ass/ADM_libass/ass_rasterizer.c

/*
 * Copyright (C) 2014 Vabishchevich Nikolay <vabnick@gmail.com>
 *
 * This file is part of libass.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "ass_utils.h"
#include "ass_rasterizer.h"
#include <assert.h>

#ifdef _MSC_VER
#include <intrin.h>
#pragma intrinsic(_BitScanReverse)
#endif


static inline int ilog2(uint32_t n)  // XXX: different compilers
{
#ifdef __GNUC__
    return __builtin_clz(n) ^ 31;
#elif defined(_MSC_VER)
    int res;
    _BitScanReverse(&res, n);
    return res;
#else
    int res = 0;
    for (int ord = 16; ord; ord /= 2)
        if (n >= ((uint32_t)1 << ord)) {
            res += ord;
            n >>= ord;
        }
    return res;
#endif
}


void rasterizer_init(RasterizerData *rst, int outline_error)
{
    rst->outline_error = outline_error;
    rst->linebuf[0] = rst->linebuf[1] = NULL;
    rst->size[0] = rst->capacity[0] = 0;
    rst->size[1] = rst->capacity[1] = 0;
}

/**
 * \brief Ensure sufficient buffer size (allocate if necessary)
 * \param index index (0 or 1) of the input segment buffer (rst->linebuf)
 * \param delta requested size increase
 * \return zero on error
 */
static inline int check_capacity(RasterizerData *rst, int index, size_t delta)
{
    delta += rst->size[index];
    if (rst->capacity[index] >= delta)
        return 1;

    size_t capacity = FFMAX(2 * rst->capacity[index], 64);
    while (capacity < delta)
        capacity *= 2;
    void *ptr = realloc(rst->linebuf[index], sizeof(struct segment) * capacity);
    if (!ptr)
        return 0;

    rst->linebuf[index] = (struct segment *)ptr;
    rst->capacity[index] = capacity;
    return 1;
}

void rasterizer_done(RasterizerData *rst)
{
    free(rst->linebuf[0]);
    free(rst->linebuf[1]);
}


/*
 * Tiled Rasterization Algorithm
 *
 * 1) Convert splines into polylines using recursive subdivision.
 *
 * 2) Determine which segments of resulting polylines fall into each tile.
 * That's done through recursive splitting of segment array with horizontal or vertical lines.
 * Each individual segment can lie fully left(top) or right(bottom) from the splitting line or cross it.
 * In the latter case copies of such segment go to both output arrays. Also winding count
 * of the top-left corner of the second result rectangle gets calculated simultaneously with splitting.
 * Winding count of the first result rectangle is the same as of the source rectangle.
 *
 * 3) When the splitting is done to the tile level, there are 3 possible outcome:
 * - Tile doesn't have segments at all--fill it with solid color in accordance with winding count.
 * - Tile have only 1 segment--use simple half-plane filling algorithm.
 * - Generic case with 2 or more segments.
 * In the latter case each segment gets rasterized as right trapezoid into buffer
 * with additive or subtractive blending.
 */


typedef struct {
    int32_t x, y;
} OutlinePoint;

// Helper struct for spline split decision
typedef struct {
    OutlinePoint r;
    int64_t r2, er;
} OutlineSegment;

static inline void segment_init(OutlineSegment *seg,
                                OutlinePoint beg, OutlinePoint end,
                                int32_t outline_error)
{
    int32_t x = end.x - beg.x;
    int32_t y = end.y - beg.y;
    int32_t abs_x = x < 0 ? -x : x;
    int32_t abs_y = y < 0 ? -y : y;

    seg->r.x = x;
    seg->r.y = y;
    seg->r2 = x * (int64_t)x + y * (int64_t)y;
    seg->er = outline_error * (int64_t)FFMAX(abs_x, abs_y);
}

static inline int segment_subdivide(const OutlineSegment *seg,
                                    OutlinePoint beg, OutlinePoint pt)
{
    int32_t x = pt.x - beg.x;
    int32_t y = pt.y - beg.y;
    int64_t pdr = seg->r.x * (int64_t)x + seg->r.y * (int64_t)y;
    int64_t pcr = seg->r.x * (int64_t)y - seg->r.y * (int64_t)x;
    return pdr < -seg->er || pdr > seg->r2 + seg->er ||
        (pcr < 0 ? -pcr : pcr) > seg->er;
}

/**
 * \brief Add new segment to polyline
 */
static inline int add_line(RasterizerData *rst, OutlinePoint pt0, OutlinePoint pt1)
{
    int32_t x = pt1.x - pt0.x;
    int32_t y = pt1.y - pt0.y;
    if (!x && !y)
        return 1;

    if (!check_capacity(rst, 0, 1))
        return 0;
    struct segment *line = rst->linebuf[0] + rst->size[0];
    ++rst->size[0];

    line->flags = SEGFLAG_EXACT_LEFT | SEGFLAG_EXACT_RIGHT |
                  SEGFLAG_EXACT_TOP | SEGFLAG_EXACT_BOTTOM;
    if (x < 0)
        line->flags ^= SEGFLAG_UL_DR;
    if (y >= 0)
        line->flags ^= SEGFLAG_DN | SEGFLAG_UL_DR;

    line->x_min = FFMIN(pt0.x, pt1.x);
    line->x_max = FFMAX(pt0.x, pt1.x);
    line->y_min = FFMIN(pt0.y, pt1.y);
    line->y_max = FFMAX(pt0.y, pt1.y);

    line->a = y;
    line->b = -x;
    line->c = y * (int64_t)pt0.x - x * (int64_t)pt0.y;

    // halfplane normalization
    int32_t abs_x = x < 0 ? -x : x;
    int32_t abs_y = y < 0 ? -y : y;
    uint32_t max_ab = (abs_x > abs_y ? abs_x : abs_y);
    int shift = 30 - ilog2(max_ab);
    max_ab <<= shift + 1;
    line->a *= 1 << shift;
    line->b *= 1 << shift;
    line->c *= 1 << shift;
    line->scale = (uint64_t)0x53333333 * (uint32_t)(max_ab * (uint64_t)max_ab >> 32) >> 32;
    line->scale += 0x8810624D - (0xBBC6A7EF * (uint64_t)max_ab >> 32);
    //line->scale = ((uint64_t)1 << 61) / max_ab;
    return 1;
}

/**
 * \brief Add quadratic spline to polyline
 * Performs recursive subdivision if necessary.
 */
static int add_quadratic(RasterizerData *rst,
                         OutlinePoint pt0, OutlinePoint pt1, OutlinePoint pt2)
{
    OutlineSegment seg;
    segment_init(&seg, pt0, pt2, rst->outline_error);
    if (!segment_subdivide(&seg, pt0, pt1))
        return add_line(rst, pt0, pt2);

    OutlinePoint p01, p12, c;  // XXX: overflow?
    p01.x = pt0.x + pt1.x;
    p01.y = pt0.y + pt1.y;
    p12.x = pt1.x + pt2.x;
    p12.y = pt1.y + pt2.y;
    c.x = (p01.x + p12.x + 2) >> 2;
    c.y = (p01.y + p12.y + 2) >> 2;
    p01.x >>= 1;
    p01.y >>= 1;
    p12.x >>= 1;
    p12.y >>= 1;
    return add_quadratic(rst, pt0, p01, c) && add_quadratic(rst, c, p12, pt2);
}

/**
 * \brief Add cubic spline to polyline
 * Performs recursive subdivision if necessary.
 */
static int add_cubic(RasterizerData *rst,
                     OutlinePoint pt0, OutlinePoint pt1, OutlinePoint pt2, OutlinePoint pt3)
{
    OutlineSegment seg;
    segment_init(&seg, pt0, pt3, rst->outline_error);
    if (!segment_subdivide(&seg, pt0, pt1) && !segment_subdivide(&seg, pt0, pt2))
        return add_line(rst, pt0, pt3);

    OutlinePoint p01, p12, p23, p012, p123, c;  // XXX: overflow?
    p01.x = pt0.x + pt1.x;
    p01.y = pt0.y + pt1.y;
    p12.x = pt1.x + pt2.x + 2;
    p12.y = pt1.y + pt2.y + 2;
    p23.x = pt2.x + pt3.x;
    p23.y = pt2.y + pt3.y;
    p012.x = p01.x + p12.x;
    p012.y = p01.y + p12.y;
    p123.x = p12.x + p23.x;
    p123.y = p12.y + p23.y;
    c.x = (p012.x + p123.x - 1) >> 3;
    c.y = (p012.y + p123.y - 1) >> 3;
    p01.x >>= 1;
    p01.y >>= 1;
    p012.x >>= 2;
    p012.y >>= 2;
    p123.x >>= 2;
    p123.y >>= 2;
    p23.x >>= 1;
    p23.y >>= 1;
    return add_cubic(rst, pt0, p01, p012, c) && add_cubic(rst, c, p123, p23, pt3);
}


int rasterizer_set_outline(RasterizerData *rst, const ASS_Outline *path)
{
    enum Status {
        S_ON, S_Q, S_C1, S_C2
    };

    size_t i, j = 0;
    rst->size[0] = 0;
    for (i = 0; i < path->n_contours; ++i) {
        OutlinePoint start, p[4];
        int process_end = 1;
        enum Status st;

        int last = path->contours[i];
        if (j > last)
            return 0;

        switch (FT_CURVE_TAG(path->tags[j])) {
        case FT_CURVE_TAG_ON:
            p[0].x =  path->points[j].x;
            p[0].y = -path->points[j].y;
            start = p[0];
            st = S_ON;
            break;

        case FT_CURVE_TAG_CONIC:
            switch (FT_CURVE_TAG(path->tags[last])) {
            case FT_CURVE_TAG_ON:
                p[0].x =  path->points[last].x;
                p[0].y = -path->points[last].y;
                p[1].x =  path->points[j].x;
                p[1].y = -path->points[j].y;
                process_end = 0;
                st = S_Q;
                break;

            case FT_CURVE_TAG_CONIC:
                p[1].x =  path->points[j].x;
                p[1].y = -path->points[j].y;
                p[0].x = (p[1].x + path->points[last].x) >> 1;
                p[0].y = (p[1].y - path->points[last].y) >> 1;
                start = p[0];
                st = S_Q;
                break;

            default:
                return 0;
            }
            break;

        default:
            return 0;
        }

        for (j++; j <= last; ++j)
            switch (FT_CURVE_TAG(path->tags[j])) {
            case FT_CURVE_TAG_ON:
                switch (st) {
                case S_ON:
                    p[1].x =  path->points[j].x;
                    p[1].y = -path->points[j].y;
                    if (!add_line(rst, p[0], p[1]))
                        return 0;
                    p[0] = p[1];
                    break;

                case S_Q:
                    p[2].x =  path->points[j].x;
                    p[2].y = -path->points[j].y;
                    if (!add_quadratic(rst, p[0], p[1], p[2]))
                        return 0;
                    p[0] = p[2];
                    st = S_ON;
                    break;

                case S_C2:
                    p[3].x =  path->points[j].x;
                    p[3].y = -path->points[j].y;
                    if (!add_cubic(rst, p[0], p[1], p[2], p[3]))
                        return 0;
                    p[0] = p[3];
                    st = S_ON;
                    break;

                default:
                    return 0;
                }
                break;

            case FT_CURVE_TAG_CONIC:
                switch (st) {
                case S_ON:
                    p[1].x =  path->points[j].x;
                    p[1].y = -path->points[j].y;
                    st = S_Q;
                    break;

                case S_Q:
                    p[3].x =  path->points[j].x;
                    p[3].y = -path->points[j].y;
                    p[2].x = (p[1].x + p[3].x) >> 1;
                    p[2].y = (p[1].y + p[3].y) >> 1;
                    if (!add_quadratic(rst, p[0], p[1], p[2]))
                        return 0;
                    p[0] = p[2];
                    p[1] = p[3];
                    break;

                default:
                    return 0;
                }
                break;

            case FT_CURVE_TAG_CUBIC:
                switch (st) {
                case S_ON:
                    p[1].x =  path->points[j].x;
                    p[1].y = -path->points[j].y;
                    st = S_C1;
                    break;

                case S_C1:
                    p[2].x =  path->points[j].x;
                    p[2].y = -path->points[j].y;
                    st = S_C2;
                    break;

                default:
                    return 0;
                }
                break;

            default:
                return 0;
            }

        if (process_end)
            switch (st) {
            case S_ON:
                if (!add_line(rst, p[0], start))
                    return 0;
                break;

            case S_Q:
                if (!add_quadratic(rst, p[0], p[1], start))
                    return 0;
                break;

            case S_C2:
                if (!add_cubic(rst, p[0], p[1], p[2], start))
                    return 0;
                break;

            default:
                return 0;
            }
    }

    size_t k;
    rst->x_min = rst->y_min = 0x7FFFFFFF;
    rst->x_max = rst->y_max = 0x80000000;
    for (k = 0; k < rst->size[0]; ++k) {
        rst->x_min = FFMIN(rst->x_min, rst->linebuf[0][k].x_min);
        rst->x_max = FFMAX(rst->x_max, rst->linebuf[0][k].x_max);
        rst->y_min = FFMIN(rst->y_min, rst->linebuf[0][k].y_min);
        rst->y_max = FFMAX(rst->y_max, rst->linebuf[0][k].y_max);
    }
    return 1;
}


static void segment_move_x(struct segment *line, int32_t x)
{
    line->x_min -= x;
    line->x_max -= x;
    line->x_min = FFMAX(line->x_min, 0);
    line->c -= line->a * (int64_t)x;

    static const int test = SEGFLAG_EXACT_LEFT | SEGFLAG_UL_DR;
    if (!line->x_min && (line->flags & test) == test)
        line->flags &= ~SEGFLAG_EXACT_TOP;
}

static void segment_move_y(struct segment *line, int32_t y)
{
    line->y_min -= y;
    line->y_max -= y;
    line->y_min = FFMAX(line->y_min, 0);
    line->c -= line->b * (int64_t)y;

    static const int test = SEGFLAG_EXACT_TOP | SEGFLAG_UL_DR;
    if (!line->y_min && (line->flags & test) == test)
        line->flags &= ~SEGFLAG_EXACT_LEFT;
}

static void segment_split_horz(struct segment *line, struct segment *next, int32_t x)
{
    assert(x > line->x_min && x < line->x_max);

    *next = *line;
    next->c -= line->a * (int64_t)x;
    next->x_min = 0;
    next->x_max -= x;
    line->x_max = x;

    line->flags &= ~SEGFLAG_EXACT_TOP;
    next->flags &= ~SEGFLAG_EXACT_BOTTOM;
    if (line->flags & SEGFLAG_UL_DR) {
        int32_t tmp = line->flags;
        line->flags = next->flags;
        next->flags = tmp;
    }
    line->flags |= SEGFLAG_EXACT_RIGHT;
    next->flags |= SEGFLAG_EXACT_LEFT;
}

static void segment_split_vert(struct segment *line, struct segment *next, int32_t y)
{
    assert(y > line->y_min && y < line->y_max);

    *next = *line;
    next->c -= line->b * (int64_t)y;
    next->y_min = 0;
    next->y_max -= y;
    line->y_max = y;

    line->flags &= ~SEGFLAG_EXACT_LEFT;
    next->flags &= ~SEGFLAG_EXACT_RIGHT;
    if (line->flags & SEGFLAG_UL_DR) {
        int32_t tmp = line->flags;
        line->flags = next->flags;
        next->flags = tmp;
    }
    line->flags |= SEGFLAG_EXACT_BOTTOM;
    next->flags |= SEGFLAG_EXACT_TOP;
}

static inline int segment_check_left(const struct segment *line, int32_t x)
{
    if (line->flags & SEGFLAG_EXACT_LEFT)
        return line->x_min >= x;
    int64_t cc = line->c - line->a * (int64_t)x -
        line->b * (int64_t)(line->flags & SEGFLAG_UL_DR ? line->y_min : line->y_max);
    if (line->a < 0)
        cc = -cc;
    return cc >= 0;
}

static inline int segment_check_right(const struct segment *line, int32_t x)
{
    if (line->flags & SEGFLAG_EXACT_RIGHT)
        return line->x_max <= x;
    int64_t cc = line->c - line->a * (int64_t)x -
        line->b * (int64_t)(line->flags & SEGFLAG_UL_DR ? line->y_max : line->y_min);
    if (line->a > 0)
        cc = -cc;
    return cc >= 0;
}

static inline int segment_check_top(const struct segment *line, int32_t y)
{
    if (line->flags & SEGFLAG_EXACT_TOP)
        return line->y_min >= y;
    int64_t cc = line->c - line->b * (int64_t)y -
        line->a * (int64_t)(line->flags & SEGFLAG_UL_DR ? line->x_min : line->x_max);
    if (line->b < 0)
        cc = -cc;
    return cc >= 0;
}

static inline int segment_check_bottom(const struct segment *line, int32_t y)
{
    if (line->flags & SEGFLAG_EXACT_BOTTOM)
        return line->y_max <= y;
    int64_t cc = line->c - line->b * (int64_t)y -
        line->a * (int64_t)(line->flags & SEGFLAG_UL_DR ? line->x_max : line->x_min);
    if (line->b > 0)
        cc = -cc;
    return cc >= 0;
}

/**
 * \brief Split list of segments horizontally
 * \param src in: input array, can coincide with *dst0 or *dst1
 * \param n_src in: input array size
 * \param dst0, dst1 out: pointers to output arrays of at least n_src size
 * \param x in: split coordinate
 * \return winding difference between bottom-split and bottom-left points
 */
static int polyline_split_horz(const struct segment *src, size_t n_src,
                               struct segment **dst0, struct segment **dst1, int32_t x)
{
    int winding = 0;
    const struct segment *end = src + n_src;
    for (; src != end; ++src) {
        int delta = 0;
        if (!src->y_min && (src->flags & SEGFLAG_EXACT_TOP))
            delta = src->a < 0 ? 1 : -1;
        if (segment_check_right(src, x)) {
            winding += delta;
            if (src->x_min >= x)
                continue;
            **dst0 = *src;
            (*dst0)->x_max = FFMIN((*dst0)->x_max, x);
            ++(*dst0);
            continue;
        }
        if (segment_check_left(src, x)) {
            **dst1 = *src;
            segment_move_x(*dst1, x);
            ++(*dst1);
            continue;
        }
        if (src->flags & SEGFLAG_UL_DR)
            winding += delta;
        **dst0 = *src;
        segment_split_horz(*dst0, *dst1, x);
        ++(*dst0);
        ++(*dst1);
    }
    return winding;
}

/**
 * \brief Split list of segments vertically
 */
static int polyline_split_vert(const struct segment *src, size_t n_src,
                               struct segment **dst0, struct segment **dst1, int32_t y)
{
    int winding = 0;
    const struct segment *end = src + n_src;
    for (; src != end; ++src) {
        int delta = 0;
        if (!src->x_min && (src->flags & SEGFLAG_EXACT_LEFT))
            delta = src->b < 0 ? 1 : -1;
        if (segment_check_bottom(src, y)) {
            winding += delta;
            if (src->y_min >= y)
                continue;
            **dst0 = *src;
            (*dst0)->y_max = (*dst0)->y_max < y ? (*dst0)->y_max : y;
            ++(*dst0);
            continue;
        }
        if (segment_check_top(src, y)) {
            **dst1 = *src;
            segment_move_y(*dst1, y);
            ++(*dst1);
            continue;
        }
        if (src->flags & SEGFLAG_UL_DR)
            winding += delta;
        **dst0 = *src;
        segment_split_vert(*dst0, *dst1, y);
        ++(*dst0);
        ++(*dst1);
    }
    return winding;
}


static inline void rasterizer_fill_solid(const BitmapEngine *engine,
                                         uint8_t *buf, int width, int height, ptrdiff_t stride,
                                         int set)
{
    assert(!(width  & ((1 << engine->tile_order) - 1)));
    assert(!(height & ((1 << engine->tile_order) - 1)));

    int i, j;
    ptrdiff_t step = 1 << engine->tile_order;
    ptrdiff_t tile_stride = stride * (1 << engine->tile_order);
    width  >>= engine->tile_order;
    height >>= engine->tile_order;
    for (j = 0; j < height; ++j) {
        for (i = 0; i < width; ++i)
            engine->fill_solid(buf + i * step, stride, set);
        buf += tile_stride;
    }
}

static inline void rasterizer_fill_halfplane(const BitmapEngine *engine,
                                             uint8_t *buf, int width, int height, ptrdiff_t stride,
                                             int32_t a, int32_t b, int64_t c, int32_t scale)
{
    assert(!(width  & ((1 << engine->tile_order) - 1)));
    assert(!(height & ((1 << engine->tile_order) - 1)));
    if (width == 1 << engine->tile_order && height == 1 << engine->tile_order) {
        engine->fill_halfplane(buf, stride, a, b, c, scale);
        return;
    }

    uint32_t abs_a = a < 0 ? -a : a;
    uint32_t abs_b = b < 0 ? -b : b;
    int64_t size = (int64_t)(abs_a + abs_b) << (engine->tile_order + 5);
    int64_t offs = ((int64_t)a + b) * (1 << (engine->tile_order + 5));

    int i, j;
    ptrdiff_t step = 1 << engine->tile_order;
    ptrdiff_t tile_stride = stride * (1 << engine->tile_order);
    width  >>= engine->tile_order;
    height >>= engine->tile_order;
    for (j = 0; j < height; ++j) {
        for (i = 0; i < width; ++i) {
            int64_t cc = c - (a * (int64_t)i + b * (int64_t)j) * (1 << (engine->tile_order + 6));
            int64_t offs_c = offs - cc;
            int64_t abs_c = offs_c < 0 ? -offs_c : offs_c;
            if (abs_c < size)
                engine->fill_halfplane(buf + i * step, stride, a, b, cc, scale);
            else
                engine->fill_solid(buf + i * step, stride,
                                   ((uint32_t)(offs_c >> 32) ^ scale) & 0x80000000);
        }
        buf += tile_stride;
    }
}

/**
 * \brief Main quad-tree filling function
 * \param index index (0 or 1) of the input segment buffer (rst->linebuf)
 * \param offs current offset from the beginning of the buffer
 * \param winding bottom-left winding value
 * \return zero on error
 * Rasterizes (possibly recursive) one quad-tree level.
 * Truncates used input buffer.
 */
static int rasterizer_fill_level(const BitmapEngine *engine, RasterizerData *rst,
                                 uint8_t *buf, int width, int height, ptrdiff_t stride,
                                 int index, size_t offs, int winding)
{
    assert(width > 0 && height > 0);
    assert((unsigned)index < 2u && offs <= rst->size[index]);
    assert(!(width  & ((1 << engine->tile_order) - 1)));
    assert(!(height & ((1 << engine->tile_order) - 1)));

    size_t n = rst->size[index] - offs;
    struct segment *line = rst->linebuf[index] + offs;
    if (!n) {
        rasterizer_fill_solid(engine, buf, width, height, stride, winding);
        return 1;
    }
    if (n == 1) {
        static const int test = SEGFLAG_UL_DR | SEGFLAG_EXACT_LEFT;
        if (((line->flags & test) != test) == !(line->flags & SEGFLAG_DN))
            winding++;

        int flag = 0;
        if (winding)
            flag ^= 1;
        if (winding - 1)
            flag ^= 3;
        if (flag & 1)
            rasterizer_fill_halfplane(engine, buf, width, height, stride,
                                      line->a, line->b, line->c,
                                      flag & 2 ? -line->scale : line->scale);
        else
            rasterizer_fill_solid(engine, buf, width, height, stride, flag & 2);
        rst->size[index] = offs;
        return 1;
    }
    if (width == 1 << engine->tile_order && height == 1 << engine->tile_order) {
        engine->fill_generic(buf, stride, line, rst->size[index] - offs, winding);
        rst->size[index] = offs;
        return 1;
    }

    size_t offs1 = rst->size[index ^ 1];
    if (!check_capacity(rst, index ^ 1, n))
        return 0;
    struct segment *dst0 = line;
    struct segment *dst1 = rst->linebuf[index ^ 1] + offs1;

    int winding1 = winding;
    uint8_t *buf1 = buf;
    int width1  = width;
    int height1 = height;
    if (width > height) {
        width = 1 << ilog2(width - 1);
        width1 -= width;
        buf1 += width;
        winding1 += polyline_split_horz(line, n, &dst0, &dst1, (int32_t)width << 6);
    } else {
        height = 1 << ilog2(height - 1);
        height1 -= height;
        buf1 += height * stride;
        winding1 += polyline_split_vert(line, n, &dst0, &dst1, (int32_t)height << 6);
    }
    rst->size[index ^ 0] = dst0 - rst->linebuf[index ^ 0];
    rst->size[index ^ 1] = dst1 - rst->linebuf[index ^ 1];

    if (!rasterizer_fill_level(engine, rst, buf,  width,  height,  stride, index ^ 0, offs,  winding))
        return 0;
    assert(rst->size[index ^ 0] == offs);
    if (!rasterizer_fill_level(engine, rst, buf1, width1, height1, stride, index ^ 1, offs1, winding1))
        return 0;
    assert(rst->size[index ^ 1] == offs1);
    return 1;
}

int rasterizer_fill(const BitmapEngine *engine, RasterizerData *rst,
                    uint8_t *buf, int x0, int y0, int width, int height, ptrdiff_t stride)
{
    assert(width > 0 && height > 0);
    assert(!(width  & ((1 << engine->tile_order) - 1)));
    assert(!(height & ((1 << engine->tile_order) - 1)));
    x0 *= 1 << 6;  y0 *= 1 << 6;

    size_t n = rst->size[0];
    struct segment *line = rst->linebuf[0];
    struct segment *end = line + n;
    for (; line != end; ++line) {
        line->x_min -= x0;
        line->x_max -= x0;
        line->y_min -= y0;
        line->y_max -= y0;
        line->c -= line->a * (int64_t)x0 + line->b * (int64_t)y0;
    }
    rst->x_min -= x0;
    rst->x_max -= x0;
    rst->y_min -= y0;
    rst->y_max -= y0;

    int index = 0;
    int winding = 0;
    if (!check_capacity(rst, 1, rst->size[0]))
        return 0;
    int32_t size_x = (int32_t)width << 6;
    int32_t size_y = (int32_t)height << 6;
    if (rst->x_max >= size_x) {
        struct segment *dst0 = rst->linebuf[index];
        struct segment *dst1 = rst->linebuf[index ^ 1];
        polyline_split_horz(rst->linebuf[index], n, &dst0, &dst1, size_x);
        n = dst0 - rst->linebuf[index];
    }
    if (rst->y_max >= size_y) {
        struct segment *dst0 = rst->linebuf[index];
        struct segment *dst1 = rst->linebuf[index ^ 1];
        polyline_split_vert(rst->linebuf[index], n, &dst0, &dst1, size_y);
        n = dst0 - rst->linebuf[index];
    }
    if (rst->x_min <= 0) {
        struct segment *dst0 = rst->linebuf[index];
        struct segment *dst1 = rst->linebuf[index ^ 1];
        polyline_split_horz(rst->linebuf[index], n, &dst0, &dst1, 0);
        index ^= 1;
        n = dst1 - rst->linebuf[index];
    }
    if (rst->y_min <= 0) {
        struct segment *dst0 = rst->linebuf[index];
        struct segment *dst1 = rst->linebuf[index ^ 1];
        winding = polyline_split_vert(rst->linebuf[index], n, &dst0, &dst1, 0);
        index ^= 1;
        n = dst1 - rst->linebuf[index];
    }
    rst->size[index] = n;
    rst->size[index ^ 1] = 0;
    return rasterizer_fill_level(engine, rst, buf, width, height, stride,
                                 index, 0, winding);
}