C++实现简化 QtBase（5）：通过IEventLoopHost扩展实现win32消息循环

在上一篇文章《C++实现简化版Qt的QObject（4）：增加简单实用的事件机制》中，我们实现了普通线程的事件机制。
但是事件机制往往需要和操作系统主线程消息循环一起工作。

因此，今天，我们在之前的CEventLoop的实现之上，通过IEventLoopHost扩展，实现一个windows系统的主线程消息循环扩展，使得我们可以在主线程post task。

CEventLoop 代码

首先，昨天我们写的CEventLoop代码如下：

	class CEventLoop {
   
	public:
		using Clock = std::chrono::steady_clock;
		using TimePoint = Clock::time_point;
		using Duration = Clock::duration;
		using Handler = std::function<void()>;
		struct TimedHandler {
   
			TimePoint time;
			Handler handler;
			bool operator<(const TimedHandler& other) const {
   
				return time > other.time;
			}
		};
		class IEventLoopHost {
   
		public:
			virtual void onPostTask() = 0;
			virtual void onWaitForTask(std::condition_variable& cond, std::unique_lock<std::mutex>& locker) = 0;
			virtual void onEvent(TimedHandler& event) = 0;
			virtual void onWaitForRun(std::condition_variable& cond, std::unique_lock<std::mutex>& locker, const TimePoint& timePoint) = 0;
		};
	private:
		IEventLoopHost* host = nullptr;
		std::priority_queue<TimedHandler> tasks_;
		std::mutex mutex_;
		std::condition_variable cond_;
		std::atomic<bool> running_{
    true };

	public:
		void setHost(IEventLoopHost* host) {
   
			this->host = host;
		}
		void post(Handler handler, Duration delay = Duration::zero()) {
   
			std::unique_lock<std::mutex> lock(mutex_);
			tasks_.push({
    Clock::now() + delay, std::move(handler) });
			cond_.notify_one();
			if (host) {
   
				host->onPostTask();
			}
		}

		void run() {
   
			while (running_) {
   
				std::unique_lock<std::mutex>