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. 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.
Animation to or from auto heights is a very commonly requested feature by web developers because 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 feature fits the desire to do such animations into the way that CSS transitions and animations work. More generally, this allows animating any height that can currently be specified in CSS to zero or to/from a small fixed value.
The CSS Working Group has so far had only a brief synchronous discussion of the proposal, so I didn't get a good sense of what other engine developers think of the proposal (and they also haven't yet had a lot of time to examine it). However, given the history of developer demand for the feature, I think a (hopefully) compelling prototype in Chromium may help make a strong case for implementation in other engines.
Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?
None
Expected to be similar to existing CSS calc() function.
No milestones specified