refreshtest example: newbie understanding problems

[emigrand]

Hello everyone - thx for reading!

I am working on a plot for an ad-converter. Because I'm new to C++, Qt and Qwt, I am currently studying the refreshtest example to get a clue of how to implement the plot. I think I get most of the code, but the following is not clear to me:

When and by what are these functions called:

QPointF CircularBuffer::sample(size_t i) const
{
    const int size = d_values.size();
 
    int index = d_startIndex + i;
    if ( index >= size )
        index -= size; 
 
    const double x = i * d_step - d_offset - d_interval;
    const double y = d_values.data()[index];
 
    return QPointF(x, y);
}
 
QRectF CircularBuffer::boundingRect() const
{
    return QRectF(-1.0, -d_interval, 2.0, d_interval);
}

QPointF CircularBuffer::sample(size_t i) const
{
    const int size = d_values.size();
    
    int index = d_startIndex + i;
    if ( index >= size )
        index -= size; 

    const double x = i * d_step - d_offset - d_interval;
    const double y = d_values.data()[index];

    return QPointF(x, y);
}

QRectF CircularBuffer::boundingRect() const
{
    return QRectF(-1.0, -d_interval, 2.0, d_interval);
}

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Since this is the Qwt forum, I desisted from posting the whole code of the example. I hope thats fine.


Looking forward for your help!
Emi