I would create an extra QwtPlotPicker for this usecase, where you return false from it eventFilter, when you don't want to forward the event to the zoomer. But this is not necessary to solve your problem.
Here we are back to my previous hint. Translate point and marker position into widget coordinates - then you can use a fixed distance in pixels, regardless of the zoom level.But the way I implement is not picking the line properly when the zoom level is too deep, so normally it works perfectly.
Bookmarks