Properly lock bins when iterating their children

1 files changed, 56 insertions, 26 deletions

diff --git a/src/QuickStreamer/item.cpp b/src/QuickStreamer/item.cpp
index e757dda..53aef4b 100644
--- a/src/QuickStreamer/item.cpp
+++ b/src/QuickStreamer/item.cpp
@@ -12,7 +12,24 @@
 namespace QQuickStreamer {
 namespace Private {
 
-typedef QQmlListProperty<Item> ElementList;
+class ObjectLocker
+{
+public:
+    explicit ObjectLocker(GstObject *object)
+        : m_object(object)
+    {
+        Q_ASSERT(m_object);
+        GST_OBJECT_LOCK(m_object);
+    }
+
+    ~ObjectLocker()
+    {
+        GST_OBJECT_UNLOCK(m_object);
+    }
+
+private:
+    GstObject *const m_object;
+};
 
 struct PropertyInfo
 {
@@ -281,40 +298,53 @@ static void writeNothing(Item *item, const QByteArray &name, const void *)
              G_OBJECT_TYPE_NAME(item->target()), name.constData());
 }
 
-static void appendChild(ElementList *list, Item *child)
+class ElementList : public QQmlListProperty<Item>
 {
-    auto *const parent = static_cast<Item *>(list->object);
+public:
+    explicit ElementList(Item *item = Q_NULLPTR)
+        : QQmlListProperty<Item>(item, Q_NULLPTR,
+                                 &ElementList::appendChild,
+                                 &ElementList::countChildren,
+                                 &ElementList::childAt,
+                                 &ElementList::clearChildren)
+    {
+    }
 
-    gst_bin_add(GST_BIN(parent->target()),
-                GST_ELEMENT(child->target()));
-}
+    static void appendChild(QQmlListProperty<Item> *list, Item *child)
+    {
+        auto *const parent = static_cast<Item *>(list->object);
+        gst_bin_add(GST_BIN(parent->target()), GST_ELEMENT(child->target()));
+    }
 
-static int countChildren(ElementList *list)
-{
-    auto *const parentItem = static_cast<Item *>(list->object);
-    return GST_BIN_NUMCHILDREN(parentItem->target());
-}
+    static int countChildren(QQmlListProperty<Item> *list)
+    {
+        auto *const parent = static_cast<Item *>(list->object);
+        ObjectLocker locker(parent->target());
 
-static Item *childAt(ElementList *list, int offset)
-{
-    // FIXME: need to store the wrapper object somewhere
-    qDebug() << Q_FUNC_INFO;
-    return Q_NULLPTR;
-}
+        return GST_BIN_NUMCHILDREN(parent->target());
+    }
 
-static void clearChildren(ElementList *list)
-{
-    auto *const parentItem = static_cast<Item *>(list->object);
-    auto *const elementBin = GST_BIN(parentItem->target());
+    static Item *childAt(QQmlListProperty<Item> *list, int offset)
+    {
+        // FIXME: need to store the wrapper object somewhere
+        qDebug() << Q_FUNC_INFO;
+        return Q_NULLPTR;
+    }
 
-    while (elementBin->children)
-        gst_bin_remove(elementBin, GST_ELEMENT(elementBin->children->data));
-}
+    static void clearChildren(QQmlListProperty<Item> *list)
+    {
+        auto *const parent = static_cast<Item *>(list->object);
+        auto *const elementBin = GST_BIN(parent->target());
+        ObjectLocker locker(parent->target());
+
+        while (elementBin->children)
+            gst_bin_remove(elementBin, GST_ELEMENT(elementBin->children->data));
+    }
+};
 
 static void readChildren(Item *item, void *value)
 {
-    *static_cast<ElementList *>(value) =
-            ElementList(item, Q_NULLPTR, &appendChild, &countChildren, &childAt, &clearChildren);
+    *static_cast<ElementList *>(value) = ElementList(item);
 }
 
 static void readState(Item *item, void *value)