Dialog::OnTimer is not getting called

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Hi,
I am streaming from a camera and at the same time I am trying to display the seconds on a static box.On a button click event, while(EventMsg.message != WM_QUIT) I am streaming and displaying the images from the camera.Now to display the seconds I am using MFC timers and when WM_TIMER is notified to window on each 1000ms my CStreamDlg::OnTimer(UINT nIDEvent) function is supposed to be called which is not happening.
My CStreamDlg::OnTimer(UINT nIDEvent) function looks like the following:

void CStreamDlg::OnTimer(UINT nIDEvent) {
    char msg[10];
    if(nIDEvent == ID_TIMER_SECOND){
        iSeconds+=1;
        sprintf_s(msg,10,"%d",iSeconds);
        ((CStatic*)GetDlgItem(IDC_STATIC_SECS))->SetWindowTextA(msg);
    }
}

Thanks in advance

Posted 28-Jun-11 20:40pm

hakz.code

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harish85 29-Jun-11 3:11am

does it get called once?
Can you put info on your settimer ,I dont see you calling Ontimer again..

Sergey Alexandrovich Kryukov 29-Jun-11 3:27am

Oh, timers... who needs them? Use threads.
--SA

Joan M 29-Jun-11 3:43am

Which advantages would have using threads to get a timer behavior? (being curious here)

Sergey Alexandrovich Kryukov 29-Jun-11 4:57am

Oh, I can explain... timers cause much more trouble. Imagine what happens if a timer callback code is not finished when a new timers event comes. Imagine this timing (execution time of the callback code) is probabilistic (in essence, it's always so). This is OK of course, but the logic can rely on the fact it does not happen. Threads a free from this; in worse case it will be delayed a bit, but you can always check real time inside code (if it's needed for animation of physics, for example).
--SA

Joan M 29-Jun-11 5:06am

Yes... sounds correct... I guess everything depends on the work loads and on what does one expect to get from the "timer" itself... anyway I had never thought on using threads and not timers... it is an interesting approach... I'll take a deeper look at it whenever I need another timer somewhere... ^^

hakz.code 29-Jun-11 7:33am

Ok I get it,so if a callback is getting executed and at the same time another timer fires the WM_TIMER then the current code execution is halted and may never be continued,but this is not in case of threads.But how to ensure that a thread is executed on mentioned milliSeconds all the time?! do we have to have an infinitive loop inside that thread?
Anyway please correct me if my assumptions are wrong :-)

Joan M 29-Jun-11 8:44am

If my memory doesn't cheat me the way to get a precise timer is using multimedia timers... a normal timer won't ensure you precision... it will be correct in most cases, but not precise. I'll put a couple o links more in my original answer that will help you to understand it a little bit more... ;)

Sergey Alexandrovich Kryukov 29-Jun-11 12:14pm

Please see my comment "Threading timing is probabilistic..." for some explanation.
--SA

Sergey Alexandrovich Kryukov 29-Jun-11 12:13pm

Threading timing is probabilistic. If you say System.Threading.Thread.Sleep it will sleep this time and will be awaken, but could be later. A timer handler will be called in time, but the code can be switched off to some period of time anyway, depending on situation. So, the accuracy of your real response is equally questionable. The problem of guaranteed response can never be solved by definition, because this is not real-time system. However, working in real time in certain sense is quite possible. For example, you animate some physics. The ball should move according to acceleration (gravitational field) and should be in right position at right time. This is quite possible. At the moment of rendering, one needs to use real time (say, from a very accurate Stopwatch) to calculate coordinate, not assuming periodic timing in the thread cycle. More complex thing is rendering video/audio. Each frame is shown at right time, so the rythm is never broken, but some detail is skipped, with some reasonably low probability.
--SA

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Joan M · Accepted Answer · 2011-06-28T21:48:00

At the end of your OnTimer call you should put something like

CDialog::OnTimer(nIDEvent);

And you should configure and start the timer using

m_nTimer = SetTimer (ID_TIMER_SECOND, 1000, 0);

And don't forget to kill the timer at the end...

Killtimer(m_nTimer);

Hope this helps... :thumbsup:

PS: I'm sure that the proposal from SAKryukov will be at least interesting so it would be nice for you to take a look at it... meanwhile, as he is suggesting to use threads to get the same behavior, and I don't know if you are comfortable using them or not or even if you can do it from your requirements, here you have a classic timer approach...

Two links that explain timers in a nice way:

The first one is from Nemanja Trifunovic[^] and is a timers tutorial[^].

The second one is from a commercial company that will try to sell their product[^]... Anyway, you can get some extra information and numbers on the different type of timers out there...