[svgwg] Issue: SVGAnimatedLength initial value for `fx` and `fy` (#1054) marked as Agenda+

karlcow has just labeled an issue for https://github.com/w3c/svgwg as "Agenda+":

== SVGAnimatedLength initial value for `fx` and `fy` ==
While looking into following WPT:

WPT Test Case: https://wpt.fyi/results/svg/types/scripted/SVGAnimatedLength-initial-values.html?label=master&label=experimental&aligned&q=initial

WPT Test Case (Source Code): https://github.com/web-platform-tests/wpt/blob/17ed18c17a/svg/types/scripted/SVGAnimatedLength-initial-values.html

^ It seems the following assumes that the default value for `fx` and `fy` is 50%.

```
{ interface: 'SVGRadialGradientElement', attributes: [ 'cx', 'cy', 'r', 'fx', 'fy', 'fr' ],
    cx: { initial: '50%' }, cy: { initial: '50%' }, r: { initial: '50%' },
    fx: { initial: '50%' }, fy: { initial: '50%' }, fr: { initial: '0%' } },
```

But if I read the specification:

https://svgwg.org/svg2-draft/pservers.html#RadialGradientElementFXAttribute

```
initial value - see below
```

Which tells:

If attribute ‘[fx](https://svgwg.org/svg2-draft/pservers.html#RadialGradientElementFXAttribute)’ is not specified, ‘[fx](https://svgwg.org/svg2-draft/pservers.html#RadialGradientElementFXAttribute)’ will coincide with the presentational value of ‘[cx](https://svgwg.org/svg2-draft/pservers.html#RadialGradientElementCXAttribute)’ for the element whether the value for 'cx' was inherited or not. If the element references an element that specifies a value for 'fx', then the value of 'fx' is inherited from the referenced element.

similarly for `fy`: https://svgwg.org/svg2-draft/pservers.html#RadialGradientElementFYAttribute

____

If I am interpretating it right - if `fx` value is missing or invalid then we should fallback to value of `cx` and `cy` and if even those are missing then we should fallback to `50%` (which is initial value of `cx` and `cy`).

Is my understanding correct? Should we clarify this in specification?

Just wanted to get clarification.

Thanks!


See https://github.com/w3c/svgwg/issues/1054


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Received on Tuesday, 20 January 2026 06:44:43 UTC