ProgressDialog.cpp Example File

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    #include "ProgressDialog.hpp"

    #include <qtconcurrentmap.h>

    /**
     * The 'computation' method that is used to burn some CPU cycles.
     */
    void spin(int &iteration)
    {
        Q_UNUSED(iteration)

        const int work = 1000 * 1000 * 40;
        volatile int v = 0;
        for (int j = 0; j < work; ++j)
            ++v;
    }

    ProgressDialog::ProgressDialog()
        : m_progressMinimum(0)
        , m_progressMaximum(0)
        , m_progressValue(0)
    {
        // Forward state change signals from the watcher to our 'active' property
        connect(&m_futureWatcher, SIGNAL(started()), this, SIGNAL(activeChanged()));
        connect(&m_futureWatcher, SIGNAL(finished()), this, SIGNAL(activeChanged()));

        // Monitor progress changes of the future to update our own properties
        connect(&m_futureWatcher, SIGNAL(progressRangeChanged(int, int)),
                this, SLOT(progressRangeChanged(int, int)));
        connect(&m_futureWatcher, SIGNAL(progressValueChanged(int)),
                this, SLOT(progressValueChanged(int)));
        connect(&m_futureWatcher, SIGNAL(finished()),
                this, SLOT(calculationFinished()));
    }

    int ProgressDialog::numberOfCores() const
    {
        /**
         * The QtConcurrent framework uses QThreadPool::globalInstance()
         * for computation and that one uses as many thread contexts as
         * returned by QThread::idelThreadCount().
         */
        return QThread::idealThreadCount();
    }

    bool ProgressDialog::active() const
    {
        // Return whether there is currently an active Future
        return m_futureWatcher.isRunning();
    }

    int ProgressDialog::progressMinimum() const
    {
        return m_progressMinimum;
    }

    int ProgressDialog::progressMaximum() const
    {
        return m_progressMaximum;
    }

    int ProgressDialog::progressValue() const
    {
        return m_progressValue;
    }

    void ProgressDialog::startComputation()
    {
        // Prepare the vector
        QVector<int> vector;
        for (int i = 0; i < 40; ++i)
            vector.append(i);

        /**
         * Start the computation.
         * The returned Future object is just a handle to the running operation, which
         * is executed asynchronously in separated threads.
         */
        const QFuture<void> future = QtConcurrent::map(vector, spin);

        // Let the future watcher monitor the progress of this Future
        m_futureWatcher.setFuture(future);
    }

    void ProgressDialog::cancelComputation()
    {
        // Stop the computation
        m_futureWatcher.cancel();
    }

    void ProgressDialog::progressRangeChanged(int minimum, int maximum)
    {
        m_progressMinimum = minimum;
        m_progressMaximum = maximum;

        emit progressRangeChanged();
    }

    void ProgressDialog::progressValueChanged(int value)
    {
        if (m_progressValue == value)
            return;

        m_progressValue = value;
        emit progressValueChanged();
    }

    void ProgressDialog::calculationFinished()
    {
        // Reset the progress indicator after calculation has finished or was canceled
        m_progressValue = 0;
        emit progressValueChanged();
    }