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RE: [css3-writing-modes] text-combine: cluster

From: Koji Ishii <kojiishi@gluesoft.co.jp>
Date: Mon, 25 Oct 2010 23:45:20 -0400
To: Ambrose LI <ambrose.li@gmail.com>, John Daggett <jdaggett@mozilla.com>
CC: www-style list <www-style@w3.org>
Message-ID: <A592E245B36A8949BDB0A302B375FB4E0AA36341DA@MAILR001.mail.lan>
I agree that this one is not very important to work further at this point, and also spec needs more description.

But I just wanted to make some clarifications.

Text-combine:cluster represents a typeset feature to put several characters into 1em-box. There are some pre-composed Unicode code point for the common usage at:
http://www.unicode.org/charts/PDF/U3300.pdf

As I guess from feature name, the font feature is to replace specific set of strings to one of the corresponding pre-composed letters. Am I correct?

This feature is to support other cases where pre-composed Unicode code point is not available. I suspect the font feature John mentioned doesn't support such cases, but can you please confirm, John?

Assuming so, the features do not overwrap each other. Its origin was a typeset feature, and there're rules how to typeset multiple characters into 1em-box. That is why the glyph changes by the text flow. To ease typesetting the common cases, pre-composed characters are created, but the original typeset feature is still active. I believe I knew the typesetting rules long time ago, but can't remember from my head.

So. I'm fine to postpone this priority wise; its priority is much less than vertical text flow. I just wanted to make sure we understand the features are different, and there're still some demands for the feature. As you talked to me before, I'll check with experts why this didn't make into JIS 4051 nor JLREQ. That'd an interesting question for me too.

Oh, and BTW, I didn't know this is available in OpenType feature, is supported by CSS3 fonts, and also is implemented in Firefox! It's just amazing. Wonderful. Thank you for your great job, John!


Regards,
Koji
Received on Tuesday, 26 October 2010 03:43:19 GMT

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