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Re: Text anti-aliasing on the Mac

From: Simon Fraser <smfr@me.com>
Date: Tue, 02 Oct 2012 10:50:02 -0700
Cc: "Tab Atkins Jr." <jackalmage@gmail.com>, www-style list <www-style@w3.org>
Message-id: <7EEFB47C-5F67-44BC-8474-E55A93664FD8@me.com>
To: robert@ocallahan.org
On Oct 2, 2012, at 3:43 AM, Robert O'Callahan <robert@ocallahan.org> wrote:

> On Tue, Oct 2, 2012 at 7:06 AM, Tab Atkins Jr. <jackalmage@gmail.com> wrote:
> Previously, Chrome had some properties that incidentally switched text
> to grayscale anti-aliasing, which people used to avoid this pop.  As
> well, some designers simply dislike the "fat text" effect that LCD
> anti-aliasing causes on Macs (particularly in their heading fonts,
> which looked bold on Mac but normal elsewhere), and so used these
> properties to switch to grayscale anti-aliasing in general.  Chrome 22
> changed the behavior of some of these properties so that they no
> longer switched the anti-aliasing to grayscale, which caused a lot of
> people to complain.  We're reverting this change for now, but we still
> have the unsolved problem of the "pop", and designer's general desire
> to avoid "fat text".
> 
> So, I bring this to you, the WG.  How do Firefox and Opera deal with
> this?  (IE, you get a pass this time.)  Safari, any opinions?
> 
> I'm not exactly sure what you mean by "this". We don't offer a supported way to turn off subpixel AA (on any platform) and I'm not aware of any clamor for it. I don't know why that is; maybe Web designers have bigger complaints about our rendering, or maybe our support for subpixel positioning and always-on text shaping mitigates the problem.

WebKit supports a -webkit-font-smoothing property with values auto/none/antialiased/subpixel-antialiased.

Text "popping" in WebKit can occur when rendering text into transparency layers for < 1 opacity, and into "compositing" layers for transforms etc, because the OS is unable to do subpixel antialiasing when rendering into a transparent context.

Some sites use -webkit-font-smoothing: antialiased to permanently turn off subpixel antialiasing to avoid this text popping. http://apple.com is one such site.

So there seems to be a need for such a property, although it is exposing an implementation detail that I hope will one day go away.

Simon
Received on Tuesday, 2 October 2012 17:50:31 GMT

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