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[css-fonts] About the breaking change to CSSFontFaceRule interface

From: Xidorn Quan <me@upsuper.org>
Date: Tue, 02 Aug 2016 16:59:36 +1000
Message-Id: <1470121176.2479040.683391897.62A9C1C9@webmail.messagingengine.com>
To: "www-style list" <www-style@w3.org>
Cc: John Daggett <jdaggett@gmail.com>
Currently, the CSSFontFaceRule interface described in CSS Fonts spec is
not what is implemented in browsers. There were some discussions in the
mailing list last year, and John Daggett said he would try to implement
the new interface in Firefox [1], but it seems he didn't get a chance to
finish that before he left Mozilla.

Now I'd like to try finishing that work, but before that I want to hear
from other engines if you are happy with the current shape of
CSSFontFaceRule interface in the spec, and willing to implement this
breaking change and take the compatibility risk soonish if Gecko does.

I found that Chrome Platform Status added a measure for
CSSFontFaceRule.style at the end of last year, and the data shows
~0.045% of pages try to access that attribute [2]. IIRC, Chrome's
safe-to-break line is 0.03%, so it's higher than that line. Do you think
breaking this would be acceptable?

The current impls aren't quite interoperable, e.g. the object returned
from CSSFontFaceRule.style includes all properties from
CSSStyleDeclaration in all engines except Gecko, and setting attributes
of that object would lead to different behavior in different engines. So
we would need to do something anyway.

What do you think?

In addition, any idea about how websites are currently using that
attribute would be helpful as well.

[1] https://lists.w3.org/Archives/Public/www-style/2015Dec/0144.html
[2]
https://www.chromestatus.com/metrics/feature/timeline/popularity/1082

- Xidorn
Received on Tuesday, 2 August 2016 07:02:14 UTC

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