Add delayed property to Binding.

Provide a way to avoid potentially expensive or unexpected intermediate
values.

[ChangeLog][Binding] Add delayed property to Binding as a way to avoid potentially expensive or unexpected intermediate values.

Change-Id: I6aaca570859cc1344eeb9c9f19f32660e8c0b4e0
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>

1 files changed, 22 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmlbinding/tst_qqmlbinding.cpp b/tests/auto/qml/qqmlbinding/tst_qqmlbinding.cpp
index 3e8dfbdb12..6f1d82eca5 100644
--- a/tests/auto/qml/qqmlbinding/tst_qqmlbinding.cpp
+++ b/tests/auto/qml/qqmlbinding/tst_qqmlbinding.cpp
@@ -49,6 +49,7 @@ private slots:
     void warningOnReadOnlyProperty();
     void disabledOnUnknownProperty();
     void disabledOnReadonlyProperty();
+    void delayed();
 
 private:
     QQmlEngine engine;
@@ -281,6 +282,27 @@ void tst_qqmlbinding::disabledOnReadonlyProperty()
     QCOMPARE(messageHandler.messages().count(), 0);
 }
 
+void tst_qqmlbinding::delayed()
+{
+    QQmlEngine engine;
+    QQmlComponent c(&engine, testFileUrl("delayed.qml"));
+    QQuickItem *item = qobject_cast<QQuickItem*>(c.create());
+
+    QVERIFY(item != 0);
+    // update on creation
+    QCOMPARE(item->property("changeCount").toInt(), 1);
+
+    QMetaObject::invokeMethod(item, "updateText");
+    // doesn't update immediately
+    QCOMPARE(item->property("changeCount").toInt(), 1);
+
+    QCoreApplication::processEvents();
+    // only updates once (non-delayed would update twice)
+    QCOMPARE(item->property("changeCount").toInt(), 2);
+
+    delete item;
+}
+
 QTEST_MAIN(tst_qqmlbinding)
 
 #include "tst_qqmlbinding.moc"