ctkCallback::callback is const, not the function pointer itself

It fails to compile on Visual Studio.

Libs/Core/ctkCallback.cpp

@@ -31,9 +31,9 @@ ctkCallback::ctkCallback(QObject * parentObject) : QObject(parentObject)
 }
 
 // --------------------------------------------------------------------------
-ctkCallback::ctkCallback(void (*callback)(), QObject * parentObject) : QObject(parentObject)
+ctkCallback::ctkCallback(void (*newCallback)(), QObject * parentObject) : QObject(parentObject)
 {
-  this->setCallback(callback);
+  this->setCallback(newCallback);
 }
 
 // --------------------------------------------------------------------------
@@ -42,15 +42,15 @@ ctkCallback::~ctkCallback()
 }
 
 // --------------------------------------------------------------------------
-void (*ctkCallback::callback())()const
+void (*ctkCallback::callback()const)()
 {
   return this->Callback;
 }
   
 // --------------------------------------------------------------------------
-void ctkCallback::setCallback(void (*callback)())
+void ctkCallback::setCallback(void (*newCallback)())
 {
-  this->Callback = callback;
+  this->Callback = newCallback;
 }
 
 // --------------------------------------------------------------------------

Libs/Core/ctkCallback.h

@@ -27,7 +27,7 @@
 // CTK includes
 #include "ctkCoreExport.h"
 
-//------------------------------------------------------------------------------
+//---------------------------------------------------------------------------
 class CTK_CORE_EXPORT ctkCallback : public QObject
 {
   Q_OBJECT
@@ -36,11 +36,14 @@ public:
   ctkCallback(QObject * parentObject = 0);
   ctkCallback(void (*callback)(), QObject * parentObject = 0);
   virtual ~ctkCallback();
-  
-  void (*callback())()const;
+
+  /// Returns the current pointer function
+  void (*callback()const)();
+  /// Sets a pointer function to call when invoke() is called.
   void setCallback(void (*callback)());
   
 public slots:
+  /// Internally calls the pointer function \a callback.
   virtual void invoke();
   
 private: