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Re: [css3-ui] Negative values in outline-offset?

From: Leif Arne Storset <lstorset@opera.com>
Date: Thu, 16 Feb 2012 11:10:31 +0100
To: fantasai <fantasai.lists@inkedblade.net>, "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: www-style@w3.org
Message-ID: <op.v9rnvt1xtmo5g6@localhost.localdomain>
Tab Atkins Jr. <jackalmage@gmail.com> skreiv Wed, 15 Feb 2012 22:45:07  

> On Wed, Feb 15, 2012 at 7:33 AM, fantasai  
> <fantasai.lists@inkedblade.net> wrote:
>> On 02/15/2012 03:02 AM, Kang-Hao (Kenny) Lu wrote:
>>> (An old thread about outline-offset being negative)
>>> (11/05/02 20:49), Boris Zbarsky wrote:
>>>> No, it just means that some implementations may not support all
>>>> negative values for some properties even though per spec they really
>>>> should.
>>> What should happen when the absolute value is bigger than half of the
>>> smaller outer border edge than? Test case:
>>> data:text/html,<p style="outline: solid; outline-offset: -2em;">Test
>>> WebKit browsers draw no outline in this case and Firefox....  I can't
>>> quite describe it... it's something like a normal outline without two
>>> top corners.
>>> I suggest we either explicitly mark it undefined (this case is  
>>> contrived
>>> anyway) or spec WebKit's behavior.
>> IMO the UA should floor it at the least offset it can support. It  
>> shouldn't
>> *not* draw the outline.
> Yes, our behavior sounds like a silly bug.  We can floor it instead.
> That should be an easy thing to change.

Just to make sure I understand: The new suggested behavior would be to  
floor the outline-offset to the lowest value that will draw the entire  
outline. In Kenny's test case, this would draw an "outline" in the middle  
of the element - sort of like strikethrough, only it would be a few pixels  
tall, invert the text by default, start after the start of the text and  
extend almost to the width of the P element.

An illustration of this boundary condition, based on Kenny's TC:

data:text/html,<p style="height: 20px; outline: solid; outline-offset:  

No objections to the change, if I have understood it correctly; the  
outline should reliably be visible.

Leif Arne Storset
Core Technology Developer, Opera Software
Oslo, Norway
Received on Thursday, 16 February 2012 10:11:12 UTC

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