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Thread: QwtPlotShapeItem does not display line shapes (height or width = 0)

  1. #1
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    Default QwtPlotShapeItem does not display line shapes (height or width = 0)

    Hello,
    we use the class QwtPlotShapeItem to display various shapes on a canvas. One shape is a QPainterPath with only one start and one end point. Once the start and end point
    lies either on a vertical or horizontal line, the shape is not displayed any more. The most obvious reason for this might be in the method QwtPlotShapeItem::draw (line 379 in qwt_plot_shapeitem.cpp):

    The command
    Qt Code:
    1. d_data->boundingRect.intersects( cRect )
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    returns false, since
    Qt Code:
    1. d_data->boundingRect
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    has either a width or height of 0.000.
    Then the intersects command of Qt returns false and no line is drawn. Is it possible to change this code to allows such shapes? One workaround might also be to create
    a bounding box with a width or height slightly bigger than zero. Or is it not desired to print such shapes using this class? What is the right way then?

    Thanks in advance.

    Cheers
    Marc

  2. #2
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    Default Re: QwtPlotShapeItem does not display line shapes (height or width = 0)

    IMO this is just a bug - the intention of the check is to clip away content, that is not in the visible area.
    Please add a bug report at http://sourceforge.net/p/qwt/bugs - I will fix it soon ( next time I'm working on the code ).

    Thanks for reporting,
    Uwe

  3. #3
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    Default Re: QwtPlotShapeItem does not display line shapes (height or width = 0)

    Hi Uwe,

    thanks for the answer. I created the bugfix under https://sourceforge.net/p/qwt/bugs/255/. I also tested a fix in the plots of our open source software itom (http://itom.bitbucket.org) that works. I posted the possible solution in the bug report, too.
    Hopefully, it helps you to easily fix this.

    Thanks
    Marc

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