diff --git a/Mixer.cpp b/Mixer.cpp
index 11f4188..6072a1e 100644
--- a/Mixer.cpp
+++ b/Mixer.cpp
@@ -125,7 +125,6 @@ Mixer::Mixer() : session_(nullptr), back_session_(nullptr), current_view_(nullpt
     setCurrentView( (View::Mode) Settings::application.current_view );
 }
 
-
 void Mixer::update()
 {
     // change session when threaded loading is finished
@@ -140,6 +139,7 @@ void Mixer::update()
             Settings::application.recentSessions.push(sessionFilename_);
         }
     }
+
     // confirm when threaded saving is finished
     if (sessionSaveFinished_) {
         sessionSaveFinished_ = false;
@@ -155,16 +155,17 @@ void Mixer::update()
     float dt = static_cast<float>( GST_TIME_AS_MSECONDS(current_time - update_time_) ) * 0.001f;
     update_time_ = current_time;
 
-    // update session and associted sources
+    // update session and associated sources
     session_->update(dt);
 
     // update views
     mixing_.update(dt);
     geometry_.update(dt);
     layer_.update(dt);
-    // TODO other views
-
+    // TODO other views?
 
+    // optimize the reordering in depth for views
+    View::need_reordering_ = false;
 }
 
 void Mixer::draw()
@@ -199,10 +200,8 @@ void Mixer::insertSource(Source *s)
     mixing_.scene.fg()->attach(s->group(View::MIXING));
     geometry_.scene.fg()->attach(s->group(View::GEOMETRY));
     layer_.scene.fg()->attach(s->group(View::LAYER));
-
 }
 
-
 void Mixer::deleteCurrentSource()
 {
     deleteSource( currentSource() );
@@ -366,7 +365,6 @@ void Mixer::saveas(const std::string& filename)
 
     // launch a thread to save the session
     std::thread (saveSession, filename, session_).detach();
-
 }
 
 void Mixer::open(const std::string& filename)
@@ -382,10 +380,8 @@ void Mixer::open(const std::string& filename)
 
     // launch a thread to load the session into back_session
     std::thread (loadSession, filename, back_session_).detach();
-
 }
 
-
 void Mixer::swap()
 {
     if (!back_session_)
@@ -434,7 +430,6 @@ void Mixer::swap()
     back_session_ = nullptr;
 }
 
-
 void Mixer::newSession()
 {
     // delete previous back session if needed
diff --git a/Scene.cpp b/Scene.cpp
index eb9ac17..4a1e749 100644
--- a/Scene.cpp
+++ b/Scene.cpp
@@ -52,7 +52,6 @@ void Node::update( float )
 {
     // update transform matrix from attributes
     transform_ = GlmToolkit::transform(translation_, rotation_, scale_);
-
 }
 
 void Node::accept(Visitor& v)
diff --git a/View.cpp b/View.cpp
index 37816ff..76d3822 100644
--- a/View.cpp
+++ b/View.cpp
@@ -22,6 +22,8 @@
 #define CIRCLE_PIXELS 64
 #define CIRCLE_PIXEL_RADIUS 1024.0
 
+bool View::need_reordering_ = true;
+
 View::View(Mode m) : mode_(m)
 {
 }
@@ -43,8 +45,9 @@ void View::update(float dt)
     // recursive update from root of scene
     scene.update( dt );
 
-    // reorder depth
-    scene.fg()->sort();
+    // reorder depth if needed
+    if (View::need_reordering_)
+        scene.fg()->sort();
 }
 
 void View::drag (glm::vec2 from, glm::vec2 to)
@@ -84,7 +87,6 @@ MixingView::MixingView() : View(MIXING)
     Mesh *circle = new Mesh("mesh/circle.ply");
     circle->shader()->color = pink;
     scene.bg()->attach(circle);
-
 }
 
 MixingView::~MixingView()
@@ -106,7 +108,6 @@ void MixingView::zoom( float factor )
     scene.root()->scale_.y = z;
 }
 
-
 void MixingView::grab (glm::vec2 from, glm::vec2 to, Source *s, std::pair<Node *, glm::vec2>)
 {
     if (!s)
@@ -133,7 +134,6 @@ void MixingView::grab (glm::vec2 from, glm::vec2 to, Source *s, std::pair<Node *
     s->touch();
 }
 
-
 uint MixingView::textureMixingQuadratic()
 {
     static GLuint texid = 0;
@@ -194,7 +194,6 @@ RenderView::~RenderView()
         delete frame_buffer_;
 }
 
-
 void RenderView::setResolution(glm::vec3 resolution)
 {
     if (resolution.x < 128.f || resolution.y < 128.f)
@@ -355,7 +354,6 @@ LayerView::LayerView() : View(LAYER), aspect_ratio(1.f)
     Frame *border = new Frame(Frame::ROUND_SHADOW);
     border->color = glm::vec4( 0.8f, 0.f, 0.8f, 0.7f );
     scene.bg()->attach(border);
-
 }
 
 LayerView::~LayerView()
@@ -365,7 +363,6 @@ LayerView::~LayerView()
 
 void LayerView::draw ()
 {
-
     // update rendering of render frame
     FrameBuffer *output = Mixer::manager().session()->frame();
     if (output)
@@ -420,5 +417,8 @@ void LayerView::grab (glm::vec2 from, glm::vec2 to, Source *s, std::pair<Node *,
 
     // request update
     s->touch();
+
+    // request reordering
+    View::need_reordering_ = true;
 }
 
diff --git a/View.h b/View.h
index e03f98d..042988a 100644
--- a/View.h
+++ b/View.h
@@ -27,6 +27,9 @@ public:
 
     Scene scene;
 
+    // hack to avoid reordering scene of view if not necessary
+    static bool need_reordering_;
+
 protected:
     Mode mode_;
 };
@@ -60,7 +63,6 @@ public:
     glm::vec3 resolution() const { return frame_buffer_->resolution(); }
 
     inline FrameBuffer *frameBuffer () const { return frame_buffer_; }
-
 };
 
 class GeometryView : public View