mapnik/agg/include/agg_span_subdiv_adaptor.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_SPAN_SUBDIV_ADAPTOR_INCLUDED
#define AGG_SPAN_SUBDIV_ADAPTOR_INCLUDED

#include "agg_basics.h"

namespace agg
{

    //=================================================span_subdiv_adaptor
    template<class Interpolator, unsigned SubpixelShift = 8> 
    class span_subdiv_adaptor
    {
    public:
        typedef Interpolator interpolator_type;
        typedef typename interpolator_type::trans_type trans_type;

        enum sublixel_scale_e
        {
            subpixel_shift = SubpixelShift,
            subpixel_scale = 1 << subpixel_shift
        };


        //----------------------------------------------------------------
        span_subdiv_adaptor() :
            m_subdiv_shift(4),
            m_subdiv_size(1 << m_subdiv_shift),
            m_subdiv_mask(m_subdiv_size - 1) {}

        span_subdiv_adaptor(interpolator_type& interpolator, 
                             unsigned subdiv_shift = 4) : 
            m_subdiv_shift(subdiv_shift),
            m_subdiv_size(1 << m_subdiv_shift),
            m_subdiv_mask(m_subdiv_size - 1),
            m_interpolator(&interpolator) {}

        span_subdiv_adaptor(interpolator_type& interpolator, 
                             double x, double y, unsigned len,
                             unsigned subdiv_shift = 4) :
            m_subdiv_shift(subdiv_shift),
            m_subdiv_size(1 << m_subdiv_shift),
            m_subdiv_mask(m_subdiv_size - 1),
            m_interpolator(&interpolator)
        {
            begin(x, y, len);
        }


        //----------------------------------------------------------------
        const interpolator_type& interpolator() const { return *m_interpolator; }
        void interpolator(interpolator_type& intr) { m_interpolator = &intr; }

        //----------------------------------------------------------------
        const trans_type& transformer() const 
        { 
            return *m_interpolator->transformer(); 
        }
        void transformer(const trans_type& trans) 
        { 
            m_interpolator->transformer(trans); 
        }

        //----------------------------------------------------------------
        unsigned subdiv_shift() const { return m_subdiv_shift; }
        void subdiv_shift(unsigned shift) 
        {
            m_subdiv_shift = shift;
            m_subdiv_size = 1 << m_subdiv_shift;
            m_subdiv_mask = m_subdiv_size - 1;
        }

        //----------------------------------------------------------------
        void begin(double x, double y, unsigned len)
        {
            m_pos   = 1;
            m_src_x = iround(x * subpixel_scale) + subpixel_scale;
            m_src_y = y;
            m_len   = len;
            if(len > m_subdiv_size) len = m_subdiv_size;
            m_interpolator->begin(x, y, len);
        }

        //----------------------------------------------------------------
        void operator++()
        {
            ++(*m_interpolator);
            if(m_pos >= m_subdiv_size)
            {
                unsigned len = m_len;
                if(len > m_subdiv_size) len = m_subdiv_size;
                m_interpolator->resynchronize(double(m_src_x) / double(subpixel_scale) + len, 
                                              m_src_y, 
                                              len);
                m_pos = 0;
            }
            m_src_x += subpixel_scale;
            ++m_pos;
            --m_len;
        }

        //----------------------------------------------------------------
        void coordinates(int* x, int* y) const
        {
            m_interpolator->coordinates(x, y);
        }

        //----------------------------------------------------------------
        void local_scale(int* x, int* y) const
        {
            m_interpolator->local_scale(x, y);
        }


    private:
        unsigned m_subdiv_shift;
        unsigned m_subdiv_size;
        unsigned m_subdiv_mask;
        interpolator_type* m_interpolator;
        int      m_src_x;
        double   m_src_y;
        unsigned m_pos;
        unsigned m_len;
    };

}

#endif