[Qt-interest] QGraphicsSceneItem Rotate an object using the center of object

[Samuel Rødal]

Jesús Fernández wrote:
> Hi,
> 
> I need to rotate an object but I need to use the center of the object as 
> the center of coordinates system, which is the best method to do this?
> 
> Thanks

Hi,

either you can make sure your item is centered at the origin by having 
the boundingRect() function return a rect with center (0, 0) and doing 
your painting appropriately, or you can do a translate to the item's 
center, the rotate, and then the inverse translate. Example:

QPointF center = item->boundingRect().center();
item->translate(center.x(), center.y());
item->rotate(angle);
item->translate(-center.x(), -center.y());

Regards,
Samuel