Re: How to write Armenian ligatures?

John Hudson <[email protected]>
Newsgroups gmane.text.unicode.devel
Message-ID <[email protected]>
Michael S. Kaplan wrote:

> Vista Notepad implements font instructions for non-discretionary 
> features using Uniscribe.

The term 'discretionary' may be confusing in this context, because there are three 
possible states for an OTL feature:

On by default; not possible to turn off (e.g. <rlig>)

On by default; possible to turn off* (e.g. <liga>)

Off by default; possible to turn on* (e.g. <dlig>)


* Of course, the possibility to turn a feature on or off depends on having a UI or markup 
capable of performing these functions. In the case of Notepad, the second state -- 0n by 
default; possible to turn off -- is effectively the same as the first state, because there 
is no mechanism to turn the feature off. I believe this is the correct decision in the 
absence of such a mechanism, because if the font developer had not intended the <liga> 
feature ligatures to be on by default he would have put them in the <dlig> feature.

Perhaps unsurprisingly, I think typeface designers are best qualified to make decisions 
about which lookups should be associated with which features and, hence, which should be 
on by default.

If some users don't want the <liga> feature ligatures in their texts, then they should ask 
application developers to implement proper typographic control UI, so that they can turn 
these ligatures off. That is how the OpenType font architecture is designed to be used.

John Hudson

-- 

Tiro Typeworks        www.tiro.com
Gulf Islands, BC      [email protected]

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