get size of QGraphicsView from QGraphicsItem

Question

Q: How can I get graphicsview width and height from my own graphicsItem that subclass from QGraphicsItem ?

Answer 1

Assuming that there is only one view of your scene:

#include <QtWidgets>

class SimpleItem : public QGraphicsItem
{
public:
    QRectF boundingRect() const
    {
        qreal penWidth = 1;
        return QRectF(-10 - penWidth / 2, -10 - penWidth / 2, 20 + penWidth, 20 + penWidth);
    }

    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
    {
        QGraphicsView *view = scene()->views().first();
        qDebug() << "View width:" << view->width() << "height:" << view->height();
        painter->drawRect(-10, -10, 20, 20);
    }
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QGraphicsView view;
    QGraphicsScene *scene = new QGraphicsScene;
    scene->addItem(new SimpleItem());
    view.setScene(scene);
    view.show();
    return app.exec();
}

See QGraphicsItem::scene() and QGraphicsScene::views().