Open design decisions about skribo HOT 1 OPEN

I've tried to implement a simple shaper-driven itemization using fontconfig, but immediately stumbled on a lot of problems.

My algorithm is pretty simple:

• Shape a string using harfbuzz.
• Check for missing glyphs.
• Detect their scripts.
• Query fonts for each script via font-kit.

So all I need is a font-kit method like:

Source::select_by_script(script: unicode_script::Script, properties: &Properties) -> Result<Handle, SelectionError>

The problem is that fontconfig doesn't support this at all. I can query a font by lang and by charset.

lang is fontconfig's own languages/scripts/whatever list, which doesn't map on Unicode Script, or locale, or anything. Qt, for example, uses it's own Unicode Script list, that it calls WritingSystem and it matches it with fontconfig's lang manually. So if we want to match Unicode Script with lang than we have to do this ourselves.
Also, lang is a sort of simplified. For example, Han, Hiragana, and Katakana in fontconfig is just ja.

We can also use charset, which basically checks that font has the specified code point. But I'm not sure how correct it is. Also, querying fonts for each code point will be way slower than by lang/script and redundant.

I didn't look into DirectWrite and Core Text yet.

Also, I saw your attempt to add get_fallback to font-kit, but I don't understand how it works. It returns only one font, but what if a string has like 5 different scripts and needs 5 different fonts (in worst case scenario)?

from skribo.