recalculate lables in QwtScaleDraw

[tavla]

hello.

I have a source of data that is displayed in real time. the x-axis is current coordinate and it varies randomly (depending on the speed and direction). so for chart on the x-axis I'm using the current number of points, and replace it when displayed on the coordinate in QwtScaleDraw:

// in QwtPlotCurve *pcd I fill data:
for (int i = 0; (i < data.length); i++){
    xAlias[i] = i;
    x[i] = data_x[i];
    y[i] = data_y[i];
}
setSamples(xAlias, y, data.length);
 
// in QwtScaleDraw I take real value by alias:
QwtText myQwtScaleDraw::label(double v) const
{
    return QString("%1").arg(pcd->x[((int)v)]);
}
 
// in main Widget:
myPlot->setAxisScale(QwtPlot::xBottom, 0, data.length, 0);
myPlot->replot();

// in QwtPlotCurve *pcd I fill data:
for (int i = 0; (i < data.length); i++){
    xAlias[i] = i;
    x[i] = data_x[i];
    y[i] = data_y[i];
}
setSamples(xAlias, y, data.length);

// in QwtScaleDraw I take real value by alias:
QwtText myQwtScaleDraw::label(double v) const
{
    return QString("%1").arg(pcd->x[((int)v)]);
}

// in main Widget:
myPlot->setAxisScale(QwtPlot::xBottom, 0, data.length, 0);
myPlot->replot();

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but this only works if there is a change of xAlias[]. if I change the array x referenced by the xAlias, repainting occurs.
how to make a graph to be redrawn manually?
myPlot->repaint(), myPlot->update(), myPlot->axisWidget( QwtPlot::xBottom )->update(); does not work too.

Thanks in advance.