HotkeyEngine.cpp

#include "HotkeyEngine.h"
#include <ntstatus.h>

#define OBJECT_WAIT_TIMEOUT	5000	//5 secs

std::unique_ptr<HotkeyEngine> HotkeyEngine::instance;
LPARAM HotkeyEngine::event_param=0;
HotkeyEngine::KeyPressFn HotkeyEngine::OnKeyPress=NULL;

//When exiting or terminating thread we should set exit code
//Here it is just formality because hook's thread exit code is never queried and not passed outside of class
//For the sake of completeness, possible exit codes:
//	0 - indicates that thread exited normally
//	1 - indicates that thread exited due to error
//	2 - indicates that thread was forcefully terminated because it failed to respond in specified time

HotkeyEngine* HotkeyEngine::MakeInstance()
{
	instance.reset(new HotkeyEngine());
	return instance.get();
}

HotkeyEngine::HotkeyEngine():
	running(false), hook_thread_handle(NULL), hook_thread_id(0), stack_commit(0)
{}

HotkeyEngine::~HotkeyEngine() 
{
	Stop();
}

bool HotkeyEngine::IsRunning()
{
	return running;
}

bool HotkeyEngine::Stop()
{
	if (!running)
		return false;
	
	if (!PostThreadMessage(hook_thread_id, WM_QUIT, 0, 0)||									//Post WM_QUIT to hook thread to exit it
		WaitForSingleObject(hook_thread_handle, OBJECT_WAIT_TIMEOUT)!=WAIT_OBJECT_0)		//Wait for thread to exit
			TerminateThread(hook_thread_handle, 2);											//Or terminate it in case of error or timeout (exit code = 2)
	CloseHandle(hook_thread_handle);
	
	running=false;
	return true;
}

bool HotkeyEngine::Start()
{
	if (!running&&OnKeyPress) {
		HANDLE success_or_exited[2];	//Array for two events
												
		if ((success_or_exited[0]=CreateEvent(NULL, TRUE, FALSE, NULL))) {		//Success event
			if ((success_or_exited[1]=hook_thread_handle=CreateThread(NULL, stack_commit, ThreadProc, (LPVOID)success_or_exited[0], CREATE_SUSPENDED, &hook_thread_id))) {
				SetThreadPriority(hook_thread_handle, THREAD_PRIORITY_TIME_CRITICAL);	//Set higher priority for hook thread
				ResumeThread(hook_thread_handle);
				switch (WaitForMultipleObjects(2, success_or_exited, FALSE, OBJECT_WAIT_TIMEOUT)) {
					case WAIT_OBJECT_0:		//Success event signalled
						CloseHandle(success_or_exited[0]);
						running=true;
						return true;
					case WAIT_OBJECT_0+1:	//Thread exited
						break;
					default:				//Error or timeout happened - terminate thread (exit code = 2)
						TerminateThread(hook_thread_handle, 2);
						break;
				} 
				CloseHandle(hook_thread_handle);
			}
			CloseHandle(success_or_exited[0]);
		}
	}
	
	return false;
}

bool HotkeyEngine::Set(LPARAM event_param, KeyPressFn OnKeyPress, size_t stack_commit)
{
	if (!running) {
		HotkeyEngine::OnKeyPress=OnKeyPress;
		this->event_param=event_param;
		this->stack_commit=stack_commit;
		return true;
	} else
		return false;
}

bool HotkeyEngine::StartNew(LPARAM event_param, KeyPressFn OnKeyPress, size_t stack_commit)
{
	if (!running) {
		HotkeyEngine::OnKeyPress=OnKeyPress;
		this->event_param=event_param;
		this->stack_commit=stack_commit;
		return Start();
	} else
		return false;
}

DWORD WINAPI HotkeyEngine::ThreadProc(LPVOID lpParameter)
{
	HHOOK kb_hook;

	if ((kb_hook=SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc, GetModuleHandle(NULL), 0))) {
		SetEvent((HANDLE)lpParameter);	//Signal success event and continue
	} else {
		return 1;	//Exit (exit code = 1)
	}
	
	//For hook to work thread should have message loop, though it can be pretty castrated
	//Only GetMessage is needed because hook callback is actually called inside this one function
	MSG msg;
	while (GetMessage(&msg, NULL, 0, 0)); //GetMessage returns 0 if WM_QUIT, and we are ignoring -1 (error) so not have to check if hook thread has killed itself
	
	//WM_QUIT happened - unhook and exit thread (exit code = 0)
	UnhookWindowsHookEx(kb_hook);
	return 0;
}

LRESULT CALLBACK HotkeyEngine::LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)
{
	//HOOKPROC requires that on less-than-zero nCode CallNextHookEx should be returned immediately
	//We should return non-zero value if event shouldn't be passed further down the keyboard handlers chain (OnKeyPress returned TRUE)
	if (nCode>=0&&OnKeyPress(event_param, wParam, (KBDLLHOOKSTRUCT*)lParam))
		return 1;
	
	//Let CallNextHookEx handle everything else
	return CallNextHookEx(NULL, nCode, wParam, lParam);
}