'Return the visible width of the text in line buffer up to position.'

def visible_line_width(self, position=Point):

    extra_char_width = len([None for c in self[:position].line_buffer if (8211 <= ord(c) <= 65533)])
    return ((len(self[:position].quoted_text()) + (self[:position].line_buffer.count(u' DCTB ') * 7)) + extra_char_width)
