Re: [css3-fonts] "font-feature-settings: none" shorthand?

On Thu, May 30, 2013 at 6:48 PM, John Hudson <tiro@tiro.com> wrote:

> On 30/05/13 9:57 AM, Glenn Adams wrote:
>
>  I respectfully disagree. In discussing an early implementation of this
>> property in the Apache FOP project (as an extension for XSL-FO), a user
>> has asked for the ability to turn off all font features unilaterally.
>> For their use cases, they offer that for experimentation with font
>> features (in general), they want to experiment with behavioral results,
>> and want to turn off all features without having to specify all features
>> individually or have to know which features are supported and specifying
>> them as off as a subset of all features.
>>
>
> To be clear, when you refer to turning off 'all features', do you means
> absolutely all -- including those used by script engines for basic text
> shaping, or do you mean only those discretionary layout features that are
> normally on by default. If what you are asking for is a mechanism to
> globally disable discretionary layout features, that seems reasonable,
> although obviously relies on being able to tell the difference between
> required and discretionary features.
>

I mean that 'none' would be the same as enumerating all features supported
by the font and specifying 'off' or an equivalent value. It is nothing more
than a convenient shorthand, that makes it easier to do the longhand
version of the same effect.

I'm assuming here (and I may be wrong because I haven't checked) that it is
possible for every feature to specify 'feat' off or something equivalent,
even for nominally required features.


>
> But if you mean, in effect, disable all OpenType Layout for a font, then I
> think it would not only be dangerous but also likely to produce different
> results depending on user agent interactions with shaping engines, and on
> individual developer notions of what really is really, really required
> layout for, say, Devanagari text.


Yes, clearly specifying none for fonts when used with scripts like Arabic
or Indic will produce, let's say, unusual results.

I'm not asking for a global switch to turn of the shaping engine for all
text, but one authors can use on a per-text basis as they desire, whether
for testing, or because they *really* want to turn off the shaping engine
for a specific piece of content.





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> JH
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