[Development] FW: how to improve GraphicsView performance

[song.7.liu at nokia.com]

Hi,

FYI. Can someone help us here ? thanks very much ;)

Thanks,
Song

From: Jiang Wenjun (Nokia-MP/Beijing)
Sent: Tuesday, August 21, 2012 4:21 PM
To: Liu Song.7 (Nokia-MP/Beijing)
Subject: FW: how to improve GraphicsView performance
Importance: High


Hi, all

I'm using QGraphicsView to implement google weather in a low-end(CPU: 300MHz) hardware. All are nice except the performance.
When I set the position of the GraphicsItems, the refresh rate is quite slow. Code about item moving is here.

void GraphicsView::mouseMoveEvent(QMouseEvent *event)
{
    QPoint current_pos = event->pos();
    int deltaY = current_pos.y() - m_lastPos.y();
    int current_weatherY = m_currentweatherwidget->pos().y();
    if ((current_weatherY + deltaY > -320) && (current_weatherY + deltaY <= 0))
    {
        m_currentweatherwidget->setY(current_weatherY + deltaY);
        int forecast_weatherY = m_forecastweatherwidget->pos().y();
        m_forecastweatherwidget->setY(forecast_weatherY+deltaY);
    }
    m_lastPos = event->pos();
event->accept();
}

I tried many methods to optimize the performance, all seem no effect, including:

1.       setCacheMode(QGraphicsView::CacheBackground)

2.       scene->setItemIndexMethod(QGraphicsScene::NoIndex)

3.       setViewportUpdateMode(QGraphicsView::BoundingRectViewportUpdate);

4.       setOptimizationFlags(QGraphicsView::DontAdjustForAntialiasing | QGraphicsView::DontSavePainterState | QGraphicsView::DontClipPainter);

5.       QGraphicsItem::setCacheMode(QGraphicsItem::DeviceCoordinateCache) ...

Is there any other idea? Thanks!
Best regards!
-Jiang wenjun

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