Quote Originally Posted by Spitfire View Post
You didn't say which Qwt you're using and that's quite imrpotant.

On Windows I've noticed significant difference between Qwt 6.x.x and 5.x.x where latter is faster.
It was discussed on the forum.

In the end I've managed to plot 5 milion points in less than 150ms.
You can't rely on Qwt to do all the optimizations.
In my case I'm 'compressing' my points to fit width of the screen and draw few hunderd lines instead of milions of points.
No loss in details at all.

Depending on your data you'll have to do something similar, otherwise the speed will degrade as Qwt draws every point every time you redraw, and you can't add/remove points without redrawing the whole thing.

There's few other things you can try to improve speed:
- polygon clipping,
- use Qwt 5.x.x if you're using windows
and few other things I can't remember at the moment :/
How could you compress millions of points to few hundred lines?
could you tell me the data processing method?