Disable background scaling for a QGraphicsView/QGraphicsScene

ProfessorFang

Basically what I'm looking to do is replicate photoshop's transparency pattern in a QGraphicsScene, but when I scale the scene, the background scales also. I subclassed QGraphicsView and set it's background brush (as I understand it, it overrides the scene's background brush) but that didn't work either. I also tried overriding the drawBackground event in my subclassed QGraphicsView like so:
@
void FontPageView::drawBackground(QPainter *painter, const QRectF &rect)
{
painter->fillRect(rect, backgroundBrush());
}
@
but that still scaled the background. Does anyone know how I could keep the background image from scaling?

msx_br

Look at:

Examples -> Elastic Nodes Example -> graphicsview/elasticnodes/graphwidget.cpp

In the drawBackground() the examples shows how to paint directly in the QPainter.

So you can apply the scale factor as you want...

ProfessorFang

[quote author="msx_br" date="1331514413"]Look at:

Examples -> Elastic Nodes Example -> graphicsview/elasticnodes/graphwidget.cpp

In the drawBackground() the examples shows how to paint directly in the QPainter.

So you can apply the scale factor as you want...

[/quote]

Thanks, but that doesn't really help. I am already drawing directly to the QPainter of the QGraphicsView exactly like they are. Their background gradient also scales.

Edit:
I see now that the QPainter has a scale, so all I needed to do was keep track of the scaling manually and inverse the scaling right before drawing the background and rescale right after, like so:

@void FontPageView::drawBackground(QPainter *painter, const QRectF &rect)
{
QRectF sceneRect = this->sceneRect();

QRectF bgrects = sceneRect;
//scale the rectangle so that it actually covers the area it's supposed to
bgrects.setBottomRight(bgrects.bottomRight() * scalefact);
painter->scale(1/scalefact, 1/scalefact);
painter->fillRect(bgrects, bgbr);
painter->scale(scalefact, scalefact);

}@

Asperamanca

Maybe QGraphicsItem::ItemIgnoresTransformations is what you are looking for.

Arsen

This code from Qt SVG viewer example disables background scaling

void SvgView::drawBackground(QPainter *p, const QRectF &)
{
    p->save();
    p->resetTransform();
    p->drawTiledPixmap(viewport()->rect(), backgroundBrush().texture());
    p->restore();
}