--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Framework/Scene2D/CompositorHelper.cpp	Fri Apr 19 17:57:58 2019 +0200
@@ -0,0 +1,139 @@
+/**
+ * Stone of Orthanc
+ * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, Belgium
+ * Copyright (C) 2017-2019 Osimis S.A., Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Affero General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Affero General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+
+#include "CompositorHelper.h"
+
+#include <Core/OrthancException.h>
+
+namespace OrthancStone
+{
+  class CompositorHelper::Item : public boost::noncopyable
+  {
+  private:
+    std::auto_ptr<ILayerRenderer>  renderer_;
+    const ISceneLayer&             layer_;
+    uint64_t                       lastRevision_;
+
+  public:
+    Item(ILayerRenderer* renderer,     // Takes ownership
+         const ISceneLayer& layer) :
+      renderer_(renderer),
+      layer_(layer),
+      lastRevision_(layer.GetRevision())
+    {
+      if (renderer == NULL)
+      {
+        throw Orthanc::OrthancException(Orthanc::ErrorCode_NullPointer);
+      }
+    }
+
+    ILayerRenderer& GetRenderer() const
+    {
+      assert(renderer_.get() != NULL);
+      return *renderer_;
+    }
+
+    const ISceneLayer& GetLayer() const
+    {
+      return layer_;
+    }
+
+    uint64_t GetLastRevision() const
+    {
+      return lastRevision_;
+    }
+
+    void UpdateRenderer()
+    {
+      assert(renderer_.get() != NULL);
+      renderer_->Update(layer_);
+      lastRevision_ = layer_.GetRevision();
+    }
+  };
+
+
+  void CompositorHelper::Visit(const ISceneLayer& layer,
+                               int depth)
+  {
+    Content::iterator found = content_.find(depth);
+
+    assert(found == content_.end() ||
+           found->second != NULL);
+
+    if (found == content_.end() ||
+        &found->second->GetLayer() != &layer)
+    {
+      // This is the first time this layer is rendered, or the layer
+      // is not the same as before
+      if (found != content_.end())
+      {
+        delete found->second;
+        content_.erase(found);
+      }
+
+      std::auto_ptr<ILayerRenderer> renderer(factory_.Create(layer));
+
+      if (renderer.get() != NULL)
+      {
+        renderer->Render(sceneTransform_);
+        content_[depth] = new Item(renderer.release(), layer);
+      }
+    }
+    else
+    {
+      // This layer has already been rendered
+      if (found->second->GetLastRevision() < layer.GetRevision())
+      {
+        found->second->UpdateRenderer();
+      }
+
+      found->second->GetRenderer().Render(sceneTransform_);
+    }
+
+    // Check invariants
+    assert(content_.find(depth) == content_.end() ||
+           (&content_[depth]->GetLayer() == &layer &&
+            content_[depth]->GetLastRevision() == layer.GetRevision()));
+  }
+
+
+  CompositorHelper::~CompositorHelper()
+  {
+    for (Content::iterator it = content_.begin(); it != content_.end(); ++it)
+    {
+      assert(it->second != NULL);
+      delete it->second;
+    }
+  }
+
+  
+  void CompositorHelper::Refresh(unsigned int canvasWidth,
+                                 unsigned int canvasHeight)
+  {
+    // Bring coordinate (0,0) to the center of the canvas
+    AffineTransform2D offset = AffineTransform2D::CreateOffset(
+      static_cast<double>(canvasWidth) / 2.0,
+      static_cast<double>(canvasHeight) / 2.0);
+
+    sceneTransform_ = AffineTransform2D::Combine(offset, scene_.GetSceneToCanvasTransform());
+    scene_.Apply(*this);
+  }
+}