QwtPlotMarker performance limits

[<Edw...@gt...>]

Hi Uwe and others,

Our application uses Qt 4.6+, Qwt 5.2 and subclasses QWidget and QwtPlotMarker to draw custom markers hooked into Qt events, slots etc. within a scatter (well, bubble) plot.  As our datasets have gotten bigger, we've run into some performance issues with this approach a la:  http://comments.gmane.org/gmane.comp.graphics.qwt.general/2813

Water under the bridge, unfortunately, so I'm mostly concerned right now with a few things:

+ any ideas what makes plot markers perform so much worse than curves?  In some simple tests, just attaching the markers is pretty fast (1000s/sec) up to about 50K points then slows down dramatically (~100-150 adds/sec).  After adding, rendering is fine up to 1000s of markers, but slows down >10K and starts segfaulting on >40K markers.  These "tests" were done over a remote X11 session to my win32 X server, however.

+ our custom marker class encodes data using the symbol size and color, responds to mouse click and hover events, and has a Qt context menu attached to it as well.  Given the post referenced above and our requirements, can we use QwtPlotSpectroCurve (or QwtPlotCurve) to generate large sets of points with *varying-size* symbols?  My glance at the API docs don't indicate a good way to do this with either Plot[Spectro]Curve class?

+ Performance-wise, how are curves:  can we use 1 curve (of either type) to replace all (100K+) markers, or divide them up into series with X=??? points apiece?

+ The QwtPolar page states its "corresponding" Qwt version is 5.2--does that mean is currently works or doesn't with 6.0?

Thanks,

Ed