mapnik/deps/agg/include/agg_vcgen_smooth_poly1.h

//----------------------------------------------------------------------------
// Anti-Grain Geometry - Version 2.4
// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
//
// Permission to copy, use, modify, sell and distribute this software 
// is granted provided this copyright notice appears in all copies. 
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
//
//----------------------------------------------------------------------------
// Contact: mcseem@antigrain.com
//          mcseemagg@yahoo.com
//          http://www.antigrain.com
//----------------------------------------------------------------------------

#ifndef AGG_VCGEN_SMOOTH_POLY1_INCLUDED
#define AGG_VCGEN_SMOOTH_POLY1_INCLUDED

#include "agg_basics.h"
#include "agg_vertex_sequence.h"


namespace agg
{

    //======================================================vcgen_smooth
    //
    // Smooth polygon generator
    //
    //------------------------------------------------------------------------
    template <class Calculate>
    class vcgen_smooth
    {
        enum status_e
        {
            initial,
            ready,
            polygon,
            ctrl_b,
            ctrl_e,
            ctrl1,
            ctrl2,
            end_poly,
            stop
        };

    public:
        typedef vertex_sequence<vertex_dist, 6> vertex_storage;

        vcgen_smooth() :
            m_src_vertices(),
            m_smooth_value(0.5),
            m_closed(0),
            m_status(initial),
            m_src_vertex(0) { }

        vcgen_smooth(vcgen_smooth &&) = default;

        void   smooth_value(double v) { m_smooth_value = v * 0.5; }
        double smooth_value() const { return m_smooth_value * 2.0; }

        // Vertex Generator Interface
        void remove_all()
        {
            m_src_vertices.remove_all();
            m_closed = 0;
            m_status = initial;
        }

        void add_vertex(double x, double y, unsigned cmd)
        {
            m_status = initial;
            if(is_move_to(cmd))
            {
                m_src_vertices.modify_last(vertex_dist(x, y));
            }
            else
            {
                if(is_vertex(cmd))
                {
                    m_src_vertices.add(vertex_dist(x, y));
                }
                else
                {
                    m_closed = get_close_flag(cmd);
                }
            }
        }

        // Vertex Source Interface
        void rewind(unsigned)
        {
            if(m_status == initial)
            {
                m_src_vertices.close(m_closed != 0);
            }
            m_status = ready;
            m_src_vertex = 0;
        }

        unsigned vertex(double* x, double* y)
        {
            unsigned cmd = path_cmd_line_to;
            while(!is_stop(cmd))
            {
                switch(m_status)
                {
                case initial:
                    rewind(0);

                case ready:
                    if(m_src_vertices.size() <  2)
                    {
                        cmd = path_cmd_stop;
                        break;
                    }

                    if(m_src_vertices.size() == 2)
                    {
                        *x = m_src_vertices[m_src_vertex].x;
                        *y = m_src_vertices[m_src_vertex].y;
                        m_src_vertex++;
                        if(m_src_vertex == 1) return path_cmd_move_to;
                        if(m_src_vertex == 2) return path_cmd_line_to;
                        cmd = path_cmd_stop;
                        break;
                    }

                    cmd = path_cmd_move_to;
                    m_status = polygon;
                    m_src_vertex = 0;

                case polygon:
                    if(m_closed)
                    {
                        if(m_src_vertex >= m_src_vertices.size())
                        {
                            *x = m_src_vertices[0].x;
                            *y = m_src_vertices[0].y;
                            m_status = end_poly;
                            return path_cmd_curve4;
                        }
                    }
                    else
                    {
                        if(m_src_vertex >= m_src_vertices.size() - 1)
                        {
                            *x = m_src_vertices[m_src_vertices.size() - 1].x;
                            *y = m_src_vertices[m_src_vertices.size() - 1].y;
                            m_status = end_poly;
                            return path_cmd_curve3;
                        }
                    }

                    std::tie(m_ctrl1, m_ctrl2) = Calculate::apply(
                        m_src_vertices.prev(m_src_vertex),
                        m_src_vertices.curr(m_src_vertex),
                        m_src_vertices.next(m_src_vertex),
                        m_src_vertices.next(m_src_vertex + 1),
                        m_smooth_value);

                    *x = m_src_vertices[m_src_vertex].x;
                    *y = m_src_vertices[m_src_vertex].y;
                    m_src_vertex++;

                    if(m_closed)
                    {
                        m_status = ctrl1;
                        return ((m_src_vertex == 1) ?
                                path_cmd_move_to :
                                path_cmd_curve4);
                    }
                    else
                    {
                        if(m_src_vertex == 1)
                        {
                            m_status = ctrl_b;
                            return path_cmd_move_to;
                        }
                        if(m_src_vertex >= m_src_vertices.size() - 1)
                        {
                            m_status = ctrl_e;
                            return path_cmd_curve3;
                        }
                        m_status = ctrl1;
                        return path_cmd_curve4;
                    }
                    break;

                case ctrl_b:
                    *x = m_ctrl2.x;
                    *y = m_ctrl2.y;
                    m_status = polygon;
                    return path_cmd_curve3;

                case ctrl_e:
                    *x = m_ctrl1.x;
                    *y = m_ctrl1.y;
                    m_status = polygon;
                    return path_cmd_curve3;

                case ctrl1:
                    *x = m_ctrl1.x;
                    *y = m_ctrl1.y;
                    m_status = ctrl2;
                    return path_cmd_curve4;

                case ctrl2:
                    *x = m_ctrl2.x;
                    *y = m_ctrl2.y;
                    m_status = polygon;
                    return path_cmd_curve4;

                case end_poly:
                    m_status = stop;
                    return path_cmd_end_poly | m_closed;

                case stop:
                    return path_cmd_stop;
                }
            }
            return cmd;
        }

    private:
        vcgen_smooth(const vcgen_smooth&);
        const vcgen_smooth& operator = (const vcgen_smooth&);

        vertex_storage m_src_vertices;
        double         m_smooth_value;
        unsigned       m_closed;
        status_e       m_status;
        unsigned       m_src_vertex;
        point_d        m_ctrl1;
        point_d        m_ctrl2;
    };

    struct calculate_poly1
    {
        using result_type = std::pair<point_d, point_d>;

        static result_type apply(const vertex_dist& v0,
                                 const vertex_dist& v1,
                                 const vertex_dist& v2,
                                 const vertex_dist& v3,
                                 double smooth_value)
        {
            double k1 = v0.dist / (v0.dist + v1.dist);
            double k2 = v1.dist / (v1.dist + v2.dist);

            double xm1 = v0.x + (v2.x - v0.x) * k1;
            double ym1 = v0.y + (v2.y - v0.y) * k1;
            double xm2 = v1.x + (v3.x - v1.x) * k2;
            double ym2 = v1.y + (v3.y - v1.y) * k2;

            return {
                {v1.x + smooth_value * (v2.x - xm1),
                 v1.y + smooth_value * (v2.y - ym1)},
                {v2.x + smooth_value * (v1.x - xm2),
                 v2.y + smooth_value * (v1.y - ym2)}
            };
        }
    };

    using vcgen_smooth_poly1 = vcgen_smooth<calculate_poly1>;

}


#endif