Question

I am trying to implement winEventFilter in my QT application using QT Creator, QT SDK and Windows APIs

Declared the below in my class file

bool winEventFilter( MSG * msg, long * result )
{
    if( msg->message == WM_QUERYENDSESSION)
        DebugLog("shutdown");
    else
        DebugLog("Quit") ;    
}

I am calling the above method in the following way

MSG * msg;
long * result;

winEventFilter(msg, result);

When I logoff or shutting down my computer it never prints the log shutdown

Answer 1

The condition msg->message == WM_QUERYENDSESSION will never be true, since you’re calling the function with an unitialized pointer (MSG * msg).

You need to pass a meaningful msg.

However, this is not how you want to implement winEventFilter.

winEventFilter is a method of QCoreApplication that you should use by reimplementing it in your QCoreApplication subclass. Then it will be called automatically for you.

See http://qt-project.org/doc/qt-4.8/qcoreapplication.html#winEventFilter for more details.