/Users/jab/Documents/Teaching/02585/GEL2_and_demos/GEL/src/GLGraphics/QuatTrackBall.h

#ifndef __GLGRAPHICS_TrackBall_H__
#define __GLGRAPHICS_TrackBall_H__

#include "CGLA/Vec2i.h"
#include "CGLA/Vec2f.h"
#include "CGLA/Vec3f.h"
#include "CGLA/Vec3Hf.h"
#include "CGLA/Quatf.h"

namespace GLGraphics
{

        enum TrackBallAction
                {
                        NO_ACTION = 0,
                        ROTATE_ACTION,
                        PAN_ACTION,
                        ZOOM_ACTION
                };

        class QuatTrackBall 
        {
                CGLA::Vec3f centre;
                CGLA::Vec2i screen_centre;

                unsigned width, height;
                CGLA::Quatf     qrot;
                CGLA::Quatf     qinc;
                CGLA::Vec2f     trans;
                float scale;
                float   ballsize;
                float eye_dist;
                CGLA::Vec2f last_pos;
                TrackBallAction current_action;

                void rotate(const CGLA::Vec2f&);
                void pan(const CGLA::Vec2f&);
                void zoom(const CGLA::Vec2f&);

                void calcRotation(const CGLA::Vec2f&);
                float projectToSphere(const CGLA::Vec2f&);
                CGLA::Vec2f scalePoint(const CGLA::Vec2i&) const;

                void set_position(const CGLA::Vec2f&);

        public:

                QuatTrackBall(const CGLA::Vec3f&, float, unsigned, unsigned);

                void set_screen_window(unsigned _width, unsigned _height)
                {
                        width = _width;
                        height = _height;
                        screen_centre[0] = static_cast<int>(width/2.0f);
                        screen_centre[1] = static_cast<int>(height/2.0f);
                }
        
                void set_centre(const CGLA::Vec3f& _centre)
                {
                        centre = _centre;
                }

                void set_screen_centre(const CGLA::Vec2i& _screen_centre) 
                {
                        screen_centre[0] = _screen_centre[0];
                        screen_centre[1] = height - _screen_centre[1];
                }

                const CGLA::Quatf& get_rotation() const 
                {
                        return qrot;
                }

                void set_rotation(const CGLA::Quatf& _qrot)
                {
                        qrot = _qrot;
                }

                void set_eye_dist(float _eye_dist)
                {
                        eye_dist = _eye_dist;
                }

                float get_eye_dist() const
                {
                        return eye_dist;
                }

                void set_gl_modelview() const;

                void do_spin();

                bool is_spinning() const;
        
                void stop_spin();
        
                void grab_ball(TrackBallAction,const CGLA::Vec2i&);

                void roll_ball(const CGLA::Vec2i&);

                void release_ball() 
                {
                        current_action = NO_ACTION;
                }

                bool is_grabbed() const 
                {
                        if(current_action == NO_ACTION) 
                                return false;
                        return true;
                }

                void get_view_param(CGLA::Vec3f& eye, 
                                                                                                CGLA::Vec3f& _centre, CGLA::Vec3f& up) const;

                TrackBallAction get_current_action() 
                {
                        return current_action;
                }

        };

}

#endif