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[css3-ui] stacking behavior of outline

From: Florian Rivoal <florian@rivoal.net>
Date: Sun, 15 Feb 2015 23:03:22 +0900
Message-Id: <4BAFE8B7-7343-4A7F-90DB-37AF101D6DB9@rivoal.net>
Cc: Tantek Çelik <tantek@cs.stanford.edu>
To: www-style list <www-style@w3.org>
(Logged as Issue 79)

CSS3-UI states:

This specification does not define
how multiple overlapping outlines are drawn,
or how outlines are drawn for boxes
that are partially obscured behind other elements.

However, for the second part of the sentence, CSS2.1 has something to say. Appendix E.2 is a detailed definition of the painting order, which includes a description of where the outline should be drawn.

css-position has an updated version of this definition.

Both definitions actually allow two alternative positioning for the outline. This does not give a definitive answer as to where the outline should be, but it does constrain the answers, and CSS3-UI should reflect it.

So, while "This specification does not define" is accurate,other specifications do (at least for the case of boxes partially obscured behind other elements), so we should at least point to either CSS2.1, or if it is considered reasonably stable, to css-position.

Alternatively, since as far as I can tell, IE, Firefox, Chrome and Safari are interoperable, and out of the two options proposed by CSS2.1 and css-position, all implement the recommended one, we could specify that behavior. But as I don't know why two options were provided, I'd rather hear from someone who know why before we removed that option.

- Florian
Received on Sunday, 15 February 2015 14:11:31 UTC

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