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background shorthand serialization issues

From: Brian Manthos <brianman@microsoft.com>
Date: Wed, 16 Jun 2010 18:55:55 +0000
To: "www-style@w3.org" <www-style@w3.org>
CC: Arron Eicholz <Arron.Eicholz@microsoft.com>, Jesse Mohrland <jessem@microsoft.com>, Prabs Chawla <pchawla@microsoft.com>, "Sylvain Galineau" <sylvaing@microsoft.com>
Message-ID: <FA122FEC823D524CB516E4E0374D9DCF0154001A@TK5EX14MBXC132.redmond.corp.microsoft.com>
Specifications:
a. http://www.w3.org/TR/2008/REC-CSS2-20080411/colors.html

background
[<'background-color'> || <'background-image'> || <'background-repeat'> || <'background-attachment'> || <'background-position'>]

b. http://dev.w3.org/csswg/css3-background/#the-background

background
(With expansion of <bg-layer> and <final-bg-layer>)
[<bg-image> || <bg-position> [ / <bg-size> ]? || <repeat-style> || <attachment> || <box>{1,2} , ]* <bg-image> || <bg-position> [ / <bg-size> ]? || <repeat-style> || <attachment> || <box>{1,2} || <'background-color'>

c. http://dev.w3.org/csswg/cssom/Overview.html#serializing-css-values

"Where multiple CSS component values can appear in any order without changing the meaning of the value (typically represented by a double bar || in the value syntax), use the order as given in the syntax."

d. http://www.w3.org/TR/2008/REC-CSS2-20080411/colors.html

background-color
value:	<color> | transparent | inherit
initial:	transparent

e. http://dev.w3.org/csswg/cssom/Overview.html#serializing-css-values

5.6.2.1
Before		background:none
After		background:rgba(0, 0, 0, 0)


Issue 1:
If the web page specifies
	background:fixed right url("1.jpg")
then the serialization outputs are:
	CSS2:	url("1.jpg") fixed right
	CSS3:	url("1.jpg") right fixed

Issue 2:
If the web page specifies
	background:blue url("2.jpg")
then the serialization outputs are
	CSS2:	blue url("2.jpg")
	CSS3:	url("2.jpg") blue

Issue 3:
If the web page specifies
	background:scroll
then the serialization outputs are
	CSS2 as per quotes a, c & d:	transparent
	CSS2 as per quote e:		rgba(0, 0, 0, 0)
	CSS3 as per quotes b & c:	none


If all the 3 specifications were in draft, then the quickest path to a simple, cross-spec-consistency would be:
i. update quote 'b' to move "<repeat-style> || <attachment> ||" in front of "<bg-position>"
	- addresses issue #1
ii. update quote 'a' to move "<background-color>" to the end
iii. update quote 'e' to correct the example "After" result to be "background:transparent" 


- Brian

Received on Wednesday, 16 June 2010 18:56:38 GMT

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