Add a mechanism for overriding and resetting variables in a derived blackboard source

blackboard/blackboard_source.cpp

@@ -92,9 +92,21 @@ void BlackboardSource::_get_property_list(List<PropertyInfo> *p_list) const {
 	}
 }
 
+bool BlackboardSource::_property_can_revert(const StringName &p_name) const {
+	return base.is_valid() && base->data.has(p_name);
+}
+
+bool BlackboardSource::_property_get_revert(const StringName &p_name, Variant &r_property) const {
+	if (base->data.has(p_name)) {
+		r_property = base->data[p_name].get_value();
+		return true;
+	}
+	return false;
+}
+
 void BlackboardSource::set_base_source(const Ref<BlackboardSource> &p_base) {
 	base = p_base;
-	sync_base();
+	sync_with_base_source();
 	emit_changed();
 }
 
@@ -133,7 +145,10 @@ PackedStringArray BlackboardSource::list_vars() const {
 	return ret;
 }
 
-void BlackboardSource::sync_base() {
+void BlackboardSource::sync_with_base_source() {
+	if (base.is_null()) {
+		return;
+	}
 	for (const KeyValue<String, BBVariable> &kv : base->data) {
 		if (!data.has(kv.key)) {
 			data.insert(kv.key, kv.value.duplicate());

blackboard/blackboard_source.h

@@ -22,13 +22,17 @@ class BlackboardSource : public Resource {
 
 private:
 	HashMap<String, BBVariable> data;
+
+	// When base is not null, the source is considered to be derived from the base source.
+	// A derived source can only have variables that exist in the base source.
 	Ref<BlackboardSource> base;
-	// HashMap<String, BBVariable> overrides;
 
 protected:
 	bool _set(const StringName &p_name, const Variant &p_value);
 	bool _get(const StringName &p_name, Variant &r_ret) const;
 	void _get_property_list(List<PropertyInfo> *p_list) const;
+	bool _property_can_revert(const StringName &p_name) const;
+	bool _property_get_revert(const StringName &p_name, Variant &r_property) const;
 
 public:
 	void set_base_source(const Ref<BlackboardSource> &p_base);
@@ -42,7 +46,9 @@ public:
 	PackedStringArray list_vars() const;
 	bool is_empty() const { return data.is_empty(); }
 
-	void sync_base();
+	void sync_with_base_source();
+	bool is_derived() { return base.is_valid(); }
+
 	Ref<Blackboard> create_blackboard();
 	void populate_blackboard(const Ref<Blackboard> &p_blackboard, bool overwrite);
 

bt/bt_player.cpp

@@ -69,7 +69,7 @@ void BTPlayer::_update_blackboard_source() {
 			blackboard_source = Ref<BlackboardSource>(memnew(BlackboardSource));
 		}
 		if (blackboard_source == behavior_tree->get_blackboard_source()) {
-			blackboard_source->sync_base();
+			blackboard_source->sync_with_base_source();
 		} else {
 			blackboard_source->set_base_source(behavior_tree->get_blackboard_source());
 		}

bt/bt_state.cpp

@@ -32,7 +32,7 @@ void BTState::_update_blackboard_source() {
 			set_blackboard_source(Ref<BlackboardSource>(memnew(BlackboardSource)));
 		}
 		if (get_blackboard_source() == behavior_tree->get_blackboard_source()) {
-			get_blackboard_source()->sync_base();
+			get_blackboard_source()->sync_with_base_source();
 		} else {
 			get_blackboard_source()->set_base_source(behavior_tree->get_blackboard_source());
 		}

bt/tasks/decorators/bt_new_scope.cpp

@@ -36,5 +36,5 @@ void BTNewScope::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_blackboard_source", "p_source"), &BTNewScope::set_blackboard_source);
 	ClassDB::bind_method(D_METHOD("get_blackboard_source"), &BTNewScope::get_blackboard_source);
 
-	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "blackboard_source", PROPERTY_HINT_RESOURCE_TYPE, "BlackboardSource", PROPERTY_USAGE_DEFAULT), "set_blackboard_source", "get_blackboard_source");
+	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "blackboard_source", PROPERTY_HINT_RESOURCE_TYPE, "BlackboardSource", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_EDITOR_INSTANTIATE_OBJECT), "set_blackboard_source", "get_blackboard_source");
 }