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Re: Another view (sorry) on XBL and behaviours

From: John Lewis <lewi0371@mrs.umn.edu>
Date: Tue, 7 Jan 2003 08:17:38 -0600
Message-ID: <15255198545.20030107081738@cda.mrs.umn.edu>
To: www-style@w3.org

Shelby wrote on Tuesday, January 7, 2003 at 4:01:01 AM:

>> Ian Hickson wrote:
>>   code { binding: url(code.xml#brief); } 
>>   code:hover { binding: url(code.xml#details); } 

> I was waiting to see if any one else would point out that Ian
> proposed a logical endless loop condition.

> When you dynamically replace the implementation (binding), then the
> bounding box can change, then the :hover state can osscillate. You
> could send the UA into an endless loop.

The same thing is possible in pure CSS with the display, content,
font-weight, font-size, font-stretch, letter-spacing, word-spacing,
text-transform, white-space, width, and height properties (and perhaps
other properties) in conjunction with :hover. For example:

  code{font-size:2em}
  code:hover{font-size:1em}

However, CSS does allow UAs to ignore rules like the above:

 "User agents are not required to reflow a currently displayed
  document due to pseudo-class transitions. For instance, a style
  sheet may specify that the 'font-size' of an :active link should be
  larger than that of an inactive link, but since this may cause
  letters to change position when the reader selects the link, a UA
  may ignore the corresponding style rule."
<http://www.w3.org/TR/REC-CSS2/selector.html#dynamic-pseudo-classes>

> This is just one of many examples, wherein when you violate the
> separation of presentation and markup, then all kinds of
> unpredictable, _CATASTROPHIC_ things will happen.

Unfortunately this problem already exists in CSS, as indicated above,
and I don't see how it's directly related to the separation of
presentation and markup.

-- 
John
Received on Tuesday, 7 January 2003 09:18:08 GMT

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