code: private Icon getSynthDisabledIcon(AbstractButton b, Icon defaultIcon) {
          ButtonModel model = b.getModel();
          Icon        icon;
  
          if (model.isSelected()) {
              icon = getIcon(b, b.getDisabledSelectedIcon(), defaultIcon, SynthConstants.DISABLED | SynthConstants.SELECTED);
          } else {
              icon = getIcon(b, b.getDisabledIcon(), defaultIcon, SynthConstants.DISABLED);
          }
  
          return icon;
      }
docs: DOCUMENT ME!
  
  @param  b           DOCUMENT ME!
  @param  defaultIcon DOCUMENT ME!
  
  @return DOCUMENT ME!