IDMAnagement: Add owner ID pointer to embedded ones.

Add a dedicated `owner_id` pointer to ID types that can be embedded
(Collections and NodeTrees), and modify slightly come code to make
handling those more safe and consistent.

This implements first part of T69169.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D15838

1 files changed, 25 insertions, 12 deletions

diff --git a/source/blender/blenkernel/intern/collection.c b/source/blender/blenkernel/intern/collection.c
index caf59a9b363..572a0caa3c7 100644
--- a/source/blender/blenkernel/intern/collection.c
+++ b/source/blender/blenkernel/intern/collection.c
@@ -143,6 +143,9 @@ static void collection_foreach_id(ID *id, LibraryForeachIDData *data)
 {
   Collection *collection = (Collection *)id;
 
+  BKE_LIB_FOREACHID_PROCESS_ID(
+      data, collection->owner_id, IDWALK_CB_LOOPBACK | IDWALK_CB_NEVER_SELF);
+
   LISTBASE_FOREACH (CollectionObject *, cob, &collection->gobject) {
     BKE_LIB_FOREACHID_PROCESS_IDSUPER(data, cob->ob, IDWALK_CB_USER);
   }
@@ -162,7 +165,7 @@ static void collection_foreach_id(ID *id, LibraryForeachIDData *data)
   }
 }
 
-static ID *collection_owner_get(Main *bmain, ID *id, ID *owner_id_hint)
+static ID *collection_owner_get(Main *bmain, ID *id, ID *UNUSED(owner_id_hint))
 {
   if ((id->flag & LIB_EMBEDDED_DATA) == 0) {
     return id;
@@ -171,20 +174,21 @@ static ID *collection_owner_get(Main *bmain, ID *id, ID *owner_id_hint)
 
   Collection *master_collection = (Collection *)id;
   BLI_assert((master_collection->flag & COLLECTION_IS_MASTER) != 0);
+  BLI_assert(master_collection->owner_id != NULL);
 
-  if (owner_id_hint != NULL && GS(owner_id_hint->name) == ID_SCE &&
-      ((Scene *)owner_id_hint)->master_collection == master_collection) {
-    return owner_id_hint;
-  }
-
+#ifndef NDEBUG
+  bool is_owner_found = false;
   LISTBASE_FOREACH (Scene *, scene, &bmain->scenes) {
     if (scene->master_collection == master_collection) {
-      return &scene->id;
+      BLI_assert(master_collection->owner_id == &scene->id);
+      BLI_assert(!is_owner_found);
+      is_owner_found = true;
     }
   }
+  BLI_assert(is_owner_found);
+#endif
 
-  BLI_assert_msg(0, "Embedded collection with no owner. Critical Main inconsistency.");
-  return NULL;
+  return master_collection->owner_id;
 }
 
 void BKE_collection_blend_write_nolib(BlendWriter *writer, Collection *collection)
@@ -233,8 +237,13 @@ void BKE_collection_compat_blend_read_data(BlendDataReader *reader, SceneCollect
 }
 #endif
 
-void BKE_collection_blend_read_data(BlendDataReader *reader, Collection *collection)
+void BKE_collection_blend_read_data(BlendDataReader *reader, Collection *collection, ID *owner_id)
 {
+  /* Special case for this pointer, do not rely on regular `lib_link` process here. Avoids needs
+   * for do_versioning, and ensures coherence of data in any case. */
+  BLI_assert((collection->id.flag & LIB_EMBEDDED_DATA) != 0 || owner_id == NULL);
+  collection->owner_id = owner_id;
+
   BLO_read_list(reader, &collection->gobject);
   BLO_read_list(reader, &collection->children);
 
@@ -265,7 +274,7 @@ void BKE_collection_blend_read_data(BlendDataReader *reader, Collection *collect
 static void collection_blend_read_data(BlendDataReader *reader, ID *id)
 {
   Collection *collection = (Collection *)id;
-  BKE_collection_blend_read_data(reader, collection);
+  BKE_collection_blend_read_data(reader, collection, NULL);
 }
 
 static void lib_link_collection_data(BlendLibReader *reader, Library *lib, Collection *collection)
@@ -849,14 +858,18 @@ Base *BKE_collection_or_layer_objects(const ViewLayer *view_layer, Collection *c
 /** \name Scene Master Collection
  * \{ */
 
-Collection *BKE_collection_master_add()
+Collection *BKE_collection_master_add(Scene *scene)
 {
+  BLI_assert(scene != NULL && scene->master_collection == NULL);
+
   /* Not an actual datablock, but owned by scene. */
   Collection *master_collection = BKE_libblock_alloc(
       NULL, ID_GR, BKE_SCENE_COLLECTION_NAME, LIB_ID_CREATE_NO_MAIN);
   master_collection->id.flag |= LIB_EMBEDDED_DATA;
+  master_collection->owner_id = &scene->id;
   master_collection->flag |= COLLECTION_IS_MASTER;
   master_collection->color_tag = COLLECTION_COLOR_NONE;
+
   return master_collection;
 }