Asset System: Data-block asset metadata storage, reading and API

Asset metadata is what turns a regular data-block into an asset. It is a small
data-structure, but a key part of the technical design of the asset system.

The design foresees that asset data-blocks store an `ID.asset_data` pointer of
type `AssetMetaData`. This data **must not** have dependencies on other
data-blocks or data-block data, it must be an independent unit. That way we can
read asset-metadata from .blends without reading anything else from the file.
The Asset Browser will use this metadata (together with the data-block name,
preview and file path) to represent assets in the file list.

Includes:
* New `ID.asset_data` for asset metadata.
* Asset tags, description and custom properties.
* BKE code to manage asset meta-data and asset tags.
* Code to read asset data from files, without reading IDs.
* RNA for asset metadata (including tags)

Part of the first Asset Browser milestone. Check the #asset_browser_milestone_1
project milestone on developer.blender.org.

Differential Revision: https://developer.blender.org/D9716

Reviewed by: Bastien Montagne, Brecht Van Lommel

22 files changed, 666 insertions, 2 deletions

diff --git a/source/blender/CMakeLists.txt b/source/blender/CMakeLists.txt
index c38da14be96..efd30ba8509 100644
--- a/source/blender/CMakeLists.txt
+++ b/source/blender/CMakeLists.txt
@@ -23,6 +23,7 @@ set(SRC_DNA_INC
   ${CMAKE_CURRENT_SOURCE_DIR}/makesdna/DNA_action_types.h
   ${CMAKE_CURRENT_SOURCE_DIR}/makesdna/DNA_anim_types.h
   ${CMAKE_CURRENT_SOURCE_DIR}/makesdna/DNA_armature_types.h
+  ${CMAKE_CURRENT_SOURCE_DIR}/makesdna/DNA_asset_types.h
   ${CMAKE_CURRENT_SOURCE_DIR}/makesdna/DNA_boid_types.h
   ${CMAKE_CURRENT_SOURCE_DIR}/makesdna/DNA_brush_enums.h
   ${CMAKE_CURRENT_SOURCE_DIR}/makesdna/DNA_brush_types.h
diff --git a/source/blender/blenkernel/BKE_asset.h b/source/blender/blenkernel/BKE_asset.h
new file mode 100644
index 00000000000..edd49dd9851
--- /dev/null
+++ b/source/blender/blenkernel/BKE_asset.h
@@ -0,0 +1,56 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __BKE_ASSET_H__
+#define __BKE_ASSET_H__
+
+/** \file
+ * \ingroup bke
+ */
+
+#include "BLI_utildefines.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct BlendWriter;
+struct BlendDataReader;
+struct ID;
+struct PreviewImage;
+
+struct AssetMetaData *BKE_asset_metadata_create(void);
+void BKE_asset_metadata_free(struct AssetMetaData **asset_data);
+
+struct AssetTagEnsureResult {
+  struct AssetTag *tag;
+  /* Set to false if a tag of this name was already present. */
+  bool is_new;
+};
+
+struct AssetTag *BKE_asset_metadata_tag_add(struct AssetMetaData *asset_data, const char *name);
+struct AssetTagEnsureResult BKE_asset_metadata_tag_ensure(struct AssetMetaData *asset_data,
+                                                          const char *name);
+void BKE_asset_metadata_tag_remove(struct AssetMetaData *asset_data, struct AssetTag *tag);
+
+void BKE_asset_metadata_write(struct BlendWriter *writer, struct AssetMetaData *asset_data);
+void BKE_asset_metadata_read(struct BlendDataReader *reader, struct AssetMetaData *asset_data);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __BKE_ASSET_H__ */
diff --git a/source/blender/blenkernel/CMakeLists.txt b/source/blender/blenkernel/CMakeLists.txt
index d440d3e4d64..156d731d4a7 100644
--- a/source/blender/blenkernel/CMakeLists.txt
+++ b/source/blender/blenkernel/CMakeLists.txt
@@ -77,6 +77,7 @@ set(SRC
   intern/armature.c
   intern/armature_deform.c
   intern/armature_update.c
+  intern/asset.c
   intern/attribute.c
   intern/attribute_access.cc
   intern/autoexec.c
@@ -271,6 +272,7 @@ set(SRC
   BKE_attribute.h
   BKE_attribute_access.hh
   BKE_autoexec.h
+  BKE_asset.h
   BKE_blender.h
   BKE_blender_copybuffer.h
   BKE_blender_undo.h
diff --git a/source/blender/blenkernel/intern/asset.c b/source/blender/blenkernel/intern/asset.c
new file mode 100644
index 00000000000..92400d10fe5
--- /dev/null
+++ b/source/blender/blenkernel/intern/asset.c
@@ -0,0 +1,143 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup bke
+ */
+
+#include <string.h>
+
+#include "BLI_listbase.h"
+#include "BLI_string.h"
+#include "BLI_string_utils.h"
+#include "BLI_utildefines.h"
+
+#include "BKE_asset.h"
+#include "BKE_icons.h"
+#include "BKE_idprop.h"
+
+#include "DNA_ID.h"
+#include "DNA_asset_types.h"
+#include "DNA_defaults.h"
+
+#include "BLO_read_write.h"
+
+#include "MEM_guardedalloc.h"
+
+AssetMetaData *BKE_asset_metadata_create(void)
+{
+  AssetMetaData *asset_data = MEM_callocN(sizeof(*asset_data), __func__);
+  memcpy(asset_data, DNA_struct_default_get(AssetMetaData), sizeof(*asset_data));
+  return asset_data;
+}
+
+void BKE_asset_metadata_free(AssetMetaData **asset_data)
+{
+  if ((*asset_data)->properties) {
+    IDP_FreeProperty((*asset_data)->properties);
+  }
+  MEM_SAFE_FREE((*asset_data)->description);
+  BLI_freelistN(&(*asset_data)->tags);
+
+  MEM_SAFE_FREE(*asset_data);
+}
+
+static AssetTag *asset_metadata_tag_add(AssetMetaData *asset_data, const char *const name)
+{
+  AssetTag *tag = MEM_callocN(sizeof(*tag), __func__);
+  BLI_strncpy(tag->name, name, sizeof(tag->name));
+
+  BLI_addtail(&asset_data->tags, tag);
+  asset_data->tot_tags++;
+  /* Invariant! */
+  BLI_assert(BLI_listbase_count(&asset_data->tags) == asset_data->tot_tags);
+
+  return tag;
+}
+
+AssetTag *BKE_asset_metadata_tag_add(AssetMetaData *asset_data, const char *name)
+{
+  AssetTag *tag = asset_metadata_tag_add(asset_data, name);
+  BLI_uniquename(&asset_data->tags, tag, name, '.', offsetof(AssetTag, name), sizeof(tag->name));
+  return tag;
+}
+
+/**
+ * Make sure there is a tag with name \a name, create one if needed.
+ */
+struct AssetTagEnsureResult BKE_asset_metadata_tag_ensure(AssetMetaData *asset_data,
+                                                          const char *name)
+{
+  struct AssetTagEnsureResult result = {.tag = NULL};
+  if (!name[0]) {
+    return result;
+  }
+
+  AssetTag *tag = BLI_findstring(&asset_data->tags, name, offsetof(AssetTag, name));
+
+  if (tag) {
+    result.tag = tag;
+    result.is_new = false;
+    return result;
+  }
+
+  tag = asset_metadata_tag_add(asset_data, name);
+
+  result.tag = tag;
+  result.is_new = true;
+  return result;
+}
+
+void BKE_asset_metadata_tag_remove(AssetMetaData *asset_data, AssetTag *tag)
+{
+  BLI_assert(BLI_findindex(&asset_data->tags, tag) >= 0);
+  BLI_freelinkN(&asset_data->tags, tag);
+  asset_data->tot_tags--;
+  /* Invariant! */
+  BLI_assert(BLI_listbase_count(&asset_data->tags) == asset_data->tot_tags);
+}
+
+/* .blend file API -------------------------------------------- */
+
+void BKE_asset_metadata_write(BlendWriter *writer, AssetMetaData *asset_data)
+{
+  BLO_write_struct(writer, AssetMetaData, asset_data);
+
+  if (asset_data->properties) {
+    IDP_BlendWrite(writer, asset_data->properties);
+  }
+
+  if (asset_data->description) {
+    BLO_write_string(writer, asset_data->description);
+  }
+  LISTBASE_FOREACH (AssetTag *, tag, &asset_data->tags) {
+    BLO_write_struct(writer, AssetTag, tag);
+  }
+}
+
+void BKE_asset_metadata_read(BlendDataReader *reader, AssetMetaData *asset_data)
+{
+  /* asset_data itself has been read already. */
+
+  if (asset_data->properties) {
+    BLO_read_data_address(reader, &asset_data->properties);
+    IDP_BlendDataRead(reader, &asset_data->properties);
+  }
+
+  BLO_read_data_address(reader, &asset_data->description);
+  BLO_read_list(reader, &asset_data->tags);
+  BLI_assert(BLI_listbase_count(&asset_data->tags) == asset_data->tot_tags);
+}
diff --git a/source/blender/blenkernel/intern/lib_id.c b/source/blender/blenkernel/intern/lib_id.c
index 8113417b55f..61b5e6f85bb 100644
--- a/source/blender/blenkernel/intern/lib_id.c
+++ b/source/blender/blenkernel/intern/lib_id.c
@@ -56,6 +56,7 @@
 
 #include "BKE_anim_data.h"
 #include "BKE_armature.h"
+#include "BKE_asset.h"
 #include "BKE_bpath.h"
 #include "BKE_context.h"
 #include "BKE_global.h"
@@ -2362,6 +2363,10 @@ void BKE_id_reorder(const ListBase *lb, ID *id, ID *relative, bool after)
 
 void BKE_id_blend_write(BlendWriter *writer, ID *id)
 {
+  if (id->asset_data) {
+    BKE_asset_metadata_write(writer, id->asset_data);
+  }
+
   /* ID_WM's id->properties are considered runtime only, and never written in .blend file. */
   if (id->properties && !ELEM(GS(id->name), ID_WM)) {
     IDP_BlendWrite(writer, id->properties);
diff --git a/source/blender/blenkernel/intern/lib_id_delete.c b/source/blender/blenkernel/intern/lib_id_delete.c
index 1e45a3c1163..7199bd0f13c 100644
--- a/source/blender/blenkernel/intern/lib_id_delete.c
+++ b/source/blender/blenkernel/intern/lib_id_delete.c
@@ -31,6 +31,7 @@
 #include "BLI_listbase.h"
 
 #include "BKE_anim_data.h"
+#include "BKE_asset.h"
 #include "BKE_idprop.h"
 #include "BKE_idtype.h"
 #include "BKE_key.h"
@@ -64,6 +65,10 @@ void BKE_libblock_free_data(ID *id, const bool do_id_user)
     id->override_library = NULL;
   }
 
+  if (id->asset_data) {
+    BKE_asset_metadata_free(&id->asset_data);
+  }
+
   BKE_animdata_free(id, do_id_user);
 }
 
diff --git a/source/blender/blenloader/BLO_readfile.h b/source/blender/blenloader/BLO_readfile.h
index 0ab9a5e9e14..1d7c5d8a1d3 100644
--- a/source/blender/blenloader/BLO_readfile.h
+++ b/source/blender/blenloader/BLO_readfile.h
@@ -119,12 +119,20 @@ void BLO_blendfiledata_free(BlendFileData *bfd);
 /** \name BLO Blend File Handle API
  * \{ */
 
+struct BLODataBlockInfo {
+  char name[64]; /* MAX_NAME */
+  struct AssetMetaData *asset_data;
+};
+
 BlendHandle *BLO_blendhandle_from_file(const char *filepath, struct ReportList *reports);
 BlendHandle *BLO_blendhandle_from_memory(const void *mem, int memsize);
 
 struct LinkNode *BLO_blendhandle_get_datablock_names(BlendHandle *bh,
                                                      int ofblocktype,
                                                      int *tot_names);
+struct LinkNode *BLO_blendhandle_get_datablock_info(BlendHandle *bh,
+                                                    int ofblocktype,
+                                                    int *tot_info_items);
 struct LinkNode *BLO_blendhandle_get_previews(BlendHandle *bh, int ofblocktype, int *tot_prev);
 struct LinkNode *BLO_blendhandle_get_linkable_groups(BlendHandle *bh);
 
diff --git a/source/blender/blenloader/intern/readblenentry.c b/source/blender/blenloader/intern/readblenentry.c
index 1aecba5ba90..3a1ccbeda01 100644
--- a/source/blender/blenloader/intern/readblenentry.c
+++ b/source/blender/blenloader/intern/readblenentry.c
@@ -160,6 +160,51 @@ LinkNode *BLO_blendhandle_get_datablock_names(BlendHandle *bh, int ofblocktype,
 }
 
 /**
+ * Gets the names and asset-data (if ID is an asset) of all the data-blocks in a file of a certain
+ * type (e.g. all the scene names in a file).
+ *
+ * \param bh: The blendhandle to access.
+ * \param ofblocktype: The type of names to get.
+ * \param tot_info_items: The length of the returned list.
+ * \return A BLI_linklist of BLODataBlockInfo *. The links and #BLODataBlockInfo.asset_data should
+ *         be freed with MEM_freeN.
+ */
+LinkNode *BLO_blendhandle_get_datablock_info(BlendHandle *bh, int ofblocktype, int *tot_info_items)
+{
+  FileData *fd = (FileData *)bh;
+  LinkNode *infos = NULL;
+  BHead *bhead;
+  int tot = 0;
+
+  for (bhead = blo_bhead_first(fd); bhead; bhead = blo_bhead_next(fd, bhead)) {
+    if (bhead->code == ofblocktype) {
+      struct BLODataBlockInfo *info = MEM_mallocN(sizeof(*info), __func__);
+      const char *name = blo_bhead_id_name(fd, bhead) + 2;
+
+      STRNCPY(info->name, name);
+
+      /* Lastly, read asset data from the following blocks. */
+      info->asset_data = blo_bhead_id_asset_data_address(fd, bhead);
+      if (info->asset_data) {
+        bhead = blo_read_asset_data_block(fd, bhead, &info->asset_data);
+        /* blo_read_asset_data_block() reads all DATA heads and already advances bhead to the next
+         * non-DATA one. Go back, so the loop doesn't skip the non-DATA head. */
+        bhead = blo_bhead_prev(fd, bhead);
+      }
+
+      BLI_linklist_prepend(&infos, info);
+      tot++;
+    }
+    else if (bhead->code == ENDB) {
+      break;
+    }
+  }
+
+  *tot_info_items = tot;
+  return infos;
+}
+
+/**
  * Gets the previews of all the data-blocks in a file of a certain type
  * (e.g. all the scene previews in a file).
  *
diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index fd10eac4302..8dff1aa1ed0 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -44,6 +44,7 @@
 #define DNA_DEPRECATED_ALLOW
 
 #include "DNA_anim_types.h"
+#include "DNA_asset_types.h"
 #include "DNA_cachefile_types.h"
 #include "DNA_collection_types.h"
 #include "DNA_fileglobal_types.h"
@@ -73,6 +74,7 @@
 
 #include "BKE_anim_data.h"
 #include "BKE_animsys.h"
+#include "BKE_asset.h"
 #include "BKE_collection.h"
 #include "BKE_global.h" /* for G */
 #include "BKE_idprop.h"
@@ -957,12 +959,21 @@ static BHead *blo_bhead_read_full(FileData *fd, BHead *thisblock)
 }
 #endif /* USE_BHEAD_READ_ON_DEMAND */
 
-/* Warning! Caller's responsibility to ensure given bhead **is** and ID one! */
+/* Warning! Caller's responsibility to ensure given bhead **is** an ID one! */
 const char *blo_bhead_id_name(const FileData *fd, const BHead *bhead)
 {
   return (const char *)POINTER_OFFSET(bhead, sizeof(*bhead) + fd->id_name_offs);
 }
 
+/* Warning! Caller's responsibility to ensure given bhead **is** an ID one! */
+AssetMetaData *blo_bhead_id_asset_data_address(const FileData *fd, const BHead *bhead)
+{
+  BLI_assert(BKE_idtype_idcode_is_valid(bhead->code));
+  return (fd->id_asset_data_offs >= 0) ?
+             *(AssetMetaData **)POINTER_OFFSET(bhead, sizeof(*bhead) + fd->id_asset_data_offs) :
+             NULL;
+}
+
 static void decode_blender_header(FileData *fd)
 {
   char header[SIZEOFBLENDERHEADER], num[4];
@@ -1040,6 +1051,8 @@ static bool read_file_dna(FileData *fd, const char **r_error_message)
         /* used to retrieve ID names from (bhead+1) */
         fd->id_name_offs = DNA_elem_offset(fd->filesdna, "ID", "char", "name[]");
         BLI_assert(fd->id_name_offs != -1);
+        fd->id_asset_data_offs = DNA_elem_offset(
+            fd->filesdna, "ID", "AssetMetaData", "*asset_data");
 
         return true;
       }
@@ -2360,6 +2373,11 @@ static void direct_link_id_common(
     return;
   }
 
+  if (id->asset_data) {
+    BLO_read_data_address(reader, &id->asset_data);
+    BKE_asset_metadata_read(reader, id->asset_data);
+  }
+
   /*link direct data of ID properties*/
   if (id->properties) {
     BLO_read_data_address(reader, &id->properties);
@@ -3608,6 +3626,27 @@ static BHead *read_libblock(FileData *fd,
 /** \} */
 
 /* -------------------------------------------------------------------- */
+/** \name Read Asset Data
+ * \{ */
+
+BHead *blo_read_asset_data_block(FileData *fd, BHead *bhead, AssetMetaData **r_asset_data)
+{
+  BLI_assert(BKE_idtype_idcode_is_valid(bhead->code));
+
+  bhead = read_data_into_datamap(fd, bhead, "asset-data read");
+
+  BlendDataReader reader = {fd};
+  BLO_read_data_address(&reader, r_asset_data);
+  BKE_asset_metadata_read(&reader, *r_asset_data);
+
+  oldnewmap_clear(fd->datamap);
+
+  return bhead;
+}
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
 /** \name Read Global Data
  * \{ */
 
diff --git a/source/blender/blenloader/intern/readfile.h b/source/blender/blenloader/intern/readfile.h
index fb950e37da8..3e7cdb30e1f 100644
--- a/source/blender/blenloader/intern/readfile.h
+++ b/source/blender/blenloader/intern/readfile.h
@@ -112,6 +112,9 @@ typedef struct FileData {
   int fileversion;
   /** Used to retrieve ID names from (bhead+1). */
   int id_name_offs;
+  /** Used to retrieve asset data from (bhead+1). NOTE: This may not be available in old files,
+   * will be -1 then! */
+  int id_asset_data_offs;
   /** For do_versions patching. */
   int globalf, fileflags;
 
@@ -159,6 +162,8 @@ void blo_end_packed_pointer_map(FileData *fd, struct Main *oldmain);
 void blo_add_library_pointer_map(ListBase *old_mainlist, FileData *fd);
 void blo_make_old_idmap_from_main(FileData *fd, struct Main *bmain);
 
+BHead *blo_read_asset_data_block(FileData *fd, BHead *bhead, struct AssetMetaData **r_asset_data);
+
 void blo_cache_storage_init(FileData *fd, struct Main *bmain);
 void blo_cache_storage_old_bmain_clear(FileData *fd, struct Main *bmain_old);
 void blo_cache_storage_end(FileData *fd);
@@ -170,6 +175,7 @@ BHead *blo_bhead_next(FileData *fd, BHead *thisblock);
 BHead *blo_bhead_prev(FileData *fd, BHead *thisblock);
 
 const char *blo_bhead_id_name(const FileData *fd, const BHead *bhead);
+struct AssetMetaData *blo_bhead_id_asset_data_address(const FileData *fd, const BHead *bhead);
 
 /* do versions stuff */
 
diff --git a/source/blender/makesdna/DNA_ID.h b/source/blender/makesdna/DNA_ID.h
index f2d860a2851..84757e313ed 100644
--- a/source/blender/makesdna/DNA_ID.h
+++ b/source/blender/makesdna/DNA_ID.h
@@ -264,7 +264,12 @@ typedef struct IDOverrideLibrary {
 typedef struct ID {
   void *next, *prev;
   struct ID *newid;
+
   struct Library *lib;
+
+  /** If the ID is an asset, this pointer is set. Owning pointer. */
+  struct AssetMetaData *asset_data;
+
   /** MAX_ID_NAME. */
   char name[66];
   /**
@@ -310,6 +315,7 @@ typedef struct ID {
   struct ID *orig_id;
 
   void *py_instance;
+  void *_pad1;
 } ID;
 
 /**
diff --git a/source/blender/makesdna/DNA_asset_defaults.h b/source/blender/makesdna/DNA_asset_defaults.h
new file mode 100644
index 00000000000..ff00ba79cf0
--- /dev/null
+++ b/source/blender/makesdna/DNA_asset_defaults.h
@@ -0,0 +1,37 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup DNA
+ */
+
+#pragma once
+
+/* Struct members on own line. */
+/* clang-format off */
+
+/* -------------------------------------------------------------------- */
+/** \name Asset Struct
+ * \{ */
+
+#define _DNA_DEFAULT_AssetMetaData \
+  { \
+    0 \
+  }
+
+/** \} */
+
+/* clang-format on */
diff --git a/source/blender/makesdna/DNA_asset_types.h b/source/blender/makesdna/DNA_asset_types.h
new file mode 100644
index 00000000000..671012e54ef
--- /dev/null
+++ b/source/blender/makesdna/DNA_asset_types.h
@@ -0,0 +1,62 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup DNA
+ */
+
+#ifndef __DNA_ASSET_TYPES_H__
+#define __DNA_ASSET_TYPES_H__
+
+#include "DNA_listBase.h"
+
+/**
+ * \brief User defined tag.
+ * Currently only used by assets, could be used more often at some point.
+ * Maybe add a custom icon and color to these in future?
+ */
+typedef struct AssetTag {
+  struct AssetTag *next, *prev;
+  char name[64]; /* MAX_NAME */
+} AssetTag;
+
+/**
+ * \brief The meta-data of an asset.
+ * By creating and giving this for a data-block (#ID.asset_data), the data-block becomes an asset.
+ *
+ * \note This struct must be readable without having to read anything but blocks from the ID it is
+ *       attached to! That way, asset information of a file can be read, without reading anything
+ *       more than that from the file. So pointers to other IDs or ID data are strictly forbidden.
+ */
+typedef struct AssetMetaData {
+  /** Custom asset meta-data. Cannot store pointers to IDs (#STRUCT_NO_DATABLOCK_IDPROPERTIES)! */
+  struct IDProperty *properties;
+
+  /** Optional description of this asset for display in the UI. Dynamic length. */
+  char *description;
+  /** User defined tags for this asset. The asset manager uses these for filtering, but how they
+   * function exactly (e.g. how they are registered to provide a list of searchable available tags)
+   * is up to the asset-engine. */
+  ListBase tags; /* AssetTag */
+  short active_tag;
+  /** Store the number of tags to avoid continuous counting. Could be turned into runtime data, we
+   * can always reliably reconstruct it from the list. */
+  short tot_tags;
+
+  char _pad[4];
+} AssetMetaData;
+
+#endif /* __DNA_ASSET_TYPES_H__ */
diff --git a/source/blender/makesdna/intern/CMakeLists.txt b/source/blender/makesdna/intern/CMakeLists.txt
index 2051335dd7e..a7adaa7e258 100644
--- a/source/blender/makesdna/intern/CMakeLists.txt
+++ b/source/blender/makesdna/intern/CMakeLists.txt
@@ -138,6 +138,7 @@ set(SRC
   ../../blenlib/intern/hash_mm2a.c
   ../../blenlib/intern/listbase.c
 
+  ../DNA_asset_defaults.h
   ../DNA_brush_defaults.h
   ../DNA_cachefile_defaults.h
   ../DNA_camera_defaults.h
diff --git a/source/blender/makesdna/intern/dna_defaults.c b/source/blender/makesdna/intern/dna_defaults.c
index 1a8bd25215f..3e4d5d87fb0 100644
--- a/source/blender/makesdna/intern/dna_defaults.c
+++ b/source/blender/makesdna/intern/dna_defaults.c
@@ -85,6 +85,7 @@
 #include "DNA_defaults.h"
 
 #include "DNA_armature_types.h"
+#include "DNA_asset_types.h"
 #include "DNA_brush_types.h"
 #include "DNA_cachefile_types.h"
 #include "DNA_camera_types.h"
@@ -117,6 +118,7 @@
 #include "DNA_world_types.h"
 
 #include "DNA_armature_defaults.h"
+#include "DNA_asset_defaults.h"
 #include "DNA_brush_defaults.h"
 #include "DNA_cachefile_defaults.h"
 #include "DNA_camera_defaults.h"
@@ -148,6 +150,9 @@
 #define SDNA_DEFAULT_DECL_STRUCT(struct_name) \
   static const struct_name DNA_DEFAULT_##struct_name = _DNA_DEFAULT_##struct_name
 
+/* DNA_asset_defaults.h */
+SDNA_DEFAULT_DECL_STRUCT(AssetMetaData);
+
 /* DNA_armature_defaults.h */
 SDNA_DEFAULT_DECL_STRUCT(bArmature);
 
@@ -338,7 +343,10 @@ extern const bTheme U_theme_default;
 /** Keep headers sorted. */
 const void *DNA_default_table[SDNA_TYPE_MAX] = {
 
-    /* DNA_arnature_defaults.h */
+    /* DNA_asset_defaults.h */
+    SDNA_DEFAULT_DECL(AssetMetaData),
+
+    /* DNA_armature_defaults.h */
     SDNA_DEFAULT_DECL(bArmature),
 
     /* DNA_brush_defaults.h */
diff --git a/source/blender/makesdna/intern/makesdna.c b/source/blender/makesdna/intern/makesdna.c
index 81a7da7b4d8..54d2bc88d16 100644
--- a/source/blender/makesdna/intern/makesdna.c
+++ b/source/blender/makesdna/intern/makesdna.c
@@ -139,6 +139,7 @@ static const char *includefiles[] = {
     "DNA_volume_types.h",
     "DNA_simulation_types.h",
     "DNA_pointcache_types.h",
+    "DNA_asset_types.h",
 
     /* see comment above before editing! */
 
@@ -1533,6 +1534,7 @@ int main(int argc, char **argv)
 #include "DNA_action_types.h"
 #include "DNA_anim_types.h"
 #include "DNA_armature_types.h"
+#include "DNA_asset_types.h"
 #include "DNA_boid_types.h"
 #include "DNA_brush_types.h"
 #include "DNA_cachefile_types.h"
diff --git a/source/blender/makesrna/RNA_access.h b/source/blender/makesrna/RNA_access.h
index 4aeb9b9e5f7..da15489370a 100644
--- a/source/blender/makesrna/RNA_access.h
+++ b/source/blender/makesrna/RNA_access.h
@@ -70,6 +70,8 @@ extern StructRNA RNA_ArrayGpencilModifier;
 extern StructRNA RNA_ArrayModifier;
 extern StructRNA RNA_Attribute;
 extern StructRNA RNA_AttributeGroup;
+extern StructRNA RNA_AssetMetaData;
+extern StructRNA RNA_AssetTag;
 extern StructRNA RNA_BackgroundImage;
 extern StructRNA RNA_BevelModifier;
 extern StructRNA RNA_BezierSplinePoint;
diff --git a/source/blender/makesrna/intern/CMakeLists.txt b/source/blender/makesrna/intern/CMakeLists.txt
index 3ebbb98934e..2ce1acb0074 100644
--- a/source/blender/makesrna/intern/CMakeLists.txt
+++ b/source/blender/makesrna/intern/CMakeLists.txt
@@ -31,6 +31,7 @@ set(DEFSRC
   rna_animviz.c
   rna_armature.c
   rna_attribute.c
+  rna_asset.c
   rna_boid.c
   rna_brush.c
   rna_cachefile.c
diff --git a/source/blender/makesrna/intern/makesrna.c b/source/blender/makesrna/intern/makesrna.c
index 8b861d20e4e..c2c95c59002 100644
--- a/source/blender/makesrna/intern/makesrna.c
+++ b/source/blender/makesrna/intern/makesrna.c
@@ -4270,6 +4270,7 @@ static RNAProcessItem PROCESS_ITEMS[] = {
     {"rna_animviz.c", NULL, RNA_def_animviz},
     {"rna_armature.c", "rna_armature_api.c", RNA_def_armature},
     {"rna_attribute.c", NULL, RNA_def_attribute},
+    {"rna_asset.c", NULL, RNA_def_asset},
     {"rna_boid.c", NULL, RNA_def_boid},
     {"rna_brush.c", NULL, RNA_def_brush},
     {"rna_cachefile.c", NULL, RNA_def_cachefile},
diff --git a/source/blender/makesrna/intern/rna_ID.c b/source/blender/makesrna/intern/rna_ID.c
index f63cf0271b8..7c67bfc360b 100644
--- a/source/blender/makesrna/intern/rna_ID.c
+++ b/source/blender/makesrna/intern/rna_ID.c
@@ -1528,6 +1528,11 @@ static void rna_def_ID(BlenderRNA *brna)
   RNA_def_property_override_flag(prop, PROPOVERRIDE_NO_COMPARISON);
   RNA_def_property_ui_text(prop, "Library", "Library file the data-block is linked from");
 
+  prop = RNA_def_property(srna, "asset_data", PROP_POINTER, PROP_NONE);
+  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+  RNA_def_property_override_flag(prop, PROPOVERRIDE_NO_COMPARISON);
+  RNA_def_property_ui_text(prop, "Asset Data", "Additional data for an asset data-block");
+
   prop = RNA_def_pointer(
       srna, "override_library", "IDOverrideLibrary", "Library Override", "Library override data");
   RNA_def_property_clear_flag(prop, PROP_EDITABLE);
diff --git a/source/blender/makesrna/intern/rna_asset.c b/source/blender/makesrna/intern/rna_asset.c
new file mode 100644
index 00000000000..1af53e95cc9
--- /dev/null
+++ b/source/blender/makesrna/intern/rna_asset.c
@@ -0,0 +1,228 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup RNA
+ */
+
+#include <stdlib.h>
+
+#include "RNA_define.h"
+#include "RNA_enum_types.h"
+
+#include "DNA_asset_types.h"
+#include "DNA_defs.h"
+
+#include "rna_internal.h"
+
+#ifdef RNA_RUNTIME
+
+#  include "BKE_asset.h"
+#  include "BKE_idprop.h"
+
+#  include "BLI_listbase.h"
+
+#  include "RNA_access.h"
+
+static AssetTag *rna_AssetMetaData_tag_new(AssetMetaData *asset_data,
+                                           ReportList *reports,
+                                           const char *name,
+                                           bool skip_if_exists)
+{
+  AssetTag *tag = NULL;
+
+  if (skip_if_exists) {
+    struct AssetTagEnsureResult result = BKE_asset_metadata_tag_ensure(asset_data, name);
+
+    if (!result.is_new) {
+      BKE_reportf(
+          reports, RPT_WARNING, "Tag '%s' already present for given asset", result.tag->name);
+      /* Report, but still return valid item. */
+    }
+    tag = result.tag;
+  }
+  else {
+    tag = BKE_asset_metadata_tag_add(asset_data, name);
+  }
+
+  return tag;
+}
+
+static void rna_AssetMetaData_tag_remove(AssetMetaData *asset_data,
+                                         ReportList *reports,
+                                         PointerRNA *tag_ptr)
+{
+  AssetTag *tag = tag_ptr->data;
+  if (BLI_findindex(&asset_data->tags, tag) == -1) {
+    BKE_reportf(reports, RPT_ERROR, "Tag '%s' not found in given asset", tag->name);
+    return;
+  }
+
+  BKE_asset_metadata_tag_remove(asset_data, tag);
+  RNA_POINTER_INVALIDATE(tag_ptr);
+}
+
+static IDProperty *rna_AssetMetaData_idprops(PointerRNA *ptr, bool create)
+{
+  AssetMetaData *asset_data = ptr->data;
+
+  if (create && !asset_data->properties) {
+    IDPropertyTemplate val = {0};
+    asset_data->properties = IDP_New(IDP_GROUP, &val, "RNA_AssetMetaData group");
+  }
+
+  return asset_data->properties;
+}
+
+static void rna_AssetMetaData_description_get(PointerRNA *ptr, char *value)
+{
+  AssetMetaData *asset_data = ptr->data;
+
+  if (asset_data->description) {
+    strcpy(value, asset_data->description);
+  }
+  else {
+    value[0] = '\0';
+  }
+}
+
+static int rna_AssetMetaData_description_length(PointerRNA *ptr)
+{
+  AssetMetaData *asset_data = ptr->data;
+  return asset_data->description ? strlen(asset_data->description) : 0;
+}
+
+static void rna_AssetMetaData_description_set(PointerRNA *ptr, const char *value)
+{
+  AssetMetaData *asset_data = ptr->data;
+
+  if (asset_data->description) {
+    MEM_freeN(asset_data->description);
+  }
+
+  if (value[0]) {
+    asset_data->description = BLI_strdup(value);
+  }
+  else {
+    asset_data->description = NULL;
+  }
+}
+
+static void rna_AssetMetaData_active_tag_range(
+    PointerRNA *ptr, int *min, int *max, int *softmin, int *softmax)
+{
+  const AssetMetaData *asset_data = ptr->data;
+  *min = *softmin = 0;
+  *max = *softmax = MAX2(asset_data->tot_tags - 1, 0);
+}
+
+#else
+
+static void rna_def_asset_tag(BlenderRNA *brna)
+{
+  StructRNA *srna;
+  PropertyRNA *prop;
+
+  srna = RNA_def_struct(brna, "AssetTag", NULL);
+  RNA_def_struct_ui_text(srna, "Asset Tag", "User defined tag (name token)");
+
+  prop = RNA_def_property(srna, "name", PROP_STRING, PROP_NONE);
+  RNA_def_property_string_maxlength(prop, MAX_NAME);
+  RNA_def_property_ui_text(prop, "Name", "The identifier that makes up this tag");
+  RNA_def_struct_name_property(srna, prop);
+}
+
+static void rna_def_asset_tags_api(BlenderRNA *brna, PropertyRNA *cprop)
+{
+  StructRNA *srna;
+
+  FunctionRNA *func;
+  PropertyRNA *parm;
+
+  RNA_def_property_srna(cprop, "AssetTags");
+  srna = RNA_def_struct(brna, "AssetTags", NULL);
+  RNA_def_struct_sdna(srna, "AssetMetaData");
+  RNA_def_struct_ui_text(srna, "Asset Tags", "Collection of custom asset tags");
+
+  /* Tag collection */
+  func = RNA_def_function(srna, "new", "rna_AssetMetaData_tag_new");
+  RNA_def_function_ui_description(func, "Add a new tag to this asset");
+  RNA_def_function_flag(func, FUNC_USE_REPORTS);
+  parm = RNA_def_string(func, "name", NULL, MAX_NAME, "Name", "");
+  RNA_def_parameter_flags(parm, 0, PARM_REQUIRED);
+  parm = RNA_def_boolean(func,
+                         "skip_if_exists",
+                         false,
+                         "Skip if Exists",
+                         "Do not add a new tag if one of the same type already exists");
+  /* return type */
+  parm = RNA_def_pointer(func, "tag", "AssetTag", "", "New tag");
+  RNA_def_function_return(func, parm);
+
+  func = RNA_def_function(srna, "remove", "rna_AssetMetaData_tag_remove");
+  RNA_def_function_ui_description(func, "Remove an existing tag from this asset");
+  RNA_def_function_flag(func, FUNC_USE_REPORTS);
+  /* tag to remove */
+  parm = RNA_def_pointer(func, "tag", "AssetTag", "", "Removed tag");
+  RNA_def_parameter_flags(parm, PROP_NEVER_NULL, PARM_REQUIRED | PARM_RNAPTR);
+  RNA_def_parameter_clear_flags(parm, PROP_THICK_WRAP, 0);
+}
+
+static void rna_def_asset_data(BlenderRNA *brna)
+{
+  StructRNA *srna;
+  PropertyRNA *prop;
+
+  srna = RNA_def_struct(brna, "AssetMetaData", NULL);
+  RNA_def_struct_ui_text(srna, "Asset Data", "Additional data stored for an asset data-block");
+  //  RNA_def_struct_ui_icon(srna, ICON_ASSET); /* TODO: Icon doesn't exist!. */
+  /* The struct has custom properties, but no pointer properties to other IDs! */
+  RNA_def_struct_idprops_func(srna, "rna_AssetMetaData_idprops");
+  RNA_def_struct_flag(srna, STRUCT_NO_DATABLOCK_IDPROPERTIES); /* Mandatory! */
+
+  prop = RNA_def_property(srna, "description", PROP_STRING, PROP_NONE);
+  RNA_def_property_string_funcs(prop,
+                                "rna_AssetMetaData_description_get",
+                                "rna_AssetMetaData_description_length",
+                                "rna_AssetMetaData_description_set");
+  RNA_def_property_ui_text(
+      prop, "Description", "A description of the asset to be displayed for the user");
+
+  prop = RNA_def_property(srna, "tags", PROP_COLLECTION, PROP_NONE);
+  RNA_def_property_struct_type(prop, "AssetTag");
+  RNA_def_property_flag(prop, PROP_EDITABLE);
+  RNA_def_property_ui_text(prop,
+                           "Tags",
+                           "Custom tags (name tokens) for the asset, used for filtering and "
+                           "general asset management");
+  rna_def_asset_tags_api(brna, prop);
+
+  prop = RNA_def_property(srna, "active_tag", PROP_INT, PROP_NONE);
+  RNA_def_property_int_funcs(prop, NULL, NULL, "rna_AssetMetaData_active_tag_range");
+  RNA_def_property_ui_text(prop, "Active Tag", "Index of the tag set for editing");
+}
+
+void RNA_def_asset(BlenderRNA *brna)
+{
+  RNA_define_animate_sdna(false);
+
+  rna_def_asset_tag(brna);
+  rna_def_asset_data(brna);
+
+  RNA_define_animate_sdna(true);
+}
+
+#endif
diff --git a/source/blender/makesrna/intern/rna_internal.h b/source/blender/makesrna/intern/rna_internal.h
index d4fdac390b2..76c3e17e128 100644
--- a/source/blender/makesrna/intern/rna_internal.h
+++ b/source/blender/makesrna/intern/rna_internal.h
@@ -152,6 +152,7 @@ void RNA_def_animation(struct BlenderRNA *brna);
 void RNA_def_animviz(struct BlenderRNA *brna);
 void RNA_def_armature(struct BlenderRNA *brna);
 void RNA_def_attribute(struct BlenderRNA *brna);
+void RNA_def_asset(struct BlenderRNA *brna);
 void RNA_def_boid(struct BlenderRNA *brna);
 void RNA_def_brush(struct BlenderRNA *brna);
 void RNA_def_cachefile(struct BlenderRNA *brna);