* @param anchor the coordinates of the child extents rectangle
* used for calculations of grouping, scaling, and rotation
* behavior of shapes placed within a group.
*/
public void setInteriorAnchor(Rectangle2D anchor){
CTGroupTransform2D xfrm = _spPr.isSetXfrm() ? _spPr.getXfrm() : _spPr.addNewXfrm();
CTPoint2D off = xfrm.isSetChOff() ? xfrm.getChOff() : xfrm.addNewChOff();
long x = Units.toEMU(anchor.getX());
long y = Units.toEMU(anchor.getY());
off.setX(x);
off.setY(y);
CTPositiveSize2D ext = xfrm.isSetChExt() ? xfrm.getChExt() : xfrm.addNewChExt();
long cx = Units.toEMU(anchor.getWidth());
long cy = Units.toEMU(anchor.getHeight());
ext.setCx(cx);
ext.setCy(cy);
}