PDF4QT/Pdf4QtLib/sources/pdfpagenavigation.cpp

//    Copyright (C) 2020-2021 Jakub Melka
//
//    This file is part of PDF4QT.
//
//    PDF4QT is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Lesser General Public License as published by
//    the Free Software Foundation, either version 3 of the License, or
//    with the written consent of the copyright owner, any later version.
//
//    PDF4QT is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU Lesser General Public License for more details.
//
//    You should have received a copy of the GNU Lesser General Public License
//    along with PDF4QT.  If not, see <https://www.gnu.org/licenses/>.

#include "pdfpagenavigation.h"

namespace pdf
{

PDFPageNavigation::PDFPageNavigation(const PDFDocument* document, QObject* parent) :
    QObject(parent),
    m_currentPageIndex(0),
    m_document(document)
{
    if (m_document && m_document->getCatalog()->getPageCount() > 0)
    {
        navigateToPage(0);
    }
}

void PDFPageNavigation::navigateToPage(size_t pageIndex)
{
    if (m_currentPageIndex == pageIndex)
    {
        // Jakub Melka: We are at the same page! Do nothing.
        return;
    }

    const bool isForward = pageIndex > m_currentPageIndex;
    const PDFObjectStorage* const storage = &m_document->getStorage();
    const PDFPage* page = m_document->getCatalog()->getPage(pageIndex);

    // We will perform steps as in PDF 2.0 specification, chapter 12.4.4.2
    // Step a) navigate to page and set current navigation node
    m_currentPageIndex = pageIndex;
    m_transition = PDFPageTransition::parse(storage, page->getTransition(storage));
    m_currentNavigationNode = PDFNavigationNode::parse(storage, page->getFirstSubpageNavigationNode(storage));

    // Step b) Execute initially page navigation node. If we are navigating forward,
    //         then "next" action should be executed and current node should be changed to next.
    //         If we are navigating backward, then "previous" action should be executed
    //         and current node should be changed to previous.
    executeNavigationNode(isForward ? Direction::Forward : Direction::Backward);

    // Step c) Navigate to new page - send navigation request.
    emit pageChangeRequest(m_currentPageIndex, &m_transition);
}

void PDFPageNavigation::navigateForward()
{
    if (m_currentNavigationNode)
    {
        executeNavigationNode(Direction::Forward);
    }
    else if (m_currentPageIndex + 1 < m_document->getCatalog()->getPageCount())
    {
        navigateToPage(m_currentPageIndex + 1);
    }
}

void PDFPageNavigation::navigateBackward()
{
    if (m_currentNavigationNode)
    {
        executeNavigationNode(Direction::Backward);
    }
    else if (m_currentPageIndex > 0)
    {
        navigateToPage(m_currentPageIndex - 1);
    }
}

void PDFPageNavigation::executeNavigationNode(Direction direction)
{
    if (!m_currentNavigationNode)
    {
        return;
    }

    // We will make a copy of object, because this object can change,
    // when actions are executed.
    PDFNavigationNode copy = *m_currentNavigationNode;
    m_currentNavigationNode = PDFNavigationNode::parse(&m_document->getStorage(), m_document->getObjectByReference((direction == Direction::Forward) ? copy.getNextNode() : copy.getPreviousNode()));

    switch (direction)
    {
        case Direction::Forward:
        {
            if (const PDFAction* action = copy.getNextAction().get())
            {
                for (const PDFAction* currentAction : action->getActionList())
                {
                    emit actionTriggered(currentAction);
                }
            }
            break;
        }

        case Direction::Backward:
        {
            if (const PDFAction* action = copy.getPreviousAction().get())
            {
                for (const PDFAction* currentAction : action->getActionList())
                {
                    emit actionTriggered(currentAction);
                }
            }
            break;
        }

        default:
            Q_ASSERT(false);
            break;
    }
}

PDFActionPtr PDFNavigationNode::getPreviousAction() const
{
    return m_previousAction;
}

PDFActionPtr PDFNavigationNode::getNextAction() const
{
    return m_nextAction;
}

PDFObjectReference PDFNavigationNode::getPreviousNode() const
{
    return m_previousNode;
}

PDFObjectReference PDFNavigationNode::getNextNode() const
{
    return m_nextNode;
}

PDFReal PDFNavigationNode::getDuration() const
{
    return m_duration;
}

std::optional<PDFNavigationNode> PDFNavigationNode::parse(const PDFObjectStorage* storage, PDFObject object)
{
    std::optional<PDFNavigationNode> result;

    if (const PDFDictionary* dictionary = storage->getDictionaryFromObject(object))
    {
        PDFDocumentDataLoaderDecorator loader(storage);

        result = PDFNavigationNode();
        result->m_nextAction = PDFAction::parse(storage, dictionary->get("NA"));
        result->m_previousAction = PDFAction::parse(storage, dictionary->get("PA"));
        result->m_previousNode = loader.readReferenceFromDictionary(dictionary, "Prev");
        result->m_nextNode = loader.readReferenceFromDictionary(dictionary, "Next");
        result->m_duration = loader.readNumberFromDictionary(dictionary, "Dur", 0.0);
    }

    return result;
}

}   // namespace pdf