Re: SetTimer not working

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See below...
On Sat, 9 May 2009 16:34:45 -0400, "Jeova Almeida" <jeovaalmeida@xxxxxxxxx> wrote:

Hello,

I have a welcome dialog which registers my users to a web server just after
the application is installed. This registragion may take from 5 to 30
seconds:

void CWelcomeDlg::OnBnClickedOK()

{

DoLengthyProcessing();

this->EndDialog(1);
****
What does "1" mean? EndDialog usually takes some useful value, like IDOK.
****

}



As I said, the processing takes long to finish, so I wanted to show a
feedback to my users that the program hasn't stopped working. I inserted a
Static control and implemented a simple animation:
*****
If you have a lengthy computation it is generally a Bad Idea to do this processing in the
main GUI thread. Note that OnTimer only happens when the message pump retrieves a
message, so if you are off doing something lengthy, you are not processing messages and
there will be no notification. If you do it in a secondary thread, you can continue to
get all messages and terminate the thread according to one or more of several protocols.

You can assume that a design that does lengthy processing in the main GUI thread should
have its design carefully reconsidered. In your case, it is not a viable solution.
****



void CWelcomeDlg::OnTimer(UINT_PTR nIDEvent)

{

CStatic* pLabel = (CStatic*)GetDlgItem(IDC_LBL_PROCESSING);
****
Why in the world would you use GetDlgItem? We aren't programming 16-bit WIndows and we
aren't programming in the raw API. Create a control variable and bind to that with the
Add Variable option. Using GetDlgItem almost always is a design error.
****

CString strVal;

pLabel->GetWindowText(strVal);

if (strVal == L"/")

pLabel->SetWindowTextW(L"\\");

else if (strVal == L"\\")

pLabel->SetWindowTextW(L"/");
****
Actually, there are horizontal modes. So the correct solution is to have a counter
running modulo 4:

state = (state + 1) % 4;
switch(state)
{
case 0:
strVal = _T("|");
break;
case 1:
strval = _T("/");
break;
case 2:
strval = _T("-");
break;
case 3:
strval = _T("\\");
break;
}
Label.SetWindowText(strVal);

Although I tend to do this using a sequence of 16 icons in a circular format that make a
nicer effect, and I usually display it in a static control. But to do this, you cannot
have the message pump stop. It is just a bad idea to do a lengthy computation in the main
GUI thread.
*****

CDialog::OnTimer(nIDEvent);

}



and changed the previous click event shown before to start the timer:



void CWelcomeDlg::OnBnClickedOK()

{

m_nTimer = SetTimer(1, 1000, NULL);

DoLengthyProcessing();
****
Create a thread:
AfxBeginThread(LengthyProcessing, this);

See my essays on worker threads on my MVP Tips site
****

KillTimer(m_nTimer);

this->EndDialog(1);

}



The problem is the timer isn't working while the lengthy procesing is
running. If I put the SetTimer() and KillTimer() inside the click event of
two command buttons, it works fine.
****
Yes, and that is exactly what is supposed to happen.
****

The processing connects with a Windows Service via named pipe, and the
Windows Service makes the needed registration via web.
****
Then you could use asynchronous I/O on the named pipe and handle the completion in the
thread associated with an I/O Completion Port
****

Why the timer isn't working? How can I do the same if not with timer?
****
It isn't working because as you designed your code, it isn't supposed to work.
****

I tried moving the lengthy processing into a thread and kept the timer in
the main thread, but it not worked as well.
****
Then there is something else wrong. You would have to show the code you used. If, for
example, a WaitForSingleObject appeared that was waiting on the thread handle, you created
a complex way to do a subroutine call in the main thread, and the exact same problem
remains.

Start a thread or an asynchronous I/O operation and return to the main message pump. You
will need to disable certain controls until the thread or I/O operation completes, but
that's trivial stuff. Key is to never, ever try to force an asynchronous thread to
exhibit synchronous behavior.
joe
****

Please help.



Jeova

Joseph M. Newcomer [MVP]
email: newcomer@xxxxxxxxxxxx
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm
.

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