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

12 files changed, 23 insertions, 18 deletions

diff --git a/source/blender/modifiers/intern/MOD_cloth.c b/source/blender/modifiers/intern/MOD_cloth.c
index 6c5baabe756..8f4a675b797 100644
--- a/source/blender/modifiers/intern/MOD_cloth.c
+++ b/source/blender/modifiers/intern/MOD_cloth.c
@@ -115,7 +115,7 @@ static void deformVerts(ModifierData *md,
       float(*layerorco)[3];
       if (!(layerorco = CustomData_get_layer(&mesh_src->vdata, CD_CLOTH_ORCO))) {
         layerorco = CustomData_add_layer(
-            &mesh_src->vdata, CD_CLOTH_ORCO, CD_CALLOC, NULL, mesh_src->totvert);
+            &mesh_src->vdata, CD_CLOTH_ORCO, CD_SET_DEFAULT, NULL, mesh_src->totvert);
       }
 
       memcpy(layerorco, kb->data, sizeof(float[3]) * verts_num);
diff --git a/source/blender/modifiers/intern/MOD_nodes.cc b/source/blender/modifiers/intern/MOD_nodes.cc
index d3b43176700..c571a4821b4 100644
--- a/source/blender/modifiers/intern/MOD_nodes.cc
+++ b/source/blender/modifiers/intern/MOD_nodes.cc
@@ -1044,7 +1044,7 @@ static void store_computed_output_attributes(
     if (attributes.add(store.name,
                        store.domain,
                        blender::bke::cpp_type_to_custom_data_type(store.data.type()),
-                       blender::bke::AttributeInitMove(store.data.data()))) {
+                       blender::bke::AttributeInitMoveArray(store.data.data()))) {
       continue;
     }
 
@@ -1277,13 +1277,13 @@ static void modifyGeometry(ModifierData *md,
      * assumed that the output mesh does not have a mapping to the original mesh. */
     Mesh &mesh = *geometry_set.get_mesh_for_write();
     if (use_orig_index_verts) {
-      CustomData_add_layer(&mesh.vdata, CD_ORIGINDEX, CD_DEFAULT, nullptr, mesh.totvert);
+      CustomData_add_layer(&mesh.vdata, CD_ORIGINDEX, CD_SET_DEFAULT, nullptr, mesh.totvert);
     }
     if (use_orig_index_edges) {
-      CustomData_add_layer(&mesh.edata, CD_ORIGINDEX, CD_DEFAULT, nullptr, mesh.totedge);
+      CustomData_add_layer(&mesh.edata, CD_ORIGINDEX, CD_SET_DEFAULT, nullptr, mesh.totedge);
     }
     if (use_orig_index_polys) {
-      CustomData_add_layer(&mesh.pdata, CD_ORIGINDEX, CD_DEFAULT, nullptr, mesh.totpoly);
+      CustomData_add_layer(&mesh.pdata, CD_ORIGINDEX, CD_SET_DEFAULT, nullptr, mesh.totpoly);
     }
   }
 }
diff --git a/source/blender/modifiers/intern/MOD_normal_edit.c b/source/blender/modifiers/intern/MOD_normal_edit.c
index 5a92aac6cda..9e3e06fb4dc 100644
--- a/source/blender/modifiers/intern/MOD_normal_edit.c
+++ b/source/blender/modifiers/intern/MOD_normal_edit.c
@@ -562,7 +562,7 @@ static Mesh *normalEditModifier_do(NormalEditModifierData *enmd,
   }
 
   if (clnors == NULL) {
-    clnors = CustomData_add_layer(ldata, CD_CUSTOMLOOPNORMAL, CD_CALLOC, NULL, loops_num);
+    clnors = CustomData_add_layer(ldata, CD_CUSTOMLOOPNORMAL, CD_SET_DEFAULT, NULL, loops_num);
   }
 
   MOD_get_vgroup(ob, result, enmd->defgrp_name, &dvert, &defgrp_index);
diff --git a/source/blender/modifiers/intern/MOD_ocean.c b/source/blender/modifiers/intern/MOD_ocean.c
index ea9049200cc..c84d1b56cec 100644
--- a/source/blender/modifiers/intern/MOD_ocean.c
+++ b/source/blender/modifiers/intern/MOD_ocean.c
@@ -292,7 +292,7 @@ static Mesh *generate_ocean_geometry(OceanModifierData *omd, Mesh *mesh_orig, co
   /* add uvs */
   if (CustomData_number_of_layers(&result->ldata, CD_MLOOPUV) < MAX_MTFACE) {
     gogd.mloopuvs = CustomData_add_layer(
-        &result->ldata, CD_MLOOPUV, CD_CALLOC, NULL, polys_num * 4);
+        &result->ldata, CD_MLOOPUV, CD_SET_DEFAULT, NULL, polys_num * 4);
 
     if (gogd.mloopuvs) { /* unlikely to fail */
       gogd.ix = 1.0 / gogd.rx;
@@ -378,12 +378,16 @@ static Mesh *doOcean(ModifierData *md, const ModifierEvalContext *ctx, Mesh *mes
       const int loops_num = result->totloop;
       MLoop *mloops = result->mloop;
       MLoopCol *mloopcols = CustomData_add_layer_named(
-          &result->ldata, CD_PROP_BYTE_COLOR, CD_CALLOC, NULL, loops_num, omd->foamlayername);
+          &result->ldata, CD_PROP_BYTE_COLOR, CD_SET_DEFAULT, NULL, loops_num, omd->foamlayername);
 
       MLoopCol *mloopcols_spray = NULL;
       if (omd->flag & MOD_OCEAN_GENERATE_SPRAY) {
-        mloopcols_spray = CustomData_add_layer_named(
-            &result->ldata, CD_PROP_BYTE_COLOR, CD_CALLOC, NULL, loops_num, omd->spraylayername);
+        mloopcols_spray = CustomData_add_layer_named(&result->ldata,
+                                                     CD_PROP_BYTE_COLOR,
+                                                     CD_SET_DEFAULT,
+                                                     NULL,
+                                                     loops_num,
+                                                     omd->spraylayername);
       }
 
       if (mloopcols) { /* unlikely to fail */
diff --git a/source/blender/modifiers/intern/MOD_screw.c b/source/blender/modifiers/intern/MOD_screw.c
index 6095be48f8f..b2ebf2ffeec 100644
--- a/source/blender/modifiers/intern/MOD_screw.c
+++ b/source/blender/modifiers/intern/MOD_screw.c
@@ -398,7 +398,7 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
   medge_new = result->medge;
 
   if (!CustomData_has_layer(&result->pdata, CD_ORIGINDEX)) {
-    CustomData_add_layer(&result->pdata, CD_ORIGINDEX, CD_CALLOC, NULL, (int)maxPolys);
+    CustomData_add_layer(&result->pdata, CD_ORIGINDEX, CD_SET_DEFAULT, NULL, (int)maxPolys);
   }
 
   int *origindex = CustomData_get_layer(&result->pdata, CD_ORIGINDEX);
diff --git a/source/blender/modifiers/intern/MOD_skin.c b/source/blender/modifiers/intern/MOD_skin.c
index 84795cdb2d9..b41c730024c 100644
--- a/source/blender/modifiers/intern/MOD_skin.c
+++ b/source/blender/modifiers/intern/MOD_skin.c
@@ -1888,7 +1888,7 @@ static void skin_set_orig_indices(Mesh *mesh)
   int *orig, totpoly;
 
   totpoly = mesh->totpoly;
-  orig = CustomData_add_layer(&mesh->pdata, CD_ORIGINDEX, CD_CALLOC, NULL, totpoly);
+  orig = CustomData_add_layer(&mesh->pdata, CD_ORIGINDEX, CD_SET_DEFAULT, NULL, totpoly);
   copy_vn_i(orig, totpoly, ORIGINDEX_NONE);
 }
 
diff --git a/source/blender/modifiers/intern/MOD_solidify_extrude.c b/source/blender/modifiers/intern/MOD_solidify_extrude.c
index 47277577d3e..15e8bd25997 100644
--- a/source/blender/modifiers/intern/MOD_solidify_extrude.c
+++ b/source/blender/modifiers/intern/MOD_solidify_extrude.c
@@ -994,7 +994,7 @@ Mesh *MOD_solidify_extrude_modifyMesh(ModifierData *md, const ModifierEvalContex
     if (dvert == NULL) {
       /* Add a valid data layer! */
       dvert = CustomData_add_layer(
-          &result->vdata, CD_MDEFORMVERT, CD_CALLOC, NULL, result->totvert);
+          &result->vdata, CD_MDEFORMVERT, CD_SET_DEFAULT, NULL, result->totvert);
     }
     /* Ultimate security check. */
     if (dvert != NULL) {
diff --git a/source/blender/modifiers/intern/MOD_solidify_nonmanifold.c b/source/blender/modifiers/intern/MOD_solidify_nonmanifold.c
index 8a5b600974c..9205083e836 100644
--- a/source/blender/modifiers/intern/MOD_solidify_nonmanifold.c
+++ b/source/blender/modifiers/intern/MOD_solidify_nonmanifold.c
@@ -1981,7 +1981,7 @@ Mesh *MOD_solidify_nonmanifold_modifyMesh(ModifierData *md,
     if (dvert == NULL) {
       /* Add a valid data layer! */
       dvert = CustomData_add_layer(
-          &result->vdata, CD_MDEFORMVERT, CD_CALLOC, NULL, result->totvert);
+          &result->vdata, CD_MDEFORMVERT, CD_SET_DEFAULT, NULL, result->totvert);
     }
     result->dvert = dvert;
   }
diff --git a/source/blender/modifiers/intern/MOD_uvproject.c b/source/blender/modifiers/intern/MOD_uvproject.c
index 4646ba41a74..ccef867b752 100644
--- a/source/blender/modifiers/intern/MOD_uvproject.c
+++ b/source/blender/modifiers/intern/MOD_uvproject.c
@@ -124,7 +124,7 @@ static Mesh *uvprojectModifier_do(UVProjectModifierData *umd,
    * (e.g. if a preceding modifier could not preserve it). */
   if (!CustomData_has_layer(&mesh->ldata, CD_MLOOPUV)) {
     CustomData_add_layer_named(
-        &mesh->ldata, CD_MLOOPUV, CD_DEFAULT, NULL, mesh->totloop, umd->uvlayer_name);
+        &mesh->ldata, CD_MLOOPUV, CD_SET_DEFAULT, NULL, mesh->totloop, umd->uvlayer_name);
   }
 
   /* make sure we're using an existing layer */
diff --git a/source/blender/modifiers/intern/MOD_weighted_normal.c b/source/blender/modifiers/intern/MOD_weighted_normal.c
index 039497b725b..5b5d464a710 100644
--- a/source/blender/modifiers/intern/MOD_weighted_normal.c
+++ b/source/blender/modifiers/intern/MOD_weighted_normal.c
@@ -609,7 +609,8 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
    * it helps when generating clnor spaces and default normals. */
   const bool has_clnors = clnors != NULL;
   if (!clnors) {
-    clnors = CustomData_add_layer(&result->ldata, CD_CUSTOMLOOPNORMAL, CD_CALLOC, NULL, loops_num);
+    clnors = CustomData_add_layer(
+        &result->ldata, CD_CUSTOMLOOPNORMAL, CD_SET_DEFAULT, NULL, loops_num);
   }
 
   MDeformVert *dvert;
diff --git a/source/blender/modifiers/intern/MOD_weightvgedit.c b/source/blender/modifiers/intern/MOD_weightvgedit.c
index 2a509ddf220..d71813c7dd5 100644
--- a/source/blender/modifiers/intern/MOD_weightvgedit.c
+++ b/source/blender/modifiers/intern/MOD_weightvgedit.c
@@ -203,7 +203,7 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
   }
   else {
     /* Add a valid data layer! */
-    dvert = CustomData_add_layer(&mesh->vdata, CD_MDEFORMVERT, CD_CALLOC, NULL, verts_num);
+    dvert = CustomData_add_layer(&mesh->vdata, CD_MDEFORMVERT, CD_SET_DEFAULT, NULL, verts_num);
   }
   /* Ultimate security check. */
   if (!dvert) {
diff --git a/source/blender/modifiers/intern/MOD_weightvgmix.c b/source/blender/modifiers/intern/MOD_weightvgmix.c
index aa648eaec97..1d38333f15b 100644
--- a/source/blender/modifiers/intern/MOD_weightvgmix.c
+++ b/source/blender/modifiers/intern/MOD_weightvgmix.c
@@ -268,7 +268,7 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
   }
   else {
     /* Add a valid data layer! */
-    dvert = CustomData_add_layer(&mesh->vdata, CD_MDEFORMVERT, CD_CALLOC, NULL, verts_num);
+    dvert = CustomData_add_layer(&mesh->vdata, CD_MDEFORMVERT, CD_SET_DEFAULT, NULL, verts_num);
   }
   /* Ultimate security check. */
   if (!dvert) {