Qwt canvas using QGLWidget?

[Uwe]

Is it possible to use Qwt on top of QGLWidget?

No.

Some time ago I played with an OpenGL plot canvas and for a couple of situations things were faster, for others it was slower. The main reason for this surprising result was that in combination with OpenGL the canvas got only update requests for its complete size ( also incremental painting is not possible at all. ) But this is a couple of years ago - maybe things have improved since then.

I decided to implement an optional OpenGL canvas not before Qt3 support has been dropped. So it is on my TODO list now - but not for Qwt 6.0 anymore.

Since QwtPlotCanvas serves as a QPainter for all the plot items, maybe it would be possible to use QGLWidget in there somewhere?

The plot canvas itsself is no problem at all - it's more about organizing its backing store ( paint cache ), that can't be a QPixmap then.

I'm asking because our custom plot items are rendering quite slowly, and maybe (I'm not sure, but just maybe) GL-based rendering would be faster?

I don't know about your plot items, but in general it's more effective to avoid painting instead of trying to accelerate it. Often weeding and clipping or other optimizations for your specific situation are more important.

When you are talking about raster items with a certain resolution almost all time should be lost in the image composition ( that needs to be done by the CPU ). Here using OpenGL would have no notable effect at all - better try to improve the image composition.

Uwe