--- a/Framework/Scene2DViewport/MeasureCommands.cpp	Wed Mar 04 09:44:34 2020 +0100
+++ b/Framework/Scene2DViewport/MeasureCommands.cpp	Wed Mar 04 09:45:38 2020 +0100
@@ -20,6 +20,8 @@
 
 #include "MeasureCommands.h"
 
+#include <memory>
+
 #include <boost/make_shared.hpp>
 #include <boost/ref.hpp>
 
@@ -27,19 +29,21 @@
 {
   void CreateMeasureCommand::Undo()
   {
+    std::unique_ptr<OrthancStone::IViewport::ILock> lock(viewport_.Lock());
     // simply disable the measure tool upon undo
     GetMeasureTool()->Disable();
-    GetController()->RemoveMeasureTool(GetMeasureTool());
+    lock->GetController().RemoveMeasureTool(GetMeasureTool());
   }
 
   void CreateMeasureCommand::Redo()
   {
+    std::unique_ptr<OrthancStone::IViewport::ILock> lock(viewport_.Lock());
     GetMeasureTool()->Enable();
-    GetController()->AddMeasureTool(GetMeasureTool());
+    lock->GetController().AddMeasureTool(GetMeasureTool());
   }
 
-  CreateMeasureCommand::CreateMeasureCommand(boost::weak_ptr<ViewportController> controllerW)
-    : MeasureCommand(controllerW)
+  CreateMeasureCommand::CreateMeasureCommand(IViewport& viewport)
+    : MeasureCommand(viewport)
   {
 
   }
@@ -52,15 +56,17 @@
 
   void DeleteMeasureCommand::Redo()
   {
+    std::unique_ptr<OrthancStone::IViewport::ILock> lock(viewport_.Lock());
     // simply disable the measure tool upon undo
     GetMeasureTool()->Disable();
-    GetController()->RemoveMeasureTool(GetMeasureTool());
+    lock->GetController().RemoveMeasureTool(GetMeasureTool());
   }
 
   void DeleteMeasureCommand::Undo()
   {
+    std::unique_ptr<OrthancStone::IViewport::ILock> lock(viewport_.Lock());
     GetMeasureTool()->Enable();
-    GetController()->AddMeasureTool(GetMeasureTool());
+    lock->GetController().AddMeasureTool(GetMeasureTool());
   }
 
   DeleteMeasureCommand::~DeleteMeasureCommand()
@@ -69,18 +75,19 @@
     // we thus leave it as is
   }
 
-  DeleteMeasureCommand::DeleteMeasureCommand(boost::shared_ptr<MeasureTool> measureTool, boost::weak_ptr<ViewportController> controllerW)
-    : MeasureCommand(controllerW)
+  DeleteMeasureCommand::DeleteMeasureCommand(boost::shared_ptr<MeasureTool> measureTool, IViewport& viewport)
+    : MeasureCommand(viewport)
     , mementoOriginal_(measureTool->GetMemento())
     , measureTool_(measureTool)
     , mementoModified_(measureTool->GetMemento())
   {
+    std::unique_ptr<OrthancStone::IViewport::ILock> lock(viewport_.Lock());
     GetMeasureTool()->Disable();
-    GetController()->RemoveMeasureTool(GetMeasureTool());
+    lock->GetController().RemoveMeasureTool(GetMeasureTool());
   }
 
-  EditMeasureCommand::EditMeasureCommand(boost::shared_ptr<MeasureTool> measureTool, boost::weak_ptr<ViewportController> controllerW)
-    : MeasureCommand(controllerW)
+  EditMeasureCommand::EditMeasureCommand(boost::shared_ptr<MeasureTool> measureTool, IViewport& viewport)
+    : MeasureCommand(viewport)
     , mementoOriginal_(measureTool->GetMemento())
     , mementoModified_(measureTool->GetMemento())
   {
@@ -102,11 +109,4 @@
   {
     GetMeasureTool()->SetMemento(mementoModified_);
   }
-
-  boost::shared_ptr<ViewportController> MeasureCommand::GetController()
-  {
-    boost::shared_ptr<ViewportController> controller = controllerW_.lock();
-    assert(controller); // accessing dead object?
-    return controller;
-  }
 }