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

  Program:   Visualization Toolkit
  Module:    vtkAngleWidget.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 vtkAngleWidget - measure the angle between two rays (defined by three points)
// .SECTION Description
// The vtkAngleWidget is used to measure the angle between two rays (defined
// by three points). The three points (two end points and a center)
// can be positioned independently, and when they are released, a special
// PlacePointEvent is invoked so that special operations may be take to
// reposition the point (snap to grid, etc.) The widget has two different
// modes of interaction: when initially defined (i.e., placing the three
// points) and then a manipulate mode (adjusting the position of the 
// three points).
// 
// To use this widget, specify an instance of vtkAngleWidget and a
// representation (a subclass of vtkAngleRepresentation). The widget is
// implemented using three instances of vtkHandleWidget which are used to
// position the three points. The representations for these handle widgets
// are provided by the vtkAngleRepresentation.
//
// .SECTION Event Bindings
// By default, the widget responds to the following VTK events (i.e., it
// watches the vtkRenderWindowInteractor for these events):
// <pre>
//   LeftButtonPressEvent - add a point or select a handle 
//   MouseMoveEvent - position the second or third point, or move a handle
//   LeftButtonReleaseEvent - release the selected handle
// </pre>
//
// Note that the event bindings described above can be changed using this
// class's vtkWidgetEventTranslator. This class translates VTK events 
// into the vtkAngleWidget's widget events:
// <pre>
//   vtkWidgetEvent::AddPoint -- add one point; depending on the state
//                               it may the first, second or third point 
//                               added. Or, if near a handle, select the handle.
//   vtkWidgetEvent::Move -- position the second or third point, or move the
//                           handle depending on the state.
//   vtkWidgetEvent::EndSelect -- the handle manipulation process has completed.
// </pre>
//
// This widget invokes the following VTK events on itself (which observers
// can listen for):
// <pre>
//   vtkCommand::StartInteractionEvent (beginning to interact)
//   vtkCommand::EndInteractionEvent (completing interaction)
//   vtkCommand::InteractionEvent (moving a handle)
//   vtkCommand::PlacePointEvent (after a point is positioned; 
//                                call data includes handle id (0,1,2))
// </pre>

// .SECTION See Also
// vtkHandleWidget vtkDistanceWidget


#ifndef __vtkAngleWidget_h
#define __vtkAngleWidget_h

#include "vtkAbstractWidget.h"

class vtkAngleRepresentation;
class vtkHandleWidget;
class vtkAngleWidgetCallback;


class VTK_WIDGETS_EXPORT vtkAngleWidget : public vtkAbstractWidget
{
public:
  // Description:
  // Instantiate this class.
  static vtkAngleWidget *New();

  // Description:
  // Standard methods for a VTK class.
  vtkTypeMacro(vtkAngleWidget,vtkAbstractWidget);
  void PrintSelf(ostream& os, vtkIndent indent);

  // Description:
  // The method for activiating and deactiviating this widget. This method
  // must be overridden because it is a composite widget and does more than
  // its superclasses' vtkAbstractWidget::SetEnabled() method.
  virtual void SetEnabled(int);

  // Description:
  // Specify an instance of vtkWidgetRepresentation used to represent this
  // widget in the scene. Note that the representation is a subclass of vtkProp
  // so it can be added to the renderer independent of the widget.
  void SetRepresentation(vtkAngleRepresentation *r)
    {this->Superclass::SetWidgetRepresentation(reinterpret_cast<vtkWidgetRepresentation*>(r));}
  
  // Description:
  // Create the default widget representation if one is not set. 
  void CreateDefaultRepresentation();

  // Description:
  // A flag indicates whether the angle is valid. The angle value only becomes
  // valid after two of the three points are placed.
  int IsAngleValid();

  // Description:
  // Methods to change the whether the widget responds to interaction.
  // Overridden to pass the state to component widgets.
  virtual void SetProcessEvents(int);

protected:
  vtkAngleWidget();
  ~vtkAngleWidget();

  // The state of the widget
//BTX
  enum {Start=0,Define,Manipulate};
//ETX
  int WidgetState;
  int CurrentHandle;

  // Callback interface to capture events when
  // placing the widget.
  static void AddPointAction(vtkAbstractWidget*);
  static void MoveAction(vtkAbstractWidget*);
  static void EndSelectAction(vtkAbstractWidget*);
  
  // The positioning handle widgets
  vtkHandleWidget *Point1Widget;
  vtkHandleWidget *CenterWidget;
  vtkHandleWidget *Point2Widget;
  vtkAngleWidgetCallback *AngleWidgetCallback1;
  vtkAngleWidgetCallback *AngleWidgetCenterCallback;
  vtkAngleWidgetCallback *AngleWidgetCallback2;
  
  // Methods invoked when the handles at the
  // end points of the widget are manipulated
  void StartAngleInteraction(int handleNum);
  void AngleInteraction(int handleNum);
  void EndAngleInteraction(int handleNum);
  
//BTX
  friend class vtkAngleWidgetCallback;
//ETX  

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

#endif
