diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/corelib/kernel/qobject.cpp | 42 |
1 files changed, 35 insertions, 7 deletions
diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp index aa1a00c..91e8fbb 100644 --- a/src/corelib/kernel/qobject.cpp +++ b/src/corelib/kernel/qobject.cpp @@ -566,13 +566,6 @@ void QMetaCallEvent::placeMetaCall(QObject *object) details. A convenience handler, childEvent(), can be reimplemented to catch child events. - Events are delivered in the thread in which the object was - created; see \l{Thread Support in Qt} and thread() for details. - Note that event processing is not done at all for QObjects with no - thread affinity (thread() returns zero). Use the moveToThread() - function to change the thread affinity for an object and its - children (the object cannot be moved if it has a parent). - Last but not least, QObject provides the basic timer support in Qt; see QTimer for high-level support for timers. @@ -593,6 +586,41 @@ void QMetaCallEvent::placeMetaCall(QObject *object) Some QObject functions, e.g. children(), return a QObjectList. QObjectList is a typedef for QList<QObject *>. + \section1 Thread Affinity + + A QObject instance is said to have a \e{thread affinity}, or that + it \e{lives} in a certain thread. When a QObject receives a + \l{Qt::QueuedConnection}{queued signal} or a \l{The Event + System#Sending Events}{posted event}, the slot or event handler + will run in the thread that the object lives in. + + \note If a QObject has no thread affinity (that is, if thread() + returns zero), or if it lives in a thread that has no running event + loop, then it cannot receive queued signals or posted events. + + By default, a QObject lives in the thread in which it is created. + An object's thread affinity can be queried using thread() and + changed using moveToThread(). + + All QObjects must live in the same thread as their parent. Consequently: + + \list + \li setParent() will fail if the two QObjects involved live in + different threads. + \li When a QObject is moved to another thread, all its children + will be automatically moved too. + \li moveToThread() will fail if the QObject has a parent. + \li If \l{QObject}s are created within QThread::run(), they cannot + become children of the QThread object because the QThread does + not live in the thread that calls QThread::run(). + \endlist + + \note A QObject's member variables \e{do not} automatically become + its children. The parent-child relationship must be set by either + passing a pointer to the child's \l{QObject()}{constructor}, or by + calling setParent(). Without this step, the object's member variables + will remain in the old thread when moveToThread() is called. + \target No copy constructor \section1 No copy constructor or assignment operator |