question: public void zoomOrigin ( int oldGridSize , int newGridSize ) { log . trace ( "Zoom origin to: " + origin ) ; origin . setLocation ( origin . x * newGridSize / oldGridSize , origin . y * newGridSize / oldGridSize ) ; }
target:  AB: Zoom the origin from the old grid size to the new grid size this method is mainly used by the DiagramHandler classes setGridAndZoom method.