Re: [csswg-drafts] [css-backgrounds] Always serialize 'background-size' and `mask-size` as two values (#7802)

Hi, I would like to ask about the effect on CSSOM/Typed OM.

For example:

```js
element.style.backgroundSize = '1px';

const cssom_value = element.style.backgroundSize;

const typed_om_value = element.attributeStyleMap.get('background-size');
```

What should be the value of `cssom_value` and `typed_om_value`?

Should we also update tests like [css/css-typed-om/the-stylepropertymap/properties/background-size.html](https://github.com/web-platform-tests/wpt/blob/master/css/css-typed-om/the-stylepropertymap/properties/background-size.html) to mark `<length>` and `<percentage>` as unsupported?

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Received on Wednesday, 4 March 2026 12:18:50 UTC