question: public Point2D convertReferenceToWindow ( Point2D refPoint ) { if ( scrollBackReferenceRect == null ) return null ; else return new Point2D . Double ( Math . round ( refPoint . getX ( ) * scrollBackReferenceRect . getWidth ( ) + scrollBackReferenceRect . getX ( ) ) , Math . round ( refPoint . getY ( ) * scrollBackReferenceRect . getHeight ( ) + scrollBackReferenceRect . getY ( ) ) ) ; }
target:  converts a point from reference coordinates to window coordinates