path: root/source/blender/blenlib/intern/scanfill.c

/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
 * All rights reserved.
 * (uit traces) maart 95
 */

/** \file
 * \ingroup bli
 *
 * Triangulate multiple 2D/3D polygon with support for holes,
 * use for tessellating curves, fonts and geometry.
 * See main function #BLI_scanfill_calc
 *
 * Uses sweep-line method.
 *
 * \note There is a similar API in polyfill2d.c
 * which uses ear clipping, but has no hole support.
 */

#include <limits.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "MEM_guardedalloc.h"

#include "BLI_listbase.h"
#include "BLI_math.h"
#include "BLI_memarena.h"
#include "BLI_utildefines.h"

#include "BLI_scanfill.h" /* own include */

#include "BLI_strict_flags.h"

/* local types */
typedef struct PolyFill {
  unsigned int edges, verts;
  float min_xy[2], max_xy[2];
  unsigned short nr;
  bool f;
} PolyFill;

typedef struct ScanFillVertLink {
  ScanFillVert *vert;
  ScanFillEdge *edge_first, *edge_last;
} ScanFillVertLink;

/* local funcs */

#define SF_EPSILON 0.00003f
#define SF_EPSILON_SQ (SF_EPSILON * SF_EPSILON)

/* ScanFillVert.status */
#define SF_VERT_NEW 0       /* all new verts have this flag set */
#define SF_VERT_AVAILABLE 1 /* available - in an edge */
#define SF_VERT_ZERO_LEN 2

/* ScanFillEdge.status */
/* Optionally set ScanFillEdge f to this to mark original boundary edges.
 * Only needed if there are internal diagonal edges passed to BLI_scanfill_calc. */
#define SF_EDGE_NEW 0 /* all new edges have this flag set */
// #define SF_EDGE_BOUNDARY 1  /* UNUSED */
#define SF_EDGE_INTERNAL 2 /* edge is created while scan-filling */

/* PolyFill.status */
#define SF_POLY_NEW 0   /* all polys initialized to this */
#define SF_POLY_VALID 1 /* has at least 3 verts */

/* ****  FUNCTIONS FOR QSORT *************************** */

static int vergscdata(const void *a1, const void *a2)
{
  const ScanFillVertLink *x1 = a1, *x2 = a2;

  if (x1->vert->xy[1] < x2->vert->xy[1]) {
    return 1;
  }
  if (x1->vert->xy[1] > x2->vert->xy[1]) {
    return -1;
  }
  if (x1->vert->xy[0] > x2->vert->xy[0]) {
    return 1;
  }
  if (x1->vert->xy[0] < x2->vert->xy[0]) {
    return -1;
  }

  return 0;
}

static int vergpoly(const void *a1, const void *a2)
{
  const PolyFill *x1 = a1, *x2 = a2;

  if (x1->min_xy[0] > x2->min_xy[0]) {
    return 1;
  }
  if (x1->min_xy[0] < x2->min_xy[0]) {
    return -1;
  }
  if (x1->min_xy[1] > x2->min_xy[1]) {
    return 1;
  }
  if (x1->min_xy[1] < x2->min_xy[1]) {
    return -1;
  }

  return 0;
}

/* ****  FILL ROUTINES *************************** */

ScanFillVert *BLI_scanfill_vert_add(ScanFillContext *sf_ctx, const float vec[3])
{
  ScanFillVert *sf_v;

  sf_v = BLI_memarena_alloc(sf_ctx->arena, sizeof(ScanFillVert));

  BLI_addtail(&sf_ctx->fillvertbase, sf_v);

  sf_v->tmp.p = NULL;
  copy_v3_v3(sf_v->co, vec);

  /* just zero out the rest */
  zero_v2(sf_v->xy);
  sf_v->keyindex = 0;
  sf_v->poly_nr = sf_ctx->poly_nr;
  sf_v->edge_tot = 0;
  sf_v->f = SF_VERT_NEW;
  sf_v->user_flag = 0;

  return sf_v;
}

ScanFillEdge *BLI_scanfill_edge_add(ScanFillContext *sf_ctx, ScanFillVert *v1, ScanFillVert *v2)
{
  ScanFillEdge *sf_ed;

  sf_ed = BLI_memarena_alloc(sf_ctx->arena, sizeof(ScanFillEdge));
  BLI_addtail(&sf_ctx->filledgebase, sf_ed);

  sf_ed->v1 = v1;
  sf_ed->v2 = v2;

  /* just zero out the rest */
  sf_ed->poly_nr = sf_ctx->poly_nr;
  sf_ed->f = SF_EDGE_NEW;
  sf_ed->user_flag = 0;
  sf_ed->tmp.c = 0;

  return sf_ed;
}

static void addfillface(ScanFillContext *sf_ctx,
                        ScanFillVert *v1,
                        ScanFillVert *v2,
                        ScanFillVert *v3)
{
  /* does not make edges */
  ScanFillFace *sf_tri;

  sf_tri = BLI_memarena_alloc(sf_ctx->arena, sizeof(ScanFillFace));
  BLI_addtail(&sf_ctx->fillfacebase, sf_tri);

  sf_tri->v1 = v1;
  sf_tri->v2 = v2;
  sf_tri->v3 = v3;
}

static bool boundisect(PolyFill *pf2, PolyFill *pf1)
{
  /* has pf2 been touched (intersected) by pf1 ? with bounding box */
  /* test first if polys exist */

  if (pf1->edges == 0 || pf2->edges == 0) {
    return false;
  }

  if (pf2->max_xy[0] < pf1->min_xy[0]) {
    return false;
  }
  if (pf2->max_xy[1] < pf1->min_xy[1]) {
    return false;
  }

  if (pf2->min_xy[0] > pf1->max_xy[0]) {
    return false;
  }
  if (pf2->min_xy[1] > pf1->max_xy[1]) {
    return false;
  }

  /* join */
  if (pf2->max_xy[0] < pf1->max_xy[0]) {
    pf2->max_xy[0] = pf1->max_xy[0];
  }
  if (pf2->max_xy[1] < pf1->max_xy[1]) {
    pf2->max_xy[1] = pf1->max_xy[1];
  }

  if (pf2->min_xy[0] > pf1->min_xy[0]) {
    pf2->min_xy[0] = pf1->min_xy[0];
  }
  if (pf2->min_xy[1] > pf1->min_xy[1]) {
    pf2->min_xy[1] = pf1->min_xy[1];
  }

  return true;
}

/* add pf2 to pf1 */
static void mergepolysSimp(ScanFillContext *sf_ctx, PolyFill *pf1, PolyFill *pf2)
{
  ScanFillVert *eve;
  ScanFillEdge *eed;

  /* replace old poly numbers */
  for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
    if (eve->poly_nr == pf2->nr) {
      eve->poly_nr = pf1->nr;
    }
  }

  for (eed = sf_ctx->filledgebase.first; eed; eed = eed->next) {
    if (eed->poly_nr == pf2->nr) {
      eed->poly_nr = pf1->nr;
    }
  }

  pf1->verts += pf2->verts;
  pf1->edges += pf2->edges;
  pf2->verts = pf2->edges = 0;
  pf1->f = (pf1->f | pf2->f);
}

static bool testedgeside(const float v1[2], const float v2[2], const float v3[2])
/* is v3 to the right of v1-v2 ? With exception: v3 == v1 || v3 == v2 */
{
  float inp;

  inp = (v2[0] - v1[0]) * (v1[1] - v3[1]) + (v1[1] - v2[1]) * (v1[0] - v3[0]);

  if (inp < 0.0f) {
    return false;
  }
  if (inp == 0.0f) {
    if (v1[0] == v3[0] && v1[1] == v3[1]) {
      return false;
    }
    if (v2[0] == v3[0] && v2[1] == v3[1]) {
      return false;
    }
  }
  return true;
}

static bool addedgetoscanvert(ScanFillVertLink *sc, ScanFillEdge *eed)
{
  /* find first edge to the right of eed, and insert eed before that */
  ScanFillEdge *ed;
  float fac, fac1, x, y;

  if (sc->edge_first == NULL) {
    sc->edge_first = sc->edge_last = eed;
    eed->prev = eed->next = NULL;
    return 1;
  }

  x = eed->v1->xy[0];
  y = eed->v1->xy[1];

  fac1 = eed->v2->xy[1] - y;
  if (fac1 == 0.0f) {
    fac1 = 1.0e10f * (eed->v2->xy[0] - x);
  }
  else {
    fac1 = (x - eed->v2->xy[0]) / fac1;
  }

  for (ed = sc->edge_first; ed; ed = ed->next) {

    if (ed->v2 == eed->v2) {
      return false;
    }

    fac = ed->v2->xy[1] - y;
    if (fac == 0.0f) {
      fac = 1.0e10f * (ed->v2->xy[0] - x);
    }
    else {
      fac = (x - ed->v2->xy[0]) / fac;
    }

    if (fac > fac1) {
      break;
    }
  }
  if (ed) {
    BLI_insertlinkbefore((ListBase *)&(sc->edge_first), ed, eed);
  }
  else {
    BLI_addtail((ListBase *)&(sc->edge_first), eed);
  }

  return true;
}

static ScanFillVertLink *addedgetoscanlist(ScanFillVertLink *scdata,
                                           ScanFillEdge *eed,
                                           unsigned int len)
{
  /* inserts edge at correct location in ScanFillVertLink list */
  /* returns sc when edge already exists */
  ScanFillVertLink *sc, scsearch;
  ScanFillVert *eve;

  /* which vert is left-top? */
  if (eed->v1->xy[1] == eed->v2->xy[1]) {
    if (eed->v1->xy[0] > eed->v2->xy[0]) {
      eve = eed->v1;
      eed->v1 = eed->v2;
      eed->v2 = eve;
    }
  }
  else if (eed->v1->xy[1] < eed->v2->xy[1]) {
    eve = eed->v1;
    eed->v1 = eed->v2;
    eed->v2 = eve;
  }
  /* find location in list */
  scsearch.vert = eed->v1;
  sc = (ScanFillVertLink *)bsearch(&scsearch, scdata, len, sizeof(ScanFillVertLink), vergscdata);

  if (UNLIKELY(sc == NULL)) {
    printf("Error in search edge: %p\n", (void *)eed);
  }
  else if (addedgetoscanvert(sc, eed) == false) {
    return sc;
  }

  return NULL;
}

static bool boundinsideEV(ScanFillEdge *eed, ScanFillVert *eve)
/* is eve inside boundbox eed */
{
  float minx, maxx, miny, maxy;

  if (eed->v1->xy[0] < eed->v2->xy[0]) {
    minx = eed->v1->xy[0];
    maxx = eed->v2->xy[0];
  }
  else {
    minx = eed->v2->xy[0];
    maxx = eed->v1->xy[0];
  }
  if (eve->xy[0] >= minx && eve->xy[0] <= maxx) {
    if (eed->v1->xy[1] < eed->v2->xy[1]) {
      miny = eed->v1->xy[1];
      maxy = eed->v2->xy[1];
    }
    else {
      miny = eed->v2->xy[1];
      maxy = eed->v1->xy[1];
    }
    if (eve->xy[1] >= miny && eve->xy[1] <= maxy) {
      return true;
    }
  }
  return false;
}

static void testvertexnearedge(ScanFillContext *sf_ctx)
{
  /* only vertices with (->edge_tot == 1) are being tested for
   * being close to an edge, if true insert */

  ScanFillVert *eve;
  ScanFillEdge *eed, *ed1;

  for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
    if (eve->edge_tot == 1) {
      /* find the edge which has vertex eve,
       * NOTE: we _know_ this will crash if 'ed1' becomes NULL
       * but this will never happen. */
      for (ed1 = sf_ctx->filledgebase.first; !(ed1->v1 == eve || ed1->v2 == eve);
           ed1 = ed1->next) {
        /* do nothing */
      }

      if (ed1->v1 == eve) {
        ed1->v1 = ed1->v2;
        ed1->v2 = eve;
      }

      for (eed = sf_ctx->filledgebase.first; eed; eed = eed->next) {
        if (eve != eed->v1 && eve != eed->v2 && eve->poly_nr == eed->poly_nr) {
          if (compare_v2v2(eve->xy, eed->v1->xy, SF_EPSILON)) {
            ed1->v2 = eed->v1;
            eed->v1->edge_tot++;
            eve->edge_tot = 0;
            break;
          }
          if (compare_v2v2(eve->xy, eed->v2->xy, SF_EPSILON)) {
            ed1->v2 = eed->v2;
            eed->v2->edge_tot++;
            eve->edge_tot = 0;
            break;
          }

          if (boundinsideEV(eed, eve)) {
            const float dist = dist_squared_to_line_v2(eed->v1->xy, eed->v2->xy, eve->xy);
            if (dist < SF_EPSILON_SQ) {
              /* new edge */
              ed1 = BLI_scanfill_edge_add(sf_ctx, eed->v1, eve);

              // printf("fill: vertex near edge %x\n", eve);
              ed1->poly_nr = eed->poly_nr;
              eed->v1 = eve;
              eve->edge_tot = 3;
              break;
            }
          }
        }
      }
    }
  }
}

static void splitlist(ScanFillContext *sf_ctx,
                      ListBase *tempve,
                      ListBase *temped,
                      unsigned short nr)
{
  /* everything is in templist, write only poly nr to fillist */
  ScanFillVert *eve, *eve_next;
  ScanFillEdge *eed, *eed_next;

  BLI_movelisttolist(tempve, &sf_ctx->fillvertbase);
  BLI_movelisttolist(temped, &sf_ctx->filledgebase);

  for (eve = tempve->first; eve; eve = eve_next) {
    eve_next = eve->next;
    if (eve->poly_nr == nr) {
      BLI_remlink(tempve, eve);
      BLI_addtail(&sf_ctx->fillvertbase, eve);
    }
  }

  for (eed = temped->first; eed; eed = eed_next) {
    eed_next = eed->next;
    if (eed->poly_nr == nr) {
      BLI_remlink(temped, eed);
      BLI_addtail(&sf_ctx->filledgebase, eed);
    }
  }
}

static unsigned int scanfill(ScanFillContext *sf_ctx, PolyFill *pf, const int flag)
{
  ScanFillVertLink *scdata;
  ScanFillVertLink *sc = NULL, *sc1;
  ScanFillVert *eve, *v1, *v2, *v3;
  ScanFillEdge *eed, *eed_next, *ed1, *ed2, *ed3;
  unsigned int a, b, verts, maxface, totface;
  const unsigned short nr = pf->nr;
  bool twoconnected = false;

  /* PRINTS */
#if 0
  verts = pf->verts;
  for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
    printf("vert: %x co: %f %f\n", eve, eve->xy[0], eve->xy[1]);
  }

  for (eed = sf_ctx->filledgebase.first; eed; eed = eed->next) {
    printf("edge: %x  verts: %x %x\n", eed, eed->v1, eed->v2);
  }
#endif

  /* STEP 0: remove zero sized edges */
  if (flag & BLI_SCANFILL_CALC_REMOVE_DOUBLES) {
    for (eed = sf_ctx->filledgebase.first; eed; eed = eed->next) {
      if (equals_v2v2(eed->v1->xy, eed->v2->xy)) {
        if (eed->v1->f == SF_VERT_ZERO_LEN && eed->v2->f != SF_VERT_ZERO_LEN) {
          eed->v2->f = SF_VERT_ZERO_LEN;
          eed->v2->tmp.v = eed->v1->tmp.v;
        }
        else if (eed->v2->f == SF_VERT_ZERO_LEN && eed->v1->f != SF_VERT_ZERO_LEN) {
          eed->v1->f = SF_VERT_ZERO_LEN;
          eed->v1->tmp.v = eed->v2->tmp.v;
        }
        else if (eed->v2->f == SF_VERT_ZERO_LEN && eed->v1->f == SF_VERT_ZERO_LEN) {
          eed->v1->tmp.v = eed->v2->tmp.v;
        }
        else {
          eed->v2->f = SF_VERT_ZERO_LEN;
          eed->v2->tmp.v = eed->v1;
        }
      }
    }
  }

  /* STEP 1: make using FillVert and FillEdge lists a sorted
   * ScanFillVertLink list
   */
  sc = scdata = MEM_mallocN(sizeof(*scdata) * pf->verts, "Scanfill1");
  verts = 0;
  for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
    if (eve->poly_nr == nr) {
      if (eve->f != SF_VERT_ZERO_LEN) {
        verts++;
        eve->f = SF_VERT_NEW; /* Flag for connect edges later on. */
        sc->vert = eve;
        sc->edge_first = sc->edge_last = NULL;
        /* NOTE: debug print only will work for curve poly-fill, union is in use for mesh. */
        /* if (even->tmp.v == NULL) eve->tmp.u = verts; */
        sc++;
      }
    }
  }

  qsort(scdata, verts, sizeof(ScanFillVertLink), vergscdata);

  if (flag & BLI_SCANFILL_CALC_REMOVE_DOUBLES) {
    for (eed = sf_ctx->filledgebase.first; eed; eed = eed_next) {
      eed_next = eed->next;
      BLI_remlink(&sf_ctx->filledgebase, eed);
      /* This code is for handling zero-length edges that get
       * collapsed in step 0. It was removed for some time to
       * fix trunk bug T4544, so if that comes back, this code
       * may need some work, or there will have to be a better
       * fix to T4544.
       *
       * warning, this can hang on un-ordered edges, see: T33281.
       * for now disable 'BLI_SCANFILL_CALC_REMOVE_DOUBLES' for ngons.
       */
      if (eed->v1->f == SF_VERT_ZERO_LEN) {
        v1 = eed->v1;
        while ((eed->v1->f == SF_VERT_ZERO_LEN) && (eed->v1->tmp.v != v1) &&
               (eed->v1 != eed->v1->tmp.v)) {
          eed->v1 = eed->v1->tmp.v;
        }
      }
      if (eed->v2->f == SF_VERT_ZERO_LEN) {
        v2 = eed->v2;
        while ((eed->v2->f == SF_VERT_ZERO_LEN) && (eed->v2->tmp.v != v2) &&
               (eed->v2 != eed->v2->tmp.v)) {
          eed->v2 = eed->v2->tmp.v;
        }
      }
      if (eed->v1 != eed->v2) {
        addedgetoscanlist(scdata, eed, verts);
      }
    }
  }
  else {
    for (eed = sf_ctx->filledgebase.first; eed; eed = eed_next) {
      eed_next = eed->next;
      BLI_remlink(&sf_ctx->filledgebase, eed);
      if (eed->v1 != eed->v2) {
        addedgetoscanlist(scdata, eed, verts);
      }
    }
  }
#if 0
  sc = sf_ctx->_scdata;
  for (a = 0; a < verts; a++) {
    printf("\nscvert: %x\n", sc->vert);
    for (eed = sc->edge_first; eed; eed = eed->next) {
      printf(" ed %x %x %x\n", eed, eed->v1, eed->v2);
    }
    sc++;
  }
#endif

  /* STEP 2: FILL LOOP */

  if (pf->f == SF_POLY_NEW) {
    twoconnected = true;
  }

  /* (temporal) security: never much more faces than vertices */
  totface = 0;
  if (flag & BLI_SCANFILL_CALC_HOLES) {
    maxface = 2 * verts; /* 2*verts: based at a filled circle within a triangle */
  }
  else {
    /* when we don't calc any holes, we assume face is a non overlapping loop */
    maxface = verts - 2;
  }

  sc = scdata;
  for (a = 0; a < verts; a++) {
    // printf("VERTEX %d index %d\n", a, sc->vert->tmp.u);
    /* Set connect-flags. */
    for (ed1 = sc->edge_first; ed1; ed1 = eed_next) {
      eed_next = ed1->next;
      if (ed1->v1->edge_tot == 1 || ed1->v2->edge_tot == 1) {
        BLI_remlink((ListBase *)&(sc->edge_first), ed1);
        BLI_addtail(&sf_ctx->filledgebase, ed1);
        if (ed1->v1->edge_tot > 1) {
          ed1->v1->edge_tot--;
        }
        if (ed1->v2->edge_tot > 1) {
          ed1->v2->edge_tot--;
        }
      }
      else {
        ed1->v2->f = SF_VERT_AVAILABLE;
      }
    }
    while (sc->edge_first) { /* for as long there are edges */
      ed1 = sc->edge_first;
      ed2 = ed1->next;

      /* commented out... the ESC here delivers corrupted memory
       * (and doesn't work during grab). */
      /* if (callLocalInterruptCallBack()) break; */
      if (totface >= maxface) {
        // printf("Fill error: endless loop. Escaped at vert %d,  tot: %d.\n", a, verts);
        a = verts;
        break;
      }
      if (ed2 == NULL) {
        sc->edge_first = sc->edge_last = NULL;
        // printf("just 1 edge to vert\n");
        BLI_addtail(&sf_ctx->filledgebase, ed1);
        ed1->v2->f = SF_VERT_NEW;
        ed1->v1->edge_tot--;
        ed1->v2->edge_tot--;
      }
      else {
        /* test rest of vertices */
        ScanFillVertLink *best_sc = NULL;
        float angle_best_cos = -1.0f;
        float miny;
        bool firsttime = false;

        v1 = ed1->v2;
        v2 = ed1->v1;
        v3 = ed2->v2;

        /* this happens with a serial of overlapping edges */
        if (v1 == v2 || v2 == v3) {
          break;
        }

        // printf("test verts %d %d %d\n", v1->tmp.u, v2->tmp.u, v3->tmp.u);
        miny = min_ff(v1->xy[1], v3->xy[1]);
        sc1 = sc + 1;

        for (b = a + 1; b < verts; b++, sc1++) {
          if (sc1->vert->f == SF_VERT_NEW) {
            if (sc1->vert->xy[1] <= miny) {
              break;
            }
            if (testedgeside(v1->xy, v2->xy, sc1->vert->xy)) {
              if (testedgeside(v2->xy, v3->xy, sc1->vert->xy)) {
                if (testedgeside(v3->xy, v1->xy, sc1->vert->xy)) {
                  /* point is in triangle */

                  /* Because multiple points can be inside triangle
                   * (concave holes) we continue searching and pick the
                   * one with sharpest corner. */
                  if (best_sc == NULL) {
                    /* even without holes we need to keep checking T35861. */
                    best_sc = sc1;
                  }
                  else {
                    /* Prevent angle calc for the simple cases
                     * only 1 vertex is found. */
                    if (firsttime == false) {
                      angle_best_cos = cos_v2v2v2(v2->xy, v1->xy, best_sc->vert->xy);
                      firsttime = true;
                    }

                    const float angle_test_cos = cos_v2v2v2(v2->xy, v1->xy, sc1->vert->xy);
                    if (angle_test_cos > angle_best_cos) {
                      best_sc = sc1;
                      angle_best_cos = angle_test_cos;
                    }
                  }
                }
              }
            }
          }
        }

        if (best_sc) {
          /* make new edge, and start over */
          // printf("add new edge %d %d and start again\n", v2->tmp.u, best_sc->vert->tmp.u);

          ed3 = BLI_scanfill_edge_add(sf_ctx, v2, best_sc->vert);
          BLI_remlink(&sf_ctx->filledgebase, ed3);
          BLI_insertlinkbefore((ListBase *)&(sc->edge_first), ed2, ed3);
          ed3->v2->f = SF_VERT_AVAILABLE;
          ed3->f = SF_EDGE_INTERNAL;
          ed3->v1->edge_tot++;
          ed3->v2->edge_tot++;
        }
        else {
          /* new triangle */
          // printf("add face %d %d %d\n", v1->tmp.u, v2->tmp.u, v3->tmp.u);
          addfillface(sf_ctx, v1, v2, v3);
          totface++;
          BLI_remlink((ListBase *)&(sc->edge_first), ed1);
          BLI_addtail(&sf_ctx->filledgebase, ed1);
          ed1->v2->f = SF_VERT_NEW;
          ed1->v1->edge_tot--;
          ed1->v2->edge_tot--;
          /* ed2 can be removed when it's a boundary edge */
          if (((ed2->f == SF_EDGE_NEW) && twoconnected) /* || (ed2->f == SF_EDGE_BOUNDARY) */) {
            BLI_remlink((ListBase *)&(sc->edge_first), ed2);
            BLI_addtail(&sf_ctx->filledgebase, ed2);
            ed2->v2->f = SF_VERT_NEW;
            ed2->v1->edge_tot--;
            ed2->v2->edge_tot--;
          }

          /* new edge */
          ed3 = BLI_scanfill_edge_add(sf_ctx, v1, v3);
          BLI_remlink(&sf_ctx->filledgebase, ed3);
          ed3->f = SF_EDGE_INTERNAL;
          ed3->v1->edge_tot++;
          ed3->v2->edge_tot++;

          // printf("add new edge %x %x\n", v1, v3);
          sc1 = addedgetoscanlist(scdata, ed3, verts);

          if (sc1) { /* ed3 already exists: remove if a boundary */
            // printf("Edge exists\n");
            ed3->v1->edge_tot--;
            ed3->v2->edge_tot--;

            for (ed3 = sc1->edge_first; ed3; ed3 = ed3->next) {
              if ((ed3->v1 == v1 && ed3->v2 == v3) || (ed3->v1 == v3 && ed3->v2 == v1)) {
                if (twoconnected /* || (ed3->f == SF_EDGE_BOUNDARY) */) {
                  BLI_remlink((ListBase *)&(sc1->edge_first), ed3);
                  BLI_addtail(&sf_ctx->filledgebase, ed3);
                  ed3->v1->edge_tot--;
                  ed3->v2->edge_tot--;
                }
                break;
              }
            }
          }
        }
      }

      /* test for loose edges */
      for (ed1 = sc->edge_first; ed1; ed1 = eed_next) {
        eed_next = ed1->next;
        if (ed1->v1->edge_tot < 2 || ed1->v2->edge_tot < 2) {
          BLI_remlink((ListBase *)&(sc->edge_first), ed1);
          BLI_addtail(&sf_ctx->filledgebase, ed1);
          if (ed1->v1->edge_tot > 1) {
            ed1->v1->edge_tot--;
          }
          if (ed1->v2->edge_tot > 1) {
            ed1->v2->edge_tot--;
          }
        }
      }
      /* done with loose edges */
    }

    sc++;
  }

  MEM_freeN(scdata);

  BLI_assert(totface <= maxface);

  return totface;
}

void BLI_scanfill_begin(ScanFillContext *sf_ctx)
{
  memset(sf_ctx, 0, sizeof(*sf_ctx));
  sf_ctx->poly_nr = SF_POLY_UNSET;
  sf_ctx->arena = BLI_memarena_new(BLI_SCANFILL_ARENA_SIZE, __func__);
}

void BLI_scanfill_begin_arena(ScanFillContext *sf_ctx, MemArena *arena)
{
  memset(sf_ctx, 0, sizeof(*sf_ctx));
  sf_ctx->poly_nr = SF_POLY_UNSET;
  sf_ctx->arena = arena;
}

void BLI_scanfill_end(ScanFillContext *sf_ctx)
{
  BLI_memarena_free(sf_ctx->arena);
  sf_ctx->arena = NULL;

  BLI_listbase_clear(&sf_ctx->fillvertbase);
  BLI_listbase_clear(&sf_ctx->filledgebase);
  BLI_listbase_clear(&sf_ctx->fillfacebase);
}

void BLI_scanfill_end_arena(ScanFillContext *sf_ctx, MemArena *arena)
{
  BLI_memarena_clear(arena);
  BLI_assert(sf_ctx->arena == arena);

  BLI_listbase_clear(&sf_ctx->fillvertbase);
  BLI_listbase_clear(&sf_ctx->filledgebase);
  BLI_listbase_clear(&sf_ctx->fillfacebase);
}

unsigned int BLI_scanfill_calc_ex(ScanFillContext *sf_ctx, const int flag, const float nor_proj[3])
{
  /*
   * - fill works with its own lists, so create that first (no faces!)
   * - for vertices, put in ->tmp.v the old pointer
   * - struct elements xs en ys are not used here: don't hide stuff in it
   * - edge flag ->f becomes 2 when it's a new edge
   * - mode: & 1 is check for crossings, then create edges (TO DO )
   * - returns number of triangle faces added.
   */
  ListBase tempve, temped;
  ScanFillVert *eve;
  ScanFillEdge *eed, *eed_next;
  PolyFill *pflist, *pf;
  float *min_xy_p, *max_xy_p;
  unsigned int totfaces = 0; /* total faces added */
  unsigned short a, c, poly = 0;
  bool ok;
  float mat_2d[3][3];

  BLI_assert(!nor_proj || len_squared_v3(nor_proj) > FLT_EPSILON);

#ifdef DEBUG
  for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
    /* these values used to be set,
     * however they should always be zero'd so check instead */
    BLI_assert(eve->f == 0);
    BLI_assert(sf_ctx->poly_nr || eve->poly_nr == 0);
    BLI_assert(eve->edge_tot == 0);
  }
#endif

  /* first test vertices if they are in edges */
  /* including resetting of flags */
  for (eed = sf_ctx->filledgebase.first; eed; eed = eed->next) {
    BLI_assert(sf_ctx->poly_nr != SF_POLY_UNSET || eed->poly_nr == SF_POLY_UNSET);
    eed->v1->f = SF_VERT_AVAILABLE;
    eed->v2->f = SF_VERT_AVAILABLE;
  }

  for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
    if (eve->f == SF_VERT_AVAILABLE) {
      break;
    }
  }

  if (UNLIKELY(eve == NULL)) {
    return 0;
  }

  float n[3];

  if (nor_proj) {
    copy_v3_v3(n, nor_proj);
  }
  else {
    /* define projection: with 'best' normal */
    /* Newell's Method */
    /* Similar code used elsewhere, but this checks for double ups
     * which historically this function supports so better not change */

    /* warning: this only gives stable direction with single polygons,
     * ideally we'd calculate connectivity and each polys normal, see T41047 */
    const float *v_prev;

    zero_v3(n);
    eve = sf_ctx->fillvertbase.last;
    v_prev = eve->co;

    for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
      if (LIKELY(!compare_v3v3(v_prev, eve->co, SF_EPSILON))) {
        add_newell_cross_v3_v3v3(n, v_prev, eve->co);
        v_prev = eve->co;
      }
    }
  }

  if (UNLIKELY(normalize_v3(n) == 0.0f)) {
    return 0;
  }

  axis_dominant_v3_to_m3_negate(mat_2d, n);

  /* STEP 1: COUNT POLYS */
  if (sf_ctx->poly_nr != SF_POLY_UNSET) {
    poly = (unsigned short)(sf_ctx->poly_nr + 1);
    sf_ctx->poly_nr = SF_POLY_UNSET;
  }

  if (flag & BLI_SCANFILL_CALC_POLYS && (poly == 0)) {
    for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
      mul_v2_m3v3(eve->xy, mat_2d, eve->co);

      /* get first vertex with no poly number */
      if (eve->poly_nr == SF_POLY_UNSET) {
        unsigned int toggle = 0;
        /* now a sort of select connected */
        ok = true;
        eve->poly_nr = poly;

        while (ok) {

          ok = false;

          toggle++;
          for (eed = (toggle & 1) ? sf_ctx->filledgebase.first : sf_ctx->filledgebase.last; eed;
               eed = (toggle & 1) ? eed->next : eed->prev) {
            if (eed->v1->poly_nr == SF_POLY_UNSET && eed->v2->poly_nr == poly) {
              eed->v1->poly_nr = poly;
              eed->poly_nr = poly;
              ok = true;
            }
            else if (eed->v2->poly_nr == SF_POLY_UNSET && eed->v1->poly_nr == poly) {
              eed->v2->poly_nr = poly;
              eed->poly_nr = poly;
              ok = true;
            }
            else if (eed->poly_nr == SF_POLY_UNSET) {
              if (eed->v1->poly_nr == poly && eed->v2->poly_nr == poly) {
                eed->poly_nr = poly;
                ok = true;
              }
            }
          }
        }

        poly++;
      }
    }
    // printf("amount of poly's: %d\n", poly);
  }
  else if (poly) {
    /* we pre-calculated poly_nr */
    for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
      mul_v2_m3v3(eve->xy, mat_2d, eve->co);
    }
  }
  else {
    poly = 1;

    for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
      mul_v2_m3v3(eve->xy, mat_2d, eve->co);
      eve->poly_nr = 0;
    }

    for (eed = sf_ctx->filledgebase.first; eed; eed = eed->next) {
      eed->poly_nr = 0;
    }
  }

  /* STEP 2: remove loose edges and strings of edges */
  if (flag & BLI_SCANFILL_CALC_LOOSE) {
    unsigned int toggle = 0;
    for (eed = sf_ctx->filledgebase.first; eed; eed = eed->next) {
      if (eed->v1->edge_tot++ > 250) {
        break;
      }
      if (eed->v2->edge_tot++ > 250) {
        break;
      }
    }
    if (eed) {
      /* otherwise it's impossible to be sure you can clear vertices */
#ifdef DEBUG
      printf("No vertices with 250 edges allowed!\n");
#endif
      return 0;
    }

    /* does it only for vertices with (->edge_tot == 1) */
    testvertexnearedge(sf_ctx);

    ok = true;
    while (ok) {
      ok = false;

      toggle++;
      for (eed = (toggle & 1) ? sf_ctx->filledgebase.first : sf_ctx->filledgebase.last; eed;
           eed = eed_next) {
        eed_next = (toggle & 1) ? eed->next : eed->prev;
        if (eed->v1->edge_tot == 1) {
          eed->v2->edge_tot--;
          BLI_remlink(&sf_ctx->fillvertbase, eed->v1);
          BLI_remlink(&sf_ctx->filledgebase, eed);
          ok = true;
        }
        else if (eed->v2->edge_tot == 1) {
          eed->v1->edge_tot--;
          BLI_remlink(&sf_ctx->fillvertbase, eed->v2);
          BLI_remlink(&sf_ctx->filledgebase, eed);
          ok = true;
        }
      }
    }
    if (BLI_listbase_is_empty(&sf_ctx->filledgebase)) {
      // printf("All edges removed\n");
      return 0;
    }
  }
  else {
    /* skip checks for loose edges */
    for (eed = sf_ctx->filledgebase.first; eed; eed = eed->next) {
      eed->v1->edge_tot++;
      eed->v2->edge_tot++;
    }
#ifdef DEBUG
    /* ensure we're right! */
    for (eed = sf_ctx->filledgebase.first; eed; eed = eed->next) {
      BLI_assert(eed->v1->edge_tot != 1);
      BLI_assert(eed->v2->edge_tot != 1);
    }
#endif
  }

  /* CURRENT STATUS:
   * - `eve->f`:        1 = available in edges.
   * - `eve->poly_nr`:  poly-number.
   * - `eve->edge_tot`: amount of edges connected to vertex.
   * - `eve->tmp.v`:    store! original vertex number.
   *
   * - `eed->f`:        1 = boundary edge (optionally set by caller).
   * - `eed->poly_nr`:  poly number.
   */

  /* STEP 3: MAKE POLYFILL STRUCT */
  pflist = MEM_mallocN(sizeof(*pflist) * (size_t)poly, "edgefill");
  pf = pflist;
  for (a = 0; a < poly; a++) {
    pf->edges = pf->verts = 0;
    pf->min_xy[0] = pf->min_xy[1] = 1.0e20f;
    pf->max_xy[0] = pf->max_xy[1] = -1.0e20f;
    pf->f = SF_POLY_NEW;
    pf->nr = a;
    pf++;
  }
  for (eed = sf_ctx->filledgebase.first; eed; eed = eed->next) {
    pflist[eed->poly_nr].edges++;
  }

  for (eve = sf_ctx->fillvertbase.first; eve; eve = eve->next) {
    pflist[eve->poly_nr].verts++;
    min_xy_p = pflist[eve->poly_nr].min_xy;
    max_xy_p = pflist[eve->poly_nr].max_xy;

    min_xy_p[0] = (min_xy_p[0]) < (eve->xy[0]) ? (min_xy_p[0]) : (eve->xy[0]);
    min_xy_p[1] = (min_xy_p[1]) < (eve->xy[1]) ? (min_xy_p[1]) : (eve->xy[1]);
    max_xy_p[0] = (max_xy_p[0]) > (eve->xy[0]) ? (max_xy_p[0]) : (eve->xy[0]);
    max_xy_p[1] = (max_xy_p[1]) > (eve->xy[1]) ? (max_xy_p[1]) : (eve->xy[1]);
    if (eve->edge_tot > 2) {
      pflist[eve->poly_nr].f = SF_POLY_VALID;
    }
  }

  /* STEP 4: FIND HOLES OR BOUNDS, JOIN THEM
   *  ( bounds just to divide it in pieces for optimization,
   *    the edgefill itself has good auto-hole detection)
   * WATCH IT: ONLY WORKS WITH SORTED POLYS!!! */

  if ((flag & BLI_SCANFILL_CALC_HOLES) && (poly > 1)) {
    unsigned short *polycache, *pc;

    /* so, sort first */
    qsort(pflist, (size_t)poly, sizeof(PolyFill), vergpoly);

#if 0
    pf = pflist;
    for (a = 0; a < poly; a++) {
      printf("poly:%d edges:%d verts:%d flag: %d\n", a, pf->edges, pf->verts, pf->f);
      PRINT2(f, f, pf->min[0], pf->min[1]);
      pf++;
    }
#endif

    polycache = pc = MEM_callocN(sizeof(*polycache) * (size_t)poly, "polycache");
    pf = pflist;
    for (a = 0; a < poly; a++, pf++) {
      for (c = (unsigned short)(a + 1); c < poly; c++) {

        /* if 'a' inside 'c': join (bbox too)
         * Careful: 'a' can also be inside another poly.
         */
        if (boundisect(pf, pflist + c)) {
          *pc = c;
          pc++;
        }
        /* only for optimize! */
        /* else if (pf->max_xy[0] < (pflist+c)->min[cox]) break; */
      }
      while (pc != polycache) {
        pc--;
        mergepolysSimp(sf_ctx, pf, pflist + *pc);
      }
    }
    MEM_freeN(polycache);
  }

#if 0
  printf("after merge\n");
  pf = pflist;
  for (a = 0; a < poly; a++) {
    printf("poly:%d edges:%d verts:%d flag: %d\n", a, pf->edges, pf->verts, pf->f);
    pf++;
  }
#endif

  /* STEP 5: MAKE TRIANGLES */

  tempve.first = sf_ctx->fillvertbase.first;
  tempve.last = sf_ctx->fillvertbase.last;
  temped.first = sf_ctx->filledgebase.first;
  temped.last = sf_ctx->filledgebase.last;
  BLI_listbase_clear(&sf_ctx->fillvertbase);
  BLI_listbase_clear(&sf_ctx->filledgebase);

  pf = pflist;
  for (a = 0; a < poly; a++) {
    if (pf->edges > 1) {
      splitlist(sf_ctx, &tempve, &temped, pf->nr);
      totfaces += scanfill(sf_ctx, pf, flag);
    }
    pf++;
  }
  BLI_movelisttolist(&sf_ctx->fillvertbase, &tempve);
  BLI_movelisttolist(&sf_ctx->filledgebase, &temped);

  /* FREE */

  MEM_freeN(pflist);

  return totfaces;
}

unsigned int BLI_scanfill_calc(ScanFillContext *sf_ctx, const int flag)
{
  return BLI_scanfill_calc_ex(sf_ctx, flag, NULL);
}