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RE: [css3-background] Further correction to the <position> grammar

From: Brian Manthos <brianman@microsoft.com>
Date: Sun, 22 Jan 2012 22:53:19 +0000
To: Tab Atkins Jr. <jackalmage@gmail.com>, www-style list <www-style@w3.org>
Message-ID: <9710FCC2E88860489239BE0308AC5D170EB0D536@TK5EX14MBXC264.redmond.corp.microsoft.com>
TR
[
  [ top | bottom ]
|
  [ <percentage> | <length> | left | center | right ]
  [ <percentage> | <length> | top | center | bottom ]?
|
  [ center | [ left | right ] [ <percentage> | <length> ]? ] &&
  [ center | [ top | bottom ] [ <percentage> | <length> ]? ]
]


ED (modified as per Tab below)
[
 [ left | center | right | top | bottom | <percentage> | <length> ]
|
  [ left | center | right | <percentage> | <length> ]
  [ top | center | bottom | <percentage> | <length> ]
|
  [ center | [ left | right ] [ <percentage> | <length> ]? ] &&
  [ center | [ top | bottom ] [ <percentage> | <length> ]? ]
]


Marking the sub-clauses...

TR
(A)  [ top | bottom ]
(B)  [ <percentage> | <length> | left | center | right ]
  [ <percentage> | <length> | top | center | bottom ]?
(C)  [ center | [ left | right ] [ <percentage> | <length> ]? ] &&
  [ center | [ top | bottom ] [ <percentage> | <length> ]? ]

ED(m)
(A) [ left | center | right | top | bottom | <percentage> | <length> ]
(B)  [ left | center | right | <percentage> | <length> ]
  [ top | center | bottom | <percentage> | <length> ]
(C)  [ center | [ left | right ] [ <percentage> | <length> ]? ] &&
  [ center | [ top | bottom ] [ <percentage> | <length> ]? ]


TRC and EDmC match, so let's ignore those for the moment.


Unless I'm misreading it, (A) has become more complicated just so 1 character can be removed from (B).


Tab, why is the ED version of (A)+(B) considered an improvement over the TR version of (A)+(B)?

Shouldn't it be demonstrably better to be worth changing? 

> -----Original Message-----
> From: Tab Atkins Jr. [mailto:jackalmage@gmail.com]
> Sent: Friday, January 20, 2012 8:04 PM
> To: www-style list
> Subject: [css3-background] Further correction to the <position> grammar
> 
> Lea Verou and I were working on fixing the <position> grammar to be
> more readable.  We finally came up with a simple, easy, and completely
> correct version, but before we posted it, I happened to look at the
> ED, and noticed that the grammar there was *exactly what we came up
> with*, except with an extra, superfluous clause.
> 
> So, the grammar currently in the ED should remove its second clause -
> it's completely subsumed by the fourth clause.
> 
> ~TJ
> 

Received on Sunday, 22 January 2012 22:54:03 GMT

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