[HarfBuzz] Ligatures

[Khaled Hosny]

> On May 23, 2020, at 8:26 PM, Eli Zaretskii <eliz at gnu.org> wrote:
> 
>> From: Khaled Hosny <dr.khaled.hosny at gmail.com>
>> Date: Sat, 23 May 2020 20:09:50 +0200
>> Cc: harfbuzz at lists.freedesktop.org
>> 
>> Overall, if you can’t send the whole text (words are the absolute minimum, but this has its issues as well), don’t just send arbitrary parts of it as the result will be some inconsistent mess.
> 
> I almost understand (and agree), sans one part: the "arbitrary parts"
> of what you wrote.  If we want to produce a ligature out of "ffi", the
> shaper will get "fii" and nothing more.  Which part here is arbitrary?

Sending “ffi” alone is an arbitrary decision. The font might have kerning between “ffi” and what comes before and after it, but you won’t get it. The font might not hav a ligature for “ffi” at all, but using kerning instead, so you will get kerning between “ffi” glyphs and not other glyphs which is arbitrary. It might be a cursive font that changes glyph shapes based on surrounding glyphs, and you will get that for “ffi” and not elsewhere which is arbitrary.

That is just plain wrong, there is no way around it.