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[css3-images][css3-background] Specify "CSS View Box" in B&B

From: Leif Arne Storset <lstorset@opera.com>
Date: Tue, 08 Feb 2011 12:51:50 +0100
To: "Tab Atkins, jr." <jackalmage@gmail.com>, "Brad Kemper" <brad.kemper@gmail.com>, fantasai <fantasai.lists@inkedblade.net>, "bert@w3.org" <bert@w3.org>
Cc: "www-style@w3.org" <www-style@w3.org>, "Rafal Chlodnicki" <rchlodnicki@opera.com>
Message-ID: <op.vqk1woo5tmo5g6@nynorsk>
This is somewhat related to yesterday's border-image discussion [0]. Brad  
and Tab seem to say that the the rendering for dimensionless background  
images is clear, but I think it needs a little bit of work.

Reading [1] and a message from 2009 [2], it seems the intention is that  
when scaling gradients using background-size, B&B's "intrinsic size" [3]  
should be understood as the "CSS View Box" defined in the Images spec [4].  
(The attachment, which contains a gradient with 'background-size: 60px',  
illustrates that Gecko and WebKit follow this interpretation.) Is my  
understanding correct?

If this is correct, then either B&B should specify the "CSS View Box" and  
use it in the definition of background-size [3], or Images should specify  
that a gradient's "intrinsic size" should be considered the size of its  
CSS View Box for purposes of sizing [5]. The former seems simpler and  

In the current revision, background-size says to use 100% for 'auto' [3]  
(since gradients explicitly have no intrinsic size [5] and there is no  
mention of any implicit ratio).

0. http://lists.w3.org/Archives/Public/www-style/2011Feb/0170.html
1. http://lists.w3.org/Archives/Public/www-style/2011Feb/0127.html
2. http://lists.w3.org/Archives/Public/www-style/2009Dec/0128.html
3. http://dev.w3.org/csswg/css3-background/#auto
4. http://dev.w3.org/csswg/css3-images/#css-view-box
5. http://dev.w3.org/csswg/css3-images/#gradients

Leif Arne Storset
Core Technology Developer, Opera Software
Oslo, Norway
Received on Tuesday, 8 February 2011 11:52:12 UTC

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