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[css3-transitions] more precise rules for animating 'visibility'

From: L. David Baron <dbaron@dbaron.org>
Date: Tue, 27 Mar 2012 13:06:26 -0700
To: www-style@w3.org
Message-ID: <20120327200626.GA12317@crum.dbaron.org>
We resolved in the 2012 March 7 teleconference (minutes at
http://lists.w3.org/Archives/Public/www-style/2012Mar/0195.html ) to
make transitions of 'visibility' where one of the endpoints is
'visible' (i.e., transitions between visible/hidden or
visible/collapse) should be interpolable and have all intermediate
values be 'visible', whereas transitions between 'hidden' and
'collapse' should not be interpolable.

One thing I realize that we didn't discuss is what happens when the
output of the timing function (e.g., for cubic-bezier() functions
with Y values outside of [0, 1]).

It seems most sensible to me that any values of the timing function
that are <=0 or >=1 should lead to 'visibility' interpolating to the
nearer endpoint (rather than being "always visible").

So I'm proposing the spec say:
  # <strong>visibility</strong>: if one of the values is
  # 'visible', interpolated as a discrete step where values of the
  # timing function between 0 and 1 map to 'visible' and other
  # values of the timing function (which occur only at the
  # start/end of the transition or as a result of 'cubic-bezier()'
  # functions with Y values outside of [0, 1]) map to the closer
  # endpoint; if neither value is 'visible' then not interpolable.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Tuesday, 27 March 2012 20:06:50 GMT

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