source/blender/blenkernel/BKE_anonymous_attribute_id.hh

@@ -10,24 +10,6 @@
 
 namespace blender::bke {
 
-class AnonymousAttributeID;
-
-class AnonymousAttributeIDCOW : public bCopyOnWrite {
- private:
-  AnonymousAttributeID *id_;
-
- public:
-  AnonymousAttributeIDCOW(AnonymousAttributeID *id) : bCopyOnWrite(1), id_(id)
-  {
-  }
-
- private:
-  void delete_self_with_data() override
-  {
-    MEM_delete(id_);
-  }
-};
-
 /**
  * An #AnonymousAttributeID contains information about a specific anonymous attribute.
  * Like normal attributes, anonymous attributes are also identified by their name, so one should
@@ -50,10 +32,7 @@ class AnonymousAttributeIDCOW : public bCopyOnWrite {
  * because that is not available in C code. If possible, the #AutoAnonymousAttributeID wrapper
  * should be used to avoid manual reference counting in C++ code.
  */
-class AnonymousAttributeID {
- private:
-  AnonymousAttributeIDCOW cow_;
-
+class AnonymousAttributeID : public bCopyOnWriteMixin<AnonymousAttributeID> {
  protected:
   std::string name_;
 
@@ -68,12 +47,7 @@ class AnonymousAttributeID {
 
   virtual std::string user_name() const;
 
-  const bCopyOnWrite &cow() const
-  {
-    return cow_;
-  }
-
-  void cow_delete_self() const
+  void delete_self() const
   {
     MEM_delete(this);
   }

source/blender/blenkernel/BKE_geometry_set.hh

@@ -38,30 +38,14 @@ class CurvesEditHints;
 class Instances;
 }  // namespace blender::bke
 
-class GeometryComponent;
-
-class GeometryComponentCOW : public bCopyOnWrite {
- private:
-  GeometryComponent *component_;
-
- public:
-  GeometryComponentCOW(GeometryComponent *component) : bCopyOnWrite(1), component_(component)
-  {
-  }
-
- private:
-  void delete_self_with_data() override;
-};
-
 /**
  * This is the base class for specialized geometry component types. A geometry component handles
  * a user count to allow avoiding duplication when it is wrapped with #UserCounter. It also handles
  * the attribute API, which generalizes storing and modifying generic information on a geometry.
  */
-class GeometryComponent {
+class GeometryComponent : public bCopyOnWriteMixin<GeometryComponent> {
  private:
   GeometryComponentType type_;
-  GeometryComponentCOW cow_;
 
  public:
   GeometryComponent(GeometryComponentType type);
@@ -80,22 +64,20 @@ class GeometryComponent {
   /* The returned component should be of the same type as the type this is called on. */
   virtual GeometryComponent *copy() const = 0;
 
-  const bCopyOnWrite &cow() const
-  {
-    return cow_;
-  }
-
   /* Direct data is everything except for instances of objects/collections.
    * If this returns true, the geometry set can be cached and is still valid after e.g. modifier
    * evaluation ends. Instances can only be valid as long as the data they instance is valid. */
   virtual bool owns_direct_data() const = 0;
   virtual void ensure_owns_direct_data() = 0;
 
-  bool is_mutable() const;
-
   GeometryComponentType type() const;
 
   virtual bool is_empty() const;
+
+  void delete_self()
+  {
+    delete this;
+  }
 };
 
 template<typename T>

source/blender/blenkernel/intern/anonymous_attribute_id.cc

@@ -4,9 +4,7 @@
 
 namespace blender::bke {
 
-AnonymousAttributeID::AnonymousAttributeID() : cow_(this)
-{
-}
+AnonymousAttributeID::AnonymousAttributeID() = default;
 
 std::string AnonymousAttributeID::user_name() const
 {

source/blender/blenkernel/intern/customdata.cc

@@ -2297,7 +2297,7 @@ static bool customdata_merge_internal(const CustomData *source,
 
     if (src_layer.anonymous_id != nullptr) {
       new_layer->anonymous_id = src_layer.anonymous_id;
-      new_layer->anonymous_id->cow().add_user();
+      new_layer->anonymous_id->add_user();
     }
   }
 
@@ -2473,7 +2473,7 @@ void CustomData_copy_without_data(const struct CustomData *source,
 static void customData_free_layer__internal(CustomDataLayer *layer, const int totelem)
 {
   if (layer->anonymous_id != nullptr) {
-    layer->anonymous_id->cow().remove_user_and_delete_if_last();
+    layer->anonymous_id->remove_user_and_delete_if_last();
     layer->anonymous_id = nullptr;
   }
   const eCustomDataType type = eCustomDataType(layer->type);
@@ -2998,7 +2998,7 @@ void *CustomData_add_layer_anonymous(CustomData *data,
     return nullptr;
   }
 
-  anonymous_id->cow().add_user();
+  anonymous_id->add_user();
   layer->anonymous_id = anonymous_id;
   return layer->data;
 }
@@ -3019,7 +3019,7 @@ const void *CustomData_add_layer_anonymous_with_existing_data(
   if (layer == nullptr) {
     return nullptr;
   }
-  anonymous_id->cow().add_user();
+  anonymous_id->add_user();
   layer->anonymous_id = anonymous_id;
   return layer->data;
 }

source/blender/blenkernel/intern/geometry_set.cc

@@ -35,16 +35,11 @@ using blender::Vector;
 using blender::bke::InstanceReference;
 using blender::bke::Instances;
 
-void GeometryComponentCOW::delete_self_with_data()
-{
-  delete component_;
-}
-
 /* -------------------------------------------------------------------- */
 /** \name Geometry Component
  * \{ */
 
-GeometryComponent::GeometryComponent(GeometryComponentType type) : type_(type), cow_(this)
+GeometryComponent::GeometryComponent(GeometryComponentType type) : type_(type)
 {
 }
 
@@ -89,11 +84,6 @@ std::optional<blender::bke::MutableAttributeAccessor> GeometryComponent::attribu
   return std::nullopt;
 }
 
-bool GeometryComponent::is_mutable() const
-{
-  return cow_.is_mutable();
-}
-
 GeometryComponentType GeometryComponent::type() const
 {
   return type_;
@@ -188,7 +178,7 @@ void GeometrySet::remove_geometry_during_modify()
 void GeometrySet::add(const GeometryComponent &component)
 {
   BLI_assert(!components_[component.type()]);
-  component.cow().add_user();
+  component.add_user();
   components_[component.type()] = const_cast<GeometryComponent *>(&component);
 }
 

source/blender/blenlib/BLI_copy_on_write.hh

@@ -55,3 +55,18 @@ struct bCopyOnWrite : blender::NonCopyable, blender::NonMovable {
  private:
   virtual void delete_self_with_data() = 0;
 };
+
+template<typename T> struct bCopyOnWriteMixin : public bCopyOnWrite {
+ public:
+  bCopyOnWriteMixin() : bCopyOnWrite(1)
+  {
+  }
+
+ private:
+  void delete_self_with_data() override
+  {
+    static_assert(std::is_base_of_v<bCopyOnWriteMixin<T>, T>);
+    T *data = static_cast<T *>(this);
+    data->delete_self();
+  }
+};

source/blender/blenlib/BLI_copy_on_write_user.hh

@@ -131,14 +131,14 @@ template<typename T> class COWUser {
   static void add_user(T *data)
   {
     if (data != nullptr) {
-      data->cow().add_user();
+      data->add_user();
     }
   }
 
   static void remove_user_and_delete_if_last(T *data)
   {
     if (data != nullptr) {
-      data->cow().remove_user_and_delete_if_last();
+      data->remove_user_and_delete_if_last();
     }
   }
 };

source/blender/geometry/intern/mesh_split_edges.cc

@@ -82,7 +82,7 @@ static void add_new_edges(Mesh &mesh,
     }
     else {
       anonymous_ids.append(&id.anonymous_id());
-      id.anonymous_id().cow().add_user();
+      id.anonymous_id().add_user();
     }
   }
   Vector<bke::AttributeIDRef> local_edge_ids;

source/blender/geometry/intern/realize_instances.cc

@@ -598,7 +598,7 @@ static void gather_realize_tasks_recursive(GatherTasksInfo &gather_info,
       case GEO_COMPONENT_TYPE_VOLUME: {
         const VolumeComponent *volume_component = static_cast<const VolumeComponent *>(component);
         if (!gather_info.r_tasks.first_volume) {
-          volume_component->cow().add_user();
+          volume_component->add_user();
           gather_info.r_tasks.first_volume = const_cast<VolumeComponent *>(volume_component);
         }
         break;
@@ -607,7 +607,7 @@ static void gather_realize_tasks_recursive(GatherTasksInfo &gather_info,
         const GeometryComponentEditData *edit_component =
             static_cast<const GeometryComponentEditData *>(component);
         if (!gather_info.r_tasks.first_edit_data) {
-          edit_component->cow().add_user();
+          edit_component->add_user();
           gather_info.r_tasks.first_edit_data = edit_component;
         }
         break;