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

From: MURAKAMI Shinyu <murakami@antenna.co.jp>
Date: Tue, 18 Mar 2014 01:56:09 +0900
To: www-style@w3.org
Message-Id: <20140318015609.E9BA.C598BCD7@antenna.co.jp>
7.7 Table Caption Mappings: the caption-side keywords

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.

BTW, the 'float' property will have same problem when 'top' and 'bottom' 
(or 'block-start' and 'block-end') values are added.
I discussed with HÃ¥kon about this.
His idea is 'top' = 'block-start' (aliases). See:


Shinyu Murakami
Antenna House
Received on Monday, 17 March 2014 16:56:39 UTC

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