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Re: [css-writing-modes] the caption-side keywords

From: fantasai <fantasai.lists@inkedblade.net>
Date: Thu, 17 Sep 2015 02:21:33 -0400
To: MURAKAMI Shinyu <murakami@antenna.co.jp>, www-style@w3.org
Message-ID: <55FA5BED.1040704@inkedblade.net>
On 03/17/2014 12:56 PM, MURAKAMI Shinyu wrote:
> 7.7 Table Caption Mappings: the caption-side keywords
> http://dev.w3.org/csswg/css-writing-modes/#caption-side
>
> The spec says:
> |  New values: block-start | block-end
>   ...
> |  For implementations that support the 'top-outside' and
> |  'bottom-outside' model, corresponding 'start-outside' and
> |  'end-outside' are similarly introduced.
>
> I think these should be 'block-start-outside' and 'block-end-outside'
> for consistency.
>
> I have also a concern about treatment of existing values (top/bottom/left/right).
>
> The spec says:
> |  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.
>
> I checked existing implementations, Webkit and Blink, and found that
> they treat the 'bottom' as 'block-end', and other values (top/left/right)
> as 'block-start'. The value 'block-end' (or its old name 'after') are
> not supported.
>
> As a result, the only way to specify the caption to the block-end side
> in vertical writing mode is 'caption-side: bottom'.
> However, the spec says 'bottom' must be treated as 'block-start'.
> This may cause problem.
> It would be better 'bottom' treated as block-end?
>
> I am rethinking about caption-side CSS2 keywords.
> The following definition would be better?
>
> 'top' is the alias for 'block-start' (the right side in vertical-rl mode).
> 'bottom' is the alias for 'block-end' (the left side in vertical-rl mode).
> 'left' is the line-left (the top side in vertical-rl mode).
> 'right' is the line-right (the bottom side in vertical-rl mode).
>
> I think it would be natural that the keyword 'right' of 'caption-side',
> 'text-align', and 'float' would have all same meaning, the bottom side in
> vertical-rl writing mode.
> Also the keyword 'top' and 'bottom' of the 'vertical-align' on table-cell
> mean block-start and block-end (right and left in vertical-rl writing mode)
> obviously and for the caption-side would be the same.

The CSSWG discussed 'caption-side' at the F2F and decided to
treat 'caption-side' top/bottom/left/right as logical values.

So it will be as you write:
   top == block-start
   bottom == block-end
   left == line-left
   right == line-right

(Note this will make these keywords inconsistent with their
meaning in logical properties generally, where they are purely
physical.)

As a result, we will drop the block-start/block-end values
from caption-side.

Let me know if this is acceptable.

~fantasai
Received on Thursday, 17 September 2015 06:22:02 UTC

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