diff --git a/CMakeLists.txt b/CMakeLists.txt
index e0ce21f..6be5b5f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -210,6 +210,7 @@ set(VMIX_SRCS
     Source.cpp
     Session.cpp
     SessionVisitor.cpp
+    GarbageVisitor.cpp
     SessionCreator.cpp
     Mixer.cpp
     Settings.cpp
diff --git a/GarbageVisitor.cpp b/GarbageVisitor.cpp
new file mode 100644
index 0000000..b2925a8
--- /dev/null
+++ b/GarbageVisitor.cpp
@@ -0,0 +1,164 @@
+#include <algorithm>
+
+#include "Log.h"
+#include "Scene.h"
+#include "GarbageVisitor.h"
+
+
+GarbageVisitor::GarbageVisitor(Node *nodetocollect) : Visitor()
+{
+    targets_.push_front(nodetocollect);
+    current_ = nullptr;
+    found_ == false;
+}
+
+GarbageVisitor::GarbageVisitor(Source *sourcetocollect) : Visitor()
+{
+    targets_.push_front(sourcetocollect->group(View::MIXING));
+    targets_.push_front(sourcetocollect->group(View::GEOMETRY));
+    targets_.push_front(sourcetocollect->group(View::RENDERING));
+    current_ = nullptr;
+    found_ == false;
+}
+
+
+void GarbageVisitor::visit(Node &n)
+{
+    // found the target
+//    if (n.id() == target_->id())
+//    if ( &n == target_ )
+    if ( std::count(targets_.begin(), targets_.end(), &n) )
+    {
+        // end recursive
+        found_ = true;
+
+        // take the node out of the Tree
+        if (current_)
+            current_->detatchChild(&n);
+
+    }
+
+}
+
+GarbageVisitor::~GarbageVisitor()
+{
+    // actually delete the Node
+
+}
+
+
+void GarbageVisitor::visit(Group &n)
+{
+    // no need to go further if the node was found (or is this group)
+    if (found_)
+        return;
+
+    // current group
+    current_ = &n;
+
+    // loop over members of a group
+    // and stop when found
+    for (NodeSet::iterator node = n.begin(); !found_ && node != n.end(); node++) {
+        // visit the child node
+        (*node)->accept(*this);
+        // un-stack recursive browsing
+        current_ = &n;
+    }
+
+}
+
+void GarbageVisitor::visit(Scene &n)
+{
+    n.root()->accept(*this);
+}
+
+void GarbageVisitor::visit(Switch &n)
+{
+
+}
+
+void GarbageVisitor::visit(Animation &n)
+{
+
+}
+
+void GarbageVisitor::visit(Primitive &n)
+{
+
+}
+
+void GarbageVisitor::visit(Surface &n)
+{
+
+}
+
+void GarbageVisitor::visit(ImageSurface &n)
+{
+
+}
+
+void GarbageVisitor::visit(FrameBufferSurface &n)
+{
+
+}
+
+void GarbageVisitor::visit(MediaSurface &n)
+{
+
+}
+
+void GarbageVisitor::visit(MediaPlayer &n)
+{
+
+}
+
+void GarbageVisitor::visit(Shader &n)
+{
+
+}
+
+void GarbageVisitor::visit(ImageShader &n)
+{
+
+}
+
+void GarbageVisitor::visit(ImageProcessingShader &n)
+{
+
+}
+
+void GarbageVisitor::visit(LineStrip &n)
+{
+
+}
+
+void GarbageVisitor::visit(LineSquare &)
+{
+
+}
+
+void GarbageVisitor::visit(LineCircle &n)
+{
+
+}
+
+void GarbageVisitor::visit(Mesh &n)
+{
+
+}
+
+void GarbageVisitor::visit(Frame &n)
+{
+
+}
+
+
+void GarbageVisitor::visit (Source& s)
+{
+
+}
+
+void GarbageVisitor::visit (MediaSource& s)
+{
+
+}
diff --git a/GarbageVisitor.h b/GarbageVisitor.h
new file mode 100644
index 0000000..6e2138d
--- /dev/null
+++ b/GarbageVisitor.h
@@ -0,0 +1,47 @@
+#ifndef GARBAGEVISITOR_H
+#define GARBAGEVISITOR_H
+
+#include <list>
+
+#include "Source.h"
+#include "Visitor.h"
+
+
+class GarbageVisitor : public Visitor {
+
+    Group *current_;
+    std::list<Node *> targets_;
+    bool found_;
+
+public:
+    GarbageVisitor(Source *sourcetocollect);
+    GarbageVisitor(Node *nodetocollect);
+    ~GarbageVisitor();
+
+    void visit(Scene& n) override;
+    void visit(Node& n) override;
+    void visit(Group& n) override;
+    void visit(Switch& n) override;
+    void visit(Animation& n) override;
+    void visit(Primitive& n) override;
+    void visit(Surface& n) override;
+    void visit(ImageSurface& n) override;
+    void visit(MediaSurface& n) override;
+    void visit(FrameBufferSurface& n) override;
+    void visit(LineStrip& n) override;
+    void visit(LineSquare&) override;
+    void visit(LineCircle& n) override;
+    void visit(Mesh& n) override;
+    void visit(Frame& n) override;
+
+    void visit(MediaPlayer& n) override;
+    void visit(Shader& n) override;
+    void visit(ImageShader& n) override;
+    void visit(ImageProcessingShader& n) override;
+
+    void visit (Source& s) override;
+    void visit (MediaSource& s) override;
+
+};
+
+#endif // GARBAGEVISITOR_H
diff --git a/ImageProcessingShader.h b/ImageProcessingShader.h
index 0283f6f..468aac8 100644
--- a/ImageProcessingShader.h
+++ b/ImageProcessingShader.h
@@ -11,7 +11,7 @@ class ImageProcessingShader : public Shader
 public:
 
     ImageProcessingShader();
-    virtual ~ImageProcessingShader() {}
+//    virtual ~ImageProcessingShader() {}
 
     void use() override;
     void reset() override;
diff --git a/ImageShader.cpp b/ImageShader.cpp
index 1bdf7bb..d619ae0 100644
--- a/ImageShader.cpp
+++ b/ImageShader.cpp
@@ -5,7 +5,7 @@
 #include "ImageShader.h"
 #include "Resource.h"
 
-ShadingProgram imageShadingProgram("shaders/image.vs", "shaders/image.fs");
+static ShadingProgram imageShadingProgram("shaders/image.vs", "shaders/image.fs");
 
 const char* ImageShader::mask_names[10] = { "None", "Vignette", "Halo", "Circle", "Round", "Top", "Botton", "Left", "Right", "Custom" };
 std::vector< uint > ImageShader::mask_presets;
@@ -50,7 +50,7 @@ void ImageShader::reset()
 {
     Shader::reset();
 
-    // setup double texturing
+    // setup double texturing (TODO : do it only once)
     program_->use();
     program_->setUniform("iChannel0", 0);
     program_->setUniform("iChannel1", 1);
diff --git a/ImageShader.h b/ImageShader.h
index cfc0d67..97111e9 100644
--- a/ImageShader.h
+++ b/ImageShader.h
@@ -16,7 +16,7 @@ class ImageShader : public Shader
 public:
 
     ImageShader();
-    virtual ~ImageShader() {}
+//    virtual ~ImageShader() {}
 
     void use() override;
     void reset() override;
diff --git a/Mesh.cpp b/Mesh.cpp
index 26b291c..1762041 100644
--- a/Mesh.cpp
+++ b/Mesh.cpp
@@ -333,22 +333,18 @@ Mesh::Mesh(const std::string& ply_path, const std::string& tex_path) : Primitive
     }
 
     // default non texture shader (deleted in Primitive)
-    shader_ = new Shader;
+    shader_ = new Shader();
 }
 
 
 void Mesh::setTexture(uint textureindex)
 {
     if (textureindex) {
-
         // replace previous shader with a new Image Shader
-        if (shader_)
-            delete shader_;
-        shader_ = new ImageShader;
-
+        replaceShader( new ImageShader() );
+        // set texture
         textureindex_ = textureindex;
     }
-
 }
 
 void Mesh::init()
diff --git a/Mixer.cpp b/Mixer.cpp
index 252b825..54722f3 100644
--- a/Mixer.cpp
+++ b/Mixer.cpp
@@ -13,6 +13,7 @@ using namespace tinyxml2;
 #include "Settings.h"
 #include "SystemToolkit.h"
 #include "ImageProcessingShader.h"
+#include "GarbageVisitor.h"
 #include "SessionVisitor.h"
 #include "SessionCreator.h"
 
@@ -84,8 +85,35 @@ void Mixer::insertSource(Source *s)
 }
 void Mixer::deleteSource(Source *s)
 {
+//    SessionVisitor visit;
+//    geometry_.scene.accept(visit);
+//    visit.doc()->SaveFile("./geombefore.xml");
+//    SessionVisitor visitm;
+//    mixing_.scene.accept(visitm);
+//    visitm.doc()->SaveFile("./mixbefore.xml");
+
     unsetCurrentSource();
+
+    // remove source Nodes from views
+//    GarbageVisitor mixingremover(s->group(View::MIXING));
+//    mixingremover.visit(mixing_.scene);
+//    GarbageVisitor geomremover(s->group(View::GEOMETRY));
+//    geomremover.visit(geometry_.scene);
+
+    Log::Info("MIXING");
+    mixing_.scene.root()->detatchChild( s->group(View::MIXING) );
+    Log::Info("GEOMETRY");
+    geometry_.scene.root()->detatchChild( s->group(View::GEOMETRY) );
+
+    // delete source
     session_->deleteSource(s);
+
+//    SessionVisitor visit2;
+//    geometry_.scene.accept(visit2);
+//    visit2.doc()->SaveFile("./geomafter.xml");
+//    SessionVisitor visit2m;
+//    mixing_.scene.accept(visit2m);
+//    visit2m.doc()->SaveFile("./mixmafter.xml");
 }
 
 void Mixer::renameSource(Source *s, const std::string &newname)
@@ -114,12 +142,19 @@ void Mixer::renameSource(Source *s, const std::string &newname)
 
 void Mixer::setCurrentSource(SourceList::iterator it)
 {
-    unsetCurrentSource();
+    // nothing to do if already current
+    if ( current_source_ == it )
+        return;
+
+    // change current
     if ( it != session_->end() ) {
         current_source_ = it;
         current_source_index_ = session_->index(it);
         (*current_source_)->setOverlayVisible(true);
     }
+    // default
+    else
+        unsetCurrentSource();
 }
 
 void Mixer::setCurrentSource(Node *node)
@@ -217,6 +252,7 @@ void Mixer::save(const std::string& filename)
     for (iter = session_->begin(); iter != session_->end(); iter++)
     {
         SessionVisitor sv(&xmlDoc, session);
+        // source visitor
         (*iter)->accept(sv);
     }
 
@@ -267,11 +303,11 @@ bool Mixer::open(const std::string& filename)
         newSession( new_session );
 
         // insert nodes of sources into views
-        SourceList::iterator iter;
-        for (iter = new_session->begin(); iter != new_session->end(); iter++)
+        SourceList::iterator source_iter;
+        for (source_iter = new_session->begin(); source_iter != new_session->end(); source_iter++)
         {
-            mixing_.scene.root()->addChild( (*iter)->group(View::MIXING) );
-            geometry_.scene.root()->addChild( (*iter)->group(View::GEOMETRY) );
+            mixing_.scene.root()->addChild( (*source_iter)->group(View::MIXING) );
+            geometry_.scene.root()->addChild( (*source_iter)->group(View::GEOMETRY) );
         }
 
     }
@@ -295,13 +331,25 @@ bool Mixer::open(const std::string& filename)
 
 void Mixer::newSession(Session *newsession)
 {
-    // TODO : remove roots of scenes for views?
-//    mixing_.scene.clear();
-//    geometry_.scene.clear();
 
     // delete session : delete all sources
-    if (session_)
+    if (session_) {
+        // remove nodes from views
+        for (auto source_iter = session_->begin(); source_iter != session_->end(); source_iter++)
+        {
+//            GarbageVisitor mixingremover( (*source_iter)->group(View::MIXING) );
+//            mixingremover.visit(mixing_.scene);
+//            GarbageVisitor geomremover( (*source_iter)->group(View::GEOMETRY) );
+//            geomremover.visit(geometry_.scene);
+
+            Log::Info("MIXING");
+            mixing_.scene.root()->detatchChild( (*source_iter)->group(View::MIXING) );
+            Log::Info("GEOMETRY");
+            geometry_.scene.root()->detatchChild( (*source_iter)->group(View::GEOMETRY) );
+        }
+        // clear session
         delete session_;
+    }
 
     // validate new session
     if (newsession)
diff --git a/Primitives.cpp b/Primitives.cpp
index ff28a4f..4ffa6b6 100644
--- a/Primitives.cpp
+++ b/Primitives.cpp
@@ -40,6 +40,11 @@ Surface::Surface(Shader *s) : Primitive(s), textureindex_(0)
 }
 
 
+Surface::~Surface()
+{
+
+}
+
 void Surface::init()
 {
     // use static unique vertex array object
@@ -58,7 +63,7 @@ void Surface::init()
         // 2. remember global vertex array object
         unique_vao_ = vao_;
         unique_drawCount = drawCount_;
-        // 3. unique_vao_ will NOT be deleted because ImageSurface::deleteGLBuffers_() is empty
+        // 3. unique_vao_ will NOT be deleted
     }
 }
 
@@ -283,6 +288,12 @@ void LineSquare::accept(Visitor& v)
     v.visit(*this);
 }
 
+LineSquare::~LineSquare()
+{
+    if (shader_)
+        delete shader_;
+}
+
 
 LineCircle::LineCircle(glm::vec4 color, uint linewidth) : LineStrip(std::vector<glm::vec3>(), color, linewidth)
 {
@@ -330,3 +341,9 @@ void LineCircle::accept(Visitor& v)
     v.visit(*this);
 }
 
+
+LineCircle::~LineCircle()
+{
+    if (shader_)
+        delete shader_;
+}
diff --git a/Primitives.h b/Primitives.h
index 1f07228..db5f062 100644
--- a/Primitives.h
+++ b/Primitives.h
@@ -19,8 +19,6 @@ class FrameBuffer;
  */
 class Surface : public Primitive {
 
-    void deleteGLBuffers_() override {}
-
 public:
     Surface(Shader *s = new ImageShader);
 
@@ -33,6 +31,7 @@ public:
 
 protected:
     uint textureindex_;
+    virtual ~Surface();
 };
 
 
@@ -152,13 +151,13 @@ public:
  */
 class LineSquare : public LineStrip {
 
-    void deleteGLBuffers_() override {}
-
 public:
     LineSquare(glm::vec4 color, uint linewidth = 1);
 
     void init() override;
     void accept(Visitor& v) override;
+
+    virtual ~LineSquare();
 };
 
 
@@ -167,13 +166,13 @@ public:
  */
 class LineCircle : public LineStrip {
 
-    void deleteGLBuffers_() override {}
-
 public:
     LineCircle(glm::vec4 color, uint linewidth = 1);
 
     void init() override;
     void accept(Visitor& v) override;
+
+    virtual ~LineCircle();
 };
 
 
diff --git a/Scene.cpp b/Scene.cpp
index 1ba6b7d..5608a78 100644
--- a/Scene.cpp
+++ b/Scene.cpp
@@ -3,8 +3,11 @@
 #include "Shader.h"
 #include "Primitives.h"
 #include "Visitor.h"
+#include "GarbageVisitor.h"
 #include "Log.h"
 
+#include "SessionVisitor.h"
+
 #include <glad/glad.h>
 
 #include <glm/gtc/type_ptr.hpp>
@@ -17,7 +20,7 @@
 #include <algorithm>
 
 
-Group *Scene::limbo = new Group;
+//Group *Scene::limbo = new Group;
 
 glm::mat4 transform(glm::vec3 translation, glm::vec3 rotation, glm::vec3 scale)
 {
@@ -30,7 +33,7 @@ glm::mat4 transform(glm::vec3 translation, glm::vec3 rotation, glm::vec3 scale)
 }
 
 // Node
-Node::Node() : initialized_(false), visible_(true)
+Node::Node() : initialized_(false), visible_(true), refcount_(0)
 {
     // create unique id
     auto duration = std::chrono::system_clock::now().time_since_epoch();
@@ -61,16 +64,19 @@ void Node::accept(Visitor& v)
 
 // Primitive
 
+
 Primitive::~Primitive()
 {
-    deleteGLBuffers_();
+    if ( vao_ )
+        glDeleteVertexArrays ( 1, &vao_);
     if (shader_)
         delete shader_;
 }
 
 void Primitive::init()
 {
-    deleteGLBuffers_();
+    if ( vao_ )
+        glDeleteVertexArrays ( 1, &vao_);
 
     // Vertex Array
     glGenVertexArrays( 1, &vao_ );
@@ -171,23 +177,21 @@ void Primitive::replaceShader( Shader *newshader )
     }
 }
 
-void Primitive::deleteGLBuffers_()
-{
-    if ( vao_ )
-        glDeleteVertexArrays ( 1, &vao_);
-}
-
 
 // Group
 Group::~Group()
 {
+    Log::Info("Delete Group %d ", id());
     for(NodeSet::iterator it = children_.begin(); it != children_.end(); ) {
-        // this group is not parent of that node anymore
-        (*it)->parents_.remove(this);
+        Log::Info(" Child %d (%d)", (*it)->id(), (*it)->refcount_);
+        (*it)->refcount_--;
         // if this group was the only remaining parent
-        if ( (*it)->parents_.size() < 1 )
-            // put the child in limbo
-            Scene::limbo->addChild( *it );
+        if ( (*it)->refcount_ < 1 ) {
+
+            Log::Info(" Deleting %d (%d)", (*it)->id(), (*it)->refcount_);
+            // delete
+            delete (*it);
+        }
         // erase this iterator from the list
         it = children_.erase(it);
     }
@@ -196,19 +200,33 @@ Group::~Group()
 void Group::addChild(Node *child)
 {
     children_.insert(child);
-    child->parents_.push_back(this);
+    child->refcount_++;
+
+//    children_.push_back(child);  // list test
+
+//    child->parents_.push_back(this);
 }
 
 
 void Group::detatchChild(Node *child)
 {
-    NodeSet::iterator it = std::find_if(children_.begin(), children_.end(), hasId(child->id()));
 
-    if ( it != children_.end())
-    {
-        child->parents_.remove(this);
+    Log::Info("Group %d (N=%d) detaching %d", id(), numChildren(), child->id());
+
+    // find the node with this id, and erase it out of the list of children
+    // NB: do NOT delete with remove : this takes all nodes with same depth (i.e. equal depth in set)
+    NodeSet::iterator it = std::find_if(children_.begin(), children_.end(), hasId(child->id()));
+    if ( it != children_.end())  {
+        // detatch child from group parent
         children_.erase(it);
+        child->refcount_--;
+//        // detatch parent from child
+//        (*it)->parents_.remove(this);
     }
+
+//    children_.remove(child);
+    Log::Info("Group %d (N=%d)", id(), numChildren());
+
 }
 
 void Group::update( float dt )
@@ -294,11 +312,11 @@ void Switch::addChild(Node *child)
     setActiveChild(child);
 }
 
-void Switch::detatchChild(Node *child)
-{
-    Group::detatchChild(child);
-    active_ = children_.begin();
-}
+//void Switch::detatchChild(Node *child)
+//{
+//    Group::detatchChild(child);
+//    active_ = children_.begin();
+//}
 
 
 void Switch::unsetActiveChild ()
@@ -385,24 +403,30 @@ Scene::Scene(): root_(nullptr)
 
 Scene::~Scene()
 {
-    deleteNode(root_);
+//    deleteNode(root_);
+
 }
 
 
 void Scene::deleteNode(Node *node)
 {
-    for(auto it = node->parents_.begin(); it != node->parents_.end();){
-        (*it)->detatchChild(node);
-    }    
 
-    limbo->addChild(node);
+    GarbageVisitor remover(node);
+    remover.visit(*this);
+
+//    // remove this node to the list of chidren of all its parents
+//    for(auto parent = node->parents_.begin(); parent != node->parents_.end(); parent++){
+//        (*parent)->children_.erase(node);
+//    }
+//    node->parents_.clear();
+
+//    limbo->addChild(node);
 }
 
 void Scene::update(float dt)
 {
     root_->update( dt );
 
-    // remove nodes from limbo
 }
 
 void Scene::accept(Visitor& v)
diff --git a/Scene.h b/Scene.h
index 2d402ac..1774641 100644
--- a/Scene.h
+++ b/Scene.h
@@ -45,13 +45,11 @@ class Node {
     int       id_;
     bool      initialized_;
 
-
 public:
     Node ();
 
     // unique identifyer generated at instanciation
     inline int id () const { return id_; }
-//    void detatch();
 
     // must initialize the node before draw
     virtual void init() { initialized_ = true; }
@@ -67,14 +65,14 @@ public:
     virtual void accept (Visitor& v);
 
     // public members, to manipulate with care
-    std::list<Group*> parents_;
     bool      visible_;
+    uint refcount_;
 
     glm::mat4 transform_;
     glm::vec3 scale_, rotation_, translation_;
 
-protected:
     virtual ~Node ();
+
 };
 
 
@@ -107,6 +105,7 @@ public:
     inline Shader *shader () const { return shader_; }
     void replaceShader (Shader* newshader);
 
+    virtual ~Primitive();
 protected:
     Shader*   shader_;
     uint vao_, drawMode_, drawCount_;
@@ -114,8 +113,7 @@ protected:
     std::vector<glm::vec4>     colors_;
     std::vector<glm::vec2>     texCoords_;
     std::vector<uint>  indices_;
-    virtual void deleteGLBuffers_();
-    virtual ~Primitive();
+
 };
 
 //
@@ -131,6 +129,8 @@ struct z_comparator
 };
 typedef std::multiset<Node*, z_comparator> NodeSet;
 
+//typedef std::list<Node*> NodeSet;
+
 struct hasId: public std::unary_function<Node*, bool>
 {
     inline bool operator()(const Node* e) const
@@ -142,6 +142,7 @@ private:
     int _id;
 };
 
+
 /**
  * @brief The Group class contains a list of pointers to Nodes.
  *
@@ -157,9 +158,11 @@ private:
  */
 class Group : public Node {
 
+    friend class Scene;
 
 public:
     Group() : Node() {}
+    virtual ~Group();
 
     virtual void update (float dt) override;
     virtual void accept (Visitor& v) override;
@@ -172,10 +175,10 @@ public:
     NodeSet::iterator end();
     uint numChildren() const;
 
+
 protected:
     NodeSet children_;
-    // destructor
-    virtual ~Group();
+
 };
 
 /**
@@ -195,7 +198,7 @@ public:
     virtual void draw (glm::mat4 modelview, glm::mat4 projection) override;
 
     void addChild (Node *child) override;
-    void detatchChild (Node *child) override;
+//    void detatchChild (Node *child) override;
 
     void unsetActiveChild ();
     void setActiveChild (Node *child);
@@ -257,8 +260,9 @@ public:
     // Node *find(int id);
     // void remove(Node *n);
     //
-    static void deleteNode(Node *node);
-    static Group *limbo;
+    void deleteNode(Node *node);
+
+//    static Group *limbo;
 };
 
 
diff --git a/Session.cpp b/Session.cpp
index 78a5cb8..3c28504 100644
--- a/Session.cpp
+++ b/Session.cpp
@@ -1,7 +1,9 @@
 #include <algorithm>
 
 #include "defines.h"
+#include "FrameBuffer.h"
 #include "Session.h"
+#include "GarbageVisitor.h"
 
 Session::Session()
 {
@@ -11,10 +13,8 @@ Session::~Session()
 {
     // delete all sources
     for(auto it = sources_.begin(); it != sources_.end(); ) {
-        // delete source
-        delete (*it);
-        // erase this iterator from the list
-        it = sources_.erase(it);
+        // erase this source from the list
+        it = deleteSource(*it);
     }
 
 }
@@ -22,14 +22,15 @@ Session::~Session()
 // update all sources
 void Session::update(float dt)
 {
-    // render of all sources
+    // pre-render of all sources
     for( SourceList::iterator it = sources_.begin(); it != sources_.end(); it++){
         (*it)->render( );
     }
 
+    // update the scene tree
     render_.update(dt);
 
-    // always draw render view
+    // draw render view in Frame Buffer
     render_.draw();
 }
 
@@ -50,19 +51,24 @@ SourceList::iterator Session::deleteSource(Source *s)
     SourceList::iterator its = find(s);
     // ok, its in the list !
     if (its != sources_.end()) {
-        // iterate backward to previous element in the list (hopefully exist)
-        its--;
 
-        // remove the source and delete it
-        sources_.remove(s);
+        // remove Node from the rendering scene
+//        GarbageVisitor remover(s->group(View::RENDERING));
+//        remover.visit(render_.scene);
 
+        render_.scene.root()->detatchChild( s->group(View::RENDERING) );
+
+        // erase the source from the update list & get next element
+        its = sources_.erase(its);
+
+        // delete the source : safe now
         delete s;
 
-        // return
-        return its;
+        // NB: GarbageVisitor ends here, and deletes the Group RENDERING
     }
 
-    return sources_.end();
+    // return end of next element
+    return its;
 }
 
 
diff --git a/Shader.h b/Shader.h
index d0677ee..9f6a57e 100644
--- a/Shader.h
+++ b/Shader.h
@@ -41,7 +41,7 @@ class Shader
 
 public:
     Shader();
-    virtual ~Shader() {}
+//    virtual ~Shader() {}
 
     // unique identifyer generated at instanciation
     inline int id () const { return id_; }
diff --git a/Source.cpp b/Source.cpp
index b8bd1fb..47d8235 100644
--- a/Source.cpp
+++ b/Source.cpp
@@ -50,12 +50,10 @@ Source::~Source()
 
     // all groups and their children are deleted in the scene
     // this includes rendersurface_ , overlay_, blendingshader_ and rendershader_
-//    delete groups_[View::RENDERING];
-//    delete groups_[View::MIXING];
-//    delete groups_[View::GEOMETRY];
-    Scene::deleteNode(groups_[View::RENDERING]);
-    Scene::deleteNode(groups_[View::MIXING]);
-    Scene::deleteNode(groups_[View::GEOMETRY]);
+    delete groups_[View::RENDERING];
+    delete groups_[View::MIXING];
+    delete groups_[View::GEOMETRY];
+
     groups_.clear();
 
 }
@@ -120,7 +118,9 @@ MediaSource::MediaSource(const std::string &name) : Source(name), uri_("")
 
 MediaSource::~MediaSource()
 {
-    delete mediasurface_;
+    // TODO delete media surface with visitor
+    //delete mediasurface_;
+
     delete mediaplayer_;
     // TODO verify that all surfaces and node is deleted in Source destructor
 }
@@ -162,7 +162,7 @@ void MediaSource::init()
 //            rendershader_->iChannelResolution[0] = glm::vec3(mediaplayer()->width(), mediaplayer()->height(), 0.f);
 
             // create the surfaces to draw the frame buffer in the views
-            // TODO Provide the source specific effect shader
+            // TODO Provide the source custom effect shader
             rendersurface_ = new FrameBufferSurface(renderbuffer_, blendingshader_);
             groups_[View::RENDERING]->addChild(rendersurface_);
             groups_[View::GEOMETRY]->addChild(rendersurface_);
diff --git a/UserInterfaceManager.cpp b/UserInterfaceManager.cpp
index 37e3236..7a30877 100644
--- a/UserInterfaceManager.cpp
+++ b/UserInterfaceManager.cpp
@@ -50,7 +50,8 @@
 static TextEditor editor;
 
 
-static std::thread FileDialogThread_;
+//static std::thread *FileDialogThread_;
+static bool FileDialogPending_ = false;
 static bool FileDialogFinished_ = false;
 static std::string FileDialogFilename_ = "";
 
@@ -60,7 +61,9 @@ void ShowAboutOpengl(bool* p_open);
 void ShowAbout(bool* p_open);
 
 static void FileDialogOpen(std::string path)
-{ 
+{
+     FileDialogPending_ = true;
+
      char const * lTheOpenFileName;
      char const * lFilterPatterns[2] = { "*.vmx" };
 
@@ -313,6 +316,7 @@ void UserInterface::NewFrame()
     // handle FileDialog
     if (FileDialogFinished_) {
         FileDialogFinished_ = false;
+        FileDialogPending_ = false;
         Mixer::manager().open(FileDialogFilename_);
     }
 }
@@ -320,7 +324,6 @@ void UserInterface::NewFrame()
 void UserInterface::Render()
 {
 //    ImVec2 geometry(static_cast<float>(Rendering::manager().Width()), static_cast<float>(Rendering::manager().Height()));
-
 //    // file modal dialog
 //    geometry.x *= 0.4f;
 //    geometry.y *= 0.4f;
@@ -332,8 +335,7 @@ void UserInterface::Render()
 //        }
 //        FileDialog::Instance()->CloseDialog(currentFileDialog.c_str());
 //    }
-
-    FileDialog::RenderCurrent();
+//    FileDialog::RenderCurrent();
 
     // warning modal dialog
     Log::Render();
@@ -378,16 +380,16 @@ void UserInterface::Terminate()
 void UserInterface::showMenuFile()
 {
     // TODO : New
-    if (ImGui::MenuItem( ICON_FA_FILE "  New", "Ctrl+W")) {
+    if (ImGui::MenuItem( ICON_FA_FILE "  New", "Ctrl+W", false, !FileDialogPending_)) {
         Mixer::manager().newSession();
         navigator.hidePannel();
     }
-    if (ImGui::MenuItem( ICON_FA_FILE_UPLOAD "  Open", "Ctrl+O")) {
+    if (ImGui::MenuItem( ICON_FA_FILE_UPLOAD "  Open", "Ctrl+O", false, !FileDialogPending_)) {
         // launch file dialog to open a session file
-        FileDialogThread_ = std::thread(FileDialogOpen, "./");
+        std::thread (FileDialogOpen, "./").detach();
         navigator.hidePannel();
     }
-    if (ImGui::MenuItem( ICON_FA_FILE_DOWNLOAD "  Save", "Ctrl+S")) {
+    if (ImGui::MenuItem( ICON_FA_FILE_DOWNLOAD "  Save", "Ctrl+S", false, !FileDialogPending_)) {
 //                UserInterface::manager().OpenFileMedia();
     }
     // TODO : Save As...