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[csswg-drafts] [css-backgrounds-3] background-size with "<length-percentage> auto" and gradient image is not interoperably implemented

From: Matt Rakow via GitHub <sysbot+gh@w3.org>
Date: Fri, 11 May 2018 23:31:43 +0000
To: public-css-archive@w3.org
Message-ID: <issues.opened-322461377-1526081502-sysbot+gh@w3.org>
ChumpChief has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-backgrounds-3] background-size with "<length-percentage> auto" and gradient image is not interoperably implemented ==
Per https://drafts.csswg.org/css-backgrounds-3/#valdef-background-size-length-percentage

> The first value gives the width of the corresponding image, the second value its height. If only one value is given the second is assumed to be auto.
> A percentage is relative to the background positioning area.
> An auto value for one dimension is resolved by using the image’s intrinsic ratio and the size of the other dimension, or failing that, using the image’s intrinsic size, or failing that, treating it as 100%.

Since gradients have no intrinsic size (per https://drafts.csswg.org/css-images-3/#gradients), I believe Firefox has the spec-compliant rendering on this test page:
https://jsfiddle.net/mecvebx8/

Edge/Chrome/Safari currently produce the same non-spec-compliant rendering.  I don't have a particular preference for either behavior, but would like to reach full interoperability between implementers with a matching spec.  Do we all agree that the spec/FF behavior is the correct/desirable behavior, and are other implementers open to making the change to match?  We can make the change in Edge if others are also on board.

The same discrepancy in implementation also exists for mask-size.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/2675 using your GitHub account
Received on Friday, 11 May 2018 23:31:48 UTC

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