Add new filter API, enclosed in QHelpFilterEngine

Implement new filter mechanism and provide component
filtering.

Task-number: QTCREATORBUG-19724
Task-number: QTCREATORBUG-7301
Change-Id: I48400e3bc969495a66c3002fed13a7c3ddb1e249
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

29 files changed, 1150 insertions, 605 deletions

diff --git a/src/assistant/assistant/filternamedialog.cpp b/src/assistant/assistant/filternamedialog.cpp
index 33b19cff8..4c17d3332 100644
--- a/src/assistant/assistant/filternamedialog.cpp
+++ b/src/assistant/assistant/filternamedialog.cpp
@@ -25,7 +25,6 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-#include "tracer.h"
 
 #include <QtWidgets/QPushButton>
 
@@ -36,7 +35,6 @@ QT_BEGIN_NAMESPACE
 FilterNameDialog::FilterNameDialog(QWidget *parent)
     : QDialog(parent)
 {
-    TRACE_OBJ
     m_ui.setupUi(this);
     connect(m_ui.buttonBox->button(QDialogButtonBox::Ok), &QAbstractButton::clicked,
             this, &QDialog::accept);
@@ -47,15 +45,19 @@ FilterNameDialog::FilterNameDialog(QWidget *parent)
     m_ui.buttonBox->button(QDialogButtonBox::Ok)->setDisabled(true);
 }
 
+void FilterNameDialog::setFilterName(const QString &filter)
+{
+    m_ui.lineEdit->setText(filter);
+    m_ui.lineEdit->selectAll();
+}
+
 QString FilterNameDialog::filterName() const
 {
-    TRACE_OBJ
     return m_ui.lineEdit->text();
 }
 
 void FilterNameDialog::updateOkButton()
 {
-    TRACE_OBJ
     m_ui.buttonBox->button(QDialogButtonBox::Ok)
         ->setDisabled(m_ui.lineEdit->text().isEmpty());
 }
diff --git a/src/assistant/assistant/filternamedialog.h b/src/assistant/assistant/filternamedialog.h
index 8e46bfd0b..522b611af 100644
--- a/src/assistant/assistant/filternamedialog.h
+++ b/src/assistant/assistant/filternamedialog.h
@@ -40,6 +40,8 @@ class FilterNameDialog : public QDialog
 
 public:
     FilterNameDialog(QWidget *parent = nullptr);
+
+    void setFilterName(const QString &filter);
     QString filterName() const;
 
 private slots:
diff --git a/src/assistant/assistant/helpenginewrapper.cpp b/src/assistant/assistant/helpenginewrapper.cpp
index 3aef5bb99..17e4bde8c 100644
--- a/src/assistant/assistant/helpenginewrapper.cpp
+++ b/src/assistant/assistant/helpenginewrapper.cpp
@@ -39,13 +39,13 @@
 #include <QtCore/QTimer>
 #include <QtHelp/QHelpContentModel>
 #include <QtHelp/QHelpEngine>
+#include <QtHelp/QHelpFilterEngine>
 #include <QtHelp/QHelpIndexModel>
 #include <QtHelp/QHelpSearchEngine>
 
 QT_BEGIN_NAMESPACE
 
 namespace {
-    const QString Unfiltered;
     const QString AppFontKey(QLatin1String("appFont"));
     const QString AppWritingSystemKey(QLatin1String("appWritingSystem"));
     const QString BookmarksKey(QLatin1String("Bookmarks"));
@@ -104,14 +104,6 @@ private:
     QMap<QString, RecentSignal> m_recentQchUpdates;
 };
 
-const QString HelpEngineWrapper::TrUnfiltered()
-{
-    static QString s;
-    if (s.isEmpty())
-        s = HelpEngineWrapper::tr("Unfiltered");
-    return s;
-}
-
 HelpEngineWrapper *HelpEngineWrapper::helpEngineWrapper = nullptr;
 
 HelpEngineWrapper &HelpEngineWrapper::instance(const QString &collectionFile)
@@ -154,8 +146,6 @@ HelpEngineWrapper::HelpEngineWrapper(const QString &collectionFile)
             this, &HelpEngineWrapper::documentationRemoved);
     connect(d, &HelpEngineWrapperPrivate::documentationUpdated,
             this, &HelpEngineWrapper::documentationUpdated);
-    connect(d->m_helpEngine, &QHelpEngineCore::currentFilterChanged,
-            this, &HelpEngineWrapper::handleCurrentFilterChanged);
     connect(d->m_helpEngine, &QHelpEngineCore::setupFinished,
             this, &HelpEngineWrapper::setupFinished);
 }
@@ -259,43 +249,6 @@ bool HelpEngineWrapper::setupData()
     return d->m_helpEngine->setupData();
 }
 
-bool HelpEngineWrapper::addCustomFilter(const QString &filterName,
-                                        const QStringList &attributes)
-{
-    TRACE_OBJ
-    return d->m_helpEngine->addCustomFilter(filterName, attributes);
-}
-
-bool HelpEngineWrapper::removeCustomFilter(const QString &filterName)
-{
-    TRACE_OBJ
-    return d->m_helpEngine->removeCustomFilter(filterName);
-}
-
-void HelpEngineWrapper::setCurrentFilter(const QString &currentFilter)
-{
-    TRACE_OBJ
-    const QString &filter
-            = currentFilter == TrUnfiltered() ? Unfiltered : currentFilter;
-    d->m_helpEngine->setCurrentFilter(filter);
-}
-
-const QString HelpEngineWrapper::currentFilter() const
-{
-    TRACE_OBJ
-    const QString &filter = d->m_helpEngine->currentFilter();
-    return filter == Unfiltered ? TrUnfiltered() : filter;
-}
-
-const QStringList HelpEngineWrapper::customFilters() const
-{
-    TRACE_OBJ
-    QStringList filters = d->m_helpEngine->customFilters();
-    filters.removeOne(Unfiltered);
-    filters.prepend(TrUnfiltered());
-    return filters;
-}
-
 QUrl HelpEngineWrapper::findFile(const QUrl &url) const
 {
     TRACE_OBJ
@@ -314,22 +267,15 @@ QMap<QString, QUrl> HelpEngineWrapper::linksForIdentifier(const QString &id) con
     return d->m_helpEngine->linksForIdentifier(id);
 }
 
-const QStringList HelpEngineWrapper::filterAttributes() const
-{
-    TRACE_OBJ
-    return d->m_helpEngine->filterAttributes();
-}
-
-const QStringList HelpEngineWrapper::filterAttributes(const QString &filterName) const
+QString HelpEngineWrapper::error() const
 {
     TRACE_OBJ
-    return d->m_helpEngine->filterAttributes(filterName);
+    return d->m_helpEngine->error();
 }
 
-QString HelpEngineWrapper::error() const
+QHelpFilterEngine *HelpEngineWrapper::filterEngine() const
 {
-    TRACE_OBJ
-    return d->m_helpEngine->error();
+    return d->m_helpEngine->filterEngine();
 }
 
 const QStringList HelpEngineWrapper::qtDocInfo(const QString &component) const
@@ -694,14 +640,6 @@ void HelpEngineWrapper::setBrowserWritingSystem(QFontDatabase::WritingSystem sys
     d->m_helpEngine->setCustomValue(BrowserWritingSystemKey, system);
 }
 
-void HelpEngineWrapper::handleCurrentFilterChanged(const QString &filter)
-{
-    TRACE_OBJ
-    const QString &filterToReport
-            = filter == Unfiltered ? TrUnfiltered() : filter;
-    emit currentFilterChanged(filterToReport);
-}
-
 bool HelpEngineWrapper::showTabs() const
 {
     TRACE_OBJ
@@ -753,9 +691,8 @@ HelpEngineWrapperPrivate::HelpEngineWrapperPrivate(const QString &collectionFile
       m_qchWatcher(new QFileSystemWatcher(this))
 {
     TRACE_OBJ
-    if (!m_helpEngine->customFilters().contains(Unfiltered))
-        m_helpEngine->addCustomFilter(Unfiltered, QStringList());
     initFileSystemWatchers();
+    m_helpEngine->setUsesFilterEngine(true);
 }
 
 void HelpEngineWrapperPrivate::initFileSystemWatchers()
diff --git a/src/assistant/assistant/helpenginewrapper.h b/src/assistant/assistant/helpenginewrapper.h
index 08474f697..6026a0473 100644
--- a/src/assistant/assistant/helpenginewrapper.h
+++ b/src/assistant/assistant/helpenginewrapper.h
@@ -45,6 +45,7 @@ class QHelpContentWidget;
 class QHelpIndexModel;
 class QHelpIndexWidget;
 class QHelpSearchEngine;
+class QHelpFilterEngine;
 
 enum {
     ShowHomePage = 0,
@@ -76,19 +77,13 @@ public:
     const QString collectionFile() const;
     bool registerDocumentation(const QString &docFile);
     bool unregisterDocumentation(const QString &namespaceName);
-    bool addCustomFilter(const QString &filterName,
-                         const QStringList &attributes);
-    bool removeCustomFilter(const QString &filterName);
-    void setCurrentFilter(const QString &filterName);
-    const QString currentFilter() const;
-    const QStringList customFilters() const;
     QUrl findFile(const QUrl &url) const;
     QByteArray fileData(const QUrl &url) const;
     QMap<QString, QUrl> linksForIdentifier(const QString &id) const;
-    const QStringList filterAttributes() const;
-    const QStringList filterAttributes(const QString &filterName) const;
     QString error() const;
 
+    QHelpFilterEngine *filterEngine() const;
+
     /*
      * To be called after assistant has finished looking for new documentation.
      * This will mainly cause the search index to be updated, if necessary.
@@ -175,8 +170,6 @@ public:
     bool showTabs() const;
     void setShowTabs(bool show);
 
-    static const QString TrUnfiltered();
-
     bool fullTextSearchFallbackEnabled() const;
 
     const QByteArray topicChooserGeometry() const;
@@ -189,12 +182,8 @@ signals:
     void documentationUpdated(const QString &namespaceName);
 
     // Forwarded from QHelpEngineCore.
-    void currentFilterChanged(const QString &currentFilter);
     void setupFinished();
 
-private slots:
-    void handleCurrentFilterChanged(const QString &filter);
-
 private:
     HelpEngineWrapper(const QString &collectionFile);
     ~HelpEngineWrapper();
diff --git a/src/assistant/assistant/mainwindow.cpp b/src/assistant/assistant/mainwindow.cpp
index 392af9224..c9c120950 100644
--- a/src/assistant/assistant/mainwindow.cpp
+++ b/src/assistant/assistant/mainwindow.cpp
@@ -80,6 +80,7 @@
 #include <QtHelp/QHelpEngineCore>
 #include <QtHelp/QHelpIndexModel>
 #include <QtHelp/QHelpSearchEngine>
+#include <QtHelp/QHelpFilterEngine>
 
 #include <cstdlib>
 
@@ -268,8 +269,8 @@ MainWindow::MainWindow(CmdLineParser *cmdLine, QWidget *parent)
 
     if (!m_cmdLine->currentFilter().isEmpty()) {
         const QString &curFilter = m_cmdLine->currentFilter();
-        if (helpEngineWrapper.customFilters().contains(curFilter))
-            helpEngineWrapper.setCurrentFilter(curFilter);
+        if (helpEngineWrapper.filterEngine()->filters().contains(curFilter))
+            helpEngineWrapper.filterEngine()->setActiveFilter(curFilter);
     }
 
     if (usesDefaultCollection())
@@ -737,9 +738,9 @@ void MainWindow::setupFilterToolbar()
 
     connect(&helpEngine, &HelpEngineWrapper::setupFinished,
             this, &MainWindow::setupFilterCombo, Qt::QueuedConnection);
-    connect(m_filterCombo, QOverload<const QString &>::of(&QComboBox::activated),
+    connect(m_filterCombo, QOverload<int>::of(&QComboBox::activated),
             this, &MainWindow::filterDocumentation);
-    connect(&helpEngine, &HelpEngineWrapper::currentFilterChanged,
+    connect(helpEngine.filterEngine(), &QHelpFilterEngine::filterActivated,
             this, &MainWindow::currentFilterChanged);
 
     setupFilterCombo();
@@ -1048,21 +1049,27 @@ void MainWindow::setupFilterCombo()
 {
     TRACE_OBJ
     HelpEngineWrapper &helpEngine = HelpEngineWrapper::instance();
-    QString curFilter = m_filterCombo->currentText();
-    if (curFilter.isEmpty())
-        curFilter = helpEngine.currentFilter();
+    const QString currentFilter = helpEngine.filterEngine()->activeFilter();
     m_filterCombo->clear();
-    m_filterCombo->addItems(helpEngine.customFilters());
-    int idx = m_filterCombo->findText(curFilter);
+    m_filterCombo->addItem(tr("Unfiltered"));
+    const QStringList allFilters = helpEngine.filterEngine()->filters();
+    if (!allFilters.isEmpty())
+        m_filterCombo->insertSeparator(1);
+    for (const QString &filter : allFilters)
+        m_filterCombo->addItem(filter, filter);
+
+    int idx = m_filterCombo->findData(currentFilter);
     if (idx < 0)
         idx = 0;
     m_filterCombo->setCurrentIndex(idx);
 }
 
-void MainWindow::filterDocumentation(const QString &customFilter)
+void MainWindow::filterDocumentation(int filterIndex)
 {
     TRACE_OBJ
-    HelpEngineWrapper::instance().setCurrentFilter(customFilter);
+
+    const QString filter = m_filterCombo->itemData(filterIndex).toString();
+    HelpEngineWrapper::instance().filterEngine()->setActiveFilter(filter);
 }
 
 void MainWindow::expandTOC(int depth)
@@ -1143,8 +1150,9 @@ QString MainWindow::defaultHelpCollectionFileName()
 void MainWindow::currentFilterChanged(const QString &filter)
 {
     TRACE_OBJ
-    const int index = m_filterCombo->findText(filter);
-    Q_ASSERT(index != -1);
+    int index = m_filterCombo->findData(filter);
+    if (index < 0)
+        index = 0;
     m_filterCombo->setCurrentIndex(index);
 }
 
diff --git a/src/assistant/assistant/mainwindow.h b/src/assistant/assistant/mainwindow.h
index 86451f839..c5bf5837e 100644
--- a/src/assistant/assistant/mainwindow.h
+++ b/src/assistant/assistant/mainwindow.h
@@ -90,7 +90,7 @@ private slots:
     void showNewAddress(const QUrl &url);
     void showTopicChooser(const QMap<QString, QUrl> &links, const QString &keyword);
     void updateApplicationFont();
-    void filterDocumentation(const QString &customFilter);
+    void filterDocumentation(int filterIndex);
     void setupFilterCombo();
     void lookForNewQtDocumentation();
     void indexingStarted();
diff --git a/src/assistant/assistant/openpagesmanager.cpp b/src/assistant/assistant/openpagesmanager.cpp
index 3151cb534..f3acb4656 100644
--- a/src/assistant/assistant/openpagesmanager.cpp
+++ b/src/assistant/assistant/openpagesmanager.cpp
@@ -237,7 +237,7 @@ void OpenPagesManager::closeOrReloadPages(const QString &nameSpace, bool tryRelo
         HelpViewer *page = m_model->pageAt(i);
         if (page->source().host() != nameSpace)
             continue;
-        if (tryReload  && HelpEngineWrapper::instance().findFile(page->source()).isValid())
+        if (tryReload && HelpEngineWrapper::instance().findFile(page->source()).isValid())
             page->reload();
         else if (m_model->rowCount() == 1)
             page->setSource(QUrl(QLatin1String("about:blank")));
diff --git a/src/assistant/assistant/preferencesdialog.cpp b/src/assistant/assistant/preferencesdialog.cpp
index 4647f154f..bcc661690 100644
--- a/src/assistant/assistant/preferencesdialog.cpp
+++ b/src/assistant/assistant/preferencesdialog.cpp
@@ -32,106 +32,20 @@
 #include "fontpanel.h"
 #include "helpenginewrapper.h"
 #include "openpagesmanager.h"
-#include "tracer.h"
 
-#include <QtCore/QAbstractListModel>
-#include <QtCore/QtAlgorithms>
-#include <QtCore/QFileSystemWatcher>
-#include <QtCore/QSortFilterProxyModel>
-#include <QtCore/QVector>
-
-#include <QtWidgets/QDesktopWidget>
-#include <QtWidgets/QFileDialog>
 #include <QtGui/QFontDatabase>
-#include <QtWidgets/QHeaderView>
-#include <QtWidgets/QMenu>
 #include <QtWidgets/QMessageBox>
 
 #include <QtHelp/QHelpEngineCore>
+#include <QtHelp/QHelpFilterData>
+#include <QtHelp/QHelpFilterEngine>
+#include <QtHelp/QHelpCollectionDetails>
 
-#include <algorithm>
-
-QT_BEGIN_NAMESPACE
-
-struct RegisteredDocEntry
-{
-    QString nameSpace;
-    QString fileName;
-};
-
-typedef QVector<RegisteredDocEntry> RegisteredDocEntries;
-
-class RegisteredDocsModel : public QAbstractListModel {
-public:
-
-    explicit RegisteredDocsModel(const RegisteredDocEntries &e = RegisteredDocEntries(), QObject *parent = nullptr)
-        : QAbstractListModel(parent), m_docEntries(e) {}
-
-    int rowCount(const QModelIndex & = QModelIndex()) const override { return m_docEntries.size(); }
-    QVariant data(const QModelIndex &index, int role) const override;
-
-    bool contains(const QString &nameSpace) const
-    {
-        return m_docEntries.cend() !=
-            std::find_if(m_docEntries.cbegin(), m_docEntries.cend(),
-                         [nameSpace] (const RegisteredDocEntry &e) { return e.nameSpace == nameSpace; });
-    }
-
-    void append(const RegisteredDocEntry &e);
-
-    const RegisteredDocEntries &docEntries() const { return m_docEntries; }
-    void setDocEntries(const RegisteredDocEntries &);
-
-private:
-    RegisteredDocEntries m_docEntries;
-};
-
-QVariant RegisteredDocsModel::data(const QModelIndex &index, int role) const
-{
-    QVariant result;
-    const int row = index.row();
-    if (index.isValid() && row < m_docEntries.size()) {
-        switch (role) {
-        case Qt::DisplayRole:
-            result = QVariant(m_docEntries.at(row).nameSpace);
-            break;
-        case Qt::ToolTipRole:
-            result = QVariant(QDir::toNativeSeparators(m_docEntries.at(row).fileName));
-            break;
-        default:
-            break;
-        }
-    }
-    return result;
-}
-
-void RegisteredDocsModel::append(const RegisteredDocEntry &e)
-{
-    beginInsertRows(QModelIndex(), m_docEntries.size(), m_docEntries.size());
-    m_docEntries.append(e);
-    endInsertRows();
-}
+#include <QtWidgets/QFileDialog>
 
-void RegisteredDocsModel::setDocEntries(const RegisteredDocEntries &e)
-{
-    beginResetModel();
-    m_docEntries = e;
-    endResetModel();
-}
+#include <QtDebug>
 
-static RegisteredDocEntries registeredDocEntries(const HelpEngineWrapper &wrapper)
-{
-    RegisteredDocEntries result;
-    const QStringList &nameSpaces = wrapper.registeredDocumentations();
-    result.reserve(nameSpaces.size());
-    for (const QString &nameSpace : nameSpaces) {
-        RegisteredDocEntry entry;
-        entry.nameSpace = nameSpace;
-        entry.fileName = wrapper.documentationFileName(nameSpace);
-        result.append(entry);
-    }
-    return result;
-}
+QT_BEGIN_NAMESPACE
 
 PreferencesDialog::PreferencesDialog(QWidget *parent)
     : QDialog(parent)
@@ -141,52 +55,50 @@ PreferencesDialog::PreferencesDialog(QWidget *parent)
     , m_hideFiltersTab(!helpEngine.filterFunctionalityEnabled())
     , m_hideDocsTab(!helpEngine.documentationManagerEnabled())
 {
-    TRACE_OBJ
     m_ui.setupUi(this);
 
-    m_registeredDocsModel =
-        new RegisteredDocsModel(m_hideDocsTab ? RegisteredDocEntries() : registeredDocEntries(helpEngine));
-    m_registereredDocsFilterModel = new QSortFilterProxyModel(m_ui.registeredDocsListView);
-    m_registereredDocsFilterModel->setSourceModel(m_registeredDocsModel);
-    m_ui.registeredDocsListView->setModel(m_registereredDocsFilterModel);
-    connect(m_ui.registeredDocsFilterLineEdit, &QLineEdit::textChanged,
-            m_registereredDocsFilterModel, &QSortFilterProxyModel::setFilterFixedString);
+    // TODO: filter docs via lineedit
 
     connect(m_ui.buttonBox->button(QDialogButtonBox::Ok), &QAbstractButton::clicked,
-            this, &PreferencesDialog::applyChanges);
+            this, &PreferencesDialog::okClicked);
+    connect(m_ui.buttonBox->button(QDialogButtonBox::Apply), &QAbstractButton::clicked,
+            this, &PreferencesDialog::applyClicked);
     connect(m_ui.buttonBox->button(QDialogButtonBox::Cancel), &QAbstractButton::clicked,
             this, &QDialog::reject);
 
-    if (!m_hideFiltersTab) {
-        m_ui.attributeWidget->header()->hide();
-        m_ui.attributeWidget->setRootIsDecorated(false);
-
-        connect(m_ui.attributeWidget, &QTreeWidget::itemChanged,
-                this, &PreferencesDialog::updateFilterMap);
-        connect(m_ui.filterWidget, &QListWidget::currentItemChanged,
-                this, &PreferencesDialog::updateAttributes);
+    m_originalSetup = readOriginalSetup();
+    m_currentSetup = m_originalSetup;
 
-        connect(m_ui.filterAddButton, &QAbstractButton::clicked,
-                this, &PreferencesDialog::addFilter);
-        connect(m_ui.filterRemoveButton, &QAbstractButton::clicked,
-                this, &PreferencesDialog::removeFilter);
-
-        updateFilterPage();
+    if (m_hideDocsTab) {
+        m_ui.tabWidget->removeTab(m_ui.tabWidget->indexOf(m_ui.docsTab));
     } else {
-        m_ui.tabWidget->removeTab(m_ui.tabWidget->indexOf(m_ui.filtersTab));
-    }
-
-    if (!m_hideDocsTab) {
         connect(m_ui.docAddButton, &QAbstractButton::clicked,
-                this, &PreferencesDialog::addDocumentationLocal);
+                this, &PreferencesDialog::addDocumentation);
         connect(m_ui.docRemoveButton, &QAbstractButton::clicked,
                 this, &PreferencesDialog::removeDocumentation);
 
-        m_docsBackup.reserve(m_registeredDocsModel->rowCount());
-        for (const RegisteredDocEntry &e : m_registeredDocsModel->docEntries())
-            m_docsBackup.append(e.nameSpace);
+        updateDocumentationPage();
+    }
+
+    if (m_hideFiltersTab) {
+        m_ui.tabWidget->removeTab(m_ui.tabWidget->indexOf(m_ui.filtersTab));
     } else {
-        m_ui.tabWidget->removeTab(m_ui.tabWidget->indexOf(m_ui.docsTab));
+        connect(m_ui.componentWidget, &OptionsWidget::optionSelectionChanged,
+                this, &PreferencesDialog::componentsChanged);
+        connect(m_ui.filterWidget, &QListWidget::currentItemChanged,
+                this, &PreferencesDialog::filterSelected);
+        connect(m_ui.filterWidget, &QListWidget::itemDoubleClicked,
+                this, &PreferencesDialog::renameFilterClicked);
+
+        // TODO: repeat these actions on context menu
+        connect(m_ui.filterAddButton, &QAbstractButton::clicked,
+                this, &PreferencesDialog::addFilterClicked);
+        connect(m_ui.filterRenameButton, &QAbstractButton::clicked,
+                this, &PreferencesDialog::renameFilterClicked);
+        connect(m_ui.filterRemoveButton, &QAbstractButton::clicked,
+                this, &PreferencesDialog::removeFilterClicked);
+
+        updateFilterPage();
     }
 
     updateFontSettingsPage();
@@ -198,7 +110,6 @@ PreferencesDialog::PreferencesDialog(QWidget *parent)
 
 PreferencesDialog::~PreferencesDialog()
 {
-    TRACE_OBJ
     if (m_appFontChanged) {
         helpEngine.setAppFont(m_appFontPanel->selectedFont());
         helpEngine.setUseAppFont(m_appFontPanel->isChecked());
@@ -222,259 +133,365 @@ PreferencesDialog::~PreferencesDialog()
     helpEngine.setStartOption(option);
 }
 
+FilterSetup PreferencesDialog::readOriginalSetup() const
+{
+    FilterSetup filterSetup;
+
+    filterSetup.m_namespaceToComponent = helpEngine.filterEngine()->namespaceToComponent();
+    for (auto it = filterSetup.m_namespaceToComponent.constBegin();
+         it != filterSetup.m_namespaceToComponent.constEnd(); ++it) {
+        const QString namespaceName = it.key();
+        const QString namespaceFileName = helpEngine.documentationFileName(namespaceName);
+        filterSetup.m_namespaceToFileName.insert(namespaceName, namespaceFileName);
+        filterSetup.m_fileNameToNamespace.insert(namespaceFileName, namespaceName);
+        filterSetup.m_componentToNamespace[it.value()].append(namespaceName);
+    }
+    const QStringList allFilters = helpEngine.filterEngine()->filters();
+    for (const QString &filter : allFilters)
+        filterSetup.m_filterToComponents.insert(filter, helpEngine.filterEngine()->filterData(filter).components());
+
+    return filterSetup;
+}
+
 void PreferencesDialog::showDialog()
 {
-    TRACE_OBJ
     if (exec() != Accepted)
         m_appFontChanged = m_browserFontChanged = false;
 }
 
 void PreferencesDialog::updateFilterPage()
 {
-    TRACE_OBJ
+    if (m_hideFiltersTab)
+        return;
+
+    const QString &currentFilter = m_itemToFilter.value(m_ui.filterWidget->currentItem());
+
+    m_currentSetup = m_originalSetup;
+
     m_ui.filterWidget->clear();
-    m_ui.attributeWidget->clear();
+    m_ui.componentWidget->clear();
+    m_itemToFilter.clear();
+    m_filterToItem.clear();
+
+    for (const QString &filterName : m_currentSetup.m_filterToComponents.keys()) {
+        QListWidgetItem *item = new QListWidgetItem(filterName);
+        m_ui.filterWidget->addItem(item);
+        m_itemToFilter.insert(item, filterName);
+        m_filterToItem.insert(filterName, item);
+        if (filterName == currentFilter)
+            m_ui.filterWidget->setCurrentItem(item);
+    }
 
-    m_filterMapBackup.clear();
-    const QStringList &filters = helpEngine.customFilters();
-    for (const QString &filter : filters) {
-        if (filter == HelpEngineWrapper::TrUnfiltered())
-            continue;
-        QStringList atts = helpEngine.filterAttributes(filter);
-        m_filterMapBackup.insert(filter, atts);
-        if (!m_filterMap.contains(filter))
-            m_filterMap.insert(filter, atts);
+    if (!m_ui.filterWidget->currentItem() && !m_filterToItem.isEmpty())
+        m_ui.filterWidget->setCurrentItem(m_filterToItem.first());
+
+    updateCurrentFilter();
+}
+
+void PreferencesDialog::updateCurrentFilter()
+{
+    if (m_hideFiltersTab)
+        return;
+
+    const QString &currentFilter = m_itemToFilter.value(m_ui.filterWidget->currentItem());
+
+    const bool filterSelected = !currentFilter.isEmpty();
+    m_ui.componentWidget->setEnabled(filterSelected);
+    m_ui.filterRenameButton->setEnabled(filterSelected);
+    m_ui.filterRemoveButton->setEnabled(filterSelected);
+
+    m_ui.componentWidget->setOptions(m_currentSetup.m_componentToNamespace.keys(),
+                                     m_currentSetup.m_filterToComponents.value(currentFilter));
+}
+
+void PreferencesDialog::updateDocumentationPage()
+{
+    if (m_hideDocsTab)
+        return;
+
+    m_ui.registeredDocsListWidget->clear();
+    m_namespaceToItem.clear();
+    m_itemToNamespace.clear();
+
+    for (const QString &namespaceName : m_currentSetup.m_namespaceToFileName.keys()) {
+        QListWidgetItem *item = new QListWidgetItem(namespaceName);
+        m_namespaceToItem.insert(namespaceName, item);
+        m_itemToNamespace.insert(item, namespaceName);
+        m_ui.registeredDocsListWidget->addItem(item);
     }
+}
+
+void PreferencesDialog::filterSelected(QListWidgetItem *item)
+{
+    Q_UNUSED(item)
+
+    updateCurrentFilter();
+}
+
+void PreferencesDialog::componentsChanged(const QStringList &components)
+{
+    const QString &currentFilter = m_itemToFilter.value(m_ui.filterWidget->currentItem());
+    if (currentFilter.isEmpty())
+        return;
+
+    m_currentSetup.m_filterToComponents[currentFilter] = components;
+}
 
-    m_ui.filterWidget->addItems(m_filterMap.keys());
+QString PreferencesDialog::suggestedNewFilterName(const QString &initialFilterName) const
+{
+    QString newFilterName = initialFilterName;
 
-    for (const QString &a : helpEngine.filterAttributes())
-        new QTreeWidgetItem(m_ui.attributeWidget, QStringList() << a);
+    int counter = 1;
+    while (m_filterToItem.contains(newFilterName)) {
+        newFilterName = initialFilterName + QLatin1Char(' ')
+                + QString::number(++counter);
+    }
 
-    if (!m_filterMap.isEmpty())
-        m_ui.filterWidget->setCurrentRow(0);
+    return newFilterName;
 }
 
-void PreferencesDialog::updateAttributes(QListWidgetItem *item)
+QString PreferencesDialog::getUniqueFilterName(const QString &windowTitle,
+                                               const QString &initialFilterName)
 {
-    TRACE_OBJ
-    const QStringList &checkedList = item ? m_filterMap.value(item->text()) : QStringList();
-
-    for (int i = 0; i < m_ui.attributeWidget->topLevelItemCount(); ++i) {
-        QTreeWidgetItem *itm = m_ui.attributeWidget->topLevelItem(i);
-        if (checkedList.contains(itm->text(0)))
-            itm->setCheckState(0, Qt::Checked);
-        else
-            itm->setCheckState(0, Qt::Unchecked);
+    QString newFilterName = initialFilterName;
+    while (1) {
+        FilterNameDialog dialog(this);
+        dialog.setWindowTitle(windowTitle);
+        dialog.setFilterName(newFilterName);
+        if (dialog.exec() == QDialog::Rejected)
+            return QString();
+
+        newFilterName = dialog.filterName();
+        if (!m_filterToItem.contains(newFilterName))
+            break;
+
+        if (QMessageBox::warning(this, tr("Filter Exists"),
+                                 tr("The filter \"%1\" already exists.")
+                                 .arg(newFilterName),
+                                 QMessageBox::Retry | QMessageBox::Cancel)
+                == QMessageBox::Cancel) {
+            return QString();
+        }
     }
+
+    return newFilterName;
+}
+
+void PreferencesDialog::addFilterClicked()
+{
+    const QString newFilterName = getUniqueFilterName(tr("Add Filter"),
+                                  suggestedNewFilterName(tr("New Filter")));
+    if (newFilterName.isEmpty())
+        return;
+
+    addFilter(newFilterName, QStringList());
 }
 
-void PreferencesDialog::updateFilterMap()
+void PreferencesDialog::renameFilterClicked()
 {
-    TRACE_OBJ
-    if (!m_ui.filterWidget->currentItem())
+    const QString &currentFilter = m_itemToFilter.value(m_ui.filterWidget->currentItem());
+    if (currentFilter.isEmpty())
         return;
-    QString filter = m_ui.filterWidget->currentItem()->text();
-    if (!m_filterMap.contains(filter))
+
+    const QString newFilterName = getUniqueFilterName(tr("Rename Filter"), currentFilter);
+    if (newFilterName.isEmpty())
         return;
 
-    QStringList newAtts;
-    QTreeWidgetItem *itm = nullptr;
-    for (int i = 0; i < m_ui.attributeWidget->topLevelItemCount(); ++i) {
-        itm = m_ui.attributeWidget->topLevelItem(i);
-        if (itm->checkState(0) == Qt::Checked)
-            newAtts.append(itm->text(0));
-    }
-    m_filterMap[filter] = newAtts;
+    const QStringList oldComponents = m_currentSetup.m_filterToComponents.value(currentFilter);
+    removeFilter(currentFilter);
+    addFilter(newFilterName, oldComponents);
 }
 
-void PreferencesDialog::addFilter()
+void PreferencesDialog::removeFilterClicked()
 {
-    TRACE_OBJ
-    FilterNameDialog dia(this);
-    if (dia.exec() == QDialog::Rejected)
+    const QString &currentFilter = m_itemToFilter.value(m_ui.filterWidget->currentItem());
+    if (currentFilter.isEmpty())
         return;
 
-    QString filterName = dia.filterName();
-    if (!m_filterMap.contains(filterName)) {
-        m_filterMap.insert(filterName, QStringList());
-        m_ui.filterWidget->addItem(filterName);
+    if (QMessageBox::question(this, tr("Remove Filter"),
+                              tr("Are you sure you want to remove the \"%1\" filter?")
+                              .arg(currentFilter),
+                              QMessageBox::Yes | QMessageBox::No)
+            != QMessageBox::Yes) {
+        return;
     }
 
-    QList<QListWidgetItem*> lst = m_ui.filterWidget
-        ->findItems(filterName, Qt::MatchCaseSensitive);
-    m_ui.filterWidget->setCurrentItem(lst.first());
+    removeFilter(currentFilter);
 }
 
-void PreferencesDialog::removeFilter()
+void PreferencesDialog::addFilter(const QString &filterName, const QStringList &components)
 {
-    TRACE_OBJ
-    QListWidgetItem *item =
-        m_ui.filterWidget ->takeItem(m_ui.filterWidget->currentRow());
-    if (!item)
-        return;
+    QListWidgetItem *item = new QListWidgetItem(filterName);
+    m_currentSetup.m_filterToComponents.insert(filterName, components);
+    m_filterToItem.insert(filterName, item);
+    m_itemToFilter.insert(item, filterName);
+    m_ui.filterWidget->insertItem(m_filterToItem.keys().indexOf(filterName), item);
+
+    m_ui.filterWidget->setCurrentItem(item);
+    updateCurrentFilter();
+}
 
-    m_filterMap.remove(item->text());
-    m_removedFilters.append(item->text());
+void PreferencesDialog::removeFilter(const QString &filterName)
+{
+    QListWidgetItem *item = m_filterToItem.value(filterName);
+    m_itemToFilter.remove(item);
+    m_filterToItem.remove(filterName);
     delete item;
-    if (m_ui.filterWidget->count())
-        m_ui.filterWidget->setCurrentRow(0);
+
+    m_currentSetup.m_filterToComponents.remove(filterName);
 }
 
-void PreferencesDialog::addDocumentationLocal()
+void PreferencesDialog::addDocumentation()
 {
-    TRACE_OBJ
     const QStringList &fileNames = QFileDialog::getOpenFileNames(this,
         tr("Add Documentation"), QString(), tr("Qt Compressed Help Files (*.qch)"));
     if (fileNames.isEmpty())
         return;
 
-    QStringList invalidFiles;
-    QStringList alreadyRegistered;
+    bool added = false;
+
     for (const QString &fileName : fileNames) {
-        const QString nameSpace = QHelpEngineCore::namespaceName(fileName);
-        if (nameSpace.isEmpty()) {
-            invalidFiles.append(fileName);
+        const QHelpCollectionDetails details = QHelpCollectionDetails::helpDetails(fileName);
+        const QString namespaceName = details.namespaceName();
+
+        if (m_currentSetup.m_namespaceToFileName.contains(namespaceName))
             continue;
-        }
 
-        if (m_registeredDocsModel->contains(nameSpace)) {
-                alreadyRegistered.append(nameSpace);
-                continue;
-        }
+        if (m_currentSetup.m_fileNameToNamespace.contains(fileName))
+            continue;
 
-        if (helpEngine.registerDocumentation(fileName)) {
-            RegisteredDocEntry entry;
-            entry.nameSpace = nameSpace;
-            entry.fileName = fileName;
-            m_registeredDocsModel->append(entry);
-            m_unregDocs.removeAll(nameSpace);
-        }
-    }
+        const QString component = details.component();
+        m_currentSetup.m_namespaceToFileName.insert(namespaceName, fileName);
+        m_currentSetup.m_fileNameToNamespace.insert(fileName, namespaceName);
 
-    if (!invalidFiles.isEmpty() || !alreadyRegistered.isEmpty()) {
-        QString message;
-        if (!alreadyRegistered.isEmpty()) {
-            for (const QString &ns : qAsConst(alreadyRegistered)) {
-                message += tr("The namespace %1 is already registered!")
-                    .arg(QString("<b>%1</b>").arg(ns)) + QLatin1String("<br>");
-            }
-            if (!invalidFiles.isEmpty())
-                message.append(QLatin1String("<br>"));
-        }
+        m_currentSetup.m_namespaceToComponent.insert(namespaceName, component);
+        m_currentSetup.m_componentToNamespace[component].append(namespaceName);
 
-        if (!invalidFiles.isEmpty()) {
-            message += tr("The specified file is not a valid Qt Help File!");
-            message.append(QLatin1String("<ul>"));
-            for (const QString &file : qAsConst(invalidFiles))
-                message += QLatin1String("<li>") + file + QLatin1String("</li>");
-            message.append(QLatin1String("</ul>"));
-        }
-        QMessageBox::warning(this, tr("Add Documentation"), message);
+        QListWidgetItem *item = new QListWidgetItem(namespaceName);
+        m_namespaceToItem.insert(namespaceName, item);
+        m_itemToNamespace.insert(item, namespaceName);
+        m_ui.registeredDocsListWidget->insertItem(m_namespaceToItem.keys().indexOf(namespaceName), item);
+
+        added = true;
     }
 
-    updateFilterPage();
+    if (added)
+        updateCurrentFilter();
 }
 
-QList<int> PreferencesDialog::currentRegisteredDocsSelection() const
+void PreferencesDialog::removeDocumentation()
 {
-    QList<int> result;
-    for (const QModelIndex &index : m_ui.registeredDocsListView->selectionModel()->selectedRows())
-        result.append(m_registereredDocsFilterModel->mapToSource(index).row());
-    std::sort(result.begin(), result.end());
-    return result;
+    const QList<QListWidgetItem *> selectedItems = m_ui.registeredDocsListWidget->selectedItems();
+    if (selectedItems.isEmpty())
+        return;
+
+    for (QListWidgetItem *item : selectedItems) {
+        const QString namespaceName = m_itemToNamespace.value(item);
+        m_itemToNamespace.remove(item);
+        m_namespaceToItem.remove(namespaceName);
+        delete item;
+
+        const QString fileName = m_currentSetup.m_namespaceToFileName.value(namespaceName);
+        const QString component = m_currentSetup.m_namespaceToComponent.value(namespaceName);
+        m_currentSetup.m_namespaceToComponent.remove(namespaceName);
+        m_currentSetup.m_namespaceToFileName.remove(namespaceName);
+        m_currentSetup.m_fileNameToNamespace.remove(fileName);
+        m_currentSetup.m_componentToNamespace[component].removeOne(namespaceName);
+        if (m_currentSetup.m_componentToNamespace[component].isEmpty())
+            m_currentSetup.m_componentToNamespace.remove(component);
+    }
+
+    updateCurrentFilter();
 }
 
-void PreferencesDialog::removeDocumentation()
+void PreferencesDialog::okClicked()
 {
-    TRACE_OBJ
+    applyChanges();
+    accept();
+}
 
-    const QList<int> currentSelection = currentRegisteredDocsSelection();
-    if (currentSelection.isEmpty())
-        return;
+void PreferencesDialog::applyClicked()
+{
+    applyChanges();
+    m_originalSetup = readOriginalSetup();
+    m_currentSetup = m_originalSetup;
+    updateDocumentationPage();
+    updateFilterPage();
+}
 
-    RegisteredDocEntries entries = m_registeredDocsModel->docEntries();
-
-    bool foundBefore = false;
-    for (int i = currentSelection.size() - 1; i >= 0; --i) {
-        const int row = currentSelection.at(i);
-        const QString &ns = entries.at(row).nameSpace;
-        if (!foundBefore && OpenPagesManager::instance()->pagesOpenForNamespace(ns)) {
-            if (0 == QMessageBox::information(this, tr("Remove Documentation"),
-                tr("Some documents currently opened in Assistant reference the "
-                   "documentation you are attempting to remove. Removing the "
-                   "documentation will close those documents."), tr("Cancel"),
-                tr("OK"))) return;
-            foundBefore = true;
-        }
+template <class T>
+static QMap<QString, T> subtract(const QMap<QString, T> &minuend,
+                                 const QMap<QString, T> &subtrahend)
+{
+    QMap<QString, T> result = minuend;
 
-        m_unregDocs.append(ns);
-        entries.removeAt(row);
+    for (auto itSubtrahend = subtrahend.cbegin(); itSubtrahend != subtrahend.cend(); ++itSubtrahend) {
+        auto itResult = result.find(itSubtrahend.key());
+        if (itResult != result.end() && itSubtrahend.value() == itResult.value())
+            result.erase(itResult);
     }
 
-    m_registeredDocsModel->setDocEntries(entries);
-
-    if (m_registereredDocsFilterModel->rowCount()) {
-        const QModelIndex &first = m_registereredDocsFilterModel->index(0, 0);
-        m_ui.registeredDocsListView->selectionModel()->setCurrentIndex(first,
-                                                                       QItemSelectionModel::ClearAndSelect);
-    }
+    return result;
 }
 
 void PreferencesDialog::applyChanges()
 {
-    TRACE_OBJ
-    bool filtersWereChanged = false;
-    if (!m_hideFiltersTab) {
-        if (m_filterMap.count() != m_filterMapBackup.count()) {
-            filtersWereChanged = true;
-        } else {
-            for (auto it = m_filterMapBackup.cbegin(), end = m_filterMapBackup.cend(); it != end && !filtersWereChanged; ++it) {
-                if (!m_filterMap.contains(it.key())) {
-                    filtersWereChanged = true;
-                } else {
-                    const QStringList &a = it.value();
-                    const QStringList &b = m_filterMap.value(it.key());
-                    if (a.count() != b.count()) {
-                        filtersWereChanged = true;
-                    } else {
-                        for (const QString &aStr : a) {
-                            if (!b.contains(aStr)) {
-                                filtersWereChanged = true;
-                                break;
-                            }
-                        }
-                    }
-                }
-            }
-        }
+    bool changed = false;
+
+    const QMap<QString, QString> docsToRemove = subtract(
+                m_originalSetup.m_namespaceToFileName,
+                m_currentSetup.m_namespaceToFileName);
+    const QMap<QString, QString> docsToAdd = subtract(
+                m_currentSetup.m_namespaceToFileName,
+                m_originalSetup.m_namespaceToFileName);
+
+    for (const QString &namespaceName : docsToRemove.keys()) {
+        if (!helpEngine.unregisterDocumentation(namespaceName))
+            qWarning() << "Cannot unregister documentation:" << namespaceName;
+        changed = true;
     }
 
-    if (filtersWereChanged) {
-        for (const QString &filter : qAsConst(m_removedFilters))
-            helpEngine.removeCustomFilter(filter);
-        for (auto it = m_filterMap.cbegin(), end = m_filterMap.cend(); it != end; ++it)
-            helpEngine.addCustomFilter(it.key(), it.value());
+    for (const QString &fileName : docsToAdd.values()) {
+        if (!helpEngine.registerDocumentation(fileName))
+            qWarning() << "Cannot register documentation file:" << fileName;
+        changed = true;
     }
 
-    for (const QString &doc : qAsConst(m_unregDocs)) {
-        OpenPagesManager::instance()->closePages(doc);
-        helpEngine.unregisterDocumentation(doc);
+    const QMap<QString, QStringList> filtersToRemove = subtract(
+                m_originalSetup.m_filterToComponents,
+                m_currentSetup.m_filterToComponents);
+    const QMap<QString, QStringList> filtersToAdd = subtract(
+                m_currentSetup.m_filterToComponents,
+                m_originalSetup.m_filterToComponents);
+
+    const QString &currentFilter = helpEngine.filterEngine()->activeFilter();
+
+    for (const QString &filter : filtersToRemove.keys()) {
+        helpEngine.filterEngine()->removeFilter(filter);
+        if (currentFilter == filter && !filtersToAdd.contains(filter))
+            helpEngine.filterEngine()->setActiveFilter(QString());
+        changed = true;
     }
 
-    if (filtersWereChanged || !m_unregDocs.isEmpty())
+    for (auto it = filtersToAdd.cbegin(); it != filtersToAdd.cend(); ++it) {
+        QHelpFilterData data;
+        data.setComponents(it.value());
+        helpEngine.filterEngine()->setFilterData(it.key(), data);
+        changed = true;
+    }
+
+    // in order to update the filtercombobox and indexwidget
+    // according to the new filter configuration
+    if (changed)
         helpEngine.setupData();
 
     helpEngine.setShowTabs(m_ui.showTabs->isChecked());
     if (m_showTabs != m_ui.showTabs->isChecked())
         emit updateUserInterface();
-
-    accept();
 }
 
 void PreferencesDialog::updateFontSettingsPage()
 {
-    TRACE_OBJ
     m_browserFontPanel = new FontPanel(this);
     m_browserFontPanel->setCheckable(true);
     m_ui.stackedWidget_2->insertWidget(0, m_browserFontPanel);
@@ -526,35 +543,30 @@ void PreferencesDialog::updateFontSettingsPage()
 
 void PreferencesDialog::appFontSettingToggled(bool on)
 {
-    TRACE_OBJ
     Q_UNUSED(on)
     m_appFontChanged = true;
 }
 
 void PreferencesDialog::appFontSettingChanged(int index)
 {
-    TRACE_OBJ
     Q_UNUSED(index)
     m_appFontChanged = true;
 }
 
 void PreferencesDialog::browserFontSettingToggled(bool on)
 {
-    TRACE_OBJ
     Q_UNUSED(on)
     m_browserFontChanged = true;
 }
 
 void PreferencesDialog::browserFontSettingChanged(int index)
 {
-    TRACE_OBJ
     Q_UNUSED(index)
     m_browserFontChanged = true;
 }
 
 void PreferencesDialog::updateOptionsPage()
 {
-    TRACE_OBJ
     m_ui.homePageLineEdit->setText(helpEngine.homePage());
 
     int option = helpEngine.startOption();
@@ -573,13 +585,11 @@ void PreferencesDialog::updateOptionsPage()
 
 void PreferencesDialog::setBlankPage()
 {
-    TRACE_OBJ
     m_ui.homePageLineEdit->setText(QLatin1String("about:blank"));
 }
 
 void PreferencesDialog::setCurrentPage()
 {
-    TRACE_OBJ
     QString homepage = CentralWidget::instance()->currentSource().toString();
     if (homepage.isEmpty())
         homepage = QLatin1String("help");
@@ -589,7 +599,6 @@ void PreferencesDialog::setCurrentPage()
 
 void PreferencesDialog::setDefaultPage()
 {
-    TRACE_OBJ
     m_ui.homePageLineEdit->setText(helpEngine.defaultHomePage());
 }
 
diff --git a/src/assistant/assistant/preferencesdialog.h b/src/assistant/assistant/preferencesdialog.h
index 72dd81eda..1e45d9b6d 100644
--- a/src/assistant/assistant/preferencesdialog.h
+++ b/src/assistant/assistant/preferencesdialog.h
@@ -36,9 +36,17 @@ QT_BEGIN_NAMESPACE
 
 class FontPanel;
 class HelpEngineWrapper;
-class RegisteredDocsModel;
 class QFileSystemWatcher;
-class QSortFilterProxyModel;
+
+struct FilterSetup {
+    QMap<QString, QString>     m_namespaceToComponent;
+    QMap<QString, QStringList> m_componentToNamespace;
+
+    QMap<QString, QString>     m_namespaceToFileName;
+    QMap<QString, QString>     m_fileNameToNamespace;
+
+    QMap<QString, QStringList> m_filterToComponents;
+};
 
 class PreferencesDialog : public QDialog
 {
@@ -51,12 +59,17 @@ public:
     void showDialog();
 
 private slots:
-    void updateAttributes(QListWidgetItem *item);
-    void updateFilterMap();
-    void addFilter();
-    void removeFilter();
-    void addDocumentationLocal();
+    void filterSelected(QListWidgetItem *item);
+    void componentsChanged(const QStringList &components);
+    void addFilterClicked();
+    void renameFilterClicked();
+    void removeFilterClicked();
+    void addFilter(const QString &filterName, const QStringList &components);
+    void removeFilter(const QString &filterName);
+    void addDocumentation();
     void removeDocumentation();
+    void okClicked();
+    void applyClicked();
     void applyChanges();
     void appFontSettingToggled(bool on);
     void appFontSettingChanged(int index);
@@ -73,19 +86,27 @@ signals:
     void updateUserInterface();
 
 private:
+    QString suggestedNewFilterName(const QString &initialFilterName) const;
+    QString getUniqueFilterName(const QString &windowTitle,
+                                const QString &initialFilterName = QString());
     void updateFilterPage();
+    void updateCurrentFilter();
+    void updateDocumentationPage();
     void updateFontSettingsPage();
     void updateOptionsPage();
-    QList<int> currentRegisteredDocsSelection() const;
+    FilterSetup readOriginalSetup() const;
 
     Ui::PreferencesDialogClass m_ui;
-    QMap<QString, QStringList> m_filterMapBackup;
-    QMap<QString, QStringList> m_filterMap;
-    QStringList m_removedFilters;
-    QStringList m_docsBackup;
-    RegisteredDocsModel *m_registeredDocsModel;
-    QSortFilterProxyModel *m_registereredDocsFilterModel;
-    QStringList m_unregDocs;
+
+    FilterSetup m_originalSetup;
+    FilterSetup m_currentSetup;
+
+    QMap<QString, QListWidgetItem *> m_namespaceToItem;
+    QHash<QListWidgetItem *, QString> m_itemToNamespace;
+
+    QMap<QString, QListWidgetItem *> m_filterToItem;
+    QHash<QListWidgetItem *, QString> m_itemToFilter;
+
     FontPanel *m_appFontPanel;
     FontPanel *m_browserFontPanel;
     bool m_appFontChanged;
diff --git a/src/assistant/assistant/preferencesdialog.ui b/src/assistant/assistant/preferencesdialog.ui
index ebefa2458..70a90dd74 100644
--- a/src/assistant/assistant/preferencesdialog.ui
+++ b/src/assistant/assistant/preferencesdialog.ui
@@ -6,24 +6,24 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>375</width>
-    <height>342</height>
+    <width>378</width>
+    <height>341</height>
    </rect>
   </property>
   <property name="windowTitle">
    <string>Preferences</string>
   </property>
-  <layout class="QVBoxLayout">
+  <layout class="QVBoxLayout" name="verticalLayout_6">
    <item>
     <widget class="QTabWidget" name="tabWidget">
      <property name="currentIndex">
-      <number>0</number>
+      <number>1</number>
      </property>
      <widget class="QWidget" name="fontsTab">
       <attribute name="title">
        <string>Fonts</string>
       </attribute>
-      <layout class="QGridLayout">
+      <layout class="QGridLayout" name="gridLayout">
        <item row="0" column="0">
         <layout class="QHBoxLayout">
          <item>
@@ -69,45 +69,46 @@
       <attribute name="title">
        <string>Filters</string>
       </attribute>
-      <layout class="QGridLayout">
-       <item row="0" column="0" colspan="2">
+      <layout class="QGridLayout" name="gridLayout_2">
+       <item row="0" column="0">
         <widget class="QLabel" name="label">
          <property name="text">
           <string>Filter:</string>
          </property>
         </widget>
        </item>
-       <item row="0" column="2">
+       <item row="0" column="3">
         <widget class="QLabel" name="label_2">
          <property name="frameShape">
           <enum>QFrame::NoFrame</enum>
          </property>
          <property name="text">
-          <string>Attributes:</string>
+          <string>Components:</string>
          </property>
         </widget>
        </item>
-       <item row="1" column="0" colspan="2">
+       <item row="1" column="0" colspan="3">
         <widget class="QListWidget" name="filterWidget"/>
        </item>
-       <item row="1" column="2" rowspan="2">
-        <widget class="QTreeWidget" name="attributeWidget">
-         <column>
-          <property name="text">
-           <string>1</string>
-          </property>
-         </column>
-        </widget>
+       <item row="1" column="3">
+        <widget class="OptionsWidget" name="componentWidget" native="true"/>
        </item>
        <item row="2" column="0">
-        <widget class="QPushButton" name="filterAddButton">
+        <widget class="QToolButton" name="filterAddButton">
          <property name="text">
-          <string>Add</string>
+          <string>Add...</string>
          </property>
         </widget>
        </item>
        <item row="2" column="1">
-        <widget class="QPushButton" name="filterRemoveButton">
+        <widget class="QToolButton" name="filterRenameButton">
+         <property name="text">
+          <string>Rename...</string>
+         </property>
+        </widget>
+       </item>
+       <item row="2" column="2">
+        <widget class="QToolButton" name="filterRemoveButton">
          <property name="text">
           <string>Remove</string>
          </property>
@@ -119,73 +120,62 @@
       <attribute name="title">
        <string>Documentation</string>
       </attribute>
-      <layout class="QVBoxLayout" name="verticalLayout_5">
-       <item>
+      <layout class="QGridLayout" name="gridLayout_3">
+       <item row="0" column="0">
         <widget class="QLabel" name="label_3">
          <property name="text">
           <string>Registered Documentation:</string>
          </property>
         </widget>
        </item>
-       <item>
-        <layout class="QHBoxLayout" name="horizontalLayout_4">
+       <item row="1" column="0">
+        <widget class="QLineEdit" name="registeredDocsFilterLineEdit">
+         <property name="placeholderText">
+          <string>&lt;Filter&gt;</string>
+         </property>
+         <property name="clearButtonEnabled">
+          <bool>true</bool>
+         </property>
+        </widget>
+       </item>
+       <item row="1" column="1" rowspan="2">
+        <layout class="QVBoxLayout" name="verticalLayout_4">
          <item>
-          <layout class="QVBoxLayout" name="verticalLayout_4">
-           <item>
-            <widget class="QLineEdit" name="registeredDocsFilterLineEdit">
-             <property name="placeholderText">
-              <string>&lt;Filter&gt;</string>
-             </property>
-             <property name="clearButtonEnabled">
-              <bool>true</bool>
-             </property>
-            </widget>
-           </item>
-           <item>
-            <widget class="QListView" name="registeredDocsListView">
-             <property name="selectionMode">
-              <enum>QAbstractItemView::ExtendedSelection</enum>
-             </property>
-            </widget>
-           </item>
-          </layout>
+          <widget class="QPushButton" name="docAddButton">
+           <property name="text">
+            <string>Add...</string>
+           </property>
+          </widget>
          </item>
          <item>
-          <layout class="QVBoxLayout">
-           <property name="spacing">
-            <number>6</number>
+          <widget class="QPushButton" name="docRemoveButton">
+           <property name="text">
+            <string>Remove</string>
            </property>
-           <item>
-            <widget class="QPushButton" name="docAddButton">
-             <property name="text">
-              <string>Add...</string>
-             </property>
-            </widget>
-           </item>
-           <item>
-            <widget class="QPushButton" name="docRemoveButton">
-             <property name="text">
-              <string>Remove</string>
-             </property>
-            </widget>
-           </item>
-           <item>
-            <spacer>
-             <property name="orientation">
-              <enum>Qt::Vertical</enum>
-             </property>
-             <property name="sizeHint" stdset="0">
-              <size>
-               <width>20</width>
-               <height>40</height>
-              </size>
-             </property>
-            </spacer>
-           </item>
-          </layout>
+          </widget>
+         </item>
+         <item>
+          <spacer>
+           <property name="orientation">
+            <enum>Qt::Vertical</enum>
+           </property>
+           <property name="sizeHint" stdset="0">
+            <size>
+             <width>20</width>
+             <height>40</height>
+            </size>
+           </property>
+          </spacer>
          </item>
         </layout>
        </item>
+       <item row="2" column="0">
+        <widget class="QListWidget" name="registeredDocsListWidget">
+         <property name="selectionMode">
+          <enum>QAbstractItemView::ExtendedSelection</enum>
+         </property>
+        </widget>
+       </item>
       </layout>
      </widget>
      <widget class="QWidget" name="optionsTab">
@@ -348,38 +338,23 @@
     </widget>
    </item>
    <item>
-    <layout class="QHBoxLayout">
-     <property name="spacing">
-      <number>6</number>
+    <widget class="QDialogButtonBox" name="buttonBox">
+     <property name="standardButtons">
+      <set>QDialogButtonBox::Apply|QDialogButtonBox::Cancel|QDialogButtonBox::Ok</set>
      </property>
-     <item>
-      <spacer>
-       <property name="orientation">
-        <enum>Qt::Horizontal</enum>
-       </property>
-       <property name="sizeHint" stdset="0">
-        <size>
-         <width>40</width>
-         <height>20</height>
-        </size>
-       </property>
-      </spacer>
-     </item>
-     <item>
-      <widget class="QDialogButtonBox" name="buttonBox">
-       <property name="orientation">
-        <enum>Qt::Horizontal</enum>
-       </property>
-       <property name="standardButtons">
-        <set>QDialogButtonBox::Cancel|QDialogButtonBox::Ok</set>
-       </property>
-      </widget>
-     </item>
-    </layout>
+    </widget>
    </item>
   </layout>
  </widget>
  <layoutdefault spacing="6" margin="11"/>
+ <customwidgets>
+  <customwidget>
+   <class>OptionsWidget</class>
+   <extends>QWidget</extends>
+   <header>optionswidget.h</header>
+   <container>1</container>
+  </customwidget>
+ </customwidgets>
  <resources/>
  <connections>
   <connection>
diff --git a/src/assistant/assistant/remotecontrol.cpp b/src/assistant/assistant/remotecontrol.cpp
index cab7b5db6..7fdbee41e 100644
--- a/src/assistant/assistant/remotecontrol.cpp
+++ b/src/assistant/assistant/remotecontrol.cpp
@@ -42,6 +42,7 @@
 #include <QtWidgets/QApplication>
 
 #include <QtHelp/QHelpEngine>
+#include <QtHelp/QHelpFilterEngine>
 #include <QtHelp/QHelpIndexWidget>
 #include <QtHelp/QHelpSearchQueryWidget>
 
@@ -223,12 +224,12 @@ void RemoteControl::handleExpandTocCommand(const QString &arg)
 void RemoteControl::handleSetCurrentFilterCommand(const QString &arg)
 {
     TRACE_OBJ
-    if (helpEngine.customFilters().contains(arg)) {
+    if (helpEngine.filterEngine()->filters().contains(arg)) {
         if (m_caching) {
             clearCache();
             m_currentFilter = arg;
         } else {
-            helpEngine.setCurrentFilter(arg);
+            helpEngine.filterEngine()->setActiveFilter(arg);
         }
     }
 }
@@ -270,7 +271,7 @@ void RemoteControl::applyCache()
         if (!links.isEmpty())
             CentralWidget::instance()->setSource(links.first());
     } else if (!m_currentFilter.isEmpty()) {
-        helpEngine.setCurrentFilter(m_currentFilter);
+        helpEngine.filterEngine()->setActiveFilter(m_currentFilter);
     }
 
     if (m_syncContents)
diff --git a/src/assistant/help/help.pro b/src/assistant/help/help.pro
index 5bdc501fc..a1616b233 100644
--- a/src/assistant/help/help.pro
+++ b/src/assistant/help/help.pro
@@ -14,6 +14,7 @@ SOURCES += qhelpenginecore.cpp \
     qhelpengine.cpp \
     qhelpcollectiondetails.cpp \
     qhelpfilterdata.cpp \
+    qhelpfilterengine.cpp \
     qhelpdbreader.cpp \
     qhelpcontentwidget.cpp \
     qhelpindexwidget.cpp \
@@ -31,6 +32,7 @@ HEADERS += qhelpenginecore.h \
     qhelpengine_p.h \
     qhelpcollectiondetails.h \
     qhelpfilterdata.h \
+    qhelpfilterengine.h \
     qhelp_global.h \
     qhelpdbreader_p.h \
     qhelpcontentwidget.h \
diff --git a/src/assistant/help/qhelpcollectionhandler.cpp b/src/assistant/help/qhelpcollectionhandler.cpp
index e59acaac5..0cb6264dd 100644
--- a/src/assistant/help/qhelpcollectionhandler.cpp
+++ b/src/assistant/help/qhelpcollectionhandler.cpp
@@ -925,8 +925,8 @@ bool QHelpCollectionHandler::fileExists(const QUrl &url) const
     if (fileInfo.namespaceName.isEmpty())
         return false;
 
-    m_query->prepare(QLatin1String("SELECT COUNT (DISTINCT NamespaceTable.Id)"
-                                   "FROM"
+    m_query->prepare(QLatin1String("SELECT COUNT (DISTINCT NamespaceTable.Id) "
+                                   "FROM "
                                        "FileNameTable, "
                                        "NamespaceTable, "
                                        "FolderTable "
diff --git a/src/assistant/help/qhelpcontentwidget.cpp b/src/assistant/help/qhelpcontentwidget.cpp
index 412e14528..901c4c56b 100644
--- a/src/assistant/help/qhelpcontentwidget.cpp
+++ b/src/assistant/help/qhelpcontentwidget.cpp
@@ -76,15 +76,18 @@ public:
     ~QHelpContentProvider() override;
     void collectContents(const QString &customFilterName);
     void stopCollecting();
-    QHelpContentItem *rootItem();
+    QHelpContentItem *takeContentItem();
 
 private:
     void run() override;
 
     QHelpEnginePrivate *m_helpEngine;
+    QString m_currentFilter;
     QStringList m_filterAttributes;
-    QQueue<QHelpContentItem*> m_rootItems;
+    QString m_collectionFile;
+    QHelpContentItem *m_rootItem = nullptr;
     QMutex m_mutex;
+    bool m_usesFilterEngine = false;
     bool m_abort = false;
 };
 
@@ -194,7 +197,10 @@ QHelpContentProvider::~QHelpContentProvider()
 void QHelpContentProvider::collectContents(const QString &customFilterName)
 {
     m_mutex.lock();
+    m_currentFilter = customFilterName;
     m_filterAttributes = m_helpEngine->q->filterAttributes(customFilterName);
+    m_collectionFile = m_helpEngine->collectionHandler->collectionFile();
+    m_usesFilterEngine = m_helpEngine->usesFilterEngine;
     m_mutex.unlock();
 
     if (isRunning())
@@ -215,16 +221,16 @@ void QHelpContentProvider::stopCollecting()
         // either way never resetting m_abort to false from within the run() method
         m_abort = false;
     }
-    qDeleteAll(m_rootItems);
-    m_rootItems.clear();
+    delete m_rootItem;
+    m_rootItem = nullptr;
 }
 
-QHelpContentItem *QHelpContentProvider::rootItem()
+QHelpContentItem *QHelpContentProvider::takeContentItem()
 {
     QMutexLocker locker(&m_mutex);
-    if (m_rootItems.isEmpty())
-        return nullptr;
-    return m_rootItems.dequeue();
+    QHelpContentItem *content = m_rootItem;
+    m_rootItem = nullptr;
+    return content;
 }
 
 // TODO: this is a copy from helpcollectionhandler, make it common
@@ -258,8 +264,12 @@ void QHelpContentProvider::run()
 
     m_mutex.lock();
     QHelpContentItem * const rootItem = new QHelpContentItem(QString(), QString(), nullptr);
+    const QString currentFilter = m_currentFilter;
     const QStringList attributes = m_filterAttributes;
-    const QString collectionFile = m_helpEngine->collectionHandler->collectionFile();
+    const QString collectionFile = m_collectionFile;
+    const bool usesFilterEngine = m_usesFilterEngine;
+    delete m_rootItem;
+    m_rootItem = nullptr;
     m_mutex.unlock();
 
     if (collectionFile.isEmpty())
@@ -269,8 +279,9 @@ void QHelpContentProvider::run()
     if (!collectionHandler.openCollectionFile())
         return;
 
-    const QList<QHelpCollectionHandler::ContentsData> result
-            = collectionHandler.contentsForFilter(attributes);
+    const QList<QHelpCollectionHandler::ContentsData> result = usesFilterEngine
+            ? collectionHandler.contentsForFilter(currentFilter)
+            : collectionHandler.contentsForFilter(attributes);
 
     for (const auto &contentsData : result) {
         m_mutex.lock();
@@ -328,7 +339,7 @@ CHECK_DEPTH:
     }
 
     m_mutex.lock();
-    m_rootItems.enqueue(rootItem);
+    m_rootItem = rootItem;
     m_abort = false;
     m_mutex.unlock();
 }
@@ -375,11 +386,6 @@ QHelpContentModel::~QHelpContentModel()
     delete d;
 }
 
-void QHelpContentModel::invalidateContents(bool onShutDown)
-{
-    Q_UNUSED(onShutDown)
-}
-
 /*!
     Creates new contents by querying the help system
     for contents specified for the \a customFilterName.
@@ -405,7 +411,7 @@ void QHelpContentModel::insertContents()
     if (d->qhelpContentProvider->isRunning())
         return;
 
-    QHelpContentItem * const newRootItem = d->qhelpContentProvider->rootItem();
+    QHelpContentItem * const newRootItem = d->qhelpContentProvider->takeContentItem();
     if (!newRootItem)
         return;
     beginResetModel();
diff --git a/src/assistant/help/qhelpcontentwidget.h b/src/assistant/help/qhelpcontentwidget.h
index 01594d60f..b316ebba9 100644
--- a/src/assistant/help/qhelpcontentwidget.h
+++ b/src/assistant/help/qhelpcontentwidget.h
@@ -100,7 +100,6 @@ Q_SIGNALS:
 
 private Q_SLOTS:
     void insertContents();
-    void invalidateContents(bool onShutDown = false);
 
 private:
     QHelpContentModel(QHelpEnginePrivate *helpEngine);
diff --git a/src/assistant/help/qhelpengine.cpp b/src/assistant/help/qhelpengine.cpp
index 28825e2ed..19e44cd91 100644
--- a/src/assistant/help/qhelpengine.cpp
+++ b/src/assistant/help/qhelpengine.cpp
@@ -44,6 +44,7 @@
 #include "qhelpindexwidget.h"
 #include "qhelpsearchengine.h"
 #include "qhelpcollectionhandler_p.h"
+#include "qhelpfilterengine.h"
 
 #include <QtCore/QDir>
 #include <QtCore/QFile>
@@ -68,6 +69,8 @@ void QHelpEnginePrivate::init(const QString &collectionFile,
             this, &QHelpEnginePrivate::scheduleApplyCurrentFilter);
     connect(helpEngineCore, &QHelpEngineCore::currentFilterChanged,
             this, &QHelpEnginePrivate::scheduleApplyCurrentFilter);
+    connect(helpEngineCore->filterEngine(), &QHelpFilterEngine::filterActivated,
+            this, &QHelpEnginePrivate::scheduleApplyCurrentFilter);
 }
 
 void QHelpEnginePrivate::scheduleApplyCurrentFilter()
@@ -85,8 +88,11 @@ void QHelpEnginePrivate::scheduleApplyCurrentFilter()
 void QHelpEnginePrivate::applyCurrentFilter()
 {
     m_isApplyCurrentFilterScheduled = false;
-    contentModel->createContents(currentFilter);
-    indexModel->createIndex(currentFilter);
+    const QString filter = usesFilterEngine
+            ? q->filterEngine()->activeFilter()
+            : currentFilter;
+    contentModel->createContents(filter);
+    indexModel->createIndex(filter);
 }
 
 void QHelpEnginePrivate::setContentsWidgetBusy()
diff --git a/src/assistant/help/qhelpengine_p.h b/src/assistant/help/qhelpengine_p.h
index 847715eb3..558013e77 100644
--- a/src/assistant/help/qhelpengine_p.h
+++ b/src/assistant/help/qhelpengine_p.h
@@ -68,6 +68,7 @@ class QHelpIndexModel;
 class QHelpIndexWidget;
 class QHelpSearchEngine;
 class QHelpCollectionHandler;
+class QHelpFilterEngine;
 
 class QHelpEngineCorePrivate : public QObject
 {
@@ -82,10 +83,12 @@ public:
     bool setup();
 
     QHelpCollectionHandler *collectionHandler = nullptr;
+    QHelpFilterEngine *filterEngine = nullptr;
     QString currentFilter;
     QString error;
     bool needsSetup = true;
     bool autoSaveFilter = true;
+    bool usesFilterEngine = false;
 
 protected:
     QHelpEngineCore *q;
diff --git a/src/assistant/help/qhelpenginecore.cpp b/src/assistant/help/qhelpenginecore.cpp
index fc6366d2a..6f1794a60 100644
--- a/src/assistant/help/qhelpenginecore.cpp
+++ b/src/assistant/help/qhelpenginecore.cpp
@@ -41,6 +41,7 @@
 #include "qhelpengine_p.h"
 #include "qhelpdbreader_p.h"
 #include "qhelpcollectionhandler_p.h"
+#include "qhelpfilterengine.h"
 
 #include <QtCore/QDir>
 #include <QtCore/QFile>
@@ -59,6 +60,7 @@ void QHelpEngineCorePrivate::init(const QString &collectionFile,
     collectionHandler = new QHelpCollectionHandler(collectionFile, helpEngineCore);
     connect(collectionHandler, &QHelpCollectionHandler::error,
             this, &QHelpEngineCorePrivate::errorReceived);
+    filterEngine->setCollectionHandler(collectionHandler);
     needsSetup = true;
 }
 
@@ -111,11 +113,14 @@ void QHelpEngineCorePrivate::errorReceived(const QString &msg)
     depends on the currently set custom filter. Depending on the filter,
     the function may return different results.
 
-    Every help engine can contain any number of custom filters. A custom
-    filter is defined by a name and set of filter attributes and can be
-    added to the help engine by calling addCustomFilter(). Analogous,
-    it is removed by calling removeCustomFilter(). customFilters() returns
-    all defined filters.
+    The help engine can contain any number of custom filters.
+    The management of the filters, including adding new filters,
+    changing filter definitions, or removing existing filters,
+    is done through the QHelpFilterEngine class, which can be accessed
+    by the filterEngine() method. This replaces older filter API that is
+    deprecated since Qt 5.13. Please call setUsesFilterEngine() with
+    \c true to enable the new functionality.
+
 
     The help engine also offers the possibility to set and read values
     in a persistant way comparable to ini files or Windows registry
@@ -152,6 +157,9 @@ void QHelpEngineCorePrivate::errorReceived(const QString &msg)
 
 /*!
     \fn void QHelpEngineCore::currentFilterChanged(const QString &newFilter)
+    \obsolete
+
+    QHelpFilterEngine::filterActivated() should be used instead.
 
     This signal is emitted when the current filter is changed to
     \a newFilter.
@@ -173,6 +181,7 @@ QHelpEngineCore::QHelpEngineCore(const QString &collectionFile, QObject *parent)
     : QObject(parent)
 {
     d = new QHelpEngineCorePrivate();
+    d->filterEngine = new QHelpFilterEngine(this);
     d->init(collectionFile, this);
 }
 
@@ -184,6 +193,7 @@ QHelpEngineCore::QHelpEngineCore(QHelpEngineCorePrivate *helpEngineCorePrivate,
     : QObject(parent)
 {
     d = helpEngineCorePrivate;
+    d->filterEngine = new QHelpFilterEngine(this);
 }
 
 /*!
@@ -222,6 +232,19 @@ void QHelpEngineCore::setCollectionFile(const QString &fileName)
 }
 
 /*!
+    \since 5.13
+
+    Returns the filter engine associated with this help engine.
+    The filter engine allows for adding, changing, and removing existing
+    filters for this help engine. To use the engine you also have to call
+    \l setUsesFilterEngine() set to \c true.
+*/
+QHelpFilterEngine *QHelpEngineCore::filterEngine() const
+{
+    return d->filterEngine;
+}
+
+/*!
     Sets up the help engine by processing the information found
     in the collection file and returns true if successful; otherwise
     returns false.
@@ -345,6 +368,10 @@ QStringList QHelpEngineCore::registeredDocumentations() const
 }
 
 /*!
+    \obsolete
+
+    QHelpFilterEngine::filters() should be used instead.
+
     Returns a list of custom filters.
 
     \sa addCustomFilter(), removeCustomFilter()
@@ -357,6 +384,10 @@ QStringList QHelpEngineCore::customFilters() const
 }
 
 /*!
+    \obsolete
+
+    QHelpFilterEngine::setFilterData() should be used instead.
+
     Adds the new custom filter \a filterName. The filter attributes
     are specified by \a attributes. If the filter already exists,
     its attribute set is replaced. The function returns true if
@@ -373,6 +404,10 @@ bool QHelpEngineCore::addCustomFilter(const QString &filterName,
 }
 
 /*!
+    \obsolete
+
+    QHelpFilterEngine::removeFilter() should be used instead.
+
     Returns true if the filter \a filterName was removed successfully,
     otherwise false.
 
@@ -386,6 +421,10 @@ bool QHelpEngineCore::removeCustomFilter(const QString &filterName)
 }
 
 /*!
+    \obsolete
+
+    QHelpFilterEngine::availableComponents() should be used instead.
+
     Returns a list of all defined filter attributes.
 */
 QStringList QHelpEngineCore::filterAttributes() const
@@ -396,6 +435,10 @@ QStringList QHelpEngineCore::filterAttributes() const
 }
 
 /*!
+    \obsolete
+
+    QHelpFilterEngine::filterData() should be used instead.
+
     Returns a list of filter attributes used by the custom
     filter \a filterName.
 */
@@ -407,10 +450,13 @@ QStringList QHelpEngineCore::filterAttributes(const QString &filterName) const
 }
 
 /*!
+    \obsolete
     \property QHelpEngineCore::currentFilter
     \brief the name of the custom filter currently applied.
     \since 4.5
 
+    QHelpFilterEngine::activeFilter() should be used instead.
+
     Setting this property will save the new custom filter permanently in the
     help collection file. To set a custom filter without saving it
     permanently, disable the auto save filter mode.
@@ -446,6 +492,10 @@ void QHelpEngineCore::setCurrentFilter(const QString &filterName)
 }
 
 /*!
+    \obsolete
+
+    QHelpFilterEngine::filterData() should be used instead.
+
     Returns a list of filter attributes for the different filter sections
     defined in the Qt compressed help file with the given namespace
     \a namespaceName.
@@ -459,6 +509,10 @@ QList<QStringList> QHelpEngineCore::filterAttributeSets(const QString &namespace
 }
 
 /*!
+    \obsolete
+
+    files() should be used instead.
+
     Returns a list of files contained in the Qt compressed help file \a
     namespaceName. The files can be filtered by \a filterAttributes as
     well as by their extension \a extensionFilter (e.g. 'html').
@@ -485,22 +539,55 @@ QList<QUrl> QHelpEngineCore::files(const QString namespaceName,
 }
 
 /*!
-    Returns an invalid URL if the file \a url cannot be found.
-    If the file exists, either the same url is returned or a
-    different url if the file is located in a different namespace
-    which is merged via a common virtual folder.
+    Returns a list of files contained in the Qt compressed help file
+    for \a namespaceName. The files can be filtered by \a filterName as
+    well as by their extension \a extensionFilter (for example, 'html').
+*/
+QList<QUrl> QHelpEngineCore::files(const QString namespaceName,
+    const QString &filterName,
+    const QString &extensionFilter)
+{
+    QList<QUrl> res;
+    if (!d->setup())
+        return res;
+
+    QUrl url;
+    url.setScheme(QLatin1String("qthelp"));
+    url.setAuthority(namespaceName);
+
+    const QStringList &files = d->collectionHandler->files(
+                namespaceName, filterName, extensionFilter);
+    for (const QString &file : files) {
+        url.setPath(QLatin1String("/") + file);
+        res.append(url);
+    }
+    return res;
+}
+
+/*!
+    Returns the corrected URL for the \a url that may refer to
+    a different namespace defined by the virtual folder defined
+    as a part of the \a url. If the virtual folder matches the namespace
+    of the \a url, the method just checks if the file exists and returns
+    the same \a url. When the virtual folder doesn't match the namespace
+    of the \a url, it tries to find the best matching namespace according
+    to the active filter. When the namespace is found, it returns the
+    corrected URL if the file exists, otherwise it returns an invalid URL.
 */
 QUrl QHelpEngineCore::findFile(const QUrl &url) const
 {
     if (!d->setup())
         return url;
 
-    const QStringList &attributes = filterAttributes(currentFilter());
-    QUrl result = d->collectionHandler->findFile(url, attributes);
+    QUrl result = d->usesFilterEngine
+            ? d->collectionHandler->findFile(url, d->filterEngine->activeFilter())
+            : d->collectionHandler->findFile(url, filterAttributes(currentFilter())); // obsolete
     if (!result.isEmpty())
         return result;
 
-    result = d->collectionHandler->findFile(url, QStringList());
+    result = d->usesFilterEngine
+            ? d->collectionHandler->findFile(url, QString())
+            : d->collectionHandler->findFile(url, QStringList()); // obsolete
     if (!result.isEmpty())
         return result;
 
@@ -522,30 +609,37 @@ QByteArray QHelpEngineCore::fileData(const QUrl &url) const
 }
 
 /*!
-    Returns documents found for the \a id. The map contains the
-    document titles and their URLs.
-    The returned map contents depends on the current filter, meaning only the keywords
-    registered for the current filter will be returned.
+    Returns a map of the documents found for the \a id. The map contains the
+    document titles and their URLs. The returned map contents depend on
+    the current filter, and therefore only the identifiers registered for
+    the current filter will be returned.
 */
 QMap<QString, QUrl> QHelpEngineCore::linksForIdentifier(const QString &id) const
 {
     if (!d->setup())
         return QMap<QString, QUrl>();
 
+    if (d->usesFilterEngine)
+        return d->collectionHandler->linksForIdentifier(id, d->filterEngine->activeFilter());
+
+    // obsolete
     return d->collectionHandler->linksForIdentifier(id, filterAttributes(d->currentFilter));
 }
 
 /*!
-    \since 4.5
-
-    Returns all documents found for the \a keyword. The returned map consists of the
-    document titles and their URLs.
+    Returns a map of all the documents found for the \a keyword. The map
+    contains the document titles and URLs. The returned map contents depend
+    on the current filter, and therefore only the keywords registered for
+    the current filter will be returned.
 */
 QMap<QString, QUrl> QHelpEngineCore::linksForKeyword(const QString &keyword) const
 {
     if (!d->setup())
         return QMap<QString, QUrl>();
 
+    if (d->usesFilterEngine)
+        return d->collectionHandler->linksForKeyword(keyword, d->filterEngine->activeFilter());
+
     return d->collectionHandler->linksForKeyword(keyword, filterAttributes(d->currentFilter));
 }
 
@@ -621,7 +715,7 @@ QString QHelpEngineCore::error() const
     \since 4.5
 
     If QHelpEngineCore is in auto save filter mode, the current filter is
-    automatically saved when it is changed by the setCurrentFilter()
+    automatically saved when it is changed by the QHelpFilterEngine::setActiveFilter()
     function. The filter is saved persistently in the help collection file.
 
     By default, this mode is on.
@@ -636,4 +730,29 @@ bool QHelpEngineCore::autoSaveFilter() const
     return d->autoSaveFilter;
 }
 
+/*!
+    \since 5.13
+
+    Enables or disables the new filter engine functionality
+    inside the help engine, according to the passed \a uses parameter.
+
+    \sa filterEngine()
+*/
+void QHelpEngineCore::setUsesFilterEngine(bool uses)
+{
+    d->usesFilterEngine = uses;
+}
+
+/*!
+    \since 5.13
+
+    Returns whether the help engine uses the new filter functionality.
+
+    \sa filterEngine()
+*/
+bool QHelpEngineCore::usesFilterEngine() const
+{
+    return d->usesFilterEngine;
+}
+
 QT_END_NAMESPACE
diff --git a/src/assistant/help/qhelpenginecore.h b/src/assistant/help/qhelpenginecore.h
index 6a2bf0e7d..91950290e 100644
--- a/src/assistant/help/qhelpenginecore.h
+++ b/src/assistant/help/qhelpenginecore.h
@@ -49,8 +49,8 @@
 
 QT_BEGIN_NAMESPACE
 
-
 class QHelpEngineCorePrivate;
+class QHelpFilterEngine;
 
 class QHELP_EXPORT QHelpEngineCore : public QObject
 {
@@ -63,6 +63,8 @@ public:
     explicit QHelpEngineCore(const QString &collectionFile, QObject *parent = nullptr);
     virtual ~QHelpEngineCore();
 
+    QHelpFilterEngine *filterEngine() const;
+
     bool setupData();
 
     QString collectionFile() const;
@@ -74,7 +76,10 @@ public:
     bool registerDocumentation(const QString &documentationFileName);
     bool unregisterDocumentation(const QString &namespaceName);
     QString documentationFileName(const QString &namespaceName);
+    QStringList registeredDocumentations() const;
+    QByteArray fileData(const QUrl &url) const;
 
+#if QT_DEPRECATED_SINCE(5,13)
     QStringList customFilters() const;
     bool removeCustomFilter(const QString &filterName);
     bool addCustomFilter(const QString &filterName,
@@ -86,13 +91,16 @@ public:
     QString currentFilter() const;
     void setCurrentFilter(const QString &filterName);
 
-    QStringList registeredDocumentations() const;
     QList<QStringList> filterAttributeSets(const QString &namespaceName) const;
     QList<QUrl> files(const QString namespaceName,
         const QStringList &filterAttributes,
         const QString &extensionFilter = QString());
+#endif
+
+    QList<QUrl> files(const QString namespaceName,
+                      const QString &filterName,
+                      const QString &extensionFilter = QString());
     QUrl findFile(const QUrl &url) const;
-    QByteArray fileData(const QUrl &url) const;
 
     QMap<QString, QUrl> linksForIdentifier(const QString &id) const;
     QMap<QString, QUrl> linksForKeyword(const QString &keyword) const;
@@ -110,12 +118,18 @@ public:
     void setAutoSaveFilter(bool save);
     bool autoSaveFilter() const;
 
+    void setUsesFilterEngine(bool uses);
+    bool usesFilterEngine() const;
+
 Q_SIGNALS:
     void setupStarted();
     void setupFinished();
-    void currentFilterChanged(const QString &newFilter);
     void warning(const QString &msg);
+
+#if QT_DEPRECATED_SINCE(5,13)
+    void currentFilterChanged(const QString &newFilter);
     void readersAboutToBeInvalidated();
+#endif
 
 protected:
     QHelpEngineCore(QHelpEngineCorePrivate *helpEngineCorePrivate,
diff --git a/src/assistant/help/qhelpfilterdata.cpp b/src/assistant/help/qhelpfilterdata.cpp
index 0cd6ad3fb..3063136ed 100644
--- a/src/assistant/help/qhelpfilterdata.cpp
+++ b/src/assistant/help/qhelpfilterdata.cpp
@@ -54,31 +54,65 @@ public:
     QStringList m_components;
 };
 
+/*!
+    \class QHelpFilterData
+    \since 5.13
+    \inmodule QtHelp
+    \brief The QHelpFilterData class provides details for the filters
+    used by QHelpFilterEngine.
+
+    By using setComponents() you may constrain the search results to
+    documents that belong only to components specified on the given list.
+
+    \sa QHelpFilterEngine
+*/
+
+/*!
+    Constructs the empty filter.
+*/
 QHelpFilterData::QHelpFilterData()
     : d(new QHelpFilterDataPrivate)
 {
 }
 
+/*!
+    Constructs a copy of \a other.
+*/
 QHelpFilterData::QHelpFilterData(const QHelpFilterData &other)
     : d(other.d)
 {
 }
 
+/*!
+    Destroys the filter.
+*/
 QHelpFilterData::~QHelpFilterData()
 {
 }
 
+/*!
+    Assigns \a other to this filter and returns a reference to this filter.
+*/
 QHelpFilterData &QHelpFilterData::operator=(const QHelpFilterData &other)
 {
     d = other.d;
     return *this;
 }
 
+/*!
+    Specifies the component list that is used for filtering
+    the search results. Only the results which match the \a components
+    will be returned.
+*/
 void QHelpFilterData::setComponents(const QStringList &components)
 {
     d->m_components = components;
 }
 
+/*!
+    Returns the component list that is used for filtering
+    the search results.
+*/
 QStringList QHelpFilterData::components() const
 {
     return d->m_components;
diff --git a/src/assistant/help/qhelpfilterengine.cpp b/src/assistant/help/qhelpfilterengine.cpp
new file mode 100644
index 000000000..6a57e1cdc
--- /dev/null
+++ b/src/assistant/help/qhelpfilterengine.cpp
@@ -0,0 +1,277 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Assistant of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qhelpfilterengine.h"
+#include "qhelpenginecore.h"
+#include "qhelpfilterdata.h"
+#include "qhelpdbreader_p.h"
+#include "qhelpcollectionhandler_p.h"
+
+#include <QtCore/QThread>
+
+QT_BEGIN_NAMESPACE
+
+static const char ActiveFilter[] = "activeFilter";
+
+class QHelpFilterEnginePrivate
+{
+public:
+    bool setup();
+
+    QHelpFilterEngine *q = nullptr;
+    QHelpEngineCore *m_helpEngine = nullptr;
+    QHelpCollectionHandler *m_collectionHandler = nullptr;
+    QString m_currentFilter;
+    bool m_needsSetup = true;
+};
+
+bool QHelpFilterEnginePrivate::setup()
+{
+    if (!m_collectionHandler)
+        return false;
+
+    if (!m_needsSetup)
+        return true;
+
+    if (!m_helpEngine->setupData())
+        return false;
+
+    m_needsSetup = false;
+
+    const QString filter = m_collectionHandler->customValue(
+                QLatin1String(ActiveFilter), QString()).toString();
+    if (!filter.isEmpty() && m_collectionHandler->filters().contains(filter))
+        m_currentFilter = filter;
+
+    emit q->filterActivated(m_currentFilter);
+    return true;
+}
+
+//////////////
+
+/*!
+    \class QHelpFilterEngine
+    \since 5.13
+    \inmodule QtHelp
+    \brief The QHelpFilterEngine class provides a filtered view of the
+    help contents.
+
+    The filter engine allows the management of filters associated with
+    a QHelpEngineCore instance. The help engine internally creates an
+    instance of the filter engine, which can be accessed by calling
+    QHelpEngineCore::filterEngine(). Therefore, the public constructor
+    of this class is disabled.
+
+    The filters are identified by a filter name string. Filter details are
+    described by the \l QHelpFilterData class.
+
+    The filter engine allows for adding new filters and changing the existing
+    filters' data through the setFilterData() method. An existing filter can
+    be removed through the removeFilter() method.
+
+    Out of the registered filters one can be marked as the active one.
+    The active filter will be used by the associated help engine for returning
+    filtered results of many different functions, such as content, index, or
+    search results. If no filter is marked active, the help engine returns the
+    full results list available.
+
+    The active filter is returned by activeFilter() and it can be changed by
+    setActiveFilter().
+
+    \sa QHelpEngineCore
+*/
+
+/*!
+    \fn void QHelpFilterEngine::filterActivated(const QString &newFilter)
+
+    This signal is emitted when the active filter is set. \a newFilter
+    specifies the name of the filter.
+
+    \sa setActiveFilter()
+*/
+
+/*!
+    \internal
+    Constructs the filter engine for \a helpEngine.
+*/
+QHelpFilterEngine::QHelpFilterEngine(QHelpEngineCore *helpEngine)
+    : QObject(helpEngine),
+      d(new QHelpFilterEnginePrivate)
+{
+    d->q = this;
+    d->m_helpEngine = helpEngine;
+}
+
+/*!
+    \internal
+    Destroys the existing filter engine.
+*/
+QHelpFilterEngine::~QHelpFilterEngine()
+{
+    delete d;
+}
+
+/*!
+    \internal
+    Sets the \a collectionHandler to be used for this filter engine.
+*/
+void QHelpFilterEngine::setCollectionHandler(QHelpCollectionHandler *collectionHandler)
+{
+    d->m_collectionHandler = collectionHandler;
+    d->m_currentFilter = QString();
+    d->m_needsSetup = true;
+}
+
+/*!
+    Returns the map of all the available namespaces as keys
+    together with their associated components as values.
+*/
+QMap<QString, QString> QHelpFilterEngine::namespaceToComponent() const
+{
+    if (!d->setup())
+        return QMap<QString, QString>();
+    return d->m_collectionHandler->namespaceToComponent();
+}
+
+/*!
+    Returns the list of all filter names defined inside the filter engine.
+*/
+QStringList QHelpFilterEngine::filters() const
+{
+    if (!d->setup())
+        return QStringList();
+    return d->m_collectionHandler->filters();
+}
+
+/*!
+    Returns the list of all available components defined in all
+    registered documentation files.
+*/
+QStringList QHelpFilterEngine::availableComponents() const
+{
+    if (!d->setup())
+        return QStringList();
+    return d->m_collectionHandler->availableComponents();
+}
+
+/*!
+    Returns the filter details associated with \a filterName.
+*/
+QHelpFilterData QHelpFilterEngine::filterData(const QString &filterName) const
+{
+    if (!d->setup())
+        return QHelpFilterData();
+    return d->m_collectionHandler->filterData(filterName);
+}
+
+/*!
+    Changes the existing filter details of the filter identified by
+    \a filterName to \a filterData. If the filter does not exist, a
+    new filter is created.
+
+    Returns \c true if setting the filter succeeded, otherwise returns \c false.
+*/
+bool QHelpFilterEngine::setFilterData(const QString &filterName, const QHelpFilterData &filterData)
+{
+    if (!d->setup())
+        return false;
+    return d->m_collectionHandler->setFilterData(filterName, filterData);
+}
+
+/*!
+    Removes the filter identified by \a filterName.
+
+    Returns \c true if removing the filter succeeded, otherwise returns
+    \c false.
+*/
+bool QHelpFilterEngine::removeFilter(const QString &filterName)
+{
+    if (!d->setup())
+        return false;
+    return d->m_collectionHandler->removeFilter(filterName);
+}
+
+/*!
+    Returns the name of the currently active filter.
+*/
+QString QHelpFilterEngine::activeFilter() const
+{
+    if (!d->setup())
+        return QString();
+    return d->m_currentFilter;
+}
+
+/*!
+    Changes the currently active filter to \a filterName.
+
+    Returns \c true if changing the filter succeeded, otherwise
+    returns \c false.
+*/
+bool QHelpFilterEngine::setActiveFilter(const QString &filterName)
+{
+    if (!d->setup())
+        return false;
+
+    if (filterName == d->m_currentFilter)
+        return true;
+
+    if (!filterName.isEmpty() && !d->m_collectionHandler->filters().contains(filterName))
+        return false;
+
+    d->m_currentFilter = filterName;
+    d->m_collectionHandler->setCustomValue(QLatin1String(ActiveFilter),
+            d->m_currentFilter);
+
+    emit filterActivated(d->m_currentFilter);
+
+    return true;
+}
+
+/*!
+    Returns the list of all registered documentation namespaces that match
+    the filter identified by \a filterName.
+*/
+QStringList QHelpFilterEngine::namespacesForFilter(const QString &filterName) const
+{
+    if (!d->setup())
+        return QStringList();
+    return  d->m_collectionHandler->namespacesForFilter(filterName);
+}
+
+QT_END_NAMESPACE
diff --git a/src/assistant/help/qhelpfilterengine.h b/src/assistant/help/qhelpfilterengine.h
new file mode 100644
index 000000000..717b0ed60
--- /dev/null
+++ b/src/assistant/help/qhelpfilterengine.h
@@ -0,0 +1,95 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Assistant of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QHELPFILTERENGINE_H
+#define QHELPFILTERENGINE_H
+
+#include <QtHelp/qhelp_global.h>
+
+#include <QtCore/QObject>
+
+QT_BEGIN_NAMESPACE
+
+class QUrl;
+template <class K, class T>
+class QMap;
+
+class QHelpCollectionHandler;
+class QHelpEngineCore;
+class QHelpFilterData;
+class QHelpFilterEnginePrivate;
+
+class QHELP_EXPORT QHelpFilterEngine : public QObject
+{
+    Q_OBJECT
+public:
+    QMap<QString, QString> namespaceToComponent() const;
+
+    QStringList filters() const;
+
+    QString activeFilter() const;
+    bool setActiveFilter(const QString &filterName);
+
+    QStringList availableComponents() const;
+
+    QHelpFilterData filterData(const QString &filterName) const;
+    bool setFilterData(const QString &filterName, const QHelpFilterData &filterData);
+
+    bool removeFilter(const QString &filterName);
+
+    QStringList namespacesForFilter(const QString &filterName) const;
+
+Q_SIGNALS:
+    void filterActivated(const QString &newFilter);
+
+protected:
+    explicit QHelpFilterEngine(QHelpEngineCore *helpEngine);
+    virtual ~QHelpFilterEngine();
+
+private:
+    void setCollectionHandler(QHelpCollectionHandler *collectionHandler);
+
+    QHelpFilterEnginePrivate *d;
+    friend class QHelpEngineCore;
+    friend class QHelpEngineCorePrivate;
+};
+
+QT_END_NAMESPACE
+
+#endif // QHELPFILTERENGINE_H
diff --git a/src/assistant/help/qhelpindexwidget.cpp b/src/assistant/help/qhelpindexwidget.cpp
index e76dd4fb4..fa70dd438 100644
--- a/src/assistant/help/qhelpindexwidget.cpp
+++ b/src/assistant/help/qhelpindexwidget.cpp
@@ -65,8 +65,9 @@ private:
     void run() override;
 
     QHelpEnginePrivate *m_helpEngine;
-    QStringList m_indices;
+    QString m_currentFilter;
     QStringList m_filterAttributes;
+    QStringList m_indices;
     mutable QMutex m_mutex;
 };
 
@@ -98,6 +99,7 @@ QHelpIndexProvider::~QHelpIndexProvider()
 void QHelpIndexProvider::collectIndices(const QString &customFilterName)
 {
     m_mutex.lock();
+    m_currentFilter = customFilterName;
     m_filterAttributes = m_helpEngine->q->filterAttributes(customFilterName);
     m_mutex.unlock();
 
@@ -122,9 +124,10 @@ QStringList QHelpIndexProvider::indices() const
 void QHelpIndexProvider::run()
 {
     m_mutex.lock();
-    m_indices.clear();
+    const QString currentFilter = m_currentFilter;
     const QStringList attributes = m_filterAttributes;
     const QString collectionFile = m_helpEngine->collectionHandler->collectionFile();
+    m_indices = QStringList();
     m_mutex.unlock();
 
     if (collectionFile.isEmpty())
@@ -134,7 +137,9 @@ void QHelpIndexProvider::run()
     if (!collectionHandler.openCollectionFile())
         return;
 
-    const QStringList result = collectionHandler.indicesForFilter(attributes);
+    const QStringList result = m_helpEngine->usesFilterEngine
+            ? collectionHandler.indicesForFilter(currentFilter)
+            : collectionHandler.indicesForFilter(attributes);
 
     m_mutex.lock();
     m_indices = result;
@@ -181,11 +186,6 @@ QHelpIndexModel::~QHelpIndexModel()
     delete d;
 }
 
-void QHelpIndexModel::invalidateIndex(bool onShutDown)
-{
-    Q_UNUSED(onShutDown)
-}
-
 /*!
     Creates a new index by querying the help system for
     keywords for the specified \a customFilterName.
diff --git a/src/assistant/help/qhelpindexwidget.h b/src/assistant/help/qhelpindexwidget.h
index 46d4937b7..58dda5e39 100644
--- a/src/assistant/help/qhelpindexwidget.h
+++ b/src/assistant/help/qhelpindexwidget.h
@@ -70,7 +70,6 @@ Q_SIGNALS:
 
 private Q_SLOTS:
     void insertIndices();
-    void invalidateIndex(bool onShutDown = false);
 
 private:
     QHelpIndexModel(QHelpEnginePrivate *helpEngine);
diff --git a/src/assistant/help/qhelpsearchengine.cpp b/src/assistant/help/qhelpsearchengine.cpp
index 3ee9904e2..af7247cc3 100644
--- a/src/assistant/help/qhelpsearchengine.cpp
+++ b/src/assistant/help/qhelpsearchengine.cpp
@@ -231,7 +231,8 @@ private:
 
         m_searchInput = searchInput;
         indexReader->cancelSearching();
-        indexReader->search(helpEngine->collectionFile(), indexFilesFolder(), searchInput);
+        indexReader->search(helpEngine->collectionFile(), indexFilesFolder(),
+                            searchInput, helpEngine->usesFilterEngine());
     }
 
     void cancelSearching()
diff --git a/src/assistant/help/qhelpsearchindexreader.cpp b/src/assistant/help/qhelpsearchindexreader.cpp
index 71be91f9f..8aaa5cc47 100644
--- a/src/assistant/help/qhelpsearchindexreader.cpp
+++ b/src/assistant/help/qhelpsearchindexreader.cpp
@@ -56,7 +56,7 @@ void QHelpSearchIndexReader::cancelSearching()
 }
 
 void QHelpSearchIndexReader::search(const QString &collectionFile, const QString &indexFilesFolder,
-    const QString &searchInput)
+    const QString &searchInput, bool usesFilterEngine)
 {
     wait();
 
@@ -65,6 +65,7 @@ void QHelpSearchIndexReader::search(const QString &collectionFile, const QString
     m_searchInput = searchInput;
     m_collectionFile = collectionFile;
     m_indexFilesFolder = indexFilesFolder;
+    m_usesFilterEngine = usesFilterEngine;
 
     start(QThread::NormalPriority);
 }
diff --git a/src/assistant/help/qhelpsearchindexreader_default.cpp b/src/assistant/help/qhelpsearchindexreader_default.cpp
index 25f9a13f2..650d8227f 100644
--- a/src/assistant/help/qhelpsearchindexreader_default.cpp
+++ b/src/assistant/help/qhelpsearchindexreader_default.cpp
@@ -38,6 +38,7 @@
 ****************************************************************************/
 
 #include "qhelpenginecore.h"
+#include "qhelpfilterengine.h"
 #include "qhelpsearchindexreader_default_p.h"
 
 #include <QtCore/QSet>
@@ -52,12 +53,20 @@ namespace qt {
 void Reader::setIndexPath(const QString &path)
 {
     m_indexPath = path;
-    m_namespaces.clear();
+    m_namespaceAttributes.clear();
+    m_filterEngineNamespaceList.clear();
+    m_useFilterEngine = false;
 }
 
-void Reader::addNamespace(const QString &namespaceName, const QStringList &attributes)
+void Reader::addNamespaceAttributes(const QString &namespaceName, const QStringList &attributes)
 {
-    m_namespaces.insert(namespaceName, attributes);
+    m_namespaceAttributes.insert(namespaceName, attributes);
+}
+
+void Reader::setFilterEngineNamespaceList(const QStringList &namespaceList)
+{
+    m_useFilterEngine = true;
+    m_filterEngineNamespaceList = namespaceList;
 }
 
 static QString namespacePlaceholders(const QMultiMap<QString, QStringList> &namespaces)
@@ -106,18 +115,42 @@ static void bindNamespacesAndAttributes(QSqlQuery *query, const QMultiMap<QStrin
     }
 }
 
+static QString namespacePlaceholders(const QStringList &namespaceList)
+{
+    QString placeholders;
+    bool firstNS = true;
+    for (int i = namespaceList.count(); i; --i) {
+        if (firstNS)
+            firstNS = false;
+        else
+            placeholders += QLatin1String(" OR ");
+        placeholders += QLatin1String("namespace = ?");
+    }
+    return placeholders;
+}
+
+static void bindNamespacesAndAttributes(QSqlQuery *query, const QStringList &namespaceList)
+{
+    for (const QString &ns : namespaceList)
+        query->addBindValue(ns);
+}
+
 QVector<QHelpSearchResult> Reader::queryTable(const QSqlDatabase &db,
                                          const QString &tableName,
                                          const QString &searchInput) const
 {
-    const QString &nsPlaceholders = namespacePlaceholders(m_namespaces);
+    const QString nsPlaceholders = m_useFilterEngine
+            ? namespacePlaceholders(m_filterEngineNamespaceList)
+            : namespacePlaceholders(m_namespaceAttributes);
     QSqlQuery query(db);
     query.prepare(QLatin1String("SELECT url, title, snippet(") + tableName +
                   QLatin1String(", -1, '<b>', '</b>', '...', '10') FROM ") + tableName +
                   QLatin1String(" WHERE (") + nsPlaceholders +
                   QLatin1String(") AND ") + tableName +
                   QLatin1String(" MATCH ? ORDER BY rank"));
-    bindNamespacesAndAttributes(&query, m_namespaces);
+    m_useFilterEngine
+            ? bindNamespacesAndAttributes(&query, m_filterEngineNamespaceList)
+            : bindNamespacesAndAttributes(&query, m_namespaceAttributes);
     query.addBindValue(searchInput);
     query.exec();
 
@@ -140,6 +173,7 @@ void Reader::searchInDB(const QString &searchInput)
         QSqlDatabase db = QSqlDatabase::addDatabase(QLatin1String("QSQLITE"), uniqueId);
         db.setConnectOptions(QLatin1String("QSQLITE_OPEN_READONLY"));
         db.setDatabaseName(m_indexPath + QLatin1String("/fts"));
+
         if (db.open()) {
             const QVector<QHelpSearchResult> titleResults = queryTable(db,
                                              QLatin1String("titles"), searchInput);
@@ -197,6 +231,7 @@ void QHelpSearchIndexReaderDefault::run()
     const QString searchInput = m_searchInput;
     const QString collectionFile = m_collectionFile;
     const QString indexPath = m_indexFilesFolder;
+    const bool usesFilterEngine = m_usesFilterEngine;
 
     lock.unlock();
 
@@ -207,26 +242,31 @@ void QHelpSearchIndexReaderDefault::run()
     if (!engine.setupData())
         return;
 
-    const QStringList &registeredDocs = engine.registeredDocumentations();
-
     emit searchingStarted();
 
-    const QStringList &currentFilter = engine.filterAttributes(engine.currentFilter());
-
     // setup the reader
     m_reader.setIndexPath(indexPath);
-    for (const QString &namespaceName : registeredDocs) {
-        const QList<QStringList> &attributeSets =
-            engine.filterAttributeSets(namespaceName);
 
-        for (const QStringList &attributes : attributeSets) {
-            if (attributesMatchFilter(attributes, currentFilter)) {
-                m_reader.addNamespace(namespaceName, attributes);
+    if (usesFilterEngine) {
+        m_reader.setFilterEngineNamespaceList(
+                    engine.filterEngine()->namespacesForFilter(
+                        engine.filterEngine()->activeFilter()));
+    } else {
+        const QStringList &registeredDocs = engine.registeredDocumentations();
+        const QStringList &currentFilter = engine.filterAttributes(engine.currentFilter());
+
+        for (const QString &namespaceName : registeredDocs) {
+            const QList<QStringList> &attributeSets =
+                    engine.filterAttributeSets(namespaceName);
+
+            for (const QStringList &attributes : attributeSets) {
+                if (attributesMatchFilter(attributes, currentFilter)) {
+                    m_reader.addNamespaceAttributes(namespaceName, attributes);
+                }
             }
         }
     }
 
-
     lock.relock();
     if (m_cancel) {
         emit searchingFinished(0);   // TODO: check this, speed issue while locking???
diff --git a/src/assistant/help/qhelpsearchindexreader_default_p.h b/src/assistant/help/qhelpsearchindexreader_default_p.h
index b31b532c6..c183a2357 100644
--- a/src/assistant/help/qhelpsearchindexreader_default_p.h
+++ b/src/assistant/help/qhelpsearchindexreader_default_p.h
@@ -64,7 +64,8 @@ class Reader
 {
 public:
     void setIndexPath(const QString &path);
-    void addNamespace(const QString &namespaceName, const QStringList &attributes);
+    void addNamespaceAttributes(const QString &namespaceName, const QStringList &attributes);
+    void setFilterEngineNamespaceList(const QStringList &namespaceList);
 
     void searchInDB(const QString &term);
     QVector<QHelpSearchResult> searchResults() const;
@@ -74,9 +75,11 @@ private:
                                           const QString &tableName,
                                           const QString &searchInput) const;
 
-    QString m_indexPath;
-    QMultiMap<QString, QStringList> m_namespaces;
+    QMultiMap<QString, QStringList> m_namespaceAttributes;
+    QStringList m_filterEngineNamespaceList;
     QVector<QHelpSearchResult> m_searchResults;
+    QString m_indexPath;
+    bool m_useFilterEngine = false;
 };
 
 
diff --git a/src/assistant/help/qhelpsearchindexreader_p.h b/src/assistant/help/qhelpsearchindexreader_p.h
index f6f3ee305..57295693b 100644
--- a/src/assistant/help/qhelpsearchindexreader_p.h
+++ b/src/assistant/help/qhelpsearchindexreader_p.h
@@ -74,7 +74,8 @@ public:
     void cancelSearching();
     void search(const QString &collectionFile,
                 const QString &indexFilesFolder,
-                const QString &searchInput);
+                const QString &searchInput,
+                bool usesFilterEngine = false);
     int searchResultCount() const;
     QVector<QHelpSearchResult> searchResults(int start, int end) const;
 
@@ -89,6 +90,7 @@ protected:
     QString m_collectionFile;
     QString m_searchInput;
     QString m_indexFilesFolder;
+    bool m_usesFilterEngine = false;
 
 private:
     void run() override = 0;