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Thread: Cuting the Qwt curve and deleting previous curve part by part

  1. #1
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    Default Cuting the Qwt curve and deleting previous curve part by part

    Hello!

    I'm using Qwt to plot a curve in a ECG-style. In other words, the curve is ploted from X=0 to X=1000 (example) and when the X=1000 is recognized, it should come back to X=0 and plot from there once again.

    Now just that I know how to do. The problem is that in the way that I know how to do it, two problems arise: first, the "come back plotting" is connected by a line stead of really starting once again. In other words, the new ploting in X=0 is is connected by a horizontal line to the end of the ploting, in X=1000:
    Captura_de_tela.jpg

    Not just that: in order to continue ploting in the end of the graph, I need to continuously erase, point by point, the previous line ploted. Is not good to erase everything and being once again; the erasing process must be at the same speed of the new plot.

    Does somebody knows how to do that?

    Thanks!

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    Default Re: Cuting the Qwt curve and deleting previous curve part by part

    You can draw something on top of an existing plot ( QwtPlotDirectPainter f.e. used in the oscilloscope example), but when you have to erase something you have to replot.

    Check the refreshtest example about the performance of your system first.

    Uwe

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    Default Re: Cuting the Qwt curve and deleting previous curve part by part

    Quote Originally Posted by Uwe View Post
    You can draw something on top of an existing plot ( QwtPlotDirectPainter f.e. used in the oscilloscope example), but when you have to erase something you have to replot.

    Check the refreshtest example about the performance of your system first.

    Uwe
    Sorry Uwe, but I was incapable of understanding what I should do. I look to the oscilloscope example and I didn't understand what the QwtPlotDirectPainter do there. Same thing with the refreshtest example; I didn't understand in which place there is a code that can help me with what I should do.

    Could you please enter in more details?


    Thanks!

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