Debug messages

[Perdrix]

I've followed a suggestion to integrate Qt logging into my application trace to record the Qt errors in my log file to track down the source of some Qt debug messages:

QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::setRenderHint: Painter must be active to set rendering hints

This led me to the following code:

    void ImageView::drawOnPixmap()
    {
        ZFUNCTRACE_RUNTIME();
        QPainter painter(&m_drawingPixmap);
        QPalette palette{ QGuiApplication::palette() };
        QBrush brush{ palette.dark() };

        qDebug() << "painter.setRenderHint(QPainter::Antialiasing);";
        painter.setRenderHint(QPainter::Antialiasing);
        qDebug() << "painter.setRenderHint(QPainter::SmoothPixmapTransform);";
        painter.setRenderHint(QPainter::SmoothPixmapTransform);

What am I doing wrong or not doing?

Thank you
David

[JoeCFD]

@Perdrix said in Debug messages:

you may need to check if m_drawingPixmap is empty?

    void ImageView::drawOnPixmap()
    {
        if (  m_drawingPixmap.isNull() ) 
        {
              return;
        }

        ZFUNCTRACE_RUNTIME();
        QPainter painter(&m_drawingPixmap);

[SGaist]

Hi,

When are you calling that function ?

[JoeCFD]

@Perdrix said in Debug messages:

you may need to check if m_drawingPixmap is empty?

    void ImageView::drawOnPixmap()
    {
        if (  m_drawingPixmap.isNull() ) 
        {
              return;
        }

        ZFUNCTRACE_RUNTIME();
        QPainter painter(&m_drawingPixmap);

[Perdrix]

@JoeCFD Good thought - it shouldn't be called with a null pixmap but ...

[JoeCFD]

@Perdrix "Paint device returned engine == 0" may indicate: the image is empty.

[Perdrix]

@JoeCFD Yes, that was the problem Adding the proposed code fixed the problem.