[mpeg-OTspec] Re: [OpenType] Allowing DFLT to take languages

[John Hudson]

On 11/04/16 11:20, Sairus Patel sppatel at adobe.com [mpeg-OTspec] wrote:

> Is there a real-world example of someone desiring an actual language 
> system tag under DFLT script?

Maybe...

An oddity we've found is that we can't reliably apply a Stylistic Set 
substitution to the danda punctuation characters in Bengali, which we 
want in order to substitute a traditional form of these that are used in 
typesetting poetry. If I put the SS substitution lookup in the <bng2> 
script, it doesn't get processed in InDesign: I'm guessing because the 
danda characters, from the Devanagari block, are not being rolled into 
runs with the Bengali (presumably a bug, but in the absence of any 
specification on how to do OTL script itemisation and run segmentation 
properly, who's to say?). If I put the substitution in the DFLT script 
tag, then it works.

Now for this purpose, in the particular fonts I've been making, I don't 
need a language system tag under DFLT, because they're Bengali-only 
fonts, and the SS feature only does this one thing. But if I we were 
making a large, multiscript font — especially if integrating from 
different individual fonts and wanting to maintain feature compatibility 
with previous versions —, I might find myself in a situation where I 
wanted to vary by language the behaviour of this or other features that 
fall back to DFLT script processing.

JH



-- 

John Hudson
Tiro Typeworks Ltd    www.tiro.com
Salish Sea, BC        tiro at tiro.com

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