Intent to Implement: CSS text-underline-offset

[Charlie Marlow]

Intent to Implement: CSS text-underline-offset

Summary: text-underline-offset allows users to control the distance between text and the underline text decoration. Positive values move it up “above” the text for horizontal text, and negative values move it down the page. It would allow web-developers to have more control over the style of text.

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1552062 <https://bugzilla.mozilla.org/show_bug.cgi?id=1552062>

Spec: https://drafts.csswg.org/css-text-decor-4/#underline-offset <https://drafts.csswg.org/css-text-decor-4/#underline-offset>

Platform coverage: All platforms using gecko rendering engine

Estimated release to Mozilla-central: next 1-2 weeks

Preference behind which this will be implemented:
layout.css.text-underline-offset.enabled

Is this feature enabled by default in sandboxed frames? Yes

DevTools bug: None needed

Support in other browsers: As of right now, Safari Technology Preview is the only browser supporting this feature.

Web-platform-tests:
- parsing tests: https://searchfox.org/mozilla-central/source/testing/web-platform/tests/css/css-text-decor <https://searchfox.org/mozilla-central/source/testing/web-platform/tests/css/css-text-decor>
- text-underline-offset-* tests
- Ref tests: https://bugzilla.mozilla.org/show_bug.cgi?id=1557857 <https://bugzilla.mozilla.org/show_bug.cgi?id=1557857>

- Charlie Marlow