How to temporarily disable a redraw of one of the curves

[ttvo]

I have a QwtPlot that contains a QwtPlotCurve and one or many custom QwtPlotItem. The QwtPlotCurve can be big in size. I have a custom QwtData to store the values as float instead of double.

Quite often, the QwtPlotCurve doesn't change once created. How can I override QwtPlot::drawItems(...) to disable the re-plotting of the huge QwtPlotItem when I only changed my custom QwtPlotItems? Thanks.

[Uwe]

A paint event clears the canvas and repaints it completely. So you can't skip painting of an item.

What you can do is to render your curve to a image with a transparent background, or to introduce a paint cache ( pixmap ) for items with z values below a certain limit.

Uwe

[ttvo]

Could you elaborate on the two options, perhaps with some code snippet? Thanks.