MFC do while loop - c++

Question

I am doing a measurement system and I have got a do while loop in my program. In the loop, it is checking if any motor is moving before it could take measurement as it require it to reach the target position before doing anything.
While doing the measurement, it is suppose to tell me how long does it took to do this measurement.
However, whenever it runs in the do while loop, all my timer function stop as if they are put to Sleep mode.
Is there any other method where I could implement this? If there is, please help me.
Any help would be much appreciated.
SetTimer(TIMERECHO, 1000, NULL);
BOOL bMoving = FALSE;
do
{
if (IsMoving(ID, NULL, &bMoving))
GetPosition();
} while (bMoving);
void CLHMDlg::OnTimer(UINT_PTR nIDEvent)
{
// TODO: Add your message handler code here and/or call default
switch(nIDEvent)
{
case TIMERECHO:
UpdateData(FALSE);
m_Seconds++;
m_TimerEcho.Format(_T("Total time: %ds"), m_Seconds);
break;
}
CDialogEx::OnTimer(nIDEvent);
}

Answer 1

MFC has a message loop that gets and dispatches messages such as WM_TIMER. If you do a while loop that message loop is not running. It's not sleeping, it's just waiting until you stop hogging the processor.
You have two options: (1) Get rid of the lengthy loop and do whatever it does periodically on a WM_TIMER message. (2) Use a second thread to do the lengthy operation. This has numerous difficulties for a beginner.

Answer 2

It's because your loop isn't processing messages. onTimer is called as a result of a windows message. You need to keep processing messages in the loop or use a callback based timer.
One method is using CreateTimerQueueTimer
http://msdn.microsoft.com/en-us/library/windows/desktop/ms682485%28v=vs.85%29.aspx

Answer 3

A very simple solution (but not perfect) to get you running is to move your IsMoving to the timer as below:
void CLHMDlg::OnTimer(UINT_PTR nIDEvent)
{
// TODO: Add your message handler code here and/or call default
switch(nIDEvent)
{
case TIMERECHO:
if (IsMoving(ID, NULL, &bMoving))
GetPosition();
UpdateData(FALSE);
m_Seconds++;
m_TimerEcho.Format(_T("Total time: %ds"), m_Seconds);
break;
}
CDialogEx::OnTimer(nIDEvent);
}
However for a proper solution you have to use threads for this, the complexity of that will vary for simple to better solutions there as well. I have written some code on the fly for you, it may not compile but you get the idea.
AfxBeginThread(monitor_motor, this);
UINT monitor_motor(LPVOId lParam)
{
CMyDlg * dlg = (CMyDlg *) lParam;
HWND hWnd = (HWND) dlg->m_hWnd;
do
{
if (IsMoving(ID, NULL, &dlg->bMoving))
GetPosition();
Sleep(100); // maybe you don't have to poll too hard and give other hardware chance to communicate?..that's upto you
PostMessage( hWnd, UPDATE_TIMER_AND_STUFF );
} while (dlg->bMoving);
PostMessage( hWnd, UPDATE_MOTOR_MOVED_COMPLETELY );
}