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Re: [css3-2d-transforms][css3-images] <position> grammar is duplicated or points to the wrong spec

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 24 Jan 2012 11:26:52 -0800
Message-ID: <CAAWBYDB5Z-fDsyCAKH=R_LBR159V1Mpn0q7AFdsQn3FVF+bPiA@mail.gmail.com>
To: "L. David Baron" <dbaron@dbaron.org>
Cc: Brian Manthos <brianman@microsoft.com>, Sylvain Galineau <sylvaing@microsoft.com>, fantasai <fantasai@inkedblade.net>, www-style list <www-style@w3.org>
On Tue, Jan 24, 2012 at 11:17 AM, L. David Baron <dbaron@dbaron.org> wrote:
> On Tuesday 2012-01-24 19:03 +0000, Brian Manthos wrote:
>> Tab:
>> >Brian:
>> >> The fact that "background-position: 10%;" and "background-position: calc(10%);"
>> >> can result in differ renderings is perhaps unfortunate, but required by the specs as I read them.
>> > Yes, it's currently required by the specs.  I've stated this several times.
>>
>> You might be saying that.  My interpretation of David's comments
>> is that he was saying otherwise.
>
> I don't understand the current calc() spec well enough to comment on
> what it says.
>
> However, I firmly believe that if Tab's assertion about what it
> currently says is correct (which I believe is at the very least what
> it's trying to say), then the spec is wrong and needs to be fixed.
> I think calc() should not have any discontinuities, i.e., putting
> "calc()" around a valid value shouldn't change its behavior, and
> putting a "+1px" inside a calc() should move change the result by
> 1px.

I earlier quoted the relevant parts of the current spec for fantasai:

"A math expression has a resolved type, which is one of ‘<length>’,
‘<frequency>’, ‘<angle>’, ‘<time>’, or ‘<number>’. [...] If
percentages are accepted in the context in which the expression is
placed, a PERCENTAGE token has the type of the value that percentages
are relative to; otherwise, a math expression containing percentages
is invalid."

I agree that the spec should be changed here.

~TJ
Received on Tuesday, 24 January 2012 19:27:47 GMT

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