Revamp QtConcurrent examples to C++11

I updated signals and slots and for each loops to the new syntax and
replaced most free functions with std::function.

Task-number: QTBUG-60641
Change-Id: I7693f81f71c7f53fcbe83189a0de2fb76ddf99a8
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

examples/qtconcurrent/imagescaling/imagescaling.cpp

@@ -48,15 +48,10 @@
 **
 ****************************************************************************/
 #include "imagescaling.h"
+
 #include <qmath.h>
 
-const int imageSize = 100;
+#include <functional>
-
-QImage scale(const QString &imageFileName)
-{
-    QImage image(imageFileName);
-    return image.scaled(QSize(imageSize, imageSize), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
-}
 
 Images::Images(QWidget *parent)
     : QWidget(parent)
@@ -65,19 +60,19 @@ Images::Images(QWidget *parent)
     resize(800, 600);
 
     imageScaling = new QFutureWatcher<QImage>(this);
-    connect(imageScaling, SIGNAL(resultReadyAt(int)), SLOT(showImage(int)));
+    connect(imageScaling, &QFutureWatcher<QImage>::resultReadyAt, this, &Images::showImage);
-    connect(imageScaling, SIGNAL(finished()), SLOT(finished()));
+    connect(imageScaling, &QFutureWatcher<QImage>::finished, this, &Images::finished);
 
     openButton = new QPushButton(tr("Open Images"));
-    connect(openButton, SIGNAL(clicked()), SLOT(open()));
+    connect(openButton, &QPushButton::clicked, this, &Images::open);
 
     cancelButton = new QPushButton(tr("Cancel"));
     cancelButton->setEnabled(false);
-    connect(cancelButton, SIGNAL(clicked()), imageScaling, SLOT(cancel()));
+    connect(cancelButton, &QPushButton::clicked, imageScaling, &QFutureWatcher<QImage>::cancel);
 
     pauseButton = new QPushButton(tr("Pause/Resume"));
     pauseButton->setEnabled(false);
-    connect(pauseButton, SIGNAL(clicked()), imageScaling, SLOT(togglePaused()));
+    connect(pauseButton, &QPushButton::clicked, imageScaling, &QFutureWatcher<QImage>::togglePaused);
 
     QHBoxLayout *buttonLayout = new QHBoxLayout();
     buttonLayout->addWidget(openButton);
@@ -113,9 +108,11 @@ void Images::open()
                             QStandardPaths::writableLocation(QStandardPaths::PicturesLocation),
                             "*.jpg *.png");
 
-    if (files.count() == 0)
+    if (files.isEmpty())
         return;
 
+    const int imageSize = 100;
+
     // Do a simple layout.
     qDeleteAll(labels);
     labels.clear();
@@ -130,6 +127,11 @@ void Images::open()
         }
     }
 
+    std::function<QImage(const QString&)> scale = [imageSize](const QString &imageFileName) {
+        QImage image(imageFileName);
+        return image.scaled(QSize(imageSize, imageSize), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
+    };
+
     // Use mapped to run the thread safe scale function on the files.
     imageScaling->setFuture(QtConcurrent::mapped(files, scale));
 

examples/qtconcurrent/imagescaling/imagescaling.h

@@ -57,9 +57,9 @@ class Images : public QWidget
 {
 Q_OBJECT
 public:
-    Images(QWidget *parent = 0);
+    Images(QWidget *parent = nullptr);
     ~Images();
-public Q_SLOTS:
+public slots:
     void open();
     void showImage(int num);
     void finished();

examples/qtconcurrent/map/main.cpp

@@ -55,11 +55,7 @@
 #include <QGuiApplication>
 #include <qtconcurrentmap.h>
 
-QImage scale(const QImage &image)
+#include <functional>
-{
-    qDebug() << "Scaling image in thread" << QThread::currentThread();
-    return image.scaled(QSize(100, 100), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
-}
 
 int main(int argc, char *argv[])
 {
@@ -72,6 +68,12 @@ int main(int argc, char *argv[])
     for (int i = 0; i < imageCount; ++i)
         images.append(QImage(1600, 1200, QImage::Format_ARGB32_Premultiplied));
 
+    std::function<QImage(const QImage&)> scale = [](const QImage &image) -> QImage
+    {
+        qDebug() << "Scaling image in thread" << QThread::currentThread();
+        return image.scaled(QSize(100, 100), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
+    };
+
     // Use QtConcurrentBlocking::mapped to apply the scale function to all the
     // images in the list.
     QList<QImage> thumbnails = QtConcurrent::blockingMapped(images, scale);

examples/qtconcurrent/progressdialog/main.cpp

@@ -51,24 +51,16 @@
 #include <QtWidgets>
 #include <QtConcurrent>
 
+#include <functional>
+
 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);
 
+    const int iterations = 20;
+
     // Prepare the vector.
     QVector<int> vector;
     for (int i = 0; i < iterations; ++i)
@@ -80,10 +72,20 @@ int main(int argc, char **argv)
 
     // Create a QFutureWatcher and connect signals and slots.
     QFutureWatcher<void> futureWatcher;
-    QObject::connect(&futureWatcher, SIGNAL(finished()), &dialog, SLOT(reset()));
+    QObject::connect(&futureWatcher, &QFutureWatcher<void>::finished, &dialog, &QProgressDialog::reset);
-    QObject::connect(&dialog, SIGNAL(canceled()), &futureWatcher, SLOT(cancel()));
+    QObject::connect(&dialog, &QProgressDialog::canceled, &futureWatcher, &QFutureWatcher<void>::cancel);
-    QObject::connect(&futureWatcher, SIGNAL(progressRangeChanged(int,int)), &dialog, SLOT(setRange(int,int)));
+    QObject::connect(&futureWatcher,  &QFutureWatcher<void>::progressRangeChanged, &dialog, &QProgressDialog::setRange);
-    QObject::connect(&futureWatcher, SIGNAL(progressValueChanged(int)), &dialog, SLOT(setValue(int)));
+    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(vector, spin));

examples/qtconcurrent/wordcount/main.cpp

@@ -65,15 +65,17 @@ using namespace QtConcurrent;
 /*
     Utility function that recursivily searches for files.
 */
-QStringList findFiles(const QString &startDir, QStringList filters)
+QStringList findFiles(const QString &startDir, const QStringList &filters)
 {
     QStringList names;
     QDir dir(startDir);
 
-    foreach (QString file, dir.entryList(filters, QDir::Files))
+    const auto files = dir.entryList(filters, QDir::Files);
+    for (const QString &file : files)
         names += startDir + '/' + file;
 
-    foreach (QString subdir, dir.entryList(QDir::AllDirs | QDir::NoDotAndDotDot))
+    const auto subdirs =  dir.entryList(QDir::AllDirs | QDir::NoDotAndDotDot);
+    for (const QString &subdir : subdirs)
         names += findFiles(startDir + '/' + subdir, filters);
     return names;
 }
@@ -83,17 +85,18 @@ typedef QMap<QString, int> WordCount;
 /*
     Single threaded word counter function.
 */
-WordCount singleThreadedWordCount(QStringList files)
+WordCount singleThreadedWordCount(const QStringList &files)
 {
     WordCount wordCount;
-    foreach (QString file, files) {
+    for (const QString &file : files) {
         QFile f(file);
         f.open(QIODevice::ReadOnly);
         QTextStream textStream(&f);
-        while (textStream.atEnd() == false)
+        while (!textStream.atEnd()) {
-            foreach (const QString &word, textStream.readLine().split(' '))
+            const auto words =  textStream.readLine().split(' ');
+            for (const QString &word : words)
                 wordCount[word] += 1;
-
+        }
     }
     return wordCount;
 }
@@ -109,9 +112,11 @@ WordCount countWords(const QString &file)
     QTextStream textStream(&f);
     WordCount wordCount;
 
-    while (textStream.atEnd() == false)
+    while (!textStream.atEnd()) {
-        foreach (const QString &word, textStream.readLine().split(' '))
+        const auto words =  textStream.readLine().split(' ');
+        for (const QString &word : words)
             wordCount[word] += 1;
+    }
 
     return wordCount;
 }
@@ -137,8 +142,6 @@ int main(int argc, char** argv)
 
     qDebug() << "warmup";
     {
-        QTime time;
-        time.start();
         WordCount total = singleThreadedWordCount(files);
     }