diff options
author | Tor Arne Vestbø <tor.arne.vestbo@qt.io> | 2023-12-14 15:16:40 +0100 |
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committer | Tor Arne Vestbø <tor.arne.vestbo@qt.io> | 2023-12-19 19:41:28 +0100 |
commit | 7fac2fac9a512cef2d5cdefd9837d76f8be7de05 (patch) | |
tree | f6ffed5662628f2b2599d4d424089068e18c542b /src/corelib/kernel/qobject.cpp | |
parent | a03d0a33b574677be1c9040e706591c5a1f8ec69 (diff) |
Document how to process deferred deletes in a plugin-scenario
When Qt is not driving the event dispatching, the event loop level
of the thread will stay 0. As a result, we will not automatically
bump the deferred delete event's scope level to 1 when the deferred
delete happens from a code path that doesn't raise the scope level
via QScopedScopeLevelCounter, leaving the event with loop and scope
level 0.
As we only process these 0+0 deferred delete events automatically from
QCoreApplicationPrivate::execCleanup(), which is not going to be called
when the app doesn't call QCoreAppliction::exec(), we were failing to
process the deferred deletes both during the application's runtime,
as well as on shutdown.
Task-number: QTBUG-120124
Fixes: QTBUG-117975
Pick-to: 6.7 6.6 6.5
Change-Id: I2b8accb432517a48370923ee2d760f8e2e4a8055
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Diffstat (limited to 'src/corelib/kernel/qobject.cpp')
-rw-r--r-- | src/corelib/kernel/qobject.cpp | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp index 73fd0e2480..3a5921628a 100644 --- a/src/corelib/kernel/qobject.cpp +++ b/src/corelib/kernel/qobject.cpp @@ -2413,6 +2413,21 @@ void QObject::removeEventFilter(QObject *obj) event loop was still running: the Qt event loop will delete those objects as soon as the new nested event loop starts. + In situations where Qt is not driving the event dispatcher via e.g. + QCoreApplication::exec() or QEventLoop::exec(), deferred deletes + will not be processed automatically. To ensure deferred deletion in + this scenario, the following workaround can be used: + + \code + const auto *eventDispatcher = QThread::currentThread()->eventDispatcher(); + QObject::connect(eventDispatcher, &QAbstractEventDispatcher::aboutToBlock, + QThread::currentThread(), []{ + if (QThread::currentThread()->loopLevel() == 0) + QCoreApplication::sendPostedEvents(nullptr, QEvent::DeferredDelete); + } + ); + \endcode + \note It is safe to call this function more than once; when the first deferred deletion event is delivered, any pending events for the object are removed from the event queue. |