/*=========================================================================

  Program:   Visualization Toolkit
  Module:    Cone2.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
//
// This example shows how to add an observer to a C++ program. It extends
// the Step1/Cxx/Cone.cxx C++ example (see that example for information on
// the basic setup).
//
// VTK uses a command/observer design pattern. That is, observers watch for
// particular events that any vtkObject (or subclass) may invoke on
// itself. For example, the vtkRenderer invokes a "StartEvent" as it begins
// to render. Here we add an observer that invokes a command when this event
// is observed.
//

// first include the required header files for the vtk classes we are using
#include "vtkActor.h"
#include "vtkCamera.h"
#include "vtkCommand.h"
#include "vtkConeSource.h"
#include "vtkPolyDataMapper.h"
#include "vtkRenderWindow.h"
#include "vtkRenderer.h"

// Callback for the interaction
class vtkMyCallback : public vtkCommand
{
public:
  static vtkMyCallback* New() { return new vtkMyCallback; }
  void Execute(vtkObject* caller, unsigned long, void*) override
  {
    vtkRenderer* renderer = reinterpret_cast<vtkRenderer*>(caller);
    cout << renderer->GetActiveCamera()->GetPosition()[0] << " "
         << renderer->GetActiveCamera()->GetPosition()[1] << " "
         << renderer->GetActiveCamera()->GetPosition()[2] << "\n";
  }
};

int main()
{
  //
  // The pipeline creation is documented in Step1
  //
  vtkConeSource* cone = vtkConeSource::New();
  cone->SetHeight(3.0);
  cone->SetRadius(1.0);
  cone->SetResolution(10);

  vtkPolyDataMapper* coneMapper = vtkPolyDataMapper::New();
  coneMapper->SetInputConnection(cone->GetOutputPort());
  vtkActor* coneActor = vtkActor::New();
  coneActor->SetMapper(coneMapper);

  vtkRenderer* ren1 = vtkRenderer::New();
  ren1->AddActor(coneActor);
  ren1->SetBackground(0.1, 0.2, 0.4);
  ren1->ResetCamera();

  vtkRenderWindow* renWin = vtkRenderWindow::New();
  renWin->AddRenderer(ren1);
  renWin->SetSize(300, 300);

  // Here is where we setup the observer, we do a new and ren1 will
  // eventually free the observer
  vtkMyCallback* mo1 = vtkMyCallback::New();
  ren1->AddObserver(vtkCommand::StartEvent, mo1);
  mo1->Delete();

  //
  // now we loop over 360 degrees and render the cone each time
  //
  int i;
  for (i = 0; i < 360; ++i)
  {
    // render the image
    renWin->Render();
    // rotate the active camera by one degree
    ren1->GetActiveCamera()->Azimuth(1);
  }

  //
  // Free up any objects we created
  //
  cone->Delete();
  coneMapper->Delete();
  coneActor->Delete();
  ren1->Delete();
  renWin->Delete();

  return 0;
}
