Fix performance of ListModel::get()

When called, the function would return a full-fledged QObject that maps the
list element addressed. It would contain a _copy_ of all values in the list
item and it would create a new meta-object for each list element.

This function exists for the JavaScript API, and therefore we now return a much
more lightweight object. For compatbility reasons it still has to be a QObject,
but the meta-object of it is created on-demand, i.e. only when accessing
properties from the C++ side or when connecting to the changed signal of a
property. Otherwise the JavaScript wrapper will return the live values from the
model without copying them.

Change-Id: Iabf3ca22192d2aee06ae9d4b4cfb2fcde2a021b1
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
Reviewed-by: Michael Brasser <michael.brasser@live.com>
Reviewed-by: Spencer Schumann <spencer.schumann@echostar.com>

1 files changed, 2 insertions, 4 deletions

diff --git a/src/qml/memory/qv4mm.cpp b/src/qml/memory/qv4mm.cpp
index 38b4e1eaf1..b880c9c8d5 100644
--- a/src/qml/memory/qv4mm.cpp
+++ b/src/qml/memory/qv4mm.cpp
@@ -373,7 +373,7 @@ void MemoryManager::mark()
     for (PersistentValueStorage::Iterator it = m_weakValues->begin(); it != m_weakValues->end(); ++it) {
         if (!(*it).isManaged())
             continue;
-        if ((*it).managed()->d()->vtable() != QObjectWrapper::staticVTable())
+        if (!(*it).as<QObjectWrapper>())
             continue;
         QObjectWrapper *qobjectWrapper = static_cast<QObjectWrapper*>((*it).managed());
         QObject *qobject = qobjectWrapper->object();
@@ -410,10 +410,8 @@ void MemoryManager::sweep(bool lastSweep)
             continue;
         // we need to call detroyObject on qobjectwrappers now, so that they can emit the destroyed
         // signal before we start sweeping the heap
-        if ((*it).managed()->d()->vtable() == QObjectWrapper::staticVTable()) {
-            QObjectWrapper *qobjectWrapper = static_cast<QObjectWrapper*>((*it).managed());
+        if (QObjectWrapper *qobjectWrapper = (*it).as<QObjectWrapper>())
             qobjectWrapper->destroyObject(lastSweep);
-        }
 
         (*it) = Primitive::undefinedValue();
     }