DocDiff application: basic functionality, opening documents

Pdf4QtDocDiff/mainwindow.cpp

@@ -21,24 +21,47 @@
 #include "aboutdialog.h"
 
 #include "pdfwidgetutils.h"
+#include "pdfdocumentreader.h"
 
 #include <QToolBar>
 #include <QDesktopWidget>
 #include <QDesktopServices>
+#include <QMessageBox>
+#include <QInputDialog>
+#include <QFileDialog>
 
 namespace pdfdocdiff
 {
 
 MainWindow::MainWindow(QWidget* parent) :
     QMainWindow(parent),
-    ui(new Ui::MainWindow)
+    ui(new Ui::MainWindow),
+    m_progress(new pdf::PDFProgress(this)),
+    m_taskbarButton(new QWinTaskbarButton(this)),
+    m_progressTaskbarIndicator(nullptr),
+    m_diff(nullptr),
+    m_isChangingProgressStep(false),
+    m_dontDisplayErrorMessage(false)
 {
     ui->setupUi(this);
 
     setMinimumSize(pdf::PDFWidgetUtils::scaleDPI(this, QSize(800, 600)));
 
+    // Initialize task bar progress
+    m_progressTaskbarIndicator = m_taskbarButton->progress();
+
     ui->actionGet_Source->setData(int(Operation::GetSource));
     ui->actionAbout->setData(int(Operation::About));
+    ui->actionOpen_Left->setData(int(Operation::OpenLeft));
+    ui->actionOpen_Right->setData(int(Operation::OpenRight));
+    ui->actionCompare->setData(int(Operation::Compare));
+    ui->actionClose->setData(int(Operation::Close));
+
+    QToolBar* mainToolbar = addToolBar(tr("Main"));
+    mainToolbar->setObjectName("main_toolbar");
+    mainToolbar->addActions({ ui->actionOpen_Left, ui->actionOpen_Right });
+    mainToolbar->addSeparator();
+    mainToolbar->addAction(ui->actionCompare);
 
     QSize iconSize = pdf::PDFWidgetUtils::scaleDPI(this, QSize(24, 24));
     auto toolbars = findChildren<QToolBar*>();
@@ -61,6 +84,14 @@ MainWindow::MainWindow(QWidget* parent) :
         }
     }
 
+    connect(m_progress, &pdf::PDFProgress::progressStarted, this, &MainWindow::onProgressStarted);
+    connect(m_progress, &pdf::PDFProgress::progressStep, this, &MainWindow::onProgressStep);
+    connect(m_progress, &pdf::PDFProgress::progressFinished, this, &MainWindow::onProgressFinished);
+
+    m_diff.setProgress(m_progress);
+    m_diff.setOption(pdf::PDFDiff::Asynchronous, true);
+    connect(&m_diff, &pdf::PDFDiff::comparationFinished, this, &MainWindow::onComparationFinished);
+
     m_diff.setLeftDocument(&m_leftDocument);
     m_diff.setRightDocument(&m_rightDocument);
 
@@ -74,11 +105,32 @@ MainWindow::~MainWindow()
     delete ui;
 }
 
+void MainWindow::showEvent(QShowEvent* event)
+{
+    Q_UNUSED(event);
+    m_taskbarButton->setWindow(windowHandle());
+}
+
+void MainWindow::closeEvent(QCloseEvent* event)
+{
+    BaseClass::closeEvent(event);
+    m_diff.stop();
+}
+
 void MainWindow::onMappedActionTriggered(int actionId)
 {
     performOperation(static_cast<Operation>(actionId));
 }
 
+void MainWindow::onComparationFinished()
+{
+    auto result = m_diff.getResult().getResult();
+    if (!result && !m_dontDisplayErrorMessage)
+    {
+        QMessageBox::critical(this, tr("Error"), result.getErrorMessage());
+    }
+}
+
 void MainWindow::updateActions()
 {
     QList<QAction*> actions = findChildren<QAction*>();
@@ -138,6 +190,10 @@ bool MainWindow::canPerformOperation(Operation operation) const
 {
     switch (operation)
     {
+        case Operation::OpenLeft:
+        case Operation::OpenRight:
+        case Operation::Compare:
+        case Operation::Close:
         case Operation::GetSource:
         case Operation::About:
             return true;
@@ -154,9 +210,103 @@ void MainWindow::performOperation(Operation operation)
 {
     switch (operation)
     {
+        case Operation::OpenLeft:
+        {
+            pdf::PDFTemporaryValueChange guard(&m_dontDisplayErrorMessage, true);
+            m_diff.stop();
+
+            std::optional<pdf::PDFDocument> document = openDocument();
+            if (document)
+            {
+                m_leftDocument = std::move(*document);
+
+                const size_t pageCount = m_leftDocument.getCatalog()->getPageCount();
+                if (pageCount > 1)
+                {
+                    ui->leftPageSelectionEdit->setText(QString("1-%2").arg(pageCount));
+                }
+                else if (pageCount == 1)
+                {
+                    ui->leftPageSelectionEdit->setText("1");
+                }
+                else
+                {
+                    ui->leftPageSelectionEdit->clear();
+                }
+            }
+            break;
+        }
+
+        case Operation::OpenRight:
+        {
+            pdf::PDFTemporaryValueChange guard(&m_dontDisplayErrorMessage, true);
+            m_diff.stop();
+
+            std::optional<pdf::PDFDocument> document = openDocument();
+            if (document)
+            {
+                m_rightDocument = std::move(*document);
+
+                const size_t pageCount = m_rightDocument.getCatalog()->getPageCount();
+                if (pageCount > 1)
+                {
+                    ui->rightPageSelectionEdit->setText(QString("1-%2").arg(pageCount));
+                }
+                else if (pageCount == 1)
+                {
+                    ui->rightPageSelectionEdit->setText("1");
+                }
+                else
+                {
+                    ui->rightPageSelectionEdit->clear();
+                }
+            }
+            break;
+        }
+
+        case Operation::Compare:
+        {
+            pdf::PDFTemporaryValueChange guard(&m_dontDisplayErrorMessage, true);
+            m_diff.stop();
+
+            QString errorMessage;
+
+            pdf::PDFClosedIntervalSet rightPageIndices;
+            pdf::PDFClosedIntervalSet leftPageIndices = pdf::PDFClosedIntervalSet::parse(1, qMax<pdf::PDFInteger>(1, m_leftDocument.getCatalog()->getPageCount()), ui->leftPageSelectionEdit->text(), &errorMessage);
+
+            if (errorMessage.isEmpty())
+            {
+                rightPageIndices = pdf::PDFClosedIntervalSet::parse(1, qMax<pdf::PDFInteger>(1, m_rightDocument.getCatalog()->getPageCount()), ui->rightPageSelectionEdit->text(), &errorMessage);
+            }
+
+            // Check if pages are succesfully parsed
+            if (!errorMessage.isEmpty())
+            {
+                QMessageBox::critical(this, tr("Error"), errorMessage);
+                break;
+            }
+
+            leftPageIndices.translate(-1);
+            rightPageIndices.translate(-1);
+
+            m_diff.setPagesForLeftDocument(std::move(leftPageIndices));
+            m_diff.setPagesForRightDocument(std::move(rightPageIndices));
+
+            m_diff.start();
+            break;
+        }
+
+        case Operation::Close:
+        {
+            close();
+            break;
+        }
+
         case Operation::GetSource:
+        {
             QDesktopServices::openUrl(QUrl("https://github.com/JakubMelka/PDF4QT"));
             break;
+        }
 
         case Operation::About:
         {
@@ -174,4 +324,63 @@ void MainWindow::performOperation(Operation operation)
     updateActions();
 }
 
+std::optional<pdf::PDFDocument> MainWindow::openDocument()
+{
+    QString fileName = QFileDialog::getOpenFileName(this, tr("Select PDF document"), m_settings.directory, tr("PDF document (*.pdf)"));
+    if (fileName.isEmpty())
+    {
+        return std::nullopt;
+    }
+
+    auto queryPassword = [this](bool* ok)
+    {
+        *ok = false;
+        return QInputDialog::getText(this, tr("Encrypted document"), tr("Enter password to access document content"), QLineEdit::Password, QString(), ok);
+    };
+
+    // Mark current directory as this
+    QFileInfo fileInfo(fileName);
+    m_settings.directory = fileInfo.dir().absolutePath();
+
+    // Try to open a new document
+    pdf::PDFDocumentReader reader(nullptr, qMove(queryPassword), true, false);
+    pdf::PDFDocument document = reader.readFromFile(fileName);
+
+    QString errorMessage = reader.getErrorMessage();
+    pdf::PDFDocumentReader::Result result = reader.getReadingResult();
+    if (result == pdf::PDFDocumentReader::Result::OK)
+    {
+        return document;
+    }
+    else if (result == pdf::PDFDocumentReader::Result::Failed)
+    {
+        QMessageBox::critical(this, tr("Error"), errorMessage);
+    }
+
+    return pdf::PDFDocument();
+}
+
+void MainWindow::onProgressStarted(pdf::ProgressStartupInfo info)
+{
+    m_progressTaskbarIndicator->setRange(0, 100);
+    m_progressTaskbarIndicator->reset();
+    m_progressTaskbarIndicator->show();
+}
+
+void MainWindow::onProgressStep(int percentage)
+{
+    if (m_isChangingProgressStep)
+    {
+        return;
+    }
+
+    pdf::PDFTemporaryValueChange guard(&m_isChangingProgressStep, true);
+    m_progressTaskbarIndicator->setValue(percentage);
+}
+
+void MainWindow::onProgressFinished()
+{
+    m_progressTaskbarIndicator->hide();
+}
+
 }   // namespace pdfdocdiff

Pdf4QtDocDiff/mainwindow.h

@@ -23,6 +23,8 @@
 
 #include <QMainWindow>
 #include <QSignalMapper>
+#include <QWinTaskbarButton>
+#include <QWinTaskbarProgress>
 
 namespace Ui
 {
@@ -36,21 +38,36 @@ class MainWindow : public QMainWindow
 {
     Q_OBJECT
 
+private:
+    using BaseClass = QMainWindow;
+
 public:
     explicit MainWindow(QWidget* parent);
     virtual ~MainWindow() override;
 
     enum class Operation
     {
+        OpenLeft,
+        OpenRight,
+        Compare,
+        Close,
         GetSource,
         About
     };
 
+    virtual void showEvent(QShowEvent* event) override;
+    virtual void closeEvent(QCloseEvent* event) override;
+
 private slots:
     void updateActions();
 
 private:
     void onMappedActionTriggered(int actionId);
+    void onComparationFinished();
+
+    void onProgressStarted(pdf::ProgressStartupInfo info);
+    void onProgressStep(int percentage);
+    void onProgressFinished();
 
     void loadSettings();
     void saveSettings();
@@ -58,6 +75,8 @@ private:
     bool canPerformOperation(Operation operation) const;
     void performOperation(Operation operation);
 
+    std::optional<pdf::PDFDocument> openDocument();
+
     struct Settings
     {
         QString directory;
@@ -65,9 +84,15 @@ private:
 
     Ui::MainWindow* ui;
 
+    pdf::PDFProgress* m_progress;
+    QWinTaskbarButton* m_taskbarButton;
+    QWinTaskbarProgress* m_progressTaskbarIndicator;
+
     Settings m_settings;
     QSignalMapper m_mapper;
     pdf::PDFDiff m_diff;
+    bool m_isChangingProgressStep;
+    bool m_dontDisplayErrorMessage;
 
     pdf::PDFDocument m_leftDocument;
     pdf::PDFDocument m_rightDocument;

Pdf4QtDocDiff/mainwindow.ui

@@ -81,6 +81,9 @@
     <property name="title">
      <string>File</string>
     </property>
+    <addaction name="actionOpen_Left"/>
+    <addaction name="actionOpen_Right"/>
+    <addaction name="actionClose"/>
    </widget>
    <widget class="QMenu" name="menuHelp">
     <property name="title">
@@ -94,15 +97,22 @@
      <string>Toolbars</string>
     </property>
    </widget>
+   <widget class="QMenu" name="menuCompare">
+    <property name="title">
+     <string>Compare</string>
+    </property>
+    <addaction name="actionCompare"/>
+   </widget>
    <addaction name="menuFile"/>
+   <addaction name="menuCompare"/>
    <addaction name="menuToolbars"/>
    <addaction name="menuHelp"/>
   </widget>
   <widget class="QStatusBar" name="statusbar"/>
   <action name="actionGet_Source">
    <property name="icon">
-    <iconset>
+    <iconset resource="resources.qrc">
-     <normaloff>:/pdfdocpage/resources/get-source.svg</normaloff>:/pdfdocpage/resources/get-source.svg</iconset>
+     <normaloff>:/pdfdocdiff/resources/get-source.svg</normaloff>:/pdfdocdiff/resources/get-source.svg</iconset>
    </property>
    <property name="text">
     <string>Get Source</string>
@@ -110,8 +120,8 @@
   </action>
   <action name="actionAbout">
    <property name="icon">
-    <iconset>
+    <iconset resource="resources.qrc">
-     <normaloff>:/pdfdocpage/resources/about.svg</normaloff>:/pdfdocpage/resources/about.svg</iconset>
+     <normaloff>:/pdfdocdiff/resources/about.svg</normaloff>:/pdfdocdiff/resources/about.svg</iconset>
    </property>
    <property name="text">
     <string>About</string>
@@ -120,7 +130,51 @@
     <string>F1</string>
    </property>
   </action>
+  <action name="actionOpen_Left">
+   <property name="icon">
+    <iconset resource="resources.qrc">
+     <normaloff>:/pdfdocdiff/resources/open-left.svg</normaloff>:/pdfdocdiff/resources/open-left.svg</iconset>
+   </property>
+   <property name="text">
+    <string>Open Left</string>
+   </property>
+  </action>
+  <action name="actionOpen_Right">
+   <property name="icon">
+    <iconset resource="resources.qrc">
+     <normaloff>:/pdfdocdiff/resources/open-right.svg</normaloff>:/pdfdocdiff/resources/open-right.svg</iconset>
+   </property>
+   <property name="text">
+    <string>Open Right</string>
+   </property>
+  </action>
+  <action name="actionCompare">
+   <property name="icon">
+    <iconset resource="resources.qrc">
+     <normaloff>:/pdfdocdiff/resources/compare.svg</normaloff>:/pdfdocdiff/resources/compare.svg</iconset>
+   </property>
+   <property name="text">
+    <string>Compare</string>
+   </property>
+   <property name="shortcut">
+    <string>F5</string>
+   </property>
+  </action>
+  <action name="actionClose">
+   <property name="icon">
+    <iconset resource="resources.qrc">
+     <normaloff>:/pdfdocdiff/resources/close.svg</normaloff>:/pdfdocdiff/resources/close.svg</iconset>
+   </property>
+   <property name="text">
+    <string>Close</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+F4</string>
+   </property>
+  </action>
  </widget>
- <resources/>
+ <resources>
+  <include location="resources.qrc"/>
+ </resources>
  <connections/>
 </ui>

Pdf4QtDocDiff/resources.qrc

@@ -1,5 +1,10 @@
 <RCC>
     <qresource prefix="/pdfdocdiff">
         <file>resources/about.svg</file>
+        <file>resources/close.svg</file>
+        <file>resources/compare.svg</file>
+        <file>resources/get-source.svg</file>
+        <file>resources/open-left.svg</file>
+        <file>resources/open-right.svg</file>
     </qresource>
 </RCC>

Pdf4QtDocDiff/resources/close.svg

@@ -0,0 +1,108 @@
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+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   width="30mm"
+   height="30mm"
+   viewBox="0 0 30 30"
+   version="1.1"
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+        <dc:title></dc:title>
+        <dc:creator>
+          <cc:Agent>
+            <dc:title>Jakub Melka</dc:title>
+          </cc:Agent>
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Pdf4QtDocDiff/resources/compare.svg

@@ -0,0 +1,108 @@
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+        <dc:title></dc:title>
+        <dc:creator>
+          <cc:Agent>
+            <dc:title>Jakub Melka</dc:title>
+          </cc:Agent>
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+        <cc:requires
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+        <cc:permits
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Pdf4QtDocDiff/resources/get-source.svg

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+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
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+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
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Pdf4QtDocDiff/resources/open-left.svg

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+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
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Pdf4QtDocDiff/resources/open-right.svg

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+<!-- Created with Inkscape (http://www.inkscape.org/) -->
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+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
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+   viewBox="0 0 30 30"
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+     bordercolor="#666666"
+     borderopacity="1.0"
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+     inkscape:document-units="mm"
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+        <cc:requires
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Pdf4QtLib/sources/pdfdiff.cpp

@@ -16,23 +16,34 @@
 //    along with PDF4QT.  If not, see <https://www.gnu.org/licenses/>.
 
 #include "pdfdiff.h"
+#include "pdfdocumenttextflow.h"
+
+#include <QtConcurrent/QtConcurrent>
 
 namespace pdf
 {
 
 PDFDiff::PDFDiff(QObject* parent) :
     BaseClass(parent),
+    m_progress(nullptr),
     m_leftDocument(nullptr),
-    m_rightDocument(nullptr)
+    m_rightDocument(nullptr),
+    m_options(Asynchronous),
+    m_cancelled(false)
 {
 
 }
 
+PDFDiff::~PDFDiff()
+{
+    stop();
+}
+
 void PDFDiff::setLeftDocument(const PDFDocument* leftDocument)
 {
     if (m_leftDocument != leftDocument)
     {
-        clear();
+        stop();
         m_leftDocument = leftDocument;
     }
 }
@@ -41,15 +52,147 @@ void PDFDiff::setRightDocument(const PDFDocument* rightDocument)
 {
     if (m_rightDocument != rightDocument)
     {
-        clear();
+        stop();
         m_rightDocument = rightDocument;
     }
 }
 
-void PDFDiff::clear()
+void PDFDiff::setPagesForLeftDocument(PDFClosedIntervalSet pagesForLeftDocument)
 {
-    stopEngine();
+    stop();
+    m_pagesForLeftDocument = std::move(pagesForLeftDocument);
 }
 
+void PDFDiff::setPagesForRightDocument(PDFClosedIntervalSet pagesForRightDocument)
+{
+    stop();
+    m_pagesForRightDocument = std::move(pagesForRightDocument);
+}
+
+void PDFDiff::start()
+{
+    // Jakub Melka: First, we must ensure, that comparation
+    // process is finished, otherwise we must wait for end.
+    // Then, create a new future watcher.
+    stop();
+
+    m_cancelled = false;
+
+    if (m_options.testFlag(Asynchronous))
+    {
+        m_futureWatcher = std::nullopt;
+        m_futureWatcher.emplace();
+
+        m_future = QtConcurrent::run(std::bind(&PDFDiff::perform, this));
+        connect(&*m_futureWatcher, &QFutureWatcher<PDFDiffResult>::finished, this, &PDFDiff::onComparationPerformed);
+        m_futureWatcher->setFuture(m_future);
+    }
+    else
+    {
+        // Just do comparation immediately
+        m_result = perform();
+        emit comparationFinished();
+    }
+}
+
+void PDFDiff::stop()
+{
+    if (m_futureWatcher && !m_futureWatcher->isFinished())
+    {
+        // Do stop only if process doesn't finished already.
+        // If we are finished, we do not want to set cancelled state.
+        m_cancelled = true;
+        m_futureWatcher->waitForFinished();
+    }
+}
+
+PDFDiffResult PDFDiff::perform()
+{
+    PDFDiffResult result;
+
+    if (!m_leftDocument || !m_rightDocument)
+    {
+        result.setResult(tr("No document to be compared."));
+        return result;
+    }
+
+    if (m_pagesForLeftDocument.isEmpty() || m_pagesForRightDocument.isEmpty())
+    {
+        result.setResult(tr("No page to be compared."));
+        return result;
+    }
+
+    auto leftPages = m_pagesForLeftDocument.unfold();
+    auto rightPages = m_pagesForRightDocument.unfold();
+
+    const size_t leftDocumentPageCount = m_leftDocument->getCatalog()->getPageCount();
+    const size_t rightDocumentPageCount = m_rightDocument->getCatalog()->getPageCount();
+
+    if (leftPages.front() < 0 ||
+        leftPages.back() >= PDFInteger(leftDocumentPageCount) ||
+        rightPages.front() < 0 ||
+        rightPages.back() >= PDFInteger(rightDocumentPageCount))
+    {
+        result.setResult(tr("Invalid page range."));
+        return result;
+    }
+
+    if (m_progress)
+    {
+        ProgressStartupInfo info;
+        info.showDialog = false;
+        info.text = tr("");
+        m_progress->start(StepLast, std::move(info));
+    }
+
+    // StepExtractContentLeftDocument
+    stepProgress();
+
+    // StepExtractContentRightDocument
+    stepProgress();
+
+    // StepExtractTextLeftDocument
+    pdf::PDFDocumentTextFlowFactory factoryLeftDocumentTextFlow;
+    factoryLeftDocumentTextFlow.setCalculateBoundingBoxes(true);
+    PDFDocumentTextFlow leftTextFlow = factoryLeftDocumentTextFlow.create(m_leftDocument, leftPages, PDFDocumentTextFlowFactory::Algorithm::Auto);
+    stepProgress();
+
+    // StepExtractTextRightDocument
+    pdf::PDFDocumentTextFlowFactory factoryRightDocumentTextFlow;
+    factoryRightDocumentTextFlow.setCalculateBoundingBoxes(true);
+    PDFDocumentTextFlow rightTextFlow = factoryRightDocumentTextFlow.create(m_rightDocument, rightPages, PDFDocumentTextFlowFactory::Algorithm::Auto);
+    stepProgress();
+
+    // StepCompare
+    stepProgress();
+
+    if (m_progress)
+    {
+        m_progress->finish();
+    }
+
+    return result;
+}
+
+void PDFDiff::stepProgress()
+{
+    if (m_progress)
+    {
+        m_progress->step();
+    }
+}
+
+void PDFDiff::onComparationPerformed()
+{
+    m_cancelled = false;
+    m_result = m_future.result();
+    emit comparationFinished();
+}
+
+PDFDiffResult::PDFDiffResult() :
+    m_result(true)
+{
+
+}
 
 }   // namespace pdf

Pdf4QtLib/sources/pdfdiff.h

@@ -19,14 +19,32 @@
 #define PDFDIFF_H
 
 #include "pdfdocument.h"
+#include "pdfprogress.h"
+#include "pdfutils.h"
 
 #include <QObject>
+#include <QFuture>
+#include <QFutureWatcher>
+
+#include <atomic>
 
 namespace pdf
 {
 
+class PDFDiffResult
+{
+public:
+    explicit PDFDiffResult();
+
+    void setResult(PDFOperationResult result) { m_result = std::move(result); }
+    const PDFOperationResult& getResult() const { return m_result; }
+
+private:
+    PDFOperationResult m_result;
+};
+
 /// Diff engine for comparing two pdf documents.
-class PDFDiff : public QObject
+class PDF4QTLIBSHARED_EXPORT PDFDiff : public QObject
 {
     Q_OBJECT
 
@@ -35,19 +53,84 @@ private:
 
 public:
     explicit PDFDiff(QObject* parent);
+    virtual ~PDFDiff() override;
 
+    enum Option
+    {
+        None            = 0x0000,
+        Asynchronous    = 0x0001,   ///< Compare document asynchronously
+    };
+    Q_DECLARE_FLAGS(Options, Option)
+
+    /// Source document (left)
+    /// \param leftDocument Document
     void setLeftDocument(const PDFDocument* leftDocument);
+
+    /// Source document (right)(
+    /// \param rightDocument Document
     void setRightDocument(const PDFDocument* rightDocument);
 
-    /// Clears data (but not source document pointers,
+    /// Source pages to be compared (left document)
-    /// for them, use setters), also stops comparing engine.
+    /// \param pagesForLeftDocument Page indices
-    void clear();
+    void setPagesForLeftDocument(PDFClosedIntervalSet pagesForLeftDocument);
+
+    /// Source pages to be compared (right document)
+    /// \param pagesForRightDocument Page indices
+    void setPagesForRightDocument(PDFClosedIntervalSet pagesForRightDocument);
+
+    /// Sets progress object
+    /// \param progress Progress object
+    void setProgress(PDFProgress* progress) { m_progress = progress; }
+
+    /// Enables or disables comparator engine option
+    /// \param option Option
+    /// \param enable Enable or disable option?
+    void setOption(Option option, bool enable) { m_options.setFlag(option, enable); }
+
+    /// Starts comparator engine. If asynchronous engine option
+    /// is enabled, then separate thread is started, in which two
+    /// document is compared, and then signal \p comparationFinished,
+    /// otherwise this function is blocking until comparation process
+    /// is finished.
+    void start();
+
+    /// Stops comparator engine. Result data are cleared.
+    void stop();
+
+    /// Returns result of a comparation process
+    const PDFDiffResult& getResult() const { return m_result; }
+
+signals:
+    void comparationFinished();
 
 private:
-    void stopEngine();
 
+    enum Steps
+    {
+        StepExtractContentLeftDocument,
+        StepExtractContentRightDocument,
+        StepExtractTextLeftDocument,
+        StepExtractTextRightDocument,
+        StepCompare,
+        StepLast
+    };
+
+    PDFDiffResult perform();
+    void stepProgress();
+
+    void onComparationPerformed();
+
+    PDFProgress* m_progress;
     const PDFDocument* m_leftDocument;
     const PDFDocument* m_rightDocument;
+    PDFClosedIntervalSet m_pagesForLeftDocument;
+    PDFClosedIntervalSet m_pagesForRightDocument;
+    Options m_options;
+    std::atomic_bool m_cancelled;
+    PDFDiffResult m_result;
+
+    QFuture<PDFDiffResult> m_future;
+    std::optional<QFutureWatcher<PDFDiffResult>> m_futureWatcher;
 };
 
 }   // namespace pdf

Pdf4QtLib/sources/pdfutils.cpp

@@ -367,6 +367,15 @@ std::vector<PDFInteger> PDFClosedIntervalSet::unfold() const
     return result;
 }
 
+void PDFClosedIntervalSet::translate(PDFInteger offset)
+{
+    for (auto& interval : m_intervals)
+    {
+        interval.first += offset;
+        interval.second += offset;
+    }
+}
+
 PDFClosedIntervalSet PDFClosedIntervalSet::parse(PDFInteger first, PDFInteger last, const QString& text, QString* errorMessage)
 {
     PDFClosedIntervalSet result;

Pdf4QtLib/sources/pdfutils.h

@@ -694,6 +694,10 @@ public:
     /// Returns true, if interval set is empty
     bool isEmpty() const { return m_intervals.empty(); }
 
+    /// Translates interval set by a given offset
+    /// \param offset Offset
+    void translate(PDFInteger offset);
+
     /// Parses text into closed interval set, text should be in form "1,3,4,7,-11,12-,52-53,-",
     /// where 1,3,4,7 means single pages, -11 means range from \p first to 11, 12- means range
     /// from 12 to \p last, and 52-53 means closed interval [52, 53]. If text is not in this form,