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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkInteractorObserver.h,v $

  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 vtkInteractorObserver - an abstract superclass for classes observing events invoked by vtkRenderWindowInteractor
// .SECTION Description
// vtkInteractorObserver is an abstract superclass for subclasses that observe
// events invoked by vtkRenderWindowInteractor. These subclasses are 
// typically things like 3D widgets; objects that interact with actors
// in the scene, or interactively probe the scene for information.
//
// vtkInteractorObserver defines the method SetInteractor() and enables and
// disables the processing of events by the vtkInteractorObserver. Use the
// methods EnabledOn() or SetEnabled(1) to turn on the interactor observer,
// and the methods EnabledOff() or SetEnabled(0) to turn off the interactor.
//
// To support interactive manipulation of objects, this class (and
// subclasses) invoke the events StartInteractionEvent, InteractionEvent, and
// EndInteractionEvent.  These events are invoked when the
// vtkInteractorObserver enters a state where rapid response is desired:
// mouse motion, etc. The events can be used, for example, to set the desired
// update frame rate (StartInteractionEvent), operate on data or update a
// pipeline (InteractionEvent), and set the desired frame rate back to normal
// values (EndInteractionEvent). Two other events, EnableEvent and
// DisableEvent, are invoked when the interactor observer is enabled or
// disabled.

// .SECTION See Also
// vtk3DWidget vtkBoxWidget vtkLineWidget

#ifndef __vtkInteractorObserver_h
#define __vtkInteractorObserver_h

#include "vtkObject.h"

class vtkRenderWindowInteractor;
class vtkRenderer;
class vtkCallbackCommand;

class VTK_RENDERING_EXPORT vtkInteractorObserver : public vtkObject
{
public:
  vtkTypeRevisionMacro(vtkInteractorObserver,vtkObject);
  void PrintSelf(ostream& os, vtkIndent indent);

  // Description:
  // Methods for turning the interactor observer on and off, and determining
  // its state. All subclasses must provide the SetEnabled() method.
  // Enabling a vtkInteractorObserver has the side effect of adding
  // observers; disabling it removes the observers. Prior to enabling the
  // vtkInteractorObserver you must set the render window interactor (via
  // SetInteractor()).
  virtual void SetEnabled(int) {};
  int GetEnabled() {return this->Enabled;}
  void EnabledOn() {this->SetEnabled(1);}
  void EnabledOff() {this->SetEnabled(0);}
  void On() {this->SetEnabled(1);}
  void Off() {this->SetEnabled(0);}

  // Description:
  // This method is used to associate the widget with the render window
  // interactor.  Observers of the appropriate events invoked in the render
  // window interactor are set up as a result of this method invocation.
  // The SetInteractor() method must be invoked prior to enabling the
  // vtkInteractorObserver.
  virtual void SetInteractor(vtkRenderWindowInteractor* iren);
  vtkGetObjectMacro(Interactor, vtkRenderWindowInteractor);

  // Description:
  // Set/Get the priority at which events are processed. This is used when
  // multiple interactor observers are used simultaneously. The default value
  // is 0.0 (lowest priority.) Note that when multiple interactor observer
  // have the same priority, then the last observer added will process the
  // event first. (Note: once the SetInteractor() method has been called,
  // changing the priority does not effect event processing. You will have
  // to SetInteractor(NULL), change priority, and then SetInteractor(iren)
  // to have the priority take effect.)
  vtkSetClampMacro(Priority,float,0.0f,1.0f);
  vtkGetMacro(Priority,float);

  // Description:
  // Enable/Disable of the use of a keypress to turn on and off the
  // interactor observer. (By default, the keypress is 'i' for "interactor
  // observer".)  Set the KeyPressActivationValue to change which key
  // activates the widget.)
  vtkSetMacro(KeyPressActivation,int);
  vtkGetMacro(KeyPressActivation,int);
  vtkBooleanMacro(KeyPressActivation,int);
  
  // Description:
  // Specify which key press value to use to activate the interactor observer
  // (if key press activation is enabled). By default, the key press
  // activation value is 'i'. Note: once the SetInteractor() method is
  // invoked, changing the key press activation value will not affect the key
  // press until SetInteractor(NULL)/SetInteractor(iren) is called.
  vtkSetMacro(KeyPressActivationValue,char);
  vtkGetMacro(KeyPressActivationValue,char);

  // Description:
  // Set/Get the default renderer to use when activating the interactor 
  // observer. Normally when the widget is activated (SetEnabled(1) or when 
  // keypress activation takes place), the renderer over which the mouse
  // pointer is positioned is used. Alternatively, you can specify the
  // renderer to bind the interactor to when the interactor observer is
  // activated. 
  vtkGetObjectMacro(DefaultRenderer,vtkRenderer);
  virtual void SetDefaultRenderer(vtkRenderer*);

  // Description:
  // Set/Get the current renderer. Normally when the widget is activated 
  // (SetEnabled(1) or when keypress activation takes place), the renderer
  // over which the mouse pointer is positioned is used and assigned to
  // this Ivar. Alternatively, you might want to set the CurrentRenderer
  // explicitly.
  // WARNING: note that if the DefaultRenderer Ivar is set (see above), 
  // it will always override the parameter passed to SetCurrentRenderer,
  // unless it is NULL.
  // (i.e., SetCurrentRenderer(foo) = SetCurrentRenderer(DefaultRenderer).
  vtkGetObjectMacro(CurrentRenderer,vtkRenderer);
  virtual void SetCurrentRenderer(vtkRenderer*);

  // Sets up the keypress-i event. 
  virtual void OnChar();
  
  // Convenience methods for outside classes. Make sure that the
  // parameter "ren" is not-null.
  static void ComputeDisplayToWorld(vtkRenderer *ren, double x, double y, 
                                    double z, double worldPt[4]);
  static void ComputeWorldToDisplay(vtkRenderer *ren, double x, double y, 
                                    double z, double displayPt[3]);

protected:
  vtkInteractorObserver();
  ~vtkInteractorObserver();

  // Description:
  // Utility routines used to start and end interaction.
  // For example, it switches the display update rate. It does not invoke
  // the corresponding events.
  virtual void StartInteraction();
  virtual void EndInteraction();

  // Description:
  // Handles the char widget activation event. Also handles the delete event.
  static void ProcessEvents(vtkObject* object, 
                            unsigned long event,
                            void* clientdata, 
                            void* calldata);

  // Description:
  // Helper method for subclasses.
  void ComputeDisplayToWorld(double x, double y, double z, 
                             double worldPt[4]);
  void ComputeWorldToDisplay(double x, double y, double z, 
                             double displayPt[3]);
    
  // The state of the widget, whether on or off (observing events or not)
  int Enabled;
  
  // Used to process events
  vtkCallbackCommand* EventCallbackCommand; //subclasses use one
  vtkCallbackCommand* KeyPressCallbackCommand; //listens to key activation

  // Priority at which events are processed
  float Priority;

  // Keypress activation controls
  int KeyPressActivation;
  char KeyPressActivationValue;

  // Used to associate observers with the interactor
  vtkRenderWindowInteractor *Interactor;
  
  // Internal ivars for processing events
  vtkRenderer *CurrentRenderer;
  vtkRenderer *DefaultRenderer;

  unsigned long CharObserverTag;
  unsigned long DeleteObserverTag;

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

#endif