Fix crash with StackView::initialItem

The following binding

    initialView: Qt.createComponent("blah.qml")

works with QQC1 but crashes with QQC2 as soon as the garbage collector
kicks in. In QQC1 StackView was implemented in a .qml file and the
property was declared as

    property var initialItem

For such declared properties the QML engine takes care of ensuring that
the reference assigned is a strong reference towards the GC and it also
tracks the life-time of the QObject in case it's explicitly deleted by
somebody else.

In QQC2 the property continues to be documented as "var" property,
however it is implemented in C++ as QVariant property. The QVariant is
not known to the GC at all and it also doesn't do life-cycle tracking.

The C++ equivalent to "var" in QML is QJSValue, which is a strong
reference and also ends up using a QPointer internally when holding a
QObject.

Task-number: QTBUG-67118
Change-Id: I43e473c7bf2c40f9843e9d50fe4fd805b54fd256
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/quicktemplates2/qquickstackview_p.h b/src/quicktemplates2/qquickstackview_p.h
index e347ba9d..ba6fe106 100644
--- a/src/quicktemplates2/qquickstackview_p.h
+++ b/src/quicktemplates2/qquickstackview_p.h
@@ -65,7 +65,7 @@ class Q_QUICKTEMPLATES2_PRIVATE_EXPORT QQuickStackView : public QQuickControl
     Q_PROPERTY(bool busy READ isBusy NOTIFY busyChanged FINAL)
     Q_PROPERTY(int depth READ depth NOTIFY depthChanged FINAL)
     Q_PROPERTY(QQuickItem *currentItem READ currentItem NOTIFY currentItemChanged FINAL)
-    Q_PROPERTY(QVariant initialItem READ initialItem WRITE setInitialItem FINAL)
+    Q_PROPERTY(QJSValue initialItem READ initialItem WRITE setInitialItem FINAL)
     Q_PROPERTY(QQuickTransition *popEnter READ popEnter WRITE setPopEnter NOTIFY popEnterChanged FINAL)
     Q_PROPERTY(QQuickTransition *popExit READ popExit WRITE setPopExit NOTIFY popExitChanged FINAL)
     Q_PROPERTY(QQuickTransition *pushEnter READ pushEnter WRITE setPushEnter NOTIFY pushEnterChanged FINAL)
@@ -93,8 +93,8 @@ public:
     };
     Q_ENUM(Status)
 
-    QVariant initialItem() const;
-    void setInitialItem(const QVariant &item);
+    QJSValue initialItem() const;
+    void setInitialItem(const QJSValue &item);
 
     QQuickTransition *popEnter() const;
     void setPopEnter(QQuickTransition *enter);