qeventloop.cpp

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#include "qeventloop.h"

#include "qabstracteventdispatcher.h"
#include "qcoreapplication.h"
#include "qelapsedtimer.h"

#include "qobject_p.h"
#include <private/qthread_p.h>

QT_BEGIN_NAMESPACE

class QEventLoopPrivate : public QObjectPrivate
{
    Q_DECLARE_PUBLIC(QEventLoop)
public:
    inline QEventLoopPrivate()
        : exit(true), inExec(false), returnCode(-1)
    { }
    bool exit, inExec;
    int returnCode;
};

QEventLoop::QEventLoop(QObject *parent)
    : QObject(*new QEventLoopPrivate, parent)
{
    Q_D(QEventLoop);
    if (!QCoreApplication::instance()) {
        qWarning("QEventLoop: Cannot be used without QApplication");
    } else if (!d->threadData->eventDispatcher) {
        QThreadPrivate::createEventDispatcher(d->threadData);
    }
}

QEventLoop::~QEventLoop()
{ }


bool QEventLoop::processEvents(ProcessEventsFlags flags)
{
    Q_D(QEventLoop);
    if (!d->threadData->eventDispatcher)
        return false;
    if (flags & DeferredDeletion)
        QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
    return d->threadData->eventDispatcher->processEvents(flags);
}

int QEventLoop::exec(ProcessEventsFlags flags)
{
    Q_D(QEventLoop);
    //we need to protect from race condition with QThread::exit
    QMutexLocker locker(&static_cast<QThreadPrivate *>(QObjectPrivate::get(d->threadData->thread))->mutex);
    if (d->threadData->quitNow)
        return -1;

    if (d->inExec) {
        qWarning("QEventLoop::exec: instance %p has already called exec()", this);
        return -1;
    }
    d->inExec = true;
    d->exit = false;
    ++d->threadData->loopLevel;
    d->threadData->eventLoops.push(this);
    locker.unlock();

    // remove posted quit events when entering a new event loop
    QCoreApplication *app = QCoreApplication::instance();
    if (app && app->thread() == thread())
        QCoreApplication::removePostedEvents(app, QEvent::Quit);

#if defined(QT_NO_EXCEPTIONS)
    while (!d->exit)
        processEvents(flags | WaitForMoreEvents | EventLoopExec);
#else
    try {
        while (!d->exit)
            processEvents(flags | WaitForMoreEvents | EventLoopExec);
    } catch (...) {
        qWarning("Qt has caught an exception thrown from an event handler. Throwing\n"
                 "exceptions from an event handler is not supported in Qt. You must\n"
                 "reimplement QApplication::notify() and catch all exceptions there.\n");

        // copied from below
        locker.relock();
        QEventLoop *eventLoop = d->threadData->eventLoops.pop();
        Q_ASSERT_X(eventLoop == this, "QEventLoop::exec()", "internal error");
        Q_UNUSED(eventLoop); // --release warning
        d->inExec = false;
        --d->threadData->loopLevel;

        throw;
    }
#endif

    // copied above
    locker.relock();
    QEventLoop *eventLoop = d->threadData->eventLoops.pop();
    Q_ASSERT_X(eventLoop == this, "QEventLoop::exec()", "internal error");
    Q_UNUSED(eventLoop); // --release warning
    d->inExec = false;
    --d->threadData->loopLevel;

    return d->returnCode;
}

void QEventLoop::processEvents(ProcessEventsFlags flags, int maxTime)
{
    Q_D(QEventLoop);
    if (!d->threadData->eventDispatcher)
        return;

    QElapsedTimer start;
    start.start();
    if (flags & DeferredDeletion)
        QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
    while (processEvents(flags & ~WaitForMoreEvents)) {
        if (start.elapsed() > maxTime)
            break;
        if (flags & DeferredDeletion)
            QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
    }
}

void QEventLoop::exit(int returnCode)
{
    Q_D(QEventLoop);
    if (!d->threadData->eventDispatcher)
        return;

    d->returnCode = returnCode;
    d->exit = true;
    d->threadData->eventDispatcher->interrupt();
}

bool QEventLoop::isRunning() const
{
    Q_D(const QEventLoop);
    return !d->exit;
}

void QEventLoop::wakeUp()
{
    Q_D(QEventLoop);
    if (!d->threadData->eventDispatcher)
        return;
    d->threadData->eventDispatcher->wakeUp();
}

void QEventLoop::quit()
{ exit(0); }

QT_END_NAMESPACE