Restricting cursor movement (or appearance) to follow only the curve

[Uwe]

I'm not sure what you mean in 3).
Are you talking about mouse cursor and restricting it's movement?

It should be about the rubber band of the picker.

Now the difficult part: you can't use QwtPlot facilities to get curve Y value at cetain X (at least I don't know how).

Read also: http://www.qtcentre.org/threads/4505...point-of-curve

Uwe