1 files changed, 58 insertions, 0 deletions
diff --git a/examples/quickcontrols/filesystemexplorer/linenumbermodel.cpp b/examples/quickcontrols/filesystemexplorer/linenumbermodel.cpp
new file mode 100644
index 0000000000..5a7982dca9
--- /dev/null
+++ b/examples/quickcontrols/filesystemexplorer/linenumbermodel.cpp
@@ -0,0 +1,58 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "linenumbermodel.h"
+
+#include <QQmlInfo>
+
+/*!
+    When using an integer model based on the line count of the editor,
+    any changes in that line count cause all delegates to be destroyed
+    and recreated. That's inefficient, so instead, we add/remove model
+    items as necessary ourselves, based on the lineCount property.
+*/
+LineNumberModel::LineNumberModel(QObject *parent)
+    : QAbstractListModel(parent)
+{
+}
+
+int LineNumberModel::lineCount() const
+{
+    return m_lineCount;
+}
+
+void LineNumberModel::setLineCount(int lineCount)
+{
+    if (lineCount < 0) {
+        qmlWarning(this) << "lineCount must be greater than zero";
+        return;
+    }
+
+    if (m_lineCount == lineCount)
+        return;
+
+    if (m_lineCount < lineCount) {
+        beginInsertRows(QModelIndex(), m_lineCount, lineCount - 1);
+        m_lineCount = lineCount;
+        endInsertRows();
+    } else if (m_lineCount > lineCount) {
+        beginRemoveRows(QModelIndex(), lineCount, m_lineCount - 1);
+        m_lineCount = lineCount;
+        endRemoveRows();
+    }
+
+    emit lineCountChanged();
+}
+
+int LineNumberModel::rowCount(const QModelIndex &) const
+{
+    return m_lineCount;
+}
+
+QVariant LineNumberModel::data(const QModelIndex &index, int role) const
+{
+    if (!checkIndex(index) || role != Qt::DisplayRole)
+        return QVariant();
+
+    return index.row();
+}