Maybe, some precomposed glyphs (without standardized code points) are included in the font, and the registered IDS strings are internally converted to the glyph index to them, by ligature feature of OpenType. I guess, the "composition"-like behaviour is just visible for the set of IDS registered in the font, and the unregistered IDS string would not be displayed as single composed glyph.
gfb hjjhjh wrote: > Seems like Source Han Serif have just implemented such functionality? Or is > this just partial. https://twitter.com/tualatrix/status/849178587680735232 >
