Qt Reference Documentation

# main.cpp Example File

qtconcurrent/progressdialog/main.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2015 The Qt Company Ltd.
     ** Contact: http://www.qt.io/licensing/
     **
     ** This file is part of the examples of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:BSD$
     ** You may use this file under the terms of the BSD license as follows:
     **
     ** "Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions are
     ** met:
     **   * Redistributions of source code must retain the above copyright
     **     notice, this list of conditions and the following disclaimer.
     **   * Redistributions in binary form must reproduce the above copyright
     **     notice, this list of conditions and the following disclaimer in
     **     the documentation and/or other materials provided with the
     **     distribution.
     **   * Neither the name of The Qt Company Ltd nor the names of its
     **     contributors may be used to endorse or promote products derived
     **     from this software without specific prior written permission.
     **
     **
     ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
     **
     ** $QT_END_LICENSE$
     **
     ****************************************************************************/

     #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 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();
     }

     #else

     int main(int argc, char *argv[])
     {
         QApplication app(argc, argv);
         QString text("Qt Concurrent is not yet supported on this platform");

         QLabel *label = new QLabel(text);
         label->setWordWrap(true);

     #if defined(Q_WS_S60) || defined(Q_WS_MAEMO_5)
         label->showMaximized();
     #else
         label->show();
     #endif
         qDebug() << text;

         app.exec();
     }

     #endif