1925802 - Support resolution of `anchor()` and `anchor-size()` in getComputedStyle

Status: RESOLVED WORKSFORME

(Core :: Layout: Positioned, enhancement, P3)

Description

[Jonathan Watt [:jwatt]]

This won't magically just work. We'll need to pass a bunch of information to resolve the functions against, possibly caching that information so that it's available.

Comment 1

[David Shin[:dshin]]

This is fun for e.g. max-size: calc(1% + anchor-size(width, 1px)) - we need to resolve the anchor-size portion without resolving the percentage, because its computed value stays in the percentage form. i.e. The example should serialize to max-size: calc(1% + 1px)

Comment 2

[Jonathan Watt [:jwatt]]

A good next step here would be to go through the tests to determine how thorough Chrome's support is:

https://searchfox.org/mozilla-central/search?q=getComputedStyle&path=testing%2Fweb-platform%2F**%2Fcss%2Fcss-anchor-position%2F

For example, currently there are no tests involving calc() or percentage values. What does Chrome do for such values? How complete do we need to be for a first release?

Comment 3

[David Shin[:dshin]]

Attachment: Minimum Reproducible Case

True - Testcase attached. Chrome outputs the same computed value calc(1% + 1px) for these.

Comment 4

[David Shin[:dshin]]

FWIW, this seems to work now with pref on, and since Bug 1973507 we don't do another anchor lookup.
I still don't think there are WPT tests covering the attached test case, though.

Comment 5

[David Shin[:dshin]]

Given the attached test case now works, and they do an identical resolution to actual anchor positioning, I feel it's safe to close this out as already done.

Comment 6

[Jonathan Watt [:jwatt]]

Agreed.