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

On Jul 17, 2013, at 2:57 pm, L. David Baron <> 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 issue.

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 disable
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.

> Property and value naming
> =========================
> I'd like the name of this property to reflect that it is
> operating-system specific.  Such a name would help provide a clue to
> its temporary nature, and will also make it far less likely to
> conflict with other names that the CSS Working Group might want to
> use for standardization in the future.  Names I would consider (in
> order of preference) are:
>  mac-font-smoothing
>  osx-font-smoothing
>  macosx-font-smoothing
>  coregraphics-font-smoothing

The desktop operating system is now called "OS X", so having "Mac" in the name is
not appropriate.

In addition, it's conceivable that this same issue could show up on iOS, which uses
the same graphics subsystem, so I really don't like putting a platform name in the
property name. For the reasons I stated above, I think it's likely that authors
will want control over sub pixel AA on other platforms too, which would argue for
simply "font-smoothing", and also suggest that this property would not be as temporary
as you suggest.


Received on Thursday, 18 July 2013 04:24:00 UTC