It would be very useful if you could implement ascent-override, descent-override, and line-gap-override. More info: https://bugs.chromium.org/p/chromium/issues/detail?id=800693 (especially comments #20, #30 and #31) https://tobireif.com/non_site_stuff/test_case_for_font_position_report_yet_another_font/ https://www.w3.org/TR/css-fonts-4/#font-metrics-override-desc
Chrome supports it (tested on MacOS vs Windows).
<rdar://problem/72419793>
Here's one reason why it's important to implement this feature: https://tobireif.com/posts/ensuring_the_correct_vertical_position_of_large_text/ (And there's another reason listed in the post below "Another use case".)