QQmlApplicationEngine: mark rootObjects() as const

This method does not modify the object.
Can't change the API, so overload and mark the old function
for removal in Qt 6.

Change-Id: I15943c770b30460f8ccd14239526e2249c59a242
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

2 files changed, 20 insertions, 3 deletions

diff --git a/src/qml/qml/qqmlapplicationengine.cpp b/src/qml/qml/qqmlapplicationengine.cpp
index fef2da753b..1a912d53e6 100644
--- a/src/qml/qml/qqmlapplicationengine.cpp
+++ b/src/qml/qml/qqmlapplicationengine.cpp
@@ -287,14 +287,27 @@ void QQmlApplicationEngine::loadData(const QByteArray &data, const QUrl &url)
   Returns a list of all the root objects instantiated by the
   QQmlApplicationEngine. This will only contain objects loaded via load() or a
   convenience constructor.
+
+  \note In Qt versions prior to 5.9, this function is marked as non-\c{const}.
 */
 
-QList<QObject *> QQmlApplicationEngine::rootObjects()
+QList<QObject *> QQmlApplicationEngine::rootObjects() const
 {
-    Q_D(QQmlApplicationEngine);
+    Q_D(const QQmlApplicationEngine);
     return d->objects;
 }
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+/*!
+    \overload
+    \internal
+*/
+QList<QObject *> QQmlApplicationEngine::rootObjects()
+{
+    return qAsConst(*this).rootObjects();
+}
+#endif // < Qt 6
+
 QT_END_NAMESPACE
 
 #include "moc_qqmlapplicationengine.cpp"
diff --git a/src/qml/qml/qqmlapplicationengine.h b/src/qml/qml/qqmlapplicationengine.h
index ff7dce5f8b..e64d7495cd 100644
--- a/src/qml/qml/qqmlapplicationengine.h
+++ b/src/qml/qml/qqmlapplicationengine.h
@@ -58,7 +58,11 @@ public:
     QQmlApplicationEngine(const QString &filePath, QObject *parent = Q_NULLPTR);
     ~QQmlApplicationEngine();
 
-    QList<QObject*> rootObjects();
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+    QList<QObject*> rootObjects(); // ### Qt 6: remove
+#endif
+    QList<QObject*> rootObjects() const;
+
 public Q_SLOTS:
     void load(const QUrl &url);
     void load(const QString &filePath);