code: String showScriptContextHTML( String s, int lineNo, int context )
      {
          StringBuilder sb = new StringBuilder();
          BufferedReader br = new BufferedReader( new StringReader(s) );
  
          int beginLine = Math.max( 1, lineNo-context );
          int endLine = lineNo + context;
          for( int i=1; i<=lineNo+context+1; i++ )
          {
              if ( i < beginLine )
              {
                  try {
                      br.readLine();
                  } catch ( IOException e ) {
                      throw new RuntimeException( e.toString() );
                  }
                  continue;
              }
              if ( i > endLine )
                  break;
  
              String line;
              try {
                  line = br.readLine();
              } catch ( IOException e ) {
                  throw new RuntimeException( e.toString() );
              }
  
              if ( line == null )
                  break;
              if ( i == lineNo )
                  sb.append( "<font color=\"red\">"+i+": "+line +"</font><br/>" );
              else
                  sb.append( i+": " +line +"<br/>" );
          }
  
          return sb.toString();
      }
docs: /*
  Show context number lines of string before and after target line.
  Add HTML formatting to bold the target line.