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RE: [css3-background] 'background-size: auto auto' and images with intrinsic size in one dimension

From: Brian Manthos <brianman@microsoft.com>
Date: Mon, 8 Aug 2011 20:03:50 +0000
To: Tab Atkins Jr. <jackalmage@gmail.com>
CC: "L. David Baron" <dbaron@dbaron.org>, "Boris Zbarsky (bzbarsky@MIT.EDU)" <bzbarsky@mit.edu>, "www-style@w3.org" <www-style@w3.org>
Message-ID: <9710FCC2E88860489239BE0308AC5D17115BA5@TK5EX14MBXC264.redmond.corp.microsoft.com>
My point was NOT that a ratio is established by that quote.

My point was that the percentage resolves to a length and thus you have a height.  By having a specified width combined with a resolved height, you no longer have a need for aspect ratio in deciding how to apply background-size.

I'm interpreting the language "they indicate a portion of the viewport that is actually covered by image data" to include the meaning "resolve percentage widths and heights against the viewport to establish the size of 'image data' (when used for purposes such as background-image)".

For right or wrong, I believe that's roughly how it was interpreted or IE9's implementation.

-Brian

-----Original Message-----
From: Tab Atkins Jr. [mailto:jackalmage@gmail.com] 
Sent: Monday, August 08, 2011 12:24 PM
To: Brian Manthos
Cc: L. David Baron; Boris Zbarsky (bzbarsky@MIT.EDU); www-style@w3.org
Subject: Re: [css3-background] 'background-size: auto auto' and images with intrinsic size in one dimension

On Mon, Aug 8, 2011 at 11:24 AM, Brian Manthos <brianman@microsoft.com> wrote:
> I forgot to mention this linkage in the chain of evaluation ...
>
> http://www.w3.org/TR/SVGMobile12/coords.html#IntrinsicSizing

>
> My recollection is that this explains how the percentages interact with the attachment location.
>
> My other recollection is that, although it's in SVG Tiny 1.2, it was the preferred model and that it was going to be moved or replicated somewhere else in spec land.
>
>
> Like I said, I'm fuzzy on this area but this combined with the other references led some of us (and definitely me) to the conclusion that we had no SVG-provided examples of the absence of intrinsic ratio during IE9 development.  And none of the new feature set of IE10 has shaken that understanding.

Read that section you linked again - it still agrees with what we've said, and in fact does so in much clearer terms than SVG1.1 did.  In particular, note this fragment: "Specifically, percentage values do not provide an intrinsic width or height, and do not indicate a percentage of the containing block. Rather, they indicate the portion of the viewport that is actually covered by image data."

Thus, in the example I gave, there is no intrinsic height (as it took the lacuna value of 100%), and there is no intrinsic aspect ratio (as there was no viewBox, and one of the width/height values was a percentage).  There is only an intrinsic width.

~TJ

Received on Monday, 8 August 2011 20:04:28 GMT

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