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

From: L. David Baron <dbaron@dbaron.org>
Date: Tue, 27 Mar 2012 12:18:42 -0700
To: www-style@w3.org
Message-ID: <20120327191842.GA11546@crum.dbaron.org>
In http://lists.w3.org/Archives/Public/www-style/2012Mar/0013.html
we agreed to accept my proposal in 
http://lists.w3.org/Archives/Public/www-style/2012Feb/1083.html for
https://www.w3.org/Bugs/Public/show_bug.cgi?id=15838 :  that is, we
agreed that when transition-duration and transition-delay are both
0s that there should be no transition (and thus no events).

However, we didn't agree whether that was the only case.  I realized
that there are a set of other cases where there probably shouldn't
be a transition:  in particular, when transition delay is as
negative or more negative than transition duration is positive.  In
these cases the transition end event would have a firing time at or
before the time the transition started, which suggests to me that
maybe it shouldn't fire at all.

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?

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Tuesday, 27 March 2012 19:19:06 GMT

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