/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2003 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSGGA_TRACKBALLMANIPULATOR
#define OSGGA_TRACKBALLMANIPULATOR 1

#include <osgGA/CameraManipulator>

namespace osgGA{

class OSGGA_EXPORT TrackballManipulator : public CameraManipulator
{
    public:

        TrackballManipulator();
        virtual ~TrackballManipulator();

        virtual const char* className() { return "Trackball"; }

        /** Attach a node to the manipulator. 
            Automatically detaches previously attached node.
            setNode(NULL) detaches previously nodes.
            Is ignored by manipulators which do not require a reference model.*/
        virtual void setNode(osg::Node*);

        /** Return node if attached.*/
        virtual const osg::Node* getNode() const;

        /** Return node if attached.*/
        virtual osg::Node* getNode();

        /** Move the camera to the default position. 
            May be ignored by manipulators if home functionality is not appropriate.*/
        virtual void home(const GUIEventAdapter& ea,GUIActionAdapter& us);
        
        /** Start/restart the manipulator.*/
        virtual void init(const GUIEventAdapter& ea,GUIActionAdapter& us);

        /** handle events, return true if handled, false otherwise.*/
        virtual bool handle(const GUIEventAdapter& ea,GUIActionAdapter& us);

        /** Get the keyboard and mouse usage of this manipulator.*/
        virtual void getUsage(osg::ApplicationUsage& usage) const;

    protected:

        /** Reset the internal GUIEvent stack.*/
        void flushMouseEventStack();
        /** Add the current mouse GUIEvent to internal stack.*/
        void addMouseEvent(const GUIEventAdapter& ea);

        void computeLocalDataFromCamera();

        void computeCameraFromLocalData();

        /** For the give mouse movement calculate the movement of the camera.
            Return true is camera has moved and a redraw is required.*/
        bool calcMovement();
        
        void trackball(osg::Vec3& axis,float& angle, float p1x, float p1y, float p2x, float p2y);
        float tb_project_to_sphere(float r, float x, float y);


        /** Check the speed at which the mouse is moving.
            If speed is below a threshold then return false, otherwise return true.*/
        bool isMouseMoving();

        // Internal event stack comprising last three mouse events.
        osg::ref_ptr<const GUIEventAdapter> _ga_t1;
        osg::ref_ptr<const GUIEventAdapter> _ga_t0;

        osg::ref_ptr<osg::Node>       _node;

        float _modelScale;
        float _minimumZoomScale;

        bool _thrown;
        
        osg::Vec3   _center;
        osg::Quat   _rotation;
        float       _distance;

};

}

#endif