[Webkit-unassigned] [Bug 170834] New: background-position with only one [ <length | <percent> ] value with gradient incorrectly rendered

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Thu Apr 13 16:47:06 PDT 2017


            Bug ID: 170834
           Summary: background-position with only one [ <length |
                    <percent> ] value with gradient incorrectly rendered
           Product: WebKit
           Version: Safari 10
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: CSS
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: phiw2 at l-c-n.com

Example URL:

Per CSS3 - backgrounds:

For background-size:

> [ <length-percentage> | auto ]{1,2}
> 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’.

further, for “auto”, the text notes:

> 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%.

For a gradient (as in the example), the “image” has no intrinsic size, thus 100% should be used. That is what Firefox / Gecko does.

Chrome and Safari are wrong.

one <percent> value



one <length> value


What is the expected behavior?
Filled green square and no red

What went wrong?
sliver of green and large area of red

(related discussion on the CSS WG list: https://lists.w3.org/Archives/Public/www-style/2017Apr/thread.html#msg29

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