Value of `p:blipFill/a:srcRect/@{attr_name}` or 0.0 if not present.

def _srcRect_x(self, attr_name):
        """
        Value of `p:blipFill/a:srcRect/@{attr_name}` or 0.0 if not present.
        """
        srcRect = self.blipFill.srcRect
        if srcRect is None:
            return 0.0
        return getattr(srcRect, attr_name)