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

The CSS Working Group just discussed ``[css-backgrounds] Always serialize 'background-size' and `mask-size` as two values``, and agreed to the following:

* `RESOLVED: background-size and mask-size both always serialize to two values, as an explicit exception to the shorthest-serialization principle`
* `ACTION: Contact httparchive to check usage of single-value background-size`

<details><summary>The full IRC log of that discussion</summary>
&lt;fantasai> ntim: -webkit-background-size, if you put a single value, has a different meaning than single value on standard background-size<br>
&lt;fantasai> ntim: in -webkit-background-size, the value duplicates<br>
&lt;fantasai> ntim: whereas in background-size we default to auto<br>
&lt;fantasai> ntim: that's slightly different behavior<br>
&lt;fantasai> ntim: Right now 2 engines serialize single-value form to one value, but WebKit serializes as 2 values due to this ambiguity<br>
&lt;fantasai> ntim++<br>
&lt;fantasai> ntim: spec says "use shortest form that doesn't introduce ambiguity"<br>
&lt;fantasai> ntim: because of -webkit-background-size quirk, suggest to serialize as 2 values<br>
&lt;astearns> ack fantasai<br>
&lt;TabAtkins> fantasai: I'm on the record as saying that defaulting to auto was a mistake, i'm sorry. we should have duplicated the value<br>
&lt;TabAtkins> fantasai: historical context is we didn't really have stretch images back then. seemed important to preserve the aspect ratio, but that was the wrong behavior in hindsight<br>
&lt;TabAtkins> fantasai: i'm in support of serializing two values<br>
&lt;TabAtkins> fantasai: if it was web compatible i'd prefer to change the defaulting behavior too<br>
&lt;TabAtkins> fantasai: but probably can't do that<br>
&lt;TabAtkins> astearns: so we'd be amking an execption to the shortest-serialization-principle for this property, to always serialize to two values<br>
&lt;TabAtkins> astearns: objections?<br>
&lt;TabAtkins> ntim: also for mask-size<br>
&lt;fantasai> s/stretch/stretchy/<br>
&lt;TabAtkins> RESOLVED: background-size and mask-size both always serialize to two values, as an explicit exception to the shorthest-serialization principle<br>
&lt;TabAtkins> fantasai: can we do an httparchive to see if anyone uses single-value background-size?<br>
&lt;TabAtkins> TabAtkins: use counters seem plausible<br>
&lt;TabAtkins> fantasai: how do we do that?<br>
&lt;TabAtkins> lea: we contact the httparchvie people and ask them<br>
&lt;TabAtkins> astearns: maybe someone should document how to make a request<br>
&lt;TabAtkins> lea: i'm contacting the person i've previousl gotten to help, think he's pulled back some but maybe he can point us to who to ask<br>
&lt;fantasai> ACTION: Contact httparchive to check usage of single-value background-size<br>
</details>


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Received on Tuesday, 1 April 2025 20:30:11 UTC