Quote Originally Posted by lni View Post
Maybe the document for QGraphicsRectItem::setRect() should be more clear, I did think it was the same as setGeometry and use it as setGeometry, and now I have to toss my codes...
Please don't blame the docs, they are very clear about this, it's just you didn't read them carefully enough.

The Graphics View coordinate system.

Another question about setPos and translate: it appears that both functions have exactly the same visual effect.
Yes, that's correct.
I did scale and rotate after setPos and translate, both produce identical view. Can you give example where they will produce different result after some operations?
QGraphicsItem::pos() will probably return a different value which can be very important in many situations.

I will be using a lot setPos and/or translate, I hope you can give more detailed info on them so I don't make mistake again...
Use setPos() and forget about translate(), it's purely for completeness.

Also, what is the chance to have QGraphicsAbstractBuilder and QGraphicsBuilder, just as QFormBuilder? Serializing QGraphicsScene and its content is very useful...
None, I guess. There is no data format for storing graphics items. The easiest way to do serialization is to use QDataStream.