[Bf-blender-cvs] [178868cf425] master: Fix T79304: improve uv island calculation when in edge selection mode

[Chris Blackbourn]

Commit: 178868cf42594bf7eedfa4db93ba8b7f3bf017ce
Author: Chris Blackbourn
Date:   Thu Jul 14 12:40:43 2022 +1200
Branches: master
https://developer.blender.org/rB178868cf42594bf7eedfa4db93ba8b7f3bf017ce

Fix T79304: improve uv island calculation when in edge selection mode

Differential Revision: https://developer.blender.org/D15419

===================================================================

M	source/blender/editors/mesh/editmesh_utils.c

===================================================================

diff --git a/source/blender/editors/mesh/editmesh_utils.c b/source/blender/editors/mesh/editmesh_utils.c
index 60a666ee755..ac5530c8ea9 100644
--- a/source/blender/editors/mesh/editmesh_utils.c
+++ b/source/blender/editors/mesh/editmesh_utils.c
@@ -595,6 +595,132 @@ UvMapVert *BM_uv_vert_map_at_index(UvVertMap *vmap, uint v)
 
 #define INVALID_ISLAND ((unsigned int)-1)
 
+static void bm_uv_assign_island(UvElementMap *element_map,
+                                UvElement *element,
+                                int nisland,
+                                uint *map,
+                                UvElement *islandbuf,
+                                int islandbufsize)
+{
+  element->island = nisland;
+  map[element - element_map->buf] = islandbufsize;
+
+  /* Copy *element to islandbuf[islandbufsize]. */
+  islandbuf[islandbufsize].l = element->l;
+  islandbuf[islandbufsize].separate = element->separate;
+  islandbuf[islandbufsize].loop_of_poly_index = element->loop_of_poly_index;
+  islandbuf[islandbufsize].island = element->island;
+  islandbuf[islandbufsize].flag = element->flag;
+}
+
+static int bm_uv_edge_select_build_islands(UvElementMap *element_map,
+                                           const Scene *scene,
+                                           UvElement *islandbuf,
+                                           uint *map,
+                                           bool uv_selected,
+                                           int cd_loop_uv_offset)
+{
+  int totuv = element_map->totalUVs;
+
+  /* For each UvElement, locate the "separate" UvElement that precedes it in the linked list. */
+  UvElement **head_table = MEM_mallocN(sizeof(*head_table) * totuv, "uv_island_head_table");
+  for (int i = 0; i < totuv; i++) {
+    UvElement *head = element_map->buf + i;
+    if (head->separate) {
+      UvElement *element = head;
+      while (element) {
+        head_table[element - element_map->buf] = head;
+        element = element->next;
+        if (element && element->separate) {
+          break;
+        }
+      }
+    }
+  }
+
+  /* Depth first search the graph, building islands as we go. */
+  int nislands = 0;
+  int islandbufsize = 0;
+  int stack_upper_bound = totuv;
+  UvElement **stack_uv = MEM_mallocN(sizeof(*stack_uv) * stack_upper_bound,
+                                     "uv_island_element_stack");
+  int stacksize_uv = 0;
+  for (int i = 0; i < totuv; i++) {
+    UvElement *element = element_map->buf + i;
+    if (element->island != INVALID_ISLAND) {
+      /* Unique UV (element and all it's children) are already part of an island. */
+      continue;
+    }
+
+    /* Create a new island, i.e. nislands++. */
+
+    BLI_assert(element->separate); /* Ensure we're the head of this unique UV. */
+
+    /* Seed the graph search. */
+    stack_uv[stacksize_uv++] = element;
+    while (element) {
+      bm_uv_assign_island(element_map, element, nislands, map, islandbuf, islandbufsize++);
+      element = element->next;
+      if (element && element->separate) {
+        break;
+      }
+    }
+
+    /* Traverse the graph. */
+    while (stacksize_uv) {
+      BLI_assert(stacksize_uv < stack_upper_bound);
+      element = stack_uv[--stacksize_uv];
+      while (element) {
+
+        /* Scan forwards around the BMFace that contains element->l. */
+        if (!uv_selected || uvedit_edge_select_test(scene, element->l, cd_loop_uv_offset)) {
+          UvElement *next = BM_uv_element_get(element_map, element->l->next->f, element->l->next);
+          if (next->island == INVALID_ISLAND) {
+            UvElement *tail = head_table[next - element_map->buf];
+            stack_uv[stacksize_uv++] = tail;
+            while (tail) {
+              bm_uv_assign_island(element_map, tail, nislands, map, islandbuf, islandbufsize++);
+              tail = tail->next;
+              if (tail && tail->separate) {
+                break;
+              }
+            }
+          }
+        }
+
+        /* Scan backwards around the BMFace that contains element->l. */
+        if (!uv_selected || uvedit_edge_select_test(scene, element->l->prev, cd_loop_uv_offset)) {
+          UvElement *prev = BM_uv_element_get(element_map, element->l->prev->f, element->l->prev);
+          if (prev->island == INVALID_ISLAND) {
+            UvElement *tail = head_table[prev - element_map->buf];
+            stack_uv[stacksize_uv++] = tail;
+            while (tail) {
+              bm_uv_assign_island(element_map, tail, nislands, map, islandbuf, islandbufsize++);
+              tail = tail->next;
+              if (tail && tail->separate) {
+                break;
+              }
+            }
+          }
+        }
+
+        /* The same for all the UvElements in this unique UV. */
+        element = element->next;
+        if (element && element->separate) {
+          break;
+        }
+      }
+    }
+    nislands++;
+  }
+  BLI_assert(islandbufsize == totuv);
+
+  MEM_SAFE_FREE(stack_uv);
+  MEM_SAFE_FREE(head_table);
+
+  return nislands;
+}
+
 UvElementMap *BM_uv_element_map_create(BMesh *bm,
                                        const Scene *scene,
                                        const bool uv_selected,
@@ -783,6 +909,15 @@ UvElementMap *BM_uv_element_map_create(BMesh *bm,
     island_number = MEM_mallocN(sizeof(*island_number) * totfaces, "uv_island_number_face");
     copy_vn_i(island_number, totfaces, INVALID_ISLAND);
 
+    const bool use_uv_edge_connectivity = scene->toolsettings->uv_flag & UV_SYNC_SELECTION ?
+                                              scene->toolsettings->selectmode & SCE_SELECT_EDGE :
+                                              scene->toolsettings->uv_selectmode & UV_SELECT_EDGE;
+    if (use_uv_edge_connectivity) {
+      nislands = bm_uv_edge_select_build_islands(
+          element_map, scene, islandbuf, map, uv_selected, cd_loop_uv_offset);
+      islandbufsize = totuv;
+    }
+
     /* at this point, every UvElement in vert points to a UvElement sharing the same vertex.
      * Now we should sort uv's in islands. */
     for (i = 0; i < totuv; i++) {
@@ -810,13 +945,8 @@ UvElementMap *BM_uv_element_map_create(BMesh *bm,
               if (element->l->f == efa) {
                 /* found the uv corresponding to our face and vertex.
                  * Now fill it to the buffer */
-                element->island = nislands;
-                map[element - element_map->buf] = islandbufsize;
-                islandbuf[islandbufsize].l = element->l;
-                islandbuf[islandbufsize].separate = element->separate;
-                islandbuf[islandbufsize].loop_of_poly_index = element->loop_of_poly_index;
-                islandbuf[islandbufsize].island = nislands;
-                islandbufsize++;
+                bm_uv_assign_island(
+                    element_map, element, nislands, map, islandbuf, islandbufsize++);
 
                 for (element = initelement; element; element = element->next) {
                   if (element->separate && element != initelement) {