W3C home > Mailing lists > Public > www-style@w3.org > October 2012

Re: Text anti-aliasing on the Mac

From: Andrew Fedoniouk <news@terrainformatica.com>
Date: Tue, 2 Oct 2012 16:49:24 -0700
Message-ID: <CALRQH79UDDMZq5S-vXNp5quiJ6bH1ELj2W_9V+EgKLkw6wKT=w@mail.gmail.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: www-style list <www-style@w3.org>
I think that UAs shall obey user's choice. For example on Windows you
can disable/enable
AA font rendering and so if UA is a good desktop citizen it should use
this settings.

But I agree that in some cases some configuration is needed.
For example I was forced to introduce property

  font-rendering-mode: snap-pixel | sub-pixel;

for my engine running Direct2D backend on Windows.

font-rendering-mode:snap-pixel; is what Windows GDI uses for rendering
fonts in desktop UI - glyphs snap to pixel grid. That is good for e.g.
input elements especially edit elements.
and text having relatively small font-sizes (but not always).
font-rendering-mode: sub-pixel; is when glyph allowed to start
anywhere inside single pixel.
That is good for text under non-trivial transformations and relatively
large fonts.

AFAIR Firefox does the same by using some heuristic rather than doing
this explicitly through

But with high DPI displays this problem will be less and less actual.
After 300 DPI we will probably don't need AA at all so I think using
system settings for now
is enough for AA. + vendor specific properties for particular
platforms and used AA algorithms.
If needed.

Andrew Fedoniouk.


On Tue, Oct 2, 2012 at 1:07 PM, Tab Atkins Jr. <jackalmage@gmail.com> wrote:
> More investigation into this issue has shown that the problem is
> different than what I explained at the start of the page.  It's not
> *really* about the AA.  However, a proprietary property we have
> (-webkit-font-smoothing) which lets you switch between AA modes *also*
> has the effect of turning hinting on or off.  Chrome 22 changed that,
> so that it no longer had this side effect.
> I'm still investigating the problem in more detail, but it seems like
> the "dilation" of text that makes it look fat and bold is an intrinsic
> property of the Mac's hinting engine.  That's why, back when
> "-webkit-font-smoothing: antialiased" turned off hinting, it solved
> people's problem - the text now looked like it did on other platforms
> (not fat).
> roc, does your always-on text shaping mean that you do your own
> hinting, rather than relying on the system to do it for you?  If so,
> that would explain why Firefox hasn't had to deal with the issue - it
> simply doesn't exist there!
> ~TJ
Received on Tuesday, 2 October 2012 23:49:52 UTC

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