[css3-images] interaction of parts of the definitions of object sizing from Tab Atkins Jr. on 2012-03-16 (www-style@w3.org from March 2012) (original) (raw)

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 UTC