Re: Thread and Timer

"AliR \(VC++ MVP\)" <AliR@online.nospam>
Thu, 13 Mar 2008 14:44:56 -0500
I'm not talking about callbacks. I'm talking about using

I guess I will let the code explain it.

class CMyThread : public CWinThread

 CMyThread(); // protected constructor used by dynamic creation
 virtual ~CMyThread();

 virtual BOOL InitInstance();
 virtual int ExitInstance();

   afx_msg void OnTimer(WPARAM,LPARAM);

   UINT m_TimerID;




BOOL CMyThread::InitInstance()
   m_TimerID = SetTimer(NULL,0,5000,NULL);
   return TRUE;

int CMyThread::ExitInstance()
 // TODO: perform any per-thread cleanup here
 return CWinThread::ExitInstance();


// CMyThread message handlers

void CMyThread::OnTimer(WPARAM nTimerID,LPARAM)
   if (nTimerID == m_TimerID)


"Joseph M. Newcomer" <> wrote in message

To get WM_TIMER messages, yes. This trick is actually pretty common; for
CAsyncSocket creates a dummy window to handle callback notifications,
which are sent as
window messages; SAPI creates a dummy window to handle Text-to-Speech
notifications; and I
knew about the trick years ago. Any generic derived-direct-from-CWnd
class will do

Timer callbacks will work without a window, but overall they suck badly,
because there is
no user-specified data object passed in (as I explain to my students, the
function has four parameters, three of which are totally useless and one
of which is never
used anyway, so why do we have four useless parameters? Bad design. You
can't really
make a thread-safe callback without a lot of effort; __declspec(thread)
helps, or direct
use of Thread Local Storage.

My "timer-in-a-CDocument" essay shows how this can be done in a way that
lets a CDocument
maintain an internal timer which has nothing to do with a view, which is
useful if the
"document" is virtual and is implemented at the other end of a
communication wire (RS232,
RS485, USB, etc.) and the timeouts deal with the document's communication
with its virtual
implementation and should not be visible to the views.

On Thu, 13 Mar 2008 14:18:09 GMT, "AliR \(VC++ MVP\)" <AliR@online.nospam>

Joe you must be kidding, he needs a window in his UI thread just use

::SetTimer works just fine in CWinThread. All you have to do is set a
ON_THREAD_MESSAGE(WM_TIMER,OnTimer) in your message map.


"Joseph M. Newcomer" <> wrote in message

Is it a UI thread? Is the timer associated with a window in the UI
thread? (You may have
to create an invisible top-level window to get this to work...)

On Thu, 13 Mar 2008 02:42:20 -0700 (PDT), Stefano <>

On 12 Mar, 16:39, Joseph M. Newcomer <> wrote:

Why not do something very simple: ON_WM_TIMER()?

I tryed with ON_WM_TIMER but it's never called.

You do not need a g_iTmer, g_hWnd, or g_iMessage here, if this were a
handler for
WM_TIMER. Get rid of them. I can't even imagine why they are needed at
all, since they
coudl be member variables of the CWatchDog class.

Yes you are right. I copyed and paste the code from the the callback.

Joseph M. Newcomer [MVP]
MVP Tips:

Joseph M. Newcomer [MVP]
MVP Tips:

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