W3C home > Mailing lists > Public > www-style@w3.org > July 2013

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

From: Rik Cabanier <cabanier@gmail.com>
Date: Wed, 17 Jul 2013 19:39:53 -0700
Message-ID: <CAGN7qDB_YPugX0jTL=8yGDxH7QfM8VAbXY75BQeCcNs2g+Wxww@mail.gmail.com>
To: "L. David Baron" <dbaron@dbaron.org>
Cc: www-style@w3.org
On Wed, Jul 17, 2013 at 5:58 PM, L. David Baron <dbaron@dbaron.org> wrote:

> On Wednesday 2013-07-17 17:04 -0700, Rik Cabanier wrote:
> > Other cases where you might want to turn off anti-aliasing:
> > - animations
> > when animating text, you don't want to anti-alias because of performance
> > and also because subpixel AA will cause "jiggling" of characters when you
> > move a text run
>
> The jiggling is a result of subpixel *positioning* of text (which
> also requires re-rasterizing for the different subpixel positions,
> which integer shifts don't).  I think that's independent of
> antialiasing.
>

It depends how you do subpixel AA. I agree that in most cases you won't be
able to tell the difference.


>
> > - content that will end up in a 3d transform
>
> Implementations already know how to disable subpixel AA here;
> authors don't need to give hints.
>

I think you misunderstood.
What I meant is that if you have text that *is going to be *animated,
transitioned or will have a 3d transform applied to it, you want to disable
subpixel positioning. Otherwise you will notice a change in rendering when
it is animated.

Other cases where an author might want this, is if the element that
contains the text:
- becomes transparent
- has a filter applied to it
- has blending applied to it


>
> > - match canvas text
> > Text in canvas never uses subpixel-AA (although there are some browsers
> > that allow it) and an author might want to match HTML text with Canvas
> text
>
> I don't think this is a strong use case.
>

Unsure. How about text in an SVG image?


>
> > Maybe for background-clip you might want the text to be a hard clip and
> not
> > antialiased?
>
> I don't think antialiasing of text will ever cause it to extend
> outside a clip that it's in.
>

Doesn't background-clip use the text as a clipping path for the background
image? If so, you might not want blurry edges


>
> > Because of transition, animations and 3d transform, I don't believe that
> > this will be a temporary solution (unless of course display technology
> > advances so much that subpixel-AA is no longer needed)
>
> I think in the long run, as display densities increase, we may well
> be moving towards subpixel AA no longer being needed.  But that's
> probably a long ways off.  I don't think your other examples are use
> cases for author control (nor have I heard of such author control
> ever being provided on platforms other than Mac).
>
> -David
>
> --
> 𝄞   L. David Baron                         http://dbaron.org/   𝄂
> 𝄢   Mozilla                           http://www.mozilla.org/   𝄂
>
Received on Thursday, 18 July 2013 02:40:21 UTC

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