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Re: [css3-transitions] under what transition-duration/delay conditions should there be a transition?

From: L. David Baron <dbaron@dbaron.org>
Date: Fri, 20 Apr 2012 15:43:43 -0300
To: Sylvain Galineau <sylvaing@microsoft.com>
Cc: "www-style@w3.org" <www-style@w3.org>
Message-ID: <20120420184343.GA26482@crum.dbaron.org>
On Friday 2012-04-20 00:37 +0000, Sylvain Galineau wrote:
> [L. David Baron:]
> > Thus, I've written:
> >   # When the computed value of a property changes, implementations
> >   # must start transitions based on the relevant item (see the
> >   # definition of ‘transition-property’) in the computed value of
> >   # ‘transition-property’. Corresponding to this item there are
> >   # values of ‘transition-duration’ and ‘transition-delay’ (see the
> >   # rules on matching lists). Define the combined duration of the
> >   # transition as the sum of max(‘transition-duration’, ‘0s’) and
> >   # ‘transition-delay’. When the combined duration is greater than
> >   # ‘0s’, then a transition starts based on the values of
> >   # ‘transition-duration’, ‘transition-delay’, and
> >   # ‘transition-timing-function’; in other cases transitions do not
> >   # occur.
> > 
> > Does this seem reasonable to others?
> > 
> My apologies for catching this so late; I agree with the resolution and had
> only one minor editorial question: is the "max(‘transition-duration’, ‘0s’)" 
> expression needed in this prose given that transition-duration explicitly maps 
> negative <time> values to 0s? Or is this just an editorial reminder to the reader?

http://dev.w3.org/csswg/css3-transitions/#transition-duration-property
says "is treated as '0s'", but it also says that the computed value
is unchanged from the specified value (and thus still negative when
less than zero).  I think prose referring to the value of a property
on an element should generally be presumed to be referring to the
computed value unless stated otherwise (though that's yet something
else we probably ought to be more explicit about in this spec and
others), so I think it probably does need to be stated.  So I think
I'll make the change:
  Corresponding to this item there are <ins>computed</ins> values
in the text above.

(This is all, of course, separate from the issue of whether this
mapping of negative values from negative values to '0s' should
actually happen.)

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Friday, 20 April 2012 18:44:12 GMT

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