'dist' ignores marks that its rules would otherwise apply to

[dscorbett]

Fonts

NotoSansMalayalam-Regular.otf
NotoSerifMalayalam-Regular.otf

Where the fonts came from, and when

Site: https://github.com/notofonts/malayalam/releases/tag/NotoSansMalayalam-v2.104
Site: https://github.com/notofonts/malayalam/releases/tag/NotoSerifMalayalam-v2.104
Date: 2023-03-31

Font version

Version 2.104

Issue

'dist' ignores marks in these fonts, but some of the glyphs in its rules are mark glyphs, so the rules do not apply. 'dist' should only ignore non-spacing marks.

There should probably be a Font Bakery check to make sure no lookup ignores any glyphs that its rules would otherwise apply to.

Character data

ഺൄ
U+0D3A MALAYALAM LETTER TTTA
U+0D44 MALAYALAM VOWEL SIGN VOCALIC RR

Screenshots

Cf. the intended rendering:

[simoncozens]

The weird thing is that since at least 2.101, the dist feature has looked like this:

pos .notdef .notdef 0

There are some dist lookups in the prefix, but they're not connected to anything in the feature list. 2.001 had a working dist feature. We lost it all when we converted the Monotype sources to AFDKO.

I don't know whether to drop the subsidiary lookups or try to restore the original 2.001 dist feature. I don't know if it's actually a problem or not.