Fix T78071: Drivers reading object visibility not updating automatically

A driver reading `Object.hide_viewport` would break when that object was
hidden. Hidden objects don't have the `OBJECT_BASE_FLAGS` node in the
depsgraph, but that node was required for the driver to work.

Now the `OBJECT_FROM_LAYER` component (which optionally contains the
`OBJECT_FROM_LAYER` node) has explicit `ENTRY` and `EXIT` nodes, which
are used for relations with other components. These relations now remain
valid, even when the `OBJECT_FROM_LAYER` node is absent.

Differential Revision: https://developer.blender.org/D8124

Reviewed By: sergey

source/blender/depsgraph/intern/builder/deg_builder_nodes.cc

@@ -594,7 +594,7 @@ void DepsgraphNodeBuilder::build_object(int base_index,
   }
   id_node->has_base |= (base_index != -1);
   /* Various flags, flushing from bases/collections. */
-  build_object_flags(base_index, object, linked_state);
+  build_object_from_layer(base_index, object, linked_state);
   /* Transform. */
   build_object_transform(object);
   /* Parent. */
@@ -662,6 +662,21 @@ void DepsgraphNodeBuilder::build_object(int base_index,
                      function_bind(BKE_object_sync_to_original, _1, object_cow));
 }
 
+void DepsgraphNodeBuilder::build_object_from_layer(int base_index,
+                                                   Object *object,
+                                                   eDepsNode_LinkedState_Type linked_state)
+{
+
+  OperationNode *entry_node = add_operation_node(
+      &object->id, NodeType::OBJECT_FROM_LAYER, OperationCode::OBJECT_FROM_LAYER_ENTRY);
+  entry_node->set_as_entry();
+  OperationNode *exit_node = add_operation_node(
+      &object->id, NodeType::OBJECT_FROM_LAYER, OperationCode::OBJECT_FROM_LAYER_EXIT);
+  exit_node->set_as_exit();
+
+  build_object_flags(base_index, object, linked_state);
+}
+
 void DepsgraphNodeBuilder::build_object_flags(int base_index,
                                               Object *object,
                                               eDepsNode_LinkedState_Type linked_state)

source/blender/depsgraph/intern/builder/deg_builder_nodes.h

@@ -168,6 +168,9 @@ class DepsgraphNodeBuilder : public DepsgraphBuilder {
   virtual void build_object_proxy_from(Object *object, bool is_object_visible);
   virtual void build_object_proxy_group(Object *object, bool is_object_visible);
   virtual void build_object_instance_collection(Object *object, bool is_object_visible);
+  virtual void build_object_from_layer(int base_index,
+                                       Object *object,
+                                       eDepsNode_LinkedState_Type linked_state);
   virtual void build_object_flags(int base_index,
                                   Object *object,
                                   eDepsNode_LinkedState_Type linked_state);

source/blender/depsgraph/intern/builder/deg_builder_relations.cc

@@ -621,12 +621,9 @@ void DepsgraphRelationBuilder::build_collection(LayerCollection *from_layer_coll
   }
 }
 
-void DepsgraphRelationBuilder::build_object(Base *base, Object *object)
+void DepsgraphRelationBuilder::build_object(Base * /*base*/, Object *object)
 {
   if (built_map_.checkIsBuiltAndTag(object)) {
-    if (base != nullptr) {
-      build_object_flags(base, object);
-    }
     return;
   }
   /* Object Transforms */
@@ -644,7 +641,7 @@ void DepsgraphRelationBuilder::build_object(Base *base, Object *object)
   OperationKey ob_eval_key(&object->id, NodeType::TRANSFORM, OperationCode::TRANSFORM_EVAL);
   add_relation(init_transform_key, local_transform_key, "Transform Init");
   /* Various flags, flushing from bases/collections. */
-  build_object_flags(base, object);
+  build_object_from_layer_relations(object);
   /* Parenting. */
   if (object->parent != nullptr) {
     /* Make sure parent object's relations are built. */
@@ -755,20 +752,34 @@ void DepsgraphRelationBuilder::build_object_proxy_group(Object *object)
   add_relation(proxy_group_eval_key, transform_eval_key, "Proxy Group Transform");
 }
 
-void DepsgraphRelationBuilder::build_object_flags(Base *base, Object *object)
+void DepsgraphRelationBuilder::build_object_from_layer_relations(Object *object)
 {
-  if (base == nullptr) {
+  OperationKey object_from_layer_entry_key(
-    return;
+      &object->id, NodeType::OBJECT_FROM_LAYER, OperationCode::OBJECT_FROM_LAYER_ENTRY);
-  }
+  OperationKey object_from_layer_exit_key(
-  OperationKey view_layer_done_key(
+      &object->id, NodeType::OBJECT_FROM_LAYER, OperationCode::OBJECT_FROM_LAYER_EXIT);
-      &scene_->id, NodeType::LAYER_COLLECTIONS, OperationCode::VIEW_LAYER_EVAL);
   OperationKey object_flags_key(
       &object->id, NodeType::OBJECT_FROM_LAYER, OperationCode::OBJECT_BASE_FLAGS);
-  add_relation(view_layer_done_key, object_flags_key, "Base flags flush");
+
+  /* Only connect Entry -> Exit if there is no OBJECT_BASE_FLAGS node. */
+  if (has_node(object_flags_key)) {
+    /* Entry -> OBJECT_BASE_FLAGS -> Exit */
+    add_relation(object_from_layer_entry_key, object_flags_key, "Base flags flush Entry");
+    add_relation(object_flags_key, object_from_layer_exit_key, "Base flags flush Exit");
+
     /* Synchronization back to original object. */
     OperationKey synchronize_key(
         &object->id, NodeType::SYNCHRONIZATION, OperationCode::SYNCHRONIZE_TO_ORIGINAL);
-  add_relation(object_flags_key, synchronize_key, "Synchronize to Original");
+    add_relation(object_from_layer_exit_key, synchronize_key, "Synchronize to Original");
+  }
+  else {
+    /* Directly connect Entry -> Exit. */
+    add_relation(object_from_layer_entry_key, object_from_layer_exit_key, "Object from Layer");
+  }
+
+  OperationKey view_layer_done_key(
+      &scene_->id, NodeType::LAYER_COLLECTIONS, OperationCode::VIEW_LAYER_EVAL);
+  add_relation(view_layer_done_key, object_from_layer_entry_key, "View Layer flags to Object");
 }
 
 void DepsgraphRelationBuilder::build_object_data(Object *object)

source/blender/depsgraph/intern/builder/deg_builder_relations.h

@@ -213,7 +213,7 @@ class DepsgraphRelationBuilder : public DepsgraphBuilder {
   virtual void build_object(Base *base, Object *object);
   virtual void build_object_proxy_from(Object *object);
   virtual void build_object_proxy_group(Object *object);
-  virtual void build_object_flags(Base *base, Object *object);
+  virtual void build_object_from_layer_relations(Object *object);
   virtual void build_object_data(Object *object);
   virtual void build_object_data_camera(Object *object);
   virtual void build_object_data_geometry(Object *object);

source/blender/depsgraph/intern/depsgraph_tag.cc

@@ -109,7 +109,7 @@ void depsgraph_select_tag_to_component_opcode(const ID *id,
   }
   else if (id_type == ID_OB) {
     *component_type = NodeType::OBJECT_FROM_LAYER;
-    *operation_code = OperationCode::OBJECT_BASE_FLAGS;
+    *operation_code = OperationCode::OBJECT_FROM_LAYER_ENTRY;
   }
   else if (id_type == ID_MC) {
     *component_type = NodeType::BATCH_CACHE;

source/blender/depsgraph/intern/node/deg_node_operation.cc

@@ -63,8 +63,12 @@ const char *operationCodeAsString(OperationCode opcode)
     case OperationCode::AUDIO_VOLUME:
       return "AUDIO_VOLUME";
     /* Object related. */
+    case OperationCode::OBJECT_FROM_LAYER_ENTRY:
+      return "OBJECT_FROM_LAYER_ENTRY";
     case OperationCode::OBJECT_BASE_FLAGS:
       return "OBJECT_BASE_FLAGS";
+    case OperationCode::OBJECT_FROM_LAYER_EXIT:
+      return "OBJECT_FROM_LAYER_EXIT";
     case OperationCode::DIMENSIONS:
       return "DIMENSIONS";
     /* Transform. */

source/blender/depsgraph/intern/node/deg_node_operation.h

@@ -63,7 +63,9 @@ enum class OperationCode {
   AUDIO_VOLUME,
 
   /* Object related. ------------------------------------------------------ */
+  OBJECT_FROM_LAYER_ENTRY,
   OBJECT_BASE_FLAGS,
+  OBJECT_FROM_LAYER_EXIT,
   DIMENSIONS,
 
   /* Transform. ----------------------------------------------------------- */