One of the drawbacks of QwtPlot is that its API is 
only designed for displaying complete curves. For watching
measurements while they are running, an API for dynamicly growing
curves is necessary. 

As a bonus I added an implementation of advanced stacked zooming.
It shows how to add scrollbars, but well ...

1) Dynamic plots

If a curve consists of too many points a complete replot is much
too slow for incoming data in short intervalls. 
The performance can be seen if you create f.g 100000 points
and zoom in. Appending 10 points in pieces of 1 point will take
10 times of what you saw.
So IncrementalPlot::drawCurveIntervall offers an API to paint
only a set of points. ( This might be a candidate for the qwtlib itsself )
	  
The example produces random data when you push the start button.
With 'Timer' you can adjust the intervall between the
the generation of the points, with 'Points' you can set the number
of points.


2) Stacked Zooming

This is just an example how advanced zooming might look like. You
can zoom in until the zoomed area gets too small for the significance
of the axes labels. You can move up on the stack using the 
middle mouse button and you get the full size using the right button.
This example works only for plots without autoscaling and with
only 2 axis.
