[css-transforms] Have scale function accept percentage value

[Ernedar]

Hello,
I would like to suggest adding percentage for scale function in transformations.

Current state: scale() is using [-NUM, NUM] where NUM is whole number (integer)
Suggestion: scale() will support [-NUM, NUM] and [-%, %]
Example:
transform: scale(120%) will work same as transform:scale(1.2) is working right now.

It is not a game-breaker but it is nice to have.

Thank you for your work.

[AmeliaBR]

Agree this is a nice to have, would be more intuitive for many authors (scale(50%) instead of scale(0.5), scale(150%) instead of scale(1.5)). The impact on implementations would be restricted to parsing time — computed/serialized values would remain numbers.

It's very similar to the change in alpha values to support percentages, which the WG re-affirmed in #3342 after browser teams emphasized their plan to ship.

[css-meeting-bot]

The CSS Working Group just discussed Have scale function accept percentage value, and agreed to the following:

• RESOLVED: Allow percentages inside the scale

The full IRC log of that discussion

<dael> Topic: Have scale function accept percentage value
<dael> github: https://github.com//issues/3399
<dael> AmeliaBR: This was a community suggestion that scale transforms that current accept number also accept % values, transform-scale: 150% instead of 1.5
<dael> AmeliaBR: Question of author conveience and intuitiveness. We've done this recently for opacity. Just like that it would only effect parsing. Actual rendering wouldn't change.
<dael> AmeliaBR: Question of if people think it's enough value to users to change parsing code
<dael> Rossen_: Any expection for how computed serializes
<dael> AmeliaBR: I would assume convert to simple number
<dael> TabAtkins: Given this is a place where number represents same as % I'm fine with it. It's low value, but low effort and I'm good with being more consistent across the language.
<dael> TabAtkins: Idea is it would parse into a number internally and serialize as a number
<dael> AmeliaBR: smfr can correct, but I assume this is transforms 2. I don't think any rush to get that to PR so we have time to ship impl
<heycam> +1 for consistency across all values that accept a proportion-like value
<dael> smfr: I think that's true. Would effect 2d transform functions. New in transforms 2. Fine with this
<dael> Rossen_: Obj to accept proposal Allow percentages inside the scale
<dael> RESOLVED: Allow percentages inside the scale

[birtles]

Presumably this should also apply to the individual scale property (and not just the scale() function).

[Crissov]

A convenient way, e.g. a keyword, to scale by √2 ≈ 1.414 or √½ ≈ 0.707 (as in ISO paper and pens) might also be nice. scale(sqrt(2)) also works, of course.

[tabatkins]

Yes, now that sqrt() exists, that case is well handled.

[BorisChiou]

Presumably this should also apply to the individual scale property (and not just the scale() function).

Agree, and Gecko just landed it (based on the spec PR).