ScrollIndicator: fix memory leak when attached to a non-Flickable

We must pass the attachee QObject as a parent instead of passing
a qobject_casted QQuickFlickable, which may be a null pointer.

Change-Id: I2e229ff59363246fc4515b1c7cbf1850dd2b1d43
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

2 files changed, 11 insertions, 14 deletions

diff --git a/src/quicktemplates2/qquickscrollindicator.cpp b/src/quicktemplates2/qquickscrollindicator.cpp
index 8080d325..05ec2063 100644
--- a/src/quicktemplates2/qquickscrollindicator.cpp
+++ b/src/quicktemplates2/qquickscrollindicator.cpp
@@ -174,11 +174,7 @@ QQuickScrollIndicator::QQuickScrollIndicator(QQuickItem *parent)
 
 QQuickScrollIndicatorAttached *QQuickScrollIndicator::qmlAttachedProperties(QObject *object)
 {
-    QQuickFlickable *flickable = qobject_cast<QQuickFlickable *>(object);
-    if (!flickable)
-        qmlWarning(object) << "ScrollIndicator must be attached to a Flickable";
-
-    return new QQuickScrollIndicatorAttached(flickable);
+    return new QQuickScrollIndicatorAttached(object);
 }
 
 /*!
@@ -298,8 +294,8 @@ void QQuickScrollIndicator::setOrientation(Qt::Orientation orientation)
 class QQuickScrollIndicatorAttachedPrivate : public QObjectPrivate, public QQuickItemChangeListener
 {
 public:
-    QQuickScrollIndicatorAttachedPrivate(QQuickFlickable *flickable)
-        : flickable(flickable),
+    QQuickScrollIndicatorAttachedPrivate()
+        : flickable(nullptr),
           horizontal(nullptr),
           vertical(nullptr)
     {
@@ -379,14 +375,15 @@ void QQuickScrollIndicatorAttachedPrivate::itemDestroyed(QQuickItem *item)
         vertical = nullptr;
 }
 
-QQuickScrollIndicatorAttached::QQuickScrollIndicatorAttached(QQuickFlickable *flickable)
-    : QObject(*(new QQuickScrollIndicatorAttachedPrivate(flickable)), flickable)
+QQuickScrollIndicatorAttached::QQuickScrollIndicatorAttached(QObject *parent)
+    : QObject(*(new QQuickScrollIndicatorAttachedPrivate), parent)
 {
     Q_D(QQuickScrollIndicatorAttached);
-    if (flickable) {
-        QQuickItemPrivate *p = QQuickItemPrivate::get(flickable);
-        p->updateOrAddGeometryChangeListener(d, QQuickGeometryChange::Size);
-    }
+    d->flickable = qobject_cast<QQuickFlickable *>(parent);
+    if (d->flickable)
+        QQuickItemPrivate::get(d->flickable)->updateOrAddGeometryChangeListener(d, QQuickGeometryChange::Size);
+    else if (parent)
+        qmlWarning(parent) << "ScrollIndicator must be attached to a Flickable";
 }
 
 QQuickScrollIndicatorAttached::~QQuickScrollIndicatorAttached()
diff --git a/src/quicktemplates2/qquickscrollindicator_p.h b/src/quicktemplates2/qquickscrollindicator_p.h
index 13be7394..c4408500 100644
--- a/src/quicktemplates2/qquickscrollindicator_p.h
+++ b/src/quicktemplates2/qquickscrollindicator_p.h
@@ -107,7 +107,7 @@ class Q_QUICKTEMPLATES2_PRIVATE_EXPORT QQuickScrollIndicatorAttached : public QO
     Q_PROPERTY(QQuickScrollIndicator *vertical READ vertical WRITE setVertical NOTIFY verticalChanged FINAL)
 
 public:
-    explicit QQuickScrollIndicatorAttached(QQuickFlickable *flickable);
+    explicit QQuickScrollIndicatorAttached(QObject *parent = nullptr);
     ~QQuickScrollIndicatorAttached();
 
     QQuickScrollIndicator *horizontal() const;