Global key listener (Windows)

main.cpp

#include <thread>
#include <atomic>
#include <functional>
#include <windows.h>

static thread_local const std::function<void(WPARAM,DWORD)>* LLKP_data;
static LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam){
	if(nCode == HC_ACTION)
		(*LLKP_data)(wParam, reinterpret_cast<PKBDLLHOOKSTRUCT>(lParam)->vkCode);
	return CallNextHookEx(NULL, nCode, wParam, lParam);
}

class GlobalKeyListener : protected std::thread{
	private:
		std::atomic_bool stop = ATOMIC_VAR_INIT(false);
	public:
		GlobalKeyListener(const std::function<void(WPARAM,DWORD)> receiver) : std::thread([this,receiver](){
				const HHOOK hook = SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc, NULL, 0);
				if(hook){
					LLKP_data = &receiver;
					MSG msg;
					while(!this->stop){
						const auto timer_id = SetTimer(NULL, 0, 200, NULL);
						GetMessage(&msg, NULL, 0, 0);
						KillTimer(NULL, timer_id);
						if(msg.message != WM_TIMER){
							TranslateMessage(&msg);
							DispatchMessageW(&msg);
						}
					}
					UnhookWindowsHookEx(hook);
				}else
					this->stop = true;
		}){}
		
		bool Running() const{
			return !this->stop;
		}
		
		~GlobalKeyListener(){
			this->stop = true;
			this->join();
		}
};

#include <iostream>

int main(){
	GlobalKeyListener gkl([](WPARAM wParam, DWORD vkCode){
		std::cout << '\n' << wParam << ' ' << vkCode << std::endl;
	});
	std::cin.get();
	return 0;
}