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Re: Alternative for CSS2 Section 10.6.4

From: Bert Bos <bert@w3.org>
Date: Wed, 4 Apr 2001 20:57:38 +0200 (MEST)
To: "www-style@w3.org" <www-style@w3.org>
Message-ID: <15051.27527.255650.626052@lanalana.inria.fr>
ValerieGSharp writes:
> The CSS2 Errata 
> (http://www.w3.org/Style/css2-updates/REC-CSS2-19980512-errata)
> contains proposed changes to the calculation of heights in Section
> 10.6.4 Absolutely positioned, non-replaced elements.
> (http://www.w3.org/TR/REC-CSS2/visudet.html#abs-non-replaced-height)
> 
> I propose the following alternative for the calculation of such heights.
> Bearing in mind that the default value for margins is zero, the aim is
> to allow greater use of 'auto' values on margins, especially where it is
> desired that 'height' should be based on content.

It makes sense. I think the working group should have a look at it.

> 
> PROPOSAL:
> 
> 10.6.4 Absolutely positioned, non-replaced elements
> 
> For absolutely positioned elements, the vertical dimensions must satisfy
> this constraint: 
> 
> 'top' + 'margin-top' + 'border-top-width' + 'padding-top' + 'height' +
> 'padding-bottom' + 'border-bottom-width' + 'margin-bottom' + 'bottom' =
> height of containing block
> 
> (If the border style is 'none', use '0' as the border width.) The
> solution to this constraint is reached through a number of substitutions
> in the following order: 
> 
> 1. If 'height' plus any of 'top', 'bottom', 'margin-top' or
> 'margin-bottom' are 'auto', then the height is based on the content.
> 
> 2. If 'top' plus any of 'bottom', 'margin-top' or 'margin-bottom' are
> 'auto', then treat 'top' like 'static-position'.
> 
> 3. If 'bottom' is 'auto', then set any other 'auto' values to 0.
> 
> 4. If both 'margin-top' and 'margin-bottom' are 'auto', solve the
> equation under the extra constraint that the two margins get equal
> values. 
> 
> 5. If at this point the values are over-constrained, ignore the value
> for 'bottom' and solve for that value.
> 
> 6. If at this point there is only one 'auto' left, solve the equation
> for that value. 
> 
> 
> 
> A Decision Table comparing results for W3C proposed changes in CSS2
> Errata (W3C), and the alternative suggestion (New) can be found at
> 
> http://members.netscapeonline.co.uk/valeriegsharp/W3Cstyles/index.html



Bert
-- 
  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos/                              W3C/INRIA
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Wednesday, 4 April 2001 14:57:44 GMT

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