Re: Multiple Preposed Marks

From: Richard Wordingham <richard.wordingham_at_ntlworld.com>
Date: Tue, 8 Nov 2016 23:42:53 +0000

On Wed, 9 Nov 2016 00:00:01 +0100
Philippe Verdy <verdy_p_at_wanadoo.fr> wrote:

> 2016-11-08 9:30 GMT+01:00 Richard Wordingham <
> richard.wordingham_at_ntlworld.com>:
>
> > TUS Section 2.11 says, "If the combining characters can interact
> > typographically—for example, U+0304 combining macron and U+0308
> > combining diaeresis — then the order of graphic display is
> > determined by the order of coded characters (see Table 2-5).
> > By default, the diacritics or other combining characters are
> > positioned from the base character’s glyph outward".
 
> The interpretation of "If the combining characters can interact
> typographically" should be better read as "If the combining
> characters have the same non-zero combining class or any one of them
> has a zero combining class".

The combining marks in question both have canonical combining class 0.

> But now normalization is everywhere and causes the pairs using the
> condition above to be freely reordered (or decomposed and recomposed,
> meaning that the encoding order is NOT significant at all).

I believe a renderer is permitted to treat canonically equivalent
sequence differently so long as it does not believe it should treat
them differently. However, that is irrelevant to this case.

Richard.
Received on Tue Nov 08 2016 - 17:43:53 CST

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