#include <QApplication>
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QGraphicsItem>
#include <QPainter>
#include <QHBoxLayout>
#include <limits>
#include <QScrollBar>

class MyItem : public QGraphicsItem
{
public:

    explicit MyItem(const QPolygonF &polygon)
            : mPolygon{polygon}
    {}

    ~MyItem() override = default;

    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override
    {
        painter->drawPolyline(mPolygon);
    }

    QRectF boundingRect() const override
    {
        return mPolygon.boundingRect();
    }

private:
    QPolygonF mPolygon;
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    constexpr double maxInt{std::numeric_limits<int>::max()};
    constexpr double start{10.0};
    constexpr double okayY{maxInt + start - 1};
    constexpr double tooMuchY{maxInt + start};

    const QPolygonF polygon1{QVector<QPointF>{{start, start}, {start, okayY}}};
    const QPolygonF polygon2{QVector<QPointF>{{start, start}, {start, tooMuchY}}};

    QWidget mainWidget;
    QHBoxLayout layout;
    mainWidget.setLayout(&layout);
    mainWidget.setFixedWidth(400);
    mainWidget.show();

    const auto makeSceneWithItem{[](const QPolygonF &polygon)
                                 {
                                     auto *scene{new QGraphicsScene};
                                     scene->addItem(new MyItem{polygon});

                                     auto *view{new QGraphicsView};
                                     view->setScene(scene);
                                     return view;
                                 }};
    layout.addWidget(makeSceneWithItem(polygon1));
    layout.addWidget(makeSceneWithItem(polygon2));

    return QCoreApplication::exec();
}

#include "main.moc"