QGraphicsItem disappear when zoom is too large.

Hi at all,

I have in my scene a custom QGraphicsItem. When I apply to the scene a certain zoom it suddently disapperas? Why? And how can I prevent if from happening?

Thank you all, and sorry for my bad english!

Can you post the code of your Item paint() method?

This is my code.

Code:

---

void CMCanvasPointer::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) {
 
	Q_UNUSED(option);
	Q_UNUSED(widget);
	painter->setPen(QPen(QColor(Qt::red), 2));
 
	float x = center->x();
	float y = center->y();
 
	painter->drawLine( QLineF(x,   y+2, x,   y+length ) );
	painter->drawLine( QLineF(x,   y-2, x,   y-length ) );
	painter->drawLine( QLineF(x+2, y,   x+length, y   ) );
	painter->drawLine( QLineF(x-2, y,   x-length, y   ) );
 
	painter->drawRect(boundingRect());
}

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It make a "+" in a scene and moving che point "center" it can translate in the window.

What is the value of length??

if length is 2, you're painting 4 points

length is a global variable and the value is 20.

From QT Docs

Quote:

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void QGraphicsItem::paint ( QPainter * painter, const QStyleOptionGraphicsItem * option, QWidget * widget = 0 ) [pure virtual]
...
Make sure to constrain all painting inside the boundaries of boundingRect() to avoid rendering artifacts (as QGraphicsView does not clip the painter for you).
...

---

How do you set the boundingRect() ?
Show the code of CMCanvasPointer::boundingRect().

What zoom level does the object disappear at? You may be over- or under-flowing the painter's underlying units.