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

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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