The float value in ./c:x@val when ./c:xMode@val == "factor". 0.0 when
        ./c:x is not present or ./c:xMode@val != "factor".

def horz_offset(self):
        """
        The float value in ./c:x@val when ./c:xMode@val == "factor". 0.0 when
        ./c:x is not present or ./c:xMode@val != "factor".
        """
        x, xMode = self.x, self.xMode
        if x is None or xMode is None or xMode.val != ST_LayoutMode.FACTOR:
            return 0.0
        return x.val