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Re: [CSS2.1] [CSS3 Background] [CSS3 Page] background-position poorly defined

From: Ognyan Kulev <ogi@fmi.uni-sofia.bg>
Date: Thu, 12 Apr 2007 14:28:02 +0300
Message-ID: <461E17C2.6090503@fmi.uni-sofia.bg>
To: www-style@w3.org

fantasai написа:
>   <percentage>
>     A percentage X aligns the point X% across (for horizontal) or
>     down (for vertical) the image with the point X% across (for
>     horizontal) or down (for vertical) the element's padding box.
>     For example, a value pair of '0% 0%' ... padding box.

I would like to raise another issue: 
<http://lists.w3.org/Archives/Public/www-style/2006Sep/0257.html>. In 
short, I would like "margin-left:auto; margin-right:auto" and 
"background-position:50% X" to center the same way. This is currently 
not so "only" in IE where 'background-position' uses rounding and 
'margin' uses truncing (ceiling). If my proposed change is accepted, I 
see no technical problem for Microsoft to have a slight change in 
calculations - I can't imagine any web site that will break after such 
change.

For consistency, "background-position:X 50%" and "display:table-cell; 
vertical-align:middle" should align the same.

In both cases, I would like to have explicit text in CSS21 that pixel 
aligning should be same for 50% in background-position, margin:X auto 
and vertical-align:middle. Here is my proposal:

   <percentage>
     A percentage X aligns the point X% across (for horizontal) or
     down (for vertical) the image with the point X% across (for
     horizontal) or down (for vertical) the element's padding box.
     Value 50% should align background the same way as left and right
     margins with value 'auto' (for horizontal) or as vertical align
     with value 'middle' in table cell (for vertical).
     For example, a value pair of '0% 0%' ... padding box.
Received on Thursday, 12 April 2007 11:28:10 GMT

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