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Re: A property for font antialiasing control on Mac OS X

From: Sylvain Galineau <galineau@adobe.com>
Date: Thu, 18 Jul 2013 08:58:06 -0700
To: Simon Fraser <smfr@me.com>, "L. David Baron" <dbaron@dbaron.org>
CC: "www-style@w3.org" <www-style@w3.org>
Message-ID: <CE0D5D8C.84A4%galineau@adobe.com>

On 7/17/13 9:47 PM, "Simon Fraser" <smfr@me.com> wrote:

>On Jul 17, 2013, at 9:34 pm, "L. David Baron" <dbaron@dbaron.org> wrote:
>> On Wednesday 2013-07-17 21:23 -0700, Simon Fraser wrote:
>>> On Jul 17, 2013, at 2:57 pm, L. David Baron <dbaron@dbaron.org> wrote:
>>>> The most significant use case for author control is that while
>>>> subpixel antialiasing (on all platforms) often provides the best
>>>> results for body text [2], its implementation on Mac OS X has a
>>>> tendency to make light text on a dark background overly or even
>>>> unreadably bold [2].  This problem is fully cross-browser on Mac OS
>>>> X, in that all browsers on Mac OS X using the native text
>>>> rasterization code (all major browsers, I believe) run into this
>>>> problem.  In other words, there are many cases where subpixel AA is
>>>> preferable, but also a number of cases where it produces very bad
>>>> results that authors want to avoid.
>>> I understand your argument that the main reason this property exists
>>>is because
>>> of this "extra weight" problem on Mac. We (Apple) are aware of this
>>> However, it would surprise me if authors didn't also want control over
>>>sub pixel-
>>> antialiasing itself.
>>> I did a quick test on Windows, looking at IE10 and Firefox, with
>>>ClearType enabled
>>> on the system. In a test case involving a 3D transform and opacity,
>>>Firefox applied
>>> subpixel-AA to only some of the elements on the page. IE 10 seems to
>>> ClearType for all web content, even though it was enabled for other UI
>>>in the system.
>>> So clearly, even without the Mac problem, subpixel AA differences
>>>exists on non-Mac
>>> platforms, and I suspect that discerning web authors would want
>>>control over it.
>> So what's the motivation for wanting this control?  Is it that the
>> difference between subpixel AA and not subpixel AA was visible
>> without close examination, and the authors wanted consistency?
>I would think this would be the most common case, yes. Consistency between
>different elements on the page, and between the same element at different
>This is certainly the primary reason for current uses of
>> Or is it that the authors have a preference for one or the other for
>> a reason that shouldn't involve leaving the choice to the user's
>> settings?

>that authors are willing to override the default font settings if they
>think it makes
>text look better (at least in the context of Mac heaviness).
>We really need to hear from designers to see if they care about
>on any platforms other than Mac.

Indeed. There is also some visible implementation variability among
browsers on other platforms like Windows e.g. GDI/DWrite, snapped-to-pixel
vs. subpixel-aligned etc.

I'll also note your feedback describes work that is neither temporary nor

Received on Thursday, 18 July 2013 15:59:00 UTC

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