[XeTeX] anti-xunicode ;-)

[Ralf Stubner]

Adam Twardoch <list.adam at twardoch.com> writes:

> Unicode assigns different combining classes to different diacritical 
> marks, and prescribe a canonical order of marks. For example, the 
> canonical order for the Yoruba character we’ve been discussing is
> \u0045\u0323\u0301 and not \u0045\u0301\u0323.
>
> However, both sequences are canonically equivalent, and Unicode 
> recommends: "Rendering systems should handle any of the canonically 
> equivalent orders of combining marks."

Thanks for the information.

> Of course XeTeX would do good if it did canonical reordering of marks. 
> As I’ve written, *well-made* fonts should not rely on marks being 
> canonically ordered, but some fonts will only contain rendering rules 
> for canonically ordered marks. Canonical reordering surely would 
> minimize the risk of bad renderings.

It looks as if XeTeX uses the characters as they are inputed. In a font
with E, Edotbellow, acutecomb and dotbellowcomb, the Edotbellow glyph is
used when I input <E><dotbellowcomb><acutecomb>, but not for
<E><acutecomb><dotbellowcomb>. Even though the first form would be the
canonically reordered form of the second. Of course, proper support for
characters like this via 'mark' or 'ccmp' is the right way to go.

cheerio
ralf