code: @Override
    protected void fireInsertUpdate( DocumentEvent evt )
    {
  
      super.fireInsertUpdate( evt );
  
      try
      {
        processChangedLines( evt.getOffset(), evt.getLength() );
      }
      catch( Exception ex )
      {
        System.out.println( "" + ex );
      }
    }
docs: /*
  This updates the colored text and prepares for undo event