okular/ui/painter_agg2/agg_rasterizer_scanline_aa.cpp

//----------------------------------------------------------------------------
// Anti-Grain Geometry - Version 2.3
// 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.
//
// The author gratefully acknowleges the support of David Turner, 
// Robert Wilhelm, and Werner Lemberg - the authors of the FreeType 
// libray - in producing this work. See http://www.freetype.org for details.
//
//----------------------------------------------------------------------------
// Contact: mcseem@antigrain.com
//          mcseemagg@yahoo.com
//          http://www.antigrain.com
//----------------------------------------------------------------------------
//
// Class outline_aa - implementation.
//
// Initially the rendering algorithm was designed by David Turner and the 
// other authors of the FreeType library - see the above notice. I nearly 
// created a similar renderer, but still I was far from David's work. 
// I completely redesigned the original code and adapted it for Anti-Grain 
// ideas. Two functions - render_line and render_hline are the core of 
// the algorithm - they calculate the exact coverage of each pixel cell
// of the polygon. I left these functions almost as is, because there's 
// no way to improve the perfection - hats off to David and his group!
//
// All other code is very different from the original. 
// 
//----------------------------------------------------------------------------

#include <string.h>
#include "agg_rasterizer_scanline_aa.h"


namespace agg
{

    //------------------------------------------------------------------------
    AGG_INLINE void cell_aa::set_cover(int c, int a)
    {
        cover = c;
        area = a;
    }

    //------------------------------------------------------------------------
    AGG_INLINE void cell_aa::add_cover(int c, int a)
    {
        cover += c;
        area += a;
    }

    //------------------------------------------------------------------------
    AGG_INLINE void cell_aa::set_coord(int cx, int cy)
    {
        x = int16(cx);
        y = int16(cy);
        packed_coord = (cy << 16) + cx;
    }

    //------------------------------------------------------------------------
    AGG_INLINE void cell_aa::set(int cx, int cy, int c, int a)
    {
        x = int16(cx);
        y = int16(cy);
        packed_coord = (cy << 16) + cx;
        cover = c;
        area = a;
    }

    //------------------------------------------------------------------------
    outline_aa::~outline_aa()
    {
        delete [] m_sorted_cells;
        if(m_num_blocks)
        {
            cell_aa** ptr = m_cells + m_num_blocks - 1;
            while(m_num_blocks--)
            {
                delete [] *ptr;
                ptr--;
            }
            delete [] m_cells;
        }
    }


    //------------------------------------------------------------------------
    outline_aa::outline_aa() :
        m_num_blocks(0),
        m_max_blocks(0),
        m_cur_block(0),
        m_num_cells(0),
        m_cells(0),
        m_cur_cell_ptr(0),
        m_sorted_cells(0),
        m_sorted_size(0),
        m_cur_x(0),
        m_cur_y(0),
        m_min_x(0x7FFFFFFF),
        m_min_y(0x7FFFFFFF),
        m_max_x(-0x7FFFFFFF),
        m_max_y(-0x7FFFFFFF),
        m_sorted(false)
    {
        m_cur_cell.set(0x7FFF, 0x7FFF, 0, 0);
    }


    //------------------------------------------------------------------------
    void outline_aa::reset()
    { 
        m_num_cells = 0; 
        m_cur_block = 0;
        m_cur_cell.set(0x7FFF, 0x7FFF, 0, 0);
        m_sorted = false;
        m_min_x =  0x7FFFFFFF;
        m_min_y =  0x7FFFFFFF;
        m_max_x = -0x7FFFFFFF;
        m_max_y = -0x7FFFFFFF;
    }



    //------------------------------------------------------------------------
    void outline_aa::allocate_block()
    {
        if(m_cur_block >= m_num_blocks)
        {
            if(m_num_blocks >= m_max_blocks)
            {
                cell_aa** new_cells = new cell_aa* [m_max_blocks + cell_block_pool];
                if(m_cells)
                {
                    memcpy(new_cells, m_cells, m_max_blocks * sizeof(cell_aa*));
                    delete [] m_cells;
                }
                m_cells = new_cells;
                m_max_blocks += cell_block_pool;
            }
            m_cells[m_num_blocks++] = new cell_aa [unsigned(cell_block_size)];
        }
        m_cur_cell_ptr = m_cells[m_cur_block++];
    }


    //------------------------------------------------------------------------
    AGG_INLINE void outline_aa::add_cur_cell()
    {
        if(m_cur_cell.area | m_cur_cell.cover)
        {
            if((m_num_cells & cell_block_mask) == 0)
            {
                if(m_num_blocks >= cell_block_limit) return;
                allocate_block();
            }
            *m_cur_cell_ptr++ = m_cur_cell;
            ++m_num_cells;
            if(m_cur_cell.x < m_min_x) m_min_x = m_cur_cell.x;
            if(m_cur_cell.x > m_max_x) m_max_x = m_cur_cell.x;
        }
    }



    //------------------------------------------------------------------------
    AGG_INLINE void outline_aa::set_cur_cell(int x, int y)
    {
        if(m_cur_cell.packed_coord != (y << 16) + x)
        {
            add_cur_cell();
            m_cur_cell.set(x, y, 0, 0);
        }
    }



    //------------------------------------------------------------------------
    AGG_INLINE void outline_aa::render_hline(int ey, int x1, int y1, int x2, int y2)
    {
        int ex1 = x1 >> poly_base_shift;
        int ex2 = x2 >> poly_base_shift;
        int fx1 = x1 & poly_base_mask;
        int fx2 = x2 & poly_base_mask;

        int delta, p, first, dx;
        int incr, lift, mod, rem;

        //trivial case. Happens often
        if(y1 == y2)
        {
            set_cur_cell(ex2, ey);
            return;
        }

        //everything is located in a single cell.  That is easy!
        if(ex1 == ex2)
        {
            delta = y2 - y1;
            m_cur_cell.add_cover(delta, (fx1 + fx2) * delta);
            return;
        }

        //ok, we'll have to render a run of adjacent cells on the same
        //hline...
        p     = (poly_base_size - fx1) * (y2 - y1);
        first = poly_base_size;
        incr  = 1;

        dx = x2 - x1;

        if(dx < 0)
        {
            p     = fx1 * (y2 - y1);
            first = 0;
            incr  = -1;
            dx    = -dx;
        }

        delta = p / dx;
        mod   = p % dx;

        if(mod < 0)
        {
            delta--;
            mod += dx;
        }

        m_cur_cell.add_cover(delta, (fx1 + first) * delta);

        ex1 += incr;
        set_cur_cell(ex1, ey);
        y1  += delta;

        if(ex1 != ex2)
        {
            p     = poly_base_size * (y2 - y1 + delta);
            lift  = p / dx;
            rem   = p % dx;

            if (rem < 0)
            {
                lift--;
                rem += dx;
            }

            mod -= dx;

            while (ex1 != ex2)
            {
                delta = lift;
                mod  += rem;
                if(mod >= 0)
                {
                    mod -= dx;
                    delta++;
                }

                m_cur_cell.add_cover(delta, (poly_base_size) * delta);
                y1  += delta;
                ex1 += incr;
                set_cur_cell(ex1, ey);
            }
        }
        delta = y2 - y1;
        m_cur_cell.add_cover(delta, (fx2 + poly_base_size - first) * delta);
    }






    //------------------------------------------------------------------------
    void outline_aa::render_line(int x1, int y1, int x2, int y2)
    {
        int ey1 = y1 >> poly_base_shift;
        int ey2 = y2 >> poly_base_shift;
        int fy1 = y1 & poly_base_mask;
        int fy2 = y2 & poly_base_mask;

        int dx, dy, x_from, x_to;
        int p, rem, mod, lift, delta, first, incr;

        dx = x2 - x1;
        dy = y2 - y1;

        //everything is on a single hline
        if(ey1 == ey2)
        {
            render_hline(ey1, x1, fy1, x2, fy2);
            return;
        }

        //Vertical line - we have to calculate start and end cells,
        //and then - the common values of the area and coverage for
        //all cells of the line. We know exactly there's only one 
        //cell, so, we don't have to call render_hline().
        incr  = 1;
        if(dx == 0)
        {
            int ex = x1 >> poly_base_shift;
            int two_fx = (x1 - (ex << poly_base_shift)) << 1;
            int area;

            first = poly_base_size;
            if(dy < 0)
            {
                first = 0;
                incr  = -1;
            }

            x_from = x1;

            //render_hline(ey1, x_from, fy1, x_from, first);
            delta = first - fy1;
            m_cur_cell.add_cover(delta, two_fx * delta);

            ey1 += incr;
            set_cur_cell(ex, ey1);

            delta = first + first - poly_base_size;
            area = two_fx * delta;
            while(ey1 != ey2)
            {
                //render_hline(ey1, x_from, poly_base_size - first, x_from, first);
                m_cur_cell.set_cover(delta, area);
                ey1 += incr;
                set_cur_cell(ex, ey1);
            }
            //render_hline(ey1, x_from, poly_base_size - first, x_from, fy2);
            delta = fy2 - poly_base_size + first;
            m_cur_cell.add_cover(delta, two_fx * delta);
            return;
        }

        //ok, we have to render several hlines
        p     = (poly_base_size - fy1) * dx;
        first = poly_base_size;

        if(dy < 0)
        {
            p     = fy1 * dx;
            first = 0;
            incr  = -1;
            dy    = -dy;
        }

        delta = p / dy;
        mod   = p % dy;

        if(mod < 0)
        {
            delta--;
            mod += dy;
        }

        x_from = x1 + delta;
        render_hline(ey1, x1, fy1, x_from, first);

        ey1 += incr;
        set_cur_cell(x_from >> poly_base_shift, ey1);

        if(ey1 != ey2)
        {
            p     = poly_base_size * dx;
            lift  = p / dy;
            rem   = p % dy;

            if(rem < 0)
            {
                lift--;
                rem += dy;
            }
            mod -= dy;

            while(ey1 != ey2)
            {
                delta = lift;
                mod  += rem;
                if (mod >= 0)
                {
                    mod -= dy;
                    delta++;
                }

                x_to = x_from + delta;
                render_hline(ey1, x_from, poly_base_size - first, x_to, first);
                x_from = x_to;

                ey1 += incr;
                set_cur_cell(x_from >> poly_base_shift, ey1);
            }
        }
        render_hline(ey1, x_from, poly_base_size - first, x2, fy2);
    }


    //------------------------------------------------------------------------
    void outline_aa::move_to(int x, int y)
    {
        if(m_sorted) reset();
        set_cur_cell(x >> poly_base_shift, y >> poly_base_shift);
        m_cur_x = x;
        m_cur_y = y;
    }



    //------------------------------------------------------------------------
    void outline_aa::line_to(int x, int y)
    {
        render_line(m_cur_x, m_cur_y, x, y);
        m_cur_x = x;
        m_cur_y = y;
        m_sorted = false;
    }

    
    //------------------------------------------------------------------------
    enum
    {
        qsort_threshold = 9
    };


    //------------------------------------------------------------------------
    template <class T> static AGG_INLINE void swap_cells(T* a, T* b)
    {
        T temp = *a;
        *a = *b;
        *b = temp;
    }

    //------------------------------------------------------------------------
    template <class T> static AGG_INLINE bool less_than(T* a, T* b)
    {
        return (*a)->packed_coord < (*b)->packed_coord;
    }



    //------------------------------------------------------------------------
    void outline_aa::qsort_cells(cell_aa** start, unsigned num)
    {
        cell_aa**  stack[80];
        cell_aa*** top; 
        cell_aa**  limit;
        cell_aa**  base;

        limit = start + num;
        base  = start;
        top   = stack;

        for (;;)
        {
            int len = int(limit - base);

            cell_aa** i;
            cell_aa** j;
            cell_aa** pivot;

            if(len > qsort_threshold)
            {
                // we use base + len/2 as the pivot
                pivot = base + len / 2;
                swap_cells(base, pivot);

                i = base + 1;
                j = limit - 1;

                // now ensure that *i <= *base <= *j 
                if(less_than(j, i))
                {
                    swap_cells(i, j);
                }

                if(less_than(base, i))
                {
                    swap_cells(base, i);
                }

                if(less_than(j, base))
                {
                    swap_cells(base, j);
                }

                for(;;)
                {
                    do i++; while( less_than(i, base) );
                    do j--; while( less_than(base, j) );

                    if ( i > j )
                    {
                        break;
                    }

                    swap_cells(i, j);
                }

                swap_cells(base, j);

                // now, push the largest sub-array
                if(j - base > limit - i)
                {
                    top[0] = base;
                    top[1] = j;
                    base   = i;
                }
                else
                {
                    top[0] = i;
                    top[1] = limit;
                    limit  = j;
                }
                top += 2;
            }
            else
            {
                // the sub-array is small, perform insertion sort
                j = base;
                i = j + 1;

                for(; i < limit; j = i, i++)
                {
                    for(; less_than(j + 1, j); j--)
                    {
                        swap_cells(j + 1, j);
                        if (j == base)
                        {
                            break;
                        }
                    }
                }
                if(top > stack)
                {
                    top  -= 2;
                    base  = top[0];
                    limit = top[1];
                }
                else
                {
                    break;
                }
            }
        }
    }





    //------------------------------------------------------------------------
    void outline_aa::sort_cells()
    {
        if(m_num_cells == 0) return;
        if(m_num_cells > m_sorted_size)
        {
            delete [] m_sorted_cells;
            m_sorted_size = m_num_cells;
            m_sorted_cells = new cell_aa* [m_num_cells + 1];
        }

        cell_aa** sorted_ptr = m_sorted_cells;
        cell_aa** block_ptr = m_cells;
        cell_aa*  cell_ptr;

        unsigned nb = m_num_cells >> cell_block_shift;
        unsigned i;

        while(nb--)
        {
            cell_ptr = *block_ptr++;
            i = cell_block_size;
            while(i--) 
            {
                *sorted_ptr++ = cell_ptr++;
            }
        }

        cell_ptr = *block_ptr++;
        i = m_num_cells & cell_block_mask;
        while(i--) 
        {
            *sorted_ptr++ = cell_ptr++;
        }
        m_sorted_cells[m_num_cells] = 0;
        qsort_cells(m_sorted_cells, m_num_cells);
        m_min_y = m_sorted_cells[0]->y;
        m_max_y = m_sorted_cells[m_num_cells - 1]->y;
    }




    //------------------------------------------------------------------------
    const cell_aa* const* outline_aa::cells()
    {
        //Perform sort only the first time.
        if(!m_sorted)
        {
            add_cur_cell();
            sort_cells();
            m_sorted = true;
        }
        return m_sorted_cells;
    }





}