[Qt-interest] What is the use of QCoreApplication::processEvents()

[Ankit Agarwal]

Hi,
As far as my knowledge stands,
Qt puts all the events in a Queue and processes it sequentially while user
may keep doing other tasks. This may sound a little odd but things are
processed at a very high speed.
If you call QCoreApplication::processEvents, then the Qt engin shall process
all the pending events in the queue before proceeding.

You may check out the following link for further details:
http://doc.trolltech.com/qq/qq27-responsive-guis.html

On Mon, Apr 6, 2009 at 4:04 PM, shariff <shariff at mic.co.in> wrote:

>  Hi everybody,
>
> Can any one explain me the exact use of
> *void QCoreApplication::processEvents ( **QEventLoop::ProcessEventsFlags**
> flags = QEventLoop::AllEvents )*
> **
> I have gone through the docs.... but I cannot understand the actual use of
> it.
> It was used in "*Find Files*" example in relation with Progress dialog
> updation.
>
> Code:
>
> *QStringList Window::findFiles(const QDir &directory, const QStringList
> &files,
>                                const QString &text)
> {
>      QProgressDialog progressDialog(this);
>      progressDialog.setCancelButtonText(tr("&Cancel"));
>      progressDialog.setRange(0, files.size());
>      progressDialog.setWindowTitle(tr("Find Files"));
>
>      QStringList foundFiles;
>
>      for (int i = 0; i < files.size(); ++i) {
>          progressDialog.setValue(i);
>          progressDialog.setLabelText(tr("Searching file number %1 of
> %2...")
>                                      .arg(i).arg(files.size()));
>          qApp->processEvents();
>
>          if (progressDialog.wasCanceled())
>              break;
>
>          QFile file(directory.absoluteFilePath(files[i]));
>
>          if (file.open(QIODevice::ReadOnly)) {
>              QString line;
>              QTextStream in(&file);
>              while (!in.atEnd()) {
>                  if (progressDialog.wasCanceled())
>                      break;
>                  line = in.readLine();
>                  if (line.contains(text)) {
>                      foundFiles << files[i];
>                      break;
>                  }
>              }
>          }
>      }
>      return foundFiles;
> }
> *
>
> What is the link between QProgress bar dialog updation and
> qApp->processEvents() in the above code? When I commented "*
> qApp->processEvents()*" below lines of code is not being executed.
>
>      *progressDialog.setCancelButtonText(tr("&Cancel"));
>      progressDialog.setRange(0, files.size());
>      progressDialog.setWindowTitle(tr("Find Files"));*
> **
> Thanks in advance
>
> Regards,
> Shariff
>
>
>
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-- 
Regards,
Ankit Agarwal
SW Engineer
Vegayan Systems
email : ankit_agarwal at vegayan.com
Blog : http://ankit17.wordpress.com
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