Two fill colors in QwtPlotCurve

Hi,

Is it possible to have two different fill colors in QwtPlotCurve ? I am 
writing a seismogram plot and the convention there is to have two 
different fill colors for positive and negative values (f.ex. fill black 
for values above baseline and white for those below).
I have used two overlapping curves and it looks kind of ok but sometimes 
I get some artifacts which I guess are caused by the two curves not 
fully overlapping for certain sizes of the widget as well as having to 
allocate twice the amount of memory.

Thanks in advance,

Kamran

-------------------------------------------------------------------------
This SF.net email is sponsored by the 2008 JavaOne(SM) Conference 
Don't miss this year's exciting event. There's still time to save $100. 
Use priority code J8TL2D2. 
http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone