qobject.cpp

QT 开发环境里面一个很重要的文件

    to retrieve a pointer to the current application, and then use
    QApplication::thread() to retrieve the thread in which the
    application lives. For example:

    \code
        myObject->moveToThread(QApplication::instance()->thread());
    \endcode

    If \a targetThread is zero, all event processing for this object
    and its children stops.

    Note that all active timers for the object will be reset. The
    timers are first stopped in the current thread and restarted (with
    the same interval) in the \a targetThread. As a result, constantly
    moving an object between threads can postpone timer events
    indefinitely.

    \warning This function is \e not thread-safe; the current thread
    must be same as the current thread affinity. In other words, this
    function can only "push" an object from the current thread to
    another thread, it cannot "pull" an object from any arbitrary
    thread to the current thread.

    \sa thread()
 */
void QObject::moveToThread(QThread *targetThread)
{
    Q_D(QObject);

    if (d->threadData->thread == targetThread) {
        // object is already in this thread
        return;
    }

    if (d->parent != 0) {
        qWarning("QObject::moveToThread: Cannot move objects with a parent");
        return;
    }
    if (d->isWidget) {
        qWarning("QObject::moveToThread: Widgets cannot be moved to a new thread");
        return;
    }

    QThreadData *currentData = QThreadData::current();
    QThreadData *targetData = targetThread ? QThreadData::get2(targetThread) : new QThreadData(0);
    if (d->threadData->thread == 0 && currentData == targetData) {
        // one exception to the rule: we allow moving objects with no thread affinity to the current thread
        currentData = d->threadData;
    } else if (d->threadData != currentData) {
        qWarning("QObject::moveToThread: Current thread (%p) is not the object's thread (%p).\n"
                 "Cannot move to target thread (%p)\n",
                 d->threadData->thread, currentData->thread, targetData->thread);
        return;
    }

    // prepare to move
    d->moveToThread_helper();

    QWriteLocker locker(QObjectPrivate::readWriteLock());
    if (currentData != targetData) {
        targetData->postEventList.mutex.lock();
        while (currentData && !currentData->postEventList.mutex.tryLock()) {
            targetData->postEventList.mutex.unlock();
            targetData->postEventList.mutex.lock();
        }
    }

    // keep currentData alive (since we've got it locked)
    currentData->ref();

    // move the object
    d_func()->setThreadData_helper(currentData, targetData);

    if (currentData != targetData) {
        targetData->postEventList.mutex.unlock();
        if (currentData)
            currentData->postEventList.mutex.unlock();
    }

    // now currentData can commit suicide if it wants to
    currentData->deref();
}

void QObjectPrivate::moveToThread_helper()
{
    Q_Q(QObject);
    QEvent e(QEvent::ThreadChange);
    QCoreApplication::sendEvent(q, &e);
    for (int i = 0; i < children.size(); ++i) {
        QObject *child = children.at(i);
        child->d_func()->moveToThread_helper();
    }
}

void QObjectPrivate::setThreadData_helper(QThreadData *currentData, QThreadData *targetData)
{
    Q_Q(QObject);

    // move posted events
    int eventsMoved = 0;
    for (int i = 0; i < currentData->postEventList.size(); ++i) {
        const QPostEvent &pe = currentData->postEventList.at(i);
        if (!pe.event)
            continue;
        if (pe.receiver == q) {
            // move this post event to the targetList
            targetData->postEventList.append(pe);
            const_cast<QPostEvent &>(pe).event = 0;
            ++eventsMoved;
        }
    }
    if (eventsMoved > 0 && targetData->eventDispatcher)
        targetData->eventDispatcher->wakeUp();

    // set new thread data
    targetData->ref();
    threadData->deref();
    threadData = targetData;

    for (int i = 0; i < children.size(); ++i) {
        QObject *child = children.at(i);
        child->d_func()->setThreadData_helper(currentData, targetData);
    }
}

void QObjectPrivate::_q_reregisterTimers(void *pointer)
{
    Q_Q(QObject);
    QList<QPair<int, int> > *timerList = reinterpret_cast<QList<QPair<int, int> > *>(pointer);
    QAbstractEventDispatcher *eventDispatcher = threadData->eventDispatcher;
    for (int i = 0; i < timerList->size(); ++i) {
        const QPair<int, int> &pair = timerList->at(i);
        eventDispatcher->registerTimer(pair.first, pair.second, q);
    }
    delete timerList;
}


//
// The timer flag hasTimer is set when startTimer is called.
// It is not reset when killing the timer because more than
// one timer might be active.
//

/*!
    Starts a timer and returns a timer identifier, or returns zero if
    it could not start a timer.

    A timer event will occur every \a interval milliseconds until
    killTimer() is called. If \a interval is 0, then the timer event
    occurs once every time there are no more window system events to
    process.

    The virtual timerEvent() function is called with the QTimerEvent
    event parameter class when a timer event occurs. Reimplement this
    function to get timer events.

    If multiple timers are running, the QTimerEvent::timerId() can be
    used to find out which timer was activated.

    Example:

    \code
        class MyObject : public QObject
        {
            Q_OBJECT

        public:
            MyObject(QObject *parent = 0);

        protected:
            void timerEvent(QTimerEvent *event);
        };

        MyObject::MyObject(QObject *parent)
            : QObject(parent)
        {
            startTimer(50);     // 50-millisecond timer
            startTimer(1000);   // 1-second timer
            startTimer(60000);  // 1-minute timer
        }

        void MyObject::timerEvent(QTimerEvent *event)
        {
            qDebug() << "Timer ID:" << event->timerId();
        }
    \endcode

    Note that QTimer's accuracy depends on the underlying operating
    system and hardware. Most platforms support an accuracy of 20
    milliseconds; some provide more. If Qt is unable to deliver the
    requested number of timer events, it will silently discard some.

    The QTimer class provides a high-level programming interface with
    single-shot timers and timer signals instead of events. There is
    also a QBasicTimer class that is more lightweight than QTimer and
    less clumsy than using timer IDs directly.

    \sa timerEvent(), killTimer(), QTimer::singleShot()
*/

int QObject::startTimer(int interval)
{
    Q_D(QObject);

    if (interval < 0) {
        qWarning("QObject::startTimer: QTimer cannot have a negative interval");
        return 0;
    }

    d->pendTimer = true;                                // set timer flag

    if (!d->threadData->eventDispatcher) {
        qWarning("QObject::startTimer: QTimer can only be used with threads started with QThread");
        return 0;
    }
    return d->threadData->eventDispatcher->registerTimer(interval, this);
}

/*!
    Kills the timer with timer identifier, \a id.

    The timer identifier is returned by startTimer() when a timer
    event is started.

    \sa timerEvent(), startTimer()
*/

void QObject::killTimer(int id)
{
    Q_D(QObject);
    if (d->threadData->eventDispatcher)
        d->threadData->eventDispatcher->unregisterTimer(id);
}


/*!
    \fn QObject *QObject::parent() const

    Returns a pointer to the parent object.

    \sa children()
*/

/*!
    \fn const QObjectList &QObject::children() const

    Returns a list of child objects.
    The QObjectList class is defined in the \c{<QObject>} header
    file as the following:

    \quotefromfile src/corelib/kernel/qobject.h
    \skipto /typedef .*QObjectList/
    \printuntil QObjectList

    The first child added is the \l{QList::first()}{first} object in
    the list and the last child added is the \l{QList::last()}{last}
    object in the list, i.e. new children are appended at the end.

    Note that the list order changes when QWidget children are
    \l{QWidget::raise()}{raised} or \l{QWidget::lower()}{lowered}. A
    widget that is raised becomes the last object in the list, and a
    widget that is lowered becomes the first object in the list.

    \sa findChild(), findChildren(), parent(), setParent()
*/

#ifdef QT3_SUPPORT
static void objSearch(QObjectList &result,
                       const QObjectList &list,
                       const char  *inheritsClass,
                       bool onlyWidgets,
                       const char  *objName,
                       QRegExp           *rx,
                       bool            recurse)
{
    for (int i = 0; i < list.size(); ++i) {
        QObject *obj = list.at(i);
        bool ok = true;
        if (onlyWidgets)
            ok = obj->isWidgetType();
        else if (inheritsClass && !obj->inherits(inheritsClass))
            ok = false;
        if (ok) {
            if (objName)
                ok = (obj->objectName() == QLatin1String(objName));
#ifndef QT_NO_REGEXP
            else if (rx)
                ok = (rx->indexIn(obj->objectName()) != -1);
#endif
        }
        if (ok)                                // match!
            result.append(obj);
        if (recurse) {
            QObjectList clist = obj->children();
            if (!clist.isEmpty())
                objSearch(result, clist, inheritsClass,
                           onlyWidgets, objName, rx, recurse);
        }
    }
}

/*!
    \internal

    Searches the children and optionally grandchildren of this object,
    and returns a list of those objects that are named or that match
    \a objName and inherit \a inheritsClass. If \a inheritsClass is 0
    (the default), all classes match. If \a objName is 0 (the
    default), all object names match.

    If \a regexpMatch is true (the default), \a objName is a regular
    expression that the objects's names must match. The syntax is that
    of a QRegExp. If \a regexpMatch is false, \a objName is a string
    and object names must match it exactly.

    Note that \a inheritsClass uses single inheritance from QObject,
    the way inherits() does. According to inherits(), QWidget
    inherits QObject but not QPaintDevice. This does not quite match
    reality, but is the best that can be done on the wide variety of
    compilers Qt supports.

    Finally, if \a recursiveSearch is true (the default), queryList()
    searches \e{n}th-generation as well as first-generation children.

    If all this seems a bit complex for your needs, the simpler
    child() function may be what you want.

    This somewhat contrived example disables all the buttons in this
    window:

    \code
        QList<QObject *> list = window()->queryList("QAbstractButton"));
        foreach (QObject *obj, list)
            static_cast<QAbstractButton *>(obj)->setEnabled(false);
    \endcode

    \warning Delete the list as soon you have finished using it. The
    list contains pointers that may become invalid at almost any time
    without notice (as soon as the user closes a window you may have
    dangling pointers, for example).

    \sa child() children(), parent(), inherits(), objectName(), QRegExp
*/

QObjectList QObject::queryList(const char *inheritsClass,
                                const char *objName,
                                bool regexpMatch,
                                bool recursiveSearch) const
{
    Q_D(const QObject);
    QObjectList list;
    bool onlyWidgets = (inheritsClass && qstrcmp(inheritsClass, "QWidget") == 0);
#ifndef QT_NO_REGEXP
    if (regexpMatch && objName) {                // regexp matching
        QRegExp rx(QString::fromLatin1(objName));
        objSearch(list, d->children, inheritsClass, onlyWidgets, 0, &rx, recursiveSearch);
    } else
#endif
    {
        objSearch(list, d->children, inheritsClass, onlyWidgets, objName, 0, recursiveSearch);
    }
    return list;
}
#endif

/*!
    \fn T *QObject::findChild(const QString &name) const

    Returns the child of this object that can be casted into type T and
    that is called \a name, or 0 if there is no such object.
    An empty string matches all object names.
    The search is performed recursively.

    If there is more than one child matching the search, the most
    direct ancestor is returned. If there are several direct
    ancestors, it is undefined which one will be returned. In that
    case, findChildren() should be used.

    This example returns a child \l{QPushButton} of \c{parentWidget}
    named \c{"button1"}:

    \code
        QPushButton *button = parentWidget->findChild<QPushButton *>("button1");
    \endcode

    This example returns a \l{QListWidget} child of \c{parentWidget}:

    \code
        QListWidget *list = parentWidget->findChild<QListWidget *>();
    \endcode

    \warning This function is not available with MSVC 6. Use
    qFindChild() instead if you need to support that version of the
    compiler.

    \sa findChildren(), qFindChild()
*/

/*!
    \fn QList<T> QObject::findChildren(const QString &name) const

    Returns all children of this object with the given \a name that can be
    cast to type T, or an empty list if there are no such objects.
    An empty string matches all object names.
    The search is performed recursively.

    The following example shows how to find a list of child \l{QWidget}s of
    the specified \c{parentWidget} named \c{widgetname}:

    \code
        QList<QWidget *> widgets = parentWidget.findChildren<QWidget *>("widgetname");
    \endcode

    This example returns all \c{QPushButton}s that are children of \c{parentWidget}: