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RE: [css3-transitions] shorthand/longhand handling in transition property

From: Sylvain Galineau <sylvaing@microsoft.com>
Date: Mon, 25 Oct 2010 22:15:15 +0000
To: Tab Atkins Jr. <jackalmage@gmail.com>
CC: Simon Fraser <smfr@me.com>, www-style list <www-style@w3.org>
Message-ID: <045A765940533D4CA4933A4A7E32597E2814C6C1@TK5EX14MBXC120.redmond.corp.microsoft.com>
> From: Tab Atkins Jr. [mailto:jackalmage@gmail.com]
> Sent: Monday, October 25, 2010 2:57 PM
> To: Sylvain Galineau
> Cc: Simon Fraser; www-style list
> Subject: Re: [css3-transitions] shorthand/longhand handling in
> transition property
> On Mon, Oct 25, 2010 at 2:47 PM, Sylvain Galineau
> <sylvaing@microsoft.com> wrote:
> > Tab Atkins wrote:
> >> (b) is certainly how I expect this to work.
> >
> > It seems David and I agree that your expectation is contrary to the
> current
> > spec prose which actually calls for a) :
> >
> > # If a property is specified multiple times in the value of
> ‘transition-property’
> > # (either on its own or via a shorthand that contains it), then the
> transition that
> > # starts uses the duration, delay, and timing function at the index
> corresponding to
> > # the last occurrence of the property.
> >
> > Note the "(either on its own or via a shorthand that contains it)"
> clause. This is what
> > WebKit does today afaict.
> I don't understand.  Dbaron is saying that the current spec text
> suggests (b).  I am supporting the same thing that dbaron appears to
> be.

What dbaron and I are saying is that the spec effectively says you should:
expand the shorthands in transition-property then apply the duplicate
handling rule.

This is not what b) is about at all. 

> > The problem with b) is that we're saying two transitions may be
> running on the same
> > shorthand but I very much doubt that's desirable. I don't think we
> can or should
> > collapse duplicates in some cases and not others.
> I'm sorry, but I can't understand this paragraph at all.

Look at b) again. What it means to say is that if you don't handle
the two border-right-widths as duplicates - i.e. one of them 'wins' - 
then you have both the shorthand and the longhand transitioning the same
property, possibly at different speeds. That's not good.

I think we want to resolve duplicates before transitioning, whether
the duplication is explicit - the authors wrote it that way - or
implicit through the use of shorthands+longhands or a keyword like 'all'.
Received on Monday, 25 October 2010 22:15:52 UTC

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