Brace matching

def cursor_position_changed(self):
        """Brace matching"""
        if self.bracepos is not None:
            self.__highlight(self.bracepos, cancel=True)
            self.bracepos = None
        cursor = self.textCursor()
        if cursor.position() == 0:
            return
        cursor.movePosition(QTextCursor.PreviousCharacter,
                            QTextCursor.KeepAnchor)
        text = to_text_string(cursor.selectedText())
        pos1 = cursor.position()
        if text in (')', ']', '}'):
            pos2 = self.find_brace_match(pos1, text, forward=False)
        elif text in ('(', '[', '{'):
            pos2 = self.find_brace_match(pos1, text, forward=True)
        else:
            return
        if pos2 is not None:
            self.bracepos = (pos1, pos2)
            self.__highlight(self.bracepos, color=self.matched_p_color)
        else:
            self.bracepos = (pos1,)
            self.__highlight(self.bracepos, color=self.unmatched_p_color)