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[css3-multicol] Font anti-aliasing (ClearType) and IE10

From: Gérard Talbot <www-style@gtalbot.org>
Date: Tue, 13 Aug 2013 15:11:48 -0400
Message-ID: <77a12d34235b14c9be5bea42d8b8d6a7.squirrel@ed-sh-cp3.entirelydigital.com>
To: "Morten Stenshorne" <mstensho@opera.com>
Cc: "www-style mailing list" <www-style@w3.org>, "Arron Eicholz" <Arron.Eicholz@microsoft.com>
Le Mer 7 août 2013 4:23, Morten Stenshorne a écrit :

> It's displayed almost perfectly in IE10, but
> something seems to be off by half (?) a pixel or so. Looks like font
> anti-aliasing. You could avoid the issue by replacing every two-letter
> "word" with a regular block of width:2em and height:1em with blue or
> black background. No need for the Ahem font then. Alternatively, you
> could try using Ahem BOTH in the test and in the ref, but that may still
> be tricky to get right.

I went to a friend's house to see for myself how ClearType could affect or
could be affecting the rendering of multi-columns tests (on which I'm
working on) in IE10.

I first disabled ClearType. Then, restarted the operating system and
restarted IE10 again. Most tests need no adjustments. But some tests'
rendering are incomprehensible to me.

In this test:

http://www.gtalbot.org/BrowserBugsSection/CSS3Multi-Columns/Opera/multicol-clip-001-GT.xht

the first column box should have 3 line boxes (each line box respectively
having "bl", "ac" and "bl" as glyphs) and should be exactly 60px tall but
it's 62.22px tall in IE10. It seems it is 3em and 1/9 of 1em tall and not
3 em tall.

20px divided by 9 is 2.22px.

--------

In this test:

http://www.gtalbot.org/BrowserBugsSection/CSS3Multi-Columns/Opera/multicol-inherit-002-GT.xht

the first column box should have 3 line boxes and the first inner
multi-column element should be exactly 60px tall but it's 62.22px tall in
IE10.

So a) where this 2.22px difference comes from, b) why there is a 2.22px
difference and c) how to neutralize such 2.22px  - if it can be
neutralized - from within browser settings is a mystery to me.

+CC: Arron Eicholz

Gérard
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Received on Tuesday, 13 August 2013 19:12:20 UTC

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