The coordinate system

[avis_phoenix]

Hi, i have a problem with the coordinate system

In the windows coordante the y-axis is this:
|------> X
|
|
v Y

But i need (beacause the calculates needed) this coordinate system:
^Y
|
|------>X

I can change the view with QMatrix with this instruction:

QMatrix MyMatrix;
MyMatrix.scale(1,-1);
GraphicView->setMatrix(MyMatrix);

QMatrix MyMatrix;
MyMatrix.scale(1,-1);
GraphicView->setMatrix(MyMatrix);

To copy to clipboard, switch view to plain text mode 

I need this for my draws in tha scene, but i need put a text in the scene, and with this action the text also is reflected, then:

How I can change the coordinate system for my drawings and it does not to the text?

Sorry for my bad english