UV: Edge support for select shortest path operator

Calculating shortest path selection in UV edge mode was done using vertex
path logic. Since the UV editor now supports proper edge selection [0],
this approach can sometimes give incorrect results.

This problem is now fixed by adding separate logic to calculate the
shortest path in UV edge mode.

Resolves T99344.

[0]: ffaaa0bcbf477c30cf3665b9330bbbb767397169

Reviewed By: campbellbarton

Ref D15511.

3 files changed, 351 insertions, 159 deletions

diff --git a/source/blender/bmesh/tools/bmesh_path_uv.c b/source/blender/bmesh/tools/bmesh_path_uv.c
index 76697f51ac7..3d736cdc3b8 100644
--- a/source/blender/bmesh/tools/bmesh_path_uv.c
+++ b/source/blender/bmesh/tools/bmesh_path_uv.c
@@ -47,9 +47,7 @@ static float step_cost_3_v2_ex(
   return cost * (1.0f + 0.5f * (2.0f - sqrtf(fabsf(dot_v2v2(d1, d2)))));
 }
 
-static float UNUSED_FUNCTION(step_cost_3_v2)(const float v1[2],
-                                             const float v2[2],
-                                             const float v3[2])
+static float step_cost_3_v2(const float v1[2], const float v2[2], const float v3[2])
 {
   return step_cost_3_v2_ex(v1, v2, v3, false, false);
 }
@@ -60,7 +58,7 @@ static float UNUSED_FUNCTION(step_cost_3_v2)(const float v1[2],
 /** \name BM_mesh_calc_path_uv_vert
  * \{ */
 
-static void looptag_add_adjacent_uv(HeapSimple *heap,
+static void verttag_add_adjacent_uv(HeapSimple *heap,
                                     BMLoop *l_a,
                                     BMLoop **loops_prev,
                                     float *cost,
@@ -162,7 +160,7 @@ struct LinkNode *BM_mesh_calc_path_uv_vert(BMesh *bm,
     if (!BM_elem_flag_test(l, BM_ELEM_TAG)) {
       /* Adjacent loops are tagged while stepping to avoid 2x loops. */
       BM_elem_flag_enable(l, BM_ELEM_TAG);
-      looptag_add_adjacent_uv(heap, l, loops_prev, cost, params);
+      verttag_add_adjacent_uv(heap, l, loops_prev, cost, params);
     }
   }
 
@@ -185,8 +183,199 @@ struct LinkNode *BM_mesh_calc_path_uv_vert(BMesh *bm,
 /** \name BM_mesh_calc_path_uv_edge
  * \{ */
 
-/* TODO(@sidd017): Setting this as todo, since we now support proper UV edge selection (D12028).
- * Till then, continue using vertex path to fake shortest path calculation for edges. */
+static float edgetag_cut_cost_vert_uv(
+    BMLoop *l_e_a, BMLoop *l_e_b, BMLoop *l_v, const float aspect_y, const int cd_loop_uv_offset)
+{
+  BMLoop *l_v1 = (l_v->v == l_e_a->v) ? l_e_a->next : l_e_a;
+  BMLoop *l_v2 = (l_v->v == l_e_b->v) ? l_e_b->next : l_e_b;
+
+  MLoopUV *luv_v1 = BM_ELEM_CD_GET_VOID_P(l_v1, cd_loop_uv_offset);
+  MLoopUV *luv_v2 = BM_ELEM_CD_GET_VOID_P(l_v2, cd_loop_uv_offset);
+  MLoopUV *luv_v = BM_ELEM_CD_GET_VOID_P(l_v, cd_loop_uv_offset);
+
+  float uv_v1[2] = {luv_v1->uv[0], luv_v1->uv[1] / aspect_y};
+  float uv_v2[2] = {luv_v2->uv[0], luv_v2->uv[1] / aspect_y};
+  float uv_v[2] = {luv_v->uv[0], luv_v->uv[1] / aspect_y};
+
+  return step_cost_3_v2(uv_v1, uv_v, uv_v2);
+}
+
+static float edgetag_cut_cost_face_uv(
+    BMLoop *l_e_a, BMLoop *l_e_b, BMFace *f, const float aspect_v2[2], const int cd_loop_uv_offset)
+{
+  float l_e_a_cent[2], l_e_b_cent[2], f_cent[2];
+  MLoopUV *luv_e_a = BM_ELEM_CD_GET_VOID_P(l_e_a, cd_loop_uv_offset);
+  MLoopUV *luv_e_b = BM_ELEM_CD_GET_VOID_P(l_e_b, cd_loop_uv_offset);
+
+  mid_v2_v2v2(l_e_a_cent, luv_e_a->uv, luv_e_a->uv);
+  mid_v2_v2v2(l_e_b_cent, luv_e_b->uv, luv_e_b->uv);
+
+  mul_v2_v2(l_e_a_cent, aspect_v2);
+  mul_v2_v2(l_e_b_cent, aspect_v2);
+
+  BM_face_uv_calc_center_median_weighted(f, aspect_v2, cd_loop_uv_offset, f_cent);
+
+  return step_cost_3_v2(l_e_a_cent, l_e_b_cent, f_cent);
+}
+
+static void edgetag_add_adjacent_uv(HeapSimple *heap,
+                                    BMLoop *l_a,
+                                    BMLoop **loops_prev,
+                                    float *cost,
+                                    const struct BMCalcPathUVParams *params)
+{
+  BLI_assert(params->aspect_y != 0.0f);
+  const uint cd_loop_uv_offset = params->cd_loop_uv_offset;
+  BMLoop *l_a_verts[2] = {l_a, l_a->next};
+  const int l_a_index = BM_elem_index_get(l_a);
+
+  if (params->use_step_face == false) {
+    for (int i = 0; i < ARRAY_SIZE(l_a_verts); i++) {
+
+      /* Skip current UV vert if it is part of the previous UV edge in the path. */
+      if (loops_prev[l_a_index]) {
+        BMLoop *l_prev = loops_prev[l_a_index];
+        if (l_a_verts[i]->v != l_prev->v) {
+          l_prev = (l_a_verts[i]->v == l_prev->next->v) ? l_prev->next : NULL;
+        }
+        if (l_prev && BM_loop_uv_share_vert_check(l_a_verts[i], l_prev, cd_loop_uv_offset)) {
+          continue;
+        }
+      }
+
+      BMEdge *e_b;
+      BMIter eiter;
+      BM_ITER_ELEM (e_b, &eiter, l_a_verts[i]->v, BM_EDGES_OF_VERT) {
+        BMLoop *l_first, *l_b;
+        l_first = l_b = e_b->l;
+        do {
+          if (!BM_elem_flag_test(l_b, BM_ELEM_TAG)) {
+            BMLoop *l_b_vert = (l_a_verts[i]->v == l_b->v) ? l_b : l_b->next;
+            if (BM_loop_uv_share_vert_check(l_a_verts[i], l_b_vert, cd_loop_uv_offset)) {
+              /* We know 'l_b' is not visited, check it out! */
+              const int l_b_index = BM_elem_index_get(l_b);
+              const float cost_cut = params->use_topology_distance ?
+                                         1.0f :
+                                         edgetag_cut_cost_vert_uv(l_a,
+                                                                  l_b,
+                                                                  l_a_verts[i],
+                                                                  params->aspect_y,
+                                                                  cd_loop_uv_offset);
+              const float cost_new = cost[l_a_index] + cost_cut;
+
+              if (cost[l_b_index] > cost_new) {
+                cost[l_b_index] = cost_new;
+                loops_prev[l_b_index] = l_a;
+                BLI_heapsimple_insert(heap, cost_new, l_b);
+              }
+            }
+          }
+        } while ((l_b = l_b->radial_next) != l_first);
+      }
+    }
+  }
+  else {
+    const float aspect_v2[2] = {1.0f, 1.0f / params->aspect_y};
+    BMLoop *l_first, *l_iter;
+    l_iter = l_first = l_a;
+    do {
+      /* Ensures connected UVs and that they lie on the same island. */
+      if (!BM_loop_uv_share_edge_check(l_a, l_iter, cd_loop_uv_offset)) {
+        continue;
+      }
+
+      BMLoop *l_cycle_iter, *l_cycle_end;
+      l_cycle_iter = l_iter->next;
+      l_cycle_end = l_iter;
+      do {
+        BMLoop *l_b = l_cycle_iter;
+        if (!BM_elem_flag_test(l_b, BM_ELEM_TAG)) {
+          /* We know 'l_b' is not visited, check it out! */
+          const int l_b_index = BM_elem_index_get(l_b);
+          const float cost_cut = params->use_topology_distance ?
+                                     1.0f :
+                                     edgetag_cut_cost_face_uv(l_a,
+                                                              l_b,
+                                                              l_iter->f,
+                                                              aspect_v2,
+                                                              params->cd_loop_uv_offset);
+          const float cost_new = cost[l_a_index] + cost_cut;
+
+          if (cost[l_b_index] > cost_new) {
+            cost[l_b_index] = cost_new;
+            loops_prev[l_b_index] = l_a;
+            BLI_heapsimple_insert(heap, cost_new, l_b);
+          }
+        }
+      } while ((l_cycle_iter = l_cycle_iter->next) != l_cycle_end);
+    } while ((l_iter = l_iter->radial_next) != l_first);
+  }
+}
+
+struct LinkNode *BM_mesh_calc_path_uv_edge(BMesh *bm,
+                                           BMLoop *l_src,
+                                           BMLoop *l_dst,
+                                           const struct BMCalcPathUVParams *params,
+                                           bool (*filter_fn)(BMLoop *, void *),
+                                           void *user_data)
+{
+  LinkNode *path = NULL;
+
+  BMFace *f;
+  BMIter iter;
+  HeapSimple *heap;
+  float *cost;
+  BMLoop **loops_prev;
+  int i = 0, totloop;
+
+  BM_ITER_MESH (f, &iter, bm, BM_FACES_OF_MESH) {
+    BMLoop *l_first = BM_FACE_FIRST_LOOP(f);
+    BMLoop *l_iter = l_first;
+    do {
+      BM_elem_flag_set(l_iter, BM_ELEM_TAG, !filter_fn(l_iter, user_data));
+      BM_elem_index_set(l_iter, i);
+      i += 1;
+    } while ((l_iter = l_iter->next) != l_first);
+  }
+  bm->elem_index_dirty &= ~BM_LOOP;
+
+  totloop = bm->totloop;
+  loops_prev = MEM_callocN(sizeof(*loops_prev) * totloop, __func__);
+  cost = MEM_mallocN(sizeof(*cost) * totloop, __func__);
+
+  copy_vn_fl(cost, totloop, COST_INIT_MAX);
+
+  /* Regular dijkstra shortest path, but over UV loops/edges instead of vertices. */
+  heap = BLI_heapsimple_new();
+  BLI_heapsimple_insert(heap, 0.0f, l_src);
+  cost[BM_elem_index_get(l_src)] = 0.0f;
+
+  BMLoop *l = NULL;
+  while (!BLI_heapsimple_is_empty(heap)) {
+    l = BLI_heapsimple_pop_min(heap);
+
+    if ((l->e == l_dst->e) && (BM_loop_uv_share_edge_check(l, l_dst, params->cd_loop_uv_offset))) {
+      break;
+    }
+
+    if (!BM_elem_flag_test(l, BM_ELEM_TAG)) {
+      BM_elem_flag_enable(l, BM_ELEM_TAG);
+      edgetag_add_adjacent_uv(heap, l, loops_prev, cost, params);
+    }
+  }
+
+  if ((l->e == l_dst->e) && (BM_loop_uv_share_edge_check(l, l_dst, params->cd_loop_uv_offset))) {
+    do {
+      BLI_linklist_prepend(&path, l);
+    } while ((l = loops_prev[BM_elem_index_get(l)]));
+  }
+
+  MEM_freeN(loops_prev);
+  MEM_freeN(cost);
+  BLI_heapsimple_free(heap, NULL);
+
+  return path;
+}
 
 /** \} */
 
diff --git a/source/blender/bmesh/tools/bmesh_path_uv.h b/source/blender/bmesh/tools/bmesh_path_uv.h
index af7341e2219..d7b5faa70e5 100644
--- a/source/blender/bmesh/tools/bmesh_path_uv.h
+++ b/source/blender/bmesh/tools/bmesh_path_uv.h
@@ -21,6 +21,14 @@ struct LinkNode *BM_mesh_calc_path_uv_vert(BMesh *bm,
                                            void *user_data) ATTR_WARN_UNUSED_RESULT
     ATTR_NONNULL(1, 2, 3, 5);
 
+struct LinkNode *BM_mesh_calc_path_uv_edge(BMesh *bm,
+                                           BMLoop *l_src,
+                                           BMLoop *l_dst,
+                                           const struct BMCalcPathUVParams *params,
+                                           bool (*filter_fn)(BMLoop *, void *),
+                                           void *user_data) ATTR_WARN_UNUSED_RESULT
+    ATTR_NONNULL(1, 2, 3, 5);
+
 struct LinkNode *BM_mesh_calc_path_uv_face(BMesh *bm,
                                            BMFace *f_src,
                                            BMFace *f_dst,
diff --git a/source/blender/editors/uvedit/uvedit_path.c b/source/blender/editors/uvedit/uvedit_path.c
index 7c6960a634a..31a1b60167e 100644
--- a/source/blender/editors/uvedit/uvedit_path.c
+++ b/source/blender/editors/uvedit/uvedit_path.c
@@ -56,75 +56,6 @@
 #include "bmesh_tools.h"
 
 /* -------------------------------------------------------------------- */
-/** \name Local Utilities
- * \{ */
-
-/**
- * Support edge-path using vert-path calculation code.
- *
- * Cheat! Pick 2 closest loops and do vertex path,
- * in practices only obscure/contrived cases will make give noticeably worse behavior.
- *
- * While the code below is a bit awkward, it's significantly less overhead than
- * adding full edge selection which is nearly the same as vertex path in the case of UV's.
- *
- * \param use_nearest: When false use the post distant pair of loops,
- * use when filling a region as we want both verts from each edge to be included in the region.
- */
-static void bm_loop_calc_vert_pair_from_edge_pair(const bool use_nearest,
-                                                  const int cd_loop_uv_offset,
-                                                  const float aspect_y,
-                                                  BMElem **ele_src_p,
-                                                  BMElem **ele_dst_p,
-                                                  BMElem **r_ele_dst_final)
-{
-  BMLoop *l_src = (BMLoop *)*ele_src_p;
-  BMLoop *l_dst = (BMLoop *)*ele_dst_p;
-
-  const MLoopUV *luv_src_v1 = BM_ELEM_CD_GET_VOID_P(l_src, cd_loop_uv_offset);
-  const MLoopUV *luv_src_v2 = BM_ELEM_CD_GET_VOID_P(l_src->next, cd_loop_uv_offset);
-  const MLoopUV *luv_dst_v1 = BM_ELEM_CD_GET_VOID_P(l_dst, cd_loop_uv_offset);
-  const MLoopUV *luv_dst_v2 = BM_ELEM_CD_GET_VOID_P(l_dst->next, cd_loop_uv_offset);
-
-  const float uv_src_v1[2] = {luv_src_v1->uv[0], luv_src_v1->uv[1] / aspect_y};
-  const float uv_src_v2[2] = {luv_src_v2->uv[0], luv_src_v2->uv[1] / aspect_y};
-  const float uv_dst_v1[2] = {luv_dst_v1->uv[0], luv_dst_v1->uv[1] / aspect_y};
-  const float uv_dst_v2[2] = {luv_dst_v2->uv[0], luv_dst_v2->uv[1] / aspect_y};
-
-  struct {
-    int src_index;
-    int dst_index;
-    float len_sq;
-  } tests[4] = {
-      {0, 0, len_squared_v2v2(uv_src_v1, uv_dst_v1)},
-      {0, 1, len_squared_v2v2(uv_src_v1, uv_dst_v2)},
-      {1, 0, len_squared_v2v2(uv_src_v2, uv_dst_v1)},
-      {1, 1, len_squared_v2v2(uv_src_v2, uv_dst_v2)},
-  };
-  int i_best = 0;
-  for (int i = 1; i < ARRAY_SIZE(tests); i++) {
-    if (use_nearest) {
-      if (tests[i].len_sq < tests[i_best].len_sq) {
-        i_best = i;
-      }
-    }
-    else {
-      if (tests[i].len_sq > tests[i_best].len_sq) {
-        i_best = i;
-      }
-    }
-  }
-
-  *ele_src_p = (BMElem *)(tests[i_best].src_index ? l_src->next : l_src);
-  *ele_dst_p = (BMElem *)(tests[i_best].dst_index ? l_dst->next : l_dst);
-
-  /* Ensure the edge is selected, not just the vertices up until we hit it. */
-  *r_ele_dst_final = (BMElem *)(tests[i_best].dst_index ? l_dst : l_dst->next);
-}
-
-/** \} */
-
-/* -------------------------------------------------------------------- */
 /** \name Path Select Struct & Properties
  * \{ */
 
@@ -180,12 +111,12 @@ static void path_select_params_from_op(wmOperator *op, struct PathSelectParams *
  * \{ */
 
 /* callbacks */
-static bool looptag_filter_cb(BMLoop *l, void *user_data_v)
+static bool verttag_filter_cb(BMLoop *l, void *user_data_v)
 {
   struct UserData_UV *user_data = user_data_v;
   return uvedit_face_visible_test(user_data->scene, l->f);
 }
-static bool looptag_test_cb(BMLoop *l, void *user_data_v)
+static bool verttag_test_cb(BMLoop *l, void *user_data_v)
 {
   /* All connected loops are selected or we return false. */
   struct UserData_UV *user_data = user_data_v;
@@ -195,7 +126,7 @@ static bool looptag_test_cb(BMLoop *l, void *user_data_v)
   BMIter iter;
   BMLoop *l_iter;
   BM_ITER_ELEM (l_iter, &iter, l->v, BM_LOOPS_OF_VERT) {
-    if (looptag_filter_cb(l_iter, user_data)) {
+    if (verttag_filter_cb(l_iter, user_data)) {
       const MLoopUV *luv_iter = BM_ELEM_CD_GET_VOID_P(l_iter, cd_loop_uv_offset);
       if (equals_v2v2(luv->uv, luv_iter->uv)) {
         if (!uvedit_uv_select_test(scene, l_iter, cd_loop_uv_offset)) {
@@ -206,7 +137,7 @@ static bool looptag_test_cb(BMLoop *l, void *user_data_v)
   }
   return true;
 }
-static void looptag_set_cb(BMLoop *l, bool val, void *user_data_v)
+static void verttag_set_cb(BMLoop *l, bool val, void *user_data_v)
 {
   struct UserData_UV *user_data = user_data_v;
   const Scene *scene = user_data->scene;
@@ -216,7 +147,7 @@ static void looptag_set_cb(BMLoop *l, bool val, void *user_data_v)
   BMIter iter;
   BMLoop *l_iter;
   BM_ITER_ELEM (l_iter, &iter, l->v, BM_LOOPS_OF_VERT) {
-    if (looptag_filter_cb(l_iter, user_data)) {
+    if (verttag_filter_cb(l_iter, user_data)) {
       MLoopUV *luv_iter = BM_ELEM_CD_GET_VOID_P(l_iter, cd_loop_uv_offset);
       if (equals_v2v2(luv->uv, luv_iter->uv)) {
         uvedit_uv_select_set(scene, em, l_iter, val, false, cd_loop_uv_offset);
@@ -233,42 +164,10 @@ static int mouse_mesh_uv_shortest_path_vert(Scene *scene,
                                             const float aspect_y,
                                             const int cd_loop_uv_offset)
 {
-  const char uv_selectmode = ED_uvedit_select_mode_get(scene);
-  /* TODO(@sidd017): Implement logic to calculate shortest path for UV edges, since we now support
-   * proper edge selection for UVs (D12028).
-   * Till then continue using vertex path to fake shortest path calculation for edges. */
-  const bool use_fake_edge_select = (uv_selectmode & UV_SELECT_EDGE);
   BMEditMesh *em = BKE_editmesh_from_object(obedit);
   BMesh *bm = em->bm;
   int flush = 0;
 
-  /* Variables to use when `use_fake_edge_select` is set. */
-  struct {
-    BMLoop *l_dst_activate;
-    BMLoop *l_dst_add_to_path;
-  } fake_edge_select = {NULL};
-
-  if (use_fake_edge_select) {
-    fake_edge_select.l_dst_activate = l_dst;
-
-    /* Use most distant when doing region selection.
-     * without this we get dangling edges outside the region. */
-    bool use_neaerst = (op_params->use_fill == false);
-    BMElem *ele_src = (BMElem *)l_src;
-    BMElem *ele_dst = (BMElem *)l_dst;
-    BMElem *ele_dst_final = NULL;
-    bm_loop_calc_vert_pair_from_edge_pair(
-        use_neaerst, cd_loop_uv_offset, aspect_y, &ele_src, &ele_dst, &ele_dst_final);
-
-    if (op_params->use_fill == false) {
-      /* Always activate the item under the cursor. */
-      fake_edge_select.l_dst_add_to_path = (BMLoop *)ele_dst_final;
-    }
-
-    l_src = (BMLoop *)ele_src;
-    l_dst = (BMLoop *)ele_dst;
-  }
-
   struct UserData_UV user_data = {
       .scene = scene,
       .em = em,
@@ -291,33 +190,23 @@ static int mouse_mesh_uv_shortest_path_vert(Scene *scene,
                                               (BMElem *)l_src,
                                               (BMElem *)l_dst,
                                               params.cd_loop_uv_offset,
-                                              looptag_filter_cb,
+                                              verttag_filter_cb,
                                               &user_data);
     }
     else {
       is_path_ordered = true;
-      path = BM_mesh_calc_path_uv_vert(bm, l_src, l_dst, &params, looptag_filter_cb, &user_data);
+      path = BM_mesh_calc_path_uv_vert(bm, l_src, l_dst, &params, verttag_filter_cb, &user_data);
     }
   }
 
   BMLoop *l_dst_last = l_dst;
 
   if (path) {
-    if (use_fake_edge_select) {
-      if ((fake_edge_select.l_dst_add_to_path != NULL) &&
-          (BLI_linklist_index(path, fake_edge_select.l_dst_add_to_path) == -1)) {
-        /* Append, this isn't optimal compared to #BLI_linklist_append, it's a one-off lookup. */
-        LinkNode *path_last = BLI_linklist_find_last(path);
-        BLI_linklist_insert_after(&path_last, fake_edge_select.l_dst_add_to_path);
-        BLI_assert(BLI_linklist_find_last(path)->link == fake_edge_select.l_dst_add_to_path);
-      }
-    }
-
     /* toggle the flag */
     bool all_set = true;
     LinkNode *node = path;
     do {
-      if (!looptag_test_cb((BMLoop *)node->link, &user_data)) {
+      if (!verttag_test_cb((BMLoop *)node->link, &user_data)) {
         all_set = false;
         break;
       }
@@ -328,7 +217,7 @@ static int mouse_mesh_uv_shortest_path_vert(Scene *scene,
     do {
       if ((is_path_ordered == false) ||
           WM_operator_properties_checker_interval_test(&op_params->interval_params, depth)) {
-        looptag_set_cb((BMLoop *)node->link, !all_set, &user_data);
+        verttag_set_cb((BMLoop *)node->link, !all_set, &user_data);
         if (is_path_ordered) {
           l_dst_last = node->link;
         }
@@ -339,23 +228,133 @@ static int mouse_mesh_uv_shortest_path_vert(Scene *scene,
     flush = all_set ? -1 : 1;
   }
   else {
-    const bool is_act = !looptag_test_cb(l_dst, &user_data);
-    looptag_set_cb(l_dst, is_act, &user_data); /* switch the face option */
+    const bool is_act = !verttag_test_cb(l_dst, &user_data);
+    verttag_set_cb(l_dst, is_act, &user_data); /* switch the face option */
   }
 
   if (op_params->track_active) {
-    /* Fake edge selection. */
-    if (use_fake_edge_select) {
-      BMLoop *l_dst_activate = fake_edge_select.l_dst_activate;
-      /* TODO(campbell): Search for an active loop attached to 'l_dst'.
-       * when `BLI_linklist_index(path, l_dst_activate) == -1`
-       * In practice this rarely happens though. */
-      ED_uvedit_active_edge_loop_set(bm, l_dst_activate);
+    ED_uvedit_active_vert_loop_set(bm, l_dst_last);
+  }
+  return flush;
+}
+
+/* -------------------------------------------------------------------- */
+/** \name UV Edge Path
+ * \{ */
+
+/* callbacks */
+static bool edgetag_filter_cb(BMLoop *l, void *user_data_v)
+{
+  struct UserData_UV *user_data = user_data_v;
+  return uvedit_face_visible_test(user_data->scene, l->f);
+}
+static bool edgetag_test_cb(BMLoop *l, void *user_data_v)
+{
+  /* All connected loops (UV) are selected or we return false. */
+  struct UserData_UV *user_data = user_data_v;
+  const Scene *scene = user_data->scene;
+  const uint cd_loop_uv_offset = user_data->cd_loop_uv_offset;
+  BMIter iter;
+  BMLoop *l_iter;
+  BM_ITER_ELEM (l_iter, &iter, l->e, BM_LOOPS_OF_EDGE) {
+    if (edgetag_filter_cb(l_iter, user_data)) {
+      if (BM_loop_uv_share_edge_check(l, l_iter, cd_loop_uv_offset)) {
+        if (!uvedit_edge_select_test(scene, l_iter, cd_loop_uv_offset)) {
+          return false;
+        }
+      }
+    }
+  }
+  return true;
+}
+static void edgetag_set_cb(BMLoop *l, bool val, void *user_data_v)
+{
+  struct UserData_UV *user_data = user_data_v;
+  const Scene *scene = user_data->scene;
+  BMEditMesh *em = user_data->em;
+  const uint cd_loop_uv_offset = user_data->cd_loop_uv_offset;
+  uvedit_edge_select_set_with_sticky(scene, em, l, val, false, cd_loop_uv_offset);
+}
+
+static int mouse_mesh_uv_shortest_path_edge(Scene *scene,
+                                            Object *obedit,
+                                            const struct PathSelectParams *op_params,
+                                            BMLoop *l_src,
+                                            BMLoop *l_dst,
+                                            const float aspect_y,
+                                            const int cd_loop_uv_offset)
+{
+  BMEditMesh *em = BKE_editmesh_from_object(obedit);
+  BMesh *bm = em->bm;
+  int flush = 0;
+
+  struct UserData_UV user_data = {
+      .scene = scene,
+      .em = em,
+      .cd_loop_uv_offset = cd_loop_uv_offset,
+  };
+
+  const struct BMCalcPathUVParams params = {
+      .use_topology_distance = op_params->use_topology_distance,
+      .use_step_face = op_params->use_face_step,
+      .aspect_y = aspect_y,
+      .cd_loop_uv_offset = cd_loop_uv_offset,
+  };
+
+  LinkNode *path = NULL;
+  bool is_path_ordered = false;
+
+  if (l_src != l_dst) {
+    if (op_params->use_fill) {
+      path = BM_mesh_calc_path_uv_region_edge(bm,
+                                              (BMElem *)l_src,
+                                              (BMElem *)l_dst,
+                                              params.cd_loop_uv_offset,
+                                              edgetag_filter_cb,
+                                              &user_data);
     }
     else {
-      ED_uvedit_active_vert_loop_set(bm, l_dst_last);
+      is_path_ordered = true;
+      path = BM_mesh_calc_path_uv_edge(bm, l_src, l_dst, &params, edgetag_filter_cb, &user_data);
     }
   }
+
+  BMLoop *l_dst_last = l_dst;
+
+  if (path) {
+    /* toggle the flag */
+    bool all_set = true;
+    LinkNode *node = path;
+    do {
+      if (!edgetag_test_cb((BMLoop *)node->link, &user_data)) {
+        all_set = false;
+        break;
+      }
+    } while ((node = node->next));
+
+    int depth = -1;
+    node = path;
+    do {
+      if ((is_path_ordered == false) ||
+          WM_operator_properties_checker_interval_test(&op_params->interval_params, depth)) {
+        edgetag_set_cb((BMLoop *)node->link, !all_set, &user_data);
+        if (is_path_ordered) {
+          l_dst_last = node->link;
+        }
+      }
+    } while ((void)depth++, (node = node->next));
+
+    BLI_linklist_free(path, NULL);
+    flush = all_set ? -1 : 1;
+  }
+  else {
+    const bool is_act = !edgetag_test_cb(l_dst, &user_data);
+    edgetag_set_cb(l_dst, is_act, &user_data); /* switch the face option */
+  }
+
+  if (op_params->track_active) {
+    ED_uvedit_active_edge_loop_set(bm, l_dst_last);
+  }
   return flush;
 }
 
@@ -514,13 +513,24 @@ static bool uv_shortest_path_pick_ex(Scene *scene,
     ok = true;
   }
   else if (ele_src->head.htype == BM_LOOP) {
-    flush = mouse_mesh_uv_shortest_path_vert(scene,
-                                             obedit,
-                                             op_params,
-                                             (BMLoop *)ele_src,
-                                             (BMLoop *)ele_dst,
-                                             aspect_y,
-                                             cd_loop_uv_offset);
+    if (uv_selectmode & UV_SELECT_EDGE) {
+      flush = mouse_mesh_uv_shortest_path_edge(scene,
+                                               obedit,
+                                               op_params,
+                                               (BMLoop *)ele_src,
+                                               (BMLoop *)ele_dst,
+                                               aspect_y,
+                                               cd_loop_uv_offset);
+    }
+    else {
+      flush = mouse_mesh_uv_shortest_path_vert(scene,
+                                               obedit,
+                                               op_params,
+                                               (BMLoop *)ele_src,
+                                               (BMLoop *)ele_dst,
+                                               aspect_y,
+                                               cd_loop_uv_offset);
+    }
     ok = true;
   }
 
@@ -529,24 +539,9 @@ static bool uv_shortest_path_pick_ex(Scene *scene,
       const bool select = (flush == 1);
       BMEditMesh *em = BKE_editmesh_from_object(obedit);
       if (ts->uv_flag & UV_SYNC_SELECTION) {
-        if (uv_selectmode & UV_SELECT_EDGE) {
-          /* Special case as we don't use true edge selection,
-           * flush the selection from the vertices. */
-          BM_mesh_select_mode_flush_ex(em->bm, SCE_SELECT_VERTEX, BM_SELECT_LEN_FLUSH_RECALC_ALL);
-        }
         ED_uvedit_select_sync_flush(scene->toolsettings, em, select);
       }
       else {
-        if (uv_selectmode & UV_SELECT_EDGE) {
-          /* TODO(@sidd017): Remove this case when adding proper uv edge support for this operator.
-           * In the meantime, this case helps ensures proper UV selection states for edge mode. */
-          if (select) {
-            uvedit_select_flush(scene, em);
-          }
-          else {
-            uvedit_deselect_flush(scene, em);
-          }
-        }
         ED_uvedit_selectmode_flush(scene, em);
       }
     }