const RadiographyDicomLayer& dicomLayer,
+    RadiographyMaskLayer(const RadiographyScene& scene, const RadiographyDicomLayer& dicomLayer,
                          float foreground) :
-      RadiographyLayer(broker, scene),
+      RadiographyLayer(scene),
       dicomLayer_(dicomLayer),
       invalidated_(true),
       foreground_(foreground)
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyScene.cpp
--- a/Framework/Radiography/RadiographyScene.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyScene.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -142,7 +142,7 @@
 
     BroadcastMessage(GeometryChangedMessage(*this, *layer));
     BroadcastMessage(ContentChangedMessage(*this, *layer));
-    layer->RegisterObserverCallback(new Callable<RadiographyScene, RadiographyLayer::LayerEditedMessage>(*this, &RadiographyScene::OnLayerEdited));
+    Register<RadiographyLayer::LayerEditedMessage>(*layer, &RadiographyScene::OnLayerEdited);
 
     return *layer;
   }
@@ -162,9 +162,7 @@
     BroadcastMessage(RadiographyScene::LayerEditedMessage(*this, message.GetOrigin()));
   }
 
-  RadiographyScene::RadiographyScene(MessageBroker& broker) :
-    IObserver(broker),
-    IObservable(broker),
+  RadiographyScene::RadiographyScene() :
     countLayers_(0),
     hasWindowing_(false),
     windowingCenter_(0),  // Dummy initialization
@@ -284,7 +282,7 @@
                                                const std::string& utf8,
                                                RadiographyLayer::Geometry* geometry)
   {
-    std::auto_ptr<RadiographyTextLayer>  alpha(new RadiographyTextLayer(IObservable::GetBroker(), *this));
+    std::auto_ptr<RadiographyTextLayer>  alpha(new RadiographyTextLayer(*this));
     alpha->LoadText(font, utf8);
     if (geometry != NULL)
     {
@@ -328,7 +326,7 @@
                                                float foreground,
                                                RadiographyLayer::Geometry* geometry)
   {
-    std::auto_ptr<RadiographyMaskLayer>  mask(new RadiographyMaskLayer(IObservable::GetBroker(), *this, dicomLayer, foreground));
+    std::auto_ptr<RadiographyMaskLayer>  mask(new RadiographyMaskLayer(*this, dicomLayer, foreground));
     mask->SetCorners(corners);
     if (geometry != NULL)
     {
@@ -341,7 +339,7 @@
 
   RadiographyLayer& RadiographyScene::LoadAlphaBitmap(Orthanc::ImageAccessor* bitmap, RadiographyLayer::Geometry *geometry)
   {
-    std::auto_ptr<RadiographyAlphaLayer>  alpha(new RadiographyAlphaLayer(IObservable::GetBroker(), *this));
+    std::auto_ptr<RadiographyAlphaLayer>  alpha(new RadiographyAlphaLayer(*this));
     alpha->SetAlpha(bitmap);
     if (geometry != NULL)
     {
@@ -358,7 +356,7 @@
                                                      RadiographyPhotometricDisplayMode preferredPhotometricDisplayMode,
                                                      RadiographyLayer::Geometry* geometry)
   {
-    RadiographyDicomLayer& layer = dynamic_cast<RadiographyDicomLayer&>(RegisterLayer(new RadiographyDicomLayer(IObservable::GetBroker(), *this)));
+    RadiographyDicomLayer& layer = dynamic_cast<RadiographyDicomLayer&>(RegisterLayer(new RadiographyDicomLayer(*this)));
 
     layer.SetInstance(instance, frame);
 
@@ -380,7 +378,7 @@
                                                      bool httpCompression,
                                                      RadiographyLayer::Geometry* geometry)
   {
-    RadiographyDicomLayer& layer = dynamic_cast<RadiographyDicomLayer&>(RegisterLayer(new RadiographyDicomLayer(IObservable::GetBroker(), *this)));
+    RadiographyDicomLayer& layer = dynamic_cast<RadiographyDicomLayer&>(RegisterLayer(new RadiographyDicomLayer( *this)));
     layer.SetInstance(instance, frame);
 
     if (geometry != NULL)
@@ -395,7 +393,7 @@
       orthanc.GetBinaryAsync(
             uri, headers,
             new Callable<RadiographyScene, Deprecated::OrthancApiClient::BinaryResponseReadyMessage>
-            (*this, &RadiographyScene::OnTagsReceived), NULL,
+            (GetSharedObserver(), &RadiographyScene::OnTagsReceived), NULL,
             new Orthanc::SingleValueObject<size_t>(layer.GetIndex()));
     }
 
@@ -414,7 +412,7 @@
       orthanc.GetBinaryAsync(
             uri, headers,
             new Callable<RadiographyScene, Deprecated::OrthancApiClient::BinaryResponseReadyMessage>
-            (*this, &RadiographyScene::OnFrameReceived), NULL,
+            (GetSharedObserver(), &RadiographyScene::OnFrameReceived), NULL,
             new Orthanc::SingleValueObject<size_t>(layer.GetIndex()));
     }
 
@@ -424,7 +422,7 @@
 
   RadiographyLayer& RadiographyScene::LoadDicomWebFrame(Deprecated::IWebService& web)
   {
-    RadiographyLayer& layer = RegisterLayer(new RadiographyDicomLayer(IObservable::GetBroker(), *this));
+    RadiographyLayer& layer = RegisterLayer(new RadiographyDicomLayer(*this));
 
 
     return layer;
@@ -752,7 +750,7 @@
     orthanc.PostJsonAsyncExpectJson(
           "/tools/create-dicom", createDicomRequestContent,
           new Callable<RadiographyScene, Deprecated::OrthancApiClient::JsonResponseReadyMessage>
-          (*this, &RadiographyScene::OnDicomExported),
+          (GetSharedObserver(), &RadiographyScene::OnDicomExported),
           NULL, NULL);
 
   }
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyScene.h
--- a/Framework/Radiography/RadiographyScene.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyScene.h	Tue Oct 15 15:39:39 2019 +0200
@@ -22,6 +22,7 @@
 #pragma once
 
 #include "RadiographyLayer.h"
+#include "../Messages/ObserverBase.h"
 #include "../Deprecated/Toolbox/DicomFrameConverter.h"
 #include "../Deprecated/Toolbox/OrthancApiClient.h"
 #include "../StoneEnumerations.h"
@@ -33,8 +34,8 @@
   class RadiographyDicomLayer;
 
   class RadiographyScene :
-      public IObserver,
-      public IObservable
+    public ObserverBase<RadiographyScene>,
+    public IObservable
   {
   public:
     class GeometryChangedMessage : public OriginMessage<RadiographyScene>
@@ -159,7 +160,7 @@
 
     virtual void OnLayerEdited(const RadiographyLayer::LayerEditedMessage& message);
   public:
-    RadiographyScene(MessageBroker& broker);
+    RadiographyScene();
     
     virtual ~RadiographyScene();
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyTextLayer.h
--- a/Framework/Radiography/RadiographyTextLayer.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyTextLayer.h	Tue Oct 15 15:39:39 2019 +0200
@@ -34,8 +34,8 @@
     std::string                fontName_;
 
   public:
-    RadiographyTextLayer(MessageBroker& broker, const RadiographyScene& scene) :
-      RadiographyAlphaLayer(broker, scene)
+    RadiographyTextLayer(const RadiographyScene& scene) :
+      RadiographyAlphaLayer(scene)
     {
     }
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyWidget.cpp
--- a/Framework/Radiography/RadiographyWidget.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyWidget.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -181,11 +181,9 @@
   }
 
 
-  RadiographyWidget::RadiographyWidget(MessageBroker& broker,
-                                       boost::shared_ptr<RadiographyScene> scene,
+  RadiographyWidget::RadiographyWidget(boost::shared_ptr<RadiographyScene> scene,
                                        const std::string& name) :
     WorldSceneWidget(name),
-    IObserver(broker),
     invert_(false),
     interpolation_(ImageInterpolation_Nearest),
     hasSelection_(false),
@@ -288,13 +286,8 @@
 
     scene_ = scene;
 
-    scene_->RegisterObserverCallback(
-          new Callable<RadiographyWidget, RadiographyScene::GeometryChangedMessage>
-          (*this, &RadiographyWidget::OnGeometryChanged));
-
-    scene_->RegisterObserverCallback(
-          new Callable<RadiographyWidget, RadiographyScene::ContentChangedMessage>
-          (*this, &RadiographyWidget::OnContentChanged));
+    Register<RadiographyScene::GeometryChangedMessage>(*scene_, &RadiographyWidget::OnGeometryChanged);
+    Register<RadiographyScene::ContentChangedMessage>(*scene_, &RadiographyWidget::OnContentChanged);
 
     NotifyContentChanged();
 
diff -r 9d42f89b8c3c -r b537002f83a9 Framework/Radiography/RadiographyWidget.h
--- a/Framework/Radiography/RadiographyWidget.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Framework/Radiography/RadiographyWidget.h	Tue Oct 15 15:39:39 2019 +0200
@@ -22,6 +22,7 @@
 #pragma once
 
 #include "../Deprecated/Widgets/WorldSceneWidget.h"
+#include "../Messages/ObserverBase.h"
 #include "RadiographyScene.h"
 
 
@@ -31,7 +32,7 @@
 
   class RadiographyWidget :
     public Deprecated::WorldSceneWidget,
-    public IObserver
+    public ObserverBase<RadiographyWidget>
   {
   private:
     boost::shared_ptr<RadiographyScene>    scene_;
@@ -60,8 +61,7 @@
     bool IsInvertedInternal() const;
 
   public:
-    RadiographyWidget(MessageBroker& broker,
-                      boost::shared_ptr<RadiographyScene> scene,  // TODO: check how we can avoid boost::shared_ptr here since we don't want them in the public API (app is keeping a boost::shared_ptr to this right now)
+    RadiographyWidget(boost::shared_ptr<RadiographyScene> scene,  // TODO: check how we can avoid boost::shared_ptr here since we don't want them in the public API (app is keeping a boost::shared_ptr to this right now)
                       const std::string& name);
 
     RadiographyScene& GetScene() const
diff -r 9d42f89b8c3c -r b537002f83a9 Platforms/Generic/OracleDelayedCallExecutor.h
--- a/Platforms/Generic/OracleDelayedCallExecutor.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Platforms/Generic/OracleDelayedCallExecutor.h	Tue Oct 15 15:39:39 2019 +0200
@@ -36,10 +36,8 @@
     OrthancStone::NativeStoneApplicationContext& context_;
 
   public:
-    OracleDelayedCallExecutor(OrthancStone::MessageBroker& broker,
-                              Oracle& oracle,
+    OracleDelayedCallExecutor(Oracle& oracle,
                               OrthancStone::NativeStoneApplicationContext& context) :
-      IDelayedCallExecutor(broker),
       oracle_(oracle),
       context_(context)
     {
@@ -48,7 +46,7 @@
     virtual void Schedule(OrthancStone::MessageHandler<IDelayedCallExecutor::TimeoutMessage>* callback,
                           unsigned int timeoutInMs = 1000)
     {
-      oracle_.Submit(new DelayedCallCommand(broker_, callback, timeoutInMs, NULL, context_));
+      oracle_.Submit(new DelayedCallCommand(callback, timeoutInMs, NULL, context_));
     }
   };
 }
diff -r 9d42f89b8c3c -r b537002f83a9 Platforms/Generic/OracleWebService.cpp
--- a/Platforms/Generic/OracleWebService.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/Platforms/Generic/OracleWebService.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -35,13 +35,11 @@
     OrthancStone::NativeStoneApplicationContext&                                          context_;
 
   public:
-    WebServiceCachedGetCommand(OrthancStone::MessageBroker& broker,
-                               OrthancStone::MessageHandler<IWebService::HttpRequestSuccessMessage>* successCallback,  // takes ownership
+    WebServiceCachedGetCommand(OrthancStone::MessageHandler<IWebService::HttpRequestSuccessMessage>* successCallback,  // takes ownership
                                boost::shared_ptr<BaseWebService::CachedHttpRequestSuccessMessage> cachedMessage,
                                Orthanc::IDynamicObject* payload /* takes ownership */,
                                OrthancStone::NativeStoneApplicationContext& context
                                ) :
-      IObservable(broker),
       successCallback_(successCallback),
       payload_(payload),
       cachedMessage_(cachedMessage),
@@ -75,7 +73,7 @@
                                                 Orthanc::IDynamicObject* payload, // takes ownership
                                                 OrthancStone::MessageHandler<IWebService::HttpRequestSuccessMessage>* successCallback)
   {
-    oracle_.Submit(new WebServiceCachedGetCommand(GetBroker(), successCallback, cachedMessage, payload, context_));
+    oracle_.Submit(new WebServiceCachedGetCommand(successCallback, cachedMessage, payload, context_));
   }
 
 
diff -r 9d42f89b8c3c -r b537002f83a9 Platforms/Generic/OracleWebService.h
--- a/Platforms/Generic/OracleWebService.h	Tue Oct 15 14:08:15 2019 +0200
+++ b/Platforms/Generic/OracleWebService.h	Tue Oct 15 15:39:39 2019 +0200
@@ -43,11 +43,9 @@
     class WebServiceCachedGetCommand;
 
   public:
-    OracleWebService(OrthancStone::MessageBroker& broker,
-                     Oracle& oracle,
+    OracleWebService(Oracle& oracle,
                      const Orthanc::WebServiceParameters& parameters,
                      OrthancStone::NativeStoneApplicationContext& context) :
-      BaseWebService(broker),
       oracle_(oracle),
       context_(context),
       parameters_(parameters)
@@ -62,7 +60,7 @@
                            OrthancStone::MessageHandler<IWebService::HttpRequestErrorMessage>* failureCallback = NULL, // takes ownership
                            unsigned int timeoutInSeconds = 60)
     {
-      oracle_.Submit(new WebServicePostCommand(GetBroker(), successCallback, failureCallback, parameters_, uri, headers, timeoutInSeconds, body, payload, context_));
+      oracle_.Submit(new WebServicePostCommand(successCallback, failureCallback, parameters_, uri, headers, timeoutInSeconds, body, payload, context_));
     }
 
     virtual void DeleteAsync(const std::string& uri,
@@ -72,7 +70,7 @@
                              OrthancStone::MessageHandler<IWebService::HttpRequestErrorMessage>* failureCallback = NULL,
                              unsigned int timeoutInSeconds = 60)
     {
-      oracle_.Submit(new WebServiceDeleteCommand(GetBroker(), successCallback, failureCallback, parameters_, uri, headers, timeoutInSeconds, payload, context_));
+      oracle_.Submit(new WebServiceDeleteCommand(successCallback, failureCallback, parameters_, uri, headers, timeoutInSeconds, payload, context_));
     }
 
   protected:
@@ -83,7 +81,7 @@
                                   OrthancStone::MessageHandler<IWebService::HttpRequestErrorMessage>* failureCallback = NULL,// takes ownership
                                   unsigned int timeoutInSeconds = 60)
     {
-      oracle_.Submit(new WebServiceGetCommand(GetBroker(), successCallback, failureCallback, parameters_, uri, headers, timeoutInSeconds, payload, context_));
+      oracle_.Submit(new WebServiceGetCommand(successCallback, failureCallback, parameters_, uri, headers, timeoutInSeconds, payload, context_));
     }
 
     virtual void NotifyHttpSuccessLater(boost::shared_ptr<BaseWebService::CachedHttpRequestSuccessMessage> cachedHttpMessage,
diff -r 9d42f89b8c3c -r b537002f83a9 UnitTestsSources/TestMessageBroker.cpp
--- a/UnitTestsSources/TestMessageBroker.cpp	Tue Oct 15 14:08:15 2019 +0200
+++ b/UnitTestsSources/TestMessageBroker.cpp	Tue Oct 15 15:39:39 2019 +0200
@@ -21,7 +21,6 @@
 
 #include "gtest/gtest.h"
 
-#include "Framework/Messages/MessageBroker.h"
 #include "Framework/Messages/IObservable.h"
 #include "Framework/Messages/IObserver.h"
 #include "Framework/Messages/MessageForwarder.h"
@@ -47,20 +46,11 @@
       {
       }
     };
-
-    MyObservable(MessageBroker& broker) :
-      IObservable(broker)
-    {
-    }
   };
 
   class MyObserver : public IObserver
   {
   public:
-    MyObserver(MessageBroker& broker)
-      : IObserver(broker)
-    {}
-
     void HandleCompletedMessage(const MyObservable::MyCustomMessage& message)
     {
       testCounter += message.payload_;
@@ -73,12 +63,10 @@
   {
     IObservable& observedObject_;
   public:
-    MyIntermediate(MessageBroker& broker, IObservable& observedObject)
-      : IObserver(broker),
-        IObservable(broker),
-        observedObject_(observedObject)
+    MyIntermediate(IObservable& observedObject)
+      : observedObject_(observedObject)
     {
-      observedObject_.RegisterObserverCallback(new MessageForwarder<MyObservable::MyCustomMessage>(broker, *this));
+      observedObject_.RegisterObserverCallback(new MessageForwarder<MyObservable::MyCustomMessage>(*this));
     }
   };
 }
@@ -86,9 +74,8 @@
 
 TEST(MessageBroker, TestPermanentConnectionSimpleUseCase)
 {
-  MessageBroker broker;
-  MyObservable  observable(broker);
-  MyObserver    observer(broker);
+  MyObservable  observable;
+  MyObserver    observer;
 
   // create a permanent connection between an observable and an observer
   observable.RegisterObserverCallback(new Callable<MyObserver, MyObservable::MyCustomMessage>(observer, &MyObserver::HandleCompletedMessage));
@@ -111,10 +98,9 @@
 
 TEST(MessageBroker, TestMessageForwarderSimpleUseCase)
 {
-  MessageBroker broker;
-  MyObservable  observable(broker);
-  MyIntermediate intermediate(broker, observable);
-  MyObserver    observer(broker);
+  MyObservable  observable;
+  MyIntermediate intermediate(observable);
+  MyObserver    observer;
 
   // let the observer observers the intermediate that is actually forwarding the messages from the observable
   intermediate.RegisterObserverCallback(new Callable<MyObserver, MyObservable::MyCustomMessage>(observer, &MyObserver::HandleCompletedMessage));
@@ -131,9 +117,8 @@
 
 TEST(MessageBroker, TestPermanentConnectionDeleteObserver)
 {
-  MessageBroker broker;
-  MyObservable  observable(broker);
-  MyObserver*   observer = new MyObserver(broker);
+  MyObservable  observable;
+  MyObserver*   observer(new MyObserver);
 
   // create a permanent connection between an observable and an observer
   observable.RegisterObserverCallback(new Callable<MyObserver, MyObservable::MyCustomMessage>(*observer, &MyObserver::HandleCompletedMessage));
@@ -153,10 +138,9 @@
 
 TEST(MessageBroker, TestMessageForwarderDeleteIntermediate)
 {
-  MessageBroker broker;
-  MyObservable  observable(broker);
-  MyIntermediate* intermediate = new MyIntermediate(broker, observable);
-  MyObserver    observer(broker);
+  MyObservable  observable;
+  MyIntermediate* intermediate(new MyIntermediate(observable));
+  MyObserver    observer;
 
   // let the observer observers the intermediate that is actually forwarding the messages from the observable
   intermediate->RegisterObserverCallback(new Callable<MyObserver, MyObservable::MyCustomMessage>(observer, &MyObserver::HandleCompletedMessage));
@@ -173,10 +157,9 @@
 
 TEST(MessageBroker, TestCustomMessage)
 {
-  MessageBroker broker;
-  MyObservable  observable(broker);
-  MyIntermediate intermediate(broker, observable);
-  MyObserver    observer(broker);
+  MyObservable  observable;
+  MyIntermediate intermediate(observable);
+  MyObserver    observer;
 
   // let the observer observers the intermediate that is actually forwarding the messages from the observable
   intermediate.RegisterObserverCallback(new Callable<MyObserver, MyObservable::MyCustomMessage>(observer, &MyObserver::HandleCompletedMessage));
@@ -196,9 +179,8 @@
 
 TEST(MessageBroker, TestLambdaSimpleUseCase)
 {
-  MessageBroker broker;
-  MyObservable  observable(broker);
-  MyObserver*   observer = new MyObserver(broker);
+  MyObservable  observable;
+  MyObserver*   observer(new MyObserver);
 
   // create a permanent connection between an observable and an observer
   observable.RegisterObserverCallback(new LambdaCallable<MyObservable::MyCustomMessage>(*observer, [&](const MyObservable::MyCustomMessage& message) {testCounter += 2 * message.payload_;}));
@@ -222,9 +204,8 @@
     int multiplier_;  // this is a private variable we want to access in a lambda
 
   public:
-    MyObserverWithLambda(MessageBroker& broker, int multiplier, MyObservable& observable)
-      : IObserver(broker),
-        multiplier_(multiplier)
+    MyObserverWithLambda(int multiplier, MyObservable& observable)
+      : multiplier_(multiplier)
     {
       // register a callable to a lambda that access private members
       observable.RegisterObserverCallback(new LambdaCallable<MyObservable::MyCustomMessage>(*this, [this](const MyObservable::MyCustomMessage& message) {
@@ -237,9 +218,8 @@
 
 TEST(MessageBroker, TestLambdaCaptureThisAndAccessPrivateMembers)
 {
-  MessageBroker broker;
-  MyObservable  observable(broker);
-  MyObserverWithLambda*   observer = new MyObserverWithLambda(broker, 3, observable);
+  MyObservable  observable;
+  MyObserverWithLambda*   observer = new MyObserverWithLambda(3, observable);
 
   testCounter = 0;
   observable.BroadcastMessage(MyObservable::MyCustomMessage(12));