How to avoid linking both ends of a Curve Plot

[Uwe]

You could inherit from QwtSeriesData. Inside you would have an array of points and a start index. When a new point arrives you simply replace the point at the index and increment the index.
Then all you have to do is to reimplement the sample method in a way, that the start index is taken into count.

Or something similar along this idea

HTH,
Uwe