code: def visible_line_width(self, position = Point):
          
          extra_char_width = len([ None for c in self[:position].line_buffer if 0x2013 <= ord(c) <= 0xFFFD])
          return len(self[:position].quoted_text()) + self[:position].line_buffer.count(u"\t")*7 + extra_char_width
docs: Return the visible width of the text in line buffer up to position.