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Thread: QwtPlotItem inverting qwtPlot scale

  1. #1
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    Default QwtPlotItem inverting qwtPlot scale

    Hi,

    I have a weird problem where the y-axis will become inverted whenever I do a zoomBase from QwtPlotZoomer. The problem comes from the yMap's d_s1 and d_s2 values being inverted in my virtual void draw() function in my derived QwtPlotItem:

    Qt Code:
    1. class CanvasPicture: public QwtPlotItem
    2. {
    3. public:
    4. virtual void draw(QPainter *painter,
    5. const QwtScaleMap &xMap, const QwtScaleMap &yMap,
    6. const QRect &rect) const
    7. {
    8. }
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    I put a break point in this draw function, and each time I zoomBase on the qwtPlot, I see the d_s1 and d_s2 values for yMap inverting each time (-10,10) to (10,-10) to (-10,10) etc.

    My question is what would cause the yMap's scale intervals to be inverted each time draw() is being called? None of my setAxisScale() functions are being called whenever i do a zoomBase, so that's not the one that's inverting the scales.

    Thank you
    Last edited by jmsbc; 11th August 2009 at 22:31.

  2. #2
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    Default Re: QwtPlotItem inverting qwtPlot scale

    Quote Originally Posted by jmsbc View Post
    My question is what would cause the yMap's scale intervals to be inverted each time draw() is being called?
    Maybe autoscaling triggered from the replot ?

    Uwe

    PS: Are you aware of QwtScaleEngine::Inverted ?

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