It would be very useful if you could implement ascent-override, descent-override, and line-gap-override.
(especially comments #20, #30 and #31)
Chrome supports it (tested on MacOS vs Windows).
Here's one reason why it's important to implement this feature:
(And there's another reason listed in the post below "Another use case".)
Created attachment 420285 [details]
the general issue
Given that the issue can be as severe as in the attached screenshot, please consider assigning a high priority to implementing this feature.
Chrome and Edge support the properties, and they are currently getting implemented in Firefox:
I hope that they will get implemented in Safari soon.