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

  Program:   Visualization Toolkit
  Module:    vtkOpenGLModelViewProjectionMonitor

  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.

=========================================================================*/
/**
 * @class   vtkOpenGLModelViewProjectionMonitor
 * tracks state of OpenGL model-view and projection matrices.
 *
 *
 * vtkOpenGLModelViewProjectionMonitor -- A helper for painters that
 * tracks state of OpenGL model-view and projection matrices. A Painter
 * could use this to skip expensive processing that is only needed when
 * the model-view or projection matrices change.
 *
 * this is not intended to be shared. each object should use it's
 * own instance of this class. it's intended to be called once per
 * render.
*/

#ifndef vtkOpenGLModelViewProjectionMonitor_h
#define vtkOpenGLModelViewProjectionMonitor_h

#include "vtkRenderingOpenGLModule.h" // for export macro
#include "vtkObject.h"

class VTKRENDERINGOPENGL_EXPORT vtkOpenGLModelViewProjectionMonitor : public vtkObject
{
public:
  static vtkOpenGLModelViewProjectionMonitor* New();
  vtkTypeMacro(vtkOpenGLModelViewProjectionMonitor, vtkObject);
  void PrintSelf(ostream& os, vtkIndent indent) override;

  /**
   * Fetches the current GL state and updates the
   * internal copies of the data. returns true if
   * any of the tracked OpenGL matrices have changed.
   * Typically this is the only function a user needs
   * to call.
   */
  bool StateChanged();

  /**
   * Fetch and store OpenGL model view matrix. Note,
   * this is done automatically in SateChanged.
   */
  void Update();

  //@{
  /**
   * Set the matrix data.
   */
  void SetProjection(float *val);
  void SetModelView(float *val);
  //@}

protected:
  vtkOpenGLModelViewProjectionMonitor() : UpTime(0)
  { this->Initialize(); }

  ~vtkOpenGLModelViewProjectionMonitor() override{}

  void Initialize();

private:
  float Projection[16];
  float ModelView[16];
  long long UpTime;

private:
  vtkOpenGLModelViewProjectionMonitor(const vtkOpenGLModelViewProjectionMonitor&) = delete;
  void operator=(const vtkOpenGLModelViewProjectionMonitor &) = delete;
};

#endif