Refactor BMain relations temp data.

`bmain.relations` is used to store temp data of relations between IDs,
to speed-up some complex processes heavily relying on such information.

Previous implementation was failry unclear/confusing, and required a
not-so-nice hack to 'tag' some ID as processed.

New code changes as such:
* Using `from`/`to` naming (instead of `user`/`used`).
* More clear separation between `to` `id_pointer` and `from` one,
  using an union instead of hacking around difference between `ID *` and
  `ID **` pointers.
* Adds storage of `session_uuid` informations (mainly useful as
  debug/ensuring proper consistency of data currently).
* Adds a structure per ID in the mapping. This enables possibility of
  storing tags (and potentially more  data in the future) per-ID,
  without polluting the IDs themselves with very short-life info.

Differential Revision: https://developer.blender.org/D10164

1 files changed, 6 insertions, 3 deletions

diff --git a/source/blender/blenkernel/intern/lib_query.c b/source/blender/blenkernel/intern/lib_query.c
index e687e94073d..8be26fc8547 100644
--- a/source/blender/blenkernel/intern/lib_query.c
+++ b/source/blender/blenkernel/intern/lib_query.c
@@ -237,9 +237,12 @@ static void library_foreach_ID_link(Main *bmain,
        * but we might as well use it (Main->relations is always assumed valid,
        * it's responsibility of code creating it to free it,
        * especially if/when it starts modifying Main database). */
-      MainIDRelationsEntry *entry = BLI_ghash_lookup(bmain->relations->id_user_to_used, id);
-      for (; entry != NULL; entry = entry->next) {
-        BKE_lib_query_foreachid_process(&data, entry->id_pointer, entry->usage_flag);
+      MainIDRelationsEntry *entry = BLI_ghash_lookup(bmain->relations->relations_from_pointers,
+                                                     id);
+      for (MainIDRelationsEntryItem *to_id_entry = entry->to_ids; to_id_entry != NULL;
+           to_id_entry = to_id_entry->next) {
+        BKE_lib_query_foreachid_process(
+            &data, to_id_entry->id_pointer.to, to_id_entry->usage_flag);
       }
       continue;
     }