What you call "falling labels" is simply an inverted y axis, with an interval, where its min/max values are increasing by time. This is not that different to what you can see in the cpuplot example - beside, that it is a horizontal axis.
To change the range of an axis all you have to do is calling QwtPlot::setAxisScale and I really don't get why you consider this as being "deep knowledge".

Uwe