Making mfc call a function continuously until success is returned.

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Hello everyone,

I have created an mfc that is used display info about the attached device.
I want my mfc dialog to wait for the device until it gets attached. For this I have created a function that receives attach callback from the device.
Now what I want is that the mfc should continuously call this attach function(displaying a waiting for device MSG)until a success(or 1) is returned by that.

What i thought is to create an infinite while loop like this

C++

while(1)
{int x;
 x=attach()
 if(x)
 break;
}

attach() returns 1 when device is successfully attached.

I put that in the init function of mfcdlg.cpp just before return true.

But this does not work.Can someone plz provide a solution to the problem...

Posted 20-Sep-12 21:04pm

dkaku

Updated 20-Sep-12 21:21pm

Jochen Arndt

v3

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Richard MacCutchan 21-Sep-12 3:29am

"does not work" is not a useful description of your problem. Please provide some useful detail and diagnostic information.

dkaku 21-Sep-12 3:40am

By this I mean that the application gets hanged up...and no dialog or msg can be seen...

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Jochen Arndt · Accepted Answer · 2012-09-20T21:39:00

Using an infinite (or even time consuming) loop is a bad idea. It will block your application with probably high CPU load. The best solution would be posting a user defined message to the dialog from a thread that waits for the attach event.

A simpler method is using a timer inside your dialog that polls the attach state:

C++

class CMyDialog : public CDialog
{
protected:
    bool m_bAttached;
    UINT m_nTimer;
    void KillTimer();
};

BEGIN_MESSAGE_MAP(CMyDialog, CDialog)
    ON_WM_TIMER()
END_MESSAGE_MAP()

CMyDialog::CMyDialog()
{
    m_bAttached = false;
    m_nTimer = 0;
}

BOOL CMyDialog::OnInitDialog()
{
    CDialog::OnInitDialog();
    // Choose realistic time out value here
    // e.g. something in the range of 100 to 500 ms
    m_nTimer = SetTimer(1, TIME_OUT_VALUE, NULL);
    return TRUE;
}

void CMyDialog::OnTimer(UINT nIDEvent)
{
    if (m_nTimer && attach())
    {
        m_bAttached = true;
        StopTimer();
    }
    CDialog::OnTimer(nIDEvent);
}

// Call this when dialog is closed (OnOK, OnCancel())
void CMyDialog::StopTimer()
{
    if (m_nTimer)
    {
        KillTimer(m_nTimer);
        m_nTimer = 0;
    }
}