Add QPdfPageRenderer class

The QPdfPageRenderer renders a page of a QPdfDocument for a given
zoom factor. Depending on its render mode, it does the rendering
in the UI thread or a worker thread. Subsequent requests are queued
and processed in order.

Change-Id: I95820cd318cb443b2572f6d3db5a0bee53939bd1
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>

8 files changed, 646 insertions, 2 deletions

diff --git a/src/pdf/pdf.pro b/src/pdf/pdf.pro
index 319e244..dd2df76 100644
--- a/src/pdf/pdf.pro
+++ b/src/pdf/pdf.pro
@@ -24,7 +24,8 @@ SOURCES += \
     jsbridge.cpp \
     qpdfbookmarkmodel.cpp \
     qpdfdocument.cpp \
-    qpdfpagenavigation.cpp
+    qpdfpagenavigation.cpp \
+    qpdfpagerenderer.cpp
 
 HEADERS += \
     qpdfbookmarkmodel.h \
@@ -33,4 +34,5 @@ HEADERS += \
     qpdfdocumentrenderoptions.h \
     qpdfnamespace.h \
     qpdfpagenavigation.h \
+    qpdfpagerenderer.h \
     qtpdfglobal.h
diff --git a/src/pdf/qpdfdocumentrenderoptions.h b/src/pdf/qpdfdocumentrenderoptions.h
index b602bb0..1d316b9 100644
--- a/src/pdf/qpdfdocumentrenderoptions.h
+++ b/src/pdf/qpdfdocumentrenderoptions.h
@@ -85,4 +85,6 @@ Q_DECL_CONSTEXPR inline bool operator!=(QPdfDocumentRenderOptions lhs, QPdfDocum
 
 QT_END_NAMESPACE
 
+Q_DECLARE_METATYPE(QPdfDocumentRenderOptions)
+
 #endif // QPDFDOCUMENTRENDEROPTIONS_H
diff --git a/src/pdf/qpdfpagerenderer.cpp b/src/pdf/qpdfpagerenderer.cpp
new file mode 100644
index 0000000..02d6ef4
--- /dev/null
+++ b/src/pdf/qpdfpagerenderer.cpp
@@ -0,0 +1,359 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Tobias König <tobias.koenig@kdab.com>
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtPDF module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qpdfpagerenderer.h"
+
+#include <private/qobject_p.h>
+#include <QMutex>
+#include <QPdfDocument>
+#include <QPointer>
+#include <QThread>
+
+QT_BEGIN_NAMESPACE
+
+class RenderWorker : public QObject
+{
+    Q_OBJECT
+
+public:
+    RenderWorker();
+    ~RenderWorker();
+
+    void setDocument(QPdfDocument *document);
+
+public Q_SLOTS:
+    void requestPage(quint64 requestId, int page, QSize imageSize,
+                     QPdfDocumentRenderOptions options);
+
+Q_SIGNALS:
+    void pageRendered(int page, QSize imageSize, const QImage &image,
+                      QPdfDocumentRenderOptions options, quint64 requestId);
+
+private:
+    QPointer<QPdfDocument> m_document;
+    QMutex m_mutex;
+};
+
+class QPdfPageRendererPrivate : public QObjectPrivate
+{
+    Q_DECLARE_PUBLIC(QPdfPageRenderer)
+
+public:
+    QPdfPageRendererPrivate();
+    ~QPdfPageRendererPrivate();
+
+    void handleNextRequest();
+    void requestFinished(int page, QSize imageSize, const QImage &image,
+                         QPdfDocumentRenderOptions options, quint64 requestId);
+
+    QPdfPageRenderer::RenderMode m_renderMode = QPdfPageRenderer::SingleThreadedRenderMode;
+    QPointer<QPdfDocument> m_document;
+
+    struct PageRequest
+    {
+        quint64 id;
+        int pageNumber;
+        QSize imageSize;
+        QPdfDocumentRenderOptions options;
+    };
+
+    QVector<PageRequest> m_requests;
+    QVector<PageRequest> m_pendingRequests;
+    quint64 m_requestIdCounter = 1;
+
+    QThread *m_renderThread = nullptr;
+    QScopedPointer<RenderWorker> m_renderWorker;
+};
+
+Q_DECLARE_TYPEINFO(QPdfPageRendererPrivate::PageRequest, Q_PRIMITIVE_TYPE);
+
+
+RenderWorker::RenderWorker()
+    : m_document(nullptr)
+{
+}
+
+RenderWorker::~RenderWorker()
+{
+}
+
+void RenderWorker::setDocument(QPdfDocument *document)
+{
+    const QMutexLocker locker(&m_mutex);
+
+    if (m_document == document)
+        return;
+
+    m_document = document;
+}
+
+void RenderWorker::requestPage(quint64 requestId, int pageNumber, QSize imageSize,
+                               QPdfDocumentRenderOptions options)
+{
+    const QMutexLocker locker(&m_mutex);
+
+    if (!m_document || m_document->status() != QPdfDocument::Ready)
+        return;
+
+    const QImage image = m_document->render(pageNumber, imageSize, options);
+
+    emit pageRendered(pageNumber, imageSize, image, options, requestId);
+}
+
+
+QPdfPageRendererPrivate::QPdfPageRendererPrivate()
+    : QObjectPrivate()
+    , m_renderWorker(new RenderWorker)
+{
+}
+
+QPdfPageRendererPrivate::~QPdfPageRendererPrivate()
+{
+    if (m_renderThread) {
+        m_renderThread->quit();
+        m_renderThread->wait();
+    }
+}
+
+void QPdfPageRendererPrivate::handleNextRequest()
+{
+    if (m_requests.isEmpty())
+        return;
+
+    const PageRequest request = m_requests.takeFirst();
+    m_pendingRequests.append(request);
+
+    QMetaObject::invokeMethod(m_renderWorker.data(), "requestPage", Qt::QueuedConnection,
+                              Q_ARG(quint64, request.id), Q_ARG(int, request.pageNumber),
+                              Q_ARG(QSize, request.imageSize), Q_ARG(QPdfDocumentRenderOptions,
+                              request.options));
+}
+
+void QPdfPageRendererPrivate::requestFinished(int page, QSize imageSize, const QImage &image, QPdfDocumentRenderOptions options, quint64 requestId)
+{
+    const auto it = std::find_if(m_pendingRequests.begin(), m_pendingRequests.end(),
+                                 [page, imageSize, options](const PageRequest &request){ return request.pageNumber == page && request.imageSize == imageSize && request.options == options; });
+
+    if (it != m_pendingRequests.end())
+        m_pendingRequests.erase(it);
+}
+
+/*!
+    \class QPdfPageRenderer
+    \since 5.11
+    \inmodule QtPdf
+
+    \brief The QPdfPageRenderer class encapsulates the rendering of pages of a PDF document.
+
+    The QPdfPageRenderer contains a queue that collects all render requests that are invoked through
+    requestPage(). Depending on the configured RenderMode the QPdfPageRenderer processes this queue
+    in the main UI thread on next event loop invocation (SingleThreadedRenderMode) or in a separate worker thread
+    (MultiThreadedRenderMode) and emits the result through the pageRendered() signal for each request once
+    the rendering is done.
+
+    \sa QPdfDocument
+*/
+
+
+/*!
+    Constructs a page renderer object with parent object \a parent.
+*/
+QPdfPageRenderer::QPdfPageRenderer(QObject *parent)
+    : QObject(*new QPdfPageRendererPrivate(), parent)
+{
+    Q_D(QPdfPageRenderer);
+
+    qRegisterMetaType<QPdfDocumentRenderOptions>();
+
+    connect(d->m_renderWorker.data(), &RenderWorker::pageRendered, this,
+            [this,d](int page, QSize imageSize, const QImage &image, QPdfDocumentRenderOptions options, quint64 requestId) {
+                d->requestFinished(page, imageSize, image, options, requestId);
+                emit pageRendered(page, imageSize, image, options, requestId);
+                d->handleNextRequest();
+           });
+}
+
+/*!
+    Destroys the page renderer object.
+*/
+QPdfPageRenderer::~QPdfPageRenderer()
+{
+}
+
+/*!
+    \enum QPdfPageRenderer::RenderMode
+
+    This enum describes how the pages are rendered.
+
+    \value MultiThreadedRenderMode All pages are rendered in a separate worker thread.
+    \value SingleThreadedRenderMode All pages are rendered in the main UI thread (default).
+
+    \sa renderMode(), setRenderMode()
+*/
+
+/*!
+    \property QPdfPageRenderer::renderMode
+    \brief the mode the renderer renders the pages
+
+    By default, this property is \c QPdfPageRenderer::SingleThreaded.
+
+    \sa setRenderMode(), RenderMode
+*/
+
+/*!
+    Returns the mode of how the pages are rendered.
+
+    \sa RenderMode
+*/
+QPdfPageRenderer::RenderMode QPdfPageRenderer::renderMode() const
+{
+    Q_D(const QPdfPageRenderer);
+
+    return d->m_renderMode;
+}
+
+/*!
+    Sets the mode of how the pages are rendered.
+
+    \sa RenderMode
+*/
+void QPdfPageRenderer::setRenderMode(RenderMode mode)
+{
+    Q_D(QPdfPageRenderer);
+
+    if (d->m_renderMode == mode)
+        return;
+
+    d->m_renderMode = mode;
+    emit renderModeChanged(d->m_renderMode);
+
+    if (d->m_renderMode == MultiThreadedRenderMode) {
+        d->m_renderThread = new QThread;
+        d->m_renderWorker->moveToThread(d->m_renderThread);
+        d->m_renderThread->start();
+    } else {
+        d->m_renderThread->quit();
+        d->m_renderThread->wait();
+        delete d->m_renderThread;
+        d->m_renderThread = nullptr;
+
+        // pulling the object from another thread should be fine, once that thread is deleted
+        d->m_renderWorker->moveToThread(this->thread());
+    }
+}
+
+/*!
+    \property QPdfPageRenderer::document
+    \brief the document instance this object renders the pages from
+
+    By default, this property is \c nullptr.
+
+    \sa document(), setDocument(), QPdfDocument
+*/
+
+/*!
+    Returns the document this objects renders the pages from, or a \c nullptr
+    if none has been set before.
+
+    \sa QPdfDocument
+*/
+QPdfDocument* QPdfPageRenderer::document() const
+{
+    Q_D(const QPdfPageRenderer);
+
+    return d->m_document;
+}
+
+/*!
+    Sets the \a document this object renders the pages from.
+
+    \sa QPdfDocument
+*/
+void QPdfPageRenderer::setDocument(QPdfDocument *document)
+{
+    Q_D(QPdfPageRenderer);
+
+    if (d->m_document == document)
+        return;
+
+    d->m_document = document;
+    emit documentChanged(d->m_document);
+
+    d->m_renderWorker->setDocument(d->m_document);
+}
+
+/*!
+    Requests the renderer to render the page \a pageNumber into a QImage of size \a imageSize
+    according to the provided \a options.
+
+    Once the rendering is done the pageRendered() signal is emitted with the result as parameters.
+
+    The return value is an ID that uniquely identifies the render request. If a request with the
+    same parameters is still in the queue, the ID of that queued request is returned.
+*/
+quint64 QPdfPageRenderer::requestPage(int pageNumber, QSize imageSize,
+                                      QPdfDocumentRenderOptions options)
+{
+    Q_D(QPdfPageRenderer);
+
+    if (!d->m_document || d->m_document->status() != QPdfDocument::Ready)
+        return 0;
+
+    for (const auto request : qAsConst(d->m_pendingRequests)) {
+        if (request.pageNumber == pageNumber
+            && request.imageSize == imageSize
+            && request.options == options)
+            return request.id;
+    }
+
+    const auto id = d->m_requestIdCounter++;
+
+    QPdfPageRendererPrivate::PageRequest request;
+    request.id = id;
+    request.pageNumber = pageNumber;
+    request.imageSize = imageSize;
+    request.options = options;
+
+    d->m_requests.append(request);
+
+    d->handleNextRequest();
+
+    return id;
+}
+
+QT_END_NAMESPACE
+
+#include "qpdfpagerenderer.moc"
diff --git a/src/pdf/qpdfpagerenderer.h b/src/pdf/qpdfpagerenderer.h
new file mode 100644
index 0000000..8056579
--- /dev/null
+++ b/src/pdf/qpdfpagerenderer.h
@@ -0,0 +1,91 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Tobias König <tobias.koenig@kdab.com>
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtPDF module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QPDFPAGERENDERER_H
+#define QPDFPAGERENDERER_H
+
+#include "qtpdfglobal.h"
+
+#include <QObject>
+#include <QPdfDocumentRenderOptions>
+#include <QSize>
+
+QT_BEGIN_NAMESPACE
+
+class QPdfDocument;
+class QPdfPageRendererPrivate;
+
+class Q_PDF_EXPORT QPdfPageRenderer : public QObject
+{
+    Q_OBJECT
+
+    Q_PROPERTY(QPdfDocument* document READ document WRITE setDocument NOTIFY documentChanged)
+    Q_PROPERTY(RenderMode renderMode READ renderMode WRITE setRenderMode NOTIFY renderModeChanged)
+
+public:
+    enum RenderMode
+    {
+        MultiThreadedRenderMode,
+        SingleThreadedRenderMode
+    };
+    Q_ENUM(RenderMode)
+
+    explicit QPdfPageRenderer(QObject *parent = nullptr);
+    ~QPdfPageRenderer();
+
+    RenderMode renderMode() const;
+    void setRenderMode(RenderMode mode);
+
+    QPdfDocument* document() const;
+    void setDocument(QPdfDocument *document);
+
+    quint64 requestPage(int pageNumber, QSize imageSize,
+                        QPdfDocumentRenderOptions options = QPdfDocumentRenderOptions());
+
+Q_SIGNALS:
+    void documentChanged(QPdfDocument *document);
+    void renderModeChanged(RenderMode renderMode);
+
+    void pageRendered(int pageNumber, QSize imageSize, const QImage &image,
+                      QPdfDocumentRenderOptions options, quint64 requestId);
+
+private:
+    Q_DECLARE_PRIVATE(QPdfPageRenderer)
+};
+
+QT_END_NAMESPACE
+
+#endif
diff --git a/tests/auto/auto.pro b/tests/auto/auto.pro
index 388b885..a2b3fcf 100644
--- a/tests/auto/auto.pro
+++ b/tests/auto/auto.pro
@@ -2,6 +2,7 @@ TEMPLATE = subdirs
 
 SUBDIRS = \
     qpdfbookmarkmodel \
-    qpdfpagenavigation
+    qpdfpagenavigation \
+    qpdfpagerenderer
 
 qtHaveModule(printsupport): SUBDIRS += qpdfdocument
diff --git a/tests/auto/qpdfpagerenderer/pdf-sample.pagerenderer.pdf b/tests/auto/qpdfpagerenderer/pdf-sample.pagerenderer.pdf
new file mode 100644
index 0000000..c4e1aa3
--- /dev/null
+++ b/tests/auto/qpdfpagerenderer/pdf-sample.pagerenderer.pdf
diff --git a/tests/auto/qpdfpagerenderer/qpdfpagerenderer.pro b/tests/auto/qpdfpagerenderer/qpdfpagerenderer.pro
new file mode 100644
index 0000000..9ccb4e8
--- /dev/null
+++ b/tests/auto/qpdfpagerenderer/qpdfpagerenderer.pro
@@ -0,0 +1,5 @@
+CONFIG += testcase
+TARGET = tst_qpdfpagerenderer
+QT += pdf testlib network
+macos:CONFIG -= app_bundle
+SOURCES += tst_qpdfpagerenderer.cpp
diff --git a/tests/auto/qpdfpagerenderer/tst_qpdfpagerenderer.cpp b/tests/auto/qpdfpagerenderer/tst_qpdfpagerenderer.cpp
new file mode 100644
index 0000000..8eaef7c
--- /dev/null
+++ b/tests/auto/qpdfpagerenderer/tst_qpdfpagerenderer.cpp
@@ -0,0 +1,184 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Tobias König <tobias.koenig@kdab.com>
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtPDF module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QPdfDocument>
+#include <QPdfPageRenderer>
+
+#include <QtTest/QtTest>
+
+class tst_QPdfPageRenderer: public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void defaultValues();
+    void withNoDocument();
+    void withEmptyDocument();
+    void withLoadedDocumentSingleThreaded();
+    void withLoadedDocumentMultiThreaded();
+    void switchingRenderMode();
+};
+
+void tst_QPdfPageRenderer::defaultValues()
+{
+    QPdfPageRenderer pageRenderer;
+
+    QCOMPARE(pageRenderer.document(), nullptr);
+    QCOMPARE(pageRenderer.renderMode(), QPdfPageRenderer::SingleThreadedRenderMode);
+}
+
+void tst_QPdfPageRenderer::withNoDocument()
+{
+    QPdfPageRenderer pageRenderer;
+
+    const QSize imageSize(100, 100);
+    const quint64 requestId = pageRenderer.requestPage(0, imageSize);
+
+    QCOMPARE(requestId, quint64(0));
+}
+
+void tst_QPdfPageRenderer::withEmptyDocument()
+{
+    QPdfDocument document;
+    QPdfPageRenderer pageRenderer;
+
+    pageRenderer.setDocument(&document);
+
+    const QSize imageSize(100, 100);
+    const quint64 requestId = pageRenderer.requestPage(0, imageSize);
+
+    QCOMPARE(requestId, quint64(0));
+}
+
+void tst_QPdfPageRenderer::withLoadedDocumentSingleThreaded()
+{
+    QPdfDocument document;
+    QPdfPageRenderer pageRenderer;
+    pageRenderer.setDocument(&document);
+
+    QCOMPARE(document.load(QFINDTESTDATA("pdf-sample.pagerenderer.pdf")), QPdfDocument::NoError);
+
+    QSignalSpy pageRenderedSpy(&pageRenderer, &QPdfPageRenderer::pageRendered);
+
+    const QSize imageSize(100, 100);
+    const quint64 requestId = pageRenderer.requestPage(0, imageSize);
+
+    QCOMPARE(requestId, quint64(1));
+    QTRY_COMPARE(pageRenderedSpy.count(), 1);
+    QCOMPARE(pageRenderedSpy[0][0].toInt(), 0);
+    QCOMPARE(pageRenderedSpy[0][1].toSize(), imageSize);
+    QCOMPARE(pageRenderedSpy[0][2].value<QImage>().size(), imageSize);
+    QCOMPARE(pageRenderedSpy[0][4].toULongLong(), requestId);
+}
+
+void tst_QPdfPageRenderer::withLoadedDocumentMultiThreaded()
+{
+    QPdfDocument document;
+
+    QPdfPageRenderer pageRenderer;
+    pageRenderer.setDocument(&document);
+    pageRenderer.setRenderMode(QPdfPageRenderer::MultiThreadedRenderMode);
+
+    QCOMPARE(document.load(QFINDTESTDATA("pdf-sample.pagerenderer.pdf")), QPdfDocument::NoError);
+
+    QSignalSpy pageRenderedSpy(&pageRenderer, &QPdfPageRenderer::pageRendered);
+
+    const QSize imageSize(100, 100);
+    const quint64 requestId = pageRenderer.requestPage(0, imageSize);
+
+    QCOMPARE(requestId, quint64(1));
+    QTRY_COMPARE(pageRenderedSpy.count(), 1);
+    QCOMPARE(pageRenderedSpy[0][0].toInt(), 0);
+    QCOMPARE(pageRenderedSpy[0][1].toSize(), imageSize);
+    QCOMPARE(pageRenderedSpy[0][2].value<QImage>().size(), imageSize);
+    QCOMPARE(pageRenderedSpy[0][4].toULongLong(), requestId);
+}
+
+void tst_QPdfPageRenderer::switchingRenderMode()
+{
+    QPdfDocument document;
+    QPdfPageRenderer pageRenderer;
+    pageRenderer.setDocument(&document);
+
+    QCOMPARE(document.load(QFINDTESTDATA("pdf-sample.pagerenderer.pdf")), QPdfDocument::NoError);
+
+    QSignalSpy pageRenderedSpy(&pageRenderer, &QPdfPageRenderer::pageRendered);
+
+    // render single threaded
+    const QSize imageSize(100, 100);
+    const quint64 firstRequestId = pageRenderer.requestPage(0, imageSize);
+
+    QTRY_COMPARE(pageRenderedSpy.count(), 1);
+    QCOMPARE(pageRenderedSpy[0][0].toInt(), 0);
+    QCOMPARE(pageRenderedSpy[0][1].toSize(), imageSize);
+    QCOMPARE(pageRenderedSpy[0][2].value<QImage>().size(), imageSize);
+    QCOMPARE(pageRenderedSpy[0][4].toULongLong(), firstRequestId);
+
+    const QImage image = pageRenderedSpy[0][2].value<QImage>();
+
+    pageRenderedSpy.clear();
+
+    // switch to multi threaded
+    pageRenderer.setRenderMode(QPdfPageRenderer::MultiThreadedRenderMode);
+
+    const quint64 secondRequestId = pageRenderer.requestPage(0, imageSize);
+
+    QVERIFY(firstRequestId != secondRequestId);
+    QTRY_COMPARE(pageRenderedSpy.count(), 1);
+    QCOMPARE(pageRenderedSpy[0][0].toInt(), 0);
+    QCOMPARE(pageRenderedSpy[0][1].toSize(), imageSize);
+    QCOMPARE(pageRenderedSpy[0][2].value<QImage>(), image);
+    QCOMPARE(pageRenderedSpy[0][2].value<QImage>().size(), imageSize);
+    QCOMPARE(pageRenderedSpy[0][4].toULongLong(), secondRequestId);
+
+    pageRenderedSpy.clear();
+
+    // switch back to single threaded
+    pageRenderer.setRenderMode(QPdfPageRenderer::SingleThreadedRenderMode);
+
+    const quint64 thirdRequestId = pageRenderer.requestPage(0, imageSize);
+
+    QTRY_COMPARE(pageRenderedSpy.count(), 1);
+    QCOMPARE(pageRenderedSpy[0][0].toInt(), 0);
+    QCOMPARE(pageRenderedSpy[0][1].toSize(), imageSize);
+    QCOMPARE(pageRenderedSpy[0][2].value<QImage>(), image);
+    QCOMPARE(pageRenderedSpy[0][2].value<QImage>().size(), imageSize);
+    QCOMPARE(pageRenderedSpy[0][4].toULongLong(), thirdRequestId);
+}
+
+QTEST_MAIN(tst_QPdfPageRenderer)
+
+#include "tst_qpdfpagerenderer.moc"