Fix mistakes in assignment of adjacent module IDs. Swap message buffers at the end of each Engine step.

src/app/RackWidget.cpp

@@ -329,19 +329,19 @@ static void RackWidget_updateAdjacent(RackWidget *that) {
 
 			if (m == m2)
 				continue;
-			math::Vec p2 = m->box.pos.div(RACK_GRID_SIZE).round();
+			math::Vec p2 = m2->box.pos.div(RACK_GRID_SIZE).round();
 
-			// Check if m is to the right of m2
+			// Check if m is to the left of m2
 			if (pRight.isEqual(p2)) {
-				m->module->leftModuleId = m2->module->id;
-				m2->module->rightModuleId = m->module->id;
+				m->module->rightModuleId = m2->module->id;
+				m2->module->leftModuleId = m->module->id;
 				found = true;
 				break;
 			}
 		}
 
 		if (!found) {
-			m->module->leftModuleId = -1;
+			m->module->rightModuleId = -1;
 		}
 	}
 }

src/engine/Engine.cpp

@@ -267,6 +267,11 @@ static void Engine_step(Engine *that) {
 	for (Cable *cable : that->internal->cables) {
 		cable->step();
 	}
+	// Swap messages of all modules
+	for (Module *module : that->internal->modules) {
+		std::swap(module->leftProducerMessage, module->leftConsumerMessage);
+		std::swap(module->rightProducerMessage, module->rightConsumerMessage);
+	}
 }
 
 static void Engine_updateAdjacent(Engine *that, Module *m) {