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** Public License version 3.0 as published by the Free Software Foundation
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#include "qcvdisplaylink.h"

#include <QtCore/qcoreapplication.h>
#include <QtCore/qdebug.h>

QT_USE_NAMESPACE

static CVReturn CVDisplayLinkCallback(CVDisplayLinkRef displayLink,
                                 const CVTimeStamp *inNow,
                                 const CVTimeStamp *inOutputTime,
                                 CVOptionFlags flagsIn,
                                 CVOptionFlags *flagsOut,
                                 void *displayLinkContext)
{
    Q_UNUSED(displayLink);
    Q_UNUSED(inNow);
    Q_UNUSED(flagsIn);
    Q_UNUSED(flagsOut);

    QCvDisplayLink *link = (QCvDisplayLink *)displayLinkContext;

    link->displayLinkEvent(inOutputTime);
    return kCVReturnSuccess;
}


QCvDisplayLink::QCvDisplayLink(QObject *parent)
    :QObject(parent),
    m_pendingDisplayLinkEvent(false),
    m_isActive(false)
{
    // create display link for the main display
    CVDisplayLinkCreateWithCGDisplay(kCGDirectMainDisplay, &m_displayLink);
    if (m_displayLink) {
        // set the current display of a display link.
        CVDisplayLinkSetCurrentCGDisplay(m_displayLink, kCGDirectMainDisplay);

        // set the renderer output callback function
        CVDisplayLinkSetOutputCallback(m_displayLink, &CVDisplayLinkCallback, this);
    }
}

QCvDisplayLink::~QCvDisplayLink()
{
    if (m_displayLink) {
        CVDisplayLinkStop(m_displayLink);
        CVDisplayLinkRelease(m_displayLink);
        m_displayLink = NULL;
    }
}

bool QCvDisplayLink::isValid()
{
    return m_displayLink != 0;
}

bool QCvDisplayLink::isActive() const
{
    return m_isActive;
}

void QCvDisplayLink::start()
{
     if (m_displayLink && !m_isActive) {
        CVDisplayLinkStart(m_displayLink);
        m_isActive = true;
     }
}

void QCvDisplayLink::stop()
{
    if (m_displayLink && m_isActive) {
        CVDisplayLinkStop(m_displayLink);
        m_isActive = false;
    }
}

void QCvDisplayLink::displayLinkEvent(const CVTimeStamp *ts)
{
    // This function is called from a
    // thread != gui thread. So we post the event.
    // But we need to make sure that we don't post faster
    // than the event loop can eat:
    m_displayLinkMutex.lock();
    bool pending = m_pendingDisplayLinkEvent;
    m_pendingDisplayLinkEvent = true;
    m_frameTimeStamp = *ts;
    m_displayLinkMutex.unlock();

    if (!pending)
        qApp->postEvent(this, new QEvent(QEvent::User), Qt::HighEventPriority);
}

bool QCvDisplayLink::event(QEvent *event)
{
    switch (event->type()){
        case QEvent::User:  {
                m_displayLinkMutex.lock();
                m_pendingDisplayLinkEvent = false;
                CVTimeStamp ts = m_frameTimeStamp;
                m_displayLinkMutex.unlock();

                emit tick(ts);

                return false;
            }
            break;
        default:
            break;
    }
    return QObject::event(event);
}

#include "moc_qcvdisplaylink.cpp"