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pan
10th February 2011, 13:12
Hi,

I need a Qt trending/graph component, which has very low resource consumption (i.e. when a graph is updated over time it does not redraw the entire page, but only the updated section).
I am wondering if anyone knows of and/or has had experience using such packages. Suggests both open-source and paid are welcome.

Thanks.

JohannesMunk
11th February 2011, 02:02
You can have a look at qwt and its QwtPlotDirectPainter. With it you can create an oscilloscope or trending graph, that only plots new data.

This is included as example "oscilloscope" in the qwt-package.

As far as I am aware you won't get a permanent history with this approach though. When the graph is full it needs to erase everything and start from an empty plot, because the directpainter has no means to "overplot".

If you need to keep a history visible at all times, you will have to let go of only plotting new data, but qwt offers methods to subsample the curves to make plotting faster.

Joh

ChrisW67
11th February 2011, 02:02
Have you looked at Qwt?

D'oh! Pipped at the post :)

pan
11th February 2011, 09:18
Thanks for the replies. Yes Qwt is on the table for review, good to know where to look in there.
No one used anything else?