Fix performance regression of parent setting during QML object creation

This showed up in the profiles again: In QML we create a lot of objects
with many children and sending a child event each time is expensive. That's
why the VME didn't do that and hadn't done so in ages. This patch restores
that behavior and aspect of loading performance.

Change-Id: I5078fe330d913dc832b284aaecf031152dc80802
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

3 files changed, 36 insertions, 1 deletions

diff --git a/tests/auto/qml/qqmllanguage/testtypes.cpp b/tests/auto/qml/qqmllanguage/testtypes.cpp
index 8dd788869b..226206edfd 100644
--- a/tests/auto/qml/qqmllanguage/testtypes.cpp
+++ b/tests/auto/qml/qqmllanguage/testtypes.cpp
@@ -205,3 +205,20 @@ void SimpleObjectCustomParser::setCustomData(QObject *object, const QByteArray &
    o->setCustomBindingsCount(data.toInt(&ok));
    Q_ASSERT(ok);
 }
+
+
+MyQmlObject::MyQmlObject()
+    : m_value(-1)
+    , m_interface(0)
+    , m_qmlobject(0)
+    , m_childAddedEventCount(0)
+{
+    qRegisterMetaType<MyCustomVariantType>("MyCustomVariantType");
+}
+
+bool MyQmlObject::event(QEvent *event)
+{
+    if (event->type() == QEvent::ChildAdded)
+        m_childAddedEventCount++;
+    return QObject::event(event);
+}
diff --git a/tests/auto/qml/qqmllanguage/testtypes.h b/tests/auto/qml/qqmllanguage/testtypes.h
index 1a4cca2e8d..1f34309a5e 100644
--- a/tests/auto/qml/qqmllanguage/testtypes.h
+++ b/tests/auto/qml/qqmllanguage/testtypes.h
@@ -119,7 +119,7 @@ class MyQmlObject : public QObject, public MyInterface
 
     Q_INTERFACES(MyInterface)
 public:
-    MyQmlObject() : m_value(-1), m_interface(0), m_qmlobject(0) { qRegisterMetaType<MyCustomVariantType>("MyCustomVariantType"); }
+    MyQmlObject();
 
     int value() const { return m_value; }
     void setValue(int v) { m_value = v; }
@@ -161,6 +161,8 @@ public:
     QJSValue qjsvalue() const { return m_qjsvalue; }
     void setQJSValue(const QJSValue &value) { m_qjsvalue = value; emit qjsvalueChanged(); }
 
+    int childAddedEventCount() const { return m_childAddedEventCount; }
+
 public slots:
     void basicSlot() { qWarning("MyQmlObject::basicSlot"); }
     void basicSlotWithArgs(int v) { qWarning("MyQmlObject::basicSlotWithArgs(%d)", v); }
@@ -173,6 +175,9 @@ signals:
     void signalWithDefaultArg(int parameter = 5);
     void qjsvalueChanged();
 
+protected:
+    virtual bool event(QEvent *event);
+
 private:
     friend class tst_qqmllanguage;
     int m_value;
@@ -181,6 +186,7 @@ private:
     MyCustomVariantType m_custom;
     int m_propertyWithNotify;
     QJSValue m_qjsvalue;
+    int m_childAddedEventCount;
 };
 QML_DECLARE_TYPE(MyQmlObject)
 QML_DECLARE_TYPEINFO(MyQmlObject, QML_HAS_ATTACHED_PROPERTIES)
diff --git a/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp b/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
index 619c7719f6..ede499b336 100644
--- a/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
+++ b/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
@@ -236,6 +236,8 @@ private slots:
 
     void rootObjectInCreationNotForSubObjects();
 
+    void noChildEvents();
+
 private:
     QQmlEngine engine;
     QStringList defaultImportPathList;
@@ -3677,6 +3679,16 @@ void tst_qqmllanguage::rootObjectInCreationNotForSubObjects()
     QVERIFY(!ddata->rootObjectInCreation);
 }
 
+void tst_qqmllanguage::noChildEvents()
+{
+    QQmlComponent component(&engine);
+    component.setData("import QtQml 2.0; import Test 1.0; MyQmlObject { property QtObject child: QtObject {} }", QUrl());
+    VERIFY_ERRORS(0);
+    MyQmlObject *object = qobject_cast<MyQmlObject*>(component.create());
+    QVERIFY(object != 0);
+    QCOMPARE(object->childAddedEventCount(), 0);
+}
+
 QTEST_MAIN(tst_qqmllanguage)
 
 #include "tst_qqmllanguage.moc"