Computes line position on Y-Axis (at the center of the line) from line
        number.

        :param line_number: The line number for which we want to know the
                            position in pixels.
        :return: The center position of the line.

def line_pos_from_number(self, line_number):
        """
        Computes line position on Y-Axis (at the center of the line) from line
        number.

        :param line_number: The line number for which we want to know the
                            position in pixels.
        :return: The center position of the line.
        """
        editor = self._editor
        block = editor.document().findBlockByNumber(line_number)
        if block.isValid():
            return int(editor.blockBoundingGeometry(block).translated(
                editor.contentOffset()).top())
        if line_number <= 0:
            return 0
        else:
            return int(editor.blockBoundingGeometry(
                block.previous()).translated(editor.contentOffset()).bottom())