much thanks - this is the code that works for me:
Qt Code:
  1. QPainterPath path = shape();
  2.  
  3. QMatrix matrix;
  4. matrix.translate(value.toPointF().x(), value.toPointF().y());
  5. polygon = matrix.map(path);
  6.  
  7. QList<QGraphicsItem*> items = scene()->items(path, Qt::IntersectsItemShape);
  8. items.removeAll(this);
  9.  
  10. if (!items.isEmpty()) {
  11. // Collision! Don't move.
  12. return pos();
  13. }
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i didn't need the mapToParent and mapToScene calls. furthermore QPainterPath doesn't have a translate-function afaics - so i used qmatrix for that...

niko