Add optional, free-after-use usages mapping of IDs to Main.

The new MainIDRelations stores two mappings, one from ID users to ID
used, the other vice-versa.

That data is assumed to be short-living runtime, code creating it is
responsible to clear it asap. It will be much useful in places where we
handle relations between IDs for a lot of them at once.

Note: This commit is not fully functional, that is, the infamous, ugly,
PoS non-ID nodetrees will not be handled correctly when building relations.
Fix needed here is a bit noisy, so will be done in next own commit.

1 files changed, 3 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_library.h b/source/blender/blenkernel/BKE_library.h
index 2d9c35f7fd0..34035673f88 100644
--- a/source/blender/blenkernel/BKE_library.h
+++ b/source/blender/blenkernel/BKE_library.h
@@ -105,6 +105,9 @@ void BKE_main_free(struct Main *mainvar);
 void BKE_main_lock(struct Main *bmain);
 void BKE_main_unlock(struct Main *bmain);
 
+void BKE_main_relations_create(struct Main *bmain);
+void BKE_main_relations_free(struct Main *bmain);
+
 struct BlendThumbnail *BKE_main_thumbnail_from_imbuf(struct Main *bmain, struct ImBuf *img);
 struct ImBuf *BKE_main_thumbnail_to_imbuf(struct Main *bmain, struct BlendThumbnail *data);
 void BKE_main_thumbnail_create(struct Main *bmain);