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Re: [css21][css-sizing][web compat] max-width and intrinsic sizes in a table scenario

From: L. David Baron <dbaron@dbaron.org>
Date: Tue, 8 Dec 2015 21:51:01 -0500
To: Karl Dubost <kdubost@mozilla.com>
Cc: www-style@w3.org
Message-ID: <20151209025101.GA26911@pescadero.dbaron.org>
On Tuesday 2015-10-27 09:44 +0900, Karl Dubost wrote:
> Gecko (Firefox) has a Webcompat issue related to the use of `max-width` inside `table`. I put an example on Codepen [1].
> 
> For Webcompat reasons with Blink and WebKit, we will probably need to modify Gecko code (see Bugzilla [2]). In the seeAlso section of this bug, you will find some of the reported Web Compat issues. 
> 
> What I would like to know is if the CSS specification needs to be changed to reflect the reality.
[...]
> Currently Blink and Safari are reducing the image so it fits the viewport. 
> You can see this in recent Web Compat bugs
> https://webcompat.com/issues/1838
> https://webcompat.com/issues/1837
> 
> I summarized the issue in the webcompat space [4]. 

So the underlying behavior here that needs to be specified is (using
css-sizing terminology) that when either 'width' or 'max-width' on a
replaced element is a percentage, that element's min-content
contribution is zero.  Note that given that this occurs for
'max-width', this needs to override the rule that the min-content
contribution is determined by the specified size, since a replaced
element with "width: 100px; max-width: 50%" has a min-content
contribution of 0.

The relevant section of the specification is:
http://dev.w3.org/csswg/css-sizing/#replaced-intrinsic

At least, that's the relevant specification assuming a relatively
strict definition of replaced element.  This rule should not apply
to form controls and similar things that aren't explained by CSS.
It should only apply to things that do replaced element sizing such
as images, plugins, videos, and iframes.

I'm not sure if we have a clear enough definition of replaced
element, or whether we perhaps need two definitions.

-David

> [1]: http://codepen.io/anon/pen/rOdpdW
> [2]: https://bugzilla.mozilla.org/show_bug.cgi?id=823483
> [3]: https://drafts.csswg.org/css2/visudet.html#propdef-max-width
> [4]: https://github.com/whatwg/compat/issues/12

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
             Before I built a wall I'd ask to know
             What I was walling in or walling out,
             And to whom I was like to give offense.
               - Robert Frost, Mending Wall (1914)

Received on Wednesday, 9 December 2015 02:54:32 UTC

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