Re: [csswg-drafts] Clamping values and additive animation (#12648)

I’m glad you view them as deltas but I wish you would not call it a hack, because with improved support this technique could gain widespread use. Many of my proposals have been unrealistic in their demand for engineering resources, but the most gain for the least effort would come from allowing out-of-bounds keyframe values.

Una was gracious enough to explain to me over social media the reason for `transition-behavior: allow-discrete` was to not break existing sites who were transitioning `all`.

It’s not unfortunate, with the concession that if adopted, any console warnings for out-of-bounds keyframe values would simply go away in sites who neglected them and their animations would suddenly start behaving as expected.

In other words, if the W3C decided to clarify and correct this, it would not break any existing sites.

I’m not prepared to evaluate every type but incremental adoption could start with zero-to-one and length/percentage. Non-negative numbers would be nice for completeness but I can’t name a property I’d actually want to animate. It would be pointless to animate an opacity keyframe value of 10 or 100 or something, there is no use case for this. I don’t know what the answer is for such far out-of-bounds values but what harm is it if clamping is deferred?

I’m also not able to assess the performance impact of deferred clamping, other than pointing out Chromium and earlier versions of Firefox did this for opacity already.

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Received on Thursday, 28 August 2025 15:04:30 UTC