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QGLWidget performance issues



  • Good day!

    I have an old cross-platform application which has a Qt GUI, originally written using Qt4, after several years been neglected it was ported to Qt5.

    Some our users report that qt5 builds are slower that builds that use native windows GUI: qt version has lags, on scenes with a lot of objects it has much lower fps (35 vs 60).

    Unfortunately I'm new both to GL & Qt5, so I'm seeking for help what direction to move to find the root cause of that performance issues.

    P.S. Why not QOpenGLWidget - we tried to use it, but faced a lot of other bugs in fullscreen mode.



  • @375gnu said in QGLWidget performance issues:

    Some our users report that qt5 builds are slower that builds that use native windows GUI:

    If this is the case then it's not a Qt cross-platform application, is it? Please restate your question. What exactly are you comparing, and what are you expecting?



  • Our application uses different frontends (gtk+, qt5, native win32), qt frontend was started as with intent to eliminate all "native" GUIs and replace them with one common for all OSes.

    I'm comparing FPS in windows builds, one is "native" and another is qt5. Qt5 version has lower fps and lags in response to user actions.



  • most likely someone not doing the new interface "the qt way", but intead simply trying to translate the old UI code on a one-to-one basis.

    Also, build times are irrelevant. That was my point of confusion.

    You should

    1. make sure the the cross-platform Qt UI is well designed, using the Qt framework correctly
    2. test response on mutiple platforms (windoze, linx, mac-os) and see if the problem is platform specific
    3. understand that if you are using Qt on windoze under cygwin then you shouldn't expect screaming performance. You don't mention whether you are paying for the commercial Qt under windoze (which bypasses cygwin)

  • Qt Champions 2019

    @kent-dorfman said in QGLWidget performance issues:

    commercial Qt under windoze (which bypasses cygwin)

    You don't need a commercial license for Qt on Windows to not to depend on Cygvin. Qt on Windows is provided with Microsoft compiler and MinGW support as open source (LGPLv3) without any Cygvin dependencies. And the OP didn't mention Cygvin anywhere as far as I can see.



  • @jsulm said in QGLWidget performance issues:

    You don't need a commercial license for Qt on Windows to not to depend on Cygvin.

    Once upon a time it was a requirement for the OS version in windoze.


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