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, 30 insertions, 0 deletions

diff --git a/src/qml/qml/qqmlopenmetaobject.cpp b/src/qml/qml/qqmlopenmetaobject.cpp
index c6d2d44ee1..777bb0c5e1 100644
--- a/src/qml/qml/qqmlopenmetaobject.cpp
+++ b/src/qml/qml/qqmlopenmetaobject.cpp
@@ -106,6 +106,28 @@ QMetaObject *QQmlOpenMetaObjectType::metaObject() const
     return d->mem;
 }
 
+void QQmlOpenMetaObjectType::createProperties(const QVector<QByteArray> &names)
+{
+    for (int i = 0; i < names.count(); ++i) {
+        const QByteArray &name = names.at(i);
+        const int id = d->mob.propertyCount();
+        d->mob.addSignal("__" + QByteArray::number(id) + "()");
+        QMetaPropertyBuilder build = d->mob.addProperty(name, "QVariant", id);
+        propertyCreated(id, build);
+        d->names.insert(name, id);
+    }
+    free(d->mem);
+    d->mem = d->mob.toMetaObject();
+    QSet<QQmlOpenMetaObject*>::iterator it = d->referers.begin();
+    while (it != d->referers.end()) {
+        QQmlOpenMetaObject *omo = *it;
+        *static_cast<QMetaObject *>(omo) = *d->mem;
+        if (d->cache)
+            d->cache->update(omo);
+        ++it;
+    }
+}
+
 int QQmlOpenMetaObjectType::createProperty(const QByteArray &name)
 {
     int id = d->mob.propertyCount();
@@ -230,6 +252,14 @@ QQmlOpenMetaObjectType *QQmlOpenMetaObject::type() const
     return d->type;
 }
 
+void QQmlOpenMetaObject::emitPropertyNotification(const QByteArray &propertyName)
+{
+    QHash<QByteArray, int>::ConstIterator iter = d->type->d->names.constFind(propertyName);
+    if (iter == d->type->d->names.constEnd())
+        return;
+    activate(d->object, *iter + d->type->d->signalOffset, 0);
+}
+
 int QQmlOpenMetaObject::metaCall(QMetaObject::Call c, int id, void **a)
 {
     if (( c == QMetaObject::ReadProperty || c == QMetaObject::WriteProperty)