[OpenFontLibrary] font linking bandwidth issues: sub-setting fonts or complex scripts

[Christopher Fynn]

Font sub-setting is very tricky for complex Indic and Arabic scripts 
that use OpeenType lookups in the font to select and position the final 
glyphs to be rendered. As these lookups reference glyphs by their index 
value in a font, if you sub-set the font then the lookups also need to 
be updated. Substitution lookups also often rely on glyphs which may not 
rendered in the final output, so though they are not rendered on a site 
they may need to be present in a sub-setted font for the lookups to 
function.

Any font sub-setting tool that does handle these things is only going to 
be practical for scripts like Latin, Greek, Cyrillic, and CJK that do 
not normally rely on applying OpenType features for correct rendering.

Microsoft's WEFT tool for creating EOT fonts seems to handle OpenType 
fonts for complex scripts. Do any of the other font sub-setting tools 
that have been mentioned in this thread do this?

- Chris