W3C home > Mailing lists > Public > www-style@w3.org > May 2011

Re: Transitioning top and bottom properties.

From: Alan Gresley <alan@css-class.com>
Date: Wed, 01 Jun 2011 03:46:45 +1000
Message-ID: <4DE52985.8080009@css-class.com>
To: Brad Kemper <brad.kemper@gmail.com>
CC: Simon Fraser <smfr@me.com>, Maarten Billemont <lhunath@gmail.com>, www-style list <www-style@w3.org>
On 31/05/2011 1:52 AM, Brad Kemper wrote:
> On May 30, 2011, at 8:30 AM, Simon Fraser wrote:
>> On May 28, 2011, at 2:41 pm, Maarten Billemont wrote:
>>> Consider the following test case: http://jsfiddle.net/An6vn/3/
>>> Here, the point is to have a container of set size (eg. an image)
>>> with a caption attached to the bottom of it. The caption would
>>> have a single line that provides the name of the image, after
>>> which a paragraph of description could follow. The case
>>> demonstrates a style where only the first line is visible by
>>> default and the rest appears on hover, by means of transitioning
>>> from top:100%; margin-top:-1em; ->  top:auto; bottom:0;
>>> Without transitioning, this works very well.  Add CSS
>>> transitioning and Chrome transitions the top to 0 (moving the
>>> caption all the way to the top), after which the caption suddenly
>>> appears on the very bottom (applying bottom:0). Firefox refuses
>>> to transition to auto, at all.
>>> I would expect that each would determine the begin and end
>>> y-position of the caption relative to its parent in each instance
>>> and transition from one to the other.  Unfortunately, this isn't
>>> how it works.
>> Neither Chrome (really WebKit) nor Firefox do the right thing when
>> transitioning to/from 'auto' values.
>> See the thread starting
>> at<http://lists.w3.org/Archives/Public/www-style/2010Apr/0526.html>
> Is there any possibility for figuring out what the right thing is,
> and getting that into the spec and implementations? Transitioning to
> and from 'auto' for width, height, and the trbl positioning
> properties is a gigantic use case. 'Auto' has got to be the most
> common value for those properties, and transitioning from that to a
> specific length is extremely useful.

I would appreciate seeing use cases with width, height, etc with auto.

What you have with auto offsets are just placeholders for any offsets 
that have a value that _are not auto_. Anyway, you would have to change 
the behavior of how offset now work.



Note that Opera 11.11 does it all wrong since the absolutely positioned 
element (on the left with salmon background) stops the margin collapse 
of the first inflow element (div#move with "Hover Me"). To prove this, 
select margin-top: 200px.

Considering that transitions can cause elements to move around when 
resizing the viewport or perhaps CJK horizontal text becoming vertical 
text on a mobile due to orientation and many more reasons I can list, I 
think we just leave auto offsets alone.

Alan Gresley
Received on Tuesday, 31 May 2011 17:47:16 UTC

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