static protected void UpdateLineColumn(char c)
  {
    column++;

    if (prevCharIsLF)
    {
      prevCharIsLF = false;
      line += (column = 1);
    }
    else if (prevCharIsCR)
    {
      prevCharIsCR = false;
      if (c == '\n')
      {
        prevCharIsLF = true;
      }
      else
        line += (column = 1);
    }

    switch (c)
    {
      case '\r' :
        prevCharIsCR = true;
        break;
      case '\n' :
        prevCharIsLF = true;
        break;
      case '\t' :
        column--;
        column += (tabSize - (column % tabSize));
        break;
      default :
        break;
    }

    bufline[bufpos] = line;
    bufcolumn[bufpos] = column;
  }