[css-multicol] column-width bound (>0) is illegal

Per our design patterns for CSS properties (apparently not written
down anywhere, unfortunately*), we don't use open continuous
intervals, because then whether something is valid or invalid depends
on unpredictable and UA-specific rounding behavior.

However, 'column-width' states that its value must be a <length>
greater than zero.  This violates that constraint.

I suggest that we instead state that there is a minimum size for
columns (1px? ua-specific?), and that values less than this minimum
are clamped to the minimum.  Values less than zero are still invalid,
as they're nonsensical.

This allows authors to confidently use small values without worrying
about whether some UA is going to drop the declaration entirely and
screw everything up.

* I've got some pending edits to
<http://wiki.csswg.org/spec/limited-ranges> explaining the "always use
closed intervals" logic, and how to actually do it, but I can't
actually edit the page right now.

~TJ

Received on Tuesday, 15 October 2013 15:38:51 UTC