Swing/WhitespaceMark のバックアップ(No.8)

class WhitespaceLabelView extends LabelView {
  private static final Color pc = new Color(130, 140, 120);
  private static final BasicStroke dashed = new BasicStroke(1.0f, BasicStroke.CAP_BUTT,
       BasicStroke.JOIN_MITER, 10.0f, new float[] {1.0f}, 0.0f);
  public WhitespaceLabelView(Element elem) {
    super(elem);
  }
  @Override public void paint(Graphics g, Shape a) {
    super.paint(g,a);
    Graphics2D g2 = (Graphics2D)g;
    Stroke stroke = g2.getStroke();
    Rectangle alloc = (a instanceof Rectangle) ? (Rectangle)a : a.getBounds();
    FontMetrics fontMetrics = g.getFontMetrics();
    int spaceWidth = fontMetrics.stringWidth("　");
    int sumOfTabs  = 0;
    String text = getText(getStartOffset(),getEndOffset()).toString();
    for(int i=0;i<text.length();i++) {
      String s = text.substring(i,i+1);
      int previousStringWidth = fontMetrics.stringWidth(text.substring(0,i)) + sumOfTabs;
      int sx = alloc.x+previousStringWidth;
      int sy = alloc.y+alloc.height-fontMetrics.getDescent();
      if("　".equals(s)) {
        g2.setStroke(dashed);
        g2.setPaint(pc);
        g2.drawLine(sx+1, sy-1, sx+spaceWidth-2, sy-1);
        g2.drawLine(sx+2,   sy, sx+spaceWidth-2, sy);
      }else if("\t".equals(s)) {
        int tabWidth = (int)getTabExpander().nextTabStop((float)sx, i)-sx;
        g2.setColor(pc);
        g2.drawLine(sx+2, sy-0, sx+2+2, sy-0);
        g2.drawLine(sx+2, sy-1, sx+2+1, sy-1);
        g2.drawLine(sx+2, sy-2, sx+2+0, sy-2);
        g2.setStroke(dashed);
        g2.drawLine(sx+2, sy, sx+tabWidth-2, sy);
        sumOfTabs+=tabWidth;
      }
      g2.setStroke(stroke);
    }
  }
}