diff options
| author | Arno Rehn <a.rehn@menlosystems.com> | 2023-05-08 15:28:11 +0200 |
|---|---|---|
| committer | Arno Rehn <a.rehn@menlosystems.com> | 2023-05-30 21:42:46 +0200 |
| commit | 07d6d31a4c0c17d8c897d783a9b0841df6834b02 (patch) | |
| tree | 851fa5478368fb537523eed5ced7fb7581e5cc96 /src/corelib/thread/qbasicfuturewatcher.cpp | |
| parent | 86c044176f16674616a20cd8e6a88b5a2dcf3775 (diff) | |
QFuture: Gracefully handle a destroyed context in continuations
This patch relaxes the requirements on the context object of
continuations. Instead of having to stay alive during execution of the
whole chain, it now only has to stay alive during setup of the chain.
If the context object is destroyed before the chain finishes, the
respective future is canceled.
This patch works by using QFutureCallOutInterface and signals instead
of direct invocation of the continuation by the parent future, similar
to how QFutureWatcher is implemented.
If a continuation is used with a context object, a QBasicFutureWatcher
is connected to the QFuture via a QFutureCallOutInterface. When the
future finishes, QBasicFutureWatcher::finished() triggers the
continuation with a signal/slot connection.
This way, we require the context object to stay alive only during setup;
the required synchronization is guaranteed by the existing event and
signal-slot mechanisms. The continuation itself does not need to know
about the context object anymore.
[ChangeLog][QtCore][QFuture] Added support for context objects of
continuations being destroyed before the continuation finishes. In
these cases the future is cancelled immediately.
Fixes: QTBUG-112958
Change-Id: Ie0ef3470b2a0ccfa789d2ae7604b92e509c14591
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Diffstat (limited to 'src/corelib/thread/qbasicfuturewatcher.cpp')
| -rw-r--r-- | src/corelib/thread/qbasicfuturewatcher.cpp | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/src/corelib/thread/qbasicfuturewatcher.cpp b/src/corelib/thread/qbasicfuturewatcher.cpp new file mode 100644 index 00000000000..2602995e8fa --- /dev/null +++ b/src/corelib/thread/qbasicfuturewatcher.cpp @@ -0,0 +1,80 @@ +// Copyright (C) 2023 The Qt Company Ltd. +// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only + +#include "qbasicfuturewatcher.h" +#include "qcoreapplication.h" +#include "qfutureinterface.h" +#include "qfutureinterface_p.h" + +#include <QtCore/private/qobject_p.h> + +QT_BEGIN_NAMESPACE + +namespace QtPrivate { + +class QBasicFutureWatcherPrivate : public QObjectPrivate, QFutureCallOutInterface +{ +public: + Q_DECLARE_PUBLIC(QBasicFutureWatcher) + + QFutureInterfaceBase future; + + void postCallOutEvent(const QFutureCallOutEvent &event) override; + void callOutInterfaceDisconnected() override; +}; + +void QBasicFutureWatcherPrivate::postCallOutEvent(const QFutureCallOutEvent &event) +{ + Q_Q(QBasicFutureWatcher); + if (q->thread() == QThread::currentThread()) { + // If we are in the same thread, don't queue up anything. + std::unique_ptr<QFutureCallOutEvent> clonedEvent(event.clone()); + QCoreApplication::sendEvent(q, clonedEvent.get()); + } else { + QCoreApplication::postEvent(q, event.clone()); + } +} + +void QBasicFutureWatcherPrivate::callOutInterfaceDisconnected() +{ + Q_Q(QBasicFutureWatcher); + QCoreApplication::removePostedEvents(q, QEvent::FutureCallOut); +} + +/* + * QBasicFutureWatcher is a more lightweight version of QFutureWatcher for internal use + */ +QBasicFutureWatcher::QBasicFutureWatcher(QObject *parent) + : QObject(*new QBasicFutureWatcherPrivate, parent) +{ +} + +QBasicFutureWatcher::~QBasicFutureWatcher() +{ + Q_D(QBasicFutureWatcher); + d->future.d->disconnectOutputInterface(d); +} + +void QBasicFutureWatcher::setFuture(QFutureInterfaceBase &fi) +{ + Q_D(QBasicFutureWatcher); + d->future = fi; + d->future.d->connectOutputInterface(d); +} + +bool QtPrivate::QBasicFutureWatcher::event(QEvent *event) +{ + if (event->type() == QEvent::FutureCallOut) { + QFutureCallOutEvent *callOutEvent = static_cast<QFutureCallOutEvent *>(event); + if (callOutEvent->callOutType == QFutureCallOutEvent::Finished) + emit finished(); + return true; + } + return QObject::event(event); +} + +} // namespace QtPrivate + +QT_END_NAMESPACE + +#include "moc_qbasicfuturewatcher.cpp" |