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Thread: Weird issue with QProgressBar

  1. #1
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    Default Weird issue with QProgressBar

    Hello everyone,
    I’m currently having a very weird issue with QProgressBar when displaying then in “busy mode” (when maximum and minimum are set to 0). Sometimes the bar will stay at the beginning of the and act kind of like a normal progress bar that stops after a very short distance (kinda hard to describe) and resets continually. The normal comportment would be of a fixed length and would move along the progress bar continually. After many tests and looking at the code for a long time, I haven’t been able to isolate a cause (either from Qt or somewhere in my code). There are two elements to know though about this problem:

    1. It only happens on linux, and on a very specific distribution of linux (we are using a custom version made with linuxfromscratch). The bug is not reproduced on XFCE, for example.
    2. The Qt version used is 4.8.0. It is not an option to upgrade the Qt version at this time because it requires tons of work. The immediate goal is either to fix the bug or to find a workaround.

    My question is basically : is there a known bug that causes this type of behaviour? I know there were issues with the progress bar in Qt 4.7 but this seems to have been fixed. I have also seen some forum posts about similar issues but there doesn’t seem to be any bug on this on the bugtracker.

    Thanks

  2. #2
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    Default Re: Weird issue with QProgressBar

    Make sure to try with a different widget style, just in case it is a bug in the style rather than QProgressBar

    Cheers,
    _

  3. #3
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    Default Re: Weird issue with QProgressBar

    We are actually using a custom stylesheet and i've tried using it with or without this stylesheet and the bug happened either way. I suppose if we're using custom stylesheets the style shouldn't matter, right? I'm not exactly sure how style works but I assumed that style sheets were kind of overriding them.

  4. #4
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    Default Re: Weird issue with QProgressBar

    No, stylesheets customize certain visualisation aspects, a style can include all kinds of code for interaction handling or animations.
    If there is some problem with widget drawing it is always good to test with different styles to either verify or falsify that it is a style issue.

    Cheers,
    _

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