[OpenType] RE: Proposal: deprecate ReqFeatureIndex

[John Hudson]

On 22/08/12 5:07 AM, Behdad Esfahbod wrote:

>> And I agree with you that the ReqFeatureIndex is just daffy.

> IMO you are contradicting yourself, as ReqFeatureIndex does *exactly* what you
> are asking for.  Ie, a feature that can't be turned off!

No, it does not do what I want. What I want is a feature for contextual 
variants that should not be turned off, entirely akin to the <rlig> 
feature vs the other ligature features. The ReqFeatureIndex provides for 
a single developer-selected layout feature to be identified as required. 
That doesn't seem to me useful in the context of what I want to do. To 
what existing layout feature should I apply ReqFeatureIndex? I can't 
apply it to <calt> because I have lookups in that feature that are 
discretionary and can be safely turned off. And what if I have a font 
with required contextual alternates and also some other feature that I'd 
like to be required?

Like it or not, I think we're in a place where the only reliable means 
to affect required layout is to register required features. This could 
have been otherwise -- I would have favoured a required flag at the 
lookup level --, but the ReqFeatureIndex seems to me a bizarre, 
half-baked idea and I'm not surprised it isn't universally implemented.

Where Sairus and I disagree is over how strong the wording of required 
feature descriptions should be. I'd like it to be explicit that these 
features should not be turned off, but I can live with the wording of 
e.g. <rlig> as a model given the implementations of that approach.

JH



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