Provide API to access singletons associated with a QQmlEngine

This patch adds allows C++ code to retrieve the instance of a registered
singleton type. Until now this required a deturn via QML expression.

Two methods are added to QQmlEngine: A generic one that encapsulates all
singleton objects in a QJSValue and a template function for QObject-derived
singleton types.

An additional convenience function is added to query the QML type id.  This
function may also be used for other purposes in the future.

[ChangeLog][QtQml][QQmlEngine] Added API to access singletons associated with
a QQmlEngine.

Task-number: QTBUG-39970
Change-Id: I67c132ede35f80b9aaf1c5e5456715cf4f1b0848
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 6 insertions, 1 deletions

diff --git a/src/qml/qml/qqmlmetatype_p.h b/src/qml/qml/qqmlmetatype_p.h
index 51bf485a3e..6df439cd7a 100644
--- a/src/qml/qml/qqmlmetatype_p.h
+++ b/src/qml/qml/qqmlmetatype_p.h
@@ -91,11 +91,16 @@ public:
     static QList<QQmlType> qmlSingletonTypes();
     static QList<QQmlType> qmlAllTypes();
 
+    enum class TypeIdCategory {
+        MetaType,
+        QmlType
+    };
+
     static QQmlType qmlType(const QString &qualifiedName, int, int);
     static QQmlType qmlType(const QHashedStringRef &name, const QHashedStringRef &module, int, int);
     static QQmlType qmlType(const QMetaObject *);
     static QQmlType qmlType(const QMetaObject *metaObject, const QHashedStringRef &module, int version_major, int version_minor);
-    static QQmlType qmlType(int);
+    static QQmlType qmlType(int typeId, TypeIdCategory category = TypeIdCategory::MetaType);
     static QQmlType qmlType(const QUrl &unNormalizedUrl, bool includeNonFileImports = false);
 
     static QQmlPropertyCache *propertyCache(const QMetaObject *metaObject);