[csswg-drafts] Animation and clamping of width, height, and size (#12645)

KevinDoughty has just created a new issue for https://github.com/w3c/csswg-drafts:

== Animation and clamping of width, height, and size ==
As per https://github.com/w3c/csswg-drafts/issues/3340#issuecomment-441488781 there is a reason to have negative opacity Keyframe values, namely additive animation.

Width and height behave differently. Values are clamped to disallow negative values. The same reason to allow negative opacity values applies to width and height.

The introduction of a size shorthand for width and height offers a unique and exciting opportunity to correct this discrepancy going forward. https://github.com/w3c/csswg-drafts/issues/820

The following CodePen shows expected behavior for translation and opacity but failure of width and height, when using manually constructed Web-Animations. This would apply to additive CSS Animations as well. https://codepen.io/kvndy/pen/dPYKYov

Please allow negative width and height values for the size shorthand in the creation of Keyframes. Thanks.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/12645 using your GitHub account


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Received on Saturday, 23 August 2025 16:47:39 UTC