Double Buffering for plot graphs

[Tavit]

Hi,
I new to Qt tool.I have written a program to plot a graph using double Buffer concept.I got the plot graph.But i have problem with this Function.
That name is adjust Axis();

void PlotSettings::adjustAxis(double &min, double &max,
                              int &numTicks)
{
    const int MinTicks = 4;
    double grossStep = (max - min) / MinTicks;
    double step = pow(10.0, floor(log10(grossStep)));
 
    if (5 * step < grossStep) {
        step *= 5;
    } else if (2 * step < grossStep) {
        step *= 2;
    }
 
    numTicks = int(ceil(max / step) - floor(min / step));
    if (numTicks < MinTicks)
        numTicks = MinTicks;
    min = floor(min / step) * step;
    max = ceil(max / step) * step;
}

void PlotSettings::adjustAxis(double &min, double &max,
                              int &numTicks)
{
    const int MinTicks = 4;
    double grossStep = (max - min) / MinTicks;
    double step = pow(10.0, floor(log10(grossStep)));

    if (5 * step < grossStep) {
        step *= 5;
    } else if (2 * step < grossStep) {
        step *= 2;
    }

    numTicks = int(ceil(max / step) - floor(min / step));
    if (numTicks < MinTicks)
        numTicks = MinTicks;
    min = floor(min / step) * step;
    max = ceil(max / step) * step;
}

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i copied this code from QT Gui programming Book.How it works i didn't understand.So could you tell me brief discussion About...
Thank you......



Regards,
Tavit.