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Re: [css3-ui] what to do if outline-offset is sufficiently negative (issue 38)

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Mon, 24 Nov 2014 12:59:02 -0800
Message-ID: <CAAWBYDAORqHHZywcgc+dxCdyXVH4iZfyn9nK2=wS7NA2o+iV0A@mail.gmail.com>
To: Florian Rivoal <florian@rivoal.net>
Cc: www-style list <www-style@w3.org>, Tantek Çelik <tantek@cs.stanford.edu>, Kang-Hao Lu <kennyluck@csail.mit.edu>
On Mon, Nov 24, 2014 at 8:53 AM, Florian Rivoal <florian@rivoal.net> wrote:
> Raised here:
> https://wiki.csswg.org/spec/css3-ui#issue38
>
> about this:
> http://dev.w3.org/csswg/css-ui/#outline-offset
>
> The spec does not forbid negative values for outline-offset. In general this is fine, but if the negative value is large enough (in absolute value), the sides of the outline will meet in the middle of the box and pass each other, giving confusing and uninteroperable results.
>
> Forbidding negative values entirely is probably not what we want, as small negative values are not problematic.
>
> The most reasonable possibility suggested last time this was discussed would be for UAs to floor the at the largest (in absolute terms) value that doesn’t cause issues. Remains to define exactly where that is.
>
> Possibilities:
> a - at least 1px of the outline is still visible
> b - the entire outline’s thickness is still visible
> c - something else
>
> Given that outline-style:auto can result in all sorts of shapes, including fuzzy ones where the last 1 px could be highly transparent, I’d favour b.

I'd go with B as well.  The use-cases for negative offsets on outlines
don't seem to want to make the outlines disappear at any point, just
move slightly inward; making any part of them disappear would
generally not be great.  It's also an easy thing to spec, because it's
simply floored at the smaller of (half width) and (half height).

~TJ
Received on Monday, 24 November 2014 20:59:50 UTC

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