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

  Program:   Visualization Toolkit
  Module:    vtkObserverMediator.h

  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.

=========================================================================*/
// .NAME vtkObserverMediator - manage contention for cursors and other resources
// .SECTION Description
// The vtkObserverMediator is a helper class that manages requests for
// cursor changes from multiple interactor observers (e.g. widgets). It keeps
// a list of widgets (and their priorities) and their current requests for
// cursor shape. It then satisfies requests based on widget priority and the
// relative importance of the request (e.g., a lower priority widget
// requesting a particular cursor shape will overrule a higher priority
// widget requesting a default shape).

// .SECTION See Also
// vtkAbstractWidget vtkWidgetRepresentation


#ifndef __vtkObserverMediator_h
#define __vtkObserverMediator_h

#include "vtkObject.h"

class vtkRenderWindowInteractor;
class vtkInteractorObserver;
class vtkObserverMap;


class VTK_RENDERING_EXPORT vtkObserverMediator : public vtkObject
{
public:
  // Description:
  // Instantiate the class.
  static vtkObserverMediator *New();

  // Description:
  // Standard macros.
  vtkTypeRevisionMacro(vtkObserverMediator,vtkObject);
  void PrintSelf(ostream& os, vtkIndent indent);

  // Description:
  // Specify the instance of vtkRenderWindow whose cursor shape is
  // to be managed.
  void SetInteractor(vtkRenderWindowInteractor* iren);
  vtkGetObjectMacro(Interactor, vtkRenderWindowInteractor);

  // Description:
  // Method used to request a cursor shape. Note that the shape is specified
  // using one of the integral values determined in vtkRenderWindow.h. The 
  // method returns a non-zero value if the shape was successfully changed.
  int RequestCursorShape(vtkInteractorObserver*, int cursorShape);

  // Description:
  // Remove all requests for cursor shape from a given interactor.
  void RemoveAllCursorShapeRequests(vtkInteractorObserver*);
  
protected:
  vtkObserverMediator();
  ~vtkObserverMediator();

  // The render window whose cursor we are controlling
  vtkRenderWindowInteractor *Interactor;
  
  // A map whose key is the observer*, and whose data value is a cursor
  // request. Note that a special compare function is used to sort the
  // widgets based on the observer's priority.
  vtkObserverMap *ObserverMap; //given a widget*, return its data
  
  // The current observer and cursor shape
  vtkInteractorObserver *CurrentObserver;
  int                    CurrentCursorShape;

private:
  vtkObserverMediator(const vtkObserverMediator&);  //Not implemented
  void operator=(const vtkObserverMediator&);  //Not implemented
};

#endif
