Is there any way to know what are doing the paint system on QGraphicsScene-view ?

Up to I know, I only can subclass paintevent, drawbackground, etc.
But I'd need to know more about the process.

- How many items are goiing to be drawed.
- The progress of painting of theese.
- A way to hide-show items by its type
- A way to know when a painting process has ended and a way to stop if i want.
- If it is a way to have something like model-view. Have I to see at paintengine ?

There is no reference information about this.
Any useful information would be appreciated, Thanks.