uvedit_smart_stitch.c

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/*
 * 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.
 */
 
#include <math.h>
#include <stdlib.h>
#include <string.h>
 
#include "MEM_guardedalloc.h"
 
#include "DNA_meshdata_types.h"
#include "DNA_object_types.h"
#include "DNA_scene_types.h"
 
#include "BLI_ghash.h"
#include "BLI_math.h"
#include "BLI_math_vector.h"
#include "BLI_string.h"
#include "BLI_utildefines.h"
 
#include "BLT_translation.h"
 
#include "BKE_context.h"
#include "BKE_customdata.h"
#include "BKE_editmesh.h"
#include "BKE_layer.h"
#include "BKE_mesh_mapping.h"
 
#include "DEG_depsgraph.h"
 
#include "UI_interface.h"
 
#include "ED_mesh.h"
#include "ED_screen.h"
#include "ED_space_api.h"
#include "ED_uvedit.h"
 
#include "GPU_batch.h"
#include "GPU_state.h"
 
#include "RNA_access.h"
#include "RNA_define.h"
 
#include "WM_api.h"
#include "WM_types.h"
 
#include "UI_resources.h"
#include "UI_view2d.h"
 
#include "uvedit_intern.h"
 
/* ********************** smart stitch operator *********************** */
 
/* object that stores display data for previewing before confirming stitching */
typedef struct StitchPreviewer {
  /* here we'll store the preview triangle indices of the mesh */
  float *preview_polys;
  /* uvs per polygon. */
  uint *uvs_per_polygon;
  /*number of preview polygons */
  uint num_polys;
  /* preview data. These will be either the previewed vertices or edges
   * depending on stitch mode settings */
  float *preview_stitchable;
  float *preview_unstitchable;
  /* here we'll store the number of elements to be drawn */
  uint num_stitchable;
  uint num_unstitchable;
  uint preview_uvs;
  /* ...and here we'll store the static island triangles */
  float *static_tris;
  uint num_static_tris;
} StitchPreviewer;
 
struct IslandStitchData;
 
typedef struct IslandStitchData {
  /* rotation can be used only for edges, for vertices there is no such notion */
  float rotation;
  float rotation_neg;
  float translation[2];
  /* Used for rotation, the island will rotate around this point */
  float medianPoint[2];
  int numOfElements;
  int num_rot_elements;
  int num_rot_elements_neg;
  /* flag to remember if island has been added for preview */
  char addedForPreview;
  /* flag an island to be considered for determining static island */
  char stitchableCandidate;
  /* if edge rotation is used, flag so that vertex rotation is not used */
  bool use_edge_rotation;
} IslandStitchData;
 
/* just for averaging UVs */
typedef struct UVVertAverage {
  float uv[2];
  ushort count;
} UVVertAverage;
 
typedef struct UvEdge {
  uint uv1;
  uint uv2;
  uchar flag;
  UvElement *element;
  struct UvEdge *next;
  struct UvEdge *first;
} UvEdge;
 
/* stitch state object */
typedef struct StitchState {
  float aspect;
  /* object for editmesh */
  Object *obedit;
  /* editmesh, cached for use in modal handler */
  BMEditMesh *em;
 
  /* element map for getting info about uv connectivity */
  UvElementMap *element_map;
  /* edge container */
  UvEdge *uvedges;
  /* container of first of a group of coincident uvs, these will be operated upon */
  UvElement **uvs;
  /* maps uvelements to their first coincident uv */
  int *map;
  /* 2D normals per uv to calculate rotation for snapping */
  float *normals;
  /* edge storage */
  UvEdge *edges;
  /* hash for quick lookup of edges */
  GHash *edge_hash;
  /* which islands to stop at (to make active) when pressing 'I' */
  bool *island_is_stitchable;
 
  /* count of separate uvs and edges */
  int total_separate_edges;
  int total_separate_uvs;
  /* hold selection related information */
  void **selection_stack;
  int selection_size;
 
  /* store number of primitives per face so that we can allocate the active island buffer later */
  uint *tris_per_island;
  /* preview data */
  StitchPreviewer *stitch_preview;
} StitchState;
 
/* Stitch state container. */
typedef struct StitchStateContainer {
  /* clear seams of stitched edges after stitch */
  bool clear_seams;
  /* use limit flag */
  bool use_limit;
  /* limit to operator, same as original operator */
  float limit_dist;
  /* snap uv islands together during stitching */
  bool snap_islands;
  /* stitch at midpoints or at islands */
  bool midpoints;
  /* vert or edge mode used for stitching */
  char mode;
  /* handle for drawing */
  void *draw_handle;
  /* island that stays in place */
  int static_island;
 
  /* Objects and states are aligned. */
  int objects_len;
  Object **objects;
  StitchState **states;
 
  int active_object_index;
} StitchStateContainer;
 
typedef struct PreviewPosition {
  int data_position;
  int polycount_position;
} PreviewPosition;
/*
 * defines for UvElement/UcEdge flags
 */
#define STITCH_SELECTED 1
#define STITCH_STITCHABLE 2
#define STITCH_PROCESSED 4
#define STITCH_BOUNDARY 8
#define STITCH_STITCHABLE_CANDIDATE 16
 
#define STITCH_NO_PREVIEW -1
 
enum StitchModes {
  STITCH_VERT,
  STITCH_EDGE,
};
 
typedef struct UvElementID {
  int faceIndex;
  int elementIndex;
} UvElementID;
 
typedef struct StitchStateInit {
  int uv_selected_count;
  UvElementID *to_select;
} StitchStateInit;
 
/* constructor */
static StitchPreviewer *stitch_preview_init(void)
{
  StitchPreviewer *stitch_preview;
 
  stitch_preview = MEM_mallocN(sizeof(StitchPreviewer), "stitch_previewer");
  stitch_preview->preview_polys = NULL;
  stitch_preview->preview_stitchable = NULL;
  stitch_preview->preview_unstitchable = NULL;
  stitch_preview->uvs_per_polygon = NULL;
 
  stitch_preview->preview_uvs = 0;
  stitch_preview->num_polys = 0;
  stitch_preview->num_stitchable = 0;
  stitch_preview->num_unstitchable = 0;
 
  stitch_preview->static_tris = NULL;
 
  stitch_preview->num_static_tris = 0;
 
  return stitch_preview;
}
 
/* destructor...yeah this should be C++ :) */
static void stitch_preview_delete(StitchPreviewer *stitch_preview)
{
  if (stitch_preview) {
    if (stitch_preview->preview_polys) {
      MEM_freeN(stitch_preview->preview_polys);
      stitch_preview->preview_polys = NULL;
    }
    if (stitch_preview->uvs_per_polygon) {
      MEM_freeN(stitch_preview->uvs_per_polygon);
      stitch_preview->uvs_per_polygon = NULL;
    }
    if (stitch_preview->preview_stitchable) {
      MEM_freeN(stitch_preview->preview_stitchable);
      stitch_preview->preview_stitchable = NULL;
    }
    if (stitch_preview->preview_unstitchable) {
      MEM_freeN(stitch_preview->preview_unstitchable);
      stitch_preview->preview_unstitchable = NULL;
    }
    if (stitch_preview->static_tris) {
      MEM_freeN(stitch_preview->static_tris);
      stitch_preview->static_tris = NULL;
    }
    MEM_freeN(stitch_preview);
  }
}
 
/* This function updates the header of the UV editor when the stitch tool updates its settings */
static void stitch_update_header(StitchStateContainer *ssc, bContext *C)
{
  const char *str = TIP_(
      "Mode(TAB) %s, "
      "(S)nap %s, "
      "(M)idpoints %s, "
      "(L)imit %.2f (Alt Wheel adjust) %s, "
      "Switch (I)sland, "
      "shift select vertices");
 
  char msg[UI_MAX_DRAW_STR];
  ScrArea *area = CTX_wm_area(C);
 
  if (area) {
    BLI_snprintf(msg,
                 sizeof(msg),
                 str,
                 ssc->mode == STITCH_VERT ? TIP_("Vertex") : TIP_("Edge"),
                 WM_bool_as_string(ssc->snap_islands),
                 WM_bool_as_string(ssc->midpoints),
                 ssc->limit_dist,
                 WM_bool_as_string(ssc->use_limit));
 
    ED_workspace_status_text(C, msg);
  }
}
 
static int getNumOfIslandUvs(UvElementMap *elementMap, int island)
{
  if (island == elementMap->totalIslands - 1) {
    return elementMap->totalUVs - elementMap->islandIndices[island];
  }
  return elementMap->islandIndices[island + 1] - elementMap->islandIndices[island];
}
 
static void stitch_uv_rotate(const float mat[2][2],
                             const float medianPoint[2],
                             float uv[2],
                             float aspect)
{
  float uv_rotation_result[2];
 
  uv[1] /= aspect;
 
  sub_v2_v2(uv, medianPoint);
  mul_v2_m2v2(uv_rotation_result, mat, uv);
  add_v2_v2v2(uv, uv_rotation_result, medianPoint);
 
  uv[1] *= aspect;
}
 
/* check if two uvelements are stitchable.
 * This should only operate on -different- separate UvElements */
static bool stitch_check_uvs_stitchable(UvElement *element,
                                        UvElement *element_iter,
                                        StitchStateContainer *ssc,
                                        StitchState *state)
{
  BMesh *bm = state->em->bm;
  float limit;
 
  if (element_iter == element) {
    return 0;
  }
 
  limit = ssc->limit_dist;
 
  if (ssc->use_limit) {
    MLoopUV *luv, *luv_iter;
    BMLoop *l;
 
    l = element->l;
    luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
    l = element_iter->l;
    luv_iter = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
    if (fabsf(luv->uv[0] - luv_iter->uv[0]) < limit &&
        fabsf(luv->uv[1] - luv_iter->uv[1]) < limit) {
      return 1;
    }
    return 0;
  }
  return 1;
}
 
static bool stitch_check_edges_stitchable(UvEdge *edge,
                                          UvEdge *edge_iter,
                                          StitchStateContainer *ssc,
                                          StitchState *state)
{
  BMesh *bm = state->em->bm;
  float limit;
 
  if (edge_iter == edge) {
    return 0;
  }
 
  limit = ssc->limit_dist;
 
  if (ssc->use_limit) {
    BMLoop *l;
    MLoopUV *luv_orig1, *luv_iter1;
    MLoopUV *luv_orig2, *luv_iter2;
 
    l = state->uvs[edge->uv1]->l;
    luv_orig1 = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
    l = state->uvs[edge_iter->uv1]->l;
    luv_iter1 = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
    l = state->uvs[edge->uv2]->l;
    luv_orig2 = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
    l = state->uvs[edge_iter->uv2]->l;
    luv_iter2 = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
    if (fabsf(luv_orig1->uv[0] - luv_iter1->uv[0]) < limit &&
        fabsf(luv_orig1->uv[1] - luv_iter1->uv[1]) < limit &&
        fabsf(luv_orig2->uv[0] - luv_iter2->uv[0]) < limit &&
        fabsf(luv_orig2->uv[1] - luv_iter2->uv[1]) < limit) {
      return 1;
    }
    return 0;
  }
  return 1;
}
 
static bool stitch_check_uvs_state_stitchable(UvElement *element,
                                              UvElement *element_iter,
                                              StitchStateContainer *ssc,
                                              StitchState *state)
{
  if ((ssc->snap_islands && element->island == element_iter->island) ||
      (!ssc->midpoints && element->island == element_iter->island)) {
    return 0;
  }
 
  return stitch_check_uvs_stitchable(element, element_iter, ssc, state);
}
 
static bool stitch_check_edges_state_stitchable(UvEdge *edge,
                                                UvEdge *edge_iter,
                                                StitchStateContainer *ssc,
                                                StitchState *state)
{
  if ((ssc->snap_islands && edge->element->island == edge_iter->element->island) ||
      (!ssc->midpoints && edge->element->island == edge_iter->element->island)) {
    return 0;
  }
 
  return stitch_check_edges_stitchable(edge, edge_iter, ssc, state);
}
 
/* calculate snapping for islands */
static void stitch_calculate_island_snapping(StitchState *state,
                                             PreviewPosition *preview_position,
                                             StitchPreviewer *preview,
                                             IslandStitchData *island_stitch_data,
                                             int final)
{
  BMesh *bm = state->em->bm;
  int i;
  UvElement *element;
 
  for (i = 0; i < state->element_map->totalIslands; i++) {
    if (island_stitch_data[i].addedForPreview) {
      int numOfIslandUVs = 0, j;
      int totelem = island_stitch_data[i].num_rot_elements_neg +
                    island_stitch_data[i].num_rot_elements;
      float rotation;
      float rotation_mat[2][2];
 
      /* check to avoid divide by 0 */
      if (island_stitch_data[i].num_rot_elements > 1) {
        island_stitch_data[i].rotation /= island_stitch_data[i].num_rot_elements;
      }
 
      if (island_stitch_data[i].num_rot_elements_neg > 1) {
        island_stitch_data[i].rotation_neg /= island_stitch_data[i].num_rot_elements_neg;
      }
 
      if (island_stitch_data[i].numOfElements > 1) {
        island_stitch_data[i].medianPoint[0] /= island_stitch_data[i].numOfElements;
        island_stitch_data[i].medianPoint[1] /= island_stitch_data[i].numOfElements;
 
        island_stitch_data[i].translation[0] /= island_stitch_data[i].numOfElements;
        island_stitch_data[i].translation[1] /= island_stitch_data[i].numOfElements;
      }
 
      island_stitch_data[i].medianPoint[1] /= state->aspect;
      if ((island_stitch_data[i].rotation + island_stitch_data[i].rotation_neg < (float)M_PI_2) ||
          island_stitch_data[i].num_rot_elements == 0 ||
          island_stitch_data[i].num_rot_elements_neg == 0) {
        rotation = (island_stitch_data[i].rotation * island_stitch_data[i].num_rot_elements -
                    island_stitch_data[i].rotation_neg *
                        island_stitch_data[i].num_rot_elements_neg) /
                   totelem;
      }
      else {
        rotation = (island_stitch_data[i].rotation * island_stitch_data[i].num_rot_elements +
                    (2.0f * (float)M_PI - island_stitch_data[i].rotation_neg) *
                        island_stitch_data[i].num_rot_elements_neg) /
                   totelem;
      }
 
      angle_to_mat2(rotation_mat, rotation);
      numOfIslandUVs = getNumOfIslandUvs(state->element_map, i);
      element = &state->element_map->buf[state->element_map->islandIndices[i]];
      for (j = 0; j < numOfIslandUVs; j++, element++) {
        /* stitchable uvs have already been processed, don't process */
        if (!(element->flag & STITCH_PROCESSED)) {
          MLoopUV *luv;
          BMLoop *l;
 
          l = element->l;
          luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
          if (final) {
 
            stitch_uv_rotate(
                rotation_mat, island_stitch_data[i].medianPoint, luv->uv, state->aspect);
 
            add_v2_v2(luv->uv, island_stitch_data[i].translation);
          }
 
          else {
 
            int face_preview_pos =
                preview_position[BM_elem_index_get(element->l->f)].data_position;
 
            stitch_uv_rotate(rotation_mat,
                             island_stitch_data[i].medianPoint,
                             preview->preview_polys + face_preview_pos +
                                 2 * element->loop_of_poly_index,
                             state->aspect);
 
            add_v2_v2(preview->preview_polys + face_preview_pos + 2 * element->loop_of_poly_index,
                      island_stitch_data[i].translation);
          }
        }
        /* cleanup */
        element->flag &= STITCH_SELECTED;
      }
    }
  }
}
 
static void stitch_island_calculate_edge_rotation(UvEdge *edge,
                                                  StitchStateContainer *ssc,
                                                  StitchState *state,
                                                  UVVertAverage *uv_average,
                                                  const uint *uvfinal_map,
                                                  IslandStitchData *island_stitch_data)
{
  BMesh *bm = state->em->bm;
  UvElement *element1, *element2;
  float uv1[2], uv2[2];
  float edgecos, edgesin;
  int index1, index2;
  float rotation;
  MLoopUV *luv1, *luv2;
 
  element1 = state->uvs[edge->uv1];
  element2 = state->uvs[edge->uv2];
 
  luv1 = CustomData_bmesh_get(&bm->ldata, element1->l->head.data, CD_MLOOPUV);
  luv2 = CustomData_bmesh_get(&bm->ldata, element2->l->head.data, CD_MLOOPUV);
 
  if (ssc->mode == STITCH_VERT) {
    index1 = uvfinal_map[element1 - state->element_map->buf];
    index2 = uvfinal_map[element2 - state->element_map->buf];
  }
  else {
    index1 = edge->uv1;
    index2 = edge->uv2;
  }
  /* the idea here is to take the directions of the edges and find the rotation between
   * final and initial direction. This, using inner and outer vector products,
   * gives the angle. Directions are differences so... */
  uv1[0] = luv2->uv[0] - luv1->uv[0];
  uv1[1] = luv2->uv[1] - luv1->uv[1];
 
  uv1[1] /= state->aspect;
 
  uv2[0] = uv_average[index2].uv[0] - uv_average[index1].uv[0];
  uv2[1] = uv_average[index2].uv[1] - uv_average[index1].uv[1];
 
  uv2[1] /= state->aspect;
 
  normalize_v2(uv1);
  normalize_v2(uv2);
 
  edgecos = dot_v2v2(uv1, uv2);
  edgesin = cross_v2v2(uv1, uv2);
  rotation = acosf(max_ff(-1.0f, min_ff(1.0f, edgecos)));
 
  if (edgesin > 0.0f) {
    island_stitch_data[element1->island].num_rot_elements++;
    island_stitch_data[element1->island].rotation += rotation;
  }
  else {
    island_stitch_data[element1->island].num_rot_elements_neg++;
    island_stitch_data[element1->island].rotation_neg += rotation;
  }
}
 
static void stitch_island_calculate_vert_rotation(UvElement *element,
                                                  StitchStateContainer *ssc,
                                                  StitchState *state,
                                                  IslandStitchData *island_stitch_data)
{
  float edgecos = 1.0f, edgesin = 0.0f;
  int index;
  UvElement *element_iter;
  float rotation = 0, rotation_neg = 0;
  int rot_elem = 0, rot_elem_neg = 0;
  BMLoop *l;
 
  if (element->island == ssc->static_island && !ssc->midpoints) {
    return;
  }
 
  l = element->l;
 
  index = BM_elem_index_get(l->v);
 
  element_iter = state->element_map->vert[index];
 
  for (; element_iter; element_iter = element_iter->next) {
    if (element_iter->separate &&
        stitch_check_uvs_state_stitchable(element, element_iter, ssc, state)) {
      int index_tmp1, index_tmp2;
      float normal[2];
 
      /* only calculate rotation against static island uv verts */
      if (!ssc->midpoints && element_iter->island != ssc->static_island) {
        continue;
      }
 
      index_tmp1 = element_iter - state->element_map->buf;
      index_tmp1 = state->map[index_tmp1];
      index_tmp2 = element - state->element_map->buf;
      index_tmp2 = state->map[index_tmp2];
 
      negate_v2_v2(normal, state->normals + index_tmp2 * 2);
      edgecos = dot_v2v2(normal, state->normals + index_tmp1 * 2);
      edgesin = cross_v2v2(normal, state->normals + index_tmp1 * 2);
      if (edgesin > 0.0f) {
        rotation += acosf(max_ff(-1.0f, min_ff(1.0f, edgecos)));
        rot_elem++;
      }
      else {
        rotation_neg += acosf(max_ff(-1.0f, min_ff(1.0f, edgecos)));
        rot_elem_neg++;
      }
    }
  }
 
  if (ssc->midpoints) {
    rotation /= 2.0f;
    rotation_neg /= 2.0f;
  }
  island_stitch_data[element->island].num_rot_elements += rot_elem;
  island_stitch_data[element->island].rotation += rotation;
  island_stitch_data[element->island].num_rot_elements_neg += rot_elem_neg;
  island_stitch_data[element->island].rotation_neg += rotation_neg;
}
 
static void state_delete(StitchState *state)
{
  if (state) {
    if (state->island_is_stitchable) {
      MEM_freeN(state->island_is_stitchable);
    }
    if (state->element_map) {
      BM_uv_element_map_free(state->element_map);
    }
    if (state->uvs) {
      MEM_freeN(state->uvs);
    }
    if (state->selection_stack) {
      MEM_freeN(state->selection_stack);
    }
    if (state->tris_per_island) {
      MEM_freeN(state->tris_per_island);
    }
    if (state->map) {
      MEM_freeN(state->map);
    }
    if (state->normals) {
      MEM_freeN(state->normals);
    }
    if (state->edges) {
      MEM_freeN(state->edges);
    }
    if (state->stitch_preview) {
      stitch_preview_delete(state->stitch_preview);
    }
    if (state->edge_hash) {
      BLI_ghash_free(state->edge_hash, NULL, NULL);
    }
    MEM_freeN(state);
  }
}
 
static void state_delete_all(StitchStateContainer *ssc)
{
  if (ssc) {
    for (uint ob_index = 0; ob_index < ssc->objects_len; ob_index++) {
      state_delete(ssc->states[ob_index]);
    }
    MEM_freeN(ssc->states);
    MEM_freeN(ssc->objects);
    MEM_freeN(ssc);
  }
}
 
static void stitch_uv_edge_generate_linked_edges(GHash *edge_hash, StitchState *state)
{
  UvEdge *edges = state->edges;
  const int *map = state->map;
  UvElementMap *element_map = state->element_map;
  UvElement *first_element = element_map->buf;
  int i;
 
  for (i = 0; i < state->total_separate_edges; i++) {
    UvEdge *edge = edges + i;
 
    if (edge->first) {
      continue;
    }
 
    /* only boundary edges can be stitched. Yes. Sorry about that :p */
    if (edge->flag & STITCH_BOUNDARY) {
      UvElement *element1 = state->uvs[edge->uv1];
      UvElement *element2 = state->uvs[edge->uv2];
 
      /* Now iterate through all faces and try to find edges sharing the same vertices */
      UvElement *iter1 = element_map->vert[BM_elem_index_get(element1->l->v)];
      UvEdge *last_set = edge;
      int elemindex2 = BM_elem_index_get(element2->l->v);
 
      edge->first = edge;
 
      for (; iter1; iter1 = iter1->next) {
        UvElement *iter2 = NULL;
 
        /* check to see if other vertex of edge belongs to same vertex as */
        if (BM_elem_index_get(iter1->l->next->v) == elemindex2) {
          iter2 = BM_uv_element_get(element_map, iter1->l->f, iter1->l->next);
        }
        else if (BM_elem_index_get(iter1->l->prev->v) == elemindex2) {
          iter2 = BM_uv_element_get(element_map, iter1->l->f, iter1->l->prev);
        }
 
        if (iter2) {
          int index1 = map[iter1 - first_element];
          int index2 = map[iter2 - first_element];
          UvEdge edgetmp;
          UvEdge *edge2, *eiter;
          bool valid = true;
 
          /* make sure the indices are well behaved */
          if (index1 > index2) {
            SWAP(int, index1, index2);
          }
 
          edgetmp.uv1 = index1;
          edgetmp.uv2 = index2;
 
          /* get the edge from the hash */
          edge2 = BLI_ghash_lookup(edge_hash, &edgetmp);
 
          /* more iteration to make sure non-manifold case is handled nicely */
          for (eiter = edge; eiter; eiter = eiter->next) {
            if (edge2 == eiter) {
              valid = false;
              break;
            }
          }
 
          if (valid) {
            /* here I am taking care of non manifold case, assuming more than two matching edges.
             * I am not too sure we want this though */
            last_set->next = edge2;
            last_set = edge2;
            /* set first, similarly to uv elements.
             * Now we can iterate among common edges easily */
            edge2->first = edge;
          }
        }
      }
    }
    else {
      /* so stitchability code works */
      edge->first = edge;
    }
  }
}
 
/* checks for remote uvs that may be stitched with a certain uv, flags them if stitchable. */
static void determine_uv_stitchability(UvElement *element,
                                       StitchStateContainer *ssc,
                                       StitchState *state,
                                       IslandStitchData *island_stitch_data)
{
  int vert_index;
  UvElement *element_iter;
  BMLoop *l;
 
  l = element->l;
 
  vert_index = BM_elem_index_get(l->v);
  element_iter = state->element_map->vert[vert_index];
 
  for (; element_iter; element_iter = element_iter->next) {
    if (element_iter->separate) {
      if (stitch_check_uvs_stitchable(element, element_iter, ssc, state)) {
        island_stitch_data[element_iter->island].stitchableCandidate = 1;
        island_stitch_data[element->island].stitchableCandidate = 1;
        element->flag |= STITCH_STITCHABLE_CANDIDATE;
      }
    }
  }
}
 
static void determine_uv_edge_stitchability(UvEdge *edge,
                                            StitchStateContainer *ssc,
                                            StitchState *state,
                                            IslandStitchData *island_stitch_data)
{
  UvEdge *edge_iter = edge->first;
 
  for (; edge_iter; edge_iter = edge_iter->next) {
    if (stitch_check_edges_stitchable(edge, edge_iter, ssc, state)) {
      island_stitch_data[edge_iter->element->island].stitchableCandidate = 1;
      island_stitch_data[edge->element->island].stitchableCandidate = 1;
      edge->flag |= STITCH_STITCHABLE_CANDIDATE;
    }
  }
}
 
/* set preview buffer position of UV face in editface->tmp.l */
static void stitch_set_face_preview_buffer_position(BMFace *efa,
                                                    StitchPreviewer *preview,
                                                    PreviewPosition *preview_position)
{
  int index = BM_elem_index_get(efa);
 
  if (preview_position[index].data_position == STITCH_NO_PREVIEW) {
    preview_position[index].data_position = preview->preview_uvs * 2;
    preview_position[index].polycount_position = preview->num_polys++;
    preview->preview_uvs += efa->len;
  }
}
 
/* setup face preview for all coincident uvs and their faces */
static void stitch_setup_face_preview_for_uv_group(UvElement *element,
                                                   StitchStateContainer *ssc,
                                                   StitchState *state,
                                                   IslandStitchData *island_stitch_data,
                                                   PreviewPosition *preview_position)
{
  StitchPreviewer *preview = state->stitch_preview;
 
  /* static island does not change so returning immediately */
  if (ssc->snap_islands && !ssc->midpoints && ssc->static_island == element->island) {
    return;
  }
 
  if (ssc->snap_islands) {
    island_stitch_data[element->island].addedForPreview = 1;
  }
 
  do {
    stitch_set_face_preview_buffer_position(element->l->f, preview, preview_position);
    element = element->next;
  } while (element && !element->separate);
}
 
/* checks if uvs are indeed stitchable and registers so that they can be shown in preview */
static void stitch_validate_uv_stitchability(UvElement *element,
                                             StitchStateContainer *ssc,
                                             StitchState *state,
                                             IslandStitchData *island_stitch_data,
                                             PreviewPosition *preview_position)
{
  StitchPreviewer *preview = state->stitch_preview;
 
  /* If not the active object, then it's unstitchable */
  if (ssc->states[ssc->active_object_index] != state) {
    preview->num_unstitchable++;
    return;
  }
 
  UvElement *element_iter;
  int vert_index;
  BMLoop *l;
 
  l = element->l;
 
  vert_index = BM_elem_index_get(l->v);
 
  element_iter = state->element_map->vert[vert_index];
 
  for (; element_iter; element_iter = element_iter->next) {
    if (element_iter->separate) {
      if (element_iter == element) {
        continue;
      }
      if (stitch_check_uvs_state_stitchable(element, element_iter, ssc, state)) {
        if ((element_iter->island == ssc->static_island) ||
            (element->island == ssc->static_island)) {
          element->flag |= STITCH_STITCHABLE;
          preview->num_stitchable++;
          stitch_setup_face_preview_for_uv_group(
              element, ssc, state, island_stitch_data, preview_position);
          return;
        }
      }
    }
  }
 
  /* this can happen if the uvs to be stitched are not on a stitchable island */
  if (!(element->flag & STITCH_STITCHABLE)) {
    preview->num_unstitchable++;
  }
}
 
static void stitch_validate_edge_stitchability(UvEdge *edge,
                                               StitchStateContainer *ssc,
                                               StitchState *state,
                                               IslandStitchData *island_stitch_data,
                                               PreviewPosition *preview_position)
{
  StitchPreviewer *preview = state->stitch_preview;
 
  /* If not the active object, then it's unstitchable */
  if (ssc->states[ssc->active_object_index] != state) {
    preview->num_unstitchable++;
    return;
  }
 
  UvEdge *edge_iter = edge->first;
 
  for (; edge_iter; edge_iter = edge_iter->next) {
    if (edge_iter == edge) {
      continue;
    }
    if (stitch_check_edges_state_stitchable(edge, edge_iter, ssc, state)) {
      if ((edge_iter->element->island == ssc->static_island) ||
          (edge->element->island == ssc->static_island)) {
        edge->flag |= STITCH_STITCHABLE;
        preview->num_stitchable++;
        stitch_setup_face_preview_for_uv_group(
            state->uvs[edge->uv1], ssc, state, island_stitch_data, preview_position);
        stitch_setup_face_preview_for_uv_group(
            state->uvs[edge->uv2], ssc, state, island_stitch_data, preview_position);
        return;
      }
    }
  }
 
  /* this can happen if the uvs to be stitched are not on a stitchable island */
  if (!(edge->flag & STITCH_STITCHABLE)) {
    preview->num_unstitchable++;
  }
}
 
static void stitch_propagate_uv_final_position(Scene *scene,
                                               UvElement *element,
                                               int index,
                                               PreviewPosition *preview_position,
                                               UVVertAverage *final_position,
                                               StitchStateContainer *ssc,
                                               StitchState *state,
                                               const bool final)
{
  BMesh *bm = state->em->bm;
  StitchPreviewer *preview = state->stitch_preview;
 
  const int cd_loop_uv_offset = CustomData_get_offset(&bm->ldata, CD_MLOOPUV);
 
  if (element->flag & STITCH_STITCHABLE) {
    UvElement *element_iter = element;
    /* propagate to coincident uvs */
    do {
      BMLoop *l;
      MLoopUV *luv;
 
      l = element_iter->l;
      luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
      element_iter->flag |= STITCH_PROCESSED;
      /* either flush to preview or to the MTFace, if final */
      if (final) {
        copy_v2_v2(luv->uv, final_position[index].uv);
 
        uvedit_uv_select_enable(scene, state->em, l, false, cd_loop_uv_offset);
      }
      else {
        int face_preview_pos =
            preview_position[BM_elem_index_get(element_iter->l->f)].data_position;
        if (face_preview_pos != STITCH_NO_PREVIEW) {
          copy_v2_v2(preview->preview_polys + face_preview_pos +
                         2 * element_iter->loop_of_poly_index,
                     final_position[index].uv);
        }
      }
 
      /* end of calculations, keep only the selection flag */
      if ((!ssc->snap_islands) ||
          ((!ssc->midpoints) && (element_iter->island == ssc->static_island))) {
        element_iter->flag &= STITCH_SELECTED;
      }
 
      element_iter = element_iter->next;
    } while (element_iter && !element_iter->separate);
  }
}
 
/* main processing function. It calculates preview and final positions. */
static int stitch_process_data(StitchStateContainer *ssc,
                               StitchState *state,
                               Scene *scene,
                               int final)
{
  int i;
  StitchPreviewer *preview;
  IslandStitchData *island_stitch_data = NULL;
  int previous_island = ssc->static_island;
  BMesh *bm = state->em->bm;
  BMFace *efa;
  BMIter iter;
  UVVertAverage *final_position = NULL;
  bool is_active_state = (state == ssc->states[ssc->active_object_index]);
 
  char stitch_midpoints = ssc->midpoints;
  /* used to map uv indices to uvaverage indices for selection */
  uint *uvfinal_map = NULL;
  /* per face preview position in preview buffer */
  PreviewPosition *preview_position = NULL;
 
  /* cleanup previous preview */
  stitch_preview_delete(state->stitch_preview);
  preview = state->stitch_preview = stitch_preview_init();
  if (preview == NULL) {
    return 0;
  }
 
  preview_position = MEM_mallocN(bm->totface * sizeof(*preview_position),
                                 "stitch_face_preview_position");
  /* each face holds its position in the preview buffer in tmp. -1 is uninitialized */
  for (i = 0; i < bm->totface; i++) {
    preview_position[i].data_position = STITCH_NO_PREVIEW;
  }
 
  island_stitch_data = MEM_callocN(sizeof(*island_stitch_data) * state->element_map->totalIslands,
                                   "stitch_island_data");
  if (!island_stitch_data) {
    return 0;
  }
 
  /* store indices to editVerts and Faces. May be unneeded but ensuring anyway */
  BM_mesh_elem_index_ensure(bm, BM_VERT | BM_FACE);
 
  /****************************************
   * First determine stitchability of uvs *
   ****************************************/
 
  for (i = 0; i < state->selection_size; i++) {
    if (ssc->mode == STITCH_VERT) {
      UvElement *element = (UvElement *)state->selection_stack[i];
      determine_uv_stitchability(element, ssc, state, island_stitch_data);
    }
    else {
      UvEdge *edge = (UvEdge *)state->selection_stack[i];
      determine_uv_edge_stitchability(edge, ssc, state, island_stitch_data);
    }
  }
 
  /* remember stitchable candidates as places the 'I' button  */
  /* will stop at.                                            */
  for (int island_idx = 0; island_idx < state->element_map->totalIslands; island_idx++) {
    state->island_is_stitchable[island_idx] = island_stitch_data[island_idx].stitchableCandidate ?
                                                  true :
                                                  false;
  }
 
  if (is_active_state) {
    /* set static island to one that is added for preview */
    ssc->static_island %= state->element_map->totalIslands;
    while (!(island_stitch_data[ssc->static_island].stitchableCandidate)) {
      ssc->static_island++;
      ssc->static_island %= state->element_map->totalIslands;
      /* this is entirely possible if for example limit stitching
       * with no stitchable verts or no selection */
      if (ssc->static_island == previous_island) {
        break;
      }
    }
  }
 
  for (i = 0; i < state->selection_size; i++) {
    if (ssc->mode == STITCH_VERT) {
      UvElement *element = (UvElement *)state->selection_stack[i];
      if (element->flag & STITCH_STITCHABLE_CANDIDATE) {
        element->flag &= ~STITCH_STITCHABLE_CANDIDATE;
        stitch_validate_uv_stitchability(
            element, ssc, state, island_stitch_data, preview_position);
      }
      else {
        /* add to preview for unstitchable */
        preview->num_unstitchable++;
      }
    }
    else {
      UvEdge *edge = (UvEdge *)state->selection_stack[i];
      if (edge->flag & STITCH_STITCHABLE_CANDIDATE) {
        edge->flag &= ~STITCH_STITCHABLE_CANDIDATE;
        stitch_validate_edge_stitchability(edge, ssc, state, island_stitch_data, preview_position);
      }
      else {
        preview->num_unstitchable++;
      }
    }
  }
 
  /*********************************************************************
   * Setup the stitchable & unstitchable preview buffers and fill      *
   * them with the appropriate data                                    *
   *********************************************************************/
  if (!final) {
    BMLoop *l;
    MLoopUV *luv;
    int stitchBufferIndex = 0, unstitchBufferIndex = 0;
    int preview_size = (ssc->mode == STITCH_VERT) ? 2 : 4;
    /* initialize the preview buffers */
    preview->preview_stitchable = (float *)MEM_mallocN(
        preview->num_stitchable * sizeof(float) * preview_size, "stitch_preview_stitchable_data");
    preview->preview_unstitchable = (float *)MEM_mallocN(preview->num_unstitchable *
                                                             sizeof(float) * preview_size,
                                                         "stitch_preview_unstitchable_data");
 
    /* will cause cancel and freeing of all data structures so OK */
    if (!preview->preview_stitchable || !preview->preview_unstitchable) {
      return 0;
    }
 
    /* fill the appropriate preview buffers */
    if (ssc->mode == STITCH_VERT) {
      for (i = 0; i < state->total_separate_uvs; i++) {
        UvElement *element = (UvElement *)state->uvs[i];
        if (element->flag & STITCH_STITCHABLE) {
          l = element->l;
          luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
          copy_v2_v2(&preview->preview_stitchable[stitchBufferIndex * 2], luv->uv);
 
          stitchBufferIndex++;
        }
        else if (element->flag & STITCH_SELECTED) {
          l = element->l;
          luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
          copy_v2_v2(&preview->preview_unstitchable[unstitchBufferIndex * 2], luv->uv);
          unstitchBufferIndex++;
        }
      }
    }
    else {
      for (i = 0; i < state->total_separate_edges; i++) {
        UvEdge *edge = state->edges + i;
        UvElement *element1 = state->uvs[edge->uv1];
        UvElement *element2 = state->uvs[edge->uv2];
 
        if (edge->flag & STITCH_STITCHABLE) {
          l = element1->l;
          luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
          copy_v2_v2(&preview->preview_stitchable[stitchBufferIndex * 4], luv->uv);
 
          l = element2->l;
          luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
          copy_v2_v2(&preview->preview_stitchable[stitchBufferIndex * 4 + 2], luv->uv);
 
          stitchBufferIndex++;
          BLI_assert(stitchBufferIndex <= preview->num_stitchable);
        }
        else if (edge->flag & STITCH_SELECTED) {
          l = element1->l;
          luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
          copy_v2_v2(&preview->preview_unstitchable[unstitchBufferIndex * 4], luv->uv);
 
          l = element2->l;
          luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
          copy_v2_v2(&preview->preview_unstitchable[unstitchBufferIndex * 4 + 2], luv->uv);
 
          unstitchBufferIndex++;
          BLI_assert(unstitchBufferIndex <= preview->num_unstitchable);
        }
      }
    }
  }
 
  if (ssc->states[ssc->active_object_index] != state) {
    /* This is not the active object/state, exit here */
    MEM_freeN(island_stitch_data);
    MEM_freeN(preview_position);
    return 1;
  }
 
  /****************************************
   * Setup preview for stitchable islands *
   ****************************************/
  if (ssc->snap_islands) {
    for (i = 0; i < state->element_map->totalIslands; i++) {
      if (island_stitch_data[i].addedForPreview) {
        int numOfIslandUVs = 0, j;
        UvElement *element;
        numOfIslandUVs = getNumOfIslandUvs(state->element_map, i);
        element = &state->element_map->buf[state->element_map->islandIndices[i]];
        for (j = 0; j < numOfIslandUVs; j++, element++) {
          stitch_set_face_preview_buffer_position(element->l->f, preview, preview_position);
        }
      }
    }
  }
 
  /*********************************************************************
   * Setup the remaining preview buffers and fill them with the        *
   * appropriate data                                                  *
   *********************************************************************/
  if (!final) {
    BMIter liter;
    BMLoop *l;
    MLoopUV *luv;
    uint buffer_index = 0;
 
    /* initialize the preview buffers */
    preview->preview_polys = MEM_mallocN(sizeof(float[2]) * preview->preview_uvs,
                                         "tri_uv_stitch_prev");
    preview->uvs_per_polygon = MEM_mallocN(sizeof(*preview->uvs_per_polygon) * preview->num_polys,
                                           "tri_uv_stitch_prev");
 
    preview->static_tris = MEM_mallocN(
        (sizeof(float[6]) * state->tris_per_island[ssc->static_island]),
        "static_island_preview_tris");
 
    preview->num_static_tris = state->tris_per_island[ssc->static_island];
    /* will cause cancel and freeing of all data structures so OK */
    if (!preview->preview_polys) {
      return 0;
    }
 
    /* copy data from MLoopUVs to the preview display buffers */
    BM_ITER_MESH (efa, &iter, bm, BM_FACES_OF_MESH) {
      /* just to test if face was added for processing.
       * uvs of unselected vertices will return NULL */
      UvElement *element = BM_uv_element_get(state->element_map, efa, BM_FACE_FIRST_LOOP(efa));
 
      if (element) {
        int numoftris = efa->len - 2;
        int index = BM_elem_index_get(efa);
        int face_preview_pos = preview_position[index].data_position;
        if (face_preview_pos != STITCH_NO_PREVIEW) {
          preview->uvs_per_polygon[preview_position[index].polycount_position] = efa->len;
          BM_ITER_ELEM_INDEX (l, &liter, efa, BM_LOOPS_OF_FACE, i) {
            luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
            copy_v2_v2(preview->preview_polys + face_preview_pos + i * 2, luv->uv);
          }
        }
 
        /* if this is the static_island on the active object */
        if (element->island == ssc->static_island) {
          BMLoop *fl = BM_FACE_FIRST_LOOP(efa);
          MLoopUV *fuv = CustomData_bmesh_get(&bm->ldata, fl->head.data, CD_MLOOPUV);
 
          BM_ITER_ELEM_INDEX (l, &liter, efa, BM_LOOPS_OF_FACE, i) {
            if (i < numoftris) {
              /* using next since the first uv is already accounted for */
              BMLoop *lnext = l->next;
              MLoopUV *luvnext = CustomData_bmesh_get(
                  &bm->ldata, lnext->next->head.data, CD_MLOOPUV);
              luv = CustomData_bmesh_get(&bm->ldata, lnext->head.data, CD_MLOOPUV);
 
              memcpy(preview->static_tris + buffer_index, fuv->uv, sizeof(float[2]));
              memcpy(preview->static_tris + buffer_index + 2, luv->uv, sizeof(float[2]));
              memcpy(preview->static_tris + buffer_index + 4, luvnext->uv, sizeof(float[2]));
              buffer_index += 6;
            }
            else {
              break;
            }
          }
        }
      }
    }
  }
 
  /******************************************************
   * Here we calculate the final coordinates of the uvs *
   ******************************************************/
 
  if (ssc->mode == STITCH_VERT) {
    final_position = MEM_callocN(state->selection_size * sizeof(*final_position),
                                 "stitch_uv_average");
    uvfinal_map = MEM_mallocN(state->element_map->totalUVs * sizeof(*uvfinal_map),
                              "stitch_uv_final_map");
  }
  else {
    final_position = MEM_callocN(state->total_separate_uvs * sizeof(*final_position),
                                 "stitch_uv_average");
  }
 
  /* first pass, calculate final position for stitchable uvs of the static island */
  for (i = 0; i < state->selection_size; i++) {
    if (ssc->mode == STITCH_VERT) {
      UvElement *element = state->selection_stack[i];
 
      if (element->flag & STITCH_STITCHABLE) {
        BMLoop *l;
        MLoopUV *luv;
        UvElement *element_iter;
 
        l = element->l;
        luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
        uvfinal_map[element - state->element_map->buf] = i;
 
        copy_v2_v2(final_position[i].uv, luv->uv);
        final_position[i].count = 1;
 
        if (ssc->snap_islands && element->island == ssc->static_island && !stitch_midpoints) {
          continue;
        }
 
        element_iter = state->element_map->vert[BM_elem_index_get(l->v)];
 
        for (; element_iter; element_iter = element_iter->next) {
          if (element_iter->separate) {
            if (stitch_check_uvs_state_stitchable(element, element_iter, ssc, state)) {
              l = element_iter->l;
              luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
              if (stitch_midpoints) {
                add_v2_v2(final_position[i].uv, luv->uv);
                final_position[i].count++;
              }
              else if (element_iter->island == ssc->static_island) {
                /* if multiple uvs on the static island exist,
                 * last checked remains. to disambiguate we need to limit or use
                 * edge stitch */
                copy_v2_v2(final_position[i].uv, luv->uv);
              }
            }
          }
        }
      }
      if (stitch_midpoints) {
        final_position[i].uv[0] /= final_position[i].count;
        final_position[i].uv[1] /= final_position[i].count;
      }
    }
    else {
      UvEdge *edge = state->selection_stack[i];
 
      if (edge->flag & STITCH_STITCHABLE) {
        MLoopUV *luv2, *luv1;
        BMLoop *l;
        UvEdge *edge_iter;
 
        l = state->uvs[edge->uv1]->l;
        luv1 = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
        l = state->uvs[edge->uv2]->l;
        luv2 = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
        copy_v2_v2(final_position[edge->uv1].uv, luv1->uv);
        copy_v2_v2(final_position[edge->uv2].uv, luv2->uv);
        final_position[edge->uv1].count = 1;
        final_position[edge->uv2].count = 1;
 
        state->uvs[edge->uv1]->flag |= STITCH_STITCHABLE;
        state->uvs[edge->uv2]->flag |= STITCH_STITCHABLE;
 
        if (ssc->snap_islands && edge->element->island == ssc->static_island &&
            !stitch_midpoints) {
          continue;
        }
 
        for (edge_iter = edge->first; edge_iter; edge_iter = edge_iter->next) {
          if (stitch_check_edges_state_stitchable(edge, edge_iter, ssc, state)) {
            l = state->uvs[edge_iter->uv1]->l;
            luv1 = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
            l = state->uvs[edge_iter->uv2]->l;
            luv2 = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
            if (stitch_midpoints) {
              add_v2_v2(final_position[edge->uv1].uv, luv1->uv);
              final_position[edge->uv1].count++;
              add_v2_v2(final_position[edge->uv2].uv, luv2->uv);
              final_position[edge->uv2].count++;
            }
            else if (edge_iter->element->island == ssc->static_island) {
              copy_v2_v2(final_position[edge->uv1].uv, luv1->uv);
              copy_v2_v2(final_position[edge->uv2].uv, luv2->uv);
            }
          }
        }
      }
    }
  }
 
  /* take mean position here.
   * For edge case, this can't be done inside the loop for shared uvverts */
  if (ssc->mode == STITCH_EDGE && stitch_midpoints) {
    for (i = 0; i < state->total_separate_uvs; i++) {
      final_position[i].uv[0] /= final_position[i].count;
      final_position[i].uv[1] /= final_position[i].count;
    }
  }
 
  /* second pass, calculate island rotation and translation before modifying any uvs */
  if (ssc->snap_islands) {
    if (ssc->mode == STITCH_VERT) {
      for (i = 0; i < state->selection_size; i++) {
        UvElement *element = state->selection_stack[i];
 
        if (element->flag & STITCH_STITCHABLE) {
          BMLoop *l;
          MLoopUV *luv;
 
          l = element->l;
          luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
          /* accumulate each islands' translation from stitchable elements.
           * It is important to do here because in final pass MTFaces
           * get modified and result is zero. */
          island_stitch_data[element->island].translation[0] += final_position[i].uv[0] -
                                                                luv->uv[0];
          island_stitch_data[element->island].translation[1] += final_position[i].uv[1] -
                                                                luv->uv[1];
          island_stitch_data[element->island].medianPoint[0] += luv->uv[0];
          island_stitch_data[element->island].medianPoint[1] += luv->uv[1];
          island_stitch_data[element->island].numOfElements++;
        }
      }
 
      /* only calculate rotation when an edge has been fully selected */
      for (i = 0; i < state->total_separate_edges; i++) {
        UvEdge *edge = state->edges + i;
        if ((edge->flag & STITCH_BOUNDARY) && (state->uvs[edge->uv1]->flag & STITCH_STITCHABLE) &&
            (state->uvs[edge->uv2]->flag & STITCH_STITCHABLE)) {
          stitch_island_calculate_edge_rotation(
              edge, ssc, state, final_position, uvfinal_map, island_stitch_data);
          island_stitch_data[state->uvs[edge->uv1]->island].use_edge_rotation = true;
        }
      }
 
      /* clear seams of stitched edges */
      if (final && ssc->clear_seams) {
        for (i = 0; i < state->total_separate_edges; i++) {
          UvEdge *edge = state->edges + i;
          if ((state->uvs[edge->uv1]->flag & STITCH_STITCHABLE) &&
              (state->uvs[edge->uv2]->flag & STITCH_STITCHABLE)) {
            BM_elem_flag_disable(edge->element->l->e, BM_ELEM_SEAM);
          }
        }
      }
 
      for (i = 0; i < state->selection_size; i++) {
        UvElement *element = state->selection_stack[i];
        if (!island_stitch_data[element->island].use_edge_rotation) {
          if (element->flag & STITCH_STITCHABLE) {
            stitch_island_calculate_vert_rotation(element, ssc, state, island_stitch_data);
          }
        }
      }
    }
    else {
      for (i = 0; i < state->total_separate_uvs; i++) {
        UvElement *element = state->uvs[i];
 
        if (element->flag & STITCH_STITCHABLE) {
          BMLoop *l;
          MLoopUV *luv;
 
          l = element->l;
          luv = CustomData_bmesh_get(&bm->ldata, l->head.data, CD_MLOOPUV);
 
          /* accumulate each islands' translation from stitchable elements.
           * it is important to do here because in final pass MTFaces
           * get modified and result is zero. */
          island_stitch_data[element->island].translation[0] += final_position[i].uv[0] -
                                                                luv->uv[0];
          island_stitch_data[element->island].translation[1] += final_position[i].uv[1] -
                                                                luv->uv[1];
          island_stitch_data[element->island].medianPoint[0] += luv->uv[0];
          island_stitch_data[element->island].medianPoint[1] += luv->uv[1];
          island_stitch_data[element->island].numOfElements++;
        }
      }
 
      for (i = 0; i < state->selection_size; i++) {
        UvEdge *edge = state->selection_stack[i];
 
        if (edge->flag & STITCH_STITCHABLE) {
          stitch_island_calculate_edge_rotation(
              edge, ssc, state, final_position, NULL, island_stitch_data);
          island_stitch_data[state->uvs[edge->uv1]->island].use_edge_rotation = true;
        }
      }
 
      /* clear seams of stitched edges */
      if (final && ssc->clear_seams) {
        for (i = 0; i < state->selection_size; i++) {
          UvEdge *edge = state->selection_stack[i];
          if (edge->flag & STITCH_STITCHABLE) {
            BM_elem_flag_disable(edge->element->l->e, BM_ELEM_SEAM);
          }
        }
      }
    }
  }
 
  /* third pass, propagate changes to coincident uvs */
  for (i = 0; i < state->selection_size; i++) {
    if (ssc->mode == STITCH_VERT) {
      UvElement *element = state->selection_stack[i];
 
      stitch_propagate_uv_final_position(
          scene, element, i, preview_position, final_position, ssc, state, final);
    }
    else {
      UvEdge *edge = state->selection_stack[i];
 
      stitch_propagate_uv_final_position(scene,
                                         state->uvs[edge->uv1],
                                         edge->uv1,
                                         preview_position,
                                         final_position,
                                         ssc,
                                         state,
                                         final);
      stitch_propagate_uv_final_position(scene,
                                         state->uvs[edge->uv2],
                                         edge->uv2,
                                         preview_position,
                                         final_position,
                                         ssc,
                                         state,
                                         final);
 
      edge->flag &= (STITCH_SELECTED | STITCH_BOUNDARY);
    }
  }
 
  /* final pass, calculate Island translation/rotation if needed */
  if (ssc->snap_islands) {
    stitch_calculate_island_snapping(state, preview_position, preview, island_stitch_data, final);
  }
 
  MEM_freeN(final_position);
  if (ssc->mode == STITCH_VERT) {
    MEM_freeN(uvfinal_map);
  }
  MEM_freeN(island_stitch_data);
  MEM_freeN(preview_position);
 
  return 1;
}
 
static int stitch_process_data_all(StitchStateContainer *ssc, Scene *scene, int final)
{
  for (uint ob_index = 0; ob_index < ssc->objects_len; ob_index++) {
    if (!stitch_process_data(ssc, ssc->states[ob_index], scene, final)) {
      return 0;
    }
  }
 
  return 1;
}
 
/* Stitch hash initialization functions */
static uint uv_edge_hash(const void *key)
{
  const UvEdge *edge = key;
  return (BLI_ghashutil_uinthash(edge->uv2) + BLI_ghashutil_uinthash(edge->uv1));
}
 
static bool uv_edge_compare(const void *a, const void *b)
{
  const UvEdge *edge1 = a;
  const UvEdge *edge2 = b;
 
  if ((edge1->uv1 == edge2->uv1) && (edge1->uv2 == edge2->uv2)) {
    return 0;
  }
  return 1;
}
 
/* select all common edges */
static void stitch_select_edge(UvEdge *edge, StitchState *state, int always_select)
{
  UvEdge *eiter;
  UvEdge **selection_stack = (UvEdge **)state->selection_stack;
 
  for (eiter = edge->first; eiter; eiter = eiter->next) {
    if (eiter->flag & STITCH_SELECTED) {
      int i;
      if (always_select) {
        continue;
      }
 
      eiter->flag &= ~STITCH_SELECTED;
      for (i = 0; i < state->selection_size; i++) {
        if (selection_stack[i] == eiter) {
          (state->selection_size)--;
          selection_stack[i] = selection_stack[state->selection_size];
          break;
        }
      }
    }
    else {
      eiter->flag |= STITCH_SELECTED;
      selection_stack[state->selection_size++] = eiter;
    }
  }
}
 
/* Select all common uvs */
static void stitch_select_uv(UvElement *element, StitchState *state, int always_select)
{
  BMLoop *l;
  UvElement *element_iter;
  UvElement **selection_stack = (UvElement **)state->selection_stack;
 
  l = element->l;
 
  element_iter = state->element_map->vert[BM_elem_index_get(l->v)];
  /* first deselect all common uvs */
  for (; element_iter; element_iter = element_iter->next) {
    if (element_iter->separate) {
      /* only separators go to selection */
      if (element_iter->flag & STITCH_SELECTED) {
        int i;
        if (always_select) {
          continue;
        }
 
        element_iter->flag &= ~STITCH_SELECTED;
        for (i = 0; i < state->selection_size; i++) {
          if (selection_stack[i] == element_iter) {
            (state->selection_size)--;
            selection_stack[i] = selection_stack[state->selection_size];
            break;
          }
        }
      }
      else {
        element_iter->flag |= STITCH_SELECTED;
        selection_stack[state->selection_size++] = element_iter;
      }
    }
  }
}
 
static void stitch_set_selection_mode(StitchState *state, const char from_stitch_mode)
{
  void **old_selection_stack = state->selection_stack;
  int old_selection_size = state->selection_size;
  state->selection_size = 0;
 
  if (from_stitch_mode == STITCH_VERT) {
    int i;
    state->selection_stack = MEM_mallocN(state->total_separate_edges *
                                             sizeof(*state->selection_stack),
                                         "stitch_new_edge_selection_stack");
 
    /* check if both elements of an edge are selected */
    for (i = 0; i < state->total_separate_edges; i++) {
      UvEdge *edge = state->edges + i;
      UvElement *element1 = state->uvs[edge->uv1];
      UvElement *element2 = state->uvs[edge->uv2];
 
      if ((element1->flag & STITCH_SELECTED) && (element2->flag & STITCH_SELECTED)) {
        stitch_select_edge(edge, state, true);
      }
    }
 
    /* unselect selected uvelements */
    for (i = 0; i < old_selection_size; i++) {
      UvElement *element = old_selection_stack[i];
 
      element->flag &= ~STITCH_SELECTED;
    }
  }
  else {
    int i;
    state->selection_stack = MEM_mallocN(state->total_separate_uvs *
                                             sizeof(*state->selection_stack),
                                         "stitch_new_vert_selection_stack");
 
    for (i = 0; i < old_selection_size; i++) {
      UvEdge *edge = old_selection_stack[i];
      UvElement *element1 = state->uvs[edge->uv1];
      UvElement *element2 = state->uvs[edge->uv2];
 
      stitch_select_uv(element1, state, true);
      stitch_select_uv(element2, state, true);
 
      edge->flag &= ~STITCH_SELECTED;
    }
  }
  MEM_freeN(old_selection_stack);
}
 
static void stitch_switch_selection_mode_all(StitchStateContainer *ssc)
{
  for (uint ob_index = 0; ob_index < ssc->objects_len; ob_index++) {
    stitch_set_selection_mode(ssc->states[ob_index], ssc->mode);
  }
 
  if (ssc->mode == STITCH_VERT) {
    ssc->mode = STITCH_EDGE;
  }
  else {
    ssc->mode = STITCH_VERT;
  }
}
 
static void stitch_calculate_edge_normal(BMEditMesh *em, UvEdge *edge, float *normal, float aspect)
{
  BMLoop *l1 = edge->element->l;
  MLoopUV *luv1, *luv2;
  float tangent[2];
 
  luv1 = CustomData_bmesh_get(&em->bm->ldata, l1->head.data, CD_MLOOPUV);
  luv2 = CustomData_bmesh_get(&em->bm->ldata, l1->next->head.data, CD_MLOOPUV);
 
  sub_v2_v2v2(tangent, luv2->uv, luv1->uv);
 
  tangent[1] /= aspect;
 
  normal[0] = tangent[1];
  normal[1] = -tangent[0];
 
  normalize_v2(normal);
}
 
static void stitch_draw_vbo(GPUVertBuf *vbo, GPUPrimType prim_type, const float col[4])
{
  GPUBatch *batch = GPU_batch_create_ex(prim_type, vbo, NULL, GPU_BATCH_OWNS_VBO);
  GPU_batch_program_set_builtin(batch, GPU_SHADER_2D_UNIFORM_COLOR);
  GPU_batch_uniform_4fv(batch, "color", col);
  GPU_batch_draw(batch);
  GPU_batch_discard(batch);
}
 
/* TODO make things pretier : store batches inside StitchPreviewer instead of the bare verts pos */
static void stitch_draw(const bContext *UNUSED(C), ARegion *UNUSED(region), void *arg)
{
 
  StitchStateContainer *ssc = (StitchStateContainer *)arg;
 
  for (uint ob_index = 0; ob_index < ssc->objects_len; ob_index++) {
    int j, index = 0;
    uint num_line = 0, num_tri, tri_idx = 0, line_idx = 0;
    StitchState *state = ssc->states[ob_index];
    StitchPreviewer *stitch_preview = state->stitch_preview;
    GPUVertBuf *vbo, *vbo_line;
    float col[4];
 
    static GPUVertFormat format = {0};
    static uint pos_id;
    if (format.attr_len == 0) {
      pos_id = GPU_vertformat_attr_add(&format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
    }
 
    GPU_blend(GPU_BLEND_ALPHA);
 
    /* Static Tris */
    if (stitch_preview->static_tris) {
      UI_GetThemeColor4fv(TH_STITCH_PREVIEW_ACTIVE, col);
      vbo = GPU_vertbuf_create_with_format(&format);
      GPU_vertbuf_data_alloc(vbo, stitch_preview->num_static_tris * 3);
      for (int i = 0; i < stitch_preview->num_static_tris * 3; i++) {
        GPU_vertbuf_attr_set(vbo, pos_id, i, &stitch_preview->static_tris[i * 2]);
      }
      stitch_draw_vbo(vbo, GPU_PRIM_TRIS, col);
    }
 
    /* Preview Polys */
    if (stitch_preview->preview_polys) {
      for (int i = 0; i < stitch_preview->num_polys; i++) {
        num_line += stitch_preview->uvs_per_polygon[i];
      }
 
      num_tri = num_line - 2 * stitch_preview->num_polys;
 
      /* we need to convert the polys into triangles / lines */
      vbo = GPU_vertbuf_create_with_format(&format);
      vbo_line = GPU_vertbuf_create_with_format(&format);
 
      GPU_vertbuf_data_alloc(vbo, num_tri * 3);
      GPU_vertbuf_data_alloc(vbo_line, num_line * 2);
 
      for (int i = 0; i < stitch_preview->num_polys; i++) {
        BLI_assert(stitch_preview->uvs_per_polygon[i] >= 3);
 
        /* Start line */
        GPU_vertbuf_attr_set(vbo_line, pos_id, line_idx++, &stitch_preview->preview_polys[index]);
        GPU_vertbuf_attr_set(
            vbo_line, pos_id, line_idx++, &stitch_preview->preview_polys[index + 2]);
 
        for (j = 1; j < stitch_preview->uvs_per_polygon[i] - 1; j++) {
          GPU_vertbuf_attr_set(vbo, pos_id, tri_idx++, &stitch_preview->preview_polys[index]);
          GPU_vertbuf_attr_set(
              vbo, pos_id, tri_idx++, &stitch_preview->preview_polys[index + (j + 0) * 2]);
          GPU_vertbuf_attr_set(
              vbo, pos_id, tri_idx++, &stitch_preview->preview_polys[index + (j + 1) * 2]);
 
          GPU_vertbuf_attr_set(
              vbo_line, pos_id, line_idx++, &stitch_preview->preview_polys[index + (j + 0) * 2]);
          GPU_vertbuf_attr_set(
              vbo_line, pos_id, line_idx++, &stitch_preview->preview_polys[index + (j + 1) * 2]);
        }
 
        /* Closing line */
        GPU_vertbuf_attr_set(vbo_line, pos_id, line_idx++, &stitch_preview->preview_polys[index]);
        /* j = uvs_per_polygon[i] - 1*/
        GPU_vertbuf_attr_set(
            vbo_line, pos_id, line_idx++, &stitch_preview->preview_polys[index + j * 2]);
 
        index += stitch_preview->uvs_per_polygon[i] * 2;
      }
 
      UI_GetThemeColor4fv(TH_STITCH_PREVIEW_FACE, col);
      stitch_draw_vbo(vbo, GPU_PRIM_TRIS, col);
      UI_GetThemeColor4fv(TH_STITCH_PREVIEW_EDGE, col);
      stitch_draw_vbo(vbo_line, GPU_PRIM_LINES, col);
    }
 
    GPU_blend(GPU_BLEND_NONE);
 
    /* draw stitch vert/lines preview */
    if (ssc->mode == STITCH_VERT) {
      GPU_point_size(UI_GetThemeValuef(TH_VERTEX_SIZE) * 2.0f);
 
      UI_GetThemeColor4fv(TH_STITCH_PREVIEW_STITCHABLE, col);
      vbo = GPU_vertbuf_create_with_format(&format);
      GPU_vertbuf_data_alloc(vbo, stitch_preview->num_stitchable);
      for (int i = 0; i < stitch_preview->num_stitchable; i++) {
        GPU_vertbuf_attr_set(vbo, pos_id, i, &stitch_preview->preview_stitchable[i * 2]);
      }
      stitch_draw_vbo(vbo, GPU_PRIM_POINTS, col);
 
      UI_GetThemeColor4fv(TH_STITCH_PREVIEW_UNSTITCHABLE, col);
      vbo = GPU_vertbuf_create_with_format(&format);
      GPU_vertbuf_data_alloc(vbo, stitch_preview->num_unstitchable);
      for (int i = 0; i < stitch_preview->num_unstitchable; i++) {
        GPU_vertbuf_attr_set(vbo, pos_id, i, &stitch_preview->preview_unstitchable[i * 2]);
      }
      stitch_draw_vbo(vbo, GPU_PRIM_POINTS, col);
    }
    else {
      UI_GetThemeColor4fv(TH_STITCH_PREVIEW_STITCHABLE, col);
      vbo = GPU_vertbuf_create_with_format(&format);
      GPU_vertbuf_data_alloc(vbo, stitch_preview->num_stitchable * 2);
      for (int i = 0; i < stitch_preview->num_stitchable * 2; i++) {
        GPU_vertbuf_attr_set(vbo, pos_id, i, &stitch_preview->preview_stitchable[i * 2]);
      }
      stitch_draw_vbo(vbo, GPU_PRIM_LINES, col);
 
      UI_GetThemeColor4fv(TH_STITCH_PREVIEW_UNSTITCHABLE, col);
      vbo = GPU_vertbuf_create_with_format(&format);
      GPU_vertbuf_data_alloc(vbo, stitch_preview->num_unstitchable * 2);
      for (int i = 0; i < stitch_preview->num_unstitchable * 2; i++) {
        GPU_vertbuf_attr_set(vbo, pos_id, i, &stitch_preview->preview_unstitchable[i * 2]);
      }
      stitch_draw_vbo(vbo, GPU_PRIM_LINES, col);
    }
  }
}
 
static UvEdge *uv_edge_get(BMLoop *l, StitchState *state)
{
  UvEdge tmp_edge;
 
  UvElement *element1 = BM_uv_element_get(state->element_map, l->f, l);
  UvElement *element2 = BM_uv_element_get(state->element_map, l->f, l->next);
 
  int uv1 = state->map[element1 - state->element_map->buf];
  int uv2 = state->map[element2 - state->element_map->buf];
 
  if (uv1 < uv2) {
    tmp_edge.uv1 = uv1;
    tmp_edge.uv2 = uv2;
  }
  else {
    tmp_edge.uv1 = uv2;
    tmp_edge.uv2 = uv1;
  }
 
  return BLI_ghash_lookup(state->edge_hash, &tmp_edge);
}
 
static StitchState *stitch_init(bContext *C,
                                wmOperator *op,
                                StitchStateContainer *ssc,
                                Object *obedit,
                                StitchStateInit *state_init)
{
  /* for fast edge lookup... */
  GHash *edge_hash;
  /* ...and actual edge storage */
  UvEdge *edges;
  int total_edges;
  /* maps uvelements to their first coincident uv */
  int *map;
  int counter = 0, i;
  BMFace *efa;
  BMLoop *l;
  BMIter iter, liter;
  GHashIterator gh_iter;
  UvEdge *all_edges;
  StitchState *state;
  Scene *scene = CTX_data_scene(C);
  ToolSettings *ts = scene->toolsettings;
  float aspx, aspy;
 
  BMEditMesh *em = BKE_editmesh_from_object(obedit);
  const int cd_loop_uv_offset = CustomData_get_offset(&em->bm->ldata, CD_MLOOPUV);
 
  state = MEM_callocN(sizeof(StitchState), "stitch state obj");
 
  /* initialize state */
  state->obedit = obedit;
  state->em = em;
 
  /* Workaround for sync-select & face-select mode which implies all selected faces are detached,
   * for stitch this isn't useful behavior, see T86924. */
  const int selectmode_orig = scene->toolsettings->selectmode;
  scene->toolsettings->selectmode = SCE_SELECT_VERTEX;
 
  /* in uv synch selection, all uv's are visible */
  if (ts->uv_flag & UV_SYNC_SELECTION) {
    state->element_map = BM_uv_element_map_create(state->em->bm, scene, false, false, true, true);
  }
  else {
    state->element_map = BM_uv_element_map_create(state->em->bm, scene, true, false, true, true);
  }
 
  scene->toolsettings->selectmode = selectmode_orig;
 
  if (!state->element_map) {
    state_delete(state);
    return NULL;
  }
 
  ED_uvedit_get_aspect(obedit, &aspx, &aspy);
  state->aspect = aspx / aspy;
 
  /* Count 'unique' uvs */
  for (i = 0; i < state->element_map->totalUVs; i++) {
    if (state->element_map->buf[i].separate) {
      counter++;
    }
  }
 
  /* explicitly set preview to NULL,
   * to avoid deleting an invalid pointer on stitch_process_data */
  state->stitch_preview = NULL;
  /* Allocate the unique uv buffers */
  state->uvs = MEM_mallocN(sizeof(*state->uvs) * counter, "uv_stitch_unique_uvs");
  /* internal uvs need no normals but it is hard and slow to keep a map of
   * normals only for boundary uvs, so allocating for all uvs */
  state->normals = MEM_callocN(sizeof(*state->normals) * counter * 2, "uv_stitch_normals");
  state->total_separate_uvs = counter;
  state->map = map = MEM_mallocN(sizeof(*map) * state->element_map->totalUVs,
                                 "uv_stitch_unique_map");
  /* Allocate the edge stack */
  edge_hash = BLI_ghash_new(uv_edge_hash, uv_edge_compare, "stitch_edge_hash");
  all_edges = MEM_mallocN(sizeof(*all_edges) * state->element_map->totalUVs, "ssc_edges");
 
  if (!state->uvs || !map || !edge_hash || !all_edges) {
    state_delete(state);
    return NULL;
  }
 
  /* So that we can use this as index for the UvElements */
  counter = -1;
  /* initialize the unique UVs and map */
  for (i = 0; i < em->bm->totvert; i++) {
    UvElement *element = state->element_map->vert[i];
    for (; element; element = element->next) {
      if (element->separate) {
        counter++;
        state->uvs[counter] = element;
      }
      /* pointer arithmetic to the rescue, as always :)*/
      map[element - state->element_map->buf] = counter;
    }
  }
 
  counter = 0;
  /* Now, on to generate our uv connectivity data */
  BM_ITER_MESH (efa, &iter, em->bm, BM_FACES_OF_MESH) {
    if (!(ts->uv_flag & UV_SYNC_SELECTION) &&
        ((BM_elem_flag_test(efa, BM_ELEM_HIDDEN)) || !BM_elem_flag_test(efa, BM_ELEM_SELECT))) {
      continue;
    }
 
    BM_ITER_ELEM (l, &liter, efa, BM_LOOPS_OF_FACE) {
      UvElement *element = BM_uv_element_get(state->element_map, efa, l);
      int offset1, itmp1 = element - state->element_map->buf;
      int offset2,
          itmp2 = BM_uv_element_get(state->element_map, efa, l->next) - state->element_map->buf;
      UvEdge *edge;
 
      offset1 = map[itmp1];
      offset2 = map[itmp2];
 
      all_edges[counter].next = NULL;
      all_edges[counter].first = NULL;
      all_edges[counter].flag = 0;
      all_edges[counter].element = element;
      /* using an order policy, sort uvs according to address space. This avoids
       * Having two different UvEdges with the same uvs on different positions  */
      if (offset1 < offset2) {
        all_edges[counter].uv1 = offset1;
        all_edges[counter].uv2 = offset2;
      }
      else {
        all_edges[counter].uv1 = offset2;
        all_edges[counter].uv2 = offset1;
      }
 
      edge = BLI_ghash_lookup(edge_hash, &all_edges[counter]);
      if (edge) {
        edge->flag = 0;
      }
      else {
        BLI_ghash_insert(edge_hash, &all_edges[counter], &all_edges[counter]);
        all_edges[counter].flag = STITCH_BOUNDARY;
      }
      counter++;
    }
  }
 
  total_edges = BLI_ghash_len(edge_hash);
  state->edges = edges = MEM_mallocN(sizeof(*edges) * total_edges, "stitch_edges");
 
  /* I assume any system will be able to at least allocate an iterator :p */
  if (!edges) {
    state_delete(state);
    return NULL;
  }
 
  state->total_separate_edges = total_edges;
 
  /* fill the edges with data */
  i = 0;
  GHASH_ITER (gh_iter, edge_hash) {
    edges[i++] = *((UvEdge *)BLI_ghashIterator_getKey(&gh_iter));
  }
 
  /* cleanup temporary stuff */
  MEM_freeN(all_edges);
 
  BLI_ghash_free(edge_hash, NULL, NULL);
 
  /* Refill an edge hash to create edge connectivity data. */
  state->edge_hash = edge_hash = BLI_ghash_new(uv_edge_hash, uv_edge_compare, "stitch_edge_hash");
  for (i = 0; i < total_edges; i++) {
    BLI_ghash_insert(edge_hash, edges + i, edges + i);
  }
  stitch_uv_edge_generate_linked_edges(edge_hash, state);
 
  /***** calculate 2D normals for boundary uvs *****/
 
  /* we use boundary edges to calculate 2D normals.
   * to disambiguate the direction of the normal, we also need
   * a point "inside" the island, that can be provided by
   * the winding of the polygon (assuming counter-clockwise flow). */
 
  for (i = 0; i < total_edges; i++) {
    UvEdge *edge = edges + i;
    float normal[2];
    if (edge->flag & STITCH_BOUNDARY) {
      stitch_calculate_edge_normal(em, edge, normal, state->aspect);
 
      add_v2_v2(state->normals + edge->uv1 * 2, normal);
      add_v2_v2(state->normals + edge->uv2 * 2, normal);
 
      normalize_v2(state->normals + edge->uv1 * 2);
      normalize_v2(state->normals + edge->uv2 * 2);
    }
  }
 
  /***** fill selection stack *******/
 
  state->selection_size = 0;
 
  /* Load old selection if redoing operator with different settings */
  if (state_init != NULL) {
    int faceIndex, elementIndex;
    UvElement *element;
    enum StitchModes stored_mode = RNA_enum_get(op->ptr, "stored_mode");
 
    BM_mesh_elem_table_ensure(em->bm, BM_FACE);
 
    int selected_count = state_init->uv_selected_count;
 
    if (stored_mode == STITCH_VERT) {
      state->selection_stack = MEM_mallocN(sizeof(*state->selection_stack) *
                                               state->total_separate_uvs,
                                           "uv_stitch_selection_stack");
 
      while (selected_count--) {
        faceIndex = state_init->to_select[selected_count].faceIndex;
        elementIndex = state_init->to_select[selected_count].elementIndex;
        efa = BM_face_at_index(em->bm, faceIndex);
        element = BM_uv_element_get(
            state->element_map, efa, BM_iter_at_index(NULL, BM_LOOPS_OF_FACE, efa, elementIndex));
        stitch_select_uv(element, state, 1);
      }
    }
    else {
      state->selection_stack = MEM_mallocN(sizeof(*state->selection_stack) *
                                               state->total_separate_edges,
                                           "uv_stitch_selection_stack");
 
      while (selected_count--) {
        UvEdge tmp_edge, *edge;
        int uv1, uv2;
        faceIndex = state_init->to_select[selected_count].faceIndex;
        elementIndex = state_init->to_select[selected_count].elementIndex;
        efa = BM_face_at_index(em->bm, faceIndex);
        element = BM_uv_element_get(
            state->element_map, efa, BM_iter_at_index(NULL, BM_LOOPS_OF_FACE, efa, elementIndex));
        uv1 = map[element - state->element_map->buf];
 
        element = BM_uv_element_get(
            state->element_map,
            efa,
            BM_iter_at_index(NULL, BM_LOOPS_OF_FACE, efa, (elementIndex + 1) % efa->len));
        uv2 = map[element - state->element_map->buf];
 
        if (uv1 < uv2) {
          tmp_edge.uv1 = uv1;
          tmp_edge.uv2 = uv2;
        }
        else {
          tmp_edge.uv1 = uv2;
          tmp_edge.uv2 = uv1;
        }
 
        edge = BLI_ghash_lookup(edge_hash, &tmp_edge);
 
        stitch_select_edge(edge, state, true);
      }
    }
    /* if user has switched the operator mode after operation, we need to convert
     * the stored format */
    if (ssc->mode != stored_mode) {
      stitch_set_selection_mode(state, stored_mode);
    }
  }
  else {
    if (ssc->mode == STITCH_VERT) {
      state->selection_stack = MEM_mallocN(sizeof(*state->selection_stack) *
                                               state->total_separate_uvs,
                                           "uv_stitch_selection_stack");
 
      BM_ITER_MESH (efa, &iter, em->bm, BM_FACES_OF_MESH) {
        BM_ITER_ELEM_INDEX (l, &liter, efa, BM_LOOPS_OF_FACE, i) {
          if (uvedit_uv_select_test(scene, l, cd_loop_uv_offset)) {
            UvElement *element = BM_uv_element_get(state->element_map, efa, l);
            if (element) {
              stitch_select_uv(element, state, 1);
            }
          }
        }
      }
    }
    else {
      state->selection_stack = MEM_mallocN(sizeof(*state->selection_stack) *
                                               state->total_separate_edges,
                                           "uv_stitch_selection_stack");
 
      BM_ITER_MESH (efa, &iter, em->bm, BM_FACES_OF_MESH) {
        if (!(ts->uv_flag & UV_SYNC_SELECTION) && ((BM_elem_flag_test(efa, BM_ELEM_HIDDEN)) ||
                                                   !BM_elem_flag_test(efa, BM_ELEM_SELECT))) {
          continue;
        }
 
        BM_ITER_ELEM (l, &liter, efa, BM_LOOPS_OF_FACE) {
          if (uvedit_edge_select_test(scene, l, cd_loop_uv_offset)) {
            UvEdge *edge = uv_edge_get(l, state);
            if (edge) {
              stitch_select_edge(edge, state, true);
            }
          }
        }
      }
    }
  }
 
  /***** initialize static island preview data *****/
 
  state->tris_per_island = MEM_mallocN(
      sizeof(*state->tris_per_island) * state->element_map->totalIslands, "stitch island tris");
  for (i = 0; i < state->element_map->totalIslands; i++) {
    state->tris_per_island[i] = 0;
  }
 
  BM_ITER_MESH (efa, &iter, em->bm, BM_FACES_OF_MESH) {
    UvElement *element = BM_uv_element_get(state->element_map, efa, BM_FACE_FIRST_LOOP(efa));
 
    if (element) {
      state->tris_per_island[element->island] += (efa->len > 2) ? efa->len - 2 : 0;
    }
  }
 
  state->island_is_stitchable = MEM_callocN(sizeof(bool) * state->element_map->totalIslands,
                                            "stitch I stops");
  if (!state->island_is_stitchable) {
    state_delete(state);
    return NULL;
  }
 
  if (!stitch_process_data(ssc, state, scene, false)) {
    state_delete(state);
    return NULL;
  }
 
  return state;
}
 
static bool goto_next_island(StitchStateContainer *ssc)
{
  StitchState *active_state = ssc->states[ssc->active_object_index];
  StitchState *original_active_state = active_state;
 
  int original_island = ssc->static_island;
 
  do {
    ssc->static_island++;
    if (ssc->static_island >= active_state->element_map->totalIslands) {
      /* go to next object */
      ssc->active_object_index++;
      ssc->active_object_index %= ssc->objects_len;
 
      active_state = ssc->states[ssc->active_object_index];
      ssc->static_island = 0;
    }
 
    if (active_state->island_is_stitchable[ssc->static_island]) {
      /* We're at an island to make active */
      return true;
    }
  } while (!(active_state == original_active_state && ssc->static_island == original_island));
 
  return false;
}
 
static int stitch_init_all(bContext *C, wmOperator *op)
{
  ARegion *region = CTX_wm_region(C);
  if (!region) {
    return 0;
  }
 
  Scene *scene = CTX_data_scene(C);
  ToolSettings *ts = scene->toolsettings;
 
  StitchStateContainer *ssc = MEM_callocN(sizeof(StitchStateContainer), "stitch collection");
 
  op->customdata = ssc;
 
  ssc->use_limit = RNA_boolean_get(op->ptr, "use_limit");
  ssc->limit_dist = RNA_float_get(op->ptr, "limit");
  ssc->snap_islands = RNA_boolean_get(op->ptr, "snap_islands");
  ssc->midpoints = RNA_boolean_get(op->ptr, "midpoint_snap");
  ssc->clear_seams = RNA_boolean_get(op->ptr, "clear_seams");
  ssc->active_object_index = RNA_int_get(op->ptr, "active_object_index");
  ssc->static_island = 0;
 
  if (RNA_struct_property_is_set(op->ptr, "mode")) {
    ssc->mode = RNA_enum_get(op->ptr, "mode");
  }
  else {
    if (ts->uv_flag & UV_SYNC_SELECTION) {
      if (ts->selectmode & SCE_SELECT_VERTEX) {
        ssc->mode = STITCH_VERT;
      }
      else {
        ssc->mode = STITCH_EDGE;
      }
    }
    else {
      if (ts->uv_selectmode & UV_SELECT_VERTEX) {
        ssc->mode = STITCH_VERT;
      }
      else {
        ssc->mode = STITCH_EDGE;
      }
    }
  }
 
  ssc->objects_len = 0;
  ssc->states = NULL;
 
  ViewLayer *view_layer = CTX_data_view_layer(C);
  View3D *v3d = CTX_wm_view3d(C);
  uint objects_len = 0;
  Object **objects = BKE_view_layer_array_from_objects_in_edit_mode_unique_data_with_uvs(
      view_layer, v3d, &objects_len);
 
  if (objects_len == 0) {
    MEM_freeN(objects);
    state_delete_all(ssc);
    return 0;
  }
 
  ssc->objects = MEM_callocN(sizeof(Object *) * objects_len, "Object *ssc->objects");
  ssc->states = MEM_callocN(sizeof(StitchState *) * objects_len, "StitchState");
  ssc->objects_len = 0;
 
  int *objs_selection_count = NULL;
  UvElementID *selected_uvs_arr = NULL;
  StitchStateInit *state_init = NULL;
 
  if (RNA_struct_property_is_set(op->ptr, "selection") &&
      RNA_struct_property_is_set(op->ptr, "objects_selection_count")) {
    /* Retrieve list of selected UVs, one list contains all selected UVs
     * for all objects. */
 
    objs_selection_count = MEM_mallocN(sizeof(int *) * objects_len, "objects_selection_count");
    RNA_int_get_array(op->ptr, "objects_selection_count", objs_selection_count);
 
    int total_selected = 0;
    for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
      total_selected += objs_selection_count[ob_index];
    }
 
    selected_uvs_arr = MEM_callocN(sizeof(UvElementID) * total_selected, "selected_uvs_arr");
    int sel_idx = 0;
    RNA_BEGIN (op->ptr, itemptr, "selection") {
      BLI_assert(sel_idx < total_selected);
      selected_uvs_arr[sel_idx].faceIndex = RNA_int_get(&itemptr, "face_index");
      selected_uvs_arr[sel_idx].elementIndex = RNA_int_get(&itemptr, "element_index");
      sel_idx++;
    }
    RNA_END;
 
    RNA_collection_clear(op->ptr, "selection");
 
    state_init = MEM_callocN(sizeof(StitchStateInit), "UV_init_selected");
    state_init->to_select = selected_uvs_arr;
  }
 
  for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
    Object *obedit = objects[ob_index];
 
    if (state_init != NULL) {
      state_init->uv_selected_count = objs_selection_count[ob_index];
    }
 
    StitchState *stitch_state_ob = stitch_init(C, op, ssc, obedit, state_init);
 
    if (state_init != NULL) {
      /* Move pointer to beginning of next object's data. */
      state_init->to_select += state_init->uv_selected_count;
    }
 
    if (stitch_state_ob) {
      ssc->objects[ssc->objects_len] = obedit;
      ssc->states[ssc->objects_len] = stitch_state_ob;
      ssc->objects_len++;
    }
  }
 
  MEM_freeN(objects);
  MEM_SAFE_FREE(selected_uvs_arr);
  MEM_SAFE_FREE(objs_selection_count);
  MEM_SAFE_FREE(state_init);
 
  if (ssc->objects_len == 0) {
    state_delete_all(ssc);
    return 0;
  }
 
  ssc->active_object_index %= ssc->objects_len;
 
  ssc->static_island = RNA_int_get(op->ptr, "static_island");
 
  StitchState *state = ssc->states[ssc->active_object_index];
  ssc->static_island %= state->element_map->totalIslands;
 
  /* If the initial active object doesn't have any stitchable islands */
  /* then no active island will be seen in the UI. Make sure we're on */
  /* a stitchable object and island.                                  */
  if (!state->island_is_stitchable[ssc->static_island]) {
    goto_next_island(ssc);
    state = ssc->states[ssc->active_object_index];
  }
 
  /* process active stitchobj again now that it can detect it's the active stitchobj */
  stitch_process_data(ssc, state, scene, false);
 
  stitch_update_header(ssc, C);
 
  ssc->draw_handle = ED_region_draw_cb_activate(
      region->type, stitch_draw, ssc, REGION_DRAW_POST_VIEW);
 
  return 1;
}
 
static int stitch_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event))
{
  if (!stitch_init_all(C, op)) {
    return OPERATOR_CANCELLED;
  }
 
  WM_event_add_modal_handler(C, op);
 
  Scene *scene = CTX_data_scene(C);
  ToolSettings *ts = scene->toolsettings;
  const bool synced_selection = (ts->uv_flag & UV_SYNC_SELECTION) != 0;
 
  StitchStateContainer *ssc = (StitchStateContainer *)op->customdata;
 
  for (uint ob_index = 0; ob_index < ssc->objects_len; ob_index++) {
    StitchState *state = ssc->states[ob_index];
    Object *obedit = state->obedit;
    BMEditMesh *em = BKE_editmesh_from_object(obedit);
 
    if (synced_selection && (em->bm->totvertsel == 0)) {
      continue;
    }
 
    WM_event_add_notifier(C, NC_GEOM | ND_DATA, obedit->data);
  }
 
  return OPERATOR_RUNNING_MODAL;
}
 
static void stitch_exit(bContext *C, wmOperator *op, int finished)
{
  Scene *scene = CTX_data_scene(C);
  SpaceImage *sima = CTX_wm_space_image(C);
  ScrArea *area = CTX_wm_area(C);
 
  StitchStateContainer *ssc = (StitchStateContainer *)op->customdata;
 
  if (finished) {
    RNA_float_set(op->ptr, "limit", ssc->limit_dist);
    RNA_boolean_set(op->ptr, "use_limit", ssc->use_limit);
    RNA_boolean_set(op->ptr, "snap_islands", ssc->snap_islands);
    RNA_boolean_set(op->ptr, "midpoint_snap", ssc->midpoints);
    RNA_boolean_set(op->ptr, "clear_seams", ssc->clear_seams);
    RNA_enum_set(op->ptr, "mode", ssc->mode);
    RNA_enum_set(op->ptr, "stored_mode", ssc->mode);
    RNA_int_set(op->ptr, "active_object_index", ssc->active_object_index);
 
    RNA_int_set(op->ptr, "static_island", ssc->static_island);
 
    int *objs_selection_count = NULL;
    objs_selection_count = MEM_mallocN(sizeof(int *) * ssc->objects_len,
                                       "objects_selection_count");
 
    /* Store selection for re-execution of stitch
     * - Store all selected UVs in "selection"
     * - Store how many each object has in "objects_selection_count". */
    RNA_collection_clear(op->ptr, "selection");
    for (uint ob_index = 0; ob_index < ssc->objects_len; ob_index++) {
      StitchState *state = ssc->states[ob_index];
      Object *obedit = state->obedit;
 
      PointerRNA itemptr;
      for (int i = 0; i < state->selection_size; i++) {
        UvElement *element;
 
        if (ssc->mode == STITCH_VERT) {
          element = state->selection_stack[i];
        }
        else {
          element = ((UvEdge *)state->selection_stack[i])->element;
        }
        RNA_collection_add(op->ptr, "selection", &itemptr);
 
        RNA_int_set(&itemptr, "face_index", BM_elem_index_get(element->l->f));
        RNA_int_set(&itemptr, "element_index", element->loop_of_poly_index);
      }
      uvedit_live_unwrap_update(sima, scene, obedit);
 
      objs_selection_count[ob_index] = state->selection_size;
    }
 
    PropertyRNA *prop = RNA_struct_find_property(op->ptr, "objects_selection_count");
    RNA_def_property_array(prop, ssc->objects_len);
    RNA_int_set_array(op->ptr, "objects_selection_count", objs_selection_count);
    MEM_freeN(objs_selection_count);
  }
 
  if (area) {
    ED_workspace_status_text(C, NULL);
  }
 
  ED_region_draw_cb_exit(CTX_wm_region(C)->type, ssc->draw_handle);
 
  ToolSettings *ts = scene->toolsettings;
  const bool synced_selection = (ts->uv_flag & UV_SYNC_SELECTION) != 0;
 
  for (uint ob_index = 0; ob_index < ssc->objects_len; ob_index++) {
    StitchState *state = ssc->states[ob_index];
    Object *obedit = state->obedit;
    BMEditMesh *em = BKE_editmesh_from_object(obedit);
 
    if (synced_selection && (em->bm->totvertsel == 0)) {
      continue;
    }
 
    DEG_id_tag_update(obedit->data, 0);
    WM_event_add_notifier(C, NC_GEOM | ND_DATA, obedit->data);
  }
 
  state_delete_all(ssc);
 
  op->customdata = NULL;
}
 
static void stitch_cancel(bContext *C, wmOperator *op)
{
  stitch_exit(C, op, 0);
}
 
static int stitch_exec(bContext *C, wmOperator *op)
{
  Scene *scene = CTX_data_scene(C);
 
  if (!stitch_init_all(C, op)) {
    return OPERATOR_CANCELLED;
  }
  if (stitch_process_data_all((StitchStateContainer *)op->customdata, scene, 1)) {
    stitch_exit(C, op, 1);
    return OPERATOR_FINISHED;
  }
  stitch_cancel(C, op);
  return OPERATOR_CANCELLED;
}
 
static StitchState *stitch_select(bContext *C,
                                  Scene *scene,
                                  const wmEvent *event,
                                  StitchStateContainer *ssc)
{
  /* add uv under mouse to processed uv's */
  float co[2];
  ARegion *region = CTX_wm_region(C);
  UvNearestHit hit = UV_NEAREST_HIT_INIT_MAX(&region->v2d);
 
  UI_view2d_region_to_view(&region->v2d, event->mval[0], event->mval[1], &co[0], &co[1]);
 
  if (ssc->mode == STITCH_VERT) {
    if (uv_find_nearest_vert_multi(scene, ssc->objects, ssc->objects_len, co, 0.0f, &hit)) {
      /* Add vertex to selection, deselect all common uv's of vert other than selected and
       * update the preview. This behavior was decided so that you can do stuff like deselect
       * the opposite stitchable vertex and the initial still gets deselected */
 
      /* find StitchState from hit->ob */
      StitchState *state = NULL;
      for (uint ob_index = 0; ob_index < ssc->objects_len; ob_index++) {
        if (hit.ob == ssc->objects[ob_index]) {
          state = ssc->states[ob_index];
          break;
        }
      }
 
      /* This works due to setting of tmp in find nearest uv vert */
      UvElement *element = BM_uv_element_get(state->element_map, hit.efa, hit.l);
      stitch_select_uv(element, state, false);
 
      return state;
    }
  }
  else if (uv_find_nearest_edge_multi(scene, ssc->objects, ssc->objects_len, co, &hit)) {
    /* find StitchState from hit->ob */
    StitchState *state = NULL;
    for (uint ob_index = 0; ob_index < ssc->objects_len; ob_index++) {
      if (hit.ob == ssc->objects[ob_index]) {
        state = ssc->states[ob_index];
        break;
      }
    }
 
    UvEdge *edge = uv_edge_get(hit.l, state);
    stitch_select_edge(edge, state, false);
 
    return state;
  }
 
  return NULL;
}
 
static int stitch_modal(bContext *C, wmOperator *op, const wmEvent *event)
{
  StitchStateContainer *ssc;
  Scene *scene = CTX_data_scene(C);
 
  ssc = op->customdata;
  StitchState *active_state = ssc->states[ssc->active_object_index];
 
  switch (event->type) {
    case MIDDLEMOUSE:
      return OPERATOR_PASS_THROUGH;
 
      /* Cancel */
    case EVT_ESCKEY:
      stitch_cancel(C, op);
      return OPERATOR_CANCELLED;
 
    case LEFTMOUSE:
    case EVT_PADENTER:
    case EVT_RETKEY:
      if (event->val == KM_PRESS) {
        if (stitch_process_data(ssc, active_state, scene, true)) {
          stitch_exit(C, op, 1);
          return OPERATOR_FINISHED;
        }
 
        stitch_cancel(C, op);
        return OPERATOR_CANCELLED;
      }
      return OPERATOR_PASS_THROUGH;
 
      /* Increase limit */
    case EVT_PADPLUSKEY:
    case WHEELUPMOUSE:
      if (event->val == KM_PRESS && event->alt) {
        ssc->limit_dist += 0.01f;
        if (!stitch_process_data(ssc, active_state, scene, false)) {
          stitch_cancel(C, op);
          return OPERATOR_CANCELLED;
        }
        break;
      }
      else {
        return OPERATOR_PASS_THROUGH;
      }
      /* Decrease limit */
    case EVT_PADMINUS:
    case WHEELDOWNMOUSE:
      if (event->val == KM_PRESS && event->alt) {
        ssc->limit_dist -= 0.01f;
        ssc->limit_dist = MAX2(0.01f, ssc->limit_dist);
        if (!stitch_process_data(ssc, active_state, scene, false)) {
          stitch_cancel(C, op);
          return OPERATOR_CANCELLED;
        }
        break;
      }
      else {
        return OPERATOR_PASS_THROUGH;
      }
 
      /* Use Limit (Default off) */
    case EVT_LKEY:
      if (event->val == KM_PRESS) {
        ssc->use_limit = !ssc->use_limit;
        if (!stitch_process_data(ssc, active_state, scene, false)) {
          stitch_cancel(C, op);
          return OPERATOR_CANCELLED;
        }
        break;
      }
      return OPERATOR_RUNNING_MODAL;
 
    case EVT_IKEY:
      if (event->val == KM_PRESS) {
        /* Move to next island and maybe next object */
 
        if (goto_next_island(ssc)) {
          StitchState *new_active_state = ssc->states[ssc->active_object_index];
 
          /* active_state is the original active state */
          if (active_state != new_active_state) {
            if (!stitch_process_data(ssc, active_state, scene, false)) {
              stitch_cancel(C, op);
              return OPERATOR_CANCELLED;
            }
          }
 
          if (!stitch_process_data(ssc, new_active_state, scene, false)) {
            stitch_cancel(C, op);
            return OPERATOR_CANCELLED;
          }
        }
        break;
      }
      return OPERATOR_RUNNING_MODAL;
 
    case EVT_MKEY:
      if (event->val == KM_PRESS) {
        ssc->midpoints = !ssc->midpoints;
        if (!stitch_process_data(ssc, active_state, scene, false)) {
          stitch_cancel(C, op);
          return OPERATOR_CANCELLED;
        }
      }
      break;
 
      /* Select geometry */
    case RIGHTMOUSE:
      if (!event->shift) {
        stitch_cancel(C, op);
        return OPERATOR_CANCELLED;
      }
      if (event->val == KM_PRESS) {
        StitchState *selected_state = stitch_select(C, scene, event, ssc);
 
        if (selected_state && !stitch_process_data(ssc, selected_state, scene, false)) {
          stitch_cancel(C, op);
          return OPERATOR_CANCELLED;
        }
        break;
      }
      return OPERATOR_RUNNING_MODAL;
 
      /* snap islands on/off */
    case EVT_SKEY:
      if (event->val == KM_PRESS) {
        ssc->snap_islands = !ssc->snap_islands;
        if (!stitch_process_data(ssc, active_state, scene, false)) {
          stitch_cancel(C, op);
          return OPERATOR_CANCELLED;
        }
        break;
      }
      else {
        return OPERATOR_RUNNING_MODAL;
      }
 
      /* switch between edge/vertex mode */
    case EVT_TABKEY:
      if (event->val == KM_PRESS) {
        stitch_switch_selection_mode_all(ssc);
 
        if (!stitch_process_data_all(ssc, scene, false)) {
          stitch_cancel(C, op);
          return OPERATOR_CANCELLED;
        }
      }
      break;
 
    default:
      return OPERATOR_RUNNING_MODAL;
  }
 
  /* if updated settings, renew feedback message */
  stitch_update_header(ssc, C);
  ED_region_tag_redraw(CTX_wm_region(C));
 
  return OPERATOR_RUNNING_MODAL;
}
 
void UV_OT_stitch(wmOperatorType *ot)
{
  PropertyRNA *prop;
 
  static const EnumPropertyItem stitch_modes[] = {
      {STITCH_VERT, "VERTEX", 0, "Vertex", ""},
      {STITCH_EDGE, "EDGE", 0, "Edge", ""},
      {0, NULL, 0, NULL, NULL},
  };
 
  /* identifiers */
  ot->name = "Stitch";
  ot->description = "Stitch selected UV vertices by proximity";
  ot->idname = "UV_OT_stitch";
  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 
  /* api callbacks */
  ot->invoke = stitch_invoke;
  ot->modal = stitch_modal;
  ot->exec = stitch_exec;
  ot->cancel = stitch_cancel;
  ot->poll = ED_operator_uvedit;
 
  /* properties */
  RNA_def_boolean(
      ot->srna, "use_limit", 0, "Use Limit", "Stitch UVs within a specified limit distance");
  RNA_def_boolean(ot->srna,
                  "snap_islands",
                  1,
                  "Snap Islands",
                  "Snap islands together (on edge stitch mode, rotates the islands too)");
 
  RNA_def_float(ot->srna,
                "limit",
                0.01f,
                0.0f,
                FLT_MAX,
                "Limit",
                "Limit distance in normalized coordinates",
                0.0,
                FLT_MAX);
  RNA_def_int(ot->srna,
              "static_island",
              0,
              0,
              INT_MAX,
              "Static Island",
              "Island that stays in place when stitching islands",
              0,
              INT_MAX);
  RNA_def_int(ot->srna,
              "active_object_index",
              0,
              0,
              INT_MAX,
              "Active Object",
              "Index of the active object",
              0,
              INT_MAX);
  RNA_def_boolean(ot->srna,
                  "midpoint_snap",
                  0,
                  "Snap at Midpoint",
                  "UVs are stitched at midpoint instead of at static island");
  RNA_def_boolean(ot->srna, "clear_seams", 1, "Clear Seams", "Clear seams of stitched edges");
  RNA_def_enum(ot->srna,
               "mode",
               stitch_modes,
               STITCH_VERT,
               "Operation Mode",
               "Use vertex or edge stitching");
  prop = RNA_def_enum(ot->srna,
                      "stored_mode",
                      stitch_modes,
                      STITCH_VERT,
                      "Stored Operation Mode",
                      "Use vertex or edge stitching");
  RNA_def_property_flag(prop, PROP_HIDDEN);
  prop = RNA_def_collection_runtime(
      ot->srna, "selection", &RNA_SelectedUvElement, "Selection", "");
  /* Selection should not be editable or viewed in toolbar */
  RNA_def_property_flag(prop, PROP_HIDDEN);
 
  /* test should not be editable or viewed in toolbar */
  prop = RNA_def_int_array(ot->srna,
                           "objects_selection_count",
                           1,
                           NULL,
                           0,
                           INT_MAX,
                           "Objects Selection Count",
                           "",
                           0,
                           INT_MAX);
  RNA_def_property_array(prop, 6);
  RNA_def_property_flag(prop, PROP_HIDDEN);
}