def _cursor_down(self, value):
        """
        Moves the cursor down by ``value``.
        """
        self._cursor.clearSelection()
        if self._cursor.atEnd():
            self._cursor.insertText('\n')
        else:
            self._cursor.movePosition(self._cursor.Down, self._cursor.MoveAnchor, value)
        self._last_cursor_pos = self._cursor.position()