Fix T81060: CustomData Correction sometimes breaks UVs and Vertex Colors

`CustomData_bmesh_interp` use the same CustomData decryptor (in this case, `bm->ldata`) in both blocks.

So make sure that all CustomData layers match.

This commit also removes redundant `BM_elem_attrs_copy_ex` calls.

Maniphest Tasks: T81060

Differential Revision: https://developer.blender.org/D9159

source/blender/bmesh/intern/bmesh_construct.c

@@ -606,6 +606,47 @@ void BM_mesh_copy_init_customdata(BMesh *bm_dst, BMesh *bm_src, const BMAllocTem
   CustomData_bmesh_init_pool(&bm_dst->pdata, allocsize->totface, BM_FACE);
 }
 
+/**
+ * Similar to #BM_mesh_copy_init_customdata but copies all layers ignoring
+ * flags like #CD_FLAG_NOCOPY.
+ *
+ * \param bm_dst: BMesh whose custom-data layers will be added.
+ * \param bm_src: BMesh whose custom-data layers will be copied.
+ * \param htype: Specifies which custom-datas will be initiated.
+ * \param allocsize: Estimated number of elements to init the mempool.
+ */
+void BM_mesh_copy_init_customdata_all_layers(BMesh *bm_dst,
+                                             BMesh *bm_src,
+                                             const char htype,
+                                             const BMAllocTemplate *allocsize)
+{
+  if (allocsize == NULL) {
+    allocsize = &bm_mesh_allocsize_default;
+  }
+
+  const char htypes[4] = {BM_VERT, BM_EDGE, BM_LOOP, BM_FACE};
+  BLI_assert(((&bm_dst->vdata + 1) == &bm_dst->edata) &&
+             ((&bm_dst->vdata + 2) == &bm_dst->ldata) && ((&bm_dst->vdata + 3) == &bm_dst->pdata));
+
+  BLI_assert(((&allocsize->totvert + 1) == &allocsize->totedge) &&
+             ((&allocsize->totvert + 2) == &allocsize->totloop) &&
+             ((&allocsize->totvert + 3) == &allocsize->totface));
+
+  for (int i = 0; i < 4; i++) {
+    if (!(htypes[i] & htype)) {
+      continue;
+    }
+    CustomData *dst = &bm_dst->vdata + i;
+    CustomData *src = &bm_src->vdata + i;
+    const int size = *(&allocsize->totvert + i);
+
+    for (int l = 0; l < src->totlayer; l++) {
+      CustomData_add_layer(dst, src->layers[l].type, CD_CALLOC, NULL, 0);
+    }
+    CustomData_bmesh_init_pool(dst, size, htypes[i]);
+  }
+}
+
 BMesh *BM_mesh_copy(BMesh *bm_old)
 {
   BMesh *bm_new;

source/blender/bmesh/intern/bmesh_construct.h

@@ -69,6 +69,10 @@ void BM_elem_select_copy(BMesh *bm_dst, void *ele_dst_v, const void *ele_src_v);
 void BM_mesh_copy_init_customdata(BMesh *bm_dst,
                                   BMesh *bm_src,
                                   const struct BMAllocTemplate *allocsize);
+void BM_mesh_copy_init_customdata_all_layers(BMesh *bm_dst,
+                                             BMesh *bm_src,
+                                             const char htype,
+                                             const struct BMAllocTemplate *allocsize);
 BMesh *BM_mesh_copy(BMesh *bm_old);
 
 char BM_face_flag_from_mflag(const char mflag);

source/blender/editors/transform/transform_convert_mesh.c

@@ -1176,8 +1176,9 @@ static void mesh_customdatacorrect_init_container_generic(TransDataContainer *UN
                                                   .use_toolflags = false,
                                               }));
 
-  /* We need to have matching custom-data. */
-  BM_mesh_copy_init_customdata(bm_origfaces, bm, NULL);
+  /* We need to have matching loop custom-data. */
+  BM_mesh_copy_init_customdata_all_layers(bm_origfaces, bm, BM_LOOP, NULL);
+
   tcld->origfaces = origfaces;
   tcld->bm_origfaces = bm_origfaces;
 
@@ -1359,9 +1360,6 @@ static void mesh_customdatacorrect_apply_vert(struct TransCustomDataLayer *tcld,
      * and we do not want to mess up other shape keys */
     BM_loop_interp_from_face(bm, l, f_copy, false, false);
 
-    /* make sure face-attributes are correct (e.g. #MLoopUV, #MLoopCol) */
-    BM_elem_attrs_copy_ex(tcld->bm_origfaces, bm, f_copy, l->f, BM_ELEM_SELECT, CD_MASK_NORMAL);
-
     /* weight the loop */
     if (do_loop_weight) {
       const float eps = 1.0e-8f;
@@ -1514,8 +1512,6 @@ static void mesh_customdatacorrect_restore(struct TransInfo *t)
         BM_elem_attrs_copy(bm_copy, bm, l_copy, l_iter);
         l_copy = l_copy->next;
       } while ((l_iter = l_iter->next) != l_first);
-
-      BM_elem_attrs_copy_ex(bm_copy, bm, f_copy, f, BM_ELEM_SELECT, CD_MASK_NORMAL);
     }
   }
 }