Add an option to free scene without doing id-counters

This is similar to some other datablocks. Mainly applies to collections,
so freeing scene does not involve changing any non-directly owned data.

There are two main usecases foreseen for the future:

- Less CPU ticks on bmain free, where everything is freed anyway and
  there is no need to preserve id counters.

- Easier freeing of temporary data, including data which is used by
  depsgraph's copy-on-write mechanism.

Neither of those are currently implemented, but will be shortly.

4 files changed, 22 insertions, 14 deletions

diff --git a/source/blender/blenkernel/BKE_collection.h b/source/blender/blenkernel/BKE_collection.h
index 35d8f336207..0adac4500f8 100644
--- a/source/blender/blenkernel/BKE_collection.h
+++ b/source/blender/blenkernel/BKE_collection.h
@@ -46,7 +46,7 @@ struct SceneCollection *BKE_collection_add(struct Scene *scene, struct SceneColl
 bool BKE_collection_remove(struct Scene *scene, struct SceneCollection *sc);
 struct SceneCollection *BKE_collection_master(const struct Scene *scene);
 void BKE_collection_rename(const struct Scene *scene, struct SceneCollection *sc, const char *name);
-void BKE_collection_master_free(struct Scene *scene);
+void BKE_collection_master_free(struct Scene *scene, const bool do_id_user);
 void BKE_collection_object_add(const struct Scene *scene, struct SceneCollection *sc, struct Object *object);
 void BKE_collection_object_add_from(struct Scene *scene, struct Object *ob_src, struct Object *ob_dst);
 void BKE_collection_object_remove(struct Main *bmain, const struct Scene *scene, struct SceneCollection *sc, struct Object *object, const bool free_us);
diff --git a/source/blender/blenkernel/BKE_scene.h b/source/blender/blenkernel/BKE_scene.h
index cd59ef98903..5047070012c 100644
--- a/source/blender/blenkernel/BKE_scene.h
+++ b/source/blender/blenkernel/BKE_scene.h
@@ -71,6 +71,7 @@ struct Base *_setlooper_base_step(struct Scene **sce_iter, struct Base *base);
 void free_avicodecdata(struct AviCodecData *acd);
 void free_qtcodecdata(struct QuicktimeCodecData *acd);
 
+void BKE_scene_free_ex(struct Scene *sce, const bool do_id_user);
 void BKE_scene_free(struct Scene *sce);
 void BKE_scene_init(struct Scene *sce);
 struct Scene *BKE_scene_add(struct Main *bmain, const char *name);
diff --git a/source/blender/blenkernel/intern/collection.c b/source/blender/blenkernel/intern/collection.c
index 507ae1a4e70..3bf3a5ce5a4 100644
--- a/source/blender/blenkernel/intern/collection.c
+++ b/source/blender/blenkernel/intern/collection.c
@@ -75,20 +75,22 @@ SceneCollection *BKE_collection_add(Scene *scene, SceneCollection *sc_parent, co
 /**
  * Free the collection items recursively
  */
-static void collection_free(SceneCollection *sc)
+static void collection_free(SceneCollection *sc, const bool do_id_user)
 {
-	for (LinkData *link = sc->objects.first; link; link = link->next) {
-		id_us_min(link->data);
+	if (do_id_user) {
+		for (LinkData *link = sc->objects.first; link; link = link->next) {
+			id_us_min(link->data);
+		}
+		for (LinkData *link = sc->filter_objects.first; link; link = link->next) {
+			id_us_min(link->data);
+		}
 	}
-	BLI_freelistN(&sc->objects);
 
-	for (LinkData *link = sc->filter_objects.first; link; link = link->next) {
-		id_us_min(link->data);
-	}
+	BLI_freelistN(&sc->objects);
 	BLI_freelistN(&sc->filter_objects);
 
 	for (SceneCollection *nsc = sc->scene_collections.first; nsc; nsc = nsc->next) {
-		collection_free(nsc);
+		collection_free(nsc, do_id_user);
 	}
 	BLI_freelistN(&sc->scene_collections);
 }
@@ -160,7 +162,7 @@ bool BKE_collection_remove(Scene *scene, SceneCollection *sc)
 	}
 
 	/* clear the collection items */
-	collection_free(sc);
+	collection_free(sc, true);
 
 	/* check all layers that use this collection and clear them */
 	for (SceneLayer *sl = scene->render_layers.first; sl; sl = sl->next) {
@@ -218,9 +220,9 @@ void BKE_collection_rename(const Scene *scene, SceneCollection *sc, const char *
  * Free (or release) any data used by the master collection (does not free the master collection itself).
  * Used only to clear the entire scene data since it's not doing re-syncing of the LayerCollection tree
  */
-void BKE_collection_master_free(Scene *scene)
+void BKE_collection_master_free(Scene *scene, const bool do_id_user)
 {
-	collection_free(BKE_collection_master(scene));
+	collection_free(BKE_collection_master(scene), do_id_user);
 }
 
 static void collection_object_add(const Scene *scene, SceneCollection *sc, Object *ob)
diff --git a/source/blender/blenkernel/intern/scene.c b/source/blender/blenkernel/intern/scene.c
index d2e6450f0de..94372588957 100644
--- a/source/blender/blenkernel/intern/scene.c
+++ b/source/blender/blenkernel/intern/scene.c
@@ -482,7 +482,7 @@ void BKE_scene_make_local(Main *bmain, Scene *sce, const bool lib_local)
 }
 
 /** Free (or release) any data used by this scene (does not free the scene itself). */
-void BKE_scene_free(Scene *sce)
+void BKE_scene_free_ex(Scene *sce, const bool do_id_user)
 {
 	SceneRenderLayer *srl;
 
@@ -590,7 +590,7 @@ void BKE_scene_free(Scene *sce)
 	}
 
 	/* Master Collection */
-	BKE_collection_master_free(sce);
+	BKE_collection_master_free(sce, do_id_user);
 	MEM_freeN(sce->collection);
 	sce->collection = NULL;
 
@@ -609,6 +609,11 @@ void BKE_scene_free(Scene *sce)
 	}
 }
 
+void BKE_scene_free(Scene *sce)
+{
+	return BKE_scene_free_ex(sce, true);
+}
+
 void BKE_scene_init(Scene *sce)
 {
 	ParticleEditSettings *pset;