Bug 238982 – Resolve logical viewport units properly in font-size

• Status: RESOLVED
• Resolution: FIXED
• Component: CSS

[Emilio Cobos Álvarez (:emilio)]

Now that we have writing-mode relative units relative to the element style (both for both container-queries and viewport) it's not enough to have two groups of properties (high-priority / others), since font-size depends on writing-mode.

https://bug1763750.bmoattachments.org/attachment.cgi?id=9271418 is an example of a test-case that Firefox gets wrong once we implement these in https://bugzilla.mozilla.org/show_bug.cgi?id=1610815 (and I'll fix soon after that lands).

I guess WebKit's behavior hasn't been updated to depend on the writing-mode of the element itself and it seems relative to the root style: https://webkit-search.igalia.com/webkit/rev/3bf802d5a84565f2dc7e50dacf561e366bf1c147/Source/WebCore/css/CSSPrimitiveValue.cpp#888, but once you do, you'd need to handle writing-mode-dependent properties explicitly in the cascade before font-size.

[Myles C. Maxfield]

So the vi unit is dependent on writing mode, and font-size can depend on vi units, and the em unit depends on font-size, and other properties can depend on em units...

[Emilio Cobos Álvarez (:emilio)]

Yes, but the font-relative units on font-size resolve against the parent style, so I _think_ there's no real cycle per spec (yet...)

[Radar WebKit Bug Importer]

<rdar://problem/91795163>

[Tim Nguyen (:ntim)]

Pull request: https://github.com/WebKit/WebKit/pull/2980

[EWS]

Committed 253087@main (5cd7506926c2): <https://commits.webkit.org/253087@main>

Reviewed commits have been landed. Closing PR #2980 and removing active labels.