Re: font features in CSS

On 1 Nov 2009, at 20:54, Stephen Zilles wrote:

> +1 for Rob's suggestion below from me as well.
> And, like Hakon, I am for keeping the #font-face rule behavior as it  
> is now.
> My only concern, however, is that turning features on or off needs  
> to occur in the content not just in the font descriptor. Yes, I know  
> that one can have two fonts that are identical except for the  
> feature of interest and switch fonts to effect the turning on and  
> off of the feature, but that seems rather a complex way to make a  
> temporary "binary" change. And, if there are a lot of features to  
> control, this could lead to a lot of font descriptors.

Agreed; it seems clear to me that we should be able to switch features  
on and off in the content, without requiring a new font descriptor for  
every combination of features. It's perfectly reasonable to want  
certain features within just a restricted part of the content (e.g.,  
tabular numerals within a table, but proportional ones elsewhere;  
decorative swashes or other alternates applied to certain spans only;  
a fractions feature applied just to the actual fractions, so that  
digits elsewhere in the text are unaffected; etc.) Things like this  
should not require new @font-face rules with separate family names.

I'm happy to *also* allow such features to be specified within the  
@font-face rule. In this case, they would become defaults for the face  
in question, adding to (or subtracting from) the initial set of  
features such as canonical compositions, standard ligatures and  
kerning that the shaping engine should be applying by default. Any  
feature changes specified in the content would then be applied to this  
new set of defaults for the font.

It would also be wrong for us to try and divide features into two  
classes, and insist that some can be specified only within the @font- 
face rule and others within the content. It's true that if an author  
specifies certain features in a context where the font is not known  
with any certainty -- e.g., system font fallback is happening -- then  
the results may be somewhat arbitrary; but this is no worse than the  
unpredictability of using system font fallback in the first place,  
when the exact glyphs that will appear are not known, and depend on  
the fonts that happen to be on the user's system.


Received on Monday, 2 November 2009 04:03:45 UTC