[luatex] Problems with obscure macOS fonts

[Bruno Voisin]

Hi,

When performing a systematic test of all the fonts in macOS 10.15 Catalina Public Beta, I noticed that some more or less obscure fonts exhibit problems with LuaHBTeX:

- Apple Color Emoji ("Apple Color Emoji.ttc" from /System/Library/Fonts): it's Apple's bitmap emoji font, part of the core OS fonts at /System/Library/Fonts. LuaHBTeX returns no warning or error when processing it, but the font is blank in the output. Khaled Hosny looked at the problem for HarfTeX, identified the bug to be in HarfBuzz and fixed it there

	https://github.com/harfbuzz/harfbuzz/pull/1851

Maybe LuaHBTeX built with a recent HarfBuzz would be devoid of the problem. I do not know where to find such recent x86_64-darwin build, I'm using that from tlcontrib and it still exhibits the problem.

- BM Dohyeon, BM Hanna 11yrs Old, BM Kirang Haerang and BM Yeonsung (BMDoHyeon-Regular.otf, BMHanna11yrs-Regular.otf, BMKirangHaerang-Regular.otf and BMYeongSung-Regular.otf from /System/Library/AssetsV2/com_apple_MobileAsset_Font6): these are four downloadable Hangul fonts, not installed by default but which the user can download in the built-in Font Book app; they are also downloaded silently in the background when an app or a document requests them. They crash LuaHBTeX with `Fatal error: ``Invalid character'''. Again, Khaled identified the problem in the HarfTeX engine and fixed it

	https://github.com/khaledhosny/harftex/commit/02f5131

I don't know whether this fix translates immediately into LuaHBTeX.

Luigi Scarso is aware of the problems and has all the test files already.

In case you want to know more about the background, an archive of the macOS font test (tex source and pdf output for HarfTeX, LuaHBTeX, LuaTeX and XeTeX, plus reference rendering in Apple's Pages) is at

	https://servbox.legi.grenoble-inp.fr/file.php?h=R385dca317ed57a1346ee6e545a35863d

(37 MB, link valid for a month).

Cheers,

Bruno Voisin