On 18/05/2020 12.08, Eli Zaretskii wrote:
> On second thought, I think I misunderstood you.  If the font that is
> used shows "ffi" as a _single_ glyph ffi, and LibreOffice indeed
> highlights parts of this glyph, then I'd like to know how it does
> that, and how far does this capability extend.  I mean, what does it
> do with ligatures like ae, displayed as æ -- does it highlight the
> common vertical stroke for both parts?  And what about "st", displayed
> as st -- this has a curved "hand" connecting s and t -- to which of the
> 2 does it belong for the purposes of highlighting?  There's also "hv"
> displayed as ƕ, let alone "fs" displayed as ẞ and "fz" displayed as
> ß.

I've attached a screenshot with a few examples, though I couldn't find a font that displays ae as æ.

Firefox does the same as LibreOffice (try it here, for example: https://developer.mozilla.org/en-US/docs/Web/CSS/font-variant-ligatures).  Since Firefox uses Harbuzz, I think there's a good chance we can support that feature too :)