how to zoom out item in View/Scene

[wysota]

and then I set QGraphicsItem::ItemIgnoresTransformations flag for all items, then all item's shape gets changed to original shape.

Set the flag right after creating each item.

I dont want this behaviour, whatever the last zoom size shoud maintinan same for next zoom in.

You said you wanted your background to scale and items to remain the same. Isn't it what you got?

How could I use the drawBackground() to achieve this ??

I'm not sure what you want to achieve, so it's hard for me to propose a solution. If you tried to explain what effect you want to obtain, maybe it'd be easier to find a solution.