alias: ref-width

Set width of the subelement relatively to the width of the element referenced to by the selector in `ref` attribute. If the value is in the `[0, 1]` interval (or expressed in percentages, e.g. `'80%'`), the width of the subelement will be set as a percentage of the width of the referenced element. If the value is `<0` or `>1`, the width of the subelement will be smaller/bigger than the width of the referenced element by the amount specified. For example, `'ref-width': .75` sets the width of the subelement to `75%` of the width of the referenced element. `'ref-width': 20` makes the width to be `20px` less than the width of the referenced element. Note that this makes sense only for SVG elements that support `width` and `height` attributes, such as `<rect>`.