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, 13 insertions, 14 deletions

diff --git a/source/blender/blenkernel/intern/lib_id.c b/source/blender/blenkernel/intern/lib_id.c
index 838f3046ed0..54c2f5f5565 100644
--- a/source/blender/blenkernel/intern/lib_id.c
+++ b/source/blender/blenkernel/intern/lib_id.c
@@ -1795,32 +1795,31 @@ static void library_make_local_copying_check(ID *id,
     return; /* Already checked, nothing else to do. */
   }
 
-  MainIDRelationsEntry *entry = BLI_ghash_lookup(id_relations->id_used_to_user, id);
+  MainIDRelationsEntry *entry = BLI_ghash_lookup(id_relations->relations_from_pointers, id);
   BLI_gset_insert(loop_tags, id);
-  for (; entry != NULL; entry = entry->next) {
-
-    /* Used_to_user stores ID pointer, not pointer to ID pointer. */
-    ID *par_id = (ID *)entry->id_pointer;
-
+  for (MainIDRelationsEntryItem *from_id_entry = entry->from_ids; from_id_entry != NULL;
+       from_id_entry = from_id_entry->next) {
     /* Our oh-so-beloved 'from' pointers... Those should always be ignored here, since the actual
      * relation we want to check is in the other way around. */
-    if (entry->usage_flag & IDWALK_CB_LOOPBACK) {
+    if (from_id_entry->usage_flag & IDWALK_CB_LOOPBACK) {
       continue;
     }
 
+    ID *from_id = from_id_entry->id_pointer.from;
+
     /* Shape-keys are considered 'private' to their owner ID here, and never tagged
      * (since they cannot be linked), so we have to switch effective parent to their owner.
      */
-    if (GS(par_id->name) == ID_KE) {
-      par_id = ((Key *)par_id)->from;
+    if (GS(from_id->name) == ID_KE) {
+      from_id = ((Key *)from_id)->from;
     }
 
-    if (par_id->lib == NULL) {
+    if (from_id->lib == NULL) {
       /* Local user, early out to avoid some gset querying... */
       continue;
     }
-    if (!BLI_gset_haskey(done_ids, par_id)) {
-      if (BLI_gset_haskey(loop_tags, par_id)) {
+    if (!BLI_gset_haskey(done_ids, from_id)) {
+      if (BLI_gset_haskey(loop_tags, from_id)) {
         /* We are in a 'dependency loop' of IDs, this does not say us anything, skip it.
          * Note that this is the situation that can lead to archipelagoes of linked data-blocks
          * (since all of them have non-local users, they would all be duplicated,
@@ -1829,10 +1828,10 @@ static void library_make_local_copying_check(ID *id,
         continue;
       }
       /* Else, recursively check that user ID. */
-      library_make_local_copying_check(par_id, loop_tags, id_relations, done_ids);
+      library_make_local_copying_check(from_id, loop_tags, id_relations, done_ids);
     }
 
-    if (par_id->tag & LIB_TAG_DOIT) {
+    if (from_id->tag & LIB_TAG_DOIT) {
       /* This user will be fully local in future, so far so good,
        * nothing to do here but check next user. */
     }