Fix T97408: Temporary fix for attribute convert undo

Sculpt undo now detects if an attribute layer has
changed type/domain and unconverts it back.  This
is a temporary workaround to a more fundamental
bug in the undo system.

Memfile undo assumes it can always rebuild the
application state from the prior undo step,
which isn't true with incremental undo systems.

The correct fix is to push an extra undo step prior
to running an operator if an incremental undo system
is active and the operator is using memfile undo.

1 files changed, 36 insertions, 0 deletions

diff --git a/source/blender/editors/geometry/geometry_attributes.cc b/source/blender/editors/geometry/geometry_attributes.cc
index 05f9e19da71..17784a50bca 100644
--- a/source/blender/editors/geometry/geometry_attributes.cc
+++ b/source/blender/editors/geometry/geometry_attributes.cc
@@ -33,6 +33,7 @@
 #include "UI_interface.h"
 #include "UI_resources.h"
 
+#include "ED_geometry.h"
 #include "ED_object.h"
 
 #include "geometry_intern.hh"
@@ -580,3 +581,38 @@ void GEOMETRY_OT_attribute_convert(wmOperatorType *ot)
 }
 
 }  // namespace blender::ed::geometry
+
+using blender::CPPType;
+using blender::GVArray;
+
+bool ED_geometry_attribute_convert(Mesh *mesh,
+                                   const char *layer_name,
+                                   CustomDataType old_type,
+                                   AttributeDomain old_domain,
+                                   CustomDataType new_type,
+                                   AttributeDomain new_domain)
+{
+  CustomDataLayer *layer = BKE_id_attribute_find(&mesh->id, layer_name, old_type, old_domain);
+  const std::string name = layer->name;
+
+  if (!layer) {
+    return false;
+  }
+
+  MeshComponent mesh_component;
+  mesh_component.replace(mesh, GeometryOwnershipType::Editable);
+  GVArray src_varray = mesh_component.attribute_get_for_read(name, new_domain, new_type);
+
+  const CPPType &cpp_type = src_varray.type();
+  void *new_data = MEM_malloc_arrayN(src_varray.size(), cpp_type.size(), __func__);
+  src_varray.materialize_to_uninitialized(new_data);
+  mesh_component.attribute_try_delete(name);
+  mesh_component.attribute_try_create(name, new_domain, new_type, AttributeInitMove(new_data));
+
+  int *active_index = BKE_id_attributes_active_index_p(&mesh->id);
+  if (*active_index > 0) {
+    *active_index -= 1;
+  }
+
+  return true;
+}