question: public void mouseWheelMoved ( MouseWheelEvent e ) { boolean accepted = checkModifiers ( e ) ; if ( accepted == true ) { VisualizationViewer < ? , ? > vv = ( VisualizationViewer < ? , ? > ) e . getSource ( ) ; Point2D mouse = e . getPoint ( ) ; Point2D center = vv . getCenter ( ) ; int amount = e . getWheelRotation ( ) ; if ( zoomAtMouse ) { if ( amount > 0 ) { scaler . scale ( vv , in , mouse ) ; } else if ( amount < 0 ) { scaler . scale ( vv , out , mouse ) ; } } else { if ( amount > 0 ) { scaler . scale ( vv , in , center ) ; } else if ( amount < 0 ) { scaler . scale ( vv , out , center ) ; } } e . consume ( ) ; vv . repaint ( ) ; } }
target:  zoom the display in or out, depending on the direction of the mouse wheel motion.