TOC: Add collapse/expand options

Large specifications with many (nested) sections are painful to navigate
through when the TOC is expanded by default. Introduce four new options,
"Expand/Collapse whole section" is based on Kate's document view while
"Expand/Collapse all" was added to handle the top-level sections.

As for other viewers, PDF.js uses shift-click to handle the former while
using double-click on a the TOC icon to handle the latter. That is not
very obvious, so extending the context menu seems the next best option.

BUG: 216870

Differential Revision: https://phabricator.kde.org/D14904

part.cpp

@@ -2948,7 +2948,7 @@ void Part::slotPrintPreview()
 
 void Part::slotShowTOCMenu(const Okular::DocumentViewport &vp, const QPoint &point, const QString &title)
 {
-    showMenu(m_document->page(vp.pageNumber), point, title, vp);
+    showMenu(m_document->page(vp.pageNumber), point, title, vp, true);
 }
 
 void Part::slotShowMenu(const Okular::Page *page, const QPoint &point)
@@ -2956,7 +2956,7 @@ void Part::slotShowMenu(const Okular::Page *page, const QPoint &point)
     showMenu(page, point);
 }
 
-void Part::showMenu(const Okular::Page *page, const QPoint &point, const QString &bookmarkTitle, const Okular::DocumentViewport &vp)
+void Part::showMenu(const Okular::Page *page, const QPoint &point, const QString &bookmarkTitle, const Okular::DocumentViewport &vp, bool showTOCActions)
 {
     if ( m_embedMode == PrintPreviewMode )
        return;
@@ -2990,6 +2990,19 @@ void Part::showMenu(const Okular::Page *page, const QPoint &point, const QString
     }
 
     QMenu *popup = new QMenu( widget() );
+    if (showTOCActions)
+    {
+        popup->addAction( i18n("Expand whole section"),
+                          m_toc.data(), &TOC::expandRecursively );
+        popup->addAction( i18n("Collapse whole section"),
+                          m_toc.data(), &TOC::collapseRecursively );
+        popup->addAction( i18n("Expand all"),
+                          m_toc.data(), &TOC::expandAll );
+        popup->addAction( i18n("Collapse all"),
+                          m_toc.data(), &TOC::collapseAll );
+        reallyShow = true;
+    }
+
     QAction *addBookmark = nullptr;
     QAction *removeBookmark = nullptr;
     QAction *fitPageWidth = nullptr;

part.h

@@ -254,7 +254,7 @@ class OKULARPART_EXPORT Part : public KParts::ReadWritePart, public Okular::Docu
 
     private:
         bool aboutToShowContextMenu(QMenu *menu, QAction *action, QMenu *contextMenu);
-        void showMenu(const Okular::Page *page, const QPoint &point, const QString &bookmarkTitle = QString(), const Okular::DocumentViewport &vp = DocumentViewport());
+        void showMenu(const Okular::Page *page, const QPoint &point, const QString &bookmarkTitle = QString(), const Okular::DocumentViewport &vp = DocumentViewport(), bool showTOCActions = false);
         bool eventFilter(QObject * watched, QEvent * event) override;
         Document::OpenResult doOpenFile(const QMimeType &mime, const QString &fileNameToOpen, bool *isCompressedFile);
         bool openUrl( const QUrl &url, bool swapInsteadOfOpening );

ui/toc.cpp

@@ -187,4 +187,50 @@ void TOC::contextMenuEvent(QContextMenuEvent* e)
     emit rightClick(viewport, e->globalPos(), m_model->data(index).toString());
 }
 
+void TOC::expandRecursively()
+{
+    QList<QModelIndex> worklist = { m_treeView->currentIndex() };
+    if ( !worklist[0].isValid() )
+    {
+        return;
+    }
+    while ( !worklist.isEmpty() )
+    {
+        QModelIndex index = worklist.takeLast();
+        m_treeView->expand( index );
+        for ( int i = 0; i < m_model->rowCount(index); i++ )
+        {
+            worklist += m_model->index( i, 0, index );
+        }
+    }
+}
+
+void TOC::collapseRecursively()
+{
+    QList<QModelIndex> worklist = { m_treeView->currentIndex() };
+    if ( !worklist[0].isValid() )
+    {
+        return;
+    }
+    while ( !worklist.isEmpty() )
+    {
+        QModelIndex index = worklist.takeLast();
+        m_treeView->collapse( index );
+        for ( int i = 0; i < m_model->rowCount(index); i++ )
+        {
+            worklist += m_model->index( i, 0, index );
+        }
+    }
+}
+
+void TOC::expandAll()
+{
+    m_treeView->expandAll();
+}
+
+void TOC::collapseAll()
+{
+    m_treeView->collapseAll();
+}
+
 #include "moc_toc.cpp"

ui/toc.h

@@ -47,6 +47,12 @@ Q_OBJECT
         void rollbackReload();
         void finishReload();
 
+    public Q_SLOTS:
+        void expandRecursively();
+        void collapseRecursively();
+        void expandAll();
+        void collapseAll();
+
     Q_SIGNALS:
         void hasTOC(bool has);
         void rightClick( const Okular::DocumentViewport &, const QPoint &, const QString & );