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[css3-transitions] Repeating background-positions

From: Rune Lillesveen <rune@opera.com>
Date: Tue, 29 Nov 2011 23:28:43 +0100
To: "www-style list" <www-style@w3.org>
Message-ID: <op.v5qbd5058isf1p@id-c1005.oslo.osa>
 From the current CSS3 Transitions ED:

"list of above types: If the lists have the same number of items, each  
item in the list is interpolated using the rules above. Otherwise the  
interpolation is determined by the property rules. If the property extends  
its list by repeating values, then this repeated form will be used in the  
interpolation (‘background-position’ in an example of a property that  
would transition between lists of different lengths). If the property does  
not allow extending its list, then no interpolation will occur."

That means that if you transition background-position from a list of 7  
positions to a list of 11 positions you actually need 77 different  
background positions for the computed style while transitioning (unless my  
math fails me). Repetition of transitions will happen at the product of  
the lengths of the two lists divided by the lengths' gcd.

Is that a correct interpretation of the spec?

Firefox (8.0) doesn't transition if the <position> counts differ, Chrome  
(15.0.874.121 m) returns a computed style during the transition that is  
combining the two lists, but limits the count to the number of background  
images (even when not transitioning, which should be wrong).

-- 
Rune Lillesveen
Layout Group Manager
Core Technology Department
Opera Software ASA
Received on Tuesday, 29 November 2011 22:30:06 GMT

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