CPU Load with Qt Quick much higher than with Qt Widget



  • Hello,

    On my embedded system with Linux Kernel OS I've tested a Qt Quick Application and a Qt Widget Application. Both only with one Window. Moving only the mouse with a normal speed there is a very big difference for CPU load.

    For Qt Quick it's much higher than for Qt Widget. It can be 21 % vs. 7 %.

    Has somebody an idea what's the cause could be ? Is there another mechanism for rendering the mouse cursor ? I don' t know..

    Thanks.

    Best regards

    snoopy


  • Moderators

    @Snoopy That doesn't surprise me much. QML is doing a lot more under the scenes than a C++ Widget would do.

    It could also be something you're doing in your QML. Here is a nice write up on QML performance and how to optimize your controls:

    http://doc.qt.io/qt-5/qtquick-performance.html



  • @ambershark okay. Thanks for the info.
    But one more question because we want to use Qt Quick:
    Would be CPU load for touch gesture the same how it is for using the mouse ? Or is that another mechansim again ?
    At the moment we can't test this because the display with touch we will get later.

    Best regards

    snoopy


  • Moderators

    @Snoopy I'm not sure. It would be easy to test, but I don't have the setup necessary for a quick test.

    My guess is that it will not do that on a touch device, but I could be wrong. It could be flooding signals or something "onMouseDown" that is causing it. Which could be something that happens with "onFingerDown" or similar.


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