agg_rasterizer_cells_aa.h

windows ce 下的画各种b样条曲线

                incr  = -1;
            }

            x_from = x1;

            //render_hline(ey1, x_from, fy1, x_from, first);
            delta = first - fy1;
            m_curr_cell.cover += delta;
            m_curr_cell.area  += two_fx * delta;

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

            delta = first + first - poly_subpixel_scale;
            area = two_fx * delta;
            while(ey1 != ey2)
            {
                //render_hline(ey1, x_from, poly_subpixel_scale - first, x_from, first);
                m_curr_cell.cover = delta;
                m_curr_cell.area  = area;
                ey1 += incr;
                set_curr_cell(ex, ey1);
            }
            //render_hline(ey1, x_from, poly_subpixel_scale - first, x_from, fy2);
            delta = fy2 - poly_subpixel_scale + first;
            m_curr_cell.cover += delta;
            m_curr_cell.area  += two_fx * delta;
            return;
        }

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

        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_curr_cell(x_from >> poly_subpixel_shift, ey1);

        if(ey1 != ey2)
        {
            p     = poly_subpixel_scale * 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_subpixel_scale - first, x_to, first);
                x_from = x_to;

                ey1 += incr;
                set_curr_cell(x_from >> poly_subpixel_shift, ey1);
            }
        }
        render_hline(ey1, x_from, poly_subpixel_scale - first, x2, fy2);
    }

    //------------------------------------------------------------------------
    template<class Cell> 
    void rasterizer_cells_aa<Cell>::allocate_block()
    {
        if(m_curr_block >= m_num_blocks)
        {
            if(m_num_blocks >= m_max_blocks)
            {
                cell_type** new_cells = 
                    pod_allocator<cell_type*>::allocate(m_max_blocks + 
                                                        cell_block_pool);

                if(m_cells)
                {
                    memcpy(new_cells, m_cells, m_max_blocks * sizeof(cell_type*));
                    pod_allocator<cell_type*>::deallocate(m_cells, m_max_blocks);
                }
                m_cells = new_cells;
                m_max_blocks += cell_block_pool;
            }

            m_cells[m_num_blocks++] = 
                pod_allocator<cell_type>::allocate(cell_block_size);

        }
        m_curr_cell_ptr = m_cells[m_curr_block++];
    }



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


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


    //------------------------------------------------------------------------
    template<class Cell>
    void qsort_cells(Cell** start, unsigned num)
    {
        Cell**  stack[80];
        Cell*** top; 
        Cell**  limit;
        Cell**  base;

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

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

            Cell** i;
            Cell** j;
            Cell** 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((*j)->x < (*i)->x)
                {
                    swap_cells(i, j);
                }

                if((*base)->x < (*i)->x)
                {
                    swap_cells(base, i);
                }

                if((*j)->x < (*base)->x)
                {
                    swap_cells(base, j);
                }

                for(;;)
                {
                    int x = (*base)->x;
                    do i++; while( (*i)->x < x );
                    do j--; while( x < (*j)->x );

                    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(; j[1]->x < (*j)->x; j--)
                    {
                        swap_cells(j + 1, j);
                        if (j == base)
                        {
                            break;
                        }
                    }
                }

                if(top > stack)
                {
                    top  -= 2;
                    base  = top[0];
                    limit = top[1];
                }
                else
                {
                    break;
                }
            }
        }
    }


    //------------------------------------------------------------------------
    template<class Cell> 
    void rasterizer_cells_aa<Cell>::sort_cells()
    {
        if(m_sorted) return; //Perform sort only the first time.

        add_curr_cell();
        m_curr_cell.x     = 0x7FFFFFFF;
        m_curr_cell.y     = 0x7FFFFFFF;
        m_curr_cell.cover = 0;
        m_curr_cell.area  = 0;

        if(m_num_cells == 0) return;

// DBG: Check to see if min/max works well.
//for(unsigned nc = 0; nc < m_num_cells; nc++)
//{
//    cell_type* cell = m_cells[nc >> cell_block_shift] + (nc & cell_block_mask);
//    if(cell->x < m_min_x || 
//       cell->y < m_min_y || 
//       cell->x > m_max_x || 
//       cell->y > m_max_y)
//    {
//        cell = cell; // Breakpoint here
//    }
//}
        // Allocate the array of cell pointers
        m_sorted_cells.allocate(m_num_cells, 16);

        // Allocate and zero the Y array
        m_sorted_y.allocate(m_max_y - m_min_y + 1, 16);
        m_sorted_y.zero();

        // Create the Y-histogram (count the numbers of cells for each Y)
        cell_type** block_ptr = m_cells;
        cell_type*  cell_ptr;
        unsigned nb = m_num_cells >> cell_block_shift;
        unsigned i;
        while(nb--)
        {
            cell_ptr = *block_ptr++;
            i = cell_block_size;
            while(i--) 
            {
                m_sorted_y[cell_ptr->y - m_min_y].start++;
                ++cell_ptr;
            }
        }

        cell_ptr = *block_ptr++;
        i = m_num_cells & cell_block_mask;
        while(i--) 
        {
            m_sorted_y[cell_ptr->y - m_min_y].start++;
            ++cell_ptr;
        }

        // Convert the Y-histogram into the array of starting indexes
        unsigned start = 0;
        for(i = 0; i < m_sorted_y.size(); i++)
        {
            unsigned v = m_sorted_y[i].start;
            m_sorted_y[i].start = start;
            start += v;
        }

        // Fill the cell pointer array sorted by Y
        block_ptr = m_cells;
        nb = m_num_cells >> cell_block_shift;
        while(nb--)
        {
            cell_ptr = *block_ptr++;
            i = cell_block_size;
            while(i--) 
            {
                sorted_y& curr_y = m_sorted_y[cell_ptr->y - m_min_y];
                m_sorted_cells[curr_y.start + curr_y.num] = cell_ptr;
                ++curr_y.num;
                ++cell_ptr;
            }
        }
        
        cell_ptr = *block_ptr++;
        i = m_num_cells & cell_block_mask;
        while(i--) 
        {
            sorted_y& curr_y = m_sorted_y[cell_ptr->y - m_min_y];
            m_sorted_cells[curr_y.start + curr_y.num] = cell_ptr;
            ++curr_y.num;
            ++cell_ptr;
        }

        // Finally arrange the X-arrays
        for(i = 0; i < m_sorted_y.size(); i++)
        {
            const sorted_y& curr_y = m_sorted_y[i];
            if(curr_y.num)
            {
                qsort_cells(m_sorted_cells.data() + curr_y.start, curr_y.num);
            }
        }
        m_sorted = true;
    }



    //------------------------------------------------------scanline_hit_test
    class scanline_hit_test
    {
    public:
        scanline_hit_test(int x) : m_x(x), m_hit(false) {}

        void reset_spans() {}
        void finalize(int) {}
        void add_cell(int x, int)
        {
            if(m_x == x) m_hit = true;
        }
        void add_span(int x, int len, int)
        {
            if(m_x >= x && m_x < x+len) m_hit = true;
        }
        unsigned num_spans() const { return 1; }
        bool hit() const { return m_hit; }

    private:
        int  m_x;
        bool m_hit;
    };


}

#endif