[Qt-interest] QGraphicItem rotate problem

[Sean Harmer]

Hi,

On Monday 28 Sep 2009 14:18:50 Riccardo Roasio wrote:
> Hi,
>
> I need to rotate a QGraphicItem and make a union between its QPolygon
> and another QGraphicItem QPolygon in this way:
>
> QString Table::attachBrother(Table *b)
> {
>       int i;
>
>       int my_x=this->x();
>       int my_y=this->y();
>       int brother_x=b->x();
>       int brother_y=b->y();
>
>       int x_diff=brother_x-my_x;
>       int y_diff=brother_y-my_y;
>
>       attached_brothers<<b;
>
>
>       QPolygon polygon=b->getTablePolygon();
>
>       polygon.translate(x_diff,y_diff);
>
>
>       table_polygon=table_polygon.united(polygon);
>                std::cout << "Brother attached" << std::endl;
>        update();
>
> ....
>
>
> If both objects have 0 degrees of rotation all is ok, but if i rotate
> one or both of them so the union result in strange stuff.
> I think is because rotating aa QGraphicItem mantains the original
> points,so if one point is at -10,-10 and another is at -10,-20 after
> the rotation they are in the same positions so this cause
> preoblems....
>
> There is  a way to rotate also these points?
>From the docs:

"QPointF QGraphicsItem::mapToScene ( const QPointF & point ) const

Maps the point point, which is in this item's coordinate system, to the 
scene's coordinate system, and returns the mapped coordinate."

I think this sounds like what you need.

Cheers,

Sean