The Custom Highlight API is not 100% feature-complete, but it is in a state good enough to enable it, as there is small risk of breaking existing webapps.

Setting the pref should be done after the code freeze for 116 is over, i.e. at July 4th.

Backed out for causing mochitest failures in test_interfaces.html

• Backout link
• Push with failures
• Failure Log
• Failure line: TEST-UNEXPECTED-FAIL | dom/tests/mochitest/general/test_interfaces.html | If this is failing: DANGER, are you sure you want to expose the new interface HighlightRegistry to all webpages as a property on 'window'? Do not make a change to this file without a review from a DOM peer for that specific change!!! (or a JS peer for changes to ecmaGlobals)

And xpcshell failures: https://treeherder.mozilla.org/logviewer?job_id=421473216&repo=autoland

Backed out for causing multiple failures related to highlight.

• Push with failures

• Failure log for mochitest-plain failures

• Failure log for wr failures

• Backout link

https://hg.mozilla.org/mozilla-central/rev/e0d642bf72e6

Did you want to add this to the Nightly release notes? Feel free to nominate by setting the relnote-firefox flag to ? if yes!

Release Note Request (optional, but appreciated)
[Why is this notable]: Custom highlight API allows web developers to give ranges an appearance.
[Affects Firefox for Android]: Yes
[Suggested wording]: Partial support for the custom highlight API is now available in Nightly.
[Links (documentation, blog post, etc)]: https://drafts.csswg.org/css-highlight-api-1/

Thanks, added to the Fx117 Nightly release notes.

FF117 MDN docs work for this can be tracked in https://github.com/mdn/content/issues/28291

Above this is described as "Partial support for the custom highlight API".

• Looking at the IDL and objects created it looks like the API for is "complete" in terms of objects.
• Most of the tests in http://wpt.live/css/css-highlight-api/ appear to work
• I can see in https://bugzilla.mozilla.org/show_bug.cgi?id=1845446 that text-decoration properties do not all work. Is that something we should capture in the compatibility table for https://developer.mozilla.org/en-US/docs/Web/CSS/::highlight ?

Essentially "can you outline what is partial about the implementation?" so I can work out how to record this in the compatibility table.

Hi Hamish, sure!

• Text-decoration and Text-Shadow do not work yet.
• There are failing tests regarding inheritance (e.g. this test)
• The topic of event handling hasn't been dealt with at all, but that is also not yet finalized in the spec.

For the moment, custom highlight API is only enabled on Nightly to give it some exposure and to enable fuzzing. Our plans are to implement the remaining features and ship custom highlight for all users in H2.

Thanks very much Jan - just what I needed. Captured in the compatibility data.

This has been dropped from the Nightly release notes now that we're more than 3 cycles out since it was added. Feel free to re-nominate once this is ready to ride the trains to release.