Refactor: Replace BKE_attributes_supported with C++ API

This removes `BKE_attributes_supported`.
Instead, a static method `from_id`
is added to the `AttributeAccessor` class that constructs
the accessor from the given ID. If this fails, `std::nullopt`
is returned.

Pull Request: https://projects.blender.org/blender/blender/pulls/124245

source/blender/blenkernel/BKE_attribute.h

@@ -18,7 +18,8 @@
 
 namespace blender::bke {
 enum class AttrDomain : int8_t;
-}
+class AttributeAccessor;
+}  // namespace blender::bke
 struct CustomData;
 struct CustomDataLayer;
 struct ID;
@@ -73,8 +74,6 @@ class AttributeOwner {
 
 /* Attributes. */
 
-bool BKE_attributes_supported(const AttributeOwner &owner);
-
 /**
  * Create a new attribute layer.
  */

source/blender/blenkernel/BKE_attribute.hh

@@ -477,6 +477,11 @@ class AttributeAccessor {
   {
   }
 
+  /**
+   * Construct an #AttributeAccessor from an ID.
+   */
+  static std::optional<AttributeAccessor> from_id(const ID &id);
+
   /**
    * \return True, when the attribute is available.
    */

source/blender/blenkernel/intern/attribute.cc

@@ -188,17 +188,6 @@ static std::optional<blender::bke::MutableAttributeAccessor> get_attribute_acces
 
 }  // namespace blender::bke
 
-bool BKE_attributes_supported(const AttributeOwner &owner)
-{
-  const std::array<DomainInfo, ATTR_DOMAIN_NUM> info = get_domains(owner);
-  for (const int domain : IndexRange(ATTR_DOMAIN_NUM)) {
-    if (info[domain].customdata) {
-      return true;
-    }
-  }
-  return false;
-}
-
 static bool bke_attribute_rename_if_exists(AttributeOwner &owner,
                                            const char *old_name,
                                            const char *new_name,

source/blender/blenkernel/intern/attribute_access.cc

@@ -5,12 +5,17 @@
 #include <utility>
 
 #include "BKE_attribute_math.hh"
+#include "BKE_curves.hh"
 #include "BKE_customdata.hh"
 #include "BKE_deform.hh"
 #include "BKE_geometry_set.hh"
 #include "BKE_type_conversions.hh"
 
+#include "DNA_ID.h"
+#include "DNA_grease_pencil_types.h"
+#include "DNA_mesh_types.h"
 #include "DNA_meshdata_types.h"
+#include "DNA_pointcloud_types.h"
 
 #include "BLI_array_utils.hh"
 #include "BLI_color.hh"
@@ -582,6 +587,23 @@ static GVArray try_adapt_data_type(GVArray varray, const CPPType &to_type)
   return conversions.try_convert(std::move(varray), to_type);
 }
 
+std::optional<AttributeAccessor> AttributeAccessor::from_id(const ID &id)
+{
+  switch (GS(id.name)) {
+    case ID_ME:
+      return reinterpret_cast<const Mesh &>(id).attributes();
+    case ID_PT:
+      return reinterpret_cast<const PointCloud &>(id).attributes();
+    case ID_CV:
+      return reinterpret_cast<const Curves &>(id).geometry.wrap().attributes();
+    case ID_GP:
+      return reinterpret_cast<const GreasePencil &>(id).attributes();
+    default:
+      return {};
+  }
+  return {};
+}
+
 GAttributeReader AttributeAccessor::lookup(const AttributeIDRef &attribute_id,
                                            const std::optional<AttrDomain> domain,
                                            const std::optional<eCustomDataType> data_type) const

source/blender/editors/geometry/geometry_attributes.cc

@@ -211,15 +211,17 @@ bool attribute_set_poll(bContext &C, const ID &object_data)
 
 static bool geometry_attributes_poll(bContext *C)
 {
+  using namespace blender::bke;
   const Object *ob = object::context_object(C);
   const Main *bmain = CTX_data_main(C);
-  ID *data = (ob) ? static_cast<ID *>(ob->data) : nullptr;
+  if (!ob || !BKE_id_is_editable(bmain, &ob->id)) {
-  AttributeOwner owner = AttributeOwner::from_id(data);
-  if (!owner.is_valid()) {
     return false;
   }
-  return (ob && BKE_id_is_editable(bmain, &ob->id) && data && BKE_id_is_editable(bmain, data)) &&
+  const ID *data = (ob) ? static_cast<const ID *>(ob->data) : nullptr;
-         BKE_attributes_supported(owner);
+  if (!data || !BKE_id_is_editable(bmain, data)) {
+    return false;
+  }
+  return AttributeAccessor::from_id(*data).has_value();
 }
 
 static bool geometry_attributes_remove_poll(bContext *C)