making clangd happy and making script to compile/build with run.sh

.gitignore

@@ -0,0 +1 @@
+build/

CMakeLists.txt

@@ -0,0 +1,25 @@
+# Copyright (C) 2022 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+cmake_minimum_required(VERSION 3.16)
+project(documentviewer LANGUAGES CXX)
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets
+             OPTIONAL_COMPONENTS PrintSupport Pdf PdfWidgets)
+
+qt_standard_project_setup()
+
+add_compile_definitions(QT_NO_CAST_FROM_ASCII)
+
+if(NOT DEFINED INSTALL_EXAMPLESDIR)
+    set(INSTALL_EXAMPLESDIR "examples")
+endif()
+
+if(TARGET Qt6::PrintSupport)
+    add_compile_definitions(QT_DOCUMENTVIEWER_PRINTSUPPORT)
+endif()
+
+set(INSTALL_EXAMPLEDIR "${INSTALL_EXAMPLESDIR}/demos/documentviewer")
+
+add_subdirectory(app)
+add_subdirectory(plugins)

CMakeLists.txt.user

@@ -0,0 +1,417 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE QtCreatorProject>
+<!-- Written by QtCreator 12.0.2, 2024-02-07T12:39:19. -->
+<qtcreator>
+ <data>
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+  <value type="qlonglong">0</value>
+ </data>
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+   <value type="bool" key="EditorConfiguration.AutoSpacesForTabs">false</value>
+   <value type="bool" key="EditorConfiguration.CamelCaseNavigation">true</value>
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+    <value type="QString" key="language">Cpp</value>
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+    </valuemap>
+   </valuemap>
+   <valuemap type="QVariantMap" key="EditorConfiguration.CodeStyle.1">
+    <value type="QString" key="language">QmlJS</value>
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+    </valuemap>
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+   <value type="bool" key="EditorConfiguration.KeyboardTooltips">false</value>
+   <value type="int" key="EditorConfiguration.MarginColumn">80</value>
+   <value type="bool" key="EditorConfiguration.MouseHiding">true</value>
+   <value type="bool" key="EditorConfiguration.MouseNavigation">true</value>
+   <value type="int" key="EditorConfiguration.PaddingMode">1</value>
+   <value type="int" key="EditorConfiguration.PreferAfterWhitespaceComments">0</value>
+   <value type="bool" key="EditorConfiguration.PreferSingleLineComments">false</value>
+   <value type="bool" key="EditorConfiguration.ScrollWheelZooming">true</value>
+   <value type="bool" key="EditorConfiguration.ShowMargin">false</value>
+   <value type="int" key="EditorConfiguration.SmartBackspaceBehavior">0</value>
+   <value type="bool" key="EditorConfiguration.SmartSelectionChanging">true</value>
+   <value type="bool" key="EditorConfiguration.SpacesForTabs">true</value>
+   <value type="int" key="EditorConfiguration.TabKeyBehavior">0</value>
+   <value type="int" key="EditorConfiguration.TabSize">8</value>
+   <value type="bool" key="EditorConfiguration.UseGlobal">true</value>
+   <value type="bool" key="EditorConfiguration.UseIndenter">false</value>
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+   <value type="QString" key="EditorConfiguration.ignoreFileTypes">*.md, *.MD, Makefile</value>
+   <value type="bool" key="EditorConfiguration.inEntireDocument">false</value>
+   <value type="bool" key="EditorConfiguration.skipTrailingWhitespace">true</value>
+   <value type="bool" key="EditorConfiguration.tintMarginArea">true</value>
+  </valuemap>
+ </data>
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+    <value type="bool" key="AutoTest.Framework.Catch">true</value>
+    <value type="bool" key="AutoTest.Framework.GTest">true</value>
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app/CMakeLists.txt

@@ -0,0 +1,68 @@
+cmake_minimum_required(VERSION 3.16)
+project(documentviewer LANGUAGES CXX)
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets)
+
+set(CMAKE_AUTORCC ON)
+
+qt_standard_project_setup()
+
+qt_add_library(abstractviewer STATIC
+    abstractviewer.cpp abstractviewer.h
+)
+
+qt_add_executable(documentviewer
+    main.cpp
+    mainwindow.cpp mainwindow.h mainwindow.ui
+    viewerfactory.cpp viewerfactory.h
+    recentfiles.cpp recentfiles.h
+    recentfilemenu.cpp recentfilemenu.h
+    viewerinterfaces.h
+    documentviewer.qrc
+)
+
+set_target_properties(documentviewer PROPERTIES
+    WIN32_EXECUTABLE TRUE
+    MACOSX_BUNDLE TRUE
+)
+
+target_link_libraries(documentviewer PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Widgets
+    abstractviewer
+)
+
+target_link_libraries(abstractviewer PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Widgets
+)
+
+set(plugin_targets
+    jsonviewer
+    txtviewer
+)
+
+if(TARGET pdfviewer)
+    list(APPEND plugin_targets pdfviewer)
+endif()
+
+if(QT6_IS_SHARED_LIBS_BUILD)
+    add_dependencies(documentviewer ${plugin_targets})
+else()
+    target_link_libraries(documentviewer PRIVATE ${plugin_targets})
+endif()
+
+if(TARGET Qt6::PrintSupport)
+    target_link_libraries(documentviewer PRIVATE Qt6::PrintSupport)
+    target_link_libraries(abstractviewer PRIVATE Qt6::PrintSupport)
+    add_compile_definitions(QT_DOCUMENTVIEWER_PRINTSUPPORT)
+endif()
+
+install(TARGETS documentviewer
+    RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
+    BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
+    LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
+)
+

app/abstractviewer.cpp

@@ -0,0 +1,281 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "abstractviewer.h"
+
+#include <QApplication>
+#include <QMainWindow>
+#include <QMenu>
+#include <QMenuBar>
+#include <QMessageBox>
+#include <QScrollArea>
+#include <QStatusBar>
+#include <QTabWidget>
+#include <QToolBar>
+
+#include <QAction>
+
+#include <QFile>
+#include <QSettings>
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+#include <QPrinter>
+#include <QPrintDialog>
+#endif // QT_DOCUMENTVIEWER_PRINTSUPPORT
+
+using namespace Qt::StringLiterals;
+
+AbstractViewer::AbstractViewer() : m_file(nullptr), m_widget(nullptr)
+{
+}
+
+void AbstractViewer::init(QFile *file, QWidget *widget, QMainWindow *mainWindow)
+{
+    m_file.reset(file);
+    m_widget = widget;
+    Q_ASSERT(widget);
+    Q_ASSERT(mainWindow);
+    m_uiAssets.mainWindow = mainWindow;
+}
+
+AbstractViewer::~AbstractViewer()
+{
+    AbstractViewer::cleanup();
+}
+
+bool AbstractViewer::isEmpty() const
+{
+    return !hasContent();
+}
+
+bool AbstractViewer::isPrintingEnabled() const
+{
+    return m_printingEnabled;
+}
+
+bool AbstractViewer::hasContent() const
+{
+    return false;
+}
+
+bool AbstractViewer::supportsOverview() const
+{
+    return false;
+}
+
+bool AbstractViewer::isModified() const
+{
+    return false;
+}
+
+bool AbstractViewer::saveDocument()
+{
+    return false;
+}
+
+bool AbstractViewer::saveDocumentAs()
+{
+    return false;
+}
+
+QList<QAction *> AbstractViewer::actions() const
+{
+    return m_actions;
+}
+
+QWidget *AbstractViewer::widget() const
+{
+    return m_widget;
+}
+
+QList<QMenu *> AbstractViewer::menus() const
+{
+    return m_menus;
+}
+
+QMainWindow *AbstractViewer::mainWindow() const
+{
+    return m_uiAssets.mainWindow;
+}
+
+QStatusBar *AbstractViewer::statusBar() const
+{
+    return mainWindow()->statusBar();
+}
+
+QMenuBar *AbstractViewer::menuBar() const
+{
+    return mainWindow()->menuBar();
+}
+
+void AbstractViewer::maybeEnablePrinting()
+{
+    maybeSetPrintingEnabled(true);
+}
+
+void AbstractViewer::disablePrinting()
+{
+    maybeSetPrintingEnabled(false);
+}
+
+bool AbstractViewer::isDefaultViewer() const
+{
+    return false;
+}
+
+AbstractViewer *AbstractViewer::viewer()
+{
+    return this;
+}
+
+const AbstractViewer *AbstractViewer::viewer() const
+{
+    return this;
+}
+
+void AbstractViewer::statusMessage(const QString &message, const QString &type, int timeout)
+{
+    const QString msg = viewerName()
+                        + (type.isEmpty() ? ": "_L1 : "/"_L1 + type + ": "_L1) + message;
+    emit showMessage(msg, timeout);
+}
+
+QToolBar *AbstractViewer::addToolBar(const QString &title)
+{
+    auto *bar = mainWindow()->addToolBar(title);
+    QString name = title;
+    name.remove(u' ');
+    bar->setObjectName(name);
+    m_toolBars.append(bar);
+    return bar;
+}
+
+QMenu *AbstractViewer::addMenu(const QString &title)
+{
+    QMenu *menu = new QMenu(title, menuBar());
+    menu->setObjectName(title);
+    menuBar()->insertMenu(m_uiAssets.help, menu);
+    m_menus.append(menu);
+    return menu;
+}
+
+void AbstractViewer::cleanup()
+{
+    // delete all objects created by the viewer which need to be displayed
+    // and therefore parented on MainWindow
+    if (m_file)
+        m_file.reset();
+
+    qDeleteAll(m_menus);
+    m_menus.clear();
+    qDeleteAll(m_toolBars);
+    m_toolBars.clear();
+
+    for (const auto &connection : m_connections)
+        QObject::disconnect(connection);
+
+    m_connections.clear();
+}
+
+QMenu *AbstractViewer::fileMenu()
+{
+    static constexpr QLatin1StringView name = QLatin1StringView("qtFileMenu");
+    static QMenu *fileMenu = nullptr;
+    if (fileMenu)
+        return fileMenu;
+
+    const QList<QMenu *> menus = mainWindow()->findChildren<QMenu *>();
+    for (auto *menu : menus) {
+        if (menu->objectName() == name) {
+            fileMenu = menu;
+            return fileMenu;
+        }
+    }
+    fileMenu = addMenu(tr("&File"));
+    fileMenu->setObjectName(name);
+    return fileMenu;
+}
+
+void AbstractViewer::print()
+{
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+    static const QString type = tr("Printing");
+    if (!hasContent()) {
+        statusMessage(tr("No content to print."), type);
+        return;
+    }
+
+    QPrinter printer(QPrinter::HighResolution);
+    QPrintDialog dlg(&printer, mainWindow());
+    dlg.setWindowTitle(tr("Print Document"));
+    if (dlg.exec() == QDialog::Accepted) {
+        printDocument(&printer);
+    } else {
+        statusMessage(tr("Printing canceled!"), type);
+        return;
+    }
+
+    const QPrinter::PrinterState state = printer.printerState();
+    QString message = viewerName() + " :"_L1;
+    switch (state) {
+    case QPrinter::PrinterState::Aborted:
+        message += tr("Printing aborted.");
+        break;
+    case QPrinter::PrinterState::Active:
+        message += tr("Printing active.");
+        break;
+    case QPrinter::PrinterState::Idle:
+        message += tr("Printing completed.");
+        break;
+    case QPrinter::PrinterState::Error:
+        message += tr("Printing error.");
+        break;
+    }
+    statusMessage(message, type);
+#else
+    statusMessage(tr("Printing not supported!"));
+#endif
+}
+
+/*!
+   \brief AbstractViewer::setPrintingEnabled
+   Enables / disables printing.
+   If printing is not supported or the viewer has no content to display,
+   \param enabled is overridden with \c false;
+   The signal printingEnabledChanged is emitted if the status has changed.
+ */
+void AbstractViewer::maybeSetPrintingEnabled(bool enabled)
+{
+#ifndef QT_DOCUMENTVIEWER_PRINTSUPPORT
+    enabled = false;
+#else
+    if (!hasContent())
+        enabled = false;
+#endif
+
+    if (enabled == m_printingEnabled)
+        return;
+
+    m_printingEnabled = enabled;
+    emit printingEnabledChanged(enabled);
+}
+
+void AbstractViewer::initViewer(QAction *back, QAction *forward, QAction *help, QTabWidget *tabs)
+{
+    // Viewers need back & forward buttons and a tab widget.
+    Q_ASSERT(back);
+    Q_ASSERT(forward);
+    Q_ASSERT(tabs);
+    Q_ASSERT(help);
+
+    m_uiAssets.back = back;
+    m_uiAssets.forward = forward;
+    m_uiAssets.help = help;
+    m_uiAssets.tabs = tabs;
+
+    // Tabs can be populated individually by the viewer, if it supports overview
+    tabs->clear();
+    tabs->setVisible(supportsOverview());
+
+    emit uiInitialized();
+}

app/abstractviewer.h

@@ -0,0 +1,101 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef ABSTRACTVIEWER_H
+#define ABSTRACTVIEWER_H
+
+#include <QObject>
+
+QT_BEGIN_NAMESPACE
+class QAction;
+class QFile;
+class QMainWindow;
+class QMenu;
+class QMenuBar;
+class QPrinter;
+class QToolBar;
+class QTabWidget;
+class QScrollArea;
+class QStatusBar;
+QT_END_NAMESPACE
+
+class AbstractViewer : public QObject
+{
+    Q_OBJECT
+
+protected:
+    AbstractViewer();
+
+public:
+    virtual ~AbstractViewer();
+    virtual void init(QFile *file, QWidget *widget, QMainWindow *mainWindow);
+    void initViewer(QAction *back, QAction *forward, QAction *help, QTabWidget *tabs);
+    virtual bool isModified() const;
+    virtual bool saveDocument();
+    virtual bool saveDocumentAs();
+    virtual QString viewerName() const = 0;
+    virtual bool supportsOverview() const;
+    virtual QByteArray saveState() const = 0;
+    virtual bool restoreState(QByteArray &) = 0;
+    virtual bool hasContent() const;
+    virtual QStringList supportedMimeTypes() const = 0;
+    virtual bool isDefaultViewer() const;
+    virtual void cleanup();
+    bool isEmpty() const;
+    bool isPrintingEnabled() const;
+    AbstractViewer *viewer();
+    const AbstractViewer *viewer() const;
+
+    QList<QAction *> actions() const;
+    QWidget *widget() const;
+    QList<QMenu *> menus() const;
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+protected:
+    virtual void printDocument(QPrinter *) const {};
+#endif
+
+signals:
+    void uiInitialized();
+    void printingEnabledChanged(bool enabled);
+    void showMessage(const QString &message, int timeout = 8000);
+    void documentLoaded(const QString &fileName);
+
+public slots:
+    void print();
+
+protected:
+
+    struct UiAssets {
+        QMainWindow *mainWindow = nullptr;
+        QAction *back = nullptr;
+        QAction *forward = nullptr;
+        QAction *help = nullptr;
+        QTabWidget *tabs = nullptr;
+    } m_uiAssets;
+
+    void statusMessage(const QString &message, const QString &type = QString(), int timeout = 8000);
+    QToolBar *addToolBar(const QString &);
+    QMenu *addMenu(const QString &);
+    QMenu *fileMenu();
+    QMainWindow *mainWindow() const;
+    QStatusBar *statusBar() const;
+    QMenuBar *menuBar() const;
+
+    std::unique_ptr<QFile> m_file;
+    QList<QAction *> m_actions;
+    QWidget *m_widget = nullptr;
+    QList<QMetaObject::Connection> m_connections;
+
+protected slots:
+    void maybeSetPrintingEnabled(bool enabled);
+    void maybeEnablePrinting();
+    void disablePrinting();
+
+private:
+    QList<QMenu *> m_menus;
+    QList<QToolBar *> m_toolBars;
+    bool m_printingEnabled = false;
+};
+
+#endif // ABSTRACTVIEWER_H

app/documentviewer.qrc

@@ -0,0 +1,42 @@
+<!DOCTYPE RCC><RCC version="1.0">
+<qresource prefix="demos/documentviewer">
+    <file>images/copy@2x.png</file>
+    <file>images/copy.png</file>
+    <file>images/cut@2x.png</file>
+    <file>images/cut.png</file>
+    <file>images/go-next-view@2x.png</file>
+    <file>images/go-next-view-page@2x.png</file>
+    <file>images/go-next-view-page.png</file>
+    <file>images/go-next-view.png</file>
+    <file>images/go-previous-view@2x.png</file>
+    <file>images/go-previous-view-page@2x.png</file>
+    <file>images/go-previous-view-page.png</file>
+    <file>images/go-previous-view.png</file>
+    <file>images/magnifier@2x.png</file>
+    <file>images/magnifier.png</file>
+    <file>images/open@2x.png</file>
+    <file>images/open.png</file>
+    <file>images/paste@2x.png</file>
+    <file>images/paste.png</file>
+    <file>images/print2x.png</file>
+    <file>images/print.png</file>
+    <file>images/qt-logo@2x.png</file>
+    <file>images/qt-logo.png</file>
+    <file>images/zoom-fit-best@2x.png</file>
+    <file>images/zoom-fit-best.png</file>
+    <file>images/zoom-fit-width@2x.png</file>
+    <file>images/zoom-fit-width.png</file>
+    <file>images/zoom-in@2x.png</file>
+    <file>images/zoom-in.png</file>
+    <file>images/zoom-original@2x.png</file>
+    <file>images/zoom-original.png</file>
+    <file>images/zoom-out@2x.png</file>
+    <file>images/zoom-out.png</file>
+    <file>images/zoom-previous@2x.png</file>
+    <file>images/zoom-previous.png</file>
+    <file>images/document-open-recent.svgz</file>
+    <file>images/go-next.svgz</file>
+    <file>images/go-previous.svgz</file>
+    <file>images/help-about.svgz</file>
+</qresource>
+</RCC>

app/main.cpp

@@ -0,0 +1,36 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "mainwindow.h"
+#include <QApplication>
+#include <QCommandLineParser>
+
+using namespace Qt::StringLiterals;
+
+int main(int argc, char *argv[])
+{
+    QApplication app(argc, argv);
+    QCoreApplication::setOrganizationName("QtProject"_L1);
+    QCoreApplication::setApplicationName("DocumentViewer"_L1);
+    QCoreApplication::setApplicationVersion("1.0"_L1);
+
+    QCommandLineParser parser;
+    parser.setApplicationDescription(QApplication::translate("main",
+                                                     "A viewer for JSON, PDF and text files"));
+    parser.addHelpOption();
+    parser.addVersionOption();
+    parser.addPositionalArgument("File"_L1, QApplication::translate("main",
+                                                                    "JSON, PDF or text file to open"));
+    parser.process(app);
+
+    const QStringList &positionalArguments = parser.positionalArguments();
+    const QString &fileName = (positionalArguments.count() > 0) ? positionalArguments.at(0)
+                                                                : QString();
+
+    MainWindow w;
+    w.show();
+    if (!fileName.isEmpty())
+        w.openFile(fileName);
+
+    return app.exec();
+}

app/mainwindow.cpp

@@ -0,0 +1,190 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "mainwindow.h"
+#include "ui_mainwindow.h"
+#include "viewerfactory.h"
+#include "abstractviewer.h"
+#include "recentfiles.h"
+#include "recentfilemenu.h"
+
+#include <QFileDialog>
+#include <QToolButton>
+#include <QMessageBox>
+
+#include <QDir>
+#include <QSettings>
+
+using namespace Qt::StringLiterals;
+
+MainWindow::MainWindow(QWidget *parent) :
+    QMainWindow(parent),
+    ui(new Ui::MainWindow)
+{
+    ui->setupUi(this);
+    connect(ui->actionOpen, &QAction::triggered, this, &MainWindow::onActionOpenTriggered);
+    connect(ui->actionAbout, &QAction::triggered, this, &MainWindow::onActionAboutTriggered);
+    connect(ui->actionAboutQt, &QAction::triggered, this, &MainWindow::onActionAboutQtTriggered);
+
+    m_recentFiles.reset(new RecentFiles(ui->actionRecent));
+    connect(m_recentFiles.get(), &RecentFiles::countChanged, this, [&](int count){
+        ui->actionRecent->setText(tr("%n recent files", nullptr, count));
+    });
+
+    readSettings();
+    m_factory.reset(new ViewerFactory(ui->viewArea, this));
+    const QStringList &viewers = m_factory->viewerNames();
+
+    const QString msg = tr("Available viewers: %1").arg(viewers.join(", "_L1));
+    statusBar()->showMessage(msg);
+
+    auto *menu = new RecentFileMenu(this, m_recentFiles.get());
+    ui->actionRecent->setMenu(menu);
+    connect(menu, &RecentFileMenu::fileOpened, this, &MainWindow::openFile);
+    QWidget *w = ui->mainToolBar->widgetForAction(ui->actionRecent);
+    auto *button = qobject_cast<QToolButton *>(w);
+    if (button)
+        connect(ui->actionRecent, &QAction::triggered, button, &QToolButton::showMenu);
+}
+
+MainWindow::~MainWindow()
+{
+    saveSettings();
+}
+
+void MainWindow::onActionOpenTriggered()
+{
+    QFileDialog fileDialog(this, tr("Open Document"), m_currentDir.absolutePath());
+    while (fileDialog.exec() == QDialog::Accepted
+           && !openFile(fileDialog.selectedFiles().constFirst())) {
+    }
+}
+
+bool MainWindow::openFile(const QString &fileName)
+{
+    QFile *file = new QFile(fileName);
+    if (!file->exists()) {
+        statusBar()->showMessage(tr("File %1 could not be opened")
+                                 .arg(QDir::toNativeSeparators(fileName)));
+        delete file;
+        return false;
+    }
+
+    QFileInfo fileInfo(*file);
+    m_currentDir = fileInfo.dir();
+    m_recentFiles->addFile(fileInfo.absoluteFilePath());
+
+    // If a viewer is already open, clean it up and save its settings
+    resetViewer();
+    m_viewer = m_factory->viewer(file);
+    if (!m_viewer) {
+        statusBar()->showMessage(tr("File %1 can't be opened.")
+                                 .arg(QDir::toNativeSeparators(fileName)));
+        return false;
+    }
+
+    ui->actionPrint->setEnabled(m_viewer->hasContent());
+    connect(m_viewer, &AbstractViewer::printingEnabledChanged, ui->actionPrint, &QAction::setEnabled);
+    connect(ui->actionPrint, &QAction::triggered, m_viewer, &AbstractViewer::print);
+    connect(m_viewer, &AbstractViewer::showMessage, statusBar(), &QStatusBar::showMessage);
+
+    m_viewer->initViewer(ui->actionBack, ui->actionForward, ui->menuHelp->menuAction(), ui->tabWidget);
+    restoreViewerSettings();
+    ui->scrollArea->setWidget(m_viewer->widget());
+    return true;
+}
+
+void MainWindow::onActionAboutTriggered()
+{
+    const QString viewerNames = m_factory->viewerNames().join(", "_L1);
+    const QString mimeTypes = m_factory->supportedMimeTypes().join(u'\n');
+    QString text = tr("A Widgets application to display and print JSON, "
+                      "text and PDF files. Demonstrates various features to use "
+                      "in widget applications: Using QSettings, query and save "
+                      "user preferences, manage file histories and control cursor "
+                      "behavior when hovering over widgets.\n\n"
+                      "This version has loaded the following plugins:\n%1\n"
+                      "\n\nIt supports the following mime types:\n%2")
+                    .arg(viewerNames, mimeTypes);
+
+    if (auto *def = m_factory->defaultViewer())
+        text += tr("\n\nOther mime types will be displayed with %1.").arg(def->viewerName());
+
+    QMessageBox::about(this, tr("About Document Viewer Demo"), text);
+}
+
+void MainWindow::onActionAboutQtTriggered()
+{
+    QMessageBox::aboutQt(this);
+}
+
+void MainWindow::readSettings()
+{
+    QSettings settings;
+
+    // Restore working directory
+    if (settings.contains(settingsDir))
+        m_currentDir = QDir(settings.value(settingsDir).toString());
+    else
+        m_currentDir = QDir::current();
+
+    // Restore QMainWindow state
+    if (settings.contains(settingsMainWindow)) {
+        QByteArray mainWindowState = settings.value(settingsMainWindow).toByteArray();
+        restoreState(mainWindowState);
+    }
+
+    // Restore recent files
+    m_recentFiles->restoreFromSettings(settings, settingsFiles);
+}
+
+void MainWindow::saveSettings() const
+{
+    QSettings settings;
+
+    // Save working directory
+    settings.setValue(settingsDir, m_currentDir.absolutePath());
+
+    // Save QMainWindow state
+    settings.setValue(settingsMainWindow, saveState());
+
+    // Save recent files
+    m_recentFiles->saveSettings(settings, settingsFiles);
+
+    settings.sync();
+}
+
+void MainWindow::saveViewerSettings() const
+{
+    if (!m_viewer)
+        return;
+
+    QSettings settings;
+    settings.beginGroup(settingsViewers);
+        settings.setValue(m_viewer->viewerName(), m_viewer->saveState());
+    settings.endGroup();
+    settings.sync();
+}
+
+void MainWindow::resetViewer() const
+{
+    if (!m_viewer)
+        return;
+
+    saveViewerSettings();
+    m_viewer->cleanup();
+}
+
+void MainWindow::restoreViewerSettings()
+{
+    if (!m_viewer)
+        return;
+
+    QSettings settings;
+    settings.beginGroup(settingsViewers);
+    QByteArray viewerSettings = settings.value(m_viewer->viewerName(), QByteArray()).toByteArray();
+    settings.endGroup();
+    if (!viewerSettings.isEmpty())
+        m_viewer->restoreState(viewerSettings);
+}
+

app/mainwindow.h

@@ -0,0 +1,56 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef MAINWINDOW_H
+#define MAINWINDOW_H
+
+#include <QMainWindow>
+#include <QDir>
+#include <QStringLiteral>
+
+class AbstractViewer;
+class RecentFiles;
+class ViewerFactory;
+
+QT_BEGIN_NAMESPACE
+namespace Ui {
+class MainWindow;
+}
+QT_END_NAMESPACE
+
+class MainWindow : public QMainWindow
+{
+    Q_OBJECT
+
+public:
+    explicit MainWindow(QWidget *parent = nullptr);
+    ~MainWindow();
+
+public slots:
+    bool openFile(const QString &fileName);
+
+private slots:
+    void onActionOpenTriggered();
+    void onActionAboutTriggered();
+    void onActionAboutQtTriggered();
+
+private:
+    void readSettings();
+    void saveSettings() const;
+    void restoreViewerSettings();
+    void resetViewer() const;
+    void saveViewerSettings() const;
+
+    QDir m_currentDir;
+    AbstractViewer *m_viewer = nullptr;
+    std::unique_ptr<Ui::MainWindow> ui;
+    std::unique_ptr<RecentFiles> m_recentFiles;
+    std::unique_ptr<ViewerFactory> m_factory;
+
+    static constexpr QLatin1StringView settingsDir = QLatin1StringView("WorkingDir");
+    static constexpr QLatin1StringView settingsMainWindow = QLatin1StringView("MainWindow");
+    static constexpr QLatin1StringView settingsViewers = QLatin1StringView("Viewers");
+    static constexpr QLatin1StringView settingsFiles = QLatin1StringView("RecentFiles");
+};
+
+#endif // MAINWINDOW_H

app/mainwindow.ui

@@ -0,0 +1,272 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>MainWindow</class>
+ <widget class="QMainWindow" name="MainWindow">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>983</width>
+    <height>602</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>Document Viewer Demo</string>
+  </property>
+  <property name="windowIcon">
+   <iconset resource="documentviewer.qrc">
+    <normaloff>:/demos/documentviewer/images/qt-logo.png</normaloff>:/demos/documentviewer/images/qt-logo.png</iconset>
+  </property>
+  <widget class="QWidget" name="centralwidget">
+   <property name="enabled">
+    <bool>true</bool>
+   </property>
+   <layout class="QVBoxLayout" name="verticalLayout">
+    <item>
+     <widget class="QWidget" name="viewArea" native="true">
+      <layout class="QVBoxLayout" name="verticalLayout_2">
+       <item>
+        <widget class="QSplitter" name="splitter">
+         <property name="orientation">
+          <enum>Qt::Horizontal</enum>
+         </property>
+         <widget class="QTabWidget" name="tabWidget">
+          <property name="tabPosition">
+           <enum>QTabWidget::West</enum>
+          </property>
+          <property name="currentIndex">
+           <number>0</number>
+          </property>
+          <widget class="QWidget" name="bookmarkTab">
+           <attribute name="title">
+            <string>Pages</string>
+           </attribute>
+          </widget>
+          <widget class="QWidget" name="pagesTab">
+           <attribute name="title">
+            <string>Bookmarks</string>
+           </attribute>
+          </widget>
+         </widget>
+         <widget class="QScrollArea" name="scrollArea">
+          <property name="sizePolicy">
+           <sizepolicy hsizetype="Expanding" vsizetype="Expanding">
+            <horstretch>0</horstretch>
+            <verstretch>0</verstretch>
+           </sizepolicy>
+          </property>
+          <property name="minimumSize">
+           <size>
+            <width>800</width>
+            <height>0</height>
+           </size>
+          </property>
+          <property name="widgetResizable">
+           <bool>true</bool>
+          </property>
+          <widget class="QWidget" name="scrollAreaWidgetContents">
+           <property name="geometry">
+            <rect>
+             <x>0</x>
+             <y>0</y>
+             <width>798</width>
+             <height>479</height>
+            </rect>
+           </property>
+          </widget>
+         </widget>
+        </widget>
+       </item>
+      </layout>
+     </widget>
+    </item>
+   </layout>
+  </widget>
+  <widget class="QMenuBar" name="menubar">
+   <property name="geometry">
+    <rect>
+     <x>0</x>
+     <y>0</y>
+     <width>983</width>
+     <height>23</height>
+    </rect>
+   </property>
+   <widget class="QMenu" name="qtFileMenu">
+    <property name="title">
+     <string>File</string>
+    </property>
+    <addaction name="actionOpen"/>
+    <addaction name="actionRecent"/>
+    <addaction name="actionPrint"/>
+    <addaction name="actionQuit"/>
+   </widget>
+   <widget class="QMenu" name="menuHelp">
+    <property name="title">
+     <string>Help</string>
+    </property>
+    <addaction name="actionAbout"/>
+    <addaction name="actionAboutQt"/>
+   </widget>
+   <addaction name="qtFileMenu"/>
+   <addaction name="menuHelp"/>
+  </widget>
+  <widget class="QStatusBar" name="statusbar"/>
+  <widget class="QToolBar" name="mainToolBar">
+   <property name="windowTitle">
+    <string>toolBar</string>
+   </property>
+   <attribute name="toolBarArea">
+    <enum>TopToolBarArea</enum>
+   </attribute>
+   <attribute name="toolBarBreak">
+    <bool>false</bool>
+   </attribute>
+   <addaction name="actionOpen"/>
+   <addaction name="actionRecent"/>
+   <addaction name="actionPrint"/>
+   <addaction name="separator"/>
+   <addaction name="actionBack"/>
+   <addaction name="actionForward"/>
+   <addaction name="separator"/>
+  </widget>
+  <action name="actionOpen">
+   <property name="icon">
+    <iconset resource="documentviewer.qrc">
+     <normaloff>:/demos/documentviewer/images/open.png</normaloff>:/demos/documentviewer/images/open.png</iconset>
+   </property>
+   <property name="text">
+    <string>Open</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+O</string>
+   </property>
+  </action>
+  <action name="actionAbout">
+   <property name="icon">
+    <iconset theme="help-about" resource="documentviewer.qrc">
+     <normaloff>:/demos/documentviewer/images/help-about.svgz</normaloff>:/demos/documentviewer/images/help-about.svgz</iconset>
+   </property>
+   <property name="text">
+    <string>about documentviewer</string>
+   </property>
+   <property name="toolTip">
+    <string>Show information about the Document Viewer deomo.</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+H</string>
+   </property>
+  </action>
+  <action name="actionForward">
+   <property name="icon">
+    <iconset resource="documentviewer.qrc">
+     <normaloff>:/demos/documentviewer/images/go-next.svgz</normaloff>:/demos/documentviewer/images/go-next.svgz</iconset>
+   </property>
+   <property name="text">
+    <string>actionForward</string>
+   </property>
+   <property name="toolTip">
+    <string>One step forward</string>
+   </property>
+   <property name="shortcut">
+    <string>Right</string>
+   </property>
+  </action>
+  <action name="actionBack">
+   <property name="icon">
+    <iconset resource="documentviewer.qrc">
+     <normaloff>:/demos/documentviewer/images/go-previous.svgz</normaloff>:/demos/documentviewer/images/go-previous.svgz</iconset>
+   </property>
+   <property name="text">
+    <string>actionBack</string>
+   </property>
+   <property name="toolTip">
+    <string>One step back</string>
+   </property>
+   <property name="shortcut">
+    <string>Left</string>
+   </property>
+  </action>
+  <action name="actionPrint">
+   <property name="enabled">
+    <bool>false</bool>
+   </property>
+   <property name="icon">
+    <iconset theme="document-print" resource="documentviewer.qrc">
+     <normaloff>:/demos/documentviewer/images/print2x.png</normaloff>:/demos/documentviewer/images/print2x.png</iconset>
+   </property>
+   <property name="text">
+    <string>Print</string>
+   </property>
+   <property name="toolTip">
+    <string>Print current file</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+P</string>
+   </property>
+  </action>
+  <action name="actionAboutQt">
+   <property name="icon">
+    <iconset resource="documentviewer.qrc">
+     <normaloff>:/demos/documentviewer/images/qt-logo.png</normaloff>
+     <normalon>:/demos/documentviewer/images/qt-logo.png</normalon>:/demos/documentviewer/images/qt-logo.png</iconset>
+   </property>
+   <property name="text">
+    <string>About Qt</string>
+   </property>
+   <property name="toolTip">
+    <string>Show Qt license information</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+I</string>
+   </property>
+  </action>
+  <action name="actionRecent">
+   <property name="icon">
+    <iconset resource="documentviewer.qrc">
+     <normaloff>:/demos/documentviewer/images/document-open-recent.svgz</normaloff>:/demos/documentviewer/images/document-open-recent.svgz</iconset>
+   </property>
+   <property name="text">
+    <string>Recently opened...</string>
+   </property>
+   <property name="shortcut">
+    <string>Meta+R</string>
+   </property>
+  </action>
+  <action name="actionQuit">
+   <property name="icon">
+    <iconset theme="application-exit">
+     <normaloff>.</normaloff>.</iconset>
+   </property>
+   <property name="text">
+    <string>Quit</string>
+   </property>
+   <property name="toolTip">
+    <string>Quit the application</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+Q</string>
+   </property>
+  </action>
+ </widget>
+ <resources>
+  <include location="documentviewer.qrc"/>
+ </resources>
+ <connections>
+  <connection>
+   <sender>actionQuit</sender>
+   <signal>triggered()</signal>
+   <receiver>MainWindow</receiver>
+   <slot>close()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>-1</x>
+     <y>-1</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>491</x>
+     <y>300</y>
+    </hint>
+   </hints>
+  </connection>
+ </connections>
+</ui>

app/recentfilemenu.cpp

@@ -0,0 +1,36 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "recentfilemenu.h"
+#include "recentfiles.h"
+
+#include <QAction>
+
+RecentFileMenu::RecentFileMenu(QWidget *parent, RecentFiles *recent) :
+    QMenu(parent), m_recentFiles(recent)
+{
+    Q_ASSERT(recent);
+    connect(m_recentFiles, &RecentFiles::changed, this, &RecentFileMenu::updateList);
+    connect(m_recentFiles, &QObject::destroyed, this, &QObject::deleteLater);
+    updateList();
+}
+
+void RecentFileMenu::updateList()
+{
+    QList<QAction *> acts = actions();
+    qDeleteAll(acts);
+
+    if (m_recentFiles->isEmpty()) {
+        addAction(tr("<no recent files>"));
+        return;
+    }
+
+    for (const QString &fileName : m_recentFiles->recentFiles()) {
+        QAction *action = addAction(fileName);
+        connect(action, &QAction::triggered, this, [&](){
+            QAction *action = qobject_cast<QAction *>(sender());
+            Q_ASSERT(action);
+            emit fileOpened(action->text());
+        });
+    }
+}

app/recentfilemenu.h

@@ -0,0 +1,28 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef RECENTFILEMENU_H
+#define RECENTFILEMENU_H
+
+#include <QMenu>
+
+class RecentFiles;
+
+class RecentFileMenu : public QMenu
+{
+    Q_OBJECT
+
+public:
+    explicit RecentFileMenu(QWidget *parent, RecentFiles *recent);
+
+signals:
+    void fileOpened(const QString &fileName);
+
+private slots:
+    void updateList();
+
+private:
+    RecentFiles *m_recentFiles;
+};
+
+#endif // RECENTFILEMENU_H

app/recentfiles.cpp

@@ -0,0 +1,128 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "recentfiles.h"
+#include <QFileInfo>
+#include <QSettings>
+
+// Test if file exists and can be opened
+static bool testFileAccess(const QString &fileName)
+{
+    return QFileInfo(fileName).isReadable();
+}
+
+void RecentFiles::clear()
+{
+    if (isEmpty())
+        return;
+
+    m_files.clear();
+    emit countChanged(0);
+}
+
+void RecentFiles::addFile(const QString &fileName, EmitPolicy policy)
+{
+    if (!testFileAccess(fileName))
+        return;
+
+    // Remember size, as cleanup can result in a change without size change
+    const qsizetype c = m_files.count();
+
+    // Clean dangling and duplicate files
+    for (qsizetype i = 0; i < m_files.size(); ) {
+        const QString &file = m_files.at(i);
+        if (!testFileAccess(file)) {
+            removeFile(file, RemoveReason::Other);
+        } else if (file == fileName) {
+            removeFile(file, RemoveReason::Duplicate);
+        } else {
+            ++i;
+        }
+    }
+
+    // Cut tail
+    while (m_files.count() > m_maxFiles)
+        removeFile((m_files.count() - 1), RemoveReason::Other);
+
+    m_files.prepend(fileName);
+
+    switch (policy) {
+    case EmitPolicy::NeverEmit:
+        return;
+
+    case EmitPolicy::EmitWhenChanged:
+        emit changed();
+
+        if (c != m_files.count())
+            emit countChanged(m_files.count());
+
+        return;
+    }
+}
+
+void RecentFiles::addFiles(const QStringList &files)
+{
+    if (files.isEmpty())
+        return;
+
+    if (files.count() == 1) {
+        addFile(files.at(0));
+        return;
+    }
+
+    const qsizetype c = m_files.count();
+
+    for (const auto &file : files)
+        addFile(file, EmitPolicy::NeverEmit);
+
+    emit changed();
+    if (m_files.count() != c)
+        emit countChanged(m_files.count());
+}
+
+void RecentFiles::removeFile(qsizetype index, RemoveReason reason)
+{
+    if (index < 0 || index >= m_files.count())
+        return;
+
+    m_files.remove(index);
+
+    // No emit for duplicate removal, add emits changed later.
+    if (reason != RemoveReason::Duplicate)
+        emit changed();
+}
+
+void RecentFiles::saveSettings(QSettings &settings, const QString &key) const
+{
+    settings.beginGroup(key);
+    settings.setValue(s_maxFiles, maxFiles());
+    if (!isEmpty()) {
+        settings.beginWriteArray(s_fileNames, m_files.count());
+        for (int index = 0; index < m_files.count(); ++index) {
+            settings.setArrayIndex(index);
+            settings.setValue(s_file, m_files.at(index));
+        }
+        settings.endArray();
+    }
+    settings.endGroup();
+}
+
+bool RecentFiles::restoreFromSettings(QSettings &settings, const QString &key)
+{
+    settings.beginGroup(key);
+    const qsizetype mxFiles = settings.value(s_maxFiles, maxFiles()).toLongLong();
+    setMaxFiles(mxFiles);
+    m_files.clear(); // clear list without emitting
+    const int numberFiles = settings.beginReadArray(s_fileNames);
+    for (int index = 0; index < numberFiles; ++index) {
+        settings.setArrayIndex(index);
+        const QString absoluteFilePath = settings.value(s_file).toString();
+        addFile(absoluteFilePath, EmitPolicy::NeverEmit);
+    }
+    settings.endArray();
+    settings.endGroup();
+    if (!m_files.isEmpty())
+        emit changed();
+
+    return true;
+}

app/recentfiles.h

@@ -0,0 +1,71 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef RECENTFILES_H
+#define RECENTFILES_H
+
+#include <QMenu>
+#include <QFile>
+
+QT_BEGIN_NAMESPACE
+class QSettings;
+QT_END_NAMESPACE
+
+class RecentFiles : public QObject
+{
+    Q_OBJECT
+public:
+    enum class RemoveReason {
+        Other,
+        Duplicate
+    };
+    Q_ENUM(RemoveReason)
+
+    using QObject::QObject;
+
+    // Access to QStringList member functions
+    const QStringList recentFiles() const {return m_files; }
+    bool isEmpty() const { return m_files.isEmpty(); }
+
+    // Properties
+    qsizetype maxFiles() const { return m_maxFiles; }
+    void setMaxFiles(qsizetype maxFiles) { m_maxFiles = maxFiles; }
+
+public slots:
+    void addFile(const QString &fileName) { addFile(fileName, EmitPolicy::EmitWhenChanged); }
+    void addFiles(const QStringList &fileNames);
+    void removeFile(const QString &fileName) { removeFile(m_files.indexOf(fileName)); }
+    void removeFile(qsizetype index) {removeFile(index, RemoveReason::Other); }
+    void saveSettings(QSettings &settings, const QString &key) const;
+    bool restoreFromSettings(QSettings &settings, const QString &key);
+    void clear();
+
+signals:
+    void countChanged(int count);
+    void changed();
+
+private:
+    // Private removers with reason
+    void removeFile(qsizetype index, RemoveReason reason);
+    void removeFile(const QString &fileName, RemoveReason reason) {removeFile(m_files.indexOf(fileName), reason); }
+
+    // Private adder with emit policy
+    enum class EmitPolicy {
+        EmitWhenChanged,
+        NeverEmit
+    };
+
+    void addFile(const QString &fileName, EmitPolicy policy);
+
+    qsizetype m_maxFiles = 10;
+
+    QStringList m_files;
+
+    // Constexprs for settings
+    static constexpr QLatin1StringView s_maxFiles = QLatin1StringView("maxFiles");
+    static constexpr QLatin1StringView s_openMode = QLatin1StringView("openMode");
+    static constexpr QLatin1StringView s_fileNames = QLatin1StringView("fileNames");
+    static constexpr QLatin1StringView s_file = QLatin1StringView("file");
+};
+
+#endif // RECENTFILES_H

app/viewerfactory.cpp

@@ -0,0 +1,189 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "abstractviewer.h"
+#include "viewerfactory.h"
+#include "viewerinterfaces.h"
+
+#include <QApplication>
+#include <QMessageBox>
+#include <QWidget>
+
+#include <QDir>
+#include <QMimeDatabase>
+#include <QMimeType>
+#include <QPluginLoader>
+#include <QTimer>
+
+using namespace Qt::StringLiterals;
+
+ViewerFactory::ViewerFactory(QWidget *displayWidget, QMainWindow *mainWindow, DefaultPolicy policy)
+    : m_defaultPolicy(policy),
+      m_displayWidget(displayWidget),
+      m_mainWindow(mainWindow)
+{
+    Q_ASSERT(m_displayWidget);
+    Q_ASSERT(m_mainWindow);
+    loadViewerPlugins();
+}
+
+ViewerFactory::~ViewerFactory()
+{
+    unload();
+}
+
+AbstractViewer *ViewerFactory::viewer(QFile *file) const
+{
+    Q_ASSERT(file);
+
+    const QFileInfo info(*file);
+    QMimeDatabase db;
+    const auto mimeType = db.mimeTypeForFile(info);
+
+    AbstractViewer *viewer = ViewerFactory::viewer(mimeType);
+    if (!viewer) {
+        qWarning() << "Mime type" << mimeType.name() << "not supported.";
+        return nullptr;
+    }
+
+    viewer->init(file, m_displayWidget, m_mainWindow);
+    return viewer;
+}
+
+void ViewerFactory::loadViewerPlugins()
+{
+    if (!m_viewers.isEmpty())
+        return;
+
+    // Load static plugins
+    const QObjectList &staticPlugins = QPluginLoader::staticInstances();
+    for (auto *plugin : staticPlugins)
+        addViewer(plugin);
+
+    // Load shared plugins
+    QDir pluginsDir = QDir(QApplication::applicationDirPath());
+
+#if defined(Q_OS_WINDOWS)
+    pluginsDir.cd("app"_L1);
+#elif defined(Q_OS_DARWIN)
+    if (pluginsDir.dirName() == "MacOS"_L1) {
+        pluginsDir.cdUp();
+        pluginsDir.cdUp();
+        pluginsDir.cdUp();
+    }
+#endif
+    const auto entryList = pluginsDir.entryList(QDir::Files);
+    for (const QString &fileName : entryList) {
+        QPluginLoader loader(pluginsDir.absoluteFilePath(fileName));
+        QObject *plugin = loader.instance();
+        if (plugin)
+            addViewer(plugin);
+#if 0
+        else
+            qDebug() << loader.errorString();
+#endif
+    }
+}
+
+void ViewerFactory::unload()
+{
+    qDeleteAll(viewers());
+    m_viewers.clear();
+}
+
+void ViewerFactory::addViewer(QObject *viewerObject)
+{
+    auto *interface = qobject_cast<ViewerInterface *>(viewerObject);
+    if (!interface)
+        return;
+
+    // Set custom default viewer
+    if (interface->viewer()->isDefaultViewer())
+        m_defaultViewer = interface->viewer();
+
+    m_viewers.insert(interface->viewerName(), interface->viewer());
+}
+
+QStringList ViewerFactory::viewerNames(bool showDefault) const
+{
+    if (!showDefault)
+        return m_viewers.keys();
+
+    QStringList list;
+    for (auto it = m_viewers.constBegin(); it != m_viewers.constEnd(); ++it) {
+        QString name = it.key();
+        if ((m_defaultViewer && it.value()->isDefaultViewer())
+             || (!m_defaultViewer && it.key() == "TxtViewer"_L1)) {
+            name += "(default)"_L1;
+        }
+        list.append(name);
+    }
+    return list;
+}
+
+ViewerFactory::ViewerList ViewerFactory::viewers() const
+{
+    return m_viewers.values();
+}
+
+AbstractViewer *ViewerFactory::findViewer(const QString &viewerName) const
+{
+    const ViewerList &viewerList = viewers();
+    for (auto *viewer : viewerList) {
+        if (viewer->viewerName() == viewerName)
+            return viewer;
+    }
+    qWarning() << "Plugin" << viewerName << "not loaded.";
+    return nullptr;
+}
+
+AbstractViewer *ViewerFactory::viewer(const QMimeType &mimeType) const
+{
+    const ViewerList &viewerList = viewers();
+
+    for (AbstractViewer *viewer : viewerList) {
+        for (const QString &type : viewer->supportedMimeTypes()) {
+            if (mimeType.inherits(type))
+                return viewer;
+        }
+    }
+
+    AbstractViewer *viewer = defaultViewer();
+
+    if (m_defaultWarning) {
+        QMessageBox mbox;
+        mbox.setIcon(QMessageBox::Warning);
+        mbox.setText(QObject::tr("Mime type %1 not supported. Falling back to %2.")
+                     .arg(mimeType.name(), viewer->viewerName()));
+        mbox.setStandardButtons(QMessageBox::Ok);
+        QTimer::singleShot(8000, &mbox, [&mbox](){ mbox.close(); });
+        mbox.exec();
+    }
+
+    return viewer;
+}
+
+AbstractViewer *ViewerFactory::defaultViewer() const
+{
+    switch (m_defaultPolicy) {
+    case DefaultPolicy::NeverDefault:
+        return nullptr;
+    case DefaultPolicy::DefaultToCustomViewer:
+        return m_defaultViewer ? m_defaultViewer : findViewer("TxtViewer"_L1);
+    case DefaultPolicy::DefaultToTxtViewer:
+        return findViewer("TxtViewer"_L1);
+    }
+    Q_UNREACHABLE();
+}
+
+QStringList ViewerFactory::supportedMimeTypes() const
+{
+    static QStringList mimeTypes;
+    if (!mimeTypes.isEmpty())
+        return mimeTypes;
+
+    const ViewerList &viewerList = viewers();
+    for (auto viewer : viewerList)
+        mimeTypes.append(viewer->supportedMimeTypes());
+    return mimeTypes;
+}

app/viewerfactory.h

@@ -0,0 +1,62 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef VIEWERFACTORY_H
+#define VIEWERFACTORY_H
+
+#include <QString>
+#include <QMap>
+
+QT_BEGIN_NAMESPACE
+class QMimeType;
+class QWidget;
+class QMainWindow;
+class QFile;
+QT_END_NAMESPACE
+
+class AbstractViewer;
+
+class ViewerFactory
+{
+public:
+    enum class DefaultPolicy {
+        NeverDefault,
+        DefaultToTxtViewer,
+        DefaultToCustomViewer
+    };
+
+    explicit ViewerFactory(QWidget *displayWidget, QMainWindow *mainWindow,
+                           DefaultPolicy policy = DefaultPolicy::DefaultToTxtViewer);
+    ~ViewerFactory();
+
+    DefaultPolicy defaultPolicy() const { return m_defaultPolicy; }
+    void setDefaultPolicy(DefaultPolicy policy) { m_defaultPolicy = policy; }
+    bool defaultWarning() const { return m_defaultWarning; }
+    void setDefaultWarning(bool on) { m_defaultWarning = on; }
+
+    AbstractViewer *viewer(QFile *file) const;
+
+
+    using ViewerMap = QMap<QString, AbstractViewer *>;
+    using ViewerList = QList<AbstractViewer *>;
+    QStringList viewerNames(bool showDefault = false) const;
+    ViewerList viewers() const;
+    AbstractViewer *findViewer(const QString &viewerName) const;
+    AbstractViewer *defaultViewer() const;
+    QStringList supportedMimeTypes() const;
+
+private:
+    DefaultPolicy m_defaultPolicy;
+    QWidget *m_displayWidget;
+    QMainWindow *m_mainWindow;
+    ViewerMap m_viewers;
+    AbstractViewer *m_defaultViewer = nullptr;
+    bool m_defaultWarning = true;
+
+    void loadViewerPlugins();
+    void addViewer(QObject *viewerObject);
+    AbstractViewer *viewer(const QMimeType &type) const;
+    void unload();
+};
+
+#endif // VIEWERFACTORY_H

app/viewerinterfaces.h

@@ -0,0 +1,35 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef VIEWERINTERFACES_H
+#define VIEWERINTERFACES_H
+
+#include "abstractviewer.h"
+
+#include <QtPlugin>
+
+QT_BEGIN_NAMESPACE
+class QPrinter;
+QT_END_NAMESPACE
+
+class ViewerInterface : public AbstractViewer
+{
+public:
+    virtual ~ViewerInterface() = default;
+    virtual QString viewerName() const override = 0;
+    virtual QByteArray saveState() const override = 0;
+    virtual bool restoreState(QByteArray &) override = 0;
+    virtual bool supportsOverview() const override = 0;
+    virtual bool hasContent() const override = 0;
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+    virtual void printDocument(QPrinter *) const override = 0;
+    virtual QStringList supportedMimeTypes() const override = 0;
+#endif
+};
+
+QT_BEGIN_NAMESPACE
+#define ViewerInterface_iid "org.qt-project.Qt.Examples.DocumentViewer.ViewerInterface/1.0"
+Q_DECLARE_INTERFACE(ViewerInterface, ViewerInterface_iid)
+QT_END_NAMESPACE
+
+#endif //VIEWERINTERFACES_H

compile_commands.json

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+{
+  "directory": "/home/talksik/code/qt-tinkering/documentviewer/build/plugins/txtviewer",
+  "command": "/usr/bin/c++ -DQT_CORE_LIB -DQT_DEPRECATED_WARNINGS -DQT_DOCUMENTVIEWER_PRINTSUPPORT -DQT_GUI_LIB -DQT_NO_CAST_FROM_ASCII -DQT_PLUGIN -DQT_PRINTSUPPORT_LIB -DQT_WIDGETS_LIB -Dtxtviewer_EXPORTS -I/home/talksik/code/qt-tinkering/documentviewer/build/plugins/txtviewer/txtviewer_autogen/include -I/home/talksik/code/qt-tinkering/documentviewer/plugins/txtviewer/../../app -isystem /home/talksik/Qt/6.6.1/gcc_64/include/QtCore -isystem /home/talksik/Qt/6.6.1/gcc_64/include -isystem /home/talksik/Qt/6.6.1/gcc_64/mkspecs/linux-g++ -isystem /home/talksik/Qt/6.6.1/gcc_64/include/QtGui -isystem /home/talksik/Qt/6.6.1/gcc_64/include/QtWidgets -isystem /home/talksik/Qt/6.6.1/gcc_64/include/QtPrintSupport -g -fPIC -fPIC -o CMakeFiles/txtviewer.dir/txtviewer_autogen/mocs_compilation.cpp.o -c /home/talksik/code/qt-tinkering/documentviewer/build/plugins/txtviewer/txtviewer_autogen/mocs_compilation.cpp",
+  "file": "/home/talksik/code/qt-tinkering/documentviewer/build/plugins/txtviewer/txtviewer_autogen/mocs_compilation.cpp"
+},
+{
+  "directory": "/home/talksik/code/qt-tinkering/documentviewer/build/plugins/txtviewer",
+  "command": "/usr/bin/c++ -DQT_CORE_LIB -DQT_DEPRECATED_WARNINGS -DQT_DOCUMENTVIEWER_PRINTSUPPORT -DQT_GUI_LIB -DQT_NO_CAST_FROM_ASCII -DQT_PLUGIN -DQT_PRINTSUPPORT_LIB -DQT_WIDGETS_LIB -Dtxtviewer_EXPORTS -I/home/talksik/code/qt-tinkering/documentviewer/build/plugins/txtviewer/txtviewer_autogen/include -I/home/talksik/code/qt-tinkering/documentviewer/plugins/txtviewer/../../app -isystem /home/talksik/Qt/6.6.1/gcc_64/include/QtCore -isystem /home/talksik/Qt/6.6.1/gcc_64/include -isystem /home/talksik/Qt/6.6.1/gcc_64/mkspecs/linux-g++ -isystem /home/talksik/Qt/6.6.1/gcc_64/include/QtGui -isystem /home/talksik/Qt/6.6.1/gcc_64/include/QtWidgets -isystem /home/talksik/Qt/6.6.1/gcc_64/include/QtPrintSupport -g -fPIC -fPIC -o CMakeFiles/txtviewer.dir/txtviewer.cpp.o -c /home/talksik/code/qt-tinkering/documentviewer/plugins/txtviewer/txtviewer.cpp",
+  "file": "/home/talksik/code/qt-tinkering/documentviewer/plugins/txtviewer/txtviewer.cpp"
+}
+]

doc/src/documentviewer.qdoc

@@ -0,0 +1,288 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
+
+/*!
+    \title Document Viewer
+    \ingroup examples-widgets
+    \example demos/documentviewer
+    \examplecategory {Application Examples}
+    \meta {tag} {demo,widgets,mainwindow}
+    \brief A Widgets application to display and print JSON, text, and PDF files.
+
+
+    \e{Document Viewer} demonstrates how to use a QMainWindow with static
+    and dynamic toolbars, menus, and actions. Additionally, it demonstrates
+    the following features in widget-based applications:
+
+    \list
+        \li Using QSettings to query and save user preferences,
+            and managing previously opened file history.
+        \li Controlling cursor behavior when hovering over widgets.
+        \li Creating dynamically loaded plugins.
+    \endlist
+
+    \image documentviewer_open.png
+
+
+    \section1 Creating an application and the main window
+
+    The application and its main window is constructed in \c main.cpp.
+    The main() function uses QCommandLineParser to process command line
+    arguments -- \e help, \e version, and an optional positional
+    argument, \e file. If the user provided a path to a file when
+    launching the application, the main window opens it:
+
+    \quotefromfile demos/documentviewer/app/main.cpp
+    \skipto int main
+    \printuntil exec
+    \printline }
+
+
+    \section1 MainWindow class
+
+    The \c MainWindow class provides an application screen with menus,
+    actions, and a toolbar. It can open a file, automatically detecting its
+    content type. It also maintains a list of previously opened files, using
+    QSettings to store and reload settings when launched. The MainWindow
+    creates a suitable \e viewer for the opened file, based on its content type,
+    and provides support for printing a document.
+
+    MainWindow's constructor initializes the user interface created in Qt
+    Designer. The \c mainwindow.ui file provides a QTabWidget on the left,
+    showing bookmarks and thumbnails. On the right, there is a QScrollArea for
+    viewing file content.
+
+
+    \section1 ViewerFactory class
+
+    The \c ViewerFactory class manages viewers for known file types. These viewers
+    are implemented as plugins. When an instance of a ViewerFactory is created,
+    pointers to the view area and the main window are passed to the constructor:
+
+    \code
+    m_factory.reset(new ViewerFactory(ui->viewArea, this));
+    \endcode
+
+    ViewerFactory loads all available plugins on construction. It provides
+    a public API to query the loaded plugins, their names, and supported MIME
+    types:
+
+    \quotefromfile demos/documentviewer/app/viewerfactory.h
+    \skipto ViewerList
+    \printuntil QStringList supportedMimeTypes() const;
+
+    The \c viewer() function returns a pointer to the plugin suitable to open
+    the QFile passed as an argument:
+
+    \code
+    m_viewer = m_factory->viewer(file);
+    \endcode
+
+    If the application settings contain a section for the viewer, it's passed
+    to the viewer's virtual \c restoreState() function:
+
+    \quotefromfile demos/documentviewer/app/mainwindow.cpp
+    \skipto MainWindow::restoreViewerSettings
+    \printuntil restoreState
+    \printline }
+
+    Then, the standard UI assets are passed to the viewer and the main scroll
+    area is set to show the viewer's display widget:
+
+    \quotefromfile demos/documentviewer/app/mainwindow.cpp
+    \skipuntil bool MainWindow::openFile
+    \skipto m_viewer->initViewer
+    \printuntil }
+
+
+    \section1 AbstractViewer class
+
+    \c AbstractViewer provides a generalized API to view, save, and print a
+    document. Properties of both the document and the viewer can be queried:
+
+    \list
+        \li Does the document have content?
+        \li Has it been modified?
+        \li Is an overview (thumbnails or bookmarks) supported?
+    \endlist
+
+    AbstractViewer provides protected methods for derived classes to create
+    actions and menus on the main window. In order to display these
+    assets on the main window, they are parented to it. AbstractViewer is
+    responsible for removing and destroying the UI assets it creates. It
+    inherits from QObject to implement signals and slots.
+
+    \section2 Signals
+
+    \c {void uiInitialized();}
+
+    This signal is emitted after a viewer receives all necessary information
+    about UI assets on the main window.
+
+    \c {void printingEnabledChanged(bool enabled);}
+
+    This signal is emitted when document printing is either enabled or
+    disabled. This happens after a new document was successfully loaded,
+    or, for example, all content was removed.
+
+    \c {void printStatusChanged(AbstractViewer::PrintStatus status);}
+
+    After starting the printing process, this signal notifies about changes in
+    its progress.
+
+    \c {void documentLoaded(const QString &fileName);}
+
+    This signal notifies the application that a document was successfully
+    loaded.
+
+
+    \section1 TxtViewer class
+
+    \c TxtViewer is a simple text viewer, inheriting from AbstractViewer.
+    It supports editing text files, copy/cut and paste, printing, and
+    saving changes.
+
+
+    \section1 JsonViewer class
+
+    \c JsonViewer displays a JSON file in a QTreeView. Internally, it loads
+    the contents of a file into a QJsonDocument and uses it to populate a
+    custom tree model with \c JsonItemModel.
+
+    The JSON viewer plugin demonstrates how to implement a custom item model
+    inherited from QAbstractItemModel. The \c JsonTreeItem class provides a
+    basic API for manipulating JSON data and propagating it back to the
+    underlying QJsonDocument.
+
+    JsonViewer uses the top-level objects of the document as bookmarks for
+    navigation. Other nodes (keys and values) can be added as additional
+    bookmarks, or removed from the bookmark list. A QLineEdit is used as a
+    search field to navigate through the JSON tree.
+
+
+    \section1 PdfViewer class
+
+    The \c PdfViewer class (and plugin) is a fork of the \l {PDF Viewer
+    Widget Example}. It demonstrates the use of QScroller to smoothly
+    flick through a document.
+
+
+    \section1 Other relevant classes
+
+    \section2 HoverWatcher class
+
+    The \c HoverWatcher class sets an override cursor when hovering the
+    mouse over a widget, restoring it upon departure. To prevent multiple
+    HoverWatcher instances being created for the same widget, it is
+    implemented as a singleton per widget.
+
+    HoverWatcher inherits from QObject and takes the QWidget it watches
+    as the instance's parent. It installs an event filter to intercept hover
+    events without consuming them:
+
+    \quotefromfile demos/documentviewer/plugins/pdfviewer/hoverwatcher.cpp
+    \skipto HoverWatcher::HoverWatcher
+    \printuntil }
+
+    The \c HoverAction enum lists the actions that HoverWatcher reacts to:
+
+    \quotefromfile demos/documentviewer/plugins/pdfviewer/hoverwatcher.h
+    \skipto enum HoverAction
+    \printuntil };
+
+    Static functions create watchers, check their existence for a specific
+    QWidget, or dismiss a watcher:
+
+    \quotefromfile demos/documentviewer/plugins/pdfviewer/hoverwatcher.h
+    \skipto static HoverWatcher
+    \printuntil static void dismiss
+
+    A cursor shape can be set or unset for each HoverAction. If there is
+    no associated cursor shape, the application's override cursor is
+    restored when the action is triggered.
+
+    \quotefromfile demos/documentviewer/plugins/pdfviewer/hoverwatcher.h
+    \skipto public slots
+    \printuntil void unSetCursorShape
+
+    The \c mouseButtons property holds the mouse buttons to consider for a
+    \c MousePress action:
+
+    \quotefromfile demos/documentviewer/plugins/pdfviewer/hoverwatcher.h
+    \skipuntil public slots
+    \skipto setMouseButtons
+    \printuntil setMouseButton(
+
+    Action-specific signals are emitted after processing an action:
+
+    \quotefromfile demos/documentviewer/plugins/pdfviewer/hoverwatcher.h
+    \skipto signals
+    \printuntil left();
+
+    A general signal is emitted which passes the processed action as an
+    argument:
+
+    \code
+    void hoverAction(HoverAction action);
+    \endcode
+
+    \section2 RecentFiles class
+
+    \c RecentFiles is a QStringList that is specialized to manage a list of
+    recently opened files.
+
+    RecentFiles has slots to add either a single file or multiple files in one
+    go. An entry is added to the list of recent files if the path points to a
+    file that exists and can be opened. If a file is already in the list, it
+    is removed from its original position and added to the top.
+
+    \quotefromfile demos/documentviewer/app/recentfiles.h
+    \skipto public slots
+    \printuntil addFiles
+
+    Files are removed from the list either by name or by index:
+
+    \quotefromfile demos/documentviewer/app/recentfiles.h
+    \skipuntil public slots
+    \skipto removeFile
+    \printuntil qsizetype index
+
+    Slots that implement saving and restoring from QSettings:
+
+    \quotefromfile demos/documentviewer/app/recentfiles.h
+    \skipuntil public slots
+    \skipto saveSettings
+    \printuntil restoreFromSettings
+
+    When restoring settings, nonexistent files are ignored. The \c maxFiles
+    property holds the maximum amount of recent files to store (default is
+    10).
+
+    \code
+    qsizetype maxFiles();
+    void setMaxFiles(qsizetype maxFiles);
+    \endcode
+
+    \c {RecentFiles} verifies that a file can be read before
+    accepting it.
+
+    \section2 RecentFileMenu class
+
+    \c {RecentFileMenu} is a QMenu, specialized to display a
+    \l{RecentFiles class}{RecentFiles} object as a submenu.
+
+    Its constructor takes a pointer to a parent QObject and a pointer to a
+    RecentFiles object, the content of which it will visualize.
+    Its \c fileOpened() signal, triggered when the user selects a recent file
+    from the list, passes the absolute path to the file as an argument.
+
+    \note \c {RecentFileMenu} is destroyed either by its parent widget, or by the
+          \c {RecentFiles} object passed to its constructor.
+
+    \quotefromfile demos/documentviewer/app/recentfilemenu.h
+    \skipto class RecentFileMenu
+    \printuntil void fileOpened
+    \dots
+    \skipuntil RecentFiles
+    \printline }
+*/

doc/src/txtviewer.qdoc

@@ -0,0 +1,111 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
+
+/*!
+    \example demos/documentviewer/plugins/txtviewer
+    \title Qt Widgets - Text Viewer Plugin Example
+    \examplecategory {Graphics & Multimedia}
+    \ingroup examples-mainwindow
+
+    \brief A widget example with menus, toolbars and a status bar.
+
+    The Text Viewer example is a text editor built around QPlainTextEdit,
+    in the form of a plugin for a general-purpose \l {Document Viewer}.
+
+    \image txtviewer_screenshot.png
+
+    All of the code for the Text Viewer example is in the \c TxtViewer class,
+    which inherits \c AbstractViewer. \c AbstractViewer provides the framework
+    for interaction between a viewer and the main window. The application provides
+    \uicontrol{File}, \uicontrol{Edit}, and \uicontrol{Help} entries in the menu
+    bar.
+
+    The status bar at the bottom of the main window shows a message provided by
+    the application to its user.
+
+    Recently opened files are shown in the \uicontrol{File} menu.
+    The example can only load one file at a time.
+
+    \section1 Class Definition
+
+    \snippet demos/documentviewer/plugins/txtviewer/txtviewer.h interfacing
+
+    The class definition starts with the \c Q_OBJECT macro, which handles
+    signals and slots. It is followed by the \c Q_PLUGIN_METADATA and
+    \c Q_INTERFACES macros which are necessary to register the plugin.
+
+    The class inherits from \c ViewerInterface, which inherits from
+    \c AbstractViewer. The \c ViewerInterface class is used to provide an interface
+    between the main window application and the plugin.
+
+    \c QPluginLoader also requires the file txtviewer.json, which has to contain
+    the plugin's key:
+    \code
+    { "Keys": [ "txtviewer" ] }
+    \endcode
+
+    \snippet demos/documentviewer/plugins/txtviewer/txtviewer.h classDefinition
+
+    The class defines no constructor, which means that only a standard constructor
+    without arguments is available. All other functions, including the destructor,
+    re-implement virtual functions of \c ViewerInterface. They are used to exchange
+    data, information, and instructions with the main application.
+
+    No functionality is implemented to save and restore settings.
+    The \c supportsOverview function always returns \c false, which tells the main
+    application that no window for thumbnail navigation has to be displayed.
+
+    \section1 TxtViewer Class Implementation
+
+    \snippet demos/documentviewer/plugins/txtviewer/txtviewer.cpp init
+
+    We start by including the header files necessary to access all classes used by
+    \c TxtViewer. We also include \c txtviewer.h.
+
+    \c QPrinter and \c QPrintDialog are only included if print support is enabled
+    on the compilation system.
+
+    You might wonder why we don't include these headers in \c mainwindow.h and
+    be done with it. The reason is that including multiple large headers from another
+    header file can rapidly degrade performance. Here, it wouldn't do any harm,
+    but it's still generally a good idea to include only the header files that are
+    strictly necessary from another header file.
+
+    The implementation starts with an empty destructor. It could be completely omitted.
+    It's good practice to implement it empty in order to point out to code readers that
+    nothing needs to be done in the destructor.
+
+    The destructor is followed by an initialization function, taking three arguments:
+    \list
+    \li \c file, the pointer to the file to be opened and displayed.
+    \li \c parent, pointing to the \c QWidget inside which the editor shall be placed.
+    \li \c mainWindow, pointing to the application's main window, where menus and menu bars
+    are handled.
+    \endlist
+    The function calls the base init function of \c AbstractViwer.
+    A new QPlainTextEdit widget is created, which will display the file's contents.
+    Then, \c TxtViewer's setup function is connected to the base class' uiInitialized signal.
+
+    The next function returns the list of mime types, which the text viewer supports.
+    Only plain text is supported.
+
+    The last initialization function adds viewer specific UI components like menus,
+    icons, buttons, and tooltips. It uses functionality provided by \c AbstractViewer
+    to make sure that these components are removed from the application's main window,
+    once another file is displayed with another viewer plugin.
+
+    \snippet demos/documentviewer/plugins/txtviewer/txtviewer.cpp open
+
+    \c openFile opens a file, transfers its contents into the QPlainTextEdit, and prints
+    a status message for the user, depending on whether or not the opening was successful.
+
+    \snippet demos/documentviewer/plugins/txtviewer/txtviewer.cpp infoPrintAndSave
+
+    The next re-implemented function tells the main application whether or not the viewer
+    plugin is actually displaying content.
+
+    If printing is supported on the compiling system, the next section implements it.
+
+    The last two re-implementations provide functionality to save the current file or
+    to save it under a new name.
+*/

plugins/CMakeLists.txt

@@ -0,0 +1,9 @@
+# Copyright (C) 2023 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+add_subdirectory(jsonviewer)
+add_subdirectory(txtviewer)
+
+if(TARGET Qt6::PdfWidgets)
+    add_subdirectory(pdfviewer)
+endif()

plugins/jsonviewer/CMakeLists.txt

@@ -0,0 +1,35 @@
+# Copyright (C) 2023 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+qt_add_plugin(jsonviewer
+    CLASS_NAME JsonViewer
+    jsonviewer.cpp jsonviewer.h
+)
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets
+                 OPTIONAL_COMPONENTS PrintSupport)
+
+set_target_properties(jsonviewer PROPERTIES
+    LIBRARY_OUTPUT_DIRECTORY "${PROJECT_BINARY_DIR}/app"
+)
+
+target_include_directories(jsonviewer PRIVATE
+    ../../app
+)
+
+target_link_libraries(jsonviewer PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Widgets
+    abstractviewer
+)
+
+if(TARGET Qt6::PrintSupport)
+    target_link_libraries(jsonviewer PRIVATE Qt6::PrintSupport)
+endif()
+
+install(TARGETS jsonviewer
+    BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}/plugins"
+    LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}/plugins"
+)
+

plugins/jsonviewer/jsonviewer.cpp

@@ -0,0 +1,525 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "jsonviewer.h"
+
+#include <QApplication>
+#include <QHeaderView>
+#include <QLabel>
+#include <QLineEdit>
+#include <QListWidget>
+#include <QMenu>
+#include <QToolBar>
+#include <QTreeView>
+
+#include <QDrag>
+#include <QEvent>
+#include <QMouseEvent>
+
+#include <QDir>
+#include <QFile>
+#include <QJsonArray>
+#include <QJsonDocument>
+#include <QJsonObject>
+#include <QJsonValue>
+#include <QMimeData>
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+#include <QPrinter>
+#include <QPainter>
+#endif
+
+using namespace Qt::StringLiterals;
+
+JsonViewer::JsonViewer()
+{
+    connect(this, &AbstractViewer::uiInitialized, this, &JsonViewer::setupJsonUi);
+}
+
+void JsonViewer::init(QFile *file, QWidget *parent, QMainWindow *mainWindow)
+{
+    AbstractViewer::init(file, new QTreeView(parent), mainWindow);
+    m_tree = qobject_cast<QTreeView *>(widget());
+}
+
+JsonViewer::~JsonViewer()
+{
+    delete m_toplevel;
+}
+
+QStringList JsonViewer::supportedMimeTypes() const
+{
+    return {"application/json"_L1};
+}
+
+void JsonViewer::setupJsonUi()
+{
+    // Build Menus and toolbars
+    QMenu *menu  = addMenu(tr("Json"));
+    QToolBar *tb = addToolBar(tr("Json Actions"));
+
+    const QIcon zoomInIcon = QIcon::fromTheme("zoom-in"_L1);
+    QAction *a = menu->addAction(zoomInIcon,  tr("&+Expand all"), m_tree, &QTreeView::expandAll);
+    tb->addAction(a);
+    a->setPriority(QAction::LowPriority);
+    a->setShortcut(QKeySequence::New);
+
+    const QIcon zoomOutIcon = QIcon::fromTheme("zoom-out"_L1);
+    a = menu->addAction(zoomOutIcon,  tr("&-Collapse all"), m_tree, &QTreeView::collapseAll);
+    tb->addAction(a);
+    a->setPriority(QAction::LowPriority);
+    a->setShortcut(QKeySequence::New);
+
+    if (!m_searchKey)
+        m_searchKey = new QLineEdit(tb);
+
+    auto *label = new QLabel(tb);
+    const QPixmap magnifier = QPixmap(":/icons/images/magnifier.png"_L1).scaled(QSize(28, 28));
+    label->setPixmap(magnifier);
+    tb->addWidget(label);
+    tb->addWidget(m_searchKey);
+    connect(m_searchKey, &QLineEdit::textEdited, m_tree, &QTreeView::keyboardSearch);
+
+    openJsonFile();
+
+    if (m_root.isEmpty())
+        return;
+
+    // Populate bookmarks with toplevel
+    m_uiAssets.tabs->clear();
+    m_toplevel = new QListWidget(m_uiAssets.tabs);
+    m_uiAssets.tabs->addTab(m_toplevel, tr("Bookmarks"));
+    qRegisterMetaType<QModelIndex>();
+    for (int i = 0; i < m_tree->model()->rowCount(); ++i) {
+        const auto &index = m_tree->model()->index(i, 0);
+        m_toplevel->addItem(index.data().toString());
+        auto *item = m_toplevel->item(i);
+        item->setData(Qt::UserRole, index);
+        item->setToolTip(tr("Toplevel Item %1").arg(i));
+    }
+    m_toplevel->setAcceptDrops(true);
+    m_tree->setDragEnabled(true);
+    m_tree->setContextMenuPolicy(Qt::CustomContextMenu);
+    m_toplevel->setContextMenuPolicy(Qt::CustomContextMenu);
+
+    connect(m_toplevel, &QListWidget::itemClicked, this, &JsonViewer::onTopLevelItemClicked);
+    connect(m_toplevel, &QListWidget::itemDoubleClicked, this, &JsonViewer::onTopLevelItemDoubleClicked);
+    connect(m_toplevel, &QListWidget::customContextMenuRequested, this, &JsonViewer::onBookmarkMenuRequested);
+    connect(m_tree, &QTreeView::customContextMenuRequested, this, &JsonViewer::onJsonMenuRequested);
+
+    // Connect back and forward
+    connect(m_uiAssets.back, &QAction::triggered, m_tree, [&](){
+        const QModelIndex &index = m_tree->indexAbove(m_tree->currentIndex());
+        if (index.isValid())
+            m_tree->setCurrentIndex(index);
+    });
+    connect(m_uiAssets.forward, &QAction::triggered, m_tree, [&](){
+        QModelIndex current = m_tree->currentIndex();
+        QModelIndex next = m_tree->indexBelow(current);
+        if (next.isValid()) {
+            m_tree->setCurrentIndex(next);
+            return;
+        }
+
+        // Expand last item to go beyond
+        if (!m_tree->isExpanded(current)) {
+            m_tree->expand(current);
+            QModelIndex next = m_tree->indexBelow(current);
+            if (next.isValid()) {
+                m_tree->setCurrentIndex(next);
+            }
+        }
+    });
+}
+
+void resizeToContents(QTreeView *tree)
+{
+    for (int i = 0; i < tree->header()->count(); ++i)
+        tree->resizeColumnToContents(i);
+}
+
+bool JsonViewer::openJsonFile()
+{
+    disablePrinting();
+
+    QJsonParseError err;
+    m_file->open(QIODevice::ReadOnly);
+    m_root = QJsonDocument::fromJson(m_file->readAll(), &err);
+    const QString type = tr("open");
+    if (err.error != QJsonParseError::NoError) {
+        statusMessage(tr("Unable to parse Json document from %1. %2")
+                      .arg(QDir::toNativeSeparators(m_file->fileName()),
+                           err.errorString()), type);
+        return false;
+    }
+
+    statusMessage(tr("Json document %1 opened")
+                  .arg(QDir::toNativeSeparators(m_file->fileName())), type);
+    m_file->close();
+
+    maybeEnablePrinting();
+
+    JsonItemModel *model = new JsonItemModel(m_root, this);
+    m_tree->setModel(model);
+
+    return true;
+}
+
+QModelIndex indexOf(const QListWidgetItem *item)
+{
+    return qvariant_cast<QModelIndex>(item->data(Qt::UserRole));
+}
+
+// Move to the clicked toplevel index
+void JsonViewer::onTopLevelItemClicked(QListWidgetItem *item)
+{
+    // return in the unlikely case that the tree has not been built
+    if (Q_UNLIKELY(!m_tree->model()))
+        return;
+
+    auto index = indexOf(item);
+    if (Q_UNLIKELY(!index.isValid()))
+        return;
+
+    m_tree->setCurrentIndex(index);
+}
+
+// Toggle double clicked index between collaps/expand
+void JsonViewer::onTopLevelItemDoubleClicked(QListWidgetItem *item)
+{
+    // return in the unlikely case that the tree has not been built
+    if (Q_UNLIKELY(!m_tree->model()))
+        return;
+
+    auto index = indexOf(item);
+    if (Q_UNLIKELY(!index.isValid()))
+        return;
+
+    if (m_tree->isExpanded(index)) {
+        m_tree->collapse(index);
+        return;
+    }
+
+    // Make sure the node and all parents are expanded
+    while (index.isValid()) {
+        m_tree->expand(index);
+        index = index.parent();
+    }
+}
+
+void JsonViewer::onJsonMenuRequested(const QPoint &pos)
+{
+    const auto &index = m_tree->indexAt(pos);
+    if (!index.isValid())
+        return;
+
+    // Don't show a context menu, if the index is already a bookmark
+    for (int i = 0; i < m_toplevel->count(); ++i) {
+        if (indexOf(m_toplevel->item(i)) == index)
+            return;
+    }
+
+    QMenu menu(m_tree);
+    QAction *action = new QAction(tr("Add bookmark"));
+    action->setData(index);
+    menu.addAction(action);
+    connect(action, &QAction::triggered, this, &JsonViewer::onBookmarkAdded);
+    menu.exec(m_tree->mapToGlobal(pos));
+}
+
+void JsonViewer::onBookmarkMenuRequested(const QPoint &pos)
+{
+    auto *item = m_toplevel->itemAt(pos);
+    if (!item)
+        return;
+
+    // Don't delete toplevel items
+    const QModelIndex index = indexOf(item);
+    if (!index.parent().isValid())
+        return;
+
+    QMenu menu;
+    QAction *action = new QAction(tr("Delete bookmark"));
+    action->setData(m_toplevel->row(item));
+    menu.addAction(action);
+    connect(action, &QAction::triggered, this, &JsonViewer::onBookmarkDeleted);
+    menu.exec(m_toplevel->mapToGlobal(pos));
+}
+
+void JsonViewer::onBookmarkAdded()
+{
+    const QAction *action = qobject_cast<QAction *>(sender());
+    if (!action)
+        return;
+
+    const QModelIndex index = qvariant_cast<QModelIndex>(action->data());
+    if (!index.isValid())
+        return;
+
+    auto *item = new QListWidgetItem(index.data(Qt::DisplayRole).toString(), m_toplevel);
+    item->setData(Qt::UserRole, index);
+
+    // Set a tooltip that shows where the item is located in the tree
+    QModelIndex parent = index.parent();
+    QString tooltip = index.data(Qt::DisplayRole).toString();
+    while (parent.isValid()) {
+        tooltip = parent.data(Qt::DisplayRole).toString() + "->"_L1 + tooltip;
+        parent = parent.parent();
+    }
+    item->setToolTip(tooltip);
+}
+
+void JsonViewer::onBookmarkDeleted()
+{
+    const QAction *action = qobject_cast<QAction *>(sender());
+    if (!action)
+        return;
+
+    const int row = action->data().toInt();
+    if (row < 0 || row >= m_toplevel->count())
+        return;
+
+    delete m_toplevel->takeItem(row);
+}
+
+bool JsonViewer::hasContent() const
+{
+    return !m_root.isEmpty();
+}
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+void JsonViewer::printDocument(QPrinter *printer) const
+{
+    if (!hasContent())
+        return;
+
+    const QTextDocument doc(QString::fromUtf8(m_root.toJson(QJsonDocument::JsonFormat::Indented)));
+    doc.print(printer);
+}
+
+#endif // QT_DOCUMENTVIEWER_PRINTSUPPORT
+
+QByteArray JsonViewer::saveState() const
+{
+    QByteArray array;
+    QDataStream stream(&array, QIODevice::WriteOnly);
+    stream << QString(viewerName());
+    stream << m_tree->header()->saveState();
+    return array;
+}
+
+bool JsonViewer::restoreState(QByteArray &array)
+{
+    QDataStream stream(&array, QIODevice::ReadOnly);
+    QString viewer;
+    stream >> viewer;
+    if (viewer != viewerName())
+        return false;
+    QByteArray header;
+    stream >> header;
+    return m_tree->header()->restoreState(header);
+}
+
+JsonTreeItem::JsonTreeItem(JsonTreeItem *parent)
+{
+    m_parent = parent;
+}
+
+JsonTreeItem::~JsonTreeItem()
+{
+    qDeleteAll(m_children);
+}
+
+void JsonTreeItem::appendChild(JsonTreeItem *item)
+{
+    m_children.append(item);
+}
+
+JsonTreeItem *JsonTreeItem::child(int row)
+{
+    return m_children.value(row);
+}
+
+JsonTreeItem *JsonTreeItem::parent()
+{
+    return m_parent;
+}
+
+int JsonTreeItem::childCount() const
+{
+    return m_children.count();
+}
+
+int JsonTreeItem::row() const
+{
+    if (m_parent)
+        return m_parent->m_children.indexOf(const_cast<JsonTreeItem*>(this));
+
+    return 0;
+}
+
+void JsonTreeItem::setKey(const QString &key)
+{
+    m_key = key;
+}
+
+void JsonTreeItem::setValue(const QVariant &value)
+{
+    m_value = value;
+}
+
+void JsonTreeItem::setType(const QJsonValue::Type &type)
+{
+    m_type = type;
+}
+
+JsonTreeItem* JsonTreeItem::load(const QJsonValue& value, JsonTreeItem* parent)
+{
+    JsonTreeItem *rootItem = new JsonTreeItem(parent);
+    rootItem->setKey("root"_L1);
+
+    if (value.isObject()) {
+        const QStringList &keys = value.toObject().keys();
+        for (const QString &key : keys) {
+            QJsonValue v = value.toObject().value(key);
+            JsonTreeItem *child = load(v, rootItem);
+            child->setKey(key);
+            child->setType(v.type());
+            rootItem->appendChild(child);
+        }
+    } else if (value.isArray()) {
+        int index = 0;
+        const QJsonArray &array = value.toArray();
+        for (const QJsonValue &val : array) {
+            JsonTreeItem *child = load(val, rootItem);
+            child->setKey(QString::number(index));
+            child->setType(val.type());
+            rootItem->appendChild(child);
+            ++index;
+        }
+    } else {
+        rootItem->setValue(value.toVariant());
+        rootItem->setType(value.type());
+    }
+
+    return rootItem;
+}
+
+JsonItemModel::JsonItemModel(QObject *parent)
+    : QAbstractItemModel(parent)
+    , m_rootItem{new JsonTreeItem}
+{
+    m_headers.append("Key"_L1);
+    m_headers.append("Value"_L1);
+}
+
+JsonItemModel::JsonItemModel(const QJsonDocument &doc, QObject *parent)
+    : QAbstractItemModel(parent)
+    , m_rootItem{new JsonTreeItem}
+{
+    // Append header lines and return on empty document
+    m_headers.append("Key"_L1);
+    m_headers.append("Value"_L1);
+    if (doc.isNull())
+        return;
+
+    // Reset the model. Root can either be a value or an array.
+    beginResetModel();
+    delete m_rootItem;
+    if (doc.isArray()) {
+        m_rootItem = JsonTreeItem::load(QJsonValue(doc.array()));
+        m_rootItem->setType(QJsonValue::Array);
+
+    } else {
+        m_rootItem = JsonTreeItem::load(QJsonValue(doc.object()));
+        m_rootItem->setType(QJsonValue::Object);
+    }
+    endResetModel();
+}
+
+JsonItemModel::~JsonItemModel()
+{
+    delete m_rootItem;
+}
+
+QVariant JsonItemModel::data(const QModelIndex &index, int role) const
+{
+    if (!index.isValid())
+        return {};
+
+    JsonTreeItem *item = itemFromIndex(index);
+
+    switch (role) {
+    case Qt::DisplayRole:
+        if (index.column() == 0)
+            return item->key();
+        if (index.column() == 1)
+            return item->value();
+        break;
+    case Qt::EditRole:
+        if (index.column() == 1)
+            return item->value();
+        break;
+    default:
+        break;
+    }
+    return {};
+}
+
+QVariant JsonItemModel::headerData(int section, Qt::Orientation orientation, int role) const
+{
+    if (role != Qt::DisplayRole)
+        return {};
+
+    if (orientation == Qt::Horizontal)
+        return m_headers.value(section);
+    else
+        return {};
+}
+
+QModelIndex JsonItemModel::index(int row, int column, const QModelIndex &parent) const
+{
+    if (!hasIndex(row, column, parent))
+        return {};
+
+    JsonTreeItem *parentItem;
+
+    if (!parent.isValid())
+        parentItem = m_rootItem;
+    else
+        parentItem = itemFromIndex(parent);
+
+    JsonTreeItem *childItem = parentItem->child(row);
+    if (childItem)
+        return createIndex(row, column, childItem);
+    else
+        return {};
+}
+
+QModelIndex JsonItemModel::parent(const QModelIndex &index) const
+{
+    if (!index.isValid())
+        return {};
+
+    JsonTreeItem *childItem = itemFromIndex(index);
+    JsonTreeItem *parentItem = childItem->parent();
+
+    if (parentItem == m_rootItem)
+        return QModelIndex();
+
+    return createIndex(parentItem->row(), 0, parentItem);
+}
+
+int JsonItemModel::rowCount(const QModelIndex &parent) const
+{
+    JsonTreeItem *parentItem;
+    if (parent.column() > 0)
+        return 0;
+
+    if (!parent.isValid())
+        parentItem = m_rootItem;
+    else
+        parentItem = itemFromIndex(parent);
+
+    return parentItem->childCount();
+}

plugins/jsonviewer/jsonviewer.h

@@ -0,0 +1,109 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef JSONVIEWER_H
+#define JSONVIEWER_H
+
+#include "viewerinterfaces.h"
+
+#include <QJsonValue>
+#include <QJsonDocument>
+#include <QAbstractItemModel>
+
+QT_BEGIN_NAMESPACE
+class QTreeView;
+class QListWidget;
+class QListWidgetItem;
+class QLineEdit;
+QT_END_NAMESPACE
+
+class JsonViewer : public ViewerInterface
+{
+    Q_OBJECT
+    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.Examples.DocumentViewer.ViewerInterface/1.0" FILE "jsonviewer.json")
+    Q_INTERFACES(ViewerInterface)
+public:
+    JsonViewer();
+    ~JsonViewer() override;
+
+    void init(QFile *file, QWidget *parent, QMainWindow *mainWindow) override;
+    QString viewerName() const override { return QLatin1StringView(staticMetaObject.className()); };
+    QStringList supportedMimeTypes() const override;
+    QByteArray saveState() const override;
+    bool restoreState(QByteArray &) override;
+    bool supportsOverview() const override { return true; }
+    bool hasContent() const override;
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+protected:
+    void printDocument(QPrinter *printer) const override;
+#endif // QT_ABSTRACTVIEWER_PRINTSUPPORT
+
+private slots:
+    void setupJsonUi();
+    void onTopLevelItemClicked(QListWidgetItem *item);
+    void onTopLevelItemDoubleClicked(QListWidgetItem *item);
+    void onJsonMenuRequested(const QPoint &pos);
+    void onBookmarkMenuRequested(const QPoint &pos);
+    void onBookmarkAdded();
+    void onBookmarkDeleted();
+
+private:
+    bool openJsonFile();
+
+    QTreeView *m_tree;
+    QListWidget *m_toplevel = nullptr;
+    QJsonDocument m_root;
+
+    QPointer<QLineEdit> m_searchKey;
+};
+
+class JsonTreeItem
+{
+public:
+    JsonTreeItem(JsonTreeItem *parent = nullptr);
+    ~JsonTreeItem();
+    void appendChild(JsonTreeItem *item);
+    JsonTreeItem *child(int row);
+    JsonTreeItem *parent();
+    int childCount() const;
+    int row() const;
+    void setKey(const QString& key);
+    void setValue(const QVariant& value);
+    void setType(const QJsonValue::Type& type);
+    QString key() const { return m_key; };
+    QVariant value() const { return m_value; };
+    QJsonValue::Type type() const { return m_type; };
+
+    static JsonTreeItem* load(const QJsonValue& value, JsonTreeItem *parent = nullptr);
+
+private:
+    QString m_key;
+    QVariant m_value;
+    QJsonValue::Type m_type;
+    QList<JsonTreeItem*> m_children;
+    JsonTreeItem *m_parent = nullptr;
+};
+
+class JsonItemModel : public QAbstractItemModel
+{
+    Q_OBJECT
+public:
+    explicit JsonItemModel(QObject *parent = nullptr);
+    JsonItemModel(const QJsonDocument& doc, QObject *parent = nullptr);
+    ~JsonItemModel();
+    QVariant data(const QModelIndex &index, int role) const override;
+    QVariant headerData(int section, Qt::Orientation orientation, int role) const override;
+    QModelIndex index(int row, int column,const QModelIndex &parent = QModelIndex()) const override;
+    QModelIndex parent(const QModelIndex &index) const override;
+    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
+    int columnCount(const QModelIndex & = QModelIndex()) const override { return 2; };
+
+private:
+    JsonTreeItem *m_rootItem = nullptr;
+    QStringList m_headers;
+    static JsonTreeItem *itemFromIndex(const QModelIndex &index)
+    {return static_cast<JsonTreeItem*>(index.internalPointer()); }
+};
+
+#endif //JSONVIEWER_H

plugins/jsonviewer/jsonviewer.json

@@ -0,0 +1 @@
+{ "Keys": [ "jsonviewer" ] }

plugins/pdfviewer/CMakeLists.txt

@@ -0,0 +1,39 @@
+# Copyright (C) 2023 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets PdfWidgets
+                 OPTIONAL_COMPONENTS PrintSupport)
+
+qt_add_plugin(pdfviewer
+    CLASS_NAME PdfViewer
+    pdfviewer.cpp pdfviewer.h
+    zoomselector.cpp zoomselector.h
+    hoverwatcher.cpp hoverwatcher.h
+)
+
+set_target_properties(pdfviewer PROPERTIES
+    LIBRARY_OUTPUT_DIRECTORY "${PROJECT_BINARY_DIR}/app"
+)
+
+target_include_directories(pdfviewer PRIVATE
+    ../../app
+    ..
+)
+
+target_link_libraries(pdfviewer PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Widgets
+    Qt6::PdfWidgets
+    abstractviewer
+)
+
+if(TARGET Qt6::PrintSupport)
+    target_link_libraries(pdfviewer PRIVATE Qt6::PrintSupport)
+endif()
+
+install(TARGETS pdfviewer
+    BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}/plugins"
+    LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}/plugins"
+)
+

plugins/pdfviewer/hoverwatcher.cpp

@@ -0,0 +1,212 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+#include "hoverwatcher.h"
+#include <QGuiApplication>
+#include <QWidget>
+#include <QMouseEvent>
+
+HoverWatcher::HoverWatcher(QWidget *watched)
+    : QObject(watched), m_watched(watched)
+{
+    Q_ASSERT(watched);
+    m_cursorShapes[Entered].emplace(Qt::OpenHandCursor);
+    m_cursorShapes[MousePress].emplace(Qt::ClosedHandCursor);
+    m_cursorShapes[MouseRelease].emplace(Qt::OpenHandCursor);
+    // no default for Left => restore override cursor
+    m_watched->installEventFilter(this);
+}
+
+HoverWatcher::~HoverWatcher()
+{
+    m_watched->removeEventFilter(this);
+}
+
+typedef QHash<QWidget *, HoverWatcher*> WatchMap;
+Q_GLOBAL_STATIC(WatchMap, qt_allHoverWatchers)
+
+HoverWatcher *HoverWatcher::watcher(QWidget *watched)
+{
+    if (qt_allHoverWatchers()->contains(watched))
+        return qt_allHoverWatchers()->value(watched);
+
+    HoverWatcher *watcher = new HoverWatcher(watched);
+    qt_allHoverWatchers()->insert(watched, watcher);
+    return watcher;
+}
+
+/*!
+   \overload Const version of watcher
+ */
+const HoverWatcher *HoverWatcher::watcher(const QWidget *watched)
+{
+    return watcher(const_cast<QWidget *>(watched));
+}
+
+void HoverWatcher::dismiss(QWidget *watched)
+{
+    if (!hasWatcher(watched))
+        return;
+
+    delete qt_allHoverWatchers()->take(watched);
+}
+
+bool HoverWatcher::hasWatcher(QWidget *widget)
+{
+    return qt_allHoverWatchers()->contains(widget);
+}
+
+static constexpr HoverWatcher::HoverAction toHoverAction(QEvent::Type et)
+{
+    switch (et) {
+    case QEvent::Type::Enter:
+        return HoverWatcher::HoverAction::Entered;
+    case QEvent::Type::Leave:
+        return HoverWatcher::HoverAction::Left;
+    case QEvent::Type::MouseButtonPress:
+        return HoverWatcher::HoverAction::MousePress;
+    case QEvent::Type::MouseButtonRelease:
+        return HoverWatcher::HoverAction::MouseRelease;
+    default:
+        return HoverWatcher::HoverAction::Ignore;
+    }
+}
+
+void HoverWatcher::handleAction (HoverWatcher::HoverAction action)
+{
+    const Qt::CursorShape newShape = cursorShape(action);
+    if (QGuiApplication::overrideCursor()
+            && (QGuiApplication::overrideCursor()->shape() == newShape
+            || action == HoverAction::Ignore)) {
+        return;
+    }
+
+    QGuiApplication::setOverrideCursor(cursorShape(action));
+    emit hoverAction(action);
+
+    switch (action) {
+    case HoverAction::Entered:
+        emit entered();
+        break;
+    case HoverAction::Left:
+        emit left();
+        break;
+    case HoverAction::MousePress:
+        emit mousePressed();
+        break;
+    case HoverAction::MouseRelease: {
+        emit mouseReleased();
+    }
+        break;
+    case HoverAction::Ignore:
+        break;
+    }
+}
+
+bool HoverWatcher::hasShape(HoverAction action) const
+{
+    return action != HoverAction::Ignore && m_cursorShapes[action].has_value();
+}
+
+void HoverWatcher::setApplicationCursor(HoverAction action) const
+{
+    if (!hasShape(action)) {
+        QGuiApplication::restoreOverrideCursor();
+        return;
+    }
+
+    QGuiApplication::setOverrideCursor(cursorShape(action));
+}
+
+bool HoverWatcher::eventFilter(QObject *obj, QEvent *event)
+{
+    Q_ASSERT(obj == m_watched); // don't install event filters elsewhere
+
+    // Ignore irrelevant events
+    const auto action = toHoverAction(event->type());
+    if (action == HoverAction::Ignore)
+        return false;
+
+    // React to a QScroller having been installed or removed
+    // A Scroller sends a fake mouse release to QPoint (-1, -1)
+    // => needs to be ignored and end of scrolling processed instead
+    static bool hasScroller = false;
+    if (QScroller::hasScroller(m_watched) != hasScroller) {
+        hasScroller = QScroller::hasScroller(m_watched);
+        static QMetaObject::Connection con;
+        if (hasScroller) {
+            con = connect(QScroller::scroller(m_watched), &QScroller::stateChanged,
+                          this, &HoverWatcher::handleScrollerStateChange);
+        } else {
+            disconnect(con);
+        }
+    }
+
+    // Ignore fake mouse release event sent by scroller
+    if (action == HoverAction::MouseRelease && hasScroller) {
+        QMouseEvent *me = static_cast<QMouseEvent *>(event);
+        if (me->pos().x() < -9000000 )
+            return false;
+    }
+
+    // Ignore unpermitted mouse buttons
+    if (action == HoverAction::MousePress) {
+        QMouseEvent *me = static_cast<QMouseEvent *>(event);
+        if (!m_mouseButtons.testFlag(me->button()))
+            return false;
+    }
+
+    handleAction(action);
+    return false;
+}
+
+Qt::CursorShape HoverWatcher::cursorShape(HoverAction type) const
+{
+    const Qt::CursorShape fallback = Qt::ArrowCursor;
+    if (type == HoverAction::Ignore)
+        return fallback;
+
+    return m_cursorShapes[type].value_or(fallback);
+}
+
+void HoverWatcher::setCursorShape(HoverAction type, Qt::CursorShape shape)
+{
+    if (type == HoverAction::Ignore)
+        return;
+    m_cursorShapes[type].emplace(shape);
+}
+
+void HoverWatcher::unSetCursorShape(HoverAction type)
+{
+    if (type == HoverAction::Ignore)
+        return;
+    m_cursorShapes[type].reset();
+}
+
+void HoverWatcher::setMouseButtons(Qt::MouseButtons buttons)
+{
+    m_mouseButtons = buttons;
+}
+
+void HoverWatcher::setMouseButton(Qt::MouseButton button, bool enable)
+{
+    m_mouseButtons.setFlag(button, enable);;
+}
+
+/*!
+   \brief This slot handles a QScroller state change, in case the watched
+    widget uses a scroller. It translates \param state into the appropriate
+    action.
+ */
+void HoverWatcher::handleScrollerStateChange(QScroller::State state)
+{
+    switch (state) {
+    case QScroller::State::Pressed:
+    case QScroller::State::Dragging:
+    case QScroller::State::Scrolling:
+        handleAction(HoverAction::MousePress);
+        break;
+    case QScroller::State::Inactive:
+        handleAction(HoverAction::MouseRelease);
+        break;
+    }
+}

plugins/pdfviewer/hoverwatcher.h

@@ -0,0 +1,69 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef HOVERWATCHER_H
+#define HOVERWATCHER_H
+#include <QObject>
+#include <QEvent>
+#include <QScroller>
+
+QT_BEGIN_NAMESPACE
+class QWidget;
+QT_END_NAMESPACE
+
+class HoverWatcher : public QObject
+{
+    Q_OBJECT
+
+private:
+    explicit HoverWatcher(QWidget *watched);
+    static QMap<QWidget *, HoverWatcher *> m_hoverWatchers;
+
+public:
+    ~HoverWatcher();
+
+    enum HoverAction {
+        Entered,
+        MousePress,
+        MouseRelease,
+        Left,
+        Ignore
+    };
+    Q_ENUM(HoverAction);
+
+    bool eventFilter(QObject *obj, QEvent *event) override;
+
+    Qt::CursorShape cursorShape(HoverAction type) const;
+    Qt::MouseButtons mouseButtons() const { return m_mouseButtons; }
+
+    static HoverWatcher *watcher(QWidget *watched);
+    static const HoverWatcher *watcher(const QWidget *watched);
+    static bool hasWatcher(QWidget *widget);
+    static void dismiss(QWidget *watched);
+
+public slots:
+    void setCursorShape(HoverAction type, Qt::CursorShape shape);
+    void unSetCursorShape(HoverAction type);
+    void setMouseButtons(Qt::MouseButtons buttons);
+    void setMouseButton(Qt::MouseButton button, bool enable);
+
+signals:
+    void entered();
+    void mousePressed();
+    void mouseReleased();
+    void left();
+    void hoverAction(HoverAction action);
+
+private slots:
+    void handleScrollerStateChange(QScroller::State state);
+
+private:
+    QWidget *m_watched;
+    std::array<std::optional<Qt::CursorShape>, HoverAction::Ignore> m_cursorShapes;
+    Qt::MouseButtons m_mouseButtons = Qt::MouseButton::LeftButton;
+    void handleAction(HoverAction action);
+    void setApplicationCursor(HoverAction action) const;
+    bool hasShape(HoverAction action) const;
+};
+
+#endif // HOVERWATCHER_H

plugins/pdfviewer/pdfviewer.cpp

@@ -0,0 +1,266 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "pdfviewer.h"
+#include "zoomselector.h"
+#include "hoverwatcher.h"
+
+#include <QApplication>
+#include <QEvent>
+#include <QFile>
+#include <QMouseEvent>
+
+#include <QPdfBookmarkModel>
+#include <QPdfDocument>
+#include <QPdfPageNavigator>
+#include <QPdfView>
+#if QT_VERSION >= QT_VERSION_CHECK(6,6,0)
+#include <QPdfPageSelector>
+#endif
+
+#include <QtMath>
+#include <QDir>
+#include <QStandardPaths>
+
+#include <QListView>
+#include <QPdfView>
+#include <QStandardPaths>
+
+#include <QtMath>
+#include <QStandardPaths>
+
+#include <QListView>
+#include <QListWidget>
+#include <QMainWindow>
+#include <QScrollBar>
+#include <QScroller>
+#include <QSpinBox>
+#include <QToolBar>
+#include <QTreeView>
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+#include <QPrinter>
+#include <QPainter>
+#endif
+
+Q_LOGGING_CATEGORY(lcExample, "qt.examples.pdfviewer")
+
+using namespace Qt::StringLiterals;
+
+PdfViewer::PdfViewer()
+{
+    connect(this, &AbstractViewer::uiInitialized, this, &PdfViewer::initPdfViewer);
+}
+
+void PdfViewer::init(QFile *file, QWidget *parent, QMainWindow *mainWindow)
+{
+    AbstractViewer::init(file, new QPdfView(parent), mainWindow);
+    m_document = new QPdfDocument(this);
+    m_pdfView = qobject_cast<QPdfView *>(widget());
+}
+
+void PdfViewer::cleanup()
+{
+    delete m_pageSelector;
+    m_pageSelector = nullptr;
+    delete m_zoomSelector;
+    m_zoomSelector = nullptr;
+    delete m_pages;
+    m_pages = nullptr;
+    delete m_bookmarks;
+    m_bookmarks = nullptr;
+    delete m_document;
+    m_document = nullptr;
+    AbstractViewer::cleanup();
+}
+
+PdfViewer::~PdfViewer()
+{
+    PdfViewer::cleanup();
+}
+
+QStringList PdfViewer::supportedMimeTypes() const
+{
+    return {"application/pdf"_L1};
+}
+
+void PdfViewer::initPdfViewer()
+{
+    m_toolBar = addToolBar(tr("PDF"));
+    m_zoomSelector = new ZoomSelector(m_toolBar);
+
+    auto *nav = m_pdfView->pageNavigator();
+#if QT_VERSION >= QT_VERSION_CHECK(6,6,0)
+    m_pageSelector = new QPdfPageSelector(m_toolBar);
+    m_toolBar->insertWidget(m_uiAssets.forward, m_pageSelector);
+    m_pageSelector->setDocument(m_document);
+    connect(m_pageSelector, &QPdfPageSelector::currentPageChanged,
+            this, &PdfViewer::pageSelected);
+    connect(m_pageSelector, &QPdfPageSelector::currentPageChanged,
+            this, &PdfViewer::pageSelected);
+    connect(nav, &QPdfPageNavigator::currentPageChanged,
+            m_pageSelector, &QPdfPageSelector::setCurrentPage);
+#endif
+
+    connect(m_pdfView->pageNavigator(), &QPdfPageNavigator::backAvailableChanged,
+            m_uiAssets.back, &QAction::setEnabled);
+    m_actionBack = m_uiAssets.back;
+    m_actionForward = m_uiAssets.forward;
+    m_connections.append(connect(m_uiAssets.back, &QAction::triggered,
+                                 this, &PdfViewer::onActionBackTriggered));
+    m_connections.append(connect(m_uiAssets.forward, &QAction::triggered,
+                                 this, &PdfViewer::onActionForwardTriggered));
+
+    m_toolBar->addSeparator();
+    m_toolBar->addWidget(m_zoomSelector);
+
+    auto *actionZoomIn = m_toolBar->addAction(tr("Zoom in"));
+    actionZoomIn->setToolTip(tr("Increase zoom level"));
+    actionZoomIn->setIcon(QIcon(":/demos/documentviewer/images/zoom-in.png"_L1));
+    m_toolBar->addAction(actionZoomIn);
+    connect(actionZoomIn, &QAction::triggered, this, &PdfViewer::onActionZoomInTriggered);
+
+    auto *actionZoomOut = m_toolBar->addAction(tr("Zoom out"));
+    actionZoomOut->setToolTip(tr("Decrease zoom level"));
+    actionZoomOut->setIcon(QIcon(":/demos/documentviewer/images/zoom-out.png"_L1));
+    m_toolBar->addAction(actionZoomOut);
+    connect(actionZoomOut, &QAction::triggered, this, &PdfViewer::onActionZoomOutTriggered);
+
+    connect(nav, &QPdfPageNavigator::backAvailableChanged, m_actionBack, &QAction::setEnabled);
+    connect(nav, &QPdfPageNavigator::forwardAvailableChanged, m_actionForward, &QAction::setEnabled);
+
+    connect(m_zoomSelector, &ZoomSelector::zoomModeChanged, m_pdfView, &QPdfView::setZoomMode);
+    connect(m_zoomSelector, &ZoomSelector::zoomFactorChanged, m_pdfView, &QPdfView::setZoomFactor);
+    m_zoomSelector->reset();
+
+    QPdfBookmarkModel *bookmarkModel = new QPdfBookmarkModel(this);
+    bookmarkModel->setDocument(m_document);
+    m_uiAssets.tabs->clear();
+    m_bookmarks = new QTreeView(m_uiAssets.tabs);
+    connect(m_bookmarks, &QAbstractItemView::activated, this, &PdfViewer::bookmarkSelected);
+    m_bookmarks->setModel(bookmarkModel);
+    m_pdfView->setDocument(m_document);
+    m_pdfView->setPageMode(QPdfView::PageMode::MultiPage);
+
+    openPdfFile();
+    if (!m_document->pageCount())
+        return;
+
+    m_pages = new QListView(m_uiAssets.tabs);
+    m_pages->setModel(m_document->pageModel());
+    connect(m_pages->selectionModel(), &QItemSelectionModel::currentRowChanged, m_pages, [&]
+            (const QModelIndex &current, const QModelIndex &previous){
+        if (previous == current)
+            return;
+
+        auto *nav = m_pdfView->pageNavigator();
+        const int &row = current.row();
+        if (nav->currentPage() == row)
+            return;
+
+        nav->jump(row, QPointF(), nav->currentZoom());
+    });
+
+    connect(m_pdfView->pageNavigator(), &QPdfPageNavigator::currentPageChanged, m_pages, [&](int page){
+       if (m_pages->currentIndex().row() == page)
+           return;
+
+       m_pages->setCurrentIndex(m_pages->model()->index(page, 0));
+    });
+
+    m_uiAssets.tabs->addTab(m_pages, tr("Pages"));
+    m_uiAssets.tabs->addTab(m_bookmarks, tr("Bookmarks"));
+    QScroller::grabGesture(m_pdfView->viewport(), QScroller::ScrollerGestureType::LeftMouseButtonGesture);
+    HoverWatcher::watcher(m_pdfView->viewport());
+}
+
+void PdfViewer::openPdfFile()
+{
+    disablePrinting();
+
+    if (m_file->open(QIODevice::ReadOnly))
+        m_document->load(m_file.get());
+
+    const auto documentTitle = m_document->metaData(QPdfDocument::MetaDataField::Title).toString();
+    statusMessage(documentTitle.isEmpty() ? "PDF Viewer"_L1 : documentTitle);
+    pageSelected(0);
+
+    statusMessage(tr("Opened PDF file %1")
+                  .arg(QDir::toNativeSeparators(m_file->fileName())));
+    qCDebug(lcExample) << "Opened file" << m_file->fileName();
+
+    maybeEnablePrinting();
+}
+
+bool PdfViewer::hasContent() const
+{
+    return m_document ? m_document->pageCount() > 0 : false;
+}
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+void PdfViewer::printDocument(QPrinter *printer) const
+{
+    if (!hasContent())
+        return;
+
+    QPainter painter;
+    painter.begin(printer);
+    const QRect pageRect = printer->pageRect(QPrinter::Unit::DevicePixel).toRect();
+    const QSize pageSize = pageRect.size();
+    for (int i = 0; i < m_document->pageCount(); ++i) {
+        if (i > 0)
+            printer->newPage();
+        const QImage &page = m_document->render(i, pageSize);
+        painter.drawImage(pageRect, page);
+    }
+    painter.end();
+}
+#endif // QT_DOCUMENTVIEWER_PRINTSUPPORT
+
+void PdfViewer::bookmarkSelected(const QModelIndex &index)
+{
+    if (!index.isValid())
+        return;
+
+    const int page = index.data(int(QPdfBookmarkModel::Role::Page)).toInt();
+    const qreal zoomLevel = index.data(int(QPdfBookmarkModel::Role::Level)).toReal();
+    m_pdfView->pageNavigator()->jump(page, {}, zoomLevel);
+}
+
+void PdfViewer::pageSelected(int page)
+{
+    auto nav = m_pdfView->pageNavigator();
+    nav->jump(page, {}, nav->currentZoom());
+}
+
+void PdfViewer::onActionZoomInTriggered()
+{
+    m_pdfView->setZoomFactor(m_pdfView->zoomFactor() * zoomMultiplier);
+}
+
+void PdfViewer::onActionZoomOutTriggered()
+{
+    m_pdfView->setZoomFactor(m_pdfView->zoomFactor() / zoomMultiplier);
+}
+
+void PdfViewer::onActionPreviousPageTriggered()
+{
+    auto nav = m_pdfView->pageNavigator();
+    nav->jump(nav->currentPage() - 1, {}, nav->currentZoom());
+}
+
+void PdfViewer::onActionNextPageTriggered()
+{
+    auto nav = m_pdfView->pageNavigator();
+    nav->jump(nav->currentPage() + 1, {}, nav->currentZoom());
+}
+
+void PdfViewer::onActionBackTriggered()
+{
+    m_pdfView->pageNavigator()->back();
+}
+
+void PdfViewer::onActionForwardTriggered()
+{
+    m_pdfView->pageNavigator()->forward();
+}

plugins/pdfviewer/pdfviewer.h

@@ -0,0 +1,76 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef PDFVIEWER_H
+#define PDFVIEWER_H
+
+#include "viewerinterfaces.h"
+#include <QLoggingCategory>
+
+Q_DECLARE_LOGGING_CATEGORY(lcExample)
+
+QT_BEGIN_NAMESPACE
+class QMainWindow;
+class QPdfDocument;
+class QPdfView;
+class QPdfPageSelector;
+class QListView;
+class QTabWidget;
+class QTreeView;
+QT_END_NAMESPACE
+
+class ZoomSelector;
+class PdfViewer : public ViewerInterface
+{
+    Q_OBJECT
+    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.Examples.DocumentViewer.ViewerInterface" FILE "pdfviewer.json")
+    Q_INTERFACES(ViewerInterface)
+public:
+    PdfViewer();
+    ~PdfViewer() override;
+    void init(QFile *file, QWidget *parent, QMainWindow *mainWindow) override;
+    void cleanup() override;
+    QString viewerName() const override { return QLatin1StringView(staticMetaObject.className()); };
+    QStringList supportedMimeTypes() const override;
+    bool supportsOverview() const override { return true; }
+    bool hasContent() const override;
+    QByteArray saveState() const override { return QByteArray(); }
+    bool restoreState(QByteArray &) override { return true; }
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+protected:
+    void printDocument(QPrinter *printer) const override;
+#endif // QT_DOCUMENTVIEWER_PRINTSUPPORT
+
+public slots:
+    void openPdfFile();
+
+private slots:
+    void initPdfViewer();
+    void bookmarkSelected(const QModelIndex &index);
+    void pageSelected(int page);
+
+    // action handlers
+    void onActionZoomInTriggered();
+    void onActionZoomOutTriggered();
+    void onActionPreviousPageTriggered();
+    void onActionNextPageTriggered();
+    void onActionBackTriggered();
+    void onActionForwardTriggered();
+
+private:
+    void populateQuestions();
+
+    const qreal zoomMultiplier = qSqrt(2.0);
+    QToolBar *m_toolBar = nullptr;
+    ZoomSelector *m_zoomSelector = nullptr;
+    QPdfPageSelector *m_pageSelector = nullptr;
+    QPdfDocument *m_document = nullptr;
+    QPdfView *m_pdfView = nullptr;
+    QAction *m_actionForward = nullptr;
+    QAction *m_actionBack = nullptr;
+    QTreeView *m_bookmarks = nullptr;
+    QListView *m_pages = nullptr;
+};
+
+#endif //PDFVIEWER_H

plugins/pdfviewer/pdfviewer.json

@@ -0,0 +1 @@
+{ "Keys": [ "pdfviewer" ] }

plugins/pdfviewer/zoomselector.cpp

@@ -0,0 +1,64 @@
+// Copyright (C) 2017 Klaralvdalens Datakonsult AB (KDAB).
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "zoomselector.h"
+
+#include <QLineEdit>
+
+ZoomSelector::ZoomSelector(QWidget *parent)
+    : QComboBox(parent)
+{
+    setEditable(true);
+
+    addItem(tr("Fit Width"));
+    addItem(tr("Fit Page"));
+    addItem(tr("12%"));
+    addItem(tr("25%"));
+    addItem(tr("33%"));
+    addItem(tr("50%"));
+    addItem(tr("66%"));
+    addItem(tr("75%"));
+    addItem(tr("100%"));
+    addItem(tr("125%"));
+    addItem(tr("150%"));
+    addItem(tr("200%"));
+    addItem(tr("400%"));
+
+    connect(this, &QComboBox::currentTextChanged,
+            this, &ZoomSelector::onCurrentTextChanged);
+
+    connect(lineEdit(), &QLineEdit::editingFinished,
+            this, [this](){onCurrentTextChanged(lineEdit()->text()); });
+}
+
+void ZoomSelector::setZoomFactor(qreal zoomFactor)
+{
+    setCurrentText(QString::number(qRound(zoomFactor * 100)) + QLatin1String("%"));
+}
+
+void ZoomSelector::reset()
+{
+    setCurrentIndex(8); // 100%
+}
+
+void ZoomSelector::onCurrentTextChanged(const QString &text)
+{
+    if (text == QLatin1String("Fit Width")) {
+        emit zoomModeChanged(QPdfView::ZoomMode::FitToWidth);
+    } else if (text == QLatin1String("Fit Page")) {
+        emit zoomModeChanged(QPdfView::ZoomMode::FitInView);
+    } else {
+        qreal factor = 1.0;
+
+        QString withoutPercent(text);
+        withoutPercent.remove(QLatin1Char('%'));
+
+        bool ok = false;
+        const int zoomLevel = withoutPercent.toInt(&ok);
+        if (ok)
+            factor = zoomLevel / 100.0;
+
+        emit zoomModeChanged(QPdfView::ZoomMode::Custom);
+        emit zoomFactorChanged(factor);
+    }
+}

plugins/pdfviewer/zoomselector.h

@@ -0,0 +1,30 @@
+// Copyright (C) 2017 Klaralvdalens Datakonsult AB (KDAB).
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef ZOOMSELECTOR_H
+#define ZOOMSELECTOR_H
+
+#include <QComboBox>
+#include <QPdfView>
+
+class ZoomSelector : public QComboBox
+{
+    Q_OBJECT
+
+public:
+    explicit ZoomSelector(QWidget *parent = nullptr);
+
+public slots:
+    void setZoomFactor(qreal zoomFactor);
+
+    void reset();
+
+signals:
+    void zoomModeChanged(QPdfView::ZoomMode zoomMode);
+    void zoomFactorChanged(qreal zoomFactor);
+
+private slots:
+    void onCurrentTextChanged(const QString &text);
+};
+
+#endif // ZOOMSELECTOR_H

plugins/txtviewer/CMakeLists.txt

@@ -0,0 +1,35 @@
+# Copyright (C) 2023 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets
+                 OPTIONAL_COMPONENTS PrintSupport)
+
+qt_add_plugin(txtviewer
+    CLASS_NAME TxtViewer
+    txtviewer.cpp txtviewer.h
+)
+
+set_target_properties(txtviewer PROPERTIES
+    LIBRARY_OUTPUT_DIRECTORY "${PROJECT_BINARY_DIR}/app"
+)
+
+target_include_directories(txtviewer PRIVATE
+    ../../app
+)
+
+target_link_libraries(txtviewer PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Widgets
+    abstractviewer
+)
+
+if(TARGET Qt6::PrintSupport)
+    target_link_libraries(txtviewer PRIVATE Qt6::PrintSupport)
+endif()
+
+install(TARGETS jsonviewer
+    BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}/plugins"
+    LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}/plugins"
+)
+

plugins/txtviewer/txtviewer.cpp

@@ -0,0 +1,196 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+//! [init]
+#include "txtviewer.h"
+
+#include <QFileDialog>
+#include <QMainWindow>
+#include <QMenu>
+#include <QMenuBar>
+#include <QPlainTextEdit>
+#include <QScrollBar>
+#include <QToolBar>
+
+#include <QGuiApplication>
+#include <QPainter>
+#include <QTextDocument>
+
+#include <QDir>
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+#include <QPrinter>
+#include <QPrintDialog>
+#endif
+
+using namespace Qt::StringLiterals;
+
+TxtViewer::TxtViewer()
+{
+    connect(this, &AbstractViewer::uiInitialized, this, &TxtViewer::setupTxtUi);
+}
+
+TxtViewer::~TxtViewer() = default;
+
+void TxtViewer::init(QFile *file, QWidget *parent, QMainWindow *mainWindow)
+{
+    AbstractViewer::init(file, new QPlainTextEdit(parent), mainWindow);
+    m_textEdit = qobject_cast<QPlainTextEdit *>(widget());
+}
+
+QStringList TxtViewer::supportedMimeTypes() const
+{
+    return {"text/plain"_L1};
+}
+
+void TxtViewer::setupTxtUi()
+{
+    QMenu *editMenu = addMenu(tr("&Edit"));
+    QToolBar *editToolBar = addToolBar(tr("Edit"));
+#ifndef QT_NO_CLIPBOARD
+    const QIcon cutIcon = QIcon::fromTheme("edit-cut"_L1,
+                                           QIcon(":/demos/documentviewer/images/cut.png"_L1));
+    QAction *cutAct = new QAction(cutIcon, tr("Cu&t"), this);
+    cutAct->setShortcuts(QKeySequence::Cut);
+    cutAct->setStatusTip(tr("Cut the current selection's contents to the "
+                            "clipboard"));
+    connect(cutAct, &QAction::triggered, m_textEdit, &QPlainTextEdit::cut);
+    editMenu->addAction(cutAct);
+    editToolBar->addAction(cutAct);
+
+    const QIcon copyIcon = QIcon::fromTheme("edit-copy"_L1,
+                                            QIcon(":/demos/documentviewer/images/copy.png"_L1));
+    QAction *copyAct = new QAction(copyIcon, tr("&Copy"), this);
+    copyAct->setShortcuts(QKeySequence::Copy);
+    copyAct->setStatusTip(tr("Copy the current selection's contents to the "
+                             "clipboard"));
+    connect(copyAct, &QAction::triggered, m_textEdit, &QPlainTextEdit::copy);
+    editMenu->addAction(copyAct);
+    editToolBar->addAction(copyAct);
+
+    const QIcon pasteIcon = QIcon::fromTheme("edit-paste"_L1,
+                                             QIcon(":/demos/documentviewer/images/paste.png"_L1));
+    QAction *pasteAct = new QAction(pasteIcon, tr("&Paste"), this);
+    pasteAct->setShortcuts(QKeySequence::Paste);
+    pasteAct->setStatusTip(tr("Paste the clipboard's contents into the current "
+                              "selection"));
+    connect(pasteAct, &QAction::triggered, m_textEdit, &QPlainTextEdit::paste);
+    editMenu->addAction(pasteAct);
+    editToolBar->addAction(pasteAct);
+
+    menuBar()->addSeparator();
+
+    cutAct->setEnabled(false);
+    copyAct->setEnabled(false);
+    connect(m_textEdit, &QPlainTextEdit::copyAvailable, cutAct, &QAction::setEnabled);
+    connect(m_textEdit, &QPlainTextEdit::copyAvailable, copyAct, &QAction::setEnabled);
+#endif // !QT_NO_CLIPBOARD
+
+    openFile();
+
+    connect(m_textEdit, &QPlainTextEdit::textChanged, this, [&](){
+        maybeSetPrintingEnabled(hasContent());
+    });
+
+    connect(m_uiAssets.back, &QAction::triggered, m_textEdit, [&](){
+        auto *bar = m_textEdit->verticalScrollBar();
+        if (bar->value() > bar->minimum())
+            bar->setValue(bar->value() - 1);
+    });
+
+    connect(m_uiAssets.forward, &QAction::triggered, m_textEdit, [&](){
+        auto *bar = m_textEdit->verticalScrollBar();
+        if (bar->value() < bar->maximum())
+            bar->setValue(bar->value() + 1);
+    });
+}
+//! [init]
+
+//! [open]
+void TxtViewer::openFile()
+{
+    const QString type = tr("open");
+    if (!m_file->open(QFile::ReadOnly | QFile::Text)) {
+        statusMessage(tr("Cannot read file %1:\n%2.")
+                      .arg(QDir::toNativeSeparators(m_file->fileName()),
+                           m_file->errorString()), type);
+        return;
+    }
+
+    QTextStream in(m_file.get());
+#ifndef QT_NO_CURSOR
+    QGuiApplication::setOverrideCursor(Qt::WaitCursor);
+#endif
+    if (!m_textEdit->toPlainText().isEmpty()) {
+        m_textEdit->clear();
+        disablePrinting();
+    }
+    m_textEdit->setPlainText(in.readAll());
+#ifndef QT_NO_CURSOR
+    QGuiApplication::restoreOverrideCursor();
+#endif
+
+    statusMessage(tr("File %1 loaded.")
+                  .arg(QDir::toNativeSeparators(m_file->fileName())), type);
+    maybeEnablePrinting();
+}
+//! [open]
+
+//! [infoPrintAndSave]
+bool TxtViewer::hasContent() const
+{
+    return (!m_textEdit->toPlainText().isEmpty());
+}
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+void TxtViewer::printDocument(QPrinter *printer) const
+{
+    if (!hasContent())
+        return;
+
+    m_textEdit->print(printer);
+}
+#endif // QT_DOCUMENTVIEWER_PRINTSUPPORT
+
+bool TxtViewer::saveFile(QFile *file)
+{
+    QString errorMessage;
+
+    QGuiApplication::setOverrideCursor(Qt::WaitCursor);
+    if (file->open(QFile::WriteOnly | QFile::Text)) {
+        QTextStream out(file);
+        out << m_textEdit->toPlainText();
+    } else {
+        errorMessage = tr("Cannot open file %1 for writing:\n%2.")
+                       .arg(QDir::toNativeSeparators(file->fileName())),
+                            file->errorString();
+    }
+    QGuiApplication::restoreOverrideCursor();
+
+    if (!errorMessage.isEmpty()) {
+        statusMessage(errorMessage);
+        return false;
+    }
+
+    statusMessage(tr("File %1 saved")
+                  .arg(QDir::toNativeSeparators(file->fileName())));
+    return true;
+}
+
+bool TxtViewer::saveDocumentAs()
+{
+    QFileDialog dialog(mainWindow());
+    dialog.setWindowModality(Qt::WindowModal);
+    dialog.setAcceptMode(QFileDialog::AcceptSave);
+    if (dialog.exec() != QDialog::Accepted)
+        return false;
+
+    const QStringList &files = dialog.selectedFiles();
+    if (files.isEmpty())
+        return false;
+
+    //newFile();
+    m_file->setFileName(files.first());
+    return saveDocument();
+}
+//! [infoPrintAndSave]

plugins/txtviewer/txtviewer.h

@@ -0,0 +1,50 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef TXTVIEWER_H
+#define TXTVIEWER_H
+
+#include "viewerinterfaces.h"
+
+QT_BEGIN_NAMESPACE
+class QPlainTextEdit;
+QT_END_NAMESPACE
+
+//! [interfacing]
+class TxtViewer : public ViewerInterface
+{
+    Q_OBJECT
+    Q_PLUGIN_METADATA(IID "org.qt-project.Qt.Examples.DocumentViewer.ViewerInterface" FILE "txtviewer.json")
+    Q_INTERFACES(ViewerInterface)
+//! [interfacing]
+//! [classDefinition]
+public:
+    TxtViewer();
+    ~TxtViewer() override;
+    void init(QFile *file, QWidget *parent, QMainWindow *mainWindow) override;
+    QString viewerName() const override { return QLatin1StringView(staticMetaObject.className()); };
+    QStringList supportedMimeTypes() const override;
+    bool saveDocument() override { return saveFile(m_file.get()); };
+    bool saveDocumentAs() override;
+    bool hasContent() const override;
+    QByteArray saveState() const override { return {}; }
+    bool restoreState(QByteArray &) override { return true; }
+    bool supportsOverview() const override { return false; }
+
+#ifdef QT_DOCUMENTVIEWER_PRINTSUPPORT
+protected:
+    void printDocument(QPrinter *printer) const override;
+#endif // QT_DOCUMENTVIEWER_PRINTSUPPORT
+
+private slots:
+    void setupTxtUi();
+
+private:
+    void openFile();
+    bool saveFile (QFile *file);
+
+    QPlainTextEdit *m_textEdit;
+};
+//! [classDefinition]
+
+#endif //TXTVIEWER_H

plugins/txtviewer/txtviewer.json

@@ -0,0 +1 @@
+{ "Keys": [ "txtviewer" ] }

run.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+rm -rf build/
+mkdir -p build/
+cd build
+
+# Build the project
+cmake -G "Unix Makefiles" -DCMAKE_PREFIX_PATH=$HOME/Qt/6.6.1/gcc_64/ \
+-DCMAKE_BUILD_TYPE=Debug -DCMAKE_EXPORT_COMPILE_COMMANDS=ON ..
+
+make
+
+cp ./compile_commands.json ../