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

2 files changed, 45 insertions, 0 deletions

diff --git a/source/blender/bmesh/intern/bmesh_construct.c b/source/blender/bmesh/intern/bmesh_construct.c
index 81494b03558..757ab735134 100644
--- a/source/blender/bmesh/intern/bmesh_construct.c
+++ b/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;
diff --git a/source/blender/bmesh/intern/bmesh_construct.h b/source/blender/bmesh/intern/bmesh_construct.h
index 3523c4aec1a..f5102283ede 100644
--- a/source/blender/bmesh/intern/bmesh_construct.h
+++ b/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);