Fading out a QLabel



  • Hi

    While searching the web I found many hints on this. However, I don't get what I am doing wrong. My code compiles without error but crashes at runtime.

    void QTGUI_MainWindow::ShowAndFadeLivePauseInfo()
    {
    qDebug() << "Start of FadeOut .. turn on";
    
      QGraphicsOpacityEffect *effect = new QGraphicsOpacityEffect(ui->lblLivePause);
      ui->lblLivePause->setGraphicsEffect(effect);
      QPropertyAnimation* animation = new QPropertyAnimation(effect, "opacity");
      animation->setDuration(LP_FADEOUT_DURATION);
      animation->setStartValue(1.0);
      animation->setEndValue(0.0);
      animation->setEasingCurve(QEasingCurve::OutQuad);
      connect(animation,SIGNAL(finished()),this,SLOT(FadeLivePauseInfoEnded()));
      animation->start(QAbstractAnimation::DeleteWhenStopped);
      ui->lblLivePause->show();
    }
    

    What did I miss?
    Thanks
    McL



  • Hi, I made a FadingLabel to use where I need it.
    You can see my Class below, hope this helps.

    fadinglabel.h

    #ifndef FADINGLABEL_H
    #define FADINGLABEL_H
    #include <QLabel>
    #include <QGraphicsOpacityEffect>
    #include <QPropertyAnimation>
    #include <QEasingCurve>
    class FadingLabel : public QLabel
    {
    public:
        FadingLabel(QWidget *parent=0);
        void startFading(int num_fade=-1);
        ~FadingLabel();
        void setFadingOptions(int duration_msec, int interval_msec, QEasingCurve curve_type);
        void setDisabled();
    private:
        QGraphicsOpacityEffect *m_opacityEffect;
        QPropertyAnimation *m_opacityAnimation;
        int m_fadingTimer;
        void timerEvent(QTimerEvent *e);
        int m_durationMsec;
        int m_intervalMsec;
        QEasingCurve m_curveType;
        void fade();
        bool m_from0to1;
        int m_numFade;
        int m_executedFade;
    private slots:
        void fadingFinished();
    };
    #endif // FADINGLABEL_H
    

    fadinglabel.cpp

    #include "fadinglabel.h"
    #include <QTimerEvent>
    #include <QTimer>
    
    FadingLabel::FadingLabel(QWidget *parent) :
        QLabel(parent)
    {
        m_executedFade =0;
        m_opacityAnimation = new QPropertyAnimation(this);
        m_opacityEffect= new QGraphicsOpacityEffect(this);
        m_opacityEffect->setOpacity(0.2);
        this->setGraphicsEffect(m_opacityEffect);
        m_opacityAnimation->setTargetObject(m_opacityEffect);
        m_opacityAnimation->setPropertyName("opacity");
    
        m_from0to1 = true;
        connect(m_opacityAnimation, &QPropertyAnimation::finished, this, &FadingLabel::fadingFinished);
    }
    
    void FadingLabel::setFadingOptions(int duration_msec, int interval_msec, QEasingCurve curve_type)
    {
        m_durationMsec = duration_msec;
        m_intervalMsec = interval_msec;
        m_curveType = curve_type;
    
        m_opacityAnimation->setDuration(m_durationMsec);
        m_opacityAnimation->setEasingCurve(m_curveType);
    }
    
    void FadingLabel::setDisabled()
    {
        killTimer(m_fadingTimer);
        m_opacityAnimation->stop();
        m_opacityEffect->setOpacity(0.2);    
    }
    
    void FadingLabel::startFading(int num_fade)
    {
        m_numFade = num_fade;
        m_fadingTimer = startTimer(m_intervalMsec);
        m_from0to1 = true;
        fade();
    }
    
    FadingLabel::~FadingLabel()
    {
    
    }
    
    void FadingLabel::timerEvent(QTimerEvent *e)
    {
        if(e->timerId() == m_fadingTimer)
            fade();
    }
    
    void FadingLabel::fade()
    {
        if(m_from0to1)
        {
            m_opacityEffect->setOpacity(0);
            m_opacityAnimation->setStartValue(0);
            m_opacityAnimation->setEndValue(1.0);
            m_from0to1 = false;
        }
        else
        {
            m_opacityEffect->setOpacity(1.0);
            m_opacityAnimation->setStartValue(1.0);
            m_opacityAnimation->setEndValue(0);
            m_from0to1 = true;
        }
        m_opacityAnimation->start();
    }
    
    void FadingLabel::fadingFinished()
    {
        if(m_from0to1)
            fade();
        else
        {
            if(m_numFade!=-1)
            {
                m_executedFade++;
                if(m_executedFade>=m_numFade)
                {
                    killTimer(m_fadingTimer);
                    m_executedFade=0;
                }
            }
        }
    }
    

    Let me know.

    Luca



  • Hi Luca,

    Thanks. I'll have a look at it and maybe implement it as a class with some modifications.
    However, looking at your code, you're doing about the same I do and I still do not understand why my code is not working as expected.

    Thanks
    McL



  • @McLion Hi, have you tried to remove "DeleteWhenStopped" ?
    I never used it and by default start() has "KeepWhenStopped".

    Just to try...



  • @luca
    No joy ... thanks anyway.
    Somebody any other idea?



  • I currently have set fixed transparency in designer by adding a styleSheet "background-color: rgba(160, 160, 160, 200)" to the label.
    Can I animate the a value of the styleSheet?



  • .. bump ..
    Nobody any idea .. I'm still trying to get this going.



  • I'll bump it a gain ... really nobody any idea what I am doing wrong?



  • The code you show has no error. I made a minimal example with just a button and a label.

    void MainWindow::on_pushButton_clicked()
    {
    
        QGraphicsOpacityEffect *effect = new QGraphicsOpacityEffect();
        ui->label->setGraphicsEffect(effect);
        QPropertyAnimation *anim = new QPropertyAnimation(effect,"opacity");
        anim->setDuration(1000);
        anim->setStartValue(1.0);
        anim->setEndValue(0.0);
        anim->setEasingCurve(QEasingCurve::OutQuad);
        connect(anim, &QPropertyAnimation::finished, [=]()
        {
            ui->label->setText("gone");
        });
    
        anim->start(QAbstractAnimation::DeleteWhenStopped);
    }
    

    The label fades out as expected. Your crash is bred in another place.



  • Thanks for trying to help.
    I added a new button and a label and tried with your code, except the connect that I changed to:
    connect(anim, SIGNAL(finished()),this, SLOT(FadeLivePauseInfoEnded()));
    because the compiler did not accept what you posted.

    When I click the button Qt crashes exactly as before with this on the console:
    (!) [ 691: 17.475] --> Caught signal 11 (at 0x24, invalid address) <--
    (!!!) *** WARNING [still objects in 'Window Pool'] *** [object.c:241 in fusion_object_pool_destroy()]
    -> ref context 0x20018000...
    (!!!) *** WARNING [still objects in 'Layer Region Pool'] *** [object.c:241 in fusion_object_pool_destroy()]
    (!!!) *** WARNING [still objects in 'Layer Context Pool'] *** [object.c:241 in fusion_object_pool_destroy()]
    (!!!) *** WARNING [still objects in 'Surface Pool'] *** [object.c:241 in fusion_object_pool_destroy()]
    (!) FUSION_PROPERTY_CEDE --> Input/output error
    (!) Direct/Thread: Canceling 'Fusion Dispatch' (709)!

    Any idea?



  • just clarify:
    Did you add a new button and label to your exisiting project or did you create a new project with just a button and a label.
    In first case debug your code and find the position which causes the sigsegv and we can further investigate whats going wrong. In second case list your arch, qt-version, compiler, etc. Maybe there´s a known bug.

    Once again, the code you showed is correct and is not the cause of the sigsegv.



  • OK.
    Just created a brand new project with only a button and a label, compiled for Windows only, and it works as supposed.
    In my current working project I am developing on Windows for eLinux. If I run the code on my Windows devPC it does not crash, but also does not fade the label either. On my eLinux Target, the same code shows the widgets and crashes when I hit the button.



  • Further debugging shows that it works in my project on Windows but not when I compile for eLinux.
    Must be something that does not work with Qt 4.6.3 with DFB 1.4.3 and Fusion on eLinux.


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