text: /*
   * 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) 2004 by Blender Foundation.
   * All rights reserved.
   */
  
  /** \file
   * \ingroup edmesh
   */
  
  #include "MEM_guardedalloc.h"
  
  #include "DNA_object_types.h"
  
  #include "BLI_array.h"
  #include "BLI_math.h"
  
  #include "BKE_context.h"
  #include "BKE_editmesh.h"
  #include "BKE_layer.h"
  #include "BKE_report.h"
  
  #include "RNA_access.h"
  #include "RNA_define.h"
  
  #include "WM_types.h"
  
  #include "ED_mesh.h"
  #include "ED_screen.h"
  #include "ED_transform.h"
  #include "ED_view3d.h"
  
  #include "bmesh.h"
  #include "bmesh_tools.h"
  
  #include "mesh_intern.h" /* own include */
  
  /**
   * helper to find edge for edge_rip,
   *
   * \param inset: is used so we get some useful distance
   * when comparing multiple edges that meet at the same
   * point and would result in the same distance.
   */
  #define INSET_DEFAULT 0.00001f
  static float edbm_rip_edgedist_squared(ARegion *region,
                                         float mat[4][4],
                                         const float co1[3],
                                         const float co2[3],
                                         const float mvalf[2],
                                         const float inset)
  {
    float vec1[2], vec2[2], dist_sq;
  
    ED_view3d_project_float_v2_m4(region, co1, vec1, mat);
    ED_view3d_project_float_v2_m4(region, co2, vec2, mat);
  
    if (inset != 0.0f) {
      const float dist_2d = len_v2v2(vec1, vec2);
      if (dist_2d > FLT_EPSILON) {
        const float dist = inset / dist_2d;
        BLI_assert(isfinite(dist));
        interp_v2_v2v2(vec1, vec1, vec2, dist);
        interp_v2_v2v2(vec2, vec2, vec1, dist);
      }
    }
  
    dist_sq = dist_squared_to_line_segment_v2(mvalf, vec1, vec2);
    BLI_assert(isfinite(dist_sq));
  
    return dist_sq;
  }
  
  #if 0
  static float edbm_rip_linedist(
      ARegion *region, float mat[4][4], const float co1[3], const float co2[3], const float mvalf[2])
  {
    float vec1[2], vec2[2];
  
    ED_view3d_project_float_v2_m4(region, co1, vec1, mat);
    ED_view3d_project_float_v2_m4(region, co2, vec2, mat);
  
    return dist_to_line_v2(mvalf, vec1, vec2);
  }
  #endif
  
  /* calculaters a point along the loop tangent which can be used to measure against edges */
  static void edbm_calc_loop_co(BMLoop *l, float l_mid_co[3])
  {
    BM_loop_calc_face_tangent(l, l_mid_co);
  
    /* scale to average of surrounding edge size, only needs to be approx, but should
     * be roughly equivalent to the check below which uses the middle of the edge. */
    mul_v3_fl(l_mid_co, (BM_edge_calc_length(l->e) + BM_edge_calc_length(l->prev->e)) / 2.0f);
  
    add_v3_v3(l_mid_co, l->v->co);
  }
  
  static float edbm_rip_edge_side_measure(
      BMEdge *e, BMLoop *e_l, ARegion *region, float projectMat[4][4], const float fmval[2])
  {
    float cent[3] = {0, 0, 0}, mid[3];
  
    float vec[2];
    float fmval_tweak[2];
    float e_v1_co[2], e_v2_co[2];
    float score;
  
    BMVert *v1_other;
    BMVert *v2_other;
  
    BLI_assert(BM_vert_in_edge(e, e_l->v));
  
    /* method for calculating distance:
     *
     * for each edge: calculate face center, then made a vector
     * from edge midpoint to face center.  offset edge midpoint
     * by a small amount along this vector. */
  
    /* rather than the face center, get the middle of
     * both edge verts connected to this one */
    v1_other = BM_face_other_vert_loop(e_l->f, e->v2, e->v1)->v;
    v2_other = BM_face_other_vert_loop(e_l->f, e->v1, e->v2)->v;
    mid_v3_v3v3(cent, v1_other->co, v2_other->co);
    mid_v3_v3v3(mid, e->v1->co, e->v2->co);
  
    ED_view3d_project_float_v2_m4(region, cent, cent, projectMat);
    ED_view3d_project_float_v2_m4(region, mid, mid, projectMat);
  
    ED_view3d_project_float_v2_m4(region, e->v1->co, e_v1_co, projectMat);
    ED_view3d_project_float_v2_m4(region, e->v2->co, e_v2_co, projectMat);
  
    sub_v2_v2v2(vec, cent, mid);
    normalize_v2_length(vec, 0.01f);
  
    /* rather than adding to both verts, subtract from the mouse */
    sub_v2_v2v2(fmval_tweak, fmval, vec);
  
    score = len_v2v2(e_v1_co, e_v2_co);
  
    if (dist_squared_to_line_segment_v2(fmval_tweak, e_v1_co, e_v2_co) >
        dist_squared_to_line_segment_v2(fmval, e_v1_co, e_v2_co)) {
      return score;
    }
    return -score;
  }
  
  /* - Advanced selection handling 'ripsel' functions ----- */
  
  /**
   * How rip selection works
   *
   * Firstly - rip is basically edge split with side-selection & grab.
   * Things would be much more simple if we didn't have to worry about side selection
   *
   * The method used for checking the side of selection is as follows...
   * - First tag all rip-able edges.
   * - Build a contiguous edge list by looping over tagged edges and following each ones tagged
   *   siblings in both directions.
   *   - The loops are not stored in an array, Instead both loops on either side of each edge has
   *     its index values set to count down from the last edge, this way, once we have the 'last'
   *     edge its very easy to walk down the connected edge loops.
   *     The reason for using loops like this is because when the edges are split we don't which
   *     face user gets the newly created edge
   *     (its as good as random so we cant assume new edges will be on once side).
   *     After splitting, its very simple to walk along boundary loops since each only has one edge
   *     from a single side.
   * - The end loop pairs are stored in an array however to support multiple edge-selection-islands,
   *   so you can rip multiple selections at once.
   * - * Execute the split *
   * - For each #EdgeLoopPair walk down both sides of the split using the loops and measure
   *   which is facing the mouse.
   * - Deselect the edge loop facing away.
   *
   * Limitation!
   * This currently works very poorly with intersecting edge islands
   * (verts with more than 2 tagged edges). This is nice to but for now not essential.
   *
   * - campbell.
   */
  
  #define IS_VISIT_POSSIBLE(e) (BM_edge_is_manifold(e) && BM_elem_flag_test(e, BM_ELEM_TAG))
  #define IS_VISIT_DONE(e) ((e)->l && (BM_elem_index_get((e)->l) != INVALID_UID))
  #define INVALID_UID INT_MIN
  
  /* mark, assign uid and step */
  static BMEdge *edbm_ripsel_edge_mark_step(BMVert *v, const int uid)
  {
    BMIter iter;
    BMEdge *e;
    BM_ITER_ELEM (e, &iter, v, BM_EDGES_OF_VERT) {
      if (IS_VISIT_POSSIBLE(e) && !IS_VISIT_DONE(e)) {
        BMLoop *l_a, *l_b;
  
        BM_edge_loop_pair(e, &l_a, &l_b); /* no need to check, we know this will be true */
  
        /* so (IS_VISIT_DONE == true) */
        BM_elem_index_set(l_a, uid); /* set_dirty */
        BM_elem_index_set(l_b, uid); /* set_dirty */
  
        return e;
      }
    }
    return NULL;
  }
  
  typedef struct EdgeLoopPair {
    BMLoop *l_a;
    BMLoop *l_b;
  } EdgeLoopPair;
  
  static EdgeLoopPair *edbm_ripsel_looptag_helper(BMesh *bm)
  {
    BMIter fiter;
    BMIter liter;
  
    BMFace *f;
    BMLoop *l;
  
    int uid_start;
    int uid_end;
    int uid = bm->totedge; /* can start anywhere */
  
    EdgeLoopPair *eloop_pairs = NULL;
    BLI_array_declare(eloop_pairs);
    EdgeLoopPair *lp;
  
    /* initialize loops with dummy invalid index values */
    BM_ITER_MESH (f, &fiter, bm, BM_FACES_OF_MESH) {
      BM_ITER_ELEM (l, &liter, f, BM_LOOPS_OF_FACE) {
        BM_elem_index_set(l, INVALID_UID); /* set_dirty */
      }
    }
    bm->elem_index_dirty |= BM_LOOP;
  
    /* set contiguous loops ordered 'uid' values for walking after split */
    while (true) {
      int tot = 0;
      BMIter eiter;
      BMEdge *e_step;
      BMVert *v_step;
      BMEdge *e;
      BMEdge *e_first;
      BMEdge *e_last;
  
      e_first = NULL;
      BM_ITER_MESH (e, &eiter, bm, BM_EDGES_OF_MESH) {
        if (IS_VISIT_POSSIBLE(e) && !IS_VISIT_DONE(e)) {
          e_first = e;
          break;
        }
      }
  
      if (e_first == NULL) {
        break;
      }
  
      /* initialize  */
      e_first = e;
      v_step = e_first->v1;
      e_step = NULL; /* quiet warning, will never remain this value */
  
      uid_start = uid;
      while ((e = edbm_ripsel_edge_mark_step(v_step, uid))) {
        v_step = BM_edge_other_vert((e_step = e), v_step);
        uid++; /* only different line */
        tot++;
      }
  
      /* this edges loops have the highest uid's, store this to walk down later */
      e_last = e_step;
  
      /* always store the highest 'uid' edge for the stride */
      uid_end = uid - 1;
      uid = uid_start - 1;
  
      /* initialize */
      v_step = e_first->v1;
  
      while ((e = edbm_ripsel_edge_mark_step(v_step, uid))) {
        v_step = BM_edge_other_vert((e_step = e), v_step);
        uid--; /* only different line */
        tot++;
      }
  
      /* stride far enough not to _ever_ overlap range */
      uid_start = uid;
      uid = uid_end + bm->totedge;
  
      lp = BLI_array_append_ret(eloop_pairs);
      /* no need to check, we know this will be true */
      BM_edge_loop_pair(e_last, &lp->l_a, &lp->l_b);
  
      BLI_assert(tot == uid_end - uid_start);
  
  #if 0
      printf("%s: found contiguous edge loop of (%d)\n", __func__, uid_end - uid_start);
  #endif
    }
  
    /* null terminate */
    lp = BLI_array_append_ret(eloop_pairs);
    lp->l_a = lp->l_b = NULL;
  
    return eloop_pairs;
  }
  
  /* - De-Select the worst rip-edge side -------------------------------- */
  
  static BMEdge *edbm_ripsel_edge_uid_step(BMEdge *e_orig, BMVert **v_prev)
  {
    BMIter eiter;
    BMEdge *e;
    BMVert *v = BM_edge_other_vert(e_orig, *v_prev);
    const int uid_cmp = BM_elem_index_get(e_orig->l) - 1;
  
    BM_ITER_ELEM (e, &eiter, v, BM_EDGES_OF_VERT) {
      if (BM_elem_index_get(e->l) == uid_cmp) {
        *v_prev = v;
        return e;
      }
    }
    return NULL;
  }
  
  static BMVert *edbm_ripsel_edloop_pair_start_vert(BMEdge *e)
  {
    /* try step in a direction, if it fails we know do go the other way */
    BMVert *v_test = e->v1;
    return (edbm_ripsel_edge_uid_step(e, &v_test)) ? e->v1 : e->v2;
  }
  
  static void edbm_ripsel_deselect_helper(BMesh *bm,
                                          EdgeLoopPair *eloop_pairs,
                                          ARegion *region,
                                          float projectMat[4][4],
                                          const float fmval[2])
  {
    EdgeLoopPair *lp;
  
    for (lp = eloop_pairs; lp->l_a; lp++) {
      BMEdge *e;
      BMVert *v_prev;
  
      float score_a = 0.0f;
      float score_b = 0.0f;
  
      e = lp->l_a->e;
      v_prev = edbm_ripsel_edloop_pair_start_vert(e);
      for (; e; e = edbm_ripsel_edge_uid_step(e, &v_prev)) {
        score_a += edbm_rip_edge_side_measure(e, e->l, region, projectMat, fmval);
      }
      e = lp->l_b->e;
      v_prev = edbm_ripsel_edloop_pair_start_vert(e);
      for (; e; e = edbm_ripsel_edge_uid_step(e, &v_prev)) {
        score_b += edbm_rip_edge_side_measure(e, e->l, region, projectMat, fmval);
      }
  
      e = (score_a > score_b) ? lp->l_a->e : lp->l_b->e;
      v_prev = edbm_ripsel_edloop_pair_start_vert(e);
      for (; e; e = edbm_ripsel_edge_uid_step(e, &v_prev)) {
        BM_edge_select_set(bm, e, false);
      }
    }
  }
  /* --- end 'ripsel' selection handling code --- */
  
  /* --- face-fill code --- */
  /**
   * return an un-ordered array of loop pairs
   * use for rebuilding face-fill
   *
   * \note the method currently used fails for edges with 3+ face users and gives
   *       nasty holes in the mesh, there isnt a good way of knowing ahead of time
   *       which loops will be split apart (its possible to figure out but quite involved).
   *       So for now this is a known limitation of current rip-fill option.
   */
  
  typedef struct UnorderedLoopPair {
    BMLoop *l_pair[2];
    char flag;
  } UnorderedLoopPair;
  enum {
    ULP_FLIP_0 = (1 << 0),
    ULP_FLIP_1 = (1 << 1),
  };
  
  static UnorderedLoopPair *edbm_tagged_loop_pairs_to_fill(BMesh *bm)
  {
    BMIter iter;
    BMEdge *e;
  
    uint total_tag = 0;
    /* count tags, could be pre-calculated */
    BM_ITER_MESH (e, &iter, bm, BM_EDGES_OF_MESH) {
      if (BM_elem_flag_test(e, BM_ELEM_TAG)) {
        total_tag++;
      }
    }
  
    if (total_tag) {
      UnorderedLoopPair *uloop_pairs = MEM_mallocN(total_tag * sizeof(UnorderedLoopPair), __func__);
      UnorderedLoopPair *ulp = uloop_pairs;
  
      BM_ITER_MESH (e, &iter, bm, BM_EDGES_OF_MESH) {
        if (BM_elem_flag_test(e, BM_ELEM_TAG)) {
          BMLoop *l1, *l2;
          if (BM_edge_loop_pair(e, &l1, &l2)) {
            BMVert *v_cmp = l1->e->v1;
            ulp->flag = (((l1->v != v_cmp) ? ULP_FLIP_0 : 0) | ((l2->v == v_cmp) ? ULP_FLIP_1 : 0));
          }
          else {
            ulp->flag = 0;
          }
          ulp->l_pair[0] = l1;
          ulp->l_pair[1] = l2;
  
          ulp++;
        }
      }
  
      return uloop_pairs;
    }
    return NULL;
  }
  
  static void edbm_tagged_loop_pairs_do_fill_faces(BMesh *bm, UnorderedLoopPair *uloop_pairs)
  {
    UnorderedLoopPair *ulp;
    uint total_tag = MEM_allocN_len(uloop_pairs) / sizeof(UnorderedLoopPair);
    uint i;
  
    for (i = 0, ulp = uloop_pairs; i < total_tag; i++, ulp++) {
      if ((ulp->l_pair[0] && ulp->l_pair[1]) && (ulp->l_pair[0]->e != ulp->l_pair[1]->e)) {
        /* time has come to make a face! */
        BMVert *v_shared = BM_edge_share_vert(ulp->l_pair[0]->e, ulp->l_pair[1]->e);
        BMFace *f, *f_example = ulp->l_pair[0]->f;
        BMLoop *l_iter;
        BMVert *f_verts[4];
  
        if (v_shared == NULL) {
          /* quad */
          f_verts[0] = ulp->l_pair[0]->e->v1;
          f_verts[1] = ulp->l_pair[1]->e->v1;
          f_verts[2] = ulp->l_pair[1]->e->v2;
          f_verts[3] = ulp->l_pair[0]->e->v2;
  
          if (ulp->flag & ULP_FLIP_0) {
            SWAP(BMVert *, f_verts[0], f_verts[3]);
          }
          if (ulp->flag & ULP_FLIP_1) {
            SWAP(BMVert *, f_verts[1], f_verts[2]);
          }
        }
        else {
          /* tri */
          f_verts[0] = v_shared;
          f_verts[1] = BM_edge_other_vert(ulp->l_pair[0]->e, v_shared);
          f_verts[2] = BM_edge_other_vert(ulp->l_pair[1]->e, v_shared);
          f_verts[3] = NULL;
  
          /* don't use the flip flags */
          if (v_shared == ulp->l_pair[0]->v) {
            SWAP(BMVert *, f_verts[0], f_verts[1]);
          }
        }
  
        /* face should never exist */
        BLI_assert(!BM_face_exists(f_verts, f_verts[3] ? 4 : 3));
  
        f = BM_face_create_verts(bm, f_verts, f_verts[3] ? 4 : 3, f_example, BM_CREATE_NOP, true);
  
        l_iter = BM_FACE_FIRST_LOOP(f);
  
        if (f_verts[3]) {
          BM_elem_attrs_copy(bm, bm, BM_edge_other_loop(ulp->l_pair[0]->e, l_iter), l_iter);
          l_iter = l_iter->next;
          BM_elem_attrs_copy(bm, bm, BM_edge_other_loop(ulp->l_pair[1]->e, l_iter), l_iter);
          l_iter = l_iter->next;
          BM_elem_attrs_copy(bm, bm, BM_edge_other_loop(ulp->l_pair[1]->e, l_iter), l_iter);
          l_iter = l_iter->next;
          BM_elem_attrs_copy(bm, bm, BM_edge_other_loop(ulp->l_pair[0]->e, l_iter), l_iter);
        }
        else {
          BM_elem_attrs_copy(bm, bm, BM_edge_other_loop(ulp->l_pair[0]->e, l_iter), l_iter);
          l_iter = l_iter->next;
          BM_elem_attrs_copy(bm, bm, BM_edge_other_loop(ulp->l_pair[0]->e, l_iter), l_iter);
          l_iter = l_iter->next;
          BM_elem_attrs_copy(bm, bm, BM_edge_other_loop(ulp->l_pair[1]->e, l_iter), l_iter);
        }
      }
    }
  }
  
  /* --- end 'face-fill' code --- */
  
  /**
   * This is the main vert ripping function (rip when one vertex is selected)
   */
  static int edbm_rip_invoke__vert(bContext *C, const wmEvent *event, Object *obedit, bool do_fill)
  {
    UnorderedLoopPair *fill_uloop_pairs = NULL;
    ARegion *region = CTX_wm_region(C);
    RegionView3D *rv3d = CTX_wm_region_view3d(C);
    BMEditMesh *em = BKE_editmesh_from_object(obedit);
    BMesh *bm = em->bm;
    BMIter iter, liter;
    BMLoop *l;
    BMEdge *e_best;
    BMVert *v;
    const int totvert_orig = bm->totvert;
    int i;
    float projectMat[4][4], fmval[3] = {event->mval[0], event->mval[1]};
    float dist_sq = FLT_MAX;
    float d;
    bool is_wire, is_manifold_region;
  
    BMEditSelection ese;
    int totboundary_edge = 0;
  
    ED_view3d_ob_project_mat_get(rv3d, obedit, projectMat);
  
    /* find selected vert - same some time and check history first */
    if (BM_select_history_active_get(bm, &ese) && ese.htype == BM_VERT) {
      v = (BMVert *)ese.ele;
    }
    else {
      ese.ele = NULL;
  
      BM_ITER_MESH (v, &iter, bm, BM_VERTS_OF_MESH) {
        if (BM_elem_flag_test(v, BM_ELEM_SELECT)) {
          break;
        }
      }
    }
  
    /* (v == NULL) should be impossible */
    if ((v == NULL) || (v->e == NULL)) {
      return OPERATOR_CANCELLED;
    }
  
    is_wire = BM_vert_is_wire(v);
    is_manifold_region = BM_vert_is_manifold_region(v);
  
    e_best = NULL;
  
    {
      BMEdge *e;
      /* find closest edge to mouse cursor */
      BM_ITER_ELEM (e, &iter, v, BM_EDGES_OF_VERT) {
        /* consider wire as boundary for this purpose,
         * otherwise we can't a face away from a wire edge */
        totboundary_edge += (BM_edge_is_boundary(e) || BM_edge_is_wire(e));
        if (!BM_elem_flag_test(e, BM_ELEM_HIDDEN)) {
          if ((is_manifold_region == false) || BM_edge_is_manifold(e)) {
            d = edbm_rip_edgedist_squared(
                region, projectMat, e->v1->co, e->v2->co, fmval, INSET_DEFAULT);
            if ((e_best == NULL) || (d < dist_sq)) {
              dist_sq = d;
              e_best = e;
            }
          }
        }
      }
    }
  
    if (e_best && e_best->l && (is_manifold_region == false)) {
      /* Try to split off a non-manifold fan (when we have multiple disconnected fans) */
      BMLoop *l_sep = e_best->l->v == v ? e_best->l : e_best->l->next;
      BMVert *v_new;
  
      BLI_assert(l_sep->v == v);
      v_new = BM_face_loop_separate_multi_isolated(bm, l_sep);
      BLI_assert(BM_vert_find_first_loop(v));
  
      BM_vert_select_set(bm, v, false);
      BM_select_history_remove(bm, v);
  
      BM_vert_select_set(bm, v_new, true);
      if (ese.ele) {
        BM_select_history_store(bm, v_new);
      }
  
      if (do_fill) {
        BM_edge_create(bm, v, v_new, NULL, BM_CREATE_NOP);
      }
  
      return OPERATOR_FINISHED;
    }
  
    /* if we are ripping a single vertex from 3 faces,
     * then measure the distance to the face corner as well as the edge */
    if (BM_vert_face_count_is_equal(v, 3) && BM_vert_edge_count_is_equal(v, 3)) {
      BMEdge *e_all[3];
      BMLoop *l_all[3];
      int i1, i2;
  
      BM_iter_as_array(bm, BM_EDGES_OF_VERT, v, (void **)e_all, 3);
      BM_iter_as_array(bm, BM_LOOPS_OF_VERT, v, (void **)l_all, 3);
  
      /* not do a loop similar to the one above, but test against loops */
      for (i1 = 0; i1 < 3; i1++) {
        /* consider wire as boundary for this purpose,
         * otherwise we can't a face away from a wire edge */
        float l_mid_co[3];
        l = l_all[i1];
        edbm_calc_loop_co(l, l_mid_co);
        d = edbm_rip_edgedist_squared(region, projectMat, l->v->co, l_mid_co, fmval, INSET_DEFAULT);
        if ((e_best == NULL) || (d < dist_sq)) {
          dist_sq = d;
  
          /* find the edge that is not in this loop */
          e_best = NULL;
          for (i2 = 0; i2 < 3; i2++) {
            if (!BM_edge_in_loop(e_all[i2], l)) {
              e_best = e_all[i2];
              break;
            }
          }
          BLI_assert(e_best != NULL);
        }
      }
    }
  
    /* should we go ahead with edge rip or do we need to do special case, split off vertex?:
     * split off vertex if...
     * - we cant find an edge - this means we are ripping a faces vert that is connected to other
     *   geometry only at the vertex.
     * - the boundary edge total is greater than 2,
     *   in this case edge split _can_ work but we get far nicer results if we use this special case.
     * - there are only 2 edges but we are a wire vert. */
    if ((is_wire == false && totboundary_edge > 2) || (is_wire == true && totboundary_edge > 1)) {
      BMVert **vout;
      int vout_len;
  
      BM_vert_select_set(bm, v, false);
  
      bmesh_kernel_vert_separate(bm, v, &vout, &vout_len, true);
  
      if (vout_len < 2) {
        MEM_freeN(vout);
        /* set selection back to avoid active-unselected vertex */
        BM_vert_select_set(bm, v, true);
        /* should never happen */
        return OPERATOR_CANCELLED;
      }
  
      int vi_best = 0;
  
      if (ese.ele) {
        BM_select_history_remove(bm, ese.ele);
      }
  
      dist_sq = FLT_MAX;
  
      /* in the loop below we find the best vertex to drag based on its connected geometry,
       * either by its face corner, or connected edge (when no faces are attached) */
      for (i = 0; i < vout_len; i++) {
  
        if (BM_vert_is_wire(vout[i]) == false) {
          /* find the best face corner */
          BM_ITER_ELEM (l, &iter, vout[i], BM_LOOPS_OF_VERT) {
            if (!BM_elem_flag_test(l->f, BM_ELEM_HIDDEN)) {
              float l_mid_co[3];
  
              edbm_calc_loop_co(l, l_mid_co);
              d = edbm_rip_edgedist_squared(
                  region, projectMat, v->co, l_mid_co, fmval, INSET_DEFAULT);
  
              if (d < dist_sq) {
                dist_sq = d;
                vi_best = i;
              }
            }
          }
        }
        else {
          BMEdge *e;
          /* a wire vert, find the best edge */
          BM_ITER_ELEM (e, &iter, vout[i], BM_EDGES_OF_VERT) {
            if (!BM_elem_flag_test(e, BM_ELEM_HIDDEN)) {
              float e_mid_co[3];
  
              mid_v3_v3v3(e_mid_co, e->v1->co, e->v2->co);
              d = edbm_rip_edgedist_squared(
                  region, projectMat, v->co, e_mid_co, fmval, INSET_DEFAULT);
  
              if (d < dist_sq) {
                dist_sq = d;
                vi_best = i;
              }
            }
          }
        }
      }
  
      /* vout[0]  == best
       * vout[1]  == glue
       * vout[2+] == splice with glue (when vout_len > 2)
       */
      if (vi_best != 0) {
        SWAP(BMVert *, vout[0], vout[vi_best]);
        vi_best = 0;
      }
  
      /* select the vert from the best region */
      v = vout[vi_best];
      BM_vert_select_set(bm, v, true);
  
      if (ese.ele) {
        BM_select_history_store(bm, v);
      }
  
      /* splice all others back together */
      if (vout_len > 2) {
        for (i = 2; i < vout_len; i++) {
          BM_vert_splice(bm, vout[1], vout[i]);
        }
      }
  
      if (do_fill) {
        /* match extrude vert-order */
        BM_edge_create(bm, vout[1], vout[0], NULL, BM_CREATE_NOP);
      }
  
      MEM_freeN(vout);
  
      return OPERATOR_FINISHED;
    }
  
    if (!e_best) {
      return OPERATOR_CANCELLED;
    }
  
    /* *** Execute the split! *** */
    /* unlike edge split, for single vertex split we only use the operator in one of the cases
     * but both allocate fill */
  
    {
      BMVert *v_rip;
      BMLoop *larr[2];
      int larr_len = 0;
  
      /* rip two adjacent edges */
      if (BM_edge_is_boundary(e_best) || BM_vert_face_count_is_equal(v, 2)) {
        /* Don't run the edge split operator in this case */
  
        l = BM_edge_vert_share_loop(e_best->l, v);
        larr[larr_len] = l;
        larr_len++;
  
        /* only tag for face-fill (we don't call the operator) */
        if (BM_edge_is_boundary(e_best)) {
          BM_elem_flag_enable(e_best, BM_ELEM_TAG);
        }
        else {
          BM_elem_flag_enable(l->e, BM_ELEM_TAG);
          BM_elem_flag_enable(l->prev->e, BM_ELEM_TAG);
        }
      }
      else {
        if (BM_edge_is_manifold(e_best)) {
          BMLoop *l_iter, *l_first;
          l_iter = l_first = e_best->l;
          do {
            larr[larr_len] = BM_edge_vert_share_loop(l_iter, v);
  
            if (do_fill) {
              /* Only needed when filling...
               * Also, we never want to tag best edge,
               * that one won't change during split. See T44618. */
              if (larr[larr_len]->e == e_best) {
                BM_elem_flag_enable(larr[larr_len]->prev->e, BM_ELEM_TAG);
              }
              else {
                BM_elem_flag_enable(larr[larr_len]->e, BM_ELEM_TAG);
              }
            }
            larr_len++;
          } while ((l_iter = l_iter->radial_next) != l_first);
        }
        else {
          /* looks like there are no split edges, we could just return/report-error? - Campbell */
        }
      }
  
      /* keep directly before edgesplit */
      if (do_fill) {
        fill_uloop_pairs = edbm_tagged_loop_pairs_to_fill(bm);
      }
  
      if (larr_len) {
        v_rip = BM_face_loop_separate_multi(bm, larr, larr_len);
      }
      else {
        v_rip = NULL;
      }
  
      if (v_rip) {
        BM_vert_select_set(bm, v_rip, true);
      }
      else {
        if (fill_uloop_pairs) {
          MEM_freeN(fill_uloop_pairs);
        }
        return OPERATOR_CANCELLED;
      }
    }
  
    {
      /* --- select which vert --- */
      BMVert *v_best = NULL;
      float l_corner_co[3];
  
      dist_sq = FLT_MAX;
      BM_ITER_MESH (v, &iter, bm, BM_VERTS_OF_MESH) {
        if (BM_elem_flag_test(v, BM_ELEM_SELECT)) {
          /* disable by default, re-enable winner at end */
          BM_vert_select_set(bm, v, false);
          BM_select_history_remove(bm, v);
  
          BM_ITER_ELEM (l, &liter, v, BM_LOOPS_OF_VERT) {
  
            /* check if v_best is null in the _rare_ case there are numeric issues */
            edbm_calc_loop_co(l, l_corner_co);
            d = edbm_rip_edgedist_squared(
                region, projectMat, l->v->co, l_corner_co, fmval, INSET_DEFAULT);
            if ((v_best == NULL) || (d < dist_sq)) {
              v_best = v;
              dist_sq = d;
            }
          }
        }
      }
  
      if (v_best) {
        BM_vert_select_set(bm, v_best, true);
        if (ese.ele) {
          BM_select_history_store(bm, v_best);
        }
      }
    }
  
    if (do_fill && fill_uloop_pairs) {
      edbm_tagged_loop_pairs_do_fill_faces(bm, fill_uloop_pairs);
      MEM_freeN(fill_uloop_pairs);
    }
  
    if (totvert_orig == bm->totvert) {
      return OPERATOR_CANCELLED;
    }
  
    return OPERATOR_FINISHED;
  }
  
  /**
   * This is the main edge ripping function
   */
  static int edbm_rip_invoke__edge(bContext *C, const wmEvent *event, Object *obedit, bool do_fill)
  {
    UnorderedLoopPair *fill_uloop_pairs = NULL;
    ARegion *region = CTX_wm_region(C);
    RegionView3D *rv3d = CTX_wm_region_view3d(C);
    BMEditMesh *em = BKE_editmesh_from_object(obedit);
    BMesh *bm = em->bm;
    BMIter iter, eiter;
    BMLoop *l;
    BMEdge *e_best;
    BMVert *v;
    const int totedge_orig = bm->totedge;
    float projectMat[4][4], fmval[3] = {event->mval[0], event->mval[1]};
  
    EdgeLoopPair *eloop_pairs;
  
    ED_view3d_ob_project_mat_get(rv3d, obedit, projectMat);
  
    /* important this runs on the original selection, before tampering with tagging */
    eloop_pairs = edbm_ripsel_looptag_helper(bm);
  
    /* expand edge selection */
    BM_ITER_MESH (v, &iter, bm, BM_VERTS_OF_MESH) {
      BMEdge *e;
      bool all_manifold;
      int totedge_manifold; /* manifold, visible edges */
      int i;
  
      e_best = NULL;
      i = 0;
      totedge_manifold = 0;
      all_manifold = true;
      BM_ITER_ELEM (e, &eiter, v, BM_EDGES_OF_VERT) {
  
        if (!BM_edge_is_wire(e) && !BM_elem_flag_test(e, BM_ELEM_HIDDEN)) {
          /* important to check selection rather than tag here
           * else we get feedback loop */
          if (BM_elem_flag_test(e, BM_ELEM_SELECT)) {
            e_best = e;
            i++;
            /* Tag the edge verts so we know which verts to rip */
            BM_elem_flag_enable(e->v1, BM_ELEM_TAG);
            BM_elem_flag_enable(e->v2, BM_ELEM_TAG);
          }
          totedge_manifold++;
        }
  
        /** #BM_vert_other_disk_edge has no hidden checks so don't check hidden here */
        if ((all_manifold == true) && (BM_edge_is_manifold(e) == false)) {
          all_manifold = false;
        }
      }
  
      /* single edge, extend */
      if (i == 1 && e_best->l) {
        /* note: if the case of 3 edges has one change in loop stepping,
         * if this becomes more involved we may be better off splitting
         * the 3 edge case into its own else-if branch */
        if ((totedge_manifold == 4 || totedge_manifold == 3) || (all_manifold == false)) {
          BMLoop *l_a = e_best->l;
          BMLoop *l_b = l_a->radial_next;
  
          /* find the best face to follow, this way the edge won't point away from
           * the mouse when there are more than 4 (takes the shortest face fan around) */
          l = (edbm_rip_edge_side_measure(e_best, l_a, region, projectMat, fmval) <
               edbm_rip_edge_side_measure(e_best, l_b, region, projectMat, fmval)) ?
                  l_a :
                  l_b;
  
          l = BM_loop_other_edge_loop(l, v);
          /* Important edge is manifold else we can be attempting to split off
           * a fan that don't budge, not crashing but adds duplicate edge. */
          if (BM_edge_is_manifold(l->e)) {
            l = l->radial_next;
  
            if (totedge_manifold != 3) {
              l = BM_loop_other_edge_loop(l, v);
            }
  
            if (l) {
              BLI_assert(!BM_elem_flag_test(l->e, BM_ELEM_TAG));
              BM_elem_flag_enable(l->e, BM_ELEM_TAG);
            }
          }
        }
        else {
          e = BM_vert_other_disk_edge(v, e_best);
  
          if (e) {
            BLI_assert(!BM_elem_flag_test(e, BM_ELEM_TAG));
            BM_elem_flag_enable(e, BM_ELEM_TAG);
          }
        }
      }
    }
  
    /* keep directly before edgesplit */
    if (do_fill) {
      fill_uloop_pairs = edbm_tagged_loop_pairs_to_fill(bm);
    }
  
    BM_mesh_edgesplit(em->bm, true, true, true);
  
    /* note: the output of the bmesh operator is ignored, since we built
     * the contiguous loop pairs to split already, its possible that some
     * edge did not split even though it was tagged which would not work
     * as expected (but not crash), however there are checks to ensure
     * tagged edges will split. So far its not been an issue. */
    edbm_ripsel_deselect_helper(bm, eloop_pairs, region, projectMat, fmval);
    MEM_freeN(eloop_pairs);
  
    /* deselect loose verts */
    BM_mesh_select_mode_clean_ex(bm, SCE_SELECT_EDGE);
  
    if (do_fill && fill_uloop_pairs) {
      edbm_tagged_loop_pairs_do_fill_faces(bm, fill_uloop_pairs);
      MEM_freeN(fill_uloop_pairs);
    }
  
    if (totedge_orig == bm->totedge) {
      return OPERATOR_CANCELLED;
    }
  
    BM_select_history_validate(bm);
  
    return OPERATOR_FINISHED;
  }
  
  /* based on mouse cursor position, it defines how is being ripped */
  static int edbm_rip_invoke(bContext *C, wmOperator *op, const wmEvent *event)
  {
    ViewLayer *view_layer = CTX_data_view_layer(C);
    uint objects_len = 0;
    Object **objects = BKE_view_layer_array_from_objects_in_edit_mode_unique_data(
        view_layer, CTX_wm_view3d(C), &objects_len);
    const bool do_fill = RNA_boolean_get(op->ptr, "use_fill");
  
    bool no_vertex_selected = true;
    bool error_face_selected = true;
    bool error_disconnected_vertices = true;
    bool error_rip_failed = true;
  
    for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
      Object *obedit = objects[ob_index];
      BMEditMesh *em = BKE_editmesh_from_object(obedit);
  
      BMesh *bm = em->bm;
      BMIter iter;
      BMEdge *e;
      const bool singlesel = (bm->totvertsel == 1 && bm->totedgesel == 0 && bm->totfacesel == 0);
      int ret;
  
      if (em->bm->totvertsel == 0) {
        continue;
      }
      no_vertex_selected = false;
  
      /* running in face mode hardly makes sense, so convert to region loop and rip */
      if (bm->totfacesel) {
        /* highly nifty but hard to support since the operator can fail and we're left
         * with modified selection */
        // WM_operator_name_call(C, "MESH_OT_region_to_loop", WM_OP_INVOKE_DEFAULT, NULL);
        continue;
      }
      error_face_selected = false;
  
      /* we could support this, but not for now */
      if ((bm->totvertsel > 1) && (bm->totedgesel == 0)) {
        continue;
      }
      error_disconnected_vertices = false;
  
      /* note on selection:
       * When calling edge split we operate on tagged edges rather than selected
       * this is important because the edges to operate on are extended by one,
       * but the selection is left alone.
       *
       * After calling edge split - the duplicated edges have the same selection state as the
       * original, so all we do is de-select the far side from the mouse and we have a
       * useful selection for grabbing.
       */
  
      BM_custom_loop_normals_to_vector_layer(bm);
  
      /* BM_ELEM_SELECT --> BM_ELEM_TAG */
      BM_ITER_MESH (e, &iter, bm, BM_EDGES_OF_MESH) {
        BM_elem_flag_set(e, BM_ELEM_TAG, BM_elem_flag_test(e, BM_ELEM_SELECT));
      }
  
      /* split 2 main parts of this operator out into vertex and edge ripping */
      if (singlesel) {
        ret = edbm_rip_invoke__vert(C, event, obedit, do_fill);
      }
      else {
        ret = edbm_rip_invoke__edge(C, event, obedit, do_fill);
      }
  
      if (ret != OPERATOR_FINISHED) {
        continue;
      }
  
      BM_custom_loop_normals_from_vector_layer(bm, false);
  
      BLI_assert(singlesel ? (bm->totvertsel > 0) : (bm->totedgesel > 0));
  
      if (bm->totvertsel == 0) {
        continue;
      }
      error_rip_failed = false;
  
      EDBM_update_generic(obedit->data, true, true);
    }
  
    MEM_freeN(objects);
  
    if (no_vertex_selected) {
      /* Ignore it. */
      return OPERATOR_CANCELLED;
    }
    if (error_face_selected) {
      BKE_report(op->reports, RPT_ERROR, "Cannot rip selected faces");
      return OPERATOR_CANCELLED;
    }
    if (error_disconnected_vertices) {
      BKE_report(op->reports, RPT_ERROR, "Cannot rip multiple disconnected vertices");
      return OPERATOR_CANCELLED;
    }
    if (error_rip_failed) {
      BKE_report(op->reports, RPT_ERROR, "Rip failed");
      return OPERATOR_CANCELLED;
    }
    /* No errors, everything went fine. */
    return OPERATOR_FINISHED;
  }
  
  void MESH_OT_rip(wmOperatorType *ot)
  {
    /* identifiers */
    ot->name = "Rip";
    ot->idname = "MESH_OT_rip";
    ot->description = "Disconnect vertex or edges from connected geometry";
  
    /* api callbacks */
    ot->invoke = edbm_rip_invoke;
    ot->poll = EDBM_view3d_poll;
  
    /* flags */
    ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
  
    /* to give to transform */
    Transform_Properties(ot, P_PROPORTIONAL | P_MIRROR_DUMMY);
    RNA_def_boolean(ot->srna, "use_fill", false, "Fill", "Fill the ripped region");
  }
  