Add QObjectBindableProperyt::notify

This mirrors the functionality of QObjectCompatProperty::notify, and can
be useful to delay notifications until a class invariant has been
restored.

Change-Id: I1c16a0b1537a1b53d144c8abe48e546553edf877
Reviewed-by: Andreas Buhr <andreas.buhr@qt.io>
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/kernel/qproperty.cpp

@@ -1567,7 +1567,6 @@ QString QPropertyBindingError::description() const
   owner is notified via the Callback function.
 */
 
-
 /*!
   \fn template <typename Class, typename T, auto offset, auto Callback> template <typename Functor> QObjectBindableProperty<Class, T, offset, Callback>::QObjectBindableProperty(Functor &&f)
 
@@ -1600,14 +1599,18 @@ QString QPropertyBindingError::description() const
 */
 
 /*!
-  \fn template <typename Class, typename T, auto offset, auto Callback> void QObjectBindableProperty<Class, T, offset, Callback>::markDirty()
+  \fn template <typename Class, typename T, auto offset, auto Callback> void QObjectBindableProperty<Class, T, offset, Callback>::notify()
 
-  Programatically sets the property dirty. Any binding which depend on it will
+  Programmatically signals a change of the property. Any binding which depend on it will
-  be notified.
+  be notified, and if the property has a signal, it will be emitted.
-  This can be useful for properties which do not only depend on bindable properties,
-  but also on non-bindable properties or some other state.
 
-  \sa QProperty::markDirty()
+  This can be useful in combination with setValueBypassingBindings to defer signalling the change
+  until a class invariant has been restored.
+
+  \note If this property has a binding (i.e. hasBinding() returns true), that binding is not reevaluated when
+  notify() is called. Any binding depending on this property is still reevaluated as usual.
+
+  \sa Qt::beginProperytUpdateGroup(), setValueBypassingBindings()
 */
 
 /*!

src/corelib/kernel/qproperty.h

@@ -962,6 +962,11 @@ public:
         notify(bd);
     }
 
+    void notify() {
+        auto *bd = qGetBindingStorage(owner())->bindingData(this);
+        notify(bd);
+    }
+
     void setValue(rvalue_ref t)
     {
         auto *bd = qGetBindingStorage(owner())->bindingData(this);

tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp

@@ -82,6 +82,7 @@ private slots:
     void bindingValueReplacement();
     void quntypedBindableApi();
     void readonlyConstQBindable();
+    void qobjectBindableManualNotify();
 
     void testNewStuff();
     void qobjectObservers();
@@ -1137,6 +1138,50 @@ public:
     Q_OBJECT_COMPAT_PROPERTY(MyQObject, int, compatData, &MyQObject::setCompat)
 };
 
+
+void tst_QProperty::qobjectBindableManualNotify()
+{
+    // Given an object of type MyQObject,
+    MyQObject object;
+    // track its foo property's change count
+    auto bindable = object.bindableFoo();
+    int fooChangeCount = 0;
+    auto changeHandler = bindable.onValueChanged([&](){++fooChangeCount;});
+    // and how many changed signals it emits.
+    QSignalSpy fooChangedSpy(&object, &MyQObject::fooChanged);
+
+    // If we bypass the bindings system,
+    object.fooData.setValueBypassingBindings(42);
+    // there is no change.
+    QCOMPARE(fooChangeCount, 0);
+    QCOMPARE(fooChangedSpy.count(), 0);
+    // Once we notify manually
+    object.fooData.notify();
+    // observers are notified and the signal arrives.
+    QCOMPARE(fooChangeCount, 1);
+    QCOMPARE(fooChangedSpy.count(), 1);
+
+    // If we set a binding
+    int i = 1;
+    object.fooData.setBinding([&](){return i;});
+    // then the value changes
+    QCOMPARE(object.foo(), 1);
+    // and the change and signal count are incremented.
+    QCOMPARE(fooChangeCount, 2);
+    QCOMPARE(fooChangedSpy.count(), 2);
+    // Changing a non-property won't trigger any notification.
+    i = 2;
+    QCOMPARE(fooChangeCount, 2);
+    QCOMPARE(fooChangedSpy.count(), 2);
+    // Manually triggering the notification
+    object.fooData.notify();
+    // increments the change count
+    QCOMPARE(fooChangeCount, 3);
+    QCOMPARE(fooChangedSpy.count(), 3);
+    // but doesn't actually cause a binding reevaluation.
+    QCOMPARE(object.foo(), 1);
+}
+
 void tst_QProperty::testNewStuff()
 {
     MyQObject testReadOnly;