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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include <QtWidgets>
#include <QtConcurrent>
#include <functional>
using namespace QtConcurrent;
int main(int argc, char **argv)
{
QApplication app(argc, argv);
const int iterations = 20;
// Prepare the list.
QList<int> list;
for (int i = 0; i < iterations; ++i)
list.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, &QFutureWatcher<void>::finished, &dialog, &QProgressDialog::reset);
QObject::connect(&dialog, &QProgressDialog::canceled, &futureWatcher, &QFutureWatcher<void>::cancel);
QObject::connect(&futureWatcher, &QFutureWatcher<void>::progressRangeChanged, &dialog, &QProgressDialog::setRange);
QObject::connect(&futureWatcher, &QFutureWatcher<void>::progressValueChanged, &dialog, &QProgressDialog::setValue);
// Our function to compute
std::function<void(int&)> 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();
};
// Start the computation.
futureWatcher.setFuture(QtConcurrent::map(list, 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();
}
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