third_party/agg23/agg_rasterizer_scanline_aa.cpp

//----------------------------------------------------------------------------
// XYQ: 2006-01-22 Copied from AGG project.
// This file uses only integer data, so it's suitable for all platforms.
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
// 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
//----------------------------------------------------------------------------
//
// Adaptation for 32-bit screen coordinates has been sponsored by
// Liberty Technology Systems, Inc., visit http://lib-sys.com
//
// Liberty Technology Systems, Inc. is the provider of
// PostScript and PDF technology for software developers.
//
//----------------------------------------------------------------------------
//
// 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 <limits.h>
#include "agg_rasterizer_scanline_aa.h"
#include "third_party/base/numerics/safe_math.h"
namespace pdfium
{
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 = cx;
    y = cy;
}
AGG_INLINE void cell_aa::set(int cx, int cy, int c, int a)
{
    x = cx;
    y = cy;
    cover = c;
    area = a;
}
outline_aa::~outline_aa()
{
    if(m_num_blocks) {
        cell_aa** ptr = m_cells + m_num_blocks - 1;
        while(m_num_blocks--) {
            FX_Free(*ptr);
            ptr--;
        }
        FX_Free(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_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 = FX_Alloc( cell_aa*, m_max_blocks + cell_block_pool);
            if(m_cells) {
              memcpy(new_cells, m_cells, m_max_blocks * sizeof(cell_aa*));
              FX_Free(m_cells);
            }
            m_cells = new_cells;
            m_max_blocks += cell_block_pool;
        }
        m_cells[m_num_blocks++] = FX_AllocUninit(cell_aa, 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;
    }
}
AGG_INLINE void outline_aa::set_cur_cell(int x, int y)
{
    if(m_cur_cell.x != x || m_cur_cell.y != y) {
        add_cur_cell();
        m_cur_cell.set(x, y, 0, 0);
        if(x < m_min_x) {
            m_min_x = x;
        }
        if(x > m_max_x) {
            m_max_x = x;
        }
        if(y < m_min_y) {
            m_min_y = y;
        }
        if(y > m_max_y) {
            m_max_y = y;
        }
    }
}
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;
    if(y1 == y2) {
        set_cur_cell(ex2, ey);
        return;
    }
    if(ex1 == ex2) {
        delta = y2 - y1;
        m_cur_cell.add_cover(delta, (fx1 + fx2) * delta);
        return;
    }
    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)
{
    enum dx_limit_e { dx_limit = 16384 << poly_base_shift };
    pdfium::base::CheckedNumeric<int> safe_dx = x2;
    safe_dx -= x1;
    if (!safe_dx.IsValid())
        return;

    int dx = safe_dx.ValueOrDie();
    if(dx >= dx_limit || dx <= -dx_limit) {
        pdfium::base::CheckedNumeric<int> safe_cx = x1;
        safe_cx += x2;
        safe_cx /= 2;
        if (!safe_cx.IsValid())
            return;

        pdfium::base::CheckedNumeric<int> safe_cy = y1;
        safe_cy += y2;
        safe_cy /= 2;
        if (!safe_cy.IsValid())
            return;

        int cx = safe_cx.ValueOrDie();
        int cy = safe_cy.ValueOrDie();
        render_line(x1, y1, cx, cy);
        render_line(cx, cy, x2, y2);
    }
    int dy = y2 - y1;
    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 x_from, x_to;
    int rem, mod, lift, delta, first, incr;
    if(ey1 == ey2) {
        render_hline(ey1, x1, fy1, x2, fy2);
        return;
    }
    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;
        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) {
            m_cur_cell.set_cover(delta, area);
            ey1 += incr;
            set_cur_cell(ex, ey1);
        }
        delta = fy2 - poly_base_size + first;
        m_cur_cell.add_cover(delta, two_fx * delta);
        return;
    }
    pdfium::base::CheckedNumeric<int> safeP = poly_base_size - fy1;
    safeP *= dx;
    if (!safeP.IsValid())
      return;
    first = poly_base_size;
    if(dy < 0) {
      safeP = fy1;
      safeP *= dx;
      if (!safeP.IsValid())
        return;
      first = 0;
      incr = -1;
      dy = -dy;
    }
    delta = (safeP / dy).ValueOrDie();
    mod = (safeP % dy).ValueOrDie();
    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) {
      safeP = static_cast<int>(poly_base_size);
      safeP *= dx;
      if (!safeP.IsValid())
        return;
      lift = (safeP / dy).ValueOrDie();
      rem = (safeP % dy).ValueOrDie();
      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;
}
template <class T> static AGG_INLINE void swap_cells(T* a, T* b)
{
    T temp = *a;
    *a = *b;
    *b = temp;
}
enum {
    qsort_threshold = 9
};
static void 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) {
            pivot = base + len / 2;
            swap_cells(base, pivot);
            i = base + 1;
            j = limit - 1;
            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);
            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 {
            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;
            }
        }
    }
}
void outline_aa::sort_cells()
{
    if(m_sorted) {
        return;
    }
    add_cur_cell();
    if(m_num_cells == 0) {
        return;
    }
    m_sorted_cells.allocate(m_num_cells, 16);
    if (m_max_y > 0 && m_min_y < 0 && -m_min_y > INT_MAX - m_max_y) {
        return;
    }
    unsigned size = m_max_y - m_min_y;
    if (size + 1 < size) {
        return;
    }
    size++;
    m_sorted_y.allocate(size, 16);
    m_sorted_y.zero();
    cell_aa** block_ptr = m_cells;
    cell_aa*  cell_ptr = NULL;
    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;
        }
    }
    i = m_num_cells & cell_block_mask;
    if (i) {
        cell_ptr = *block_ptr++;
    }
    while(i--) {
        m_sorted_y[cell_ptr->y - m_min_y].start++;
        ++cell_ptr;
    }
    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;
    }
    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& cur_y = m_sorted_y[cell_ptr->y - m_min_y];
            m_sorted_cells[cur_y.start + cur_y.num] = cell_ptr;
            ++cur_y.num;
            ++cell_ptr;
        }
    }
    i = m_num_cells & cell_block_mask;
    if (i) {
        cell_ptr = *block_ptr++;
    }
    while(i--) {
        sorted_y& cur_y = m_sorted_y[cell_ptr->y - m_min_y];
        m_sorted_cells[cur_y.start + cur_y.num] = cell_ptr;
        ++cur_y.num;
        ++cell_ptr;
    }
    for(i = 0; i < m_sorted_y.size(); i++) {
        const sorted_y& cur_y = m_sorted_y[i];
        if(cur_y.num) {
            qsort_cells(m_sorted_cells.data() + cur_y.start, cur_y.num);
        }
    }
    m_sorted = true;
}
// static
int rasterizer_scanline_aa::calculate_area(int cover, int shift)
{
    unsigned int result = cover;
    result <<= shift;
    return result;
}
// static
bool rasterizer_scanline_aa::safe_add(int* op1, int op2)
{
    pdfium::base::CheckedNumeric<int> safeOp1 = *op1;
    safeOp1 += op2;
    if(!safeOp1.IsValid()) {
        return false;
    }

    *op1 = safeOp1.ValueOrDie();
    return true;
}
}
}  // namespace pdfium