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Re: Text anti-aliasing on the Mac

From: John Hudson <tiro@tiro.com>
Date: Tue, 02 Oct 2012 18:38:29 -0700
Message-ID: <506B9715.3030908@tiro.com>
CC: www-style list <www-style@w3.org>
On 02/10/12 4:49 PM, Andrew Fedoniouk wrote:

> 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.

Your terminology may be confusing for some people. It sounds like you 
are describing what Microsoft's rendering folk call full- vs sub-pixel 
*positioning*. Sub-pixel positioning is a particular kind of (usually*) 
sub-pixel rendering in which, as you say, glyphs outlines may begin 
anywhere inside the pixel (this is DirectWrite's default rendering). GDI 
ClearType does sub-pixel rendering but positioned on a full pixel grid, 
so your term 'font-rendering-mode: sub-pixel' sounds ambiguous even 
though you seem to mean specifically sub-pixel positioning.


* This all got more complicated in the Windows 8 Metro environment, in 
which greyscale 8x4 asymmetric antialiasing is applied with sub-pixel 
positioning. And if that's a surprise to you imagine how I felt when 
told of this change two weeks before code lockdown on the new UI fonts 
we were delivering. :0

JH
Received on Wednesday, 3 October 2012 01:38:58 GMT

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