Add a tree view with improved keyboard navigation

This simple derivative of QTreeWidget allows column by column navigation
with the keyboard which is crucial for accessibility.

GnuPG-bug-id: 6103

src/CMakeLists.txt

@@ -133,6 +133,8 @@ target_sources(KF5Libkleo PRIVATE
    ui/filenamerequester.h
    ui/messagebox.cpp
    ui/messagebox.h
+   ui/navigatabletreewidget.cpp
+   ui/navigatabletreewidget.h
    ui/progressbar.cpp
    ui/progressbar.h
    ui/progressdialog.cpp

src/ui/navigatabletreewidget.cpp

+/*
+    ui/navigatabletreewidget.h
+
+    This file is part of libkleopatra
+    SPDX-FileCopyrightText: 2022 g10 Code GmbH
+    SPDX-FileContributor: Ingo Klöcker <dev@ingo-kloecker.de>
+
+    SPDX-License-Identifier: GPL-2.0-or-later
+*/
+
+#include <config-libkleo.h>
+
+#include "navigatabletreewidget.h"
+
+using namespace Kleo;
+
+QModelIndex NavigatableTreeWidget::moveCursor(QAbstractItemView::CursorAction cursorAction, Qt::KeyboardModifiers modifiers)
+{
+    // make keyboard navigation with Left/Right possible by switching the selection behavior to SelectItems
+    // before calling QTreeWidget::moveCursor, because QTreeWidget::moveCursor ignores MoveLeft/MoveRight
+    // if the selection behavior is SelectRows
+    if ((cursorAction == MoveLeft) || (cursorAction == MoveRight)) {
+        setSelectionBehavior(SelectItems);
+    }
+    const auto result = QTreeWidget::moveCursor(cursorAction, modifiers);
+    if ((cursorAction == MoveLeft) || (cursorAction == MoveRight)) {
+        setSelectionBehavior(SelectRows);
+    }
+    return result;
+}
+

src/ui/navigatabletreewidget.h

+/*
+    ui/navigatabletreewidget.h
+
+    This file is part of libkleopatra
+    SPDX-FileCopyrightText: 2022 g10 Code GmbH
+    SPDX-FileContributor: Ingo Klöcker <dev@ingo-kloecker.de>
+
+    SPDX-License-Identifier: GPL-2.0-or-later
+*/
+
+#pragma once
+
+#include "kleo_export.h"
+
+#include <QTreeWidget>
+
+namespace Kleo
+{
+
+/**
+ * A tree view that allows extended keyboard navigation.
+ *
+ * The NavigatableTreeWidget allows column by column keyboard navigation even if
+ * the selection behavior is set to SelectRows. Column by column navigation is
+ * required to make a tree view accessible.
+ */
+class KLEO_EXPORT NavigatableTreeWidget : public QTreeWidget
+{
+    Q_OBJECT
+public:
+    using QTreeWidget::QTreeWidget;
+
+protected:
+    QModelIndex moveCursor(QAbstractItemView::CursorAction cursorAction, Qt::KeyboardModifiers modifiers) override;
+};
+
+}