int main(int argc, char **argv) {
QApplication app( argc, argv );
QGraphicsScene scene;
QGraphicsView view(&scene);
view.setBackgroundBrush(QBrush(Qt::black));
view.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
view.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
view.setDragMode(QGraphicsView::ScrollHandDrag);
view.show();
// view.showFullScreen();
QGraphicsRectItem *r = scene.addRect(-50, -50, 10, 10);
r->setPen(QPen(QColor(255, 0, 0)));
r->setBrush(QBrush(QColor(0, 255, 0)));
r->show();
r = scene.addRect(0, 0, 10, 10);
r->setPen(QPen(QColor(255, 0, 0)));
r->setBrush(QBrush(QColor(0, 255, 0)));
r->show();
r = scene.addRect(200, 200, 10, 10);
r->setPen(QPen(QColor(255, 0, 0)));
r->setBrush(QBrush(QColor(0, 255, 0)));
r->show();
scene.setSceneRect(-100, -100, 100, 100);
view.resize(200, 200);
return app.exec();
}
