Use Module::Expander struct for accessing expander messages.

include/engine/Module.hpp

@@ -37,36 +37,39 @@ struct Module {
 	std::vector<Light> lights;
 	std::vector<ParamQuantity*> paramQuantities;
 
-	/** ID of the Module immediately to the left, or -1 if nonexistent. */
-	int leftModuleId = -1;
-	/** Pointer to the left Module, or NULL if nonexistent. */
-	Module *leftModule = NULL;
-	/** Double buffer for receiving messages from the left adjacent module.
-	If this module intends to receive messages from the left, allocate both message buffers with identical blocks of memory (arrays, structs, etc).
-	Remember to free the buffer in the Module destructor.
-	Example:
-
-		leftProducerMessage = new MyModuleMessage;
-		leftConsumerMessage = new MyModuleMessage;
-
-	Modules must check a foreign module's `model` before attempting to write its message buffer.
-	Once the module is checked, you can reinterpret_cast its leftProducerMessage for speed.
-
-	Once you write a message, set leftMessageFlipRequested to true, to request that the messages are flipped at the end of the timestep.
-	Thus, message-passing has 1-sample latency.
-
-	You may choose for the Module to write to its own message buffer for consumption by other modules, i.e. "pull" rather than "push".
-	As long as this convention is followed by the left module, this is fine.
-	*/
-	void *leftProducerMessage = NULL;
-	void *leftConsumerMessage = NULL;
-	bool leftMessageFlipRequested = false;
-
-	int rightModuleId = -1;
-	Module *rightModule = NULL;
-	void *rightProducerMessage = NULL;
-	void *rightConsumerMessage = NULL;
-	bool rightMessageFlipRequested = true;
+	/** Represents a message-passing channel for an adjacent module. */
+	struct Expander {
+		/** ID of the expander module, or -1 if nonexistent. */
+		int moduleId = -1;
+		/** Pointer to the expander Module, or NULL if nonexistent. */
+		Module *module = NULL;
+		/** Double buffer for receiving messages from the expander module.
+		If you intend to receive messages from an expander, allocate both message buffers with identical blocks of memory (arrays, structs, etc).
+		Remember to free the buffer in the Module destructor.
+		Example:
+
+			rightExpander.producerMessage = new MyExpanderMessage;
+			rightExpander.consumerMessage = new MyExpanderMessage;
+
+		You must check the expander module's `model` before attempting to write its message buffer.
+		Once the module is checked, you can reinterpret_cast its producerMessage at no performance cost.
+
+		Producer messages are intended to be write-only.
+		Consumer messages are intended to be read-only.
+
+		Once you write a message, set messageFlipRequested to true to request that the messages are flipped at the end of the timestep.
+		This means that message-passing has 1-sample latency.
+
+		You may choose for your Module to instead write to its own message buffer for consumption by other modules, i.e. the expander "pulls" rather than this module "pushing".
+		As long as this convention is followed by the other module, this is fine.
+		*/
+		void *producerMessage = NULL;
+		void *consumerMessage = NULL;
+		bool messageFlipRequested = false;
+	};
+
+	Expander leftExpander;
+	Expander rightExpander;
 
 	/** Seconds spent in the process() method, with exponential smoothing.
 	Only written when CPU timing is enabled, since time measurement is expensive.

src/app/RackWidget.cpp

@@ -352,8 +352,8 @@ static void RackWidget_updateAdjacent(RackWidget *that) {
 		}
 
 		ModuleWidget *mw = dynamic_cast<ModuleWidget*>(w);
-		mw->module->rightModuleId = mwRight ? mwRight->module->id : -1;
-		mw->module->leftModuleId = mwLeft ? mwLeft->module->id : -1;
+		mw->module->leftExpander.moduleId = mwLeft ? mwLeft->module->id : -1;
+		mw->module->rightExpander.moduleId = mwRight ? mwRight->module->id : -1;
 	}
 }
 

src/engine/Engine.cpp

@@ -305,39 +305,26 @@ static void Engine_step(Engine *that) {
 
 	// Flip messages for each module
 	for (Module *module : that->internal->modules) {
-		if (module->leftMessageFlipRequested) {
-			std::swap(module->leftProducerMessage, module->leftConsumerMessage);
-			module->leftMessageFlipRequested = false;
+		if (module->leftExpander.messageFlipRequested) {
+			std::swap(module->leftExpander.producerMessage, module->leftExpander.consumerMessage);
+			module->leftExpander.messageFlipRequested = false;
 		}
-		if (module->rightMessageFlipRequested) {
-			std::swap(module->rightProducerMessage, module->rightConsumerMessage);
-			module->rightMessageFlipRequested = false;
+		if (module->rightExpander.messageFlipRequested) {
+			std::swap(module->rightExpander.producerMessage, module->rightExpander.consumerMessage);
+			module->rightExpander.messageFlipRequested = false;
 		}
 	}
 }
 
-static void Engine_updateAdjacent(Engine *that, Module *m) {
-	// Sync leftModule
-	if (m->leftModuleId >= 0) {
-		if (!m->leftModule || m->leftModule->id != m->leftModuleId) {
-			m->leftModule = that->getModule(m->leftModuleId);
+static void Engine_updateExpander(Engine *that, Module::Expander *expander) {
+	if (expander->moduleId >= 0) {
+		if (!expander->module || expander->module->id != expander->moduleId) {
+			expander->module = that->getModule(expander->moduleId);
 		}
 	}
 	else {
-		if (m->leftModule) {
-			m->leftModule = NULL;
-		}
-	}
-
-	// Sync rightModule
-	if (m->rightModuleId >= 0) {
-		if (!m->rightModule || m->rightModule->id != m->rightModuleId) {
-			m->rightModule = that->getModule(m->rightModuleId);
-		}
-	}
-	else {
-		if (m->rightModule) {
-			m->rightModule = NULL;
+		if (expander->module) {
+			expander->module = NULL;
 		}
 	}
 }
@@ -411,8 +398,10 @@ static void Engine_run(Engine *that) {
 		if (!internal->paused) {
 			std::lock_guard<std::recursive_mutex> lock(internal->mutex);
 
+			// Update expander pointers
 			for (Module *module : internal->modules) {
-				Engine_updateAdjacent(that, module);
+				Engine_updateExpander(that, &module->leftExpander);
+				Engine_updateExpander(that, &module->rightExpander);
 			}
 
 			// Step modules
@@ -532,15 +521,15 @@ void Engine::removeModule(Module *module) {
 		if (paramHandle->moduleId == module->id)
 			paramHandle->module = NULL;
 	}
-	// Update adjacent modules
+	// Update expander pointers
 	for (Module *m : internal->modules) {
-		if (m->leftModule == module) {
-			m->leftModuleId = -1;
-			m->leftModule = NULL;
+		if (m->leftExpander.module == module) {
+			m->leftExpander.moduleId = -1;
+			m->leftExpander.module = NULL;
 		}
-		if (m->rightModule == module) {
-			m->rightModuleId = -1;
-			m->rightModule = NULL;
+		if (m->rightExpander.module == module) {
+			m->rightExpander.moduleId = -1;
+			m->rightExpander.module = NULL;
 		}
 	}
 	// Trigger Remove event

src/engine/Module.cpp

@@ -61,12 +61,12 @@ json_t *Module::toJson() {
 	}
 
 	// leftModuleId
-	if (leftModuleId >= 0)
-		json_object_set_new(rootJ, "leftModuleId", json_integer(leftModuleId));
+	if (leftExpander.moduleId >= 0)
+		json_object_set_new(rootJ, "leftModuleId", json_integer(leftExpander.moduleId));
 
 	// rightModuleId
-	if (rightModuleId >= 0)
-		json_object_set_new(rootJ, "rightModuleId", json_integer(rightModuleId));
+	if (rightExpander.moduleId >= 0)
+		json_object_set_new(rootJ, "rightModuleId", json_integer(rightExpander.moduleId));
 
 	return rootJ;
 }
@@ -115,12 +115,12 @@ void Module::fromJson(json_t *rootJ) {
 	// leftModuleId
 	json_t *leftModuleIdJ = json_object_get(rootJ, "leftModuleId");
 	if (leftModuleIdJ)
-		leftModuleId = json_integer_value(leftModuleIdJ);
+		leftExpander.moduleId = json_integer_value(leftModuleIdJ);
 
 	// rightModuleId
 	json_t *rightModuleIdJ = json_object_get(rootJ, "rightModuleId");
 	if (rightModuleIdJ)
-		rightModuleId = json_integer_value(rightModuleIdJ);
+		rightExpander.moduleId = json_integer_value(rightModuleIdJ);
 }