Re: CEvent & WaitForSingleObject (auto-reset)

=?Utf-8?B?SmltYm9fSmltYm9iX0ppbWluYXRvcg==?= <>
Thu, 2 Jul 2009 08:09:01 -0700
Thanks Joe,

I wouldn't trust an MFC synchronization primitive as far as I
could throw a 1960s mainframe.

That's rich! ;-)
I'm going to assume that you're not a recent gym rat convert benching 350
lbs. Therefore, I should see the MFC sync thing as BAAAADDDDD.

I did get it working by using the handle as Alexander suggested. An
oversight on my part even after looking at it 100 times. I will look into
using ATL or Win32 instead.

It does amaze me though that a library that was a cornerstone in Windows
development can have so many flaws, in such an important concept, that
everyone with experience knows to avoid it.


"Joseph M. Newcomer" wrote:

I wouldn't trust an MFC synchronization primitive as far as I could throw a 1960s

You are correct in your perception of what should happen. Have you considered trying it
with a simple Event object (HANDLE h = ::CreateEvent(NULL, FALSE, FALSE, NULL)?

I would consider a semaphore a better choice. Each click increments it, each iteration
decrements it.

On Thu, 2 Jul 2009 06:16:02 -0700, Jimbo_Jimbob_Jiminator
<> wrote:

Haven't been here in a while. Haven't been doing any Windows programming for
some time.

I have an issue with CEvent & WaitForSingleObject. The likely issue is that
I have no idea what I'm doing but, if we put that aside and pretend that I
have a clue, it goes like this:

The default implementation for CEvent is auto-reset. That is how I want to
use it. I have only a main tread and a second thread so I do not have several
threads waiting.

I have looked in books and all over the web and all of the examples seem to
show how to start a thread or stop a thread with an event. In this case,
auto-reset is not that useful if you only have one worker thread anyway.

I am trying to control when a loop runs with the event. The issue is that
once the user clicks the button to allow the progress bar to be updated once,
it just keeps updating through completion. I figure that the state of the
CEvent should auto-reset and it should not run another iteration until the
user intiates it.


Here are some code snips that show it:

//This is primarily from an example I found on the web. I added the
//WaitForSingleObject as a test case.
UINT TestThread(LPVOID lParam)
    AfxMessageBox("Bite Me");

    for(int i=0;i<100;i++)
        ::WaitForSingleObject(pTis->pEvent, INFINITE) == WAIT_OBJECT_0;
        //This sends a message to the main thread to update the status bar
    delete pTis;
    return 0;

void CPPage1::OnBnClickedButton1()
    //Testing Wait Single Object. Sends message to main dlg that user clicked
    //the button
    LRESULT Rslt = ::SendMessage(m_pMainWnd->m_hWnd , UWM_TEST_WSO, 0, 0);

    //User clicked the button set event to allow progress bar another tick.
    return 0;

Joseph M. Newcomer [MVP]
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