W3C home > Mailing lists > Public > www-style@w3.org > February 2009

Re: Comments on CSS Transitions

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Fri, 27 Feb 2009 11:36:39 -0600
Message-ID: <dd0fbad0902270936p22b624acn1322237ffd5d3aed@mail.gmail.com>
To: Boris Zbarsky <bzbarsky@mit.edu>
Cc: www-style@w3.org, www-svg@w3.org
On Fri, Feb 27, 2009 at 11:04 AM, Boris Zbarsky <bzbarsky@mit.edu> wrote:
> Tab Atkins Jr. wrote:
>> It seems clear that transitions are triggered whenever the specified
>> value changes, whether through direct manipulation or through the
>> cascade.
>
> It does?  The last time I looked into this it sounded to me like a
> transition is triggered whenever the _computed_ value of a property
> should change, and that this change should happen in increments.
> Computed value changes due to a transition should be ignored during this
> process.
>
> Has the draft changed significantly on this matter?

This may simply be due to lingering confusion on my part surrounding
the value terminology.  It seems to me that an actual rule change
(such as from a :hover rule suddenly applying) changes the specified
value first, then the computed, then the used.  The transition would
gradually change the computed/used, as appropriate.

>> The start and end values, similarly, seem to obviously be the previous
>> specified value, and the newly specified value.
>
> Note that the computed value might change without the specified value
> changing, and vice versa.

Hmm, could you give an example?  It seems clear that the *used* value
can change without the specified value changing (frex, the width of
the containing block can change, altering the used value of a
percentage-width child), but I don't see how the computed value can do
so.

~TJ
Received on Friday, 27 February 2009 17:37:14 GMT

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