Qwt minimize drawing part

[lamle]

Hi all,
I am concerning about optimization when redrawing of qwt plot.
A Qwtplot has a QwtPlotItem attached. When there is new data, calling plot.replot() will redraw everything including QwtScale. Is there anyway to call QwtPlotItem to update only when there is new data to avoid the rest to update (because my QwtScale is static all the time). Caching pixmap is one solution but it is a redraw anyway.
This can be apply to barchart, xy plot, qwtDial, etc.

[Spitfire]

Time it takes to blit cached pixmap to the screen is insignificant when it comes to performance.
Redrawing the scales shouldn't be a bottleneck either.

Btw do you know rules of premature optimization?
Rule 1 : Don't optimize!
Rule 2 : Don't optimize jet!

I'm guessing that rule 1 applies here