not working yet

app/gcompose/src/ContextModel.cpp

@@ -148,6 +148,7 @@ QVariant ContextModel::data(const QModelIndex& index, int role) const {
     if (!index.isValid()) return QVariant();
 
     uLib::Object* obj = static_cast<uLib::Object*>(index.internalPointer());
+    if (!obj) return QVariant();
     
     if (role == Qt::DisplayRole) {
         QString typeName = getDemangledName(typeid(*obj));

app/gcompose/src/MainPanel.cpp

@@ -13,6 +13,7 @@
 #include <QPushButton>
 #include <QMenu>
 #include <QAction>
+#include <QShortcut>
 #include <QApplication>
 #include <QFileDialog>
 #include <QFileInfo>
@@ -104,6 +105,14 @@ MainPanel::MainPanel(QWidget* parent) : QWidget(parent), m_context(nullptr), m_m
     m_rootSplitter->setSizes(sizes);
 
     mainLayout->addWidget(m_rootSplitter, 1);
+    
+    // Shortcuts
+    auto* groupShortcut = new QShortcut(QKeySequence("Ctrl+G"), this);
+    connect(groupShortcut, &QShortcut::activated, [this]() {
+        if (auto* viewport = qobject_cast<uLib::Vtk::QViewport*>(m_firstPane->currentViewport())) {
+            viewport->GroupSelection(m_context);
+        }
+    });
 }
 
 void MainPanel::setContext(uLib::ObjectsContext* context) {

app/gcompose/src/QViewportPane.cpp

@@ -94,8 +94,8 @@ void QViewportPane::setObject(uLib::Object* obj) {
 
 void QViewportPane::setViewport(QWidget* viewport, const QString& title) {
     if (m_viewport) {
-        m_viewport->parentWidget()->layout()->removeWidget(m_viewport);
-        delete m_viewport;
+        // Use deleteLater() instead of delete to avoid crashes during repaint cycles
+        m_viewport->deleteLater();
     }
     m_viewport = viewport;
     m_titleLabel->setText(title);
@@ -105,21 +105,8 @@ void QViewportPane::setViewport(QWidget* viewport, const QString& title) {
     mainAreaLayout->insertWidget(0, m_viewport);
 }
 
-
 QViewportPane::~QViewportPane() {}
 
-void QViewportPane::setViewport(QWidget* viewport, const QString& title) {
-    if (m_viewport) {
-        m_layout->removeWidget(m_viewport);
-        delete m_viewport;
-    }
-    m_viewport = viewport;
-    m_titleLabel->setText(title);
-
-    m_viewport->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
-    m_layout->addWidget(m_viewport);
-}
-
 void QViewportPane::addVtkViewport() {
     auto* viewport = new uLib::Vtk::QViewport(this);
     setViewport(viewport, "VTK Viewport");

app/gcompose/src/ViewportPane.cpp

@@ -115,7 +115,7 @@ void ViewportPane::setObject(uLib::Object* obj) {
 
 void ViewportPane::setViewport(QWidget* viewport, const QString& title) {
     if (m_viewport) {
-        delete m_viewport;
+        m_viewport->deleteLater();
     }
     m_viewport = viewport;
     m_titleLabel->setText(title);

build.log

@@ -1,36 +1 @@
-make: Entering directory '/home/rigoni/devel/cmt/ulib/build'
-[ 30%] Building CXX object src/Math/CMakeFiles/mutomMath.dir/VoxImage.cpp.o
-[ 30%] Building CXX object src/Math/CMakeFiles/mutomMath.dir/TriangleMesh.cpp.o
-[ 30%] Building CXX object src/Core/CMakeFiles/mutomCore.dir/Options.cpp.o
-[ 30%] Building CXX object src/Math/CMakeFiles/mutomMath.dir/Dense.cpp.o
-[ 30%] Building CXX object src/Math/CMakeFiles/mutomMath.dir/StructuredGrid.cpp.o
-[ 30%] Building CXX object src/Math/CMakeFiles/mutomMath.dir/VoxRaytracer.cpp.o
-[ 30%] Building CXX object src/Math/CMakeFiles/mutomMath.dir/StructuredData.cpp.o
-[ 30%] Building CXX object src/Math/CMakeFiles/mutomMath.dir/Structured2DGrid.cpp.o
-[ 30%] Building CXX object src/Math/CMakeFiles/mutomMath.dir/Structured4DGrid.cpp.o
-[ 33%] Linking CXX shared library libmutomCore.so
-[ 33%] Built target mutomCore
-[ 36%] Linking CXX shared library libmutomMath.so
-[ 36%] Built target mutomMath
-[ 63%] Building CXX object src/Vtk/CMakeFiles/mutomVtk.dir/vtkContainerBox.cpp.o
-[ 63%] Building CXX object src/Vtk/CMakeFiles/mutomVtk.dir/uLibVtkInterface.cxx.o
-[ 63%] Building CXX object src/Vtk/CMakeFiles/mutomVtk.dir/vtkStructuredGrid.cpp.o
-[ 63%] Building CXX object src/Vtk/CMakeFiles/mutomVtk.dir/vtkMuonScatter.cxx.o
-[ 63%] Building CXX object src/Vtk/CMakeFiles/mutomVtk.dir/uLibVtkViewer.cpp.o
-[ 63%] Generating mutomRootDict.cxx, libmutomRootDict_rdict.pcm, libmutomRootDict.rootmap
-[ 63%] Building CXX object src/Vtk/CMakeFiles/mutomVtk.dir/vtkVoxImage.cpp.o
-[ 63%] Building CXX object src/Vtk/CMakeFiles/mutomVtk.dir/vtkVoxRaytracerRepresentation.cpp.o
-[ 90%] Building CXX object src/Root/CMakeFiles/mutomRoot.dir/muCastorSkinHit.cpp.o
-[ 90%] Building CXX object src/Root/CMakeFiles/mutomRoot.dir/muCastorHit.cpp.o
-[ 90%] Building CXX object src/Root/CMakeFiles/mutomRoot.dir/muCastorMCTrack.cpp.o
-[ 90%] Building CXX object src/Root/CMakeFiles/mutomRoot.dir/muCastorInfo.cpp.o
-[ 90%] Building CXX object src/Root/CMakeFiles/mutomRoot.dir/RootMuonScatter.cpp.o
-[ 90%] Building CXX object src/Root/CMakeFiles/mutomRoot.dir/muCastorPrimaryVertex.cpp.o
-[ 90%] Building CXX object src/Root/CMakeFiles/mutomRoot.dir/muCastorMuDetDIGI.cpp.o
-[ 90%] Building CXX object src/Root/CMakeFiles/mutomRoot.dir/SkinDetectorWriter.cpp.o
-[ 93%] Building CXX object src/Root/CMakeFiles/mutomRoot.dir/mutomRootDict.cxx.o
-[ 96%] Linking CXX shared library libmutomVtk.so
-[ 96%] Built target mutomVtk
-[100%] Linking CXX shared library libmutomRoot.so
-[100%] Built target mutomRoot
-make: Leaving directory '/home/rigoni/devel/cmt/ulib/build'
+ninja: error: loading 'build.ninja': No such file or directory

condaenv.yml

@@ -9,7 +9,7 @@ dependencies:
   - root
   - vtk=9.4 # VTK 9.4
   - pybind11
-#  - boost=1.86.0 # requested by VTK 9.4
+  #- boost=1.86.0 # requested by VTK 9.4
   - ninja
   - clang
   - clangxx

src/Core/DataAllocator.h

@@ -46,6 +46,8 @@ public:
   DataAllocator(size_t size = 0, bool owns_objects = true)
       : m_Size(size), m_RamData(nullptr), m_VramData(nullptr),
         m_Device(MemoryDevice::RAM), m_OwnsObjects(owns_objects) {
+    if (m_Size >= (static_cast<size_t>(1) << 60))
+        throw std::invalid_argument("DataAllocator: absurdly large size requested");
     if (m_Size > 0) {
       if (m_OwnsObjects)
         m_RamData = new T[m_Size]();
@@ -139,7 +141,7 @@ public:
   void MoveToRAM() {
     if (m_Device == MemoryDevice::RAM)
       return;
-    if (!m_RamData && m_Size > 0) {
+    if (!m_RamData && m_Size > 0 && m_Size < (static_cast<size_t>(1) << 60)) {
       if (m_OwnsObjects)
         m_RamData = new T[m_Size]();
       else
@@ -178,7 +180,7 @@ public:
     T *newRam = nullptr;
     T *newVram = nullptr;
 
-    if (size > 0) {
+    if (size > 0 && size < (static_cast<size_t>(1) << 60)) {
       if (m_OwnsObjects)
         newRam = new T[size]();
       else

src/Core/Object.cpp

@@ -208,7 +208,8 @@ void Object::PrintSelf(std::ostream &o) const {
 
 bool Object::addSignalImpl(SignalBase *sig, GenericMFPtr fptr,
                            const char *name) {
-  ObjectPrivate::Signal s = {fptr, std::string(name), sig};
+  if (!d) return false;
+  ObjectPrivate::Signal s = {fptr, std::string(name ? name : "unnamed"), sig};
   d->sigv.push_back(s);
   return true;
 }

src/Core/ObjectsContext.cpp

@@ -8,7 +8,9 @@ ObjectsContext::ObjectsContext() : Object() {}
 ObjectsContext::~ObjectsContext() {}
 
 void ObjectsContext::AddObject(Object* obj) {
-    if (obj && std::find(m_objects.begin(), m_objects.end(), obj) == m_objects.end()) {
+    if (!obj || obj == this) return;
+    
+    if (std::find(m_objects.begin(), m_objects.end(), obj) == m_objects.end()) {
         m_objects.push_back(obj);
         // Connect child's update to context's update to trigger re-renders
         Object::connect(obj, &Object::Updated, this, &Object::Updated);

src/Math/Assembly.cpp

@@ -37,27 +37,18 @@ Assembly::Assembly(const Assembly &copy)
       m_GroupSelection(copy.m_GroupSelection) {}
 
 Assembly::~Assembly() {
-    for (auto const& [obj, conn] : m_ChildConnections) {
-        conn.disconnect();
-    }
-    m_ChildConnections.clear();
 }
 
 void Assembly::AddObject(Object *obj) {
+    if (!obj || obj == this) return;
+
     if (auto *at = dynamic_cast<AffineTransform *>(obj)) {
         at->SetParent(this);
     }
+    
+    // Base class already handles the list and child->parent update connection
     ObjectsContext::AddObject(obj);
     
-    // Connect to child updates to recompute AABB
-    m_ChildConnections[obj] = Object::connect(obj, &Object::Updated, [this](){
-        this->ComputeBoundingBox();
-        this->Updated(); // Signal that assembly itself changed (AABB-wise)
-    });
-
-    // Parent -> Child propagation for world matrix updates
-    Object::connect(this, &Object::Updated, obj, &Object::Updated);
-
     this->ComputeBoundingBox();
 }
 
@@ -67,12 +58,6 @@ void Assembly::RemoveObject(Object *obj) {
             at->SetParent(nullptr);
     }
     
-    auto itConn = m_ChildConnections.find(obj);
-    if (itConn != m_ChildConnections.end()) {
-        itConn->second.disconnect();
-        m_ChildConnections.erase(itConn);
-    }
-    
     ObjectsContext::RemoveObject(obj);
     this->ComputeBoundingBox();
 }

src/Math/Assembly.h

@@ -31,6 +31,7 @@
 #include "Math/Transform.h"
 
 namespace uLib {
+namespace Vtk { class Assembly; }
 
 /**
  * @brief Assembly groups geometric objects (ContainerBox, Cylinder, etc.)
@@ -46,6 +47,7 @@ namespace uLib {
 class Assembly : public ObjectsContext, public TRS {
 public:
     uLibTypeMacro(Assembly, ObjectsContext, TRS)
+    friend class Vtk::Assembly;
     
 
     Assembly();
@@ -112,7 +114,6 @@ private:
     bool     m_ShowBoundingBox;
     bool     m_GroupSelection;
     bool     m_InUpdated = false;
-    std::map<Object*, Connection> m_ChildConnections;
 
     ULIB_DECLARE_PROPERTIES(Assembly)
 };

src/Vtk/CMakeLists.txt

@@ -4,6 +4,7 @@ set(HEADERS uLibVtkInterface.h
             vtkQViewport.h
             vtkViewport.h
             vtkObjectsContext.h
+            vtkMultiSelectionProp.h
             )
 
 set(SOURCES uLibVtkInterface.cxx
@@ -12,6 +13,7 @@ set(SOURCES uLibVtkInterface.cxx
             vtkQViewport.cpp
             vtkViewport.cpp
             vtkObjectsContext.cpp
+            vtkMultiSelectionProp.cpp
             )
 
 ## Pull in Math VTK wrappers (sets MATH_SOURCES / MATH_HEADERS)

src/Vtk/Math/testing/vtkAssemblyTest.cpp

@@ -28,33 +28,33 @@ using namespace uLib;
 int main(int argc, char **argv) {
     bool interactive = (argc > 1 && std::string(argv[1]) == "-i");
 
-    // ---- 1. Build model objects ----
-    ContainerBox box1;
-    box1.Scale(Vector3f(1_m, 2_m, 0.5_m));
-    box1.SetPosition(Vector3f(0, 0, 0));
+    // ---- 1. Build model objects on the heap (expected by uLib SmartPointer) ----
+    auto* box1 = new ContainerBox();
+    box1->Scale(Vector3f(1, 2, 0.5));
+    // box1->SetPosition(Vector3f(0, 0, 0));
 
-    ContainerBox box2;
-    box2.Scale(Vector3f(0.5_m, 0.5_m, 3_m));
-    box2.SetPosition(Vector3f(2_m, 0, 0));
+    auto* box2 = new ContainerBox();
+    box2->Scale(Vector3f(0.5, 0.5, 3));
+    box2->SetPosition(Vector3f(2, 0, 0));
 
-    Cylinder cyl(0.3_m, 1.5_m, 1);
-    cyl.SetPosition(Vector3f(0, 3_m, 0));
+    auto* cyl = new Cylinder(1, 1.5, 1);
+    cyl->SetPosition(Vector3f(0, 3, 0));
 
     // ---- 2. Create an Assembly and add objects ----
-    Assembly assembly;
-    assembly.AddObject(&box1);
-    assembly.AddObject(&box2);
-    assembly.AddObject(&cyl);
-    assembly.SetShowBoundingBox(true);
+    auto* assembly = new Assembly();
+    assembly->AddObject(box1);
+    assembly->AddObject(box2);
+    assembly->AddObject(cyl);
+    assembly->SetShowBoundingBox(true);
 
     // ---- 3. Apply a group transform ----
-    assembly.SetPosition(Vector3f(1_m, 1_m, 0));
+    // assembly->SetPosition(Vector3f(1_m, 1_m, 0));
 
     // ---- 5. Visualize (create prop3ds to set properties) ----
-    Vtk::Assembly vtkAsm(&assembly);
+    Vtk::Assembly vtkAsm(assembly); // Vtk::Assembly takes ownership of the model wrapper
 
     Vtk::Viewer viewer;
-    vtkAsm.AddToViewer(viewer); // This triggers prop3d creation via ConnectRenderer which eventually calls Prop3D::GetProp
+    vtkAsm.AddToViewer(viewer); 
     
     // Explicitly update to ensure prop3ds exist and are added to assemblies
     vtkAsm.Update();
@@ -74,16 +74,16 @@ int main(int argc, char **argv) {
             }
         };
 
-        setProps(childCtx->GetProp3D(&box1), 1.0, 0.0, 0.0); // Red
-        setProps(childCtx->GetProp3D(&box2), 0.0, 1.0, 0.0); // Green
-        setProps(childCtx->GetProp3D(&cyl),  0.0, 0.0, 1.0); // Blue
+        setProps(childCtx->GetProp3D(box1), 1.0, 0.0, 0.0); // Red
+        setProps(childCtx->GetProp3D(box2), 0.0, 1.0, 0.0); // Green
+        setProps(childCtx->GetProp3D(cyl),  0.0, 0.0, 1.0); // Blue
     }
 
     std::cout << "Prop3Ds in viewport: " << viewer.getProp3Ds().size() << " (Expected 4: 1 assembly + 3 children)" << std::endl;
 
     // ---- 4. Query the bounding box for terminal output ----
     Vector3f bbMin, bbMax;
-    assembly.GetBoundingBox(bbMin, bbMax);
+    assembly->GetBoundingBox(bbMin, bbMax);
     std::cout << "Assembly bounding box:" << std::endl;
     std::cout << "  min = " << bbMin.transpose() << std::endl;
     std::cout << "  max = " << bbMax.transpose() << std::endl;

src/Vtk/Math/vtkAssembly.cpp

@@ -45,15 +45,13 @@ Assembly::Assembly(uLib::Assembly *content)
 
 Assembly::~Assembly() {
     delete m_ChildContext;
-    if (m_BBoxActor)  m_BBoxActor->Delete();
-    if (m_VtkAsm)     m_VtkAsm->Delete();
 }
 
 // ------------------------------------------------------------------ //
 void Assembly::InstallPipe() {
-    // 1. Create the VTK library assembly that groups everything
-    m_VtkAsm = ::vtkAssembly::New();
-    m_VtkAsm->PickableOff();
+    // 1. Setup the internal VTK assembly
+    m_VtkAsm = vtkSmartPointer<::vtkAssembly>::New();
+    m_BBoxActor = vtkSmartPointer<::vtkActor>::New();
     this->SetProp(m_VtkAsm);
 
     // 2. Create the bounding-box wireframe actor
@@ -64,7 +62,6 @@ void Assembly::InstallPipe() {
     vtkNew<vtkPolyDataMapper> mapper;
     mapper->SetInputConnection(cube->GetOutputPort());
 
-    m_BBoxActor = vtkActor::New();
     m_BBoxActor->SetMapper(mapper);
     m_BBoxActor->GetProperty()->SetRepresentationToWireframe();
     m_BBoxActor->GetProperty()->SetColor(1.0, 0.85, 0.0);   // gold wireframe
@@ -93,14 +90,7 @@ void Assembly::Update() {
     if (m_InUpdate) return;
     m_InUpdate = true;
     
-    if (this->m_model && m_VtkAsm) {
-        // Apply world matrix from the assembly content
-        vtkNew<vtkMatrix4x4> m;
-        Matrix4fToVtk(this->m_model->GetMatrix(), m);
-        m_VtkAsm->SetUserMatrix(m);
-        m_VtkAsm->Modified();
-    }
-
+    // Delegate to Prop3D to handle standard transformation application (uses GetContent())
     this->Prop3D::Update();
     this->UpdateBoundingBox();
     if (m_ChildContext)
@@ -110,25 +100,29 @@ void Assembly::Update() {
 
 void Assembly::SyncFromVtk() {
     if (m_InUpdate) return;
-    if (!this->m_model || !m_VtkAsm) return;
-
     m_InUpdate = true;
-
-    // VTK -> Model: Update world matrix (accounting for model parents)
-    if (vtkProp3D* proxy = this->GetProxyProp()) {
-        this->m_model->SetWorldMatrix(VtkToMatrix4f(proxy->GetUserMatrix()));
-        this->m_model->FromMatrix(this->m_model->GetMatrix());
-    }
-
-    this->UpdateBoundingBox();
+    
+    // Sync the group-level transformation from VTK to the domain model
+    this->Prop3D::SyncFromVtk();
+    
+    // Propagate sync to children
     if (m_ChildContext)
         m_ChildContext->SyncFromVtk();
-
-    this->m_model->Updated(); // Notify change in model
-
+    
     m_InUpdate = false;
 }
 
+
+void Assembly::serialize_display(uLib::Archive::display_properties_archive &ar, const unsigned int version) {
+    // 1. Register base class appearance/transform
+    this->Prop3D::serialize_display(ar, version);
+
+    // 2. Map domain model properties (Bounding Box visibility, etc.)
+    if (this->m_model) {
+        ar & HRP("ShowBoundingBox", m_model->m_ShowBoundingBox);
+    }
+}
+
 // ------------------------------------------------------------------ //
 void Assembly::UpdateBoundingBox() {
     if (!this->m_model || !m_BBoxActor) return;
@@ -188,10 +182,6 @@ void Assembly::UpdateBoundingBox() {
     m_BBoxActor->Modified();
 }
 
-// ------------------------------------------------------------------ //
-ObjectsContext *Assembly::GetChildrenContext() const {
-    return m_ChildContext;
-}
 
 } // namespace Vtk
 } // namespace uLib

src/Vtk/Math/vtkAssembly.h

@@ -16,8 +16,9 @@
 #include "Math/Assembly.h"
 #include "Vtk/uLibVtkInterface.h"
 
-class vtkActor;
-class vtkAssembly;  // VTK library forward declaration (must be before namespace)
+#include <vtkSmartPointer.h>
+#include <vtkActor.h>
+#include <vtkAssembly.h>
 
 namespace uLib {
 namespace Vtk {
@@ -39,33 +40,36 @@ class Assembly : public Prop3D, public uLib::ObjectWrapper<uLib::Assembly> {
 public:
     uLibTypeMacro(Assembly, Prop3D)
 
-    Assembly(uLib::Assembly *content);
+    /**
+     * @brief Constructor.
+     * @param content Pointer to the domain assembly model.
+     */
+    explicit Assembly(uLib::Assembly *content);
     virtual ~Assembly();
 
     /** @brief Updates the VTK representation from the model (model→VTK). */
     virtual void Update() override;
 
-    /** @brief Synchronizes the model from the VTK representation (VTK→model). */
     virtual void SyncFromVtk() override;
 
     virtual uLib::Object* GetContent() const override { return (uLib::Object*)m_model.get(); }
     virtual uLib::ObjectsContext* GetChildren() override { return (uLib::ObjectsContext*)m_model.get(); }
 
-    /**
-     * @brief Returns the prop3d managing child objects.
-     */
+    /** @brief Returns the visualization context for children. */
+    uLib::Vtk::ObjectsContext* GetChildrenContext() const { return m_ChildContext; }
 
-    /** @brief Returns the prop3d managing child objects. */
-    ObjectsContext *GetChildrenContext() const;
+    /** @brief Property serialization for Display Properties Panel. */
+    void serialize_display(Archive::display_properties_archive &ar, const unsigned int version = 0) override;
 
 private:
     void UpdateBoundingBox();
     void InstallPipe();
 
-    ObjectsContext  *m_ChildContext;
-    vtkActor           *m_BBoxActor;
-    ::vtkAssembly      *m_VtkAsm; // VTK library assembly — NOT this class
-    bool                m_InUpdate;    // re-entrancy guard
+    vtkSmartPointer<::vtkAssembly>    m_VtkAsm;
+    vtkSmartPointer<::vtkActor>       m_BBoxActor;
+
+    uLib::Vtk::ObjectsContext *m_ChildContext;
+    bool m_InUpdate;
 };
 
 } // namespace Vtk

src/Vtk/Math/vtkContainerBox.cpp

@@ -56,7 +56,9 @@ struct ContainerBoxData {
       : m_Cube(vtkSmartPointer<vtkActor>::New()),
         m_Axes(vtkSmartPointer<vtkActor>::New()),
         m_VtkAsm(vtkSmartPointer<vtkAssembly>::New()) {}
-  ~ContainerBoxData() {}
+  ~ContainerBoxData() {
+    m_UpdateSignal.disconnect();
+  }
 };
 
 ContainerBox::ContainerBox(ContainerBox::Content *content)
@@ -93,27 +95,7 @@ void ContainerBox::Update() {
   this->Prop3D::Update();
 }
 
-void ContainerBox::SyncFromVtk() {
-  RecursiveMutex::ScopedLock lock(this->m_UpdateMutex);
-  if (!this->m_model)
-    return;
 
-  vtkProp3D *root = this->GetProxyProp();
-  if (!root)
-    return;
-
-  // VTK -> Model: Extract new world TRS from proxy, which matches the model's
-  // TRS center
-  vtkMatrix4x4 *rootMat = root->GetUserMatrix();
-  Matrix4f vtkWorld = VtkToMatrix4f(rootMat);
-
-  // Synchronize TRS property members from the updated local matrix
-  this->m_model->FromMatrix(vtkWorld);
-
-  // Since we modified the model, notify observers, but block the loop back to
-  // VTK ConnectionBlock blocker(d->m_UpdateSignal);
-  this->m_model->Updated();
-}
 
 void ContainerBox::InstallPipe() {
   if (!this->m_model)

src/Vtk/Math/vtkContainerBox.h

@@ -59,7 +59,7 @@ public:
   /**
    * @brief Synchronizes the model from the VTK representation (VTK→model).
    */
-  virtual void SyncFromVtk() override;
+
 
   virtual uLib::Object *GetContent() const override {
     return (uLib::Object *)m_model.get();

src/Vtk/Math/vtkCylinder.cpp

@@ -44,8 +44,7 @@ Cylinder::Cylinder(Cylinder::Content *content)
 }
 
 Cylinder::~Cylinder() {
-  if (m_Actor) m_Actor->Delete();
-  if (m_VtkAsm) m_VtkAsm->Delete();
+  m_UpdateSignal.disconnect();
 }
 
 void Cylinder::Update() {
@@ -85,26 +84,13 @@ void Cylinder::Update() {
   this->Prop3D::Update();
 }
 
-void Cylinder::SyncFromVtk() {
-  if (!this->m_model) return;
-  
-  vtkProp3D* root = this->GetProxyProp();
-  if (!root) return;
 
-  // VTK -> Model: Extract new world TRS from proxy
-  vtkMatrix4x4* rootMat = root->GetUserMatrix();  
-  Matrix4f vtkWorld = VtkToMatrix4f(rootMat);
-  
-  // Directly sync model from the world matrix
-  this->m_model->FromMatrix(vtkWorld);
-  this->m_model->Updated(); 
-}
 
 void Cylinder::InstallPipe() {
   if (!this->m_model)
     return;
 
-  m_VtkAsm = ::vtkAssembly::New();
+  m_VtkAsm = vtkSmartPointer<::vtkAssembly>::New();
   this->SetProp(m_VtkAsm);
 
   vtkNew<vtkCylinderSource> cylinder;
@@ -112,7 +98,7 @@ void Cylinder::InstallPipe() {
   cylinder->SetHeight(1.0);
   cylinder->SetResolution(32);
 
-  m_Actor = vtkActor::New();
+  m_Actor = vtkSmartPointer<vtkActor>::New();
   vtkNew<vtkTransform> alignment;
   m_Actor->SetUserTransform(alignment);
 

src/Vtk/Math/vtkCylinder.h

@@ -30,6 +30,7 @@
 #include "Math/Cylinder.h"
 #include "Vtk/uLibVtkInterface.h"
 #include <vtkActor.h>
+#include <vtkSmartPointer.h>
 class vtkAssembly;
 
 namespace uLib {
@@ -53,7 +54,7 @@ public:
   virtual void Update() override;
 
   /** Synchronizes the uLib model matrix with the VTK actor specifically for gizmo interactions */
-  virtual void SyncFromVtk() override;
+
 
   virtual uLib::Object *GetContent() const override {
     return (uLib::Object *)m_model.get();
@@ -63,8 +64,8 @@ protected:
   /** Sets up the VTK visualization pipeline */
   virtual void InstallPipe();
 
-  vtkActor *m_Actor;
-  ::vtkAssembly *m_VtkAsm;
+  vtkSmartPointer<vtkActor> m_Actor;
+  vtkSmartPointer<::vtkAssembly> m_VtkAsm;
   uLib::Connection m_UpdateSignal;
 };
 

src/Vtk/Math/vtkVoxImage.cpp

@@ -308,17 +308,7 @@ void VoxImage::serialize_display(uLib::Archive::display_properties_archive & ar,
       {"MIP", "Composite", "Composite Shaded", "MIP Bone", "MIP Hot", "Additive"});
 }
 
-void VoxImage::SyncFromVtk() {
-  if (auto *root = this->GetProxyProp()) {
-    vtkMatrix4x4 *rootMat = root->GetUserMatrix();
-    if (rootMat) {
-      Matrix4f vtkLocal = VtkToMatrix4f(rootMat);
-      // Synchronize TRS from VTK, compensating for local volume offset
-      this->m_model->FromMatrix(vtkLocal); // * this->m_model->GetLocalMatrix().inverse());
-      this->m_model->Updated();
-    }
-  }
-}
+
 
 void VoxImage::Update() {
   if (auto *root = vtkProp3D::SafeDownCast(this->GetProp())) {

src/Vtk/Math/vtkVoxImage.h

@@ -77,7 +77,7 @@ public:
   void RescaleShaderRange();
 
   void Update() override;
-  void SyncFromVtk() override;
+
   void serialize_display(uLib::Archive::display_properties_archive &ar,
                          const unsigned int version = 0) override;
 

src/Vtk/uLibVtkInterface.cxx

@@ -97,11 +97,24 @@ public:
         m_HighlightMode(Prop3D::HighlightPlain)
     {
         m_Color = Vector3d(-1, -1, -1);
+        m_PrevMatrix = vtkSmartPointer<vtkMatrix4x4>::New();
+        m_PrevMatrix->Identity();
     }
 
     ~Prop3DData() {
-        // No manual Delete needed for smart pointers
-
+        if (m_Renderers) {
+            m_Renderers->InitTraversal();
+            for (int i = 0; i < m_Renderers->GetNumberOfItems(); ++i) {
+                vtkRenderer* ren = m_Renderers->GetNextItem();
+                if (ren) {
+                    if (m_Prop) ren->RemoveViewProp(m_Prop);
+                    if (m_OutlineActor) ren->RemoveActor(m_OutlineActor);
+                    if (m_CubeAxesActor) ren->RemoveActor(m_CubeAxesActor);
+                    if (m_HighlightActor) ren->RemoveActor(m_HighlightActor);
+                }
+            }
+            m_Renderers->RemoveAllItems();
+        }
     }
 
     Prop3D *m_Prop3D;
@@ -128,6 +141,8 @@ public:
 
     int  m_HighlightMode; // 0: Plain, 1: Corners
 
+    vtkSmartPointer<vtkMatrix4x4> m_PrevMatrix;
+
     // 
     TRS m_Transform;
 
@@ -289,6 +304,7 @@ public:
                         vtkNew<vtkMatrix4x4> vwm;
                         Matrix4fToVtk(tr->GetWorldMatrix(), vwm);
                         m_HighlightActor->SetUserMatrix(vwm);
+                        m_PrevMatrix->DeepCopy(vwm);
                     }
                 }
             }
@@ -569,6 +585,18 @@ void Prop3D::SetOpacity(double alpha)
     pd->ApplyAppearance(pd->m_Prop);
 }
 
+void Prop3D::GetColor(double &r, double &g, double &b) const
+{
+    r = pd->m_Color[0];
+    g = pd->m_Color[1];
+    b = pd->m_Color[2];
+}
+
+double Prop3D::GetOpacity() const
+{
+    return pd->m_Opacity;
+}
+
 
 
 
@@ -608,6 +636,7 @@ void Prop3D::ApplyProp3DTransform(vtkProp3D* prop)
             Matrix4fToVtk(tr->GetMatrix(), m);
             prop->SetUserMatrix(m);
             prop->Modified();
+            pd->m_PrevMatrix->DeepCopy(m);
         }
     }
 }
@@ -618,7 +647,18 @@ void Prop3D::SyncFromVtk()
         if (auto* tr = dynamic_cast<uLib::TRS*>(content)) {
             if (auto* proxy = this->GetProxyProp()) {
                 if (vtkMatrix4x4* mat = proxy->GetUserMatrix()) {
-                    tr->FromMatrix(VtkToMatrix4f(mat));
+                    // Calculate Delta: currentMatrix * Inv(m_PrevMatrix)
+                    vtkNew<vtkMatrix4x4> invPrev;
+                    vtkMatrix4x4::Invert(pd->m_PrevMatrix, invPrev);
+                    
+                    vtkNew<vtkMatrix4x4> delta;
+                    vtkMatrix4x4::Multiply4x4(mat, invPrev, delta);
+
+                    // Apply delta to world matrix
+                    Matrix4f nextWorldMatrix = VtkToMatrix4f(delta) * tr->GetWorldMatrix();
+                    tr->SetWorldMatrix(nextWorldMatrix);
+                    
+                    pd->m_PrevMatrix->DeepCopy(mat);
                     content->Updated();
                 }
             }

src/Vtk/uLibVtkInterface.h

@@ -86,8 +86,10 @@ public:
   void DisonnectViewer(Viewer *viewer);
 
   void SetColor(double r, double g, double b);
+  void GetColor(double &r, double &g, double &b) const;
 
   void SetOpacity(double alpha);
+  double GetOpacity() const;
 
   void SetSelectable(bool selectable = true);
   bool IsSelectable() const;

src/Vtk/vtkMultiSelectionProp.cpp

@@ -0,0 +1,175 @@
+#include "uLibVtkInterface.h"
+#include "vtkMultiSelectionProp.h"
+#include <vtkActor.h>
+#include <vtkPolyDataMapper.h>
+#include <vtkCubeSource.h>
+#include <vtkProperty.h>
+#include <vtkMatrix4x4.h>
+#include <vtkRenderer.h>
+#include <vtkRendererCollection.h>
+#include "Math/Transform.h"
+#include "Vtk/Math/vtkDense.h"
+
+namespace uLib {
+namespace Vtk {
+
+MultiSelectionProp::MultiSelectionProp() : Prop3D() {
+    ((::uLib::Object*)this)->SetInstanceName("Selection Group");
+    m_PrevMatrix = vtkSmartPointer<vtkMatrix4x4>::New();
+    m_GroupHighlightActor = vtkSmartPointer<vtkActor>::New();
+    
+    vtkNew<vtkPolyDataMapper> mapper;
+    m_GroupHighlightActor->SetMapper(mapper);
+    m_GroupHighlightActor->GetProperty()->SetRepresentationToWireframe();
+    m_GroupHighlightActor->GetProperty()->SetLineWidth(2.0);
+    m_GroupHighlightActor->GetProperty()->SetLighting(0);
+    m_GroupHighlightActor->PickableOff();
+    
+    // Set default display color in Prop3D state
+    ((Prop3D*)this)->SetColor(0.0, 1.0, 0.0);
+}
+
+MultiSelectionProp::~MultiSelectionProp() {
+}
+
+MultiSelectionProp* MultiSelectionProp::Clone() const {
+    auto* copy = new MultiSelectionProp();
+    copy->SetMembers(this->m_Members);
+    ((::uLib::Object*)copy)->SetInstanceName(((::uLib::Object*)this)->GetInstanceName());
+    return copy;
+}
+
+void MultiSelectionProp::SetMembers(const std::vector<Prop3D*>& members) {
+    m_Members = members;
+    Update();
+    
+    // Reset prev matrix to current highlight position
+    if (m_GroupHighlightActor->GetUserMatrix()) {
+        m_PrevMatrix->DeepCopy(m_GroupHighlightActor->GetUserMatrix());
+    } else {
+        m_PrevMatrix->Identity();
+    }
+}
+
+void MultiSelectionProp::Update() {
+    if (m_Members.empty()) {
+        m_GroupHighlightActor->VisibilityOff();
+        return;
+    }
+    m_GroupHighlightActor->VisibilityOn();
+    double combinedBounds[6] = {VTK_DOUBLE_MAX, VTK_DOUBLE_MIN, 
+                                VTK_DOUBLE_MAX, VTK_DOUBLE_MIN, 
+                                VTK_DOUBLE_MAX, VTK_DOUBLE_MIN};
+
+    for (auto* member : m_Members) {
+        if (vtkProp* prop = member->GetProp()) {
+            double* b = prop->GetBounds();
+            if (b) {
+                for (int i = 0; i < 3; ++i) {
+                    if (b[2*i] < combinedBounds[2*i]) combinedBounds[2*i] = b[2*i];
+                    if (b[2*i+1] > combinedBounds[2*i+1]) combinedBounds[2*i+1] = b[2*i+1];
+                }
+            }
+        }
+    }
+
+    if (combinedBounds[0] > combinedBounds[1]) return;
+
+    vtkNew<vtkCubeSource> cube;
+    double maxDim = std::max({combinedBounds[1]-combinedBounds[0], 
+                              combinedBounds[3]-combinedBounds[2], 
+                              combinedBounds[5]-combinedBounds[4]});
+    double pad = maxDim * 0.02;
+    if (pad < 1e-4) pad = 0.05;
+
+    cube->SetBounds(combinedBounds[0]-pad, combinedBounds[1]+pad,
+                    combinedBounds[2]-pad, combinedBounds[3]+pad,
+                    combinedBounds[4]-pad, combinedBounds[5]+pad);
+    cube->Update();
+    
+    if (auto* mapper = vtkPolyDataMapper::SafeDownCast(m_GroupHighlightActor->GetMapper())) {
+        mapper->SetInputConnection(cube->GetOutputPort());
+    }
+
+    // Apply TRS from m_SelectionTransform
+    vtkNew<vtkMatrix4x4> trsMatrix;
+    Matrix4fToVtk(m_SelectionTransform.GetWorldMatrix(), trsMatrix);
+    m_GroupHighlightActor->SetUserMatrix(trsMatrix);
+
+    // Apply Display Properties (Color, Opacity)
+    double r, g, b;
+    ((Prop3D*)this)->GetColor(r, g, b);
+    m_GroupHighlightActor->GetProperty()->SetColor(r, g, b);
+    m_GroupHighlightActor->GetProperty()->SetOpacity(((Prop3D*)this)->GetOpacity());
+
+    // Update Prev Matrix for delta calculations
+    m_PrevMatrix->DeepCopy(trsMatrix);
+
+    // Ensure it's in the renderers
+    vtkRendererCollection* rens = ((Prop3D*)this)->GetRenderers();
+    rens->InitTraversal();
+    for (int i = 0; i < rens->GetNumberOfItems(); ++i) {
+        vtkRenderer* ren = rens->GetNextItem();
+        ren->AddActor(m_GroupHighlightActor);
+    }
+}
+
+void MultiSelectionProp::SyncFromVtk() {
+    if (m_Members.empty()) return;
+    
+    vtkMatrix4x4* currentMatrix = m_GroupHighlightActor->GetUserMatrix();
+    if (!currentMatrix) return;
+
+    // Calculate Delta: currentMatrix * Inv(m_PrevMatrix)
+    vtkNew<vtkMatrix4x4> invPrev;
+    vtkMatrix4x4::Invert(m_PrevMatrix, invPrev);
+    
+    vtkNew<vtkMatrix4x4> delta;
+    vtkMatrix4x4::Multiply4x4(currentMatrix, invPrev, delta);
+
+    // Apply delta to all members
+    for (auto* member : m_Members) {
+        if (auto* content = member->GetContent()) {
+            if (auto* tr = dynamic_cast<uLib::TRS*>(content)) {
+                vtkNew<vtkMatrix4x4> memberWorldMatrix;
+                Matrix4fToVtk(tr->GetWorldMatrix(), memberWorldMatrix);
+                
+                vtkNew<vtkMatrix4x4> nextWorldMatrix;
+                vtkMatrix4x4::Multiply4x4(delta, memberWorldMatrix, nextWorldMatrix);
+                
+                // Set the new world matrix.
+                if (tr->GetParent()) {
+                    Matrix4f invParentWorld = tr->GetParent()->GetWorldMatrix().inverse();
+                    Matrix4f nextLocalMatrix = invParentWorld * VtkToMatrix4f(nextWorldMatrix);
+                    tr->FromMatrix(nextLocalMatrix);
+                } else {
+                    tr->FromMatrix(VtkToMatrix4f(nextWorldMatrix));
+                }
+                member->Update();
+            }
+        }
+    }
+    
+    m_PrevMatrix->DeepCopy(currentMatrix);
+    m_SelectionTransform.FromMatrix(VtkToMatrix4f(currentMatrix));
+}
+
+vtkProp* MultiSelectionProp::GetProp() {
+    return m_GroupHighlightActor;
+}
+
+vtkProp3D* MultiSelectionProp::GetProxyProp() {
+    return m_GroupHighlightActor;
+}
+
+void MultiSelectionProp::serialize(Archive::property_register_archive &ar, const unsigned int version) {
+    ar & boost::serialization::make_nvp("Transform", m_SelectionTransform);
+}
+
+void MultiSelectionProp::serialize_display(uLib::Archive::display_properties_archive &ar, const unsigned int version) {
+    // Call base class to register standard display properties (Color, Opacity)
+    ((Prop3D*)this)->serialize_display(ar, version);
+}
+
+} // namespace Vtk
+} // namespace uLib

src/Vtk/vtkMultiSelectionProp.h

@@ -0,0 +1,61 @@
+#ifndef ULIB_VTK_MULTISELECTIONPROP_H
+#define ULIB_VTK_MULTISELECTIONPROP_H
+
+#include "uLibVtkInterface.h"
+#include "Math/Transform.h"
+#include <vector>
+#include <vtkSmartPointer.h>
+#include <vtkMatrix4x4.h>
+
+class vtkActor;
+class vtkProp;
+class vtkProp3D;
+
+namespace uLib {
+namespace Vtk {
+
+/**
+ * @class MultiSelectionProp
+ * @brief A proxy Prop3D that represents a group of selected Prop3Ds.
+ * It manages a combined highlight and propagates transformations to its members.
+ */
+class MultiSelectionProp : public Prop3D {
+public:
+    uLibTypeMacro(MultiSelectionProp, Prop3D)
+
+    MultiSelectionProp();
+    virtual ~MultiSelectionProp();
+
+    /** @brief Creates a new instance that is a copy of this one's selection state. */
+    MultiSelectionProp* Clone() const;
+
+    void SetMembers(const std::vector<Prop3D*>& members);
+    const std::vector<Prop3D*>& GetMembers() const { return m_Members; }
+
+    virtual void Update() override;
+    virtual void SyncFromVtk() override;
+
+    virtual vtkProp* GetProp() override;
+    virtual vtkProp3D* GetProxyProp() override;
+
+    // Serialization for Properties Panel (TRS)
+    void serialize(Archive::property_register_archive &ar, const unsigned int version);
+
+    // Serialization for Display Properties Panel (Color, Opacity)
+    void serialize_display(uLib::Archive::display_properties_archive &ar, const unsigned int version = 0) override;
+
+    virtual uLib::Object* GetContent() const override { return const_cast<MultiSelectionProp*>(this); }
+
+private:
+    std::vector<Prop3D*> m_Members;
+    uLib::TRS m_SelectionTransform;
+    vtkSmartPointer<vtkMatrix4x4> m_PrevMatrix;
+    vtkSmartPointer<vtkActor> m_GroupHighlightActor;
+
+    
+};
+
+} // namespace Vtk
+} // namespace uLib
+
+#endif // ULIB_VTK_MULTISELECTIONPROP_H

src/Vtk/vtkObjectsContext.cpp

@@ -26,15 +26,17 @@ ObjectsContext::ObjectsContext(uLib::ObjectsContext *context)
     : m_Context(context), m_Assembly(::vtkAssembly::New()) {
   this->SetProp(m_Assembly);
   if (m_Context) {
-    Object::connect(m_Context, &uLib::ObjectsContext::ObjectAdded, this,
+    m_AddedConnection = Object::connect(m_Context, &uLib::ObjectsContext::ObjectAdded, this,
                     &ObjectsContext::OnObjectAdded);
-    Object::connect(m_Context, &uLib::ObjectsContext::ObjectRemoved, this,
+    m_RemovedConnection = Object::connect(m_Context, &uLib::ObjectsContext::ObjectRemoved, this,
                     &ObjectsContext::OnObjectRemoved);
     this->Synchronize();
   }
 }
 
 ObjectsContext::~ObjectsContext() {
+  m_AddedConnection.disconnect();
+  m_RemovedConnection.disconnect();
   for (auto const &[obj, prop3d] : m_Prop3Ds) {
     delete prop3d;
   }
@@ -136,6 +138,10 @@ Prop3D *ObjectsContext::CreateProp3D(uLib::Object *obj) {
   if (!obj)
     return nullptr;
 
+  if (auto* p3d = dynamic_cast<Prop3D*>(obj)) {
+      return p3d;
+  }
+
   if (auto *vox = dynamic_cast<uLib::Abstract::VoxImage *>(obj)) {
     return new VoxImage(vox);
   } else if (auto *box = dynamic_cast<uLib::ContainerBox *>(obj)) {

src/Vtk/vtkObjectsContext.h

@@ -51,6 +51,8 @@ private:
   uLib::ObjectsContext *m_Context;
   std::map<uLib::Object*, Prop3D*> m_Prop3Ds;
   vtkAssembly *m_Assembly;
+  uLib::Connection m_AddedConnection;
+  uLib::Connection m_RemovedConnection;
 };
 
 } // namespace Vtk

src/Vtk/vtkQViewport.cpp

@@ -104,6 +104,9 @@ QViewport::QViewport(QWidget* parent)
 
 QViewport::~QViewport()
 {
+    if (m_VtkWidget && m_VtkWidget->renderWindow()) {
+        m_VtkWidget->renderWindow()->RemoveRenderer(this->GetRenderer());
+    }
 }
 
 void QViewport::SetupPipeline()

src/Vtk/vtkViewport.cpp

@@ -36,6 +36,8 @@
 #include "Vtk/Math/vtkCylinder.h"
 #include "Math/Transform.h"
 #include "Vtk/Math/vtkAssembly.h"
+#include "vtkMultiSelectionProp.h"
+#include <vtkRendererCollection.h>
 
 namespace uLib {
 namespace Vtk {
@@ -69,6 +71,7 @@ struct ViewportData {
 Viewport::Viewport()
     : pv(new ViewportData())
     , m_GridAxis(Y)
+    , m_MultiSelectionProp(new MultiSelectionProp())
 {
 }
 
@@ -100,6 +103,10 @@ Viewport::~Viewport()
         pv->m_CameraWidget->Off();
         pv->m_CameraWidget->SetInteractor(nullptr);
     }
+    if (m_MultiSelectionProp) {
+        delete m_MultiSelectionProp;
+        m_MultiSelectionProp = nullptr;
+    }
     delete pv;
 }
 
@@ -192,6 +199,11 @@ void Viewport::SetupPipeline(vtkRenderWindowInteractor* iren)
         pv->m_Renderer->SetLayer(0);
     }
 
+    // Connect MultiSelectionProp
+    if (m_MultiSelectionProp) {
+        m_MultiSelectionProp->ConnectRenderer(pv->m_Renderer);
+    }
+
     // Setup Handler Widget
     if (!std::getenv("CTEST_PROJECT_NAME")) {
         pv->m_HandlerWidget = vtkSmartPointer<HandlerWidget>::New();
@@ -206,8 +218,10 @@ void Viewport::SetupPipeline(vtkRenderWindowInteractor* iren)
         widgetInteractionCallback->SetClientData(this);
         widgetInteractionCallback->SetCallback([](vtkObject*, unsigned long, void* clientdata, void*){
             auto* self = static_cast<Viewport*>(clientdata);
-            for (auto* p : self->m_Prop3Ds) {
-                if (p->IsSelected()) {
+            if (self->m_SelectedProps.size() > 1 && self->m_MultiSelectionProp) {
+                self->m_MultiSelectionProp->SyncFromVtk();
+            } else {
+                for (auto* p : self->m_SelectedProps) {
                     p->SyncFromVtk();
                 }
             }
@@ -222,6 +236,7 @@ void Viewport::SetupPipeline(vtkRenderWindowInteractor* iren)
     clickCallback->SetCallback([](vtkObject* caller, unsigned long, void* clientdata, void*){
         auto* iren = static_cast<vtkRenderWindowInteractor*>(caller);
         auto* self = static_cast<Viewport*>(clientdata);
+        bool multiSelect = iren->GetShiftKey() != 0;
         
         int* pos = iren->GetEventPosition();
         self->pv->m_Picker->Pick(pos[0], pos[1], 0, self->pv->m_Renderer);
@@ -291,7 +306,7 @@ void Viewport::SetupPipeline(vtkRenderWindowInteractor* iren)
                 }
             }
         }
-        self->SelectProp3D(target);
+        self->SelectProp3D(target, multiSelect);
     });
     iren->AddObserver(vtkCommand::LeftButtonPressEvent, clickCallback);
 
@@ -446,6 +461,11 @@ void Viewport::RegisterProp3D(Prop3D* p, bool isPart) {
     m_Prop3Ds.push_back(p);
     p->ConnectRenderer(pv->m_Renderer);
 
+    // Ensure m_MultiSelectionProp also has the same renderers
+    if (m_MultiSelectionProp) {
+        m_MultiSelectionProp->GetRenderers()->AddItem(pv->m_Renderer);
+    }
+
     // If it's a part of an assembly, we don't want to draw it twice.
     // Assembly itself already draws its parts. 
     // But we need ConnectRenderer above to allow highliting and property updates.
@@ -497,28 +517,59 @@ void Viewport::ObserveContext(ObjectsContext* ctx) {
     });
 }
 
-void Viewport::SelectProp3D(Prop3D* prop)
+void Viewport::SelectProp3D(Prop3D* prop, bool multi)
 {
-    for (auto* p : m_Prop3Ds) {
-        p->SetSelected(p == prop);
-    }
-    
-    if (pv->m_HandlerWidget) {
+    if (multi) {
         if (prop) {
-            vtkProp3D* prop3d = prop->GetProxyProp();
+            auto it = std::find(m_SelectedProps.begin(), m_SelectedProps.end(), prop);
+            if (it != m_SelectedProps.end()) {
+                prop->SetSelected(false);
+                m_SelectedProps.erase(it);
+            } else {
+                prop->SetSelected(true);
+                m_SelectedProps.push_back(prop);
+            }
+        }
+    } else {
+        for (auto* p : m_SelectedProps) {
+            p->SetSelected(false);
+        }
+        m_SelectedProps.clear();
+        if (prop) {
+            prop->SetSelected(true);
+            m_SelectedProps.push_back(prop);
+        }
+    }
+
+    // Update HandlerWidget
+    if (pv->m_HandlerWidget) {
+        if (m_SelectedProps.empty()) {
+            pv->m_HandlerWidget->SetEnabled(0);
+            pv->m_HandlerWidget->SetProp3D(nullptr);
+            if (m_MultiSelectionProp) m_MultiSelectionProp->SetMembers({});
+        } else if (m_SelectedProps.size() == 1) {
+            Prop3D* selected = m_SelectedProps[0];
+            vtkProp3D* prop3d = selected->GetProxyProp();
             if (prop3d) {
                 pv->m_HandlerWidget->SetProp3D(prop3d);
                 pv->m_HandlerWidget->SetEnabled(1);
-                pv->m_HandlerWidget->PlaceWidget(prop3d->GetBounds()); //TODO: FIX !
+                pv->m_HandlerWidget->PlaceWidget(prop3d->GetBounds());
             }
+            if (m_MultiSelectionProp) m_MultiSelectionProp->SetMembers({});
         } else {
-            pv->m_HandlerWidget->SetEnabled(0);
-            pv->m_HandlerWidget->SetProp3D(nullptr);
+            // Multi-selection
+            if (m_MultiSelectionProp) {
+                m_MultiSelectionProp->SetMembers(m_SelectedProps);
+                vtkProp3D* proxy = m_MultiSelectionProp->GetProxyProp();
+                pv->m_HandlerWidget->SetProp3D(proxy);
+                pv->m_HandlerWidget->SetEnabled(1);
+                pv->m_HandlerWidget->PlaceWidget(proxy->GetBounds());
+            }
         }
     }
     
     Render();
-    OnSelectionChanged(prop);
+    OnSelectionChanged(m_SelectedProps.empty() ? nullptr : m_SelectedProps.back());
 }
 
 void Viewport::SetGridVisible(bool visible)
@@ -657,5 +708,19 @@ void Viewport::UpdateGrid()
     pv->m_Annotation->SetText(1, gridLabel);
 }
 
+void Viewport::GroupSelection(uLib::ObjectsContext* targetCtx) {
+    if (!targetCtx || m_SelectedProps.size() <= 1 || !m_MultiSelectionProp) return;
+
+    // Clone the current multi-selection proxy
+    MultiSelectionProp* group = m_MultiSelectionProp->Clone();
+    
+    // Add it to the context
+    targetCtx->AddObject(group);
+    
+    // Select the new group and clear multi-selection
+    m_SelectedProps.clear();
+    SelectProp3D(group);
+}
+
 } // namespace Vtk
 } // namespace uLib

src/Vtk/vtkViewport.h

@@ -29,6 +29,7 @@ namespace Vtk {
 
 struct ViewportData;
 class HandlerWidget;
+class MultiSelectionProp;
 class ObjectsContext;
 
 /**
@@ -49,7 +50,11 @@ public:
     // Prop3D / prop management
     void AddProp3D(Prop3D &prop);
     void RemoveProp3D(Prop3D &prop);
-    void SelectProp3D(Prop3D *prop);
+    /** @brief Selects a specific Prop3D. If multi is true, it toggles selection in a group. */
+    void SelectProp3D(Prop3D* target, bool multi = false);
+
+    /** @brief Creates a persistent Selection Group from the current multi-selection. */
+    void GroupSelection(uLib::ObjectsContext* targetCtx);
     void addProp(vtkProp *prop);
     void RemoveProp(vtkProp *prop);
 
@@ -91,6 +96,8 @@ protected:
     struct ViewportData *pv;
     Axis                                         m_GridAxis;
     std::vector<Prop3D*>                         m_Prop3Ds;
+    std::vector<Prop3D*>                         m_SelectedProps;
+    MultiSelectionProp*                          m_MultiSelectionProp;
     std::map<uLib::Object*, Prop3D*>             m_ObjectToProp3D;
 };