Bug 320744 – font-* properties should use the metrics of the parent element's font for font-relative unit resolution

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

[Sam Weinig]

Currently, we only special case font-size to use the parent elements font metrics for font-relative units, but the CSS Values spec says all properties of the form font-* should use the parent element. In practice, this doesn't really come up, since no other font-* property allows lengths, but through the use of calc() it can still be observed. For example,

```
<style>
#container { font-size: 10px; }
#element { font-size: 100px; font-size-adjust: calc(1em / 1px); }
</style>
<div id=container>
   <div id=element>
   </div>
</div>
```

The computed style for element's font-size-adjust property should be `10` (because it should use the parent font-size where 1em == 10px, and therefore 10px / 1px == 1), and not `100` as it is today.

[Sam Weinig]

Created attachment 480895 [details]
Test case

[Radar WebKit Bug Importer]

<rdar://problem/184336424>

[Sam Weinig]

Pull request: https://github.com/WebKit/WebKit/pull/71441

[EWS]

Committed 319052@main (c64b47e33694): <https://commits.webkit.org/319052@main>

Reviewed commits have been landed. Closing PR #71441 and removing active labels.