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main.cpp Example File
qtconcurrent/progressdialog/main.cpp

 /****************************************************************************
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 ** Copyright (C) 2007-2008 Nokia Corporation and/or its subsidiary(-ies). All rights reserved.
 **
 ** This file is part of the documentation of the Qt Toolkit.
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 ** Licensees holding a valid Qt License Agreement may use this file in
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 ** contained therein.  Please consult your licensing agreement or
 ** contact [email protected] if any conditions of this licensing
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 ** http://trolltech.com/products/appdev/licensing.
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 ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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 #include <QtGui>

 #ifndef QT_NO_CONCURRENT

 using namespace QtConcurrent;

 const int iterations = 20;

 void spin(int &iteration)
 {
     const int work = 1000 * 1000 * 40;
     volatile int v = 0;
     for (int j = 0; j < work; ++j)
         ++v;

     qDebug() << "iteration" << iteration << "in thread" << QThread::currentThreadId();
 }

 int main(int argc, char **argv)
 {
     QApplication app(argc, argv);

     // Prepare the vector.
     QVector<int> vector;
     for (int i = 0; i < iterations; ++i)
         vector.append(i);

     // Create a progress dialog.
     QProgressDialog dialog;
     dialog.setLabelText(QString("Progressing using %1 thread(s)...").arg(QThread::idealThreadCount()));

     // Create a QFutureWatcher and conncect signals and slots.
     QFutureWatcher<void> futureWatcher;
     QObject::connect(&futureWatcher, SIGNAL(finished()), &dialog, SLOT(reset()));
     QObject::connect(&dialog, SIGNAL(canceled()), &futureWatcher, SLOT(cancel()));
     QObject::connect(&futureWatcher, SIGNAL(progressRangeChanged(int, int)), &dialog, SLOT(setRange(int, int)));
     QObject::connect(&futureWatcher, SIGNAL(progressValueChanged(int)), &dialog, SLOT(setValue(int)));

     // Start the computation.
     futureWatcher.setFuture(QtConcurrent::map(vector, spin));

     // Display the dialog and start the event loop.
     dialog.exec();

     futureWatcher.waitForFinished();

     // Query the future to check if was canceled.
     qDebug() << "Canceled?" << futureWatcher.future().isCanceled();
 }

 #else

 int main()
 {
         qDebug() << "Qt Concurrent is not yet supported on this platform";
 }

 #endif