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

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Mon, 10 Jan 2011 13:30:22 -0800
Message-ID: <AANLkTi=uvGNwsWNJsxQqpynnr8tS3xNetd5WevchBhFT@mail.gmail.com>
To: Peter Moulder <peter.moulder@monash.edu>, www-style@w3.org
On Fri, Jan 7, 2011 at 7:59 PM, Peter Moulder <peter.moulder@monash.edu> wrote:
> 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?

Yeah, we don't want anything but the outer box to have negative
width/height.  Margins handle being negative; nothing else has the
right handling for it.

> 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.

'thin' shouldn't be allowed to be zero.  At minimum, it should be a hairline.

Received on Monday, 10 January 2011 21:31:15 UTC

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