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50
51#include <QtWidgets>
52#include <QtConcurrent>
53
54#include <functional>
55
56using namespace QtConcurrent;
57
58int main(int argc, char **argv)
59{
60 QApplication app(argc, argv);
61
62 const int iterations = 20;
63
64 // Prepare the vector.
65 QVector<int> vector;
66 for (int i = 0; i < iterations; ++i)
67 vector.append(t: i);
68
69 // Create a progress dialog.
70 QProgressDialog dialog;
71 dialog.setLabelText(QString("Progressing using %1 thread(s)...").arg(a: QThread::idealThreadCount()));
72
73 // Create a QFutureWatcher and connect signals and slots.
74 QFutureWatcher<void> futureWatcher;
75 QObject::connect(sender: &futureWatcher, signal: &QFutureWatcher<void>::finished, receiver: &dialog, slot: &QProgressDialog::reset);
76 QObject::connect(sender: &dialog, signal: &QProgressDialog::canceled, receiver: &futureWatcher, slot: &QFutureWatcher<void>::cancel);
77 QObject::connect(sender: &futureWatcher, signal: &QFutureWatcher<void>::progressRangeChanged, receiver: &dialog, slot: &QProgressDialog::setRange);
78 QObject::connect(sender: &futureWatcher, signal: &QFutureWatcher<void>::progressValueChanged, receiver: &dialog, slot: &QProgressDialog::setValue);
79
80 // Our function to compute
81 std::function<void(int&)> spin = [](int &iteration) {
82 const int work = 1000 * 1000 * 40;
83 volatile int v = 0;
84 for (int j = 0; j < work; ++j)
85 ++v;
86
87 qDebug() << "iteration" << iteration << "in thread" << QThread::currentThreadId();
88 };
89
90 // Start the computation.
91 futureWatcher.setFuture(QtConcurrent::map(sequence&: vector, map: spin));
92
93 // Display the dialog and start the event loop.
94 dialog.exec();
95
96 futureWatcher.waitForFinished();
97
98 // Query the future to check if was canceled.
99 qDebug() << "Canceled?" << futureWatcher.future().isCanceled();
100}
101

source code of qtbase/examples/qtconcurrent/progressdialog/main.cpp