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

1 files changed, 9 insertions, 1 deletions

diff --git a/source/blender/blenkernel/intern/customdata.cc b/source/blender/blenkernel/intern/customdata.cc
index cfb8416b0b4..a3b9f012e45 100644
--- a/source/blender/blenkernel/intern/customdata.cc
+++ b/source/blender/blenkernel/intern/customdata.cc
@@ -2353,8 +2353,16 @@ bool CustomData_merge(const CustomData *source,
       changed = true;
 
       if (layer->anonymous_id != nullptr) {
-        BKE_anonymous_attribute_id_increment_weak(layer->anonymous_id);
         newlayer->anonymous_id = layer->anonymous_id;
+        if (alloctype == CD_ASSIGN) {
+          layer->anonymous_id = nullptr;
+        }
+        else {
+          BKE_anonymous_attribute_id_increment_weak(layer->anonymous_id);
+        }
+      }
+      if (alloctype == CD_ASSIGN) {
+        layer->data = nullptr;
       }
     }
   }