QPainter in QGraphicsView::drawBackground() does not paint anything?

Niagarer

Hey,
I have a QGraphicsView class and implemented the funtion drawBackground:

void GraphWidget::drawBackground(QPainter *painter, const QRectF &rect)
{
    Q_UNUSED(rect);


    QRectF sceneRect = this->sceneRect();

    QLinearGradient sceneGradient(sceneRect.topLeft(), sceneRect.bottomRight());
    sceneGradient.setColorAt(0, Qt::white);
    sceneGradient.setColorAt(1, Qt::black);
    painter->fillRect(sceneRect, sceneGradient);
    painter->setBrush(Qt::NoBrush);
    painter->drawRect(sceneRect);
}

Unfortunately something is missing, but what?
(I am sure, the answer will be just a single line or something like that, I just took it from one of the examples and so far can't find the missing part)
Thanks for answers

Chris Kawa

Do you have a scene set? If not QGraphicsView will call the default paintEvent of the scroll view and your method won't be called.

Niagarer

@Chris-Kawa
Yes, in the constructor:

    QGraphicsScene *scene = new QGraphicsScene(this);
    scene->setItemIndexMethod(QGraphicsScene::NoIndex);
    scene->setSceneRect(-200, -200, 400, 400);
    setScene(scene);
    setCacheMode( CacheBackground );
    setViewportUpdateMode(BoundingRectViewportUpdate);
    setRenderHint((QPainter::Antialiasing));
    setTransformationAnchor(AnchorUnderMouse);
    scale(qreal(10-0), qreal(10.0));

Chris Kawa

Your sample works for me:
graphicsview

The problem must be elsewhere in your code.

Niagarer

@Chris-Kawa
Found it!
As I saw now, I also implemented the paintEvent.
So, just had to delete it.
Thanks