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[CSS21] inline elements with no content vs. HTML-empty elements

From: Anton Prowse <prowse@moonhenge.net>
Date: Tue, 10 Jun 2008 22:27:54 +0200
Message-ID: <484EE3CA.4010604@moonhenge.net>
To: "www-style@w3.org" <www-style@w3.org>

For the markup fragment <body><span></span></body> IE8b1 displays a line 
box of positive height.[1]  In order to prove that this was incorrect 
behaviour for the purposes of the bug report, I turned to the following 
parts of CSS21CR:

"Line boxes that contain no text, no preserved white space, no inline 
elements with non-zero margins, padding, or borders, and no other 
in-flow content (such as images, inline blocks or inline tables), and 
don't end with a line feed must be treated as zero-height line boxes. 
For the purposes of margin collapsing, this line box must be ignored."
[http://www.w3.org/TR/CSS21/visuren.html#inline-formatting]

and:

"Empty inline elements generate empty inline boxes, but these boxes 
still have margins, padding, borders and a line height, and thus 
influence these calculations just like elements with content."
[http://www.w3.org/TR/CSS21/visudet.html#line-height]

 From this we want to conclude that empty span => empty inline box => 
empty line box (since span is the only node of the body) => zero-height 
line box.  However, the term "Empty inline elements" in the phrase above 
is problematic: does "empty" mean empty as defined by HTML401, or merely 
"having no content"?

If "empty" means empty as defined by HTML401 then, since span is not an 
HTML-empty element, the quoted parts of CSS21 are not sufficient to 
deduce that the body in <body><span></span></body> should have zero 
height; yet I cannot see any other relevant parts of the spec to provide 
the missing link.  Moreover, in this case, shouldn't the phrase above 
should exclude inline replaced elements such as img?

If "empty" means having no content, is the phrase intended to include 
HTML-empty elements (eg param, br, input, img) as well as content-less 
non-HTML-empty elements?  Again, if so, shouldn't it exclude inline 
replaced elements?

[1] 
http://dev.moonhenge.net/bugs/ie8/css/contentless_elements/#positive-line-box-of-contentless-inline

Cheers,

Anton Prowse
http://dev.moonhenge.net
Received on Tuesday, 10 June 2008 20:28:09 GMT

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