[Webkit-unassigned] [Bug 17086] Acid3 positioned generated content overlaps border because of how antialiasing is affecting the Ahem font

[bugzilla-daemon at webkit.org]

http://bugs.webkit.org/show_bug.cgi?id=17086


webkit-bugs at gentlyusedunderwear.com changed:

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------- Comment #19 from webkit-bugs at gentlyusedunderwear.com  2008-03-26 23:17 PDT -------
"No antialiasing should be going on here. The character is exactly 1em by 1em,
1em is 20px. Thus the character is _exactly_ 20x20 pixels."

This is a very bad assumption to make. If the user has a user scale factor
enabled (you can set this in Mac OS X by changing it in
/Developer/Applications/Performance Tools/Quartz Debug.app)

If you set the user scale factor to something like 1.25 or 1.50 or anything
else that causes 20px to NOT lie on device boundaries, the test fails.

Apple has stated in the past they plan to make the user scale factor an
end-user feature sometime "this spring".

For embedded system, like the iPhone and iPod touch, that have arbitrary user
scale factors a main part of the UI, then 20px would definitely not fall on 
pixel boundaries.

And since there's no CSS property available currently to define an antialias
method, this test is making even more assumptions.

I'm including a screenshot of what Acid3 looks like at 108DPI (1.50 Scale
Factor)


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