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Re: [css-transforms] 'transform-box' defaults in svg

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Wed, 30 Sep 2015 11:18:43 -0700
Message-ID: <CAAWBYDBiKK9tZ9VoicjPuG1CRF9enw=PhoayVJNSj_o33a6DEQ@mail.gmail.com>
To: Amelia Bellamy-Royds <amelia.bellamy.royds@gmail.com>
Cc: Erik Dahlström <erik@xn--dahlstrm-t4a.net>, Dirk Schulze <dschulze@adobe.com>, "www-style@w3.org" <www-style@w3.org>, "public-fx@w3.org" <public-fx@w3.org>
On Wed, Sep 30, 2015 at 8:31 AM, Amelia Bellamy-Royds
<amelia.bellamy.royds@gmail.com> wrote:
> Erik: Are you suggesting that the `auto` value would use the viewBox as the
> reference if `transform-origin` was set in absolute units, and `fill-box` as
> a reference if it used percentages?
>
> That sounds very difficult to implement & unnecessarily confusing.  What if
> the `transform-origin` included calc() functions?  Or was animated between
> different values?  An animation between 100px and 100% is implemented as an
> animation between `calc(100px + 0%)` and `calc(0px + 100%)`.

Yes, it's unofficially illegal (at the spec design level) for
percentages to resolve differently than absolute lengths, for
precisely the calc() issue you bring up.  It makes % and px no longer
comparable units, and requires us to have special spec prose defining
how to combine them in a calc().  Some legacy values (like <position>)
have that, but we're not adding it to anything else.

~TJ
Received on Wednesday, 30 September 2015 18:19:30 UTC

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