source/blender/blenkernel/BKE_curves.hh

@@ -48,11 +48,29 @@ struct BasisCache {
 
 }  // namespace curves::nurbs
 
+template<typename T,
+         int64_t InlineBufferCapacity = default_inline_buffer_capacity(sizeof(T)),
+         typename Allocator = GuardedAllocator>
+class SharedVector : public Vector<T, InlineBufferCapacity, Allocator>,
+                     public ImplicitSharingMixin {
+
+ public:
+  SharedVector() = default;
+  SharedVector(const int64_t size) : Vector<T, InlineBufferCapacity, Allocator>(size) {}
+  SharedVector(const Span<T> data) : Vector<T, InlineBufferCapacity, Allocator>(data) {}
+  void delete_self() override
+  {
+    delete this;
+  }
+};
+
 /**
  * Contains derived data, caches, and other information not saved in files.
  */
 class CurvesGeometryRuntime {
  public:
+  ImplicitSharingPtr<SharedVector<int>> curve_offset_indices;
+
   /**
    * The cached number of curves with each type. Unlike other caches here, this is not computed
    * lazily, since it is needed so often and types are not adjusted much anyway.
@@ -846,7 +864,10 @@ inline const std::array<int, CURVE_TYPES_NUM> &CurvesGeometry::curve_type_counts
 
 inline OffsetIndices<int> CurvesGeometry::points_by_curve() const
 {
-  return OffsetIndices<int>({this->curve_offsets, this->curve_num + 1});
+  if (!this->runtime->curve_offset_indices) {
+    return {};
+  }
+  return OffsetIndices<int>(this->runtime->curve_offset_indices->as_span());
 }
 
 inline int CurvesGeometry::evaluated_points_num() const

source/blender/blenkernel/intern/curve_legacy_convert.cc

@@ -80,6 +80,9 @@ static KnotsMode knots_mode_from_legacy(const short flag)
 Curves *curve_legacy_to_curves(const Curve &curve_legacy, const ListBase &nurbs_list)
 {
   const Vector<const Nurb *> src_curves(nurbs_list);
+  if (src_curves.is_empty()) {
+    return nullptr;
+  }
 
   Curves *curves_id = curves_new_nomain(0, src_curves.size());
   CurvesGeometry &curves = curves_id->geometry.wrap();
@@ -104,10 +107,6 @@ Curves *curve_legacy_to_curves(const Curve &curve_legacy, const ListBase &nurbs_
 
   curves.update_curve_types();
 
-  if (curves.curves_num() == 0) {
-    return curves_id;
-  }
-
   const OffsetIndices points_by_curve = curves.points_by_curve();
   MutableSpan<float3> positions = curves.positions_for_write();
   SpanAttributeWriter<float> radius_attribute =

source/blender/blenkernel/intern/curves.cc

@@ -70,36 +70,13 @@ static void curves_copy_data(Main * /*bmain*/, ID *id_dst, const ID *id_src, con
   const Curves *curves_src = (const Curves *)id_src;
   curves_dst->mat = static_cast<Material **>(MEM_dupallocN(curves_src->mat));
 
-  const bke::CurvesGeometry &src = curves_src->geometry.wrap();
-  bke::CurvesGeometry &dst = curves_dst->geometry.wrap();
-
-  /* We need special handling here because the generic ID management code has already done a
-   * shallow copy from the source to the destination, and because the copy-on-write functionality
-   * isn't supported more generically yet. */
-
-  dst.point_num = src.point_num;
-  dst.curve_num = src.curve_num;
-
-  CustomData_copy(&src.point_data, &dst.point_data, CD_MASK_ALL, dst.point_num);
-  CustomData_copy(&src.curve_data, &dst.curve_data, CD_MASK_ALL, dst.curve_num);
-
-  dst.curve_offsets = static_cast<int *>(MEM_dupallocN(src.curve_offsets));
+  new (&curves_dst->geometry) bke::CurvesGeometry(curves_src->geometry.wrap());
+  BLI_assert(curves_dst->geometry.runtime->curve_offset_indices->is_shared());
 
   if (curves_src->surface_uv_map != nullptr) {
     curves_dst->surface_uv_map = BLI_strdup(curves_src->surface_uv_map);
   }
 
-  dst.runtime = MEM_new<bke::CurvesGeometryRuntime>(__func__);
-
-  dst.runtime->type_counts = src.runtime->type_counts;
-  dst.runtime->evaluated_offsets_cache = src.runtime->evaluated_offsets_cache;
-  dst.runtime->nurbs_basis_cache = src.runtime->nurbs_basis_cache;
-  dst.runtime->evaluated_position_cache = src.runtime->evaluated_position_cache;
-  dst.runtime->bounds_cache = src.runtime->bounds_cache;
-  dst.runtime->evaluated_length_cache = src.runtime->evaluated_length_cache;
-  dst.runtime->evaluated_tangent_cache = src.runtime->evaluated_tangent_cache;
-  dst.runtime->evaluated_normal_cache = src.runtime->evaluated_normal_cache;
-
   curves_dst->batch_cache = nullptr;
 }
 
@@ -155,11 +132,6 @@ static void curves_blend_read_data(BlendDataReader *reader, ID *id)
 
   BLO_read_data_address(reader, &curves->surface_uv_map);
 
-  curves->geometry.runtime = MEM_new<blender::bke::CurvesGeometryRuntime>(__func__);
-
-  /* Recalculate curve type count cache that isn't saved in files. */
-  curves->geometry.wrap().update_curve_types();
-
   /* Materials */
   BLO_read_pointer_array(reader, (void **)&curves->mat);
 }

source/blender/blenkernel/intern/curves_geometry.cc

@@ -60,13 +60,16 @@ CurvesGeometry::CurvesGeometry(const int point_num, const int curve_num)
   CustomData_add_layer_named(
       &this->point_data, CD_PROP_FLOAT3, CD_CONSTRUCT, this->point_num, ATTR_POSITION.c_str());
 
-  this->curve_offsets = (int *)MEM_malloc_arrayN(this->curve_num + 1, sizeof(int), __func__);
-#ifdef DEBUG
-  this->offsets_for_write().fill(-1);
-#endif
-  this->offsets_for_write().first() = 0;
-
   this->runtime = MEM_new<CurvesGeometryRuntime>(__func__);
+
+  if (curve_num > 0) {
+    this->runtime->curve_offset_indices = new SharedVector<int>(this->curve_num + 1);
+#ifdef DEBUG
+    this->offsets_for_write().fill(-1);
+#endif
+    this->offsets_for_write().first() = 0;
+  }
+
   /* Fill the type counts with the default so they're in a valid state. */
   this->runtime->type_counts[CURVE_TYPE_CATMULL_ROM] = curve_num;
 }
@@ -83,9 +86,7 @@ static void copy_curves_geometry(CurvesGeometry &dst, const CurvesGeometry &src)
   CustomData_copy(&src.point_data, &dst.point_data, CD_MASK_ALL, dst.point_num);
   CustomData_copy(&src.curve_data, &dst.curve_data, CD_MASK_ALL, dst.curve_num);
 
-  MEM_SAFE_FREE(dst.curve_offsets);
-  dst.curve_offsets = (int *)MEM_malloc_arrayN(dst.point_num + 1, sizeof(int), __func__);
-  dst.offsets_for_write().copy_from(src.offsets());
+  dst.runtime->curve_offset_indices = src.runtime->curve_offset_indices;
 
   dst.tag_topology_changed();
 
@@ -100,8 +101,7 @@ static void copy_curves_geometry(CurvesGeometry &dst, const CurvesGeometry &src)
   dst.runtime->evaluated_normal_cache = src.runtime->evaluated_normal_cache;
 }
 
-CurvesGeometry::CurvesGeometry(const CurvesGeometry &other)
-    : CurvesGeometry(other.point_num, other.curve_num)
+CurvesGeometry::CurvesGeometry(const CurvesGeometry &other) : CurvesGeometry()
 {
   copy_curves_geometry(*this, other);
 }
@@ -127,14 +127,10 @@ static void move_curves_geometry(CurvesGeometry &dst, CurvesGeometry &src)
   CustomData_free(&src.curve_data, src.curve_num);
   src.curve_num = 0;
 
-  std::swap(dst.curve_offsets, src.curve_offsets);
-  MEM_SAFE_FREE(src.curve_offsets);
-
   std::swap(dst.runtime, src.runtime);
 }
 
-CurvesGeometry::CurvesGeometry(CurvesGeometry &&other)
-    : CurvesGeometry(other.point_num, other.curve_num)
+CurvesGeometry::CurvesGeometry(CurvesGeometry &&other) : CurvesGeometry()
 {
   move_curves_geometry(*this, other);
 }
@@ -151,7 +147,6 @@ CurvesGeometry::~CurvesGeometry()
 {
   CustomData_free(&this->point_data, this->point_num);
   CustomData_free(&this->curve_data, this->curve_num);
-  MEM_SAFE_FREE(this->curve_offsets);
   MEM_delete(this->runtime);
   this->runtime = nullptr;
 }
@@ -324,11 +319,19 @@ MutableSpan<float3> CurvesGeometry::positions_for_write()
 
 Span<int> CurvesGeometry::offsets() const
 {
-  return {this->curve_offsets, this->curve_num + 1};
+  return this->runtime->curve_offset_indices->as_span();
 }
+
 MutableSpan<int> CurvesGeometry::offsets_for_write()
 {
-  return {this->curve_offsets, this->curve_num + 1};
+  if (!this->runtime->curve_offset_indices) {
+    return {};
+  }
+  if (this->runtime->curve_offset_indices->is_shared()) {
+    SharedVector<int> *data = new SharedVector<int>(this->runtime->curve_offset_indices);
+    this->runtime->curve_offset_indices = data;
+  }
+  return this->runtime->curve_offset_indices->as_mutable_span();
 }
 
 VArray<bool> CurvesGeometry::cyclic() const
@@ -950,8 +953,23 @@ void CurvesGeometry::resize(const int points_num, const int curves_num)
   }
   if (curves_num != this->curve_num) {
     CustomData_realloc(&this->curve_data, this->curves_num(), curves_num);
+    if (!this->runtime->curve_offset_indices) {
+      this->runtime->curve_offset_indices = new SharedVector<int>(curves_num + 1);
+      this->runtime->curve_offset_indices->first() = 0;
+      this->runtime->curve_offset_indices->last() = points_num;
+    }
+    else if (this->runtime->curve_offset_indices->is_mutable()) {
+      this->runtime->curve_offset_indices->resize(curves_num + 1);
+      this->runtime->curve_offset_indices->last() = points_num;
+    }
+    else {
+      SharedVector<int> *new_offsets = new SharedVector<int>(curves_num + 1);
+      new_offsets->as_mutable_span()
+          .take_front(this->curve_num + 1)
+          .copy_from({this->curve_offsets, this->curve_num + 1});
+      this->runtime->curve_offset_indices = new_offsets;
+    }
     this->curve_num = curves_num;
-    this->curve_offsets = (int *)MEM_reallocN(this->curve_offsets, sizeof(int) * (curves_num + 1));
   }
   this->tag_topology_changed();
 }
@@ -1585,7 +1603,15 @@ void CurvesGeometry::blend_read(BlendDataReader &reader)
   CustomData_blend_read(&reader, &this->point_data, this->point_num);
   CustomData_blend_read(&reader, &this->curve_data, this->curve_num);
 
+  this->runtime = MEM_new<blender::bke::CurvesGeometryRuntime>(__func__);
+
   BLO_read_int32_array(&reader, this->curve_num + 1, &this->curve_offsets);
+  SharedVector<int> *vector = new SharedVector<int>({this->curve_offsets, this->curve_num + 1});
+  this->runtime->curve_offset_indices = ImplicitSharingPtr(vector);
+  MEM_SAFE_FREE(this->curve_offsets);
+
+  /* Recalculate curve type count cache that isn't saved in files. */
+  this->update_curve_types();
 }
 
 void CurvesGeometry::blend_write(BlendWriter &writer, ID &id)
@@ -1600,6 +1626,7 @@ void CurvesGeometry::blend_write(BlendWriter &writer, ID &id)
   CustomData_blend_write(
       &writer, &this->curve_data, curve_layers, this->curve_num, CD_MASK_ALL, &id);
 
+  this->curve_offsets = this->runtime->curve_offset_indices->data();
   BLO_write_int32_array(&writer, this->curve_num + 1, this->curve_offsets);
 }
 

source/blender/editors/curves/intern/curves_data.cc

@@ -57,3 +57,8 @@ void ED_curves_transverts_create(Curves *curves_id, TransVertStore *tvs)
   bke::CurvesGeometry &curves = curves_id->geometry.wrap();
   ed::curves::transverts_from_curves_positions_create(curves, tvs);
 }
+
+int *ED_curves_offsets_for_write(struct Curves *curves_id)
+{
+  return curves_id->geometry.wrap().offsets_for_write().data();
+}

source/blender/editors/include/ED_curves.h

@@ -38,6 +38,8 @@ float (*ED_curves_point_normals_array_create(const struct Curves *curves_id))[3]
  */
 void ED_curves_transverts_create(struct Curves *curves_id, struct TransVertStore *tvs);
 
+int *ED_curves_offsets_for_write(struct Curves *curves_id);
+
 /** \} */
 
 #ifdef __cplusplus

source/blender/makesrna/intern/rna_curves.c

@@ -68,9 +68,9 @@ static int rna_Curves_curve_offset_data_length(PointerRNA *ptr)
 
 static void rna_Curves_curve_offset_data_begin(CollectionPropertyIterator *iter, PointerRNA *ptr)
 {
-  const Curves *curves = rna_curves(ptr);
+  Curves *curves = rna_curves(ptr);
   rna_iterator_array_begin(iter,
-                           (void *)curves->geometry.curve_offsets,
+                           ED_curves_offsets_for_write(curves),
                            sizeof(int),
                            curves->geometry.curve_num + 1,
                            false,
@@ -97,6 +97,23 @@ static int rna_CurvePoint_index_get_const(const PointerRNA *ptr)
   return (int)(co - positions);
 }
 
+static void rna_Curves_curves_begin(CollectionPropertyIterator *iter, PointerRNA *ptr)
+{
+  Curves *curves = rna_curves(ptr);
+  rna_iterator_array_begin(iter,
+                           ED_curves_offsets_for_write(curves),
+                           sizeof(int),
+                           curves->geometry.curve_num,
+                           false,
+                           NULL);
+}
+
+static int rna_Curves_curves_length(PointerRNA *ptr)
+{
+  const Curves *curves = rna_curves(ptr);
+  return curves->geometry.curve_num;
+}
+
 static int rna_Curves_position_data_length(PointerRNA *ptr)
 {
   const Curves *curves = rna_curves(ptr);
@@ -343,7 +360,15 @@ static void rna_def_curves(BlenderRNA *brna)
   /* Point and Curve RNA API helpers. */
 
   prop = RNA_def_property(srna, "curves", PROP_COLLECTION, PROP_NONE);
-  RNA_def_property_collection_sdna(prop, NULL, "geometry.curve_offsets", "geometry.curve_num");
+  RNA_def_property_collection_funcs(prop,
+                                    "rna_Curves_curves_begin",
+                                    "rna_iterator_array_next",
+                                    "rna_iterator_array_end",
+                                    "rna_iterator_array_get",
+                                    "rna_Curves_curves_length",
+                                    NULL,
+                                    NULL,
+                                    NULL);
   RNA_def_property_struct_type(prop, "CurveSlice");
   RNA_def_property_ui_text(prop, "Curves", "All curves in the data-block");
 
@@ -376,7 +401,6 @@ static void rna_def_curves(BlenderRNA *brna)
   RNA_def_property_update(prop, 0, "rna_Curves_update_data");
 
   prop = RNA_def_property(srna, "curve_offset_data", PROP_COLLECTION, PROP_NONE);
-  RNA_def_property_collection_sdna(prop, NULL, "geometry.curve_offsets", NULL);
   RNA_def_property_struct_type(prop, "IntAttributeValue");
   RNA_def_property_collection_funcs(prop,
                                     "rna_Curves_curve_offset_data_begin",