QwtPlotCurve realtime efficiency tips

[Vikram.Saralaya]

Hello,

• I have a QwtPlotCurve (say 5000 points) that is placed in a QwtPlot with axis auto scaling enabled.
• The points keep entering a circular buffer continuously and every 20ms I need to plot the latest say 5000 points in the buffer.
• Since I need to accurately auto-scale I need an iteration over all the 5000 points to calculate the bounding rectangle.

I managed to implement these but I see that its not efficient (small lag in the UI).

My question is: I would like to make it as efficient as possible. Some tips on these lines is much appreciated!
Thanks

Regards
Vikram

[Uwe]

If your series is time related I can imagine, that one dimension is increasing and min/max are the first/last coordinate. But for the other coordinate you have to iterate.
But if this loop isn't implemented in a horrible way it shouldn't be responsible for the lag you have noticed.

But a cycle of 20ms is also not necessary - even visual animations usually run at 40 fps only.

Uwe

[Vikram.Saralaya]

Hello Uwe,

Yes the x axis is the time axis. As for the y axis, I will reduce the frame rate eventually but now I am testing the limits..

I haven't done much optimization other than enabling cliprectangle and filtering. Is some kind of a buffering/overlay useful for this kind of an application?

Regards
Vikram