question: @ Override public void drawBackground ( Graphics2D g2 , CategoryPlot plot , Rectangle2D dataArea ) { float x0 = ( float ) dataArea . getX ( ) ; float x1 = x0 + ( float ) Math . abs ( this . xOffset ) ; float x3 = ( float ) dataArea . getMaxX ( ) ; float x2 = x3 - ( float ) Math . abs ( this . xOffset ) ; float y0 = ( float ) dataArea . getMaxY ( ) ; float y1 = y0 - ( float ) Math . abs ( this . yOffset ) ; float y3 = ( float ) dataArea . getMinY ( ) ; float y2 = y3 + ( float ) Math . abs ( this . yOffset ) ; GeneralPath clip = new GeneralPath ( ) ; clip . moveTo ( x0 , y0 ) ; clip . lineTo ( x0 , y2 ) ; clip . lineTo ( x1 , y3 ) ; clip . lineTo ( x3 , y3 ) ; clip . lineTo ( x3 , y1 ) ; clip . lineTo ( x2 , y0 ) ; clip . closePath ( ) ; Composite originalComposite = g2 . getComposite ( ) ; g2 . setComposite ( AlphaComposite . getInstance ( AlphaComposite . SRC_OVER , plot . getBackgroundAlpha ( ) ) ) ; Paint backgroundPaint = plot . getBackgroundPaint ( ) ; if ( backgroundPaint != null ) { g2 . setPaint ( backgroundPaint ) ; g2 . fill ( clip ) ; } GeneralPath leftWall = new GeneralPath ( ) ; leftWall . moveTo ( x0 , y0 ) ; leftWall . lineTo ( x0 , y2 ) ; leftWall . lineTo ( x1 , y3 ) ; leftWall . lineTo ( x1 , y1 ) ; leftWall . closePath ( ) ; g2 . setPaint ( getWallPaint ( ) ) ; g2 . fill ( leftWall ) ; GeneralPath bottomWall = new GeneralPath ( ) ; bottomWall . moveTo ( x0 , y0 ) ; bottomWall . lineTo ( x1 , y1 ) ; bottomWall . lineTo ( x3 , y1 ) ; bottomWall . lineTo ( x2 , y0 ) ; bottomWall . closePath ( ) ; g2 . setPaint ( getWallPaint ( ) ) ; g2 . fill ( bottomWall ) ; g2 . setPaint ( Color . lightGray ) ; Line2D corner = new Line2D . Double ( x0 , y0 , x1 , y1 ) ; g2 . draw ( corner ) ; corner . setLine ( x1 , y1 , x1 , y3 ) ; g2 . draw ( corner ) ; corner . setLine ( x1 , y1 , x3 , y1 ) ; g2 . draw ( corner ) ; Image backgroundImage = plot . getBackgroundImage ( ) ; if ( backgroundImage != null ) { Rectangle2D adjusted = new Rectangle2D . Double ( dataArea . getX ( ) + getXOffset ( ) , dataArea . getY ( ) , dataArea . getWidth ( ) - getXOffset ( ) , dataArea . getHeight ( ) - getYOffset ( ) ) ; plot . drawBackgroundImage ( g2 , adjusted ) ; } g2 . setComposite ( originalComposite ) ; }
target:  Draws the background for the plot.