source/blender/blenkernel/BKE_asset.h

@@ -26,6 +26,7 @@ struct IDProperty;
 struct PreviewImage;
 
 typedef void (*PreSaveFn)(void *asset_ptr, struct AssetMetaData *asset_data);
+typedef void (*EnsureTraitsFn)(void *asset_ptr, struct AssetMetaData *asset_data);
 
 typedef struct AssetTypeInfo {
   /**
@@ -33,6 +34,8 @@ typedef struct AssetTypeInfo {
    * saved.
    */
   PreSaveFn pre_save_fn;
+  /* Callback for custom traits. */
+  EnsureTraitsFn ensure_traits_fn;
 } AssetTypeInfo;
 
 struct AssetMetaData *BKE_asset_metadata_create(void);
@@ -60,6 +63,19 @@ struct AssetTagEnsureResult BKE_asset_metadata_tag_ensure(struct AssetMetaData *
                                                           const char *name);
 void BKE_asset_metadata_tag_remove(struct AssetMetaData *asset_data, struct AssetTag *tag);
 
+struct AssetTraitEnsureResult {
+  struct AssetTrait *trait;
+  /* Set to false if a trait with this value was already present. */
+  bool is_new;
+};
+
+/**
+ * Make sure there is a trait with value \a value, create one if needed.
+ */
+struct AssetTraitEnsureResult BKE_asset_metadata_trait_ensure(struct AssetMetaData *asset_data,
+                                                              const char *value);
+void BKE_asset_metadata_trait_remove(struct AssetMetaData *asset_data, struct AssetTrait *trait);
+
 /** Clean up the catalog ID (white-spaces removed, length reduced, etc.) and assign it. */
 void BKE_asset_metadata_catalog_id_clear(struct AssetMetaData *asset_data);
 void BKE_asset_metadata_catalog_id_set(struct AssetMetaData *asset_data,

source/blender/blenkernel/intern/asset.cc

@@ -81,6 +81,7 @@ AssetMetaData::~AssetMetaData()
   MEM_SAFE_FREE(copyright);
   MEM_SAFE_FREE(license);
   BLI_freelistN(&tags);
+  BLI_freelistN(&traits);
 }
 
 static AssetTag *asset_metadata_tag_add(AssetMetaData *asset_data, const char *const name)
@@ -134,6 +135,43 @@ void BKE_asset_metadata_tag_remove(AssetMetaData *asset_data, AssetTag *tag)
   BLI_assert(BLI_listbase_count(&asset_data->tags) == asset_data->tot_tags);
 }
 
+static AssetTrait *asset_metadata_trait_add(AssetMetaData *asset_data, const char *const value)
+{
+  AssetTrait *trait = (AssetTrait *)MEM_callocN(sizeof(*trait), __func__);
+  BLI_strncpy(trait->value, value, sizeof(trait->value));
+  BLI_addtail(&asset_data->traits, trait);
+  return trait;
+}
+
+struct AssetTraitEnsureResult BKE_asset_metadata_trait_ensure(AssetMetaData *asset_data,
+                                                              const char *value)
+{
+  struct AssetTraitEnsureResult result = {nullptr};
+  if (!value[0]) {
+    return result;
+  }
+
+  AssetTrait *trait = (AssetTrait *)BLI_findstring(&asset_data->traits, value, offsetof(AssetTrait, value));
+
+  if (trait) {
+    result.trait = trait;
+    result.is_new = false;
+    return result;
+  }
+
+  trait = asset_metadata_trait_add(asset_data, value);
+
+  result.trait = trait;
+  result.is_new = true;
+  return result;
+}
+
+void BKE_asset_metadata_trait_remove(AssetMetaData *asset_data, AssetTrait *trait)
+{
+  BLI_assert(BLI_findindex(&asset_data->traits, trait) >= 0);
+  BLI_freelinkN(&asset_data->traits, trait);
+}
+
 void BKE_asset_library_reference_init_default(AssetLibraryReference *library_ref)
 {
   memcpy(library_ref, DNA_struct_default_get(AssetLibraryReference), sizeof(*library_ref));
@@ -212,6 +250,10 @@ void BKE_asset_metadata_write(BlendWriter *writer, AssetMetaData *asset_data)
   LISTBASE_FOREACH (AssetTag *, tag, &asset_data->tags) {
     BLO_write_struct(writer, AssetTag, tag);
   }
+
+  LISTBASE_FOREACH (AssetTrait *, trait, &asset_data->traits) {
+    BLO_write_struct(writer, AssetTrait, trait);
+  }
 }
 
 void BKE_asset_metadata_read(BlendDataReader *reader, AssetMetaData *asset_data)
@@ -230,4 +272,5 @@ void BKE_asset_metadata_read(BlendDataReader *reader, AssetMetaData *asset_data)
   BLO_read_data_address(reader, &asset_data->license);
   BLO_read_list(reader, &asset_data->tags);
   BLI_assert(BLI_listbase_count(&asset_data->tags) == asset_data->tot_tags);
+  BLO_read_list(reader, &asset_data->traits);
 }

source/blender/editors/asset/intern/asset_indexer.cc

@@ -61,12 +61,13 @@ using namespace blender::bke::idprop;
  *     "copyright": "<copyright>",
  *     "license": "<license>",
  *     "tags": ["<tag>"],
+ *     "traits": ["<trait>"],
  *     "properties": [..]
  *   }]
  * }
  * \endcode
  *
- * NOTE: entries, author, description, copyright, license, tags and properties are optional
+ * NOTE: entries, author, description, copyright, license, tags, traits and properties are optional
  * attributes.
  *
  * NOTE: File browser uses name and idcode separate. Inside the index they are joined together like
@@ -83,6 +84,7 @@ constexpr StringRef ATTRIBUTE_ENTRIES_AUTHOR("author");
 constexpr StringRef ATTRIBUTE_ENTRIES_COPYRIGHT("copyright");
 constexpr StringRef ATTRIBUTE_ENTRIES_LICENSE("license");
 constexpr StringRef ATTRIBUTE_ENTRIES_TAGS("tags");
+constexpr StringRef ATTRIBUTE_ENTRIES_TRAITS("traits");
 constexpr StringRef ATTRIBUTE_ENTRIES_PROPERTIES("properties");
 
 /** Abstract class for #BlendFile and #AssetIndexFile. */
@@ -229,6 +231,21 @@ struct AssetEntryReader {
     }
   }
 
+  void add_traits_to_meta_data(AssetMetaData *asset_data) const
+  {
+    const DictionaryValue::LookupValue *value_ptr = lookup.lookup_ptr(ATTRIBUTE_ENTRIES_TRAITS);
+    if (value_ptr == nullptr) {
+      return;
+    }
+
+    const ArrayValue *array_value = (*value_ptr)->as_array_value();
+    const ArrayValue::Items &elements = array_value->elements();
+    for (const ArrayValue::Item &item : elements) {
+      const StringRefNull trait_value = item->as_string_value()->value();
+      BKE_asset_metadata_trait_ensure(asset_data, trait_value.c_str());
+    }
+  }
+
   void add_properties_to_meta_data(AssetMetaData *asset_data) const
   {
     BLI_assert(asset_data->properties == nullptr);
@@ -309,6 +326,17 @@ struct AssetEntryWriter {
     }
   }
 
+  void add_traits(const ListBase /* AssetTrait */ *asset_traits)
+  {
+    ArrayValue *traits = new ArrayValue();
+    attributes.append_as(std::pair(ATTRIBUTE_ENTRIES_TRAITS, traits));
+    ArrayValue::Items &trait_items = traits->elements();
+
+    LISTBASE_FOREACH (AssetTrait *, trait, asset_traits) {
+      trait_items.append_as(new StringValue(trait->value));
+    }
+  }
+
   void add_properties(const IDProperty *properties)
   {
     std::unique_ptr<Value> value = convert_to_serialize_values(properties);
@@ -347,6 +375,10 @@ static void init_value_from_file_indexer_entry(AssetEntryWriter &result,
     result.add_tags(&asset_data.tags);
   }
 
+  if (!BLI_listbase_is_empty(&asset_data.traits)) {
+    result.add_traits(&asset_data.traits);
+  }
+
   if (asset_data.properties != nullptr) {
     result.add_properties(asset_data.properties);
   }
@@ -431,6 +463,7 @@ static void init_indexer_entry_from_value(FileIndexerEntry &indexer_entry,
   asset_data->catalog_id = entry.get_catalog_id();
 
   entry.add_tags_to_meta_data(asset_data);
+  entry.add_traits_to_meta_data(asset_data);
   entry.add_properties_to_meta_data(asset_data);
 }
 

source/blender/editors/asset/intern/asset_mark_clear.cc

@@ -83,6 +83,13 @@ void ED_assets_pre_save(Main *bmain)
       continue;
     }
 
+    const IDTypeInfo *id_type_info = BKE_idtype_get_info_from_id(id);
+    BKE_asset_metadata_trait_ensure(id->asset_data, id_type_info->name);
+
+    if (id_type_info->asset_type_info && id_type_info->asset_type_info->ensure_traits_fn) {
+      id_type_info->asset_type_info->ensure_traits_fn(id, id->asset_data);
+    }
+
     if (id->asset_data->local_type_info->pre_save_fn) {
       id->asset_data->local_type_info->pre_save_fn(id, id->asset_data);
     }

source/blender/makesdna/DNA_asset_types.h

@@ -36,6 +36,15 @@ typedef struct AssetTag {
   char name[64]; /* MAX_NAME */
 } AssetTag;
 
+/**
+ * \brief Keywords describing type characteristics of an asset. Managed by Blender, not the user.
+ * These should never be translated for storage, only when displayed in the UI.
+ */
+typedef struct AssetTrait {
+  struct AssetTrait *next, *prev;
+  char value[64]; /* MAX_NAME */
+} AssetTrait;
+
 #
 #
 typedef struct AssetFilterSettings {
@@ -100,6 +109,9 @@ typedef struct AssetMetaData {
   short tot_tags;
 
   char _pad[4];
+
+  /** See #AssetTrait. */
+  ListBase traits;
 } AssetMetaData;
 
 typedef enum eAssetLibraryType {

source/blender/makesrna/intern/rna_asset.cc

@@ -136,6 +136,14 @@ static void rna_AssetMetaData_tag_remove(ID *id,
   RNA_POINTER_INVALIDATE(tag_ptr);
 }
 
+static char *rna_AssetTrait_path(const PointerRNA *ptr)
+{
+  const AssetTrait *asset_trait = static_cast<AssetTrait *>(ptr->data);
+  char asset_trait_value_esc[sizeof(asset_trait->value) * 2];
+  BLI_str_escape(asset_trait_value_esc, asset_trait->value, sizeof(asset_trait_value_esc));
+  return BLI_sprintfN("asset_data.traits[\"%s\"]", asset_trait_value_esc);
+}
+
 static IDProperty **rna_AssetMetaData_idprops(PointerRNA *ptr)
 {
   AssetMetaData *asset_data = static_cast<AssetMetaData *>(ptr->data);
@@ -440,6 +448,21 @@ static void rna_def_asset_tags_api(BlenderRNA *brna, PropertyRNA *cprop)
   RNA_def_parameter_clear_flags(parm, PROP_THICK_WRAP, ParameterFlag(0));
 }
 
+static void rna_def_asset_trait(BlenderRNA *brna)
+{
+  StructRNA *srna;
+  PropertyRNA *prop;
+
+  srna = RNA_def_struct(brna, "AssetTrait", NULL);
+  RNA_def_struct_path_func(srna, "rna_AssetTrait_path");
+  RNA_def_struct_ui_text(srna, "Asset Trait", "Keywords describing type characteristics of an asset (managed by Blender, not the user)");
+
+  prop = RNA_def_property(srna, "value", PROP_STRING, PROP_NONE);
+  RNA_def_property_string_maxlength(prop, MAX_NAME);
+  RNA_def_property_ui_text(prop, "Value", "The identifier that makes up this asset trait");
+  RNA_def_struct_name_property(srna, prop);
+}
+
 static void rna_def_asset_data(BlenderRNA *brna)
 {
   StructRNA *srna;
@@ -507,6 +530,15 @@ static void rna_def_asset_data(BlenderRNA *brna)
   RNA_def_property_int_funcs(prop, nullptr, nullptr, "rna_AssetMetaData_active_tag_range");
   RNA_def_property_ui_text(prop, "Active Tag", "Index of the tag set for editing");
 
+  prop = RNA_def_property(srna, "traits", PROP_COLLECTION, PROP_NONE);
+  RNA_def_property_struct_type(prop, "AssetTrait");
+  RNA_def_property_editable_func(prop, "rna_AssetMetaData_editable");
+  RNA_def_property_ui_text(
+      prop,
+      "Asset Traits",
+      "Keywords describing type characteristics of an asset. Used to determine how an asset "
+      "should behave, and to provide additional information and filtering options to the user");
+
   prop = RNA_def_property(srna, "catalog_id", PROP_STRING, PROP_NONE);
   RNA_def_property_string_funcs(prop,
                                 "rna_AssetMetaData_catalog_id_get",
@@ -614,6 +646,7 @@ void RNA_def_asset(BlenderRNA *brna)
   RNA_define_animate_sdna(false);
 
   rna_def_asset_tag(brna);
+  rna_def_asset_trait(brna);
   rna_def_asset_data(brna);
   rna_def_asset_library_reference(brna);
   rna_def_asset_handle(brna);