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Re: [css3-images] interaction of parts of the definitions of object sizing

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Thu, 15 Mar 2012 17:08:27 -0700
Message-ID: <CAAWBYDAr6kHnxYrT17YO4gZokpTGYnrBYfDrb9+0pdkMG8OVvA@mail.gmail.com>
To: "L. David Baron" <dbaron@dbaron.org>
Cc: www-style@w3.org
On Wed, Mar 14, 2012 at 1:58 PM, L. David Baron <dbaron@dbaron.org> wrote:
> http://dev.w3.org/csswg/css3-images/#default-sizing (5.3, Default
> Concrete Object Size Resolution) has a list with three cases.  The
> three cases would be exhaustive if the third one didn't have the
> wording "and has no additional constraints".  It's not clear to me
> why this wording is present only in the third case; additional
> constraints such as min-width and max-width can affect the results
> of the first two cases as well.  It seems like it would be better to
> define all cases and then say what overrides that definition.  It's
> not at all clear to me that the interaction of these rules with
> things like min-width and max-width is defined correctly.
>
> It also seems a little bothersome that these rules are then
> overridden for the most important case by the following section
> (5.4, Sizing Objects: the ‘object-fit’ property).  Perhaps section
> 5.3 should be split into two sections:
>  (a) the default sizing algorithm
>  (b) the definition of how the concrete object size is found for
>     things other than replaced elements (simply referencing that
>     algorithm)
>
> Then section 5.4 on 'object-fit' can become a parallel to (b) and
> define how the algorithm is used for replaced elements, which also
> involves defining how it interacts with min-width and max-width
> (citing CSS 2.1, sections 10.4 and 10.7).

I've substantially reworked this section now to address your comments.

* "specified size" can now be a width/height *or* a contain/cover
constraint.  It can also have a rounding constraint in either
dimension.  This change lets specs directly lean on the algorithm for
contain/cover stuff or the sort of sizing that background-repeat:round
or border-image-repeat:round does, without having to redefine it
themselves every time.

* I've moved the list of 2.1 default object sizes to a subsection, and
also added specified sizes for all of them.

* I've addressed both sizing cases in 'border-image' - when the full
image is originally sized, and when the slices are sized.

* I've split the old "replaced elements" case into three, since it was
wrong before.  There's now a section for the 'content' property
(non-replaced, which is all you can do in 2.1), a section for replaced
elements (just calling out that they *dont'* use the sizing algorithm
here, and pointing to CSS2.1 sections 10.4 and 10.7 instead), and then
a section for the *contents* of replaced elements, hooking into
'object-fit'.

* the default sizing algorithm has been expanded to deal with the
cover/contain constraints and the rounding constraints that the
specified size may have.  The rounding behavior is a straight
paraphrase of the text in B&B, so it should definitely be correct.

* 'object-fit''s values have been reworded to just declare the
"specified size" constraints they each provide.


Please review these changes and let me know if you're satisfied with them.


> It's also not clear to me why the influence of background-repeat:
> round on background-size isn't just already taken into account in
> the definition of "specified width".

It now is, by simply defining that background-repeat adds a rounding
constraint to the specified size.

~TJ
Received on Friday, 16 March 2012 00:09:16 GMT

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