Cleanup: Simplify BKE_mesh_nomain_to_mesh

- Remove "take ownership" argument which was confusing and always true
  - The argument made ownership very confusing
  - Better to avoid boolean arguments that switch a function's purpose
- Remove "mask" argument which was basically wrong and not used properly
  - "EVERYTHING" was used because developers are wary of removing data
  - Instead use `CD_MASK_MESH` for its purpose of original mesh data
- Remove use of shallow copied temporary mesh, which is unnecessary now
- Split shape key processing into separate functions and use C++ types
- Copy fields explicitly rather than using memcpy for the whole struct
- Use higher level functions and avoid redundant code
  - The whole idea is pretty simple and can be built from standard logic
- Adjust `CustomData` logic to be consistent with "assign" expectations
  - Clear the layer data from the source, and moves the anonymous ID

Differential Revision: https://developer.blender.org/D15857

4 files changed, 5 insertions, 17 deletions

diff --git a/source/blender/io/alembic/intern/abc_reader_mesh.cc b/source/blender/io/alembic/intern/abc_reader_mesh.cc
index 65d99e3f057..ebb1b5a29bd 100644
--- a/source/blender/io/alembic/intern/abc_reader_mesh.cc
+++ b/source/blender/io/alembic/intern/abc_reader_mesh.cc
@@ -619,11 +619,7 @@ void AbcMeshReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelec
 
   Mesh *read_mesh = this->read_mesh(mesh, sample_sel, MOD_MESHSEQ_READ_ALL, "", 0.0f, nullptr);
   if (read_mesh != mesh) {
-    /* XXX FIXME: after 2.80; mesh->flag isn't copied by #BKE_mesh_nomain_to_mesh(). */
-    /* read_mesh can be freed by BKE_mesh_nomain_to_mesh(), so get the flag before that happens. */
-    uint16_t autosmooth = (read_mesh->flag & ME_AUTOSMOOTH);
-    BKE_mesh_nomain_to_mesh(read_mesh, mesh, m_object, &CD_MASK_EVERYTHING, true);
-    mesh->flag |= autosmooth;
+    BKE_mesh_nomain_to_mesh(read_mesh, mesh, m_object);
   }
 
   if (m_settings->validate_meshes) {
@@ -1003,7 +999,7 @@ void AbcSubDReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelec
 
   Mesh *read_mesh = this->read_mesh(mesh, sample_sel, MOD_MESHSEQ_READ_ALL, "", 0.0f, nullptr);
   if (read_mesh != mesh) {
-    BKE_mesh_nomain_to_mesh(read_mesh, mesh, m_object, &CD_MASK_EVERYTHING, true);
+    BKE_mesh_nomain_to_mesh(read_mesh, mesh, m_object);
   }
 
   ISubDSchema::Sample sample;
diff --git a/source/blender/io/alembic/intern/abc_reader_points.cc b/source/blender/io/alembic/intern/abc_reader_points.cc
index ff189bc92dc..54ae71ad7a6 100644
--- a/source/blender/io/alembic/intern/abc_reader_points.cc
+++ b/source/blender/io/alembic/intern/abc_reader_points.cc
@@ -69,7 +69,7 @@ void AbcPointsReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSel
   Mesh *read_mesh = this->read_mesh(mesh, sample_sel, 0, "", 0.0f, nullptr);
 
   if (read_mesh != mesh) {
-    BKE_mesh_nomain_to_mesh(read_mesh, mesh, m_object, &CD_MASK_MESH, true);
+    BKE_mesh_nomain_to_mesh(read_mesh, mesh, m_object);
   }
 
   if (m_settings->validate_meshes) {
diff --git a/source/blender/io/usd/intern/usd_reader_mesh.cc b/source/blender/io/usd/intern/usd_reader_mesh.cc
index 0b96cd8ce90..7cb4c65f166 100644
--- a/source/blender/io/usd/intern/usd_reader_mesh.cc
+++ b/source/blender/io/usd/intern/usd_reader_mesh.cc
@@ -248,11 +248,7 @@ void USDMeshReader::read_object_data(Main *bmain, const double motionSampleTime)
 
   is_initial_load_ = false;
   if (read_mesh != mesh) {
-    /* FIXME: after 2.80; `mesh->flag` isn't copied by #BKE_mesh_nomain_to_mesh() */
-    /* read_mesh can be freed by BKE_mesh_nomain_to_mesh(), so get the flag before that happens. */
-    uint16_t autosmooth = (read_mesh->flag & ME_AUTOSMOOTH);
-    BKE_mesh_nomain_to_mesh(read_mesh, mesh, object_, &CD_MASK_MESH, true);
-    mesh->flag |= autosmooth;
+    BKE_mesh_nomain_to_mesh(read_mesh, mesh, object_);
   }
 
   readFaceSetsSample(bmain, mesh, motionSampleTime);
diff --git a/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc b/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc
index b1a2c7834f4..ef05534928a 100644
--- a/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc
+++ b/source/blender/io/wavefront_obj/importer/obj_import_mesh.cc
@@ -69,11 +69,7 @@ Object *MeshFromGeometry::create_mesh(Main *bmain,
   }
   transform_object(obj, import_params);
 
-  /* FIXME: after 2.80; `mesh->flag` isn't copied by #BKE_mesh_nomain_to_mesh() */
-  const uint16_t autosmooth = (mesh->flag & ME_AUTOSMOOTH);
-  Mesh *dst = static_cast<Mesh *>(obj->data);
-  BKE_mesh_nomain_to_mesh(mesh, dst, obj, &CD_MASK_EVERYTHING, true);
-  dst->flag |= autosmooth;
+  BKE_mesh_nomain_to_mesh(mesh, static_cast<Mesh *>(obj->data), obj);
 
   /* NOTE: vertex groups have to be created after final mesh is assigned to the object. */
   create_vertex_groups(obj);