paint device returned engine == 0, type: 3

What does this debugger warning means????

Code:

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paint device returned engine == 0, type: 3

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And I installed 4.3.3. Are there any bugs regarding qpainter, becuase SAME CODE worked on 4.3.2.???

Quote:

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becuase SAME CODE worked on 4.3.2.???

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Is this a warning or an error?

Probably because you are trying to paint on a null QPaintDevice...
Can you post some code?

I compiled same code under 4.3.3. and my app crashes. Then I went into debug mode with gdb and I get that warning (at runtime - after app crashes). And I do not have any clue what to do with it. I have been seeking error for 14 hours and I am desperate. :o:crying:

Here is some code, I am "playing" with the code of "Cover browser demo". Here is code:

Code:

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void CMerchandizeBrowser::drawItemAt(QPainter *p, const QPoint &loc,
                                     const QImage &img,
                                     qint16 w, qint16 h,
                                     qint16 angle)
{
    qDebug() << "Entered CMerchandizeBrowser::drawItemsAt ...";    // debug
    Q_ASSERT(p!=0);
    p->save();
    qDebug() << "After first p->save()";    // debug 
    if (!m_MirrorCache.contains(img.cacheKey())) {
        QImage mirror=mirrorImage(img);
        m_MirrorCache.insert(img.cacheKey(), mirror);
    }
 
    QPointF pt(-img.height()/2, -img.height()/2);
    QTransform trans;
    trans.scale(qreal(w)/img.width(), qreal(h)/img.height());
    trans.rotate(angle, Qt::YAxis);
    p->setTransform(trans * QTransform().translate(loc.x(), loc.y()), true);
 
    const QImage &mirror=m_MirrorCache[img.cacheKey()];
    QPointF pt2(pt.x(), img.height()/2);
    p->save();
    qDebug() << "After second p->save()";    // debug
    Q_ASSERT(p!=0);
    p->setCompositionMode(QPainter::CompositionMode_Source);
    p->drawImage(pt2, mirror);
    p->restore();
 
    p->drawImage(pt, img);
 
    p->restore();
    qDebug() << "Exiting CMerchandizeBrowser::drawItemsAt ...";    // debug
}

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That warning is written only ONCE and "After first p->save()". And under 4.3.2 this exact code worked perfectly.

Chill dude...
Post some code and someone will figure it out :)

On what paint device did you use the painter passed to the function before entering this function? Maybe that paint device has been deallocated.

The warning is laucnhed after call DrawItem at from:

Code:

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void CMerchandizeBrowser::drawItemsBeforeSelected(QPainter *p)
{
    qDebug() << "Entered CMerchandizeBrowser::drawItemsBeforeSelected ...";    // debug
    Q_ASSERT(p!=0);
    QPoint selPt(width()/2-m_ImagesList[m_iSelected].width()/2,
                 height()/2-m_ImagesList[m_iSelected].height()/4);
    qint16 widthDiff = selPt.x();
    qint16 startIdx = m_iSelected - widthDiff/pos_diff;
 
    if (startIdx < 0)
        startIdx = 0;
 
    for (qint16 i = 0, idx = startIdx; idx < m_iSelected; ++i, ++idx) {
        const QImage &img = m_ImagesList[idx];
 
        drawItemAt(p, QPoint(selPt.x()-(m_iSelected-i)*pos_diff, selPt.y()),
                   img, img.width() -size_diff, img.height()-size_diff, -55);
    }
    qDebug() << "Exiting CMerchandizeBrowser::drawItemsBeforeSelected ...";    // debug
}

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Where is the QPainter object originally created? Where does CMerchandizeBrowser::drawItemsBeforeSelected() get called from?

I think painter is created here, in line 4:

Code:

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void CMerchandizeBrowser::paintEvent(QPaintEvent *e)
{
    qDebug() << "Entered CMerchandizeBrowser::paintEvent ...";    // debug
    QPainter p(this);
    p.setClipRect(e->rect());
    p.fillRect(rect(), Qt::black);
    p.setRenderHint(QPainter::Antialiasing);
    p.setRenderHint(QPainter::SmoothPixmapTransform);
#ifdef SCALE_VIEW
    static qint16 diff = 0;
    qint16 w =  width() - diff;
    qint16 h = height() - diff;
    QTransform trans;
    trans.translate(width()/2, height()/2);
    trans.scale(qreal(w)/width(), qreal(h)/height());
    trans.translate(-width()/2, -height()/2);
    p.setTransform(trans);
#endif
    drawItemsBeforeSelected(&p);
    drawItemsAfterSelected(&p);
    drawSelectedItem(&p);
#ifdef SCALE_VIEW
    static bool goingUp = true;
    if (goingUp)
        diff += 3;
    else
        diff -= 3;
    if (diff >= 200 || diff <= 0)
        goingUp = !goingUp;
#endif
    if (m_iSelected>=m_ImagesList.count())
        m_iSelected=0;
    //QTimer::singleShot(1000/60, this, SLOT(update()));
    QTimer::singleShot(100/60, this, SLOT(update()));
    qDebug() << "Exiting CMerchandizeBrowser::paintEvent ...";    // debug
}

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You say the app is crashing, do you know where?

Quote:

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Originally Posted by MarkoSan

Code:

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void CMerchandizeBrowser::paintEvent(QPaintEvent *e)
{
    QPainter p(this);
    [...]
    //QTimer::singleShot(1000/60, this, SLOT(update()));
    QTimer::singleShot(100/60, this, SLOT(update()));
}

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Creation of QPainter looks look to me. But I hope you're aware that

• 100/60 = 1
• 1000/60 = 16

so you're attempting to schedule a paint event every one or every 16th millisecond. Of course, the platform won't succeed in delivering timer events at so tight interval and Qt will also optimize it a bit behind the curtains by merging pending paint events but it might still not be a wise thing to do.

But this code, even with short timer, worked fine in 4.3.2. I simply do not get it. Let me try to change this timer.

Same warning!:crying:

That doesn't mean anything. I suggest you use a debugger to find out where the crash occurs instead of shooting blind.

Ok, let me dig into debugger ... just to be sure where ...

Oh, my god!!!!!!!!!!!!!!

I've seen after 15 hours of debugging :D that extension of pictures are wrong. I had .png instead of .jpg. :D Now I have just one problem. Same picture is shown twice in the llne of pictures. Why is that??