Improve performance at shifting QLineSeries?

HTWAMD

Hey,

I'm using QtCharts and animated the graphs. After having more than 50 values, always the oldest got removed from the series.
Here a short code overview:

        QVector<QPointF> points = m_temperature_series.pointsVector();
        m_temperature_series.clear();
        for (int i=0;i<index;i++)
            m_temperature_series.append(i, points.at(i+1).y());

The class of m_temperature_series is QLineSeries

It's working good but it needs too much performance. With multiple graphs and a long graph history, you have a high cpu usage. But I dont know any way to optimize this code.
I hope someone can help me out here :)

SGaist

Hi,

Why not just remove the first element using takeFirst and then append your new element ?

HTWAMD

TakeFirst is basically a good idea and it removes the first element. The problem is, that the second element at X still have the value 1 and is not decremented to 0.

Edit// Just did a short test with another code... it's working but not sure about the performance

    QLineSeries Test;

    Test.append(0,0);
    Test.append(1,1);
    Test.append(2,2);
    Test.append(3,3);

    QList<QPointF> Points = Test.points();
    Points.removeFirst();

    int counter=0;
    QList<QPointF>::iterator i;
    for (i=Points.begin(); i!=Points.end();i++)
    {
        i->setX(counter);
        counter++;
    }

    Test.clear();
    Test.append(Points);

VRonin

How about using the model-view approach with QVXYModelMapper as shown in the model data example?