Thread: Need help developing an application

There is one problem, I have here. If I replace 1000 by INFINITE in WaitForSingleObject() like this --> WaitForSingleObject( pStreamReadTask->m_hThread, INFINITE ); the application stops there.

The wait is there to prevent the application thread exiting while the worker thread still exists. If the wait times out, maybe your worker thread never exits from its callback function. You need someway to signal the worker thread to exit. For instance, I have

Code:

volatile bool ReadWorker::stop_ = true;     // static variable in ReadWorker

// Creates a thread using the run method as a callback.
// Runs in the callee's thread.  
CWinThread* ReadWorker::startThread()
{
    stop_ = false;
    CWinThread* thread = AfxBeginThread(run, 0, THREAD_PRIORITY_NORMAL,
        0, CREATE_SUSPENDED);

    thread->m_bAutoDelete = false;

    thread->ResumeThread();

    return thread;
}


// Causes the thread to eventually exit
void ReadWorker::stop()
{
    stop_ = true;
}

And then in the thread's callback, the thread looks every so often at the stop_ variable. The thread's callback will eventually read changed value of stop_ and therefore exit its execution loop. When this happens, thread exit event is signaled.

(Note: Microsoft doesn't recommend WaitForSignleObject INFINITE here: "A thread that uses a wait function with no time-out interval may cause the system to become deadlocked. Two examples of code that indirectly creates windows are DDE and COM CoInitialize. Therefore, if you have a thread that creates windows, use MsgWaitForMultipleObjects or MsgWaitForMultipleObjectsEx, rather than WaitForSingleObject." But I think the problem is more likely that the worker thread never exits its callback. I suspect the problems with WaitForSignelObject creating deadlocks either only occur at specific periods of time or occurs with a different processor arrangement. I haven't been able to get my test program to deadlock.)

When I take out sleep(), the cpu usage reaches 100% and can't cancel the process.

I don't think that should occur. The worker thread is mainly doing fileio and won't be doing any extensive computation.

The code itself is kind of ugly with no error checking or exception handling. But if you want, PM me your email address and I'll send an email to you with the test program attached. The test program has a modal progress dialog, but uses a CEdit instead of a CProgressCtrl, and the files themselves are text files so it reads line by line and updates the dialog and view each time a line is read.

Originally Posted by okinrus

The wait is there to prevent the application thread exiting while the worker thread still exists. If the wait times out, maybe your worker thread never exits from its callback function. You need someway to signal the worker thread to exit.

I made a silly mistake. I didnt try to finish to the thread. With the following code, it works. Sorry for wasting your time.

Code:

	TerminateThread( pStreamReadTask->m_hThread, NULL );
	WaitForSingleObject( pStreamReadTask->m_hThread, INFINITE );
	delete pStreamReadTask;
	pStreamReadTask = NULL;

I don't think that should occur. The worker thread is mainly doing fileio and won't be doing any extensive computation.

The code itself is kind of ugly with no error checking or exception handling. But if you want, PM me your email address and I'll send an email to you with the test program attached. The test program has a modal progress dialog, but uses a CEdit instead of a CProgressCtrl, and the files themselves are text files so it reads line by line and updates the dialog and view each time a line is read.

Then, I am probably doing something wrong. Without the sleep() function, the user thread doesnt seem to be working.
I will p.m you to give you my email addy. I really appreciate what you are doing for me.

Originally Posted by novacain

>>I am having a compile error here m_ProgressBarDlg.Create(IDD_PROGRESSBAR_DLG,this);

Looks like you are just trying to create a progressbar control.

In the resource editor create a dialog with your progressbar on it. Derive a class from the dialog (CDialog).

Thank you. I will try to do it. I was stuck there.

Originally Posted by novacain

>>I am having a compile error here m_ProgressBarDlg.Create(IDD_PROGRESSBAR_DLG,this);

Looks like you are just trying to create a progressbar control.

In the resource editor create a dialog with your progressbar on it. Derive a class from the dialog (CDialog).

I have tried to follow your instructions, but I still have the same problem:

1. I created a dialog( enum { IDD = IDD_PROGRESS_BAR }; )
2. I put a progress bar on it
3. I created a class like this:

Code:

class CProgressBar : public CDialog
{
public:
...
	enum { IDD = IDD_PROGRESS_BAR };
	CProgressCtrl	m_ProgressBar;
.....
private:
};

4. I created a function to show the Dialog

Code:

BOOL CProgressBar::showPgrBarDlg( void )
{
	//check to see if the Progressbar Dlg has already been created
	if( m_ProgressBar.GetSafeHwnd())
		m_ProgressBar.ShowWindow(SW_SHOW);
	else
		m_ProgressBar.Create( IDD_PROGRESS_BAR, this );  
	//make sure visible
	m_ProgressBar.ShowWindow(SW_SHOW);
}

Unfortunately, the same compile error keeps coming out.
Any idea what may be the causes?
Thanks in advance.
Afrinux

Hi novacain! Thanks for your help. Now it works.

Code:

BOOL CDVDVideoSolutionDlg::showPrgBarDlg( void )
{
	clPrgBar = new CProgressBar();
	if( clPrgBar->GetSafeHwnd())
		clPrgBar->ShowWindow(SW_SHOW);
	else
		clPrgBar->Create( IDD_PROGRESS_BAR, this );  

 #if 1// center the dialog box
	CRect rectMain;
	GetClientRect(&rectMain);
	int xMain = rectMain.Width();
	int yMain = rectMain.Height();
    // Get dimensions of the dialog
	CRect rectView;
	clPrgBar->GetWindowRect(&rectView);
	int xView = rectView.Width();
	int yView = rectView.Height();
	// Calculate the (x,y) coordinate for Progress bar dialog.
	int x = (xMain - xView) / 2;
	int y = (yMain - yView) / 2;

	// Move the dialog.
	clPrgBar->MoveWindow(x, y, xView, yView, TRUE);
#endif

	//make sure visible
	clPrgBar->ShowWindow(SW_SHOW);
	
	return TRUE;
}

Now, I have only 2 problems:
1. Center the Progress bar dialog; the code above was supposed to do it, somehow the dialog is not centered.

2. Get the sleep() function off the code

>>CProgressBar
not the best name as it might confilct with a named class.

Thank you for the warning, I will take it into consideration from now on.
Afrinux

Originally Posted by novacain

Try adding the style, DS_CENTER to the progressbar dialog.

I got it working with this:
clPrgBar->CenterWindow( this );
Thanks. By the way, are a Man Utd fan?

Originally Posted by novacain

>>By the way, are a Man Utd fan?

No but got to admire a man who knows what is important in this life.

I second that. Thanks again for every thing.