W3C home > Mailing lists > Public > www-style@w3.org > February 2016

Re: [css-values] range-checking, calc(-5), and serialization

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 16 Feb 2016 16:03:56 -0800
Message-ID: <CAAWBYDAZwbm7cjMgc_4AQm4BkBBD70yERsGgjooX6h8L-zvQPA@mail.gmail.com>
To: fantasai <fantasai.lists@inkedblade.net>
Cc: "www-style@w3.org" <www-style@w3.org>
On Tue, Feb 16, 2016 at 4:02 PM, fantasai <fantasai.lists@inkedblade.net> wrote:
> On 02/16/2016 06:53 PM, Tab Atkins Jr. wrote:
>>
>> On Tue, Feb 16, 2016 at 3:43 PM, fantasai <fantasai.lists@inkedblade.net>
>> wrote:
>>>
>>> The definition for calc() states:
>>>
>>> https://www.w3.org/TR/2015/CR-css-values-3-20150611/
>>>   # The value resulting from an expression must be clamped to the
>>>   # range allowed in the target context.
>>>
>>> There's a few issues with this...
>>>
>>> Issue 1:
>>>    It doesn't state when this is clamped. Presumably the used value is
>>> clamped.
>>>    Assuming everyone agrees, I'll update the spec to say so.
>>>
>>> Issue 2:
>>>    This presumably means that ''width: calc(-5px)'' is valid, and treated
>>> as
>>> zero.
>>>    However, the serialization rules recently added to the spec state that
>>>      https://drafts.csswg.org/css-values-3/#calc-serialize
>>>      # If the result is a single value, serialize as that value,
>>>      # discarding the calc() wrapper.
>>>    This means that some calc() values will not be round-trippable.
>>
>>
>> Issue 2 is only an issue because of your suggested resolution for
>> Issue 1.  If the clamping happens "as soon as possible", then the
>> serialization rules would produce a "0" in that case.
>
>
> The Serialization rules don't mention clamping, only simplifying arithmetic.
> You could certainly add clamping as step 2 for serialization and still keep
> issue 1 as "used values".

Sure, that works.

~TJ
Received on Wednesday, 17 February 2016 00:04:45 UTC

This archive was generated by hypermail 2.4.0 : Friday, 25 March 2022 10:09:00 UTC