AssetsBrowser: Add ID Properties to Asset Indexer

Object/collection asset workflow would need the bounding box for snapping.
The bounding box is stored using ID properties in the scene. Currently ID properties
aren't stored in the asset index, what would break object snapping. For this reason
Asset Indexing is turned off in mater. This patch will introduce the indexing of ID
properties what will allow the indexing to be turned on again.

## Data Mapping ##

For data mapping we store the internal structure of IDProperty to the indexer (including meta-data) to be able to deserialize it back.
```
[
  {
    "name":  ..,
    "value": ..,
    "type": ..,
    /* `subtype` and `length` are only available for IDP_ARRAYs. */
    "subtype": ..,
  },
]
```

| **DNA** | **Serialize type** | **Note** |
| IDProperty.name | StringValue| |
| IDProperty.type | StringValue| "IDP_STRING", "IDP_INT", "IDP_FLOAT", "IDP_ARRAY", "IDP_GROUP", "IDP_DOUBLE"|
| IDProperty.subtype | StringValue| "IDP_INT", "IDP_FLOAT", "IDP_GROUP", "IDP_DOUBLE" |
| IDProperty.value | StringValue | When type is IDP_STRING |
| IDProperty.value | IntValue | When type is IDP_INT |
| IDProperty.value | DoubleValue | When type is IDP_FLOAT/IDP_DOUBLE |
| IDProperty.value | ArrayValue | When type is IDP_GROUP. Recursively uses the same structure as described in this section. |
| IDProperty.value | ArrayValue | When type is IDP_ARRAY. Each element holds a single element as described in this section. |

NOTE: IDP_ID and IDP_IDARRAY aren't supported. The entry will not be added.

Example
```
[
  {
    "name": "MyIntValue,
    "type": "IDP_INT",
    "value": 6,
  },
  {
    "name": "myComplexArray",
    "type": "IDP_ARRAY",
    "subtype": "IDP_GROUP",
    "value": [
        [
          {
            "name": ..
            ....
          }
        ]
    ]
  }
]
```

## Considered alternatives ##

- Add conversion functions inside `asset_indexer`; makes generic code part of a specific solution.
- Add conversion functions inside `BLI_serialize`; would add data transformation responsibilities inside a unit that is currently only responsible for formatting.
- Use direct mapping between IDP properties and Values; leads to missing information and edge cases (empty primitive arrays) that could not be de-serialized.

Reviewed By: Severin, mont29, HooglyBoogly

Maniphest Tasks: T92306

Differential Revision: https://developer.blender.org/D12990

1 files changed, 4 insertions, 3 deletions

diff --git a/source/blender/makesdna/DNA_ID.h b/source/blender/makesdna/DNA_ID.h
index a70befc155b..060b55ffe5c 100644
--- a/source/blender/makesdna/DNA_ID.h
+++ b/source/blender/makesdna/DNA_ID.h
@@ -147,17 +147,18 @@ typedef struct IDProperty {
 #define DEFAULT_ALLOC_FOR_NULL_STRINGS 64
 
 /*->type*/
-enum {
+typedef enum eIDPropertyType {
   IDP_STRING = 0,
   IDP_INT = 1,
   IDP_FLOAT = 2,
+  /** Array containing int, floats, doubles or groups. */
   IDP_ARRAY = 5,
   IDP_GROUP = 6,
   IDP_ID = 7,
   IDP_DOUBLE = 8,
   IDP_IDPARRAY = 9,
-  IDP_NUMTYPES = 10,
-};
+} eIDPropertyType;
+#define IDP_NUMTYPES 10
 
 /** Used by some IDP utils, keep values in sync with type enum above. */
 enum {