Animation to or from auto heights is commonly requested by web developers. It is important for animation of elements (such as the contents of disclosure widgets) opening/closing between a content-based height (or width) and a small (often zero) height (or width). This calc-size() proposal fits the desire to do such animations into the way that CSS transitions and animations work. More generally, this allows animating between a fixed length and almost any type of height (or width, or min/max-height/width) that can currently be specified in CSS.
The CSS calc-size() function is a CSS function similar to calc(), but that also supports operations on exactly one of the values auto, min-content, max-content, fit-content, stretch, or contain, which are the intrinsic sizing keywords. This allows transitions and animations to and from these values (or mathematical functions of these values), as long as the calc-size() function is used on at least one of the endpoints of the transition or animation to opt in.
WebKittens
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Title of the spec
CSS calc-size() function
URL to the spec
https://drafts.csswg.org/css-values-5/#calc-size
URL to the spec's repository
https://github.com/w3c/csswg-drafts/issues
Issue Tracker URL
No response
Explainer URL
https://github.com/w3c/csswg-drafts/blob/main/css-values-5/calc-size-explainer.md
TAG Design Review URL
https://github.com/w3ctag/design-reviews/issues/955
Mozilla standards-positions issue URL
https://github.com/mozilla/standards-positions/issues/1022
WebKit Bugzilla URL
https://bugs.webkit.org/show_bug.cgi?id=274177
Radar URL
No response
Description
Animation to or from auto heights is commonly requested by web developers. It is important for animation of elements (such as the contents of disclosure widgets) opening/closing between a content-based height (or width) and a small (often zero) height (or width). This
calc-size()proposal fits the desire to do such animations into the way that CSS transitions and animations work. More generally, this allows animating between a fixed length and almost any type of height (or width, or min/max-height/width) that can currently be specified in CSS.The CSS
calc-size()function is a CSS function similar tocalc(), but that also supports operations on exactly one of the valuesauto,min-content,max-content,fit-content,stretch, orcontain, which are the intrinsic sizing keywords. This allows transitions and animations to and from these values (or mathematical functions of these values), as long as thecalc-size()function is used on at least one of the endpoints of the transition or animation to opt in.