1 files changed, 52 insertions, 34 deletions

diff --git a/examples/qtconcurrent/imagescaling/imagescaling.cpp b/examples/qtconcurrent/imagescaling/imagescaling.cpp
index d674ddd085..f380ae9d90 100644
--- a/examples/qtconcurrent/imagescaling/imagescaling.cpp
+++ b/examples/qtconcurrent/imagescaling/imagescaling.cpp
@@ -1,12 +1,10 @@
-// Copyright (C) 2020 The Qt Company Ltd.
+// Copyright (C) 2023 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
 #include "imagescaling.h"
 #include "downloaddialog.h"
 
 #include <QNetworkReply>
-#include <QtMath>
-
-#include <functional>
 
 Images::Images(QWidget *parent) : QWidget(parent), downloadDialog(new DownloadDialog(this))
 {
@@ -38,6 +36,11 @@ Images::Images(QWidget *parent) : QWidget(parent), downloadDialog(new DownloadDi
     mainLayout->addStretch();
     mainLayout->addWidget(statusBar);
     setLayout(mainLayout);
+
+//! [6]
+    connect(&scalingWatcher, &QFutureWatcher<QList<QImage>>::finished,
+            this, &Images::scaleFinished);
+//! [6]
 }
 
 Images::~Images()
@@ -50,6 +53,7 @@ void Images::process()
 {
     // Clean previous state
     replies.clear();
+    addUrlsButton->setEnabled(false);
 
     if (downloadDialog->exec() == QDialog::Accepted) {
 
@@ -65,33 +69,34 @@ void Images::process()
         statusBar->showMessage(tr("Downloading..."));
 //! [3]
 
-//! [4]
-        downloadFuture.then([this](auto) { cancelButton->setEnabled(false); })
-                .then(QtFuture::Launch::Async,
-                      [this] {
-                          QMetaObject::invokeMethod(this,
-                                                    [this] { updateStatus(tr("Scaling...")); });
-                          return scaled();
-                      })
-//! [4]
-//! [5]
-                .then(this, [this](const QList<QImage> &scaled) {
-                    showImages(scaled);
-                    updateStatus(tr("Finished"));
+        //! [4]
+        downloadFuture
+                .then([this](auto) {
+                    cancelButton->setEnabled(false);
+                    updateStatus(tr("Scaling..."));
+                    //! [16]
+                    scalingWatcher.setFuture(QtConcurrent::run(Images::scaled,
+                                                               downloadFuture.results()));
+                    //! [16]
+                })
+        //! [4]
+        //! [5]
+                .onCanceled([this] {
+                    updateStatus(tr("Download has been canceled."));
                 })
-//! [5]
-//! [6]
-                .onCanceled([this] { updateStatus(tr("Download has been canceled.")); })
                 .onFailed([this](QNetworkReply::NetworkError error) {
                     updateStatus(tr("Download finished with error: %1").arg(error));
-
                     // Abort all pending requests
                     abortDownload();
                 })
                 .onFailed([this](const std::exception &ex) {
                     updateStatus(tr(ex.what()));
+                })
+        //! [5]
+                .then([this]() {
+                    cancelButton->setEnabled(false);
+                    addUrlsButton->setEnabled(true);
                 });
-//! [6]
     }
 }
 
@@ -105,22 +110,37 @@ void Images::cancel()
 }
 //! [7]
 
+//! [15]
+void Images::scaleFinished()
+{
+    const OptionalImages result = scalingWatcher.result();
+    if (result.has_value()) {
+        const auto scaled = result.value();
+        showImages(scaled);
+        updateStatus(tr("Finished"));
+    } else {
+        updateStatus(tr("Failed to extract image data."));
+    }
+    addUrlsButton->setEnabled(true);
+}
+//! [15]
+
 //! [8]
 QFuture<QByteArray> Images::download(const QList<QUrl> &urls)
-//! [8]
 {
+//! [8]
 //! [9]
     QSharedPointer<QPromise<QByteArray>> promise(new QPromise<QByteArray>());
     promise->start();
 //! [9]
 
-//! [10]
+    //! [10]
     for (const auto &url : urls) {
         QSharedPointer<QNetworkReply> reply(qnam.get(QNetworkRequest(url)));
         replies.push_back(reply);
-//! [10]
+    //! [10]
 
-//! [11]
+    //! [11]
         QtFuture::connect(reply.get(), &QNetworkReply::finished).then([=] {
             if (promise->isCanceled()) {
                 if (!promise->future().isFinished())
@@ -132,14 +152,13 @@ QFuture<QByteArray> Images::download(const QList<QUrl> &urls)
                 if (!promise->future().isFinished())
                     throw reply->error();
             }
-//! [12]
+        //! [12]
             promise->addResult(reply->readAll());
 
             // Report finished on the last download
-            if (promise->future().resultCount() == urls.size()) {
+            if (promise->future().resultCount() == urls.size())
                 promise->finish();
-            }
-//! [12]
+        //! [12]
         }).onFailed([promise] (QNetworkReply::NetworkError error) {
             promise->setException(std::make_exception_ptr(error));
             promise->finish();
@@ -150,7 +169,7 @@ QFuture<QByteArray> Images::download(const QList<QUrl> &urls)
             promise->finish();
         });
     }
-//! [11]
+    //! [11]
 
 //! [13]
     return promise->future();
@@ -158,15 +177,14 @@ QFuture<QByteArray> Images::download(const QList<QUrl> &urls)
 //! [13]
 
 //! [14]
-QList<QImage> Images::scaled() const
+Images::OptionalImages Images::scaled(const QList<QByteArray> &data)
 {
     QList<QImage> scaled;
-    const auto data = downloadFuture.results();
     for (const auto &imgData : data) {
         QImage image;
         image.loadFromData(imgData);
         if (image.isNull())
-            throw std::runtime_error("Failed to load image.");
+            return std::nullopt;
 
         scaled.push_back(image.scaled(100, 100, Qt::KeepAspectRatio));
     }