Re:Canonical ordering

From: Peter Constable (
Date: Mon May 01 2000 - 15:21:39 EDT

       So, there's no list of these anywhere? Can anybody provide a

       You mentioned language tagging. I could certainly create an
       implementation in my software that positions the diacritics
       side-by-side, perhaps based on a language tag. But that doesn't
       mean that the text can be exchanged in a way that everybody
       knows that that's supposed to happen. A solution involving
       language tagging would have to assume that everybody who's ever
       going to read the text will know that the presence of that
       language tag implies different diacritic behaviour - i.e. that
       information is registered somewhere. Is that the best solution?
       What would it take to incorporate support for this purely in


       Peter Constable asked

> On page 50 of U3, last paragraph, I read the following:

> "Some specific nonspacing marks override the default
> stacking behaviour by being positioned side-by-side rather
> than stacking or by ligaturing with an adjacent nonspacing
> mark."

> How do I tell which this applies to?

       Sometimes the Unicode script description mentions it, other
       times knowledge of the writing system is needed.
       Greek and Hebrew immediately spring to mind.

> If, suppose, there were some writing system in which
> diacricits like acute and circumflex (say) occured, but the
> could co-occur over the same base character and in that
> situation were expected to be positioned side-by-side, what
> would it take to handle that?

       Vietnamese uses the Latin script but doesn't behave as normal.
       See for example U+1EA7. Language tagging might be the best
       way around the problem. (Special forms of the accent seem to
       be frowned upon - see the deprecated U+0341.)


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