COMP: Use nullptr instead of 0 or NULL

This commit converts the usage of null pointer constants (eg. NULL, 0) to
use the new C++11 nullptr keyword.

Updates were performed following these steps:

(1) Reconfigure with CMAKE_EXPORT_COMPILE_COMMANDS

  cd /tmp/Slicer-CameraPath-
  cmake -DCMAKE_EXPORT_COMPILE_COMMANDS:BOOL=ON .

(2) Run run-clang-tidy

  cd /tmp/Slicer-CameraPath-build
  run-clang-tidy-10 -header-filter='.*' -checks='-*,modernize-use-nullptr' -fix


References:

* https://www.slicer.org/wiki/Documentation/Nightly/Developers/Tutorials/MigrationGuide#C.2B.2B11:_Update_source_code_to_use_nullptr

Modules/Loadable/CameraPath/Logic/vtkSlicerCameraPathLogic.cxx

@@ -82,7 +82,7 @@ void vtkSlicerCameraPathLogic::UpdateFromMRMLScene()
 //---------------------------------------------------------------------------
 void vtkSlicerCameraPathLogic::OnMRMLSceneNodeAdded(vtkMRMLNode* node)
 {
-  if (node==NULL)
+  if (node == nullptr)
   {
     vtkErrorMacro("An invalid node is attempted to be added");
     return;
@@ -104,7 +104,7 @@ void vtkSlicerCameraPathLogic::OnMRMLSceneNodeAdded(vtkMRMLNode* node)
 //---------------------------------------------------------------------------
 void vtkSlicerCameraPathLogic::OnMRMLSceneNodeRemoved(vtkMRMLNode* node)
 {
-  if (node==NULL)
+  if (node == nullptr)
   {
     vtkErrorMacro("An invalid node is attempted to be removed");
     return;
@@ -124,23 +124,23 @@ void vtkSlicerCameraPathLogic::OnMRMLSceneNodeRemoved(vtkMRMLNode* node)
 //---------------------------------------------------------------------------
 char* vtkSlicerCameraPathLogic::LoadCameraPath(const char *fileName, const char *nodeName)
 {
-  char *nodeIDs = NULL;
+  char *nodeIDs = nullptr;
   std::string idList;
 
   if (!fileName)
     {
     vtkErrorMacro("LoadCameraPath: null file name, cannot load");
-    return NULL;
+    return nullptr;
     }
   if (fileName[0] == '\0')
     {
     vtkErrorMacro("LoadCameraPath: empty file name, cannot load");
-    return NULL;
+    return nullptr;
     }
   if (!this->GetMRMLScene())
     {
     vtkErrorMacro("LoadCameraPath: no MRML scene, cannot load");
-    return NULL;
+    return nullptr;
     }
 
   // turn on batch processing
@@ -180,7 +180,7 @@ char* vtkSlicerCameraPathLogic::LoadCameraPath(const char *fileName, const char
     vtkErrorMacro("LoadCameraPath: coud not read data");
     this->GetMRMLScene()->RemoveNode(cameraPathNode.GetPointer());
     this->GetMRMLScene()->RemoveNode(storageNode.GetPointer());
-    return NULL;
+    return nullptr;
     }
 
   // adding camera nodes to scene

Modules/Loadable/CameraPath/MRML/vtkMRMLCameraPathNode.h

@@ -21,7 +21,7 @@ struct KeyFrame
   //bool Locked;
   //bool Visibility;
 
-  KeyFrame(vtkMRMLCameraNode* camera = NULL,
+  KeyFrame(vtkMRMLCameraNode* camera = nullptr,
            double time = 0.0):
       Camera(camera),
       Time(time)
@@ -104,9 +104,9 @@ class VTK_SLICER_CAMERAPATH_MODULE_MRML_EXPORT vtkMRMLCameraPathNode:
   KeyFrame GetKeyFrame(vtkIdType index);
   double GetKeyFrameTime(vtkIdType index);
   vtkMRMLCameraNode* GetKeyFrameCamera(vtkIdType index);
-  void GetKeyFramePosition(vtkIdType index, double position[3] = 0);
-  void GetKeyFrameFocalPoint(vtkIdType index, double focalPoint[3] = 0);
-  void GetKeyFrameViewUp(vtkIdType index, double viewUp[3] = 0);
+  void GetKeyFramePosition(vtkIdType index, double position[3] = nullptr);
+  void GetKeyFrameFocalPoint(vtkIdType index, double focalPoint[3] = nullptr);
+  void GetKeyFrameViewUp(vtkIdType index, double viewUp[3] = nullptr);
 
   void SetKeyFrames(KeyFrameVector keyFrames);
   void SetKeyFrame(vtkIdType index, KeyFrame keyFrame);
@@ -140,9 +140,9 @@ class VTK_SLICER_CAMERAPATH_MODULE_MRML_EXPORT vtkMRMLCameraPathNode:
                        vtkMRMLPointSplineNode* viewUps);
 
   void GetCameraAt(double t, vtkMRMLCameraNode* camera);
-  void GetPositionAt(double t, double position[3] = 0);
-  void GetFocalPointAt(double t, double focalPoint[3] = 0);
-  void GetViewUpAt(double t, double viewUp[3] = 0);
+  void GetPositionAt(double t, double position[3] = nullptr);
+  void GetFocalPointAt(double t, double focalPoint[3] = nullptr);
+  void GetViewUpAt(double t, double viewUp[3] = nullptr);
   double ClampTime(double t);
 
 protected:

Modules/Loadable/CameraPath/MRML/vtkMRMLPointSplineNode.cxx

@@ -115,12 +115,12 @@ void vtkMRMLPointSplineNode::PrintSelf(ostream& os, vtkIndent indent)
 //----------------------------------------------------------------------------
 void vtkMRMLPointSplineNode::CreateDefaultDisplayNodes()
 {
-  if (vtkMRMLModelDisplayNode::SafeDownCast(this->GetDisplayNode())!=NULL)
+  if (vtkMRMLModelDisplayNode::SafeDownCast(this->GetDisplayNode()) != nullptr)
     {
     // display node already exists
     return;
     }
-  if (this->GetScene()==NULL)
+  if (this->GetScene() == nullptr)
     {
     vtkErrorMacro("vtkMRMLPointSplineNode::CreateDefaultDisplayNodes failed: scene is invalid");
     return;

Modules/Loadable/CameraPath/MRML/vtkMRMLPointSplineNode.h

@@ -56,7 +56,7 @@ class VTK_SLICER_CAMERAPATH_MODULE_MRML_EXPORT vtkMRMLPointSplineNode :
   void AddPoint(double t, double point[3]);
   void RemovePoint(double t);
   void UpdatePolyData(int framerate);
-  void Evaluate(double t, double point[3]=0);
+  void Evaluate(double t, double point[3]=nullptr);
 
 protected:
   vtkMRMLPointSplineNode();

Modules/Loadable/CameraPath/qSlicerCameraPathModule.h

@@ -37,7 +37,7 @@ qSlicerCameraPathModule
 public:
 
   typedef qSlicerLoadableModule Superclass;
-  explicit qSlicerCameraPathModule(QObject *parent=0);
+  explicit qSlicerCameraPathModule(QObject *parent=nullptr);
   virtual ~qSlicerCameraPathModule();
 
   qSlicerGetTitleMacro(QTMODULE_TITLE);

Modules/Loadable/CameraPath/qSlicerCameraPathModuleWidget.cxx

@@ -98,7 +98,7 @@ qSlicerCameraPathModuleWidgetPrivate::logic() const
   Q_Q(const qSlicerCameraPathModuleWidget);
 
   vtkSlicerCameraPathLogic* logic=vtkSlicerCameraPathLogic::SafeDownCast(q->logic());
-  if (logic==NULL)
+  if (logic == nullptr)
   {
     qCritical() << "Camera path logic is invalid";
   }

Modules/Loadable/CameraPath/qSlicerCameraPathModuleWidget.h

@@ -40,7 +40,7 @@ class Q_SLICER_QTMODULES_CAMERAPATH_EXPORT qSlicerCameraPathModuleWidget :
 public:
 
   typedef qSlicerAbstractModuleWidget Superclass;
-  qSlicerCameraPathModuleWidget(QWidget *parent=0);
+  qSlicerCameraPathModuleWidget(QWidget *parent=nullptr);
   virtual ~qSlicerCameraPathModuleWidget();
 
   void travelToTime(double t);

Modules/Loadable/CameraPath/qSlicerCameraPathReader.cxx

@@ -107,7 +107,7 @@ bool qSlicerCameraPathReader::load(const IOProperties& properties)
     name = properties["name"].toString();
     }
 
-  if (d->CameraPathLogic.GetPointer() == 0)
+  if (d->CameraPathLogic.GetPointer() == nullptr)
     {
     return false;
     }
@@ -125,7 +125,7 @@ bool qSlicerCameraPathReader::load(const IOProperties& properties)
     while (ptr)
       {
       nodeIDList.append(ptr);
-      ptr = strtok(NULL, ",");
+      ptr = strtok(nullptr, ",");
       }
     this->setLoadedNodes(nodeIDList);
     }
@@ -135,5 +135,5 @@ bool qSlicerCameraPathReader::load(const IOProperties& properties)
     return false;
     }
 
-  return nodeIDs != 0;
+  return nodeIDs != nullptr;
 }

Modules/Loadable/CameraPath/qSlicerCameraPathReader.h

@@ -32,8 +32,8 @@ class qSlicerCameraPathReader
   Q_OBJECT
 public:
   typedef qSlicerFileReader Superclass;
-  qSlicerCameraPathReader(QObject* parent = 0);
-  qSlicerCameraPathReader(vtkSlicerCameraPathLogic* logic, QObject* parent = 0);
+  qSlicerCameraPathReader(QObject* parent = nullptr);
+  qSlicerCameraPathReader(vtkSlicerCameraPathLogic* logic, QObject* parent = nullptr);
   virtual ~qSlicerCameraPathReader();
 
   vtkSlicerCameraPathLogic* CameraPathLogic()const;