Re: [CSS21] rule on % height in auto-height container should apply to used value, not computed value

On Mon, Oct 24, 2011 at 9:21 PM, L. David Baron <dbaron@dbaron.org> wrote:
> http://www.w3.org/TR/CSS21/visudet.html#propdef-height says, in the
> definition of <percentage>:
>  # If the height of the containing block is not specified
>  # explicitly (i.e., it depends on content height), and this
>  # element is not absolutely positioned, the value computes to
>  # 'auto'.
>
> I believe this statement (and the corresponding bit of the "Computed
> value" line) should be updated to reflect that this change happens
> at the *used value* level but not at the *computed value* level.  I
> think it is part of the principle of the computed vs. used value
> distinction that computed values of properties should not depend on
> the identity of or properties of the element's containing block,
> though I don't know if this principle was previously stated.  Thus,
> I think it should have been changed when we introduced the concept
> of used value.
>
> (I'd note that the prose for max-height and min-height is different,
> but should probably be the same, once this is corrected.)
>
> A testcase is attached.  Gecko and WebKit agree with my
> interpretation; Opera does not.

I thought the only principle separating computed from used was that
computed values were what you get when you resolve it as far as
possible without actually doing layout; used values require layout
data to resolve.

Is the containing block of an element something that requires layout
to resolve?  I don't *think* it is.  Thus, it should be okay to have a
computed value depend on it.

~TJ