[OpenType] RE: Proposal: deprecate ReqFeatureIndex

[Sairus Patel]

Behdad,

Adobe stopped supporting ReqFeatureIndex years ago for a number of (we think good) reasons described in my posts, and after several conversations with MS. This proposal is to have the spec deprecate ReqFeatureIndex for those same good reasons.

This is doing a favor to the spec: to make it more coherent, less fractured. It's not to justify Adobe's own implementation decision simply because we chose that. We chose that for certain reasons.
	
Now, if ReqFeatureIndex can indeed be considered a good supplement to MS' layout specs, and is to be treated as a "special feature" whose ordering is specifiable to an OT layout engine just as "locl" and "init", say, are, which is what you and Peter imply (and which I totally don't deduce from the current spec), then please put together a proposal that clarifies this, and we can discuss that proposal.

Perhaps that proposal might even pave the way for the eventual toppling of the r* features (as Khaled suggests), with ReqFeatureIndex ascending to the throne.

But, as it stands, ReqFeatureIndex is at the very least ambiguously specified with respect to interaction with MS' multiple-pass model, as we've discussed on this list in the past. (Thanks for bringing that point up again in this present discussion -- I'd neglected to do so.)

Sairus


-----Original Message-----
From: listmaster at indx.co.uk [mailto:listmaster at indx.co.uk] On Behalf Of Behdad Esfahbod 
Sent: Wednesday, August 22, 2012 11:06 AM
To: multiple.recipients.of.OpenType at inbound-smtp-1.adobe.com
Subject: Re: [OpenType] RE: Proposal: deprecate ReqFeatureIndex

Message from OpenType list:


On 08/22/2012 01:54 PM, Sairus Patel wrote:
> Message from OpenType list:
> 
> 
> Behdad,
> 
>> Lets be clear: the situation right now is that ReqFeatureIndex is not universally implemented, mostly because Adobe didn't implement it in some of their products.  
> 
> I'd like to understand what you mean.
> 
> When you say "ReqFeatureIndex is not universally implemented", do you mean that it's not universally (a) present in fonts, or (b) supported by layout engines?

I meant (b).  Please correct me if I'm wrong.  My understanding of your proposal has been that "We (Adobe) have not been supporting it in Flash and some other projects, and have not got much complaints, so it's not widely used, so lets remove it."

I don't have anything against deprecating stuff in the spec.  But before all of us can agree on what features are applied by default and at what stage, I don't think there's any urgency to deprecate this particular feature.  (Which is consistent with your other email, suggesting that a group get together to document the layout model.)

behdad

> If (a), what would fonts need ReqFeatureIndex for? The example given for it in the spec (example 2 at http://www.microsoft.com/typography/otspec/chapter2.htm), substituting the proper form for Urdu numerals, clearly belongs to the 'locl' feature and so is misleading (and if nothing else, this correction to example 2, as in my proposal, should be made to the spec).
> 
> If (b), do you mean that other layout engines do not implement it because Adobe layout engines stopped supporting them a few years ago? Do you have an examples of such engines?
> 
> Sairus
> 
> 
> -----Original Message-----
> From: listmaster at indx.co.uk [mailto:listmaster at indx.co.uk] On Behalf 
> Of Behdad Esfahbod
> Sent: Wednesday, August 22, 2012 5:08 AM
> To: multiple.recipients.of.OpenType at inbound-smtp-1.corp.adobe.com
> Subject: Re: [OpenType] RE: Proposal: deprecate ReqFeatureIndex
> 
> Message from OpenType list:
> 
> 
> On 08/21/2012 07:10 PM, John Hudson wrote:
> 
>> I proposed <rclt> because I and other designers are producing type 
>> designs that rely for intended display on contextual substitutions, 
>> and that may be anything from less-than-beautiful to actually 
>> unreadable if these substitutions are turned off. In some respects, I 
>> think the OpenType assumptions of script required, language 
>> exception, and typographic optional layout are misleading, because 
>> the category of design required features does not fit neatly onto the structure.
>> This is the category where we're increasingly working.
> 
> Fair enough.
> 
>> 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!
> 
> Lets be clear: the situation right now is that ReqFeatureIndex is not universally implemented, mostly because Adobe didn't implement it in some of their products.  And because of that, it's unreliable, and as a result Adobe is requesting that it be deprecated.  Oh well...
> 
> Let me also respond to Sairus's statement that OT spec does not specify when to apply the required features.  I don't think it's a valid point, because the spec does NOT specify those kind of things for any feature...  All of us know, the details of how to use the data in the font have always been unwritten.
> 
> My 0.02CAD,
> behdad
> 
> 
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