question: protected int inBorder ( int x , int y ) { Border b = getBorder ( ) ; if ( b == null ) { return UNDEF ; } Insets i = b . getBorderInsets ( this ) ; if ( x <= i . left ) { return DOCK_WEST ; } if ( x >= getWidth ( ) - i . right ) { return DOCK_EAST ; } if ( y <= i . top ) { return DOCK_NORTH ; } if ( y >= getHeight ( ) - i . bottom ) { return DOCK_SOUTH ; } return UNDEF ; }
target:  get the border that mouse is in 