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

  Program:   ParaView
  Module:    vtkSMLink.h

  Copyright (c) Kitware, Inc.
  All rights reserved.
  See Copyright.txt or http://www.paraview.org/HTML/Copyright.html 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.

=========================================================================*/
// .NAME vtkSMLink - Abstract base class for proxy/property links.
// .SECTION Description
// Abstract base class for proxy/property links. Links provide a means
// to connect two properies(or proxies) together, thus when on is updated,
// the dependent is also updated accordingly.

#ifndef __vtkSMLink_h
#define __vtkSMLink_h

#include "vtkSMObject.h"
//BTX
class vtkCommand;
class vtkPVXMLElement;
class vtkSMProxy;
class vtkSMStateLoader;
//ETX

class VTK_EXPORT vtkSMLink : public vtkSMObject
{
public:
  vtkTypeRevisionMacro(vtkSMLink, vtkSMObject);
  void PrintSelf(ostream& os, vtkIndent indent);

//BTX
  enum UpdateDirections
    {
    NONE = 0,
    INPUT = 1,
    OUTPUT = 2
    };
//ETX

  // Description:
  // This flag determins if UpdateVTKObjects calls are to be propagated.
  // Set to 1 by default.
  vtkSetMacro(PropagateUpdateVTKObjects, int);
  vtkGetMacro(PropagateUpdateVTKObjects, int);
  vtkBooleanMacro(PropagateUpdateVTKObjects, int);

  // Description:
  // Remove all links.
  virtual void RemoveAllLinks() = 0;
protected:
  vtkSMLink();
  ~vtkSMLink();

  // Description:
  // Called when an input proxy is updated (UpdateVTKObjects). 
  // Argument is the input proxy.
  virtual void UpdateVTKObjects(vtkSMProxy* proxy)=0;

  // Description:
  // Called when a property of an input proxy is modified.
  // caller:- the input proxy.
  // pname:- name of the property being modified.
  virtual void UpdateProperties(vtkSMProxy* proxy, const char* pname)=0;

  // Description:
  // Subclasses call this method to observer events on a INPUT proxy.
  void ObserveProxyUpdates(vtkSMProxy* proxy);

  // Description:
  // Save the state of the link.
  virtual void SaveState(const char* linkname, vtkPVXMLElement* parent) = 0;

  // Description:
  // Load the link state.
  virtual int LoadState(vtkPVXMLElement* linkElement, vtkSMStateLoader* loader) = 0;

//BTX
  friend class vtkSMLinkObserver;
  friend class vtkSMStateLoader;
  friend class vtkSMProxyManager;
//ETX
  vtkCommand* Observer;
  // Set by default. In a link P1->P2, if this flag is set, when ever Proxy with P1
  // is updated i.e. UpdateVTKObjects() is called, this class calls
  // UpdateVTKObjects on Proxy with P2.
  int PropagateUpdateVTKObjects;
private:
  vtkSMLink(const vtkSMLink&); // Not implemented.
  void operator=(const vtkSMLink&); // Not implemented.

};

#endif

