Date: Tue, 9 Mar 2010 10:39:47 +0100
From: Peter Dyballa <peter_dyba...@web.de>
<snip>
Does Vietnamese have your multi-accented characters?
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Vietnamese orthography is a notable challenge for rendering multiple
diacritics on the same letter.
As a simpler example, in the de facto standard orthography for Hopi,
spoken in Arizona, USA, there are glyphs involving
1. o (or uppercase O)
2. dieresis
3. and an acute, grave or circumflex accent
The dieresis should be rendered above the o (or O), and the acute or
grave or circumflex should be rendered above the dieresis.
E.g. in Unicode you could have the following sequence of characters
U+006F LATIN SMALL LETTER O
U+0308 COMBINING DIAERESIS
U_0301 COMBINING ACUTE ACCENT
and it should be rendered correctly (o, with dieresis above, with an
acute accent stacked above the dieresis). Unicode does include a
single character with the o+dieresis, and the following sequence of
characters is equivalent and should be rendered the same by a good
rendering engine.
U+00F6 LATIN SMALL LETTER O WITH DIAERESIS
U+0301 COMBINING ACUTE ACCENT
Unicode does not provide a single letter for o, with dieresis, with an
acute, grave or circumflex accent.
When typesetting Hopi in XeTeX, I get good results with these
sequences using the Doulos SIL font. In gvim (MacVim) I get good
results using the DejaVu Sans Mono font.
I'm definitely not an expert in fonts, but I assume that the font
itself should include information for each glyph about where combining
diacritics, including stacks of combining diacritics, should be
rendered. And the rendering engine should be able to access and use
that information. In my experience, the handling of combining
diacritics is a weak point in fonts and rendering engines, let alone
the handling of _stacked_ combining diacritics.
Any correction or clarification would be appreciated.
Ken
******************************
Kenneth R. Beesley, D.Phil.
P.O. Box 540475
North Salt Lake, UT
84054 USA
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