CSS WG Blog Resolutions 2008-03 San Diego Part IV: Box…

Resolutions 2008-03 San Diego Part IV: Box Model

Box Model Module

• Noted: It was proposed that the overflow and marquee properties be split off to form their own module. These properties are needed by the Mobile Profile and are reasonably independent of the box model details. Splitting them off allows them to move forward to CR without being held back by the rest of the box module, which is quite complex and will need significantly more review. There seemed to be consensus on this idea, but no formal resolution was made.

Box-sizing

• Noted: fantasai’s proposal for adding box-sizing keywords to the ‘width’ and ‘height’ properties was discussed. Most of the working group was strongly in favor, 1/2 of one company’s representation was opposed. No resolution was recorded wrt adopting the proposal.

• Resolved:: That should the proposal be adopted, its keywords must be consistent with box-sizing.

• Noted: That the proposed keywords are applied to min-width, max-width, width, min-height, max-height, and height.

• Noted: That the proposed keywords, like box-sizing, have no effect on the behavior of auto, fit-content, min-content, max-content, and none (max-width/height only) values for these properties.

Centering

There was much discussion of horizontal and vertical centering, but no resolution on the issue. The discussion closed with fantasai and Alex assigned to write concrete proposals for horizontal and vertical alignment, respectively.

For horizontal centering, there seem to be two distinct use cases:

• Standardizing CSS syntax equivalent to the <CENTER> tag. The <CENTER> tag centers all its children, but not itself, and this centering behavior is inherited.
• Centering a single element, such as a table. This use case requires centering the element and preferably not centering its children. Auto margins can handle some but not all of these cases.

For vertical centering, it was agreed that alignment affects the element’s children (because there’s no way to center an element
in its parent without taking it out of the normal flow). Also, it was agreed that vertical alignment of an element’s children
should cause it to create a new block formatting context. This greatly simplifies things by avoiding margin-collapsing and float
complications. The default value of the new property will need to be a special value that doesn’t turn the block into a BFC.

Page Breaking

A proposal to change the way page-break-inside affects descendent elements was discussed.

Advanced Layout Module

• Bert reported that designers want non-rectangular regions, to put images in corners or in the center. However, auto-sizing non-rectangular slots (such as a C shape that has as much text above as below) is very difficult. In the interest of moving forward and getting implementations, fantasai suggested leaving the slots rectangular for this version.

• Resolved: Rename CSS Advanced Layout Module to CSS Template Layout Module.

• Noted: To avoid overlapping constraints, width and height should not apply to slots, only to columns and rows respectively.

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