I remember the xor, or, etc Pen setting to draw lines into a 'picture' .
I used it to move one element without the need of redraw all the content of the vectorial data drawed.
To get this , what can I use from painter ? Maybe I have to see Graphicscene ?
Imagine the typical line-point movement. (when edit it wiht the mouse)-.
First you have to erase the lines from point 1 - EditPoint - Point2, then draw new point1-Editpoint , Editpoint- Point 2. And ths two things at every mouse move.

Any tips ? Thanks