Shaping issues with Noto Sans Duployan font

[khaledhosny]

With NotoSansDuployan-Regular.ttf

HarfBuzz:

$ hb-view NotoSansDuployan-Regular.ttf '𛱇𛰣 𛰂𛱆 𛰆𛱄𛰉𛰅𛰋𛱁𛰄𛰃'

$ hb-view NotoSansDuployan-Regular.ttf '𛱁𛰆𛱇𛰅𛰜 𛰅𛱄𛰈 𛱊𛱁‌𛰅𛱁 𛰙𛱁‌𛰙𛱛𛰅 𛱛‌𛰅𛱛𛰅 𛰜𛱇𛱇‌𛰜𛱇𛰙 𛰅𛱄‌𛰂𛱁 𛰣𛱇‌𛰚𛱛𛰅'

kb_text_shape:

$ hb-view NotoSansDuployan-Regular.ttf '𛱇𛰣 𛰂𛱆 𛰆𛱄𛰉𛰅𛰋𛱁𛰄𛰃' --shaper=kbts

$ hb-view NotoSansDuployan-Regular.ttf '𛱁𛰆𛱇𛰅𛰜 𛰅𛱄𛰈 𛱊𛱁‌𛰅𛱁 𛰙𛱁‌𛰙𛱛𛰅 𛱛‌𛰅𛱛𛰅 𛰜𛱇𛱇‌𛰜𛱇𛰙 𛰅𛱄‌𛰂𛱁 𛰣𛱇‌𛰚𛱛𛰅' --shaper=kbts

[JimmyLefevre]

We are not applying the 'dist' feature because it seems to contain a bunch of GSUB lookups, and, right now, we are assuming 'dist' is a GPOS feature.

The OpenType spec seems to recommend that 'dist' be implemented with GPOS 1 and 2 tables, but obviously, it doesn't require it.

Does this kind of GSUB/GPOS mixing common in real-world fonts?

[khaledhosny]

There is no general agreement about this. HarfBuzz does not care whether a feature is a GSUB or GPOS one (and it is a conscious design decision on HarfBuzz part), other engines may care.