Re: [css3-fonts] low-level font features

• From: John Hudson <tiro@tiro.com>
• Date: Tue, 22 Jun 2010 17:20:18 -0700
• To: Bram Pitoyo <brampitoyo@gmail.com>
• CC: Jonathan Kew <jonathan@jfkew.plus.com>, John Daggett <jdaggett@mozilla.com>, www-font <www-font@w3.org>
• Message-ID: <4C215342.1010901@tiro.com>

Bram Pitoyo wrote:

> Good point. Like Tal and Jonathan wrote, allowing the use of
> unregistered—and therefore unmapped—feature tags will mean that users
> will get to implement their own low-level OT features rather than
> hacking existing tags to suit their needs.

With the caveat that interaction between unregistered layout features 
and standard text shaping features is likely to have poor 
predictability. Unlike AAT and Graphite, the OpenType Layout model 
presumes an intelligent layout engine that looks after standard text 
shaping by applying layout features in an ordered sequence. I'm guessing 
that layout engines encountering unregistered features, if they do 
anything with them at all, will process them after registered features, 
but to my knowledge there is no standard protocol regarding this.

JH

Received on Wednesday, 23 June 2010 00:21:04 UTC