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Re: [css3-values][css3-background][css3-transforms] <position> vs. transform-origin

From: Dirk Schulze <dschulze@adobe.com>
Date: Mon, 25 Mar 2013 11:51:13 -0700
To: Simon Sapin <simon.sapin@exyr.org>
CC: "www-style@w3.org" <www-style@w3.org>
Message-ID: <8781C032-5EE9-407D-94AF-E9899D8D657F@adobe.com>
Hi, 

On Mar 25, 2013, at 9:02 AM, Simon Sapin <simon.sapin@exyr.org> wrote:

> Kind of related to the rest of this thread.
> 
> In the Level 3 spec for background-position:
>> Note that a pair of keywords can be reordered while a combination of
>> keyword and length or percentage cannot. So ‘center left’ is valid
>> while ‘50% left’ is not.
> 
> This is indeed reflected in the grammar:
> (This is only the relevant part.)
>>  [ left | center | right | <percentage> | <length> ]
>>  [ top | center | bottom | <percentage> | <length> ]
> 
> In CSS 2.1, the grammar also has this restriction.

I checked the behavior of browsers and I checked the test suite for CSS Transforms. Both use/assume the syntax of CSS3 Background and Borders (with the exception of the missing offset). Not sure why the later one assumes it :P. Therefore, it should be no problem to fix that. I'll go ahead and do the change.

Note that the syntax of perspective-origin is not different from transform-origin with the exception of the missing, third, optional value.

> 
> transform-origin however removed this restriction:
> 
>>  [ <percentage> | <length> | left | center | right ]
>>  &&
>>  [ <percentage> | <length> | top | center | bottom ]
> 
> 
> Was there a reason to remove the restriction on one property but keep it 
> in others?

I assume that this was an mistake. Thanks for noting.

Greetings,
Dirk

> 
> -- 
> Simon Sapin
> 
Received on Monday, 25 March 2013 18:51:46 GMT

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