From ed827acc27530a97b84685920615359010d74f48 Mon Sep 17 00:00:00 2001 From: Marc Mutz Date: Thu, 1 Mar 2012 18:52:32 +0100 Subject: QSignalBlocker: (new) RAII class for QObject::blockSignals() I don't think I ever worked on a project of non-trivial size that didn't at some point add a QSignalBlocker. This commit adds code, tests and documentation. Later commits will convert naked blockSignals() calls to use QSignalBlocker. The implementation is purely inline to avoid the heavy overhead of cross-dll function calls for this miniscule task. This should not be a problem because QSignalBlocker only uses public API and a pattern that we anyway need to keep working until Qt 6, at least, so even changing the implementation later will be no problem as the old implementation lurking in non-recompiled code will be acceptable, too. This implementation is an evolution from KDTools' KDSignalBlocker, with the following changes: - Implements unblock() and reblock() - Uses the return value of blockSignals() instead of a separate signalsBlocked() call. Change-Id: I1933dfd72a0f5190324be377cfca3c54cf3d6828 Reviewed-by: Olivier Goffart --- dist/changes-5.3.0 | 2 + src/corelib/kernel/qobject.cpp | 73 +++++++++++++++++++++++ src/corelib/kernel/qobject.h | 46 ++++++++++++++ tests/auto/corelib/kernel/qobject/tst_qobject.cpp | 49 +++++++++++++++ 4 files changed, 170 insertions(+) diff --git a/dist/changes-5.3.0 b/dist/changes-5.3.0 index 87d9c771e7..035d0656ed 100644 --- a/dist/changes-5.3.0 +++ b/dist/changes-5.3.0 @@ -25,5 +25,7 @@ QtWidgets QtCore ------ +- QSignalBlocker: (new) RAII wrapper around QObject::blockSignals() + QtGui ----- diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp index a52fd25e08..72ce941b6e 100644 --- a/src/corelib/kernel/qobject.cpp +++ b/src/corelib/kernel/qobject.cpp @@ -482,6 +482,79 @@ void QMetaCallEvent::placeMetaCall(QObject *object) } } +/*! + \class QSignalBlocker + \brief Exception-safe wrapper around QObject::blockSignals() + \since 5.3 + \ingroup objectmodel + + \reentrant + + QSignalBlocker can be used whereever you would otherwise use a + pair of calls to blockSignals(). It blocks signals in its + constructor and in the destructor it resets the state to what + it was before the constructor ran. + + \code + { + const QSignalBlocker blocker(someQObject); + // no signals here + } + \endcode + is thus equivalent to + \code + const bool wasBlocked = someQObject->blockSignals(true); + // no signals here + someQObject->blockSignals(false); + \endcode + + except the code using QSignalBlocker is safe in the face of + exceptions. + + \sa QMutexLocker, QEventLoopLocker +*/ + +/*! + \fn QSignalBlocker::QSignalBlocker(QObject *object) + + Constructor. Calls \a{object}->blockSignals(true). +*/ + +/*! + \fn QSignalBlocker::QSignalBlocker(QObject &object) + \overload + + Calls \a{object}.blockSignals(true). +*/ + +/*! + \fn QSignalBlocker::~QSignalBlocker() + + Destructor. Restores the QObject::signalsBlocked() state to what it + was before the constructor ran, unless unblock() has been called + without a following reblock(), in which case it does nothing. +*/ + +/*! + \fn void QSignalBlocker::reblock() + + Re-blocks signals after a previous unblock(). + + The numbers of reblock() and unblock() calls are not counted, so + every reblock() undoes any number of unblock() calls. +*/ + +/*! + \fn void QSignalBlocker::unblock() + + Temporarily restores the QObject::signalsBlocked() state to what + it was before this QSignaBlocker's constructor ran. To undo, use + reblock(). + + The numbers of reblock() and unblock() calls are not counted, so + every unblock() undoes any number of reblock() calls. +*/ + /*! \class QObject \inmodule QtCore diff --git a/src/corelib/kernel/qobject.h b/src/corelib/kernel/qobject.h index e2000afc82..f9239bf575 100644 --- a/src/corelib/kernel/qobject.h +++ b/src/corelib/kernel/qobject.h @@ -549,6 +549,52 @@ template inline const char * qobject_interface_iid() Q_CORE_EXPORT QDebug operator<<(QDebug, const QObject *); #endif +class Q_CORE_EXPORT QSignalBlocker +{ +public: + inline explicit QSignalBlocker(QObject *o); + inline explicit QSignalBlocker(QObject &o); + inline ~QSignalBlocker(); + + inline void reblock(); + inline void unblock(); +private: + Q_DISABLE_COPY(QSignalBlocker) + QObject * const m_o; + bool m_blocked; + bool m_inhibited; +}; + +QSignalBlocker::QSignalBlocker(QObject *o) + : m_o(o), + m_blocked(o && o->blockSignals(true)), + m_inhibited(false) +{} + +QSignalBlocker::QSignalBlocker(QObject &o) + : m_o(&o), + m_blocked(o.blockSignals(true)), + m_inhibited(false) +{} + +QSignalBlocker::~QSignalBlocker() +{ + if (m_o && !m_inhibited) + m_o->blockSignals(m_blocked); +} + +void QSignalBlocker::reblock() +{ + if (m_o) m_o->blockSignals(true); + m_inhibited = false; +} + +void QSignalBlocker::unblock() +{ + if (m_o) m_o->blockSignals(m_blocked); + m_inhibited = true; +} + namespace QtPrivate { inline QObject & deref_for_methodcall(QObject &o) { return o; } inline QObject & deref_for_methodcall(QObject *o) { return *o; } diff --git a/tests/auto/corelib/kernel/qobject/tst_qobject.cpp b/tests/auto/corelib/kernel/qobject/tst_qobject.cpp index 05d81c2bd1..f429500077 100644 --- a/tests/auto/corelib/kernel/qobject/tst_qobject.cpp +++ b/tests/auto/corelib/kernel/qobject/tst_qobject.cpp @@ -102,6 +102,7 @@ private slots: #ifndef QT_NO_PROCESS void recursiveSignalEmission(); #endif + void signalBlocking(); void blockingQueuedConnection(); void childEvents(); void installEventFilter(); @@ -2979,6 +2980,54 @@ void tst_QObject::recursiveSignalEmission() } #endif +void tst_QObject::signalBlocking() +{ + SenderObject sender; + ReceiverObject receiver; + + receiver.connect(&sender, SIGNAL(signal1()), SLOT(slot1())); + + sender.emitSignal1(); + QVERIFY(receiver.called(1)); + receiver.reset(); + + { + QSignalBlocker blocker(&sender); + + sender.emitSignal1(); + QVERIFY(!receiver.called(1)); + receiver.reset(); + + sender.blockSignals(false); + + sender.emitSignal1(); + QVERIFY(receiver.called(1)); + receiver.reset(); + + sender.blockSignals(true); + + sender.emitSignal1(); + QVERIFY(!receiver.called(1)); + receiver.reset(); + + blocker.unblock(); + + sender.emitSignal1(); + QVERIFY(receiver.called(1)); + receiver.reset(); + + blocker.reblock(); + + sender.emitSignal1(); + QVERIFY(!receiver.called(1)); + receiver.reset(); + } + + sender.emitSignal1(); + QVERIFY(receiver.called(1)); + receiver.reset(); +} + void tst_QObject::blockingQueuedConnection() { { -- cgit v1.2.3