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[CSS21] WD 8.5.1: non-positive 'thin' border ?

From: Peter Moulder <peter.moulder@monash.edu>
Date: Sat, 08 Jan 2011 03:59:36 +0000
To: www-style@w3.org
Message-id: <20110108035936.GU21438@bowman.infotech.monash.edu.au>
Section 8.5.1 describes some constraints on the meanings of 'thin',
'medium' and 'thick', but I note that the current text allows them to be
non-positive lengths.  (The existing text forbids only explicit <length>
values being negative.)

I seem to recall that a problem arises if borders can in fact be
negative, though I'm afraid forget what problem; maybe something to do
with it allowing the width and height of the border box to be negative?

I suggest adding some constraint as to (or some discussion concerning)
whether 'thin' can be negative or zero, e.g. by prepending ‘0 ≤’ or ‘0 <’
to the existing line of inequalities.

If 'thin' etc. are allowed to be zero, then I think 8.3.1 (collapsing
margins) would benefit from some text drawing authors' attention to the
possibility that these keyword values aren't necessarily enough to ensure
a non-empty border area.

Received on Saturday, 8 January 2011 04:00:06 UTC

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