/* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */

/* cairo - a vector graphics library with display and print output

 *

 * Copyright © 2002 University of Southern California

 * Copyright © 2013 Intel Corporation

 *

 * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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 University of Southern

 * California.

 *

 * Contributor(s):

 *  Carl D. Worth <cworth@cworth.org>

 *  Chris Wilson <chris@chris-wilson.co.uk>

 */

#include "cairoint.h"

#include "cairo-box-inline.h"

#include "cairo-path-fixed-private.h"

#include "cairo-slope-private.h"

#include "cairo-stroke-dash-private.h"

#include "cairo-traps-private.h"

#include <float.h>

struct stroker {

    const cairo_stroke_style_t  *style;

    const cairo_matrix_t *ctm;

    const cairo_matrix_t *ctm_inverse;

    double spline_cusp_tolerance;

    double half_line_width;

    double tolerance;

    double ctm_determinant;

    cairo_bool_t ctm_det_positive;

    cairo_line_join_t line_join;

    cairo_traps_t *traps;

    cairo_pen_t pen;

    cairo_point_t first_point;

    cairo_bool_t has_initial_sub_path;

    cairo_bool_t has_current_face;

    cairo_stroke_face_t current_face;

    cairo_bool_t has_first_face;

    cairo_stroke_face_t first_face;

    cairo_stroker_dash_t dash;

    cairo_bool_t has_bounds;

    cairo_box_t tight_bounds;

    cairo_box_t line_bounds;

    cairo_box_t join_bounds;

};

static cairo_status_t

stroker_init (struct stroker    *stroker,

        const cairo_path_fixed_t  *path,

        const cairo_stroke_style_t  *style,

        const cairo_matrix_t  *ctm,

        const cairo_matrix_t  *ctm_inverse,

        double       tolerance,

        cairo_traps_t   *traps)

{

    cairo_status_t status;

    stroker->style = style;

    stroker->ctm = ctm;

    stroker->ctm_inverse = NULL;

    if (! _cairo_matrix_is_identity (ctm_inverse))

  stroker->ctm_inverse = ctm_inverse;

    stroker->line_join = style->line_join;

    stroker->half_line_width = style->line_width / 2.0;

    stroker->tolerance = tolerance;

    stroker->traps = traps;

    /* If `CAIRO_LINE_JOIN_ROUND` is selected and a joint's `arc height`

     * is greater than `tolerance` then two segments are joined with

     * round-join, otherwise bevel-join is used.

     *

     * `Arc height` is the difference of the "half of a line width" and

     * the "half of a line width" times `cos(half the angle between segment vectors)`.

     *

     * See detailed description in the `_cairo_path_fixed_stroke_to_polygon()`

     * function in the `cairo-path-stroke-polygon.c` file or follow the

     * https://gitlab.freedesktop.org/cairo/cairo/-/merge_requests/372#note_1698225

     * link to see the detailed description with an illustration.

     */

    double scaled_hlw = hypot(stroker->half_line_width * ctm->xx,

            stroker->half_line_width * ctm->yx);

    if (scaled_hlw <= tolerance) {

  stroker->spline_cusp_tolerance = -1.0;

    } else {

  stroker->spline_cusp_tolerance = 1 - tolerance / scaled_hlw;

  stroker->spline_cusp_tolerance *= stroker->spline_cusp_tolerance;

  stroker->spline_cusp_tolerance *= 2;

  stroker->spline_cusp_tolerance -= 1;

    }

    stroker->ctm_determinant = _cairo_matrix_compute_determinant (stroker->ctm);

    stroker->ctm_det_positive = stroker->ctm_determinant >= 0.0;

    status = _cairo_pen_init (&stroker->pen,

                  stroker->half_line_width,

            tolerance, ctm);

    if (unlikely (status))

  return status;

    stroker->has_current_face = FALSE;

    stroker->has_first_face = FALSE;

    stroker->has_initial_sub_path = FALSE;

    _cairo_stroker_dash_init (&stroker->dash, style);

    stroker->has_bounds = traps->num_limits;

    if (stroker->has_bounds) {

  /* Extend the bounds in each direction to account for the maximum area

   * we might generate trapezoids, to capture line segments that are outside

   * of the bounds but which might generate rendering that's within bounds.

   */

  double dx, dy;

  cairo_fixed_t fdx, fdy;

  stroker->tight_bounds = traps->bounds;

  _cairo_stroke_style_max_distance_from_path (stroker->style, path,

                stroker->ctm, &dx, &dy);

  _cairo_stroke_style_max_line_distance_from_path (stroker->style, path,

               stroker->ctm, &dx, &dy);

  fdx = _cairo_fixed_from_double (dx);

  fdy = _cairo_fixed_from_double (dy);

  stroker->line_bounds = stroker->tight_bounds;

  stroker->line_bounds.p1.x -= fdx;

  stroker->line_bounds.p2.x += fdx;

  stroker->line_bounds.p1.y -= fdy;

  stroker->line_bounds.p2.y += fdy;

  _cairo_stroke_style_max_join_distance_from_path (stroker->style, path,

               stroker->ctm, &dx, &dy);

  fdx = _cairo_fixed_from_double (dx);

  fdy = _cairo_fixed_from_double (dy);

  stroker->join_bounds = stroker->tight_bounds;

  stroker->join_bounds.p1.x -= fdx;

  stroker->join_bounds.p2.x += fdx;

  stroker->join_bounds.p1.y -= fdy;

  stroker->join_bounds.p2.y += fdy;

    }

    return CAIRO_STATUS_SUCCESS;

}

static void

stroker_fini (struct stroker *stroker)

{

    _cairo_pen_fini (&stroker->pen);

}

static void

translate_point (cairo_point_t *point, cairo_point_t *offset)

{

    point->x += offset->x;

    point->y += offset->y;

}

static int

join_is_clockwise (const cairo_stroke_face_t *in,

       const cairo_stroke_face_t *out)

{

    return _cairo_slope_compare (&in->dev_vector, &out->dev_vector) < 0;

}

static int

slope_compare_sgn (double dx1, double dy1, double dx2, double dy2)

{

    double c = dx1 * dy2 - dx2 * dy1;

    if (c > 0) return 1;

    if (c < 0) return -1;

    return 0;

}

static cairo_bool_t

stroker_intersects_join (const struct stroker *stroker,

       const cairo_point_t *in,

       const cairo_point_t *out)

{

    cairo_line_t segment;

    if (! stroker->has_bounds)

  return TRUE;

    segment.p1 = *in;

    segment.p2 = *out;

    return _cairo_box_intersects_line_segment (&stroker->join_bounds, &segment);

}

static void

join (struct stroker *stroker,

      cairo_stroke_face_t *in,

      cairo_stroke_face_t *out)

{

    int clockwise = join_is_clockwise (out, in);

    cairo_point_t *inpt, *outpt;

    if (in->cw.x == out->cw.x &&

  in->cw.y == out->cw.y &&

  in->ccw.x == out->ccw.x &&

  in->ccw.y == out->ccw.y)

    {

  return;

    }

    if (clockwise) {

  inpt = &in->ccw;

  outpt = &out->ccw;

    } else {

  inpt = &in->cw;

  outpt = &out->cw;

    }

    if (! stroker_intersects_join (stroker, inpt, outpt))

      return;

    switch (stroker->line_join) {

    case CAIRO_LINE_JOIN_ROUND:

  /* construct a fan around the common midpoint */

  if ((in->dev_slope.x * out->dev_slope.x +

       in->dev_slope.y * out->dev_slope.y) < stroker->spline_cusp_tolerance)

  {

      int start, stop;

      cairo_point_t tri[3], edges[4];

      cairo_pen_t *pen = &stroker->pen;

      edges[0] = in->cw;

      edges[1] = in->ccw;

      tri[0] = in->point;

      tri[1] = *inpt;

      if (clockwise) {

    _cairo_pen_find_active_ccw_vertices (pen,

                 &in->dev_vector, &out->dev_vector,

                 &start, &stop);

    while (start != stop) {

        tri[2] = in->point;

        translate_point (&tri[2], &pen->vertices[start].point);

        edges[2] = in->point;

        edges[3] = tri[2];

        _cairo_traps_tessellate_triangle_with_edges (stroker->traps,

                 tri, edges);

        tri[1] = tri[2];

        edges[0] = edges[2];

        edges[1] = edges[3];

        if (start-- == 0)

      start += pen->num_vertices;

    }

      } else {

    _cairo_pen_find_active_cw_vertices (pen,

                &in->dev_vector, &out->dev_vector,

                &start, &stop);

    while (start != stop) {

        tri[2] = in->point;

        translate_point (&tri[2], &pen->vertices[start].point);

        edges[2] = in->point;

        edges[3] = tri[2];

        _cairo_traps_tessellate_triangle_with_edges (stroker->traps,

                 tri, edges);

        tri[1] = tri[2];

        edges[0] = edges[2];

        edges[1] = edges[3];

        if (++start == pen->num_vertices)

      start = 0;

    }

      }

      tri[2] = *outpt;

      edges[2] = out->cw;

      edges[3] = out->ccw;

      _cairo_traps_tessellate_triangle_with_edges (stroker->traps,

               tri, edges);

  } else {

      cairo_point_t t[] = { { in->point.x, in->point.y}, { inpt->x, inpt->y }, { outpt->x, outpt->y } };

      cairo_point_t e[] = { { in->cw.x, in->cw.y}, { in->ccw.x, in->ccw.y },

          { out->cw.x, out->cw.y}, { out->ccw.x, out->ccw.y } };

      _cairo_traps_tessellate_triangle_with_edges (stroker->traps, t, e);

  }

  break;

    case CAIRO_LINE_JOIN_MITER:

    default: {

  /* dot product of incoming slope vector with outgoing slope vector */

  double in_dot_out = (-in->usr_vector.x * out->usr_vector.x +

           -in->usr_vector.y * out->usr_vector.y);

  double ml = stroker->style->miter_limit;

  /* Check the miter limit -- lines meeting at an acute angle

   * can generate long miters, the limit converts them to bevel

   *

   * Consider the miter join formed when two line segments

   * meet at an angle psi:

   *

   *     /.\

   *    /. .\

   *   /./ \.\

   *  /./psi\.\

   *

   * We can zoom in on the right half of that to see:

   *

   *      |\

   *      | \ psi/2

   *      |  \

   *      |   \

   *      |    \

   *      |     \

   *    miter    \

   *   length     \

   *      |        \

   *      |        .\

   *      |    .     \

   *      |.   line   \

   *       \    width  \

   *        \           \

   *

   *

   * The right triangle in that figure, (the line-width side is

   * shown faintly with three '.' characters), gives us the

   * following expression relating miter length, angle and line

   * width:

   *

   *  1 /sin (psi/2) = miter_length / line_width

   *

   * The right-hand side of this relationship is the same ratio

   * in which the miter limit (ml) is expressed. We want to know

   * when the miter length is within the miter limit. That is

   * when the following condition holds:

   *

   *  1/sin(psi/2) <= ml

   *  1 <= ml sin(psi/2)

   *  1 <= ml² sin²(psi/2)

   *  2 <= ml² 2 sin²(psi/2)

   *        2·sin²(psi/2) = 1-cos(psi)

   *  2 <= ml² (1-cos(psi))

   *

   *        in · out = |in| |out| cos (psi)

   *

   * in and out are both unit vectors, so:

   *

   *        in · out = cos (psi)

   *

   *  2 <= ml² (1 - in · out)

   *

   */

  if (2 <= ml * ml * (1 - in_dot_out)) {

      double    x1, y1, x2, y2;

      double    mx, my;

      double    dx1, dx2, dy1, dy2;

      cairo_point_t outer;

      cairo_point_t quad[4];

      double    ix, iy;

      double    fdx1, fdy1, fdx2, fdy2;

      double    mdx, mdy;

      /*

       * we've got the points already transformed to device

       * space, but need to do some computation with them and

       * also need to transform the slope from user space to

       * device space

       */

      /* outer point of incoming line face */

      x1 = _cairo_fixed_to_double (inpt->x);

      y1 = _cairo_fixed_to_double (inpt->y);

      dx1 = in->usr_vector.x;

      dy1 = in->usr_vector.y;

      cairo_matrix_transform_distance (stroker->ctm, &dx1, &dy1);

      /* outer point of outgoing line face */

      x2 = _cairo_fixed_to_double (outpt->x);

      y2 = _cairo_fixed_to_double (outpt->y);

      dx2 = out->usr_vector.x;

      dy2 = out->usr_vector.y;

      cairo_matrix_transform_distance (stroker->ctm, &dx2, &dy2);

      /*

       * Compute the location of the outer corner of the miter.

       * That's pretty easy -- just the intersection of the two

       * outer edges.  We've got slopes and points on each

       * of those edges.  Compute my directly, then compute

       * mx by using the edge with the larger dy; that avoids

       * dividing by values close to zero.

       */

      my = (((x2 - x1) * dy1 * dy2 - y2 * dx2 * dy1 + y1 * dx1 * dy2) /

      (dx1 * dy2 - dx2 * dy1));

      if (fabs (dy1) >= fabs (dy2))

    mx = (my - y1) * dx1 / dy1 + x1;

      else

    mx = (my - y2) * dx2 / dy2 + x2;

      /*

       * When the two outer edges are nearly parallel, slight

       * perturbations in the position of the outer points of the lines

       * caused by representing them in fixed point form can cause the

       * intersection point of the miter to move a large amount. If

       * that moves the miter intersection from between the two faces,

       * then draw a bevel instead.

       */

      ix = _cairo_fixed_to_double (in->point.x);

      iy = _cairo_fixed_to_double (in->point.y);

      /* slope of one face */

      fdx1 = x1 - ix; fdy1 = y1 - iy;

      /* slope of the other face */

      fdx2 = x2 - ix; fdy2 = y2 - iy;

      /* slope from the intersection to the miter point */

      mdx = mx - ix; mdy = my - iy;

      /*

       * Make sure the miter point line lies between the two

       * faces by comparing the slopes

       */

      if (slope_compare_sgn (fdx1, fdy1, mdx, mdy) !=

    slope_compare_sgn (fdx2, fdy2, mdx, mdy))

      {

    /*

     * Draw the quadrilateral

     */

    outer.x = _cairo_fixed_from_double (mx);

    outer.y = _cairo_fixed_from_double (my);

    quad[0] = in->point;

    quad[1] = *inpt;

    quad[2] = outer;

    quad[3] = *outpt;

    _cairo_traps_tessellate_convex_quad (stroker->traps, quad);

    break;

      }

  }

    }

    /* fall through ... */

    case CAIRO_LINE_JOIN_BEVEL: {

  cairo_point_t t[] = { { in->point.x, in->point.y }, { inpt->x, inpt->y }, { outpt->x, outpt->y } };

  cairo_point_t e[] = { { in->cw.x, in->cw.y }, { in->ccw.x, in->ccw.y },

            { out->cw.x, out->cw.y }, { out->ccw.x, out->ccw.y } };

  _cairo_traps_tessellate_triangle_with_edges (stroker->traps, t, e);

  break;

    }

    }

}

static void

add_cap (struct stroker *stroker, cairo_stroke_face_t *f)

{

    switch (stroker->style->line_cap) {

    case CAIRO_LINE_CAP_ROUND: {

  int start, stop;

  cairo_slope_t in_slope, out_slope;

  cairo_point_t tri[3], edges[4];

  cairo_pen_t *pen = &stroker->pen;

  in_slope = f->dev_vector;

  out_slope.dx = -in_slope.dx;

  out_slope.dy = -in_slope.dy;

  _cairo_pen_find_active_cw_vertices (pen, &in_slope, &out_slope,

              &start, &stop);

  edges[0] = f->cw;

  edges[1] = f->ccw;

  tri[0] = f->point;

  tri[1] = f->cw;

  while (start != stop) {

      tri[2] = f->point;

      translate_point (&tri[2], &pen->vertices[start].point);

      edges[2] = f->point;

      edges[3] = tri[2];

      _cairo_traps_tessellate_triangle_with_edges (stroker->traps,

               tri, edges);

      tri[1] = tri[2];

      edges[0] = edges[2];

      edges[1] = edges[3];

      if (++start == pen->num_vertices)

    start = 0;

  }

  tri[2] = f->ccw;

  edges[2] = f->cw;

  edges[3] = f->ccw;

  _cairo_traps_tessellate_triangle_with_edges (stroker->traps,

                 tri, edges);

  break;

    }

    case CAIRO_LINE_CAP_SQUARE: {

  double dx, dy;

  cairo_slope_t fvector;

  cairo_point_t quad[4];

  dx = f->usr_vector.x;

  dy = f->usr_vector.y;

  dx *= stroker->half_line_width;

  dy *= stroker->half_line_width;

  cairo_matrix_transform_distance (stroker->ctm, &dx, &dy);

  fvector.dx = _cairo_fixed_from_double (dx);

  fvector.dy = _cairo_fixed_from_double (dy);

  quad[0] = f->cw;

  quad[1].x = f->cw.x + fvector.dx;

  quad[1].y = f->cw.y + fvector.dy;

  quad[2].x = f->ccw.x + fvector.dx;

  quad[2].y = f->ccw.y + fvector.dy;

  quad[3] = f->ccw;

  _cairo_traps_tessellate_convex_quad (stroker->traps, quad);

  break;

    }

    case CAIRO_LINE_CAP_BUTT:

    default:

  break;

    }

}

static void

add_leading_cap (struct stroker     *stroker,

     cairo_stroke_face_t *face)

{

    cairo_stroke_face_t reversed;

    cairo_point_t t;

    reversed = *face;

    /* The initial cap needs an outward facing vector. Reverse everything */

    reversed.usr_vector.x = -reversed.usr_vector.x;

    reversed.usr_vector.y = -reversed.usr_vector.y;

    reversed.dev_vector.dx = -reversed.dev_vector.dx;

    reversed.dev_vector.dy = -reversed.dev_vector.dy;

    t = reversed.cw;

    reversed.cw = reversed.ccw;

    reversed.ccw = t;

    add_cap (stroker, &reversed);

}

static void

add_trailing_cap (struct stroker *stroker, cairo_stroke_face_t *face)

{

    add_cap (stroker, face);

}

static inline double

normalize_slope (double *dx, double *dy)

{

    double dx0 = *dx, dy0 = *dy;

    if (dx0 == 0.0 && dy0 == 0.0)

  return 0;

    if (dx0 == 0.0) {

  *dx = 0.0;

  if (dy0 > 0.0) {

      *dy = 1.0;

      return dy0;

  } else {

      *dy = -1.0;

      return -dy0;

  }

    } else if (dy0 == 0.0) {

  *dy = 0.0;

  if (dx0 > 0.0) {

      *dx = 1.0;

      return dx0;

  } else {

      *dx = -1.0;

      return -dx0;

  }

    } else {

  double mag = hypot (dx0, dy0);

  *dx = dx0 / mag;

  *dy = dy0 / mag;

  return mag;

    }

}

static void

compute_face (const cairo_point_t *point,

        const cairo_slope_t *dev_slope,

        struct stroker *stroker,

        cairo_stroke_face_t *face)

{

    double face_dx, face_dy;

    cairo_point_t offset_ccw, offset_cw;

    double slope_dx, slope_dy;

    slope_dx = _cairo_fixed_to_double (dev_slope->dx);

    slope_dy = _cairo_fixed_to_double (dev_slope->dy);

    face->length = normalize_slope (&slope_dx, &slope_dy);

    face->dev_slope.x = slope_dx;

    face->dev_slope.y = slope_dy;

    /*

     * rotate to get a line_width/2 vector along the face, note that

     * the vector must be rotated the right direction in device space,

     * but by 90° in user space. So, the rotation depends on

     * whether the ctm reflects or not, and that can be determined

     * by looking at the determinant of the matrix.

     */

    if (stroker->ctm_inverse) {

  cairo_matrix_transform_distance (stroker->ctm_inverse, &slope_dx, &slope_dy);

  normalize_slope (&slope_dx, &slope_dy);

  if (stroker->ctm_det_positive) {

      face_dx = - slope_dy * stroker->half_line_width;

      face_dy = slope_dx * stroker->half_line_width;

  } else {

      face_dx = slope_dy * stroker->half_line_width;

      face_dy = - slope_dx * stroker->half_line_width;

  }

  /* back to device space */

  cairo_matrix_transform_distance (stroker->ctm, &face_dx, &face_dy);

    } else {

  face_dx = - slope_dy * stroker->half_line_width;

  face_dy = slope_dx * stroker->half_line_width;

    }

    offset_ccw.x = _cairo_fixed_from_double (face_dx);

    offset_ccw.y = _cairo_fixed_from_double (face_dy);

    offset_cw.x = -offset_ccw.x;

    offset_cw.y = -offset_ccw.y;

    face->ccw = *point;

    translate_point (&face->ccw, &offset_ccw);

    face->point = *point;

    face->cw = *point;

    translate_point (&face->cw, &offset_cw);

    face->usr_vector.x = slope_dx;

    face->usr_vector.y = slope_dy;

    face->dev_vector = *dev_slope;

}

static void

add_caps (struct stroker *stroker)

{

    /* check for a degenerative sub_path */

    if (stroker->has_initial_sub_path &&

  !stroker->has_first_face &&

  !stroker->has_current_face &&

  stroker->style->line_cap == CAIRO_LINE_CAP_ROUND)

    {

  /* pick an arbitrary slope to use */

  cairo_slope_t slope = { CAIRO_FIXED_ONE, 0 };

  cairo_stroke_face_t face;

  /* arbitrarily choose first_point

   * first_point and current_point should be the same */

  compute_face (&stroker->first_point, &slope, stroker, &face);

  add_leading_cap (stroker, &face);

  add_trailing_cap (stroker, &face);

    }

    if (stroker->has_first_face)

  add_leading_cap (stroker, &stroker->first_face);

    if (stroker->has_current_face)

  add_trailing_cap (stroker, &stroker->current_face);

}

static cairo_bool_t

stroker_intersects_edge (const struct stroker *stroker,

       const cairo_stroke_face_t *start,

       const cairo_stroke_face_t *end)

{

    cairo_box_t box;

    if (! stroker->has_bounds)

  return TRUE;

    if (_cairo_box_contains_point (&stroker->tight_bounds, &start->cw))

  return TRUE;

    box.p2 = box.p1 = start->cw;

    if (_cairo_box_contains_point (&stroker->tight_bounds, &start->ccw))

  return TRUE;

    _cairo_box_add_point (&box, &start->ccw);

    if (_cairo_box_contains_point (&stroker->tight_bounds, &end->cw))

  return TRUE;

    _cairo_box_add_point (&box, &end->cw);

    if (_cairo_box_contains_point (&stroker->tight_bounds, &end->ccw))

  return TRUE;

    _cairo_box_add_point (&box, &end->ccw);

    return (box.p2.x > stroker->tight_bounds.p1.x &&

      box.p1.x < stroker->tight_bounds.p2.x &&

      box.p2.y > stroker->tight_bounds.p1.y &&

      box.p1.y < stroker->tight_bounds.p2.y);

}

static void

add_sub_edge (struct stroker *stroker,

        const cairo_point_t *p1, const cairo_point_t *p2,

        const cairo_slope_t *dev_slope,

        cairo_stroke_face_t *start, cairo_stroke_face_t *end)

{

    cairo_point_t rectangle[4];

    compute_face (p1, dev_slope, stroker, start);

    *end = *start;

    end->point = *p2;

    rectangle[0].x = p2->x - p1->x;

    rectangle[0].y = p2->y - p1->y;

    translate_point (&end->ccw, &rectangle[0]);

    translate_point (&end->cw, &rectangle[0]);

    if (p1->x == p2->x && p1->y == p2->y)

  return;

    if (! stroker_intersects_edge (stroker, start, end))

  return;

    rectangle[0] = start->cw;

    rectangle[1] = start->ccw;

    rectangle[2] = end->ccw;

    rectangle[3] = end->cw;

    _cairo_traps_tessellate_convex_quad (stroker->traps, rectangle);

}

static cairo_status_t

move_to (void *closure, const cairo_point_t *point)

{

    struct stroker *stroker = closure;

    /* Cap the start and end of the previous sub path as needed */

    add_caps (stroker);

    stroker->first_point = *point;

    stroker->current_face.point = *point;

    stroker->has_first_face = FALSE;

    stroker->has_current_face = FALSE;

    stroker->has_initial_sub_path = FALSE;

    return CAIRO_STATUS_SUCCESS;

}

static cairo_status_t

move_to_dashed (void *closure, const cairo_point_t *point)

{

    /* reset the dash pattern for new sub paths */

    struct stroker *stroker = closure;

    _cairo_stroker_dash_start (&stroker->dash);

    return move_to (closure, point);

}

static cairo_status_t

line_to (void *closure, const cairo_point_t *point)

{

    struct stroker *stroker = closure;

    cairo_stroke_face_t start, end;

    const cairo_point_t *p1 = &stroker->current_face.point;

    const cairo_point_t *p2 = point;

    cairo_slope_t dev_slope;

    stroker->has_initial_sub_path = TRUE;

    if (p1->x == p2->x && p1->y == p2->y)

  return CAIRO_STATUS_SUCCESS;

    _cairo_slope_init (&dev_slope, p1, p2);

    add_sub_edge (stroker, p1, p2, &dev_slope, &start, &end);

    if (stroker->has_current_face) {

  /* Join with final face from previous segment */

  join (stroker, &stroker->current_face, &start);

    } else if (!stroker->has_first_face) {

  /* Save sub path's first face in case needed for closing join */

  stroker->first_face = start;

  stroker->has_first_face = TRUE;

    }

    stroker->current_face = end;

    stroker->has_current_face = TRUE;

    return CAIRO_STATUS_SUCCESS;

}

/*

 * Dashed lines.  Cap each dash end, join around turns when on

 */

static cairo_status_t

line_to_dashed (void *closure, const cairo_point_t *point)

{

    struct stroker *stroker = closure;

    double mag, remain, step_length = 0;

    double slope_dx, slope_dy;

    double dx2, dy2;

    cairo_stroke_face_t sub_start, sub_end;

    const cairo_point_t *p1 = &stroker->current_face.point;

    const cairo_point_t *p2 = point;

    cairo_slope_t dev_slope;

    cairo_line_t segment;

    cairo_bool_t fully_in_bounds;

    stroker->has_initial_sub_path = stroker->dash.dash_starts_on;

    if (p1->x == p2->x && p1->y == p2->y)

  return CAIRO_STATUS_SUCCESS;

    fully_in_bounds = TRUE;

    if (stroker->has_bounds &&

  (! _cairo_box_contains_point (&stroker->join_bounds, p1) ||

   ! _cairo_box_contains_point (&stroker->join_bounds, p2)))

    {

  fully_in_bounds = FALSE;

    }

    _cairo_slope_init (&dev_slope, p1, p2);

    slope_dx = _cairo_fixed_to_double (p2->x - p1->x);

    slope_dy = _cairo_fixed_to_double (p2->y - p1->y);

    if (stroker->ctm_inverse)

  cairo_matrix_transform_distance (stroker->ctm_inverse, &slope_dx, &slope_dy);

    mag = normalize_slope (&slope_dx, &slope_dy);

    if (mag <= DBL_EPSILON)

  return CAIRO_STATUS_SUCCESS;

    remain = mag;

    segment.p1 = *p1;

    while (remain) {

  step_length = MIN (stroker->dash.dash_remain, remain);

  remain -= step_length;

  dx2 = slope_dx * (mag - remain);

  dy2 = slope_dy * (mag - remain);

  cairo_matrix_transform_distance (stroker->ctm, &dx2, &dy2);

  segment.p2.x = _cairo_fixed_from_double (dx2) + p1->x;

  segment.p2.y = _cairo_fixed_from_double (dy2) + p1->y;

  if (stroker->dash.dash_on &&

      (fully_in_bounds ||

       (! stroker->has_first_face && stroker->dash.dash_starts_on) ||

       _cairo_box_intersects_line_segment (&stroker->join_bounds, &segment)))

  {

      add_sub_edge (stroker,

        &segment.p1, &segment.p2,

        &dev_slope,

        &sub_start, &sub_end);

      if (stroker->has_current_face) {

    /* Join with final face from previous segment */

    join (stroker, &stroker->current_face, &sub_start);

    stroker->has_current_face = FALSE;

      } else if (! stroker->has_first_face && stroker->dash.dash_starts_on) {

    /* Save sub path's first face in case needed for closing join */

    stroker->first_face = sub_start;

    stroker->has_first_face = TRUE;

      } else {

    /* Cap dash start if not connecting to a previous segment */

    add_leading_cap (stroker, &sub_start);

      }

      if (remain) {

    /* Cap dash end if not at end of segment */

    add_trailing_cap (stroker, &sub_end);

      } else {

    stroker->current_face = sub_end;

    stroker->has_current_face = TRUE;

      }

  } else {

      if (stroker->has_current_face) {

    /* Cap final face from previous segment */

    add_trailing_cap (stroker, &stroker->current_face);

    stroker->has_current_face = FALSE;

      }

  }

  _cairo_stroker_dash_step (&stroker->dash, step_length);

  segment.p1 = segment.p2;

    }

    if (stroker->dash.dash_on && ! stroker->has_current_face) {

  /* This segment ends on a transition to dash_on, compute a new face

   * and add cap for the beginning of the next dash_on step.

   *

   * Note: this will create a degenerate cap if this is not the last line

   * in the path. Whether this behaviour is desirable or not is debatable.

   * On one side these degenerate caps can not be reproduced with regular

   * path stroking.