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Thread: QwtDial and QThread

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    Default QwtDial and QThread

    Hi,

    I want to use QwtDial with QThread. it mean that i call setValue in the run() of QThread. but somtimes it crashes.

    Please any idea?

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    Default Re: QwtDial and QThread

    That class name sounds like a widget, only the main thread (the one executing QApplication::exec()) is allowed to work with widgets.

    If setValue() is a slot then you can call it through a cross-thread signal/slot connection, i.e. doing any data processing in the worker thread and the painting in the main thread

    Cheers,
    _

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    Default Re: QwtDial and QThread

    i don't understand. This my function run :

    void CSpeedoMeter::Tracer(unsigned char* pPacket)
    {
    while(m_bStart)
    {

    m_dValue = *(double*) (pPacket+m_XVoie.iPositionDataTraite);
    setValue(m_dValue);
    }

    }

    and i must call setValue() in thread.

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    Default Re: QwtDial and QThread

    QwtDial:setValue() is a function on the widget object that exists in the main (UI) thread (assuming the dial is visible). You cannot safely call this function directly from another thread (through a pointer to the widget for example).

    QwtDial:setValue() is also declared as a slot. You can have a QObject in the other thread emit a signal that you connect to the slot in the object in the main (UI) thread.

    The widget cannot exist in the secondary thread as your code snippet suggests it does.

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