Agressive filtering of many points, SVN trunk, OpenGL

[r2com]

How do I properly apply that property?

Do I have to do it this way?:

curve->setPaintAttribute(QwtPlotCurve::FilterPointsAggressive, true);

curve->setPaintAttribute(QwtPlotCurve::FilterPointsAggressive, true);

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Above code did not make any difference, or am I applying it wrong?

P.S. the reason I'm now trying this is...even with OpenGL zooming IN/OUT is kinda slow...

For example, I created a file x,y with 100 million samples, the MATLAB plotter (which sucks kinda?) has almost same speed(slow speed...) when zooming in/out as my Qwt program utilizing OpenGL, why is that?