- From: ValerieGSharp <ValerieGSharp@netscapeonline.co.uk>
- Date: Thu, 15 Mar 2001 18:42:04 +0000
- To: "www-style@w3.org" <www-style@w3.org>
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. 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 -- Regards, Val Sharp - Edinburgh
Received on Thursday, 15 March 2001 13:45:33 UTC