Add a QImageIOHandler to render PDF with QtQuick Image

Now you can use Image in QML to display the first page of a PDF file
by default. (The implementation is very similar to the handler
plugin in the QtSVG module.) To display other pages, you can set
the new currentFrame property that is being added to Image in 5.14.

QPdfIOHandler uses its own instance of QPdfDocument to do the rendering.
An instance will be created each time the image needs to read a frame
from the file (on creation; each time the currentFrame property
is changed; each time sourceSize is changed to require a different
resolution rendering). This approach is not as efficient as it would
be to share the QPdfDocument instance among multiple Images that are
rendering different pages at the same time, as well as sharing with the
QML Document declaration that we plan to add. However, if you set
asynchronous: true, each Image will render its page from the PDF in
its own thread. PDFium is not thread-safe, so sharing the QPdfDocument
among multiple threads is not safe. It may be possible to make it safe
by having a dedicated PDF-rendering thread, but that is not yet done
in this patch.

Change-Id: I7a1f8cd7bd5b8f93d45fa9350752b2d9356b04fe
Reviewed-by: Michal Klocek <michal.klocek@qt.io>

7 files changed, 420 insertions, 1 deletions

diff --git a/src/plugins/imageformats/imageformats.pro b/src/plugins/imageformats/imageformats.pro
new file mode 100644
index 000000000..c3b9cb3a4
--- /dev/null
+++ b/src/plugins/imageformats/imageformats.pro
@@ -0,0 +1,2 @@
+TEMPLATE = subdirs
+SUBDIRS += pdf
diff --git a/src/plugins/imageformats/pdf/main.cpp b/src/plugins/imageformats/pdf/main.cpp
new file mode 100644
index 000000000..b4d59353c
--- /dev/null
+++ b/src/plugins/imageformats/pdf/main.cpp
@@ -0,0 +1,74 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** 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 "qpdfiohandler_p.h"
+
+QT_BEGIN_NAMESPACE
+
+class QPdfPlugin : public QImageIOPlugin
+{
+    Q_OBJECT
+    Q_PLUGIN_METADATA(IID QImageIOHandlerFactoryInterface_iid FILE "pdf.json")
+
+public:
+    Capabilities capabilities(QIODevice *device, const QByteArray &format) const override;
+    QImageIOHandler *create(QIODevice *device, const QByteArray &format = QByteArray()) const override;
+};
+
+QImageIOPlugin::Capabilities QPdfPlugin::capabilities(QIODevice *device, const QByteArray &format) const
+{
+    if (format == "pdf")
+        return Capabilities(CanRead);
+    if (!format.isEmpty())
+        return {};
+
+    Capabilities cap;
+    if (device->isReadable() && QPdfIOHandler::canRead(device))
+        cap |= CanRead;
+    return cap;
+}
+
+QImageIOHandler *QPdfPlugin::create(QIODevice *device, const QByteArray &format) const
+{
+    QPdfIOHandler *hand = new QPdfIOHandler();
+    hand->setDevice(device);
+    hand->setFormat(format);
+    return hand;
+}
+
+QT_END_NAMESPACE
+
+#include "main.moc"
diff --git a/src/plugins/imageformats/pdf/pdf.json b/src/plugins/imageformats/pdf/pdf.json
new file mode 100644
index 000000000..1f5268ca1
--- /dev/null
+++ b/src/plugins/imageformats/pdf/pdf.json
@@ -0,0 +1,4 @@
+{
+    "Keys": [ "pdf" ],
+    "MimeTypes": [ "application/pdf" ]
+}
diff --git a/src/plugins/imageformats/pdf/pdf.pro b/src/plugins/imageformats/pdf/pdf.pro
new file mode 100644
index 000000000..b820ae7d5
--- /dev/null
+++ b/src/plugins/imageformats/pdf/pdf.pro
@@ -0,0 +1,11 @@
+TARGET  = qpdf
+
+PLUGIN_TYPE = imageformats
+PLUGIN_EXTENDS = pdf
+PLUGIN_CLASS_NAME = QPdfPlugin
+load(qt_plugin)
+
+HEADERS += qpdfiohandler_p.h
+SOURCES += main.cpp \
+           qpdfiohandler.cpp
+QT += pdf
diff --git a/src/plugins/imageformats/pdf/qpdfiohandler.cpp b/src/plugins/imageformats/pdf/qpdfiohandler.cpp
new file mode 100644
index 000000000..9df85cf08
--- /dev/null
+++ b/src/plugins/imageformats/pdf/qpdfiohandler.cpp
@@ -0,0 +1,238 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** 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 "qpdfiohandler_p.h"
+#include <QLoggingCategory>
+#include <QPainter>
+
+QT_BEGIN_NAMESPACE
+
+Q_LOGGING_CATEGORY(qLcPdf, "qt.imageformat.pdf")
+
+QPdfIOHandler::QPdfIOHandler()
+{
+}
+
+bool QPdfIOHandler::canRead() const
+{
+    if (!device())
+        return false;
+    if (m_loaded)
+        return true;
+    if (QPdfIOHandler::canRead(device())) {
+        setFormat("pdf");
+        return true;
+    }
+    return false;
+}
+
+bool QPdfIOHandler::canRead(QIODevice *device)
+{
+    char buf[6];
+    device->peek(buf, 6);
+    return (!qstrncmp(buf, "%PDF-", 5) || Q_UNLIKELY(!qstrncmp(buf, "\012%PDF-", 6)));
+}
+
+int QPdfIOHandler::currentImageNumber() const
+{
+    return m_page;
+}
+
+QRect QPdfIOHandler::currentImageRect() const
+{
+    return QRect(QPoint(0, 0), m_doc.pageSize(m_page).toSize());
+}
+
+int QPdfIOHandler::imageCount() const
+{
+    int ret = 0;
+    if (const_cast<QPdfIOHandler *>(this)->load(device()))
+        ret = m_doc.pageCount();
+    qCDebug(qLcPdf) << "imageCount" << ret;
+    return ret;
+}
+
+QByteArray QPdfIOHandler::name() const
+{
+    return m_doc.metaData(QPdfDocument::MetaDataField::Title).toString().toLocal8Bit();
+}
+
+bool QPdfIOHandler::read(QImage *image)
+{
+    if (load(device())) {
+        if (m_page >= m_doc.pageCount())
+            return false;
+        if (m_page < 0)
+            m_page = 0;
+        const bool xform = (m_clipRect.isValid() || m_scaledSize.isValid() || m_scaledClipRect.isValid());
+        QSize finalSize = m_doc.pageSize(m_page).toSize();
+        QRectF bounds;
+        if (xform && !finalSize.isEmpty()) {
+            bounds = QRectF(QPointF(0,0), QSizeF(finalSize));
+            QPoint tr1, tr2;
+            QSizeF sc(1, 1);
+            if (m_clipRect.isValid()) {
+                tr1 = -m_clipRect.topLeft();
+                finalSize = m_clipRect.size();
+            }
+            if (m_scaledSize.isValid()) {
+                sc = QSizeF(qreal(m_scaledSize.width()) / finalSize.width(),
+                            qreal(m_scaledSize.height()) / finalSize.height());
+                finalSize = m_scaledSize;
+            }
+            if (m_scaledClipRect.isValid()) {
+                tr2 = -m_scaledClipRect.topLeft();
+                finalSize = m_scaledClipRect.size();
+            }
+            QTransform t;
+            t.translate(tr2.x(), tr2.y());
+            t.scale(sc.width(), sc.height());
+            t.translate(tr1.x(), tr1.y());
+            bounds = t.mapRect(bounds);
+        }
+        qCDebug(qLcPdf) << Q_FUNC_INFO << m_page << finalSize;
+        if (image->size() != finalSize || !image->reinterpretAsFormat(QImage::Format_ARGB32_Premultiplied)) {
+            *image = QImage(finalSize, QImage::Format_ARGB32_Premultiplied);
+            if (!finalSize.isEmpty() && image->isNull()) {
+                // avoid QTBUG-68229
+                qWarning("QPdfIOHandler: QImage allocation failed (size %i x %i)", finalSize.width(), finalSize.height());
+                return false;
+            }
+        }
+        if (!finalSize.isEmpty()) {
+            image->fill(m_backColor.rgba());
+            QPainter p(image);
+            QImage pageImage = m_doc.render(m_page, finalSize);
+            p.drawImage(0, 0, pageImage);
+            p.end();
+        }
+        return true;
+    }
+
+    return false;
+}
+
+QVariant QPdfIOHandler::option(ImageOption option) const
+{
+    switch (option) {
+    case ImageFormat:
+        return QImage::Format_ARGB32_Premultiplied;
+    case Size:
+        const_cast<QPdfIOHandler *>(this)->load(device());
+        return m_doc.pageSize(qMax(0, m_page));
+    case ClipRect:
+        return m_clipRect;
+    case ScaledSize:
+        return m_scaledSize;
+    case ScaledClipRect:
+        return m_scaledClipRect;
+    case BackgroundColor:
+        return m_backColor;
+    case Name:
+        return m_doc.metaData(QPdfDocument::Title);
+    default:
+        break;
+    }
+    return QVariant();
+}
+
+void QPdfIOHandler::setOption(ImageOption option, const QVariant & value)
+{
+    switch (option) {
+    case ClipRect:
+        m_clipRect = value.toRect();
+        break;
+    case ScaledSize:
+        m_scaledSize = value.toSize();
+        break;
+    case ScaledClipRect:
+        m_scaledClipRect = value.toRect();
+        break;
+    case BackgroundColor:
+        m_backColor = value.value<QColor>();
+        break;
+    default:
+        break;
+    }
+}
+
+bool QPdfIOHandler::supportsOption(ImageOption option) const
+{
+    switch (option)
+    {
+    case ImageFormat:
+    case Size:
+    case ClipRect:
+    case ScaledSize:
+    case ScaledClipRect:
+    case BackgroundColor:
+    case Name:
+        return true;
+    default:
+        break;
+    }
+    return false;
+}
+
+bool QPdfIOHandler::jumpToImage(int frame)
+{
+    qCDebug(qLcPdf) << Q_FUNC_INFO << frame;
+    if (frame < 0 || frame >= m_doc.pageCount())
+        return false;
+    m_page = frame;
+    return true;
+}
+
+bool QPdfIOHandler::jumpToNextImage()
+{
+    return jumpToImage(m_page + 1);
+}
+
+bool QPdfIOHandler::load(QIODevice *device)
+{
+    if (m_loaded)
+        return true;
+    if (format().isEmpty())
+        if (!canRead())
+            return false;
+
+    m_doc.load(device);
+    m_loaded = (m_doc.error() == QPdfDocument::DocumentError::NoError);
+
+    return m_loaded;
+}
+
+QT_END_NAMESPACE
diff --git a/src/plugins/imageformats/pdf/qpdfiohandler_p.h b/src/plugins/imageformats/pdf/qpdfiohandler_p.h
new file mode 100644
index 000000000..ca0a27581
--- /dev/null
+++ b/src/plugins/imageformats/pdf/qpdfiohandler_p.h
@@ -0,0 +1,89 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** 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 QPDFIOHANDLER_H
+#define QPDFIOHANDLER_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtGui/qimageiohandler.h>
+#include <QtPdf/QPdfDocument>
+
+QT_BEGIN_NAMESPACE
+
+class QPdfIOHandler : public QImageIOHandler
+{
+public:
+    QPdfIOHandler();
+    bool canRead() const override;
+    static bool canRead(QIODevice *device);
+    int currentImageNumber() const override;
+    QRect currentImageRect() const override;
+    int imageCount() const override;
+    QByteArray name() const override;
+    bool read(QImage *image) override;
+    QVariant option(ImageOption option) const override;
+    void setOption(ImageOption option, const QVariant & value) override;
+    bool supportsOption(ImageOption option) const override;
+    bool jumpToImage(int frame) override;
+    bool jumpToNextImage() override;
+
+private:
+    bool load(QIODevice *device);
+
+private:
+    QPdfDocument m_doc;
+    int m_page = -1;
+
+    QRect m_clipRect;
+    QSize m_scaledSize;
+    QRect m_scaledClipRect;
+    QColor m_backColor = Qt::transparent;
+    bool m_loaded = false;
+};
+
+QT_END_NAMESPACE
+
+#endif // QPDFIOHANDLER_H
diff --git a/src/plugins/plugins.pro b/src/plugins/plugins.pro
index 6698a9736..71c24e6c2 100644
--- a/src/plugins/plugins.pro
+++ b/src/plugins/plugins.pro
@@ -1,2 +1,3 @@
 TEMPLATE = subdirs
-qtHaveModule(designer): SUBDIRS += qwebengineview
+qtHaveModule(webengine-widgets): qtHaveModule(designer): SUBDIRS += qwebengineview
+qtHaveModule(pdf): qtConfig(imageformatplugin): SUBDIRS += imageformats