QML 2 performance is worse than QML 1?

[zvava]

I have an application on Qt4 with ma own class derived from QDeclarativeItem.
Here it is:
PaintArea.h Qt4
@class PaintArea : public QDeclarativeItem
{
Q_OBJECT
public:
explicit PaintArea(QDeclarativeItem *parent = 0);
~PaintArea();

protected:
void mousePress(QGraphicsSceneMouseEvent *event);
void mouseMove(QGraphicsSceneMouseEvent *event);
void paint(QPainter *p, const QStyleOptionGraphicsItem *s, QWidget *w);
void updateBufferRect(const QLine &line);
void modifyUpdateRect(const QPoint& left, const QPoint& right);
bool sceneEvent(QEvent *event);

private:
QPoint m_firstPoint;
QPoint m_lastPoint;
QPixmap *m_pix;
QRect m_updateRect;
bool m_isPainted;
};@

PaintArea.cpp Qt4
@PaintArea::PaintArea(QDeclarativeItem *parent) :
QDeclarativeItem(parent)
{
setFlag(QGraphicsItem::ItemHasNoContents, false);
setAcceptedMouseButtons(Qt::LeftButton);

m_pix = new QPixmap(1920, 1080);
m_pix->fill(Qt::transparent);

}

PaintArea::~PaintArea()
{
delete m_pix;
}

void PaintArea::paint(QPainter *p, const QStyleOptionGraphicsItem *s, QWidget *w)
{
p->drawPixmap(m_updateRect, *m_pix, m_updateRect);
m_isPainted = true;
}

void PaintArea::mousePress(QGraphicsSceneMouseEvent *mev)
{
m_isPainted = false;
m_firstPoint = m_lastPoint = mev->pos().toPoint();
}

void PaintArea::mouseMove(QGraphicsSceneMouseEvent *mev)
{
m_firstPoint = m_lastPoint;
m_lastPoint = mev->pos().toPoint();

QPoint topLeft = m_firstPoint;
QPoint bottomRight = m_lastPoint;

if (topLeft.x() > bottomRight.x()){
    int temp = topLeft.x();
    topLeft.setX(bottomRight.x());
    bottomRight.setX(temp);
}
if (topLeft.y() > bottomRight.y()){
    int temp = topLeft.y();
    topLeft.setY(bottomRight.y());
    bottomRight.setY(temp);
}

QPainter p(m_pix);
p.setPen(QPen(QBrush(Qt::red), 3));
p.setRenderHint(QPainter::Antialiasing);
p.drawLine(m_firstPoint, m_lastPoint);

if (m_isPainted)
    m_updateRect = QRect(topLeft, bottomRight);
else
    m_updateRect |= QRect(topLeft, bottomRight);

m_isPainted = false;

update(m_updateRect.adjusted(2, 2, -2, -2));

}

bool PaintArea::sceneEvent(QEvent *event)
{
switch(event->type())
{
case QEvent::GraphicsSceneMouseDoubleClick:
break;
case QEvent::GraphicsSceneMousePress:
mousePress(dynamic_cast<QGraphicsSceneMouseEvent *>(event));
event->accept();
return true;
break;
case QEvent::GraphicsSceneMouseMove:
mouseMove(dynamic_cast<QGraphicsSceneMouseEvent *>(event));
break;
default:
return QDeclarativeItem::event(event);
}
return false;
}@

I use it in QML. And performance in QML 1 is great.
But when I've migrated to Qt5 performance decreased significantly (a lot of angles in my line)

PaintArea.h Qt5
@class PaintArea : public QQuickPaintedItem
{
Q_OBJECT
public:
explicit PaintArea(QQuickItem *parent = 0);

void paint(QPainter *p);

void mousePressEvent(QMouseEvent *mev);
void mouseMoveEvent(QMouseEvent *mev);

private:
QPoint m_firstPoint;
QPoint m_lastPoint;
QPixmap *m_pix;
QRect m_updateRect;
bool m_isPainted;
};@

PaintArea.cpp Qt5
@PaintArea::PaintArea(QQuickItem *parent) :
QQuickPaintedItem(parent)
{
setAcceptedMouseButtons(Qt::LeftButton);

setRenderTarget(FramebufferObject);
m_pix = new QPixmap(1920, 1080);
m_pix->fill(Qt::transparent);

}

void PaintArea::paint(QPainter *p)
{
p->drawPixmap(m_updateRect, *m_pix, m_updateRect);
m_isPainted = true;
}

void PaintArea::mousePressEvent(QMouseEvent *mev)
{
m_isPainted = false;
m_firstPoint = m_lastPoint = mev->pos();
}

void PaintArea::mouseMoveEvent(QMouseEvent *mev)
{

m_firstPoint = m_lastPoint;
m_lastPoint = mev->pos();

QPoint topLeft = m_firstPoint;
QPoint bottomRight = m_lastPoint;

if (topLeft.x() > bottomRight.x()){
    int temp = topLeft.x();
    topLeft.setX(bottomRight.x());
    bottomRight.setX(temp);
}
if (topLeft.y() > bottomRight.y()){
    int temp = topLeft.y();
    topLeft.setY(bottomRight.y());
    bottomRight.setY(temp);
}

QPainter p(m_pix);
p.setPen(QPen(QBrush(Qt::red), 3));
p.setRenderHint(QPainter::Antialiasing);
p.drawLine(m_firstPoint, m_lastPoint);

topLeft -= QPoint(4, 4);
bottomRight += QPoint(4, 4);

if (m_isPainted)
    m_updateRect = QRect(topLeft, bottomRight);
else
    m_updateRect |= QRect(topLeft, bottomRight);

m_isPainted = false;

update(m_updateRect);

}@

Someone said me that QML 2 repaint ALL QQuickView area and when it paints the main thread is frozen and miss MouseEvents... Is it true? How to avoid this?
How to increase performance on Qt5?

PS. I've tried to use acceleration:
@qputenv("QML_FORCE_THREADED_RENDERER", "1");
qputenv("QT_QPA_EGLFS_FORCEVSYNC", "1");@

but it lags too (