Why changing x,y of rect in scene doesn't do anything?

[theateist]

I'm using the simple example from tutorial to show an rectangle on a scene.
As I understand the axises are in the middle of the graphicalView, right?
What I don't understand is why changing x,y of rectangle doesn't do anything.

Here is the code

QtGuiApplication1::QtGuiApplication1(QWidget *parent)
	: QMainWindow(parent)
{
	ui.setupUi(this);
 
	ui.graphicsView->setBackgroundBrush(Qt::red);
	_graphicsScene = new QGraphicsScene(this);
	ui.graphicsView->setScene(_graphicsScene);
 
 
	QBrush redBrush(Qt::yellow);
	QPen blackPen(Qt::black);
	blackPen.setWidth(6);
	_graphicsScene->addRect(0, 0, 100, 100, blackPen, redBrush);
}

QtGuiApplication1::QtGuiApplication1(QWidget *parent)
	: QMainWindow(parent)
{
	ui.setupUi(this);

	ui.graphicsView->setBackgroundBrush(Qt::red);
	_graphicsScene = new QGraphicsScene(this);
	ui.graphicsView->setScene(_graphicsScene);


	QBrush redBrush(Qt::yellow);
	QPen blackPen(Qt::black);
	blackPen.setWidth(6);
	_graphicsScene->addRect(0, 0, 100, 100, blackPen, redBrush);
}

To copy to clipboard, switch view to plain text mode 

The result
Untitled.jpg

Even if I change x,y of the rect to

addRect(50, 50, 100, 100, blackPen, redBrush)

addRect(50, 50, 100, 100, blackPen, redBrush)

To copy to clipboard, switch view to plain text mode 

or

addRect(10000, 10000, 100, 100, blackPen, redBrush)

addRect(10000, 10000, 100, 100, blackPen, redBrush)

To copy to clipboard, switch view to plain text mode 

it shows the same position of the rectangle. Why?
Untitled.jpg