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Re: Multiple Background Images

From: Eric A. Meyer <eric@meyerweb.com>
Date: Fri, 29 Oct 2004 10:53:17 -0400
Message-Id: <a05210610bda808ad5be4@[192.168.1.31]>
To: www-style@w3.org

At 12:59 +0200 10/28/04, Jens Brueckmann wrote:

>On Thu, 28 Oct 2004 10:51:57 +1000, Lachlan Hunt 
><lachlan.hunt@iinet.net.au> wrote:
>
>>  This is in response to Hixies latest log entry, "Multiple 
>>Background Images" http://ln.hixie.ch/?start=1098915335&count=1
>>
>>>  Given the following hypothetical CSS3:
>>>   body { background: url(foo) url(bar); }
>>>   Which background is painted on the bottom, and which is painted 
>>>on the top?
>>
>>  I couldn't find any other property that would set a precedent for 
>>this decision, but I think it would be most logical if they were 
>>painted from top to bottom, in the order they appear.  ie. in the 
>>example, foo would be painted on top of bar.
>
>Considering usual stacking order I would rather interpret it the 
>other way round, foo at lowest level, followed by bar and any other 
>image in order of appearance, much like layers are added on top of 
>each other in image editing software.

    Your proposal would make the behavior of background images 
conceptually inconsistent with font family ordering.  In font 
families, the "top choice" comes first, followed by alternate 
choices.  I suspect most authors would expect the same sort of 
behavior with background images: the "top choice" comes first, and 
then "lower" choices follow in order.
    One possible use for this ability is that the author could define 
three or four images for the background, from most advanced to least, 
thus intentionally using the multiple-image ability as a fallback 
mechanism.  In other words:

    body {background: url(bg.svg), url(bg.png), url(bg.gif) 0 0 repeat;}

Reverse the order, and then authors have to remember that fonts go 
from first choice to last choice, but backgrounds go from last choice 
to first choice.
    I'll grant you that the cases are not totally analogous, since 
font are an all-or-nothing deal whereas backgrounds could be layered 
together, but I still think they should behave as similarly as 
possible.

-- 
Eric A. Meyer  (eric@meyerweb.com)    http://www.meyerweb.com/eric/
Principal, Complex Spiral Consulting  http://www.complexspiral.com/
"CSS: The Definitive Guide," "CSS2.0 Programmer's Reference,"
"Eric Meyer on CSS," and more   http://www.meyerweb.com/eric/books/
Received on Friday, 29 October 2004 14:53:31 GMT

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