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Re: Positioned Layout proposal

From: Robert O'Callahan <robert@ocallahan.org>
Date: Tue, 19 Oct 2010 12:25:49 +1300
Message-ID: <AANLkTik8pBZTW13tDr6TzEETt73EvVpUrbDCb5CMJCng@mail.gmail.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: www-style list <www-style@w3.org>
Unfortunately, the problem of cyclic dependencies is very serious. It's not
restricted to cycles of explicit positioning constraints.

For example, the geometry of positioned elements can affect whether
overflow:auto elements have overflow, which affects whether scrollbars are
present, which can affect the available width and hence the layout of any of
the descendants of the overflow:auto element. Furthermore, the presence or
absence of a horizontal scrollbar can affect the height of an element and
hence the positions of many other elements inside and outside the
overflow:auto element. The only way I can think of to resolve those issues
in a sane way for your spec would be to have your specially positioned
elements not contribute to the "scrollable overflow area" of any of their
ancestor elements. That may cause problems for some of your use cases.

Even if we do that, the size of a positioned element still affects the
layout of its descendants, and therefore with your spec you can have cycles
where some dependencies are explicit positioning constraints and some are
implicit layout constraints.

I think you should focus on improving this area of your proposal, since I
think it's where most of the risk and complexity lies.

Rob
-- 
"Now the Bereans were of more noble character than the Thessalonians, for
they received the message with great eagerness and examined the Scriptures
every day to see if what Paul said was true." [Acts 17:11]
Received on Monday, 18 October 2010 23:26:17 GMT

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