I'm working on a color emoji font. For the skin tone modifier system, should I add the skin tone variation glyphs as non-encoded alternates and substitute them in the calt table? For example: default happy face+darkest skin modifier glyph=happy face with darkest skin tone.
For flags, is it the same idea but calt substituting regional indicator symbols
' two letter country codes for flag glyphs?
Are there any other substitutions I need to deal with other than flags and skin tones?