private void addLineSeparatorPainterIfNeeded() {
        if (lineSeparatorPainter != null) {
          return;
        }

        RangeHighlighter highlighter = getHistoryViewer().getMarkupModel()
          .addRangeHighlighter(null, 0, getDocument().getTextLength(), HighlighterLayer.ADDITIONAL_SYNTAX,
                               HighlighterTargetArea.EXACT_RANGE);
        highlighter.setGreedyToRight(true);
        highlighter.setCustomRenderer(renderer);
        lineSeparatorPainter = highlighter;
      }
private void addLineSeparatorPainterIfNeeded()