Move printing operation to a new thread

Printing operations were blocking the UI thread, so applications
were irresponsive when printing in large size or high resolution.
Introduce a new worker for the painting logic and use shared pointers
to carry the data around and avoid copying PDF data between threads.

Task-number: QTBUG-68561
Change-Id: I30633380b75acd14f1a1df87985c99540168a9f1
Reviewed-by: Michael Brüning <michael.bruning@qt.io>

1 files changed, 88 insertions, 0 deletions

diff --git a/src/webenginewidgets/printer_worker.h b/src/webenginewidgets/printer_worker.h
new file mode 100644
index 000000000..96025c90e
--- /dev/null
+++ b/src/webenginewidgets/printer_worker.h
@@ -0,0 +1,88 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtWebEngine module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** 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 https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://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.LGPL3 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-3.0.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 (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+//
+//  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.
+//
+
+#ifndef PRINTER_WORKER_H
+#define PRINTER_WORKER_H
+
+#include "qtwebenginecoreglobal_p.h"
+
+#include <QSharedPointer>
+
+QT_BEGIN_NAMESPACE
+class QPrinter;
+QT_END_NAMESPACE
+
+namespace QtWebEngineCore {
+
+class PrinterWorker : public QObject
+{
+    Q_OBJECT
+public:
+    PrinterWorker(QSharedPointer<QByteArray> data, QPrinter *printer);
+    virtual ~PrinterWorker();
+
+public Q_SLOTS:
+    void print();
+
+Q_SIGNALS:
+    void resultReady(bool success);
+
+private:
+    Q_DISABLE_COPY(PrinterWorker)
+
+    QSharedPointer<QByteArray> m_data;
+    QPrinter *m_printer;
+};
+
+} // namespace QtWebEngineCore
+
+Q_DECLARE_METATYPE(QtWebEngineCore::PrinterWorker*)
+
+#endif // PRINTER_WORKER_H