Fix: Deleting vertex group attribute can change original mesh

There was an error with the attribute API implementation for vertex
groups. If the vertex group layer referenced an original mesh, it wasn't
properly duplicated for writing.

1 files changed, 5 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/geometry_component_mesh.cc b/source/blender/blenkernel/intern/geometry_component_mesh.cc
index 104166df913..cbd7ec9155a 100644
--- a/source/blender/blenkernel/intern/geometry_component_mesh.cc
+++ b/source/blender/blenkernel/intern/geometry_component_mesh.cc
@@ -1049,6 +1049,11 @@ class VertexGroupsAttributeProvider final : public DynamicAttributesProvider {
     if (mesh->dvert == nullptr) {
       return true;
     }
+
+    /* Copy the data layer if it is shared with some other mesh. */
+    mesh->dvert = (MDeformVert *)CustomData_duplicate_referenced_layer(
+        &mesh->vdata, CD_MDEFORMVERT, mesh->totvert);
+
     for (MDeformVert &dvert : MutableSpan(mesh->dvert, mesh->totvert)) {
       MDeformWeight *weight = BKE_defvert_find_index(&dvert, index);
       BKE_defvert_remove_group(&dvert, weight);