[mpeg-OTspec] Re: [OpenType] RE: Proposal: deprecate ReqFeatureIndex

Behdad Esfahbod behdad at behdad.org
Wed Aug 22 20:02:38 CEST 2012

On 08/22/2012 01:56 PM, John Hudson wrote:
> 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?

Wrong.  ReqFeatureIndex does not have to point to an existing feature.  In
fact, a font editor can give you an option to mark certain lookups as
mandatory, and the font builder can put all those mandatory lookups in the
required feature.  You are confusing font format with what font editor UIs
provide.  What's missing is UI and support in font builders for what you want.
 Don't impose it on the font format please.

I go as far as declaring it wrong to encode any additional features before the
a clear layout spec is drafted first.  The half-documented soup of features we
already have is way more than we need, adding more is insanity to me.


> 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
> -- 
> Tiro Typeworks www.tiro.com
> Gulf Islands, BC tiro at tiro.com <mailto:tiro%40tiro.com>
> The criminologist's definition of 'public order
> crimes' comes perilously close to the historian's
> description of 'working-class leisure-time activity.'
> - Sidney Harring, _Policing a Class Society_

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