Could EventQueue.add_listener be called in a thread other than the event processing thread? about eventpp

[wqking]

The code is fine. Please show full code that includes the enque and start the thread.

[RWBYBING]

I am developing a desktop application with a GUI, and I plan to use eventpp as the communication method between the various modules of the software.

First of all, I encapsulate the eventpp part into a class called EventManager. There is a StartEventLoop function which starts the thread. Here is the full code of the class:

## "EventManager.h"

#pragma once

#include <iostream>
#include <mutex>
#include <Utils/EventManager/EventType.h>
#include <eventpp/eventdispatcher.h>
#include <eventpp/eventqueue.h>

class EventManager
{
public:
	// 获取单例实例
	static std::shared_ptr<EventManager> getInstance();
	// 销毁实例
	static void destroyInstance(EventManager* x);

private:
	static std::shared_ptr<EventManager> _instance;
	static std::mutex _mutex;
	EventManager();
	~EventManager();
	EventManager(const EventManager&) = delete;
	void operator=(const EventManager&) = delete;

public:
	// 事件发布
	void EventPublish(EventType type, const std::shared_ptr<Event> event);
	// 事件订阅
	void EventSubscribe(EventType type, std::function<void(const std::shared_ptr<Event>)> listener);
	// 开启事件监听循环
	void StartEventLoop();

private:
	// 异步事件队列
	std::unique_ptr<eventpp::EventQueue<EventType, void(const std::shared_ptr<Event>&), EventPolicies>> eventQueue;
};

## "EventManager.cpp"
#include <Utils/EventManager/EventManager.h>

std::shared_ptr<EventManager> EventManager::_instance;
std::mutex EventManager::_mutex;

EventManager::EventManager()
	: eventQueue(std::make_unique<eventpp::EventQueue<EventType, void(const std::shared_ptr<Event>&), EventPolicies>>())
{

}

void EventManager::StartEventLoop()
{
    try {
        std::thread thread([this]() {
            volatile bool _eventqueue_should_stop = false;
            std::cout << "Event Listening Thread Started" << std::endl;

            // 监听关闭事件系统的事件
            this->EventSubscribe(EventType::E_STOP_EVENT_QUEUE, [&_eventqueue_should_stop](std::shared_ptr<Event>) {
            	_eventqueue_should_stop = true;
            });

            while (!_eventqueue_should_stop)
            {
            	eventQueue->wait();
            	eventQueue->process();
            }

            std::cout << "Evnt Listening Thread Stopped" << std::endl;
        });
        thread.detach();
    }
    catch (const std::exception& e) {
        // 捕获异常
        std::cerr << "Caught exception in StartEventLoop(): " << e.what() << std::endl;
    }
}

EventManager::~EventManager()
{
	// TODO: 发布STOP_EVENT
}

std::shared_ptr<EventManager> EventManager::getInstance()
{
	// 若为空则创建
	if (_instance == nullptr)
	{
		// 加锁保证线程安全
		std::lock_guard<std::mutex> l(_mutex);
		if (_instance == nullptr)
		{
			_instance.reset(new EventManager(), destroyInstance);
		}
	}
	return _instance;
}

void EventManager::destroyInstance(EventManager* x)
{
	delete x;
}

void EventManager::EventPublish(EventType type, const std::shared_ptr<Event> event)
{
	eventQueue->enqueue(event);
}

void EventManager::EventSubscribe(EventType type, std::function<void(const std::shared_ptr<Event>)> listener)
{
	eventQueue->appendListener(type, listener);
}

Afterwards, in the GUI thread(which is also the main thread), I enqueued the event:

	// 搜索雷达按钮
	ImGui::SetCursorPosX((windowWidth - closeButtonWidth) * 0.3333f);
	ImGui::SetCursorPosY((windowHeight * 0.9f));
	if (ImGui::Button("搜索雷达", ImVec2(120, 0)))
	{
		// 发布搜索雷达事件
		EventManager::getInstance()->EventPublish(EventType::E_GUI_LIDAR_BROADCAST, std::make_shared<E_GUI_LIDAR_BROADCAST>());
	}

	ImGui::SetCursorPosX((windowWidth - closeButtonWidth) * 0.6666f);
	ImGui::SetCursorPosY((windowHeight * 0.9f));
	if (ImGui::Button("关闭", ImVec2(120, 0))) { ImGui::CloseCurrentPopup(); }

I added the listener in the main thread as well, which is in a constructor of another class.

GUITest::GUITest()
{
	std::shared_ptr<EventManager> eventManager = EventManager::getInstance();
	// 订阅雷达广播事件事件
	eventManager->EventSubscribe(EventType::E_GUI_LIDAR_BROADCAST, 
		std::bind(&GUITest::LidarBroadcastTest, this, std::placeholders::_1));
}

I've tried to add listener in the event processing thread and everything works well.

[RWBYBING]

I figured it out, it just a little typo in other part of my code. Really sorry for wasting your time!!!

And really appreciate your work!