ViewLayer: Lazy sync of scene data.

When a change happens which invalidates view layers the syncing will be postponed until the first usage.
This will improve importing or adding many objects in a single operation/script.

`BKE_view_layer_need_resync_tag` is used to tag the view layer to be out of sync. Before accessing
`BKE_view_layer_active_base_get`, `BKE_view_layer_active_object_get`, `BKE_view_layer_active_collection`
or `BKE_view_layer_object_bases` the caller should call `BKE_view_layer_synced_ensure`.

Having two functions ensures that partial syncing could be added as smaller patches in the future. Tagging a
view layer out of sync could be replaced with a partial sync. Eventually the number of full resyncs could be
reduced. After all tagging has been replaced with partial syncs the ensure_sync could be phased out.

This patch has been added to discuss the details and consequences of the current approach. For clarity
the call to BKE_view_layer_ensure_sync is placed close to the getters.
In the future this could be placed in more strategical places to reduce the number of calls or improve
performance. Finding those strategical places isn't that clear. When multiple operations are grouped
in a single script you might want to always check for resync.

Some areas found that can be improved. This list isn't complete.
These areas aren't addressed by this patch as these changes would be hard to detect to the reviewer.
The idea is to add changes to these areas as a separate patch. It might be that the initial commit would reduce
performance compared to master, but will be fixed by the additional patches.

**Object duplication**
During object duplication the syncing is temporarily disabled. With this patch this isn't useful as when disabled
the view_layer is accessed to locate bases. This can be improved by first locating the source bases, then duplicate
and sync and locate the new bases. Will be solved in a separate patch for clarity reasons ({D15886}).

**Object add**
`BKE_object_add` not only adds a new object, but also selects and activates the new base. This requires the
view_layer to be resynced. Some callers reverse the selection and activation (See `get_new_constraint_target`).
We should make the selection and activation optional. This would make it possible to add multiple objects
without having to resync per object.

**Postpone Activate Base**
Setting the basact is done in many locations. They follow a rule as after an action find the base and set
the basact. Finding the base could require a resync. The idea is to store in the view_layer the object which
base will be set in the basact during the next sync, reducing the times resyncing needs to happen.

Reviewed By: mont29

Maniphest Tasks: T73411

Differential Revision: https://developer.blender.org/D15885

6 files changed, 59 insertions, 18 deletions

diff --git a/source/blender/makesrna/intern/rna_brush.c b/source/blender/makesrna/intern/rna_brush.c
index 789a8b381b6..a6778ef67da 100644
--- a/source/blender/makesrna/intern/rna_brush.c
+++ b/source/blender/makesrna/intern/rna_brush.c
@@ -972,7 +972,9 @@ static void rna_BrushGpencilSettings_default_eraser_update(Main *bmain,
 
 static void rna_BrushGpencilSettings_use_material_pin_update(bContext *C, PointerRNA *ptr)
 {
+  const Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *ob = BKE_view_layer_active_object_get(view_layer);
   Brush *brush = (Brush *)ptr->owner_id;
 
diff --git a/source/blender/makesrna/intern/rna_layer.c b/source/blender/makesrna/intern/rna_layer.c
index 3a76b9e05c2..ae0366bebad 100644
--- a/source/blender/makesrna/intern/rna_layer.c
+++ b/source/blender/makesrna/intern/rna_layer.c
@@ -50,8 +50,10 @@
 
 static PointerRNA rna_ViewLayer_active_layer_collection_get(PointerRNA *ptr)
 {
+  const Scene *scene = (const Scene *)ptr->owner_id;
   ViewLayer *view_layer = (ViewLayer *)ptr->data;
-  LayerCollection *lc = view_layer->active_collection;
+  BKE_view_layer_synced_ensure(scene, view_layer);
+  LayerCollection *lc = BKE_view_layer_active_collection_get(view_layer);
   return rna_pointer_inherit_refine(ptr, &RNA_LayerCollection, lc);
 }
 
@@ -59,8 +61,10 @@ static void rna_ViewLayer_active_layer_collection_set(PointerRNA *ptr,
                                                       PointerRNA value,
                                                       struct ReportList *UNUSED(reports))
 {
+  const Scene *scene = (const Scene *)ptr->owner_id;
   ViewLayer *view_layer = (ViewLayer *)ptr->data;
   LayerCollection *lc = (LayerCollection *)value.data;
+  BKE_view_layer_synced_ensure(scene, view_layer);
   const int index = BKE_layer_collection_findindex(view_layer, lc);
   if (index != -1) {
     BKE_layer_collection_activate(view_layer, lc);
@@ -69,18 +73,22 @@ static void rna_ViewLayer_active_layer_collection_set(PointerRNA *ptr,
 
 static PointerRNA rna_LayerObjects_active_object_get(PointerRNA *ptr)
 {
+  const Scene *scene = (Scene *)ptr->owner_id;
   ViewLayer *view_layer = (ViewLayer *)ptr->data;
+  BKE_view_layer_synced_ensure(scene, view_layer);
   return rna_pointer_inherit_refine(
-      ptr, &RNA_Object, view_layer->basact ? view_layer->basact->object : NULL);
+      ptr, &RNA_Object, BKE_view_layer_active_object_get(view_layer));
 }
 
 static void rna_LayerObjects_active_object_set(PointerRNA *ptr,
                                                PointerRNA value,
                                                struct ReportList *reports)
 {
+  const Scene *scene = (Scene *)ptr->owner_id;
   ViewLayer *view_layer = (ViewLayer *)ptr->data;
   if (value.data) {
     Object *ob = value.data;
+    BKE_view_layer_synced_ensure(scene, view_layer);
     Base *basact_test = BKE_view_layer_base_find(view_layer, ob);
     if (basact_test != NULL) {
       view_layer->basact = basact_test;
@@ -197,7 +205,7 @@ static void rna_LayerObjects_selected_begin(CollectionPropertyIterator *iter, Po
 {
   ViewLayer *view_layer = (ViewLayer *)ptr->data;
   rna_iterator_listbase_begin(
-      iter, &view_layer->object_bases, rna_ViewLayer_objects_selected_skip);
+      iter, BKE_view_layer_object_bases_get(view_layer), rna_ViewLayer_objects_selected_skip);
 }
 
 static void rna_ViewLayer_update_tagged(ID *id_ptr,
@@ -245,7 +253,7 @@ static void rna_ObjectBase_hide_viewport_update(bContext *C, PointerRNA *UNUSED(
 {
   Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
-  BKE_layer_collection_sync(scene, view_layer);
+  BKE_view_layer_need_resync_tag(view_layer);
   DEG_id_tag_update(&scene->id, ID_RECALC_BASE_FLAGS);
   WM_event_add_notifier(C, NC_SCENE | ND_OB_SELECT, scene);
 }
@@ -309,7 +317,7 @@ static void rna_LayerCollection_exclude_update(Main *bmain, Scene *UNUSED(scene)
   const bool exclude = (lc->flag & LAYER_COLLECTION_EXCLUDE) != 0;
   BKE_layer_collection_set_flag(lc, LAYER_COLLECTION_EXCLUDE, exclude);
 
-  BKE_layer_collection_sync(scene, view_layer);
+  BKE_view_layer_need_resync_tag(view_layer);
 
   DEG_id_tag_update(&scene->id, ID_RECALC_BASE_FLAGS);
   if (!exclude) {
@@ -334,7 +342,7 @@ static void rna_LayerCollection_update(Main *UNUSED(bmain), Scene *UNUSED(scene)
   LayerCollection *lc = (LayerCollection *)ptr->data;
   ViewLayer *view_layer = BKE_view_layer_find_from_collection(scene, lc);
 
-  BKE_layer_collection_sync(scene, view_layer);
+  BKE_view_layer_need_resync_tag(view_layer);
 
   DEG_id_tag_update(&scene->id, ID_RECALC_BASE_FLAGS);
 
diff --git a/source/blender/makesrna/intern/rna_object_api.c b/source/blender/makesrna/intern/rna_object_api.c
index 6967f78026a..0b8cf601bfd 100644
--- a/source/blender/makesrna/intern/rna_object_api.c
+++ b/source/blender/makesrna/intern/rna_object_api.c
@@ -145,7 +145,7 @@ static void rna_Object_hide_set(
   }
 
   Scene *scene = CTX_data_scene(C);
-  BKE_layer_collection_sync(scene, view_layer);
+  BKE_view_layer_need_resync_tag(view_layer);
   DEG_id_tag_update(&scene->id, ID_RECALC_BASE_FLAGS);
   WM_event_add_notifier(C, NC_SCENE | ND_OB_SELECT, scene);
 }
diff --git a/source/blender/makesrna/intern/rna_scene.c b/source/blender/makesrna/intern/rna_scene.c
index e2b3276c45f..27cfe766eef 100644
--- a/source/blender/makesrna/intern/rna_scene.c
+++ b/source/blender/makesrna/intern/rna_scene.c
@@ -706,7 +706,9 @@ static void rna_GPencil_update(Main *UNUSED(bmain), Scene *scene, PointerRNA *UN
 static void rna_Gpencil_extend_selection(bContext *C, PointerRNA *UNUSED(ptr))
 {
   /* Extend selection to all points in all selected strokes. */
+  const Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *ob = BKE_view_layer_active_object_get(view_layer);
   if ((ob) && (ob->type == OB_GPENCIL)) {
     bGPdata *gpd = (bGPdata *)ob->data;
@@ -1862,13 +1864,17 @@ static void rna_Scene_editmesh_select_mode_set(PointerRNA *ptr, const bool *valu
     /* Update select mode in all the workspaces in mesh edit mode. */
     wmWindowManager *wm = G_MAIN->wm.first;
     LISTBASE_FOREACH (wmWindow *, win, &wm->windows) {
+      const Scene *scene = WM_window_get_active_scene(win);
       ViewLayer *view_layer = WM_window_get_active_view_layer(win);
-
-      if (view_layer && view_layer->basact) {
-        Mesh *me = BKE_mesh_from_object(view_layer->basact->object);
-        if (me && me->edit_mesh && me->edit_mesh->selectmode != flag) {
-          me->edit_mesh->selectmode = flag;
-          EDBM_selectmode_set(me->edit_mesh);
+      if (view_layer) {
+        BKE_view_layer_synced_ensure(scene, view_layer);
+        Object *object = BKE_view_layer_active_object_get(view_layer);
+        if (object) {
+          Mesh *me = BKE_mesh_from_object(object);
+          if (me && me->edit_mesh && me->edit_mesh->selectmode != flag) {
+            me->edit_mesh->selectmode = flag;
+            EDBM_selectmode_set(me->edit_mesh);
+          }
         }
       }
     }
@@ -1877,11 +1883,14 @@ static void rna_Scene_editmesh_select_mode_set(PointerRNA *ptr, const bool *valu
 
 static void rna_Scene_editmesh_select_mode_update(bContext *C, PointerRNA *UNUSED(ptr))
 {
+  const Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
   Mesh *me = NULL;
 
-  if (view_layer->basact) {
-    me = BKE_mesh_from_object(view_layer->basact->object);
+  BKE_view_layer_synced_ensure(scene, view_layer);
+  Object *object = BKE_view_layer_active_object_get(view_layer);
+  if (object) {
+    me = BKE_mesh_from_object(object);
     if (me && me->edit_mesh == NULL) {
       me = NULL;
     }
@@ -2220,11 +2229,14 @@ static char *rna_SequencerToolSettings_path(const PointerRNA *UNUSED(ptr))
 /* generic function to recalc geometry */
 static void rna_EditMesh_update(bContext *C, PointerRNA *UNUSED(ptr))
 {
+  const Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
   Mesh *me = NULL;
 
-  if (view_layer->basact) {
-    me = BKE_mesh_from_object(view_layer->basact->object);
+  BKE_view_layer_synced_ensure(scene, view_layer);
+  Object *object = BKE_view_layer_active_object_get(view_layer);
+  if (object) {
+    me = BKE_mesh_from_object(object);
     if (me && me->edit_mesh == NULL) {
       me = NULL;
     }
@@ -2248,7 +2260,9 @@ static char *rna_MeshStatVis_path(const PointerRNA *UNUSED(ptr))
  * given its own notifier. */
 static void rna_Scene_update_active_object_data(bContext *C, PointerRNA *UNUSED(ptr))
 {
+  const Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *ob = BKE_view_layer_active_object_get(view_layer);
 
   if (ob) {
diff --git a/source/blender/makesrna/intern/rna_sculpt_paint.c b/source/blender/makesrna/intern/rna_sculpt_paint.c
index 42523508c14..a4298c8c3aa 100644
--- a/source/blender/makesrna/intern/rna_sculpt_paint.c
+++ b/source/blender/makesrna/intern/rna_sculpt_paint.c
@@ -165,6 +165,7 @@ static void rna_ParticleEdit_redo(bContext *C, PointerRNA *UNUSED(ptr))
   Depsgraph *depsgraph = CTX_data_depsgraph_pointer(C);
   Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *ob = BKE_view_layer_active_object_get(view_layer);
   PTCacheEdit *edit = PE_get_current(depsgraph, scene, ob);
 
@@ -185,6 +186,7 @@ static void rna_ParticleEdit_update(bContext *C, PointerRNA *UNUSED(ptr))
 {
   Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *ob = BKE_view_layer_active_object_get(view_layer);
 
   if (ob) {
@@ -215,7 +217,9 @@ static const EnumPropertyItem *rna_ParticleEdit_tool_itemf(bContext *C,
                                                            PropertyRNA *UNUSED(prop),
                                                            bool *UNUSED(r_free))
 {
+  const Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *ob = BKE_view_layer_active_object_get(view_layer);
 #  if 0
   Depsgraph *depsgraph = CTX_data_depsgraph_pointer(C);
@@ -374,6 +378,7 @@ static void rna_Sculpt_update(bContext *C, PointerRNA *UNUSED(ptr))
 {
   Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *ob = BKE_view_layer_active_object_get(view_layer);
 
   if (ob) {
@@ -389,12 +394,13 @@ static void rna_Sculpt_update(bContext *C, PointerRNA *UNUSED(ptr))
 
 static void rna_Sculpt_ShowMask_update(bContext *C, PointerRNA *UNUSED(ptr))
 {
+  Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *object = BKE_view_layer_active_object_get(view_layer);
   if (object == NULL || object->sculpt == NULL) {
     return;
   }
-  Scene *scene = CTX_data_scene(C);
   Sculpt *sd = scene->toolsettings->sculpt;
   object->sculpt->show_mask = ((sd->flags & SCULPT_HIDE_MASK) == 0);
   if (object->sculpt->pbvh != NULL) {
@@ -488,6 +494,7 @@ static void rna_ImaPaint_mode_update(bContext *C, PointerRNA *UNUSED(ptr))
 {
   Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *ob = BKE_view_layer_active_object_get(view_layer);
 
   if (ob && ob->type == OB_MESH) {
@@ -505,6 +512,7 @@ static void rna_ImaPaint_stencil_update(bContext *C, PointerRNA *UNUSED(ptr))
 {
   Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *ob = BKE_view_layer_active_object_get(view_layer);
 
   if (ob && ob->type == OB_MESH) {
@@ -524,6 +532,7 @@ static void rna_ImaPaint_canvas_update(bContext *C, PointerRNA *UNUSED(ptr))
   Main *bmain = CTX_data_main(C);
   Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *ob = BKE_view_layer_active_object_get(view_layer);
   bScreen *screen;
   Image *ima = scene->toolsettings->imapaint.canvas;
diff --git a/source/blender/makesrna/intern/rna_space.c b/source/blender/makesrna/intern/rna_space.c
index 268aacfccc6..01b68cbd134 100644
--- a/source/blender/makesrna/intern/rna_space.c
+++ b/source/blender/makesrna/intern/rna_space.c
@@ -1673,7 +1673,9 @@ static bool rna_SpaceImageEditor_show_uvedit_get(PointerRNA *ptr)
   Object *obedit = NULL;
   wmWindow *win = ED_screen_window_find(screen, G_MAIN->wm.first);
   if (win != NULL) {
+    Scene *scene = WM_window_get_active_scene(win);
     ViewLayer *view_layer = WM_window_get_active_view_layer(win);
+    BKE_view_layer_synced_ensure(scene, view_layer);
     obedit = BKE_view_layer_edit_object_get(view_layer);
   }
   return ED_space_image_show_uvedit(sima, obedit);
@@ -1686,7 +1688,9 @@ static bool rna_SpaceImageEditor_show_maskedit_get(PointerRNA *ptr)
   Object *obedit = NULL;
   wmWindow *win = ED_screen_window_find(screen, G_MAIN->wm.first);
   if (win != NULL) {
+    Scene *scene = WM_window_get_active_scene(win);
     ViewLayer *view_layer = WM_window_get_active_view_layer(win);
+    BKE_view_layer_synced_ensure(scene, view_layer);
     obedit = BKE_view_layer_edit_object_get(view_layer);
   }
   return ED_space_image_check_show_maskedit(sima, obedit);
@@ -2184,9 +2188,11 @@ static void rna_SpaceDopeSheetEditor_action_set(PointerRNA *ptr,
 static void rna_SpaceDopeSheetEditor_action_update(bContext *C, PointerRNA *ptr)
 {
   SpaceAction *saction = (SpaceAction *)(ptr->data);
+  const Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
   Main *bmain = CTX_data_main(C);
 
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *obact = BKE_view_layer_active_object_get(view_layer);
   if (obact == NULL) {
     return;
@@ -2259,7 +2265,9 @@ static void rna_SpaceDopeSheetEditor_mode_update(bContext *C, PointerRNA *ptr)
 {
   SpaceAction *saction = (SpaceAction *)(ptr->data);
   ScrArea *area = CTX_wm_area(C);
+  const Scene *scene = CTX_data_scene(C);
   ViewLayer *view_layer = CTX_data_view_layer(C);
+  BKE_view_layer_synced_ensure(scene, view_layer);
   Object *obact = BKE_view_layer_active_object_get(view_layer);
 
   /* special exceptions for ShapeKey Editor mode */