LibOverride: Stash away 'leftover' objects/collections from auto-resync process.

Instead of storing those in scne's master collection, which is fairly
annoying, we now add them to a (hidden) specific collection. Easy to
ignore, or check and cleanup.

3 files changed, 49 insertions, 9 deletions

diff --git a/source/blender/blenkernel/BKE_lib_override.h b/source/blender/blenkernel/BKE_lib_override.h
index e0cb2d9abb0..f69580d38be 100644
--- a/source/blender/blenkernel/BKE_lib_override.h
+++ b/source/blender/blenkernel/BKE_lib_override.h
@@ -42,6 +42,7 @@
 extern "C" {
 #endif
 
+struct Collection;
 struct ID;
 struct IDOverrideLibrary;
 struct IDOverrideLibraryProperty;
@@ -81,6 +82,7 @@ bool BKE_lib_override_library_resync(struct Main *bmain,
                                      struct Scene *scene,
                                      struct ViewLayer *view_layer,
                                      struct ID *id_root,
+                                     struct Collection *override_resync_residual_storage,
                                      const bool do_hierarchy_enforce);
 void BKE_lib_override_library_main_resync(struct Main *bmain,
                                           struct Scene *scene,
diff --git a/source/blender/blenkernel/intern/lib_override.c b/source/blender/blenkernel/intern/lib_override.c
index cc2d384bcb8..38c115c07a1 100644
--- a/source/blender/blenkernel/intern/lib_override.c
+++ b/source/blender/blenkernel/intern/lib_override.c
@@ -663,6 +663,7 @@ static void lib_override_library_create_post_process(Main *bmain,
                                                      ViewLayer *view_layer,
                                                      ID *id_root,
                                                      ID *id_reference,
+                                                     Collection *residual_storage,
                                                      const bool is_resync)
 {
   BKE_main_collection_sync(bmain);
@@ -718,7 +719,12 @@ static void lib_override_library_create_post_process(Main *bmain,
         Object *ob_new = (Object *)id_root->newid;
         if (!lib_override_library_create_post_process_object_is_instantiated(
                 view_layer, ob_new, is_resync)) {
-          BKE_collection_object_add_from(bmain, scene, (Object *)id_root, ob_new);
+          if (is_resync && residual_storage != NULL) {
+            BKE_collection_object_add(bmain, residual_storage, ob_new);
+          }
+          else {
+            BKE_collection_object_add_from(bmain, scene, (Object *)id_root, ob_new);
+          }
         }
         break;
       }
@@ -734,7 +740,7 @@ static void lib_override_library_create_post_process(Main *bmain,
       BLI_assert(ob_new->id.override_library != NULL &&
                  ob_new->id.override_library->reference == &ob->id);
 
-      Collection *default_instantiating_collection = NULL;
+      Collection *default_instantiating_collection = residual_storage;
       if (!lib_override_library_create_post_process_object_is_instantiated(
               view_layer, ob_new, is_resync)) {
         if (default_instantiating_collection == NULL) {
@@ -799,7 +805,8 @@ bool BKE_lib_override_library_create(
     return success;
   }
 
-  lib_override_library_create_post_process(bmain, scene, view_layer, id_root, id_reference, false);
+  lib_override_library_create_post_process(
+      bmain, scene, view_layer, id_root, id_reference, NULL, false);
 
   /* Cleanup. */
   BKE_main_id_clear_newpoins(bmain);
@@ -858,8 +865,12 @@ bool BKE_lib_override_library_proxy_convert(Main *bmain,
  * \param id_root: The root liboverride ID to resync from.
  * \return true if override was successfully resynced.
  */
-bool BKE_lib_override_library_resync(
-    Main *bmain, Scene *scene, ViewLayer *view_layer, ID *id_root, const bool do_hierarchy_enforce)
+bool BKE_lib_override_library_resync(Main *bmain,
+                                     Scene *scene,
+                                     ViewLayer *view_layer,
+                                     ID *id_root,
+                                     Collection *override_resync_residual_storage,
+                                     const bool do_hierarchy_enforce)
 {
   BLI_assert(ID_IS_OVERRIDE_LIBRARY_REAL(id_root));
   BLI_assert(!ID_IS_LINKED(id_root));
@@ -1070,8 +1081,13 @@ bool BKE_lib_override_library_resync(
    * since we already relinked old root override collection to new resync'ed one above. So this
    * call is not expected to instantiate this new resync'ed collection anywhere, just to ensure
    * that we do not have any stray objects. */
-  lib_override_library_create_post_process(
-      bmain, scene, view_layer, id_root_reference, id_root, true);
+  lib_override_library_create_post_process(bmain,
+                                           scene,
+                                           view_layer,
+                                           id_root_reference,
+                                           id_root,
+                                           override_resync_residual_storage,
+                                           true);
 
   /* Cleanup. */
   BLI_ghash_free(linkedref_to_old_override, NULL, NULL);
@@ -1098,6 +1114,23 @@ bool BKE_lib_override_library_resync(
  */
 void BKE_lib_override_library_main_resync(Main *bmain, Scene *scene, ViewLayer *view_layer)
 {
+  /* We use a specific collection to gather/store all 'orphaned' override collections and objects
+   * generated by resyncprocess. This avoids putting them in scene's master collection. */
+#define OVERRIDE_RESYNC_RESIDUAL_STORAGE_NAME "OVERRIDE_RESYNC_LEFTOVERS"
+  Collection *override_resync_residual_storage = BLI_findstring(
+      &bmain->collections, OVERRIDE_RESYNC_RESIDUAL_STORAGE_NAME, offsetof(ID, name) + 2);
+  if (override_resync_residual_storage != NULL &&
+      override_resync_residual_storage->id.lib != NULL) {
+    override_resync_residual_storage = NULL;
+  }
+  if (override_resync_residual_storage == NULL) {
+    override_resync_residual_storage = BKE_collection_add(
+        bmain, scene->master_collection, OVERRIDE_RESYNC_RESIDUAL_STORAGE_NAME);
+    /* Hide the collection from viewport and render. */
+    override_resync_residual_storage->flag |= COLLECTION_RESTRICT_VIEWPORT |
+                                              COLLECTION_RESTRICT_RENDER;
+  }
+
   BKE_main_relations_create(bmain, 0);
   BKE_main_id_tag_all(bmain, LIB_TAG_DOIT, false);
 
@@ -1187,7 +1220,8 @@ void BKE_lib_override_library_main_resync(Main *bmain, Scene *scene, ViewLayer *
         }
         do_continue = true;
         CLOG_INFO(&LOG, 2, "Resyncing %s...", id->name);
-        const bool success = BKE_lib_override_library_resync(bmain, scene, view_layer, id, false);
+        const bool success = BKE_lib_override_library_resync(
+            bmain, scene, view_layer, id, override_resync_residual_storage, false);
         CLOG_INFO(&LOG, 2, "\tSuccess: %d", success);
         break;
       }
@@ -1198,6 +1232,10 @@ void BKE_lib_override_library_main_resync(Main *bmain, Scene *scene, ViewLayer *
     }
     FOREACH_MAIN_LISTBASE_END;
   }
+
+  if (BKE_collection_is_empty(override_resync_residual_storage)) {
+    BKE_collection_delete(bmain, override_resync_residual_storage, true);
+  }
 }
 
 /**
diff --git a/source/blender/editors/space_outliner/outliner_tools.c b/source/blender/editors/space_outliner/outliner_tools.c
index 6f3231f3bdf..dc9205106ab 100644
--- a/source/blender/editors/space_outliner/outliner_tools.c
+++ b/source/blender/editors/space_outliner/outliner_tools.c
@@ -925,7 +925,7 @@ static void id_override_library_resync_fn(bContext *C,
     }
 
     BKE_lib_override_library_resync(
-        bmain, scene, CTX_data_view_layer(C), id_root, do_hierarchy_enforce);
+        bmain, scene, CTX_data_view_layer(C), id_root, NULL, do_hierarchy_enforce);
 
     WM_event_add_notifier(C, NC_WINDOW, NULL);
   }