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Thread: Problems with vanishing ticks

  1. #1
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    Default Problems with vanishing ticks

    Hello,

    the following images describe the problem better than I could with words. In the first image, there is some data displayed. The last data point has an x value of 20.

    Image1.png

    The second image shows the same data, just shifted one pixel to the right.

    Image2.png

    As you can see, the tick with the "20" disappeared completly and leaves a blank space, although there is more than enough space apparently.

    I am aware of the method QwtScaleEngine::setAttribute and we set the "Floating" attribute to true. Still the tick at the end disappears. I also checked the methods QwtScaleWidget::setMinBorderDist and QwtScaleWidget::setBorderDist and set all values to 0 (I tried even negative numbers), but it did not help at all.

    We are using Qt 5.12 and Qwt 6.1.3.

    Has anyone a solution for the problem?

  2. #2
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    Default Re: Problems with vanishing ticks

    QwtPlot does not offer scales, where the ticks go inwards - so this is probably custom code.

    Uwe
    Last edited by Uwe; 3rd October 2019 at 14:18.

  3. #3
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    Default Re: Problems with vanishing ticks

    Quote Originally Posted by Uwe View Post
    QwtPlot does not offer scales, where the ticks go inwards - so this is probably custom code.

    Uwe
    While it is true, that we customized some parts of the QwtPlot, the inside ticks are created with means from the qwt library only. We simply created a QwtPlotScaleItem with the opposite alignment for each axis (e.g. QwtScaleDraw::RightScale for QwtPlot::yLeft). Other features (like QwtScaleEngine) were not customized. So the positioning and visibility of the ticks are still calculated by the qwt engine.

  4. #4
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    Default Re: Problems with vanishing ticks

    Quote Originally Posted by mwh View Post
    We simply created a QwtPlotScaleItem with the opposite alignment for each axis (e.g. QwtScaleDraw::RightScale for QwtPlot::yLeft).
    And how is your scale item connected to which scale engine ?

    Uwe

  5. #5
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    Default Re: Problems with vanishing ticks

    Quote Originally Posted by Uwe View Post
    And how is your scale item connected to which scale engine ?

    Uwe
    Like this:

    Qt Code:
    1. // This code is taken from your example code in the documention of QwtPlotScaleItem
    2. auto scaleItem = new QwtPlotScaleItem(QwtScaleDraw::TopScale, 0.0);
    3. scaleItem->setFont(plot->axisWidget(QwtPlot::xBottom)->font());
    4. // This is the customized part
    5. scaleItem->setXAxis(QwtPlot::xBottom);
    6. scaleItem->setScaleDivFromAxis(true);
    7. // This is from your documentation again
    8. scaleItem->attach(plot);
    To copy to clipboard, switch view to plain text mode 

    According to your documentation the setSCaleDivFromAxis method synchronizes the scale item with the corresponding axis. Am I missing anything?

  6. #6
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    Default Re: Problems with vanishing ticks

    O.k. so you are using a scale item, that is fed by the scale engine of the bottom scale, but you gave no information about how this one is set up.
    Maybe it makes more sense, that you upload a small compilable tarball demonstrating the problem.

    Uwe

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