On Fri, Feb 20, 2009 at 07:57:22PM +0100, Hans Hagen wrote:
> Khaled Hosny wrote:
>
>> Currently, when defining a font feature one has to enable all features
>> by hand which is IMHO not very user friendly as it implies prior
>> knowledge about OpenType font features and the meaning of each one, not
>> every Arabic user, for example, knows what does 'init', 'medi, etc.
>> ligatures mean yet to know that he must enable them to get proper font
>> rendering. 
>>
>> I think some font features should be on by default, so that
>> \definefontfeature[script=arabic] should be enough to get an Arabic font
>> rendered correctly with the default features as its designer intended
>> (designers assume that certain will be on while other are off by
>> default, like liga vs. dlig), and if some one wants to disable a certain
>> default feature he can turn it off, not the reverse.
>>
>> Microsoft's OpenType features list page
>> (http://www.microsoft.com/typography/otspec/features_ae.htm) gives a "UI
>> suggestion" for each feature noting if it should be on by default, I
>> think those are what most OpenType enable by default (at least the ones
>> I tested).
>
> i've been thinking of a features=default option (as there is already  
> features=yes|no)
>
> even then it can never be fully automatic as some usage of fonts (think  
> of verbatim) demands devation from defaults
>
> now, if we implement a default list then we first need to make a  
> detailed list of what the supposed defaults are (and i'm not sure if ms  
> is the only resource for that; after all, not all machineries support  
> all features)

I didn't find any other sources, and this seem to be the only published
source of such information.

> a related issue is that fonts can be used for different languages and  
> scripts and therefore a more dynamic feature switching might be needed  
> i.e. arabic might need init, but when the same font is used for latin it  
> not handy to have it enabled, so there might be a matrix of features /  
> scripts needed

I think we can make default features per script (HarfBuzz seems to do
that).

> if it was trivial i'd already done it -)

I know :) just my two cents.

> (implementing is trivial but i don't want to make the wrong decision  
> here as it will influence compatibility)

I see.

-- 
 Khaled Hosny
 Arabic localizer and member of Arabeyes.org team