I have an issue with pixmaps created for drag events. For drag events of my derived QGraphicsRectItem I create a semi-transparent pixmap from that item.
In the debug build everything looks fine.
But in the release build the drag pixmap has some periodic and random artefacts
here is the code:
QPixmap MyGraphicsRectItem::toPixmap() const
{
QRect r = boundingRect().toRect();
QPixmap pixmap(r.width(), r.height());
QColor dragColor(color);
dragColor.setAlphaF(0.5);
QPainter painter;
painter.begin(&pixmap);
painter.fillRect(pixmap.rect(), dragColor);
painter.setPen(Qt::white);
QFont font("SegoeUI");
font.setBold(true);
painter.setFont(font);
painter.drawText(pixmap.rect(), QString(" ") + textItem->toPlainText());
if (pixItem != nullptr) {
painter.setOpacity(0.5);
painter.drawPixmap(pixItem->pos(), pixItem->pixmap());
}
painter.end();
return pixmap;
}
Could that be a kind of memory issue?
The QPixmap is initialized with uninitialized data. In Debug, this is often set to a fixed pattern, but in Release it is garbage.
You should fill the pixmap with transparent color before using it.
QPixmap::QPixmap(int width, int height)
Constructs a pixmap with the given width and height. If either width or height is zero, a null pixmap is constructed.
Warning: This will create a QPixmap with uninitialized data. Call fill() to fill the pixmap with an appropriate color before drawing onto it with QPainter.
(From Qt Docs )
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