[Solved] Performance QLabel



  • I'm trying to test the performance of the text drawing of Qt.

    In our application we need to update up to 10 values around every 200 ms.
    Therefore I created a test application which consists of 32 Labels aligned in a GridLayout (which is set to the central widget of the main window). They are updated with random values every 200 ms.

    @
    QTimer *timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(UpdateLabel()));
    timer->start(200);
    @

    @
    void MainWindow::UpdateLabel()
    {
    m_poLabel1->setText(QString("%1").arg(rand()));
    //....
    }
    @

    Now the CPU loads seem to be quite high, when I draw it with OpenGL, it the CPU 1 load is around 20, the CPU 2 load is around 35.
    When drawing it with the raster engine, the CPU 1 load is around 10, the CPU 2 load is around 45.

    I replaced the QLabels with an own widget which holds a QStaticText (even though it says in the documentation that this should be used when the text and its layout is updated rarely). But the CPU 1 load is around 17 and the CPU 2 load is around 25.

    Now I wanted to know if there is a way of improving the performance of the drawing of the texts?

    If you need some further information or more code please tell me.



  • May be each change of labels text invoke recalculation positions of all other QLabels, because GridLayout adjust cells width.
    Try to set fixed size of QLabel's



  • That improved the performance a lot. Thank you!


Log in to reply
 

Looks like your connection to Qt Forum was lost, please wait while we try to reconnect.