QWT and time series

[Neekeetos]

Hi guys!

Im currently trying to use QWT in my application, which is hugely using time series data. I have re-implemented QwtScaleDraw to put dates on x-axis, yet i have problems with graph itself. Problem is that the time points requested by QWT during axis drawing are nowhere near days/hours boundaries and seem fractional , so i can not put time labels because they represent nonexisting points in data( which is hourly ).
Is there any way I can force QWT graph to use day and hour boundaries, like to put major axis labels straight on date 0:00 am , or select axis points among fixed set of possible values ?

I also have some related questions :
- how do i put overlay bar under graph to mark for example selected timespan ( ie day ) ? ( Assuming I have data range and I want to apply it to graph object )
- if I provide a set of ~1000 data points to plot it become slow to rescale. Is there something I missed in plot parameters or it is normal qwt & desktop computer to work like this with datasets of this size? If latter is actual, should i do some data preprocessing to reduce ammount of points or there is some existing soluton, maybe inside qwt?

Thanks in advance!

PS: regarding rescale , i found that it is not dependent on data point count, but related to how it works with splitter adjacent to plot itself. I've attached sample code which shows a problem.
slow_plot.zip

Is it a known issue? does any workaround exist?