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Re: CSS 2.1 WD and non-CSS presentational hints

From: Håkon Wium Lie <howcome@opera.com>
Date: Tue, 13 Aug 2002 09:50:29 +0200
Message-ID: <15704.47685.884958.842665@gargle.gargle.HOWL>
To: www-style@w3.org

Also sprach Coises:

 > In this section:
 >      http://www.w3.org/TR/2002/WD-CSS21-20020802/changes.html#q74
 > the "CSS 2.1 Specification" working draft states:
 > 
 > || If presentational hints from other sources than CSS are taken
 > || into account by a UA, it must treat them as having the same weight
 > || as the user agent's default style sheet. 
 > 
 > which is essentially the same as "CSS3 module: Cascading and inheritance"
 > <http://www.w3.org/TR/2002/WD-css3-cascade-20020219/#computing>:
 > 
 > ||  If the user agent chooses to honor presentational hints from other
 > ||  sources than style sheets, these hints must be given the same weight
 > ||  as the user agent's default style sheet. This rule is intended for
 > ||  presentational hints in HTML.  Note that non-CSS presentational hints
 > ||  had a higher weight in CSS2. 
 > 
 > 
 > I cannot grasp the logic of this.  It seems to me to be a great mistake.

To praphrase, you're saying it is a mistake to downgrade the weight of
presentational hints from "the start of the author style sheet" (which
CSS2 specifies) to be equal to the "user agent's default style sheet"
(which is used in CSS 2.1 and CSS 3)?

 > One of the more important functions of a user style sheet may be to
 > override choices in the user agent default style sheet.

Yes.

 > By using "normal"
 > (that is, not !important) rules, the user can choose new defaults for
 > presentational attributes --- many of which may not be accessible for
 > modification in the user agent default style sheet.

Yes.

 > This change would make it impossible to set defaults in a user style sheet
 > that could be overridden by old-fashioned HTML.  For example, in CSS2,
 > a user can include this rule in a user style sheet:
 >      BODY {color: navy; background: #FEC}
 > to make text appear, by default, in navy on a manilla background; a page
 > that specified either:
 >      BODY {color: white; background: url(dark.png) black}
 > or:
 >      <BODY TEXT=WHITE BGCOLOR=BLACK BACKGROUND="dark.png">
 > would override this and be displayed with the indicated attributes.  The
 > suggested change would have the thoroughly unintuitive and illogical result
 > of making these two display differently: the first would follow the author
 > specifications, but the second would follow the user specifications.

Correct, the author's attributes are weaker than the author's style sheet.

 > To a user, it makes no logical difference whether a particular effect comes
 > from a style sheet or an HTML presentational hint; these should not be
 > given opposite priorities with respect to the user style sheet.

We changed this since we don't want to encourage the use of
presentational hints. It has been a goal of CSS to eradicate the use
of presentational attributes, and lowering their influence seems a
logical way of achieving this goal. 

 > This change might also present difficulties for user agents which could
 > otherwise implement user-selected presentational defaults as a (real or
 > virtual) user style sheet; it would instead be necessary to modify the
 > (real or virtual) user agent default style sheet to set these defaults.

I didn't understand this argument. Could you expand?

Cheers,

-h&kon
              Håkon Wium Lie                          cto °þe®ª
howcome@opera.com                  http://people.opera.com/howcome
Received on Tuesday, 13 August 2002 04:01:29 GMT

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