Add QPdfPageNavigation class

The QPdfPageNavigation class encapsulates the logic of navigating
inside a QPdfDocument. It has the notion of a 'current' page and
provides slots to navigate to the previous/next page or jump
directly to a given page.
Additionally it provides properties to indicate whether there is
a previous or next page, relative to the current one.

Change-Id: I053f3c49ab4a70b2610b64d96d2c274c3d0f629b
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

3 files changed, 409 insertions, 1 deletions

diff --git a/src/pdf/pdf.pro b/src/pdf/pdf.pro
index 606a2cb36..319e24464 100644
--- a/src/pdf/pdf.pro
+++ b/src/pdf/pdf.pro
@@ -23,7 +23,8 @@ msvc {
 SOURCES += \
     jsbridge.cpp \
     qpdfbookmarkmodel.cpp \
-    qpdfdocument.cpp
+    qpdfdocument.cpp \
+    qpdfpagenavigation.cpp
 
 HEADERS += \
     qpdfbookmarkmodel.h \
@@ -31,4 +32,5 @@ HEADERS += \
     qpdfdocument_p.h \
     qpdfdocumentrenderoptions.h \
     qpdfnamespace.h \
+    qpdfpagenavigation.h \
     qtpdfglobal.h
diff --git a/src/pdf/qpdfpagenavigation.cpp b/src/pdf/qpdfpagenavigation.cpp
new file mode 100644
index 000000000..8eff89b38
--- /dev/null
+++ b/src/pdf/qpdfpagenavigation.cpp
@@ -0,0 +1,314 @@
+/****************************************************************************
+**
+** 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 "qpdfpagenavigation.h"
+
+#include "qpdfdocument.h"
+
+#include <private/qobject_p.h>
+
+#include <QPointer>
+
+QT_BEGIN_NAMESPACE
+
+class QPdfPageNavigationPrivate : public QObjectPrivate
+{
+public:
+    QPdfPageNavigationPrivate()
+        : QObjectPrivate()
+    {
+    }
+
+    void update()
+    {
+        Q_Q(QPdfPageNavigation);
+
+        const bool documentAvailable = m_document && m_document->status() == QPdfDocument::Ready;
+
+        if (documentAvailable) {
+            const int newPageCount = m_document->pageCount();
+            if (m_pageCount != newPageCount) {
+                m_pageCount = newPageCount;
+                emit q->pageCountChanged(m_pageCount);
+            }
+        } else {
+            if (m_pageCount != 0) {
+                m_pageCount = 0;
+                emit q->pageCountChanged(m_pageCount);
+            }
+        }
+
+        if (m_currentPage != 0) {
+            m_currentPage = 0;
+            emit q->currentPageChanged(m_currentPage);
+        }
+
+        updatePrevNext();
+    }
+
+    void updatePrevNext()
+    {
+        Q_Q(QPdfPageNavigation);
+
+        const bool hasPreviousPage = m_currentPage > 0;
+        const bool hasNextPage = m_currentPage < (m_pageCount - 1);
+
+        if (m_canGoToPreviousPage != hasPreviousPage) {
+            m_canGoToPreviousPage = hasPreviousPage;
+            emit q->canGoToPreviousPageChanged(m_canGoToPreviousPage);
+        }
+
+        if (m_canGoToNextPage != hasNextPage) {
+            m_canGoToNextPage = hasNextPage;
+            emit q->canGoToNextPageChanged(m_canGoToNextPage);
+        }
+    }
+
+    void documentStatusChanged()
+    {
+        update();
+    }
+
+    Q_DECLARE_PUBLIC(QPdfPageNavigation)
+
+    QPointer<QPdfDocument> m_document = nullptr;
+    int m_currentPage = 0;
+    int m_pageCount = 0;
+    bool m_canGoToPreviousPage = false;
+    bool m_canGoToNextPage = false;
+
+    QMetaObject::Connection m_documentStatusChangedConnection;
+};
+
+/*!
+    \class QPdfPageNavigation
+    \since 5.10
+    \inmodule QtPdf
+
+    \brief The QPdfPageNavigation class handles the navigation through a PDF document.
+
+    \sa QPdfDocument
+*/
+
+
+/*!
+    Constructs a page navigation object with parent object \a parent.
+*/
+QPdfPageNavigation::QPdfPageNavigation(QObject *parent)
+    : QObject(*new QPdfPageNavigationPrivate, parent)
+{
+}
+
+/*!
+    Destroys the page navigation object.
+*/
+QPdfPageNavigation::~QPdfPageNavigation()
+{
+}
+
+/*!
+    \property QPdfPageNavigation::document
+    \brief the document instance on which this object navigates
+
+    By default, this property is \c nullptr.
+
+    \sa document(), setDocument(), QPdfDocument
+*/
+
+/*!
+    Returns the document on which this object navigates, or a \c nullptr
+    if none has set before.
+
+    \sa QPdfDocument
+*/
+QPdfDocument* QPdfPageNavigation::document() const
+{
+    Q_D(const QPdfPageNavigation);
+
+    return d->m_document;
+}
+
+/*!
+    Sets the \a document this object navigates on.
+
+    After a new document has been set, the currentPage will be \c 0.
+
+    \sa QPdfDocument
+*/
+void QPdfPageNavigation::setDocument(QPdfDocument *document)
+{
+    Q_D(QPdfPageNavigation);
+
+    if (d->m_document == document)
+        return;
+
+    if (d->m_document)
+        disconnect(d->m_documentStatusChangedConnection);
+
+    d->m_document = document;
+    emit documentChanged(d->m_document);
+
+    if (d->m_document)
+        d->m_documentStatusChangedConnection = connect(d->m_document.data(), &QPdfDocument::statusChanged, this, [d](){ d->documentStatusChanged(); });
+
+    d->update();
+}
+
+/*!
+    \property QPdfPageNavigation::currentPage
+    \brief the current page number in the document
+
+    \sa currentPage(), setCurrentPage()
+*/
+
+/*!
+    Returns the current page number or \c 0 if there is no document set.
+
+    After a document has been loaded, the currentPage will always be \c 0.
+*/
+int QPdfPageNavigation::currentPage() const
+{
+    Q_D(const QPdfPageNavigation);
+
+    return d->m_currentPage;
+}
+
+/*!
+    \fn void QPdfPageNavigation::setCurrentPage(int page)
+
+    Sets the current \a page number.
+*/
+void QPdfPageNavigation::setCurrentPage(int newPage)
+{
+    Q_D(QPdfPageNavigation);
+
+    if (newPage < 0 || newPage >= d->m_pageCount)
+        return;
+
+    if (d->m_currentPage == newPage)
+        return;
+
+    d->m_currentPage = newPage;
+    emit currentPageChanged(d->m_currentPage);
+
+    d->updatePrevNext();
+}
+
+/*!
+    \property QPdfPageNavigation::pageCount
+    \brief the number of pages in the document
+
+    \sa pageCount()
+*/
+
+/*!
+    Returns the number of pages in the document or \c 0 if there
+    is no document set.
+*/
+int QPdfPageNavigation::pageCount() const
+{
+    Q_D(const QPdfPageNavigation);
+
+    return d->m_pageCount;
+}
+
+/*!
+    \property QPdfPageNavigation::canGoToPreviousPage
+    \brief whether there is a page before the current page
+
+    \sa canGoToPreviousPage(), goToPreviousPage()
+*/
+
+/*!
+    Returns whether there is a page before the current one.
+*/
+bool QPdfPageNavigation::canGoToPreviousPage() const
+{
+    Q_D(const QPdfPageNavigation);
+
+    return d->m_canGoToPreviousPage;
+}
+
+/*!
+    \property QPdfPageNavigation::canGoToNextPage
+    \brief whether there is a page after the current page
+
+    \sa canGoToNextPage(), goToNextPage()
+*/
+
+/*!
+    Returns whether there is a page after the current one.
+*/
+bool QPdfPageNavigation::canGoToNextPage() const
+{
+    Q_D(const QPdfPageNavigation);
+
+    return d->m_canGoToNextPage;
+}
+
+/*!
+    Changes the current page to the previous page.
+
+    If there is no previous page in the document, nothing happens.
+
+    \sa canGoToPreviousPage
+*/
+void QPdfPageNavigation::goToPreviousPage()
+{
+    Q_D(QPdfPageNavigation);
+
+    if (d->m_currentPage > 0)
+        setCurrentPage(d->m_currentPage - 1);
+}
+
+/*!
+    Changes the current page to the next page.
+
+    If there is no next page in the document, nothing happens.
+
+    \sa canGoToNextPage
+*/
+void QPdfPageNavigation::goToNextPage()
+{
+    Q_D(QPdfPageNavigation);
+
+    if (d->m_currentPage < d->m_pageCount - 1)
+        setCurrentPage(d->m_currentPage + 1);
+}
+
+QT_END_NAMESPACE
+
+#include "moc_qpdfpagenavigation.cpp"
diff --git a/src/pdf/qpdfpagenavigation.h b/src/pdf/qpdfpagenavigation.h
new file mode 100644
index 000000000..b3649fac6
--- /dev/null
+++ b/src/pdf/qpdfpagenavigation.h
@@ -0,0 +1,92 @@
+/****************************************************************************
+**
+** 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 QPDFPAGENAVIGATION_H
+#define QPDFPAGENAVIGATION_H
+
+#include "qtpdfglobal.h"
+
+#include <QObject>
+
+QT_BEGIN_NAMESPACE
+
+class QPdfDocument;
+class QPdfPageNavigationPrivate;
+
+class Q_PDF_EXPORT QPdfPageNavigation : public QObject
+{
+    Q_OBJECT
+
+    Q_PROPERTY(QPdfDocument* document READ document WRITE setDocument NOTIFY documentChanged)
+
+    Q_PROPERTY(int currentPage READ currentPage WRITE setCurrentPage NOTIFY currentPageChanged)
+    Q_PROPERTY(int pageCount READ pageCount NOTIFY pageCountChanged)
+    Q_PROPERTY(bool canGoToPreviousPage READ canGoToPreviousPage NOTIFY canGoToPreviousPageChanged)
+    Q_PROPERTY(bool canGoToNextPage READ canGoToNextPage NOTIFY canGoToNextPageChanged)
+
+public:
+    explicit QPdfPageNavigation(QObject *parent = nullptr);
+    ~QPdfPageNavigation();
+
+    QPdfDocument* document() const;
+    void setDocument(QPdfDocument *document);
+
+    int currentPage() const;
+    void setCurrentPage(int currentPage);
+
+    int pageCount() const;
+
+    bool canGoToPreviousPage() const;
+    bool canGoToNextPage() const;
+
+public Q_SLOTS:
+    void goToPreviousPage();
+    void goToNextPage();
+
+Q_SIGNALS:
+    void documentChanged(QPdfDocument *document);
+    void currentPageChanged(int currentPage);
+    void pageCountChanged(int pageCount);
+    void canGoToPreviousPageChanged(bool canGo);
+    void canGoToNextPageChanged(bool canGo);
+
+private:
+    Q_DECLARE_PRIVATE(QPdfPageNavigation)
+};
+
+QT_END_NAMESPACE
+
+#endif