Attributes: Improve custom data initialization options

When allocating new `CustomData` layers, often we do redundant
initialization of arrays. For example, it's common that values are
allocated, set to their default value, and then set to some other
value. This is wasteful, and it negates the benefits of optimizations
to the allocator like D15082. There are two reasons for this. The
first is array-of-structs storage that makes it annoying to initialize
values manually, and the second is confusing options in the Custom Data
API. This patch addresses the latter.

The `CustomData` "alloc type" options are rearranged. Now, besides
the options that use existing layers, there are two remaining:
* `CD_SET_DEFAULT` sets the default value.
  * Usually zeroes, but for colors this is white (how it was before).
  * Should be used when you add the layer but don't set all values.
* `CD_CONSTRUCT` refers to the "default construct" C++ term.
  * Only necessary or defined for non-trivial types like vertex groups.
  * Doesn't do anything for trivial types like `int` or `float3`.
  * Should be used every other time, when all values will be set.

The attribute API's `AttributeInit` types are updated as well.
To update code, replace `CD_CALLOC` with `CD_SET_DEFAULT` and
`CD_DEFAULT` with `CD_CONSTRUCT`. This doesn't cause any functional
changes yet. Follow-up commits will change to avoid initializing
new layers where the correctness is clear.

Differential Revision: https://developer.blender.org/D15617

3 files changed, 39 insertions, 39 deletions

diff --git a/source/blender/bmesh/intern/bmesh_construct.c b/source/blender/bmesh/intern/bmesh_construct.c
index 0ee5545527b..757d006b04d 100644
--- a/source/blender/bmesh/intern/bmesh_construct.c
+++ b/source/blender/bmesh/intern/bmesh_construct.c
@@ -513,23 +513,23 @@ void BM_mesh_copy_init_customdata_from_mesh_array(BMesh *bm_dst,
     const Mesh *me_src = me_src_array[i];
     if (i == 0) {
       CustomData_copy_mesh_to_bmesh(
-          &me_src->vdata, &bm_dst->vdata, CD_MASK_BMESH.vmask, CD_CALLOC, 0);
+          &me_src->vdata, &bm_dst->vdata, CD_MASK_BMESH.vmask, CD_SET_DEFAULT, 0);
       CustomData_copy_mesh_to_bmesh(
-          &me_src->edata, &bm_dst->edata, CD_MASK_BMESH.emask, CD_CALLOC, 0);
+          &me_src->edata, &bm_dst->edata, CD_MASK_BMESH.emask, CD_SET_DEFAULT, 0);
       CustomData_copy_mesh_to_bmesh(
-          &me_src->ldata, &bm_dst->ldata, CD_MASK_BMESH.lmask, CD_CALLOC, 0);
+          &me_src->ldata, &bm_dst->ldata, CD_MASK_BMESH.lmask, CD_SET_DEFAULT, 0);
       CustomData_copy_mesh_to_bmesh(
-          &me_src->pdata, &bm_dst->pdata, CD_MASK_BMESH.pmask, CD_CALLOC, 0);
+          &me_src->pdata, &bm_dst->pdata, CD_MASK_BMESH.pmask, CD_SET_DEFAULT, 0);
     }
     else {
       CustomData_merge_mesh_to_bmesh(
-          &me_src->vdata, &bm_dst->vdata, CD_MASK_BMESH.vmask, CD_CALLOC, 0);
+          &me_src->vdata, &bm_dst->vdata, CD_MASK_BMESH.vmask, CD_SET_DEFAULT, 0);
       CustomData_merge_mesh_to_bmesh(
-          &me_src->edata, &bm_dst->edata, CD_MASK_BMESH.emask, CD_CALLOC, 0);
+          &me_src->edata, &bm_dst->edata, CD_MASK_BMESH.emask, CD_SET_DEFAULT, 0);
       CustomData_merge_mesh_to_bmesh(
-          &me_src->ldata, &bm_dst->ldata, CD_MASK_BMESH.lmask, CD_CALLOC, 0);
+          &me_src->ldata, &bm_dst->ldata, CD_MASK_BMESH.lmask, CD_SET_DEFAULT, 0);
       CustomData_merge_mesh_to_bmesh(
-          &me_src->pdata, &bm_dst->pdata, CD_MASK_BMESH.pmask, CD_CALLOC, 0);
+          &me_src->pdata, &bm_dst->pdata, CD_MASK_BMESH.pmask, CD_SET_DEFAULT, 0);
     }
 
     cd_flag |= me_src->cd_flag;
@@ -558,10 +558,10 @@ void BM_mesh_copy_init_customdata(BMesh *bm_dst, BMesh *bm_src, const BMAllocTem
     allocsize = &bm_mesh_allocsize_default;
   }
 
-  CustomData_copy(&bm_src->vdata, &bm_dst->vdata, CD_MASK_BMESH.vmask, CD_CALLOC, 0);
-  CustomData_copy(&bm_src->edata, &bm_dst->edata, CD_MASK_BMESH.emask, CD_CALLOC, 0);
-  CustomData_copy(&bm_src->ldata, &bm_dst->ldata, CD_MASK_BMESH.lmask, CD_CALLOC, 0);
-  CustomData_copy(&bm_src->pdata, &bm_dst->pdata, CD_MASK_BMESH.pmask, CD_CALLOC, 0);
+  CustomData_copy(&bm_src->vdata, &bm_dst->vdata, CD_MASK_BMESH.vmask, CD_SET_DEFAULT, 0);
+  CustomData_copy(&bm_src->edata, &bm_dst->edata, CD_MASK_BMESH.emask, CD_SET_DEFAULT, 0);
+  CustomData_copy(&bm_src->ldata, &bm_dst->ldata, CD_MASK_BMESH.lmask, CD_SET_DEFAULT, 0);
+  CustomData_copy(&bm_src->pdata, &bm_dst->pdata, CD_MASK_BMESH.pmask, CD_SET_DEFAULT, 0);
 
   CustomData_bmesh_init_pool(&bm_dst->vdata, allocsize->totvert, BM_VERT);
   CustomData_bmesh_init_pool(&bm_dst->edata, allocsize->totedge, BM_EDGE);
@@ -596,7 +596,7 @@ void BM_mesh_copy_init_customdata_all_layers(BMesh *bm_dst,
 
     for (int l = 0; l < src->totlayer; l++) {
       CustomData_add_layer_named(
-          dst, src->layers[l].type, CD_CALLOC, NULL, 0, src->layers[l].name);
+          dst, src->layers[l].type, CD_SET_DEFAULT, NULL, 0, src->layers[l].name);
     }
     CustomData_bmesh_init_pool(dst, size, htypes[i]);
   }
diff --git a/source/blender/bmesh/intern/bmesh_interp.c b/source/blender/bmesh/intern/bmesh_interp.c
index 0c3db31dd1f..b7028dee5e1 100644
--- a/source/blender/bmesh/intern/bmesh_interp.c
+++ b/source/blender/bmesh/intern/bmesh_interp.c
@@ -846,7 +846,7 @@ void BM_data_layer_add(BMesh *bm, CustomData *data, int type)
   /* the pool is now owned by olddata and must not be shared */
   data->pool = NULL;
 
-  CustomData_add_layer(data, type, CD_DEFAULT, NULL, 0);
+  CustomData_add_layer(data, type, CD_SET_DEFAULT, NULL, 0);
 
   update_data_blocks(bm, &olddata, data);
   if (olddata.layers) {
@@ -864,7 +864,7 @@ void BM_data_layer_add_named(BMesh *bm, CustomData *data, int type, const char *
   /* the pool is now owned by olddata and must not be shared */
   data->pool = NULL;
 
-  CustomData_add_layer_named(data, type, CD_DEFAULT, NULL, 0, name);
+  CustomData_add_layer_named(data, type, CD_SET_DEFAULT, NULL, 0, name);
 
   update_data_blocks(bm, &olddata, data);
   if (olddata.layers) {
diff --git a/source/blender/bmesh/intern/bmesh_mesh_convert.cc b/source/blender/bmesh/intern/bmesh_mesh_convert.cc
index b9c004b5392..4e0e27cd051 100644
--- a/source/blender/bmesh/intern/bmesh_mesh_convert.cc
+++ b/source/blender/bmesh/intern/bmesh_mesh_convert.cc
@@ -217,10 +217,10 @@ void BM_mesh_bm_from_me(BMesh *bm, const Mesh *me, const struct BMeshFromMeshPar
 
   if (!me || !me->totvert) {
     if (me && is_new) { /* No verts? still copy custom-data layout. */
-      CustomData_copy_mesh_to_bmesh(&me->vdata, &bm->vdata, mask.vmask, CD_DEFAULT, 0);
-      CustomData_copy_mesh_to_bmesh(&me->edata, &bm->edata, mask.emask, CD_DEFAULT, 0);
-      CustomData_copy_mesh_to_bmesh(&me->ldata, &bm->ldata, mask.lmask, CD_DEFAULT, 0);
-      CustomData_copy_mesh_to_bmesh(&me->pdata, &bm->pdata, mask.pmask, CD_DEFAULT, 0);
+      CustomData_copy_mesh_to_bmesh(&me->vdata, &bm->vdata, mask.vmask, CD_CONSTRUCT, 0);
+      CustomData_copy_mesh_to_bmesh(&me->edata, &bm->edata, mask.emask, CD_CONSTRUCT, 0);
+      CustomData_copy_mesh_to_bmesh(&me->ldata, &bm->ldata, mask.lmask, CD_CONSTRUCT, 0);
+      CustomData_copy_mesh_to_bmesh(&me->pdata, &bm->pdata, mask.pmask, CD_CONSTRUCT, 0);
 
       CustomData_bmesh_init_pool(&bm->vdata, me->totvert, BM_VERT);
       CustomData_bmesh_init_pool(&bm->edata, me->totedge, BM_EDGE);
@@ -236,16 +236,16 @@ void BM_mesh_bm_from_me(BMesh *bm, const Mesh *me, const struct BMeshFromMeshPar
   }
 
   if (is_new) {
-    CustomData_copy_mesh_to_bmesh(&me->vdata, &bm->vdata, mask.vmask, CD_CALLOC, 0);
-    CustomData_copy_mesh_to_bmesh(&me->edata, &bm->edata, mask.emask, CD_CALLOC, 0);
-    CustomData_copy_mesh_to_bmesh(&me->ldata, &bm->ldata, mask.lmask, CD_CALLOC, 0);
-    CustomData_copy_mesh_to_bmesh(&me->pdata, &bm->pdata, mask.pmask, CD_CALLOC, 0);
+    CustomData_copy_mesh_to_bmesh(&me->vdata, &bm->vdata, mask.vmask, CD_SET_DEFAULT, 0);
+    CustomData_copy_mesh_to_bmesh(&me->edata, &bm->edata, mask.emask, CD_SET_DEFAULT, 0);
+    CustomData_copy_mesh_to_bmesh(&me->ldata, &bm->ldata, mask.lmask, CD_SET_DEFAULT, 0);
+    CustomData_copy_mesh_to_bmesh(&me->pdata, &bm->pdata, mask.pmask, CD_SET_DEFAULT, 0);
   }
   else {
-    CustomData_bmesh_merge(&me->vdata, &bm->vdata, mask.vmask, CD_CALLOC, bm, BM_VERT);
-    CustomData_bmesh_merge(&me->edata, &bm->edata, mask.emask, CD_CALLOC, bm, BM_EDGE);
-    CustomData_bmesh_merge(&me->ldata, &bm->ldata, mask.lmask, CD_CALLOC, bm, BM_LOOP);
-    CustomData_bmesh_merge(&me->pdata, &bm->pdata, mask.pmask, CD_CALLOC, bm, BM_FACE);
+    CustomData_bmesh_merge(&me->vdata, &bm->vdata, mask.vmask, CD_SET_DEFAULT, bm, BM_VERT);
+    CustomData_bmesh_merge(&me->edata, &bm->edata, mask.emask, CD_SET_DEFAULT, bm, BM_EDGE);
+    CustomData_bmesh_merge(&me->ldata, &bm->ldata, mask.lmask, CD_SET_DEFAULT, bm, BM_LOOP);
+    CustomData_bmesh_merge(&me->pdata, &bm->pdata, mask.pmask, CD_SET_DEFAULT, bm, BM_FACE);
   }
 
   /* -------------------------------------------------------------------- */
@@ -1016,10 +1016,10 @@ void BM_mesh_bm_to_me(Main *bmain, BMesh *bm, Mesh *me, const struct BMeshToMesh
   {
     CustomData_MeshMasks mask = CD_MASK_MESH;
     CustomData_MeshMasks_update(&mask, &params->cd_mask_extra);
-    CustomData_copy_mesh_to_bmesh(&bm->vdata, &me->vdata, mask.vmask, CD_CALLOC, me->totvert);
-    CustomData_copy_mesh_to_bmesh(&bm->edata, &me->edata, mask.emask, CD_CALLOC, me->totedge);
-    CustomData_copy_mesh_to_bmesh(&bm->ldata, &me->ldata, mask.lmask, CD_CALLOC, me->totloop);
-    CustomData_copy_mesh_to_bmesh(&bm->pdata, &me->pdata, mask.pmask, CD_CALLOC, me->totpoly);
+    CustomData_copy_mesh_to_bmesh(&bm->vdata, &me->vdata, mask.vmask, CD_SET_DEFAULT, me->totvert);
+    CustomData_copy_mesh_to_bmesh(&bm->edata, &me->edata, mask.emask, CD_SET_DEFAULT, me->totedge);
+    CustomData_copy_mesh_to_bmesh(&bm->ldata, &me->ldata, mask.lmask, CD_SET_DEFAULT, me->totloop);
+    CustomData_copy_mesh_to_bmesh(&bm->pdata, &me->pdata, mask.pmask, CD_SET_DEFAULT, me->totpoly);
   }
 
   MVert *mvert = bm->totvert ? (MVert *)MEM_callocN(sizeof(MVert) * bm->totvert, "bm_to_me.vert") :
@@ -1271,10 +1271,10 @@ void BM_mesh_bm_to_me_for_eval(BMesh *bm, Mesh *me, const CustomData_MeshMasks *
   me->totloop = bm->totloop;
   me->totpoly = bm->totface;
 
-  CustomData_add_layer(&me->vdata, CD_MVERT, CD_CALLOC, nullptr, bm->totvert);
-  CustomData_add_layer(&me->edata, CD_MEDGE, CD_CALLOC, nullptr, bm->totedge);
-  CustomData_add_layer(&me->ldata, CD_MLOOP, CD_CALLOC, nullptr, bm->totloop);
-  CustomData_add_layer(&me->pdata, CD_MPOLY, CD_CALLOC, nullptr, bm->totface);
+  CustomData_add_layer(&me->vdata, CD_MVERT, CD_SET_DEFAULT, nullptr, bm->totvert);
+  CustomData_add_layer(&me->edata, CD_MEDGE, CD_SET_DEFAULT, nullptr, bm->totedge);
+  CustomData_add_layer(&me->ldata, CD_MLOOP, CD_SET_DEFAULT, nullptr, bm->totloop);
+  CustomData_add_layer(&me->pdata, CD_MPOLY, CD_SET_DEFAULT, nullptr, bm->totface);
 
   /* Don't process shape-keys, we only feed them through the modifier stack as needed,
    * e.g. for applying modifiers or the like. */
@@ -1283,10 +1283,10 @@ void BM_mesh_bm_to_me_for_eval(BMesh *bm, Mesh *me, const CustomData_MeshMasks *
     CustomData_MeshMasks_update(&mask, cd_mask_extra);
   }
   mask.vmask &= ~CD_MASK_SHAPEKEY;
-  CustomData_merge(&bm->vdata, &me->vdata, mask.vmask, CD_CALLOC, me->totvert);
-  CustomData_merge(&bm->edata, &me->edata, mask.emask, CD_CALLOC, me->totedge);
-  CustomData_merge(&bm->ldata, &me->ldata, mask.lmask, CD_CALLOC, me->totloop);
-  CustomData_merge(&bm->pdata, &me->pdata, mask.pmask, CD_CALLOC, me->totpoly);
+  CustomData_merge(&bm->vdata, &me->vdata, mask.vmask, CD_SET_DEFAULT, me->totvert);
+  CustomData_merge(&bm->edata, &me->edata, mask.emask, CD_SET_DEFAULT, me->totedge);
+  CustomData_merge(&bm->ldata, &me->ldata, mask.lmask, CD_SET_DEFAULT, me->totloop);
+  CustomData_merge(&bm->pdata, &me->pdata, mask.pmask, CD_SET_DEFAULT, me->totpoly);
 
   BKE_mesh_update_customdata_pointers(me, false);