QGraphicsRectItem in FullScreen mode, when mouse dragging, blinking

[MarekR22]

I guess (you didn't show any code) that when object resizes (boundingRect changes) you forgot to call QGraphicsItem::prepareGeometryChange!

[stella1016]

I guess (you didn't show any code) that when object resizes (boundingRect changes) you forgot to call QGraphicsItem::prepareGeometryChange!

I do call prepareGeometryChange() when I setRect() in child item (QGraphicsRectItem) inside mouseMoveEvent.

I get some progress. I found, if in resizeEvent of QGraphicsView, code I has the blinking problem, code II doesn't. I am confused why this can cause such effect. resizeEvent is called only once when going to FullScreen mode, and never reached afterwards when I drag the edge of childItem. I can post the code of the resizeEvent:

code I:

void my_graphicsView::resizeEvent(QResizeEvent *event)
{
	setWidth(event->size().width());
	setHeight(event->size().height());
 
	fitInView(QRectF(0,0,width(),height()),Qt::KeepAspectRatioByExpanding);
	arrangeNodes();
 
	m_scene->setSceneRect(0,0,width(),height());
	this->setSceneRect(0,0,width(),height());
 
	update();
}

void my_graphicsView::resizeEvent(QResizeEvent *event)
{
	setWidth(event->size().width());
	setHeight(event->size().height());

	fitInView(QRectF(0,0,width(),height()),Qt::KeepAspectRatioByExpanding);
	arrangeNodes();

	m_scene->setSceneRect(0,0,width(),height());
	this->setSceneRect(0,0,width(),height());

	update();
}

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code II:

void my_graphicsView::resizeEvent(QResizeEvent *event)
{
	setWidth(event->size().width());
	setHeight(event->size().height());
 
	fitInView(QRectF(0,0,width(),height()),Qt::KeepAspectRatioByExpanding);
	arrangeNodes();
 
	m_scene->update(0,0,width(),height());
        update();
}

void my_graphicsView::resizeEvent(QResizeEvent *event)
{
	setWidth(event->size().width());
	setHeight(event->size().height());

	fitInView(QRectF(0,0,width(),height()),Qt::KeepAspectRatioByExpanding);
	arrangeNodes();

	m_scene->update(0,0,width(),height());
        update();
}

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[high_flyer]

I am not sure what the logic of calling QGrphicsViewe::update() is, it will update the whole visible (maybe even the not visible part, I am not sure) scene as well.
Why not just call updateScene()?