Long live QScopedPropertyUpdateGroup

A RAII wrapper around Qt::{begin,end}PropertyUpdateGroup().

[ChangeLog][QtCore][QScopedPropertyUpdateGroup] New RAII class
wrapping Qt::beginPropertyUpdateGroup() and
Qt::endPropertyUpdateGroup().

Fixes: QTBUG-110710
Change-Id: If2619e9584dd9d57985d63e3babca75421499ab9
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/corelib/animation/qabstractanimation.cpp

@@ -1121,7 +1121,7 @@ void QAbstractAnimation::setDirection(Direction direction)
         return;
     }
 
-    Qt::beginPropertyUpdateGroup();
+    const QScopedPropertyUpdateGroup guard;
     const int oldCurrentLoop = d->currentLoop;
     if (state() == Stopped) {
         if (direction == Backward) {
@@ -1148,7 +1148,6 @@ void QAbstractAnimation::setDirection(Direction direction)
     if (d->currentLoop != oldCurrentLoop)
         d->currentLoop.notify();
     d->direction.notify();
-    Qt::endPropertyUpdateGroup();
 }
 
 QBindable<QAbstractAnimation::Direction> QAbstractAnimation::bindableDirection()

src/corelib/itemmodels/qsortfilterproxymodel.cpp

@@ -2582,7 +2582,7 @@ QBindable<QRegularExpression> QSortFilterProxyModel::bindableFilterRegularExpres
 void QSortFilterProxyModel::setFilterRegularExpression(const QRegularExpression &regularExpression)
 {
     Q_D(QSortFilterProxyModel);
-    Qt::beginPropertyUpdateGroup();
+    const QScopedPropertyUpdateGroup guard;
     const bool regExpChanged = regularExpression != d->filter_regularexpression.value();
     d->filter_regularexpression.removeBindingUnlessInWrapper();
     d->filter_casesensitive.removeBindingUnlessInWrapper();
@@ -2601,7 +2601,6 @@ void QSortFilterProxyModel::setFilterRegularExpression(const QRegularExpression
         d->filter_regularexpression.notify();
     if (cs != updatedCs)
         d->filter_casesensitive.notify();
-    Qt::endPropertyUpdateGroup();
 }
 
 /*!
@@ -2677,7 +2676,7 @@ void QSortFilterProxyModel::setFilterCaseSensitivity(Qt::CaseSensitivity cs)
     if (cs == d->filter_casesensitive)
         return;
 
-    Qt::beginPropertyUpdateGroup();
+    const QScopedPropertyUpdateGroup guard;
     QRegularExpression::PatternOptions options =
             d->filter_regularexpression.value().patternOptions();
     options.setFlag(QRegularExpression::CaseInsensitiveOption, cs == Qt::CaseInsensitive);
@@ -2690,7 +2689,6 @@ void QSortFilterProxyModel::setFilterCaseSensitivity(Qt::CaseSensitivity cs)
     d->filter_changed(QSortFilterProxyModelPrivate::Direction::Rows);
     d->filter_regularexpression.notify();
     d->filter_casesensitive.notify();
-    Qt::endPropertyUpdateGroup();
 }
 
 QBindable<Qt::CaseSensitivity> QSortFilterProxyModel::bindableFilterCaseSensitivity()

src/corelib/kernel/qproperty.cpp

@@ -185,7 +185,7 @@ Q_CONSTINIT static thread_local QBindingStatus bindingStatus;
     properties need to be updated, preventing any external observer from noticing an inconsistent
     state.
 
-    \sa Qt::endPropertyUpdateGroup
+    \sa Qt::endPropertyUpdateGroup, QScopedPropertyUpdateGroup
 */
 void Qt::beginPropertyUpdateGroup()
 {
@@ -205,7 +205,7 @@ void Qt::beginPropertyUpdateGroup()
     \warning Calling endPropertyUpdateGroup without a preceding call to beginPropertyUpdateGroup
     results in undefined behavior.
 
-    \sa Qt::beginPropertyUpdateGroup
+    \sa Qt::beginPropertyUpdateGroup, QScopedPropertyUpdateGroup
 */
 void Qt::endPropertyUpdateGroup()
 {
@@ -239,6 +239,41 @@ void Qt::endPropertyUpdateGroup()
     }
 }
 
+/*!
+    \since 6.6
+    \class QScopedPropertyUpdateGroup
+    \inmodule QtCore
+    \ingroup tools
+    \brief RAII class around Qt::beginPropertyUpdateGroup()/Qt::endPropertyUpdateGroup()
+
+    This class calls Qt::beginPropertyUpdateGroup() in its constructor and
+    Qt::endPropertyUpdateGroup() in its destructor, making sure the latter
+    function is reliably called even in the presence of early returns or thrown
+    exceptions.
+
+    \note Qt::endPropertyUpdateGroup() may re-throw exceptions thrown by
+    binding evaluations. This means your application may crash
+    (\c{std::terminate()} called) if another exception is causing
+    QScopedPropertyUpdateGroup's destructor to be called during stack
+    unwinding. If you expect exceptions from binding evaluations, use manual
+    Qt::endPropertyUpdateGroup() calls and \c{try}/\c{catch} blocks.
+
+    \sa QProperty
+*/
+
+/*!
+    \fn QScopedPropertyUpdateGroup::QScopedPropertyUpdateGroup()
+
+    Calls Qt::beginPropertyUpdateGroup().
+*/
+
+/*!
+    \fn QScopedPropertyUpdateGroup::~QScopedPropertyUpdateGroup()
+
+    Calls Qt::endPropertyUpdateGroup().
+*/
+
+
 // check everything stored in QPropertyBindingPrivate's union is trivially destructible
 // (though the compiler would also complain if that weren't the case)
 static_assert(std::is_trivially_destructible_v<QPropertyBindingSourceLocation>);

src/corelib/kernel/qproperty.h

@@ -53,6 +53,16 @@ Q_CORE_EXPORT void beginPropertyUpdateGroup();
 Q_CORE_EXPORT void endPropertyUpdateGroup();
 }
 
+class [[nodiscard]] QScopedPropertyUpdateGroup
+{
+    Q_DISABLE_COPY_MOVE(QScopedPropertyUpdateGroup)
+public:
+    QScopedPropertyUpdateGroup()
+    { Qt::beginPropertyUpdateGroup(); }
+    ~QScopedPropertyUpdateGroup() noexcept(false)
+    { Qt::endPropertyUpdateGroup(); }
+};
+
 template <typename T>
 class QPropertyData : public QUntypedPropertyData
 {

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

@@ -1782,13 +1782,14 @@ void tst_QProperty::propertyAdaptorBinding()
     QCOMPARE(object.fooChangedCount, 7);
 
     // Check update group
-    Qt::beginPropertyUpdateGroup();
-    source.setValue(23);
-    source2.setValue(22);
-    QCOMPARE(object.foo(), 43);
-    QCOMPARE(dest1.value(), 43);
-    QCOMPARE(object.fooChangedCount, 7);
-    Qt::endPropertyUpdateGroup();
+    {
+        const QScopedPropertyUpdateGroup guard;
+        source.setValue(23);
+        source2.setValue(22);
+        QCOMPARE(object.foo(), 43);
+        QCOMPARE(dest1.value(), 43);
+        QCOMPARE(object.fooChangedCount, 7);
+    }
     QCOMPARE(object.foo(), 45);
     QCOMPARE(dest1.value(), 45);
     QCOMPARE(object.fooChangedCount, 8);
@@ -2085,27 +2086,29 @@ void tst_QProperty::groupedNotifications()
     QCOMPARE(nNotifications, 1);
 
     expected = 2;
-    Qt::beginPropertyUpdateGroup();
-    a = 1;
-    QCOMPARE(b.value(), 0);
-    QCOMPARE(c.value(), 0);
-    QCOMPARE(d.value(), 0);
-    QCOMPARE(nNotifications, 1);
-    Qt::endPropertyUpdateGroup();
+    {
+        const QScopedPropertyUpdateGroup guard;
+        a = 1;
+        QCOMPARE(b.value(), 0);
+        QCOMPARE(c.value(), 0);
+        QCOMPARE(d.value(), 0);
+        QCOMPARE(nNotifications, 1);
+    }
     QCOMPARE(b.value(), 1);
     QCOMPARE(c.value(), 1);
     QCOMPARE(e.value(), 2);
     QCOMPARE(nNotifications, 2);
 
     expected = 7;
-    Qt::beginPropertyUpdateGroup();
-    a = 2;
-    d = 3;
-    QCOMPARE(b.value(), 1);
-    QCOMPARE(c.value(), 1);
-    QCOMPARE(d.value(), 3);
-    QCOMPARE(nNotifications, 2);
-    Qt::endPropertyUpdateGroup();
+    {
+        const QScopedPropertyUpdateGroup guard;
+        a = 2;
+        d = 3;
+        QCOMPARE(b.value(), 1);
+        QCOMPARE(c.value(), 1);
+        QCOMPARE(d.value(), 3);
+        QCOMPARE(nNotifications, 2);
+    }
     QCOMPARE(b.value(), 2);
     QCOMPARE(c.value(), 2);
     QCOMPARE(e.value(), 7);
@@ -2128,10 +2131,11 @@ void tst_QProperty::groupedNotificationConsistency()
     j = 1;
     QVERIFY(!areEqual); // value changed runs before j = 1
 
-    Qt::beginPropertyUpdateGroup();
-    i = 2;
-    j = 2;
-    Qt::endPropertyUpdateGroup();
+    {
+        const QScopedPropertyUpdateGroup guard;
+        i = 2;
+        j = 2;
+    }
     QVERIFY(areEqual); // value changed runs after everything has been evaluated
 }