ENH: Add SetBlocked method to ObjectEventObserver

Author: Thibault-Pelletier

LayerDM/MRMLDM/vtkMRMLLayerDMObjectEventObserver.cxx

@@ -17,12 +17,18 @@ Overloaded(Ts...) -> Overloaded<Ts...>;
 
 vtkMRMLLayerDMObjectEventObserver::vtkMRMLLayerDMObjectEventObserver()
   : m_updateCommand(vtkSmartPointer<vtkCallbackCommand>::New())
+  , m_isBlocked(false)
 {
   this->m_updateCommand->SetClientData(this);
   this->m_updateCommand->SetCallback(
     [](vtkObject* caller, unsigned long eid, void* clientData, void* callData)
     {
       auto client = static_cast<vtkMRMLLayerDMObjectEventObserver*>(clientData);
+      if (client->m_isBlocked)
+      {
+        return;
+      }
+
       try
       {
         // Dispatch to callback depending on current std variant content
@@ -77,6 +83,13 @@ void vtkMRMLLayerDMObjectEventObserver::SetUpdateCallback(const std::function<vo
   this->m_callback = callback;
 }
 
+bool vtkMRMLLayerDMObjectEventObserver::SetBlocked(bool isBlocked)
+{
+  bool wasBlocked = this->m_isBlocked;
+  this->m_isBlocked = isBlocked;
+  return wasBlocked;
+}
+
 void vtkMRMLLayerDMObjectEventObserver::SetUpdateCallback(const std::function<void(vtkObject* node, unsigned long eventId)>& callback)
 {
   this->m_callback = callback;

LayerDM/MRMLDM/vtkMRMLLayerDMObjectEventObserver.h

@@ -48,6 +48,10 @@ class VTK_SLICER_LAYERDM_MODULE_MRMLDISPLAYABLEMANAGER_EXPORT vtkMRMLLayerDMObje
   void SetUpdateCallback(const std::function<void(vtkObject* node, unsigned long eventId, void* callData)>& callback);
   /// @}
 
+  /// Set update callback blocked.
+  /// @return previous blocked state.
+  bool SetBlocked(bool isBlocked);
+
 protected:
   vtkMRMLLayerDMObjectEventObserver();
   ~vtkMRMLLayerDMObjectEventObserver() override;
@@ -62,4 +66,5 @@ class VTK_SLICER_LAYERDM_MODULE_MRMLDISPLAYABLEMANAGER_EXPORT vtkMRMLLayerDMObje
                std::function<void(vtkObject* node, unsigned long eventId)>,
                std::function<void(vtkObject* node, unsigned long eventId, void* callData)>>
     m_callback;
+  bool m_isBlocked;
 };

LayerDM/Testing/Python/ObjectEventObserverScriptedTest.py

@@ -64,3 +64,16 @@ def test_can_cast_observed_call_data(self):
         assert args[0] == slicer.mrmlScene
         assert args[1] == vtkMRMLScene.NodeAddedEvent
         assert self.observer.CastCallData(args[2], VTK_OBJECT) == modelNode
+
+    def test_update_can_be_blocked(self):
+        modelNode = vtkMRMLModelNode()
+        self.observer.UpdateObserver(None, modelNode, vtkCommand.ModifiedEvent)
+        wasBlocked = self.observer.SetBlocked(True)
+        assert not wasBlocked
+
+        modelNode.Modified()
+        self.mock.assert_not_called()
+
+        self.observer.SetBlocked(wasBlocked)
+        modelNode.Modified()
+        self.mock.assert_called_once_with(modelNode, vtkCommand.ModifiedEvent, None)