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 Post subject: Scope of UTR50
PostPosted: Sun Oct 23, 2011 11:38 pm 
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Joined: Tue Oct 11, 2011 4:34 pm
Posts: 19
I'm posting this comment on behalf of the co-editors of CSS3 Writing Modes and CSS3 Text (Koji Ishii, Shinyu Muarakami, and myself):

UTR #50 scopes itself to Japanese layout. However, CSS needs to address all vertical writing systems. If the scope is not broadened to include other writing systems, we cannot rely on UTR#50.

(We define vertical writing systems as those in which entire compositions, not just small snippets such as image captions or table headers, are commonly written vertically.)


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 Post subject: Re: Scope of UTR50
PostPosted: Thu Oct 27, 2011 11:22 am 
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Joined: Fri Dec 04, 2009 9:25 pm
Posts: 76
If you consider the issue of spacing characters on a line, you will notice that the method commonly used for Western texts (adjust the width of space characters, and may be trigger letterspacing) and the method commonly used for Japanese texts (adjust the space between characters, with a system of priorities) are incompatible; applying one method to the other context leads to incorrect results for that other context. The implication is that a universal layout engine needs a way to select one or the other method (a locale may be a good start).

Similarly, there is nothing that prevents a universal layout engine from using UTR#50 for a Japanese/East Asian context, and another method for a Western context. Indeed, that seems necessary as a Western vertical line of English will typically have all its Basic Latin letters upright, which an East Asian line with have them sideways.

Furthermore, I don't think there is a lot of value in creating corresponding properties for the Western world: Western Class would split, more or less, U+0020 in one class and all the other characters in another; Western Orientation would be upright for all characters.


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