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

1 files changed, 5 insertions, 0 deletions

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);