Qwt 6.0.1 three times slower than 5.2.0

[Spitfire]

I've tested 32bit Windows XP box.

The problem is the same, with 5.2.0 plot is rendered in 1700ms, with 6.0.1 it takes 5600ms.

Let me know if you find anything interesting.
Cheers!

[Uwe]

In SVN trunk ( Qwt 6.1 ) QwtPlotCurve tries to use QPolygon instead of QPolygonF ( depending on various parameters ).

If you don't want to have this optimization you can enable the new flag QwtPlotItem::RenderFloats. Like expected setting this flag slows down the frame rate of the refreshtest example, when using the raster graphics system.

Uwe

[Uwe]

Just one more hint: in Qwt 5.2 was a flag QwtPlotCurve::PaintFiltered that removes points that are mapped to the same position as their predecessor. As long as your samples are not only noise it should have a much bigger impact on the performance than the QPolygon/QPolygonF flag.

I have reintroduced this optimization to Qwt 6.1 ( QwtPlotCurve::FilterPoints ). In situations, where the curve is rendered to an integer based paint engine ( all beside Svg and Pdf ) I would expect, that it will reduce the polygon heavily for a 2 million point series.

You can check the refreshtest example to see its effect.

Uwe