- From: Gérard Talbot <css21testsuite@gtalbot.org>
- Date: Wed, 17 Oct 2012 01:31:10 -0400
- To: "Public CSS testsuite mailing list" <public-css-testsuite@w3.org>
Hello all,
I wish to know if we should allow to allocate 1px (as a margin of error
or latitude) on each side of squares, rectangles, etc.. to take into
account anti-aliasing.
Personally, I have never done that, this never happened in CSS 2.1 test
suite as far as I know and the most active contributors do not do that.
Typically, what is being done is:
#overlapped-red {
background: red;
position: absolute;
top: 1px;
left: 1px;
width: 158px;
height: 158px;
}
#overlapping-green {
background: green;
position: absolute;
top: 0px;
left: 0px;
width: 160px;
height: 160px;
}
so that the overlapping green is 2px wider and 2px taller than the
overlapped red. The painting covers more area than needed. Furthermore,
this way of coding is in a ttwf tutorial:
http://test.csswg.org/source/contributors/ttwf/samples/ttwf-reftest-tutorial-001.html
Should we allow (tolerate) this, encourage this or disallow this?
Why would doing this be necessary anyway, to begin with?
--------
Sometimes, consequences of rounding effects could be misinterpreted as
anti-aliasing effects.
Eg. (to be viewed with Opera 12.02)
http://www.gtalbot.org/BrowserBugsSection/review/background-size-xyz.html
Rescaling from 60px to 100px implies an increase of 66.66666% and so
rounding down of percentage and then rounding down of fractional pixel
seem to occur for Opera 12.02 in such test.
Gérard
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Received on Wednesday, 17 October 2012 05:31:38 UTC