rx attribute of the subelement relatively to the width of the element referenced to by the selector in
If the value is in the
[0, 1] interval (or expressed in percentages, e.g.
rx of the subelement will be set as a percentage
of the width of the referenced element. If the value is
>1, the height
of the subelement will be smaller/bigger than the width of the referenced element by the amount specified.
Note that this makes sense only for SVG elements that support
ry attributes, such