qt-creator/tests/manual/tasking/imagescaling/imagescaling.cpp

// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

#include "imagescaling.h"
#include "downloaddialog.h"
#include <tasking/concurrentcall.h>
#include <tasking/networkquery.h>

using namespace Tasking;

Images::Images(QWidget *parent) : QWidget(parent), downloadDialog(new DownloadDialog(this))
{
    resize(800, 600);

    QPushButton *addUrlsButton = new QPushButton(tr("Add URLs"));
    connect(addUrlsButton, &QPushButton::clicked, this, &Images::process);

    cancelButton = new QPushButton(tr("Cancel"));
    cancelButton->setEnabled(false);
    connect(cancelButton, &QPushButton::clicked, this, [this] {
        statusBar->showMessage(tr("Canceled."));
        taskTreeRunner.reset();
    });

    QHBoxLayout *buttonLayout = new QHBoxLayout();
    buttonLayout->addWidget(addUrlsButton);
    buttonLayout->addWidget(cancelButton);
    buttonLayout->addStretch();

    statusBar = new QStatusBar();

    imagesLayout = new QGridLayout();

    mainLayout = new QVBoxLayout();
    mainLayout->addLayout(buttonLayout);
    mainLayout->addLayout(imagesLayout);
    mainLayout->addStretch();
    mainLayout->addWidget(statusBar);
    setLayout(mainLayout);
}

static void scale(QPromise<QImage> &promise, const QByteArray &data)
{
    const auto image = QImage::fromData(data);
    if (image.isNull())
        promise.future().cancel();
    else
        promise.addResult(image.scaled(100, 100, Qt::KeepAspectRatio));
}

void Images::process()
{
    if (downloadDialog->exec() != QDialog::Accepted)
        return;

    const auto urls = downloadDialog->getUrls();
    initLayout(urls.size());

    const LoopRepeat repeater(urls.size());
    const Storage<QByteArray> storage;

    const auto onRootSetup = [this] {
        statusBar->showMessage(tr("Downloading and Scaling..."));
        cancelButton->setEnabled(true);
    };
    const auto onRootDone = [this] {
        statusBar->showMessage(tr("Finished."));
        cancelButton->setEnabled(false);
    };

    const auto onDownloadSetup = [this, urls, repeater](NetworkQuery &query) {
        query.setNetworkAccessManager(&qnam);
        query.setRequest(QNetworkRequest(urls.at(repeater.iteration())));
    };
    const auto onDownloadDone = [this, storage, repeater](const NetworkQuery &query,
                                                                  DoneWith result) {
        const int it = repeater.iteration();
        if (result == DoneWith::Success)
            *storage = query.reply()->readAll();
        else
            labels[it]->setText(tr("Download\nError.\nCode: %1.").arg(query.reply()->error()));
    };

    const auto onScalingSetup = [storage](ConcurrentCall<QImage> &data) {
        data.setConcurrentCallData(&scale, *storage);
    };
    const auto onScalingDone = [this, repeater](const ConcurrentCall<QImage> &data,
                                                DoneWith result) {
        const int it = repeater.iteration();
        if (result == DoneWith::Success)
            labels[it]->setPixmap(QPixmap::fromImage(data.result()));
        else
            labels[it]->setText(tr("Image\nData\nError."));
    };

    const QList<GroupItem> tasks {
        finishAllAndSuccess,
        parallel,
        repeater,
        onGroupSetup(onRootSetup),
        Group {
            storage,
            NetworkQueryTask(onDownloadSetup, onDownloadDone),
            ConcurrentCallTask<QImage>(onScalingSetup, onScalingDone)
        },
        onGroupDone(onRootDone, CallDoneIf::Success)
    };

    taskTreeRunner.start(tasks);
}

void Images::initLayout(qsizetype count)
{
    // Clean old images
    QLayoutItem *child;
    while ((child = imagesLayout->takeAt(0)) != nullptr) {
        child->widget()->setParent(nullptr);
        delete child->widget();
        delete child;
    }
    labels.clear();

    // Init the images layout for the new images
    const auto dim = int(qSqrt(qreal(count))) + 1;
    for (int i = 0; i < dim; ++i) {
        for (int j = 0; j < dim; ++j) {
            QLabel *imageLabel = new QLabel;
            imageLabel->setFixedSize(100, 100);
            imageLabel->setAlignment(Qt::AlignCenter);
            imagesLayout->addWidget(imageLabel, i, j);
            labels.append(imageLabel);
        }
    }
}