Time for action – putting it all together!

Before we go on, however, and after talking a lot about items and scenes, let's see how the view, the scene, and the items all work together:

#include <QApplication>
#include <QGraphicsView>
#include <QGraphicsRectItem>
int main(int argc, char *argv[]) {
  QApplication app(argc, argv);
  QGraphicsScene scene;
  scene.addEllipse(QRectF(0, 0, 100, 100), QColor(0, 0, 0));
  scene.addLine(0, 50, 100, 50, QColor(0, 0, 255));
  QGraphicsRectItem *item = scene.addRect(0, 0, 25, 25, Qt::NoPen, Qt::red);
  item->setPos(scene.sceneRect().center() - item->rect().center());
  QGraphicsView view;
  view.setScene(&scene);
  view.show();
  return app.exec();
}

Build and run this example and you will see following image in the middle of the view:

What just happened?

What have we done here? On top, we included the needed headers and then wrote a normal main function and created a QApplication elment. Its event loop is started in the return...