QWidgetDemo/third/qwtdemo/examples/realtime

1) Incremental plots

IncrementalPlot shows an example how to implement a plot that
displays growing data. 

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 to be generated.

Unfortunately in Qt4 incremental painting is not possible with QPaintEngines
that doesn't support the QPaintEngine::PaintOutsidePaintEvent feature. 
( These are all common paint engines beside the OpenGL engine, but this one 
is not supported by Qwt yet. )
That is the reason why you can see much faster repaints with Qt3.

2) Stacked Zooming with scrollbars

ScrollZoomer adds scrollbars for zooming. There are a couple of
reasons why the implementation is a hack and therefore the class
is not part of the Qwt lib, but it should be working with all
types of QwtPlots. Copy the code of scrollbar.[h|cpp] and 
scrollzoomer.[h|cpp] to the application code.

Uwe