Avoid calling gc in QQmlEngine destructor.

GC may be expensive. GC call in QQmlEngine doesn't have much sense
because V8 will destroy all objects living in a current context.
The only problem is that V8 may decide to not invoke weak callbacks
which may cause a memory leak. To avoid that we track all QObjects that
have JavaScript ownership set and we delete them explicitly.

The change reduce time of destroying QQmlEngine by 75%, which is really
visible in qquicklistmodel test.

Change-Id: I2a3668fd23630669114baee8c241a7ecc4100e33
Reviewed-by: Chris Adams <christopher.adams@nokia.com>

1 files changed, 39 insertions, 1 deletions

diff --git a/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp b/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp
index c039429f48..ab18cdd050 100644
--- a/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp
+++ b/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp
@@ -46,6 +46,7 @@
 #include <QPointer>
 #include <QDir>
 #include <QStandardPaths>
+#include <QSignalSpy>
 #include <QDebug>
 #include <QQmlComponent>
 #include <QQmlNetworkAccessManagerFactory>
@@ -67,6 +68,13 @@ private slots:
     void outputWarningsToStandardError();
     void objectOwnership();
     void multipleEngines();
+
+public slots:
+    QObject *createAQObjectForOwnershipTest ()
+    {
+        static QObject *ptr = new QObject();
+        return ptr;
+    }
 };
 
 void tst_qqmlengine::rootContext()
@@ -326,7 +334,37 @@ void tst_qqmlengine::objectOwnership()
 
     delete o;
     }
-
+    {
+        QObject *ptr = createAQObjectForOwnershipTest();
+        QSignalSpy spy(ptr, SIGNAL(destroyed()));
+        {
+            QQmlEngine engine;
+            QQmlComponent c(&engine);
+            engine.rootContext()->setContextProperty("test", this);
+            QQmlEngine::setObjectOwnership(ptr, QQmlEngine::JavaScriptOwnership);
+            c.setData("import QtQuick 2.0; Item { property int data: test.createAQObjectForOwnershipTest() ? 0 : 1 }", QUrl());
+            QVERIFY(c.isReady());
+            QObject *o = c.create();
+            QVERIFY(o != 0);
+        }
+        QTRY_VERIFY(spy.count());
+    }
+    {
+        QObject *ptr = new QObject();
+        QSignalSpy spy(ptr, SIGNAL(destroyed()));
+        {
+            QQmlEngine engine;
+            QQmlComponent c(&engine);
+            engine.rootContext()->setContextProperty("test", ptr);
+            QQmlEngine::setObjectOwnership(ptr, QQmlEngine::JavaScriptOwnership);
+            c.setData("import QtQuick 2.0; QtObject { property var object: { var i = test; test ? 0 : 1 }  }", QUrl());
+            QVERIFY(c.isReady());
+            QObject *o = c.create();
+            QVERIFY(o != 0);
+            engine.rootContext()->setContextProperty("test", 0);
+        }
+        QTRY_VERIFY(spy.count());
+    }
 }
 
 // Test an object can be accessed by multiple engines