beta-0.89.2

[luatex.git] / source / libs / cairo / cairo-src / src / cairo-bentley-ottmann-rectangular.c

/*
 * Copyright © 2004 Carl Worth
 * Copyright © 2006 Red Hat, Inc.
 * Copyright © 2009 Chris Wilson
 *
 * This library is free software; you can redistribute it and/or
 * modify it either under the terms of the GNU Lesser General Public
 * License version 2.1 as published by the Free Software Foundation
 * (the "LGPL") or, at your option, under the terms of the Mozilla
 * Public License Version 1.1 (the "MPL"). If you do not alter this
 * notice, a recipient may use your version of this file under either
 * the MPL or the LGPL.
 *
 * You should have received a copy of the LGPL along with this library
 * in the file COPYING-LGPL-2.1; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
 * You should have received a copy of the MPL along with this library
 * in the file COPYING-MPL-1.1
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
 * OF ANY KIND, either express or implied. See the LGPL or the MPL for
 * the specific language governing rights and limitations.
 *
 * The Original Code is the cairo graphics library.
 *
 * The Initial Developer of the Original Code is Carl Worth
 *
 * Contributor(s):
 *      Carl D. Worth <cworth@cworth.org>
 *      Chris Wilson <chris@chris-wilson.co.uk>
 */

/* Provide definitions for standalone compilation */
#include "cairoint.h"

#include "cairo-boxes-private.h"
#include "cairo-error-private.h"
#include "cairo-combsort-inline.h"
#include "cairo-list-private.h"
#include "cairo-traps-private.h"

#include <setjmp.h>

typedef struct _rectangle rectangle_t;
typedef struct _edge edge_t;

struct _edge {
    edge_t *next, *prev;
    edge_t *right;
    cairo_fixed_t x, top;
    int dir;
};

struct _rectangle {
    edge_t left, right;
    int32_t top, bottom;
};

#define UNROLL3(x) x x x

/* the parent is always given by index/2 */
#define PQ_PARENT_INDEX(i) ((i) >> 1)
#define PQ_FIRST_ENTRY 1

/* left and right children are index * 2 and (index * 2) +1 respectively */
#define PQ_LEFT_CHILD_INDEX(i) ((i) << 1)

typedef struct _sweep_line {
    rectangle_t **rectangles;
    rectangle_t **stop;
    edge_t head, tail, *insert, *cursor;
    int32_t current_y;
    int32_t last_y;
    int stop_size;

    int32_t insert_x;
    cairo_fill_rule_t fill_rule;

    cairo_bool_t do_traps;
    void *container;

    jmp_buf unwind;
} sweep_line_t;

#define DEBUG_TRAPS 0

#if DEBUG_TRAPS
static void
dump_traps (cairo_traps_t *traps, const char *filename)
{
    FILE *file;
    int n;

    if (getenv ("CAIRO_DEBUG_TRAPS") == NULL)
        return;

    file = fopen (filename, "a");
    if (file != NULL) {
        for (n = 0; n < traps->num_traps; n++) {
            fprintf (file, "%d %d L:(%d, %d), (%d, %d) R:(%d, %d), (%d, %d)\n",
                     traps->traps[n].top,
                     traps->traps[n].bottom,
                     traps->traps[n].left.p1.x,
                     traps->traps[n].left.p1.y,
                     traps->traps[n].left.p2.x,
                     traps->traps[n].left.p2.y,
                     traps->traps[n].right.p1.x,
                     traps->traps[n].right.p1.y,
                     traps->traps[n].right.p2.x,
                     traps->traps[n].right.p2.y);
        }
        fprintf (file, "\n");
        fclose (file);
    }
}
#else
#define dump_traps(traps, filename)
#endif

static inline int
rectangle_compare_start (const rectangle_t *a,
                         const rectangle_t *b)
{
    return a->top - b->top;
}

static inline int
rectangle_compare_stop (const rectangle_t *a,
                         const rectangle_t *b)
{
    return a->bottom - b->bottom;
}

static inline void
pqueue_push (sweep_line_t *sweep, rectangle_t *rectangle)
{
    rectangle_t **elements;
    int i, parent;

    elements = sweep->stop;
    for (i = ++sweep->stop_size;
         i != PQ_FIRST_ENTRY &&
         rectangle_compare_stop (rectangle,
                                 elements[parent = PQ_PARENT_INDEX (i)]) < 0;
         i = parent)
    {
        elements[i] = elements[parent];
    }

    elements[i] = rectangle;
}

static inline void
rectangle_pop_stop (sweep_line_t *sweep)
{
    rectangle_t **elements = sweep->stop;
    rectangle_t *tail;
    int child, i;

    tail = elements[sweep->stop_size--];
    if (sweep->stop_size == 0) {
        elements[PQ_FIRST_ENTRY] = NULL;
        return;
    }

    for (i = PQ_FIRST_ENTRY;
         (child = PQ_LEFT_CHILD_INDEX (i)) <= sweep->stop_size;
         i = child)
    {
        if (child != sweep->stop_size &&
            rectangle_compare_stop (elements[child+1],
                                    elements[child]) < 0)
        {
            child++;
        }

        if (rectangle_compare_stop (elements[child], tail) >= 0)
            break;

        elements[i] = elements[child];
    }
    elements[i] = tail;
}

static inline rectangle_t *
rectangle_pop_start (sweep_line_t *sweep_line)
{
    return *sweep_line->rectangles++;
}

static inline rectangle_t *
rectangle_peek_stop (sweep_line_t *sweep_line)
{
    return sweep_line->stop[PQ_FIRST_ENTRY];
}

CAIRO_COMBSORT_DECLARE (_rectangle_sort,
                        rectangle_t *,
                        rectangle_compare_start)

static void
sweep_line_init (sweep_line_t    *sweep_line,
                 rectangle_t    **rectangles,
                 int              num_rectangles,
                 cairo_fill_rule_t fill_rule,
                 cairo_bool_t    do_traps,
                 void           *container)
{
    rectangles[-2] = NULL;
    rectangles[-1] = NULL;
    rectangles[num_rectangles] = NULL;
    sweep_line->rectangles = rectangles;
    sweep_line->stop = rectangles - 2;
    sweep_line->stop_size = 0;

    sweep_line->insert = NULL;
    sweep_line->insert_x = INT_MAX;
    sweep_line->cursor = &sweep_line->tail;

    sweep_line->head.dir = 0;
    sweep_line->head.x = INT32_MIN;
    sweep_line->head.right = NULL;
    sweep_line->head.prev = NULL;
    sweep_line->head.next = &sweep_line->tail;
    sweep_line->tail.prev = &sweep_line->head;
    sweep_line->tail.next = NULL;
    sweep_line->tail.right = NULL;
    sweep_line->tail.x = INT32_MAX;
    sweep_line->tail.dir = 0;

    sweep_line->current_y = INT32_MIN;
    sweep_line->last_y = INT32_MIN;

    sweep_line->fill_rule = fill_rule;
    sweep_line->container = container;
    sweep_line->do_traps = do_traps;
}

static void
edge_end_box (sweep_line_t *sweep_line, edge_t *left, int32_t bot)
{
    cairo_status_t status = CAIRO_STATUS_SUCCESS;

    /* Only emit (trivial) non-degenerate trapezoids with positive height. */
    if (likely (left->top < bot)) {
        if (sweep_line->do_traps) {
            cairo_line_t _left = {
                { left->x, left->top },
                { left->x, bot },
            }, _right = {
                { left->right->x, left->top },
                { left->right->x, bot },
            };
            _cairo_traps_add_trap (sweep_line->container, left->top, bot, &_left, &_right);
            status = _cairo_traps_status ((cairo_traps_t *) sweep_line->container);
        } else {
            cairo_box_t box;

            box.p1.x = left->x;
            box.p1.y = left->top;
            box.p2.x = left->right->x;
            box.p2.y = bot;

            status = _cairo_boxes_add (sweep_line->container,
                                       CAIRO_ANTIALIAS_DEFAULT,
                                       &box);
        }
    }
    if (unlikely (status))
        longjmp (sweep_line->unwind, status);

    left->right = NULL;
}

/* Start a new trapezoid at the given top y coordinate, whose edges
 * are `edge' and `edge->next'. If `edge' already has a trapezoid,
 * then either add it to the traps in `traps', if the trapezoid's
 * right edge differs from `edge->next', or do nothing if the new
 * trapezoid would be a continuation of the existing one. */
static inline void
edge_start_or_continue_box (sweep_line_t *sweep_line,
                            edge_t      *left,
                            edge_t      *right,
                            int          top)
{
    if (left->right == right)
        return;

    if (left->right != NULL) {
        if (left->right->x == right->x) {
            /* continuation on right, so just swap edges */
            left->right = right;
            return;
        }

        edge_end_box (sweep_line, left, top);
    }

    if (left->x != right->x) {
        left->top = top;
        left->right = right;
    }
}
/*
 * Merge two sorted edge lists.
 * Input:
 *  - head_a: The head of the first list.
 *  - head_b: The head of the second list; head_b cannot be NULL.
 * Output:
 * Returns the head of the merged list.
 *
 * Implementation notes:
 * To make it fast (in particular, to reduce to an insertion sort whenever
 * one of the two input lists only has a single element) we iterate through
 * a list until its head becomes greater than the head of the other list,
 * then we switch their roles. As soon as one of the two lists is empty, we
 * just attach the other one to the current list and exit.
 * Writes to memory are only needed to "switch" lists (as it also requires
 * attaching to the output list the list which we will be iterating next) and
 * to attach the last non-empty list.
 */
static edge_t *
merge_sorted_edges (edge_t *head_a, edge_t *head_b)
{
    edge_t *head, *prev;
    int32_t x;

    prev = head_a->prev;
    if (head_a->x <= head_b->x) {
        head = head_a;
    } else {
        head_b->prev = prev;
        head = head_b;
        goto start_with_b;
    }

    do {
        x = head_b->x;
        while (head_a != NULL && head_a->x <= x) {
            prev = head_a;
            head_a = head_a->next;
        }

        head_b->prev = prev;
        prev->next = head_b;
        if (head_a == NULL)
            return head;

start_with_b:
        x = head_a->x;
        while (head_b != NULL && head_b->x <= x) {
            prev = head_b;
            head_b = head_b->next;
        }

        head_a->prev = prev;
        prev->next = head_a;
        if (head_b == NULL)
            return head;
    } while (1);
}

/*
 * Sort (part of) a list.
 * Input:
 *  - list: The list to be sorted; list cannot be NULL.
 *  - limit: Recursion limit.
 * Output:
 *  - head_out: The head of the sorted list containing the first 2^(level+1) elements of the
 *              input list; if the input list has fewer elements, head_out be a sorted list
 *              containing all the elements of the input list.
 * Returns the head of the list of unprocessed elements (NULL if the sorted list contains
 * all the elements of the input list).
 *
 * Implementation notes:
 * Special case single element list, unroll/inline the sorting of the first two elements.
 * Some tail recursion is used since we iterate on the bottom-up solution of the problem
 * (we start with a small sorted list and keep merging other lists of the same size to it).
 */
static edge_t *
sort_edges (edge_t  *list,
            unsigned int  level,
            edge_t **head_out)
{
    edge_t *head_other, *remaining;
    unsigned int i;

    head_other = list->next;

    if (head_other == NULL) {
        *head_out = list;
        return NULL;
    }

    remaining = head_other->next;
    if (list->x <= head_other->x) {
        *head_out = list;
        head_other->next = NULL;
    } else {
        *head_out = head_other;
        head_other->prev = list->prev;
        head_other->next = list;
        list->prev = head_other;
        list->next = NULL;
    }

    for (i = 0; i < level && remaining; i++) {
        remaining = sort_edges (remaining, i, &head_other);
        *head_out = merge_sorted_edges (*head_out, head_other);
    }

    return remaining;
}

static edge_t *
merge_unsorted_edges (edge_t *head, edge_t *unsorted)
{
    sort_edges (unsorted, UINT_MAX, &unsorted);
    return merge_sorted_edges (head, unsorted);
}

static void
active_edges_insert (sweep_line_t *sweep)
{
    edge_t *prev;
    int x;

    x = sweep->insert_x;
    prev = sweep->cursor;
    if (prev->x > x) {
        do {
            prev = prev->prev;
        } while (prev->x > x);
    } else {
        while (prev->next->x < x)
            prev = prev->next;
    }

    prev->next = merge_unsorted_edges (prev->next, sweep->insert);
    sweep->cursor = sweep->insert;
    sweep->insert = NULL;
    sweep->insert_x = INT_MAX;
}

static inline void
active_edges_to_traps (sweep_line_t *sweep)
{
    int top = sweep->current_y;
    edge_t *pos;

    if (sweep->last_y == sweep->current_y)
        return;

    if (sweep->insert)
        active_edges_insert (sweep);

    pos = sweep->head.next;
    if (pos == &sweep->tail)
        return;

    if (sweep->fill_rule == CAIRO_FILL_RULE_WINDING) {
        do {
            edge_t *left, *right;
            int winding;

            left = pos;
            winding = left->dir;

            right = left->next;

            /* Check if there is a co-linear edge with an existing trap */
            while (right->x == left->x) {
                if (right->right != NULL) {
                    assert (left->right == NULL);
                    /* continuation on left */
                    left->top = right->top;
                    left->right = right->right;
                    right->right = NULL;
                }
                winding += right->dir;
                right = right->next;
            }

            if (winding == 0) {
                if (left->right != NULL)
                    edge_end_box (sweep, left, top);
                pos = right;
                continue;
            }

            do {
                /* End all subsumed traps */
                if (unlikely (right->right != NULL))
                    edge_end_box (sweep, right, top);

                /* Greedily search for the closing edge, so that we generate
                 * the * maximal span width with the minimal number of
                 * boxes.
                 */
                winding += right->dir;
                if (winding == 0 && right->x != right->next->x)
                    break;

                right = right->next;
            } while (TRUE);

            edge_start_or_continue_box (sweep, left, right, top);

            pos = right->next;
        } while (pos != &sweep->tail);
    } else {
        do {
            edge_t *right = pos->next;
            int count = 0;

            do {
                /* End all subsumed traps */
                if (unlikely (right->right != NULL))
                    edge_end_box (sweep, right, top);

                    /* skip co-linear edges */
                if (++count & 1 && right->x != right->next->x)
                    break;

                right = right->next;
            } while (TRUE);

            edge_start_or_continue_box (sweep, pos, right, top);

            pos = right->next;
        } while (pos != &sweep->tail);
    }

    sweep->last_y = sweep->current_y;
}

static inline void
sweep_line_delete_edge (sweep_line_t *sweep, edge_t *edge)
{
    if (edge->right != NULL) {
        edge_t *next = edge->next;
        if (next->x == edge->x) {
            next->top = edge->top;
            next->right = edge->right;
        } else
            edge_end_box (sweep, edge, sweep->current_y);
    }

    if (sweep->cursor == edge)
        sweep->cursor = edge->prev;

    edge->prev->next = edge->next;
    edge->next->prev = edge->prev;
}

static inline cairo_bool_t
sweep_line_delete (sweep_line_t *sweep, rectangle_t *rectangle)
{
    cairo_bool_t update;

    update = TRUE;
    if (sweep->fill_rule == CAIRO_FILL_RULE_WINDING &&
        rectangle->left.prev->dir == rectangle->left.dir)
    {
        update = rectangle->left.next != &rectangle->right;
    }

    sweep_line_delete_edge (sweep, &rectangle->left);
    sweep_line_delete_edge (sweep, &rectangle->right);

    rectangle_pop_stop (sweep);
    return update;
}

static inline void
sweep_line_insert (sweep_line_t *sweep, rectangle_t *rectangle)
{
    if (sweep->insert)
        sweep->insert->prev = &rectangle->right;
    rectangle->right.next = sweep->insert;
    rectangle->right.prev = &rectangle->left;
    rectangle->left.next = &rectangle->right;
    rectangle->left.prev = NULL;
    sweep->insert = &rectangle->left;
    if (rectangle->left.x < sweep->insert_x)
        sweep->insert_x = rectangle->left.x;

    pqueue_push (sweep, rectangle);
}

static cairo_status_t
_cairo_bentley_ottmann_tessellate_rectangular (rectangle_t      **rectangles,
                                               int                        num_rectangles,
                                               cairo_fill_rule_t          fill_rule,
                                               cairo_bool_t              do_traps,
                                               void                     *container)
{
    sweep_line_t sweep_line;
    rectangle_t *rectangle;
    cairo_status_t status;
    cairo_bool_t update = FALSE;

    sweep_line_init (&sweep_line,
                     rectangles, num_rectangles,
                     fill_rule,
                     do_traps, container);
    if ((status = setjmp (sweep_line.unwind)))
        return status;

    rectangle = rectangle_pop_start (&sweep_line);
    do {
        if (rectangle->top != sweep_line.current_y) {
            rectangle_t *stop;

            stop = rectangle_peek_stop (&sweep_line);
            while (stop != NULL && stop->bottom < rectangle->top) {
                if (stop->bottom != sweep_line.current_y) {
                    if (update) {
                        active_edges_to_traps (&sweep_line);
                        update = FALSE;
                    }

                    sweep_line.current_y = stop->bottom;
                }

                update |= sweep_line_delete (&sweep_line, stop);
                stop = rectangle_peek_stop (&sweep_line);
            }

            if (update) {
                active_edges_to_traps (&sweep_line);
                update = FALSE;
            }

            sweep_line.current_y = rectangle->top;
        }

        do {
            sweep_line_insert (&sweep_line, rectangle);
        } while ((rectangle = rectangle_pop_start (&sweep_line)) != NULL &&
                 sweep_line.current_y == rectangle->top);
        update = TRUE;
    } while (rectangle);

    while ((rectangle = rectangle_peek_stop (&sweep_line)) != NULL) {
        if (rectangle->bottom != sweep_line.current_y) {
            if (update) {
                active_edges_to_traps (&sweep_line);
                update = FALSE;
            }
            sweep_line.current_y = rectangle->bottom;
        }

        update |= sweep_line_delete (&sweep_line, rectangle);
    }

    return CAIRO_STATUS_SUCCESS;
}

cairo_status_t
_cairo_bentley_ottmann_tessellate_rectangular_traps (cairo_traps_t *traps,
                                                     cairo_fill_rule_t fill_rule)
{
    rectangle_t stack_rectangles[CAIRO_STACK_ARRAY_LENGTH (rectangle_t)];
    rectangle_t *stack_rectangles_ptrs[ARRAY_LENGTH (stack_rectangles) + 3];
    rectangle_t *rectangles, **rectangles_ptrs;
    cairo_status_t status;
    int i;

    if (unlikely (traps->num_traps <= 1))
        return CAIRO_STATUS_SUCCESS;

    assert (traps->is_rectangular);

    dump_traps (traps, "bo-rects-traps-in.txt");

    rectangles = stack_rectangles;
    rectangles_ptrs = stack_rectangles_ptrs;
    if (traps->num_traps > ARRAY_LENGTH (stack_rectangles)) {
        rectangles = _cairo_malloc_ab_plus_c (traps->num_traps,
                                              sizeof (rectangle_t) +
                                              sizeof (rectangle_t *),
                                              3*sizeof (rectangle_t *));
        if (unlikely (rectangles == NULL))
            return _cairo_error (CAIRO_STATUS_NO_MEMORY);

        rectangles_ptrs = (rectangle_t **) (rectangles + traps->num_traps);
    }

    for (i = 0; i < traps->num_traps; i++) {
        if (traps->traps[i].left.p1.x < traps->traps[i].right.p1.x) {
            rectangles[i].left.x = traps->traps[i].left.p1.x;
            rectangles[i].left.dir = 1;

            rectangles[i].right.x = traps->traps[i].right.p1.x;
            rectangles[i].right.dir = -1;
        } else {
            rectangles[i].right.x = traps->traps[i].left.p1.x;
            rectangles[i].right.dir = 1;

            rectangles[i].left.x = traps->traps[i].right.p1.x;
            rectangles[i].left.dir = -1;
        }

        rectangles[i].left.right = NULL;
        rectangles[i].right.right = NULL;

        rectangles[i].top = traps->traps[i].top;
        rectangles[i].bottom = traps->traps[i].bottom;

        rectangles_ptrs[i+2] = &rectangles[i];
    }
    /* XXX incremental sort */
    _rectangle_sort (rectangles_ptrs+2, i);

    _cairo_traps_clear (traps);
    status = _cairo_bentley_ottmann_tessellate_rectangular (rectangles_ptrs+2, i,
                                                            fill_rule,
                                                            TRUE, traps);
    traps->is_rectilinear = TRUE;
    traps->is_rectangular = TRUE;

    if (rectangles != stack_rectangles)
        free (rectangles);

    dump_traps (traps, "bo-rects-traps-out.txt");

    return status;
}

cairo_status_t
_cairo_bentley_ottmann_tessellate_boxes (const cairo_boxes_t *in,
                                         cairo_fill_rule_t fill_rule,
                                         cairo_boxes_t *out)
{
    rectangle_t stack_rectangles[CAIRO_STACK_ARRAY_LENGTH (rectangle_t)];
    rectangle_t *stack_rectangles_ptrs[ARRAY_LENGTH (stack_rectangles) + 3];
    rectangle_t *rectangles, **rectangles_ptrs;
    rectangle_t *stack_rectangles_chain[CAIRO_STACK_ARRAY_LENGTH (rectangle_t *) ];
    rectangle_t **rectangles_chain = NULL;
    const struct _cairo_boxes_chunk *chunk;
    cairo_status_t status;
    int i, j, y_min, y_max;

    if (unlikely (in->num_boxes == 0)) {
        _cairo_boxes_clear (out);
        return CAIRO_STATUS_SUCCESS;
    }

    if (in->num_boxes == 1) {
        if (in == out) {
            cairo_box_t *box = &in->chunks.base[0];

            if (box->p1.x > box->p2.x) {
                cairo_fixed_t tmp = box->p1.x;
                box->p1.x = box->p2.x;
                box->p2.x = tmp;
            }
        } else {
            cairo_box_t box = in->chunks.base[0];

            if (box.p1.x > box.p2.x) {
                cairo_fixed_t tmp = box.p1.x;
                box.p1.x = box.p2.x;
                box.p2.x = tmp;
            }

            _cairo_boxes_clear (out);
            status = _cairo_boxes_add (out, CAIRO_ANTIALIAS_DEFAULT, &box);
            assert (status == CAIRO_STATUS_SUCCESS);
        }
        return CAIRO_STATUS_SUCCESS;
    }

    y_min = INT_MAX; y_max = INT_MIN;
    for (chunk = &in->chunks; chunk != NULL; chunk = chunk->next) {
        const cairo_box_t *box = chunk->base;
        for (i = 0; i < chunk->count; i++) {
            if (box[i].p1.y < y_min)
                y_min = box[i].p1.y;
            if (box[i].p1.y > y_max)
                y_max = box[i].p1.y;
        }
    }
    y_min = _cairo_fixed_integer_floor (y_min);
    y_max = _cairo_fixed_integer_floor (y_max) + 1;
    y_max -= y_min;

    if (y_max < in->num_boxes) {
        rectangles_chain = stack_rectangles_chain;
        if (y_max > ARRAY_LENGTH (stack_rectangles_chain)) {
            rectangles_chain = _cairo_malloc_ab (y_max, sizeof (rectangle_t *));
            if (unlikely (rectangles_chain == NULL))
                return _cairo_error (CAIRO_STATUS_NO_MEMORY);
        }
        memset (rectangles_chain, 0, y_max * sizeof (rectangle_t*));
    }

    rectangles = stack_rectangles;
    rectangles_ptrs = stack_rectangles_ptrs;
    if (in->num_boxes > ARRAY_LENGTH (stack_rectangles)) {
        rectangles = _cairo_malloc_ab_plus_c (in->num_boxes,
                                              sizeof (rectangle_t) +
                                              sizeof (rectangle_t *),
                                              3*sizeof (rectangle_t *));
        if (unlikely (rectangles == NULL)) {
            if (rectangles_chain != stack_rectangles_chain)
                free (rectangles_chain);
            return _cairo_error (CAIRO_STATUS_NO_MEMORY);
        }

        rectangles_ptrs = (rectangle_t **) (rectangles + in->num_boxes);
    }

    j = 0;
    for (chunk = &in->chunks; chunk != NULL; chunk = chunk->next) {
        const cairo_box_t *box = chunk->base;
        for (i = 0; i < chunk->count; i++) {
            int h;

            if (box[i].p1.x < box[i].p2.x) {
                rectangles[j].left.x = box[i].p1.x;
                rectangles[j].left.dir = 1;

                rectangles[j].right.x = box[i].p2.x;
                rectangles[j].right.dir = -1;
            } else {
                rectangles[j].right.x = box[i].p1.x;
                rectangles[j].right.dir = 1;

                rectangles[j].left.x = box[i].p2.x;
                rectangles[j].left.dir = -1;
            }

            rectangles[j].left.right = NULL;
            rectangles[j].right.right = NULL;

            rectangles[j].top = box[i].p1.y;
            rectangles[j].bottom = box[i].p2.y;

            if (rectangles_chain) {
                h = _cairo_fixed_integer_floor (box[i].p1.y) - y_min;
                rectangles[j].left.next = (edge_t *)rectangles_chain[h];
                rectangles_chain[h] = &rectangles[j];
            } else {
                rectangles_ptrs[j+2] = &rectangles[j];
            }
            j++;
        }
    }

    if (rectangles_chain) {
        j = 2;
        for (y_min = 0; y_min < y_max; y_min++) {
            rectangle_t *r;
            int start = j;
            for (r = rectangles_chain[y_min]; r; r = (rectangle_t *)r->left.next)
                rectangles_ptrs[j++] = r;
            if (j > start + 1)
                _rectangle_sort (rectangles_ptrs + start, j - start);
        }

        if (rectangles_chain != stack_rectangles_chain)
            free (rectangles_chain);

        j -= 2;
    } else {
        _rectangle_sort (rectangles_ptrs + 2, j);
    }

    _cairo_boxes_clear (out);
    status = _cairo_bentley_ottmann_tessellate_rectangular (rectangles_ptrs+2, j,
                                                            fill_rule,
                                                            FALSE, out);
    if (rectangles != stack_rectangles)
        free (rectangles);

    return status;
}