In my project I have to draw a line with mouse.
To do this I have take some code slice from event_filter example in qwt source dir.
It works quite well if the window is "little", but it become too slow if I maximize the windows.
This issue is present also in the event_filter example, I have also have a screencast.
I hope it is not an issue of qwt, and I wonder how to speed up it

best regards
Max