- Qt 5.5
- Qt Concurrent
- QtConcurrent Progress Dialog Example
- main.cpp Example File
- Qt 5.5.1 Reference Documentation

# main.cpp Example File

progressdialog/main.cpp

    /****************************************************************************
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    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
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    ** This file is part of the examples of the Qt Toolkit.
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    #include <QtWidgets>
    #include <QtConcurrent>

    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 connect 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();
    }