Serialize primaryModule in Engine instead of relying on modules to do it themselves.

src/core/AudioInterface.cpp

@@ -371,9 +371,6 @@ struct AudioInterface : Module {
 		json_t* rootJ = json_object();
 		json_object_set_new(rootJ, "audio", port.toJson());
 
-		if (isPrimary())
-			json_object_set_new(rootJ, "primary", json_boolean(true));
-
 		json_object_set_new(rootJ, "dcFilter", json_boolean(dcFilterEnabled));
 
 		return rootJ;
@@ -384,11 +381,6 @@ struct AudioInterface : Module {
 		if (audioJ)
 			port.fromJson(audioJ);
 
-		// For not, don't deserialize primary module state.
-		// json_t* primaryJ = json_object_get(rootJ, "primary");
-		// if (primaryJ)
-		// 	setPrimary();
-
 		json_t* dcFilterJ = json_object_get(rootJ, "dcFilter");
 		if (dcFilterJ)
 			dcFilterEnabled = json_boolean_value(dcFilterJ);

src/engine/Engine.cpp

@@ -1137,6 +1137,11 @@ json_t* Engine::toJson() {
 	}
 	json_object_set_new(rootJ, "cables", cablesJ);
 
+	// primaryModule
+	if (internal->primaryModule) {
+		json_object_set_new(rootJ, "primaryModuleId", json_integer(internal->primaryModule->id));
+	}
+
 	return rootJ;
 }
 
@@ -1219,6 +1224,13 @@ void Engine::fromJson(json_t* rootJ) {
 			continue;
 		}
 	}
+
+	// primaryModule
+	json_t* primaryModuleIdJ = json_object_get(rootJ, "primaryModuleId");
+	if (primaryModuleIdJ) {
+		Module* primaryModule = getModule(json_integer_value(primaryModuleIdJ));
+		setPrimaryModule(primaryModule);
+	}
 }