Re: [css-writing-modes-3] 7.7 Table Caption Mappings: caption-side

On 11/8/15 04:44, Gérard Talbot wrote:
> Hello,
>
> "
> Implementations that support the top and bottom values of the
> caption-side property but do not support side captions (i.e. left and
> right captions in horizontal writing modes) must treat both top and
> bottom as block-start, when the table is in a vertical writing mode.
> "
> 7.7 Table Caption Mappings: the caption-side keywords
> http://www.w3.org/TR/css-writing-modes-3/#caption-side
> https://drafts.csswg.org/css-writing-modes-3/#caption-side
>
> I see 2 problems with such sentence.
>
> 1-
> If an implementation supports top and bottom values of the caption-side
> property but do not support side captions (i.e. left and right captions
> in horizontal writing modes), why it should not treat top as block-start
> on one hand and bottom as block-end on the other hand? Why treat both
> top and bottom as block-start?
>
> 2-
> The way the sentence is written could also be subject of interpretation.
> If an implementation supports top and bottom values of the caption-side
> property, then it must do "x" regardless of its support of side
> captions. The sentence could suggest that there will be a different
> normative procedure when an implementation supports side captions...
> when there should not be any difference.
>
> - - - - - - -
>
>
> "For implementations that do support side captions (i.e. the left and
> right values from the obsolete CSS 2.0 specification [CSS2]), this
> module also introduces the inline-start and inline-end values, which
> behave similarly and which position the caption on the inline-start and
> inline-end sides of the table box, calculated with respect to the
> writing mode of the table box. For such implementations, the top and
> bottom values must place the caption on the top and bottom sides of the
> table box, respectively.
> "
> 7.7 Table Caption Mappings: the caption-side keywords
> http://www.w3.org/TR/css-writing-modes-3/#caption-side
> https://drafts.csswg.org/css-writing-modes-3/#caption-side
>
> Here, I suggest to clarify the last sentence:
>
> Current is: (...) the top and bottom values must place the caption on
> the top and bottom sides of the table box, respectively.
>
> Proposing: (...) the top and bottom values must place the caption at the
> logical top and logical bottom sides of the table box, respectively.
>
> I wonder why the sentence did not just say what should have been said a
> paragraph before, which is "must treat top as block-star and bottom as
> block-end" or something similar...

I don't agree with this. It seems clear to me that the spec is intending 
the existing physical values 'top' and 'bottom' to remain physical, 
regardless of writing mode; they are NOT to be reinterpreted as 'logical 
top' and 'logical bottom'.

Otherwise, why would it introduce the new block-* values at all?

And then it's reasonable that in an implementation that does not support 
side captions, both 'top' and 'bottom' (which would correspond to the 
inline-start and inline-end sides of a vertical table) fall back to 
being treated as block-start.

This makes caption positioning similar, from an author's point of view, 
to things like margin, where we have existing physical properties that 
remain physical regardless of writing mode, and parallel logical 
properties that adapt. I think that makes sense.

JK

Received on Tuesday, 11 August 2015 09:06:16 UTC