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Re: [css-background] Animating border-position

From: Alan Stearns <stearns@adobe.com>
Date: Thu, 19 Dec 2013 19:46:18 +0000
To: fantasai <fantasai.lists@inkedblade.net>, Tab Atkins Jr. <jackalmage@gmail.com>
CC: www-style list <www-style@w3.org>, "L. David Baron" <dbaron@dbaron.org>
Message-ID: <CED88B10.35385%stearns@adobe.com>
On 12/18/13, 3:53 PM, "fantasai" <fantasai.lists@inkedblade.net> wrote:

>On 12/17/2013 06:23 PM, Tab Atkins Jr. wrote:
>> On Tue, Dec 17, 2013 at 5:43 PM, Tab Atkins Jr. <jackalmage@gmail.com>
>>wrote:
>>> On Tue, Dec 17, 2013 at 4:21 PM, fantasai
>>><fantasai.lists@inkedblade.net> wrote:
>>>> On 12/17/2013 03:32 PM, Tab Atkins Jr. wrote:
>>>>> However, as established by FF, we can at least convert values on
>>>>> opposite sides of the same axis into each other, if we establish that
>>>>> <percentage> can be preserved as a top-level type in a calc() in some
>>>>> cases, which we should do.  (I'm fiddling with V&U right now to allow
>>>>> it.  It's tricky to spec.)
>>>>
>>>> I'm confused as to why you think V&U needs changes.
>>>
>>> Because right now calc() specifies that a <percentage> resolves into a
>>> <length> (or whatever), but for <position> to work right, we need to
>>> preserve its percentage-ness.
>>
>> Never mind, turns out we'd already added a paragraph that specifies
>> this.  I just added a clarifying example to make sure it stands out,
>> using background-position directly.
>>
>> We just need to adjust how <position> is transitioned, and can
>> probably go do that in the Transitions spec.
>
>I've updated the spec's Computed Value line to be
>   | A list, each item consisting of: a pair of offsets (horizontal
>   | and vertical) from the top left origin each given as a
>   | combination of an absolute length and a percentage.
>
>I think in combination with dbaron's text for the Animatable line,
>this should be sufficient. (Though dbaron might have some suggestions
>for wording improvement...)

I’m trying to figure out how this works with the future-proofing ideas
from Tab’s proposal. For now, we assume the canonical origins are top,
left. But if we add logical origins, they would then be added as an
override to the top, left assumptions in the computed value?

Also, a reminder that I’m still looking for a response on [1] before we
take css-background to last call.

Thanks,

Alan

[1] http://lists.w3.org/Archives/Public/www-style/2013Nov/0429.html


Received on Thursday, 19 December 2013 19:46:51 UTC

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